CN117820473B

CN117820473B - Abeta 1-42 specific antibody and application thereof in Alzheimer disease auxiliary diagnosis kit

Info

Publication number: CN117820473B
Application number: CN202410252726.8A
Authority: CN
Inventors: 颜丹; 冯速; 赵驰浩; 李森
Original assignee: Hunan Novozan Medical Technology Co ltd; Vazyme Medical Co ltd
Current assignee: Hunan Novozan Medical Technology Co ltd; Vazyme Medical Co ltd
Priority date: 2024-03-06
Filing date: 2024-03-06
Publication date: 2024-05-10
Anticipated expiration: 2044-03-06
Also published as: CN117820473A

Abstract

The application discloses an Abeta 1-42 specific antibody and application thereof in an Alzheimer's disease auxiliary diagnosis kit, belongs to the technical field of immunoassay, and provides an antibody targeting beta amyloid 1-42 and a chemiluminescent kit for detecting beta amyloid 1-42. The antibody of the application has high affinity, high sensitivity and obviously shortened production period, and is more suitable for being used as a core raw material in the field of in vitro diagnostic reagents. The kit disclosed by the application can be used for auxiliary diagnosis of diseases related to Abeta 1-42, such as Alzheimer's disease.

Description

Abeta 1-42 specific antibody and application thereof in Alzheimer disease auxiliary diagnosis kit

Technical Field

The application belongs to the technical field of immunoassay, and relates to an antibody targeting Abeta 1-42, a preparation method thereof, a kit for detecting Abeta 1-42 and application of the kit in Alzheimer disease auxiliary diagnosis.

Background

Alzheimer's Disease (AD) is an age-related, progressive and irreversible neurodegenerative Disease, frequently occurring in the elderly or in the pre-senile stages. Clinical manifestations are progressive decline of memory, thinking, analytical judgment, spatial recognition, emotion, daily life ability and various neuropsychiatric symptoms and behavioral disorders in a state without consciousness disturbance. The cognitive impairment is classified as mild, moderate and severe according to its severity. Mild AD patients, although beginning to forget the location of familiar words or objects, can still be self-care of life; to moderate, patients become more amnesia, more difficult to accomplish daily tasks, and experience changes in personality and behavior; patients with severe AD can no longer respond to their environment, can no longer talk, and cannot control exercise or control stool.

It was found that the main pathological manifestations of AD are deposition of extracellular senile plaques (senile plaques) in the brain, neurofibrillary tangles (neurofibrillary tangles, NFT) in the cells, and defects in cholinergic function, etc., which ultimately lead to neuronal damage and necrosis and ultimately spongiform encephalopathy. Among them, senile plaques consisting of beta amyloid and intracellular neurofibrillary tangles consisting of phosphorylated Tau protein (Phosphorylated Tau, p-Tau) are major neuropathological features of AD. There are a number of pathogenesis attempts to explain these changes, including the aβ amyloid cascade hypothesis, tau protein hypothesis, inflammatory hypothesis, and other mechanisms such as neurovascular injury theory, oxidative stress, and mitochondrial dysfunction.

Aβ is a 39-43 amino acid polypeptide produced by proteolytic action of APP by β -and γ -secretase, and is mainly Aβ1-40, Aβ1-42, Aβ1-43. It can be produced by a variety of cells, circulating in the blood, cerebrospinal fluid and brain interstitium, mostly in combination with chaperonin molecules, and a minority in free state. The amyloid cascade hypothesis of aβ suggests that in the brain, an imbalance between aβ production and clearance is the leading cause of alzheimer's disease, and aβ oligomers directly inhibit hippocampal long-term enhancement and damage to synapses, ultimately leading to neurotransmitter dysfunction and neurological dysfunction.

