CN114835815A - Monoclonal antibody for resisting pepsinogen I as well as preparation method and application thereof - Google Patents

Abstract

The invention provides a monoclonal antibody for resisting pepsinogen I, a preparation method and application thereof, wherein the monoclonal antibody comprises the following components: antibody 3D9 and/or antibody 36a 2; the amino acid sequence of antibody 3D9 is: VH CDR1-3 is shown in SEQ ID NO.2-4 respectively; VL CDR1-3 is shown in SEQ ID NO.5-7, respectively. The amino acid sequence of antibody 36a2 is: VH CDR1-3 is shown in SEQ ID NO.10-12 respectively; VL CDR1-3 is shown in SEQ ID NO. 13-15. The antibody provided by the invention has high affinity and high specificity, and can be applied to an anti-pepsinogen I kit.

Description

Monoclonal antibody for resisting pepsinogen I as well as preparation method and application thereof

Technical Field

The invention relates to the field of biotechnology, in particular to the field of antibody and in-vitro detection. Specifically, the invention relates to an antibody for resisting pepsinogen I, a preparation method and an application thereof.

Background

Pepsinogen (pepsinogen) is synthesized by the main cells of the secretory glands and is converted into pepsin in the stomach cavity by the action of hydrochloric acid (HCl) or already active pepsin (pepsin), which decomposes the protein into fat, peptone and a small amount of polypeptides. The optimum pH for the action of this enzyme is 2, and after entering the small intestine, the enzyme activity is lost.

Pepsinogen is a precursor of pepsin, which is divided into 2 subgroups according to its biochemical properties and immunogenicity, and 1-5 components have the same immunogenicity, called pepsinogen I (PGI), and is mainly secreted by the main cells of the fundus stomach gland and the mucous neck cells; components 6 and 7 are known as pepsinogen II (PGII), which is produced in addition to secretion by the principal cells of the fundic gland and the mucous neck cells of the pyloric gland of the cardia and antrum, as well as in the upper duodenum.

The serum pepsinogen levels reflect the morphology and function of the gastric mucosa at different sites: PGI is a pointer for detecting the function of the cells of the gastric acid gland, and the PGI is increased due to the increase of gastric acid secretion, and the PGI is reduced due to the reduction of secretion or the atrophy of gastric mucosa glands; PGII is associated with greater lesion of the gastric fundus mucosa (relative to the antral mucosa), and its elevation is associated with atrophy of the gastric fundus ducts, metaplasia of the gastric epithelium or metaplasia, abnormal proliferation; progressive reduction of the PGI/II ratio correlates with progression of gastric mucosal atrophy. Thus, a combined determination of the ratio of PGI and PGII may serve as a "serological biopsy" of the mucosa of the gastric fundus gland.

The serum concentrations of PGI and PGII are changed in different degrees in various stomach diseases, but in the current domestic research on PGI antibodies, the quantity of monoclonal antibodies is small, and the antibody suitability for detecting the PGI concentration in human serum is poor.

Disclosure of Invention

The invention aims to provide a monoclonal antibody of anti-human pepsinogen I with high affinity and high specificity, which is a murine antibody with excellent properties and can specifically recognize and combine pepsinogen I in human serum.

In one aspect, the present invention provides an anti-pepsinogen I monoclonal antibody, comprising: antibody 3D9 and/or antibody 36a 2;

wherein, the amino acid sequence of the antibody 3D9 is as follows: VH CDR1 is shown in SEQ ID NO. 2; VH CDR2 is shown in SEQ ID NO. 3; VH CDR3 is shown in SEQ ID NO. 4; VL CDR1 is shown in SEQ ID NO. 5; VL CDR2 is shown in SEQ ID NO. 6; VL CDR3 is shown in SEQ ID NO. 7;

the amino acid sequence of antibody 36a2 is: VH CDR1 is shown in SEQ ID NO. 10; VH CDR2 is shown in SEQ ID NO. 11; VH CDR3 is shown in SEQ ID NO. 12; VL CDR1 is shown in SEQ ID NO. 13; VL CDR2 is shown in SEQ ID NO. 14; VL CDR3 is shown in SEQ ID NO. 15.

Further, the variable region amino acid sequence of antibody 3D9 is: the amino acid sequence of the heavy chain variable region is shown as SEQ ID NO. 8; the amino acid sequence of the light chain variable region is shown as SEQ ID NO. 9.

Further, the variable region amino acid sequence of antibody 36a2 is: the amino acid sequence of the heavy chain variable region is shown as SEQ ID NO. 16; the variable region amino acid sequence of the light chain is shown in SEQ ID NO. 17.

In a preferred embodiment, the 3 CDRs contained in the heavy chain variable region and/or the 3 CDRs contained in the light chain variable region are defined by the Chothia numbering system.

Further, the monoclonal antibody is a murine antibody, a chimeric antibody, a humanized antibody, a bispecific antibody or a multispecific antibody; the antigen binding fragment is selected from the group consisting of Fab, Fab ', (Fab') 2, Fv, disulfide linked Fv, scFv, diabody (diabody), or single domain antibody (sdAb).

Further, monoclonal antibodies also include: a heavy chain constant region (CH) of a mammalian immunoglobulin or variant 1 thereof, variant 1 having a substitution, deletion or addition of one or more amino acids compared to the sequence from which it is derived; and, a light chain constant region (CL) of a mammalian immunoglobulin or variant 2 thereof, variant 2 having conservative substitutions of up to 20 amino acids compared to the sequence from which it is derived.

In the present invention, a monoclonal antibody may include variant 3, variant 3 differing only by conservative substitutions of one or more amino acid residues as compared to the antibody from which it is derived; for example, conservative substitutions of up to 20, up to 15, up to 10, or up to 5 amino acids; or at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% sequence identity to the antibody from which it is derived, and substantially retains the above-described biological functions of the antibody from which it is derived.

Further, the heavy chain constant region of the monoclonal antibody is an IgG heavy chain constant region; the light chain constant region of the monoclonal antibody is the kappa light chain constant region.

Further, the monoclonal antibody is labeled.

