WO2024080304A1

WO2024080304A1 - Fusion protein of serum albumin and physiologically active protein

Info

Publication number: WO2024080304A1
Application number: PCT/JP2023/036884
Authority: WO
Inventors: 健一高橋; 泰功菅野; 貴士小野内
Original assignee: Ｊｃｒファーマ株式会社
Priority date: 2022-10-11
Filing date: 2023-10-11
Publication date: 2024-04-18
Also published as: JP2024056665A

Abstract

One embodiment of the present invention makes it possible to express, in the form of a fusion protein with a serum albumin (SA), a physiologically active protein that is expressed in a low amount and/or is less active when a host cell such as a CHO cell is normally used to express the physiologically active protein as a recombinant protein, thereby efficiently producing the physiologically active protein as a highly active recombinant protein. The fusion protein may be obtained by bonding the physiologically active protein to the amino-terminal side of the SA, or may be obtained by bonding the physiologically active protein to a carboxyl terminal. Further, said fusion protein can be a body coupled with a ligand or an antibody.

Description

Fusion protein of serum albumin and a biologically active protein

The present invention relates to a fusion protein in which serum albumin (SA) is bound to a protein having physiological activity (biologically active protein) and a method for producing the same. Such a fusion protein relates, for example, to one in which the C-terminus of SA is bound to the N-terminus of a biologically active protein. Some biologically active proteins have low expression levels and/or low activity when expressed as a recombinant protein by introducing a gene encoding the biologically active protein into a host cell such as a mammalian cell, particularly when expressed so that the recombinant protein is secreted from the cell and accumulated in the culture medium. The present invention relates to such a fusion protein of SA and a biologically active protein that can be efficiently produced as a highly active recombinant protein, and also relates to a method for producing the fusion protein. However, there is no particular restriction on the biologically active protein to be fused to SA, and any biologically active protein can be made into a fusion protein with SA.

The present invention relates in particular to a fusion protein in which serum albumin (SA) is bound to a lysosomal enzyme, for example, the C-terminus of SA is bound to the N-terminus of a lysosomal enzyme, or the C-terminus of a lysosomal enzyme is bound to the N-terminus of SA, either directly or via a linker. Some lysosomal enzymes have low expression levels and/or low activity when expressed as recombinant proteins by introducing a gene encoding the lysosomal enzyme into a host cell such as a mammalian cell, particularly when the recombinant protein is expressed so as to be secreted from the cell and accumulated in the culture medium. The present invention relates to such a fusion protein of a lysosomal enzyme and SA that can be efficiently produced as a highly active recombinant protein, and also relates to a method for producing the fusion protein. However, there is no particular restriction on the physiologically active protein to be fused to the lysosomal enzyme, and any lysosomal enzyme can be made into a fusion protein with SA.

The present invention also relates to a fusion protein in which serum albumin (SA) and galactosylceramidase (GALC) are bound, for example, by binding the C-terminus of SA to the N-terminus of GALC, or the C-terminus of GALC to the N-terminus of SA, either directly or via a linker. When a gene encoding GALC is introduced into a host cell such as a mammalian cell and the protein is expressed as a recombinant protein, the expression level and/or activity of GALC may be low, particularly when the recombinant protein is expressed so as to be secreted from the cell and accumulated in the culture medium. The present invention relates to such a fusion protein of GALC and SA that can be efficiently produced as a highly active recombinant protein, and to a method for producing the fusion protein.

The present invention also relates to a fusion protein in which serum albumin (SA) and glucocerebrosidase (GBA) are bound, for example, by binding the C-terminus of SA to the N-terminus of GBA, or the C-terminus of GBA to the N-terminus of SA, either directly or via a linker. When a gene encoding GBA is introduced into a host cell such as a mammalian cell and expressed as a recombinant protein, GBA may have a low expression level and/or low activity, particularly when the recombinant protein is expressed so as to be secreted from the cell and accumulated in the culture medium. The present invention relates to such a fusion protein of GBA and SA that can be efficiently produced as a highly active recombinant protein, and to a method for producing said fusion protein.

The present invention relates to a fusion protein in which serum albumin (SA) and a cytokine are bound, for example, by binding the C-terminus of SA to the N-terminus of a cytokine, or the C-terminus of a cytokine to the N-terminus of SA, either directly or via a linker. Some cytokines have low expression levels and/or low activity when expressed as a recombinant protein by introducing a gene encoding the cytokine into a host cell such as a mammalian cell, particularly when expressed so that the recombinant protein is secreted from the cell and accumulated in the culture medium. The present invention relates to such a fusion protein of cytokine and SA that can be efficiently produced as a highly active recombinant protein, and to a method for producing the fusion protein. However, there is no particular restriction on the physiologically active protein to be fused with the cytokine, and any cytokine can be made into a fusion protein with SA.

The present invention relates in particular to a fusion protein in which serum albumin (SA) and an interleukin are bound, for example, by binding the C-terminus of SA to the N-terminus of an interleukin, or the C-terminus of an interleukin to the N-terminus of SA, either directly or via a linker. Some interleukins have low expression levels and/or low activity when expressed as a recombinant protein by introducing a gene encoding the interleukin into a host cell such as a mammalian cell, particularly when the recombinant protein is expressed so as to be secreted from the cell and accumulated in the culture medium. The present invention relates to such a fusion protein of an interleukin and SA that can be efficiently produced as a highly active recombinant protein, and also relates to a method for producing the fusion protein. However, there is no particular restriction on the physiologically active protein to be fused with the interleukin, and all interleukins can be made into a fusion protein with SA.

The present invention relates in particular to a fusion protein in which serum albumin (SA) and interleukin 10 (IL-10) are bound, for example, by binding the C-terminus of SA to the N-terminus of IL-10, or the C-terminus of IL-10 to the N-terminus of SA, either directly or via a linker. When IL-10 is expressed as a recombinant protein by introducing a gene encoding IL-10 into a host cell such as a mammalian cell, the expression level and/or activity of IL-10 may be low, particularly when the recombinant protein is expressed so as to be secreted from the cell and accumulated in the culture medium. The present invention relates to such a fusion protein of IL-10 and SA that can be efficiently produced as a highly active recombinant protein, and also to a method for producing said fusion protein.

The present invention relates to a fusion protein in which serum albumin (SA) and a neurotrophic factor are bound, for example, by binding the C-terminus of SA to the N-terminus of a neurotrophic factor, or the C-terminus of a neurotrophic factor to the N-terminus of SA, either directly or via a linker. Some neurotrophic factors have low expression levels and/or low activity when expressed as recombinant proteins by introducing a gene encoding the neurotrophic factor into a host cell such as a mammalian cell, particularly when expressed so that the recombinant protein is secreted from the cell and accumulated in the culture medium. The present invention relates to such a fusion protein of a neurotrophic factor and SA that can be efficiently produced as a highly active recombinant protein, and also relates to a method for producing the fusion protein. However, there is no particular restriction on the physiologically active protein to be fused to the neurotrophic factor, and any neurotrophic factor can be made into a fusion protein with SA.

The present invention relates in particular to a fusion protein in which serum albumin (SA) and brain-derived neurotrophic factor (BDNF) are bound, for example, by binding the C-terminus of SA to the N-terminus of BDNF, or the C-terminus of BDNF to the N-terminus of SA, either directly or via a linker. When a gene encoding BDNF is introduced into a host cell such as a mammalian cell and BDNF is expressed as a recombinant protein, particularly when the recombinant protein is expressed so as to be secreted from the cell and accumulated in the culture medium, BDNF may have a low expression level and/or low activity. The present invention relates to such a fusion protein of BDNF and SA that can be efficiently produced as a highly active recombinant protein, and to a method for producing said fusion protein.

The present invention also relates to a fusion protein in which serum albumin (SA) and nerve growth factor (NGF) are bound, for example, by binding the C-terminus of SA to the N-terminus of NGF, or the C-terminus of NGF to the N-terminus of SA, either directly or via a linker. When NGF is expressed as a recombinant protein by introducing a gene encoding NGF into a host cell such as a mammalian cell, the expression level and/or activity may be low, particularly when the recombinant protein is expressed so as to be secreted from the cell and accumulated in the culture medium. The present invention relates to such a fusion protein of NGF and SA that can be efficiently produced as a highly active recombinant protein, and to a method for producing the fusion protein.

The present invention also relates to a fusion protein in which serum albumin (SA) and neurotrophin 3 (NT-3) are bound, for example, by binding the C-terminus of SA to the N-terminus of NT-3, or the C-terminus of NT-3 to the N-terminus of SA, either directly or via a linker. When NT-3 is expressed as a recombinant protein by introducing a gene encoding NT-3 into a host cell such as a mammalian cell, the expression level and/or activity may be low, particularly when the recombinant protein is expressed so as to be secreted from the cell and accumulated in the culture medium. The present invention relates to such a fusion protein of NT-3 and SA that can be efficiently produced as a highly active recombinant protein, and to a method for producing said fusion protein.

The present invention also relates to a fusion protein in which serum albumin (SA) and neurotrophin 4 (NT-4) are bound, for example, by binding the C-terminus of SA to the N-terminus of NT-4, or the C-terminus of NT-4 to the N-terminus of SA, either directly or via a linker. When NT-4 is expressed as a recombinant protein by introducing a gene encoding NT-4 into a host cell such as a mammalian cell, the expression level and/or activity may be low, particularly when the recombinant protein is expressed so as to be secreted from the cell and accumulated in the culture medium. The present invention relates to such a fusion protein of NT-4 and SA that can be efficiently produced as a highly active recombinant protein, and to a method for producing said fusion protein.

Krabbe disease, a type of lysosomal disease, is also known as galactosylceramide lipidosis or globoid cell leukodystrophy. It is a genetic disease caused by a genetic abnormality that reduces the activity or deficiency of galactosylceramidase (galactocerebrosidase, GALC), which is necessary for the breakdown of sphingolipids in lysosomes. Galactosylceramidase (GALC) uses galactosylsphingosine, galactocerebroside, and other substrates as catalysts for the hydrolysis of the galactose ester bonds in the molecules of these substrates. In patients with Krabbe disease, the substrate galactosylsphingosine and other substances accumulate in the body due to the deficiency of GALC. Galactosylsphingosine is known to have strong cytotoxicity, and its accumulation causes demyelination, which destroys the myelin sheath or myelin in the central and peripheral nerves. Krabbe disease is a progressive disease, and in severe cases, intellectual disability, paralysis, blindness, hearing loss, and pseudobulbar palsy are observed. Depending on the time of onset, Krabbe disease is classified into infantile type, which begins at about 3 to 6 months of age and is characterized by irritability and regression, and often results in death within 2 to 3 years; late infantile type, which begins at about 6 months to 3 years of age and is characterized by irritability, delayed psychomotor development, and regression; juvenile type, which begins at about 3 to 10 years of age and progresses slowly, and is characterized by visual impairment, gait disturbance, ataxia, etc.; and adult type, which begins at about 10 years of age or older and is characterized by psychiatric symptoms, etc.

Gaucher disease, a type of lysosomal disease, is a genetic disease caused by a genetic abnormality that results in a decrease in the activity or deficiency of glucocerebrosidase (β-glucosidase, GBA), an enzyme required for the breakdown of the biological glycolipid glucocerebroside in the lysosome. Glucocerebrosidase (GBA) catalyzes the hydrolysis of the dehydration condensation site of sugar and lipid in the substrate molecule using glucocerebroside as a substrate. In patients with Gaucher disease, the substrate glucocerebroside and other substances accumulate in the body due to a deficiency of GBA. Glucocerebroside accumulates in macrophages, particularly in the liver, spleen, and bones, causing anemia and thrombocytopenia due to decreased splenic function, as well as hepatosplenomegaly, bone pain, fractures, and central nervous system disorders. It is believed that the central nervous system disorders are caused by the accumulation of glucosylsphingosine, the lyso form of glucocerebroside, in the brain. Gaucher disease is classified according to the presence or absence and severity of neurological symptoms into the mildest type I (non-neurological type), which occurs at ages ranging from infancy to adulthood and is characterized by slowly progressing symptoms such as enlargement of the liver and spleen, anemia, decreased platelets, and fractures without accompanying neurological symptoms; the most severe type II (acute neurological type), which begins in infancy and, in addition to the symptoms of type I, rapidly progresses with neurological symptoms such as psychomotor developmental delay, convulsions, and neck retroversion, resulting in death from oxygen deficiency by the age of two; and the progressive type III (subacute neurological type), which develops gradually during infancy and progresses more slowly than type II.

　Lysosomal diseases other than Krabbe disease and Gaucher disease are also caused by genetic deficiencies in lysosomal enzymes. For lysosomal diseases such as Fabry disease and Hunter syndrome, enzyme replacement therapy is performed in which the genetically deficient enzyme is produced as a recombinant enzyme using genetic engineering technology and administered to the patient.

The gene encoding human GALC (hGALC) was isolated in 1993 (Non-Patent Document 1). However, there are no drugs for use as enzyme replacement therapy for Krabbe disease that contain recombinant human GALC (rhGALC) produced using this gene as the active ingredient.

The gene encoding human GBA (hGBA) was isolated in 1986 (Non-Patent Document 2). However, there are no drugs for use as enzyme replacement therapy for Gaucher disease that contain recombinant human GBA (rhGBA) produced using this gene as the active ingredient.

IL-10, a type of cytokine, is an anti-inflammatory cytokine produced by Th2 cells and can inhibit cytokine production by Th1 cells, suppressing immune responses. Due to its anti-inflammatory effect, IL-10 is expected to be effective against many inflammatory diseases, namely, neuropathic pain, multiple sclerosis, spinal cord injury, ALS, neuroinflammation, symptoms associated with arthritis and other joint diseases, and autoimmune diseases. In addition to its immunosuppressive effect, it has also been reported that IL-10 may have an anti-cancer effect (Non-Patent Document 3). The gene encoding human IL-10 was isolated in 1991 (Non-Patent Document 4). However, there are no pharmaceuticals for use as a therapeutic agent for inflammatory diseases or cancer that contain recombinant human IL-10 (rhIL-10) produced using this gene as an active ingredient.

BDNF, a type of neurotrophic factor, is a humoral protein of the nervous system that binds to a specific receptor TrkB on the surface of target cells and regulates the growth of nerve cells, such as the survival and growth of nerve cells and the enhancement of synaptic function. Due to its neurodevelopmental effect, BDNF is expected to be developed as a treatment for a variety of diseases, including neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and Huntington's disease, spinal degenerative diseases such as amyotrophic lateral sclerosis, as well as diabetic neuropathy, cerebral ischemic disease, developmental disorders such as Rett syndrome, schizophrenia, depression, and Rett syndrome. The gene encoding human BDNF was isolated in 1993 (Non-Patent Documents 5 and 6). However, there are no pharmaceuticals containing recombinant human BDNF (rhBDNF) produced using this gene as an active ingredient for use as a treatment for neurodegenerative diseases, etc.

NGF, a type of neurotrophic factor, is a protein that promotes the survival and growth of sympathetic nerve cells and spinal sensory neurons in the peripheral nervous system, and promotes the survival and differentiation of cholinergic nerve cells in the central nervous system, especially in the basal forebrain. In particular, due to its effect of preventing the decline of dendrite function, NGF is expected to be developed as a treatment for neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and Huntington's disease, but it is also expected to be effective in preventing aging and degeneration of brain function, improving brain function, preventing and treating dementia, improving memory and learning ability by building neural networks, and enhancing the action of neurotransmitters. Of the three subunits α, β, and γ that make up human NGF, a gene encoding at least the β subunit was isolated in 1990 (Non-Patent Document 7). However, there are no pharmaceuticals for use as a treatment for neurodegenerative diseases, etc., that contain recombinant human NGF (rhNGF) as an active ingredient, which is manufactured using a gene encoding human NGF.

NT-3, a type of neurotrophic factor, is known to be involved in promoting the survival and growth of nerve cells and glial cells and neurogenesis by transmitting signals through Trk receptors, particularly TrkC, and is attracting attention for its ability to promote neurotransmission and nerve repair, particularly the differentiation and regeneration of photoreceptor cells. NT-3 is therefore expected to be developed as a treatment for neurodegenerative diseases. The gene encoding human NT-3 was isolated in 1991 (Non-patent Document 8). However, there are no pharmaceuticals for use as a treatment for neurodegenerative diseases that contain recombinant human NT-3 (rhNT-3) as an active ingredient, which is produced using the gene encoding human NT-3.

NT-4, a type of neurotrophic factor, transmits signals through Trk receptors, particularly TrkB, and promotes the growth and survival of peripheral and central nervous system neurons, similar to NT-3. NT-4 is therefore expected to be developed as a treatment for neurodegenerative diseases. The gene encoding human NT-4 was isolated in 1992 (Non-patent Document 9). However, there are no pharmaceuticals for use as a treatment for neurodegenerative diseases that contain recombinant human NT-4 (rhNT-4) as an active ingredient, which is produced using the gene encoding human NT-4.

A method is known for producing growth hormone, which is rapidly degraded and loses its activity when administered to the body, as a fusion protein with serum albumin (Non-Patent Document 10). Growth hormone fused to serum albumin has increased stability in the body. Therefore, although growth hormone is normally administered subcutaneously every day, by making it into a fusion protein with serum albumin, the number of times it is administered can be reduced.

One of the objects of the present invention is to provide a physiologically active substance that is usually expressed in a low amount and/or has a low activity when expressed as a recombinant protein using a host cell such as a CHO cell, in the form of a fusion protein with serum albumin (SA). Such a fusion protein can be efficiently produced as a highly active recombinant protein. Also provided is a method for producing the fusion protein.
Another object of the present invention is to provide a lysosomal enzyme that is expressed in a low amount and/or has low activity when expressed as a recombinant protein using a host cell such as a CHO cell, particularly when expressed so that the recombinant protein is secreted from the cell and accumulated in the culture medium, in the form of a fusion protein with serum albumin. Such a fusion protein can be efficiently produced as a highly active recombinant protein. A method for producing the fusion protein is also provided. Examples of the lysosomal enzyme include hGALC and hGBA.

When expressing a recombinant protein so that it is secreted from cells and accumulated in the culture medium, a DNA sequence encoding a leader peptide is placed in frame on the 5' side of the gene encoding the recombinant protein. This allows the expressed recombinant protein to be secreted from cells. The leader peptide is preferably an SA leader peptide when an SA is located at the N-terminus of the recombinant protein, a lysosomal enzyme leader peptide when a lysosomal enzyme is located at the N-terminus of the recombinant protein, a cytokine leader peptide when a cytokine is located at the N-terminus of the recombinant protein, or a neurotrophic factor leader peptide when a neurotrophic factor is located at the N-terminus of the recombinant protein. However, instead of these, the leader peptide may be a leader peptide of a heterologous protein, such as a growth hormone leader peptide, or an artificial leader peptide.

Another object of the present invention is to provide a cytokine that is expressed in a low amount and/or has low activity when expressed as a recombinant protein using a host cell such as a CHO cell, particularly when expressed so that the recombinant protein is secreted from the cell and accumulated in a culture medium, in the form of a fusion protein with serum albumin. Such a fusion protein can be efficiently produced as a highly active recombinant protein. A method for producing the fusion protein is also provided. Here, the cytokine is, for example, an interleukin, particularly hIL-10.
Another object of the present invention is to provide a neurotrophic factor that is expressed in a low amount and/or has low activity when expressed as a recombinant protein using a host cell such as a CHO cell, particularly when expressed so that the recombinant protein is secreted from the cell and accumulates in the culture medium, in the form of a fusion protein with serum albumin. Such a fusion protein can be efficiently produced as a highly active recombinant protein. A method for producing the fusion protein is also provided. Examples of neurotrophic factors include hBDNF, hNGF, hNT-3, and hNT-4.

In research aimed at the above-mentioned object, the inventors conducted extensive investigations and found that, as a result of the discovery, when a fusion protein in which HSA is bound directly or via a linker to the N-terminus or C-terminus of human lysosomal enzymes hGALC or hGBA, as described in detail in this specification, is expressed by culturing a host cell into which an expression vector incorporating a gene encoding the fusion protein has been introduced, the expression level of the recombinant fusion protein (converted to the expression level of the portion of the recombinant fusion protein corresponding to the wild-type human lysosomal enzyme) is significantly increased compared to the expression level of the recombinant wild-type human lysosomal enzyme when the recombinant fusion protein is expressed by culturing a host cell into which an expression vector incorporating a gene encoding the wild-type human lysosomal enzyme has been introduced, thereby completing the present invention.
Furthermore, in the course of research aimed at the above-mentioned object, the present inventors conducted extensive investigations and found that, as a result of culturing and expressing a fusion protein in which HSA is bound directly or via a linker to the N-terminus or C-terminus of the human cytokine hIL-10, as described in detail herein, in a host cell into which an expression vector incorporating a gene encoding the fusion protein has been introduced, the activity of the recombinant fusion protein is significantly increased compared to the activity of recombinant wild-type hIL-10 in which the recombinant fusion protein is expressed in a host cell into which an expression vector incorporating a gene encoding wild-type hIL-10 has been introduced, thereby completing the present invention.
Furthermore, in research aimed at the above-mentioned object, the inventors have conducted extensive investigations and as a result have found that when a fusion protein in which HSA is bound directly or via a linker to the N-terminus or C-terminus of human neurotrophic factors hBDNF, hNGF, hNT-3, or hNT-4, as described in detail in this specification, is expressed by culturing a host cell into which an expression vector incorporating a gene encoding the fusion protein has been introduced, the activity of the recombinant fusion protein is significantly increased compared to the activity of recombinant wild-type human neurotrophic factor when expressed by culturing a host cell into which an expression vector incorporating a gene encoding a wild-type human neurotrophic factor has been introduced, thereby completing the present invention.
That is, the present invention includes the following.
1. A fusion protein comprising a lysosomal enzyme and serum albumin (SA).
2. The fusion protein according to claim 1, wherein the lysosomal enzyme is a human lysosomal enzyme.
3. The fusion protein according to 1 or 2 above, wherein the SA is human serum albumin (HSA).
4. The fusion protein according to any one of 1 to 3 above, wherein the lysosomal enzyme is human galactosylceramidase (hGALC) having 80% or more identity to wild-type human galactosylceramidase having the amino acid sequence shown in SEQ ID NO: 1, and the SA is human serum albumin (HSA) having 80% or more identity to wild-type human serum albumin having the amino acid sequence shown in SEQ ID NO: 3.
5. The fusion protein according to 4 above, wherein the hGALC has 90% or more identity to wild-type hGALC having the amino acid sequence shown in SEQ ID NO:1, and the HSA has 90% or more identity to wild-type HSA having the amino acid sequence shown in SEQ ID NO:3.
6. The fusion protein according to 4 above, wherein the hGALC comprises an amino acid sequence in which 1 to 10 amino acids have been substituted, deleted and/or added to the amino acid sequence of wild-type hGALC shown in SEQ ID NO:1.
7. The fusion protein according to 4 above, wherein the hGALC comprises an amino acid sequence in which 1 to 5 amino acids have been substituted, deleted and/or added to the amino acid sequence of wild-type hGALC shown in SEQ ID NO:1.
8. The fusion protein according to 4 above, wherein the hGALC comprises an amino acid sequence in which 1 to 3 amino acids have been substituted, deleted and/or added relative to the amino acid sequence of wild-type hGALC shown in SEQ ID NO:1.
9. The fusion protein according to 4 above, wherein the hGALC comprises an amino acid sequence in which one amino acid has been substituted with respect to the amino acid sequence of wild-type hGALC shown in SEQ ID NO:1.
10. The fusion protein according to 9 above, wherein the amino acid substitution is within an amino acid family in which the side chain is an amino acid that can be hydroxylated.
11. The fusion protein according to any one of 4 to 10 above, wherein the HSA comprises an amino acid sequence in which 1 to 10 amino acids have been substituted, deleted and/or added to the amino acid sequence of wild-type HSA shown in SEQ ID NO:3.
12. The fusion protein according to any one of 4 to 10 above, wherein the HSA comprises an amino acid sequence in which 1 to 5 amino acids have been substituted, deleted and/or added to the amino acid sequence of wild-type HSA shown in SEQ ID NO:3.
13. The fusion protein according to any one of 4 to 10 above, wherein the HSA comprises an amino acid sequence in which 1 to 3 amino acids have been substituted, deleted and/or added to the amino acid sequence of wild-type HSA shown in SEQ ID NO:3.
14. The fusion protein according to 4 above, wherein the hGALC comprises the amino acid sequence of wild-type hGALC shown in SEQ ID NO:1, and the HSA comprises the amino acid sequence of wild-type human serum albumin shown in SEQ ID NO:3.
15. The fusion protein according to 4 above, wherein the hGALC comprises the amino acid sequence of wild-type hGALC shown in SEQ ID NO: 1, and the HSA comprises the amino acid sequence of wild-type human serum albumin shown in SEQ ID NO: 12.
16. The fusion protein according to 4 above, wherein the hGALC comprises the amino acid sequence of wild-type hGALC shown in SEQ ID NO: 1, and the HSA comprises the amino acid sequence of wild-type human serum albumin shown in SEQ ID NO: 13.
17. The fusion protein according to any one of 4 to 16 above, wherein the HSA is bound to the C-terminus of the hGALC directly or via a linker.
18. The fusion protein according to any one of 4 to 16 above, wherein the hGALC is bound to the C-terminus of the HSA directly or via a linker.
19. The fusion protein according to 17 or 18 above, wherein the linker is a peptide chain consisting of 1 to 150 amino acids.
20. The fusion protein according to claim 19, wherein the linker comprises an amino acid sequence selected from the group consisting of the following (a) to (g):
(a) Gly;
(b) Ser;
(c) GlySer;
(d) GlyGlySer;
(e) the amino acid sequence set forth in SEQ ID NO:9;
(f) the amino acid sequence set forth in SEQ ID NO: 10; and
(g) The amino acid sequence shown in SEQ ID NO:11.
21. The fusion protein according to claim 19, wherein the linker comprises an amino acid sequence in which an amino acid sequence selected from the group consisting of the following (a) to (g) is repeated 2 to 10 times:
(a) Gly;
(b) Ser;
(c) GlySer;
(d) GlyGlySer;
(e) the amino acid sequence set forth in SEQ ID NO:9;
(f) the amino acid sequence set forth in SEQ ID NO: 10; and
(g) The amino acid sequence shown in SEQ ID NO:11.
22. The fusion protein according to 19 above, wherein the linker comprises an amino acid sequence in which an amino acid sequence selected from the group consisting of the following (a) to (g) is repeated 2 to 6 times:
(a) Gly;
(b) Ser;
(c) GlySer;
(d) GlyGlySer;
(e) the amino acid sequence set forth in SEQ ID NO:9;
(f) the amino acid sequence set forth in SEQ ID NO: 10; and
(g) The amino acid sequence shown in SEQ ID NO:11.
23. The fusion protein according to claim 19, wherein the linker comprises an amino acid sequence in which an amino acid sequence selected from the group consisting of the following (a) to (g) is repeated 3 to 5 times:
(a) Gly;
(b) Ser;
(c) GlySer;
(d) GlyGlySer;
(e) the amino acid sequence set forth in SEQ ID NO:9;
(f) the amino acid sequence set forth in SEQ ID NO: 10; and
(g) The amino acid sequence shown in SEQ ID NO:11.
24. The fusion protein according to claim 19, wherein the linker comprises the amino acid sequence Gly Ser.
25. The fusion protein according to 18 above, which comprises an amino acid sequence having 80% or more identity to the amino acid sequence shown in SEQ ID NO:5.
26. The fusion protein according to 18 above, which comprises an amino acid sequence having 90% or more identity to the amino acid sequence shown in SEQ ID NO:5.
27. The fusion protein according to claim 26, which comprises an amino acid sequence in which 1 to 10 amino acids have been substituted, deleted and/or added to the amino acid sequence shown in SEQ ID NO:5.
28. The fusion protein according to claim 26, which comprises an amino acid sequence in which 1 to 5 amino acids have been substituted, deleted and/or added to the amino acid sequence shown in SEQ ID NO:5.
29. The fusion protein according to claim 26, which comprises an amino acid sequence in which 1 to 3 amino acids have been substituted, deleted and/or added relative to the amino acid sequence shown in SEQ ID NO:5.
30. The fusion protein according to claim 18, which comprises the amino acid sequence shown in SEQ ID NO:5.
31. The fusion protein according to 17 above, which comprises an amino acid sequence having 80% or more identity to the amino acid sequence shown in SEQ ID NO:7.
32. The fusion protein according to 17 above, which comprises an amino acid sequence having 90% or more identity to the amino acid sequence shown in SEQ ID NO:7.
33. The fusion protein according to 32 above, which comprises an amino acid sequence in which 1 to 10 amino acids have been substituted, deleted and/or added to the amino acid sequence shown in SEQ ID NO:7.
34. The fusion protein according to 32 above, which comprises an amino acid sequence in which 1 to 5 amino acids have been substituted, deleted and/or added to the amino acid sequence shown in SEQ ID NO:7.
35. The fusion protein according to 32 above, which comprises an amino acid sequence in which 1 to 3 amino acids have been substituted, deleted and/or added to the amino acid sequence shown in SEQ ID NO:7.
36. The fusion protein according to claim 17, comprising the amino acid sequence shown in SEQ ID NO:7.
37. The fusion protein according to any one of 4 to 36 above, which has a specific activity of 10% or more compared with the specific activity of normal wild-type hGALC.
38. The fusion protein according to any one of 1 to 3 above, wherein the lysosomal enzyme is human glucocerebrosidase (hGBA) having 80% or more identity to wild-type human glucocerebrosidase having the amino acid sequence shown in SEQ ID NO: 37, and the SA is human serum albumin (HSA) having 80% or more identity to wild-type human serum albumin having the amino acid sequence shown in SEQ ID NO: 3.
39. The fusion protein according to claim 38, wherein said hGBA has 90% or more identity to wild-type hGBA having the amino acid sequence shown in SEQ ID NO:37, and said HSA has 90% or more identity to wild-type HSA having the amino acid sequence shown in SEQ ID NO:3.
40. The fusion protein according to 38 above, wherein the hGBA comprises an amino acid sequence in which 1 to 10 amino acids have been substituted, deleted and/or added relative to the amino acid sequence of wild-type hGBA shown in SEQ ID NO:37.
41. The fusion protein according to 38 above, wherein the hGBA comprises an amino acid sequence in which 1 to 5 amino acids have been substituted, deleted and/or added relative to the amino acid sequence of wild-type hGBA shown in SEQ ID NO:37.
42. The fusion protein according to 38 above, wherein the hGBA comprises an amino acid sequence in which 1 to 3 amino acids have been substituted, deleted and/or added relative to the amino acid sequence of wild-type hGBA shown in SEQ ID NO:37.
43. The fusion protein according to 38 above, wherein said hGBA comprises an amino acid sequence in which one amino acid has been substituted with respect to the amino acid sequence of wild-type hGBA shown in SEQ ID NO:37.
44. The fusion protein according to 43 above, wherein the amino acid substitution is within an amino acid family in which the side chain is an amino acid that can be hydroxylated.
45. The fusion protein according to any one of 38 to 44 above, wherein the HSA comprises an amino acid sequence in which 1 to 10 amino acids have been substituted, deleted and/or added to the amino acid sequence of wild-type HSA shown in SEQ ID NO:3.
46. The fusion protein according to any one of 38 to 44 above, wherein the HSA comprises an amino acid sequence in which 1 to 5 amino acids have been substituted, deleted and/or added to the amino acid sequence of wild-type HSA shown in SEQ ID NO:3.
47. The fusion protein according to any one of 38 to 44 above, wherein the HSA comprises an amino acid sequence in which 1 to 3 amino acids have been substituted, deleted and/or added to the amino acid sequence of wild-type HSA shown in SEQ ID NO:3.
48. The fusion protein according to claim 38, wherein said hGBA comprises the amino acid sequence of wild-type hGBA shown in SEQ ID NO:37, and said HSA comprises the amino acid sequence of wild-type HSA shown in SEQ ID NO:3.
49. The fusion protein according to claim 38, wherein said hGBA comprises the amino acid sequence of wild-type hGBA shown in SEQ ID NO:37, and said HSA comprises the amino acid sequence of wild-type HSA shown in SEQ ID NO:12.
50. The fusion protein according to claim 38, wherein said hGBA comprises the amino acid sequence of wild-type hGBA shown in SEQ ID NO:37, and said HSA comprises the amino acid sequence of wild-type HSA shown in SEQ ID NO:13.
51. The fusion protein according to any one of 38 to 50 above, wherein the HSA is bound to the C-terminus of the hGBA directly or via a linker.
52. The fusion protein according to any one of 38 to 50 above, wherein the hGBA is bound to the C-terminus of the HSA directly or via a linker.
53. The fusion protein according to 51 or 52 above, wherein the linker is a peptide chain consisting of 1 to 150 amino acids.
54. The fusion protein according to 53 above, wherein the linker comprises an amino acid sequence selected from the group consisting of the following (a) to (g):
(a) Gly;
(b) Ser;
(c) GlySer;
(d) GlyGlySer;
(e) the amino acid sequence set forth in SEQ ID NO:9;
(f) the amino acid sequence set forth in SEQ ID NO: 10; and
(g) The amino acid sequence shown in SEQ ID NO:11.
55. The fusion protein according to 53 above, wherein the linker comprises an amino acid sequence in which an amino acid sequence selected from the group consisting of the following (a) to (g) is repeated 2 to 10 times:
(a) Gly;
(b) Ser;
(c) GlySer;
(d) GlyGlySer;
(e) the amino acid sequence set forth in SEQ ID NO:9;
(f) the amino acid sequence set forth in SEQ ID NO: 10; and
(g) The amino acid sequence shown in SEQ ID NO:11.
56. The fusion protein according to 53 above, wherein the linker comprises an amino acid sequence in which an amino acid sequence selected from the group consisting of the following (a) to (g) is repeated 2 to 6 times:
(a) Gly;
(b) Ser;
(c) GlySer;
(d) GlyGlySer;
(e) the amino acid sequence set forth in SEQ ID NO:9;
(f) the amino acid sequence set forth in SEQ ID NO: 10; and
(g) The amino acid sequence shown in SEQ ID NO:11.
57. The fusion protein according to 53 above, wherein the linker comprises an amino acid sequence in which an amino acid sequence selected from the group consisting of the following (a) to (g) is repeated 3 to 5 times:
(a) Gly;
(b) Ser;
(c) GlySer;
(d) GlyGlySer;
(e) the amino acid sequence set forth in SEQ ID NO:9;
(f) the amino acid sequence set forth in SEQ ID NO: 10; and
(g) The amino acid sequence shown in SEQ ID NO:11.
58. The fusion protein according to the above 53, wherein the linker consists of the amino acid sequence represented by Gly Ser.
59. The fusion protein according to 52 above, comprising an amino acid sequence having 80% or more identity to the amino acid sequence shown in SEQ ID NO:39.
60. The fusion protein according to 52 above, which comprises an amino acid sequence having 90% or more identity to the amino acid sequence shown in SEQ ID NO:39.
61. The fusion protein according to 60 above, which comprises an amino acid sequence in which 1 to 10 amino acids have been substituted, deleted and/or added to the amino acid sequence shown in SEQ ID NO:39.
62. The fusion protein according to 60 above, which comprises an amino acid sequence in which 1 to 5 amino acids have been substituted, deleted and/or added to the amino acid sequence shown in SEQ ID NO:39.
63. The fusion protein according to 60 above, which comprises an amino acid sequence in which 1 to 3 amino acids have been substituted, deleted and/or added to the amino acid sequence shown in SEQ ID NO:39.
64. The fusion protein according to claim 51, comprising the amino acid sequence shown in SEQ ID NO:41.
65. The fusion protein according to claim 51, comprising an amino acid sequence having 80% or more identity to the amino acid sequence shown in SEQ ID NO:41.
66. The fusion protein according to the above item 51, comprising an amino acid sequence having 90% or more identity to the amino acid sequence shown in SEQ ID NO:41.
67. The fusion protein according to 66 above, which comprises an amino acid sequence in which 1 to 10 amino acids have been substituted, deleted and/or added to the amino acid sequence shown in SEQ ID NO:41.
68. The fusion protein according to 66 above, which comprises an amino acid sequence in which 1 to 5 amino acids have been substituted, deleted and/or added relative to the amino acid sequence shown in SEQ ID NO:41.
69. The fusion protein according to 66 above, which comprises an amino acid sequence in which 1 to 3 amino acids have been substituted, deleted and/or added relative to the amino acid sequence shown in SEQ ID NO:41.
70. The fusion protein according to claim 51, comprising the amino acid sequence shown in SEQ ID NO:41.
71. The fusion protein according to any one of 38 to 70 above, which has a specific activity of 10% or more compared with the specific activity of normal wild-type hGBA.
72. A DNA comprising a gene encoding the fusion protein according to any one of 1 to 71 above.
73. An expression vector comprising the DNA according to 72 above.
74. A mammalian cell transformed with the expression vector according to 73 above.
75. A method for producing a fusion protein, comprising the step of culturing the mammalian cell according to 74 above in a serum-free medium.
76. A conjugate of the fusion protein according to any one of 1 to 170 above with an antibody.
77. Conjugates of lysosomal enzymes, serum albumin and antibodies.
78. The conjugate according to claim 77, which is selected from the following (1) to (6):
(1) A conjugate in which serum albumin is bound to the C-terminus of the lysosomal enzyme directly or via a linker, and the antibody is further bound to the C-terminus of the serum albumin directly or via a linker;
(2) A conjugate in which an antibody is bound to the C-terminus of the lysosomal enzyme directly or via a linker, and the serum albumin is further bound to the C-terminus of the antibody directly or via a linker;
(3) A conjugate in which the lysosomal enzyme is bound to the C-terminus of the serum albumin directly or via a linker, and the antibody is further bound to the C-terminus of the lysosomal enzyme directly or via a linker;
(4) A conjugate in which the antibody is bound to the C-terminus of the serum albumin, either directly or via a linker, and the lysosomal enzyme is further bound to the C-terminus of the antibody, either directly or via a linker;
(5) A conjugate in which the lysosomal enzyme is bound to the C-terminus of the antibody, either directly or via a linker, and the serum albumin is further bound to the C-terminus of the lysosomal enzyme, either directly or via a linker;
(6) A conjugate in which the serum albumin is bound to the C-terminus of the antibody, either directly or via a linker, and the lysosomal enzyme is further bound to the C-terminus of the serum albumin, either directly or via a linker.
79. The conjugate according to any one of claims 76 to 78, wherein the antibody is an antibody against a receptor expressed on a vascular endothelial cell.
80. The conjugate according to claim 79, wherein the receptor on a vascular endothelial cell is selected from the group consisting of an insulin receptor, a transferrin receptor, a leptin receptor, a lipoprotein receptor, and an IGF receptor.
81. The conjugate according to claim 79, wherein the receptor on vascular endothelial cells is a transferrin receptor.
82. The conjugate according to any one of 76 to 81 above, wherein the antibody is any one of a Fab antibody, an F(ab') ₂ antibody, an F(ab')2 antibody, a single domain antibody, a single chain antibody, a VHH, or an Fc antibody.
83. The conjugate according to any one of 76 to 82 above, wherein the fusion protein is bound to either the C-terminus or the N-terminus of the light chain of the antibody.
84. The conjugate according to any one of 76 to 82 above, wherein the fusion protein is bound to either the C-terminus or the N-terminus of the heavy chain of the antibody.
85. The conjugate according to any one of 76 to 82 above, wherein the fusion protein is bound to either the C-terminal or N-terminal side of the light chain, or to either the C-terminal or N-terminal side of the heavy chain of the antibody, via a linker sequence.
86. The conjugate according to any one of claims 78 to 85, wherein the linker sequence consists of 1 to 50 amino acid residues.
87. The conjugate according to claim 86, wherein the linker sequence comprises an amino acid sequence selected from the group consisting of one glycine, one serine, the amino acid sequence Gly-Ser, the amino acid sequence Ser-Ser, the amino acid sequence Gly-Gly-Ser, the amino acid sequence of SEQ ID NO:9, the amino acid sequence of SEQ ID NO:10, the amino acid sequence of SEQ ID NO:11, and an amino acid sequence consisting of 1 to 10 consecutive amino acids of these amino acid sequences.
88. A DNA comprising a gene encoding the conjugate according to any one of 76 to 87 above.
89. An expression vector comprising the DNA according to 88 above.
90. A mammalian cell transformed with the expression vector according to 89 above.
91. A method for producing a conjugate of an antibody and a fusion protein of a physiologically active protein and SA, comprising the step of culturing the mammalian cell according to 90 above in a serum-free medium.

According to the present invention, for example, a human lysosomal enzyme that is relatively difficult to express as an active recombinant protein can be provided in the form of a fusion protein with HSA. Since such a fusion protein can be efficiently produced as a highly active recombinant protein, it can be stably supplied to medical institutions as a drug used for enzyme replacement therapy for patients with lysosomal diseases in which the lysosomal enzyme is deficient. In addition, according to the present invention, for example, a cytokine that is relatively difficult to express as an active recombinant protein can be provided in the form of a fusion protein with HSA. Since such a fusion protein can be efficiently produced as a recombinant protein, it can be stably supplied to medical institutions as a drug. In addition, according to the present invention, for example, a human neurotrophic factor that is relatively difficult to express as an active recombinant protein can be provided in the form of a fusion protein with HSA. Since such a fusion protein can be efficiently produced as a recombinant protein, it can be stably supplied to medical institutions as a drug. Note that the effects of the present invention are not limited to these.

The figure shows a schematic diagram of a single-chain polypeptide fusion protein having, in order from the N-terminus, HSA, a linker, and hGALC. The linker is a peptide linker, and the fusion protein is such that the C-terminus of HSA is bound to the N-terminus of the linker by a peptide bond, and the C-terminus of the linker is bound to the N-terminus of hGALC by a peptide bond. The figure shows a schematic diagram of a single-chain polypeptide fusion protein having HSA, a linker, and hGBA in that order from the N-terminus. The linker is a peptide linker, and the fusion protein is such that the C-terminus of HSA is bound to the N-terminus of the linker by a peptide bond, and the C-terminus of the linker is bound to the N-terminus of hGBA by a peptide bond. The figure shows a schematic diagram of a single-chain polypeptide fusion protein having, in order from the N-terminus, hGALC, a linker, and HSA. The linker is a peptide linker, and the fusion protein is such that the C-terminus of hGALC is bound to the N-terminus of the linker by a peptide bond, and the C-terminus of the linker is bound to the N-terminus of HSA by a peptide bond. The figure shows a schematic diagram of a single-chain polypeptide fusion protein having, in order from the N-terminus, hGBA, a linker, and HSA. The linker is a peptide linker, and the fusion protein is such that the C-terminus of hGBA is bound to the N-terminus of the linker by a peptide bond, and the C-terminus of the linker is bound to the N-terminus of HSA by a peptide bond. The figure shows a schematic diagram of a single-chain polypeptide fusion protein having, in order from the N-terminus, HSA, a linker, and hIL-10. The linker is a peptide linker, and the fusion protein is such that the C-terminus of HSA is bound to the N-terminus of the linker by a peptide bond, and the C-terminus of the linker is bound to the N-terminus of hIL-10 by a peptide bond. The figure shows a schematic diagram of a single-chain polypeptide fusion protein having, in order from the N-terminus, hIL-10, a linker, and HSA. The linker is a peptide linker, and the fusion protein is such that the C-terminus of hIL-10 is bound to the N-terminus of the linker by a peptide bond, and the C-terminus of the linker is bound to the N-terminus of HSA by a peptide bond. The figure shows a schematic diagram of a single-chain polypeptide fusion protein having, in order from the N-terminus, HSA, a linker, and hBDNF. The linker is a peptide linker, and the fusion protein is such that the C-terminus of HSA is bound to the N-terminus of the linker by a peptide bond, and the C-terminus of the linker is bound to the N-terminus of hBDNF by a peptide bond. The figure shows a schematic diagram of a single-chain polypeptide fusion protein having HSA, a linker, and hNGF in that order from the N-terminus. The linker is a peptide linker, and the fusion protein is such that the C-terminus of HSA is bound to the N-terminus of the linker by a peptide bond, and the C-terminus of the linker is bound to the N-terminus of hNGF by a peptide bond. The figure shows a schematic diagram of a single-chain polypeptide fusion protein having, in order from the N-terminus, HSA, a linker, and hNT-3. The linker is a peptide linker, and the fusion protein is such that the C-terminus of HSA is bound to the N-terminus of the linker by a peptide bond, and the C-terminus of the linker is bound to the N-terminus of hNT-3 by a peptide bond. The figure shows a schematic diagram of a single-chain polypeptide fusion protein having, in order from the N-terminus, HSA, a linker, and hNT-4. The linker is a peptide linker, and the fusion protein is such that the C-terminus of HSA is bound to the N-terminus of the linker by a peptide bond, and the C-terminus of the linker is bound to the N-terminus of hNT-4 by a peptide bond. The figure shows a schematic diagram of a single-chain polypeptide fusion protein having, in order from the N-terminus, hBDNF, a linker, and HSA. The linker is a peptide linker, and the fusion protein is such that the C-terminus of hBDNF and the N-terminus of the linker are bound by a peptide bond, and the C-terminus of the linker and the N-terminus of HSA are bound by a peptide bond. The figure shows a schematic diagram of a single-chain polypeptide fusion protein having, in order from the N-terminus, hNGF, a linker, and HSA. The linker is a peptide linker, and the fusion protein is such that the C-terminus of hNGF and the N-terminus of the linker are bound by a peptide bond, and the C-terminus of the linker and the N-terminus of HSA are bound by a peptide bond. The figure shows a schematic diagram of a single-chain polypeptide fusion protein having, in order from the N-terminus, hNT-3, a linker, and HSA. The linker is a peptide linker, and the fusion protein is such that the C-terminus of hNT-3 and the N-terminus of the linker are bound by a peptide bond, and the C-terminus of the linker and the N-terminus of HSA are bound by a peptide bond. The figure shows a schematic diagram of a single-chain polypeptide fusion protein having, in order from the N-terminus, hNT-4, a linker, and HSA. The linker is a peptide linker, and the fusion protein is such that the C-terminus of hNT-4 and the N-terminus of the linker are bound by a peptide bond, and the C-terminus of the linker and the N-terminus of HSA are bound by a peptide bond. Figure showing the results of an experiment to confirm the expression levels of wild-type hGALC, HSA-hGALC, and hGALC-HSA by transient expression. The vertical axis of the bar graph in the upper row (a) indicates the expression level of the enzyme contained in the culture supernatant in terms of enzyme activity (μM/hour). The black bars indicate the enzyme activity of wild-type hGALC, the white bars indicate the enzyme activity of HSA-hGALC, and the diagonal line bars indicate the enzyme activity of hGALC-HSA. The middle row (b) shows the results of an analysis of the culture supernatant by SDS-page, and the lower row (c) shows the results of an analysis of the culture supernatant by Western blotting, showing the positions of the bands corresponding to wild-type hGALC and the fusion protein of HSA and hGALC. From the left, the analysis results are shown 6, 7, and 8 days after the start of culture in transient expression. The figure shows the elution profiles of wild-type hGALC, HSA-hGALC, and hGALC-HSA obtained by transient expression in SE-HPLC analysis. The vertical dashed line indicates the position of the peak derived from the buffer, and the vertical straight line indicates the positions of the peaks corresponding to the HSA-hGALC and hGALC-HSA monomers. Schematic diagram showing the structure of the pCI MCS-modified vector (plasmid) Schematic diagram showing the structure of Dual(+)pCI-neo vector (plasmid) The figure shows the results of an experiment to confirm the expression levels of wild-type hGALC, Fab-HSA-hGALC, HSA-hGALC-Fab, Fab-hGALC-HSA, and hGALC-HSA-Fab by transient expression. The vertical axis shows the expression level of the enzyme contained in the culture supernatant in terms of enzyme activity (μM/hour). 1 shows the elution profiles of transiently expressed Fab-HSA-hGALC, HSA-hGALC-Fab, Fab-hGALC-HSA, and hGALC-HSA-Fab in SE-HPLC analysis. The vertical dashed line indicates the position of the peak derived from the buffer. Schematic diagram showing the structure of pEmIGS-hGBA vector (plasmid) Schematic diagram showing the structure of pCIneo-hGBA vector (plasmid) Schematic diagram showing the structure of pCIneo-HSA-hGBA vector (plasmid) The figure shows the results of an experiment (activity measurement) to confirm the expression levels of wild-type hGBA, HSA-hGBA, and hGBA-HSA by transient expression. The vertical axis shows the expression level of the enzyme contained in the culture supernatant in terms of enzyme activity (μM/hour). 1 shows the results of an experiment (SDS-PAGE) to confirm the expression levels of wild-type hGBA, HSA-hGBA, and hGBA-HSA by transient expression. The positions of the bands corresponding to wild-type hGBA and the fusion protein of HSA and hGBA are shown. The figure shows the results of an experiment (ELISA) to confirm the expression levels of wild-type mIL-10, mIL-10-MSA, and MSA-mIL-10 by transient expression. The vertical axis shows the expression level of each protein contained in the culture supernatant as a concentration (mol/L). 1 shows the results of an experiment (SDS-PAGE) to confirm the expression levels of wild-type mIL-10, mIL-10-MSA, and MSA-mIL-10 by transient expression, in which the positions of the bands corresponding to wild-type mIL-10 and the fusion protein of MSA and mIL-10 are shown. This figure shows the results of an experiment (ELISA) to confirm the expression levels of wild-type human neurotrophic factors and fusion proteins of HSA and human neurotrophic factors by transient expression. The vertical axis shows the expression level of each protein contained in the culture supernatant as concentration (mol/L). The black bars show the concentration of each wild-type human neurotrophic factor, the white bars show the concentration of each human neurotrophic factor-HSA fusion protein, and the shaded bars show the concentration of each HSA-human neurotrophic factor fusion protein. There are four types of human neurotrophic factors, and from the left in the figure, the results for hBDNF, hNGF, hNT-4, and hNT-4 are shown. Figure showing the results of an experiment (SDS-PAGE) to confirm the expression levels of wild-type human neurotrophic factor and the fusion protein of HSA and human neurotrophic factor by transient expression. Lane (a) corresponds to wild-type human neurotrophic factor, lane (b) to human neurotrophic factor-HSA fusion protein, and lane (c) to HSA-human neurotrophic factor fusion protein. The positions of the bands corresponding to wild-type human neurotrophic factor and the fusion protein of HSA and human neurotrophic factor are shown. There are four types of human neurotrophic factors, and from the left in the figure, the results for hBDNF, hNGF, hNT-4, and hNT-4 are shown. Figure showing the results of an experiment (Western blotting) to confirm the expression levels of wild-type human neurotrophic factor and the fusion protein of HSA and human neurotrophic factor by transient expression. Lane (a) corresponds to wild-type human neurotrophic factor, lane (b) to human neurotrophic factor-HSA fusion protein, and lane (c) to HSA-human neurotrophic factor fusion protein. The positions of the bands corresponding to wild-type human neurotrophic factor and the fusion protein of HSA and human neurotrophic factor are shown. There are four types of human neurotrophic factors, and from the left in the figure, the results for hBDNF, hNGF, hNT-4, and hNT-4 are shown.

In the present invention, there is no particular limit to the type of protein to be fused with serum albumin (SA), but the protein should be one that has a low expression level and/or low activity when the gene encoding the protein is introduced into a host cell and expressed as a recombinant protein. Examples of such proteins include lysosomal enzymes, cytokines, interleukins, and neurotrophic factors, or fusion proteins of these with antibodies. Interleukins belong to the cytokine category, and are a general term for cytokines distributed in particular from helper T cells.

Lysosomal enzymes include, in particular, galactosylceramidase (GALC) and glucocerebrosidase (GBA), or fusion proteins of these with antibodies or ligands. However, lysosomal enzymes are not limited to GALC and GBA. Other lysosomal enzymes that can increase the expression level and/or activity when expressed as recombinant proteins by binding with SA, particularly when expressed so that the recombinant proteins are secreted from cells and accumulated in the culture medium, are also included in the lysosomal enzymes to be bound with SA. The same applies to fusion proteins of these other lysosomal enzymes with antibodies or ligands. Furthermore, the present invention can be applied to lysosomal enzymes that are easy to produce as recombinant proteins. That is, the lysosomal enzyme is not particularly limited, and examples thereof include iduronate-2-sulfatase, α-L-iduronidase, β-galactosidase, GM2 activator protein, β-hexosaminidase A, β-hexosaminidase B, N-acetylglucosamine 1-phosphotransferase, α-mannosidase, β-mannosidase, saposin C, arylsulfatase A, α-L-fucosidase, aspartylglucosaminidase, α-N-acetylgalactosaminidase, acid sphingomyelinase, and the like. It may be enzyme, α-galactosidase A, β-glucuronidase, heparan N-sulfatase, α-N-acetylglucosaminidase, acetyl-CoA α-glucosaminide N-acetyltransferase, N-acetylglucosamine 6-sulfate sulfatase, acid ceramidase, amylo-1,6-glucosidase, sialidase, palmitoyl protein thioesterase-1, tripeptidyl peptidase-1, hyaluronidase-1, acid α-glucosidase, CLN1, or CLN2.

Cytokines include interleukins, such as IL-10, and fusion proteins of IL-10 with antibodies or ligands. However, the cytokines are not limited to IL-10. Other cytokines that can increase the expression level and/or activity when expressed as recombinant proteins by binding with SA, particularly when expressed so that the recombinant proteins are secreted from cells and accumulate in the culture medium, are also included in the cytokines to be bound with SA. The same applies to fusion proteins of these other cytokines with antibodies or ligands. However, the present invention can also be applied to cytokines that are easy to produce as recombinant proteins. In other words, fusion proteins also include fusion proteins of cytokines other than IL-10 with SA, and further fusion proteins of these with antibodies. Here, the cytokine is not particularly limited, but may be, for example, IL-1, IL-2, IL-3, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9, IL-11, IL-12, IL-13, IL-14, IL-15, IL-16, IL-17, IL-18, and IL-19 to IL-36.

The neurotrophic factors include, in particular, BDNF, NGF, NT-3, and NT-4, and fusion proteins of these with antibodies. However, the neurotrophic factors are not limited to these. Other neurotrophic factors that can increase the expression level and/or activity when expressed as a recombinant protein by binding with SA, particularly when expressed so that the recombinant protein is secreted from cells and accumulated in the culture medium, are also included in the neurotrophic factors to be bound with SA. The same applies to fusion proteins of these neurotrophic factors and antibodies. Furthermore, the present invention can be applied to neurotrophic factors that are easy to produce as recombinant proteins. In other words, the neurotrophic factors are not particularly limited, and may be, for example, glial cell line neurotrophic factor (GDNF) or NT-5.

There are no particular limitations on the biological species of the protein to be fused with SA, but it is preferably derived from humans, such as human lysosomal enzymes, human cytokines, and human growth and nutritional factors.

Fusion proteins of serum albumin (SA) and lysosomal enzymes can be used as therapeutic agents in enzyme replacement therapy for lysosomal diseases. For example, glucocerebrosidase (GBA) fused with SA can be used as a therapeutic agent for Gaucher disease, and galactosylceramidase (GALC) can be used as a therapeutic agent for Krabbe disease.

In this specification, when the term "human lysosomal enzyme" is used, it includes not only normal wild-type human lysosomal enzymes, but also mutants of human lysosomal enzymes in which one or more amino acid residues have been substituted, deleted, and/or added (in this specification, "addition" of an amino acid residue means adding a residue to the end or inside of the sequence) to the amino acid sequence of the wild-type human lysosomal enzyme, as long as the mutants have the function of a human lysosomal enzyme, such as having the enzymatic activity corresponding to the type of human lysosomal enzyme. The same applies to lysosomal enzymes of animal species other than humans.

Here, when a human lysosomal enzyme is said to have the function of a human lysosomal enzyme, it means that the human lysosomal enzyme has a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, when the specific activity of a normal wild-type human lysosomal enzyme is taken as 100%. Here, specific activity refers to the enzyme activity per mass of protein. The specific activity of a fusion protein of a human lysosomal enzyme and another protein is calculated as the enzyme activity per mass of the portion of the fusion protein that corresponds to the human lysosomal enzyme. The same can be said for lysosomal enzymes of animal species other than humans. Here, the specific activity of the human lysosomal enzyme in the fusion protein is calculated by multiplying the enzyme activity of the human lysosomal enzyme per unit mass of the fusion protein (μM/hour/mg protein) by (the molecular weight of the fusion protein/the molecular weight of the portion of the fusion protein that corresponds to the human lysosomal enzyme).

When amino acid residues in the amino acid sequence of a wild-type human lysosomal enzyme are replaced with other amino acid residues, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When amino acid residues in the amino acid sequence of a wild-type human lysosomal enzyme are deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. A mutant human lysosomal enzyme consisting of an amino acid sequence in which one amino acid residue is deleted from the N-terminus or C-terminus of a wild-type human lysosomal enzyme, a mutant human lysosomal enzyme consisting of an amino acid sequence in which two amino acid residues are deleted from the N-terminus or C-terminus of a wild-type human lysosomal enzyme, etc. are also human lysosomal enzymes. In addition, a mutation that combines the substitution and deletion of these amino acid residues can be added to the amino acid sequence of a wild-type human lysosomal enzyme. The same can be said for lysosomal enzymes of animal species other than humans.

When adding amino acid residues to the amino acid sequence of a wild-type human lysosomal enzyme, one or more amino acid residues are added into the amino acid sequence of the human lysosomal enzyme or to the N-terminus or C-terminus of the amino acid sequence. The number of amino acid residues added in this case is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. Mutations that combine the addition of these amino acid residues with the above-mentioned substitutions can also be added to the amino acid sequence of a wild-type human lysosomal enzyme, and mutations that combine the addition of these amino acid residues with the above-mentioned deletions can also be added to the amino acid sequence of a wild-type human lysosomal enzyme. The same can be said for lysosomal enzymes of animal species other than humans.

Furthermore, a combination of the above three types of mutations, substitution, deletion, and addition of amino acid residues, can be added to the amino acid sequence of a wild-type human lysosomal enzyme. For example, a human lysosomal enzyme is obtained by deleting 1 to 10 amino acid residues from the amino acid sequence of a wild-type human lysosomal enzyme, substituting 1 to 10 amino acid residues with other amino acid residues, and adding 1 to 10 amino acid residues; a human lysosomal enzyme is obtained by deleting 1 to 5 amino acid residues from the amino acid sequence of a wild-type human lysosomal enzyme, substituting 1 to 5 amino acid residues with other amino acid residues, and adding 1 to 5 amino acid residues; a human lysosomal enzyme is obtained by deleting 1 to 3 amino acid residues from the amino acid sequence of a wild-type human lysosomal enzyme, substituting 1 to 3 amino acid residues with other amino acid residues, and adding 1 to 5 amino acid residues; Human lysosomal enzymes are those in which an amino acid residue has been replaced with another amino acid residue, and 1 to 3 amino acid residues have been added. Human lysosomal enzymes are also those in which 1 or 2 amino acid residues have been deleted from the amino acid sequence of a wild-type human lysosomal enzyme, 1 or 2 amino acid residues have been replaced with another amino acid residue, and 1 or 2 amino acid residues have been added. Human lysosomal enzymes are also those in which 1 amino acid residue has been deleted from the amino acid sequence of a wild-type human lysosomal enzyme, 1 amino acid residue has been replaced with another amino acid residue, and 1 amino acid residue has been added. The same can be said about lysosomal enzymes of animal species other than humans.

The location and type (deletion, substitution, and addition) of each mutation in a human lysosomal enzyme mutant compared to a normal wild-type human lysosomal enzyme can be easily confirmed by aligning the amino acid sequences of both human lysosomal enzymes. The same can be said for lysosomal enzymes of animal species other than humans.

The amino acid sequence of the human lysosomal enzyme mutant preferably exhibits 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more or 99% or more identity, to the amino acid sequence of a normal wild-type human lysosomal enzyme. The same can be said for lysosomal enzyme mutants of animal species other than humans.

The identity between the amino acid sequence of a wild-type human lysosomal enzyme and the amino acid sequence of a mutant human lysosomal enzyme can be easily calculated using well-known homology calculation algorithms. Examples of such algorithms include BLAST (Altschul S F. J Mol. Biol. 215. 403-10, (1990)), the similarity search method of Pearson and Lipman (Proc. Natl. Acad. Sci. USA. 85. 2444 (1988)), and the local homology algorithm of Smith and Waterman (Adv. Appl. Math. 2. 482-9 (1981)). The same can be said for the lysosomal enzymes of non-human animal species, GALC, GBA, MSA, and non-human animal species SA. These algorithms can also be applied throughout this specification as homology calculation algorithms between the wild-type amino acid sequence of another protein and the amino acid sequence of a mutant of that other protein.

In this specification, when simply referring to "human galactosylceramidase", "human galactocerebrosidase", or "hGALC", it includes, without distinction, not only the normal wild-type hGALC consisting of 643 amino acid residues as shown in SEQ ID NO: 1, but also mutants of hGALC in which one or more amino acid residues have been substituted, deleted, and/or added (as used herein, "addition" of an amino acid residue means adding a residue to the end or inside of the sequence) to the amino acid sequence as shown in SEQ ID NO: 1, as long as they have the function of hGALC, such as the enzyme activity capable of decomposing sphingolipids such as galactocerebroside and/or galactosylsphingosine. Wild-type hGALC is, for example, encoded by a gene having the base sequence as shown in SEQ ID NO: 2.

In this specification, when simply referring to "mouse galactosylceramidase", "mouse galactocerebrosidase", or "mGALC", it includes, without distinction, not only the normal wild-type mGALC having the amino acid sequence shown in SEQ ID NO: 14, but also mGALC mutants in which one or more amino acid residues have been substituted, deleted, and/or added (as used herein, "addition" of an amino acid residue means adding a residue to the end or inside of the sequence) to the amino acid sequence shown in SEQ ID NO: 14, as long as they have the function of mGALC, such as having the enzymatic activity to degrade sphingolipids such as galactocerebroside and/or galactosylsphingosine. Wild-type mGALC is, for example, encoded by a gene having the base sequence shown in SEQ ID NO: 15.

When hGALC is said to have the function of hGALC, it means that hGALC preferably retains a specific activity of 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, of the specific activity of normal wild-type hGALC taken as 100%. Here, specific activity refers to the enzyme activity per mass of protein. The specific activity of a fusion protein of hGALC and another protein is calculated as the enzyme activity per mass of the portion of the fusion protein that corresponds to hGALC. The same can be said for mGALC. Here, the specific activity of hGALC in a fusion protein is calculated by multiplying the enzyme activity of hGALC per unit mass of the fusion protein (μM/hour/mg protein) by (molecular weight of the fusion protein/molecular weight of the portion of the fusion protein that corresponds to hGALC).

When amino acid residues in the amino acid sequence of wild-type hGALC are replaced with other amino acid residues, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When amino acid residues in the amino acid sequence of wild-type hGALC are deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. hGALC mutants consisting of 642 amino acid residues with one amino acid residue deleted from the N-terminus or C-terminus of wild-type hGALC, and hGALC mutants consisting of 641 amino acid residues with two amino acid residues deleted from the N-terminus or C-terminus of wild-type hGALC are also hGALC. Mutations that combine the substitution and deletion of these amino acid residues can also be added to the amino acid sequence of wild-type hGALC. The same can be said for GALC of animal species other than humans.

When amino acid residues are added to the amino acid sequence of wild-type hGALC, one or more amino acid residues are added into the amino acid sequence of hGALC or to the N-terminus or C-terminus of the amino acid sequence. The number of amino acid residues added in this case is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. Mutations that combine the addition of these amino acid residues with the above-mentioned substitutions can also be added to the amino acid sequence of wild-type hGALC, and mutations that combine the addition of these amino acid residues with the above-mentioned deletions can also be added to the amino acid sequence of wild-type hGALC. The same can be said for GALC of animal species other than humans.

Furthermore, a combination of the above three types of mutations, substitution, deletion, and addition of amino acid residues, can be added to the amino acid sequence of wild-type hGALC. For example, the amino acid sequence of wild-type hGALC shown in SEQ ID NO:1 can be obtained by deleting 1 to 10 amino acid residues, substituting 1 to 10 amino acid residues with other amino acid residues, and adding 1 to 10 amino acid residues. The amino acid sequence of wild-type hGALC shown in SEQ ID NO:1 can be obtained by deleting 1 to 5 amino acid residues, substituting 1 to 5 amino acid residues with other amino acid residues, and adding 1 to 5 amino acid residues. The amino acid sequence of wild-type hGALC shown in SEQ ID NO:1 can be obtained by deleting 1 to 3 amino acid residues, hGALC also includes those in which one to three amino acid residues have been replaced with other amino acid residues and one to three amino acid residues have been added, and those in which one or two amino acid residues have been deleted from the wild-type hGALC amino acid sequence shown in SEQ ID NO:1, one or two amino acid residues have been replaced with other amino acid residues, and one or two amino acid residues have been added, and those in which one amino acid residue has been deleted from the wild-type hGALC amino acid sequence shown in SEQ ID NO:1, one amino acid residue has been replaced with other amino acid residue, and one amino acid residue has been added. The same can be said for GALCs of animal species other than humans.

The location and type (deletion, substitution, and addition) of each mutation in the hGALC mutant compared to the normal wild-type hGALC can be easily confirmed by aligning the amino acid sequences of both hGALCs. The same can be said for GALCs of animal species other than humans.

The amino acid sequence of the hGALC mutant preferably has 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more, or 99% or more identity, to the amino acid sequence of the normal wild-type hGALC shown in SEQ ID NO: 1. The same can be said for GALC of animal species other than humans.

In this specification, when simply referring to "human glucocerebrosidase," "human β-glucosidase," or "hGBA," it includes, without distinction, not only the normal wild-type hGBA consisting of 497 amino acid residues as shown in SEQ ID NO: 37, but also mutants of hGBA in which one or more amino acid residues have been substituted, deleted, and/or added (as used herein, "addition" of an amino acid residue means adding a residue to the end or inside of the sequence) to the amino acid sequence as shown in SEQ ID NO: 37, as long as they have the function of hGBA, such as having the enzymatic activity to degrade glycolipids such as galactocerebroside and/or galactosylsphingosine. Wild-type hGBA is, for example, encoded by a gene having the base sequence as shown in SEQ ID NO: 38.

In this specification, when simply referring to "mouse glucocerebrosidase", "mouse β-glucosidase", or "mGBA", it includes, without distinction, not only the normal wild-type mGBA having the amino acid sequence shown in SEQ ID NO: 43, but also mGBA mutants in which one or more amino acid residues have been substituted, deleted, and/or added (in this specification, "addition" of an amino acid residue means adding a residue to the end or inside of the sequence) to the amino acid sequence shown in SEQ ID NO: 43, as long as they have the function of mGBA, such as having the enzymatic activity to degrade glycolipids such as galactocerebroside and/or galactosylsphingosine. Wild-type mGBA is, for example, encoded by a gene having the base sequence shown in SEQ ID NO: 44.

When hGBA is said to have the function of hGBA, it means that hGBA has a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, when the specific activity of normal wild-type hGBA is taken as 100%. Here, specific activity refers to the enzyme activity per mass of protein. The specific activity of a fusion protein of hGBA and another protein is calculated as the enzyme activity per mass of the portion of the fusion protein that corresponds to hGBA. The specific activity of hGBA in the fusion protein is calculated by multiplying the enzyme activity of hGBA per unit mass of the fusion protein (μM/hour/mg protein) by (molecular weight of the fusion protein/molecular weight of the portion of the fusion protein that corresponds to hGBA). The same can be said for GBA of animal species other than humans.

When amino acid residues in the amino acid sequence of wild-type hGBA are replaced with other amino acid residues, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When amino acid residues in the amino acid sequence of wild-type hGBA are deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. hGBA mutants consisting of 496 amino acid residues with one amino acid residue deleted from the N-terminus or C-terminus of wild-type hGBA, and hGBA mutants consisting of 495 amino acid residues with two amino acid residues deleted from the N-terminus or C-terminus of wild-type hGBA are also hGBA. Mutations that combine the substitution and deletion of these amino acid residues can also be added to the amino acid sequence of wild-type hGBA. The same can be said for GBAs of animal species other than humans.

When amino acid residues are added to the amino acid sequence of wild-type hGBA, one or more amino acid residues are added into the amino acid sequence of hGBA or to the N-terminus or C-terminus of the amino acid sequence. The number of amino acid residues added in this case is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. Mutations that combine the addition of these amino acid residues with the above-mentioned substitutions can also be added to the amino acid sequence of wild-type hGBA, and mutations that combine the addition of these amino acid residues with the above-mentioned deletions can also be added to the amino acid sequence of wild-type hGBA. The same can be said for GBAs of animal species other than humans.