At present, the detection of the Abeta 1-42 mainly adopts the technical platforms of enzyme-linked immunosorbent assay (ELISA), point of care (POCT), electrochemiluminescence, chemiluminescence and the like, and the antibody preparation technology mainly has two problems. (1) insufficient antibody sensitivity: insufficient antibody sensitivity will directly affect the sensitivity of the detection reagent, and simultaneously reduce the specificity and anti-interference performance of detection, and finally affect the reliability of the detection result; (2) the preparation process of the monoclonal antibody is insufficient: the batch-to-batch variability in the preparation of monoclonal antibodies directly affects the batch-to-batch reproducibility of the kit, and therefore, it is desirable to ensure reproducibility control.

The above problems lead to the sensitivity and accuracy of the detection kit due to the small molecular weight and the low content of amyloid beta in blood and its rarity. Therefore, development of an anti-amyloid β antibody and application thereof is urgent.

Disclosure of Invention

In order to overcome the defects in the prior art, the application provides an Anti-beta amyloid 1-42 (namely Abeta 1-42) antibody Abeta 1-42-rRmab-1, the rabbit monoclonal antibody prepared by adopting a single B cell technology has higher sensitivity and obviously shortened production period, and the kit prepared by utilizing the Anti-Abeta 1-42-rRmab-1 has high sensitivity and low detection limit, so that a tool is provided for auxiliary diagnosis of diseases related to beta amyloid 1-42, and the application of the antibody or the kit in auxiliary diagnosis of Alzheimer's disease is further provided.

In one aspect, the application provides an antibody or antigen-binding fragment thereof that specifically binds to aβ1-42.

In some embodiments, the antibody or antigen binding fragment comprises: at least comprising one, two, three, four, five or six CDRs selected from the group consisting of: (a) comprises a sequence as set forth in SEQ ID NO:1, a heavy chain variable domain CDR-H1 having 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of seq id no; (b) comprises a sequence as set forth in SEQ ID NO:2, a heavy chain variable domain CDR-H2 having 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of seq id no; (c) comprises a sequence as set forth in SEQ ID NO:3, a heavy chain variable domain CDR-H3 having 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of seq id no; (d) comprises a sequence as set forth in SEQ ID NO:4, light chain variable domain CDR-L1 having 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of seq id no; (e) Comprising a light chain variable domain CDR-L2 having, for example, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of TAS; and (f) comprises a sequence as set forth in SEQ ID NO:5, has 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of CDR-L3.

In some embodiments, the antibody or antigen-binding fragment comprises at least one, at least two, or all three VH CDR sequences selected from the group consisting of: (a) comprises a sequence as set forth in SEQ ID NO:1, a heavy chain variable domain CDR-H1 having 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence; (b) comprises a sequence as set forth in SEQ ID NO:2, a heavy chain variable domain CDR-H2 having 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of seq id no; and (c) comprises a sequence as set forth in SEQ ID NO:3, has 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of CDR-H3. In some embodiments, the antibody comprises (a) a polypeptide as set forth in SEQ ID NO:1, a heavy chain variable domain CDR-H1 having 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of seq id no; (b) comprises a sequence as set forth in SEQ ID NO:2, a heavy chain variable domain CDR-H2 having 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of seq id no; and (c) a polypeptide as set forth in SEQ ID NO:3, has 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of CDR-H3.

In some embodiments, the antibody or antigen binding fragment comprises at least one, at least two, or all three VL CDR sequences selected from the group consisting of: (a) comprises a sequence as set forth in SEQ ID NO:4, light chain variable domain CDR-L1 having 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of seq id no; (b) Comprising a light chain variable domain CDR-L2 having, for example, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of TAS; and (c) comprises a sequence as set forth in SEQ ID NO:5, has 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of CDR-L3. In some embodiments, the antibody comprises (a) a polypeptide comprising a polypeptide as set forth in SEQ ID NO:4, light chain variable domain CDR-L1 having 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of seq id no; (b) Comprising a light chain variable domain CDR-L2 having, for example, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of TAS; and (c) comprises a sequence as set forth in SEQ ID NO:5, has 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of CDR-L3.