The purpose of antibody labeling is to link a label to an antibody, form a multi-element compound through a specific reaction with a substance to be detected, and directly carry out microscopic observation or automatic determination on a test result by means of precise instruments such as a fluorescence microscope, a ray measuring instrument, an enzyme-labeled detector, an electron microscope, a luminescence immunoassay instrument and the like. The marking in the scheme is not particularly specified to a certain marking mode, and specifically can be enzyme marking, biotinylation marking, fluorescence marking, colloidal gold marking and the like; and are not limited herein.

In another aspect, the present invention provides a method for preparing a monoclonal antibody against pepsinogen I, comprising: culturing the host cell under conditions that allow expression of the monoclonal antibody; recovering the monoclonal antibody from the cultured host cell culture.

The monoclonal antibodies provided by the present invention can be prepared by various methods known in the art, for example, by genetic engineering recombination techniques. For example, DNA molecules encoding the heavy and light chain genes of the antibodies of the invention are obtained by chemical synthesis or PCR amplification. The resulting DNA molecule is inserted into an expression vector and then transfected into a host cell. The transfected host cells are then cultured under specific conditions and the antibodies of the invention are expressed.

The antigen binding fragments of the invention may be obtained by hydrolysis of the intact antibody molecule. Alternatively, these antigen binding fragments may be produced directly by the recombinant host cell. For example, Fab' fragments can be obtained directly from the host cell; fab 'fragments can be chemically coupled to form F (ab') 2 fragments. Furthermore, Fv, Fab or F (ab') 2 fragments can also be isolated directly from the culture medium of the recombinant host cell. In general, those of ordinary skill in the art are aware of other techniques for preparing these antigen-binding fragments.

In another aspect, the invention also provides an isolated nucleic acid molecule encoding a monoclonal antibody.

In another aspect, the invention also provides a vector comprising the isolated nucleic acid molecule described above.

Further, the vector is a cloning vector or an expression vector. In a preferred embodiment, the vector of the invention is, for example, a plasmid, cosmid, phage, or the like. In a preferred embodiment, the vector is capable of expressing the antibody in vivo in a subject, e.g., a mammal.

In another aspect, the invention also provides a host cell, including an isolated nucleic acid molecule or vector. Host cells include, but are not limited to: prokaryotic cells such as E.coli cells, eukaryotic cells such as yeast cells, insect cells, plant cells, animal cells such as mammalian cells, and the like. In a preferred embodiment, the host cell of the invention is a mammalian cell, such as CHO, including in particular CHO-K1, CHO-S and CHO DG 44.

In another aspect, the invention also provides a kit for detecting pepsinogen I, which comprises the monoclonal antibody.

In one embodiment, the kit comprises a first monoclonal antibody and a second monoclonal antibody; the first monoclonal antibody and the second monoclonal antibody are matched to detect a sample. Wherein the first monoclonal antibody comprises: VH CDR1 shown in SEQ ID NO.2, VH CDR2 shown in SEQ ID NO.3 and VH CDR3 shown in SEQ ID NO. 4; and VL CDR1 shown in SEQ ID NO.5, VL CDR2 shown in SEQ ID NO.6, and VL CDR3 shown in SEQ ID NO. 7. The second monoclonal antibody comprises: VH CDR1 shown in SEQ ID NO.10, VH CDR2 shown in SEQ ID NO.11, and VH CDR3 shown in SEQ ID NO. 12; and VL CDR1 shown in SEQ ID NO.13, VL CDR2 shown in SEQ ID NO.14, and VL CDR3 shown in SEQ ID NO. 15.

In one embodiment, the kit comprises the first mab or the second mab. The first monoclonal antibody and the second monoclonal antibody can also be used independently to detect pepsinogen I.

In another aspect, the present invention also provides a method for using the kit, comprising the following steps: diluting the tested sample by using a reagent R1, and adding a reagent R2 for reaction; then, measuring the absorbance value under the wavelength of 570nm by using a biochemical analyzer; and preparing a standard curve by using the pepsinogen I standard substance, and calculating the pepsinogen I content in the detected sample according to the standard curve and the light absorption value.

Wherein, the reagent R1 is a common buffer solution, which can be 0.05mM Tris buffer solution with pH7.4, and the preparation method is as follows: taking 6.057g of Tris; firstly, 800mL of deionized water is added, and concentrated hydrochloric acid is added to adjust the pH value to 7.4; the volume of the deionized water is up to 1L.

The reagent R2 is prepared by mixing a sensitization source 1 formed by coupling a first monoclonal antibody and latex particles and a sensitization source 2 formed by coupling a second monoclonal antibody and latex particles.

Possible principles of the kit of the invention include: when corresponding antigen exists in a sample, the sensitization source 1 formed by coupling the first monoclonal antibody with the latex particles and the sensitization source 2 formed by coupling the second monoclonal antibody with the latex particles can be combined with the antigen at the same time to generate an aggregation reaction. A single sensitizer is within the wavelength of the incident light and light can pass through. When two allergens aggregate, the transmitted light is reduced, and the degree of reduction is proportional to the aggregation of the allergens and also proportional to the amount of antigen. This allows a qualitative and quantitative analysis of pepsinogen I. The first monoclonal antibody and the second monoclonal antibody used for constructing the kit are respectively directed to different epitopes of the human pepsinogen I and have pairing detection effects.

The antibodies of the invention may be derivatized, for example, linked to another molecule. In general, derivatization of the antibody does not adversely affect its binding to pepsinogen I. Thus, the antibodies of the invention also include such derivatized forms. For example, an antibody of the invention can be functionally linked to one or more other molecular moieties, such as another antibody, a detection reagent, a pharmaceutical agent, and/or a protein or polypeptide capable of mediating the binding of the antibody or antigen-binding fragment to another molecule. In addition, the antibodies of the invention may also be derivatized with chemical groups, such as polyethylene glycol (PEG), methyl or ethyl, or sugar groups. These groups can be used to improve the biological properties of the antibody, for example to increase serum half-life.