Furthermore, a combination of the above three types of mutations, substitution, deletion, and addition of amino acid residues, can be added to the amino acid sequence of wild-type hGBA. For example, an hGBA is obtained by deleting 1 to 10 amino acid residues from the amino acid sequence of wild-type hGBA shown in SEQ ID NO:37, substituting 1 to 10 amino acid residues with other amino acid residues, and adding 1 to 10 amino acid residues. An hGBA is also obtained by deleting 1 to 5 amino acid residues from the amino acid sequence of wild-type hGBA shown in SEQ ID NO:37, substituting 1 to 5 amino acid residues with other amino acid residues, and adding 1 to 5 amino acid residues. An hGBA is also obtained by deleting 1 to 3 amino acid residues from the amino acid sequence of wild-type hGBA shown in SEQ ID NO:37, hGBA also includes the amino acid sequence of wild-type hGBA shown in SEQ ID NO: 37 in which one or two amino acid residues have been deleted, one or two amino acid residues have been replaced with other amino acid residues, and one or two amino acid residues have been added. hGBA also includes the amino acid sequence of wild-type hGBA shown in SEQ ID NO: 37 in which one amino acid residue has been deleted, one amino acid residue has been replaced with other amino acid residue, and one amino acid residue has been added. The same can be said for GBAs of animal species other than humans.

The location and type (deletion, substitution, and addition) of each mutation in the hGBA mutant compared to the normal wild-type hGBA can be easily confirmed by aligning the amino acid sequences of both hGBAs. The same can be said for GBAs of animal species other than humans.

The amino acid sequence of the hGBA mutant preferably has 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more, or 99% or more identity, to the amino acid sequence of normal wild-type hGBA shown in SEQ ID NO: 37. The same is true for GBA of animal species other than humans.

In the present invention, there is no particular limitation on the biological species of serum albumin (SA), but human serum albumin (HSA) is preferred.

In the present invention, the term "human serum albumin" or "HSA" includes, without distinction, wild-type human serum albumin consisting of 585 amino acids having the amino acid sequence shown in SEQ ID NO: 3, as well as mutants of HSA in which one or more amino acid residues have been substituted, deleted, and/or added to the amino acid sequence shown in SEQ ID NO: 3 (as used herein, "addition" of an amino acid residue means adding a residue to the end or inside of the sequence). Wild-type HSA is, for example, encoded by a gene having the base sequence shown in SEQ ID NO: 4.

When human serum albumin is expressed as a recombinant protein using host cells such as CHO as a fusion protein bound to a wild-type human lysosomal enzyme, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the expression amount of at least one type of wild-type human lysosomal enzyme as a human lysosomal enzyme can be increased compared to when the wild-type human lysosomal enzyme is expressed as a recombinant protein by a similar method. In particular, when human serum albumin is expressed as a recombinant protein using host cells such as CHO as a fusion protein bound to wild-type hGALC or wild-type hGBA, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the expression amount of the enzyme can be increased compared to when these wild-type enzymes are expressed as recombinant proteins by a similar method. Note that the human serum albumin here is preferably one that has the functions of human serum albumin, such as the function of binding and transporting endogenous substances in the blood and exogenous substances such as drugs, but is not limited thereto.

In the present invention, the term "mouse serum albumin" or "MSA" includes, without distinction, wild-type mouse serum albumin having the amino acid sequence shown in SEQ ID NO: 16, as well as mutants of MSA in which one or more amino acid residues have been substituted, deleted, and/or added (as used herein, "addition" of an amino acid residue means adding a residue to the end or inside of the sequence) to the amino acid sequence shown in SEQ ID NO: 16. Wild-type MSA is encoded, for example, by a gene having the base sequence shown in SEQ ID NO: 17. In addition, MSA is preferably one that has the functions of MSA, such as the function of binding and transporting endogenous substances in blood and exogenous substances such as drugs, but is not limited to this.

In the present invention, "serum albumin" or "SA" refers to a comprehensive concept including serum albumin of mammals other than humans, including mouse serum albumin (MSA) and bovine serum albumin (BSA). When serum albumin is expressed as a recombinant protein using host cells such as CHO as a fusion protein bound to a wild-type human lysosomal enzyme, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, it is possible to increase the expression amount of at least one type of wild-type human lysosomal enzyme as a human lysosomal enzyme, compared to when the wild-type human lysosomal enzyme is expressed as a recombinant protein by the same method. In particular, when serum albumin is expressed as a recombinant protein using host cells such as CHO as a fusion protein bound to wild-type hGALC or wild-type hGBA, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, it is possible to increase the expression amount of the enzyme, compared to when these wild-type enzymes are expressed as recombinant proteins by the same method.

Human serum albumin (HSA) is known to have several wild-type variants. Human serum albumin Redhill is one of them. Human serum albumin Redhill differs from the above-mentioned normal human serum albumin amino acid sequence, which consists of 585 amino acids, in that the 320th amino acid residue from the N-terminus is threonine instead of alanine, and an arginine residue is added to the N-terminus, and consists of 586 amino acids as shown in SEQ ID NO: 12. The above-mentioned change of alanine to threonine creates a sequence represented by Asn-Tyr-Thr in the amino acid sequence of human serum albumin Redhill, and the Asn (asparagine) residue in this sequence is N-linked glycosylated. This human serum albumin Redhill is also a wild-type HSA.

A preferred example of an HSA mutant is human serum albumin (HSA-A320T) consisting of 585 amino acids as shown in SEQ ID NO:13, in which the 320th amino acid residue from the N-terminus of the wild-type HSA amino acid sequence as shown in SEQ ID NO:3 is replaced with threonine. Another preferred example of an HSA mutant is one in which the 319th amino acid residue, tyrosine, is replaced with an amino acid other than proline while preserving the 318th amino acid residue from the N-terminus of the HSA mutant as shown in SEQ ID NO:13. The following describes in detail the mutations that can be made to the wild-type HSA amino acid sequence that are permissible in one embodiment of the present invention, but the mutations can also be applied to human serum albumin Redhill, the HSA mutant as shown in SEQ ID NO:13, or serum albumin of animal species other than humans.

　When amino acid residues in the amino acid sequence of wild-type HSA or HSA-A320T are replaced with other amino acid residues, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When amino acid residues in the amino acid sequence of wild-type or HSA-A320T HSA are deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. HSA mutants in which one amino acid residue is deleted at the N-terminus or C-terminus of wild-type or HSA-A320T HSA, and HSA mutants in which two amino acid residues are deleted at the N-terminus or C-terminus of wild-type or HSA-A320T HSA are also HSA. Mutations that combine the substitution and deletion of these amino acid residues can also be added to the amino acid sequence of wild-type or HSA-A320T HSA. The same can be said about SA in non-human animal species.

When amino acid residues are added to the amino acid sequence of wild-type HSA or HSA-A320T, one or more amino acid residues are added to the amino acid sequence of HSA or to the N-terminus or C-terminus of the amino acid sequence. The number of amino acid residues added in this case is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. HSA mutants in which one amino acid residue is added to the N-terminus or C-terminus of wild-type or HSA-A320T HSA, and HSA mutants in which two amino acid residues are added to the N-terminus or C-terminus of wild-type or HSA-A320T HSA, etc. are also HSA. In addition, mutations that combine the addition of these amino acid residues and the above-mentioned substitutions can also be added to the amino acid sequence of wild-type or HSA-A320T HSA, and mutations that combine the addition of these amino acid residues and the above-mentioned deletions can also be added to the amino acid sequence of wild-type or HSA-A320T HSA. The same can be said for SA of animal species other than humans.

Furthermore, a combination of the above three types of mutations, substitution, deletion, and addition of amino acid residues, can be added to the amino acid sequence of wild-type or HSA-A320T HSA. For example, HSA can be obtained by deleting 1 to 10 amino acid residues from the amino acid sequence of wild-type HSA shown in SEQ ID NO:3, substituting 1 to 10 amino acid residues with other amino acid residues, and adding 1 to 10 amino acid residues, and HSA can be obtained by deleting 1 to 5 amino acid residues from the amino acid sequence of wild-type HSA shown in SEQ ID NO:3, substituting 1 to 5 amino acid residues with other amino acid residues, and adding 1 to 5 amino acid residues, and HSA can be obtained by deleting 1 to 3 amino acid residues from the amino acid sequence of wild-type HSA shown in SEQ ID NO:3, HSA is also one in which 1 to 3 amino acid residues have been replaced with other amino acid residues and 1 to 3 amino acid residues have been added, HSA is also one in which 1 or 2 amino acid residues have been deleted from the amino acid sequence of wild-type HSA shown in SEQ ID NO: 3, 1 or 2 amino acid residues have been replaced with other amino acid residues, and 1 or 2 amino acid residues have been added, and HSA is also one in which 1 amino acid residue has been deleted from the amino acid sequence of wild-type HSA shown in SEQ ID NO: 3, 1 amino acid residue has been replaced with other amino acid residue, and 1 amino acid residue has been added. The same can be said about SA of animal species other than humans.

The location and type (deletion, substitution, and addition) of each mutation in an HSA mutant compared to normal wild-type HSA can be easily confirmed by aligning the amino acid sequences of both HSAs. The same can be said for SA of animal species other than humans.

The amino acid sequence of the HSA mutant preferably has 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more, or 99% or more identity, to the amino acid sequence of normal wild-type HSA shown in SEQ ID NO: 3. The same is true for SA of animal species other than humans.

In one embodiment of the present invention, when HSA is combined with a wild-type human lysosomal enzyme to form a fusion protein and expressed as a recombinant protein using host cells such as CHO, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the expression amount of at least one type of wild-type human lysosomal enzyme as a human lysosomal enzyme in the culture supernatant can be at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or enzyme activity, for example, 1.1 to 4 times, 1.5 to 3.6 times, 2 to 3.6 times, etc., compared to when the wild-type human lysosomal enzyme is expressed as a recombinant protein by a similar method.

In one embodiment of the present invention, when HSA is combined with wild-type hGALC to form a fusion protein and expressed as a recombinant protein using host cells such as CHO, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the amount of hGALC expressed in the culture supernatant can be at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or enzyme activity, compared to when wild-type hGALC is expressed as a recombinant protein by a similar method.

In one embodiment of the present invention, when HSA is combined with wild-type hGBA to form a fusion protein and expressed as a recombinant protein using host cells such as CHO, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the amount of hGBA expressed in the culture supernatant can be at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or enzyme activity, for example, 1.1 to 4 times, 1.5 to 3.6 times, 2 to 3.6 times, 10 to 20 times, etc., compared to when wild-type hGBA is expressed as a recombinant protein by a similar method.

In the present invention, the term "conservative amino acid substitution" refers to a substitution of an amino acid within a family of amino acids that are related in their side chains and chemical properties. Substitutions within such an amino acid family are not expected to significantly alter the function of the original protein. Examples of such amino acid families include the following (1) to (12):
(1) The acidic amino acids aspartic acid and glutamic acid,
(2) the basic amino acids histidine, lysine, and arginine;
(3) the aromatic amino acids phenylalanine, tyrosine, and tryptophan;
(4) Serine and threonine, which are amino acids having a hydroxyl group (hydroxyamino acids),
(5) the hydrophobic amino acids methionine, alanine, valine, leucine, and isoleucine,
(6) The neutral hydrophilic amino acids cysteine, serine, threonine, asparagine, and glutamine,
(7) Glycine and proline, which are amino acids that affect the orientation of peptide chains.
(8) Asparagine and glutamine, which are amide amino acids (polar amino acids),
(9) The aliphatic amino acids alanine, leucine, isoleucine, and valine,
(10) Amino acids with small side chains: alanine, glycine, serine, and threonine;
(11) Alanine and glycine, which are amino acids with particularly small side chains.
(12) The branched chain amino acids valine, leucine, and isoleucine,
(13) Proline and serine, which are amino acids whose side chains can be hydroxylated.
The same can be said for the lysosomal enzymes GALC, GBA, and SA of non-human animal species.

The substitution of an amino acid in the amino acid sequence of wild-type human lysosomal enzymes and HSA with another amino acid is preferably a conservative amino acid substitution. The same applies to lysosomal enzymes and SA of animal species other than humans. In particular, the above conservative amino acid substitutions apply to the wild-type forms of hGALC and hGBA.

　The above wild-type or mutant human lysosomal enzymes, such as hGALC or hGBA, whose constituent amino acids are modified with sugar chains are also human lysosomal enzymes. The above wild-type or mutant human lysosomal enzymes whose constituent amino acids are modified with phosphate are also human lysosomal enzymes. Those modified with something other than sugar chains and phosphate are also human lysosomal enzymes. The above wild-type or mutant human lysosomal enzymes whose constituent amino acid side chains have been converted by substitution reactions or the like are also human lysosomal enzymes. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for the lysosomal enzymes, GALC, and GBA of animal species other than humans.

In other words, human lysosomal enzymes modified with sugar chains, such as hGALC or hGBA, are included in human lysosomal enzymes with the original amino acid sequence. Human lysosomal enzymes modified with phosphate are included in human lysosomal enzymes with the original amino acid sequence. Those modified with things other than sugar chains and phosphate are also included in human lysosomal enzymes with the original amino acid sequence. Human lysosomal enzymes in which the side chains of the amino acids constituting the human lysosomal enzymes have been converted by substitution reactions or the like are also included in human lysosomal enzymes with the original amino acid sequence. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for lysosomal enzymes of animal species other than humans, GALC, and GBA.

　The above wild-type or mutant HSA in which the constituent amino acids are modified with sugar chains is also HSA. The above wild-type or mutant HSA in which the constituent amino acids are modified with phosphate is also HSA. HSA modified with something other than sugar chains and phosphate is also HSA. The above wild-type or mutant HSA in which the side chains of the constituent amino acids have been converted by substitution reactions or the like is also HSA. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for SA of animal species other than humans.

In other words, HSA modified with sugar chains is included in HSA with the original amino acid sequence. HSA modified with phosphate is included in HSA with the original amino acid sequence. HSA modified with things other than sugar chains and phosphate is also included in HSA with the original amino acid sequence. HSA with the original amino acid sequence also includes HSA with the original amino acid sequence when the side chains of the amino acids that make up HSA have been changed by substitution reactions, etc. Such changes include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for SA of animal species other than humans.

In one embodiment, the present invention relates to a fusion protein in which a polypeptide containing the amino acid sequence of a wild-type or mutant human lysosomal enzyme is bound to a polypeptide containing the amino acid sequence of a wild-type or mutant SA. Here, the term "binding polypeptides" refers to binding different polypeptides by covalent bond, either directly or indirectly via a linker. Here, the SA is preferably HSA. The human lysosomal enzyme is, for example, hGALC or hGBA.

A common method for linking two different polypeptides is, for example, to create an expression vector incorporating a DNA fragment in which a gene encoding one polypeptide is linked in-frame downstream of a gene encoding the other polypeptide, and then to express the polypeptide as a recombinant protein by culturing a host cell transformed with this expression vector. The resulting recombinant protein is a single-chain polypeptide in which the two polypeptides are peptide-linked, either directly or via different amino acid sequences.

In one embodiment of the present invention, the term "SA-human lysosomal enzyme fusion protein" or "SA-human lysosomal enzyme" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of a human lysosomal enzyme is linked to the C-terminus of the amino acid sequence of SA, either directly or via a linker, and which has the function of a human lysosomal enzyme. Here, there is no particular limitation on the animal species of the SA, but it is preferably a mammalian SA such as a primate, mouse, or cow, more preferably a primate SA, and even more preferably HSA. When it is said that the human lysosomal enzyme in the SA-human lysosomal enzyme fusion protein has the function of a human lysosomal enzyme, it means that the human lysosomal enzyme preferably retains a specific activity of 10% or more, more preferably a specific activity of 20% or more, even more preferably a specific activity of 50% or more, and even more preferably a specific activity of 80% or more, when the specific activity of a normal wild-type human lysosomal enzyme is taken as 100%. Here, the specific activity of the human lysosomal enzyme in the SA-human lysosomal enzyme fusion protein is calculated by multiplying the enzymatic activity of the human lysosomal enzyme per unit mass of the fusion protein (μM/hour/mg protein) by (molecular weight of the fusion protein/molecular weight of the portion of the fusion protein that corresponds to the human lysosomal enzyme).

In one embodiment of the present invention, the term "HSA-human lysosomal enzyme fusion protein" or "HSA-human lysosomal enzyme" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of a human lysosomal enzyme is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of HSA, and which has the function of a human lysosomal enzyme. When it is said here that the HSA-human lysosomal enzyme fusion protein has the function of a human lysosomal enzyme, the definition of the SA-human lysosomal enzyme fusion protein described above can be applied.

In the SA-human lysosomal enzyme fusion protein, it is preferable that the SA has a function as an SA, such as the function of binding and transporting endogenous substances in the blood and exogenous substances such as drugs, but is not limited to this. The same applies to the HSA-human lysosomal enzyme fusion protein.

In one embodiment of the present invention, a fusion protein having an amino acid sequence in which the N-terminus of a lysosomal enzyme of a non-human animal species is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of SA of a non-human animal species, and which has the function of a human lysosomal enzyme, is referred to as a "(non-human animal species) SA-(non-human animal species) lysosomal enzyme fusion protein." For example, a fusion protein of mouse SA and mouse lysosomal enzyme is referred to as an "MSA-mouse lysosomal enzyme fusion protein" or "MSA-mouse lysosomal enzyme." When these fusion proteins are said to have the function of a lysosomal enzyme, the definition of SA-human lysosomal enzyme fusion protein described above can be applied.

When mutations are added to an HSA-human lysosomal enzyme fusion protein, which is a fusion protein of wild-type HSA and wild-type human lysosomal enzyme, mutations can be added only to the HSA portion and not to the human lysosomal enzyme portion, mutations can be added only to the human lysosomal enzyme portion without mutations to the HSA portion, or mutations can be added to both the HSA portion and the human lysosomal enzyme portion. When mutations are added only to the HSA portion, the amino acid sequence of the portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above. When mutations are added only to the human lysosomal enzyme portion, the amino acid sequence of the portion is the amino acid sequence of human lysosomal enzyme obtained by adding a mutation to the wild-type human lysosomal enzyme described above. When mutations are added to both the HSA portion and the human lysosomal enzyme portion, the amino acid sequence of the HSA portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above, and the amino acid sequence of the human lysosomal enzyme portion is the amino acid sequence of human lysosomal enzyme obtained by adding a mutation to the wild-type human lysosomal enzyme described above. The same can be said about fusion proteins between wild-type SA (including wild-type MSA) of non-human animal species and wild-type human lysosomal enzymes.

　HSA-human lysosomal enzyme fusion proteins in which the amino acids constituting the protein are modified with sugar chains are also HSA-human lysosomal enzyme fusion proteins. HSA-human lysosomal enzyme fusion proteins in which the amino acids constituting the protein are modified with phosphate are also HSA-human lysosomal enzyme fusion proteins. HSA-human lysosomal enzyme fusion proteins modified with anything other than sugar chains and phosphate are also HSA-human lysosomal enzyme fusion proteins. HSA-human lysosomal enzyme fusion proteins in which the side chains of the amino acids constituting the protein are converted by substitution reactions or the like are also HSA-human lysosomal enzyme fusion proteins. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said about fusion proteins of SA of a non-human animal species and a human lysosomal enzyme (SA-human lysosomal enzyme), and fusion proteins of SA of a non-human animal species and a lysosomal enzyme of a non-human animal species, such as MSA-mouse lysosomal enzyme fusion proteins.

In other words, HSA-human lysosomal enzyme fusion proteins modified with sugar chains are included in HSA-human lysosomal enzyme fusion proteins having the original amino acid sequence. Also, HSA-human lysosomal enzyme fusion proteins modified with phosphate are included in HSA-human lysosomal enzyme fusion proteins having the original amino acid sequence. Also, those modified with something other than sugar chains and phosphate are included in HSA-human lysosomal enzyme fusion proteins having the original amino acid sequence. Also, those in which the side chains of the amino acids constituting the HSA-human lysosomal enzyme fusion proteins have been converted by substitution reactions or the like are included in HSA-human lysosomal enzyme fusion proteins having the original amino acid sequence. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said about fusion proteins of SA of animal species other than human and human lysosomal enzyme (SA-human lysosomal enzyme), and fusion proteins of SA of animal species other than human and lysosomal enzyme of animal species other than human, such as MSA-mouse lysosomal enzyme fusion protein.

　Also, HSA-human lysosomal enzyme fusion proteins, in which the human lysosomal enzyme that constitutes it is a precursor of human lysosomal enzyme, are also HSA-human lysosomal enzyme fusion proteins. Here, the term "precursor" refers to a type that is biosynthesized as an HSA-human lysosomal enzyme fusion protein, and after the biosynthesis, the part that functions as a human lysosomal enzyme is separated from the fusion protein during the manufacturing process or in the living body when administered to the living body, and can function as a human lysosomal enzyme by itself. In this case, after the HSA-human lysosomal enzyme fusion protein is biosynthesized, it may be cleaved at a specific site by a hydrolase or the like, and the part containing HSA and the part containing the mature human lysosomal enzyme may be separated. In this case, the obtained human lysosomal enzyme is not a fusion protein with HSA, but the HSA-human lysosomal enzyme fusion protein is synthesized once during the process of manufacturing the human lysosomal enzyme. Therefore, when human lysosomal enzyme is manufactured by such a method, the manufacturing method is included in the manufacturing method of HSA-human lysosomal enzyme fusion protein. The same can be said for fusion proteins of SA of non-human animal species and human lysosomal enzyme (SA-human lysosomal enzyme), and fusion proteins of SA of non-human animal species and lysosomal enzyme of non-human animal species, such as MSA-mouse lysosomal enzyme fusion protein.

In one embodiment of the present invention, the term "SA-hGALC fusion protein" or "SA-hGALC" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of hGALC is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of SA, and which has the function of hGALC. Here, there is no particular limitation on the animal species of the SA, but it is preferably a mammalian SA, more preferably a primate SA, and even more preferably HSA. When it is said that hGALC in the SA-hGALC fusion protein has the function of hGALC, it means that hGALC preferably retains a specific activity of 10% or more, more preferably a specific activity of 20% or more, even more preferably a specific activity of 50% or more, and even more preferably a specific activity of 80% or more, when the specific activity of normal wild-type hGALC is taken as 100%. Here, the specific activity of hGALC in the SA-hGALC fusion protein is calculated by multiplying the enzyme activity of hGALC per unit mass of the fusion protein (μM/hour/mg protein) by (molecular weight of the fusion protein/molecular weight of the portion of the fusion protein corresponding to hGALC).

In one embodiment of the present invention, the term "HSA-hGALC fusion protein" or "HSA-hGALC" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of hGALC is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of HSA, and which has the function of hGALC. When it is said here that the HSA-hGALC fusion protein has the function of hGALC, the definition of the SA-hGALC fusion protein above can be applied.

In one embodiment of the present invention, a fusion protein having an amino acid sequence in which the N-terminus of GALC of a non-human animal species is linked, directly or via a linker, to the C-terminus of the amino acid sequence of SA of a non-human animal species, and which has the function of GALC, is designated as a "(non-human animal species) SA-(non-human animal species) GALC fusion protein." For example, a fusion protein of mouse SA and mouse GALC is designated as an "MSA-mouse GALC fusion protein" or "MSA-mouse GALC." When these fusion proteins are said to have the function of GALC, the definition of the SA-hGALC fusion protein described above can be applied. In addition, in these fusion proteins, it is preferable that the SA has the function of SA, such as the function of binding and transporting endogenous substances in the blood and exogenous substances such as drugs, but this is not limited thereto.

In one embodiment of the present invention, a preferred HSA-hGALC fusion protein has, for example, the amino acid sequence shown in SEQ ID NO: 5. The HSA-hGALC fusion protein shown in SEQ ID NO: 5 is obtained by linking wild-type hGALC to the C-terminus of wild-type HSA via the linker sequence Gly-Ser. The HSA-hGALC fusion protein shown in SEQ ID NO: 5 is encoded by a gene having, for example, the base sequence shown in SEQ ID NO: 6. In addition, HSA-hGALC fusion proteins include those having an amino acid sequence in which one or more amino acid residues in the amino acid sequence shown in SEQ ID NO: 5 have been replaced with other amino acid residues, deleted, or mutated by addition, so long as they have the function of hGALC. It is preferable that the HSA-hGALC fusion protein has the function of human serum albumin, such as the function of binding and transporting endogenous substances in blood and exogenous substances such as drugs, but is not limited thereto.

In one embodiment of the present invention, the term "MSA-mGALC fusion protein" or "MSA-mGALC" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of mGALC is linked, directly or via a linker, to the C-terminus of the amino acid sequence of MSA, and which has the function of mGALC. A preferred MSA-mGALC fusion protein has, for example, the amino acid sequence shown in SEQ ID NO: 18. The MSA-mGALC fusion protein shown in SEQ ID NO: 18 is a fusion protein in which wild-type mGALC is linked to the C-terminus of wild-type MSA via the linker sequence Gly-Ser. The MSA-mGALC fusion protein shown in SEQ ID NO: 18 is encoded by a gene having, for example, the base sequence shown in SEQ ID NO: 19. In addition, MSA-mGALC fusion proteins also include those having an amino acid sequence in which one or more amino acid residues in the amino acid sequence shown in SEQ ID NO: 18 have been replaced with other amino acid residues, deleted, or mutated by addition, as long as they have the function of mGALC. It is preferable that the MSA-mGALC fusion protein has the functions of mouse serum albumin, such as binding and transporting endogenous substances in the blood and exogenous substances such as drugs, but is not limited to this.

When mutations are introduced into the HSA-hGALC fusion protein, which is a fusion protein of wild-type HSA and wild-type hGALC, mutations can be introduced only in the HSA portion and not in the hGALC portion, mutations can be introduced only in the hGALC portion without mutations in the HSA portion, or mutations can be introduced in both the HSA portion and the hGALC portion. When mutations are introduced only in the HSA portion, the amino acid sequence of the portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above. When mutations are introduced only in the hGALC portion, the amino acid sequence of the portion is the amino acid sequence of hGALC obtained by adding a mutation to the wild-type hGALC described above. When mutations are introduced in both the HSA portion and the hGALC portion, the amino acid sequence of the HSA portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above, and the amino acid sequence of the hGALC portion is the amino acid sequence of hGALC obtained by adding a mutation to the wild-type hGALC described above. The same applies to the HSA-hGALC fusion protein having the amino acid sequence shown in SEQ ID NO:5. The same can be said about MSA-mGALC fusion proteins, including those having the amino acid sequence shown in SEQ ID NO: 18. The MSA-mGALC fusion protein having the amino acid sequence shown in SEQ ID NO: 18 is encoded by a gene having the base sequence shown in SEQ ID NO: 19, for example. The same can be said about fusion proteins of wild-type SA (including wild-type MSA) of animal species other than humans and wild-type hGALC.

The following is an example of a case where a mutation is made to an HSA-hGALC fusion protein having the amino acid sequence shown in SEQ ID NO:5. When an amino acid residue in the amino acid sequence shown in SEQ ID NO:5 is replaced with another amino acid residue, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is added, one or more amino acid residues are added to the amino acid sequence shown in SEQ ID NO:5 or to the N-terminus or C-terminus of the amino acid sequence. The HSA-hGALC fusion protein may be a combination of these substitutions, deletions, and additions of amino acid residues. The mutation may be made only to the HSA portion, only to the hGALC portion, or to both portions. The same can be said for fusion proteins between SA of a non-human animal species and hGALC (SA-hGALC), and fusion proteins between SA of a non-human animal species and GALC of a non-human animal species, such as the fusion protein MSA-mouse GALC.

The position and type (deletion, substitution, and addition) of each mutation when the amino acid sequence shown in SEQ ID NO:5 is mutated can be easily confirmed by alignment of the amino acid sequence before and after the mutation. The mutated amino acid sequence preferably exhibits 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more or 99% or more identity, with the amino acid sequence shown in SEQ ID NO:5.

　HSA-hGALC fusion proteins in which the amino acids constituting the protein are modified with sugar chains are also HSA-hGALC fusion proteins. HSA-hGALC fusion proteins in which the amino acids constituting the protein are modified with phosphate are also HSA-hGALC fusion proteins. HSA-hGALC fusion proteins modified with anything other than sugar chains and phosphate are also HSA-hGALC fusion proteins. HSA-hGALC fusion proteins in which the side chains of the amino acids constituting the protein are modified by substitution reactions or the like are also HSA-hGALC fusion proteins. Such modifications include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for fusion proteins of SA of non-human animal species and hGALC (SA-hGALC), and fusion proteins of SA of non-human animal species and GALC of non-human animal species, such as the fusion protein of MSA-mouse lysosomal enzyme.

In other words, HSA-hGALC fusion proteins modified with sugar chains are included in HSA-hGALC fusion proteins having the original amino acid sequence. Also, HSA-hGALC fusion proteins modified with phosphate are included in HSA-hGALC fusion proteins having the original amino acid sequence. Also, those modified with things other than sugar chains and phosphate are included in HSA-hGALC fusion proteins having the original amino acid sequence. Also, those in which the side chains of the amino acids constituting the HSA-hGALC fusion protein have been changed by substitution reactions or the like are included in HSA-hGALC fusion proteins having the original amino acid sequence. Such changes include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for fusion proteins of SA of a non-human animal species and hGALC (SA-hGALC), and fusion proteins of SA of a non-human animal species and GALC of a non-human animal species, such as the fusion protein MSA-mouse GALC.

　Also, HSA-hGALC fusion proteins in which the constituent hGALC is a precursor of hGALC are also HSA-hGALC fusion proteins. The term "precursor" here refers to a type of protein that is biosynthesized as an HSA-hGALC fusion protein, and in which the portion that functions as hGALC after the biosynthesis is cleaved from the fusion protein during the manufacturing process or in the living body when administered to the living body, and can function as hGALC by itself. In this case, after the HSA-hGALC fusion protein is biosynthesized, it may be cleaved at a specific site by a hydrolase or the like, and the portion containing HSA and the portion containing mature hGALC may be separated. In this case, the obtained hGALC is not a fusion protein with HSA, but the HSA-hGALC fusion protein is synthesized once during the process of synthesizing the hGALC. Therefore, when hGALC is produced by such a method, the production method is included in the method for producing HSA-hGALC fusion protein. The same can be said for fusion proteins of non-human animal species SA and hGALC (SA-hGALC), and fusion proteins of non-human animal species SA and non-human animal species GALC, such as MSA-mouse GALC fusion protein.

In one embodiment of the present invention, the term "SA-hGBA fusion protein" or "SA-hGBA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of hGBA is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of SA, and which has the function of hGBA. Here, there is no particular limitation on the animal species of the SA, but it is preferably a mammalian SA, more preferably a primate SA, and even more preferably HSA. When it is said that hGBA in the SA-hGBA fusion protein has the function of hGBA, it means that hGBA retains a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, when the specific activity of normal wild-type hGBA is taken as 100%. Here, the specific activity of hGBA in the SA-hGBA fusion protein is calculated by multiplying the enzyme activity of hGBA per unit mass of the fusion protein (μM/hour/mg protein) by (molecular weight of the fusion protein/molecular weight of the portion of the fusion protein corresponding to hGBA).

In one embodiment of the present invention, the term "HSA-hGBA fusion protein" or "HSA-hGBA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of hGBA is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of HSA, and which has the function of hGBA. When it is said here that the HSA-hGBA fusion protein has the function of hGALC, the definition of the SA-hGBA fusion protein described above can be applied.

In one embodiment of the present invention, a fusion protein having an amino acid sequence in which the N-terminus of GBA of a non-human animal species is linked, directly or via a linker, to the C-terminus of the amino acid sequence of SA of a non-human animal species, and which has the function of GBA, is designated as a "(non-human animal species) SA-(non-human animal species) GBA fusion protein." For example, a fusion protein of mouse SA and mouse GBA is designated as an "MSA-mouse GBA fusion protein" or "MSA-mouse GBA." When these fusion proteins are said to have the function of GBA, the definition of the SA-hGBA fusion protein described above can be applied. In addition, in these fusion proteins, it is preferable that the SA has the function of SA, such as the function of binding and transporting endogenous substances in the blood and exogenous substances such as drugs, but this is not limited thereto.

In one embodiment of the present invention, a preferred HSA-hGBA fusion protein has, for example, the amino acid sequence shown in SEQ ID NO: 39. The HSA-hGBA fusion protein shown in SEQ ID NO: 39 is obtained by linking wild-type hGBA to the C-terminus of wild-type HSA via a linker sequence having the amino acid sequence shown in SEQ ID NO: 9. The HSA-hGBA fusion protein shown in SEQ ID NO: 39 is encoded by a gene having, for example, the base sequence shown in SEQ ID NO: 40. In addition, HSA-hGBA fusion proteins include those having an amino acid sequence in which one or more amino acid residues in the amino acid sequence shown in SEQ ID NO: 39 have been replaced with other amino acid residues, deleted, or mutated by addition, as long as they have the function of hGBA. It is preferable that the HSA-hGBA fusion protein has the function of human serum albumin, such as the function of binding and transporting endogenous substances in blood and exogenous substances such as drugs, but is not limited thereto.

In one embodiment of the present invention, the term "MSA-mGBA fusion protein" or "MSA-mGBA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of mGBA is linked, directly or via a linker, to the C-terminus of the amino acid sequence of MSA, and which has the function of mGBA. A preferred MSA-mGBA fusion protein has, for example, the amino acid sequence shown in SEQ ID NO: 45. The MSA-mGBA fusion protein shown in SEQ ID NO: 45 is a fusion protein in which wild-type mGBA is linked to the C-terminus of wild-type MSA via a linker sequence having the amino acid sequence shown in SEQ ID NO: 9. The MSA-mGBA fusion protein shown in SEQ ID NO: 45 is encoded by a gene having, for example, the base sequence shown in SEQ ID NO: 46. In addition, MSA-mGBA fusion proteins also include those having an amino acid sequence in which one or more amino acid residues in the amino acid sequence shown in SEQ ID NO: 45 are replaced with other amino acid residues, deleted, or mutated by addition, as long as they have the function of mGBA. It is preferable that the MSA-mGBA fusion protein has mouse serum albumin functions, such as binding and transporting endogenous substances in the blood and exogenous substances such as drugs, but is not limited to this.

When mutations are introduced into an HSA-hGBA fusion protein, which is a fusion protein of wild-type HSA and wild-type hGBA, mutations can be introduced only in the HSA portion and not in the hGBA portion, mutations can be introduced only in the hGBA portion without mutations in the HSA portion, or mutations can be introduced in both the HSA portion and the hGBA portion. When mutations are introduced only in the HSA portion, the amino acid sequence of the portion is the amino acid sequence of HSA obtained by mutating the wild-type HSA described above. When mutations are introduced only in the hGBA portion, the amino acid sequence of the portion is the amino acid sequence of hGBA obtained by mutating the wild-type hGBA described above. When mutations are introduced in both the HSA portion and the hGBA portion, the amino acid sequence of the HSA portion is the amino acid sequence of HSA obtained by mutating the wild-type HSA described above, and the amino acid sequence of the hGBA portion is the amino acid sequence of hGBA obtained by mutating the wild-type hGBA described above. The same applies to the HSA-hGBA fusion protein having the amino acid sequence shown in SEQ ID NO: 39. The same can be said about MSA-mGBA fusion proteins, including those having the amino acid sequence shown in SEQ ID NO: 45. The MSA-mGBA fusion protein having the amino acid sequence shown in SEQ ID NO: 45 is encoded by a gene having the base sequence shown in SEQ ID NO: 46, for example. The same can be said about fusion proteins of wild-type SA (including wild-type MSA) of animal species other than humans and wild-type hGBA.

The following is an example of a case where a mutation is made to an HSA-hGBA fusion protein having the amino acid sequence shown in SEQ ID NO:39. When an amino acid residue in the amino acid sequence shown in SEQ ID NO:39 is replaced with another amino acid residue, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is added, one or more amino acid residues are added to the amino acid sequence shown in SEQ ID NO:39 or to the N-terminus or C-terminus of the amino acid sequence. The HSA-hGBA fusion protein may be a combination of these substitutions, deletions, and additions of amino acid residues. The mutation may be made only to the HSA portion, only to the hGBA portion, or to both portions. The same can be said for fusion proteins of SA of a non-human animal species and hGBA (SA-hGBA), and fusion proteins of SA of a non-human animal species and GBA of a non-human animal species, such as the fusion protein MSA-mouse GBA.

The position and type (deletion, substitution, and addition) of each mutation when the amino acid sequence shown in SEQ ID NO:39 is mutated can be easily confirmed by alignment of the amino acid sequence before and after the mutation. The mutated amino acid sequence preferably exhibits 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more or 99% or more identity, with the amino acid sequence shown in SEQ ID NO:39.

　HSA-hGBA fusion proteins in which the amino acids constituting the protein are modified with sugar chains are also HSA-hGBA fusion proteins. HSA-hGBA fusion proteins in which the amino acids constituting the protein are modified with phosphate are also HSA-hGBA fusion proteins. HSA-hGBA fusion proteins modified with anything other than sugar chains and phosphate are also HSA-hGBA fusion proteins. HSA-hGBA fusion proteins in which the side chains of the amino acids constituting the protein have been converted by substitution reactions or the like are also HSA-hGBA fusion proteins. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for fusion proteins of SA and hGBA of non-human animal species (SA-hGBA), and fusion proteins of SA and GBA of non-human animal species, such as the fusion protein MSA-mouseGBA.

In other words, HSA-hGBA fusion proteins modified with sugar chains are included in HSA-hGBA fusion proteins having the original amino acid sequence. Also, HSA-hGBA fusion proteins modified with phosphate are included in HSA-hGBA fusion proteins having the original amino acid sequence. Also, those modified with things other than sugar chains and phosphate are included in HSA-hGBA fusion proteins having the original amino acid sequence. Also, those in which the side chains of the amino acids constituting the HSA-hGBA fusion protein have been converted by substitution reactions or the like are included in HSA-hGBA fusion proteins having the original amino acid sequence. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for fusion proteins of SA and hGBA of non-human animal species (SA-hGBA), and fusion proteins of SA of non-human animal species and GBA of non-human animal species, such as the fusion protein MSA-mouse GBA.

Also, HSA-hGBA fusion proteins in which the hGBA that constitutes them is a precursor of hGBA are also HSA-hGBA fusion proteins. Here, the term "precursor" refers to a type that is biosynthesized as an HSA-hGBA fusion protein, and in which the portion that functions as hGBA after the biosynthesis is separated from the fusion protein during the manufacturing process or in the living body when administered to the living body, and can function as hGBA by itself. In this case, after the HSA-hGBA fusion protein is biosynthesized, it may be cleaved at a specific site by a hydrolase or the like, and the portion containing HSA and the portion containing mature hGBA may be separated. In this case, the obtained hGBA is not a fusion protein with HSA, but the HSA-hGBA fusion protein is synthesized once during the process of synthesizing the hGBA. Therefore, when hGBA is produced by such a method, the production method is included in the method for producing HSA-hGBA fusion protein. The same can be said for fusion proteins of SA of a non-human animal species and hGBA (SA-hGBA), and fusion proteins of SA of a non-human animal species and GBA of a non-human animal species, such as the MSA-mouse GBA fusion protein.

In one embodiment of the present invention, the term "human lysosomal enzyme-SA fusion protein" or "human lysosomal enzyme-SA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of SA is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of a human lysosomal enzyme, and which has the function of a human lysosomal enzyme. When the human lysosomal enzyme in a human lysosomal enzyme-SA fusion protein is said to have the function of a human lysosomal enzyme, it means that the human lysosomal enzyme preferably retains a specific activity of 10% or more, more preferably a specific activity of 20% or more, even more preferably a specific activity of 50% or more, and even more preferably a specific activity of 80% or more, when the specific activity of a normal wild-type human lysosomal enzyme is taken as 100%. Here, the specific activity of the human lysosomal enzyme in the human lysosomal enzyme-SA fusion protein is calculated by multiplying the enzymatic activity of the human lysosomal enzyme per unit mass of the fusion protein (μM/hour/mg protein) by (molecular weight of the fusion protein/molecular weight of the portion of the fusion protein that corresponds to the human lysosomal enzyme).

In one embodiment of the present invention, the term "human lysosomal enzyme-HSA fusion protein" or "human lysosomal enzyme-HSA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of HSA is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of a human lysosomal enzyme, and which has the function of a human lysosomal enzyme. When it is said that the human lysosomal enzyme-HSA fusion protein has the function of a human lysosomal enzyme, the definition of human lysosomal enzyme-SA above can be applied.

In the human lysosomal enzyme-SA fusion protein, it is preferable that the SA has a function as an SA, such as the function of binding and transporting endogenous substances in the blood and exogenous substances such as drugs, but is not limited to this. The same is true for the human lysosomal enzyme-HSA fusion protein.

In one embodiment of the present invention, a fusion protein having an amino acid sequence in which the N-terminus of SA of a non-human animal species is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of a lysosomal enzyme of a non-human animal species, and which has the function of a human lysosomal enzyme, is referred to as a "(non-human animal species) lysosomal enzyme-(non-human animal species) SA fusion protein." For example, a fusion protein of mouse lysosomal enzyme and mouse SA is referred to as a "mouse lysosomal enzyme-MSA fusion protein" or "mouse lysosomal enzyme-MSA." When these fusion proteins are said to have the function of a lysosomal enzyme, the definition of the human lysosomal enzyme-SA fusion protein described above can be applied.

When a mutation is introduced into a human lysosomal enzyme-HSA fusion protein, which is a fusion protein of wild-type human lysosomal enzyme and wild-type HSA, a mutation can be introduced only into the human lysosomal enzyme portion and not into the HSA portion, a mutation can be introduced only into the HSA portion without introducing a mutation into the human lysosomal enzyme portion, or a mutation can be introduced into both the human lysosomal enzyme portion and the HSA portion. When a mutation is introduced only into the human lysosomal enzyme portion, the amino acid sequence of the portion is the amino acid sequence of the human lysosomal enzyme obtained by introducing a mutation into the wild-type human lysosomal enzyme described above. When a mutation is introduced only into the HSA portion, the amino acid sequence of the portion is the amino acid sequence of the HSA obtained by introducing a mutation into the wild-type HSA described above. When a mutation is introduced into both the human lysosomal enzyme portion and the HSA portion, the amino acid sequence of the human lysosomal enzyme portion is the amino acid sequence of the human lysosomal enzyme obtained by introducing a mutation into the wild-type human lysosomal enzyme described above, and the amino acid sequence of the HSA portion is the amino acid sequence of the HSA obtained by introducing a mutation into the wild-type HSA described above. The same can be said about fusion proteins between wild-type human lysosomal enzymes and wild-type SA (including wild-type MSA) of non-human animal species.

　Human lysosomal enzyme-HSA fusion proteins in which the amino acids constituting the protein are modified with sugar chains are also human lysosomal enzyme-HSA fusion proteins. Human lysosomal enzyme-HSA fusion proteins in which the amino acids constituting the protein are modified with phosphate are also human lysosomal enzyme-HSA fusion proteins. Human lysosomal enzyme-HSA fusion proteins modified with anything other than sugar chains and phosphate are also human lysosomal enzyme-HSA fusion proteins. Human lysosomal enzyme-HSA fusion proteins in which the side chains of the amino acids constituting the protein have been converted by a substitution reaction or the like are also human lysosomal enzyme-HSA fusion proteins. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said about fusion proteins of human lysosomal enzyme and SA of a species of animal other than human (human lysosomal enzyme-SA) and fusion proteins of lysosomal enzyme and SA of a species of animal other than human, such as mouse lysosomal enzyme-MSA.

In other words, a human lysosomal enzyme-HSA fusion protein modified with a sugar chain is included in the human lysosomal enzyme-HSA fusion protein having the original amino acid sequence. A human lysosomal enzyme-HSA fusion protein modified with phosphate is included in the human lysosomal enzyme-HSA fusion protein having the original amino acid sequence. A fusion protein modified with something other than sugar chains and phosphate is also included in the human lysosomal enzyme-HSA fusion protein having the original amino acid sequence. A human lysosomal enzyme-HSA fusion protein in which the side chains of the amino acids constituting the human lysosomal enzyme-HSA fusion protein have been converted by a substitution reaction or the like is also included in the human lysosomal enzyme-HSA fusion protein having the original amino acid sequence. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said about a fusion protein of a human lysosomal enzyme and SA of an animal species other than human (human lysosomal enzyme-SA), and a fusion protein of a lysosomal enzyme of an animal species other than human and SA of an animal species other than human.

Furthermore, a human lysosomal enzyme-HSA fusion protein in which the human lysosomal enzyme that constitutes it is a precursor of a human lysosomal enzyme is also a human lysosomal enzyme-HSA fusion protein.

In one embodiment of the present invention, the term "hGALC-SA fusion protein" or "hGALC-SA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of SA is linked, directly or via a linker, to the C-terminus of the amino acid sequence of hGALC, and which has the function of hGALC. When hGALC in an hGALC-SA fusion protein is said to have the function of hGALC, it means that hGALC retains a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, when the specific activity of normal wild-type hGALC is taken as 100%. Here, the specific activity of hGALC in the hGALC-SA fusion protein is calculated by multiplying the enzyme activity of hGALC per unit mass of the fusion protein (μM/hour/mg protein) by (the molecular weight of the fusion protein/the molecular weight of the portion of the fusion protein corresponding to hGALC).

In one embodiment of the present invention, the term "hGALC-HSA fusion protein" or "hGALC-HSA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of HSA is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of hGALC, and which has the function of hGALC. When it is said here that the hGALC-HSA fusion protein has the function of hGALC, the definition of the hGALC-SA fusion protein described above can be applied.

In one embodiment of the present invention, a fusion protein having an amino acid sequence in which the N-terminus of SA of a non-human animal species is linked, directly or via a linker, to the C-terminus of the amino acid sequence of GALC of a non-human animal species, and which has the function of GALC, is designated as a "(non-human animal species) GALC-(non-human animal species) SA fusion protein." For example, a fusion protein of mouse GALC and mouse SA is designated as a "mouse GALC-MSA fusion protein" or "mouse GALC-MSA." When these fusion proteins are said to have the function of GALC, the definition of the hGALC-HSA fusion protein described above can be applied. In addition, in these fusion proteins, it is preferable that the SA has the function of SA, such as the function of binding and transporting endogenous substances in the blood and exogenous substances such as drugs, but this is not limited thereto.

In one embodiment of the present invention, a preferred hGALC-HSA fusion protein has, for example, the amino acid sequence shown in SEQ ID NO: 7. The hGALC-HSA fusion protein shown in SEQ ID NO: 7 is obtained by linking wild-type HSA to the C-terminus of wild-type hGALC via the linker sequence Gly-Ser. The hGALC-HSA fusion protein shown in SEQ ID NO: 7 is encoded by a gene having, for example, the base sequence shown in SEQ ID NO: 8. In addition, the hGALC-HSA fusion protein also includes an amino acid sequence in which one or more amino acid residues in the amino acid sequence shown in SEQ ID NO: 7 have been replaced with other amino acid residues, deleted, or mutated by addition, so long as it has the function of hGALC. The hGALC-HSA fusion protein is preferably one that has the function of human serum albumin, such as the function of binding and transporting endogenous substances in blood and exogenous substances such as drugs, but is not limited thereto.

In one embodiment of the present invention, the term "mGALC-MSA fusion protein" or "mGALC-MSA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of MSA is linked, directly or via a linker, to the C-terminus of the amino acid sequence of mGALC, and which has the function of mGALC. A preferred mGALC-MSA fusion protein has, for example, the amino acid sequence shown in SEQ ID NO: 20. The mGALC-MSA fusion protein shown in SEQ ID NO: 20 is a fusion protein in which wild-type MSA is linked to the C-terminus of wild-type mGALC via the linker sequence Gly-Ser. The mGALC-MSA fusion protein shown in SEQ ID NO: 20 is encoded by a gene having, for example, the base sequence shown in SEQ ID NO: 21. In addition, mGALC-MSA fusion proteins also include those having an amino acid sequence in which one or more amino acid residues in the amino acid sequence shown in SEQ ID NO: 20 have been replaced with other amino acid residues, deleted, or mutated by addition, as long as they have the function of mGALC. It is preferable that the mGALC-MSA fusion protein has mouse serum albumin functions, such as binding and transporting endogenous substances in the blood and exogenous substances such as drugs, but is not limited to this.

When mutations are introduced into the hGALC-HSA fusion protein, which is a fusion protein of wild-type hGALC and wild-type HSA, mutations can be introduced only in the hGALC portion and not in the HSA portion, mutations can be introduced only in the HSA portion without mutations in the hGALC portion, or mutations can be introduced in both the hGALC portion and the HSA portion. When mutations are introduced only in the hGALC portion, the amino acid sequence of the portion is the amino acid sequence of hGALC obtained by mutating the wild-type hGALC described above. When mutations are introduced only in the HSA portion, the amino acid sequence of the portion is the amino acid sequence of HSA obtained by mutating the wild-type HSA described above. When mutations are introduced both in the hGALC portion and the HSA portion, the amino acid sequence of the hGALC portion is the amino acid sequence of hGALC obtained by mutating the wild-type hGALC described above, and the amino acid sequence of the HSA portion is the amino acid sequence of HSA obtained by mutating the wild-type HSA described above. The same applies to the hGALC-HSA fusion protein having the amino acid sequence shown in SEQ ID NO: 7. The same can be said about mGALC-MSA fusion proteins, including those having the amino acid sequence shown in SEQ ID NO: 20. The mGALC-MSA fusion protein having the amino acid sequence shown in SEQ ID NO: 20 is encoded by a gene having the base sequence shown in SEQ ID NO: 21, for example. The same can be said about fusion proteins of wild-type hGALC and wild-type SA (including wild-type MSA) of animals other than humans.

When mutations are introduced into the hGALC-HSA fusion protein, which is a fusion protein of wild-type hGALC and wild-type HSA, mutations can be introduced only in the HSA portion and not in the hGALC portion, mutations can be introduced only in the hGALC portion without mutations in the HSA portion, or mutations can be introduced in both the HSA portion and the hGALC portion. When mutations are introduced only in the HSA portion, the amino acid sequence of the portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above. When mutations are introduced only in the hGALC portion, the amino acid sequence of the portion is the amino acid sequence of hGALC obtained by adding a mutation to the wild-type hGALC described above. When mutations are introduced in both the HSA portion and the hGALC portion, the amino acid sequence of the HSA portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above, and the amino acid sequence of the hGALC portion is the amino acid sequence of hGALC obtained by adding a mutation to the wild-type hGALC described above. The same applies to the hGALC-HSA fusion protein having the amino acid sequence shown in SEQ ID NO: 7. The same can be said about mGALC-MSA fusion proteins, including those having the amino acid sequence shown in SEQ ID NO: 20. The mGALC-MSA fusion protein having the amino acid sequence shown in SEQ ID NO: 20 is encoded by a gene having the base sequence shown in SEQ ID NO: 21, for example. The same can be said about a fusion protein of wild-type hGALC and wild-type SA (hGALC-SA) of an animal other than human.

The following is an example of a case where a mutation is made to an hGALC-HSA fusion protein having the amino acid sequence shown in SEQ ID NO:7. When an amino acid residue in the amino acid sequence shown in SEQ ID NO:7 is replaced with another amino acid residue, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is added, one or more amino acid residues are added to the amino acid sequence shown in SEQ ID NO:7 or to the N-terminus or C-terminus of the amino acid sequence. The hGALC-HSA fusion protein may be a combination of these substitutions, deletions, and additions of amino acid residues. The mutation may be made only to the HSA portion, only to the hGALC portion, or to both portions. The same can be said for fusion proteins between SA and GALC of non-human animal species (SA-GALC), and fusion proteins between SA and GALC of non-human animal species, such as the fusion protein MSA-mouse GALC.

The position and type (deletion, substitution, and addition) of each mutation when the amino acid sequence shown in SEQ ID NO:7 is mutated can be easily confirmed by alignment of the amino acid sequence before and after the mutation. The mutated amino acid sequence preferably exhibits 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more or 99% or more identity, with the amino acid sequence shown in SEQ ID NO:7.

　An hGALC-HSA fusion protein in which the amino acids constituting the protein are modified with sugar chains is also an hGALC-HSA fusion protein. An hGALC-HSA fusion protein in which the amino acids constituting the protein are modified with phosphate is also an hGALC-HSA fusion protein. An hGALC-HSA fusion protein modified with something other than sugar chains and phosphate is also an hGALC-HSA fusion protein. An hGALC-HSA fusion protein in which the side chains of the amino acids constituting the protein have been changed by a substitution reaction or the like is also an hGALC-HSA fusion protein. Such a change includes, but is not limited to, the conversion of a cysteine residue to formylglycine. The same can be said about a fusion protein of GALC and SA of a non-human animal species (GALC-SA), and a fusion protein of GALC of a non-human animal species and SA of a non-human animal species, for example, a fusion protein of mouse GALC and MSA.

In other words, hGALC-HSA fusion proteins modified with sugar chains are included in the hGALC-HSA fusion proteins having the original amino acid sequence. Also, hGALC-HSA fusion proteins modified with phosphate are included in the hGALC-HSA fusion proteins having the original amino acid sequence. Also, those modified with things other than sugar chains and phosphate are included in the hGALC-HSA fusion proteins having the original amino acid sequence. Also, hGALC-HSA fusion proteins in which the side chains of the amino acids constituting the hGALC-HSA fusion protein have been changed by substitution reactions or the like are included in the hGALC-HSA fusion proteins having the original amino acid sequence. Such changes include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for fusion proteins of GALC and SA of a non-human animal species (GALC-SA), and fusion proteins of GALC of a non-human animal species and SA of a non-human animal species.

In addition, an hGALC-HSA fusion protein in which the hGALC that constitutes it is a precursor of hGALC is also an HSA-hGALC fusion protein.

In one embodiment of the present invention, the term "hGBA-SA fusion protein" or "hGBA-SA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of SA is linked, directly or via a linker, to the C-terminus of the amino acid sequence of hGBA, and which has the function of hGBA. Here, there is no particular limitation on the animal species of the SA, but it is preferably a mammalian SA, more preferably a primate SA, and even more preferably HSA. When it is said that hGBA in an hGBA-SA fusion protein has the function of hGBA, it means that hGBA retains a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, when the specific activity of normal wild-type hGBA is taken as 100%. Here, the specific activity of hGBA in the hGBA-SA fusion protein is calculated by multiplying the enzyme activity of hGBA per unit mass of the fusion protein (μM/hour/mg protein) by (molecular weight of the fusion protein/molecular weight of the portion of the fusion protein corresponding to hGBA).

In one embodiment of the present invention, the term "hGBA-HSA fusion protein" or "hGBA-HSA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of HSA is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of hGBA, and which has the function of hGBA. When it is said here that the hGBA-HSA fusion protein has the function of hGALC, the definition of the SA-hGBA fusion protein described above can be applied.

In one embodiment of the present invention, a fusion protein having an amino acid sequence in which the N-terminus of SA of a non-human animal species is linked, directly or via a linker, to the C-terminus of the amino acid sequence of GBA of a non-human animal species, and which has the function of GBA, is designated as a "(non-human animal species) GBA-(non-human animal species) SA fusion protein." For example, a fusion protein of mouse GBA and mouse SA is designated as a "mouse GBA-MSA fusion protein" or "mouse GBA-MSA." When these fusion proteins are said to have the function of GBA, the definition of the hGBA-HSA fusion protein described above can be applied. In addition, in these fusion proteins, it is preferable that the SA has the function of SA, such as the function of binding and transporting endogenous substances in the blood and exogenous substances such as drugs, but this is not limited thereto.

In one embodiment of the present invention, a preferred hGBA-HSA fusion protein has, for example, the amino acid sequence shown in SEQ ID NO: 41. The hGBA-HSA fusion protein shown in SEQ ID NO: 41 is obtained by linking wild-type HSA to the C-terminus of wild-type hGBA via a linker sequence having the amino acid sequence shown in SEQ ID NO: 9. The hGBA-HSA fusion protein shown in SEQ ID NO: 41 is encoded by a gene having, for example, the base sequence shown in SEQ ID NO: 42. In addition, hGBA-HSA fusion proteins also include those having an amino acid sequence in which one or more amino acid residues in the amino acid sequence shown in SEQ ID NO: 41 have been replaced with other amino acid residues, deleted, or mutated by addition, as long as they have the function of hGBA. It is preferable that the hGBA-HSA fusion protein has the function of human serum albumin, such as the function of binding and transporting endogenous substances in blood and exogenous substances such as drugs, but is not limited thereto.

In one embodiment of the present invention, the term "mGBA-MSA fusion protein" or "mGBA-MSA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of MSA is linked, directly or via a linker, to the C-terminus of the amino acid sequence of mGBA, and which has the function of mGBA. A preferred mGBA-MSA fusion protein has, for example, the amino acid sequence shown in SEQ ID NO: 47. The mGBA-MSA fusion protein shown in SEQ ID NO: 47 is a fusion protein in which wild-type MSA is linked to the C-terminus of wild-type mGBA via a linker sequence having the amino acid sequence shown in SEQ ID NO: 9. The mGBA-MSA fusion protein shown in SEQ ID NO: 47 is encoded by a gene having, for example, the base sequence shown in SEQ ID NO: 48. In addition, mGBA-MSA fusion proteins also include those having an amino acid sequence in which one or more amino acid residues in the amino acid sequence shown in SEQ ID NO: 47 have been replaced with other amino acid residues, deleted, or mutated by addition, as long as they have the function of mGBA. It is preferable that the mGBA-MSA fusion protein has mouse serum albumin functions, such as binding and transporting endogenous substances in the blood and exogenous substances such as drugs, but is not limited to this.

When mutations are introduced into the hGBA-HSA fusion protein, which is a fusion protein of wild-type hGBA and wild-type HSA, mutations can be introduced only in the hGBA portion and not in the HSA portion, mutations can be introduced only in the HSA portion without mutations in the hGBA portion, or mutations can be introduced in both the hGBA portion and the HSA portion. When mutations are introduced only in the hGBA portion, the amino acid sequence of the portion is the amino acid sequence of hGBA obtained by mutating the wild-type hGBA described above. When mutations are introduced only in the HSA portion, the amino acid sequence of the portion is the amino acid sequence of HSA obtained by mutating the wild-type HSA described above. When mutations are introduced both in the hGBA portion and the HSA portion, the amino acid sequence of the hGBA portion is the amino acid sequence of hGBA obtained by mutating the wild-type hGBA described above, and the amino acid sequence of the HSA portion is the amino acid sequence of HSA obtained by mutating the wild-type HSA described above. The same applies to the hGBA-HSA fusion protein having the amino acid sequence shown in SEQ ID NO: 41. The same can be said about mGBA-MSA fusion proteins, including those having the amino acid sequence shown in SEQ ID NO: 47. The mGBA-MSA fusion protein having the amino acid sequence shown in SEQ ID NO: 47 is encoded by a gene having the base sequence shown in SEQ ID NO: 48, for example. The same can be said about fusion proteins of wild-type hGBA and wild-type SA (including wild-type MSA) of an animal species other than human.

The following is an example of a case where a mutation is made to an hGBA-HSA fusion protein having the amino acid sequence shown in SEQ ID NO:41. When an amino acid residue in the amino acid sequence shown in SEQ ID NO:41 is replaced with another amino acid residue, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is added, one or more amino acid residues are added to the amino acid sequence shown in SEQ ID NO:41 or to the N-terminus or C-terminus of the amino acid sequence. The hGBA-HSA fusion protein may be a combination of these substitutions, deletions, and additions of amino acid residues. The mutation may be made only to the HSA portion, only to the hGBA portion, or to both portions. The same can be said for fusion proteins of hGBA and SA of non-human animal species (hGBA-SA), and fusion proteins of GBA of non-human animal species and SA of non-human animal species, such as mouse GBA-MSA fusion protein.

The position and type (deletion, substitution, and addition) of each mutation when the amino acid sequence shown in SEQ ID NO:41 is mutated can be easily confirmed by alignment of the amino acid sequence before and after the mutation. The mutated amino acid sequence preferably exhibits 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more or 99% or more identity, with the amino acid sequence shown in SEQ ID NO:41.

　An hGBA-HSA fusion protein in which the amino acids constituting the protein are modified with sugar chains is also an hGBA-HSA fusion protein. An hGBA-HSA fusion protein in which the amino acids constituting the protein are modified with phosphate is also an hGBA-HSA fusion protein. An hGBA-HSA fusion protein modified with something other than sugar chains and phosphate is also an hGBA-HSA fusion protein. An hGBA-HSA fusion protein in which the side chains of the amino acids constituting the protein have been converted by a substitution reaction or the like is also an hGBA-HSA fusion protein. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said about a fusion protein of hGBA and SA of a non-human animal species (hGBA-SA), and a fusion protein of GBA of a non-human animal species and SA of a non-human animal species, such as mouse GBA-MSA fusion protein.

In other words, hGBA-HSA fusion proteins modified with sugar chains are included in the hGBA-HSA fusion proteins having the original amino acid sequence. Also, hGBA-HSA fusion proteins modified with phosphate are included in the hGBA-HSA fusion proteins having the original amino acid sequence. Also, those modified with things other than sugar chains and phosphate are included in the hGBA-HSA fusion proteins having the original amino acid sequence. Also, those in which the side chains of the amino acids constituting the hGBA-HSA fusion proteins have been changed by substitution reactions or the like are included in the hGBA-HSA fusion proteins having the original amino acid sequence. Such changes include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for fusion proteins of hGBA and SA of non-human animal species (hGBA-SA) and fusion proteins of GBA of non-human animal species and SA of non-human animal species, such as mouse GBA-MSA fusion protein.

In addition, an hGBA-HSA fusion protein in which the hGBA that constitutes it is a precursor of hGBA is also an HSA-hGALC fusion protein.

In one embodiment of the present invention, the terms "fusion protein of SA and lysosomal enzyme", "fusion protein of lysosomal enzyme and SA", or "fusion protein of serum albumin and lysosomal enzyme" include both the above-mentioned "SA-lysosomal enzyme fusion protein" and "lysosomal enzyme-SA fusion protein". In addition, the terms "fusion protein of SA and GALC", "fusion protein of GALC and SA", or "fusion protein of serum albumin and galactosylceramidase" include both the above-mentioned "SA-GALC fusion protein" and "GALC-SA fusion protein". In addition, the terms "fusion protein of SA and GBA", "fusion protein of GBA and SA", or "fusion protein of serum albumin and glucocerebrosidase" include both the above-mentioned "SA-GBA fusion protein" and "GBA-SA fusion protein". The same applies when SA is HSA, when the lysosomal enzyme is human lysosomal enzyme, when GALC is hGALC, and when GBA is hGBA.

　Below, we will provide a detailed description of SA and lysosomal enzymes, taking as examples a fusion protein of HSA and hGALC and a fusion protein of HSA and hGBA, and the manufacturing method of the fusion protein, but these descriptions can also be applied to fusion proteins in which the SA is non-human, and the lysosomal enzyme is other than GALC and GBA. For example, they also apply to fusion proteins of SA of a non-human animal species and hGALC or hGBA, fusion proteins of SA of a non-human animal species and GALC or GBA of a non-human animal species, and fusion proteins of MSA and mGALC or mGBA.

In one embodiment of the fusion protein, the SA and the lysosomal enzyme are linked directly or via a linker. Here, the term "linker" refers to a structure used to link two types of proteins, or a portion that does not belong to either protein when two or more types of proteins are fused. Linkers include peptide linkers and non-peptide linkers. A peptide linker that constitutes part of a fusion protein can also be simply called a linker. The amino acid sequence of a peptide linker can also be called a linker sequence. In the case of a fusion protein of SA and a lysosomal enzyme, the linker refers to a portion that does not belong to either the amino acid sequence of SA or the amino acid sequence of the lysosomal enzyme. In other words, the linker is a peptide chain that is interposed between the SA and the lysosomal enzyme. Linkers have various functions. The functions include a function between SA and lysosomal enzyme that binds SA and lysosomal enzyme, a function to reduce mutual interference between SA and lysosomal enzyme by increasing the distance between them within the fusion protein molecule, and a function to act as a hinge between SA and lysosomal enzyme that connects SA and lysosomal enzyme and gives flexibility to the three-dimensional structure of the fusion protein. Within the fusion protein molecule, the linker exerts at least one of these functions. This is the same, for example, when the SA is HSA, and when the lysosomal enzyme is a human lysosomal enzyme, such as hGALC or hGBA.

In the fusion protein of SA and a lysosomal enzyme, the amino acid sequence of the linker is not particularly limited as long as it functions as a linker in the fusion protein molecule. The length of the peptide linker is also not particularly limited as long as it functions as a linker in the fusion protein molecule. The peptide linker is composed of one or more amino acids. When the peptide linker is composed of multiple amino acids, the number of amino acids is preferably 2 to 50, more preferably 5 to 30, and even more preferably 10 to 25. Suitable examples of peptide linkers include those consisting of Gly-Ser, Gly-Gly-Ser, or amino acid sequences shown in SEQ ID NOs: 9 to 11 (collectively referred to as basic sequences), and those containing these. For example, the peptide linker is one that contains an amino acid sequence in which the basic sequence is repeated 2 to 10 times, one that contains an amino acid sequence in which the basic sequence is repeated 2 to 6 times, and one that contains an amino acid sequence in which the basic sequence is repeated 3 to 5 times. One or more amino acids in these amino acid sequences may be deleted, replaced with other amino acids, added, etc. When deleting an amino acid, the number of amino acids to be deleted is preferably 1 or 2. When substituting an amino acid with another amino acid, the number of amino acids to be substituted is preferably 1 or 2. When adding an amino acid, the number of amino acids to be added is preferably 1 or 2. The desired amino acid sequence of the linker portion can be obtained by combining these deletions, substitutions, and additions of amino acids. The peptide linker may be composed of one amino acid, and the amino acid constituting the linker is, for example, glycine or serine. This is the same, for example, when the SA is HSA, and when the lysosomal enzyme is, for example, a human lysosomal enzyme, such as hGALC or hGBA.

A fusion protein of HSA and hGALC can be produced as a recombinant protein by preparing an expression vector incorporating a DNA fragment in which a gene encoding hGALC is linked in-frame downstream or upstream of a gene encoding HSA, and culturing a host cell transformed by introducing this expression vector. A fusion protein of HSA and hGBA can be produced as a recombinant protein by preparing an expression vector incorporating a DNA fragment in which a gene encoding hGBA is linked in-frame downstream or upstream of a gene encoding HSA, and culturing a host cell transformed by introducing this expression vector. The fusion protein produced as a recombinant protein in this way consists of a single-chain polypeptide. In the present invention, a fusion protein produced as a recombinant protein is called a recombinant fusion protein.

When preparing an HSA-hGALC fusion protein as a recombinant fusion protein, a gene encoding hGALC can be linked in-frame downstream of a gene encoding HSA to obtain a fusion protein having the amino acid sequence of hGALC at the C-terminus of the amino acid sequence of HSA. Conversely, a gene encoding hGALC can be linked in-frame upstream of a gene encoding HSA to obtain an hGALC-HSA fusion protein having the amino acid sequence of hGALC at the N-terminus of the amino acid sequence of HSA. Also, a gene encoding hGBA can be linked in-frame downstream of a gene encoding HSA to obtain an HSA-hGBA fusion protein having the amino acid sequence of hGBA at the C-terminus of the amino acid sequence of HSA. Conversely, a gene encoding hGBA can be linked in-frame upstream of a gene encoding HSA to obtain an hGBA-HSA fusion protein having the amino acid sequence of hGBA at the N-terminus of the amino acid sequence of HSA. In either case, the fusion protein prepared as a recombinant fusion protein is a single-chain polypeptide.

In the present invention, the term "single-chain polypeptide" refers to a polypeptide that has one N-terminus and one C-terminus and has no branched peptide chains. As long as this condition is met, those that have intramolecular disulfide bonds and those that are modified with sugar chains, lipids, phospholipids, etc. are also single-chain polypeptides. In addition, when single-chain polypeptides form complexes such as dimers through non-covalent bonds, each peptide chain that forms the complex is understood to be a single-chain polypeptide, and the complex itself is understood to be an assembly of single-chain polypeptides.