In some embodiments, the antibody or antigen-binding fragment comprises (a) a VH domain comprising at least one, at least two, or all three VH CDR sequences selected from the group consisting of: (i) comprises a sequence as set forth in SEQ ID NO:1, (ii) comprises a heavy chain variable domain CDR-H1 having 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of SEQ ID NO:2, (iii) comprises a heavy chain variable domain CDR-H2 having 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of SEQ ID NO:3, a heavy chain variable domain CDR-H3 having 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of seq id no; and, (b) a VL domain comprising at least one, at least two, or all three VL CDR sequences selected from the group consisting of: (i) comprises a sequence as set forth in SEQ ID NO:4, (ii) comprises a light chain variable domain CDR-L1 having, for example, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of TAS, (iii) comprises a light chain variable domain CDR-L2 having, for example, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of TAS, and (iii) comprises, for example, a sequence as set forth in SEQ ID NO:5, has 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to the amino acid sequence of CDR-L3. In some embodiments, an antibody or antigen binding fragment of the application comprises: as set forth in SEQ ID NO:1, and CDR-H1 as set forth in SEQ ID NO:2, and CDR-H2 as set forth in SEQ ID NO:3, and CDR-H3 as set forth in SEQ ID NO:4, and CDR-L2 as amino acid sequence TAS, and CDR-L1 as set forth in SEQ ID NO:5, and CDR-L3.

In some embodiments, the antibody or antigen binding fragment comprises at least one, two heavy chain variable domains selected from the group consisting of: (a) a polypeptide as set forth in SEQ ID NO:6, a heavy chain variable domain VH having at least 90%,91%,92%,93%,94%,95%,96%,97%,98%,99% or 100% sequence identity; (b) a polypeptide as set forth in SEQ ID NO:7 has at least 90%,91%,92%,93%,94%,95%,96%,97%,98%,99% or 100% sequence identity. In some embodiments, the antibody comprises the amino acid sequence as set forth in SEQ ID NO:6, and a heavy chain variable domain VH as set forth in SEQ ID NO:7, and a light chain variable domain VL.

In one aspect, the application provides a polynucleotide encoding an antibody or antigen binding fragment as described above.

In one aspect, the application provides a vector comprising a polynucleotide of the application.

In some embodiments, the vector comprises a viral vector, an expression vector, a recombinant expression vector. In some embodiments, the expression vector may be any suitable recombinant expression vector, and the vector may be selected from the group consisting of pUC series (FERMENTAS LIFE SCIENCES, GLENBURNIE, md.), pBluescript series (Stratagene, laJolla, calif.), pET series (Novagen, madison, wis.), pGEX series (PHARMACIA BIOTECH, uppsala, sweden), and pEX series (Clontech, palo Alto, calif.). Phage vectors such as λGT10, λGT11, zapII (Stratagene), λEMBL4, and λNM1149 can also be used. In some embodiments, the expression vector is pcdna3.1.

In one aspect, the application provides a host cell comprising a polynucleotide or vector of the application.

In some embodiments, the host cell is a eukaryotic cell, a prokaryotic cell. In some embodiments, the host cell is a 293 cell.

In one aspect, the application provides a kit for detecting Abeta 1-42.

In some embodiments, the kit comprises an antibody or antigen binding fragment of the application. In some embodiments, the kit detects aβ1-42 in a non-diagnostic format for immunodetection. In some embodiments, the kit is a chemiluminescent method, an electrochemiluminescent method, an ELISA. In some embodiments, the kit is a chemiluminescent immunoassay kit of the double antibody sandwich principle comprising: magnetic beads coated with a first antibody targeting amyloid-beta-1-42, and a second antibody labeled with a chemiluminescent agent targeting amyloid-beta-1-42. In some embodiments, the chemiluminescent agent is selected from at least one of acridinium ester, alkaline phosphatase (ALP), horseradish peroxidase (HRP).