Thus, in a preferred embodiment, the antibodies of the invention are coupled to latex particles. The antibodies of the invention may be conjugated to a detectable label, such as an enzyme, radionuclide, fluorescent dye, luminescent substance, or biotin. The detectable label of the present invention may be any substance detectable by fluorescence, spectroscopic, photochemical, biochemical, immunological, electrical, optical or chemical means. Such labels are well known in the art and examples include, but are not limited to, enzymes, radionuclides, fluorescent dyes, luminescent substances, magnetic beads, calorimetric labels such as colloidal gold or colored glass or plastic beads, and biotin for binding avidin modified with the above labels. Patents that teach the use of such markers include, but are not limited to, U.S. Pat. nos. 3,817,837; 3,850,752, respectively; 3,939,350, respectively; 3,996,345; 4,277,437; 4,275,149; and 4,366,241. Detectable labels as described above can be detected by methods known in the art. For example, radioactive labels can be detected using photographic film or scintillation calculators, and fluorescent labels can be detected using photodetectors to detect the emitted light. Enzyme labels are generally detected by providing a substrate for the enzyme and detecting the reaction product produced by the action of the enzyme on the substrate, and calorimetric labels are detected by simply visualizing the colored label. In certain embodiments, such labels can be suitable for use in immunological assays, e.g., enzyme-linked immunoassays, radioimmunoassays, fluorescent immunoassays, chemiluminescent immunoassays, and the like. In certain embodiments, detectable labels as described above may be attached to the antibodies of the invention through linkers of different lengths to reduce potential steric hindrance.

Definition of terms

In the present invention, unless otherwise specified, scientific and technical terms used herein have the meanings that are commonly understood by those skilled in the art. Also, the procedures of cell culture, biochemistry, nucleic acid chemistry, immunological laboratories and the like used herein are all conventional procedures widely used in the corresponding fields. Meanwhile, in order to better understand the present invention, the definitions and explanations of related terms are provided below.

As used herein, the term "antibody" refers to an immunoglobulin molecule that is typically composed of two pairs of polypeptide chains. Antibody light chains can be classified as kappa and lambda light chains. Heavy chains can be classified as μ, δ, γ, α or ε, and the antibody isotypes are defined as IgM, IgD, IgG, IgA, and IgE, respectively. Within the light and heavy chains, the variable and constant regions are connected by a "J" region of about 12 or more amino acids, and the heavy chain also contains a "D" region of about 3 or more amino acids. Each heavy chain consists of a heavy chain variable region (VH) and a heavy chain constant region (CH). The heavy chain constant region consists of 3 domains (CH1, CH2, and CH 3). Each light chain consists of a light chain variable region (VL) and a light chain constant region (CL). The light chain constant region consists of one domain CL. The constant domains are not directly involved in binding of the antibody to the antigen, but exhibit a variety of effector functions, such as may mediate binding of the immunoglobulin to host tissues or factors, including various cells of the immune system (e.g., effector cells) and the first component of the classical complement system (C1 q). The VH and VL regions can also be subdivided into regions of high denaturation, called Complementarity Determining Regions (CDRs), interspersed with regions that are more conserved, called Framework Regions (FRs). Each VH and VL are composed of, in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4 are composed of 3 CDRs and 4 FRs arranged from amino terminus to carboxy terminus. The variable regions (VH and VL) of each heavy/light chain pair form the antigen-binding sites, respectively. The assignment of amino acids in each region or domain may follow Kabat, Sequences of proteins of Immunological Interest (National Institutes of health, Bethesda, Md. (1987and 1991)), or Chothia & Lesk (1987) J.mol.biol.196: 901-; chothia et al (1989) Nature 342: 878-883.

As used herein, the term "complementarity determining region" or "CDR" refers to the amino acid residues in the variable region of an antibody that are responsible for antigen binding. There are three CDRs, named CDR1, CDR2, and CDR3, in the variable regions of the heavy and light chains, respectively. The precise boundaries of these CDRs can be defined according to various numbering systems known in the art, for example, as defined in the Kabat numbering system, the Chothia numbering system, or the IMGT numbering system. For a given antibody, one skilled in the art will readily identify the CDRs defined by each numbering system. Also, the correspondence between different numbering systems is well known to those skilled in the art.

In the present invention, the CDRs contained in the antibodies of the present invention can be determined according to various numbering systems known in the art. In certain embodiments, the CDRs contained by the antibodies of the invention are preferably determined by the Kabat, Chothia, or IMGT numbering system. In certain embodiments, the CDRs contained in the antibodies of the invention are preferably determined by the Kabat numbering system.

As used herein, the term "framework region" or "FR" residues refers to those amino acid residues in the variable region of an antibody other than the CDR residues as defined above.

The term "antibody" is not limited by any particular method of producing an antibody. For example, it includes recombinant antibodies, monoclonal antibodies and polyclonal antibodies. The antibody may be of different isotypes, for example, IgG, IgA1, IgA2, IgD, IgE or IgM antibodies.

As used herein, the term "antigen-binding fragment" of an antibody refers to a polypeptide comprising a fragment of a full-length antibody that retains the ability to specifically bind to the same antigen to which the full-length antibody binds, and/or competes with the full-length antibody for specific binding to the antigen, which is also referred to as an "antigen-binding portion". See generally, Fundamental Immunology, Ch.7(Paul, W., ed., 2 nd edition, Raven Press, N.Y. (1989), which is incorporated herein by reference in its entirety for all purposes.

As used herein, the term "full-length antibody" means an antibody consisting of two "full-length heavy chains" and two "full-length light chains". Wherein "full-length heavy chain" refers to a polypeptide chain consisting of, in the N-terminal to C-terminal direction, a heavy chain variable region (VH), a heavy chain constant region CH1 domain, a Hinge Region (HR), a heavy chain constant region CH2 domain, a heavy chain constant region CH3 domain; and, when the full-length antibody is of IgE isotype, optionally further comprising a heavy chain constant region CH4 domain. Preferably, a "full-length heavy chain" is a polypeptide chain consisting of VH, CH1, HR, CH2, and CH3 in the N-terminal to C-terminal direction. A "full-length light chain" is a polypeptide chain consisting of a light chain variable region (VL) and a light chain constant region (CL) in the N-terminal to C-terminal direction. Two pairs of full length antibody chains are linked together by a disulfide bond between CL and CH1 and a disulfide bond between HR of the two full length heavy chains. The full length antibodies of the invention may be from a single species, e.g., human; chimeric antibodies or humanized antibodies are also possible. The full-length antibody of the present invention comprises two antigen-binding sites formed by VH and VL pairs, respectively, that specifically recognize/bind to the same antigen.