When the amino acid sequence of HSA is located on the N-terminal side of the amino acid sequence of hGALC or hGBA in the single-chain polypeptide of the fusion protein, the C-terminus of HSA and the N-terminus of hGALC or hGBA are bound directly by a peptide bond or via a linker. Figure 1 shows a schematic diagram of a single-chain polypeptide HSA-hGALC fusion protein having HSA, a linker, and hGALC in this order from the N-terminus. In this HSA-hGALC fusion protein, the C-terminus of HSA and the N-terminus of the linker are bound by a peptide bond, and the C-terminus of the linker and the N-terminus of hGALC are bound by a peptide bond. Figure 2 also shows a schematic diagram of a single-chain polypeptide HSA-hGBA fusion protein having HSA, a linker, and hGBA in this order from the N-terminus. In this HSA-hGBA fusion protein, the C-terminus of HSA and the N-terminus of the linker are bound by a peptide bond, and the C-terminus of the linker and the N-terminus of hGBA are bound by a peptide bond.

In addition, when the amino acid sequence of hGALC or hGBA is located at the N-terminus of the amino acid sequence of HSA in the single-chain polypeptide of the fusion protein, the C-terminus of hGALC or hGBA and the N-terminus of HSA are bound directly by a peptide bond or via a linker. Figure 3 shows a single-chain polypeptide hGALC-HSA fusion protein having hGALC, a linker, and HSA in this order from the N-terminus. In this hGALC-HSA fusion protein, the C-terminus of hGALC and the N-terminus of the linker are bound by a peptide bond, and the C-terminus of the linker and the N-terminus of HSA are bound by a peptide bond. Figure 4 shows a single-chain polypeptide hGBA-HSA fusion protein having hGBA, a linker, and HSA in this order from the N-terminus. In this hGBA-HSA fusion protein, the C-terminus of hGBA and the N-terminus of the linker are bound by a peptide bond, and the C-terminus of the linker and the N-terminus of HSA are bound by a peptide bond.

In one embodiment of the present invention, a fusion protein of HSA and hGALC refers to a fusion protein characterized in that when expressed in host cells as a recombinant protein, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the expression amount of hGALC in the culture supernatant is at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or enzyme activity, compared to when wild-type hGALC is expressed in host cells as a recombinant protein under the same conditions. In one embodiment of the present invention, the fusion protein of HSA and hGBA refers to a fusion protein characterized in that when expressed in a host cell as a recombinant protein, particularly when expressed so that the recombinant protein is secreted from the cell and accumulated in the culture medium, the amount of hGBA expressed in the culture supernatant is at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, for example, 1.1 to 4 times, 1.5 to 3.6 times, 2 to 3.6 times, 10 to 20 times, etc., in terms of concentration or enzyme activity, compared to when wild-type hGBA is expressed in a host cell as a recombinant protein under the same conditions. Here, "under the same conditions" means that the expression vector, host cell, culture conditions, etc. are the same. The preferred host cells used in this case are mammalian cells such as CHO cells and NS/0 cells, and particularly CHO cells.

Preferred embodiments of the fusion protein of HSA and hGALC include the following (1) and (2):
(1) A polypeptide having an amino acid sequence shown in SEQ ID NO:5, in which the N-terminus of the amino acid sequence of wild-type hGALC shown in SEQ ID NO:1 is linked to the C-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO:3 via a linker represented by Gly-Ser;
(2) Having the amino acid sequence shown in SEQ ID NO: 7, in which the N-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO: 3 is linked to the C-terminus of the amino acid sequence of wild-type hGALC shown in SEQ ID NO: 1 via a linker represented by Gly-Ser.

Preferred embodiments of the fusion protein of HSA and hGBA include the following (1) and (2):
(1) having the amino acid sequence shown in SEQ ID NO: 39, in which the N-terminus of the amino acid sequence of wild-type hGBA shown in SEQ ID NO: 37 is linked to the C-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO: 3 via a linker having the amino acid sequence shown in SEQ ID NO: 9;
(2) Having the amino acid sequence shown in SEQ ID NO: 41, in which the N-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO: 3 is linked to the C-terminus of the amino acid sequence of wild-type hGBA shown in SEQ ID NO: 37 via a linker having the amino acid sequence shown in SEQ ID NO: 9.

In one embodiment of the present invention, the fusion protein of HSA and hGALC is characterized in that when expressed in a host cell as a recombinant protein, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the expression amount of hGALC in the culture supernatant is increased in terms of concentration or enzyme activity compared to when wild-type hGALC is expressed in a host cell as a recombinant protein under the same conditions. Therefore, when the fusion protein of HSA and hGALC is produced as a recombinant protein, the production efficiency can be increased compared to wild-type hGALC, and production costs can be reduced. In one embodiment of the present invention, the fusion protein of HSA and hGBA is characterized in that when expressed in a host cell as a recombinant protein, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the expression amount of hGBA in the culture supernatant is increased in terms of concentration or enzyme activity compared to when wild-type hGBA is expressed in a host cell as a recombinant protein under the same conditions. Therefore, when the fusion protein of HSA and hGBA is produced as a recombinant protein, the production efficiency can be increased compared to wild-type hGBA, and production costs can be reduced. It is known that pharmaceuticals that contain recombinant proteins as active ingredients are very expensive. Therefore, even increasing the amount of recombinant protein obtained by a few percent, for example 3-9%, when produced under the same conditions can have a significant economic effect. The same can be said about human lysosomal enzymes, such as hGALC and hGBA.

In this specification, when comparing the expression levels of a fusion protein of HSA and hGALC expressed in a host cell as a recombinant protein with wild-type hGALC expressed in a host cell under the same conditions, it is preferable to compare the GALC enzyme activity of the expressed protein rather than the mass of the expressed protein. The same applies to the expression levels of a fusion protein of HSA and hGBA, a fusion protein of SA of a non-human animal species and hGALC or hGBA, and a fusion protein of SA of a non-human animal species and GALC or GBA of a non-human animal species, for example, a fusion protein of MSA and mGALC or mGBA.

HSA/hGALC fusion protein and HSA/hGBA fusion protein can be produced as recombinant proteins by culturing host cells transformed with an expression vector incorporating a gene encoding the fusion protein.

The host cells used in this case are not particularly limited as long as they are capable of expressing a fusion protein of HSA and hGALC or a fusion protein of HSA and hGBA by introducing such an expression vector, and may be any eukaryotic cell such as a mammalian cell, yeast, plant cell, or insect cell, although mammalian cells are particularly preferred.

When mammalian cells are used as host cells, there is no particular limitation on the type of mammalian cell, but cells derived from humans, mice, or Chinese hamsters are preferred, and in particular CHO cells derived from Chinese hamster ovary cells or NS/0 cells derived from mouse myeloma are preferred. In this case, the expression vector used to incorporate and express a DNA fragment containing a gene encoding a fusion protein of HSA and hGALC or a fusion protein of HSA and hGBA can be used without particular limitation as long as it brings about expression of the gene when introduced into a mammalian cell. The gene incorporated in the expression vector is placed downstream of a DNA sequence (gene expression control site) that can regulate the frequency of gene transcription in mammalian cells. Examples of gene expression control sites that can be used in the present invention include a promoter derived from cytomegalovirus, an SV40 early promoter, a human elongation factor-1α (EF-1α) promoter, and a human ubiquitin C promoter.

Expression vectors are known in which glutamine synthetase (GS) is placed as a selection marker downstream of a gene encoding a target protein via an internal ribosome entry site (IRES) (International Patent Publications WO2012/063799, WO2013/161958). The expression vectors described in these publications are particularly suitable for producing fusion proteins of HSA and hGALC or fusion proteins of HSA and hGBA.

In one embodiment of the present invention, the term "internal ribosome binding site" refers to a region (structure) present within an mRNA strand to which a ribosome can directly bind and initiate translation independent of a cap structure, or a region (structure) of a DNA strand that generates the region by being transcribed. In addition, in the present invention, the term "gene encoding an internal ribosome binding site" refers to a region (structure) of a DNA strand that generates the region by being transcribed. Internal ribosome binding sites are generally called IRES (internal ribosome entry sites), and have been found in the 5' untranslated regions of viruses such as Picornaviridae viruses (poliovirus, rhinovirus, mouse encephalomyocarditis virus, etc.), foot and mouth disease virus, hepatitis A virus, hepatitis C virus, coronavirus, bovine enteric virus, Theiler's murine encephalomyelitis virus, and Coxsackie B virus, as well as in the 5' untranslated regions of genes such as human immunoglobulin heavy chain binding protein, Drosophila antennapedia, and Drosophila ultravithorax. In the case of picornaviruses, the IRES is a region of approximately 450 bp that exists in the 5' untranslated region of the mRNA. Here, the "5' untranslated region of the virus" refers to the 5' untranslated region of the viral mRNA, or the region (structure) of the DNA strand that produces said region by being transcribed.

For example, an expression vector for expressing a target protein, which comprises a first gene expression control site, a gene encoding the protein downstream of the first gene expression control site, an internal ribosome binding site further downstream, and a gene encoding glutamine synthetase further downstream, and further comprises a dihydrofolate reductase gene or a drug resistance gene downstream of the first gene expression control site or a second gene expression control site different from the first gene expression control site, can be suitably used for producing a fusion protein of HSA and hGALC or a fusion protein of HSA and hGBA. In this expression vector, the first gene expression control site or the second gene expression control site can be suitably used with a promoter derived from cytomegalovirus, an SV40 early promoter, a human elongation factor-1α promoter (hEF-1α promoter), or a human ubiquitin C promoter, with the hEF-1α promoter being particularly suitable.

Furthermore, as the internal ribosome binding site, those derived from the 5' untranslated region of the genome of a virus selected from the group consisting of a virus of the picornavirus family (including mouse encephalomyocarditis virus), foot and mouth disease virus, hepatitis A virus, hepatitis C virus, coronavirus, bovine enteric virus, Theiler's murine encephalomyelitis virus, and Coxsackie B virus, or a gene selected from the group consisting of the human immunoglobulin heavy chain binding protein gene, the Drosophila antennapedia gene, and the Drosophila ultravithorax gene, are preferably used, but an internal ribosome binding site derived from the 5' untranslated region of the mouse encephalomyocarditis virus genome is particularly preferable. When using an internal ribosome binding site derived from the 5' untranslated region of the mouse encephalomyocarditis virus genome, in addition to the wild type, one in which some of the multiple initiation codons contained in the wild type internal ribosome binding site have been destroyed can also be preferably used. Furthermore, in this expression vector, the drug resistance gene preferably used is a puromycin or neomycin resistance gene, and more preferably a puromycin resistance gene.

Also, for example, an expression vector for expressing a target protein, which contains a human elongation factor-1α promoter, a gene encoding the protein downstream thereof, an internal ribosome binding site derived from the 5' untranslated region of the mouse encephalomyocarditis virus genome further downstream thereof, and a gene encoding glutamine synthetase further downstream thereof, and further contains another gene expression control site and a dihydrofolate reductase gene downstream thereof, in which the internal ribosome binding site is an internal ribosome binding site in which some of the multiple initiation codons contained in the wild-type internal ribosome binding site have been destroyed, can be suitably used for producing a fusion protein of HSA and hGALC or a fusion protein of HSA and hGBA. Examples of such expression vectors include the expression vectors described in WO2013/161958.

Also, for example, an expression vector for expressing a target protein, which contains a human elongation factor-1α promoter, a gene encoding the protein downstream thereof, an internal ribosome binding site derived from the 5' untranslated region of the mouse encephalomyocarditis virus genome further downstream thereof, and a gene encoding glutamine synthetase further downstream thereof, and further contains another gene expression control site and a drug resistance gene downstream thereof, in which the internal ribosome binding site is an internal ribosome binding site in which some of the multiple initiation codons contained in the wild-type internal ribosome binding site have been destroyed, can be suitably used for producing a fusion protein of HSA and hGALC or a fusion protein of HSA and hGBA. Examples of such expression vectors include pE-mIRES-GS-puro described in WO2012/063799 and pE-mIRES-GS-mNeo described in WO2013/161958.

The 3' end of the internal ribosome binding site derived from the 5' untranslated region of the wild-type murine encephalomyocarditis virus genome contains three initiation codons (ATG). The above pE-mIRES-GS-puro and pE-mIRES-GS-mNeo are expression vectors that have an IRES in which some of the initiation codons have been destroyed.

　The fusion protein of HSA and hGALC or the fusion protein of HSA and hGBA can be expressed in cells or in a medium by culturing a host cell into which an expression vector incorporating a gene encoding the protein has been introduced. The method of expressing the fusion protein of HSA and hGALC or the fusion protein of HSA and hGBA when the host cell is a mammalian cell is described in detail below.

As a medium for culturing mammalian cells, any medium that can be used for culturing and growing mammalian cells can be used without any particular limitations, but preferably a serum-free medium is used. In the present invention, a serum-free medium used as a medium for producing recombinant proteins is preferably one containing, for example, 3 to 700 mg/L amino acids, 0.001 to 50 mg/L vitamins, 0.3 to 10 g/L monosaccharides, 0.1 to 10,000 mg/L inorganic salts, 0.001 to 0.1 mg/L trace elements, 0.1 to 50 mg/L nucleosides, 0.001 to 10 mg/L fatty acids, 0.01 to 1 mg/L biotin, 0.1 to 20 μg/L hydrocortisone, 0.1 to 20 mg/L insulin, 0.1 to 10 mg/L vitamin B12, 0.01 to 1 mg/L putrescine, 10 to 500 mg/L sodium pyruvate and a water-soluble iron compound. If desired, thymidine, hypoxanthine, conventional pH indicators, antibiotics, etc. may be added to the medium.

As a serum-free medium used as a medium for recombinant protein production, DMEM/F12 medium (mixture of DMEM and F12) may be used as a basic medium, and these media are well known to those skilled in the art. Furthermore, as a serum-free medium, DMEM(HG)HAM Improved (R5) medium, which contains sodium bicarbonate, L-glutamine, D-glucose, insulin, sodium selenite, diaminobutane, hydrocortisone, ferrous sulfate (II), asparagine, aspartic acid, serine, and polyvinyl alcohol, may be used. Furthermore, commercially available serum-free media, such as CD OptiCHO ^TM medium, CHO-S-SFM II medium, or CD CHO medium (Thermo Fisher Scientific), EX-CELL ^TM 302 medium, or EX-CELL ^TM 325-PF medium (SAFC Biosciences), may be used as a basic medium.

The fusion protein of HSA and hGALC is characterized in that when host cells into which an expression vector incorporating a gene encoding the fusion protein has been introduced are cultured in the above-mentioned serum-free medium to be expressed as a recombinant protein, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the amount of hGALC expressed in the culture supernatant is at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or enzyme activity, compared to when wild-type hGALC is expressed as a recombinant protein in host cells under the same conditions.

　Furthermore, when a fusion protein of HSA and hGBA is expressed as a recombinant protein by culturing a host cell into which an expression vector incorporating a gene encoding the fusion protein has been introduced in the above-mentioned serum-free medium, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the expression amount of hGBA in the culture supernatant is at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, for example, 1.1 to 4 times, 1.5 to 3.6 times, 2 to 3.6 times, 10 to 20 times, etc., in terms of concentration or enzyme activity, compared to when wild-type hGBA is expressed as a recombinant protein in a host cell under the same conditions. Here, "under the same conditions" means that the expression vector, host cell, culture conditions, etc. are the same. The host cell used in this case is preferably a mammalian cell, particularly a normal cell used for producing recombinant proteins, such as a CHO cell or an NS/0 cell.

When wild-type hGALC is expressed as a recombinant using a host cell transformed with an expression vector incorporating a gene encoding it, it is difficult to efficiently produce it as a recombinant due to reasons such as a decrease in the viability of the host cell. However, by expressing hGALC as a fusion protein with HSA, the decrease in the viability of the host cell observed when wild-type hGALC is expressed is suppressed. When a fusion protein of HSA and hGALC is expressed as a recombinant protein by culturing mammalian cells into which an expression vector incorporating a gene encoding it has been introduced in a serum-free medium, especially when the recombinant protein is expressed so that it is secreted from the cells and accumulated in the culture medium, the expression amount increases compared to when wild-type hGALC is expressed as a recombinant protein under the same conditions. It is considered that the suppression of the decrease in viability contributes to this increase in the expression amount. The same applies to a fusion protein of SA of an animal species other than human and hGALC, and a fusion protein of SA of an animal species other than human and GALC of an animal species other than human. The host cell used for expressing the fusion protein is preferably a mammalian cell, particularly a normal cell used for producing recombinant proteins such as CHO cells and NS/0 cells. That is, one embodiment of the present invention is a recombinant fusion protein between SA and GALC, in particular a recombinant fusion protein between HSA and hGALC.

The decrease in the survival rate of host cells when hGALC and hGBA are expressed means that the number of dead cells increases. The contents of dead cells leak out, becoming contaminants, and a process for removing the contaminants is required in the subsequent purification process of the expressed fusion protein. In other words, by expressing hGALC and hGBA in the form of a fusion protein with HSA, the number of dead cells generated during culture can be reduced, and contaminants can be reduced, making it easier to purify the expressed fusion protein. This also increases the purification efficiency during purification. It also reduces the amount of contaminants contained in the purified fusion protein.

　By culturing a host cell encoding a fusion protein of HSA and hGALC or a fusion protein of HSA and hGBA, it can be expressed in cells or in a medium. These fusion proteins can be separated from impurities and purified by methods such as column chromatography. The purified fusion protein of HSA and hGALC or fusion protein of HSA and hGBA can be used as a pharmaceutical composition. In particular, the fusion protein of HSA and hGALC can be used as a pharmaceutical composition for treating Krabbe disease (galactosylceramide lipidosis or globoid cell leukodystrophy). In particular, the fusion protein of HSA and hGBA can be used as a pharmaceutical composition for treating Gaucher disease. In this specification, the term "pharmaceutical composition" refers to a composition that contains a fusion protein as an active ingredient as well as a pharma- ceutical acceptable excipient.

　A pharmaceutical composition containing the fusion protein of HSA and hGALC or the fusion protein of HSA and hGBA as an active ingredient can be administered intravenously, intramuscularly, intraperitoneally, subcutaneously, or intracerebroventricularly as an injection. These injections can be supplied as freeze-dried preparations or aqueous liquid preparations. In the case of an aqueous liquid preparation, it may be in the form of being filled in a vial, or it can be supplied as a prefilled preparation in which it is filled in a syringe in advance. In the case of a freeze-dried preparation, it is dissolved in an aqueous medium before use and reconstituted for use. In the fusion protein of HSA and hGALC or the fusion protein of HSA and hGBA contained in the aqueous liquid preparation, the ratio of monomer to total protein (monomer mass/total protein mass x 100 (%)) is preferably 70% or more, more preferably 80% or more, even more preferably 90% or more, for example 95% or more. The same can be said for a solution obtained by dissolving a freeze-dried preparation in an aqueous medium and reconstituting it.

The fusion protein of HSA and hGALC or the fusion protein of HSA and hGBA can be further bound to an antibody or a ligand. For example, the fusion protein of HSA and hGALC in one embodiment of the present invention can be bound to an antibody or a ligand capable of specifically binding to a receptor on cerebrovascular endothelial cells. For example, the fusion protein of HSA and hGBA in one embodiment of the present invention can be bound to an antibody or a ligand capable of specifically binding to a receptor on cerebrovascular endothelial cells. The fusion protein of HSA and hGALC or the fusion protein of HSA and hGBA can bind to a receptor on cerebrovascular endothelial cells by being bound to an antibody or a ligand capable of specifically binding to a receptor on cerebrovascular endothelial cells. The fusion protein bound to the receptor on cerebrovascular endothelial cells can pass through the blood-brain barrier (BBB) and reach the tissues of the central nervous system (CNS). Therefore, by combining a fusion protein of HSA and hGALC or a fusion protein of HSA and hGBA with such an antibody or ligand, it is possible to pass through the blood-brain barrier (BBB) and exert its function in the central nervous system (CNS).

In the present invention, the term "ligand" refers to a substance having affinity for a specific substance, particularly a protein having affinity for a specific substance. In one embodiment of the present invention, such a ligand is a substance, particularly a protein, having affinity for a receptor present on cerebrovascular endothelial cells. Examples of receptors present on cerebrovascular endothelial cells include insulin receptors, transferrin receptors, leptin receptors, lipoprotein receptors, and IGF receptors, particularly, but not limited to, transferrin receptors. The receptors are preferably human-derived receptors. Ligands for insulin receptors, transferrin receptors, leptin receptors, lipoprotein receptors, and IGF receptors are insulin, transferrin, leptin, lipoprotein, and IGF (IGF-1 and IGF-2), respectively. These ligands may be full-length or fragments thereof as long as they have affinity for the receptors, and may be wild-type or mutants in which substitutions, deletions, and/or additions have been introduced into the wild-type.

When hGALC is said to have the function of hGALC in a conjugate of an antibody and a fusion protein of HSA and hGALC, it means that hGALC has a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, for example 90% or more, 95% or more, when the specific activity of normal wild-type hGALC is taken as 100%. Note that the specific activity of hGALC in the conjugate is calculated by multiplying the enzyme activity of hGALC per unit mass of the conjugate (μM/hour/mg protein) by (molecular weight of the conjugate/molecular weight of the portion of the conjugate corresponding to hGALC).

In addition, when hGBA in a conjugate of an antibody and a fusion protein of HSA and hGBA is said to have the function of hGBA, it means that, when the specific activity of normal wild-type hGBA is taken as 100%, hGBA has a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, for example 90% or more, 95% or more. Here, the specific activity of hGBA in the conjugate is calculated by multiplying the enzyme activity of hGBA per unit mass of the conjugate (μM/hour/mg protein) by (molecular weight of the conjugate/molecular weight of the portion of the conjugate corresponding to hGBA).

In one embodiment of the present invention, a conjugate of an antibody and a fusion protein of HSA and hGALC refers to a conjugate characterized in that when the conjugate is expressed as a recombinant protein in host cells, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the expression amount of hGALC in the culture supernatant is at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or enzyme activity, compared to when wild-type hGALC is expressed as a recombinant protein in host cells under the same conditions. Furthermore, in one embodiment of the present invention, a conjugate of an antibody and a fusion protein of HSA and hGBA is characterized in that when the conjugate is expressed as a recombinant protein in a host cell, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the amount of hGBA expressed in the culture supernatant is at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or enzyme activity, compared to when wild-type hGBA is expressed as a recombinant protein in a host cell under the same conditions, such as 1.1 to 4 times, 1.5 to 3.6 times, 2 to 3.6 times, 10 to 20 times, etc.

Some cytokines, particularly interleukins, are difficult to mass-produce when expressed as recombinant proteins using host cells into which an expression vector incorporating a gene encoding the wild-type cytokine is introduced, because the expression level is limited. IL-10 is one such interleukin. One embodiment of the present invention is a recombinant protein in which such a cytokine that is difficult to produce as a recombinant protein is fused with SA. Such a recombinant protein can be mass-produced more easily than the corresponding wild-type cytokine using host cells into which an expression vector incorporating a gene encoding the cytokine is introduced. Here, there is no particular restriction on the animal species of the cytokine to be bound to SA, but it is preferably a human cytokine. There is also no particular restriction on the animal species of the SA to be bound to the cytokine, but it is preferably HSA.

In this specification, when the term "human cytokine" is used simply, it includes not only normal wild-type human cytokines, but also mutant human cytokines in which one or more amino acid residues have been substituted, deleted, and/or added to the amino acid sequence of a wild-type human cytokine (as used herein, "addition" of an amino acid residue means adding a residue to the end or inside of the sequence), without any particular distinction, so long as the mutant has the function of a human cytokine, such as having physiological activity corresponding to the type of human cytokine in question. The same applies to cytokines of animal species other than humans. The same also applies to interleukins.

When a human cytokine is said to have the function of a human cytokine, it means that the human cytokine preferably retains a specific activity of 10% or more, more preferably a specific activity of 20% or more, even more preferably a specific activity of 50% or more, and even more preferably a specific activity of 80% or more, when the specific activity of a normal wild-type human cytokine is taken as 100%. Here, specific activity refers to the physiological activity per mass of the protein. The specific activity of a fusion protein of a human cytokine and another protein is determined as the physiological activity per mass of the portion of the fusion protein that corresponds to the human cytokine. Here, the specific activity of the human cytokine in the fusion protein is calculated by multiplying the physiological activity of the human cytokine per unit mass of the fusion protein by (the molecular weight of the fusion protein/the molecular weight of the portion of the fusion protein that corresponds to the human cytokine). The same applies to cytokines of animal species other than humans. The same also applies to interleukins.

When amino acid residues in the amino acid sequence of a wild-type human cytokine are replaced with other amino acid residues, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When amino acid residues in the amino acid sequence of a wild-type human cytokine are deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. A human cytokine mutant consisting of an amino acid sequence in which one amino acid residue is deleted from the N-terminus or C-terminus of a wild-type human cytokine, a human cytokine mutant consisting of an amino acid sequence in which two amino acid residues are deleted from the N-terminus or C-terminus of a wild-type human cytokine, and the like are also human cytokines. In addition, a mutation that combines the substitution and deletion of these amino acid residues can be added to the amino acid sequence of a wild-type human cytokine. The same applies to cytokines of animal species other than humans. The same applies to interleukins.

When adding amino acid residues to the amino acid sequence of a wild-type human cytokine, one or more amino acid residues are added into the amino acid sequence of the human cytokine or to the N-terminus or C-terminus of the amino acid sequence. The number of amino acid residues added in this case is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. Mutations that combine the addition of these amino acid residues with the above-mentioned substitutions can also be added to the amino acid sequence of a wild-type human cytokine, and mutations that combine the addition of these amino acid residues with the above-mentioned deletions can also be added to the amino acid sequence of a wild-type human cytokine. The same applies to cytokines of animal species other than humans. The same applies to interleukins.

Furthermore, a combination of the three types of mutations mentioned above, namely substitution, deletion, and addition of amino acid residues, can be added to the amino acid sequence of a wild-type human cytokine. For example, a human cytokine is one in which 1 to 10 amino acid residues are deleted from the amino acid sequence of a wild-type human cytokine, 1 to 10 amino acid residues are substituted with other amino acid residues, and 1 to 10 amino acid residues are added; a human cytokine is one in which 1 to 5 amino acid residues are deleted from the amino acid sequence of a wild-type human cytokine, 1 to 5 amino acid residues are substituted with other amino acid residues, and 1 to 5 amino acid residues are added; a human cytokine is one in which 1 to 3 amino acid residues are deleted from the amino acid sequence of a wild-type human cytokine, 1 to 3 amino acid residues are substituted with other amino acid residues, and 1 to 3 amino acid residues are added; a human cytokine is one in which 1 or 2 amino acid residues are deleted from the amino acid sequence of a wild-type human cytokine, 1 or 2 amino acid residues are substituted with other amino acid residues, and 1 or 2 amino acid residues are added; and a human cytokine is one in which 1 amino acid residue is deleted from the amino acid sequence of a wild-type human cytokine, 1 amino acid residue is substituted with other amino acid residues, and 1 amino acid residue is added. The same is true for cytokines in non-human animal species, and also for interleukins.

The location and type (deletion, substitution, and addition) of each mutation in a human cytokine mutant compared to a normal wild-type human cytokine can be easily confirmed by aligning the amino acid sequences of both human cytokines. The same is true for cytokines of non-human animal species, and also for interleukins.

The amino acid sequence of the human cytokine mutant preferably has 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more or 99% or more identity, to the amino acid sequence of a normal wild-type human cytokine. The same applies to cytokines of animal species other than humans. The same also applies to interleukins.

In this specification, when simply referring to "human interleukin 10", "human IL-10", or "hIL-10", it includes not only the normal wild-type hIL-10 consisting of 160 amino acid residues as shown in SEQ ID NO:24, but also includes, without any particular distinction, mutants of hIL-10 in which one or more amino acid residues have been substituted, deleted, and/or added (as used herein, "addition" of an amino acid residue means adding a residue to the end or inside of the sequence) to the amino acid sequence as shown in SEQ ID NO:24, so long as they have the functions of hIL-10, such as having physiological activity as an inhibitory cytokine that calms the immune response. Wild-type hIL-10 is encoded, for example, by a gene having the base sequence as shown in SEQ ID NO:49. The same applies to IL-10 of animal species other than humans.

Here, when hIL-10 is said to have the function of hIL-10, it means that hIL-10 retains a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, when the specific activity of normal wild-type hIL-10 is taken as 100%. Here, specific activity refers to the physiological activity per mass of the protein. The specific activity of a fusion protein of hIL-10 and another protein is calculated as the physiological activity per mass of the portion of the fusion protein that corresponds to hIL-10. Here, the specific activity of hIL-10 in the fusion protein is calculated by multiplying the physiological activity of hIL-10 per unit mass of the fusion protein by (molecular weight of the fusion protein/molecular weight of the portion of the fusion protein that corresponds to hIL-10). The same applies to IL-10 from animal species other than humans.

When amino acid residues in the amino acid sequence of wild-type hIL-10 are replaced with other amino acid residues, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When amino acid residues in the amino acid sequence of wild-type hIL-10 are deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. A mutant hIL-10 consisting of 159 amino acid residues obtained by deleting one amino acid residue at the N-terminus or C-terminus of wild-type hIL-10, and a mutant hIL-10 consisting of 158 amino acid residues obtained by deleting two amino acid residues at the N-terminus or C-terminus of wild-type hIL-10, etc. are also hIL-10. In addition, a mutation that combines the substitution and deletion of these amino acid residues can be added to the amino acid sequence of wild-type hIL-10. The same applies to IL-10 of animal species other than humans.

When amino acid residues are added to the amino acid sequence of wild-type hIL-10, one or more amino acid residues are added into the amino acid sequence of hIL-10 or to the N-terminus or C-terminus of the amino acid sequence. The number of amino acid residues added in this case is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. Mutations that combine the addition of these amino acid residues with the above-mentioned substitutions can also be added to the amino acid sequence of wild-type hIL-10, and mutations that combine the addition of these amino acid residues with the above-mentioned deletions can also be added to the amino acid sequence of wild-type hIL-10. The same applies to IL-10 from animal species other than humans.

Furthermore, a combination of the above three types of mutations, substitution, deletion, and addition of amino acid residues, can be added to the amino acid sequence of wild-type hIL-10. For example, a wild-type hIL-10 amino acid sequence shown in SEQ ID NO:24 in which 1 to 10 amino acid residues have been deleted, 1 to 10 amino acid residues have been replaced with other amino acid residues, and 1 to 10 amino acid residues have been added is also hIL-10, a wild-type hIL-10 amino acid sequence shown in SEQ ID NO:24 in which 1 to 5 amino acid residues have been deleted, 1 to 5 amino acid residues have been replaced with other amino acid residues, and 1 to 5 amino acid residues have been added is also hIL-10, and a wild-type hIL-10 amino acid sequence shown in SEQ ID NO:24 in which 1 to 3 amino acid residues have been deleted, hIL-10 also includes the wild-type hIL-10 amino acid sequence shown in SEQ ID NO:24 in which one or two amino acid residues have been deleted, one or two amino acid residues have been replaced with other amino acid residues, and one or two amino acid residues have been added. hIL-10 also includes the wild-type hIL-10 amino acid sequence shown in SEQ ID NO:24 in which one amino acid residue has been deleted, one amino acid residue has been replaced with other amino acid residue, and one amino acid residue has been added. The same applies to IL-10 from animal species other than humans.

The location and type (deletion, substitution, and addition) of each mutation in the hIL-10 mutant compared to normal wild-type hIL-10 can be easily confirmed by aligning the amino acid sequences of both hIL-10. The same is true for IL-10 from animal species other than humans.

The amino acid sequence of the hIL-10 mutant preferably has 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more, or 99% or more identity, to the amino acid sequence of normal wild-type hIL-10 shown in SEQ ID NO: 24. The same applies to IL-10 of animal species other than humans.

The substitution of an amino acid in the amino acid sequence of a wild-type human cytokine with another amino acid, the substitution of an amino acid in the amino acid sequence of a wild-type human cytokine with another amino acid, and the substitution of an amino acid in the amino acid sequence of a wild-type hIL-10 with another amino acid are preferably conservative amino acid substitutions. The same applies to cytokines, interleukins, and IL-10 of animal species other than human.

　The above wild-type or mutant human cytokines in which the constituent amino acids are modified with sugar chains are also human cytokines. The above wild-type or mutant human cytokines in which the constituent amino acids are modified with phosphate are also human cytokines. Those modified with something other than sugar chains and phosphate are also human cytokines. The above wild-type or mutant human cytokines in which the side chains of the constituent amino acids have been converted by substitution reactions or the like are also human cytokines. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same applies to cytokines of animal species other than humans. The same applies to interleukins and IL-10.

In other words, human cytokines modified with sugar chains are included in human cytokines with the original amino acid sequence. Human cytokines modified with phosphate are included in human cytokines with the original amino acid sequence. Cytokines modified with substances other than sugar chains and phosphate are also included in human cytokines with the original amino acid sequence. Cytokines in which the side chains of the amino acids that make up human cytokines have been changed by substitution reactions or the like are also included in human cytokines with the original amino acid sequence. Such changes include, but are not limited to, the conversion of cysteine residues to formylglycine. The same applies to cytokines of animal species other than humans. The same applies to interleukins and IL-10.

In one embodiment of the present invention, a wild-type human cytokine is produced as a recombinant protein fused with HSA. When such a fusion protein is expressed as a recombinant protein using a host cell such as CHO, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the amount of expression of the human cytokine in the culture supernatant can be at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or physiological activity, compared to when the wild-type human cytokine is expressed as a recombinant protein by a similar method. For example, 1.1 to 4 times, 1.5 to 3.6 times, 2 to 3.6 times, 3 to 4 times, etc.

In one embodiment of the present invention, hIL-10 is produced as a recombinant protein fused with HSA. When such a fusion protein is expressed as a recombinant protein using a host cell such as CHO, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the amount of expression of hIL-10 in the culture supernatant can be at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or physiological activity, compared to when wild-type hIL-10 is expressed as a recombinant protein by a similar method. For example, 1.1 to 4 times, 1.5 to 3.6 times, 2 to 3.6 times, 3 to 4 times, etc.

In other words, one embodiment of the present invention is a fusion protein in which a polypeptide containing the amino acid sequence of a cytokine is bound to a polypeptide containing the amino acid sequence of an SA. Here, "binding polypeptides" refers to binding different polypeptides by covalent bonding, either directly or indirectly via a linker. Here, the cytokine and SA are preferably of human origin.

Another embodiment of the present invention is a fusion protein in which a polypeptide containing the amino acid sequence of IL-10 is bound to a polypeptide containing the amino acid sequence of SA. Here, the term "binding polypeptides" refers to binding different polypeptides by covalent bonding, either directly or indirectly via a linker. Here, IL-10 and SA are preferably of human origin.

A common method for linking two different polypeptides is, for example, to create an expression vector incorporating a DNA fragment in which a gene encoding one polypeptide is linked in-frame downstream of a gene encoding the other polypeptide, and then to express the resulting protein as a recombinant protein by culturing a host cell transformed with this expression vector. The resulting recombinant protein is a single-chain polypeptide in which the two polypeptides are peptide-linked, either directly or via different amino acid sequences.

In one embodiment of the present invention, the term "SA-human cytokine fusion protein" or "SA-human cytokine" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of a human cytokine is linked to the C-terminus of the amino acid sequence of SA, either directly or via a linker, and which has the function of a human cytokine. Here, the animal species of the SA is not particularly limited, but it is preferably a mammalian SA, more preferably a primate SA, and even more preferably HSA. When it is said that a human cytokine in an SA-human cytokine fusion protein has the function of a human cytokine, it means that the human cytokine has a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, when the specific activity of a normal wild-type human cytokine is taken as 100%. Here, the specific activity of the human cytokine in the SA-human cytokine fusion protein is calculated by multiplying the physiological activity of the human cytokine per unit mass of the fusion protein by (the molecular weight of the fusion protein/the molecular weight of the portion of the fusion protein corresponding to the human cytokine).

In one embodiment of the present invention, the term "HSA-human cytokine fusion protein" or "HSA-human cytokine" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of a human cytokine is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of HSA, and which has the function of a human cytokine. When it is said here that the HSA-human cytokine fusion protein has the function of a human cytokine, the definition of the SA-human cytokine fusion protein described above can be applied.

In the SA-human cytokine fusion protein, it is preferable that the SA has a function as an SA, such as the function of binding and transporting endogenous substances in the blood and exogenous substances such as drugs, but is not limited to this. The same is true for the HSA-human lysosomal enzyme fusion protein.

When mutations are added to an HSA-human cytokine fusion protein, which is a fusion protein of wild-type HSA and wild-type human cytokine, mutations can be added only to the HSA portion and not to the human cytokine portion, mutations can be added only to the human cytokine portion without mutations to the HSA portion, or mutations can be added to both the HSA portion and the human cytokine portion. When mutations are added only to the HSA portion, the amino acid sequence of the portion is the amino acid sequence of the wild-type HSA with a mutation added. When mutations are added only to the human cytokine portion, the amino acid sequence of the portion is the amino acid sequence of the wild-type human cytokine with a mutation added. When mutations are added to both the HSA portion and the human cytokine portion, the amino acid sequence of the HSA portion is the amino acid sequence of the wild-type HSA with a mutation added, and the amino acid sequence of the human cytokine portion is the amino acid sequence of the wild-type human cytokine with a mutation added. The same can be said for fusion proteins of wild-type SA of animal species other than humans and human cytokine.

　HSA-human cytokine fusion proteins in which the amino acids constituting the protein are modified with sugar chains are also HSA-human cytokine fusion proteins. HSA-human cytokine fusion proteins in which the amino acids constituting the protein are modified with phosphate are also HSA-human cytokine fusion proteins. HSA-human cytokine fusion proteins modified with something other than sugar chains and phosphate are also HSA-human cytokine fusion proteins. HSA-human cytokine fusion proteins in which the side chains of the amino acids constituting the protein have been converted by substitution reactions or the like are also HSA-human cytokine fusion proteins. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for fusion proteins of SA of animal species other than humans and human cytokines (SA-human cytokine).

In other words, HSA-human cytokine fusion proteins modified with sugar chains are included in HSA-human cytokine fusion proteins having the original amino acid sequence. Also, HSA-human cytokine fusion proteins modified with phosphate are included in HSA-human cytokine fusion proteins having the original amino acid sequence. Also, those modified with things other than sugar chains and phosphate are also included in HSA-human cytokine fusion proteins having the original amino acid sequence. Also, those in which the side chains of the amino acids constituting the HSA-human cytokine fusion proteins have been converted by substitution reactions or the like are also included in HSA-human cytokine fusion proteins having the original amino acid sequence. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for fusion proteins of SA of other animals and human cytokines (SA-human cytokines). The same can be said for fusion proteins of SA of animal species other than humans and human cytokines (SA-human cytokines).

　Also, HSA-human cytokine fusion proteins in which the human cytokine that constitutes it is a precursor of the human cytokine are also HSA-human cytokine fusion proteins. The term "precursor" here refers to a type that is biosynthesized as an HSA-human cytokine fusion protein, and after the biosynthesis, the part that functions as a human cytokine is separated from the fusion protein during the manufacturing process or in the living body when administered to the living body, and can function as a human cytokine by itself. In this case, after the HSA-human cytokine fusion protein is biosynthesized, it may be cleaved at a specific site by a hydrolase or the like, and the part containing HSA and the part containing the mature human cytokine may be separated. In this case, the human cytokine obtained is not a fusion protein with HSA, but the HSA-human cytokine fusion protein is synthesized once during the process of manufacturing the cytokine. Therefore, when human cytokine is manufactured by such a method, the manufacturing method is included in the manufacturing method of HSA-human cytokine. The same can be said for a fusion protein of SA of an animal species other than human and a human cytokine (SA-human cytokine), and a fusion protein of SA of an animal species other than human and a cytokine of an animal species other than human, such as MSA-mouse cytokine fusion protein.

In one embodiment of the present invention, the term "SA-hIL-10 fusion protein" or "SA-hIL-10" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of hIL-10 is linked to the C-terminus of the amino acid sequence of SA, either directly or via a linker, and which has the function of hIL-10. Here, there is no particular limitation on the animal species of the SA, but it is preferably a mammalian SA, more preferably a primate SA, and even more preferably HSA. When it is said that hIL-10 in the SA-hIL-10 fusion protein has the function of hIL-10, it means that hIL-10 retains a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, when the specific activity of normal wild-type hIL-10 is taken as 100%. Here, the specific activity of hIL-10 in the SA-hIL-10 fusion protein is calculated by multiplying the physiological activity of hIL-10 per unit mass of the fusion protein by (molecular weight of the fusion protein/molecular weight of the portion of the fusion protein corresponding to hIL-10).

In one embodiment of the present invention, the term "HSA-hIL-10 fusion protein" or "HSA-hIL-10" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of hIL-10 is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of HSA, and which has the function of hIL-10. When it is said that the HSA-hIL-10 fusion protein has the function of hIL-10, the definition of the SA-hIL-10 fusion protein described above can be applied. Furthermore, in these fusion proteins, it is preferable that the SA has the function of SA, such as the function of binding and transporting endogenous substances in the blood and exogenous substances such as drugs, but this is not limited to this.

In one embodiment of the present invention, a preferred HSA-hIL-10 fusion protein has, for example, the amino acid sequence shown in SEQ ID NO: 50. The HSA-hIL-10 fusion protein shown in SEQ ID NO: 50 is a protein in which wild-type hIL-10 is directly bound to the C-terminus of wild-type HSA. The HSA-hIL-10 fusion protein shown in SEQ ID NO: 50 is encoded by a gene having, for example, the base sequence shown in SEQ ID NO: 51. In addition, HSA-hIL-10 fusion proteins also include those having an amino acid sequence in which one or more amino acid residues in the amino acid sequence shown in SEQ ID NO: 50 have been replaced with other amino acid residues, deleted, or mutated by addition, as long as they have the function of hIL-10. It is preferable that the HSA-hIL-10 fusion protein has the function of human serum albumin, such as the function of binding and transporting endogenous substances in blood and exogenous substances such as drugs, but is not limited thereto.

The position and type (deletion, substitution, and addition) of each mutation when the amino acid sequence shown in SEQ ID NO:50 is mutated can be easily confirmed by alignment of the amino acid sequence before and after the mutation. The mutated amino acid sequence preferably exhibits 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more or 99% or more identity, with the amino acid sequence shown in SEQ ID NO:50.

When mutations are added to an HSA-hIL-10 fusion protein, which is a fusion protein of wild-type HSA and wild-type hIL-10, mutations can be added only to the HSA portion and not to the hIL-10 portion, mutations can be added only to the hIL-10 portion without mutations to the HSA portion, or mutations can be added to both the HSA portion and the hIL-10 portion. When mutations are added only to the HSA portion, the amino acid sequence of the portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above. When mutations are added only to the hIL-10 portion, the amino acid sequence of the portion is the amino acid sequence of hIL-10 obtained by adding a mutation to the wild-type hIL-10 described above. When mutations are added to both the HSA portion and the hIL-10 portion, the amino acid sequence of the HSA portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above, and the amino acid sequence of the hIL-10 portion is the amino acid sequence of hIL-10 obtained by adding a mutation to the wild-type hIL-10 described above. The same is true for the HSA-hIL-10 fusion protein having the amino acid sequence shown in SEQ ID NO: 50. The same is true for a fusion protein of wild-type SA and wild-type hIL-10 of an animal species other than human.

The following is an example of a case where a mutation is made to an HSA-hIL-10 fusion protein having the amino acid sequence shown in SEQ ID NO:50. When an amino acid residue in the amino acid sequence shown in SEQ ID NO:50 is replaced with another amino acid residue, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is added, one or more amino acid residues are added to the amino acid sequence shown in SEQ ID NO:50 or to the N-terminus or C-terminus of the amino acid sequence. The HSA-hIL-10 fusion protein may be a combination of these substitutions, deletions, and additions of amino acid residues. The mutation may be made only to the HSA part, only to the hIL-10 part, or to both parts.

The position and type (deletion, substitution, and addition) of each mutation when the amino acid sequence shown in SEQ ID NO:50 is mutated can be easily confirmed by alignment of the amino acid sequence before and after the mutation. The mutated amino acid sequence preferably exhibits 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more, or 99% or more identity, with the amino acid sequence shown in SEQ ID NO:50.

　HSA-hIL-10 fusion proteins in which the amino acids constituting the protein are modified with sugar chains are also HSA-hIL-10 fusion proteins. HSA-hIL-10 fusion proteins in which the amino acids constituting the protein are modified with phosphate are also HSA-hIL-10 fusion proteins. HSA-hIL-10 fusion proteins modified with anything other than sugar chains and phosphate are also HSA-hIL-10 fusion proteins. HSA-hIL-10 fusion proteins in which the side chains of the amino acids constituting the protein are changed by substitution reactions, etc. Examples of such changes include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for fusion proteins of SA and hIL-10 of other animals (SA-hIL-10). The same can be said for fusion proteins of SA and hIL-10 of animal species other than humans (SA-hIL-10).

In other words, HSA-hIL-10 fusion proteins modified with sugar chains are included in HSA-hIL-10 fusion proteins having the original amino acid sequence. Also, HSA-hIL-10 fusion proteins modified with phosphate are included in HSA-hIL-10 fusion proteins having the original amino acid sequence. Also, those modified with something other than sugar chains and phosphate are included in HSA-hIL-10 fusion proteins having the original amino acid sequence. Also, HSA-hIL-10 fusion proteins in which the side chains of the amino acids constituting the HSA-hIL-10 fusion proteins have been changed by substitution reactions or the like are included in HSA-hIL-10 fusion proteins having the original amino acid sequence. Such changes include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for fusion proteins of SA and hIL-10 of animal species other than humans (SA-hIL-10).

　Also, HSA-hIL-10 fusion proteins in which the constituent hIL-10 is a precursor of hIL-10 are also HSA-hIL-10 fusion proteins. Here, the term "precursor" refers to a type that is biosynthesized as an HSA-hIL-10 fusion protein, and after the biosynthesis, the part that functions as hIL-10 is cleaved from the fusion protein during the manufacturing process or in the living body when administered to the living body, and can function as hIL-10 by itself. In this case, after the HSA-hIL-10 fusion protein is biosynthesized, it may be cleaved at a specific site by a hydrolase or the like, and the part containing HSA and the part containing mature hIL-10 may be separated. In this case, the obtained hIL-10 is not a fusion protein with HSA, but the HSA-hIL-10 fusion protein is synthesized once during the process of synthesizing the hIL-10. Therefore, when hIL-10 is produced by such a method, the production method is included in the method for producing HSA-hIL-10 fusion protein. The same can be said about the fusion protein of SA and hIL-10 from non-human animal species (SA-hIL-10).

In one embodiment of the present invention, the term "human cytokine-SA fusion protein" or "human cytokine-SA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of SA is linked, directly or via a linker, to the C-terminus of the amino acid sequence of a human cytokine, and which has a function as a human cytokine. When a human cytokine in a human cytokine-SA fusion protein is said to have a function as a human cytokine, it means that the human cytokine retains a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, when the specific activity of a normal wild-type human cytokine is taken as 100%. Here, the specific activity of the human cytokine in the human cytokine-SA fusion protein is calculated by multiplying the physiological activity of the human cytokine per unit mass of the fusion protein by (the molecular weight of the fusion protein/the molecular weight of the portion of the fusion protein corresponding to the human cytokine).

In one embodiment of the present invention, the term "human cytokine-HSA fusion protein" or "human cytokine-HSA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of HSA is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of a human cytokine, and which has the function of a human cytokine. When it is said that the human cytokine-HSA fusion protein has the function of a human cytokine, the definition of human cytokine-SA above can be adopted.

In the human cytokine-SA fusion protein, it is preferable that the SA has a function as an SA, such as the function of binding and transporting endogenous substances in the blood and exogenous substances such as drugs, but is not limited to this. The same is true for the human cytokine-HSA fusion protein.

When mutations are introduced into a human cytokine-HSA fusion protein, which is a fusion protein of a wild-type human cytokine and a wild-type HSA, mutations can be introduced only into the human cytokine portion and not into the HSA portion, mutations can be introduced only into the HSA portion without mutations in the human cytokine portion, or mutations can be introduced into both the human cytokine portion and the HSA portion. When mutations are introduced only into the human cytokine portion, the amino acid sequence of the portion is the amino acid sequence of the human cytokine obtained by mutating the wild-type human cytokine described above. When mutations are introduced only into the HSA portion, the amino acid sequence of the portion is the amino acid sequence of the HSA obtained by mutating the wild-type HSA described above. When mutations are introduced into both the human cytokine portion and the HSA portion, the amino acid sequence of the human cytokine portion is the amino acid sequence of the human cytokine obtained by mutating the wild-type human cytokine described above, and the amino acid sequence of the HSA portion is the amino acid sequence of the HSA obtained by mutating the wild-type HSA described above. The same can be said about a fusion protein between a wild-type human cytokine and the wild-type SA of an animal species other than human.

　A human cytokine-HSA fusion protein in which the amino acids constituting the protein are modified with sugar chains is also a human cytokine-HSA fusion protein. A human cytokine-HSA fusion protein in which the amino acids constituting the protein are modified with phosphate is also a human cytokine-HSA fusion protein. A human cytokine-HSA fusion protein modified with something other than sugar chains and phosphate is also a human cytokine-HSA fusion protein. A human cytokine-HSA fusion protein in which the side chains of the amino acids constituting the protein have been modified by a substitution reaction or the like is also a human cytokine-HSA fusion protein. Such a conversion includes, but is not limited to, the conversion of a cysteine residue to formylglycine. The same can be said about a fusion protein of a human cytokine and SA of an animal species other than human (human cytokine-SA).

In other words, a human cytokine-HSA fusion protein modified with a sugar chain is included in the human cytokine-HSA fusion protein having the original amino acid sequence. A human cytokine-HSA fusion protein modified with phosphate is included in the human cytokine-HSA fusion protein having the original amino acid sequence. A human cytokine-HSA fusion protein modified with something other than a sugar chain or phosphate is also included in the human cytokine-HSA fusion protein having the original amino acid sequence. A human cytokine-HSA fusion protein in which the side chains of the amino acids constituting the human cytokine-HSA fusion protein have been changed by a substitution reaction or the like is also included in the human cytokine-HSA fusion protein having the original amino acid sequence. Such a change includes, but is not limited to, the change of a cysteine residue to formylglycine. The same can be said about a fusion protein of a human cytokine and SA of an animal species other than human (human cytokine-SA).

　Furthermore, a human cytokine-HSA fusion protein in which the constituent human cytokine is a precursor of a human cytokine is also a human cytokine-HSA fusion protein. The same can be said for a fusion protein of a human cytokine and SA of an animal species other than human (human cytokine-SA).

In one embodiment of the present invention, the term "hIL-10-SA fusion protein" or "hIL-10-SA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of SA is linked, directly or via a linker, to the C-terminus of the amino acid sequence of hIL-10, and which has the function of hIL-10. When hIL-10 in the hIL-10-SA fusion protein is said to have the function of hIL-10, it means that hIL-10 retains a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, when the specific activity of normal wild-type hIL-10 is taken as 100%. Here, the specific activity of hIL-10 in the hIL-10-SA fusion protein is calculated by multiplying the physiological activity of hIL-10 per unit mass of the fusion protein by (the molecular weight of the fusion protein/the molecular weight of the portion of the fusion protein corresponding to hIL-10).

In one embodiment of the present invention, the term "hIL-10-HSA fusion protein" or "hIL-10-HSA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of HSA is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of hIL-10, and which has the function of hIL-10. When it is said that the hIL-10-HSA fusion protein has the function of hIL-10, the definition of hIL-10-SA above can be applied. In addition, in these fusion proteins, it is preferable that the SA has the function of SA, such as the function of binding and transporting endogenous substances in the blood and exogenous substances such as drugs, but this is not limited to this.

In one embodiment of the present invention, a preferred hIL-10-HSA fusion protein has, for example, the amino acid sequence shown in SEQ ID NO: 52. The hIL-10-HSA fusion protein shown in SEQ ID NO: 52 is a fusion protein in which wild-type HSA is directly bound to the C-terminus of wild-type hIL-10. The hIL-10-HSA fusion protein shown in SEQ ID NO: 52 is encoded by a gene having, for example, the base sequence shown in SEQ ID NO: 53. In addition, the hIL-10-HSA fusion protein also includes an amino acid sequence in which one or more amino acid residues in the amino acid sequence shown in SEQ ID NO: 52 are replaced with other amino acid residues, deleted, or mutated by addition, as long as it has the function of hIL-10. The hIL-10-HSA fusion protein is preferably one that has the function of human serum albumin, such as the function of binding and transporting endogenous substances in blood and exogenous substances such as drugs, but is not limited thereto.

The position and type (deletion, substitution, and addition) of each mutation when the amino acid sequence shown in SEQ ID NO:52 is mutated can be easily confirmed by alignment of the amino acid sequence before and after the mutation. The mutated amino acid sequence preferably exhibits 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more or 99% or more identity, with the amino acid sequence shown in SEQ ID NO:52.

When mutations are introduced into the hIL-10-HSA fusion protein, which is a fusion protein of wild-type hIL-10 and wild-type HSA, mutations can be introduced only in the HSA portion and not in the hIL-10 portion, mutations can be introduced only in the hIL-10 portion without mutations in the HSA portion, or mutations can be introduced in both the HSA portion and the hIL-10 portion. When mutations are introduced only in the HSA portion, the amino acid sequence of the portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above. When mutations are introduced only in the hIL-10 portion, the amino acid sequence of the portion is the amino acid sequence of hIL-10 obtained by adding a mutation to the wild-type hIL-10 described above. When mutations are introduced in both the HSA portion and the hIL-10 portion, the amino acid sequence of the HSA portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above, and the amino acid sequence of the hIL-10 portion is the amino acid sequence of hIL-10 obtained by adding a mutation to the wild-type hIL-10 described above. The same is true for the hIL-10-HSA fusion protein having the amino acid sequence shown in SEQ ID NO: 52. The same is true for the fusion protein of wild-type hIL-10 and wild-type SA (hIL-10-SA) of an animal species other than human.

The following is an example of a case where a mutation is made to a hIL-10-HSA fusion protein having the amino acid sequence shown in SEQ ID NO:52. When an amino acid residue in the amino acid sequence shown in SEQ ID NO:52 is replaced with another amino acid residue, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is added, one or more amino acid residues are added to the amino acid sequence shown in SEQ ID NO:52 or to the N-terminus or C-terminus of the amino acid sequence. The hIL-10-HSA fusion protein may be a combination of these substitutions, deletions, and additions of amino acid residues. The mutation may be made only to the HSA portion, only to the hIL-10 portion, or both portions.

　hIL-10-HSA fusion proteins in which the amino acids constituting the fusion protein are modified with sugar chains are also hIL-10-HSA fusion proteins. In addition, hIL-10-HSA fusion proteins in which the amino acids constituting the fusion protein are modified with phosphate are also hIL-10-HSA fusion proteins. In addition, hIL-10-HSA fusion proteins modified with anything other than sugar chains and phosphate are also hIL-10-HSA fusion proteins. In addition, hIL-10-HSA fusion proteins in which the side chains of the amino acids constituting the fusion protein are changed by a substitution reaction or the like are also hIL-10-HSA fusion proteins. Such changes include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said about fusion proteins of SA and hIL-10 of animal species other than humans (SA-hIL-10).

In other words, hIL-10-HSA fusion proteins modified with sugar chains are included in the hIL-10-HSA fusion proteins having the original amino acid sequence. Also, hIL-10-HSA fusion proteins modified with phosphate are included in the hIL-10-HSA fusion proteins having the original amino acid sequence. Also, those modified with something other than sugar chains and phosphate are also included in the hIL-10-HSA fusion proteins having the original amino acid sequence. Also, those in which the side chains of the amino acids constituting the hIL-10-HSA fusion protein have been changed by a substitution reaction or the like are also included in the hIL-10-HSA fusion proteins having the original amino acid sequence. Such changes include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for fusion proteins of SA and hIL-10 of animal species other than humans (SA-hIL-10).

　Also, a hIL-10-HSA fusion protein in which the constituent hIL-10 is a precursor of hIL-10 is also a hIL-10-HSA fusion protein. The same can be said for a fusion protein of SA and hIL-10 of a non-human animal species (SA-hIL-10). The same can be said for a fusion protein of SA and hIL-10 of a non-human animal species (SA-hIL-10), and a fusion protein of SA and IL-10 of a non-human animal species, such as a fusion protein of MSA-mouse IL-10.

In one embodiment of the present invention, the terms "HSA and human cytokine fusion protein", "human cytokine and HSA fusion protein", or "human serum albumin and human cytokine fusion protein" include both the above-mentioned "HSA-human cytokine fusion protein" and "human cytokine HSA fusion protein". In addition, the terms "HSA and hIL-10 fusion protein", "hIL-10 and HSA fusion protein", or "human serum albumin and human cytokine 10 fusion protein" include both the above-mentioned "HSA-hIL-10 fusion protein" and "hIL-10-HSA fusion protein".

　The manufacturing method and other details of the fusion protein of HSA and hIL-10 are described below, but these descriptions can also be applied when the cytokine is other than IL-10, when the SA is from an animal species other than human, or when the cytokine is from an animal species other than human. For example, they also apply to a fusion protein of SA of an animal species other than human and hIL-10, and a fusion protein of SA of an animal species other than human and IL-10 of an animal species other than human.

In one embodiment of the fusion protein, the SA and the cytokine are linked directly or via a linker. Here, the term "linker" refers to a portion that does not belong to either the amino acid sequence of the SA or the amino acid sequence of the cytokine. In other words, the linker is a peptide chain that is interposed between the SA and the cytokine. The linker has various functions. These functions include a function between the SA and the cytokine to link the SA and the cytokine, a function to reduce mutual interference between the SA and the cytokine by increasing the distance between them within the fusion protein molecule, and a function between the SA and the cytokine to act as a hinge that connects the SA and the cytokine and gives flexibility to the three-dimensional structure of the fusion protein. Within the fusion protein molecule, the linker exerts at least one of these functions. This is the same, for example, whether the SA is HSA or whether the cytokine is a human cytokine, such as hIL-10.

In the fusion protein of SA and a cytokine, the amino acid sequence of the peptide linker is not particularly limited as long as it functions as a linker in the fusion protein molecule. The length of the peptide linker is also not particularly limited as long as it functions as a linker in the fusion protein molecule. The peptide linker is composed of one or more amino acids. When the peptide linker is composed of multiple amino acids, the number of amino acids is preferably 2 to 50, more preferably 5 to 30, and even more preferably 10 to 25. Suitable examples of peptide linkers include those consisting of Gly-Ser, Gly-Gly-Ser, or amino acid sequences shown in SEQ ID NOs: 9 to 11 (collectively referred to as basic sequences), and those containing these. For example, the peptide linker is one that contains an amino acid sequence in which the basic sequence is repeated 2 to 10 times, one that contains an amino acid sequence in which the basic sequence is repeated 2 to 6 times, or one that contains an amino acid sequence in which the basic sequence is repeated 3 to 5 times. One or more amino acids in these amino acid sequences may be deleted, replaced with other amino acids, added, etc. When deleting an amino acid, the number of amino acids to be deleted is preferably 1 or 2. When replacing an amino acid with another amino acid, the number of amino acids to be replaced is preferably 1 or 2. When adding an amino acid, the number of amino acids to be added is preferably 1 or 2. The amino acid sequence of the desired linker portion can be obtained by combining these deletions, substitutions, and additions of amino acids. The peptide linker may be composed of one amino acid, and the amino acid that constitutes the linker is, for example, glycine or serine.

The fusion protein of HSA and hIL-10 can be produced as a recombinant protein by creating an expression vector incorporating a DNA fragment in which a gene encoding hIL-10 is linked in-frame to the downstream or upstream of a gene encoding HSA, and then culturing a host cell transformed with this expression vector. The fusion protein produced as a recombinant protein in this way consists of a single polypeptide chain.

When producing a fusion protein as a recombinant fusion protein, a gene encoding hIL-10 can be linked in-frame downstream of a gene encoding HSA to obtain an HSA-hIL-10 fusion protein having the amino acid sequence of hIL-10 at the C-terminus of the amino acid sequence of HSA. Conversely, a gene encoding hIL-10 can be linked in-frame upstream of a gene encoding HSA to obtain an hIL-10-HSA fusion protein having the amino acid sequence of hIL-10 at the N-terminus of the amino acid sequence of HSA. In either case, the fusion protein produced as a recombinant fusion protein is a single-chain polypeptide.

When the amino acid sequence of HSA is located on the N-terminal side of the amino acid sequence of hIL-10 within the single-chain polypeptide of the fusion protein, the C-terminus of HSA and the N-terminus of hIL-10 are bound directly by a peptide bond or via a linker. Figure 5 shows a schematic diagram of an HSA-hIL-10 fusion protein, a single-chain polypeptide having HSA, a linker, and hIL-10 in that order from the N-terminus. In the HSA-hIL-10 fusion protein, the C-terminus of HSA is bound to the N-terminus of the linker by a peptide bond, and the C-terminus of the linker is bound to the N-terminus of hIL-10 by a peptide bond.

In addition, when the amino acid sequence of hIL-10 is located at the N-terminus of the amino acid sequence of HSA within the single-chain polypeptide of the fusion protein, the C-terminus of hIL-10 and the N-terminus of HSA are bound directly by a peptide bond or via a linker. Figure 6 shows a schematic diagram of a hIL-10-HSA fusion protein, which is a single-chain polypeptide having hIL-10, a linker, and HSA in that order from the N-terminus. In the hIL-10-HSA fusion protein, the C-terminus of hIL-10 is bound to the N-terminus of the linker by a peptide bond, and the C-terminus of the linker is bound to the N-terminus of HSA by a peptide bond.

In one embodiment of the present invention, the fusion protein of HSA and hIL-10 refers to a fusion protein characterized in that when expressed in a host cell as a recombinant protein, particularly when expressed so that the recombinant protein is secreted from the cells and accumulated in the culture medium, the amount of expression of hIL-10 in the culture supernatant is at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or physiological activity, compared to when wild-type hIL-10 is expressed in a host cell as a recombinant protein under the same conditions. Here, "under the same conditions" means that the expression vector, host cell, culture conditions, etc. are the same. The preferred host cells used in this case are mammalian cells such as CHO cells and NS/0 cells, but particularly CHO cells.

Preferred embodiments of the fusion protein of HSA and hIL-10 include the following (1) to (4):
(1) A substance having an amino acid sequence shown in SEQ ID NO:50, in which the N-terminus of the amino acid sequence of wild-type hIL-10 shown in SEQ ID NO:24 is directly linked to the C-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO:3;
(2) Having the amino acid sequence shown in SEQ ID NO:52, in which the N-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO:3 is directly linked to the C-terminus of the amino acid sequence of wild-type hIL-10 shown in SEQ ID NO:24.
(3) A polypeptide having an amino acid sequence represented by SEQ ID NO:54, in which the N-terminus of the amino acid sequence of wild-type hIL-10 represented by SEQ ID NO:24 is linked to the C-terminus of the amino acid sequence of wild-type HSA represented by SEQ ID NO:3 via a linker represented by SEQ ID NO:9;
(4) Having the amino acid sequence shown in SEQ ID NO:55, in which the N-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO:3 is linked to the C-terminus of the amino acid sequence of wild-type hIL-10 shown in SEQ ID NO:24 via a linker shown in SEQ ID NO:9.

Furthermore, preferred embodiments of the fusion protein of HSA and hIL-10 include human serum albumin (HSA-A320T) consisting of 585 amino acids as shown in SEQ ID NO:13, in which the 320th amino acid residue from the N-terminus of the amino acid sequence of wild-type HSA as shown in SEQ ID NO:3 is replaced with threonine, and further include the following (5) to (8):
(5) A peptide having an amino acid sequence shown in SEQ ID NO:56, in which the N-terminus of the amino acid sequence of wild-type hIL-10 shown in SEQ ID NO:24 is directly linked to the C-terminus of the amino acid sequence of human serum albumin (HSA-A320T) shown in SEQ ID NO:13;
(6) The C-terminus of the amino acid sequence of wild-type hIL-10 shown in SEQ ID NO:24 is directly linked to the N-terminus of the amino acid sequence of human serum albumin (HSA-A320T) shown in SEQ ID NO:13, and the overall amino acid sequence is shown in SEQ ID NO:57.
(7) A peptide having an amino acid sequence represented by SEQ ID NO:58, in which the N-terminus of the amino acid sequence of wild-type hIL-10 represented by SEQ ID NO:24 is linked to the C-terminus of the amino acid sequence of human serum albumin (HSA-A320T) represented by SEQ ID NO:13 via a linker represented by SEQ ID NO:9;
(8) Having the amino acid sequence shown in SEQ ID NO:59, in which the N-terminus of the amino acid sequence of human serum albumin (HSA-A320T) shown in SEQ ID NO:13 is linked to the C-terminus of the amino acid sequence of wild-type hIL-10 shown in SEQ ID NO:24 via a linker shown in SEQ ID NO:9.

In one embodiment of the present invention, the fusion protein of HSA and hIL-10 is characterized in that when expressed in a host cell as a recombinant protein, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the amount of hIL-10 expressed in the culture supernatant is increased in terms of concentration or physiological activity, compared to when wild-type hIL-10 is expressed in a host cell as a recombinant protein under the same conditions. Therefore, when produced as a recombinant protein, the fusion protein of HSA and hIL-10 can increase the production efficiency compared to wild-type hIL-10, and therefore can reduce production costs. It is known that pharmaceuticals containing recombinant proteins as active ingredients are very expensive. Therefore, even increasing the amount of recombinant protein obtained when produced under the same conditions by a few percent, for example 3 to 9%, has a significant economic effect. The same can be said for cytokines, such as hIL-10.

In this specification, when comparing the expression levels of a fusion protein of HSA and hIL-10 expressed in a host cell as a recombinant protein with wild-type hIL-10 expressed in a host cell under the same conditions as a recombinant protein, the comparison is not based on the mass of the expressed protein, but on the number of molecules of the expressed protein or the hIL-10 physiological activity. The same applies to fusion proteins of SA and hIL-10 from animal species other than human, and fusion proteins of SA and other cytokines.

The fusion protein of HSA and hIL-10 can be produced using an expression vector, host cell, medium, etc. that can be used to produce the above-mentioned fusion protein of HSA and hGALC or the fusion protein of HSA and hGBA. The same can be said for fusion proteins of SA and cytokines in general.
is preferred

The fusion protein of HSA and hIL-10 is characterized in that when host cells into which an expression vector incorporating a gene encoding this protein has been introduced are cultured in the above-mentioned serum-free medium to be expressed as a recombinant protein, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the amount of expression of hIL-10 in the culture supernatant is at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or physiological activity, compared to when wild-type hIL-10 is expressed as a recombinant protein in host cells under the same conditions. Here, "under the same conditions" means that the expression vector, host cells, culture conditions, etc. are the same. The host cells used in this case are preferably mammalian cells, particularly ordinary cells used for producing recombinant proteins such as CHO cells and NS/0 cells.

　Wild-type hIL-10 tends to have a low expression level when expressed as a recombinant using host cells transformed with an expression vector incorporating a gene encoding it, making it difficult to efficiently mass-produce it as a recombinant. However, by expressing hIL-10 as a fusion protein with HSA, the expression level of the recombinant can be increased. In other words, when a host into which an expression vector incorporating a gene encoding it has been introduced is cultured in a serum-free medium and expressed as a recombinant protein, especially when the recombinant protein is expressed so that it is secreted from the cells and accumulated in the culture medium, the fusion protein of HSA and hIL-10 can be expressed more efficiently than when wild-type hIL-10 is expressed as a recombinant protein under the same conditions, making it suitable for mass production. The same applies to fusion proteins of SA and hIL-10 of animal species other than humans. The host cells used to express the fusion protein are preferably mammalian cells, especially ordinary cells used for producing recombinant proteins such as CHO cells and NS/0 cells. That is, one embodiment of the present invention is a recombinant fusion protein of SA and IL-10, particularly a recombinant fusion protein of HSA and hIL-10.

By culturing host cells encoding the fusion protein of HSA and hIL-10, it can be expressed in cells or in the medium. The fusion protein of HSA and hIL-10 can be purified by separating it from impurities using methods such as column chromatography. The purified fusion protein of HSA and hIL-10 can be used as a pharmaceutical composition. In particular, the fusion protein of HSA and hIL-10 can be used as a pharmaceutical composition targeting inflammatory diseases or cancer.

　A pharmaceutical composition containing a fusion protein of HSA and hIL-10 as an active ingredient can be administered intravenously, intramuscularly, intraperitoneally, subcutaneously, or intracerebroventricularly as an injection. These injections can be supplied as lyophilized preparations or aqueous liquid preparations. In the case of an aqueous liquid preparation, it may be in the form of a vial filled with the drug, or it can be supplied as a prefilled preparation in a syringe. In the case of a lyophilized preparation, it is dissolved in an aqueous medium and reconstituted before use.