In some embodiments, one antibody of the pair of first and second antibodies that targets aβ1-42 is selected from the antibodies or antigen binding fragments as described above. In some embodiments, the heavy chain CDRH1-CDRH3 amino acid sequence of the other antibody in the antibody pair consisting of the first and second antibodies targeting aβ1-42 is set forth in SEQ ID NO:18-SEQ ID NO:20, the amino acid sequence of the light chain CDRL1 is shown in SEQ ID NO:21, the amino acid sequence of the light chain CDRL2 is EAS, and the amino acid sequence of the light chain CDRL3 is shown in SEQ ID NO: shown at 22. In some embodiments, the other antibody of the antibody pair consisting of the first antibody and the second antibody that targets aβ1-42 comprises the amino acid sequence as set forth in SEQ ID NO:16 and a heavy chain variable region VH as set forth in SEQ ID NO:17, and a light chain variable region VL.

In some embodiments, the second antibody is an antibody or antigen-binding fragment of the application, and the heavy chain CDRH1-CDRH3 amino acid sequence of the first antibody is set forth in SEQ ID NO:18-SEQ ID NO:20, the amino acid sequence of the light chain CDRL1 is shown in SEQ ID NO:21, the amino acid sequence of the light chain CDRL2 is EAS, and the amino acid sequence of the light chain CDRL3 is shown in SEQ ID NO: shown at 22. In some embodiments, the second antibody is an antibody or antigen-binding fragment of the application, and the first antibody comprises an amino acid sequence as set forth in SEQ ID NO:16 and a heavy chain variable region VH as set forth in SEQ ID NO:17, and a light chain variable region VL.

In one aspect, the application provides the use of an antibody or antigen binding fragment as described above in the preparation of a reagent or kit for detecting aβ1-42.

In one aspect, the application provides the use of an antibody or antigen binding fragment as described above and a kit as described above to aid in the diagnosis of Alzheimer's disease.

In one aspect, the present application provides a method for preparing an antibody or antigen binding fragment as described above, specifically prepared by using a single B cell antibody cloning technology, comprising the steps of:

(1) Immunizing rabbits with beta amyloid 1-42 as immunogen, collecting spleen after the immunization is finished, and separating spleen cells;

(2) Screening specific B lymphocytes, extracting total RNA of the B lymphocytes, synthesizing cDNA (complementary deoxyribonucleic acid), and obtaining antibody variable region and constant region sequences by PCR (polymerase chain reaction);

(3) Inserting the amplified antibody genes into a recombinant expression vector, and transfecting 293 cells;

(4) Collecting and purifying culture supernatant to obtain the antibody.

Further, the amino acid sequence of the beta amyloid 1-42 in the step 1) is shown as SEQ ID NO: shown at 8.

Further, the primer sequence used in the PCR in the step 2) is shown in SEQ ID NO: 9-11.

The heavy chain coding region gene of the antibody is amplified, and the forward primer sequence is as follows:

caagctggctagcgtttaaacttgccaccagtcgtatgaagctaagagatc(SEQ ID NO：9)。

the heavy chain coding region gene of the antibody is amplified, and the reverse primer sequence is as follows:

tagtggatccgagctcggtacctcatttacccggagagcg(SEQ ID NO：10)。

the antibody light chain coding region gene is amplified, and the forward primer sequence is as follows:

caagctggctagcgtttaaacttgccaccagtcgtatgaagctaagagatc(SEQ ID NO：9)。

The antibody light chain coding region gene is amplified, and the reverse primer sequence is as follows:

tagtggatccgagctcggtacctcaacagtcacccctattg(SEQ ID NO：11)。

further, the purification of step 4) is specifically: the supernatant was purified by a protease A affinity column.

In one aspect, the application provides a paired screening method for antibodies or antigen binding fragments that specifically bind to aβ1-42, specifically using a fixed heavy chain variable region as set forth in SEQ ID NO:16 and the light chain variable region is set forth in SEQ ID NO:17, and screening the antibodies or antigen binding fragments by sandwich ELISA test pairing.