As used herein, the term "Fd" means an antibody fragment consisting of the VH and CH1 domains; the term "dAb fragment" means an antibody fragment consisting of a VH domain; the term "Fab fragment" means an antibody fragment consisting of the VL, VH, CL and CH1 domains; the term "F (ab') 2 fragment" means an antibody fragment comprising two Fab fragments connected by a disulfide bridge at the hinge region; the term "Fab 'fragment" means a fragment obtained by reducing the disulfide bond linking two heavy chain fragments of a F (ab') 2 fragment, consisting of one intact Fd fragment of the light and heavy chains (consisting of the VH and CH1 domains).

As used herein, the term "Fv" means an antibody fragment consisting of the VL and VH domains of a single arm of an antibody. Fv fragments are generally considered to be the smallest antibody fragments that form an entire antigen binding site. It is generally believed that the six CDRs confer antigen binding specificity on the antibody. However, even one variable region (e.g., an Fd fragment, which contains only three CDRs specific for an antigen) is capable of recognizing and binding an antigen, although its affinity may be lower than the entire binding site.

As used herein, the term "Fc" means an antibody fragment formed by disulfide bonding of the second and third constant regions of a first heavy chain and the second and third constant regions of a second heavy chain of an antibody. The Fc fragment of an antibody has a number of different functions, but is not involved in antigen binding.

As used herein, the term "scFv" refers to a single polypeptide chain comprising VL and VH domains, wherein the VL and VH are connected by a linker. Such scFv molecules can have the general structure: NH 2-VL-linker-VH-COOH or NH 2-VH-linker-VL-COOH. Suitable prior art linkers consist of repeated GGGGS amino acid sequences or variants thereof. For example, a linker having the amino acid sequence (GGGGS)4 may be used, but variants thereof may also be used, and may be used for other linkers of the present invention. In some cases, a disulfide bond may also be present between the VH and VL of the scFv.

As used herein, the term "diabody" means that its VH and VL domains are expressed on a single polypeptide chain, but that a linker is used that is too short to allow pairing between the two domains of the same chain, thereby forcing the domains to pair with the complementary domains of the other chain and generating two antigen binding sites.

As used herein, the term "single domain antibody" has the meaning commonly understood by those skilled in the art, which refers to an antibody fragment consisting of a single monomeric variable antibody domain that retains the ability to specifically bind to the same antigen to which the full-length antibody binds. Single domain antibodies are also known as nanobodies.

Each of the above antibody fragments retains the ability to specifically bind to the same antigen to which the full length antibody binds, and/or competes with the full length antibody for specific binding to the antigen.

Antigen-binding fragments of antibodies can be obtained from a given antibody using conventional techniques known to those skilled in the art, and specifically screened in the same manner as for intact antibodies.

Herein, when the term "antibody" is referred to, it includes not only intact antibodies, but also antigen-binding fragments of antibodies, unless the context clearly indicates otherwise.

As used herein, the terms "monoclonal antibody", "mAb" have the same meaning and are used interchangeably to refer to an antibody or a fragment of an antibody from a population of highly homologous antibody molecules, i.e., a population of identical antibody molecules except for natural mutations that may occur spontaneously. Monoclonal antibodies have high specificity for a single epitope on the antigen. Polyclonal antibodies are relative to monoclonal antibodies, which typically comprise at least 2 or more different antibodies that typically recognize different epitopes on an antigen. Furthermore, the modifier "monoclonal" is used merely to indicate that the antibody is characterized as being obtained from a population of highly homologous antibodies, and is not to be construed as requiring production of the antibody by any particular method.

The monoclonal antibodies of the invention can be prepared by a variety of techniques, such as hybridoma techniques, recombinant DNA techniques, or phage antibody library techniques.

Antibodies can be purified by well-known techniques, such as affinity chromatography using protein a or protein G. Subsequently or alternatively, the specific antigen or epitope thereof may be immobilized on a column and the immunospecific antibody purified by immunoaffinity chromatography.

As used herein, the term "chimeric antibody" refers to an antibody in which a portion of the light chain or/and heavy chain is derived from one antibody and another portion of the light chain or/and heavy chain is derived from another antibody, but which nevertheless retains binding activity to an antigen of interest. For example, the term "chimeric antibody" may include an antibody (e.g., a human murine chimeric antibody) in which the heavy and light chain variable regions of the antibody are from a first antibody and the heavy and light chain variable regions of the antibody are from a second antibody.

As used herein, the term "humanized antibody" refers to a non-human antibody that has been genetically engineered to have an amino acid sequence modified to increase homology to the sequence of a human antibody. Generally, all or a portion of the CDR regions of a humanized antibody are derived from a non-human antibody, and all or a portion of the non-CDR regions are derived from a human immunoglobulin. Humanized antibodies generally retain the desired properties of the donor antibody, including, but not limited to, antigen specificity, affinity, reactivity, and the like. The donor antibody may be a mouse, rat, rabbit or non-human primate antibody of the desired nature.

The chimeric antibody or humanized antibody of the present invention can be prepared based on the sequence of the murine monoclonal antibody prepared as described above. The DNA encoding the heavy and light chains can be obtained from a murine hybridoma of interest and engineered to contain non-murine immunoglobulin sequences using standard molecular biology techniques.

To prepare chimeric antibodies, the murine immunoglobulin variable region can be linked to a human immunoglobulin constant region using methods known in the art. For example, DNA encoding a VH is operably linked to another DNA molecule encoding a heavy chain constant region to obtain a full-length heavy chain gene. The sequence of the human heavy chain constant region gene is known in the art and DNA fragments containing these regions can be obtained by standard PCR amplification. The heavy chain constant region may be an IgG1, IgG2, IgG3, IgG4, IgA, IgE, IgM, or IgD constant region, but is typically preferably an IgG1 or IgG4 constant region. For example, the DNA encoding VL is operably linked to another DNA molecule encoding a light chain constant region CL to obtain a full-length light chain gene (as well as the Fab light chain gene). The sequence of the human light chain constant region gene is known in the art, and DNA fragments containing these regions can be obtained by standard PCR amplification. The light chain constant region may be a kappa or lambda constant region, but is typically preferably a kappa constant region.