The fusion protein of HSA and hIL-10 can further be conjugated with an antibody or a ligand. For example, in one embodiment of the present invention, the fusion protein of HSA and hIL-10 can be conjugated with an antibody or a ligand capable of specifically binding to a receptor on cerebrovascular endothelial cells. The fusion protein of HSA and hIL-10 or the fusion protein of HSA and hGBA can bind to a receptor on cerebrovascular endothelial cells by being conjugated with an antibody or a ligand capable of specifically binding to a receptor on cerebrovascular endothelial cells. The fusion protein bound to the receptor on cerebrovascular endothelial cells can pass through the blood-brain barrier (BBB) and reach the tissues of the central nervous system (CNS). Therefore, the fusion protein of HSA and hIL-10 can be conjugated with such an antibody or ligand to pass through the blood-brain barrier (BBB) and exert its function in the central nervous system (CNS).

When hIL-10 in a conjugate of an antibody and a fusion protein of HSA and hIL-10 is said to have the function of hIL-10, it means that, when the specific activity of normal wild-type hIL-10 is taken as 100%, hIL-10 has a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, for example 90% or more, 95% or more. Here, the specific activity of hIL-10 in the conjugate is calculated by multiplying the physiological activity of hIL-10 per unit mass of the conjugate by (the molecular weight of the conjugate/the molecular weight of the portion of the conjugate corresponding to hIL-10).

In one embodiment of the present invention, a conjugate of an antibody and a fusion protein of HSA and hIL-10 refers to a conjugate characterized in that when the conjugate is expressed as a recombinant protein in a host cell, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the amount of expression of hIL-10 in the culture supernatant is at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or physiological activity, compared to when wild-type hIL-10 is expressed as a recombinant protein in a host cell under the same conditions.

Some neurotrophic factors are relatively difficult to produce in large quantities when expressed as recombinant proteins using host cells introduced with an expression vector incorporating a gene encoding the wild-type neurotrophic factor, due to limited expression levels. Examples of such neurotrophic factors include BDNF (brain-derived neurotrophic factor), NGF (nerve growth factor), NT-3 (neurotrophin-3), NT-4 (neurotrophin-4), and NT-5 (neurotrophin-5). The difference in structure between NT-4 and NT-5 is an interspecies variation, and since these are considered to be the same factor, they may be referred to as NT-4/5, etc., but in this specification, they will be referred to as NT-4. One embodiment of the present invention is a recombinant protein in which such a neurotrophic factor, which is relatively difficult to produce as a recombinant protein, is fused with SA. Such a recombinant protein can be produced in large quantities more easily using host cells introduced with an expression vector incorporating a gene encoding the recombinant protein, compared to the corresponding neurotrophic factor. Here, there is no particular restriction on the animal species of the neurotrophic factor to be bound to SA, but human neurotrophic factor is preferable. In addition, there are no particular limitations on the animal species of SA to be bound to the neurotrophic factor, but HSA is preferred.

In this specification, when the term "human neurotrophic factor" is used, it includes not only normal wild-type human neurotrophic factor, but also mutant human neurotrophic factors in which one or more amino acid residues have been substituted, deleted, and/or added (in this specification, "addition" of an amino acid residue means adding a residue to the end or inside of the sequence) to the amino acid sequence of the wild-type human neurotrophic factor, as long as the mutant has the function of a human neurotrophic factor, such as having physiological activity corresponding to the type of human neurotrophic factor. The same applies to neurotrophic factors of animal species other than humans.

Here, when it is said that a human neurotrophic factor has a function as a human neurotrophic factor, it means that the human neurotrophic factor has a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, when the specific activity of a normal wild-type human neurotrophic factor is taken as 100%. Here, specific activity refers to the physiological activity per mass of the protein. The specific activity of a fusion protein of a human neurotrophic factor and another protein is calculated as the physiological activity per mass of the portion of the fusion protein that corresponds to the human neurotrophic factor. Here, the specific activity of the human neurotrophic factor in the fusion protein is calculated by multiplying the physiological activity of the human neurotrophic factor per unit mass of the fusion protein by (the molecular weight of the fusion protein/the molecular weight of the portion of the fusion protein that corresponds to the human neurotrophic factor). The same applies to neurotrophic factors of animal species other than humans.

When amino acid residues in the amino acid sequence of wild-type human neurotrophic factor are replaced with other amino acid residues, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When amino acid residues in the amino acid sequence of wild-type human neurotrophic factor are deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. A human neurotrophic factor mutant consisting of an amino acid sequence in which one amino acid residue is deleted from the N-terminus or C-terminus of wild-type human neurotrophic factor, a human neurotrophic factor mutant consisting of an amino acid sequence in which two amino acid residues are deleted from the N-terminus or C-terminus of wild-type human neurotrophic factor, etc. are also human neurotrophic factors. In addition, a mutation that combines the substitution and deletion of these amino acid residues can be added to the amino acid sequence of wild-type human neurotrophic factor. The same applies to neurotrophic factors of animal species other than humans.

When adding amino acid residues to the amino acid sequence of wild-type human neurotrophic factor, one or more amino acid residues are added into the amino acid sequence of human neurotrophic factor or to the N-terminus or C-terminus of the amino acid sequence. The number of amino acid residues added in this case is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. Mutations that combine the addition of these amino acid residues with the above-mentioned substitutions can also be added to the amino acid sequence of wild-type human neurotrophic factor, and mutations that combine the addition of these amino acid residues with the above-mentioned deletions can also be added to the amino acid sequence of wild-type human neurotrophic factor. The same applies to neurotrophic factors of animal species other than humans.

Furthermore, a combination of the above three types of mutations, substitution, deletion, and addition of amino acid residues, can be added to the amino acid sequence of wild-type human neurotrophic factor. For example, a human neurotrophic factor obtained by deleting 1 to 10 amino acid residues from the amino acid sequence of wild-type human neurotrophic factor, substituting 1 to 10 amino acid residues with other amino acid residues, and adding 1 to 10 amino acid residues is also a human neurotrophic factor, a human neurotrophic factor obtained by deleting 1 to 5 amino acid residues from the amino acid sequence of wild-type human neurotrophic factor, substituting 1 to 5 amino acid residues with other amino acid residues, and adding 1 to 5 amino acid residues is also a human neurotrophic factor, and a human neurotrophic factor obtained by deleting 1 to 3 amino acid residues from the amino acid sequence of wild-type human neurotrophic factor, and adding 1 to 3 amino acid residues is also a human neurotrophic factor. Human neurotrophic factors are those in which an amino acid residue has been replaced with another amino acid residue and one to three amino acid residues have been added. Human neurotrophic factors are also those in which one or two amino acid residues have been deleted from the amino acid sequence of wild-type human neurotrophic factors, one or two amino acid residues have been replaced with another amino acid residue, and one or two amino acid residues have been added. Human neurotrophic factors are also those in which one amino acid residue has been deleted from the amino acid sequence of wild-type human neurotrophic factors, one amino acid residue has been replaced with another amino acid residue, and one amino acid residue has been added. The same applies to neurotrophic factors of animal species other than humans.

The location and type (deletion, substitution, and addition) of each mutation in a human neurotrophic factor mutant compared to normal wild-type human neurotrophic factor can be easily confirmed by aligning the amino acid sequences of both human neurotrophic factors. The same applies to neurotrophic factors of animal species other than humans.

The amino acid sequence of the human neurotrophic factor mutant preferably has 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more, or 99% or more identity, to the amino acid sequence of a normal wild-type human neurotrophic factor. The same applies to neurotrophic factors of animal species other than humans.

The substitution of an amino acid in the amino acid sequence of wild-type human neurotrophic factor with another amino acid is preferably a conservative amino acid substitution. The same applies to neurotrophic factors of animal species other than humans.

　The above wild-type or mutant human neurotrophic factors in which the constituent amino acids are modified with sugar chains are also human neurotrophic factors. The above wild-type or mutant human neurotrophic factors in which the constituent amino acids are modified with phosphate are also human neurotrophic factors. In addition, human neurotrophic factors modified with something other than sugar chains and phosphate are also human neurotrophic factors. In addition, the above wild-type or mutant human neurotrophic factors in which the side chains of the constituent amino acids have been converted by a substitution reaction or the like are also human neurotrophic factors. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same applies to neurotrophic factors of animal species other than humans.

In other words, human neurotrophic factors modified with sugar chains are included in human neurotrophic factors with the original amino acid sequence. Human neurotrophic factors modified with phosphate are included in human neurotrophic factors with the original amino acid sequence. Human neurotrophic factors modified with things other than sugar chains and phosphate are also included in human neurotrophic factors with the original amino acid sequence. Human neurotrophic factors in which the side chains of the amino acids that make up human neurotrophic factors have been converted by substitution reactions or the like are also included in human neurotrophic factors with the original amino acid sequence. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same applies to neurotrophic factors of animal species other than humans.

In this specification, when simply referring to "human brain-derived neurotrophic factor," "human BDNF," or "hBDNF," it includes not only the normal wild-type hBDNF consisting of 119 amino acid residues as shown in SEQ ID NO: 60, but also includes, without any particular distinction, mutants of hBDNF in which one or more amino acid residues have been substituted, deleted, and/or added (as used herein, "addition" of an amino acid residue means adding a residue to the end or inside of the sequence) to the amino acid sequence as shown in SEQ ID NO: 60, as long as they have the functions of hBDNF, such as binding to the specific receptor TrkB on the surface of target cells and having physiological activity as a neurotrophic factor that promotes the development, growth, maintenance, and regeneration of nerve cells. Wild-type hBDNF is, for example, encoded by a gene having the base sequence as shown in SEQ ID NO: 61. The same applies to BDNF of animal species other than humans.

When hBDNF is said to have the function of hBDNF, it means that hBDNF preferably retains a specific activity of 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, of the specific activity of normal wild-type hBDNF taken as 100%. Here, specific activity refers to the physiological activity per mass of protein. The specific activity of a fusion protein of hBDNF and another protein is determined as the physiological activity per mass of the portion of the fusion protein that corresponds to hBDNF. The specific activity of hBDNF in the fusion protein is calculated by multiplying the physiological activity of hBDNF per unit mass of the fusion protein by (molecular weight of the fusion protein/molecular weight of the portion of the fusion protein that corresponds to hBDNF). The same applies to BDNF of animal species other than humans.

When amino acid residues in the amino acid sequence of wild-type hBDNF are replaced with other amino acid residues, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When amino acid residues in the amino acid sequence of wild-type hBDNF are deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. hBDNF mutants consisting of 118 amino acid residues obtained by deleting one amino acid residue at the N-terminus or C-terminus of wild-type hBDNF, and hBDNF mutants consisting of 117 amino acid residues obtained by deleting two amino acid residues at the N-terminus or C-terminus of wild-type hBDNF are also hBDNF. Mutations that combine the substitution and deletion of these amino acid residues can also be added to the amino acid sequence of wild-type hBDNF. The same applies to BDNF of animal species other than humans.

When amino acid residues are added to the amino acid sequence of wild-type hBDNF, one or more amino acid residues are added into the amino acid sequence of hBDNF or to the N-terminus or C-terminus of the amino acid sequence. The number of amino acid residues added in this case is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. Mutations that combine the addition of these amino acid residues with the above-mentioned substitutions can also be added to the amino acid sequence of wild-type hBDNF, and mutations that combine the addition of these amino acid residues with the above-mentioned deletions can also be added to the amino acid sequence of wild-type hBDNF. The same applies to BDNF of animal species other than humans.

Furthermore, a combination of the above three types of mutations, substitution, deletion, and addition of amino acid residues, can be added to the amino acid sequence of wild-type hBDNF. For example, a wild-type hBDNF shown in SEQ ID NO:60 in which 1 to 10 amino acid residues have been deleted, 1 to 10 amino acid residues have been replaced with other amino acid residues, and 1 to 10 amino acid residues have been added is also hBDNF, a wild-type hBDNF shown in SEQ ID NO:60 in which 1 to 5 amino acid residues have been deleted, 1 to 5 amino acid residues have been replaced with other amino acid residues, and 1 to 5 amino acid residues have been added is also hBDNF, and a wild-type hBDNF shown in SEQ ID NO:60 in which 1 to 3 amino acid residues have been deleted, hBDNF is also obtained by deleting one or two amino acid residues from the amino acid sequence of wild-type hBDNF shown in SEQ ID NO:60, substituting one or two amino acid residues with other amino acid residues, and adding one or two amino acid residues. hBDNF is also obtained by deleting one amino acid residue from the amino acid sequence of wild-type hBDNF shown in SEQ ID NO:60, substituting one amino acid residue with other amino acid residues, and adding one amino acid residue. The same applies to BDNF of animal species other than humans.

The location and type (deletion, substitution, and addition) of each mutation in the hBDNF mutant compared to normal wild-type hBDNF can be easily confirmed by aligning the amino acid sequences of both hBDNFs. The same is true for BDNFs of animal species other than humans.

The amino acid sequence of the hBDNF mutant preferably has 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more, or 99% or more identity, to the amino acid sequence of normal wild-type hBDNF shown in SEQ ID NO:60.

In this specification, when simply referring to "human nerve growth factor", "human NGF" or "hNGF", it includes, without distinction, not only the usual wild-type hNGF consisting of the 120 amino acid residues shown in SEQ ID NO: 62, but also mutants of hNGF in which one or more amino acid residues have been substituted, deleted and/or added (in this specification, "addition" of an amino acid residue means adding a residue to the end or inside of the sequence) to the amino acid sequence shown in SEQ ID NO: 62, as long as they have the functions of hNGF, such as the physiological activity as a neurotrophic factor, such as the action of promoting the extension of nerve axons and the synthesis of neurotransmitters, the action of maintaining nerve cells, the action of repairing damaged cells, and the action of promoting the recovery of brain nerve functions and preventing aging. Wild-type hNGF is, for example, encoded by a gene having the base sequence shown in SEQ ID NO: 63. The same applies to NGFs of animal species other than humans.

When hNGF is said to have the function of hNGF, it means that hNGF preferably retains a specific activity of 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, of the specific activity of normal wild-type hNGF taken as 100%. Here, specific activity refers to the physiological activity per mass of protein. The specific activity of a fusion protein of hNGF and another protein is determined as the physiological activity per mass of the portion of the fusion protein that corresponds to hNGF. The specific activity of hNGF in the fusion protein is calculated by multiplying the physiological activity of hNGF per unit mass of the fusion protein by (molecular weight of the fusion protein/molecular weight of the portion of the fusion protein that corresponds to hNGF). The same applies to NGFs of animal species other than humans.

When amino acid residues in the amino acid sequence of wild-type hNGF are replaced with other amino acid residues, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When amino acid residues in the amino acid sequence of wild-type hNGF are deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. hNGF mutants consisting of 119 amino acid residues obtained by deleting one amino acid residue at the N-terminus or C-terminus of wild-type hNGF, and hNGF mutants consisting of 118 amino acid residues obtained by deleting two amino acid residues at the N-terminus or C-terminus of wild-type hNGF, are also hNGF. Mutations that combine the substitution and deletion of these amino acid residues can also be added to the amino acid sequence of wild-type hNGF. The same applies to NGFs of animal species other than humans.

When amino acid residues are added to the amino acid sequence of wild-type hNGF, one or more amino acid residues are added into the amino acid sequence of hNGF or to the N-terminus or C-terminus of the amino acid sequence. The number of amino acid residues added in this case is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. Mutations that combine the addition of these amino acid residues with the above-mentioned substitutions can also be added to the amino acid sequence of wild-type hNGF, and mutations that combine the addition of these amino acid residues with the above-mentioned deletions can also be added to the amino acid sequence of wild-type hNGF. The same applies to NGFs of animal species other than humans.

Furthermore, a combination of the above three types of mutations, substitution, deletion, and addition of amino acid residues, can be added to the amino acid sequence of wild-type hNGF. For example, a wild-type hNGF shown in SEQ ID NO:62 in which 1 to 10 amino acid residues have been deleted, 1 to 10 amino acid residues have been replaced with other amino acid residues, and 1 to 10 amino acid residues have been added is also an hNGF; a wild-type hNGF shown in SEQ ID NO:62 in which 1 to 5 amino acid residues have been deleted, 1 to 5 amino acid residues have been replaced with other amino acid residues, and 1 to 5 amino acid residues have been added is also an hNGF; a wild-type hNGF shown in SEQ ID NO:62 in which 1 to 3 amino acid residues have been deleted, hNGF is also obtained by deleting one or two amino acid residues from the amino acid sequence of wild-type hNGF shown in SEQ ID NO:62, substituting one or two amino acid residues with other amino acid residues, and adding one or two amino acid residues. hNGF is also obtained by deleting one amino acid residue from the amino acid sequence of wild-type hNGF shown in SEQ ID NO:62, substituting one amino acid residue with other amino acid residues, and adding one amino acid residue. The same applies to NGFs of animal species other than humans.

The location and type (deletion, substitution, and addition) of each mutation in the hNGF mutant compared to normal wild-type hNGF can be easily confirmed by aligning the amino acid sequences of both hNGFs. The same is true for NGFs of animal species other than humans.

The amino acid sequence of the hNGF mutant preferably has 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more, or 99% or more identity, to the amino acid sequence of normal wild-type hNGF shown in SEQ ID NO:62.

In this specification, when simply referring to "human neurotrophin-3", "human NT-3", or "hNT-3", it includes, without distinction, not only the usual wild-type hNT-3 consisting of the 119 amino acid residues shown in SEQ ID NO: 64, but also mutants of hNT-3 in which one or more amino acid residues have been substituted, deleted, and/or added (as used herein, "addition" of an amino acid residue means adding a residue to the end or inside of the sequence) to the amino acid sequence shown in SEQ ID NO: 64, as long as they have the functions of hNT-3, such as having physiological activity as a nerve growth factor that acts via TrkC and is necessary for maintaining the survival and promoting differentiation of nerve cells. Wild-type hNT-3 is, for example, encoded by a gene having the base sequence shown in SEQ ID NO: 65. The same applies to hNT-3 of animal species other than humans.

When hNT-3 is said to have the function of hNT-3, it means that hNT-3 preferably retains a specific activity of 10% or more, more preferably a specific activity of 20% or more, even more preferably a specific activity of 50% or more, and even more preferably a specific activity of 80% or more, when the specific activity of normal wild-type hNT-3 is taken as 100%. Here, specific activity refers to the physiological activity per mass of the protein. The specific activity of a fusion protein of hNT-3 and another protein is determined as the physiological activity per mass of the portion of the fusion protein that corresponds to hNT-3. Here, the specific activity of hNT-3 in the fusion protein is calculated by multiplying the physiological activity of hNT-3 per unit mass of the fusion protein by (molecular weight of the fusion protein/molecular weight of the portion of the fusion protein that corresponds to hNT-3). The same applies to hNT-3 from animal species other than humans.

When amino acid residues in the amino acid sequence of wild-type hNT-3 are replaced with other amino acid residues, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When amino acid residues in the amino acid sequence of wild-type hNT-3 are deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. hNT-3 mutants consisting of 118 amino acid residues obtained by deleting one amino acid residue at the N-terminus or C-terminus of wild-type hNT-3, and hNT-3 mutants consisting of 117 amino acid residues obtained by deleting two amino acid residues at the N-terminus or C-terminus of wild-type hNT-3, etc. are also hNT-3. Mutations that combine the substitution and deletion of these amino acid residues can also be added to the amino acid sequence of wild-type hNT-3. The same applies to hNT-3 of animal species other than humans.

When amino acid residues are added to the amino acid sequence of wild-type hNT-3, one or more amino acid residues are added into the amino acid sequence of hNT-3 or to the N-terminus or C-terminus of the amino acid sequence. The number of amino acid residues added in this case is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. Mutations that combine the addition of these amino acid residues with the above-mentioned substitutions can also be added to the amino acid sequence of wild-type hNT-3, and mutations that combine the addition of these amino acid residues with the above-mentioned deletions can also be added to the amino acid sequence of wild-type hNT-3. The same applies to hNT-3 from animal species other than humans.

Furthermore, a combination of the above three types of mutations, substitution, deletion, and addition of amino acid residues, can be added to the amino acid sequence of wild-type hNT-3. For example, a wild-type hNT-3 shown in SEQ ID NO:64 has 1 to 10 amino acid residues deleted, 1 to 10 amino acid residues replaced with other amino acid residues, and 1 to 10 amino acid residues added to it, which is also an hNT-3; a wild-type hNT-3 shown in SEQ ID NO:64 has 1 to 5 amino acid residues deleted, 1 to 5 amino acid residues replaced with other amino acid residues, and 1 to 5 amino acid residues added to it, which is also an hNT-3; a wild-type hNT-3 shown in SEQ ID NO:64 has 1 to 3 amino acid residues deleted, 1 to 10 amino acid residues replaced with other amino acid residues, and 1 to 10 amino acid residues added to it, which is also an hNT-3. hNT-3 also includes a wild-type hNT-3 amino acid sequence shown in SEQ ID NO:64 in which one or two amino acid residues have been deleted, one or two amino acid residues have been replaced with other amino acid residues, and one or two amino acid residues have been added; and hNT-3 also includes a wild-type hNT-3 amino acid sequence shown in SEQ ID NO:64 in which one amino acid residue has been deleted, one amino acid residue has been replaced with other amino acid residue, and one amino acid residue has been added. The same applies to hNT-3 from animal species other than humans.

The location and type (deletion, substitution, and addition) of each mutation in the hNT-3 mutant compared to normal wild-type hNT-3 can be easily confirmed by aligning the amino acid sequences of both hNT-3. The same is true for hNT-3 from animal species other than humans.

The amino acid sequence of the hNT-3 mutant preferably has 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more, or 99% or more identity, to the amino acid sequence of the normal wild-type hNT-3 shown in SEQ ID NO:64.

In this specification, when simply referring to "human neurotrophin-4," "human NT-4," or "hNT-4," it includes, without distinction, not only the usual wild-type hNT-4 consisting of the 130 amino acid residues shown in SEQ ID NO: 66, but also mutants of hNT-4 in which one or more amino acid residues have been substituted, deleted, and/or added (as used herein, "addition" of an amino acid residue means adding a residue to the end or inside of the sequence) to the amino acid sequence shown in SEQ ID NO: 66, as long as they have the functions of hNT-4, such as having physiological activity as a nerve growth factor that acts via TrkB and is necessary for maintaining the survival and promoting differentiation of nerve cells. Wild-type hNT-4 is, for example, encoded by a gene having the base sequence shown in SEQ ID NO: 67. The same applies to hNT-4 of animal species other than humans.

When hNT-4 is said to have the function of hNT-4, it means that hNT-4 preferably retains a specific activity of 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, of the specific activity of normal wild-type hNT-4 taken as 100%. Here, specific activity refers to the physiological activity per mass of protein. The specific activity of a fusion protein of hNT-4 with another protein is determined as the physiological activity per mass of the portion of the fusion protein that corresponds to hNT-4. The specific activity of hNT-4 in the fusion protein is calculated by multiplying the physiological activity of hNT-4 per unit mass of the fusion protein by (molecular weight of the fusion protein/molecular weight of the portion of the fusion protein that corresponds to hNT-4). The same applies to hNT-4 from animal species other than humans.

When amino acid residues in the amino acid sequence of wild-type hNT-4 are replaced with other amino acid residues, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When amino acid residues in the amino acid sequence of wild-type hNT-4 are deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. hNT-4 mutants consisting of 129 amino acid residues obtained by deleting one amino acid residue at the N-terminus or C-terminus of wild-type hNT-4, and hNT-4 mutants consisting of 128 amino acid residues obtained by deleting two amino acid residues at the N-terminus or C-terminus of wild-type hNT-4, etc. are also hNT-4. Mutations that combine the substitution and deletion of these amino acid residues can also be added to the amino acid sequence of wild-type hNT-4. The same applies to hNT-4 of animal species other than humans.

When amino acid residues are added to the amino acid sequence of wild-type hNT-4, one or more amino acid residues are added into the amino acid sequence of hNT-4 or to the N-terminus or C-terminus of the amino acid sequence. The number of amino acid residues added in this case is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. Mutations that combine the addition of these amino acid residues with the above-mentioned substitutions can also be added to the amino acid sequence of wild-type hNT-4, and mutations that combine the addition of these amino acid residues with the above-mentioned deletions can also be added to the amino acid sequence of wild-type hNT-4. The same applies to hNT-4 from animal species other than humans.

Furthermore, a combination of the above three types of mutations, substitution, deletion, and addition of amino acid residues, can be added to the amino acid sequence of wild-type hNT-4. For example, a wild-type hNT-4 amino acid sequence shown in SEQ ID NO:66 in which 1 to 10 amino acid residues have been deleted, 1 to 10 amino acid residues have been replaced with other amino acid residues, and 1 to 10 amino acid residues have been added is also an hNT-4; a wild-type hNT-4 amino acid sequence shown in SEQ ID NO:66 in which 1 to 5 amino acid residues have been deleted, 1 to 5 amino acid residues have been replaced with other amino acid residues, and 1 to 5 amino acid residues have been added is also an hNT-4; a wild-type hNT-4 amino acid sequence shown in SEQ ID NO:66 in which 1 to 3 amino acid residues have been deleted, hNT-4 also includes a wild-type hNT-4 amino acid sequence shown in SEQ ID NO:66 in which one or two amino acid residues have been deleted, one or two amino acid residues have been replaced with other amino acid residues, and one or two amino acid residues have been added; and hNT-4 also includes a wild-type hNT-4 amino acid sequence shown in SEQ ID NO:66 in which one amino acid residue has been deleted, one amino acid residue has been replaced with other amino acid residue, and one amino acid residue has been added. The same applies to hNT-4 from animal species other than humans.

The location and type (deletion, substitution, and addition) of each mutation in the hNT-4 mutant compared to normal wild-type hNT-4 can be easily confirmed by aligning the amino acid sequences of both hNT-4. The same is true for hNT-4 from animal species other than humans.

The amino acid sequence of the hNT-4 mutant preferably exhibits 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more, or 99% or more identity, to the amino acid sequence of normal wild-type hNT-4 shown in SEQ ID NO:66.

　Substitutions of amino acids in the amino acid sequence of wild-type hBDNF or wild-type hNGF, wild-type hNT-3, and wild-type hNT-4 are, for example, conservative amino acid substitutions. The same is true for these neurotrophic factors of animal species other than humans.

　The above wild-type or mutant hBDNF, hNGF, hNT-3, or hNT-4, in which the constituent amino acids are modified with sugar chains, are also hBDNF, hNGF, hNT-3, or hNT-4, respectively. The same applies to these wild-type or mutant human neurotrophic factors in which the constituent amino acids are modified with phosphate. The same applies to those modified with something other than sugar chains and phosphate. The same applies to these wild-type or mutant human neurotrophic factors in which the side chains of the constituent amino acids have been changed by substitution reactions, etc. Such changes include, but are not limited to, the conversion of cysteine residues to formylglycine. The same applies to hBDNF, hNGF, hNT-3, and hNT-4. The same applies to these neurotrophic factors of animal species other than humans.

In other words, hBDNF, hNGF, hNT-3, or hNT-4 modified with sugar chains are included in hBDNF, hNGF, hNT-3, or hNT-4 having the original amino acid sequence, respectively. The same applies to these human neurotrophic factors modified with phosphate. The same applies to those modified with things other than sugar chains and phosphate. The same also applies to those in which the side chains of the amino acids that make up these human neurotrophic factors have been changed by substitution reactions, etc. One such conversion is the conversion of a cysteine residue to formylglycine. The same also applies to neurotrophic factors of animal species other than humans.

One embodiment of the present invention is a recombinant protein in which a wild-type neurotrophic factor is fused with HSA. When such a fusion protein is expressed as a recombinant protein using a host cell such as CHO, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the amount of expression of human neurotrophic factor in the culture supernatant can be at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or physiological activity, for example, 1.1 to 4 times, 1.5 to 3.6 times, 2 to 3.6 times, 10 to 20 times, 20 to 30 times, etc., compared to when wild-type human neurotrophic factor is expressed as a recombinant protein by a similar method.

Another embodiment of the present invention is a recombinant protein in which wild-type hBDNF is fused with HSA. When such a fusion protein is expressed as a recombinant protein using a host cell such as CHO, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the amount of hBDNF expressed in the culture supernatant can be at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or physiological activity, for example, 1.1 to 4 times, 1.5 to 3.6 times, 2 to 3.6 times, 10 to 20 times, 20 to 30 times, etc., compared to when wild-type hBDNF is expressed as a recombinant protein by a similar method.

Another embodiment of the present invention is a recombinant protein in which wild-type hNGF is fused with HSA. When such a fusion protein is expressed as a recombinant protein using a host cell such as CHO, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the amount of hNGF expressed in the culture supernatant can be at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or physiological activity, for example, 1.1 to 4 times, 1.5 to 3.6 times, 2 to 3.6 times, 10 to 20 times, 20 to 30 times, etc., compared to when wild-type hNGF is expressed as a recombinant protein by a similar method.

Another embodiment of the present invention is a recombinant protein in which wild-type hNT-3 is fused with HSA. When such a fusion protein is expressed as a recombinant protein using a host cell such as CHO, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the amount of expression of hNT-3 in the culture supernatant can be at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or physiological activity, for example, 1.1 to 4 times, 1.5 to 3.6 times, 2 to 3.6 times, 10 to 20 times, 20 to 30 times, etc., compared to when wild-type hNT-3 is expressed as a recombinant protein by a similar method.

Another embodiment of the present invention is a recombinant protein in which wild-type hNT-4 is fused with HSA. When such a fusion protein is expressed as a recombinant protein using a host cell such as CHO, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the amount of hNT-4 expressed in the culture supernatant can be at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or physiological activity, for example, 1.1 to 4 times, 1.5 to 3.6 times, 2 to 3.6 times, 10 to 20 times, 20 to 30 times, etc., compared to when wild-type hNT-4 is expressed as a recombinant protein by a similar method.

One embodiment of the present invention relates to a fusion protein in which a polypeptide containing the amino acid sequence of a human neurotrophic factor is bound to a polypeptide containing the amino acid sequence of SA. Here, the term "binding polypeptides" refers to binding different polypeptides by covalent bonding, either directly or indirectly via a linker. Here, the neurotrophic factor is preferably human neurotrophic factor. Also, SA is preferably HSA. Also, the human neurotrophic factor is, for example, hBDNF, hNGF, hNT-3, or hNT-4. The same applies to neurotrophic factors of animal species other than humans.

In one embodiment of the present invention, the term "SA-human neurotrophic factor fusion protein" or "SA-human neurotrophic factor" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of human neurotrophic factor is linked to the C-terminus of the amino acid sequence of SA, either directly or via a linker, and which has the function of a human neurotrophic factor. Here, the animal species of SA is not particularly limited, but preferably it is a mammalian SA, more preferably it is a primate SA, and even more preferably it is HSA. When it is said that the human neurotrophic factor in the SA-human neurotrophic factor fusion protein has the function of a human neurotrophic factor, it means that the human neurotrophic factor preferably retains a specific activity of 10% or more, more preferably a specific activity of 20% or more, even more preferably a specific activity of 50% or more, and even more preferably a specific activity of 80% or more, when the specific activity of a normal wild-type human neurotrophic factor is taken as 100%. Here, the specific activity of human neurotrophic factor in the SA-human neurotrophic factor fusion protein is calculated by multiplying the physiological activity of human neurotrophic factor per unit mass of the fusion protein by (molecular weight of the fusion protein/molecular weight of the portion of the fusion protein that corresponds to human neurotrophic factor).

In one embodiment of the present invention, the term "HSA-human neurotrophic factor fusion protein" or "HSA-human neurotrophic factor" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of human neurotrophic factor is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of HSA, and which has the function of a human neurotrophic factor. When it is said here that the HSA-human neurotrophic factor fusion protein has the function of a human neurotrophic factor, the definition of the SA-neurotrophic factor fusion protein described above can be applied.

In the SA-human neurotrophic factor fusion protein, it is preferable that the SA has a function as an SA, such as the function of binding and transporting endogenous substances in the blood and exogenous substances such as drugs, but is not limited to this. The same is true for the HSA-human neurotrophic factor fusion protein. The same is true for the HSA-hBDNF fusion protein, HSA-hNGF fusion protein, HSA-hNT-3 fusion protein, and HSA-hNT-4 fusion protein.

When mutations are added to an HSA-human neurotrophic factor fusion protein, which is a fusion protein of wild-type HSA and wild-type human neurotrophic factor, mutations can be added only to the HSA portion without mutations in the human neurotrophic factor portion, mutations can be added only to the human neurotrophic factor portion without mutations in the HSA portion, or mutations can be added to both the HSA portion and the human neurotrophic factor portion. When mutations are added only to the HSA portion, the amino acid sequence of the portion is the amino acid sequence of the wild-type HSA with a mutation added. When mutations are added only to the human neurotrophic factor portion, the amino acid sequence of the portion is the amino acid sequence of the wild-type human neurotrophic factor with a mutation added. When mutations are added to both the HSA portion and the human neurotrophic factor portion, the amino acid sequence of the HSA portion is the amino acid sequence of the wild-type HSA with a mutation added, and the amino acid sequence of the human neurotrophic factor portion is the amino acid sequence of the wild-type human neurotrophic factor with a mutation added. The same can be said about fusion proteins between wild-type SA of non-human animal species and wild-type human neurotrophic factor.

　HSA-human neurotrophic factor fusion proteins in which the amino acids constituting the protein are modified with sugar chains are also HSA-human neurotrophic factor fusion proteins. HSA-human neurotrophic factor fusion proteins in which the amino acids constituting the protein are modified with phosphate are also HSA-human neurotrophic factor fusion proteins. HSA-human neurotrophic factor fusion proteins modified with something other than sugar chains and phosphate are also HSA-human neurotrophic factor fusion proteins. HSA-human neurotrophic factor fusion proteins in which the side chains of the amino acids constituting the protein have been converted by a substitution reaction or the like are also HSA-human neurotrophic factor fusion proteins. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said about fusion proteins of SA of animal species other than humans and human neurotrophic factor (SA-human neurotrophic factor).

In other words, HSA-human neurotrophic factor fusion proteins modified with sugar chains are included in HSA-human neurotrophic factor fusion proteins having the original amino acid sequence. Also, HSA-human neurotrophic factor fusion proteins modified with phosphate are included in HSA-human neurotrophic factor fusion proteins having the original amino acid sequence. Also, those modified with things other than sugar chains and phosphate are included in HSA-human neurotrophic factor fusion proteins having the original amino acid sequence. Also, HSA-human neurotrophic factor fusion proteins in which the side chains of the amino acids constituting the HSA-human neurotrophic factor fusion proteins have been converted by substitution reactions or the like are included in HSA-human neurotrophic factor fusion proteins having the original amino acid sequence. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for fusion proteins of SA and human neurotrophic factor of animal species other than humans (SA-human neurotrophic factor).

　An HSA-human neurotrophic factor fusion protein in which the human neurotrophic factor constituting the protein is a precursor of human neurotrophic factor is also an HSA-human neurotrophic factor fusion protein. The term "precursor" used here refers to a type of protein that is biosynthesized as an HSA-human neurotrophic factor fusion protein, and in which the portion that functions as a human neurotrophic factor after the biosynthesis is cleaved from the fusion protein during the manufacturing process or in the living body when administered to the living body, and can function as a human neurotrophic factor by itself. In this case, the HSA-human neurotrophic factor fusion protein may be cleaved at a specific site after biosynthesis by a hydrolase or the like, and the portion containing HSA and the portion containing mature human neurotrophic factor may be separated. In this case, the human neurotrophic factor obtained is not a fusion protein with HSA, but the HSA-human neurotrophic factor fusion protein is synthesized once during the process of manufacturing the neurotrophic factor. Therefore, when human neurotrophic factor is manufactured by such a method, the manufacturing method is included in the manufacturing method of HSA-human neurotrophic factor. The same can be said about fusion proteins of SA from non-human animal species and human neurotrophic factor (SA-human neurotrophic factor).

In one embodiment of the present invention, the term "SA-hBDNF fusion protein" or "SA-hBDNF" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of hBDNF is linked to the C-terminus of the amino acid sequence of SA, either directly or via a linker, and which has the function of hBDNF. Here, the animal species of SA is not particularly limited, but it is preferably a mammalian SA, more preferably a primate SA, and even more preferably HSA. When hBDNF in an SA-hBDNF fusion protein is said to have the function of hBDNF, it means that hBDNF retains a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, when the specific activity of normal wild-type hBDNF is taken as 100%. Here, the specific activity of hBDNF in the SA-hBDNF fusion protein is calculated by multiplying the physiological activity of hBDNF per unit mass of the fusion protein by (the molecular weight of the fusion protein/the molecular weight of the portion of the fusion protein corresponding to hBDNF).

In one embodiment of the present invention, the term "HSA-hBDNF fusion protein" or "HSA-hBDNF" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of hBDNF is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of HSA, and which has the function of hBDNF. When it is said here that the HSA-hBDNF fusion protein has the function of hBDNF, the definition of the SA-hBDNF fusion protein described above can be applied.

In one embodiment of the present invention, a preferred HSA-hBDNF fusion protein has, for example, the amino acid sequence shown in SEQ ID NO: 68. The HSA-hBDNF fusion protein shown in SEQ ID NO: 68 is obtained by linking wild-type hBDNF to the C-terminus of wild-type HSA via the linker sequence Gly-Ser. The HSA-hBDNF fusion protein shown in SEQ ID NO: 68 is encoded by a gene having, for example, the base sequence shown in SEQ ID NO: 69. In addition, HSA-hBDNF fusion proteins include those having an amino acid sequence in which one or more amino acid residues in the amino acid sequence shown in SEQ ID NO: 68 have been replaced with other amino acid residues, deleted, or mutated by addition, as long as they have the function of hBDNF. It is preferable that the HSA-hBDNF fusion protein has the function of human serum albumin, such as the function of binding and transporting endogenous substances in blood and exogenous substances such as drugs, but is not limited thereto.

When a mutation is added to an HSA-hBDNF fusion protein, which is a fusion protein of wild-type HSA and wild-type hBDNF, a mutation may be added only to the HSA portion and not to the hBDNF portion, or a mutation may be added only to the hBDNF portion without any mutation to the HSA portion, or a mutation may be added to both the HSA portion and the hBDNF portion. When a mutation is added only to the HSA portion, the amino acid sequence of the portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above. When a mutation is added only to the hBDNF portion, the amino acid sequence of the portion is the amino acid sequence of hBDNF obtained by adding a mutation to the wild-type hBDNF described above. When a mutation is added to both the HSA portion and the hBDNF portion, the amino acid sequence of the HSA portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above, and the amino acid sequence of the hBDNF portion is the amino acid sequence of hBDNF obtained by adding a mutation to the wild-type hBDNF described above. The same applies to the HSA-hBDNF fusion protein having the amino acid sequence shown in SEQ ID NO: 68. The same can be said about fusion proteins of wild-type SA and wild-type hBDNF from non-human animal species.

The following is an example of a case where a mutation is made to an HSA-hBDNF fusion protein having the amino acid sequence shown in SEQ ID NO:68. When an amino acid residue in the amino acid sequence shown in SEQ ID NO:68 is replaced with another amino acid residue, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is added, one or more amino acid residues are added to the amino acid sequence shown in SEQ ID NO:68 or to the N-terminus or C-terminus of the amino acid sequence. The HSA-hBDNF fusion protein may be a combination of these substitutions, deletions, and additions of amino acid residues. The mutation may be made only to the HSA part, only to the hIL-10 part, or to both parts.

The position and type (deletion, substitution, and addition) of each mutation when the amino acid sequence shown in SEQ ID NO:68 is mutated can be easily confirmed by alignment of the amino acid sequence before and after the mutation. The mutated amino acid sequence preferably exhibits 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more, or 99% or more identity, with the amino acid sequence shown in SEQ ID NO:68.

　HSA-hBDNF fusion proteins in which the amino acids constituting the protein are modified with sugar chains are also HSA-hBDNF fusion proteins. HSA-hBDNF fusion proteins in which the amino acids constituting the protein are modified with phosphate are also HSA-hBDNF fusion proteins. HSA-hBDNF fusion proteins modified with something other than sugar chains and phosphate are also HSA-hBDNF fusion proteins. HSA-hBDNF fusion proteins in which the side chains of the amino acids constituting the protein have been changed by a substitution reaction or the like are also HSA-hBDNF fusion proteins. Such changes include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said about fusion proteins of SA and hBDNF of animal species other than humans (SA-hBDNF).

In other words, HSA-hBDNF fusion proteins modified with sugar chains are included in HSA-hBDNF fusion proteins with the original amino acid sequence. Also, HSA-hBDNF fusion proteins modified with phosphate are included in HSA-hBDNF fusion proteins with the original amino acid sequence. Also, those modified with things other than sugar chains and phosphate are also included in HSA-hBDNF fusion proteins with the original amino acid sequence. Also, those in which the side chains of the amino acids constituting the HSA-hBDNF fusion protein have been converted by substitution reactions or the like are also included in HSA-hBDNF fusion proteins with the original amino acid sequence. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for fusion proteins of SA and hBDNF of animal species other than humans (SA-hBDNF).

　Also, HSA-hBDNF fusion proteins in which the constituent hBDNF is a precursor of hBDNF are also HSA-hBDNF fusion proteins. Here, the term "precursor" refers to a type that is biosynthesized as an HSA-hBDNF fusion protein, and after the biosynthesis, the part that functions as hBDNF is separated from the fusion protein during the manufacturing process or in the living body when administered to the living body, and can function as hBDNF by itself. In this case, after the HSA-hBDNF fusion protein is biosynthesized, it may be cleaved at a specific site by a hydrolase or the like, and the part containing HSA and the part containing mature hBDNF may be separated. The obtained hBDNF is not a fusion protein with HSA, but the HSA-hBDNF fusion protein is synthesized once during the process of manufacturing hBDNF. Therefore, when hBDNF is manufactured by such a method, the manufacturing method is included in the manufacturing method of HSA-hBDNF fusion protein. The same can be said for a fusion protein of SA and hBDNF of an animal species other than human (SA-hBDNF).

In one embodiment of the present invention, the term "SA-hNGF fusion protein" or "SA-hNGF" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of hNGF is linked to the C-terminus of the amino acid sequence of SA, either directly or via a linker, and having the function of hNGF. Here, the animal species of SA is not particularly limited, but preferably it is a mammalian SA, more preferably it is a primate SA, and even more preferably it is HSA. When it is said that hNGF in an SA-hNGF fusion protein has the function of hNGF, it means that hNGF retains a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, when the specific activity of normal wild-type hNGF is taken as 100%. Here, the specific activity of hNGF in the SA-hNGF fusion protein is calculated by multiplying the physiological activity of hNGF per unit mass of the fusion protein by (the molecular weight of the fusion protein/the molecular weight of the portion of the fusion protein corresponding to hNGF).

In one embodiment of the present invention, the term "HSA-hNGF fusion protein" or "HSA-hNGF" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of hNGF is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of HSA, and which has the function of hNGF. When it is said here that the HSA-hNGF fusion protein has the function of hNGF, the definition of the SA-hNGF fusion protein described above can be applied.

In one embodiment of the present invention, a preferred HSA-hNGF fusion protein has, for example, the amino acid sequence shown in SEQ ID NO: 70. The HSA-hNGF fusion protein shown in SEQ ID NO: 70 is obtained by linking wild-type hNGF to the C-terminus of wild-type HSA via the linker sequence Gly-Ser. The HSA-hNGF fusion protein shown in SEQ ID NO: 70 is encoded by a gene having, for example, the base sequence shown in SEQ ID NO: 71. In addition, HSA-hNGF fusion proteins also include those having an amino acid sequence in which one or more amino acid residues in the amino acid sequence shown in SEQ ID NO: 70 have been replaced with other amino acid residues, deleted, or mutated by addition, as long as they have the function of hNGF. It is preferable that the HSA-hNGF fusion protein has the function of human serum albumin, such as the function of binding and transporting endogenous substances in blood and exogenous substances such as drugs, but is not limited thereto.

When mutations are introduced into an HSA-hNGF fusion protein, which is a fusion protein of wild-type HSA and wild-type hNGF, mutations can be introduced only in the HSA portion and not in the hNGF portion, mutations can be introduced only in the hNGF portion without mutations in the HSA portion, or mutations can be introduced in both the HSA portion and the hNGF portion. When mutations are introduced only in the HSA portion, the amino acid sequence of the portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above. When mutations are introduced only in the hNGF portion, the amino acid sequence of the portion is the amino acid sequence of hNGF obtained by adding a mutation to the wild-type hNGF described above. When mutations are introduced in both the HSA portion and the hNGF portion, the amino acid sequence of the HSA portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above, and the amino acid sequence of the hNGF portion is the amino acid sequence of hNGF obtained by adding a mutation to the wild-type hNGF described above. The same applies to the HSA-hNGF fusion protein having the amino acid sequence shown in SEQ ID NO: 70. The same can be said about fusion proteins of wild-type SA and wild-type hNGF from animal species other than humans.

The following is an example of a case where a mutation is made to an HSA-hNGF fusion protein having the amino acid sequence shown in SEQ ID NO:70. When an amino acid residue in the amino acid sequence shown in SEQ ID NO:70 is replaced with another amino acid residue, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is added, one or more amino acid residues are added to the amino acid sequence shown in SEQ ID NO:70 or to the N-terminus or C-terminus of the amino acid sequence. The HSA-hNGF fusion protein may be a combination of these substitutions, deletions, and additions of amino acid residues. The mutation may be made only to the HSA portion, only to the hNGF portion, or to both portions. The same applies to a fusion protein of SA and hNGF of an animal species other than human (SA-hNGF).

The position and type (deletion, substitution, and addition) of each mutation when the amino acid sequence shown in SEQ ID NO:70 is mutated can be easily confirmed by alignment of the amino acid sequence before and after the mutation. The mutated amino acid sequence preferably exhibits 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more, or 99% or more identity, with the amino acid sequence shown in SEQ ID NO:70.

　HSA-hNGF fusion proteins in which the amino acids constituting the protein are modified with sugar chains are also HSA-hNGF fusion proteins. HSA-hNGF fusion proteins in which the amino acids constituting the protein are modified with phosphate are also HSA-hNGF fusion proteins. HSA-hNGF fusion proteins modified with anything other than sugar chains and phosphate are also HSA-hNGF fusion proteins. HSA-hNGF fusion proteins in which the side chains of the amino acids constituting the protein are modified by substitution reactions, etc., are also HSA-hNGF fusion proteins. Such modifications include, but are not limited to, the conversion of cysteine residues to formylglycine. Mutations may be made only to the HSA portion, only to the hNGF portion, or to both portions. The same can be said about fusion proteins of SA and hNGF of animal species other than humans (SA-hNGF).

　In other words, HSA-hNGF fusion proteins modified with sugar chains are included in HSA-hNGF fusion proteins having the original amino acid sequence. Also, HSA-hNGF fusion proteins modified with phosphate are included in HSA-hNGF fusion proteins having the original amino acid sequence. Also, those modified with things other than sugar chains and phosphate are included in HSA-hNGF fusion proteins having the original amino acid sequence. Also, HSA-hNGF fusion proteins in which the side chains of the amino acids constituting the HSA-hNGF fusion protein have been changed by substitution reactions or the like are included in HSA-hNGF fusion proteins having the original amino acid sequence. Such changes include, but are not limited to, the conversion of cysteine residues to formylglycine. Mutations may be made only to the HSA portion, only to the hNGF portion, or to both portions. The same can be said for fusion proteins of SA and hNGF of animal species other than humans (SA-hNGF).

　Also, HSA-hNGF fusion proteins in which the hNGF constituting the protein is a precursor of hNGF are also HSA-hNGF fusion proteins. The term "precursor" here refers to a type of protein that is biosynthesized as an HSA-hNGF fusion protein, and after the biosynthesis, the portion that functions as hNGF is separated from the fusion protein during the manufacturing process or in the living body when administered to the living body, and can function as hNGF by itself. In this case, after the HSA-hNGF fusion protein is biosynthesized, it may be cleaved at a specific site by a hydrolase or the like, and the portion containing HSA and the portion containing mature hNGF may be separated. The resulting hNGF is not a fusion protein with HSA, but the HSA-hNGF fusion protein is synthesized once during the process of manufacturing hNGF. Therefore, when hNGF is manufactured by such a method, the manufacturing method is included in the manufacturing method of HSA-hNGF fusion protein. The mutation may be added only to the HSA portion, only to the hNGF portion, or both portions. The same can be said about fusion proteins of SA and hNGF from non-human animal species (SA-hNGF).

In one embodiment of the present invention, the term "SA-hNT-3 fusion protein" or "SA-hNT-3" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of hNT-3 is linked, directly or via a linker, to the C-terminus of the amino acid sequence of SA, and which has the function of hNT-3. Here, there is no particular limitation on the animal species of SA, but it is preferably a mammalian SA, more preferably a primate SA, and even more preferably HSA. When it is said that hNT-3 in the SA-hNT-3 fusion protein has the function of hNT-3, it means that hNT-3 preferably retains a specific activity of 10% or more, more preferably a specific activity of 20% or more, even more preferably a specific activity of 50% or more, and even more preferably a specific activity of 80% or more, when the specific activity of normal wild-type hNT-3 is taken as 100%. Here, the specific activity of hNT-3 in the SA-hNT-3 fusion protein is calculated by multiplying the physiological activity of hNT-3 per unit mass of the fusion protein by (molecular weight of the fusion protein/molecular weight of the portion of the fusion protein corresponding to hNT-3).

In one embodiment of the present invention, the term "HSA-hNT-3 fusion protein" or "HSA-hNT-3" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of hNT-3 is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of HSA, and which has the function of hNT-3. When it is said here that the HSA-hNT-3 fusion protein has the function of hNT-3, the definition of the SA-hNT-3 fusion protein described above can be applied.

In one embodiment of the present invention, a preferred HSA-hNT-3 fusion protein has, for example, the amino acid sequence shown in SEQ ID NO: 72. The HSA-hNT-3 fusion protein shown in SEQ ID NO: 72 is obtained by linking wild-type hNT-3 to the C-terminus of wild-type HSA via the linker sequence Gly-Ser. The HSA-hNT-3 fusion protein shown in SEQ ID NO: 72 is encoded by a gene having, for example, the base sequence shown in SEQ ID NO: 73. In addition, HSA-hNT-3 fusion proteins also include those having an amino acid sequence in which one or more amino acid residues in the amino acid sequence shown in SEQ ID NO: 72 have been replaced with other amino acid residues, deleted, or mutated by addition, as long as they have the function of hNT-3. It is preferable that the HSA-hNT-3 fusion protein has the function of human serum albumin, such as the function of binding and transporting endogenous substances in blood and exogenous substances such as drugs, but is not limited thereto.

When mutations are introduced into the HSA-hNT-3 fusion protein, which is a fusion protein of wild-type HSA and wild-type hNT-3, mutations can be introduced only in the HSA portion and not in the hNT-3 portion, mutations can be introduced only in the hNT-3 portion without mutations in the HSA portion, or mutations can be introduced in both the HSA portion and the hNT-3 portion. When mutations are introduced only in the HSA portion, the amino acid sequence of the portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above. When mutations are introduced only in the hNT-3 portion, the amino acid sequence of the portion is the amino acid sequence of hNT-3 obtained by adding a mutation to the wild-type hNT-3 described above. When mutations are introduced in both the HSA portion and the hNT-3 portion, the amino acid sequence of the HSA portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above, and the amino acid sequence of the hNT-3 portion is the amino acid sequence of hNT-3 obtained by adding a mutation to the wild-type hNT-3 described above. The same is true for the HSA-hNT-3 fusion protein having the amino acid sequence shown in SEQ ID NO: 72. The same is true for a fusion protein of wild-type SA and wild-type hNT-3 of an animal species other than human.

The following is an example of a case where a mutation is made to an HSA-hNT-3 fusion protein having the amino acid sequence shown in SEQ ID NO:72. When an amino acid residue in the amino acid sequence shown in SEQ ID NO:72 is replaced with another amino acid residue, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is added, one or more amino acid residues are added to the amino acid sequence shown in SEQ ID NO:72 or to the N-terminus or C-terminus of the amino acid sequence. The HSA-hNT-3 fusion protein may be a combination of these substitutions, deletions, and additions of amino acid residues. The mutation may be made only to the HSA portion, only to the hGALC portion, or to both portions.

The position and type (deletion, substitution, and addition) of each mutation when the amino acid sequence shown in SEQ ID NO:72 is mutated can be easily confirmed by alignment of the amino acid sequence before and after the mutation. The mutated amino acid sequence preferably exhibits 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more, or 99% or more identity, with the amino acid sequence shown in SEQ ID NO:72.

　HSA-hNT-3 fusion proteins in which the amino acids constituting the protein are modified with sugar chains are also HSA-hNT-3 fusion proteins. HSA-hNT-3 fusion proteins in which the amino acids constituting the protein are modified with phosphate are also HSA-hNT-3 fusion proteins. HSA-hNT-3 fusion proteins modified with something other than sugar chains and phosphate are also HSA-hNT-3 fusion proteins. HSA-hNT-3 fusion proteins in which the side chains of the amino acids constituting the protein have been changed by a substitution reaction or the like are also HSA-hNT-3 fusion proteins. Such changes include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said about fusion proteins of SA and hNT-3 of animal species other than humans (SA-hNT-3).

In other words, HSA-hNT-3 fusion proteins modified with sugar chains are included in HSA-hNT-3 fusion proteins having the original amino acid sequence. Also, HSA-hNT-3 fusion proteins modified with phosphate are included in HSA-hNT-3 fusion proteins having the original amino acid sequence. Also, those modified with things other than sugar chains and phosphate are also included in HSA-hNT-3 fusion proteins having the original amino acid sequence. Also, HSA-hNT-3 fusion proteins in which the side chains of the amino acids constituting the HSA-hNT-3 fusion proteins have been converted by substitution reactions or the like are also included in HSA-hNT-3 fusion proteins having the original amino acid sequence. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for fusion proteins of SA and hNT-3 of animal species other than humans (SA-hNT-3).

　Also, HSA-hNT-3 fusion proteins in which the hNT-3 constituting the protein is a precursor of hNT-3 are also HSA-hNT-3 fusion proteins. The term "precursor" here refers to a type of protein that is biosynthesized as an HSA-hNT-3 fusion protein, and in which the portion that functions as hNT-3 after the biosynthesis is cleaved from the fusion protein during the manufacturing process or in the living body when administered to the living body, and can function as hNT-3 by itself. In this case, after the HSA-hNT-3 fusion protein is biosynthesized, it may be cleaved at a specific site by a hydrolase or the like, and the portion containing HSA and the portion containing mature hNT-3 may be separated. The resulting hNT-3 is not a fusion protein with HSA, but the HSA-hNT-3 fusion protein is synthesized once during the process of synthesizing the hNT-3. Therefore, when hNT-3 is manufactured by such a method, the manufacturing method is included in the manufacturing method of HSA-hNT-3 fusion protein. The same can be said about the fusion protein of SA and hNT-3 from non-human animal species (SA-hNT-3).

In one embodiment of the present invention, the term "SA-hNT-4 fusion protein" or "SA-hNT-4" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of hNT-4 is linked, directly or via a linker, to the C-terminus of the amino acid sequence of SA, and which has the function of hNT-4. Here, there is no particular limitation on the animal species of SA, but it is preferably a mammalian SA, more preferably a primate SA, and even more preferably HSA. When it is said that hNT-4 in the SA-hNT-4 fusion protein has the function of hNT-4, it means that hNT-4 preferably retains a specific activity of 10% or more, more preferably a specific activity of 20% or more, even more preferably a specific activity of 50% or more, and even more preferably a specific activity of 80% or more, when the specific activity of normal wild-type hNT-4 is taken as 100%. Here, the specific activity of hNT-4 in the SA-hNT-4 fusion protein is calculated by multiplying the physiological activity of hNT-4 per unit mass of the fusion protein by (molecular weight of the fusion protein/molecular weight of the portion of the fusion protein corresponding to hNT-4).

In one embodiment of the present invention, the term "HSA-hNT-4 fusion protein" or "HSA-hNT-4" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of hNT-4 is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of HSA, and which has the function of hNT-4. When it is said here that the HSA-hNT-4 fusion protein has the function of hNT-4, the definition of the SA-hNT-4 fusion protein above can be applied.

In one embodiment of the present invention, a preferred HSA-hNT-4 fusion protein has, for example, the amino acid sequence shown in SEQ ID NO: 74. The HSA-hNT-4 fusion protein shown in SEQ ID NO: 74 is obtained by linking wild-type hNT-4 to the C-terminus of wild-type HSA via the linker sequence Gly-Ser. The HSA-hNT-4 fusion protein shown in SEQ ID NO: 74 is encoded by a gene having, for example, the base sequence shown in SEQ ID NO: 75. In addition, HSA-hNT-4 fusion proteins also include those having an amino acid sequence in which one or more amino acid residues in the amino acid sequence shown in SEQ ID NO: 74 have been replaced with other amino acid residues, deleted, or mutated by addition, as long as they have the function of hNT-4. It is preferable that the HSA-hNT-4 fusion protein has the function of human serum albumin, such as the function of binding and transporting endogenous substances in blood and exogenous substances such as drugs, but is not limited thereto.

When mutations are introduced into the HSA-hNT-4 fusion protein, which is a fusion protein of wild-type HSA and wild-type hNT-4, mutations can be introduced only in the HSA portion and not in the hNT-4 portion, mutations can be introduced only in the hNT-4 portion without mutations in the HSA portion, or mutations can be introduced in both the HSA portion and the hNT-4 portion. When mutations are introduced only in the HSA portion, the amino acid sequence of the portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above. When mutations are introduced only in the hNT-4 portion, the amino acid sequence of the portion is the amino acid sequence of hNT-4 obtained by adding a mutation to the wild-type hNT-4 described above. When mutations are introduced in both the HSA portion and the hNT-4 portion, the amino acid sequence of the HSA portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above, and the amino acid sequence of the hNT-4 portion is the amino acid sequence of hNT-4 obtained by adding a mutation to the wild-type hNT-4 described above. The same is true for the HSA-hNT-4 fusion protein having the amino acid sequence shown in SEQ ID NO: 74. The same is true for the fusion protein of wild-type SA and wild-type hNT-4 of an animal species other than human.

The following is an example of a case where a mutation is made to an HSA-hNT-4 fusion protein having the amino acid sequence shown in SEQ ID NO:74. When an amino acid residue in the amino acid sequence shown in SEQ ID NO:74 is replaced with another amino acid residue, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is added, one or more amino acid residues are added to the amino acid sequence shown in SEQ ID NO:74 or to the N-terminus or C-terminus of the amino acid sequence. The HSA-hNT-4 fusion protein may be a combination of these substitutions, deletions, and additions of amino acid residues. The mutation may be made only to the HSA portion, only to the hNT-4 portion, or to both portions. The same can be said about the fusion protein (SA-hNT-4) of SA and hNT-3 from non-human animal species.

The position and type (deletion, substitution, and addition) of each mutation when the amino acid sequence shown in SEQ ID NO:74 is mutated can be easily confirmed by alignment of the amino acid sequence before and after the mutation. The mutated amino acid sequence preferably shows 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more, or 99% or more identity, with the amino acid sequence shown in SEQ ID NO:74.

　HSA-hNT-4 fusion proteins in which the amino acids constituting the protein are modified with sugar chains are also HSA-hNT-4 fusion proteins. HSA-hNT-4 fusion proteins in which the amino acids constituting the protein are modified with phosphate are also HSA-hNT-4 fusion proteins. HSA-hNT-4 fusion proteins modified with something other than sugar chains and phosphate are also HSA-hNT-4 fusion proteins. HSA-hNT-4 fusion proteins in which the side chains of the amino acids constituting the protein have been changed by a substitution reaction or the like are also HSA-hNT-4 fusion proteins. Such changes include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said about fusion proteins (SA-hNT-4) of SA and hNT-3 of animal species other than humans.

In other words, HSA-hNT-4 fusion proteins modified with sugar chains are included in HSA-hNT-4 fusion proteins having the original amino acid sequence. Also, HSA-hNT-4 fusion proteins modified with phosphate are included in HSA-hNT-4 fusion proteins having the original amino acid sequence. Also, those modified with things other than sugar chains and phosphate are also included in HSA-hNT-4 fusion proteins having the original amino acid sequence. Also, HSA-hNT-4 fusion proteins in which the side chains of the amino acids constituting the HSA-hNT-4 fusion protein have been converted by substitution reactions or the like are also included in HSA-hNT-4 fusion proteins having the original amino acid sequence. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for fusion proteins of SA and hNT-3 of animal species other than humans (SA-hNT-4).

　Also, HSA-hNT-4 fusion proteins in which the constituent hNT-4 is a precursor of hNT-4 are also HSA-hNT-4 fusion proteins. Here, the term "precursor" refers to a type of protein that is biosynthesized as an HSA-hNT-4 fusion protein, and in which the portion that functions as hNT-4 after the biosynthesis is cleaved from the fusion protein during the manufacturing process or in the living body when administered to the living body, and can function as hNT-4 by itself. In this case, after the HSA-hNT-4 fusion protein is biosynthesized, it may be cleaved at a specific site by a hydrolase or the like, and the portion containing HSA and the portion containing hNT-4 may be separated. The resulting hNT-4 is not a fusion protein with HSA, but the HSA-hNT-4 fusion protein is synthesized once during the process of synthesizing the hNT-4. Therefore, when hNT-4 is manufactured by such a method, the manufacturing method is included in the manufacturing method of HSA-hNT-4 fusion protein. The same can be said about the fusion protein of SA and hNT-4 from non-human animal species (SA-hNT-4).

In one embodiment of the present invention, the term "human neurotrophic factor-SA fusion protein" or "human neurotrophic factor-SA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of SA is linked directly or via a linker to the C-terminus of the amino acid sequence of human neurotrophic factor, and which has the function of human neurotrophic factor. When the human neurotrophic factor in the human neurotrophic factor-SA fusion protein is said to have the function of human neurotrophic factor, it means that the human neurotrophic factor retains a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, when the specific activity of a normal wild-type human neurotrophic factor is taken as 100%. Here, the specific activity of human neurotrophic factor in the human neurotrophic factor-SA fusion protein is calculated by multiplying the physiological activity of human neurotrophic factor per unit mass of the fusion protein by (the molecular weight of the fusion protein/the molecular weight of the portion of the fusion protein corresponding to human neurotrophic factor).

In one embodiment of the present invention, the term "human neurotrophic factor-HSA fusion protein" or "human neurotrophic factor-HSA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of HSA is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of human neurotrophic factor, and which has the function of a human neurotrophic factor. When it is said that the human neurotrophic factor-HSA fusion protein has the function of a human neurotrophic factor, the definition of the neurotrophic factor-HSA fusion protein described above can be applied.

In human neurotrophic factor-SA fusion protein, it is preferable that the SA has a function as an SA, such as the function of binding and transporting endogenous substances in the blood and exogenous substances such as drugs, but is not limited to this. The same is true for human neurotrophic factor-HSA fusion protein. The same is true for hBDNF-HSA fusion protein, hNGF-HSA fusion protein, hNT-3-HSA fusion protein, and hNT-4-HSA fusion protein.

In one embodiment of the present invention, a fusion protein having an amino acid sequence in which the N-terminus of SA of a non-human animal species is linked, directly or via a linker, to the C-terminus of the amino acid sequence of a neurotrophic factor of a non-human animal species, and which has a function as a neurotrophic factor, is referred to as a "(non-human animal species) neurotrophic factor-(non-human animal species) SA fusion protein." For example, a fusion protein of mouse neurotrophic factor and mouse SA is referred to as a "mouse neurotrophic factor-MSA fusion protein" or "mouse neurotrophic factor-MSA." When these fusion proteins are said to have a function as a neurotrophic factor, the definition of the human neurotrophic factor-SA fusion protein described above can be applied. In addition, in these fusion proteins, it is preferable that the SA has a function as an SA, such as a function to bind and transport endogenous substances in the blood and exogenous substances such as drugs, but this is not limited thereto.

When a mutation is added to a human neurotrophic factor-HSA fusion protein, which is a fusion protein of wild-type human neurotrophic factor and wild-type HSA, a mutation can be added only to the human neurotrophic factor portion and not to the HSA portion, a mutation can be added only to the HSA portion without adding a mutation to the human neurotrophic factor portion, or a mutation can be added to both the human neurotrophic factor portion and the HSA portion. When a mutation is added only to the human neurotrophic factor portion, the amino acid sequence of that portion is the amino acid sequence of the human neurotrophic factor obtained by adding a mutation to the wild-type human neurotrophic factor described above. When a mutation is added only to the HSA portion, the amino acid sequence of that portion is the amino acid sequence of the HSA obtained by adding a mutation to the wild-type HSA described above. When a mutation is added to both the human neurotrophic factor portion and the HSA portion, the amino acid sequence of the human neurotrophic factor portion is the amino acid sequence of the human neurotrophic factor obtained by adding a mutation to the wild-type human neurotrophic factor described above, and the amino acid sequence of the HSA portion is the amino acid sequence of the HSA obtained by adding a mutation to the wild-type HSA described above. The same can be said about fusion proteins between wild-type human neurotrophic factor and wild-type SA of non-human animal species.

Human neurotrophic factor-HSA fusion proteins in which the amino acids constituting the protein are modified with sugar chains are also human neurotrophic factor-HSA fusion proteins. Human neurotrophic factor-HSA fusion proteins in which the amino acids constituting the protein are modified with phosphate are also human neurotrophic factor-HSA fusion proteins. Human neurotrophic factor-HSA fusion proteins modified with something other than sugar chains and phosphate are also human neurotrophic factor-HSA fusion proteins. Human neurotrophic factor-HSA fusion proteins in which the side chains of the amino acids constituting the protein have been converted by a substitution reaction or the like are also human neurotrophic factor-HSA fusion proteins. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said about fusion proteins of human neurotrophic factor and SA of animal species other than human (human neurotrophic factor-SA).

In other words, a human neurotrophic factor-HSA fusion protein modified by a sugar chain is included in the human neurotrophic factor-HSA fusion protein having the original amino acid sequence. A human neurotrophic factor-HSA fusion protein modified by phosphate is included in the human neurotrophic factor-HSA fusion protein having the original amino acid sequence. A human neurotrophic factor-HSA fusion protein modified by something other than a sugar chain or phosphate is also included in the human neurotrophic factor-HSA fusion protein having the original amino acid sequence. A human neurotrophic factor-HSA fusion protein in which the side chains of the amino acids constituting the human neurotrophic factor-HSA fusion protein have been converted by a substitution reaction or the like is also included in the human neurotrophic factor-HSA fusion protein having the original amino acid sequence. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said about a fusion protein of human neurotrophic factor and SA of an animal species other than human (human neurotrophic factor-SA).

　In addition, a human neurotrophic factor-HSA fusion protein in which the human neurotrophic factor that constitutes it is a precursor of human neurotrophic factor is also a human neurotrophic factor-HSA fusion protein. However, if the precursor of human neurotrophic factor does not exhibit the function of human neurotrophic factor, it is necessary that it is processed in vivo or in vitro and converted into one that exhibits the function of human neurotrophic factor.

In one embodiment of the present invention, the term "hBDNF-SA fusion protein" or "hBDNF-SA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of SA is linked, directly or via a linker, to the C-terminus of the amino acid sequence of hBDNF, and which has the function of hBDNF. When hBDNF in an hBDNF-SA fusion protein is said to have the function of hBDNF, it means that hBDNF retains a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, when the specific activity of normal wild-type hBDNF is taken as 100%. Here, the specific activity of hBDNF in an hBDNF-SA fusion protein is calculated by multiplying the physiological activity of hBDNF per unit mass of the fusion protein by (the molecular weight of the fusion protein/the molecular weight of the portion of the fusion protein corresponding to hBDNF).

In one embodiment of the present invention, the term "hBDNF-HSA fusion protein" or "hBDNF-HSA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of HSA is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of hBDNF, and which has the function of hBDNF. When it is said here that the hBDNF-HSA fusion protein has the function of hBDNF, the definition of the hBDNF-SA fusion protein described above can be applied.

In the present invention, a fusion protein having an amino acid sequence in which the N-terminus of SA of a non-human animal species is linked, directly or via a linker, to the C-terminus of the amino acid sequence of BDNF of a non-human animal species, and which has the function of BDNF, is referred to as a "(non-human animal species) BDNF-(non-human animal species) SA fusion protein." For example, a fusion protein of mouse BDNF and mouse SA is referred to as a "mouse BDNF-mouse SA fusion protein" or "mouse BDNF-MSA." When these fusion proteins are said to have the function of BDNF, the definition of hBDNF-SA fusion protein described above can be applied.