The beneficial effects of the application are that

The application provides a novel antibody targeting beta amyloid 1-42 and a kit comprising the same, and the antibody produced by utilizing a single B cell technology has high affinity, high sensitivity and obviously shortened production period, and is more suitable for being used as a core raw material in the field of in-vitro diagnostic reagents.

Drawings

FIG. 1 is a diagram of antigen-specific single B cell flow cytometer sorting;

FIG. 2 is a graph showing the correlation between the detection result and clinical value of the clinical sample of the quantitative gradient of chemiluminescent detection of the anti-beta amyloid 1-42 antibody of the present application.

Detailed Description

The following detailed description of the present disclosure is provided in connection with examples, but the implementation of the present disclosure is not limited thereto, and it is apparent that the examples described below are only some examples of the present disclosure, and that other similar examples are within the scope of protection of the present disclosure without inventive faculty for those skilled in the art.

Unless defined otherwise, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. All patents, patent applications, and publications cited throughout the disclosure are incorporated herein by reference in their entirety. If there are multiple definitions for terms herein, those in this section control.

The technical solutions provided by the present disclosure are described in detail below with reference to examples, but they should not be construed as limiting the scope of the present disclosure.

Example 1: preparation of anti-Abeta 1-42 monoclonal antibody

1. Antigen preparation

The present example selects the amyloid-beta 1-42 (Abeta 1-42) polypeptide as the immunogen. In the synthesis of Aβ1-42 polypeptide, cysteine C is added at the N-terminus for labelling the carrier protein KLH.

When the Abeta 1-42 polypeptide is synthesized, the N end is connected with a carrier protein BSA through cysteine, and the carrier protein BSA is used for detecting the titer of animal immune serum and detecting the subsequent rabbit monoclonal antibody expression supernatant.

Aβ1-42 is synthesized as a polypeptide of the sequence: CDAEFRHDSGYEVHHQKLVFFAEDVGSNKGAIIGLMVGGVVIA (SEQ ID NO: 8).

The carrier proteins KLH and BSA are self-grinding proteins and can be purchased in the market.

Carrier protein KLH marked Abeta 1-42 polypeptide is immunized with New Zealand white rabbits, each of which is immunized by 500ug. For the first immunization, the immunogen is mixed with equivalent Freund's adjuvant to prepare an emulsifier, the emulsifier is prepared by taking 250ug of the immunogen and equivalent Freund's adjuvant at intervals of 3 weeks, and the emulsifier is prepared by subcutaneous multipoint injection and boosting twice. PBMC samples are collected after three immunizations, abeta 1-42 polypeptide coated plates marked by carrier protein BSA are used for measuring serum titers by an ELISA method, rabbits with high serum titers are taken, and after 250ug of immunogen is subjected to subcutaneous multipoint injection for enhancing immunization once, spleen of the rabbits is taken.

2. Single B cell suspension preparation

The separation and preparation of rabbit spleen sample lymphocytes is to prepare single cell suspension by physically grinding rabbit spleen and filtering through a porous filter screen. Single cell suspensions were used for cell staining and flow sorting work.

3. Antigen-specific single B cell sorting

Antigen specific single B cell sorting is based on specific recognition of lymphocyte B cell surface characteristic markers by using a flow cell sorting technology, and the acquisition of specific single B cells in lymphocyte suspension is completed.

In this example, the raw coupled FITC dye was selected.

Anti-rabbit IgG secondary antibodies are self-grinding type antibodies. And coupling PE dye.

At the time of cell labeling, DAPI dye was added to differentiate Dead/living cells (Dead/Live cells).

Cell labeling protocol, lymphocyte B cell sorting protocol: read/Live-/IgG+/anti+.