To make humanized antibodies, murine CDR regions can be inserted into human framework sequences using methods known in the art. Alternatively, transgenic animals can also be used which are capable of not producing endogenous immunoglobulins after immunization and which are capable of producing a complete human antibody repertoire. For example, it has been reported that homozygous deletion of the antibody heavy chain joining region (JH) gene completely suppresses endogenous antibody production in chimeric and germline mutant mice, and then transfer of a human germline immunoglobulin gene array into the germline mutant mice results in the mice producing human antibodies upon antigen challenge. Non-limiting examples of such transgenic animals include, HuMAb mice, which contain human immunoglobulin gene miniloci encoding unrearranged human heavy (μ and γ) and kappa light chain immunoglobulin sequences, plus targeted mutations that inactivate endogenous μ and kappa chain loci; or "KM mouse TM" carrying a human heavy chain transgene and a human light chain transchromosome. Other methods of antibody humanization include phage display techniques.

As used herein, the term "specific binding" refers to a non-random binding reaction between two molecules, such as a reaction between an antibody and an antigen against which it is directed. The strength or affinity of a specific binding interaction can be represented by the equilibrium dissociation constant (KD) of the interaction. In the present invention, the term "KD" refers to the dissociation equilibrium constant of a particular antibody-antigen interaction, which is used to describe the binding affinity between an antibody and an antigen. The smaller the equilibrium dissociation constant, the more tight the antibody-antigen binding and the higher the affinity between the antibody and the antigen. In certain embodiments, an antibody that specifically binds to (or is specific for) an antigen means that the antibody has less than about 10 ^-9 M, e.g. less than about 10 ^-9 M、10 ^-10 M、10 ^-11 M or 10 ^-12 M or less binds to the antigen with an affinity (KD). Specific binding properties between two molecules can be determined using methods well known in the art, for example in a BIACORE instrument using Surface Plasmon Resonance (SPR).

As used herein, the term "identity" is used to refer to the match of sequences between two polypeptides or between two nucleic acids. When a position in both compared sequences is occupied by the same base or amino acid monomer subunit, then the molecules are identical at that position. The "percent identity" between two sequences is a function of the number of matching positions shared by the two sequences divided by the number of positions compared x 100. For example, if 6 of 10 positions of two sequences match, then the two sequences have 60% identity. For example, the DNA sequences CTGACT and CAGGTT share 50% identity (3 of the total 6 positions match). Typically, the comparison is made when the two sequences are aligned to yield maximum identity. Such alignment can be achieved using, for example, the method of Needleman et al (1970) J.Mol.biol.48: 443-. The algorithm of E.Meyers and W.Miller (Compout.appl biosci.,4:11-17(1988)) which has been incorporated into the ALIGN program (version 2.0) can also be used to determine percent identity between two amino acid sequences using a PAM120 weight residue table (weight residue table), a gap length penalty of 12, and a gap penalty of 4. Furthermore, percent identity between two amino acid sequences can be determined using the Needleman and Wunsch (J MoIBiol.48:444-453(1970)) algorithms that have been incorporated into the GAP program of the GCG software package, using either the Blossum 62 matrix or the PAM250 matrix with GAP weights of 16, 14, 12, 10, 8, 6, or 4 and length weights of 1, 2,3, 4, 5, or 6.

As used herein, the term "conservative substitution" means an amino acid substitution that does not adversely affect or alter the intended properties of the protein/polypeptide comprising the amino acid sequence. For example, conservative substitutions may be introduced by standard techniques known in the art, such as site-directed mutagenesis and PCR-mediated mutagenesis. Conservative amino acid substitutions include those in which an amino acid residue is replaced with an amino acid residue having a similar side chain, e.g., a substitution with a residue that is physically or functionally similar to the corresponding amino acid residue. Families of amino acid residues with similar side chains have been defined in the art. These families include amino acids with basic side chains, acidic side chains, uncharged polar side chains, nonpolar side chains, beta-branched side chains, and aromatic side chains. Thus, it is preferred to replace the corresponding amino acid residue with another amino acid residue from the same side chain family. Methods for identifying conservative substitutions of amino acids are well known in the art.

The twenty conventional amino acids referred to herein are written following conventional usage. In the present invention, the terms "polypeptide" and "protein" have the same meaning and are used interchangeably. Also, in the present invention, amino acids are generally represented by single-letter and three-letter abbreviations as is well known in the art. For example, alanine can be represented by A or Ala.

By adopting the technical scheme provided by the invention, the beneficial effects that can be achieved are as follows: the monoclonal antibody provided by the invention can be specifically combined with PGI protein; the double-antibody sandwich immunoturbidimetric assay method can effectively detect the content of PGI protein in human serum, has high sensitivity, the lowest limit of 10 mug/L and wide assay linearity of 10-600 mug/L, and can meet the requirement of clinical assay.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a graph of the linear range determination of PGI of example 2 of the present invention;

FIG. 2 is a graph showing the correlation between the PGI detection method and a certain brand matching reagent/detection method in example 2 of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The main reagents and apparatus of this example are shown in tables 1 and 2, respectively:

table 1: primary reagent

Table 2: the main apparatus is as follows:

name (R)	Manufacturer of the product	Model number
			Liquid transfer device	Eppendorf	/
Constant temperature incubator	PhiPHC	MCO-170AICL-PC
			Biological safety cabinet	JINAN BIOBASE BIOTECH Co.,Ltd.	BSC-1100IIA2-X
Biological microscope	Ningbo perpetual optics	N-117M
			Inverted biological microscope	Ningbo perpetual optics	XD-202
Desk type centrifuge	Luxiang instrument	TD4
			Plate washing machine	Shandong Boke	ST-96W
Enzyme-linked immunosorbent assay (ELISA) instrument	American birotang	ELX800
			Biochemical instrument	HITACHI	7180

Antigen:

the recombinant PGI protein is expressed by HEK293 cells, and the amino acid sequence is shown as SEQ ID NO. 1;

human PGI protein, from human gastric mucosa, available from Lee Biosolutions, Cat. 440-50.