In one embodiment of the present invention, a preferred hBDNF-HSA fusion protein has, for example, the amino acid sequence shown in SEQ ID NO: 76. The hBDNF-HSA fusion protein shown in SEQ ID NO: 76 is obtained by linking wild-type HSA to the C-terminus of wild-type hBDNF via the linker sequence Gly-Ser. The hBDNF-HSA fusion protein shown in SEQ ID NO: 76 is encoded by a gene having, for example, the base sequence shown in SEQ ID NO: 77. In addition, the hBDNF-HSA fusion protein also includes an amino acid sequence in which one or more amino acid residues in the amino acid sequence shown in SEQ ID NO: 76 have been replaced with other amino acid residues, deleted, or mutated by addition, as long as it has the function of hBDNF. The hBDNF-HSA fusion protein is preferably one that has the function of human serum albumin, such as the function of binding and transporting endogenous substances in blood and exogenous substances such as drugs, but is not limited thereto.

The position and type (deletion, substitution, and addition) of each mutation when the amino acid sequence shown in SEQ ID NO:76 is mutated can be easily confirmed by alignment of the amino acid sequence before and after the mutation. The mutated amino acid sequence preferably exhibits 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more, or 99% or more identity, with the amino acid sequence shown in SEQ ID NO:76.

When mutations are added to an hBDNF-HSA fusion protein, which is a fusion protein of wild-type hBDNF and wild-type HSA, mutations can be added only to the HSA portion and not to the hBDNF portion, mutations can be added only to the hBDNF portion without mutations to the HSA portion, or mutations can be added to both the HSA portion and the hBDNF portion. When mutations are added only to the HSA portion, the amino acid sequence of the portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above. When mutations are added only to the hBDNF portion, the amino acid sequence of the portion is the amino acid sequence of hBDNF obtained by adding a mutation to the wild-type hBDNF described above. When mutations are added to both the HSA portion and the hBDNF portion, the amino acid sequence of the HSA portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above, and the amino acid sequence of the hBDNF portion is the amino acid sequence of hBDNF obtained by adding a mutation to the wild-type hBDNF described above. The same applies to the hBDNF-HSA fusion protein having the amino acid sequence shown in SEQ ID NO: 76. The same can be said about fusion proteins of wild-type hBDNF and wild-type SA of non-human animal species (hBDNF-SA).

The following is an example of a case where a mutation is made to an hBDNF-HSA fusion protein having the amino acid sequence shown in SEQ ID NO:76. When an amino acid residue in the amino acid sequence shown in SEQ ID NO:76 is replaced with another amino acid residue, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is added, one or more amino acid residues are added to the amino acid sequence shown in SEQ ID NO:76 or to the N-terminus or C-terminus of the amino acid sequence. The hBDNF-HSA fusion protein may be a combination of these substitutions, deletions, and additions of amino acid residues. The mutation may be made only to the HSA portion, only to the hBDNF portion, or to both portions. The same applies to a fusion protein of hBDNF and SA of an animal species other than human (hBDNF-SA).

　An hBDNF-HSA fusion protein in which the constituent amino acids are modified with sugar chains is also an hBDNF-HSA fusion protein. An hBDNF-HSA fusion protein in which the constituent amino acids are modified with phosphate is also an hBDNF-HSA fusion protein. An hBDNF-HSA fusion protein modified with something other than sugar chains and phosphate is also an hBDNF-HSA fusion protein. An hBDNF-HSA fusion protein in which the side chains of the constituent amino acids have been converted by a substitution reaction or the like is also an hBDNF-HSA fusion protein. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said about a fusion protein of hBDNF and SA of an animal species other than human (hBDNF-SA).

In other words, hBDNF-HSA fusion proteins modified with sugar chains are included in hBDNF-HSA fusion proteins having the original amino acid sequence. Also, hBDNF-HSA fusion proteins modified with phosphate are included in hBDNF-HSA fusion proteins having the original amino acid sequence. Also, those modified with things other than sugar chains and phosphate are also included in hBDNF-HSA fusion proteins having the original amino acid sequence. Also, hBDNF-HSA fusion proteins in which the side chains of the amino acids constituting the hBDNF-HSA fusion protein have been changed by substitution reactions or the like are also included in hBDNF-HSA fusion proteins having the original amino acid sequence. Such changes include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for fusion proteins of hBDNF and SA of animal species other than human (hBDNF-SA).

　An hBDNF-HSA fusion protein in which the hBDNF that constitutes it is a precursor of hBDNF is also an hBDNF-HSA fusion protein. However, if the hBDNF-HSA fusion protein in which hBDNF is a precursor does not exhibit the functions of hBDNF, it is necessary that it be processed in vivo or in vitro and converted into one that exhibits the functions of hBDNF.

In one embodiment of the present invention, the term "hNGF-SA fusion protein" or "hNGF-SA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of SA is linked to the C-terminus of the amino acid sequence of hNGF, either directly or via a linker, and which has the function of hNGF. When hNGF in an hNGF-SA fusion protein is said to have the function of hNGF, it means that hNGF retains a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, when the specific activity of normal wild-type hNGF is taken as 100%. Here, the specific activity of hNGF in an hNGF-SA fusion protein is calculated by multiplying the physiological activity of hNGF per unit mass of the fusion protein by (the molecular weight of the fusion protein/the molecular weight of the portion of the fusion protein corresponding to hNGF).

In one embodiment of the present invention, the term "hNGF-HSA fusion protein" or "hNGF-HSA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of HSA is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of hNGF, and which has the function of hNGF. When it is said here that the hNGF-HSA fusion protein has the function of hNGF, the definition of the hNGF-SA fusion protein described above can be applied.

In one embodiment of the present invention, a fusion protein having an amino acid sequence in which the N-terminus of SA of a non-human animal species is linked, directly or via a linker, to the C-terminus of the amino acid sequence of NGF of a non-human animal species, and which has the function of NGF, is referred to as a "(non-human animal species) NGF-(non-human animal species) SA fusion protein." For example, a fusion protein of mouse NGF and mouse SA is referred to as a "mouse NGF-mouse SA fusion protein" or "mouse NGF-MSA." When these fusion proteins are said to have the function of NGF, the definition of the hNGF-SA fusion protein described above can be applied. In addition,

In one embodiment of the present invention, a preferred hNGF-HSA fusion protein has, for example, the amino acid sequence shown in SEQ ID NO: 78. The hNGF-HSA fusion protein shown in SEQ ID NO: 78 is obtained by linking wild-type HSA to the C-terminus of wild-type hNGF via the linker sequence Gly-Ser. The hNGF-HSA fusion protein shown in SEQ ID NO: 78 is encoded by a gene having, for example, the base sequence shown in SEQ ID NO: 79. In addition, the hNGF-HSA fusion protein also includes an amino acid sequence in which one or more amino acid residues in the amino acid sequence shown in SEQ ID NO: 78 have been replaced with other amino acid residues, deleted, or mutated by addition, as long as it has the function of hNGF. The hNGF-HSA fusion protein is preferably one that has the function of human serum albumin, such as the function of binding and transporting endogenous substances in blood and exogenous substances such as drugs, but is not limited thereto.

The position and type (deletion, substitution, and addition) of each mutation when the amino acid sequence shown in SEQ ID NO:78 is mutated can be easily confirmed by alignment of the amino acid sequence before and after the mutation. The mutated amino acid sequence preferably exhibits 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more or 99% or more identity, with the amino acid sequence shown in SEQ ID NO:78.

When mutations are introduced into an hNGF-HSA fusion protein, which is a fusion protein of wild-type hNGF and wild-type HSA, mutations can be introduced only in the HSA portion and not in the hNGF portion, mutations can be introduced only in the hNGF portion without mutations in the HSA portion, or mutations can be introduced in both the HSA portion and the hNGF portion. When mutations are introduced only in the HSA portion, the amino acid sequence of the portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above. When mutations are introduced only in the hNGF portion, the amino acid sequence of the portion is the amino acid sequence of hNGF obtained by adding a mutation to the wild-type hNGF described above. When mutations are introduced in both the HSA portion and the hNGF portion, the amino acid sequence of the HSA portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above, and the amino acid sequence of the hNGF portion is the amino acid sequence of hNGF obtained by adding a mutation to the wild-type hNGF described above. The same applies to the hNGF-HSA fusion protein having the amino acid sequence shown in SEQ ID NO: 78. The same can be said about fusion proteins between wild-type hNGF and wild-type SA (hNGF-SA) of non-human animal species.

The following is an example of a case where a mutation is made to an hNGF-HSA fusion protein having the amino acid sequence shown in SEQ ID NO:78. When an amino acid residue in the amino acid sequence shown in SEQ ID NO:78 is replaced with another amino acid residue, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is added, one or more amino acid residues are added to the amino acid sequence shown in SEQ ID NO:78 or to the N-terminus or C-terminus of the amino acid sequence. The hNGF-HSA fusion protein may be a combination of these substitutions, deletions, and additions of amino acid residues. The mutation may be made only to the HSA portion, only to the hNGF portion, or to both portions. The same can be said for fusion proteins of non-human animal species' NGF and HSA (NGF-SA), and fusion proteins of non-human animal species' NGF and non-human animal species' SA.

　An hNGF-HSA fusion protein in which the amino acids constituting the protein are modified with sugar chains is also an hNGF-HSA fusion protein. An hNGF-HSA fusion protein in which the amino acids constituting the protein are modified with phosphate is also an hNGF-HSA fusion protein. An hNGF-HSA fusion protein modified with something other than sugar chains and phosphate is also an hNGF-HSA fusion protein. An hNGF-HSA fusion protein in which the side chains of the amino acids constituting the protein have been changed by a substitution reaction or the like is also an hNGF-HSA fusion protein. Such a change includes, but is not limited to, the change of a cysteine residue to formylglycine. The same can be said about a fusion protein (hNGF-SA) between hNGF and SA of an animal species other than human.

In other words, hNGF-HSA fusion proteins modified with sugar chains are included in the hNGF-HSA fusion proteins having the original amino acid sequence. Also, hNGF-HSA fusion proteins modified with phosphate are included in the hNGF-HSA fusion proteins having the original amino acid sequence. Also, those modified with things other than sugar chains and phosphate are included in the hNGF-HSA fusion proteins having the original amino acid sequence. Also, hNGF-HSA fusion proteins in which the side chains of the amino acids constituting the hNGF-HSA fusion proteins have been changed by substitution reactions or the like are included in the hNGF-HSA fusion proteins having the original amino acid sequence. Such changes include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said about fusion proteins of hNGF and SA of animals other than humans (hNGF-SA).

　An hNGF-HSA fusion protein in which the hNGF that constitutes it is a precursor of hNGF is also an hNGF-HSA fusion protein. However, if the hNGF-HSA fusion protein, in which hNGF is a precursor, does not function as hNGF, it is necessary that it be processed in vivo or in vitro and converted into one that functions as hNGF. The same can be said for a fusion protein of hNGF and SA of an animal species other than human (hNGF-SA).

In one embodiment of the present invention, the term "hNT-3-SA fusion protein" or "hNT-3-SA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of SA is linked, directly or via a linker, to the C-terminus of the amino acid sequence of hNT-3, and which has the function of hNT-3. When hNT-3 in an hNT-3-SA fusion protein is said to have the function of hNT-3, it means that hNT-3 retains a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, when the specific activity of normal wild-type hNT-3 is taken as 100%. Here, the specific activity of hNT-3 in the hNT-3-SA fusion protein is calculated by multiplying the physiological activity of hNT-3 per unit mass of the fusion protein by (the molecular weight of the fusion protein/the molecular weight of the portion of the fusion protein corresponding to hNT-3).

In one embodiment of the present invention, the term "hNT-3-HSA fusion protein" or "hNT-3-HSA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of HSA is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of hNT-3, and which has the function of hNT-3. When it is said here that the hNT-3-HSA fusion protein has the function of hNT-3, the definition of the hNT-3-SA fusion protein described above can be applied.

In one embodiment of the present invention, a fusion protein having an amino acid sequence in which the N-terminus of SA of a non-human animal species is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of NT-3 of a non-human animal species, and which has the function of NT-3, is referred to as a "(non-human animal species) NT-3-(non-human animal species) SA fusion protein." For example, a fusion protein of mouse NT-3 and mouse SA is referred to as a "mouse NT-3-mouse SA fusion protein" or "mouse NT-3-MSA." When these fusion proteins are said to have the function of NT-3, the definition of hNT-3-SA fusion protein described above can be applied.

In one embodiment of the present invention, a preferred hNT-3-HSA fusion protein has, for example, the amino acid sequence shown in SEQ ID NO: 80. The hNT-3-HSA fusion protein shown in SEQ ID NO: 80 is obtained by linking wild-type HSA to the C-terminus of wild-type hNT-3 via the linker sequence Gly-Ser. The hNT-3-HSA fusion protein shown in SEQ ID NO: 80 is encoded by a gene having, for example, the base sequence shown in SEQ ID NO: 81. In addition, the hNT-3-HSA fusion protein also includes an amino acid sequence in which one or more amino acid residues in the amino acid sequence shown in SEQ ID NO: 80 have been replaced with other amino acid residues, deleted, or mutated by addition, as long as it has the function of hNT-3. The hNT-3-HSA fusion protein is preferably one that has the function of human serum albumin, such as the function of binding and transporting endogenous substances in blood and exogenous substances such as drugs, but is not limited thereto.

The position and type (deletion, substitution, and addition) of each mutation when the amino acid sequence shown in SEQ ID NO:80 is mutated can be easily confirmed by alignment of the amino acid sequence before and after the mutation. The mutated amino acid sequence preferably exhibits 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more, or 99% or more identity, with the amino acid sequence shown in SEQ ID NO:80.

When mutations are introduced into the hNT-3-HSA fusion protein, which is a fusion protein of wild-type hNT-3 and wild-type HSA, mutations can be introduced only in the HSA portion and not in the hNT-3 portion, mutations can be introduced only in the hNT-3 portion without mutations in the HSA portion, or mutations can be introduced in both the HSA portion and the hNT-3 portion. When mutations are introduced only in the HSA portion, the amino acid sequence of the portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above. When mutations are introduced only in the hNT-3 portion, the amino acid sequence of the portion is the amino acid sequence of hNT-3 obtained by adding a mutation to the wild-type hNT-3 described above. When mutations are introduced both in the HSA portion and the hNT-3 portion, the amino acid sequence of the HSA portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above, and the amino acid sequence of the hNT-3 portion is the amino acid sequence of hNT-3 obtained by adding a mutation to the wild-type hNT-3 described above. The same is true for the hNT-3-HSA fusion protein having the amino acid sequence shown in SEQ ID NO: 80. The same is true for the fusion protein of wild-type hNT-3 and wild-type SA (hNT-3-SA) of an animal species other than human.

The following is an example of a case where a mutation is made to an hNT-3-HSA fusion protein having the amino acid sequence shown in SEQ ID NO:80. When an amino acid residue in the amino acid sequence shown in SEQ ID NO:80 is replaced with another amino acid residue, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is added, one or more amino acid residues are added to the amino acid sequence shown in SEQ ID NO:80 or to the N-terminus or C-terminus of the amino acid sequence. The hNT-3-HSA fusion protein may be a combination of these substitutions, deletions, and additions of amino acid residues. The mutation may be made only to the HSA portion, only to the hNT-3 portion, or to both portions. The same can be said about the fusion protein (hNT-3-SA) between hNT-3 and SA of a non-human animal species.

　An hNT-3-HSA fusion protein in which the amino acids constituting the protein are modified with sugar chains is also an hNT-3-HSA fusion protein. An hNT-3-HSA fusion protein in which the amino acids constituting the protein are modified with phosphate is also an hNT-3-HSA fusion protein. An hNT-3-HSA fusion protein modified with something other than sugar chains and phosphate is also an hNT-3-HSA fusion protein. An hNT-3-HSA fusion protein in which the side chains of the amino acids constituting the protein have been converted by a substitution reaction or the like is also an hNT-3-HSA fusion protein. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said about a fusion protein (hNT-3-SA) of hNT-3 and SA of an animal species other than human.

In other words, hNT-3-HSA fusion proteins modified with sugar chains are included in the hNT-3-HSA fusion proteins having the original amino acid sequence. Also, hNT-3-HSA fusion proteins modified with phosphate are included in the hNT-3-HSA fusion proteins having the original amino acid sequence. Also, those modified with things other than sugar chains and phosphate are included in the hNT-3-HSA fusion proteins having the original amino acid sequence. Also, hNT-3-HSA fusion proteins in which the side chains of the amino acids constituting the hNT-3-HSA fusion proteins have been converted by substitution reactions or the like are included in the hNT-3-HSA fusion proteins having the original amino acid sequence. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for fusion proteins of hNT-3 and SA of animal species other than human (hNT-3-SA).

　An hNT-3-HSA fusion protein in which the hNT-3 that constitutes it is a precursor of hNT-3 is also an hNT-3-HSA fusion protein. However, if the hNT-3-HSA fusion protein, of which hNT-3 is a precursor, does not function as hNT-3, it is necessary that it be processed in vivo or in vitro and converted into one that functions as hNT-3. The same can be said for a fusion protein of hNT-3 and SA of an animal species other than human (hNT-3-SA).

In one embodiment of the present invention, the term "hNT-4-SA fusion protein" or "hNT-4-SA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of SA is linked, directly or via a linker, to the C-terminus of the amino acid sequence of hNT-4, and which has the function of hNT-4. When hNT-4 in an hNT-4-SA fusion protein is said to have the function of hNT-4, it means that hNT-4 retains a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, when the specific activity of normal wild-type hNT-4 is taken as 100%. Here, the specific activity of hNT-4 in the hNT-4-SA fusion protein is calculated by multiplying the physiological activity of hNT-4 per unit mass of the fusion protein by (the molecular weight of the fusion protein/the molecular weight of the portion of the fusion protein corresponding to hNT-4).

In one embodiment of the present invention, the term "hNT-4-HSA fusion protein" or "hNT-4-HSA" refers to a fusion protein having an amino acid sequence in which the N-terminus of the amino acid sequence of HSA is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of hNT-4, and which has the function of hNT-4. When it is said here that the hNT-4-HSA fusion protein has the function of hNT-4, the definition of the hNT-4-SA fusion protein described above can be applied.

In one embodiment of the present invention, a fusion protein having an amino acid sequence in which the N-terminus of SA of a non-human animal species is linked, either directly or via a linker, to the C-terminus of the amino acid sequence of NT-4 of a non-human animal species, and which has the function of NT-4, is referred to as a "(non-human animal species) NT-4-(non-human animal species) SA fusion protein." For example, a fusion protein of mouse NT-4 and mouse SA is referred to as a "mouse NT-4-mouse SA fusion protein" or "mouse NT-4-MSA." When these fusion proteins are said to have the function of NT-4, the definition of hNT-4-SA fusion protein described above can be applied.

In one embodiment of the present invention, a preferred hNT-4-HSA fusion protein has, for example, the amino acid sequence shown in SEQ ID NO: 82. The hNT-4-HSA fusion protein shown in SEQ ID NO: 82 is obtained by linking wild-type HSA to the C-terminus of wild-type hNT-4 via the linker sequence Gly-Ser. The hNT-4-HSA fusion protein shown in SEQ ID NO: 82 is encoded by a gene having, for example, the base sequence shown in SEQ ID NO: 83. In addition, the hNT-4-HSA fusion protein also includes an amino acid sequence in which one or more amino acid residues in the amino acid sequence shown in SEQ ID NO: 82 have been replaced with other amino acid residues, deleted, or mutated by addition, as long as it has the function of hNT-4. The hNT-4-HSA fusion protein is preferably one that has the function of human serum albumin, such as the function of binding and transporting endogenous substances in blood and exogenous substances such as drugs, but is not limited thereto.

The position and type (deletion, substitution, and addition) of each mutation when the amino acid sequence shown in SEQ ID NO:82 is mutated can be easily confirmed by alignment of the amino acid sequence before and after the mutation. The mutated amino acid sequence preferably has 80% or more identity, 85% or more identity, 90% or more identity, or 95% or more identity, for example, 98% or more, or 99% or more identity, with the amino acid sequence shown in SEQ ID NO:82.

When mutations are introduced into the hNT-4-HSA fusion protein, which is a fusion protein of wild-type hNT-4 and wild-type HSA, mutations can be introduced only in the HSA portion and not in the hNT-4 portion, mutations can be introduced only in the hNT-4 portion without mutations in the HSA portion, or mutations can be introduced in both the HSA portion and the hNT-4 portion. When mutations are introduced only in the HSA portion, the amino acid sequence of the portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above. When mutations are introduced only in the hNT-4 portion, the amino acid sequence of the portion is the amino acid sequence of hNT-4 obtained by adding a mutation to the wild-type hNT-4 described above. When mutations are introduced in both the HSA portion and the hNT-4 portion, the amino acid sequence of the HSA portion is the amino acid sequence of HSA obtained by adding a mutation to the wild-type HSA described above, and the amino acid sequence of the hNT-4 portion is the amino acid sequence of hNT-4 obtained by adding a mutation to the wild-type hNT-4 described above. The same is true for the hNT-4-HSA fusion protein having the amino acid sequence shown in SEQ ID NO: 82. The same is true for the fusion protein of wild-type hNT-4 and wild-type SA (hNT-4-SA) of an animal species other than human.

The following is an example of a case where a mutation is made to an hNT-4-HSA fusion protein having the amino acid sequence shown in SEQ ID NO:82. When an amino acid residue in the amino acid sequence shown in SEQ ID NO:82 is replaced with another amino acid residue, the number of amino acid residues to be replaced is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is deleted, the number of amino acid residues to be deleted is 1 to 10, 1 to 5, or 1 to 3, for example, 1 or 2. When an amino acid residue is added, one or more amino acid residues are added to the amino acid sequence shown in SEQ ID NO:82 or to the N-terminus or C-terminus of the amino acid sequence. The hNT-4-HSA fusion protein may be a combination of these substitutions, deletions, and additions of amino acid residues. The mutation may be made only to the HSA portion, only to the hNT-4 portion, or to both portions. The same can be said about the fusion protein of hNT-4 and SA of a non-human animal species (hNT-4-SA).

　An hNT-4-HSA fusion protein in which the amino acids constituting the protein are modified with sugar chains is also an hNT-4-HSA fusion protein. An hNT-4-HSA fusion protein in which the amino acids constituting the protein are modified with phosphate is also an hNT-4-HSA fusion protein. An hNT-4-HSA fusion protein in which the amino acids constituting the protein are modified with something other than sugar chains and phosphate is also an hNT-4-HSA fusion protein. An hNT-4-HSA fusion protein in which the side chains of the amino acids constituting the protein have been converted by a substitution reaction or the like is also an hNT-4-HSA fusion protein. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for a fusion protein of NT-4 of a non-human animal species and HSA (NT-4-SA), and a fusion protein of NT-4 of a non-human animal species and SA of a non-human animal species.

In other words, hNT-4-HSA fusion proteins modified with sugar chains are included in the hNT-4-HSA fusion proteins having the original amino acid sequence. Also, hNT-4-HSA fusion proteins modified with phosphate are included in the hNT-4-HSA fusion proteins having the original amino acid sequence. Also, those modified with things other than sugar chains and phosphate are included in the hNT-4-HSA fusion proteins having the original amino acid sequence. Also, those in which the side chains of the amino acids constituting the hNT-4-HSA fusion protein have been converted by a substitution reaction or the like are included in the hNT-4-HSA fusion protein having the original amino acid sequence. Such conversions include, but are not limited to, the conversion of cysteine residues to formylglycine. The same can be said for the fusion protein of NT-4 of a non-human animal species and HSA (NT-4-SA), and the fusion protein of NT-4 of a non-human animal species and SA of a non-human animal species.

　An hNT-4-HSA fusion protein in which the hNT-4 that constitutes it is a precursor of hNT-4 is also an hNT-4-HSA fusion protein. However, if the hNT-4-HSA fusion protein, of which hNT-4 is a precursor, does not exhibit the function of hNT-4, it is necessary that it be processed in vivo or in vitro and converted into one that exhibits the function of hNT-4.

In one embodiment of the present invention, the terms "fusion protein of HSA and human neurotrophic factor", "fusion protein of human neurotrophic factor and HSA", or "fusion protein of human serum albumin and human neurotrophic factor" include both the above-mentioned "HSA-human neurotrophic factor fusion protein" and "human neurotrophic factor-HSA fusion protein". These also apply when SA is from an animal species other than human, or when nerve growth factor is from an animal species other than human.

　In addition, when we say "a fusion protein of HSA and hBDNF," "a fusion protein of hBDNF and HSA," or "a fusion protein of human serum albumin and human brain-derived trophic factor," we include both the above-mentioned "HSA-hBDNF fusion protein" and "hBDNF-HSA fusion protein." These also apply when SA is from an animal species other than human, or when BDNF is from an animal species other than human.

　In addition, when we say "a fusion protein of HSA and hNGF," "a fusion protein of hNGF and HSA," or "a fusion protein of human serum albumin and human nerve growth factor," we include both the above-mentioned "HSA-hNGF fusion protein" and "hNGF-HSA fusion protein." These also apply when SA is from an animal species other than human, or when NGF is from an animal species other than human.

Furthermore, when we say "a fusion protein of HSA and hNT-3," "a fusion protein of hNT-3 and HSA," or "a fusion protein of human serum albumin and human neurotrophin-3," we include both the above-mentioned "HSA-hNT-3 fusion protein" and "hNT-3-HSA fusion protein." These also apply when SA is of an animal species other than human, or when NT-3 is of an animal species other than human.

Furthermore, when we say "a fusion protein of HSA and hNT-4," "a fusion protein of hNT-4 and HSA," or "a fusion protein of human serum albumin and human neurotrophin-4," we include both the above-mentioned "HSA-hNT-4 fusion protein" and "hNT-4-HSA fusion protein." These also apply when SA is from an animal species other than human, or when NT-4 is from an animal species other than human.

In one embodiment of the present invention, in the fusion protein of SA and a neurotrophic factor, the SA and the neurotrophic factor are linked directly or via a linker. Here, the term "linker" refers to a portion that does not belong to either the amino acid sequence of SA or the amino acid sequence of a neurotrophic factor. In other words, the linker is a peptide chain that is interposed between the SA and the neurotrophic factor. The linker has various functions. These functions include a function between the SA and the neurotrophic factor to bind the SA and the neurotrophic factor, a function to reduce mutual interference between the SA and the neurotrophic factor by increasing the distance between them in the fusion protein molecule, and a function between the SA and the neurotrophic factor to act as a hinge that connects the SA and the neurotrophic factor and gives flexibility to the three-dimensional structure of the fusion protein. In the molecule of the fusion protein, the linker exerts at least one of these functions. These are applicable regardless of the animal species of the SA and the animal species of the nerve growth factor. They are not limited to cases where the neurotrophic factor is BDNF, NGF, NT-3, or NT-4, but also apply to other neurotrophic factors.

　Below, the methods for producing fusion proteins of SA and neurotrophic factors are described in detail, taking as examples a fusion protein of HSA and hBDNF, a fusion protein of HSA and hNGF, a fusion protein of HSA and hNT-3, and a fusion protein of HSA and hNT-4. The matters described in detail here can be applied when SA is from an animal species other than human, or when BDNF, NGF, NT-3, or NT-4 is from an animal species other than human. They can also be applied to neurotrophic factors other than BDNF, NGF, NT-3, or NT-4.

A fusion protein of HSA and hBDNF can be produced as a recombinant protein by preparing an expression vector incorporating a DNA fragment in which a gene encoding hBDNF is linked in-frame downstream or upstream of a gene encoding HSA, and culturing a host cell transformed with the expression vector. A fusion protein of HSA and hNGF can be produced as a recombinant protein by preparing an expression vector incorporating a DNA fragment in which a gene encoding hNGF is linked in-frame downstream or upstream of a gene encoding HSA, and culturing a host cell transformed with the expression vector. A fusion protein of HSA and hNT-3 can be produced as a recombinant protein by preparing an expression vector incorporating a DNA fragment in which a gene encoding hNT-3 is linked in-frame downstream or upstream of a gene encoding HSA, and culturing a host cell transformed with the expression vector. In addition, a fusion protein of HSA and hNT-4 can be produced as a recombinant protein by preparing an expression vector incorporating a DNA fragment in which a gene encoding hNT-4 is linked in-frame to the downstream or upstream of a gene encoding HSA, and culturing a host cell transformed with the expression vector. The fusion protein produced as a recombinant protein in this way consists of a single polypeptide chain.

When preparing a fusion protein as a recombinant fusion protein, a gene encoding hBDNF can be linked in-frame downstream of a gene encoding HSA to obtain a fusion protein having the amino acid sequence of hBDNF at the C-terminus of the amino acid sequence of HSA. Conversely, a gene encoding hBDNF can be linked in-frame upstream of a gene encoding HSA to obtain a fusion protein having the amino acid sequence of hBDNF at the N-terminus of the amino acid sequence of HSA. When preparing a fusion protein as a recombinant fusion protein, a gene encoding hNGF can be linked in-frame downstream of a gene encoding HSA to obtain a fusion protein having the amino acid sequence of hNGF at the C-terminus of the amino acid sequence of HSA. Conversely, a gene encoding hNGF can be linked in-frame upstream of a gene encoding HSA to obtain a fusion protein having the amino acid sequence of hNGF at the N-terminus of the amino acid sequence of HSA. When preparing a fusion protein as a recombinant fusion protein, a gene encoding hNT-3 can be linked in-frame downstream of a gene encoding HSA to obtain a fusion protein having the amino acid sequence of hNT-3 at the C-terminus of the amino acid sequence of HSA. Conversely, by linking a gene encoding hNT-3 in frame upstream of the gene encoding HSA, a fusion protein having the amino acid sequence of hNT-3 at the N-terminus of the amino acid sequence of HSA can be obtained. In addition, when producing a fusion protein as a recombinant fusion protein, by linking a gene encoding hNT-4 in frame downstream of the gene encoding HSA, a fusion protein having the amino acid sequence of hNT-4 at the C-terminus of the amino acid sequence of HSA can be obtained. Conversely, by linking a gene encoding hNT-4 in frame upstream of the gene encoding HSA, a fusion protein having the amino acid sequence of hNT-4 at the N-terminus of the amino acid sequence of HSA can be obtained. In either case, the fusion protein produced as a recombinant fusion protein is a single-chain polypeptide.

In the single-chain polypeptide of the fusion protein, when the amino acid sequence of HSA is located on the N-terminal side of the amino acid sequence of hBDNF, hNGF, hNT-3 or hNT-4, the C-terminus of HSA and the N-terminus of hBDNF, hNGF, hNT-3 or hNT-4 are linked directly by a peptide bond or via a linker. Here, the "linker" refers to a portion of the single-chain polypeptide that is present between the C-terminus of HSA and the N-terminus of hBDNF, hNGF, hNT-3 or hNT-4 and has an amino acid sequence that does not belong to HSA, hBDNF, hNGF, hNT-3 or hNT-4. Figure 7 shows a schematic diagram of a single-chain polypeptide HSA-hBDNF fusion protein that has HSA, a linker and hBDNF in this order from the N-terminus. In the HSA-hBDNF fusion protein, the C-terminus of HSA and the N-terminus of the linker are linked by a peptide bond, and the C-terminus of the linker and the N-terminus of hBDNF are linked by a peptide bond. FIG. 8 shows a schematic diagram of a single-chain polypeptide HSA-hNGF fusion protein having HSA, a linker, and hNGF in this order from the N-terminus. In the HSA-hNGF fusion protein, the C-terminus of HSA is bound to the N-terminus of the linker by a peptide bond, and the C-terminus of the linker is bound to the N-terminus of hNGF by a peptide bond. FIG. 9 shows a schematic diagram of a single-chain polypeptide HSA-hNT-3 fusion protein having HSA, a linker, and hNT-3 in this order from the N-terminus. In the HSA-hNT-3 fusion protein, the C-terminus of HSA is bound to the N-terminus of the linker by a peptide bond, and the C-terminus of the linker is bound to the N-terminus of hNT-3 by a peptide bond ... FIG. 10 shows a schematic diagram of a single-chain polypeptide HSA-hNT-4 fusion protein having HSA, a linker, and hNT-4 in this order from the N-terminus. The HSA-hNT-4 fusion protein is composed of the C-terminus of HSA and the N-terminus of the linker bound by a peptide bond, and the C-terminus of the linker and the N-terminus of hNT-4 bound by a peptide bond.

In addition, when the amino acid sequence of hBDNF, hNGF, hNT-3 or hNT-4 is located at the N-terminus of the amino acid sequence of HSA in the single-chain polypeptide of the fusion protein, the C-terminus of hBDNF, hNGF, hNT-3 or hNT-4 and the N-terminus of HSA are linked directly by a peptide bond or via a linker. Here, the "linker" refers to a portion of the single-chain polypeptide that is present between the C-terminus of hBDNF, hNGF, hNT-3 or hNT-4 and the N-terminus of HSA and has an amino acid sequence that does not belong to HSA, hBDNF, hNGF, hNT-3 or hNT-4. Figure 11 shows a schematic diagram of a single-chain polypeptide hBDNF-HSA fusion protein having hBDNF, a linker and HSA in that order from the N-terminus. In the hBDNF-HSA fusion protein, the C-terminus of hBDNF and the N-terminus of the linker are bound by a peptide bond, and the C-terminus of the linker and the N-terminus of HSA are bound by a peptide bond. FIG. 12 shows a schematic representation of a single-chain polypeptide hNGF-HSA fusion protein having hNGF, a linker, and HSA in this order from the N-terminus. In the hNGF-HSA fusion protein, the C-terminus of hNGF and the N-terminus of the linker are bound by a peptide bond, and the C-terminus of the linker and the N-terminus of HSA are bound by a peptide bond ... FIG. 13 shows a schematic representation of a single-chain polypeptide hNT-3-HSA fusion protein having hNT-3, a linker, and HSA in this order from the N-terminus. In the hNT-3-HSA fusion protein, the C-terminus of hNT-3 and the N-terminus of the linker are bound by a peptide bond, and the C-terminus of the linker and the N-terminus of HSA are bound by a peptide bond. In addition, Figure 14 shows a schematic diagram of the hNT-4-HSA fusion protein, which is a single-chain polypeptide having, in order from the N-terminus, hNT-4, a linker, and HSA. In the hNT-4-HSA fusion protein, the C-terminus of hNT-4 and the N-terminus of the linker are bound by a peptide bond, and the C-terminus of the linker and the N-terminus of HSA are bound by a peptide bond.

There is no particular limitation on the amino acid sequence of the peptide linker, so long as it functions as a linker in the fusion protein molecule. There is also no particular limitation on the length of the peptide linker, so long as it functions as a linker in the fusion protein molecule. The peptide linker is composed of one or more amino acids. When the peptide linker is composed of multiple amino acids, the number of amino acids is preferably 2 to 50, more preferably 5 to 30, and even more preferably 10 to 25. Suitable examples of peptide linkers include those consisting of Gly-Ser, Gly-Gly-Ser, or amino acid sequences shown in SEQ ID NOs: 9 to 11 (collectively referred to as basic sequences), and those containing these. For example, the peptide linker is one that contains an amino acid sequence in which the basic sequence is repeated 2 to 10 times, one that contains an amino acid sequence in which the basic sequence is repeated 2 to 6 times, or one that contains an amino acid sequence in which the basic sequence is repeated 3 to 5 times. One or more amino acids in these amino acid sequences may be deleted, replaced with other amino acids, added, etc. When deleting an amino acid, the number of amino acids to be deleted is preferably 1 or 2. When replacing an amino acid with another amino acid, the number of amino acids to be replaced is preferably 1 or 2. When adding an amino acid, the number of amino acids to be added is preferably 1 or 2. The amino acid sequence of the desired linker portion can be obtained by combining these deletions, substitutions, and additions of amino acids. The peptide linker may be composed of one amino acid, and the amino acid that constitutes the linker is, for example, glycine or serine.

In one embodiment of the present invention,
(1) A fusion protein of HSA and hBDNF refers to a fusion protein characterized in that when expressed in a host cell as a recombinant protein, particularly when expressed so that the recombinant protein is secreted from the cells and accumulated in the culture medium, the amount of hBDNF expressed in the culture supernatant is at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or physiological activity, compared to when wild-type hBDNF is expressed in a host cell as a recombinant protein under the same conditions, such as 1.1 to 4 times, 1.5 to 3.6 times, 2 to 3.6 times, 10 to 20 times, 20 to 30 times, etc.
(2) In one embodiment of the present invention, the term "fusion protein of HSA and hNGF" refers to a fusion protein characterized in that, when expressed in a host cell as a recombinant protein, in particular when expressed so that the recombinant protein is secreted from the cells and accumulated in the culture medium, the amount of hNGF expressed in the culture supernatant is at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or physiological activity, compared to when wild-type hNGF is expressed in a host cell as a recombinant protein under the same conditions, such as 1.1 to 4 times, 1.5 to 3.6 times, 2 to 3.6 times, 10 to 20 times, 20 to 30 times, etc.
(3) In one embodiment of the present invention, a fusion protein of HSA and hNT-3 refers to a fusion protein characterized in that, when expressed in a host cell as a recombinant protein, particularly when expressed so that the recombinant protein is secreted from the cells and accumulated in the culture medium, the expression amount of hNT-3 in the culture supernatant is at least 1.1 times or more, 1.2 times or more, 1.5 times or more, 2 times or more, 2.5 times or more, or 3.5 times or more, in terms of concentration or physiological activity, compared to when wild-type hNT-3 is expressed in a host cell as a recombinant protein under the same conditions,
(4) In one embodiment of the present invention, a fusion protein of HSA and hNT-4 refers to a fusion protein characterized in that, when expressed in host cells as a recombinant protein, in particular when expressed so that the recombinant protein is secreted from the cells and accumulated in the culture medium, the expression amount of hNT-4 in the culture supernatant is at least 1.1 times or more, 1.2 times or more, 1.5 times or more, 2 times or more, 2.5 times or more, or 3.5 times or more, in terms of concentration or physiological activity, compared to when wild-type hNT-4 is expressed in host cells as a recombinant protein under the same conditions.

In the above embodiments (1) to (4), "under the same conditions" means that the expression vector, host cells, culture conditions, etc. are the same. The preferred host cells used in this case are mammalian cells such as CHO cells and NS/0 cells, and particularly CHO cells.

Preferred embodiments of the fusion protein of HSA and hBDNF include the following (1) to (4):
(1) A peptide having an amino acid sequence shown in SEQ ID NO:68, in which the N-terminus of the amino acid sequence of wild-type hBDNF shown in SEQ ID NO:60 is linked to the C-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO:3 via the linker sequence Gly-Ser;
(2) Having the amino acid sequence shown in SEQ ID NO: 76, in which the N-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO: 3 is linked to the C-terminus of the amino acid sequence of wild-type hBDNF shown in SEQ ID NO: 60 via the linker sequence Gly-Ser.
(3) A peptide having an amino acid sequence shown in SEQ ID NO: 85, in which the N-terminus of the amino acid sequence of wild-type hBDNF (pro-form) shown in SEQ ID NO: 84 is linked to the C-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO: 3 via the linker sequence Gly-Ser;
(4) Having the amino acid sequence shown in SEQ ID NO: 86, in which the N-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO: 3 is linked to the C-terminus of the amino acid sequence of wild-type hBDNF (pro-form) shown in SEQ ID NO: 84 via the linker sequence Gly-Ser.

Preferred embodiments of the fusion protein of HSA and hNGF include the following (1) to (4):
(1) A peptide having an amino acid sequence shown in SEQ ID NO: 70, in which the N-terminus of the amino acid sequence of wild-type hNGF shown in SEQ ID NO: 62 is linked to the C-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO: 3 via the linker sequence Gly-Ser;
(2) Having the amino acid sequence shown in SEQ ID NO: 78, in which the N-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO: 3 is linked to the C-terminus of the amino acid sequence of wild-type hNGF shown in SEQ ID NO: 62 via the linker sequence Gly-Ser.
(3) A peptide having an amino acid sequence shown in SEQ ID NO: 88, in which the N-terminus of the amino acid sequence of wild-type hNGF (pro-form) shown in SEQ ID NO: 87 is linked to the C-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO: 3 via the linker sequence Gly-Ser;
(4) Having the amino acid sequence shown in SEQ ID NO: 89, in which the N-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO: 3 is linked to the C-terminus of the amino acid sequence of wild-type hNGF (pro-form) shown in SEQ ID NO: 87 via the linker sequence Gly-Ser.

Furthermore, preferred embodiments of the fusion protein of HSA and hNT-3 include the following (1) to (4):
(1) A peptide having an amino acid sequence shown in SEQ ID NO: 72, in which the N-terminus of the amino acid sequence of wild-type hNT-3 shown in SEQ ID NO: 64 is linked to the C-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO: 3 via the linker sequence Gly-Ser;
(2) Having the amino acid sequence shown in SEQ ID NO: 80, in which the N-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO: 3 is linked to the C-terminus of the amino acid sequence of wild-type hNT-3 shown in SEQ ID NO: 64 via the linker sequence Gly-Ser.
(3) A peptide having an amino acid sequence shown in SEQ ID NO: 91, in which the N-terminus of the amino acid sequence of wild-type hNT-3 (pro-form) shown in SEQ ID NO: 90 is linked via a linker sequence Gly-Ser to the C-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO: 3;
(4) Having the amino acid sequence shown in SEQ ID NO: 92, in which the N-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO: 3 is linked to the C-terminus of the amino acid sequence of wild-type hNT-3 (pro-form) shown in SEQ ID NO: 90 via the linker sequence Gly-Ser.

Preferred embodiments of the fusion protein of HSA and hNT-4 include the following (1) to (4):
(1) A peptide having an amino acid sequence shown in SEQ ID NO: 74, in which the N-terminus of the amino acid sequence of wild-type hNT-4 shown in SEQ ID NO: 66 is linked to the C-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO: 3 via the linker sequence Gly-Ser;
(2) Having the amino acid sequence shown in SEQ ID NO: 82, in which the N-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO: 3 is linked to the C-terminus of the amino acid sequence of wild-type hNT-4 shown in SEQ ID NO: 66 via the linker sequence Gly-Ser.
(3) A peptide having an amino acid sequence shown in SEQ ID NO: 94, in which the N-terminus of the amino acid sequence of wild-type hNT-4 (pro-form) shown in SEQ ID NO: 93 is linked to the C-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO: 3 via the linker sequence Gly-Ser;
(4) Having the amino acid sequence shown in SEQ ID NO:95, in which the N-terminus of the amino acid sequence of wild-type HSA shown in SEQ ID NO:3 is linked to the C-terminus of the amino acid sequence of wild-type hNT-4 (pro-form) shown in SEQ ID NO:93 via the linker sequence Gly-Ser.

In one embodiment of the present invention, the fusion protein of HSA and hBDNF is characterized in that when expressed in a host cell as a recombinant protein, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the amount of hBDNF expressed in the culture supernatant is increased in terms of concentration or physiological activity compared to when wild-type hBDNF is expressed in a host cell as a recombinant protein under the same conditions. Therefore, when produced as a recombinant protein, the fusion protein of HSA and hBDNF can increase production efficiency compared to wild-type hBDNF, thereby reducing production costs. It is known that pharmaceuticals containing recombinant proteins as active ingredients are very expensive. Therefore, even increasing the amount of recombinant protein obtained when produced under the same conditions by a few percent, for example 3 to 9%, has a significant economic effect. The same can be said for neurotrophic factors such as hBDNF, hNGF, hNT-3, and hNT-4.

In this specification, when comparing the expression levels of a fusion protein of HSA and hBDNF expressed in a host cell as a recombinant protein with wild-type hBDNF expressed in a host cell under the same conditions, the comparison is not based on the mass of the expressed protein, but on the number of molecules of the expressed protein or on the hBDNF biological activity. This rule also applies to fusion proteins of HSA and hNGF, fusion proteins of HSA and hNT-3, and fusion proteins of HSA and hNT-4. This rule also applies regardless of the animal species of the SA and nerve growth factor that make up the fusion protein.

HSA and hBDNF fusion protein, HSA and hNGF fusion protein, HSA and hNT-3 fusion protein, and HSA and hNT-4 fusion protein can be produced as recombinant proteins by culturing host cells transformed with an expression vector incorporating a gene encoding the fusion protein. In this case, they can be produced using an expression vector, host cells, culture medium, etc. that can be used to produce the above-mentioned HSA and hGALC fusion protein or HSA and hGBA fusion protein.

By culturing host cells encoding a fusion protein of HSA and hBDNF, a fusion protein of HSA and hNGF, a fusion protein of HSA and hNT-3, or a fusion protein of HSA and hNT-4, the protein can be expressed in cells or in the medium. These fusion proteins can be separated from impurities and purified by methods such as column chromatography.

　The purified fusion protein of HSA and hBDNF, the fusion protein of HSA and hNGF, the fusion protein of HSA and hNT-3, or the fusion protein of HSA and hNT-4 can be used as a pharmaceutical composition. In particular, the fusion protein of HSA and hBDNF can be used as a pharmaceutical composition for treating neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and Huntington's disease, spinal degenerative diseases such as amyotrophic lateral sclerosis, and other diseases such as diabetic neuropathy, cerebral ischemic disease, developmental disorders such as Rett syndrome, schizophrenia, depression, and Rett syndrome. In particular, the fusion protein of HSA and hNGF can be used as a pharmaceutical composition for treating neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and Huntington's disease. In particular, the fusion protein of HSA and hNT-3 and the fusion protein of HSA and hNT-4 can be used as a pharmaceutical composition for treating neurodegenerative diseases.

　A pharmaceutical composition containing as an active ingredient a fusion protein of HSA and hBDNF, a fusion protein of HSA and hNGF, a fusion protein of HSA and hNT-3, or a fusion protein of HSA and hNT-4 can be administered intravenously, intramuscularly, intraperitoneally, subcutaneously, or intracerebroventricularly as an injection. These injections can be supplied as lyophilized preparations or aqueous liquid preparations. In the case of an aqueous liquid preparation, it may be in the form of a vial filled with the preparation, or it can be supplied as a prefilled preparation in which the preparation is filled in a syringe beforehand. In the case of a lyophilized preparation, it is dissolved in an aqueous medium and reconstituted before use.

The fusion protein of HSA and hBDNF, the fusion protein of HSA and hNGF, the fusion protein of HSA and hNT-3, or the fusion protein of HSA and hNT-4 can be further bound to an antibody or a ligand to form a conjugate. For example, the fusion protein of HSA and hBDNF or a ligand, the fusion protein of HSA and hNGF, the fusion protein of HSA and hNT-3, and the fusion protein of HSA and hNT-4 can each be bound to an antibody or a ligand that can specifically bind to a receptor on cerebrovascular endothelial cells. The fusion proteins of HSA and hBDNF, HSA and hNGF, HSA and hNT-3, and HSA and hNT-4 can bind to the receptor on cerebrovascular endothelial cells by being bound to an antibody or a ligand that can specifically bind to the receptor on cerebrovascular endothelial cells. The fusion proteins bound to the receptor on cerebrovascular endothelial cells can pass through the blood-brain barrier (BBB) and reach the tissues of the central nervous system (CNS). Therefore, these fusion proteins can be conjugated with such antibodies or ligands to pass through the blood-brain barrier (BBB) and exert their functions in the central nervous system (CNS). The same applies when the SA is from an animal species other than human, and when BDNF, NGF, hNT-3, and hNT-4 are from an animal species other than human. The same applies when the neurotrophic factors are neurotrophic factors other than BDNF, NGF, hNT-3, and hNT-4.

When hBDNF is said to have the function of hBDNF in a conjugate of a fusion protein of HSA and hBDNF with an antibody or ligand, it means that hBDNF has a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, for example 90% or more, 95% or more, when the specific activity of normal wild-type hBDNF is taken as 100%. Here, the specific activity of hBDNF in the conjugate is calculated by multiplying the physiological activity of hBDNF per unit mass of the conjugate by (molecular weight of the conjugate/molecular weight of the portion of the conjugate corresponding to hBDNF). These apply both when SA is derived from an animal species other than human and when BDNF is derived from an animal species other than human.

In addition, when hNGF is said to have the function of hNGF in a conjugate of a fusion protein of HSA and hNGF with an antibody or ligand, it means that hNGF has a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, for example 90% or more, 95% or more, when the specific activity of normal wild-type hNGF is taken as 100%. Here, the specific activity of hNGF in the conjugate is calculated by multiplying the physiological activity of hNGF per unit mass of the conjugate by (molecular weight of the conjugate/molecular weight of the portion of the conjugate corresponding to hNGF). These apply whether SA is derived from an animal species other than human or NGF is derived from an animal species other than human.

In addition, when hNT-3 in a conjugate of a fusion protein of HSA and hNT-3 with an antibody or ligand is said to have the function of hNT-3, it means that hNT-3 has a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, for example 90% or more, 95% or more, when the specific activity of normal wild-type hNT-3 is taken as 100%. Here, the specific activity of hNT-3 in the conjugate is calculated by multiplying the physiological activity of hNT-3 per unit mass of the conjugate by (molecular weight of the conjugate/molecular weight of the portion of the conjugate corresponding to hNT-3). These apply both when SA is derived from an animal species other than human and when NT-3 is derived from an animal species other than human.

In addition, when hNT-4 is said to have the function of hNT-4 in a conjugate of a fusion protein of HSA and hNT-4 with an antibody or ligand, it means that hNT-4 has a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, for example 90% or more, 95% or more, when the specific activity of normal wild-type hNT-4 is taken as 100%. Here, the specific activity of hNT-4 in the conjugate is calculated by multiplying the physiological activity of hNT-4 per unit mass of the conjugate by (molecular weight of the conjugate/molecular weight of the portion of the conjugate corresponding to hNT-4). These apply both when SA is derived from an animal species other than human and when NT-4 is derived from an animal species other than human.

In one embodiment of the present invention, a conjugate between a fusion protein of HSA and hBDNF and an antibody or ligand is characterized in that when the conjugate is expressed as a recombinant protein in a host cell, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the amount of hBDNF expressed in the culture supernatant is at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or physiological activity, compared to when wild-type hBDNF is expressed as a recombinant protein in a host cell under the same conditions, such as 1.1 to 4 times, 1.5 to 3.6 times, 2 to 3.6 times, 10 to 20 times, 20 to 30 times, etc.

In one embodiment of the present invention, a conjugate between a fusion protein of HSA and hNGF and an antibody or ligand is characterized in that when the conjugate is expressed as a recombinant protein in a host cell, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the amount of hNGF expressed in the culture supernatant is at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or physiological activity, compared to when wild-type hNGF is expressed as a recombinant protein in a host cell under the same conditions.

In one embodiment of the present invention, a conjugate between a fusion protein of HSA and hNT-3 and an antibody or ligand is characterized in that when the conjugate is expressed as a recombinant protein in a host cell, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the expression amount of hNT-3 in the culture supernatant is at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or physiological activity, compared to when wild-type hNT-3 is expressed as a recombinant protein in a host cell under the same conditions.

In one embodiment of the present invention, a conjugate between a fusion protein of HSA and hNT-4 and an antibody or ligand is characterized in that when the conjugate is expressed as a recombinant protein in a host cell, particularly when the recombinant protein is expressed so as to be secreted from the cells and accumulated in the culture medium, the expression amount of hNT-4 in the culture supernatant is at least 1.1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, or 3.5 times, in terms of concentration or physiological activity, compared to when wild-type hNT-4 is expressed as a recombinant protein in a host cell under the same conditions, and is 1.1 to 4 times, 1.5 to 3.6 times, 2 to 3.6 times, 10 to 20 times, 20 to 30 times, etc.

Some neurotrophic factors are difficult to produce in large quantities when expressed as recombinant proteins using host cells introduced with an expression vector incorporating a gene encoding the wild-type neurotrophic factor, because the expression level is limited. Examples of such neurotrophic factors include BDNF, NGF, NT-3, and NT-4. One embodiment of the present invention is a recombinant protein in which such a neurotrophic factor that is difficult to produce as a recombinant protein is fused with SA. Such a recombinant protein can be produced in large quantities more easily using host cells introduced with an expression vector incorporating a gene encoding the recombinant protein, compared to the corresponding wild-type neurotrophic factor. Here, there is no particular restriction on the animal species of the neurotrophic factor to be bound to SA, but human neurotrophic factor is preferred. There is also no particular restriction on the animal species of the SA to be bound to the neurotrophic factor, but HSA is preferred.

In the present invention, the term "antibody" primarily refers to human antibodies, mouse antibodies, humanized antibodies, antibodies derived from camelids (including alpacas), chimeric antibodies between human antibodies and antibodies from other mammals, and chimeric antibodies between mouse antibodies and antibodies from other mammals, but is not limited to these as long as it has the property of specifically binding to a specific antigen, and there is also no particular restriction on the animal species of the antibody.

In the present invention, the term "human antibody" refers to an antibody whose entire protein is encoded by a gene of human origin. However, "human antibodies" also include antibodies encoded by genes in which mutations have been added to the original human gene without changing the original amino acid sequence for the purpose of increasing gene expression efficiency, etc. In addition, antibodies produced by combining two or more genes encoding human antibodies and replacing a part of a human antibody with a part of another human antibody are also "human antibodies". Human antibodies have three complementarity determining regions (CDRs) in the light chain and three complementarity determining regions (CDRs) in the heavy chain. The three CDRs in the light chain are called CDR1, CDR2, and CDR3, starting from the N-terminus. The three CDRs in the heavy chain are also called CDR1, CDR2, and CDR3, starting from the N-terminus. Antibodies in which the antigen specificity, affinity, etc. of a human antibody have been modified by replacing the CDR of a certain human antibody with the CDR of another human antibody are also included in human antibodies.

In the present invention, the term "human antibody" also includes antibodies in which mutations such as substitution, deletion, and addition have been added to the amino acid sequence of the original antibody by modifying the gene of the original human antibody. When an amino acid in the amino acid sequence of the original antibody is replaced with another amino acid, the number of amino acids to be replaced is preferably 1 to 20, more preferably 1 to 5, and even more preferably 1 to 3. When an amino acid in the amino acid sequence of the original antibody is deleted, the number of amino acids to be deleted is preferably 1 to 20, more preferably 1 to 5, and even more preferably 1 to 3. Furthermore, antibodies in which mutations that combine these amino acid substitutions and deletions have been added are also human antibodies. When amino acids are added, preferably 1 to 20, more preferably 1 to 5, and even more preferably 1 to 3 amino acids are added to the amino acid sequence or the N-terminus or C-terminus of the original antibody. Antibodies in which mutations that combine these amino acid additions, substitutions, and deletions have been added are also human antibodies. The amino acid sequence of the mutated antibody preferably exhibits 80% or more identity to the amino acid sequence of the original antibody, more preferably 90% or more identity, even more preferably 95% or more identity, and even more preferably 98% or more identity. When the above mutations are added to a human antibody, the mutations can be added to the variable region of the antibody. When the above mutations are added to the variable region of the antibody, the mutations can be added to either the CDR or framework region of the variable region, but are particularly added to the framework region. In other words, the term "human-derived gene" includes not only the original human-derived gene, but also genes obtained by modifying it.

In the present invention, the term "humanized antibody" refers to an antibody in which the amino acid sequence of a part of the variable region (e.g., all or part of the CDR in particular) is derived from a mammal other than human, and the other regions are derived from humans. For example, a humanized antibody can be an antibody produced by replacing the three complementarity determining regions (CDRs) of the light chain and the three complementarity determining regions (CDRs) of the heavy chain that constitute a human antibody with the CDRs of another mammal. The species of the other mammal from which the CDRs are grafted to the appropriate positions of the human antibody are derived is not particularly limited as long as it is a mammal other than human, but is preferably a mouse, rat, rabbit, horse, or a non-human primate, more preferably a mouse or rat, and even more preferably a mouse. In addition, an antibody in which the amino acid sequence of the original humanized antibody is modified with the same mutations as those that can be added to the above-mentioned human antibody is also included in the "humanized antibody".

In the present invention, the term "chimeric antibody" refers to an antibody that is formed by linking fragments of two or more different antibodies derived from two or more different species.

A chimeric antibody between a human antibody and an antibody of another mammal is an antibody in which a part of a human antibody is replaced by a part of an antibody of a mammal other than human. The antibody consists of an Fc region, a Fab region, and a hinge region, which are explained below. A specific example of such a chimeric antibody is a chimeric antibody in which the Fc region is derived from a human antibody while the Fab region is derived from an antibody of another mammal. The hinge region is derived from either a human antibody or an antibody of another mammal. Conversely, a chimeric antibody in which the Fc region is derived from another mammal while the Fab region is derived from a human antibody is included. The hinge region is derived from either a human antibody or an antibody of another mammal.

An antibody can also be said to be composed of a variable region and a constant region. Other specific examples of chimeric antibodies include those in which the heavy chain constant region ( _CH ) and the light chain constant region ( _CL ) are derived from a human antibody, while the heavy chain variable region ( _VH ) and the light chain variable region ( _VL ) are derived from an antibody of another mammal, and conversely, those in which the heavy chain constant region ( _CH ) and the light chain constant region ( _CL ) are derived from an antibody of another mammal, while the heavy chain variable region ( _VH ) and the light chain variable region ( _VL ) are derived from a human antibody. Here, the species of the other mammal is not particularly limited as long as it is a mammal other than human, but is preferably a mouse, rat, rabbit, horse, or a non-human primate, such as a mouse.

In one embodiment of the present invention, an antibody has a basic structure consisting of a total of four polypeptide chains: two immunoglobulin light chains (or simply "light chains") and two immunoglobulin heavy chains (or simply "heavy chains"). However, when referring to an "antibody", in addition to those having this basic structure,
(1) Consists of two polypeptide chains, one light chain and one heavy chain,
(2) Those consisting of a Fab region in which the Fc region has been deleted from the basic structure of an antibody in the original sense, and those consisting of a Fab region and all or part of the hinge region (including Fab, F(ab') and F(ab') ₂ ),
(3) A single-chain antibody, which is composed of a light chain with a linker at its C-terminus and a heavy chain at its C-terminus.
(4) A single-chain antibody, which is composed of a heavy chain with a linker at its C-terminus and a light chain at its C-terminus.
(5) An antibody that is composed of an Fc region in which the Fab region has been deleted from the basic structure of the original antibody, and the amino acid sequence of the Fc region has been modified so as to have the property of specifically binding to a specific antigen (Fc antibody).
(6) Single domain antibodies, described below, are also included in the term "antibody."

The antibody in one embodiment of the present invention is an antibody derived from a camelid (including an alpaca). Some camelid antibodies are composed of two heavy chains linked by a disulfide bond. An antibody composed of two heavy chains is called a heavy chain antibody. A VHH is an antibody composed of a single heavy chain including the variable region of the heavy chain constituting a heavy chain antibody, or an antibody composed of a single heavy chain lacking the constant region (CH) constituting a heavy chain antibody. A VHH is also one of the antibodies in an embodiment of the present invention. Another antibody in an embodiment of the present invention is an antibody composed of two light chains linked by a disulfide bond. An antibody composed of two light chains is called a light chain antibody. In order to reduce the antigenicity of an antibody derived from a camelid (including a VHH) when administered to a human, an antibody in one embodiment of the present invention is also an antibody in which a mutation has been added to the amino acid sequence of an antibody of a camelid. When a mutation is added to the amino acid of an antibody of a camelid, the same mutation as that which can be added to an antibody described in this specification can be added.

The antibody in one embodiment of the present invention is a shark-derived antibody. A shark antibody consists of two heavy chains linked by a disulfide bond. An antibody consisting of these two heavy chains is called a heavy chain antibody. A VNAR is an antibody consisting of a single heavy chain that includes the variable region of the heavy chain that constitutes a heavy chain antibody, or an antibody consisting of a single heavy chain that lacks the constant region (CH) that constitutes a heavy chain antibody. VNAR is also one of the antibodies in an embodiment of the present invention. In order to reduce the antigenicity of a shark-derived antibody (including VNAR) when administered to a human, an antibody in one embodiment of the present invention is also an antibody in one embodiment of the present invention in which mutations have been added to the amino acid sequence of the shark antibody. When mutations are added to the amino acids of a shark antibody, the same mutations that can be added to the antibodies described in this specification can be added. A humanized shark antibody is also one of the antibodies in one embodiment of the present invention.

An antibody has a basic structure consisting of four polypeptide chains, two light chains and two heavy chains, and has three complementarity determining regions (CDRs) in the variable region of the light chain (V _L ) and three complementarity determining regions (CDRs) in the variable region of the heavy chain (V _H ). The three CDRs in the light chain are called CDR1, CDR2, and CDR3, starting from the N-terminus. The three CDRs in the heavy chain are also called CDR1, CDR2, and CDR3, starting from the N-terminus. However, even if some or all of these CDRs are incomplete or absent, they are included in the antibody as long as they have the property of specifically binding to a specific antigen. The regions other than the CDRs in the variable regions of the light and heavy chains (V _L and V _H ) are called framework regions (FR). The FRs are called FR1, FR2, FR3, and FR4, starting from the N-terminus. Typically, CDRs and FRs are present in the following order from the N-terminus: FR1, CDR1, FR2, CDR2, FR3, CDR3, and FR4.

In one embodiment of the present invention, the antibody also includes an antibody in which a mutation such as substitution, deletion, or addition has been added to the amino acid sequence of the original antibody. When an amino acid in the amino acid sequence of the original antibody is replaced with another amino acid, the number of amino acids to be replaced is preferably 1 to 20, more preferably 1 to 5, and even more preferably 1 to 3. When an amino acid in the amino acid sequence of the original antibody is deleted, the number of amino acids to be deleted is preferably 1 to 20, more preferably 1 to 5, and even more preferably 1 to 3. In addition, an antibody in which a mutation combining these amino acid substitutions and deletions has been added is also an antibody. When an amino acid is added, preferably 1 to 20, more preferably 1 to 5, and even more preferably 1 to 3 amino acids are added to the amino acid sequence or the N-terminus or C-terminus of the original antibody. An antibody in which a mutation has been added combining these amino acid additions, substitutions, and deletions is also an antibody. The amino acid sequence of the mutated antibody preferably exhibits 80% or more identity with the amino acid sequence of the original antibody, more preferably 85% or more identity, and even more preferably 90% or more, 95% or more, or 98% or more identity.

In one embodiment of the present invention, the antibody also includes an antibody in which a mutation such as substitution, deletion, or addition has been added to the amino acid sequence of the variable region of the original antibody. When an amino acid in the amino acid sequence of the original antibody is replaced with another amino acid, the number of amino acids to be replaced is preferably 1 to 10, more preferably 1 to 5, and even more preferably 1 to 3. When an amino acid in the amino acid sequence of the original antibody is deleted, the number of amino acids to be deleted is preferably 1 to 10, more preferably 1 to 5, and even more preferably 1 to 3. In addition, an antibody in which a mutation that combines the substitution and deletion of these amino acids has been added is also an antibody. When an amino acid is added, preferably 1 to 10, more preferably 1 to 5, and even more preferably 1 to 3 amino acids are added to the amino acid sequence or the N-terminus or C-terminus of the original antibody. An antibody in which a mutation has been added is also an antibody in which a mutation that combines the addition, substitution, and deletion of these amino acids has been added is also an antibody. The amino acid sequence of the antibody in which the mutation has been added is preferably 80% or more identical to the amino acid sequence of the original antibody, more preferably 85% or more identical, and even more preferably 90% or more, 95% or more, or 98% or more identical. When mutations are made to the variable region of an antibody, the mutations may be made in either the CDR or framework region of the variable region, but are particularly made in the framework region.

In one embodiment of the present invention, the antibody also includes an antibody in which a mutation such as substitution, deletion, or addition has been added to the amino acid sequence of the framework region of the variable region of the original antibody. When an amino acid in the amino acid sequence of the original antibody is replaced with another amino acid, the number of amino acids to be replaced is preferably 1 to 10, more preferably 1 to 5, and even more preferably 1 to 3. When an amino acid in the amino acid sequence of the original antibody is deleted, the number of amino acids to be deleted is preferably 1 to 10, more preferably 1 to 5, and even more preferably 1 to 3. In addition, an antibody in which a mutation that combines these amino acid substitutions and deletions has been added is also an antibody. When an amino acid is added, preferably 1 to 10, more preferably 1 to 5, and even more preferably 1 to 3 amino acids are added to the amino acid sequence or the N-terminus or C-terminus of the original antibody. An antibody in which a mutation that combines these amino acid additions, substitutions, and deletions has been added is also an antibody. The amino acid sequence of the mutated antibody preferably exhibits 80% or more identity to the amino acid sequence of the original antibody, more preferably 85% or more identity, and even more preferably 90% or more, 95% or more, or 98% or more identity.

In one embodiment of the present invention, the antibody also includes an antibody in which a mutation such as substitution, deletion, or addition has been added to the amino acid sequence in the CDR region of the variable region of the original antibody. When an amino acid in the amino acid sequence of the original antibody is replaced with another amino acid, the number of amino acids to be replaced is preferably 1 to 5, more preferably 1 to 3, and even more preferably 1 or 2. When an amino acid in the amino acid sequence of the original antibody is deleted, the number of amino acids to be deleted is preferably 1 to 5, more preferably 1 to 3, and even more preferably 1 or 2. In addition, an antibody in which a mutation combining these amino acid substitutions and deletions has been added is also an antibody. When an amino acid is added, preferably 1 to 5, more preferably 1 to 3, and even more preferably 1 or 2 amino acids are added to the amino acid sequence or the N-terminus or C-terminus of the original antibody. An antibody in which a mutation combining these amino acid additions, substitutions, and deletions has been added is also an antibody. The amino acid sequence of the mutated antibody preferably exhibits 80% or more identity to the amino acid sequence of the original antibody, more preferably 85% or more identity, and even more preferably 90% or more, 95% or more, or 98% or more identity.

In one embodiment of the present invention, Fab refers to a molecule in which one light chain including a variable region and a _CL region (light chain constant region) and one heavy chain including a variable region and a _CH1 region (part 1 of the heavy chain constant region) are bound by disulfide bonds between cysteine residues present in each. In Fab, the heavy chain may further include a part of the hinge region in addition to the variable region and the _CH1 region (part 1 of the heavy chain constant region), but in this case, the hinge region lacks cysteine residues present in the hinge region that bind the heavy chains of the antibody. In Fab, the light chain and the heavy chain are bound by disulfide bonds formed between cysteine residues present in the light chain constant region ( _CL region) and cysteine residues present in the heavy chain constant region ( _CH1 region) or hinge region. The heavy chain that forms Fab is called a Fab heavy chain. Fab lacks the cysteine residues present in the hinge region that bind the heavy chains of an antibody, and therefore consists of one light chain and one heavy chain. The light chain that constitutes Fab contains a variable region and a _CL region. The heavy chain that constitutes Fab may be composed of a variable region and a _CH1 region, or may contain a part of the hinge region in addition to the variable region and the _CH1 region. In this case, however, the hinge region is selected so as not to contain a cysteine residue that binds the heavy chains, so that a disulfide bond is not formed between the two heavy chains at the hinge region. In F(ab'), the heavy chain contains the whole or part of the hinge region that contains the cysteine residue that binds the heavy chains, in addition to the variable region and the _CH1 region. F(ab') ₂ refers to a molecule in which two F(ab') are bound by disulfide bonds between the cysteine residues present in the hinge regions of each other. The heavy chain that forms F(ab') or F(ab') ₂ is called a Fab' heavy chain. In addition, polymers such as dimers and trimers formed by binding multiple antibodies directly or via a linker are also antibodies. Furthermore, not limited to these, any one that contains a part of an antibody molecule and has the property of specifically binding to an antigen is included in the "antibody" as used in the present invention. That is, the term "light chain" includes one that is derived from a light chain and has all or part of the amino acid sequence of its variable region. In addition, the term "heavy chain" includes one that is derived from a heavy chain and has all or part of the amino acid sequence of its variable region. Therefore, as long as it has all or part of the amino acid sequence of the variable region, for example, one that has deleted the Fc region is also a heavy chain.

Furthermore, Fc or Fc region herein refers to a region in an antibody molecule that includes a fragment consisting of the _CH2 region (part 2 of the heavy chain constant region) and the _CH3 region (part 3 of the heavy chain constant region).

Furthermore, the antibody in one embodiment of the present invention comprises:
(7) Also included are scFab, scF(ab'), and scF(ab') ₂ , which are single-chain antibodies formed by linking the light chain and the heavy chain constituting Fab, F(ab'), or F(ab') ₂ shown in (2) above via a linker. Here, scFab, scF(ab'), and scF(ab') ₂ may be formed by linking a linker to the C-terminus of the light chain and further linking a heavy chain to the C-terminus, or may be formed by linking a linker to the C-terminus of the heavy chain and further linking a light chain to the C-terminus. Furthermore, antibodies also include scFv, which is a single-chain antibody formed by linking a light chain variable region and a heavy chain variable region via a linker. For scFv, it may be formed by linking a linker to the C-terminus of the light chain variable region and further linking a heavy chain variable region to the C-terminus, or may be formed by linking a linker to the C-terminus of the heavy chain variable region and further linking a light chain variable region to the C-terminus.

Furthermore, the term "antibody" as used herein includes full-length antibodies, as well as those listed in (1) to (7) above, and also includes antigen-binding fragments (antibody fragments) in which a portion of a full-length antibody is deleted, which is a broader concept including (1) to (7). Antigen-binding fragments include heavy chain antibodies, light chain antibodies, VHHs, VNARs, and those in which a portion of these antibodies is deleted.

The term "antigen-binding fragment" refers to a fragment of an antibody that retains at least a part of the specific binding activity with an antigen. Examples of binding fragments include Fab, Fab', F(ab') ₂ , variable region (Fv), single-chain antibody (scFv) in which the heavy chain variable region ( _VH ) and the light chain variable region ( _VL ) are linked with an appropriate linker, diabody, which is a dimer of a polypeptide containing a heavy chain variable region ( _VH ) and a light chain variable region ( _VL ), minibody, which is a dimer of a scFv heavy chain (H chain) bound to a part of the constant region ( _CH3 ), other low molecular weight antibodies, etc. However, it is not limited to these molecules as long as it has the ability to bind to an antigen.

In one embodiment of the present invention, the term "single-chain antibody" refers to a protein that can specifically bind to a specific antigen, which is composed of an amino acid sequence containing all or part of the variable region of a light chain, to which a linker is attached at the C-terminus, and to which an amino acid sequence containing all or part of the variable region of a heavy chain is further attached at the C-terminus. Also, a protein that can specifically bind to a specific antigen, which is composed of an amino acid sequence containing all or part of the variable region of a heavy chain, to which a linker is attached at the C-terminus, and to which an amino acid sequence containing all or part of the variable region of a light chain is further attached at the C-terminus, is also a "single-chain antibody". In a single-chain antibody in which a light chain is attached to the C-terminus of a heavy chain via a linker, the heavy chain usually lacks an Fc region. The variable region of the light chain has three complementarity determining regions (CDRs) that are involved in the antigen specificity of the antibody. Similarly, the variable region of the heavy chain also has three CDRs. These CDRs are the main regions that determine the antigen specificity of the antibody. Therefore, it is preferred that a single chain antibody contains all three CDRs of the heavy chain and all three CDRs of the light chain. However, a single chain antibody can also be one in which one or more CDRs are deleted, so long as the antigen-specific affinity of the antibody is maintained.

In a single-chain antibody, the linker disposed between the light and heavy chains of the antibody is preferably a peptide chain composed of 2 to 50, more preferably 8 to 50, even more preferably 10 to 30, even more preferably 12 to 18 or 15 to 25, for example 15 or 25 amino acid residues. There are no limitations on the amino acid sequence of such a linker, so long as the anti-hTfR antibody formed by linking both chains by the linker retains affinity for hTfR, but it is preferably composed of only glycine or glycine and serine, and includes, for example, the amino acid sequence Gly-Ser, the amino acid sequence Gly-Gly-Ser, the amino acid sequence Gly-Gly-Gly, the amino acid sequence Gly-Gly-Gly-Gly-Gly-Ser (SEQ ID NO: 9), the amino acid sequence Gly-Gly-Gly-Gly-Gly-Ser (SEQ ID NO: 10), the amino acid sequence Ser-Gly-Gly-Gly-Gly (SEQ ID NO: 11), or a sequence in which these amino acid sequences are repeated 2 to 10 times or 2 to 5 times. For example, when linking a light chain variable region via a linker to the C-terminus of an amino acid sequence consisting of the entire region of the heavy chain variable region, a linker containing a total of 15 amino acids corresponding to three consecutive amino acid sequences Gly-Gly-Gly-Gly-Ser (SEQ ID NO: 9) is preferred.

In one embodiment of the present invention, a single domain antibody refers to an antibody that has the property of specifically binding to an antigen through a single variable region. Single domain antibodies include antibodies whose variable region consists only of the variable region of a heavy chain (heavy chain single domain antibodies) and antibodies whose variable region consists only of the variable region of a light chain (light chain single domain antibodies). VHH and VNAR are types of single domain antibodies.

In one embodiment of the present invention, the term "human transferrin receptor" refers to a membrane protein having the amino acid sequence shown in SEQ ID NO: 22. In one embodiment, the antibody of the present invention specifically binds to the portion of the amino acid sequence shown in SEQ ID NO: 22 from the 89th cysteine residue from the N-terminus to the phenylalanine at the C-terminus (the extracellular domain of the transferrin receptor), but is not limited thereto.

The most common method for producing antibodies against a desired protein is to produce a recombinant protein using cells that have been introduced with an expression vector incorporating a gene that codes for the protein, and then immunize animals such as mice with this recombinant protein. After immunization, antibody-producing cells against the recombinant protein are extracted from the animal, and these are then fused with myeloma cells to produce hybridoma cells capable of producing antibodies against the recombinant protein.

　Also, by immunizing immune system cells obtained from an animal such as a mouse with a desired protein by in vitro immunization, cells that produce antibodies against the protein can be obtained. When using in vitro immunization, there is no particular limitation on the animal species from which the immune system cells are derived, but preferred are mice, rats, rabbits, guinea pigs, dogs, cats, horses, and primates including humans, more preferably mice, rats, and humans, and even more preferably mice and humans. For example, splenocytes prepared from mouse spleens can be used as mouse immune system cells. For human immune system cells, cells prepared from human peripheral blood, bone marrow, spleen, etc. can be used. When human immune system cells are immunized by in vitro immunization, human antibodies against the recombinant protein can be obtained.

　Immune system cells can be immunized by in vitro immunization, and then fused with myeloma cells to produce hybridoma cells capable of producing antibodies. It is also possible to extract mRNA from the immunized cells, synthesize cDNA, and use this cDNA as a template to amplify DNA fragments containing genes encoding the light and heavy chains of immunoglobulins through PCR reactions, which can then be used to artificially reconstruct antibody genes.

Hybridoma cells obtained as is by the above method also include cells that produce antibodies that recognize non-target proteins as antigens. Furthermore, not all hybridoma cells that produce antibodies against a desired protein necessarily produce antibodies that exhibit the desired properties, such as having high affinity for that protein.

Similarly, artificially reconstructed antibody genes also include genes that code for antibodies that recognize untargeted proteins as antigens. Furthermore, not all genes that code for antibodies against a desired protein necessarily code for antibodies that exhibit the desired properties, such as having high affinity for that protein.

Therefore, a step is required to select hybridoma cells that produce antibodies with the desired characteristics from the hybridoma cells obtained as described above. Furthermore, in the case of artificially reconstructed antibody genes, a step is required to select genes that code for antibodies with the desired characteristics from the antibody genes. For example, the method described in detail below is effective as a method for selecting hybridoma cells that produce antibodies that show high affinity for a desired protein (high affinity antibodies), or genes that code for high affinity antibodies.

For example, when selecting hybridoma cells that produce antibodies with high affinity to a desired protein, the protein is added to a plate and retained thereon, then the culture supernatant of the hybridoma cells is added, and antibodies that are not bound to the protein are removed from the plate, and the amount of antibody retained on the plate is measured. According to this method, the higher the affinity of the antibody contained in the culture supernatant of the hybridoma cells added to the plate for the protein, the greater the amount of antibody retained on the plate. Therefore, the amount of antibody retained on the plate can be measured, and the hybridoma cells corresponding to the plate that retain more antibodies can be selected as cell lines that produce antibodies with relatively high affinity for the protein. From the cell line selected in this way, mRNA can be extracted to synthesize cDNA, and the cDNA can be used as a template to amplify a DNA fragment containing a gene encoding an antibody against the protein using PCR, thereby isolating a gene encoding a high-affinity antibody.

When selecting a gene encoding an antibody against a target protein having high affinity from the above artificially reconstructed antibody genes, the artificially reconstructed antibody gene is first incorporated into an expression vector, and this expression vector is introduced into a host cell. In this case, the cells used as the host cell are not particularly limited, regardless of whether they are prokaryotic or eukaryotic, as long as they can express the antibody gene by introducing an expression vector incorporating the artificially reconstructed antibody gene, but cells derived from mammals such as humans, mice, and Chinese hamsters are preferred, and CHO cells derived from Chinese hamster ovaries or NS/0 cells derived from mouse myeloma are particularly preferred. In addition, the expression vector used to incorporate and express a gene encoding an antibody gene can be used without any particular limitation as long as it expresses the gene when introduced into a mammalian cell. The gene incorporated into the expression vector is located downstream of a DNA sequence (gene expression control site) that can regulate the frequency of gene transcription in a mammalian cell. Examples of gene expression control sites that can be used in the present invention include a promoter derived from a cytomegalovirus, an SV40 early promoter, a human elongation factor-1 alpha (EF-1α) promoter, and a human ubiquitin C promoter.

　Mammalian cells into which such an expression vector has been introduced will express the above-mentioned artificially reconstructed antibody incorporated in the expression vector. When selecting cells that produce antibodies with high affinity for antibodies against a desired protein from the cells thus obtained that express the artificially reconstructed antibodies, a method is used in which the protein is added to a plate and retained thereon, the cell culture supernatant is brought into contact with the protein, and then antibodies that are not bound to the protein are removed from the plate, and the amount of antibody retained on the plate is measured. According to this method, the higher the affinity of the antibody contained in the cell culture supernatant for the protein, the greater the amount of antibody retained on the plate. Therefore, by measuring the amount of antibody retained on the plate, cells corresponding to the plate that retain a greater number of antibodies can be selected as cell lines that produce antibodies with relatively high affinity for the protein, and thus a gene encoding an antibody with high affinity for the protein can be selected. From the cell line thus selected, a DNA fragment containing a gene encoding an antibody against the protein can be amplified using PCR to isolate a gene encoding a high affinity antibody.

In one embodiment of the present invention, a method for producing a conjugate in which a fusion protein of SA and a lysosomal enzyme, a fusion protein of SA and a cytokine, or a fusion protein of SA and a neurotrophic factor is bound to an antibody is a method in which the fusion protein and the antibody are bound via a non-peptide linker or a peptide linker. As the non-peptide linker, polyethylene glycol, polypropylene glycol, a copolymer of ethylene glycol and propylene glycol, polyoxyethylated polyol, polyvinyl alcohol, polysaccharides, dextran, polyvinyl ether, biodegradable polymers, lipid polymers, chitins, and hyaluronic acid, or derivatives thereof, or combinations thereof, can be used. The peptide linker is a peptide chain or a derivative thereof consisting of 1 to 50 amino acids bound by peptide bonds, and its N-terminus and C-terminus form covalent bonds with either the fusion protein or the antibody, respectively, thereby binding the fusion protein and the antibody. Here, the SA, lysosomal enzyme, cytokine, and neurotrophic factor may each be derived from a human or a non-human animal.

A conjugate of a fusion protein and an antibody is produced by producing the fusion protein and the antibody separately, then reacting them with a non-peptide linker or a peptide linker to bind the fusion protein to one end of the linker and the antibody to the other end. The fusion protein and the antibody can each be produced as recombinant proteins. According to this production method, for example, a conjugate in which a fusion protein of HSA and a human lysosomal enzyme is bound to an antibody via a non-peptide linker or a peptide linker, a conjugate in which a fusion protein of HSA and a human cytokine is bound to an antibody via a non-peptide linker or a peptide linker, or a conjugate in which a fusion protein of HSA and a human neurotrophic factor is bound to an antibody via a non-peptide linker or a peptide linker can be produced.

By using this manufacturing method, for example, a fusion protein of HSA and hGALC, a fusion protein of HSA and hGBA, a fusion protein of HSA and hIL-10, a fusion protein of HSA and hBDNF, a fusion protein of HSA and hNGF, a fusion protein of HSA and hNT-3, or a fusion protein of HSA and hNT-4 can be obtained in which the fusion protein is bound to an antibody or a ligand via a non-peptide linker or a peptide linker.

In one embodiment of the present invention, a conjugate formed by binding a fusion protein of SA and a lysosomal enzyme, a fusion protein of SA and a cytokine, or a fusion protein of SA and a neurotrophic factor to an antibody or a ligand can be produced by binding the C-terminus or N-terminus of these fusion proteins to the N-terminus or C-terminus of an antibody or ligand via a peptide bond, either directly or via a linker. Such conjugates can be produced as recombinant proteins by the production methods exemplified below.

For example, an antibody and a fusion protein of HSA and hGALC can be produced by binding the N-terminus or C-terminus of the fusion protein to the C-terminus or N-terminus of the heavy or light chain of the antibody via a peptide bond, either directly or via a linker. In this way, a conjugate formed by binding an antibody to a fusion protein of HSA and hGALC can be obtained as a conjugate protein by inserting a DNA fragment in which the cDNA encoding the fusion protein of HSA and hGALC is placed in frame at the 3'-terminus or 5'-terminus of the cDNA encoding the heavy or light chain of the antibody, either directly or via a DNA fragment encoding a linker, into an expression vector for mammalian cells, and culturing mammalian cells into which this expression vector has been introduced. In the case where a DNA fragment encoding a fusion protein of HSA and hGALC is bound to a heavy chain, an expression vector for mammalian cells incorporating a cDNA fragment encoding the light chain of an antibody can also be introduced into the same host cell, and in the case where a DNA fragment encoding a fusion protein of HSA and hGALC is bound to a light chain, an expression vector for mammalian cells incorporating a cDNA fragment encoding the heavy chain of an antibody can also be introduced into the same host cell. In the case where the antibody is a single-chain antibody or VHH, the conjugate of the antibody and the fusion protein of HSA and hGALC can be obtained as a recombinant protein by incorporating a DNA fragment encoding a single-chain antibody or VHH linked to the 5'-end or 3'-end of the cDNA encoding the fusion protein of HSA and hGALC directly or via a DNA fragment encoding a linker into an expression vector (for mammalian cells, eukaryotic cells such as yeast, or prokaryotic cells such as E. coli) and expressing the DNA fragment in the cells into which the expression vector has been introduced. Conjugates of the fusion protein of HSA and hGBA and an antibody, conjugates of the fusion protein of HSA and hIL-10 and an antibody, conjugates of the fusion protein of HSA and hBDNF and an antibody, conjugates of the fusion protein of HSA and hNGF and an antibody, conjugates of the fusion protein of HSA and hNT-3 and an antibody, and conjugates of the fusion protein of HSA and hNT-4 and an antibody can also be obtained as recombinant proteins in the same manner as the conjugates of the fusion protein of HSA and hGALC and an antibody.

Antibody, HSA and hGALC can also be conjugated in a form in which an antibody is interposed between HSA and hGALC. In this case, the N-terminus of the heavy or light chain of the antibody can be bound to the C-terminus of HSA via a linker or directly, and hGALC can be bound to the C-terminus via a peptide bond either via a linker or directly. Alternatively, the N-terminus of the heavy or light chain of the antibody can be bound to the C-terminus of hGALC via a linker or directly, and HSA can be bound to the C-terminus via a linker or directly, respectively. Even if the antibody is a single-chain antibody or VHH, the antibody, HSA and hGALC can be made into a fusion protein in a form in which an antibody is interposed between HSA and hGALC. In this case, the N-terminus of the single-chain antibody or VHH can be bound to the C-terminus of HSA via a linker or directly, and hGALC can be bound to the C-terminus via a peptide bond either via a linker or directly. Alternatively, the N-terminus of a single chain antibody or VHH can be bound to the C-terminus of hGALC via a linker or directly, and HSA can be bound to the C-terminus of the N-terminus of the single chain antibody or VHH via a linker or directly, respectively, by peptide bonds. Similar conjugates can also be produced for lysosomal enzymes other than hGALC, such as hGBA, cytokines, such as hIL-10, and neurotrophic factors, such as hBDNF, hNGF, hNT-3, and hNT-4. For the sake of convenience, conjugates in this manner that involve an antibody are also referred to as fusion proteins of an antibody, another human lysosomal enzyme, and HSA, fusion proteins of an antibody, another human cytokine, and HSA, and fusion proteins of an antibody, another human neurotrophic factor, and HSA.

The above method can also be applied to the production of conjugates of fusion proteins of other human lysosomal enzymes and HSA, fusion proteins of other human cytokines and HSA, or fusion proteins of other human neurotrophic factors and HSA, and antibodies. It can also be applied to the production of conjugates in which the SA is from an animal species other than human, and conjugates in which the lysosomal enzymes, cytokines, and neurotrophic factors are from an animal species other than human.

The expression vectors, host cells, media, etc. that can be used to produce the above-mentioned fusion protein of HSA and hGALC or the fusion protein of HSA and hGBA can also be used to produce a conjugate of the above-mentioned fusion protein and antibody.

Preferred embodiments of the conjugates of antibody, HSA and hGALC include the following (1) to (4):
(1) A conjugate in which a fusion protein of HSA and hGALC is bound to the C-terminus of an antibody heavy chain directly or via a linker, and an antibody light chain;
(2) A conjugate in which a fusion protein of HSA and hGALC is bound to the N-terminus of an antibody heavy chain directly or via a linker, and an antibody light chain;
(3) A conjugate in which a fusion protein of HSA and hGALC is bound to the C-terminus of an antibody light chain directly or via a linker, and an antibody heavy chain;
(4) A conjugate in which a fusion protein of HSA and hGALC is bound to the N-terminus of an antibody light chain directly or via a linker, and an antibody heavy chain;
(5) A conjugate in which a single-chain antibody or VHH is bound to the C-terminus of HSA directly or via a linker, and hGALC is further bound to the C-terminus of the single-chain antibody or VHH;
(6) A conjugate in which a single-chain antibody or VHH is bound to the C-terminus of hGALC directly or via a linker, and HSA is further bound to the C-terminus of the antibody or VHH.
A preferred example of (1) is a conjugate A in which a Fab heavy chain having the amino acid sequence of SEQ ID NO:25 is connected to its C-terminus with a linker having an amino acid sequence in which SEQ ID NO:9 is repeated three times, and further connected to its C-terminus with HSA having the amino acid sequence of SEQ ID NO:3, and further connected to its C-terminus with a linker having the amino acid sequence of SEQ ID NO:9, and further connected to its C-terminus with hGALC having the amino acid sequence of SEQ ID NO:1, and a light chain of SEQ ID NO:23. Here, conjugate A has the amino acid sequence of SEQ ID NO:28.
A suitable example of (2) is a conjugate B in which a linker having the amino acid sequence of SEQ ID NO: 9 is attached to the C-terminus of HSA having the amino acid sequence of SEQ ID NO: 3, hGALC having the amino acid sequence of SEQ ID NO: 1 at its C-terminus, a linker having an amino acid sequence in which SEQ ID NO: 9 is repeated three times at its C-terminus, and a Fab heavy chain having the amino acid sequence of SEQ ID NO: 25 at its C-terminus is attached to the light chain of SEQ ID NO: 23. Here, conjugate B has the amino acid sequence of SEQ ID NO: 30.
A preferred example of (3) is a conjugate C in which a linker having an amino acid sequence of SEQ ID NO: 25, an amino acid sequence in which SEQ ID NO: 9 is repeated three times, and hGALC having the amino acid sequence of SEQ ID NO: 1 at its C-terminus, a linker having the amino acid sequence of SEQ ID NO: 9 at its C-terminus, and HSA having the amino acid sequence of SEQ ID NO: 3 at its C-terminus are bound to the light chain of SEQ ID NO: 23. Here, the conjugate C has the amino acid sequence of SEQ ID NO: 32.
A preferred example of (4) is a conjugate D in which hGALC having the amino acid sequence of SEQ ID NO:1 is connected to its C-terminus with a linker having the amino acid sequence of SEQ ID NO:9, and further connected to its C-terminus with HSA having the amino acid sequence of SEQ ID NO:3, and further connected to its C-terminus with a linker having an amino acid sequence in which SEQ ID NO:9 is repeated three times, and further connected to its C-terminus with a Fab heavy chain having the amino acid sequence of SEQ ID NO:25, and a light chain of SEQ ID NO:23. Here, conjugate C has the amino acid sequence of SEQ ID NO:34.

Preferred embodiments of the conjugates of antibody, HSA and hGBA include the following (1) to (4):
(1) A conjugate in which a fusion protein of HSA and hGBA is bound to the C-terminus of an antibody heavy chain directly or via a linker, and an antibody light chain;
(2) A conjugate in which a fusion protein of HSA and hGBA is bound to the N-terminus of an antibody heavy chain directly or via a linker, and an antibody light chain;
(3) A conjugate in which a fusion protein of HSA and hGBA is bound to the C-terminus of an antibody light chain directly or via a linker, and an antibody heavy chain;
(4) A conjugate in which a fusion protein of HSA and hGBA is bound to the N-terminus of an antibody light chain directly or via a linker, and an antibody heavy chain;
(5) A conjugate in which a single-chain antibody or VHH is bound to the C-terminus of HSA directly or via a linker, and hGBA is further bound to the C-terminus of the single-chain antibody or VHH;
(6) A conjugate in which a single-chain antibody or VHH is bound to the C-terminus of hGBA directly or via a linker, and HSA is further bound to the C-terminus of the antibody or VHH.

Preferred embodiments of the conjugate of an antibody, HSA and hIL-10 include the following (1) to (4):
(1) A conjugate in which a fusion protein of HSA and hIL-10 is bound to the C-terminus of an antibody heavy chain directly or via a linker, and an antibody light chain;
(2) A conjugate in which a fusion protein of HSA and hIL-10 is bound to the N-terminus of an antibody heavy chain directly or via a linker, and an antibody light chain;
(3) A conjugate in which a fusion protein of HSA and hIL-10 is bound to the C-terminus of an antibody light chain directly or via a linker, and an antibody heavy chain;
(4) A conjugate in which a fusion protein of HSA and hIL-10 is bound to the N-terminus of an antibody light chain directly or via a linker, and an antibody heavy chain;
(5) A conjugate in which a single-chain antibody or VHH is bound to the C-terminus of HSA directly or via a linker, and hIL-10 is further bound to the C-terminus of the single-chain antibody or VHH;
(6) A conjugate in which a single-chain antibody or VHH is bound to the C-terminus of hIL-10 directly or via a linker, and HSA is further bound to the C-terminus of the antibody or VHH.

Preferred embodiments of the conjugate of an antibody, HSA and hBDNF include the following (1) to (4):
(1) A conjugate in which a fusion protein of HSA and hBDNF is bound to the C-terminus of an antibody heavy chain directly or via a linker, and an antibody light chain;
(2) A conjugate in which a fusion protein of HSA and hBDNF is bound to the N-terminus of an antibody heavy chain directly or via a linker, and an antibody light chain;
(3) A conjugate in which a fusion protein of HSA and hBDNF is bound to the C-terminus of an antibody light chain directly or via a linker, and an antibody heavy chain;
(4) A conjugate in which a fusion protein of HSA and hBDNF is bound to the N-terminus of an antibody light chain directly or via a linker, and an antibody heavy chain;
(5) A conjugate in which a single-chain antibody or VHH is bound to the C-terminus of HSA directly or via a linker, and hBDNF is further bound to the C-terminus of the single-chain antibody or VHH;
(6) A conjugate in which a single-chain antibody or VHH is bound to the C-terminus of hBDNF directly or via a linker, and HSA is further bound to the C-terminus of the antibody or VHH.

Preferred embodiments of the conjugate of antibody, HSA and hNGF include the following (1) to (4):
(1) A conjugate in which a fusion protein of HSA and hNGF is bound to the C-terminus of an antibody heavy chain directly or via a linker, and an antibody light chain;
(2) A conjugate in which a fusion protein of HSA and hNGF is bound to the N-terminus of an antibody heavy chain directly or via a linker, and an antibody light chain;
(3) A conjugate in which a fusion protein of HSA and hNGF is bound to the C-terminus of an antibody light chain directly or via a linker, and an antibody heavy chain;
(4) A conjugate in which a fusion protein of HSA and hNGF is bound to the N-terminus of an antibody light chain directly or via a linker, and an antibody heavy chain;
(5) A conjugate in which a single-chain antibody or VHH is bound to the C-terminus of HSA directly or via a linker, and hNGF is further bound to the C-terminus of the single-chain antibody or VHH;
(6) A conjugate in which a single-chain antibody or VHH is bound to the C-terminus of hNGF directly or via a linker, and HSA is further bound to the C-terminus of the antibody or VHH.

Preferred embodiments of the conjugate of an antibody, HSA and hNT-3 include the following (1) to (4):
(1) A conjugate in which a fusion protein of HSA and hNT-3 is bound to the C-terminus of an antibody heavy chain directly or via a linker, and an antibody light chain;
(2) A conjugate in which a fusion protein of HSA and hNT-3 is bound to the N-terminus of an antibody heavy chain directly or via a linker, and an antibody light chain;
(3) A conjugate in which a fusion protein of HSA and hNT-3 is bound to the C-terminus of an antibody light chain directly or via a linker, and an antibody heavy chain;
(4) A conjugate in which a fusion protein of HSA and hNT-3 is bound to the N-terminus of an antibody light chain directly or via a linker, and an antibody heavy chain;
(5) A conjugate in which a single-chain antibody or VHH is bound to the C-terminus of HSA directly or via a linker, and hNT-3 is further bound to the C-terminus of the single-chain antibody or VHH;
(6) A conjugate in which a single-chain antibody or VHH is bound to the C-terminus of hNT-3 directly or via a linker, and HSA is further bound to the C-terminus of the antibody or VHH.

Preferred embodiments of the conjugate of an antibody, HSA and hNT-4 include the following (1) to (4):
(1) A conjugate in which a fusion protein of HSA and hNT-4 is bound to the C-terminus of an antibody heavy chain directly or via a linker, and an antibody light chain;
(2) A conjugate in which a fusion protein of HSA and hNT-4 is bound to the N-terminus of an antibody heavy chain directly or via a linker, and an antibody light chain;
(3) A conjugate in which a fusion protein of HSA and hNT-4 is bound to the C-terminus of an antibody light chain directly or via a linker, and an antibody heavy chain;
(4) A conjugate in which a fusion protein of HSA and hNT-4 is bound to the N-terminus of an antibody light chain directly or via a linker, and an antibody heavy chain;
(5) A conjugate in which a single-chain antibody or VHH is bound to the C-terminus of HSA directly or via a linker, and hNT-4 is further bound to the C-terminus of the single-chain antibody or VHH;
(6) A conjugate in which a single-chain antibody or VHH is bound to the C-terminus of hNT-4 directly or via a linker, and HSA is further bound to the C-terminus of the antibody or VHH.

　Linkers used when binding antibodies to a fusion protein of SA and a lysosomal enzyme, a fusion protein of SA and a cytokine, or a fusion protein of SA and a neurotrophic factor are described in detail below. These linkers are particularly suitable as linkers when binding antibodies to a fusion protein of HSA and hGALC, a fusion protein of HSA and hGBA, a fusion protein of HSA and hIL-10, a fusion protein of HSA and hBDNF, a fusion protein of HSA and hNGF, a fusion protein of HSA and hNT-3, or a fusion protein of HSA and hNT-4.

The linker disposed between the antibody or ligand and the fusion protein is preferably a peptide chain composed of 1 to 60 or 1 to 50, more preferably 1 to 17, even more preferably 1 to 10, and even more preferably 1 to 5 amino acids, but the number of amino acids constituting the linker can be appropriately adjusted to 1, 2, 3, 1 to 17, 1 to 10, 10 to 40, 20 to 34, 23 to 31, 25 to 29, 27, etc. Such a linker is not limited in its amino acid sequence as long as the antibody linked thereto retains affinity for a receptor on cerebrovascular endothelial cells and the fusion protein linked by the linker can exert the physiological activity of the fusion protein under physiological conditions, but is preferably composed of glycine and serine. For example, those consisting of one amino acid of either glycine or serine, the amino acid sequence Gly-Ser, the amino acid sequence Ser-Ser, the amino acid sequence Gly-Gly-Ser, the amino acid sequence Gly-Gly-Gly-Gly-Gly-Ser (SEQ ID NO: 9), the amino acid sequence Gly-Gly-Gly-Gly-Gly-Gly-Ser (SEQ ID NO: 10), the amino acid sequence Ser-Gly-Gly-Gly-Gly (SEQ ID NO: 11), or those containing a sequence consisting of 1 to 10 or 2 to 5 consecutive amino acids of these amino acid sequences. Those having a sequence consisting of 1 to 50 amino acids, 2 to 17, 2 to 10, 10 to 40, 20 to 34, 23 to 31, 25 to 29, or 27 amino acids, etc. For example, those containing the amino acid sequence Gly-Ser can be suitably used as a linker. In addition, a linker containing a total of 27 amino acids consisting of the amino acid sequence Gly-Ser followed by five consecutive amino acid sequences of Gly-Gly-Gly-Gly-Ser (SEQ ID NO: 9) can be preferably used as the linker. Furthermore, a linker containing a total of 25 amino acids consisting of five consecutive amino acid sequences of Gly-Gly-Gly-Gly-Ser (SEQ ID NO: 9) can also be preferably used as the linker.
In the present invention, when one peptide chain contains multiple linkers, for convenience, each linker is named, starting from the N-terminus, as the first linker, the second linker, and so on.

Specific examples of antibodies to be bound to the fusion protein of SA and a lysosomal enzyme, the fusion protein of SA and a cytokine, or the fusion protein of SA and a neurotrophic factor include the following anti-human transferrin receptor antibodies (anti-hTfR antibodies).
(1) a light chain variable region comprising the amino acid sequence of SEQ ID NO:96 as CDR1, the amino acid sequence of SEQ ID NO:97 as CDR2, and the amino acid sequence of SEQ ID NO:98 as CDR3, and a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:99 as CDR1, the amino acid sequence of SEQ ID NO:100 as CDR2, and the amino acid sequence of SEQ ID NO:101 as CDR3, respectively; and (2) a light chain variable region comprising the amino acid sequence of SEQ ID NO:96 as CDR1, the amino acid sequence of SEQ ID NO:97 as CDR2, and the amino acid sequence of SEQ ID NO:98 as CDR3, respectively, and a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:102 as CDR1, the amino acid sequence of SEQ ID NO:103 as CDR2, and the amino acid sequence of SEQ ID NO:104 as CDR3,
However, the present invention is not limited to these, and the above amino acid sequences may be appropriately mutated by substitution, deletion, addition, etc. The above anti-hTfR antibodies (1) and (2) are humanized anti-hTfR antibodies. The above anti-hTfR antibodies (1) and (2) may be Fab.

The anti-hTfR antibodies (1) and (2) above are particularly suitable as antibodies to be bound to a fusion protein of HSA and hGALC, a fusion protein of HSA and hGBA, a fusion protein of HSA and hIL-10, a fusion protein of HSA and hBDNF, a fusion protein of HSA and hNGF, a fusion protein of HSA and hNT-3, or a fusion protein of HSA and hNT-4.

The anti-hTfR antibodies (1) and (2) above with substitutions, additions, deletions, etc. can also be used as antibodies constituting the conjugate, so long as they retain their affinity for the human transferrin receptor.

When replacing amino acids in the amino acid sequence of the light chain of the anti-hTfR antibody of (1) and (2) above with other amino acids, the number of amino acids to be replaced is preferably 1 to 10, more preferably 1 to 5, even more preferably 1 to 3, and even more preferably 1 or 2. When deleting amino acids in the amino acid sequence of the light chain, the number of amino acids to be deleted is preferably 1 to 10, more preferably 1 to 5, even more preferably 1 to 3, and even more preferably 1 or 2. Mutations that combine these amino acid replacements and deletions can also be added.

When amino acids are added to the amino acid sequence of the light chain of the anti-hTfR antibody of (1) and (2) above, preferably 1 to 10 amino acids, more preferably 1 to 5 amino acids, even more preferably 1 to 3 amino acids, and even more preferably 1 or 2 amino acids are added to the amino acid sequence of the light chain or to the N-terminus or C-terminus. Mutations that combine the addition, substitution, and deletion of these amino acids can also be added. The amino acid sequence of the mutated light chain preferably has an identity of 80% or more, more preferably an identity of 90% or more, and even more preferably an identity of 95% or more, with the amino acid sequence of the original light chain.

When amino acids in the amino acid sequence of the heavy chain of the anti-hTfR antibody of (1) and (2) above are replaced with other amino acids, the number of amino acids to be replaced is preferably 1 to 10, more preferably 1 to 5, even more preferably 1 to 3, and even more preferably 1 or 2. When amino acids in the amino acid sequence of the heavy chain are deleted, the number of amino acids to be deleted is preferably 1 to 10, more preferably 1 to 5, even more preferably 1 to 3, and even more preferably 1 or 2. Mutations that combine these amino acid substitutions and deletions can also be added.

When amino acids are added to the amino acid sequence of the heavy chain of the anti-hTfR antibody of (1) and (2) above, preferably 1 to 10 amino acids, more preferably 1 to 5 amino acids, even more preferably 1 to 3 amino acids, and even more preferably 1 or 2 amino acids are added to the amino acid sequence of the heavy chain or to the N-terminus or C-terminus. Mutations that combine the addition, substitution, and deletion of these amino acids can also be added. The amino acid sequence of the mutated heavy chain preferably has an identity of 80% or more, more preferably an identity of 90% or more, and even more preferably an identity of 95% or more, with the amino acid sequence of the original heavy chain.

Specific examples of antibodies to be bound to the fusion protein of SA and a lysosomal enzyme, the fusion protein of SA and a cytokine, or the fusion protein of SA and a neurotrophic factor include the following anti-hTfR heavy chain antibody variable region (VHH) peptides (hTfR affinity peptides):
(3) An hTfR affinity peptide comprising the amino acid sequence of SEQ ID NO: 105 or SEQ ID NO: 106 as CDR1, the amino acid sequence of SEQ ID NO: 107 or SEQ ID NO: 108 as CDR2, and the amino acid sequence of SEQ ID NO: 109 or SEQ ID NO: 110 as CDR3, and (4) an hTfR affinity peptide comprising the amino acid sequence of SEQ ID NO: 105 or SEQ ID NO: 106 as CDR1, the amino acid sequence of SEQ ID NO: 111 or SEQ ID NO: 112 as CDR2, and the amino acid sequence of SEQ ID NO: 109 or SEQ ID NO: 110 as CDR3,
However, the present invention is not limited to these, and the above amino acid sequences may be appropriately mutated by substitution, deletion, addition, etc. The above hTfR affinity peptides (3) and (4) are included in the antibody referred to in this specification.

The hTfR affinity peptides (3) and (4) above are particularly suitable as antibodies to be bound to a fusion protein of HSA and hGALC, a fusion protein of HSA and hGBA, a fusion protein of HSA and hIL-10, a fusion protein of HSA and hBDNF, a fusion protein of HSA and hNGF, a fusion protein of HSA and hNT-3, or a fusion protein of HSA and hNT-4.

The above hTfR affinity peptides (3) and (4) can also be used as antibodies that contain substitutions, additions, deletions, etc., as long as they retain their affinity for the human transferrin receptor.

When amino acids in the amino acid sequence of the hTfR affinity peptide in (3) and (4) above are replaced with other amino acids, the number of amino acids to be replaced is preferably 1 to 10, more preferably 1 to 5, even more preferably 1 to 3, and even more preferably 1 or 2. When amino acids in the amino acid sequence of the hTfR affinity peptide are deleted, the number of amino acids to be deleted is preferably 1 to 10, more preferably 1 to 5, even more preferably 1 to 3, and even more preferably 1 or 2. Mutations that combine these amino acid substitutions and deletions can also be added.

When amino acids are added to the amino acid sequence of the hTfR affinity peptide in (3) and (4) above, preferably 1 to 10 amino acids are added to the amino acid sequence of the light chain or to the N-terminus or C-terminus, more preferably 1 to 5 amino acids, even more preferably 1 to 3 amino acids, and even more preferably 1 or 2 amino acids. Mutations that combine the addition, substitution, and deletion of these amino acids can also be added. The amino acid sequence of the mutated light chain preferably has an identity of 80% or more, more preferably 90% or more, and even more preferably 95% or more with the amino acid sequence of the original hTfR affinity peptide.

The fusion protein of HSA and hGALC can be bound to an antibody or ligand for a receptor on cerebrovascular endothelial cells to form a conjugate that can pass through the blood-brain barrier and function in the brain. Therefore, the conjugate can be used to manufacture a drug for administration into the blood to treat central nervous system diseases caused by GALC deficiency, such as Krabbe disease. The conjugate can also be used in a treatment method that includes administering a therapeutically effective amount of the conjugate into the blood (including intravenous injection such as intravenous drip) to a patient for central nervous system diseases caused by GALC deficiency, such as Krabbe disease. The conjugate administered into the blood can reach not only the brain, but also other organs and tissues that express GALC. The drug can also be used to prevent the onset of the disease.

The fusion protein of HSA and hGBA can be bound to an antibody or ligand for a receptor on cerebrovascular endothelial cells to form a conjugate that can pass through the blood-brain barrier and function in the brain. Therefore, the conjugate can be used to manufacture a drug for administration into the blood to treat central nervous system diseases caused by GBA deficiency, such as Gaucher disease. The conjugate can also be used in a treatment method that includes administering a therapeutically effective amount of the conjugate into the blood (including intravenous injection such as intravenous drip) to a patient for central nervous system diseases caused by GBA deficiency, such as Gaucher disease. The conjugate administered into the blood can reach not only the brain but also other organs and tissues. The drug can also be used to prevent the onset of the disease.

The fusion protein of HSA and hIL-10 can be bound to an antibody or ligand for a receptor on cerebrovascular endothelial cells to form a conjugate that can pass through the blood-brain barrier and exert its function in the brain. Therefore, the conjugate can be used to manufacture a drug for administration to the blood for the treatment of a disease of the central nervous system. The conjugate can also be used in a treatment method that includes administering a therapeutically effective amount of the disease of the central nervous system to a patient in the blood (including intravenous injection such as intravenous drip). The conjugate administered to the blood can reach not only the brain, but also other organs and tissues in which a therapeutic effect can be exerted by IL-10. The drug can also be used to prevent the onset of the disease.

The fusion protein of HSA and hBDNF can be bound to an antibody or ligand for a receptor on cerebrovascular endothelial cells to form a conjugate that can pass through the blood-brain barrier and exert its function in the brain. Therefore, the conjugate can be used to manufacture a drug for administration to the blood for the treatment of a disease of the central nervous system. The conjugate can also be used in a treatment method that includes administering a therapeutically effective amount of the disease of the central nervous system to a patient in the blood (including intravenous injection such as intravenous drip). The conjugate administered to the blood can reach not only the brain, but also other organs and tissues in which BDNF can exert a therapeutic effect. The drug can also be used to prevent the onset of the disease.

The fusion protein of HSA and hNGF can be bound to an antibody or ligand for a receptor on cerebrovascular endothelial cells to form a conjugate that can pass through the blood-brain barrier and exert its function in the brain. Therefore, the conjugate can be used to manufacture a drug for administration to the blood for the treatment of diseases of the central nervous system. The conjugate can also be used in a treatment method that includes administering a therapeutically effective amount of the conjugate to the blood of a patient (including intravenous injection such as intravenous drip infusion). The conjugate administered to the blood can reach not only the brain, but also other organs and tissues in which NGF can exert a therapeutic effect. The drug can also be used to prevent the onset of the disease.

The fusion protein of HSA and hNT-3 can be bound to an antibody or ligand for a receptor on cerebrovascular endothelial cells to form a conjugate that can pass through the blood-brain barrier and exert its function in the brain. Therefore, the conjugate can be used to manufacture a drug for administration to the blood for the treatment of diseases of the central nervous system. The conjugate can also be used in a treatment method that includes administering a therapeutically effective amount of the drug to a patient in the blood (including intravenous injection such as intravenous drip infusion). The conjugate administered to the blood can reach not only the brain, but also other organs and tissues in which NT-3 can exert a therapeutic effect. The drug can also be used to prevent the onset of the disease.

The fusion protein of HSA and hNT-4 can be bound to an antibody or ligand for a receptor on cerebrovascular endothelial cells to form a conjugate that can pass through the blood-brain barrier and exert its function in the brain. Therefore, the conjugate can be used to manufacture a drug for administration to the blood for the treatment of a disease of the central nervous system. The conjugate can also be used in a treatment method that includes administering a therapeutically effective amount of the disease of the central nervous system to a patient in the blood (including intravenous injection such as intravenous drip). The conjugate administered to the blood can reach not only the brain, but also other organs and tissues in which NT-4 can exert a therapeutic effect. The drug can also be used to prevent the onset of the disease.

HSA-hGALC fusion protein, HSA-hGBA fusion protein, HSA-hIL-10 fusion protein, HSA-hBDNF fusion protein, HSA-hNGF fusion protein, HSA-hNT-3 fusion protein, and HSA-hNT-4 fusion protein can be used as drugs that are administered into the blood and exert their medicinal effects in the central nervous system (CNS) by binding to antibodies or ligands for receptors on cerebrovascular endothelial cells. Such drugs are generally administered to patients by intravenous injection, subcutaneous injection, or intramuscular injection, but there are no particular limitations on the administration route.

When it is said that hGALC has the function of hGALC in a conjugate of an antibody and a fusion protein of HSA and hGALC, it means that hGALC has a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, for example 90% or more or 95% or more, when the specific activity of normal wild-type hGALC is taken as 100%. Also, when it is said that hGALC has the function of hGALC in a conjugate of an antibody and a fusion protein of HSA and hGALC, it means that hGALC has a specific activity of preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, and even more preferably 80% or more, for example 90% or more or 95% or more, when the specific activity of normal wild-type hGALC is taken as 100%. The specific activity of hGALC in the conjugate is calculated by multiplying the enzyme activity of hGALC per unit mass of the conjugate (μM/hour/mg protein) by (molecular weight of the conjugate/molecular weight of the portion of the conjugate corresponding to hGALC). The same can be said for the conjugate of the fusion protein of HSA and hGBA and an antibody. The same can be said for the conjugate of the fusion protein of HSA and hIL-10 and an antibody, the conjugate of the fusion protein of HSA and hBDNF and an antibody, the conjugate of the fusion protein of HSA and hNGF and an antibody, the conjugate of the fusion protein of HSA and hNT-3 and an antibody, and the conjugate of the fusion protein of HSA and hNT-4 and an antibody, although hIL-10, hBDNF, hNGF, hNT-3, and hNT-4 are not enzymes, so the specific activity is based on the physiological activity of each of the proteins hIL-10, hBDNF, hNGF, hNT-3, and hNT-4, rather than on the enzyme activity.

In one embodiment of the present invention, the fusion protein of SA and a lysosomal enzyme, the fusion protein of SA and a cytokine, or the fusion protein of SA and a neurotrophic factor may be a conjugate with a ligand. Here, the SA, the lysosomal enzyme, the cytokine, and the neurotrophic factor may all be derived from humans or from animals other than humans. For example, examples of the fusion protein of SA and a lysosomal enzyme include a fusion protein of HSA and hGALC and a fusion protein of HSA and hGBA, examples of the fusion protein of SA and a cytokine include a fusion protein of HSA and hIL-10, and examples of the fusion protein of SA and a neurotrophic factor include a fusion protein of HSA and hBDNF, a fusion protein of HSA and hNGF, a fusion protein of HSA and hNT-3, and a fusion protein of HSA and hNT-4.

Here, the ligand is, for example, one that can specifically bind to a receptor on cerebrovascular endothelial cells, such as the insulin receptor, transferrin receptor, leptin receptor, lipoprotein receptor, and IGF receptor. The corresponding ligands for the insulin receptor, transferrin receptor, leptin receptor, lipoprotein receptor, and IGF receptor are insulin, leptin, lipoprotein, and IGF (IGF-1, IGF-2), respectively. The ligand may be a wild type or a mutant wild type, so long as it can specifically bind to the target receptor. Also, it may be a fragment of the ligand, so long as it can specifically bind to the target receptor. These ligands are particularly suitable as ligands to be bound to a fusion protein of HSA and hGALC, a fusion protein of HSA and hGBA, a fusion protein of HSA and hIL-10, a fusion protein of HSA and hBDNF, a fusion protein of HSA and hNGF, a fusion protein of HSA and hNT-3, or a fusion protein of HSA and hNT-4.

For example, when the ligand is transferrin (Tf), the transferrin may be human Tf or Tf of an animal species other than human, but is preferably human Tf. The transferrin may be wild-type, or may have a mutation introduced therein, so long as it has affinity for the transferrin receptor (TfR). The mutation may be, for example, a substitution, addition, or deletion of one or two amino acids. The transferrin may be full-length, or may be a fragment thereof, so long as it has affinity for the transferrin receptor (TfR). The same can be said for insulin, leptin, lipoproteins, and IGF (IGF-1, IGF-2).

In one embodiment of the present invention, a conjugate of a fusion protein of SA and a lysosomal enzyme, a fusion protein of SA and a cytokine, or a fusion protein of SA and a neurotrophic factor, and a ligand can be produced by the following method (1) or (2):
(1) A fusion protein and a ligand are conjugated via a non-peptide linker or a peptide linker;
(2) The fusion protein and the ligand are produced as a recombinant protein bound via a linker sequence or directly via a peptide bond.

In the case of (1) above, examples of the non-peptide linker that can be used include polyethylene glycol, polypropylene glycol, copolymers of ethylene glycol and propylene glycol, polyoxyethylated polyol, polyvinyl alcohol, polysaccharides, dextran, polyvinyl ether, biodegradable polymers, lipid polymers, chitins, and hyaluronic acid, or derivatives or combinations of these. The peptide linker is a peptide chain or derivatives consisting of 1 to 50 peptide-bonded amino acids, whose N-terminus and C-terminus form covalent bonds with either the fusion protein or the ligand, respectively, thereby binding the fusion protein and the ligand. The fusion protein and the ligand are each produced as recombinant proteins.

In the case of (2) above, the fusion protein and the ligand are produced as a recombinant protein in which the N-terminus of the ligand is bound to the C-terminus of the fusion protein via a linker sequence or directly, or the N-terminus of the fusion protein is bound to the C-terminus of the ligand via a linker sequence or directly. The expression vectors, host cells, and media used to produce such recombinant proteins can be those used to produce the above-mentioned fusion protein of HSA and hGALC.

In one embodiment of the present invention, the fusion protein of SA and a lysosomal enzyme, the fusion protein of SA and a cytokine, or the fusion protein of SA and a neurotrophic factor can be a conjugate with another protein (A) as well as an antibody and a ligand. Here, the SA, the lysosomal enzyme, the cytokine, and the neurotrophic factor may be derived from humans or animals other than humans. For example, examples of the fusion protein of SA and a lysosomal enzyme include a fusion protein of HSA and hGALC and a fusion protein of HSA and hGBA, examples of the fusion protein of SA and a cytokine include a fusion protein of HSA and hIL-10, and examples of the fusion protein of SA and a neurotrophic factor include a fusion protein of HSA and hBDNF, a fusion protein of HSA and hNGF, a fusion protein of HSA and hNT-3, and a fusion protein of HSA and hNT-4.

In one embodiment of the present invention, a conjugate of a fusion protein of SA and a lysosomal enzyme, a fusion protein of SA and a cytokine, or a fusion protein of SA and a neurotrophic factor, and a protein (A) can be produced by the following method (1) or (2):
(1) The fusion protein and protein (A) are conjugated via a non-peptide linker or a peptide linker;
(2) The fusion protein and protein (A) are produced as a recombinant protein by binding them via a linker sequence or directly via a peptide bond.

In the case of (1) above, examples of the non-peptide linker that can be used include polyethylene glycol, polypropylene glycol, copolymers of ethylene glycol and propylene glycol, polyoxyethylated polyol, polyvinyl alcohol, polysaccharides, dextran, polyvinyl ether, biodegradable polymers, lipid polymers, chitins, and hyaluronic acid, or derivatives or combinations of these. The peptide linker is a peptide chain or derivatives thereof consisting of 1 to 50 peptide-bonded amino acids, and its N-terminus and C-terminus form covalent bonds with either the fusion protein or protein (A), respectively, thereby binding the fusion protein and protein (A). The fusion protein and protein (A) are each produced as recombinant proteins.

In the case of (2) above, the fusion protein and the ligand are produced as a recombinant protein in which the N-terminus of the ligand is bound to the C-terminus of the fusion protein via a linker sequence or directly, or the N-terminus of the fusion protein is bound to the C-terminus of the ligand via a linker sequence or directly. The expression vectors, host cells, and media used to produce such recombinant proteins can be those used to produce a fusion protein of HSA and hGALC.

The conjugate of the fusion protein of HSA and hGALC with an antibody, and the conjugate of the fusion protein of HSA and hGALC with a ligand or protein (A) can both be used as a pharmaceutical composition for the treatment of Krabbe disease (galactosylceramide lipidosis, or globoid cell leukodystrophy).

The conjugate of the fusion protein of HSA and hGBA with an antibody, and the conjugate of the fusion protein of HSA and hGBA with a ligand or protein (A) can both be used as a pharmaceutical composition for the treatment of Gaucher disease.

The conjugate of the fusion protein of HSA and hIL-10 with an antibody, and the conjugate of the fusion protein of HSA and hIL-10 with a ligand or protein (A) can both be used as pharmaceutical compositions for treating inflammatory diseases, neuropathic pain, multiple sclerosis, spinal cord injury, ALS, neuroinflammation, symptoms associated with arthritis and other joint diseases, and autoimmune diseases, etc.

The conjugate of the fusion protein of HSA and hBDNF with an antibody, and the conjugate of the fusion protein of HSA and hBDNF with a ligand or protein (A) can both be used as pharmaceutical compositions for treating neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and Huntington's disease, spinal degenerative diseases such as amyotrophic lateral sclerosis, diabetic neuropathy, cerebral ischemic disease, developmental disorders such as Rett syndrome, schizophrenia, depression, and Rett syndrome, etc.

The conjugate of the fusion protein of HSA and hNGF with an antibody, and the conjugate of the fusion protein of HSA and hNGF with a ligand or protein (A) can both be used as pharmaceutical compositions for treating neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and Huntington's disease.

The conjugate of the fusion protein of HSA and hNT-3 with an antibody, and the conjugate of the fusion protein of HSA and hNT-3 with a ligand or protein (A) can both be used as a pharmaceutical composition for treating diseases such as neurodegenerative disorders.

The conjugate of the fusion protein of HSA and hNT-4 with an antibody, and the conjugate of the fusion protein of HSA and hNT-4 with a ligand or protein (A) can both be used as a pharmaceutical composition for treating diseases such as neurodegenerative disorders.

A pharmaceutical composition containing as an active ingredient a conjugate of an antibody and a fusion protein of HSA and hGALC, or a conjugate of a fusion protein of HSA and hGALC and a ligand or protein (A), can be administered intravenously, intramuscularly, intraperitoneally, subcutaneously, or intracerebroventricularly as an injection. These injections can be supplied as freeze-dried preparations or aqueous liquid preparations. In the case of an aqueous liquid preparation, it may be in the form of a vial filled with the fusion protein, or it can be supplied as a prefilled preparation in a syringe. In the case of a freeze-dried preparation, it is dissolved in an aqueous medium before use and reconstituted. In the conjugate of an antibody and a fusion protein of HSA and hGALC contained in an aqueous liquid preparation, the ratio of monomer to total protein (mass of monomer/mass of total protein x 100 (%)) is preferably 70% or more, more preferably 80% or more, even more preferably 90% or more, for example 95% or more. The same can be said for a solution obtained by dissolving a freeze-dried preparation in an aqueous medium and reconstituting it. The above-mentioned facts are not intended to limit the scope of the present invention, but are intended to provide a pharmaceutical composition comprising, as an active ingredient, a conjugate of a fusion protein of HSA and hGBA and an antibody, or a conjugate of a fusion protein of HSA and hGBA and a ligand or protein (A), a pharmaceutical composition comprising, as an active ingredient, a conjugate of a fusion protein of HSA and hIL-10 and an antibody, or a conjugate of a fusion protein of HSA and hIL-10 and a ligand or protein (A), a pharmaceutical composition comprising, as an active ingredient, a conjugate of a fusion protein of HSA and hBDNF and an antibody, or a conjugate of a fusion protein of HSA and hBDNF and a ligand or protein (A), It may also be applied to pharmaceutical compositions containing as active ingredients a conjugate of a fusion protein of SA and hNGF and an antibody, or a conjugate of a fusion protein of HSA and hNGF and a ligand or protein (A), a conjugate of a fusion protein of HSA and NT-3 and an antibody, or a conjugate of a fusion protein of HSA and hNT-3 and a ligand or protein (A), and a conjugate of a fusion protein of HSA and NT-4 and an antibody, or a conjugate of a fusion protein of HSA and hNT-4 and a ligand or protein (A).

When wild-type hGALC is expressed as a recombinant protein, it is obtained as a dimer, tetramer, or other polymer. In contrast, when a fusion protein of HSA and hGALC is expressed as a recombinant protein, most of it is obtained as a monomer. In the fusion protein of HSA and hGALC produced as a recombinant protein, the ratio of monomers to the total protein (monomer mass/total protein mass x 100(%)) is preferably 70% or more, more preferably 80% or more, even more preferably 90% or more, for example 95% or more.

HSA-hGALC fusion proteins, such as HSA-hGALC and hGALC-HSA, can be expressed as recombinant proteins to obtain homogeneous monomers. From the standpoint of production control, the method of producing hGALC as a fusion protein with HSA can be said to be an excellent method of producing hGALC.

In addition, when the conjugate of the antibody and the fusion protein of HSA and hGALC is expressed as a recombinant protein, most of it is obtained as a monomer. In the conjugate produced as a recombinant protein, the ratio of monomer to total protein (monomer mass/total protein mass x 100(%)) is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more, for example 95% or more.

When the conjugate of the fusion protein of HSA and hGALC with an antibody is expressed as a recombinant protein, a homogeneous monomer can be obtained. Therefore, from the standpoint of production control, the method of producing hGALC as a fusion protein of HSA and an antibody can be said to be an excellent method of producing hGALC.

　A fusion protein between SA and a lysosomal enzyme, a fusion protein between SA and a cytokine, or a fusion protein between SA and a neurotrophic factor, as well as a nucleic acid molecule containing a gene encoding the conjugate, can be used in gene therapy. In addition, a nucleic acid molecule containing a gene encoding a conjugate between any of these fusion proteins and an antibody, a nucleic acid molecule containing a gene encoding a conjugate between any of these fusion proteins and a ligand, and a nucleic acid molecule containing a gene encoding a conjugate between any of these fusion proteins and protein (A) can also be used in gene therapy.

Here, the fusion protein is, for example, a fusion protein of HSA and hGALC, a fusion protein of HSA and hGBA, a fusion protein of HSA and hIL-10, a fusion protein of HSA and hBDNF, a fusion protein of HSA and hNGF, a fusion protein of HSA and hNT-3, or a fusion protein of HSA and hNT-4. The antibody is, for example, an anti-transferrin receptor antibody. The ligand is, for example, transferrin or a fragment thereof.

In one embodiment of the present invention, a nucleic acid molecule that can be used for gene therapy includes, for example, one having the following base sequence:
(1) A base sequence including a first inverted terminal repeat (ITR) or a functional equivalent thereof, a base sequence including a gene expression control site downstream of the first inverted terminal repeat (ITR), a base sequence encoding a fusion protein further downstream, and a base sequence including a second inverted terminal repeat (ITR) or a functional equivalent thereof further downstream;
(2) a nucleotide sequence containing a first long terminal repeat (LTR) or a functional equivalent thereof, a nucleotide sequence downstream thereof containing a gene expression control site, a nucleotide sequence further downstream thereof encoding a fusion protein, and a nucleotide sequence further downstream thereof containing a second long terminal repeat (LTR) or a functional equivalent thereof;
(3) a base sequence containing a leader or a functional equivalent thereof, a base sequence downstream thereof containing a gene expression control site, a base sequence further downstream thereof encoding a fusion protein, and a base sequence further downstream thereof containing a trailer or a functional equivalent thereof;
(4) a nucleotide sequence containing a first inverted terminal repeat (ITR) or a functional equivalent thereof, a nucleotide sequence containing a gene expression control site downstream of the first inverted terminal repeat (ITR), a nucleotide sequence encoding a conjugate of a fusion protein and an antibody further downstream, and a nucleotide sequence containing a second inverted terminal repeat (ITR) or a functional equivalent thereof further downstream;
(5) a nucleotide sequence containing a first long terminal repeat (LTR) or a functional equivalent thereof, a nucleotide sequence downstream thereof containing a gene expression control site, a nucleotide sequence further downstream thereof encoding a conjugate of a fusion protein and an antibody, and a nucleotide sequence further downstream thereof containing a second long terminal repeat (LTR) or a functional equivalent thereof;
(6) a nucleotide sequence containing a leader or a functional equivalent thereof, followed downstream by a nucleotide sequence containing a gene expression control site, followed further downstream by a nucleotide sequence encoding a conjugate of a fusion protein and an antibody, followed further downstream by a nucleotide sequence containing a trailer or a functional equivalent thereof;
(7) A base sequence including a first inverted terminal repeat (ITR) or a functional equivalent thereof, a base sequence including a gene expression control site downstream of the first inverted terminal repeat (ITR), a base sequence encoding a conjugate of a fusion protein and a ligand further downstream, and a base sequence including a second inverted terminal repeat (ITR) or a functional equivalent thereof further downstream;
(8) A base sequence including a first long terminal repeat (LTR) or a functional equivalent thereof, a base sequence including a gene expression control site downstream of the first long terminal repeat (LTR), a base sequence further downstream encoding a conjugate of a fusion protein and a ligand, and a base sequence including a second long terminal repeat (LTR) or a functional equivalent thereof downstream of the first long terminal repeat (LTR);
(9) A base sequence containing a leader or a functional equivalent thereof, a base sequence downstream thereof containing a gene expression control site, a base sequence further downstream thereof encoding a conjugate of a fusion protein and a ligand, and a base sequence further downstream thereof containing a trailer or a functional equivalent thereof;
(10) a base sequence including a first inverted terminal repeat (ITR) or a functional equivalent thereof, a base sequence including a gene expression control site downstream of the first inverted terminal repeat (ITR), a base sequence encoding a conjugate of a fusion protein and protein (A) further downstream, and a base sequence including a second inverted terminal repeat (ITR) or a functional equivalent thereof further downstream;
(11) a base sequence comprising a first long terminal repeat (LTR) or a functional equivalent thereof, a base sequence comprising a gene expression control site downstream thereof, a base sequence encoding a conjugate of a fusion protein and protein (A) further downstream, and a base sequence comprising a second long terminal repeat (LTR) or a functional equivalent thereof; and (12) a base sequence comprising a leader or a functional equivalent thereof, a base sequence comprising a gene expression control site downstream thereof, a base sequence encoding a conjugate of a fusion protein and protein (A) further downstream, and a trailer or a functional equivalent thereof further downstream.

In the present invention, the term "nucleic acid molecule" refers primarily to either DNA, which is a polymer of deoxyribonucleotides formed by phosphodiester bonds, or RNA, which is a polymer of ribonucleotides formed by phosphodiester bonds.

When the "nucleic acid molecule" is DNA, the DNA may be single-stranded (single-stranded) or double-stranded with a complementary strand. When the DNA is single-stranded, the DNA may be a (+) strand or a (-) strand. The individual deoxyribonucleotides constituting the DNA may be of a naturally occurring type or may be modified from the natural type, so long as the gene encoding the protein contained in the DNA can be translated into mRNA in the cells of a mammal (particularly a human). In one embodiment of the present invention, the individual deoxyribonucleotides constituting the DNA may be of a naturally occurring type or may be modified from the natural type, so long as the gene encoding the protein contained in the DNA can be translated into mRNA in the cells of a mammal (particularly a human) and the whole or part of the DNA can be replicated.

In addition, when the "nucleic acid molecule" is RNA, the RNA may be single-stranded (single-stranded) or double-stranded with a complementary strand. When the RNA is single-stranded, the RNA may be a (+) strand or a (-) strand. In one embodiment of the present invention, the individual ribonucleotides constituting the RNA may be of a naturally occurring type or may be modified, so long as the gene encoding the protein contained in the RNA can be reverse transcribed into DNA in a mammalian (particularly human) cell. In one embodiment of the present invention, the individual ribonucleotides constituting the RNA may be of a naturally occurring type or may be modified, so long as the gene encoding the protein contained in the RNA can be translated into a protein in a mammalian (particularly human) cell. Modification of ribonucleotides is performed, for example, to suppress degradation of RNA by RNase and to increase the stability of RNA in cells.

In one embodiment of the present invention, the term "inverted terminal repeat (ITR)" refers to a base sequence that exists at the end of the viral genome and in which the same sequence is repeated. As ITR, those derived from adeno-associated virus and those derived from adenovirus can be preferably used. For example, the ITR of the adeno-associated virus is a region of approximately 145 bases in length and functions as a replication origin, etc. In one embodiment of the present invention, there are two inverted terminal repeats (ITR) in the nucleic acid molecule, which are called the first inverted terminal repeat (ITR) and the second inverted terminal repeat (ITR), respectively. Here, when a gene encoding a fusion protein is placed between two ITRs, the ITR located on the 5' side is called the first inverted terminal repeat (ITR), and the ITR located on the 3' side is called the second inverted terminal repeat (ITR). The inverted terminal repeat (ITR) may be derived from any virus as long as it has at least one of the functions of an original ITR, such as functioning as an origin of replication or inserting a gene into a host cell, and the ITR of the adeno-associated virus is one suitable one.

When the ITR is an adeno-associated virus, the serotype of AAV is not particularly limited and may be any of

serotypes

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11. For example, the inverted terminal repeat (ITR) of AAV serotype 2 has a first ITR that contains the base sequence shown in SEQ ID NO: 113 and a second ITR that contains the base sequence shown in SEQ ID NO: 114.

In addition, the ITR is not limited to the wild-type ITR, and may be modified by substitution, deletion, addition, or the like, in the base sequence of the wild-type ITR. When a base in the base sequence of the wild-type ITR is replaced with another base, the number of bases to be replaced is preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 3. When a base sequence of the wild-type ITR is deleted, the number of bases to be deleted is preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 3. In addition, a mutation combining these base substitutions and deletions can also be added. When a base is added to the wild-type ITR, preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 3 bases are added in the base sequence of the ITR or to the 5' end or 3' end. A mutation combining these base additions, substitutions, and deletions can also be added. The nucleotide sequence of the mutated ITR preferably exhibits 80% or more identity to the nucleotide sequence of the wild-type ITR, more preferably 85% or more identity, even more preferably 90% or more identity, even more preferably 95% or more identity, and even more preferably 98% or more identity.

A functional equivalent of an ITR is something that can be used functionally in place of an ITR. In addition, an ITR artificially constructed based on an ITR is also a functional equivalent of an ITR as long as it can replace an ITR.

　A functional equivalent of an AAV ITR is one that can be used functionally in place of an AAV ITR. In addition, an ITR artificially constructed based on an AAV ITR is also a functional equivalent of an AAV ITR as long as it can replace an AAV ITR.

An example of a functional equivalent of the artificially constructed first AAV inverted terminal repeat (first AAV-ITR) is one having the base sequence shown in SEQ ID NO: 115 (functional equivalent of the first AAV-ITR). This base sequence shown in SEQ ID NO: 115 to which substitutions, deletions, or mutations have been added is also included in the functional equivalent of the first AAV-ITR, so long as it can be used functionally in place of the ITR of the first AAV. When bases in the base sequence shown in SEQ ID NO: 115 are replaced with other bases, the number of bases to be replaced is preferably 1 to 20, more preferably 1 to 10, even more preferably 1 to 5, and even more preferably 1 to 3. When bases in the base sequence shown in SEQ ID NO: 115 are deleted, the number of bases to be deleted is preferably 1 to 20, more preferably 1 to 10, even more preferably 1 to 5, and even more preferably 1 to 3. In addition, an ITR to which mutations that combine the substitution and deletion of these bases have been added is also a functional equivalent of the first AAV-ITR. When bases are added to the base sequence shown in SEQ ID NO:115, preferably 1 to 20 bases, more preferably 1 to 10 bases, even more preferably 1 to 5 bases, and even more preferably 1 to 3 bases are added to the base sequence or to the 5' end or 3' end. ITRs with mutations that combine the addition, substitution, and deletion of these bases are also included in the functional equivalent of the first AAV-ITR. The base sequence of the mutated ITR preferably shows 80% or more identity to the base sequence shown in SEQ ID NO:115, more preferably shows 85% or more identity, even more preferably shows 90% or more identity, even more preferably shows 95% or more identity, and even more preferably shows 98% or more identity.

Furthermore, an example of a functional equivalent of an artificially constructed second inverted terminal repeat (second AAV-ITR) is one having the base sequence shown in SEQ ID NO: 116 (functional equivalent of the second AAV-ITR). This base sequence shown in SEQ ID NO: 116 to which substitutions, deletions, or mutations have been added is also included in the functional equivalent of the ITR of the second AAV, so long as it can be used functionally in place of the ITR of the second AAV. When bases in the base sequence shown in SEQ ID NO: 116 are replaced with other bases, the number of bases to be replaced is preferably 1 to 20, more preferably 1 to 10, even more preferably 1 to 5, and even more preferably 1 to 3. When bases in the base sequence shown in SEQ ID NO: 116 are deleted, the number of bases to be deleted is preferably 1 to 20, more preferably 1 to 10, even more preferably 1 to 5, and even more preferably 1 to 3. In addition, an ITR to which mutations have been added that combine the substitution and deletion of these bases is also a functional equivalent of the ITR of the second AAV. When bases are added to the base sequence shown in SEQ ID NO:116, preferably 1 to 20 bases, more preferably 1 to 10 bases, even more preferably 1 to 5 bases, and even more preferably 1 to 3 bases are added to the base sequence or to the 5' end or 3' end. ITRs with mutations that combine the addition, substitution, and deletion of these bases are also included in the functional equivalent of the ITR of the second AAV. The base sequence of the mutated ITR preferably shows 85% or more identity with the base sequence shown in SEQ ID NO:116, more preferably shows 85% or more identity, even more preferably shows 90% or more identity, even more preferably shows 95% or more identity, and even more preferably shows 98% or more identity.

In one embodiment of the present invention, the term "long terminal repeat (LTR)" refers to a base sequence in which the same sequence is repeated hundreds to thousands of times, for example, at the end of a retrotransposon of a eukaryote, or a retrovirus genome, lentivirus genome, etc. In one embodiment of the present invention, there are two long terminal repeats (LTRs) in a nucleic acid molecule, which are called the first long terminal repeat (LTR) and the second long terminal repeat (LTR). Here, when a gene encoding a fusion protein is placed between two LTRs, the LTR located on the 5' side is called the first long terminal repeat (LTR), and the LTR located on the 3' side is called the second long terminal repeat (LTR). The long terminal repeat (LTR) may be derived from any virus as long as it has at least one of the functions of an original LTR, such as a function as a replication origin or gene insertion into a host cell, and preferred examples include retrovirus genomes and lentiviruses. In addition, the LTR is not limited to a wild-type LTR, and may be a wild-type LTR with a modified base sequence, such as a substitution, deletion, or addition.

When bases in the wild-type LTR base sequence are replaced with other bases, the number of bases to be replaced is preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 3. When the wild-type LTR base sequence is deleted, the number of bases to be deleted is preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 3. Mutations combining these base substitutions and deletions can also be added. When bases are added to the wild-type LTR, preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 3 bases are added in the LTR base sequence or at the 5' end or 3' end. Mutations combining these base additions, substitutions, and deletions can also be added. The mutated LTR base sequence preferably exhibits 80% or more identity with the wild-type LTR base sequence, more preferably 85% or more identity, even more preferably 90% or more identity, even more preferably 95% or more identity, and even more preferably 98% or more identity.

　A functional equivalent of an LTR is something that can be used functionally in place of an LTR. In addition, an artificially constructed LTR based on an LTR is also a functional equivalent of an LTR as long as it can replace an LTR.

　A functional equivalent of a lentiviral LTR is one that can be used functionally in place of the lentiviral LTR. In addition, an artificially constructed LTR based on a lentiviral LTR is also a functional equivalent of the lentiviral LTR as long as it can replace the lentiviral LTR.

　A functional equivalent of a retroviral LTR is one that can be used functionally in place of a retroviral LTR. In addition, an artificially constructed LTR based on a retroviral LTR is also a functional equivalent of a retroviral LTR as long as it can replace the retroviral LTR.