Experimental animals:

Balb/C mice: SPF (specific Pathologen free) grade Balb/C mice were purchased from Shanghai Ling Biotech, Inc.

Preparing a buffer solution:

the Phosphate Buffered Saline (PBS) formulation was: NaCl, 8 g; KCl, 0.2 g; na (Na) ₂ HPO _4· 12H ₂ O，2.9g；KH ₂ PO ₄ 0.2 g; H2O constant volume to 1L

The formula of the 10 XPBST lotion is as follows: NaCl, 80 g; KCl, 2 g; na (Na) ₂ HPO ₄ ·12H ₂ O，29g；KH ₂ PO ₄ ，2g；TWEEN-20，5ml；H ₂ O constant volume is 1L

The formulation of glycine eluent with pH2.7 is as follows: glycine 1.9g, H ₂ And O is metered to 500mL, and the pH value is 2.68-2.72.

The formulation of glycine eluent with pH1.9 is as follows: glycine 1.9g, H ₂ And O is metered to 500mL, and the pH value is 1.88-1.92.

Example 1: preparation and screening of PGI monoclonal antibody

The immunogen was prepared by mixing the recombinant PGI protein (1mg/ml) with the adjuvants CFA and IFA. That is, the recombinant protein is first mixed with CFA in a volume ratio of 1:1 to serve as immunogen A, and then mixed with IFA in a volume ratio of 1:1 to serve as immunogen B. Immunogen a is the primary immunization and immunogen B is the second, third and fourth booster immunizations. Mice were immunized subcutaneously with 2 mice, and after the fourth booster immunization, tail blood was collected on day 14 and the tail blood antibody titer was evaluated by indirect ELISA.

Coating an enzyme label plate (2 mu g/mL) with PGI recombinant protein, adding 100 mu L of the enzyme label plate per well, and reacting at 4 ℃ overnight; wash plates 3 times with PBST solution, block with 5% BSA for 2h at 37 ℃; then, after washing the plate for 3 times by using a PBST solution, adding mouse tail blood which is diluted by using a 5% BSA solution in a gradient manner, and reacting for 2h at 37 ℃; the plates were then washed 3 times with PBST solution, adding 1: 20000 times diluted goat anti-mouse IgG secondary antibody labeled with HRP reacts for 1h at 37 ℃; washing the plate with PBST solution for 5 times, drying, adding 100 μ L TMB color development solution, and reacting at 37 deg.C in dark for 15 min; then 50. mu.L of stop solution (2M H) was added ₂ SO ₄ ) And after mixing, reading the OD450 value on a microplate reader. The results of the indirect ELISA evaluation of the tail blood of the mice at 14 days after immunization are shown in Table 3.

Table 3: evaluation of mouse tail blood antibody titer 14 days after four PGI immunizations

	No.1 mouse	No.2 mouse
			1/10000	2.098	1.968
1/20000	1.809	1.719
			1/40000	1.603	1.48
1/80000	1.305	1.247
			1/160000	1.012	0.972
1/320000	0.693	0.642
			1/640000	0.466	0.436
1/1280000	0.568	0.296
			NC	0.071	0.072

Note: NC is negative control, PBS.

As seen from the results, the antibody titer of PGI recombinant protein recognized by two mouse tail blood after four immunizations exceeded 1:1280000, the mice were shock immunized with PGI recombinant protein, the spleen of the mice was taken 3 days after the shock immunization, and the spleen cells were separated and cell fused with myeloma cells SP2/0-Ag 14. More than 4000 hybridoma cell colonies were generated in 96-well plates after fusionIn addition, the cell culture supernatants in the 96-well plate were evaluated by the indirect ELISA method described above, monoclonal cell lines capable of secreting monoclonal antibodies recognizing the proteins were selected, and 48 positive clones were selected from the results of the screening and subjected to the confirmation test as follows: using human PGI protein to coat the ELISA plate (2 mug/mL), adding 100 mug L per hole, reacting overnight at 4 ℃; wash plates 3 times with PBST solution, block with 5% BSA for 2h at 37 ℃; then washing the plate for 3 times by using a PBST solution, adding cell culture supernatant diluted by 50 times by using a PBS solution, and reacting for 2 hours at 37 ℃; the plates were then washed 3 times with PBST solution, adding 1: 20000 times diluted goat anti-mouse IgG secondary antibody labeled with HRP reacts for 1h at 37 ℃; washing the plate with PBST solution for 5 times, drying, adding 100 μ L TMB color development solution, and reacting at 37 deg.C in dark for 15 min; then 50. mu.L of stop solution (2M H) was added ₂ SO ₄ ) After mixing, the OD450 values were read on a microplate reader, and the results are shown in Table 4.

Table 4: confirmation of Positive clones

Clone number	1D7	2C3	2H4	3D9	3G11	4F1	4H10	5B9	6E8	7A4
											OD450	2.097	1.413	1.338	1.868	1.556	1.8	1.398	1.671	1.687	2.138
Clone number	8F9	9D8	10C10	11B12	11F3	12B3	13G9	15H5	16C7	16F8
											OD450	1.183	1.523	1.801	1.644	2.147	1.736	2.05	1.744	1.716	1.317
Clone number	17E9	18G6	19D2	19G10	20H4	21B6	21C9	22G9	24C10	24B3
											OD450	2.132	1.05	1.551	1.429	1.798	1.445	1.315	2.194	1.997	1.487
Clone number	25H5	27F9	28E9	28G10	29F11	30B7	30B9	31C3	32D11	33G1
											OD450	2.066	1.381	1.228	1.803	1.469	2.094	1.316	1.686	1.913	1.56
Clone number	34E2	35H7	36A2	36C10	37H5	38B3	40C5	40D3	NC	PC
											OD450	1.934	1.756	2.043	1.628	1.221	2.01	1.634	1.197	0.072	2.032

Note: NC is negative control, PBS; PC was a positive control, dilution of mouse serum 1/10000 No. 1.

According to the result of the positive clone rescreening in the table 4, 25 positive clones are selected to continue to carry out a sensitivity detection experiment, an enzyme label plate (2 mug/mL) is coated by human PGI protein, 100 mug L of the enzyme label plate is added into each hole, and the overnight reaction is carried out at 4 ℃; wash plates 3 times with PBST solution, block with 5% BSA for 2h at 37 ℃; then washing the plate for 3 times by using a PBST solution, adding a cell culture supernatant which is diluted by using a PBS solution in a gradient manner, and reacting for 2 hours at 37 ℃; the plates were then washed 3 times with PBST solution, adding 1: 20000 times diluted goat anti-mouse IgG secondary antibody labeled with HRP reacts for 1h at 37 ℃; washing the plate with PBST solution for 5 times, drying, adding 100 μ L TMB color development solution, and reacting at 37 deg.C in dark for 15 min; then 50. mu.L of stop solution (2M H) was added ₂ SO ₄ ) After mixing, the OD450 values were read on a microplate reader, and the results are shown in Table 5.

Table 5: results of sensitivity test

Note: NC is negative control, PBS; PC was a positive control, dilution of mouse serum 1/10000 No. 1.

According to the results in Table 5, 16 strains 1D7,3D9,4F1,5B9,10C10,11F3,13G9,17E7,22G9,24C10,25H5,30B7,32D11,34E2,36A2 and 38B3 are selected for preparing and screening purified antibodies.

Example 2: preparation of purified antibodies

1) Preparation of ascites

1D7,3D9,4F1,5B9,10C10,11F3,13G9,17E7,22G9,24C10,25H5,30B7,32D11,34E2,36A2, 3B 7,32D11,34E2Ascites preparation with 8B3 antibody, about 1X 10 each ⁶ After injecting each cell into the abdominal cavity of 3 Balb/C mice previously injected with IFA adjuvant, about 10 days later, the ascites fluid produced by each positive clone was extracted, and then centrifuged at 12000rpm for 15min at 4 ℃ to collect the supernatant for the next G protein purification.

2) Purification of mouse monoclonal antibodies

Adding 1mL of column material coupled with G protein into an empty column, washing with PBS solution, diluting 2mL of ascites with 8mL of PBS, loading on the column, and loading the flow-through liquid on the column again; then eluting with glycine eluent of pH2.7, collecting one tube per 1mL eluent (adding 100 μ L of neutralization solution in advance, wherein the components of the neutralization solution are 1M Tris-HCl, 10mM EDTA, 1.5M NaCl, pH 8.0-8.38), and collecting 5 tubes; then eluting with glycine eluent of pH1.9, collecting one tube (300 μ L of neutralizing solution is added in advance) per 1mL of eluent, and collecting 3 tubes; then, the OD280 reading was performed on each tube of eluate, the eluates with OD280 greater than 0.5 were mixed, the OD280 of the mixture was re-measured after mixing, and the antibody concentration was calculated according to a factor of 1.4: the antibody concentration was OD 280/1.4.

Example 3: screening for purified antibodies

A part of the murine monoclonal antibody after G protein purification is labeled with biotin, a labeled antibody suffix is added with-Bio, for example, a 3D9 antibody after the biotin labeling is represented by 3D9-Bio, antibody pairing screening is carried out by using a sandwich ELSIA method, an enzyme label plate (2 mu G/mL) is coated by using an unlabeled antibody, 100 mu L of the antibody is added to each well, and the reaction is carried out overnight at 4 ℃; wash the plate 3 times with PBST solution and block with 5% BSA for 1.5h at 37 ℃; after washing the plate 3 times with PBST solution, human PGI protein (2. mu.g/mL) was added and incubated at 37 ℃ for 1.5 h; after washing the plate for 3 times by using PBST solution, adding biotin labeled antibody diluted by 5% BSA solution in a gradient manner, and reacting for 1.5h at 37 ℃; washing the plate 3 times by using PBST solution, adding HRP-labeled streptavidin diluted at a ratio of 1:500, and reacting for 1h at 37 ℃; washing the plate with PBST solution for 5 times, drying, adding 100 μ L TMB color development solution, and reacting at 37 deg.C in dark for 15 min; then 50. mu.L of stop solution (2M H) was added ₂ SO ₄ ) And after mixing, reading the OD450 value on a microplate reader. Evaluation of purified antibodySome results are shown in Table 6.

Table 6: partial results of paired antibody screening by sandwich ELISA method

Note: NC is negative control, PBS.

According to the results in table 6, selecting antibodies 3D9,17E9, 36a2 for latex-enhanced immunoturbidimetric pairing screening, and pairwise coupling the antibodies 3D9,36a2,19F10 to latex particles according to different combination modes; preparing a detection reagent R2 from the coupled latex particles for subsequent detection of a calibrator, wherein the detection result is shown in Table 7;

the detection method comprises the following steps:

the detection instrument is as follows: full-automatic biochemical analyzer 7180

The analysis method comprises the following steps: two-point end point method

The reaction direction is as follows: ascending reaction

The calibration method comprises the following steps: spline

Measuring wavelength: 570nm

Measuring temperature: 37 deg.C

Calibration products: reagent R1: reagent R2 ═ 2. mu.L, 120. mu.L

Table 7: OD570nm readings of PGI detection reagent detection calibrator prepared by different antibody combination modes

According to the results in Table 7, antibodies 3D9 and 36A2 are selected as the raw materials of the PGI content double-antibody sandwich immunoturbidimetric assay reagent.

Through sequencing analysis, the amino acid sequence of the variable region of the murine monoclonal antibody 3D9 is as follows:

the amino acid sequence of the heavy chain variable region is shown as SEQ ID NO. 8; the amino acid sequence of the light chain variable region is shown as SEQ ID NO. 9.