An example of a functional equivalent of the first LTR is one having the base sequence shown in SEQ ID NO: 117. This base sequence shown in SEQ ID NO: 117 with substitutions, deletions, or mutations is also included in the functional equivalent of the first LTR, so long as it can be functionally used as the first LTR. When bases in the base sequence shown in SEQ ID NO: 117 are replaced with other bases, the number of bases to be replaced is preferably 1 to 20, more preferably 1 to 20, even more preferably 1 to 5, and even more preferably 1 to 3. When bases in the base sequence shown in SEQ ID NO: 117 are deleted, the number of bases to be deleted is preferably 1 to 20, more preferably 1 to 10, even more preferably 1 to 5, and even more preferably 1 to 3. In addition, an LTR with a mutation that combines the substitution and deletion of these bases is also a functional equivalent of the first LTR. When bases are added to the base sequence shown in SEQ ID NO:117, preferably 1 to 20 bases, more preferably 1 to 10 bases, even more preferably 1 to 5 bases, and even more preferably 1 to 3 bases are added to the base sequence or to the 5' end or 3' end. LTRs with mutations that combine the addition, substitution, and deletion of these bases are also included in the functional equivalent of the first LTR. The base sequence of the mutated LTR preferably shows 80% or more identity with the base sequence shown in SEQ ID NO:117, more preferably shows 85% or more identity, even more preferably shows 90% or more identity, even more preferably shows 95% or more identity, and even more preferably shows 98% or more identity.

Furthermore, an example of a functional equivalent of the second LTR is one having the base sequence shown in SEQ ID NO: 118. This base sequence shown in SEQ ID NO: 118 with substitutions, deletions, or mutations is also included in the functional equivalent of the second LTR as long as it can be functionally used as the second LTR. When bases in the base sequence shown in SEQ ID NO: 118 are replaced with other bases, the number of bases to be replaced is preferably 1 to 20, more preferably 1 to 10, even more preferably 1 to 5, and even more preferably 1 to 3. When bases in the base sequence shown in SEQ ID NO: 118 are deleted, the number of bases to be deleted is preferably 1 to 20, more preferably 1 to 10, even more preferably 1 to 5, and even more preferably 1 to 3. Furthermore, an LTR with a mutation that combines the substitution and deletion of these bases is also a functional equivalent of the second LTR. When bases are added to the base sequence shown in SEQ ID NO:118, preferably 1 to 20 bases, more preferably 1 to 10 bases, even more preferably 1 to 5 bases, and even more preferably 1 to 3 bases are added to the base sequence or to the 5' or 3' end. LTRs with mutations that combine the addition, substitution, and deletion of these bases are also included in the functional equivalent of the second LTR. The base sequence of the mutated LTR preferably shows 80% or more identity with the base sequence shown in SEQ ID NO:118, more preferably shows 85% or more identity, even more preferably shows 90% or more identity, even more preferably shows 95% or more identity, and even more preferably shows 98% or more identity.

In one embodiment of the present invention, the terms leader and trailer refer to partially complementary base sequences present at the ends of the viral genome. Those derived from Sendai virus can be preferably used as leaders and trailers. Both the leader and trailer of Sendai virus are regions with a chain length of approximately 50 bases. Usually, the leader is located on the 5' side and the trailer is located on the 3' side.

Examples that are preferably used in one embodiment of the present invention include a leader derived from Sendai virus having the base sequence shown in SEQ ID NO: 119 and a trailer derived from Sendai virus having the base sequence shown in SEQ ID NO: 120.

Mutations in the leader and trailer derived from wild-type Sendai virus can also be suitably used in the present invention. When bases in the base sequence are replaced with other bases, the number of bases to be replaced is preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 3. When base sequences of the wild-type leader and/or trailer are deleted, the number of bases to be deleted is preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 3. Mutations combining these base substitutions and deletions can also be added. When bases are added, preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 3 bases are added in the base sequence of the leader and/or trailer or to the 5' end or 3' end. Mutations combining these base additions, substitutions, and deletions can also be added. The mutated base sequence preferably exhibits 80% or more identity to the wild-type base sequence, more preferably 85% or more identity, even more preferably 90% or more identity, even more preferably 95% or more identity, and even more preferably 98% or more identity.

In one embodiment of the present invention, the base sequence that can be used as the base sequence containing the gene expression control site that controls the expression of the gene of the fusion protein is not particularly limited as long as it can express the fusion protein in the cells, tissues, or living body of a mammal (especially a human) into which the gene encoding the fusion protein is introduced. However, preferred are those containing a cytomegalovirus-derived promoter (optionally containing an enhancer), SV40 early promoter, human elongation factor-1α (EF-1α) promoter, human ubiquitin C promoter, retroviral Rous sarcoma virus LTR promoter, dihydrofolate reductase promoter, and β-actin promoter, phosphoglycerate kinase (PGK) promoter, mouse albumin promoter, human albumin promoter, and human α-1 antitrypsin promoter. For example, a synthetic promoter having the base sequence shown in SEQ ID NO: 121 containing a mouse albumin promoter downstream of a mouse α-fetoprotein enhancer (mouse α-fetoprotein enhancer/mouse albumin promoter) can be preferably used as the gene expression control site. A chicken β-actin/MVM chimeric intron having the base sequence shown in SEQ ID NO: 122 may be placed downstream of the mouse α-fetoprotein enhancer/mouse albumin promoter. By placing such an intron, the expression level of the protein controlled by the gene expression control site can be increased. In the base sequence shown in SEQ ID NO: 121, the base sequence from 1 to 219 is the mouse α-fetoprotein enhancer, and the base sequence from 241 to 549 is the mouse albumin promoter.

The gene regulatory site may be a promoter of a gene that is expressed in an organ-specific or cell type-specific manner. By using an organ-specific expression promoter or a cell type-specific expression promoter, the gene encoding the fusion protein incorporated into the nucleic acid molecule can be expressed specifically in a desired organ or cell.

In one embodiment of the present invention, the nucleic acid molecule contains a gene encoding a conjugate of a fusion protein and an antibody between a first inverted terminal repeat (ITR) and a second inverted terminal repeat (ITR). Here, the fusion protein is, for example, a fusion protein of HSA and hGALC, a fusion protein of HSA and hGBA, a fusion protein of HSA and hIL-10, a fusion protein of HSA and hBDNF, a fusion protein of HSA and hNGF, a fusion protein of HSA and hNT-3, or a fusion protein of HSA and hNT-4, and the antibody is, for example, an anti-transferrin receptor antibody. The following (1) to (4) are examples of the nucleic acid molecule:
(1) A gene encoding a conjugate between a fusion protein and an antibody between a first inverted terminal repeat (ITR) and a second inverted terminal repeat (ITR), the gene including a base sequence encoding an internal ribosome binding site downstream of a gene encoding an antibody light chain, and a base sequence encoding a conjugate in which a fusion protein is bound directly or via a linker to the C-terminus or N-terminus of an antibody heavy chain downstream of the internal ribosome binding site;
(2) A gene encoding a conjugate between a first inverted terminal repeat (ITR) and a second inverted terminal repeat (ITR), the gene including a base sequence encoding an internal ribosome binding site downstream of the gene encoding a conjugate in which the fusion protein is bound directly or via a linker to the C-terminus or N-terminus of the antibody heavy chain, and a base sequence encoding an antibody light chain downstream of the base sequence encoding an internal ribosome binding site;
(3) A gene encoding a conjugate between a fusion protein and an antibody between the first inverted terminal repeat (ITR) and the second inverted terminal repeat (ITR), which contains a base sequence encoding an internal ribosome binding site downstream of a gene encoding the heavy chain of an antibody, and a base sequence encoding a conjugate in which a fusion protein is bound directly or via a linker to the C-terminal or N-terminal side of the light chain of the antibody, downstream of that base sequence; and (4) A gene encoding a conjugate between a fusion protein and an antibody between the first inverted terminal repeat (ITR) and the second inverted terminal repeat (ITR), which contains a gene encoding a conjugate between a fusion protein and an antibody between the first inverted terminal repeat (ITR) and the second inverted terminal repeat (ITR), which contains a base sequence encoding an internal ribosome binding site downstream of a gene encoding a conjugate in which a fusion protein is bound directly or via a linker to the C-terminal or N-terminal side of the light chain of the antibody, and a base sequence encoding the heavy chain of the antibody, downstream of that base sequence.

In the above (1) to (4), the nucleic acid molecule may further include a base sequence including a gene expression control site between the first inverted terminal repeat (ITR) and the gene encoding the conjugate of the fusion protein and the antibody. In the above (1) to (4), the base sequence encoding the internal ribosome binding site may be replaced with a base sequence including a gene expression control site. In addition, when the nucleic acid molecule has two gene expression control sites, for convenience, the first gene expression control site and the second gene expression control site are referred to in order from the first inverted terminal repeat (ITR). In the above (1) to (4), the base sequence encoding the internal ribosome binding site may be replaced with a base sequence encoding a 2A self-cleaving peptide. The 2A peptide derived from the porcine teschovirus is a suitable example of a 2A self-cleaving peptide.

In one embodiment of the present invention, the nucleic acid molecule contains a gene encoding a conjugate of a fusion protein and an antibody between a first long terminal repeat (LTR) and a second long terminal repeat (LTR). Here, the fusion protein is, for example, a fusion protein of HSA and hGALC, a fusion protein of HSA and hGBA, a fusion protein of HSA and hIL-10, a fusion protein of HSA and hBDNF, a fusion protein of HSA and hNGF, a fusion protein of HSA and hNT-3, or a fusion protein of HSA and hNT-4, and the antibody is, for example, an anti-transferrin receptor antibody. The following (1) to (4) are examples of the nucleic acid molecule:
(1) A gene encoding a conjugate of a fusion protein and an antibody is contained between a first long terminal repeat (LTR) and a second long terminal repeat (LTR), and the gene contains a base sequence encoding an internal ribosome binding site downstream of a gene encoding the light chain of the antibody, and a base sequence encoding a conjugate in which the fusion protein is bound directly or via a linker to the C-terminus or N-terminus of the heavy chain of the antibody downstream of the internal ribosome binding site;
(2) A gene encoding a conjugate of a fusion protein and an antibody between the first long terminal repeat (LTR) and the second long terminal repeat (LTR), the gene including a base sequence encoding an internal ribosome binding site downstream of the gene encoding a conjugate in which the fusion protein is bound directly or via a linker to the C-terminus or N-terminus of the antibody heavy chain, and a base sequence encoding an antibody light chain downstream of the base sequence encoding an internal ribosome binding site;
(3) A gene encoding a conjugate between a first long terminal repeat (LTR) and a second long terminal repeat (LTR), the gene including a base sequence encoding an internal ribosome binding site downstream of a gene encoding the heavy chain of an antibody, and a base sequence encoding a conjugate in which the fusion protein is bound directly or via a linker to the C-terminus or N-terminus of the light chain of the antibody downstream of the internal ribosome binding site;
(4) A gene encoding a conjugate between a first long terminal repeat (LTR) and a second long terminal repeat (LTR), the gene including a base sequence encoding an internal ribosome binding site downstream of the gene encoding a conjugate in which the fusion protein is bound directly or via a linker to the C-terminus or N-terminus of the antibody light chain, and a base sequence encoding an antibody heavy chain downstream of that.
In the above (1) to (4), the nucleic acid molecule may further include a base sequence including a gene expression control site between the first long terminal repeat (LTR) and the gene encoding the conjugate of the fusion protein and the antibody. In the above (1) to (4), the base sequence encoding the internal ribosome binding site may be replaced with a base sequence including a gene expression control site. In addition, when the nucleic acid molecule has two gene expression control sites, for convenience, the first gene expression control site and the second gene expression control site are referred to in order from the first inverted terminal repeat (ITR). In the above (1) to (4), the base sequence encoding the internal ribosome binding site may be replaced with a base sequence encoding a 2A self-cleaving peptide. The 2A peptide derived from the porcine teschovirus is a suitable example of the 2A self-cleaving peptide.

In the case of a nucleic acid molecule containing a base sequence encoding the above-mentioned internal ribosome binding site, the expression of one peptide chain constituting the fusion protein is controlled by the gene expression control site, while the expression of the other peptide chain is controlled by the base sequence encoding the internal ribosome binding site. The two peptide chains pair up within the cell to form a conjugate between the fusion protein and the antibody.

The nucleic acid molecule in one embodiment of the present invention can be used in an AAV vector system. When wild-type AAV infects a human host cell alone, the viral genome is site-specifically integrated into chromosome 19 via the inverted terminal repeats (ITRs) present at both ends of the viral genome. The genes of the viral genome integrated into the genome of the host cell are hardly expressed, but when the cell is infected with a helper virus, AAV is excised from the host genome and replication of the infectious virus begins. When the helper virus is an adenovirus, the genes responsible for the helper function are E1A, E1B, E2A, VA1, and E4. Here, when the host cell is a HEK293 cell, which is a human fetal kidney tissue-derived cell transformed with adenovirus E1A and E1B, the E1A and E1B genes are originally expressed in the host cell.

The wild-type AAV genome contains two genes, rep and cap. The rep proteins (rep78, rep68, rep52, and rep40) produced by the rep gene are essential for capsid formation and mediate the integration of the viral genome into the chromosome. The cap gene is responsible for the production of three capsid proteins (VP1, VP2, and VP3).

　In the wild-type AAV genome, there are ITRs at both ends, with the rep gene and the cap gene between the ITRs. This genome is packaged in a capsid to form an AAV virion. A recombinant AAV virion (rAAV virion) is a virion in which the region containing the rep gene and the cap gene has been replaced with a gene that codes for a foreign protein, and then packaged in a capsid.

rAAV virions are used as vectors to deliver foreign genes to cells for therapeutic purposes.

To produce recombinant AAV virions used to introduce foreign genes into cells, tissues, or living organisms, three types of plasmids are usually used: (1) a plasmid (plasmid 1) having a structure containing a base sequence including a first inverted terminal repeat (ITR) and a base sequence including a second inverted terminal repeat (ITR) derived from a virus such as AAV, and a gene encoding a desired protein arranged between these two ITRs; (2) a plasmid (plasmid 2) containing an AAV Rep gene having the function required to integrate the base sequence of the region (including the ITR sequence) sandwiched between the ITR sequences into the genome of a host cell, and a gene encoding an AAV capsid protein; and (3) a plasmid (plasmid 3) containing the E2A region, E4 region, and VA1 RNA region of adenovirus. However, this is not limited to this, and two types of plasmids, one formed by linking two of plasmids 1 to 3 and the remaining one, can also be used. Furthermore, one formed by linking plasmids 1 to 3 can also be used. In one embodiment of the present invention, the desired protein is a conjugate of a fusion protein and an antibody. Here, the fusion protein is, for example, a fusion protein of HSA and hGALC, a fusion protein of HSA and hGBA, a fusion protein of HSA and hIL-10, a fusion protein of HSA and hBDNF, a fusion protein of HSA and hNGF, a fusion protein of HSA and hNT-3, or a fusion protein of HSA and hNT-4, and the antibody is, for example, an anti-transferrin receptor antibody.

In general, to produce recombinant AAV virions, these three types of plasmids are first introduced into host cells, such as HEK293 cells, in which the adenovirus E1a and E1b genes have been incorporated into the genome, by a general transfection method. Then, a region containing a base sequence containing a first inverted terminal repeat (ITR), a base sequence containing a second inverted terminal repeat (ITR), and a gene encoding a desired protein arranged between these two ITRs is replicated in the host cell, and the resulting single-stranded DNA is packaged into the capsid protein of AAV to form a recombinant AAV virion. This recombinant AAV virion has infectivity and can be used to introduce a foreign gene into a cell, tissue, or living body. In one embodiment of the present invention, the foreign gene is a gene encoding a conjugate of a fusion protein and an antibody. In the cell or the like to which it is introduced, the conjugate is expressed from this gene. Here, the fusion protein is, for example, a fusion protein of HSA and hGALC, a fusion protein of HSA and hGBA, a fusion protein of HSA and hIL-10, a fusion protein of HSA and hBDNF, a fusion protein of HSA and hNGF, a fusion protein of HSA and hNT-3, or a fusion protein of HSA and hNT-4, and the antibody is, for example, an anti-transferrin receptor antibody.

The Rep protein of adeno-associated virus (AAV) is encoded by the AAV rep gene. The Rep protein has the necessary function of integrating, for example, the AAV genome into the genome of a host cell via the ITRs present in the genome. There are multiple subtypes of Rep proteins, but two types, Rep68 and Rep78, are required for the integration of the AAV genome into the genome of a host cell. Rep68 and Rep78 are the translation products of two types of mRNA transcribed by alternative splicing from the same gene. When we say AAV Rep protein, we mean one that includes at least the two types of proteins, Rep68 and Rep78.

In one embodiment of the present invention, the base sequence encoding the Rep protein of an adeno-associated virus (the base sequence of the Rep region) refers to a base sequence encoding at least Rep68 and Rep78, or a base sequence with a mutation added thereto. The Rep protein is preferably that of an AAV of serotype 2, but is not limited thereto, and may be any of

serotypes

1, 3, 4, 5, 6, 7, 8, 9, 10, or 11. A preferred example of a base sequence encoding the Rep protein of a wild-type AAV of serotype 2 is one having the base sequence shown in SEQ ID NO: 123.

　In addition, Rep68 may be a mutant in which the amino acid sequence of wild-type Rep68 of any of

AAV serotypes

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11 has been modified by substitution, deletion, addition, or other means, so long as it exerts its function. Rep68 with these mutations is also included in Rep68.

When amino acids in the amino acid sequence of wild-type Rep68 are replaced with other amino acids, the number of amino acids to be replaced is preferably 1 to 10, more preferably 1 to 5, and even more preferably 1 to 3. When amino acids in the amino acid sequence of wild-type Rep68 are deleted, the number of amino acids to be deleted is preferably 1 to 10, more preferably 1 to 5, and even more preferably 1 to 3. Rep68 with mutations that combine these amino acid substitutions and deletions is also Rep68. When amino acids are added, preferably 1 to 10, more preferably 1 to 5, and even more preferably 1 to 3 amino acids are added to the amino acid sequence or to the N-terminus or C-terminus of wild-type Rep68. Rep68 with mutations that combine these amino acid additions, substitutions, and deletions is also included in Rep68. The amino acid sequence of the mutated Rep68 preferably exhibits 80% or more identity to the amino acid sequence of wild-type Rep68, more preferably 85% or more identity, even more preferably 90% or more identity, even more preferably 95% or more identity, and even more preferably 98% or more identity.

　In addition, Rep78 may be a mutant in which the amino acid sequence of wild-type Rep78 of any of

AAV serotypes

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11 has been modified by substitution, deletion, addition, or other means, so long as it exerts its function. Rep78 with these mutations is also included in Rep78.

When amino acids in the amino acid sequence of wild-type Rep78 are replaced with other amino acids, the number of amino acids to be replaced is preferably 1 to 10, more preferably 1 to 5, and even more preferably 1 to 3. When amino acids in the amino acid sequence of wild-type Rep78 are deleted, the number of amino acids to be deleted is preferably 1 to 10, more preferably 1 to 5, and even more preferably 1 to 3. Rep78 with mutations that combine these amino acid substitutions and deletions is also Rep78. When amino acids are added, preferably 1 to 10, more preferably 1 to 5, and even more preferably 1 to 3 amino acids are added to the amino acid sequence or to the N-terminus or C-terminus of wild-type Rep78. Rep78 with mutations that combine these amino acid additions, substitutions, and deletions is also included in Rep78. The amino acid sequence of the mutated Rep78 preferably exhibits 80% or more identity to the amino acid sequence of wild-type Rep78, more preferably 85% or more identity, even more preferably 90% or more identity, even more preferably 95% or more identity, and even more preferably 98% or more identity.

The functional equivalent of the AAV Rep protein refers to a substance that can be used functionally in place of Rep68, and to a substance that can be used functionally in place of Rep78. The functional equivalent of the Rep protein may be a mutant of the wild-type Rep protein.

The base sequence shown in SEQ ID NO:123 can be modified by substitution, deletion, addition, etc., so long as it encodes functional Rep68 and Rep78. When a base in the base sequence shown in SEQ ID NO:123 is replaced with another base, the number of bases to be replaced is preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 3. When a base in the base sequence shown in SEQ ID NO:123 is deleted, the number of bases to be deleted is preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 3. Furthermore, a mutation that combines the substitution and deletion of these bases can also be used as a base sequence encoding a Rep protein. When a base is added, preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 3 bases are added to the base sequence shown in SEQ ID NO:123 or to the 5' end or 3' end. A mutation that combines the addition, substitution, and deletion of these bases can also be used as a nucleic acid molecule encoding a Rep protein. The mutated base sequence preferably exhibits 80% or more identity, more preferably 85% or more identity, even more preferably 90% or more identity, even more preferably 95% or more identity, and even more preferably 98% or more identity to the base sequence shown in SEQ ID NO: 123. However, when these mutations are added, it is preferable that the start codon of the genes encoding the Rep proteins Rep68 and Rep78 is ACG.

In one embodiment of the present invention, the base sequence encoding the Cap protein of an adeno-associated virus (base sequence of the Cap region) refers to a base sequence that encodes at least VP1, a protein that constitutes the capsid of AAV, or a base sequence that includes a mutated base sequence thereof. VP1 is preferably that of AAV serotype 8, but is not limited thereto, and may be any of

serotypes

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11. A suitable example of a base sequence of the Cap region of serotype 8 is one that includes the base sequence shown in SEQ ID NO: 124.

In addition, VP1 may be modified by substitution, deletion, addition, or other alteration to the amino acid sequence of wild-type VP1 of any of

AAV serotypes

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, so long as it exerts its function. In one embodiment of the present invention, VP1 with these mutations is also included in VP1.

When bases in the base sequence shown in SEQ ID NO: 124 are replaced with other bases, the number of bases to be replaced is preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 3. When bases in the base sequence shown in SEQ ID NO: 124 are deleted, the number of bases to be deleted is preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 3. Furthermore, a mutation that combines the substitution and deletion of these bases can also be used as a base sequence encoding a Cap protein. When bases are added, preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 3 bases are added to the base sequence shown in SEQ ID NO: 124 or to the 5' end or 3' end. A mutation that combines the addition, substitution, and deletion of these bases can also be used as a nucleic acid molecule encoding a Cap protein. The mutated base sequence preferably exhibits 80% or more identity to the base sequence shown in SEQ ID NO:124, more preferably 85% or more identity, even more preferably 90% or more identity, even more preferably 95% or more identity, and even more preferably 98% or more identity.

The AAV vector can produce a recombinant AAV virion in which a nucleic acid molecule containing a foreign gene is packaged between the first and second ITRs. The recombinant AAV virion has infectivity and can be used to introduce a foreign gene into cells, tissues, or living organisms. In one embodiment of the present invention, the foreign gene is a gene encoding a conjugate of a fusion protein and an antibody. Here, the fusion protein is, for example, a fusion protein of HSA and hGALC, a fusion protein of HSA and hGBA, a fusion protein of HSA and hIL-10, a fusion protein of HSA and hBDNF, a fusion protein of HSA and hNGF, a fusion protein of HSA and hNT-3, or a fusion protein of HSA and hNT-4, and the antibody is, for example, an anti-transferrin receptor antibody. In cells, etc., into which the gene has been introduced, the fusion protein is expressed from this gene. In addition to the AAV vector system, there is an adenovirus vector system, which is a recombinant virion in which a nucleic acid molecule containing a foreign gene is packaged between the first and second ITRs and can be used to introduce a gene into cells, etc. In the adenovirus vector system, a recombinant adenovirus virion is obtained in which a nucleic acid molecule containing a foreign gene is packaged between the first and second ITRs. The recombinant adenovirus virion has infectivity and can be used to introduce a foreign gene into a cell, tissue, or living organism.

Lentiviruses are viruses that belong to the Lentivirus genus in the Orthoretrovirinae subfamily of the Retroviridae family, and have a single-stranded (+) strand RNA genome (ssRNA). The genome of lentiviruses contains essential genes, gag (a region that codes for structural proteins including capsid proteins), pol (a region that codes for a group of enzymes including reverse transcriptase), and env (a region that codes for envelope proteins required for binding to host cells), which are sandwiched between two LTRs (5'LTR and 3'LTR). In addition to these, the genome of lentiviruses contains auxiliary genes, such as Rev (a region that codes for a protein that binds to the RRE (rev responsive element) present in the viral RNA and transports the viral RNA from the nucleus to the cytoplasm), tat (a region that codes for a protein that binds to the TAR in the 5'LTR and increases the promoter activity of the LTR), and others, such as vif, vpr, vpu, and nef.

　Lentiviruses are enveloped viruses that infect cells by fusing the envelope with the cell membrane. Lentiviruses are also RNA viruses, and reverse transcriptase is present in virions. After lentivirus infection, single-stranded plus-strand DNA is replicated from the (+) strand RNA genome by reverse transcriptase, and double-stranded DNA is then synthesized. Proteins that are components of virions are expressed from this double-stranded DNA, and the (+) strand RNA genome is packaged into this to cause virions to proliferate. In one embodiment of the present invention, the lentivirus vector has been developed based on the genome of HIV-1, a type of lentivirus, but is not limited to this.

A first-generation lentiviral vector consists of three types of plasmids: a packaging plasmid, an Env plasmid, and a transfer plasmid. The packaging plasmid has the gag and pol genes under the control of a CMV promoter, etc. The Env plasmid has the env gene under the control of a CMV promoter. The transfer plasmid has a 5'LTR, an RRE, a gene encoding a desired protein under the control of a CMV promoter, and a 3'LTR. By introducing these into a host cell by a general transfection method, a recombinant virion is obtained in which a nucleic acid molecule containing a foreign gene between the first LTR and the second LTR is packaged in the capsid protein. The packaging plasmid of the first-generation lentiviral vector also contains the auxiliary genes rev, tat, vif, vpr, vpu, and nef derived from the virus. Here, the desired protein in one embodiment of the present invention is a conjugate of a fusion protein and an antibody. Here, the fusion protein is, for example, a fusion protein of HSA and hGALC, a fusion protein of HSA and hGBA, a fusion protein of HSA and hIL-10, a fusion protein of HSA and hBDNF, a fusion protein of HSA and hNGF, a fusion protein of HSA and hNT-3, or a fusion protein of HSA and hNT-4, and the antibody is, for example, an anti-transferrin receptor antibody. Note that the promoter controlling the gene encoding the desired protein is preferably a promoter other than the CMV promoter, such as an SV40 early promoter, a human elongation factor-1α (EF-1α) promoter, a human ubiquitin C promoter, a Rous sarcoma virus LTR promoter of a retrovirus, a dihydrofolate reductase promoter, a β-actin promoter, a phosphoglycerate kinase (PGK) promoter, a mouse albumin promoter, a human albumin promoter, and a human α-1 antitrypsin promoter. For example, it can be a synthetic promoter having the base sequence shown in SEQ ID NO: 121, which includes a mouse albumin promoter downstream of a mouse alpha-fetoprotein enhancer (mouse alpha-fetoprotein enhancer/mouse albumin promoter), etc.

Second-generation lentiviral vectors, like the first-generation, consist of three plasmids: a packaging plasmid, an Env plasmid (envelope plasmid), and a transfer plasmid. However, the non-essential auxiliary genes vif, vpr, vpu, and nef have been deleted from the packaging plasmid.

Third-generation lentiviral vectors consist of four types of plasmids: packaging plasmid, Env plasmid (envelope plasmid), Rev plasmid, and transfer plasmid. In the third generation, the rev that was in the packaging plasmid in the second generation has been separated to form the Rev plasmid. In addition, tat has been deleted from the packaging plasmid. Furthermore, the TAR in the 5'LTR of the transfer plasmid has been replaced with a CMV promoter.

Since recombinant virions have infectivity, they can be used to introduce foreign genes into cells, tissues, or living organisms. In one embodiment of the present invention, the foreign gene is a gene encoding a conjugate of a fusion protein and an antibody. In cells, etc., into which the gene is introduced, the conjugate is expressed from this gene. Here, the fusion protein is, for example, a fusion protein of HSA and hGALC, a fusion protein of HSA and hGBA, a fusion protein of HSA and hIL-10, a fusion protein of HSA and hBDNF, a fusion protein of HSA and hNGF, a fusion protein of HSA and hNT-3, or a fusion protein of HSA and hNT-4, and the antibody is, for example, an anti-transferrin receptor antibody.

Retroviruses have a single-stranded (+) strand RNA genome (ssRNA). The viral genome encodes the gag (encoding structural proteins including capsid protein), pol (encoding a group of enzymes including reverse transcriptase), env (encoding envelope proteins required for binding to host cells) and packaging signal (Ψ) genes, which are flanked by two long terminal repeats (LTR, 5'LTR and 3'LTR). When a retrovirus infects a host cell, the (+) strand RNA and reverse transcriptase are transferred into the cell and reverse transcribed into double-stranded DNA.

Retroviral vectors are mainly developed based on mouse leukemia viruses, and the viral genome is divided to lose the ability to self-replicate while maintaining its infectivity in order to eliminate pathogenicity and increase safety. The first generation retroviral vector consists of a packaging plasmid (the viral genome excluding the packaging signal) and an introduction plasmid (the packaging signal, a part of gag, and a foreign gene flanked by 5'LTR and 3'LTR at both ends). Therefore, when homologous recombination occurs in the gag sequence portion that is common to the packaging plasmid and the introduction plasmid, a self-replicating retrovirus, i.e., an RC (replication competent) virus, appears. In the second generation retroviral vector, the 3' LTR of the first generation packaging plasmid is replaced with a polyA addition signal. As a result, for an RC virus to be generated, homologous recombination must occur simultaneously at two locations, the gag sequence and the upstream of the polyA addition signal, and the probability of this occurring is extremely low, increasing safety. The third generation is composed of three plasmids, and the second generation packaging plasmid is further divided into a plasmid encoding gag/pol and a plasmid encoding env. This means that for an RC virus to emerge, homologous recombination must occur simultaneously at three sites, making the probability of this occurring extremely low, further increasing safety.

In general, to produce recombinant retroviral virions, these packaging plasmids and transfer plasmids are first transferred into host cells by a general transfection method. Then, the region containing the 5'LTR and 3'LTR and the gene encoding the desired protein located between these two LTRs is replicated in the host cell, and the resulting single-stranded (+) strand RNA is packaged in the retroviral capsid protein to form a recombinant retroviral virion. This recombinant retroviral virion has infectivity and can be used to transfer a foreign gene into a cell, tissue, or living body. In one embodiment of the present invention, the foreign gene is a gene encoding a conjugate of a fusion protein and an antibody. In cells, etc., into which the gene has been introduced, the conjugate is expressed from this gene. Here, the fusion protein is, for example, a fusion protein of HSA and hGALC, a fusion protein of HSA and hGBA, a fusion protein of HSA and hIL-10, a fusion protein of HSA and hBDNF, a fusion protein of HSA and hNGF, a fusion protein of HSA and hNT-3, or a fusion protein of HSA and hNT-4, and the antibody is, for example, an anti-transferrin receptor antibody.

In one embodiment of the present invention, the nucleic acid molecule may be encapsulated in a liposome, lipid nanoparticle (LNP), or the like. A liposome is a spherical vesicle with a lipid bilayer, and is composed mainly of phospholipids, particularly phosphatidylcholine. However, the present invention is not limited to this, and liposomes may contain other lipids, such as egg yolk phosphatidylethanolamine, as long as they form a lipid bilayer. Since cell membranes are mainly composed of phospholipid bilayers, liposomes have the advantage of being highly biocompatible. A lipid nanoparticle is a particle with a diameter of 10 nm to 1000 nm, typically less than about 200 nm, that is mainly composed of lipids, and can encapsulate hydrophobic (lipophilic) molecules and is mainly composed of biocompatible lipids, such as triglycerides, diglycerides, monoglycerides, fatty acids, and steroids. It is believed that when a gene encapsulated in liposomes or lipid nanoparticles is administered to a living body, it fuses directly with the cell membrane of the cell or is taken up by endocytosis, etc., and then migrates to the nucleus and is introduced into the cell. The gene introduction method using liposomes or lipid nanoparticles is superior to gene introduction using a viral vector in that there is no limit to the size of the gene to be introduced and that it is highly safe. The liposomes, lipid nanoparticles, etc. encapsulating the nucleic acid molecule of the present invention can be used to introduce a gene of a conjugate of a fusion protein and an antibody into a cell, tissue, or living body. In the cell, etc. into which the gene is introduced, the fusion protein is expressed from the gene. In this specification, the term "liposomes, lipid nanoparticles, etc." includes not only the above-mentioned liposomes and lipid nanoparticles, but also polymer nanoparticles, micelles, emulsions, nanoemulsions, microspheres, nanospheres, microcapsules, nanocapsules, dendrimers, nanogels, metal nanoparticles, and any other nano-microparticles that can be used as a drug delivery system (DDS).

In one embodiment of the present invention, the behavior of a nucleic acid molecule introduced into a cell, tissue, or living body in the form of a plasmid, encapsulated in a recombinant virus virion, or encapsulated in a liposome, lipid nanoparticle, or the like is exemplified below as (1) to (6). However, the behavior of the nucleic acid molecule is not limited to these.
(1) In one embodiment, the nucleic acid molecule is a single-stranded (+) strand RNA, and when introduced into a cell, a gene encoding a conjugate between a fusion protein and an antibody contained in the nucleic acid molecule is translated, thereby expressing the conjugate.
(2) In one embodiment, the nucleic acid molecule is a single-stranded (+) strand RNA, which, when introduced into a cell, is reverse transcribed to form a single-stranded (+) strand DNA, which is then transcribed and translated to express the conjugate.
(3) In one embodiment, the nucleic acid molecule is a single-stranded (+) strand RNA or (-) strand RNA, and when introduced into a cell, the nucleic acid molecule is reverse transcribed to form double-stranded DNA, which is then transcribed and translated to express the conjugate.
(4) In one embodiment, the nucleic acid molecule is a single-stranded (+) or (-) RNA, and when introduced into a cell, the nucleic acid molecule is reverse transcribed to form double-stranded DNA, which then undergoes random or homologous recombination with the genome of the host cell and is integrated into the genome, and the integrated DNA is transcribed and translated to express the conjugate.
(5) In one embodiment, the nucleic acid molecule is a single-stranded (+) strand DNA, and when introduced into a cell, the nucleic acid molecule is transcribed and translated to express the conjugate.
(6) In one embodiment, the nucleic acid molecule is double-stranded DNA, and when introduced into a cell, the nucleic acid molecule is transcribed and translated to express the conjugate.

Nucleic acid molecules in the form of plasmids, encapsulated in recombinant viral virions, or encapsulated in liposomes, lipid nanoparticles, etc. can be introduced into cells, tissues, or organisms.

When the nucleic acid molecule is to be introduced into a living body, the nucleic acid molecule is administered parenterally, such as subcutaneous injection, intramuscular injection, or intravenous injection, in the form of a plasmid, encapsulated in a recombinant virus virion, or encapsulated in a liposome or lipid nanoparticle.

When the nucleic acid molecule is introduced into a cell, there is no particular limitation on the type of cell, but examples include mesenchymal stem cells, dental pulp-derived stem cells, hematopoietic stem cells, embryonic stem cells, endothelial stem cells, mammary stem cells, intestinal stem cells, hepatic stem cells, pancreatic stem cells, neural stem cells, and iPS cells.

Cells that have been transfected with the nucleic acid molecule will express the fusion protein-antibody conjugate, which can then be transplanted into a patient for therapeutic purposes.

The present invention will be explained in more detail below with reference to examples, but it is not intended that the present invention be limited to these examples.

The following Examples 1 to 13 show the experimental results of a fusion protein of HSA and hGALC.

Example 1: Preparation of wild-type hGALC expression plasmid, HSA-hGALC expression plasmid, and hGALC-HSA expression plasmid A DNA fragment having the base sequence shown in SEQ ID NO: 2, including a gene encoding wild-type hGALC having the amino acid sequence shown in SEQ ID NO: 1, was synthesized. This was treated with restriction enzymes MluI and NotI (Takara Bio Inc.) and separated by agarose gel electrophoresis. After EtBr staining, a band containing the target DNA fragment was excised under UV irradiation, and DNA was extracted from the gel using a QIAEX II Gel Extraction Kit (QIAGEN). Similarly, pCI-neo vector (Promega Corp.) was treated with restriction enzymes MluI and NotI, and gel extraction and purification were performed. Each DNA fragment treated with a restriction enzyme was mixed with each vector treated with a restriction enzyme, and a ligation reaction was performed at 16°C for 30 to 60 minutes using Ligation high Ver.2 (Toyobo Co., Ltd.), and the DNA fragment was inserted into the pCI vector. A DNA fragment containing the base sequence shown in SEQ ID NO: 6 and including a gene encoding HSA-hGALC shown in SEQ ID NO: 5, which is a fusion protein in which the C-terminus of wild-type HSA (SEQ ID NO: 3) and the N-terminus of wild-type hGALC (SEQ ID NO: 1) are linked via the linker sequence Gly-Ser, and a DNA fragment containing the base sequence shown in SEQ ID NO: 8 and including a gene encoding hGALC-HSA shown in SEQ ID NO: 7, which is a fusion protein in which the C-terminus of wild-type hGALC (SEQ ID NO: 1) and the N-terminus of wild-type HSA (SEQ ID NO: 3) are linked via the linker sequence Gly-Ser, were similarly treated with restriction enzymes, extracted, purified, and then ligated, and each DNA fragment was inserted into the pCI vector.

Escherichia coli (E. coli DH5α Competent Cells, Takara Bio) was then transformed using each ligation reaction mixture. To confirm whether the obtained transformants retained the desired plasmid DNA, single colonies were cultured overnight in LB liquid medium (LB Broth, Sigma-Aldrich), and plasmid DNA was purified from the cells using FastGene Plasmid Mini Kit (Nihon Genetics). The purified plasmid DNA was subjected to restriction enzyme treatment with MluI and NotI, and separated by agarose gel electrophoresis to confirm that the desired insert DNA had been inserted. Plasmids that were confirmed to contain wild-type hGALC, HSA-hGALC, and hGALC-HSA were purified using standard methods.

[Example 2] Transient expression of wild-type hGALC, HSA-hGALC, and hGALC-HSA For transient expression of wild-type hGALC, HSA-hGALC, and hGALC-HSA, plasmids were used in which the genes encoding wild-type hGALC, HSA-hGALC, and hGALC-HSA, respectively, were incorporated into the purified pCI-neo vector obtained in Example 1.

According to the High titer protocol of the ExpiCHO ^TM Expression System (Thermo Fisher Scientific), ExpiCHO cells were transformed with plasmids incorporating genes encoding wild-type hGALC, HSA-hGALC, and hGALC-HSA, respectively. After transformation, the cells were cultured for 8 days, and wild-type hGALC, HSA-hGALC, and hGALC-HSA were expressed in the culture supernatant, respectively. The culture solutions 6, 7, and 8 days after the start of culture were centrifuged to collect the culture supernatant.

[Example 3] Confirmation of the expression levels of wild-type hGALC, HSA-hGALC, and hGALC-HSA by transient expression (SDS page electrophoresis)
10 μL of each culture supernatant obtained in Example 2 was mixed with 8 μL of 2×Sample Buffer (Bio-Rad) and 2 μL of 2-Mercaptoethanol, and heated at 100° C. for 3 minutes to be heat-denatured under reducing conditions. 5 μL of the heat-denatured solution was added to each well of a 5-20% polyacrylamide gel placed in 50 mM Tris buffer/380 mM glycine buffer (pH 8.3) containing 0.1% SDS, and electrophoresis was performed at a constant current of 25 mA. The gel after electrophoresis was immersed in Oriole Fluorescent Gel Stain (Bio-Rad) and shaken at room temperature for 90 minutes. After washing the gel with pure water, an electrophoretic image was obtained in which the bands corresponding to each protein were visualized using a lumino image analyzer (Amersham Imager 600RGB, Cytiva).

[Example 4] Confirmation of expression levels of wild-type hGALC, HSA-hGALC, and hGALC-HSA by transient expression (Western blotting)
Electrophoresis was performed in the same manner as described in Example 3, and the nitrocellulose membrane and the gel after electrophoresis were sandwiched between blotting papers soaked in 25 mM Tris buffer/192 mM glycine buffer containing 20% methanol, and the proteins were transferred to the nitrocellulose membrane by applying electricity at 1.0 A and 25 V for 10 minutes in a blotting device. The nitrocellulose membrane after transfer was immersed in PBST containing 5% skim milk and shaken for 1 hour, and then immersed in Anti-GALC antibody (Rabbit polyclonal to GALC, Abcam) diluted to 0.4 μg/mL and shaken for 1 hour. After washing the membrane with PBST, it was immersed in Anti-mouse IgG (H+L), HRP Conjugate (Promega) solution diluted to 0.4 μg/mL and shaken for 30 minutes, and washed again with PBST. An HRP detection reagent (Bio-Rad) was dropped onto the transfer surface of the membrane and reacted for 5 minutes, and a Western blotting image was obtained using a luminometer image analyzer (Amersham Imager 600RGB, Cytiva) in which bands corresponding to each protein were visualized.

[Example 5] Confirmation of expression levels of wild-type hGALC, HSA-hGALC, and hGALC-HSA by transient expression (enzyme activity measurement)
The culture supernatant obtained in Example 2 was diluted 100-fold with citrate buffer (pH 4.5) containing 0.5% Triton X-100 to prepare a sample solution. The sample solution was further diluted appropriately as necessary and used for measurement. A standard solution was prepared by serially diluting 4-MU (4-Methylumbelliferone, Sigma-Aldrich) from 75 to 4.39 μM with 100 mM citrate buffer (pH 4.2) containing 0.1% BSA. A substrate solution was prepared by diluting 4-Methylumbelliferyl-β-D-galactopyranoside (Sigma-Aldrich), an artificial substrate for hGALC, to 1 mmol/L with citrate buffer (pH 4.5) containing 0.5% Triton X-100. 25 μL/well of the sample solution or standard solution was added to a microplate, and 25 μL of substrate solution was added to each well and mixed by stirring with a plate shaker. After the plate was left at 37°C for 1 hour, 150 μL of 200 mmol/L glycine-NaOH buffer (pH 10.6) was added to each well to stop the reaction. The fluorescence intensity of each well was then measured using a fluorescence plate reader (Gemini XPS, Molecular Devices, Inc.) (excitation wavelength 365 nm, fluorescence wavelength 460 nm). This fluorescence intensity is proportional to the concentration of 4-MU (4-Methylumbelliferone) contained in the solution in each well. A calibration curve was created based on the measurement results of the standard solution, and the measured values of each sample solution were interpolated to determine the enzyme activity (μM/hour). The unit of enzyme activity indicates the amount of substrate decomposed per hour.

[Example 6] Confirmation of expression levels of wild-type hGALC, HSA-hGALC, and hGALC-HSA by transient expression (Results)
15(a) shows the results of enzyme activity measurement of wild-type hGALC, HSA-hGALC, and hGALC-HSA by transient expression measured in Example 5. In addition, the relative amounts of wild-type hGALC, HSA-hGALC, and hGALC-HSA based on the results of enzyme activity measurement (relative amounts when the expression amount of wild-type hGALC on each measurement day is set to 1.0) are shown in Table 1.

These results show that, when looking at the expression levels (converted into enzyme activity) 6 days after the start of culture, the expression levels of HSA-hGALC and hGALC-HSA were 3.2 and 1.5 times higher, respectively, than that of wild-type hGALC. This shows that hGALC, which is difficult to mass-produce due to its low expression level when expressed as a recombinant in its wild form, can be efficiently expressed in greater amounts as a recombinant protein by expressing it in the form of HSA-hGALC or hGALC-HSA. The same can be said for 7 and 8 days after the start of culture.

Electrophoretic images and Western blotting images obtained in Example 3 are shown in Figures 15(b) and (c), respectively. From the Western blotting images, bands corresponding to wild-type hGALC, HSA-hGALC, and hGALC-HSA on the electrophoretic images were identified. The expression levels (in terms of molecular number) of the parts of wild-type hGALC, HSA-hGALC corresponding to hGALC, and the parts of hGALC-HSA corresponding to hGALC, estimated from the density of the bands in the Western blotting images, were approximately correlated with the expression levels (in terms of enzyme activity) shown in Figure 15(a) and Table 1. In other words, the relative values of the expression levels shown as the expression levels (in terms of enzyme activity) in Table 1 can be said to be the expression levels (in terms of molecular number) of the parts of wild-type hGALC, HSA-hGALC corresponding to hGALC, and hGALC-HSA corresponding to hGALC. In other words, these results show that by making wild-type hGALC into a fusion protein with HSA, it is possible to express a larger number of molecules of hGALC, which is difficult to mass-produce as a recombinant in its wild form, without reducing its specific activity by making it into a fusion protein. Note that the specific activity of hGALC in the fusion protein is calculated by multiplying the enzyme activity of hGALC per unit mass of the fusion protein (μM/hour/mg protein) by (the molecular weight of the fusion protein/the molecular weight of the portion of the fusion protein corresponding to hGALC).

[Example 7] Cell viability, etc. in transient expression of wild-type hGALC, HSA-hGALC, and hGALC-HSA In the transient expression of wild-type hGALC, HSA-hGALC, and hGALC-HSA performed in Example 2, the viable cell density and cell viability in the culture medium 6, 7, and 8 days after the start of culture of transformed ExpiCHO cells were measured using an EVE Automated Cell Counter (Nano EnTek). Table 2 shows the viable cell density and cell viability in the culture medium 6, 7, and 8 days after the start of culture for each of the cells expressing wild-type hGALC, HSA-hGALC, and hGALC-HSA.

There was no significant difference in viable cell density between cells expressing wild-type hGALC, HSA-hGALC, and hGALC-HSA. However, in terms of cell viability, cells expressing HSA-hGALC maintained a high viability of over 80% from 6 to 8 days after the start of culture, while cells expressing hGALC-HSA maintained a cell viability of over 70% from 6 to 8 days after the start of culture, although the cell viability gradually decreased from 6 to 8 days after the start of culture. On the other hand, the cell viability of cells expressing wild-type hGALC dropped significantly from 6 to 8 days after the start of culture, dropping to 60% at 8 days after the start of culture. When the viability of wild-type hGALC expressing cells on each measurement day was set to 1.0, the relative viability ratios were 1.1 and 1.1 for HSA-hGALC and hGALC-HSA expressing cells, respectively, 6 days after the start of culture, 1.3 and 1.2 for HSA-hGALC and hGALC-HSA expressing cells, respectively, 7 days after the start of culture, and 1.5 and 1.2 for HSA-hGALC and hGALC-HSA expressing cells, respectively, 8 days after the start of culture.

These results suggest that when wild-type hGALC is expressed as a recombinant protein, it causes stress to the host cells, reducing their viability, and that when wild-type hGALC is expressed as a fusion protein in which HSA is bound to the wild-type hGALC, the stress that wild-type hGALC causes to the host cells can be reduced, suppressing the reduction in viability. In other words, one factor behind the increase in expression level when expressed as a recombinant protein of HSA-hGALC or hGALC-HSA compared to wild-type hGALC, as shown in Example 6, is thought to be the reduction in the stress caused to the host cells when wild-type hGALC is expressed, thereby suppressing the reduction in cell viability.

[Example 8] Summary The above results show that when producing hGALC as a recombinant protein, producing hGALC in the form of a fusion protein of HSA-hGALC or hGALC-HSA makes it possible to obtain about 1.5 to 3.6 times the number of molecules of hGALC without decreasing the specific activity of hGALC. In other words, the method of producing recombinant hGALC by expressing hGALC in the form of a fusion protein of HSA-hGALC or hGALC-HSA can be said to be an extremely effective means for producing a large amount of recombinant hGALC. In addition, since contents of dead cells leak out and become impurities, an increase in dead cells during culture may make it difficult to purify the expressed fusion protein. Therefore, by expressing hGALC in the form of a fusion protein of HSA-hGALC or hGALC-HSA, cell death during culture can be suppressed, making it easier to purify the expressed fusion protein. This also increases the purification efficiency during purification.

[Example 9] SE-HPLC analysis of wild-type hGALC, HSA-hGALC, and hGALC-HSA obtained by transient expression In order to evaluate the physical properties of wild-type hGALC, HSA-hGALC, and hGALC-HSA obtained by transient expression, the culture supernatant of each protein was subjected to a purification process and then subjected to SE-HPLC analysis.

[Refining process]
An equal volume of 25 mM MES buffer (pH 6.5) containing 50 mM NaCl was added to the culture supernatant on day 8 containing wild-type hGALC, HSA-hGALC, and hGALC-HSA obtained by transient expression in Example 2. This solution was loaded at a constant flow rate onto a strong anion exchange column, Hitrap Q column (Cytiva), equilibrated with 25 mM MES buffer (pH 6.5) containing 50 mM NaCl. The column was then washed by supplying 5 times the column volume of the same buffer at the same flow rate. The wild-type hGALC, HSA-hGALC, and hGALC-HSA adsorbed on the strong anion exchange column were then eluted with a salt concentration gradient using 25 mM MES buffer (pH 6.5) containing 500 mM NaCl.

[SE-HPLC process]
A size-exclusion column, TSKgel G3000SWXL 5 μm column (7.8 mm diameter × 30 cm length, TOSOH) was set on a Shimadzu HPLC system LC-20A (Shimadzu Corporation). A spectrophotometer was also installed downstream of the column to continuously measure the absorbance (measurement wavelength 215 nm) of the effluent from the column. After equilibrating the column with 0.2 M sodium phosphate buffer solution containing 10% ethanol, each eluate containing wild-type hGALC, HSA-hGALC, and hGALC-HSA obtained in the above purification process was loaded onto the column, and then 0.2 M sodium phosphate buffer solution containing 10% ethanol was passed through the column at a flow rate of 0.5 mL/min. During this time, the absorbance (measurement wavelength 215 nm) of the effluent from the column was measured to obtain an elution profile.

〔Evaluation of the physical properties〕
The elution profile is shown in Figure 16. Wild-type hGALC has two main peaks, which are considered to correspond to the hGALC tetramer and the hGALC dimer, respectively, from the left side of the elution profile. On the other hand, HSA-hGALC and hGALC-HSA both have one main peak, which is considered to be the peak of the HSA-hGALC or hGALC-HSA monomer, respectively. This shows that, compared to the case where wild-type hGALC is expressed in cells, when the fusion protein of HSA and hGALC is expressed, a molecule having hGALC activity is stably obtained as a monomer. In addition, the mass ratio of the monomer to the total expression amount is 90% or more in each of HSA-hGALC and hGALC-HSA. When expressed as recombinant proteins, HSA-hGALC and hGALC-HSA can be obtained as homogeneous monomers, so from the viewpoint of production control, the method of producing hGALC as a fusion protein of hGALC with HSA can be said to be superior.

Example 10: Preparation of plasmids expressing conjugates of anti-hTfR antibody and fusion protein of HSA and hGALC Plasmids were prepared that express the four types of proteins shown below as conjugates of an anti-hTfR antibody (Fab) consisting of a heavy chain having the amino acid sequence shown in SEQ ID NO:25 and a light chain having the amino acid sequence shown in SEQ ID NO:23, and a fusion protein of HSA and hGALC.
(1) A conjugate consisting of a fusion protein in which the N-terminus of HSA-hGALC is linked via a linker to the C-terminus of the heavy chain of an anti-hTfR antibody (Fab) and the light chain of an anti-hTfR antibody (Fab) (referred to as Fab-HSA-hGALC);
(2) A conjugate consisting of a fusion protein in which the C-terminus of HSA-hGALC is linked via a linker to the N-terminus of the heavy chain of an anti-hTfR antibody (Fab) and the light chain of an anti-hTfR antibody (Fab) (HSA-hGALC-Fab);
(3) A conjugate consisting of a fusion protein in which the N-terminus of hGALC-HSA is linked via a linker to the C-terminus of the heavy chain of an anti-hTfR antibody (Fab) and a light chain of an anti-hTfR antibody (Fab) (referred to as Fab-hGALC-HSA); and (4) a conjugate consisting of a fusion protein in which the C-terminus of hGALC-HSA is linked via a linker to the N-terminus of the heavy chain of an anti-hTfR antibody (Fab) and a light chain of an anti-hTfR antibody (Fab) (referred to as hGALC-HSA-Fab).

[Construction of Dual(+)pCI-neo vector]
A primer (pCI Insert F3 primer) having the base sequence shown in SEQ ID NO: 26, which includes an NheI site, an AscI site, an NruI site, an AfeI site, and a NotI site with a NotI-disabling sequence inserted, was synthesized from the 5' side. A primer (pCI Insert R3 primer) having the base sequence shown in SEQ ID NO: 27, which includes a complementary sequence to the primer, was also synthesized. These two primers were annealed to obtain DNA digested with NheI and NotI at both ends and a DNA fragment having complementary protruding ends.

The pCI vector (Promega) was digested with NheI and NotI (Takara Bio), and the above DNA fragment was inserted into it by ligation. The resulting plasmid was named pCI MCS-modified vector (Figure 17). The pCI MCS-modified vector was digested with BamHI and BglII (Takara Bio), and a DNA fragment containing the CMV immediate-early enhancer/promoter region, multicloning site, and polyA sequence was excised. The pCI-neo vector (Promega) was digested with BamHI and treated with CIAP (Takara Bio), and the excised DNA fragment was inserted into it by ligation. The resulting plasmid was named Dual(+)pCI-neo vector (Figure 18).

[Preparation of expression plasmids for each conjugate]
A DNA fragment containing the base sequence shown in SEQ ID NO:29, including a gene encoding a conjugate (anti-hTfR antibody Fab heavy chain-HSA-hGALC) in which the N-terminus of HSA-hGALC is linked to the C-terminus of the heavy chain of an anti-hTfR antibody (Fab) having the amino acid sequence shown in SEQ ID NO:28 via a linker, was digested with restriction enzymes MluI and NotI (Takara Bio Inc.) and inserted between the MluI and NotI sites of the Dual(+)pCI-neo vector. Furthermore, the Dual(+)pCI-neo vector into which the gene encoding the anti-hTfR antibody Fab heavy chain-HSA-hGALC was inserted was digested with restriction enzymes AscI and AfeI (New England BioLabs), and a DNA fragment containing the base sequence shown in SEQ ID NO:36, including a gene encoding the light chain of an anti-hTfR antibody (Fab) having the amino acid sequence shown in SEQ ID NO:23, digested with AscI and AfeI, was inserted into the vector. The resulting plasmid was used as a Fab-HSA-hGALC expression plasmid.

In a similar manner, an HSA-hGALC-Fab expression plasmid was prepared using a DNA fragment containing the base sequence shown in SEQ ID NO: 31, which contains a gene encoding a conjugate in which the C-terminus of HSA-hGALC is linked via a linker to the N-terminus of the heavy chain of an anti-hTfR antibody (Fab) having the amino acid sequence shown in SEQ ID NO: 30, and a DNA fragment containing the base sequence shown in SEQ ID NO: 36, which contains a gene encoding the light chain of an anti-hTfR antibody (Fab) having the amino acid sequence shown in SEQ ID NO: 23.

In a similar manner, a Fab-hGALC-HSA expression plasmid was prepared using a DNA fragment containing the base sequence shown in SEQ ID NO: 33, which contains a gene encoding a conjugate in which the N-terminus of hGALC-HSA is linked via a linker to the C-terminus of the heavy chain of an anti-hTfR antibody (Fab) having the amino acid sequence shown in SEQ ID NO: 32, and a DNA fragment containing the base sequence shown in SEQ ID NO: 36, which contains a gene encoding the light chain of an anti-hTfR antibody (Fab) having the amino acid sequence shown in SEQ ID NO: 23.

In a similar manner, an hGALC-HSA-Fab expression plasmid was prepared using a DNA fragment containing the base sequence shown in SEQ ID NO: 35, which contains a gene encoding a conjugate in which the C-terminus of hGALC-HSA is linked via a linker to the N-terminus of the heavy chain of an anti-hTfR antibody (Fab) having the amino acid sequence shown in SEQ ID NO: 34, and a DNA fragment containing the base sequence shown in SEQ ID NO: 36, which contains a gene encoding the light chain of an anti-hTfR antibody (Fab) having the amino acid sequence shown in SEQ ID NO: 23.

[Example 11] Transient expression of each conjugate According to the High titer protocol of the ExpiCHO ^™ Expression System (Thermo Fisher Scientific), each conjugate expression plasmid prepared in Example 10 was used to transform ExpiCHO cells. After transformation, the cells were cultured for 8 days, and Fab-HSA-hGALC, HSA-hGALC-Fab, Fab-hGALC-HSA, and hGALC-HSA-Fab were expressed in the culture supernatant. After 8 days from the start of culture, the culture solutions were centrifuged to collect the culture supernatants.

[Example 12] Confirmation of expression levels of Fab-HSA-hGALC, HSA-hGALC-Fab, Fab-hGALC-HSA, and hGALC-HSA-Fab by transient expression (enzyme activity measurement)
Using the culture supernatant obtained in Example 11 as a sample solution, the expression levels of Fab-HSA-hGALC, HSA-hGALC-Fab, Fab-hGALC-HSA, and hGALC-HSA-Fab by transient expression were confirmed by enzyme activity measurement in the same manner as described in Example 5.

FIG. 19 shows the results of enzyme activity measurement of wild-type hGALC, Fab-HSA-hGALC, HSA-hGALC-Fab, Fab-hGALC-HSA, and hGALC-HSA-Fab. The values obtained in Example 2 using the culture supernatant 8 days after the start of culturing cells expressing wild-type hGALC as the sample solution were used for the enzyme activity measurement results. The relative amounts of wild-type hGALC, Fab-HSA-hGALC, HSA-hGALC-Fab, Fab-hGALC-HSA, and hGALC-HSA-Fab based on the results of enzyme activity measurement (relative amounts when the expression amount of wild-type hGALC 8 days after the start of culturing is set to 1.0) are shown in Table 3.

These results show that, when the expression levels (converted into enzyme activity) 8 days after the start of culture were examined, the expression levels of Fab-HSA-hGALC, HSA-hGALC-Fab, Fab-hGALC-HSA, and hGALC-HSA-Fab were approximately 3.8-fold, 2.3-fold, 3.0-fold, and 1.7-fold, respectively, compared to that of wild-type hGALC. This indicates that by converting wild-type hGALC to HSA-hGALC or hGALC-HSA, it is possible to express more hGALC as recombinant protein, even in the form of a conjugate further bound to an antibody. The above results were unexpected because all of the conjugates of anti-hTfR antibody, HSA, and hGALC fusion proteins, Fab-HSA-hGALC, HSA-hGALC-Fab, Fab-hGALC-HSA, and hGALC-HSA-Fab, which have such a complex structure and a larger molecular weight than wild-type hGALC, are expected to show reduced expression levels compared to wild-type hGALC when expressed as recombinant proteins.

[Example 13] SE-HPLC analysis of Fab-HSA-hGALC, HSA-hGALC-Fab, Fab-hGALC-HSA, and hGALC-HSA-Fab obtained by transient expression In order to evaluate the physical properties of Fab-HSA-hGALC, HSA-hGALC-Fab, Fab-hGALC-HSA, and hGALC-HSA-Fab obtained by transient expression, the culture supernatant of each protein was subjected to a purification process, followed by SE-HPLC analysis.

[Refining process]
0.1 volume of 2 M arginine solution (pH 6.5) was added to the culture supernatant on the 8th day containing Fab-HSA-hGALC, HSA-hGALC-Fab, Fab-hGALC-HSA, and hGALC-HSA-Fab by transient expression obtained in Example 11. This solution was loaded onto a Capture Select ^™ CH1-XL column (Thermo Fisher SCINTIFIC) equilibrated with 25 mM MES buffer (pH 6.5) containing 200 mM arginine in a volume 5 times the column volume, and each conjugate was adsorbed onto the column. The Capture Select ^™ CH1-XL column is an affinity column in which a ligand having the property of specifically binding to the CH1 domain of an IgG antibody is immobilized on a carrier. The column was then washed by supplying the same buffer in a volume 5 times the column volume. The column was then further washed by supplying 25 mM MES buffer (pH 6.5) in a volume 3 times the column volume. The bound proteins were then eluted with 5 column volumes of 20 mM acetate buffer (pH 4.0) and immediately neutralized in a container that had previously contained 250 mM MES buffer (pH 6.0) and 2 M NaCl solution.

[SE-HPLC process]
A size-exclusion column, TSKgel G3000SWXL 5 μm column (7.8 mm diameter × 30 cm length, TOSOH) was set on a Shimadzu HPLC system LC-20A (Shimadzu Corporation). A spectrophotometer was also installed downstream of the column to continuously measure the absorbance (measurement wavelength 215 nm) of the effluent from the column. After equilibrating the column with 0.2 M sodium phosphate buffer solution containing 10% ethanol, each eluate containing Fab-HSA-hGALC, HSA-hGALC-Fab, Fab-hGALC-HSA, and hGALC-HSA-Fab obtained in the above purification process was loaded onto the column, and 0.2 M sodium phosphate buffer solution containing 10% ethanol was further passed through the column at a flow rate of 0.5 mL/min. During this time, the absorbance (measurement wavelength 215 nm) of the effluent from the column was measured to obtain an elution profile.

〔Evaluation of the physical properties〕
The elution profile is shown in Figure 20. All of Fab-HSA-hGALC, HSA-hGALC-Fab, Fab-hGALC-HSA, and hGALC-HSA-Fab had one main peak, which is considered to be the peak of the monomer of Fab-HSA-hGALC, HSA-hGALC-Fab, Fab-hGALC-HSA, or hGALC-HSA-Fab, respectively. Compared with the fact that there were two main peaks on the elution profile of wild-type hGALC obtained in Example 9 (Figure 16), it can be seen that molecules having hGALC activity were stably obtained as monomers even when the conjugate of the fusion protein of HSA and hGALC and the antibody was expressed, compared to the case where wild-type hGALC was expressed in cells. In other words, it was shown that fusing HSA to hGALC contributes to the stabilization of hGALC, even when the fusion protein of HSA and hGALC was further conjugated with an antibody. In each of the conjugates, the mass ratio of the monomer to the total expression amount is 90% or more. When expressed as recombinant proteins, these conjugates can be obtained as homogeneous monomers, so from the viewpoint of production control, the method of producing hGALC as a conjugate of HSA and an antibody (here, Fab) can be said to be excellent.

The following Examples 14 to 20 show the experimental results of a fusion protein of HSA and hGBA.

Example 14: Preparation of wild-type hGBA expression plasmid pE-neo7 vector and pCAGIPuro vector (Miyahara M. et.al., J. Biol. Chem. 275, 613-618(2000)) were treated with restriction enzymes BamHI and NotI (Takara Bio), respectively, and separated by agarose gel electrophoresis. The pE-neo7 vector was prepared by the method described in International Publication WO2012/101998. After EtBr staining, the band containing the target DNA fragment was excised under UV irradiation, and DNA was extracted from the gel using QIAEX II Gel Extraction Kit (QIAGEN). Ligation reaction was performed at 16°C for 60 minutes using Ligation high Ver.2 (Toyobo Co., Ltd.) to complete the pEI-puro vector.
A DNA fragment having the base sequence shown in SEQ ID NO: 38, which contains a gene encoding wild-type hGBA (SEQ ID NO: 37), was synthesized. This was treated with restriction enzymes MluI and NotI (Takara Bio Inc.) and separated by agarose gel electrophoresis. After EtBr staining, the band containing the target DNA fragment was excised under UV irradiation, and DNA was extracted from the gel using a QIAEX II Gel Extraction Kit (QIAGEN).
The DNA fragment was mixed with the pEI-puro vector that had been treated with the restriction enzymes MluI and NotI, and a ligation reaction was carried out at 16°C for 60 minutes using Ligation high Ver.2 to complete the pEI-puro-hGBA vector.
The pEI-puro-hGBA vector and the pE-mIRES-GS vector were treated with restriction enzymes MluI and NotI, and then gel extracted and purified. The pE-mIRES-GS vector was prepared by the method described in International Publication WO2013/161958. The vectors treated with the restriction enzymes were mixed and ligated for 60 minutes at 16°C using Ligation high Ver.2 to complete the pEmIGS-hGBA vector (Figure 21).
).
The pEmIGS-hGBA vector and the pCIneo vector (Promega) were treated with restriction enzymes MluI and NotI, and gel extracted and purified. Then, the vectors treated with the restriction enzymes were mixed and ligated at 16°C for 60 minutes using Ligation high Ver.2 to complete the wild-type hGBA expression plasmid, the pCIneo-hGBA vector (Figure 22).

Example 15: Preparation of HSA-hGBA expression plasmid and hGBA-HSA expression plasmid A DNA fragment having a base sequence shown in SEQ ID NO: 40 was synthesized, including a gene encoding HSA-hGBA shown in SEQ ID NO: 39, which is a fusion protein in which the C-terminus of wild-type HSA (SEQ ID NO: 3) and the N-terminus of wild-type hGBA (SEQ ID NO: 37) are linked via a linker sequence shown in SEQ ID NO: 9. This was treated with restriction enzymes MluI and NotI and separated by agarose gel electrophoresis. After EtBr staining, a band containing the target DNA fragment was excised under UV irradiation, and DNA was extracted from the gel using a QIAEX II Gel Extraction Kit. Similarly, pCI-neo vector (Promega) was also treated with restriction enzymes MluI and NotI, and gel extracted and purified. The vector and DNA fragment treated with the restriction enzyme were mixed and ligated for 60 minutes at 16°C using Ligation high Ver.2 to complete the pCIneo-HSA-hGBA vector, an HSA-hGBA expression plasmid (Figure 23). A ligation reaction was also carried out in the same manner with a DNA fragment having the base sequence shown in SEQ ID NO: 42, which contains a gene encoding hGBA-HSA shown in SEQ ID NO: 41, a fusion protein in which the C-terminus of wild-type hGBA (SEQ ID NO: 37) and the N-terminus of wild-type HSA (SEQ ID NO: 3) are linked via a linker sequence shown in SEQ ID NO: 9, to complete the pCIneo-hGBA-HSA vector, an hGBA-HSA expression plasmid.

[Example 16] Confirmation and purification of each plasmid E. coli (E. coli DH5α Competent Cells, Takara Bio Inc.) was transformed with each ligation reaction solution containing the pCIneo-hGBA vector, pCIneo-HSA-hGBA vector, and pCIneo-hGBA-HSA vector obtained in Examples 14 and 15. From the obtained transformants, each of the plasmids incorporating wild-type hGBA, HSA-hGBA, and hGBA-HSA was purified by the same method as described in Example 1.

[Example 17] Transient expression of wild-type hGBA, HSA-hGBA, and hGBA-HSA For transient expression of wild-type hGBA, HSA-hGBA, and hGBA-HSA, the purified pCIneo-hGBA vector, pCIneo-HSA-hGBA vector, and pCIneo-hGBA-HSA vector obtained in Example 16 were used.

ExpiCHO cells were transformed with the pCIneo-hGBA vector, pCIneo-HSA-hGBA vector, and pCIneo-hGBA-HSA vector according to the High titer protocol of the ExpiCHO ^TM Expression System (Thermo Fisher Scientific). After transformation, the cells were cultured for 8 days, and wild-type hGBA, HSA-hGBA, and hGBA-HSA were expressed in the culture supernatant. After 8 days, the culture medium was centrifuged to collect the culture supernatant.

[Example 18] Confirmation of expression levels of wild-type hGBA, HSA-hGBA, and hGBA-HSA by transient expression (enzyme activity measurement)
The culture supernatant obtained in Example 17 was _{appropriately} diluted with 0.4 M _KH2PO4 / _0.4 M _K2HPO4 /0.125% Na-taurocholate/0.15% TrionX-100/0.1% BSA solution as a sample solution and used for measurement. As a standard solution, 4-MU (4-Methylumbelliferone, Sigma _- Aldrich) was serially diluted from 200 to 3.13 μM with _0.4 M _KH2PO4 / _0.4 M K2HPO4/0.125% Na-taurocholate/0.15% TrionX-100/0.1% BSA solution to prepare a standard solution. Substrate solution was prepared by diluting 4-Methylumbelliferyl-β-D-glucopyranoside (Sigma-Aldrich), an artificial substrate for hGBA, to 4 mmol/L with 0.4 M KH ₂ PO ₄ / 0.4 M K ₂ HPO ₄ / 0.125% Na-taurocholate / 0.15% TrionX-100 / 0.1% BSA solution. 10 μL/well of sample solution or standard solution was added to a microplate, and 70 μL of substrate solution was added to each well and mixed by shaking on a plate shaker. After leaving the plate at 37°C for 1 hour, 200 μL of 200 mM glycine / 50 mM Na2CO3 buffer (pH 10.7) was added to each well to stop the reaction. Next, the fluorescence intensity of each well was measured using a fluorescence plate reader (Gemini XPS, Molecular Devices) (excitation wavelength 365 nm, fluorescence wavelength 460 nm). This fluorescence intensity is proportional to the concentration of 4-MU (4-Methylumbelliferone) contained in the solution in each well. A calibration curve was created based on the measurement results of the standard solution, and the measured values of each sample solution were interpolated to determine the enzyme activity (μM/hour). The unit of enzyme activity indicates the amount of substrate decomposed per hour.