Further, the CDR sequences of the antibody were determined by using Immunobin BLAST (IG BLAST) (http:// www.ncbi.nlm.nih.gov/giblast /) online analysis, and the amino acid sequences thereof were: VH CDR1 is shown in SEQ ID NO. 2; VH CDR2 is shown as SEQ ID NO. 3; VH CDR3 is shown in SEQ ID NO. 4; VL CDR1 is shown in SEQ ID NO. 5; VL CDR2 is shown in SEQ ID NO. 6; VL CDR3 is shown in SEQ ID NO. 7.

Through sequencing analysis, the amino acid sequence of the variable region of the murine monoclonal antibody 36A2 is as follows:

the amino acid sequence of the heavy chain variable region is shown as SEQ ID NO. 16; the variable region amino acid sequence of the light chain is shown in SEQ ID NO. 17.

Further, using Immunolobin BLAST (IGBlast) online analysis, CDR sequences of the antibody were determined, and the amino acid sequences thereof were: VH CDR1 is shown in SEQ ID NO. 10; VH CDR2 is shown in SEQ ID NO. 11; VH CDR3 is shown in SEQ ID NO. 12; VL CDR1 is shown in SEQ ID NO. 13; VL CDR2 is shown in SEQ ID NO. 14; VL CDR3 is shown in SEQ ID NO. 15.

Example 4: double-antibody sandwich immunoturbidimetry for detecting PGI protein in sample

The method for detecting the content of pepsinogen I (PGI) utilizes pepsinogen I detection reagents R1 and R2 and a calibrator to carry out pepsinogen I detection.

The detection reagent mainly comprises the following components:

reagent R1: tris buffer

Reagent R2: 3D9 and a sensitizing source 1 formed by coupling latex particles and 36A2 and a sensitizing source 2 formed by coupling latex particles are mixed and prepared according to a certain proportion.

Calibration products: human pepsinogen I.

The detection method comprises the following steps:

the detection instrument used was: full-automatic biochemical analyzer 7180

The analysis method comprises the following steps: two-point endpoint method.

The reaction direction is as follows: raising reaction;

the calibration method comprises the following steps: a Spline;

measuring wavelength: 570 nm;

measuring temperature: 37 ℃;

sample preparation: reagent R1: reagent R2 ═ 2 μ L:120 μ L;

the method comprises the following steps:

step one, adding 2 mu L of sample and 120 mu L of reagent R1 into a reaction cup, uniformly mixing and incubating for 3 min;

step two, adding 120 mu L of reagent R2 into the mixed solution, and uniformly mixing;

respectively reading the transmission absorbance A1 of the first reading point and the transmission absorbance A2 of the second reading point at 570nm by using a full-automatic biochemical analyzer 7180;

and step five, calculating delta A-A2-A1 by software and calculating the concentration of pepsinogen I in the tested sample according to a calibration curve.

Linear range assay for pepsinogen I reagent: the PGI calibrator was used to prepare high concentration samples, which were diluted in normal saline at a conventional ratio, each sample was repeatedly measured 3 times using the PGI reagents R1 and R2 of example 2, the mean value was calculated, the regression equation was determined, and the theoretical value was calculated from the regression equation, and the results are shown in FIG. 1. The results show that the linear range of the pepsinogen I reagent is 2.5-160 mug/L, the detection sensitivity is high, the linearity is wide, and the detection requirements of high sensitivity and wide linearity in clinic are met.

The PGI detection method of the invention and the detection method of a certain domestic brand comparison reagent are subjected to correlation test, 80 serum samples are measured, correlation analysis is carried out on the measured values, the result is shown in figure 2, and the correlation coefficient R of the PGI detection method of the invention and the detection method of a certain domestic brand comparison reagent is shown in figure 2 ² 0.9977, the method has good correlation with the detection method of the national comparison reagent of a certain known brand.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

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Claims (10)

1. An anti-pepsinogen I monoclonal antibody comprising: antibody 3D9 and/or antibody 36a 2;

wherein the amino acid sequence of the antibody 3D9 is: VH CDR1 is shown in SEQ ID NO. 2; VH CDR2 is shown in SEQ ID NO. 3; VH CDR3 is shown as SEQ ID NO. 4; VL CDR1 is shown in SEQ ID NO. 5; VL CDR2 is shown in SEQ ID NO. 6; VL CDR3 is shown in SEQ ID NO. 7;

the amino acid sequence of the antibody 36a2 is: VH CDR1 is shown as SEQ ID NO. 10; VH CDR2 is shown in SEQ ID NO. 11; VH CDR3 is shown in SEQ ID NO. 12; VL CDR1 is shown as SEQ ID NO. 13; VL CDR2 is shown in SEQ ID NO. 14; VL CDR3 is shown in SEQ ID NO. 15.

2. The monoclonal antibody of claim 1, wherein the monoclonal antibody comprises the antibody 3D 9;

the amino acid sequence of the variable region of the antibody 3D9 is as follows: the amino acid sequence of the heavy chain variable region is shown as SEQ ID NO. 8; the amino acid sequence of the light chain variable region is shown as SEQ ID NO. 9.

3. The monoclonal antibody of claim 1, wherein the monoclonal antibody comprises antibody 36a 2; the variable region amino acid sequence of the antibody 36a2 is: the amino acid sequence of the heavy chain variable region is shown as SEQ ID NO. 16; the variable region amino acid sequence of the light chain is shown in SEQ ID NO. 17.

4. The monoclonal antibody of claim 1, wherein the heavy chain constant region of the monoclonal antibody is an IgG heavy chain constant region; the light chain constant region of the monoclonal antibody is a kappa light chain constant region.

5. The monoclonal antibody of claim 1, wherein the monoclonal antibody is labeled.

6. A process for the preparation of a monoclonal antibody against pepsinogen I as claimed in any one of claims 1 to 5, comprising:

culturing the host cell under conditions that allow expression of the monoclonal antibody;

recovering the monoclonal antibody from the cultured host cell culture.

7. An isolated nucleic acid molecule encoding for the preparation of a monoclonal antibody according to any one of claims 1 to 5.

8. A vector comprising the isolated nucleic acid molecule of claim 7.

9. The vector of claim 7, wherein the vector is a cloning vector or an expression vector.

10. A kit for the detection of pepsinogen I, comprising a monoclonal antibody as claimed in any one of claims 1 to 5.

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