[Example 19] Confirmation of the expression levels of wild-type hGBA, HSA-hGBA, and hGBA-HSA by transient expression (SDS page electrophoresis)
10 μL of each culture supernatant obtained in Example 17 was mixed with 10 μL of 2×Sample Buffer (Bio-Rad) to which DTT had been added so that the final concentration was 0.4 M, and the mixture was heat-denatured under reducing conditions by heating at 100° C. for 5 minutes. 15 μL of the heat-denatured solution was applied to wells of a 5-20% polyacrylamide gel placed in 50 mM Tris buffer/380 mM glycine buffer (pH 8.3) containing 0.1% SDS, and electrophoresis was performed at a constant current of 25 mA. The gel after electrophoresis was immersed in Oriole Fluorescent Gel Stain (Bio-Rad) and shaken at room temperature for 60 minutes. After washing the gel with pure water, an electrophoretic image was obtained in which the bands corresponding to each protein were visualized using a luminoimage analyzer (Amersham Imager 600RGB, Cytiva).

[Example 20] Confirmation of expression levels of wild-type hGBA, HSA-hGBA, and hGBA-HSA by transient expression (Results)
24 shows the results of enzyme activity measurement of wild-type hGBA, HSA-hGBA, and hGBA-HSA by transient expression measured in Example 18. In addition, the relative amounts of wild-type hGBA, HSA-hGBA, and hGBA-HSA based on the results of enzyme activity measurement are shown in Table 4.

The above results show that, when looking at the expression levels (converted into enzyme activity) 8 days after the start of culture, the expression levels of HSA-hGBA and hGBA-HSA were 22 and 18 times higher, respectively, than that of wild-type hGBA. This shows that hGBA is difficult to mass-produce because of its low expression level when expressed as a recombinant in its wild-type form, but by expressing it in the form of HSA-hGBA or hGBA-HSA, it is possible to efficiently express more hGBA as a recombinant protein.

Next, the SDS-PAGE electrophoresis images obtained in Example 19 are shown in Figure 25. The results of SDS-PAGE show that HSA-hGBA and hGBA-HSA have 10 to 20 times higher expression levels than wild-type hGBA, based on a comparison of band intensities, and are roughly correlated with the expression levels (converted into enzyme activity) shown in Figure 24 and Table 4. In other words, it was found that hGBA, which is difficult to mass-produce due to its low expression level when expressed as a recombinant in its wild form, can be efficiently expressed in greater amounts as a recombinant protein by expressing it in the form of HSA-hGBA or hGBA-HSA.

The above results indicate that when producing hGBA as a recombinant protein, it is possible to obtain approximately 20 times the number of hGBA molecules by producing hGBA in the form of an HSA-hGBA or hGBA-HSA fusion protein. In other words, the method of producing recombinant hGBA in which hGBA is expressed in the form of an HSA-hGBA or hGBA-HSA fusion protein can be said to be an extremely effective means of producing large quantities of recombinant hGBA.

The following Examples 21 to 26 relate to a fusion protein of mouse serum albumin (MSA) and mouse IL-10 (mIL-10). In Examples 21 to 26, the MSA used was a mutant MSA (MSA-A320T, SEQ ID NO: 125) in which the 320th amino acid, alanine, of the wild-type MSA having the amino acid sequence shown in SEQ ID NO: 16 was replaced with threonine.

Example 21: Preparation of wild-type mIL-10 expression plasmid, mIL-10-MSA expression plasmid, and MSA-mIL-10 expression plasmid A DNA fragment having the nucleotide sequence shown in SEQ ID NO: 127 and including a gene encoding wild-type mIL-10 (SEQ ID NO: 126), a DNA fragment having the nucleotide sequence shown in SEQ ID NO: 129 and including a gene encoding mIL-10-MSA (SEQ ID NO: 128), which is a fusion protein in which the C-terminus of wild-type mIL-10 (SEQ ID NO: 126) and the N-terminus of mutant MSA (SEQ ID NO: 125) are directly linked, and a DNA fragment having the nucleotide sequence shown in SEQ ID NO: 131 and including a gene encoding MSA-mIL-10 (SEQ ID NO: 130), which is a fusion protein in which the C-terminus of mutant MSA (SEQ ID NO: 125) and the N-terminus of wild-type mIL-10 (SEQ ID NO: 126) are directly linked were synthesized. These were treated with restriction enzymes MluI and NotI (Takara Bio Inc.) and separated by agarose gel electrophoresis. After EtBr staining, the band containing the target DNA fragment was excised under UV irradiation, and DNA was extracted from the gel using a QIAEX II Gel Extraction Kit (QIAGEN). Similarly, pCI-neo vector (Promega) was digested with restriction enzymes MluI and NotI, and gel extracted and purified. The restriction enzyme-treated vector was mixed with each DNA fragment, and a ligation reaction was performed at 16°C for 60 minutes using a DNA Ligation Kit Mighty Mix (Takara Bio).

Then, each ligation reaction solution was used to transform Escherichia coli (One Shot MAX Efficiency DH10B T1 Phage-Resistant Cells, Thermo Fisher Scientific). Plasmids containing the target genes were purified from the resulting transformants using the same method as described in Example 1.

[Example 22] Transient expression of wild-type mIL-10, mIL-10-MSA, and MSA-mIL-10 According to the High Titer protocol of the ExpiCHO Expression System (Thermo Fisher Scientific), ExpiCHO cells were transformed with plasmids incorporating genes encoding wild-type mIL-10, mIL-10-MSA, and MSA-mIL-10, respectively. After transformation, the cells were cultured for 8 days to express wild-type mIL-10, mIL-10-MSA, and MSA-mIL-10 in the culture supernatant, respectively. After culturing, the culture medium was centrifuged to collect the culture supernatant.

[Example 23] Confirmation of expression levels of wild-type mIL-10, mIL-10-MSA, and MSA-mIL-10 by transient expression (SDS-page electrophoresis)
6 μL of the culture supernatant obtained in Example 22 was mixed with 2 μL of 4×Sample Buffer (Bio-Rad) to which (±)-dithiothreitol (Fujifilm Wako Pure Chemical Industries, Ltd.) had been added to a concentration of 40 mg/mL, and the mixture was heated at 100°C for 3 minutes to be thermally denatured under reducing conditions. 5 μL of the thermally denatured sample was applied to wells of a 5-20% polyacrylamide gel (Fujifilm Wako Pure Chemical Industries, Ltd.) placed in 50 mM Tris buffer/380 mM glycine buffer (pH 8.3) containing 0.1% SDS, and electrophoresis was performed at a constant current of 25 mA. The gel after electrophoresis was immersed in EZFluor UV 1-step Fluorescent Protein Gel Stain (Merck) and shaken at room temperature for 60 minutes. After washing the gel with pure water, protein bands were detected using a luminometer image analyzer (Amersham ImageQuan 800, Cytiva).

[Example 24] Confirmation of expression levels of wild-type mIL-10, mIL-10-MSA, and MSA-mIL-10 by transient expression (ELISA)
ELISA was performed using Mouse IL-10 ELISA Kit (Proteintech). The culture supernatant obtained in Example 22 was diluted 50,000 times with Sample Diluent included in the kit to prepare a sample solution. For wild-type mIL-10, the Standard included in the kit was diluted with Sample Diluent to prepare a standard solution, and for mIL-10-MSA and MSA-mIL-10, the purified products obtained by the method shown in Example 25 below were diluted with Sample Diluent to prepare standard solutions. 100 μL of the sample solution or standard solution was added to each well of a 96-well plate on which anti-mouse IL-10 antibody was immobilized, and the plate was incubated at 37° C. for 100 minutes. Next, each well was washed four times with 300 μL of Wash Buffer included in the kit, and 100 μL of mouse IL-10 detection antibody was added to each well, and the plate was incubated at 37° C. for 60 minutes. After washing each well four times with 300 μL of wash buffer, 100 μL of streptavidin-HRP was added to each well and incubated at 37°C for 40 minutes. After washing each well four times with 300 μL of wash buffer, 100 μL of TMB substrate was added to each well and the color reaction was allowed to proceed at 37°C. After sufficient color development was achieved, 100 μL of TMB stop solution was added to each well to stop the reaction. The absorbance at a wavelength of 450 nm was measured using a plate reader (SpectraMax iD3, Molecular Devices), and a calibration curve was created using analysis software (SoftMax Pro 7.1, Molecular Devices), and the measured values of each sample solution were inserted into this to calculate the concentration (converted to the amount of substance) in each culture supernatant.

[Example 25] Obtaining purified products of mIL-10-MSA and MSA-mIL-10 The purified products of mIL-10-MSA and MSA-mIL-10 used for preparing the standard solution in Example 24 were obtained according to the following method.

[Construction of mIL-10-MSA expression plasmid and MSA-mIL-10 expression plasmid]
The mIL-10-MSA expression plasmid and MSA-mIL-10 expression plasmid prepared in Example 21 were treated with restriction enzymes Mlu I and Not I (Takara Bio), and DNA fragments containing the base sequence of the mIL-10-MSA gene or MSA-mIL-10 gene were separated by agarose gel electrophoresis. After EtBr staining, the band containing the target DNA fragment was excised under UV irradiation, and DNA was extracted from the gel using FastGene Gel/PCR Extraction Kit (Nihon Genetics). Similarly, the pE-mIRES-GS-puro vector was treated with restriction enzymes Mlu I and Not I, and gel extraction and purification were performed. The mIRES-GS-puro vector was constructed by the method described in WO2013/161958. The vector treated with the restriction enzymes and each DNA fragment treated with the restriction enzymes were mixed, and ligation reaction was performed at 16°C for 30 to 60 minutes using Ligation high Ver.2 (Toyobo Co., Ltd.).

Then, each ligation reaction solution was used to transform Escherichia coli (E. coli DH5α Competent Cells, Takara Bio Inc.). From the resulting transformants, plasmids incorporating the target genes were purified using the same method as described in Example 1.

[Preparation of mIL-10-MSA expressing bulk cells and MSA-mIL-10 expressing bulk cells]
Using a gene transfer device (Super Electroporator NEPA21, Nepa Gene), expression plasmids incorporating genes encoding mIL-10-MSA or MSA-mIL-10 obtained above were introduced into serum-free adapted CHO-K1 cells, and selective culture was performed in CD OptiCHO medium (Thermo Fisher Scientific) containing methionine sulfoximine (SIGMA) and Puromycin (Thermo Fisher Scientific). During selective culture, the concentrations of methionine sulfoximine and Puromycin were gradually increased to a final concentration of 300 μM for methionine sulfoximine and 10 μg/mL for Puromycin. The culture medium was replaced every 3 to 4 days, and the amount of culture medium was gradually increased. When the survival rate of the cells during culture exceeded 90%, the cells were harvested and used as mIL-10-MSA-expressing bulk cells and MSA-mIL-10-expressing bulk cells.

[Cultivation of mIL-10-MSA expressing bulk cells and MSA-mIL-10 expressing bulk cells]
The mIL-10-MSA-expressing bulk cells and MSA-mIL-10-expressing bulk cells obtained above were seeded at a cell density of 2 x ¹⁰⁵ cells/mL in CD OptiCHO medium containing 300 μM methionine sulfoximine and 10 μg/mL puromycin, and cultured with shaking at 37°C in the presence of 5% _CO2 . The MSA-mIL-10-expressing bulk cells were cultured at 32°C from the third day onwards. The culture supernatant was collected by centrifugation 10 days after the start of culture.

Purification of mIL-10-MSA and MSA-mIL-10
The culture supernatant of the mIL-10-MSA-expressing bulk cells collected above was filtered through a Rapid-Flow PES membrane filter unit (pore size 0.2 μm, Thermo Fisher Scientific) and passed through a HiTrap Q HP column (Cytiva) equilibrated with 25 mM HEPES buffer (pH 7.4) containing 100 mM NaCl to adsorb mIL-10-MSA to the resin. The column was then washed with 25 mM HEPES buffer (pH 7.4) containing 100 mM NaCl, and mIL-10-MSA was eluted from the resin with 25 mM HEPES buffer (pH 7.4) containing 350 mM NaCl.

The eluate from the HiTrap Q HP column containing mIL-10-MSA was diluted 6-fold with 25 mM MES buffer (pH 6.8) containing 5 mM phosphate, and passed through a CHT Type I column (Bio-Rad) equilibrated with 25 mM MES buffer (pH 6.8) containing 5 mM phosphate to adsorb mIL-10-MSA to the resin. The column was then washed with 25 mM MES buffer (pH 6.8) containing 5 mM phosphate, and mIL-10-MSA was eluted from the resin with 25 mM MES buffer (pH 6.8) containing 200 mM phosphate to obtain the mIL-10-MSA purified product. MSA-mIL-10 was purified in the same manner to obtain the MSA-mIL-10 purified product.

[Example 26] Confirmation of expression levels of wild-type mIL-10, mIL-10-MSA, and MSA-mIL-10 by transient expression (Results)
26 shows the results of ELISA concentration measurement of wild-type mIL-10, mIL-10-MSA, and MSA-mIL-10 by transient expression measured in Example 24. In addition, the relative amounts of wild-type mIL-10, mIL-10-MSA, and MSA-mIL-10 based on the results of ELISA concentration measurement are shown in Table 5.

The above results show that, looking at the expression levels (concentrations) 8 days after the start of culture, the expression levels of mIL-10-MSA and MSA-mIL-10 were 4.5 and 4.2 times higher, respectively, than that of wild-type mIL-10. This shows that wild-type IL-10 is difficult to mass-produce due to its low expression level when expressed as a recombinant form, but by expressing it in the form of IL-10-SA or SA-IL-10, it is possible to efficiently express more IL-10 as a recombinant protein.

Next, the electrophoretic image of SDS-PAGE obtained in Example 23 is shown in Figure 27. The results of SDS-PAGE showed that mIL-10-MSA and MSA-mIL-10 had higher expression levels than wild-type mIL-10, based on a comparison of band intensities, and corresponded to the measured values by ELISA shown in Figure 26 and Table 5. IL-10, which is expressed in low amounts when expressed as a recombinant in its wild form and is difficult to mass-produce, was found to be able to be efficiently expressed in greater amounts as a recombinant protein by expressing it in the form of IL-10-SA or SA-IL-10.

The above results indicate that when mIL-10 is produced as a recombinant protein, approximately four times the number of molecules of mIL-10 can be obtained by producing mIL-10 in the form of a mIL-10-MSA or MSA-mIL-10 fusion protein, and further indicate that when hIL-10 is produced as a recombinant protein, a greater number of molecules of hIL-10 can be obtained by producing hIL-10 in the form of a hIL-10-HSA or HSA-hIL-10 fusion protein. In other words, the method of producing recombinant IL-10 in which IL-10 is expressed in the form of an IL-10-SA or SA-IL-10 fusion protein can be said to be an extremely effective means of producing large amounts of recombinant IL-10.

Below, Examples 27 to 33 relate to fusion proteins of HSA and human neurotrophic factors (hBDNF, hNGF, hNT-3, or hNT-4).

[Example 27] Preparation of wild-type human neurotrophic factor expression plasmid The following DNA fragments (1) to (4) were synthesized:
(1) A DNA fragment having a base sequence shown in SEQ ID NO: 133, which contains a gene encoding wild-type hBDNF (SEQ ID NO: 132) to which an amino acid sequence shown by Gly-Ser (hereinafter referred to as GS) and a histidine tag having the amino acid sequence of SEQ ID NO: 195 consisting of six histidines (hereinafter referred to as His6) have been added in this order at the C-terminus,
(2) a DNA fragment having the base sequence shown in SEQ ID NO: 135, which contains a gene encoding wild-type hNGF (SEQ ID NO: 134) with His6 added to the C-terminus;
(3) A DNA fragment having the base sequence shown in SEQ ID NO: 137, which contains a gene encoding wild-type hNT-4 (SEQ ID NO: 136) with His6 added to the C-terminus, and (4) a DNA fragment having the base sequence shown in SEQ ID NO: 139, which contains a gene encoding wild-type hNT-3 (SEQ ID NO: 138) with His6 added to the C-terminus.

The DNA fragments (1) to (4) above were treated with restriction enzymes MluI and NotI (Takara Bio) and separated by agarose gel electrophoresis. After EtBr staining, the band containing the target DNA fragment was excised under UV irradiation, and the DNA was extracted from the gel using a QIAEX II Gel Extraction Kit (QIAGEN). Similarly, pCI-neo vector (Promega) was treated with restriction enzymes MluI and NotI, and gel extracted and purified. The restriction enzyme-treated vector was mixed with each of the DNA fragments, and a ligation reaction was carried out at 16°C for 30 to 60 minutes using Ligation Mix (Takara Bio).

Next, each ligation reaction solution was used to transform Escherichia coli (ECOS ^™ X Competent E. coli DH5α, Nippon Gene Co., Ltd.). From the obtained transformants, each plasmid incorporating the target gene was purified by the same method as described in Example 1. Each purified vector was used in the following experiments as a wild-type hBDNF expression vector, a wild-type hNGF expression vector, a wild-type hNT-4 expression vector, and a wild-type hNT-3 expression vector.

[Example 28] Preparation of a plasmid expressing a fusion protein of HSA and human neurotrophic factor The DNA fragments (1) to (4) synthesized in Example 27 were treated with restriction enzymes MluI and BamHI (Takara Bio Inc.) and separated by agarose gel electrophoresis.
After EtBr staining, the band containing the target DNA fragment was excised under UV irradiation, and the DNA fragment was extracted from the gel and purified using a QIAEX II Gel Extraction Kit (QIAGEN). The purified DNA fragment was designated insert DNA 1.

The following DNA fragments (1) to (5) were synthesized:
(1) A DNA fragment having the base sequence shown in SEQ ID NO: 141, which contains a gene encoding wild-type HSA (SEQ ID NO: 140) with His6 added to the C-terminus,
(2) a DNA fragment having the base sequence shown in SEQ ID NO: 133, which contains a gene encoding wild-type hBDNF (SEQ ID NO: 132) with His6 added to the C-terminus;
(3) A DNA fragment having the base sequence shown in SEQ ID NO: 135, which contains a gene encoding wild-type hNGF (SEQ ID NO: 134) with His6 added to the C-terminus.
(4) A DNA fragment having the base sequence shown in SEQ ID NO: 137, which contains a gene encoding wild-type hNT-4 (SEQ ID NO: 136) with His6 added to the C-terminus, and (5) a DNA fragment having the base sequence shown in SEQ ID NO: 139, which contains a gene encoding wild-type hNT-3 (SEQ ID NO: 138) with His6 added to the C-terminus.
Using the DNA fragments (1) to (5) above as templates, PCR reactions No. 1 to 5 were carried out using the forward and reverse primers shown in Table 6. For convenience, wild-type HSA with His6 added to the C-terminus will hereinafter be referred to as wild-type HSA. The same applies to wild-type hBDNF, wild-type hNGF, wild-type hNT-4, and wild-type hNT-3.

The DNA fragments obtained by PCR No. 1 to 5 above were treated with restriction enzymes BglII and NotI (Takara Bio), gel extracted, and purified. The purified DNA fragment was designated insert DNA 2.

　pCI-neo vector (Promega) was treated with restriction enzymes MluI and NotI, and gel extracted and purified. The above insert DNA 1 and insert DNA 2 were mixed with the restriction enzyme-treated vector in the combinations shown in Table 7, and a ligation reaction was carried out at 16°C for 30 to 60 minutes using Ligation Mix (Takara Bio). As a result of this reaction, a DNA fragment in which insert DNA 2 is linked in frame to the 3' end of insert DNA 1 is inserted into the pCI-neo vector.

Table 7 shows the target fusion proteins encoded by the genes obtained for each combination of insert DNA 1 and insert DNA 2. The names and structures of the fusion proteins in this example are as shown below in (1) to (8):
(1) hBDNF-HSA: A fusion protein having the amino acid sequence shown in SEQ ID NO: 148, in which wild-type HSA (SEQ ID NO: 3) is linked to the C-terminus of wild-type hBDNF (SEQ ID NO: 60) via a linker shown in the amino acid sequence Gly-Ser, and His6 is further linked to the C-terminus of the linker;
(2) hNGF-HSA: a fusion protein having the amino acid sequence shown in SEQ ID NO: 149, in which wild-type HSA (SEQ ID NO: 3) is linked to the C-terminus of wild-type hNGF (SEQ ID NO: 62) via a linker shown in the amino acid sequence Gly-Ser, and His6 is further linked to the C-terminus of the linker;
(3) hNT-4-HSA: a fusion protein having the amino acid sequence shown in SEQ ID NO: 150, in which wild-type HSA (SEQ ID NO: 3) is linked to the C-terminus of wild-type hNT-4 (SEQ ID NO: 66) via a linker shown in the amino acid sequence Gly-Ser, and His6 is further linked to the C-terminus of the linker;
(4) hNT-3-HSA: a fusion protein having the amino acid sequence shown in SEQ ID NO: 151, in which wild-type HSA (SEQ ID NO: 3) is linked to the C-terminus of wild-type hNT-3 (SEQ ID NO: 64) via a linker shown in the amino acid sequence Gly-Ser, and His6 is further linked to the C-terminus of the linker;
(5) HSA-hBDNF: a fusion protein having the amino acid sequence shown in SEQ ID NO: 152, in which the pro-form of wild-type hBDNF (SEQ ID NO: 84) is bound to the C-terminus of wild-type HSA (SEQ ID NO: 3) via a linker shown in the amino acid sequence Gly-Ser, and His6 is further bound to the C-terminus of the linker;
(6) HSA-hNGF: a fusion protein having the amino acid sequence shown in SEQ ID NO: 153, in which the pro-form of wild-type hNGF (SEQ ID NO: 87) is bound to the C-terminus of wild-type HSA (SEQ ID NO: 3) via a linker shown in the amino acid sequence Gly-Ser, and His6 is further bound to the C-terminus of the linker;
(7) HSA-hNT-4: a fusion protein having the amino acid sequence shown in SEQ ID NO: 154, in which the pro-form of wild-type hNT-4 (SEQ ID NO: 93) is bound to the C-terminus of wild-type HSA (SEQ ID NO: 3) via a linker shown in the amino acid sequence Gly-Ser, and His6 is further bound to the C-terminus of the wild-type hNT-4; and (8) HSA-hNT-3: a fusion protein having the amino acid sequence shown in SEQ ID NO: 155, in which the pro-form of wild-type hNT-3 (SEQ ID NO: 90) is bound to the C-terminus of wild-type HSA (SEQ ID NO: 3) via a linker shown in the amino acid sequence Gly-Ser, and His6 is further bound to the C-terminus of the wild-type hNT-3.
Here, for HSA-hBDNF, HSA-hNGF, HSA-hNT-4 and HSA-hNT-3, the human neurotrophic factors (hBDNF, hNGF, hNT-4 or hNT-3) used to be fused to the C-terminus of HSA are all in the pro-form. Therefore, when these are expressed as recombinant proteins, some or all of the molecules of the fusion protein may be cleaved, and ultimately, a single wild-type human neurotrophic factor (hBDNF, hNGF, hNT-4 or hNT-3) may be obtained. However, except for the observation of the results of SDS-PAGE and Western blotting obtained in Examples 30 and 31, all are treated as being expressed as fusion proteins.

Then, each ligation reaction solution was used to transform Escherichia coli (ECOSTM X Competent E. coli DH5α, Nippon Gene Co., Ltd.) with the expression vectors encoding the fusion proteins (1) to (8) above. From the resulting transformants, each plasmid incorporating the target gene was purified using the same method as described in Example 1.

[Example 29] Transient expression of wild-type human neurotrophic factor and fusion protein of HSA and human neurotrophic factor According to the High Titer protocol of ExpiCHO Expression System (Thermo Fisher Scientific), ExpiCHO TM cells were transformed with ^the plasmids obtained in Examples 27 and 28 incorporating genes encoding wild-type human neurotrophic factor or fusion protein of HSA and human neurotrophic factor, respectively. After transformation, the cells were cultured for 8 days to express wild-type human neurotrophic factor or fusion protein of HSA and human neurotrophic factor in the culture supernatant, respectively. After culturing, the culture medium was centrifuged to collect the culture supernatant.

[Example 30] Confirmation of expression levels of wild-type human neurotrophic factor and fusion protein of HSA and human neurotrophic factor by transient expression (SDS-PAGE)
10 μL of the culture supernatant obtained in Example 29 was mixed with 8 μL of 2×Sample Buffer (Bio-Rad) and 2 μL of 2-mercaptoethanol (Bio-Rad), and heat-denatured under reducing conditions by heating at 100°C for 3 minutes. 5 μL of the heat-denatured sample was applied to wells of a 10-20% polyacrylamide gel (Fujifilm Wako Pure Chemical Industries, Ltd.) placed in 50 mM Tris buffer/380 mM glycine buffer (pH 8.3) containing 0.1% SDS, and electrophoresis was performed at a constant current of 25 mA. The gel after electrophoresis was immersed in Oriole Fluorescent Gel Stain (Bio-Rad) and shaken at room temperature for 90 minutes. After washing the gel with pure water, protein bands were detected with a luminometer image analyzer (Amersham Imager 600RGB, Cytiva).

[Example 31] Confirmation of expression levels of wild-type human neurotrophic factor and fusion protein of HSA and human neurotrophic factor by transient expression (Western blotting)
Electrophoresis was performed in the same manner as described in Example 30, and the nitrocellulose membrane and the gel after electrophoresis were sandwiched between blotting papers soaked in 25 mM Tris buffer/192 mM glycine buffer containing 20% methanol, and the proteins were transferred to the nitrocellulose membrane by applying electricity at 1.0 A and 25 V for 10 minutes using a blotting device (Trans-Blot Turbo Transfer System, Bio-Rad). The nitrocellulose membrane after transfer was immersed in TBST containing 5% skim milk and shaken for 1 hour, and then immersed in a solution of Mouse anti-His tag mAb (Medical and Biological Laboratories) diluted to 0.4 μg/mL and shaken for 1 hour. After washing the membrane with TBST, it was immersed in a solution of Anti-mouse IgG (H+L), HRP Conjugate (Promega) diluted to 0.2 μg/mL, shaken for 60 minutes, and washed again with TBST. HRP detection reagent (Bio-Rad) was dropped on the transfer surface of the membrane, reacted for 5 minutes, and detected with a lumino image analyzer.

[Example 32] Confirmation of expression levels of wild-type human neurotrophic factor and fusion protein of HSA and human neurotrophic factor by transient expression (ELISA)
In order to compare the expression levels of wild-type human neurotrophic factor and the fusion protein of HSA and human neurotrophic factor by transient expression, ELISA measurement was performed using the Human Multi-Neurotrophin Rapid Screening ELISA Kit (Biosensis). The culture supernatant obtained in Example 29 was appropriately diluted with Assay diluent A included in the kit to prepare a sample solution, and the concentration of wild-type human neurotrophic factor or the fusion protein of HSA and human neurotrophic factor in the culture supernatant was calculated. Details are given below for each type of wild-type human neurotrophic factor alone or human neurotrophic factor fused with HSA.

[Measurement of wild-type hBDNF and fusion protein of HSA and hBDNF]
As sample solutions, the culture supernatant of ExpiCHO expressing wild-type hBDNF, hBDNF-HSA, or HSA-hBDNF obtained in Example 29 was diluted 100,000 times with Assay diluent A to prepare a standard solution. The 1000 pg/mL BDNF solution included in the kit was serially diluted with Assay diluent A to prepare 500, 250, 125, 63, 31, 16, and 8 pg/mL solutions, respectively. 100 μL of the sample solution or standard solution was added to each well of a 96-well plate on which anti-BDNF antibody was immobilized, and the plate was shaken at room temperature for 90 minutes on a plate shaker. Next, each well was washed five times with 200 μL of Wash buffer, and then 100 μL of BDNF detection antibody (biotin-labeled anti-BDNF antibody) was added to each well, and the plate was shaken at room temperature for 30 minutes on a plate shaker. Next, each well was washed five times with 200 μL of wash buffer, and 100 μL of streptavidin-HRP was added to each well and shaken on a plate shaker at room temperature for 30 minutes. After washing each well five times with 200 μL of wash buffer, 100 μL of TMB substrate was added to each well and left to stand at room temperature for color reaction. After sufficient color development was obtained, 100 μL of TMB stop solution was added to each well to stop the reaction. The absorbance at a wavelength of 450 nm was measured using a microplate reader (Spectramax 190 EXT, Molecular Device), and a calibration curve was created using analysis software (SoftMax Pro, Molecular Device), and the measured values of each sample solution were inserted into this to calculate the concentration (converted to the amount of substance) in each culture supernatant.

[Measurement of wild-type hNGF and fusion protein of HSA and hNGF]
As sample solutions, the culture supernatant of ExpiCHO expressing wild-type hNGF, hNGF-HSA, or HSA-hNGF obtained in Example 29 was diluted 100,000 times with Assay diluent A to prepare the standard solutions. The 500 pg/mL NGF solution included in the kit was serially diluted with Assay diluent A to prepare 250, 125, 63, 31, 16, 8, and 4 pg/mL solutions, respectively. 100 μL of the sample solution or standard solution was added to each well of a 96-well plate on which anti-NGF antibody was immobilized, and the plate was shaken at room temperature for 90 minutes on a plate shaker. Next, each well was washed five times with 200 μL of Wash buffer, and then 100 μL of NGF detection antibody (biotin-labeled anti-NGF antibody) was added to each well, and the plate was shaken at room temperature for 30 minutes on a plate shaker. Next, each well was washed five times with 200 μL of wash buffer, and 100 μL of streptavidin-HRP was added to each well and shaken on a plate shaker at room temperature for 30 minutes. After washing each well five times with 200 μL of wash buffer, 100 μL of TMB substrate was added to each well and left to stand at room temperature for color reaction. After sufficient color development was obtained, 100 μL of TMB stop solution was added to each well to stop the reaction. The absorbance at a wavelength of 450 nm was measured using a microplate reader (Spectramax 190 EXT, Molecular Device), and a calibration curve was created using analysis software (SoftMax Pro, Molecular Device), and the measured values of each sample solution were inserted into this to calculate the concentration (converted to the amount of substance) in each culture supernatant.

[Measurement of wild-type hNT-4 and fusion protein of HSA and hNT-4]
As sample solutions, the culture supernatants of ExpiCHO expressing wild-type hNT-4, hNT-4-HSA, and HSA-hNT-4 obtained in Example 29 were diluted 100,000 times with Assay diluent A to prepare them. As standard solutions, the 2000 pg/mL NT-4 solution included in the kit was serially diluted with Assay diluent A to prepare 1000, 500, 250, 125, 63, 31, and 16 pg/mL solutions, respectively. 100 μL of the sample solution or standard solution was added to each well of a 96-well plate on which anti-NT-4 antibody was immobilized, and the plate was shaken at room temperature for 90 minutes on a plate shaker. Next, each well was washed five times with 200 μL of Wash buffer, and then 100 μL of NT-4 detection antibody (biotin-labeled anti-NT-4 antibody) was added to each well, and the plate was shaken at room temperature for 30 minutes on a plate shaker. Next, each well was washed five times with 200 μL of Wash buffer, and 100 μL of Streptavidin-HRP was added to each well and shaken on a plate shaker at room temperature for 30 minutes. After washing each well five times with 200 μL of Wash buffer, 100 μL of TMB substrate was added to each well and left to stand at room temperature for color reaction. After sufficient color development was obtained, 100 μL of TMB stop solution was added to each well to stop the reaction. The absorbance at a wavelength of 450 nm was measured using a microplate reader (Spectramax 190 EXT, Molecular Device), and a calibration curve was created using analysis software (SoftMax Pro, Molecular Device), and the measured values of each sample solution were inserted into this to calculate the concentration in each culture supernatant (converted to the amount of substance with one monomer as one molecule).

[Measurement of wild-type hNT-3 and fusion protein of HSA and hNT-3]
As sample solutions, the culture supernatants of ExpiCHO expressing wild-type hNT-3, hNT-3-HSA, and HSA-hNT-3 obtained in Example 29 were diluted 100,000 times with Assay diluent A to prepare them. As standard solutions, the 2000 pg/mL NT-3 solution included in the kit was serially diluted with Assay diluent A to prepare 1000, 500, 250, 125, 63, 31, and 16 pg/mL solutions, respectively. 100 μL of the sample solution or standard solution was added to each well of a 96-well plate on which anti-NT-3 antibody was immobilized, and the plate was shaken at room temperature for 90 minutes on a plate shaker. Next, each well was washed five times with 200 μL of Wash buffer, and then 100 μL of NT-3 detection antibody (biotin-labeled anti-NT-3 antibody) was added to each well, and the plate was shaken at room temperature for 30 minutes on a plate shaker. Next, each well was washed five times with 200 μL of Wash buffer, and 100 μL of Streptavidin-HRP was added to each well and shaken on a plate shaker at room temperature for 30 minutes. After washing each well five times with 200 μL of Wash buffer, 100 μL of TMB substrate was added to each well and left to stand at room temperature for color reaction. After sufficient color development was obtained, 100 μL of TMB stop solution was added to each well to stop the reaction. The absorbance at a wavelength of 450 nm was measured using a microplate reader (Spectramax 190 EXT, Molecular Device), and a calibration curve was created using analysis software (SoftMax Pro, Molecular Device), and the measured values of each sample solution were inserted into this to calculate the concentration in each culture supernatant (converted to the amount of substance with one monomer as one molecule).

[Example 33] Confirmation of the expression levels of wild-type human neurotrophic factor and fusion protein of HSA and human neurotrophic factor by transient expression (Results)
28 shows the results of ELISA concentration measurement of the wild-type human neurotrophic factor and the fusion protein of HSA and human neurotrophic factor by transient expression measured in Example 32. In addition, the relative amounts of the wild-type human neurotrophic factor and the fusion protein of HSA and human neurotrophic factor based on the results of ELISA concentration measurement are shown in Table 8.

The above results show that, when the expression levels (concentrations) were examined 8 days after the start of culture, the expression levels of hBDNF-HSA and HSA-hBDNF were 29 and 3.0 times higher, respectively, than that of wild-type hBDNF. This shows that hBDNF, which is difficult to mass-produce due to its low expression level when expressed as a recombinant in its wild form, can be efficiently expressed in greater amounts as a recombinant protein by expressing it in the form of a fusion protein of hBDNF and HSA.

In addition, the expression levels of hNGF-HSA and HSA-hNGF were 1.6 and 1.3 times higher than that of wild-type hNGF, respectively. This indicates that hNGF is difficult to mass-produce because of its low expression level when expressed as a recombinant form in its wild-type form, but by expressing it in the form of a fusion protein of hNGF and HSA, it is possible to efficiently express more hNGF as a recombinant protein.

In addition, the expression levels of hNT-4-HSA and HSA-hNT-4 were 4.1 and 1.8 times higher than that of wild-type hNT-4, respectively. This indicates that hNT-4, which is difficult to mass-produce due to its low expression level when expressed as a recombinant in its wild form, can be efficiently expressed in larger amounts as a recombinant protein by expressing it in the form of a fusion protein of hNT-4 and HSA.

In addition, the expression level of hNT-3-HSA was 12 times higher than that of wild-type hNT-3. Wild-type hNT-3 is difficult to mass-produce due to its low expression level when expressed as a recombinant form, but by expressing it in the form of a fusion protein of hNT-3 and HSA, it was found that more hNT-3 could be efficiently expressed as a recombinant protein.

Next, the electrophoretic image of SDS-PAGE obtained in Example 30 is shown in Figure 29. The results of SDS-PAGE showed that hBDNF-HSA and HSA-hBDNF were expressed at higher levels than wild-type hBDNF, hNGF-HSA and HSA-hNGF were expressed at higher levels than wild-type hNGF, hNT-4-HSA and HSA-hNT-4 were expressed at higher levels than wild-type hNT-4, and hNT-3-HSA and HSA-hNT-3 were expressed at higher levels than wild-type hNT-3, which correspond to the expression levels (concentrations) shown in Figure 28 and Table 8. Human neurotrophic factor, which is expressed in low levels when expressed as a recombinant in its wild form and is difficult to mass-produce, was found to be able to be efficiently expressed in greater amounts as a recombinant protein by expressing it in the form of a fusion protein of HSA and human neurotrophic factor.

Next, the electrophoretic images of the Western blotting obtained in Example 31 are shown in Figure 30. The results of the Western blotting showed that hBDNF-HSA and HSA-hBDNF were expressed at higher levels than wild-type hBDNF, hNGF-HSA and HSA-hNGF were expressed at higher levels than wild-type hNGF, hNT-4-HSA and HSA-hNT-4 were expressed at higher levels than wild-type hNT-4, and hNT-3-HSA and HSA-hNT-3 were expressed at higher levels than wild-type hNT-3, which corresponded to the expression levels (concentrations) shown in Figure 28 and Table 8. However, for HSA-hBDNF, HSA-hNGF, HSA-hNT-4, and HSA-hNT-3, bands that were cleaved midway and detected as single mature human neurotrophic factors were also observed. Human neurotrophic factor is difficult to mass-produce because the expression level is low when expressed as a recombinant wild type. However, by expressing it in the form of a fusion protein of HSA and human neurotrophic factor, it was found that a larger amount of human neurotrophic factor can be efficiently expressed as a recombinant protein.

The above results indicate that when producing human neurotrophic factor as a recombinant protein, a larger number of molecules of human neurotrophic factor can be obtained by producing the human neurotrophic factor in the form of a fusion protein of human neurotrophic factor and HSA. In other words, a method for producing recombinant human neurotrophic factor in which human neurotrophic factor is expressed in the form of a fusion protein of human neurotrophic factor and HSA can be said to be an extremely effective means for producing large quantities of recombinant human neurotrophic factor.

According to the present invention, for example, proteins that are difficult to produce as recombinant proteins can be efficiently and industrially produced by expressing them as recombinant proteins in the form of fusion proteins with SA.

SEQ ID NO: 1: An example of the amino acid sequence of wild-type hGALC SEQ ID NO: 2: An example of a base sequence encoding wild-type hGALC, synthetic sequence SEQ ID NO: 3: An example of an amino acid sequence of wild-type HSA SEQ ID NO: 4: An example of a base sequence encoding wild-type HSA, synthetic sequence SEQ ID NO: 5: An example of an amino acid sequence of HSA-hGALC SEQ ID NO: 6: An example of a base sequence encoding HSA-hGALC, synthetic sequence SEQ ID NO: 7: An example of an amino acid sequence of hGALC-HSA SEQ ID NO: 8: An example of a base sequence encoding hGALC-HSA, synthetic sequence SEQ ID NO: 9: Example of an amino acid sequence of a linker 1
SEQ ID NO: 10: Example 2 of the amino acid sequence of the linker
SEQ ID NO: 11: Example 3 of the amino acid sequence of the linker
SEQ ID NO:12: Amino acid sequence of human serum albumin Redhill SEQ ID NO:13: Amino acid sequence of mutant human serum albumin (HSA-A320T) SEQ ID NO:14: An example of an amino acid sequence of wild-type mGALC SEQ ID NO:15: An example of a base sequence encoding wild-type mGALC, synthetic sequence SEQ ID NO:16: An example of an amino acid sequence of wild-type MSA SEQ ID NO:17: An example of a base sequence encoding wild-type MSA, synthetic sequence SEQ ID NO:18: An example of an amino acid sequence of MSA-mGALC SEQ ID NO:19: An example of a base sequence encoding MSA-mGALC, synthetic sequence SEQ ID NO:20: An example of an amino acid sequence of mGALC-MSA SEQ ID NO:21: An example of a base sequence encoding mGALC-MSA, synthetic sequence SEQ ID NO:22: Amino acid sequence of human transferrin receptor SEQ ID NO:23: Amino acid sequence of light chain of anti-hTfR antibody SEQ ID NO:24: An example of amino acid sequence of wild-type hIL-10 SEQ ID NO:25: Amino acid sequence of Fab heavy chain of anti-hTfR antibody SEQ ID NO:26: pCI Insert F3 primer, synthetic sequence SEQ ID NO:27: pCI Insert R3 primer, synthetic sequence SEQ ID NO:28: Amino acid sequence of anti-hTfR antibody Fab heavy chain-HSA-hGALC SEQ ID NO:29: Nucleotide sequence encoding anti-hTfR antibody Fab heavy chain-HSA-hGALC, synthetic sequence SEQ ID NO:30: Amino acid sequence of HSA-hGALC-anti-hTfR antibody Fab heavy chain SEQ ID NO:31: Nucleotide sequence encoding HSA-hGALC-anti-hTfR antibody Fab heavy chain, synthetic sequence SEQ ID NO:32: Amino acid sequence of anti-hTfR antibody Fab heavy chain-hGALC-HSA SEQ ID NO:33: Anti-hTfR antibody SEQ ID NO:34: Amino acid sequence of hGALC-HSA-anti-hTfR antibody Fab heavy chain SEQ ID NO:35: Base sequence encoding hGALC-HSA-anti-hTfR antibody Fab heavy chain, synthetic sequence SEQ ID NO:36: Base sequence encoding anti-hTfR antibody light chain, synthetic sequence SEQ ID NO:37: An example of the amino acid sequence of wild-type hGBA SEQ ID NO:38: An example of the base sequence encoding wild-type hGBA SEQ ID NO:39: An example of the amino acid sequence of HSA-hGBA No. 40: An example of a base sequence encoding HSA-hGBA, synthetic sequence No. 41: An example of an amino acid sequence of hGBA-HSA No. 42: An example of a base sequence encoding hGBA-HSA, synthetic sequence No. 43: An example of an amino acid sequence of wild-type mGBA No. 44: An example of a base sequence encoding wild-type mGBA No. 45: An example of an amino acid sequence of MSA-mGBA No. 46: An example of a base sequence encoding MSA-mGBA, synthetic sequence No. 47: An example of an amino acid sequence of mGBA-MSA No. 48: An example of a base sequence encoding mGBA-MSA, synthetic sequence No. 49: An example of a base sequence encoding wild-type hIL-10, synthetic sequence No. 50: An example of an amino acid sequence of HSA-hIL-10 No. 51: An example of a base sequence encoding HSA-hIL-10, synthetic sequence No. 52: An example of an amino acid sequence of hIL-10-HSA No. 53: An example of a base sequence encoding hIL-10-HSA, synthetic sequence No. 54: An example of an amino acid sequence of HSA-hIL-10 2
SEQ ID NO: 55: Example 2 of the amino acid sequence of hIL-10-HSA
SEQ ID NO: 56: An example of the amino acid sequence of HSA-hIL-10 3
SEQ ID NO: 57: An example of the amino acid sequence of hIL-10-HSA 3
SEQ ID NO: 58: An example of the amino acid sequence of HSA-hIL-10 4
SEQ ID NO: 59: An example of the amino acid sequence of hIL-10-HSA 4
SEQ ID NO:60: An example of an amino acid sequence of wild-type hBDNF SEQ ID NO:61: An example of a base sequence encoding wild-type hBDNF, synthetic sequence SEQ ID NO:62: An example of an amino acid sequence of wild-type hNGF SEQ ID NO:63: An example of a base sequence encoding wild-type hNGF, synthetic sequence SEQ ID NO:64: An example of an amino acid sequence of wild-type hNT-3 SEQ ID NO:65: An example of a base sequence encoding wild-type hNT-3, synthetic sequence SEQ ID NO:66: An example of an amino acid sequence of wild-type hNT-4 SEQ ID NO:67: An example of a base sequence encoding wild-type hNT-4, synthetic sequence SEQ ID NO:68: An example of an amino acid sequence of HSA-hBDNF SEQ ID NO:69: An example of a base sequence encoding HSA-hBDNF, synthetic sequence SEQ ID NO:70: An example of an amino acid sequence of HSA-hNGF SEQ ID NO:71: An example of a base sequence encoding HSA-hNGF, synthetic sequence SEQ ID NO:72: An example of an amino acid sequence of HSA-hNT-3 SEQ ID NO:73: An example of a base sequence encoding HSA-hNT-3, synthetic sequence SEQ ID NO: 74: An example of an amino acid sequence of HSA-hNT-4 SEQ ID NO: 75: An example of a base sequence encoding HSA-hNT-4, synthetic sequence SEQ ID NO: 76: An example of an amino acid sequence of hBDNF-HSA SEQ ID NO: 77: An example of a base sequence encoding hBDNF-HSA, synthetic sequence SEQ ID NO: 78: An example of an amino acid sequence of hNGF-HSA SEQ ID NO: 79: An example of a base sequence encoding hNGF-HSA, synthetic sequence SEQ ID NO: 80: An example of an amino acid sequence of hNT-3-HSA SEQ ID NO: 81: An example of a base sequence encoding hNT-3-HSA, synthetic sequence SEQ ID NO: 82: An example of an amino acid sequence of hNT-4-HSA SEQ ID NO: 83: An example of a base sequence encoding hNT-4-HSA, synthetic sequence SEQ ID NO: 84: An example of an amino acid sequence of wild-type hBDNF (pro-form) SEQ ID NO: 85: An example of an amino acid sequence of HSA-hBDNF 2
SEQ ID NO: 86: Example 2 of the amino acid sequence of hBDNF-HSA
SEQ ID NO: 87: An example of the amino acid sequence of wild-type hNGF (pro-form) SEQ ID NO: 88: An example of the amino acid sequence of HSA-hNGF 2
SEQ ID NO: 89: Example 2 of the amino acid sequence of hNGF-HSA
SEQ ID NO: 90: An example of the amino acid sequence of wild-type hNT-3 (pro-form) SEQ ID NO: 91: An example of the amino acid sequence of HSA-hNT-3 2
SEQ ID NO: 92: Example 2 of the amino acid sequence of hNT-3-HSA
SEQ ID NO: 93: An example of the amino acid sequence of wild-type hNT-4 (pro-form) SEQ ID NO: 94: An example of the amino acid sequence of HSA-hNT-4 2
SEQ ID NO: 95: Example 2 of the amino acid sequence of hNT-4-HSA
SEQ ID NO: 96: Amino acid sequence of the light chain CDR1 of the anti-hTfR antibody SEQ ID NO: 97: Amino acid sequence of the light chain CDR2 of the anti-hTfR antibody SEQ ID NO: 98: Amino acid sequence of the light chain CDR3 of the anti-hTfR antibody SEQ ID NO: 99: Amino acid sequence of the heavy chain CDR1 of the anti-hTfR antibody
SEQ ID NO: 100: Amino acid sequence of the heavy chain CDR2 of anti-hTfR antibody 1
SEQ ID NO: 101: Amino acid sequence of the heavy chain CDR3 of anti-hTfR antibody 1
SEQ ID NO: 102: Amino acid sequence 2 of heavy chain CDR1 of anti-hTfR antibody
SEQ ID NO: 103: Amino acid sequence 2 of the heavy chain CDR2 of anti-hTfR antibody
SEQ ID NO: 104: Amino acid sequence 2 of the heavy chain CDR3 of anti-hTfR antibody
SEQ ID NO: 105: Amino acid sequence of CDR1 of hTfR affinity peptide 1
SEQ ID NO: 106: Amino acid sequence 2 of CDR1 of hTfR affinity peptide
SEQ ID NO: 107: Amino acid sequence of CDR2 of hTfR affinity peptide 1
SEQ ID NO: 108: Amino acid sequence 2 of CDR2 of hTfR affinity peptide
SEQ ID NO: 109: Amino acid sequence of CDR3 of hTfR affinity peptide 1
SEQ ID NO: 110: Amino acid sequence 2 of CDR3 of hTfR affinity peptide
SEQ ID NO: 111: Amino acid sequence 3 of CDR2 of hTfR affinity peptide
SEQ ID NO: 112: Amino acid sequence 4 of CDR2 of hTfR affinity peptide
SEQ ID NO:113: Nucleotide sequence of the first inverted terminal repeat (first ITR) of AAV of serotype 2, wild type SEQ ID NO:114: Nucleotide sequence of the first inverted terminal repeat (second ITR) of AAV of serotype 2, wild type SEQ ID NO:115: A preferred example of the nucleotide sequence of the first inverted terminal repeat (first ITR), synthetic sequence SEQ ID NO:116: A preferred example of the nucleotide sequence of the second inverted terminal repeat (second ITR), synthetic sequence SEQ ID NO:117: A preferred example of the nucleotide sequence of the first long terminal repeat (first LTR), synthetic sequence SEQ ID NO:118: A preferred example of the nucleotide sequence of the second long terminal repeat (second LTR), synthetic sequence SEQ ID NO:119: Nucleotide sequence of the leader of the Sendai virus genome SEQ ID NO:120: Nucleotide sequence of the trailer of the Sendai virus genome SEQ ID NO:121: Mouse alpha-fetoprotein enhancer/mouse albumin enhancer SEQ ID NO:122: Nucleotide sequence of chicken β-actin/MVM chimeric intron, synthetic sequence SEQ ID NO:123: Nucleotide sequence including the Rep region of AAV2, synthetic sequence SEQ ID NO:124: Nucleotide sequence of the Cap region of AAV8 SEQ ID NO:125: Amino acid sequence of mutant mouse serum albumin (MSA-A320T) SEQ ID NO:126: An example of the amino acid sequence of wild-type mIL-10 SEQ ID NO:127: An example of the base sequence encoding wild-type mIL-10, synthetic sequence SEQ ID NO:128: An example of the amino acid sequence of mIL-10-MSA SEQ ID NO:129: An example of the base sequence encoding mIL-10-MSA, synthetic sequence SEQ ID NO:130: An example of the amino acid sequence of MSA-mIL-10 SEQ ID NO:131: An example of the base sequence encoding MSA-mIL-10, synthetic sequence SEQ ID NO:132: Amino acid sequence of wild-type hBDNF with His6 added SEQ ID NO:133: An example of a base sequence encoding wild-type hBDNF with His6 added, synthetic sequence SEQ ID NO:134: Amino acid sequence of wild-type hNGF with His6 added SEQ ID NO:135: An example of a base sequence encoding wild-type hNGF with His6 added, synthetic sequence SEQ ID NO:136: Amino acid sequence of wild-type hNT-4 with His6 added SEQ ID NO:137: An example of a base sequence encoding wild-type hNT-4 with His6 added, synthetic sequence SEQ ID NO:138: Amino acid sequence of wild-type hNT-3 with His6 added SEQ ID NO:139: An example of a base sequence encoding wild-type hNT-3 with His6 added, synthetic sequence SEQ ID NO:140: Amino acid sequence of wild-type HSA with His6 added SEQ ID NO:141: An example of a base sequence encoding wild-type HSA with His6 added An example of a base sequence to be downloaded, synthetic sequence SEQ ID NO:142: forward primer 1, synthetic sequence SEQ ID NO:143: forward primer 2, synthetic sequence SEQ ID NO:144: forward primer 3, synthetic sequence SEQ ID NO:145: forward primer 4, synthetic sequence SEQ ID NO:146: forward primer 5, synthetic sequence SEQ ID NO:147: reverse primer, synthetic sequence SEQ ID NO:148: amino acid sequence of hBDNF-HSA SEQ ID NO:149: amino acid sequence of hNGF-HSA SEQ ID NO:150: amino acid sequence of hNT-4-HSA SEQ ID NO:151: amino acid sequence of hNT-3-HSA SEQ ID NO:152: amino acid sequence of HSA-hBDNF SEQ ID NO:153: amino acid sequence of HSA-hNGF SEQ ID NO:154: amino acid sequence of HSA-hNT-4 SEQ ID NO:155: amino acid sequence of HSA-hNT-3

Claims

A fusion protein comprising a lysosomal enzyme and serum albumin (SA).
The fusion protein of claim 1, wherein the lysosomal enzyme is a human lysosomal enzyme.
The fusion protein according to claim 1 or 2, wherein the SA is human serum albumin (HSA).
The fusion protein according to any one of claims 1 to 3, wherein the lysosomal enzyme is human galactosylceramidase (hGALC) having 80% or more identity to wild-type human galactosylceramidase having the amino acid sequence shown in SEQ ID NO:1, and the SA is human serum albumin (HSA) having 80% or more identity to wild-type human serum albumin having the amino acid sequence shown in SEQ ID NO:3.
The fusion protein according to claim 4, wherein the hGALC has 90% or more identity to wild-type hGALC having the amino acid sequence shown in SEQ ID NO:1, and the HSA has 90% or more identity to wild-type HSA having the amino acid sequence shown in SEQ ID NO:3.
The fusion protein according to claim 4, wherein the hGALC comprises an amino acid sequence in which 1 to 10 amino acids have been substituted, deleted and/or added to the amino acid sequence of wild-type hGALC shown in SEQ ID NO:1.
The fusion protein according to claim 4, wherein the hGALC comprises an amino acid sequence in which 1 to 5 amino acids have been substituted, deleted and/or added to the amino acid sequence of wild-type hGALC shown in SEQ ID NO:1.
The fusion protein according to claim 4, wherein the hGALC comprises an amino acid sequence in which 1 to 3 amino acids have been substituted, deleted and/or added to the amino acid sequence of wild-type hGALC shown in SEQ ID NO:1.
The fusion protein according to claim 4, wherein the hGALC comprises an amino acid sequence in which one amino acid has been substituted with respect to the amino acid sequence of wild-type hGALC shown in SEQ ID NO:1.
The fusion protein according to claim 9, wherein the amino acid substitution is within an amino acid family in which the side chain is an amino acid that can be hydroxylated.
The fusion protein according to any one of claims 4 to 10, wherein the HSA comprises an amino acid sequence in which 1 to 10 amino acids have been substituted, deleted and/or added to the amino acid sequence of wild-type HSA shown in SEQ ID NO:3.
The fusion protein according to any one of claims 4 to 10, wherein the HSA comprises an amino acid sequence in which 1 to 5 amino acids have been substituted, deleted and/or added to the amino acid sequence of wild-type HSA shown in SEQ ID NO:3.
The fusion protein according to any one of claims 4 to 10, wherein the HSA comprises an amino acid sequence in which 1 to 3 amino acids have been substituted, deleted and/or added to the amino acid sequence of wild-type HSA shown in SEQ ID NO:3.
The fusion protein according to claim 4, wherein the hGALC comprises the amino acid sequence of wild-type hGALC shown in SEQ ID NO:1, and the HSA comprises the amino acid sequence of wild-type human serum albumin shown in SEQ ID NO:3.
The fusion protein according to claim 4, wherein the hGALC comprises the amino acid sequence of wild-type hGALC shown in SEQ ID NO:1, and the HSA comprises the amino acid sequence of wild-type human serum albumin shown in SEQ ID NO:12.
The fusion protein according to claim 4, wherein the hGALC comprises the amino acid sequence of wild-type hGALC shown in SEQ ID NO:1, and the HSA comprises the amino acid sequence of wild-type human serum albumin shown in SEQ ID NO:13.
The fusion protein according to any one of claims 4 to 16, in which the HSA is bound to the C-terminus of the hGALC directly or via a linker.
The fusion protein according to any one of claims 4 to 16, in which the hGALC is bound to the C-terminus of the HSA directly or via a linker.
The fusion protein according to claim 17 or 18, wherein the linker is a peptide chain consisting of 1 to 150 amino acids.
The fusion protein according to claim 19, wherein the linker comprises an amino acid sequence selected from the group consisting of the following (a) to (g):
(a) Gly;
(b) Ser;
(c) GlySer;
(d) GlyGlySer;
(e) the amino acid sequence set forth in SEQ ID NO:9;
(f) the amino acid sequence set forth in SEQ ID NO: 10; and
(g) The amino acid sequence shown in SEQ ID NO:11.
The fusion protein according to claim 19, wherein the linker comprises an amino acid sequence in which an amino acid sequence selected from the group consisting of the following (a) to (g) is repeated 2 to 10 times:
(a) Gly;
(b) Ser;
(c) GlySer;
(d) GlyGlySer;
(e) the amino acid sequence set forth in SEQ ID NO:9;
(f) the amino acid sequence set forth in SEQ ID NO: 10; and
(g) The amino acid sequence shown in SEQ ID NO:11.
The fusion protein according to claim 19, wherein the linker comprises an amino acid sequence in which an amino acid sequence selected from the group consisting of the following (a) to (g) is repeated 2 to 6 times:
(a) Gly;
(b) Ser;
(c) GlySer;
(d) GlyGlySer;
(e) the amino acid sequence set forth in SEQ ID NO:9;
(f) the amino acid sequence set forth in SEQ ID NO: 10; and
(g) The amino acid sequence shown in SEQ ID NO:11.
The fusion protein according to claim 19, wherein the linker comprises an amino acid sequence in which an amino acid sequence selected from the group consisting of the following (a) to (g) is repeated 3 to 5 times:
(a) Gly;
(b) Ser;
(c) GlySer;
(d) GlyGlySer;
(e) the amino acid sequence set forth in SEQ ID NO:9;
(f) the amino acid sequence set forth in SEQ ID NO: 10; and
(g) The amino acid sequence shown in SEQ ID NO:11.
The fusion protein according to claim 19, wherein the linker consists of an amino acid sequence represented by Gly Ser.
The fusion protein according to claim 18, comprising an amino acid sequence having 80% or more identity to the amino acid sequence shown in SEQ ID NO:5.
The fusion protein according to claim 18, comprising an amino acid sequence having 90% or more identity to the amino acid sequence shown in SEQ ID NO:5.
The fusion protein according to claim 26, which comprises an amino acid sequence in which 1 to 10 amino acids have been substituted, deleted and/or added to the amino acid sequence shown in SEQ ID NO:5.
The fusion protein according to claim 26, which comprises an amino acid sequence in which 1 to 5 amino acids have been substituted, deleted and/or added to the amino acid sequence shown in SEQ ID NO:5.
The fusion protein according to claim 26, which comprises an amino acid sequence in which 1 to 3 amino acids have been substituted, deleted and/or added to the amino acid sequence shown in SEQ ID NO:5.
The fusion protein according to claim 18, comprising the amino acid sequence shown in SEQ ID NO:5.
The fusion protein according to claim 17, comprising an amino acid sequence having 80% or more identity to the amino acid sequence shown in SEQ ID NO:7.
The fusion protein according to claim 17, comprising an amino acid sequence having 90% or more identity to the amino acid sequence shown in SEQ ID NO:7.
The fusion protein according to claim 32, which comprises an amino acid sequence in which 1 to 10 amino acids have been substituted, deleted and/or added to the amino acid sequence shown in SEQ ID NO:7.
The fusion protein according to claim 32, which comprises an amino acid sequence in which 1 to 5 amino acids have been substituted, deleted and/or added to the amino acid sequence shown in SEQ ID NO:7.
The fusion protein according to claim 32, which comprises an amino acid sequence in which 1 to 3 amino acids have been substituted, deleted and/or added to the amino acid sequence shown in SEQ ID NO:7.
The fusion protein according to claim 17, comprising the amino acid sequence shown in SEQ ID NO:7.
The fusion protein according to any one of claims 4 to 36, which has a specific activity of 10% or more compared to the specific activity of normal wild-type hGALC.
The fusion protein according to any one of claims 1 to 3, wherein the lysosomal enzyme is human glucocerebrosidase (hGBA) having 80% or more identity to wild-type human glucocerebrosidase having the amino acid sequence shown in SEQ ID NO: 37, and the SA is human serum albumin (HSA) having 80% or more identity to wild-type human serum albumin having the amino acid sequence shown in SEQ ID NO: 3.
The fusion protein according to claim 38, wherein the hGBA has 90% or more identity to wild-type hGBA having the amino acid sequence shown in SEQ ID NO:37, and the HSA has 90% or more identity to wild-type HSA having the amino acid sequence shown in SEQ ID NO:3.
The fusion protein according to claim 38, wherein the hGBA comprises an amino acid sequence in which 1 to 10 amino acids have been substituted, deleted and/or added to the amino acid sequence of wild-type hGBA shown in SEQ ID NO:37.
The fusion protein according to claim 38, wherein the hGBA comprises an amino acid sequence in which 1 to 5 amino acids have been substituted, deleted and/or added to the amino acid sequence of wild-type hGBA shown in SEQ ID NO:37.
The fusion protein according to claim 38, wherein the hGBA comprises an amino acid sequence in which 1 to 3 amino acids have been substituted, deleted and/or added to the amino acid sequence of wild-type hGBA shown in SEQ ID NO:37.
The fusion protein according to claim 38, wherein the hGBA comprises an amino acid sequence in which one amino acid has been substituted with respect to the amino acid sequence of wild-type hGBA shown in SEQ ID NO:37.
The fusion protein of claim 43, wherein the amino acid substitution is within an amino acid family whose side chains can be hydroxylated.
The fusion protein according to any one of claims 38 to 44, wherein the HSA comprises an amino acid sequence in which 1 to 10 amino acids have been substituted, deleted, or/and added to the amino acid sequence of wild-type HSA shown in SEQ ID NO:3.
The fusion protein according to any one of claims 38 to 44, wherein the HSA comprises an amino acid sequence in which 1 to 5 amino acids have been substituted, deleted and/or added to the amino acid sequence of wild-type HSA shown in SEQ ID NO:3.
The fusion protein according to any one of claims 38 to 44, wherein the HSA comprises an amino acid sequence in which 1 to 3 amino acids have been substituted, deleted and/or added to the amino acid sequence of wild-type HSA shown in SEQ ID NO:3.
The fusion protein of claim 38, wherein the hGBA comprises the amino acid sequence of wild-type hGBA shown in SEQ ID NO:37, and the HSA comprises the amino acid sequence of wild-type HSA shown in SEQ ID NO:3.
The fusion protein of claim 38, wherein the hGBA comprises the amino acid sequence of wild-type hGBA shown in SEQ ID NO:37, and the HSA comprises the amino acid sequence of wild-type HSA shown in SEQ ID NO:12.
The fusion protein of claim 38, wherein the hGBA comprises the amino acid sequence of wild-type hGBA shown in SEQ ID NO:37, and the HSA comprises the amino acid sequence of wild-type HSA shown in SEQ ID NO:13.
The fusion protein according to any one of claims 38 to 50, in which the HSA is bound to the C-terminus of the hGBA directly or via a linker.
The fusion protein according to any one of claims 38 to 50, in which the hGBA is bound to the C-terminus of the HSA directly or via a linker.
The fusion protein according to claim 51 or 52, wherein the linker is a peptide chain consisting of 1 to 150 amino acids.
The fusion protein of claim 53, wherein the linker comprises an amino acid sequence selected from the group consisting of:
(a) Gly;
(b) Ser;
(c) GlySer;
(d) GlyGlySer;
(e) the amino acid sequence set forth in SEQ ID NO:9;
(f) the amino acid sequence set forth in SEQ ID NO: 10; and
(g) The amino acid sequence shown in SEQ ID NO:11.
The fusion protein according to claim 53, wherein the linker comprises an amino acid sequence in which an amino acid sequence selected from the group consisting of the following (a) to (g) is repeated 2 to 10 times:
(a) Gly;
(b) Ser;
(c) GlySer;
(d) GlyGlySer;
(e) the amino acid sequence set forth in SEQ ID NO:9;
(f) the amino acid sequence set forth in SEQ ID NO: 10; and
(g) The amino acid sequence shown in SEQ ID NO:11.
The fusion protein according to claim 53, wherein the linker comprises an amino acid sequence in which an amino acid sequence selected from the group consisting of the following (a) to (g) is repeated 2 to 6 times:
(a) Gly;
(b) Ser;
(c) GlySer;
(d) GlyGlySer;
(e) the amino acid sequence set forth in SEQ ID NO:9;
(f) the amino acid sequence set forth in SEQ ID NO: 10; and
(g) The amino acid sequence shown in SEQ ID NO:11.
The fusion protein according to claim 53, wherein the linker comprises an amino acid sequence in which an amino acid sequence selected from the group consisting of the following (a) to (g) is repeated 3 to 5 times:
(a) Gly;
(b) Ser;
(c) GlySer;
(d) GlyGlySer;
(e) the amino acid sequence set forth in SEQ ID NO:9;
(f) the amino acid sequence set forth in SEQ ID NO: 10; and
(g) The amino acid sequence shown in SEQ ID NO:11.
The fusion protein according to claim 53, wherein the linker consists of an amino acid sequence represented by Gly Ser.
The fusion protein according to claim 52, comprising an amino acid sequence having 80% or more identity to the amino acid sequence shown in SEQ ID NO:39.
The fusion protein according to claim 52, comprising an amino acid sequence having 90% or more identity to the amino acid sequence shown in SEQ ID NO:39.
The fusion protein according to claim 60, which comprises an amino acid sequence in which 1 to 10 amino acids have been substituted, deleted and/or added to the amino acid sequence shown in SEQ ID NO:39.
The fusion protein according to claim 60, which comprises an amino acid sequence in which 1 to 5 amino acids have been substituted, deleted and/or added to the amino acid sequence shown in SEQ ID NO:39.
The fusion protein according to claim 60, which comprises an amino acid sequence in which 1 to 3 amino acids have been substituted, deleted and/or added to the amino acid sequence shown in SEQ ID NO:39.
The fusion protein of claim 51, comprising the amino acid sequence shown in SEQ ID NO:41.
The fusion protein according to claim 51, comprising an amino acid sequence having 80% or more identity to the amino acid sequence shown in SEQ ID NO:41.
The fusion protein according to claim 51, comprising an amino acid sequence having 90% or more identity to the amino acid sequence shown in SEQ ID NO:41.
The fusion protein according to claim 66, which comprises an amino acid sequence in which 1 to 10 amino acids have been substituted, deleted and/or added to the amino acid sequence shown in SEQ ID NO:41.
The fusion protein according to claim 66, which comprises an amino acid sequence in which 1 to 5 amino acids have been substituted, deleted and/or added to the amino acid sequence shown in SEQ ID NO:41.
The fusion protein according to claim 66, which comprises an amino acid sequence in which 1 to 3 amino acids have been substituted, deleted and/or added to the amino acid sequence shown in SEQ ID NO:41.
The fusion protein of claim 51, comprising the amino acid sequence shown in SEQ ID NO:41.
The fusion protein according to any one of claims 38 to 70, which has a specific activity of 10% or more compared to the specific activity of normal wild-type hGBA.
DNA comprising a gene encoding the fusion protein according to any one of claims 1 to 71.
An expression vector comprising the DNA of claim 72.
A mammalian cell transformed with the expression vector of claim 73.
A method for producing a fusion protein, comprising the step of culturing the mammalian cell according to claim 74 in a serum-free medium.
A conjugate of the fusion protein according to any one of claims 1 to 71 and an antibody, in which the antibody binds to a receptor on cerebrovascular endothelial cells, thereby enabling the fusion protein to pass through the blood-brain barrier (BBB).
The conjugate of claim 76, wherein the receptor on the cerebrovascular endothelial cell is selected from the group consisting of an insulin receptor, a transferrin receptor, a leptin receptor, a lipoprotein receptor, and an IGF receptor.
The conjugate of claim 76, wherein the receptor on cerebrovascular endothelial cells is a transferrin receptor.
79. The conjugate of any of claims 76 to 78, wherein the antibody is a Fab antibody, an F(ab') 2 antibody, an F(ab') antibody, a single domain antibody, a single chain antibody, or an Fc antibody.
The conjugate according to any one of claims 76 to 79, wherein the fusion protein is bound to either the C-terminus or the N-terminus of the light chain of the antibody.
The conjugate according to any one of claims 76 to 79, wherein the fusion protein is bound to either the C-terminus or the N-terminus of the heavy chain of the antibody.
The conjugate according to any one of claims 76 to 81, wherein the fusion protein is bound to either the C-terminal or N-terminal side of the light chain of the antibody, or to either the C-terminal or N-terminal side of the heavy chain, via a linker sequence.
The conjugate according to claim 82, wherein the linker sequence consists of 1 to 50 amino acid residues.
The conjugate according to claim 83, wherein the linker sequence comprises an amino acid sequence selected from the group consisting of one glycine, one serine, the amino acid sequence Gly-Ser, the amino acid sequence Ser-Ser, the amino acid sequence Gly-Gly-Ser, the amino acid sequence of SEQ ID NO: 9, the amino acid sequence of SEQ ID NO: 10, the amino acid sequence of SEQ ID NO: 11, and an amino acid sequence consisting of 1 to 10 consecutive amino acids of these amino acid sequences.
DNA comprising a gene encoding the conjugate of any one of claims 76 to 84.
An expression vector comprising the DNA of claim 85.
A mammalian cell transformed with the expression vector of claim 86.
A method for producing a conjugate of an antibody and a fusion protein of a physiologically active protein and SA, comprising the step of culturing the mammalian cell according to claim 87 in a serum-free medium.