Cell labeling operation: the rabbit lymphocyte suspension is centrifuged for 5min at 300g, 5mL buffer solution is added, the mixture is stirred upside down, and centrifuged for 5min at 300 g. The supernatant was discarded and repeated 1 time, and 30uL of the cell suspension was taken for cell counting, and 40uL of the cell suspension was taken for blank control and single-stained tubes to be labeled. The remaining cell fluid was used as a sample tube, centrifuged at 300g for 5min, and resuspended in a small amount of PBS. The blank tube was left untreated. Single-stained tubes, supplemented with PBS to 100uL, and 2uL PE, 2uL FITC, 2uL DAPI dye were added, respectively. The actual addition was calculated for the sample tube according to PE dye 1.5 uL/10 ⁶ cells, FITC dye 2 ug/10 ⁶ cells, the corresponding antibody was added in the dark, and the tube was left at 4℃for 30min. After the antibody incubation, 2mL buffer solution was added, mixed gently, centrifuged at 300g for 5min, and washed repeatedly 3 times. 1mL buffer solution was resuspended, and after cell filtration, the cells were waited for sorting on the machine.

After fluorescence compensation adjustment, based on the living cell population, PE and FITC double-positive signal cell populations are defined (figure 1), antigen-specific B cells are sorted into 96-well plates, only 1 cell is in each well, the sorted well plates need to be stored at low temperature immediately, and a dry ice box is arranged in the experiment of the embodiment, and the wells can be placed for a short time. The wells contained cell lysates and the sorted 96-well PCR plates were directly subjected to single cell antibody gene amplification.

4. Preparation of rabbit single B cell cDNA

The single B cell cDNA library is prepared based on SMART 5' RACE technology, and all reagents are N711 kit (VAZYME) of Nanjinouzan biotechnology Co., ltd. The amplification systems involved in the experiments in the examples are referred to the N711 kit instructions.

Single B cell RNA reverse transcription: after the sorting of the 96-well plates is completed, the plates are thawed and placed in a PCR instrument to run a program, and the plates are placed on ice for 2min after the program is finished.

Single B cell cDNA single-stranded synthesis: after the completion of the reverse transcription reaction procedure, a single-stranded synthesis system may be added. After the system is added, the pore plate is mixed evenly, the mixture is placed in a PCR instrument to run a program, and after the program is finished, the pore plate sample is placed on ice for 2min.

Single B cell DNA double strand synthesis: after the synthesis reaction of the cDNA single-stranded product is completed, a double-stranded synthesis system may be added. After the system is added, the pore plate is mixed evenly, centrifuged and then placed in a PCR instrument to run a program, and after the program is finished, the pore plate sample is placed on ice for standing.

5. Rabbit single B cell PCR technology amplified antibody coding gene

A single B cell cDNA library can be used for preparing the natural paired heavy chain and light chain coding genes of antibody.

The reagents used for the amplification of the coding gene are all P515 kit of Nanjinouzan biotechnology Co., ltd (VAZYME) and can be purchased from the market. The amplification system involved in the experiments in the examples can be referred to the P515 kit instructions.

The upstream primer contains homologous arms overlapping with the 3' -end of the CMV gene sequence of the promoter, so that the antibody coding gene can be directly used for constructing a linear expression frame after being called.

The downstream primer for the heavy chain coding gene of the antibody is positioned at the position of the constant region and comprises a homologous arm overlapped with the BGH-polyA gene sequence.

The downstream primer of the light chain coding gene is positioned at the position of the constant region and contains a homologous arm complementary with the BGH-polyA gene sequence, so that the antibody coding gene can be directly used for constructing a linear expression frame after being called.

caagctggctagcgtttaaacttgccaccagtcgtatgaagctaagagatc（SEQ ID NO：9）。

tagtggatccgagctcggtacctcatttacccggagagcg（SEQ ID NO：10）。

caagctggctagcgtttaaacttgccaccagtcgtatgaagctaagagatc（SEQ ID NO：9）。

tagtggatccgagctcggtacctcaacagtcacccctattg（SEQ ID NO：11）。

modulation of antibody light chain and heavy chain coding genes: adding a PCR amplification system according to the specification, mixing the pore plates lightly, placing the mixture into a PCR instrument to run a program, and standing the pore plate sample on ice after the program is finished.

In the embodiment, the amplification product pairing positive rate of the antibody light chain and heavy chain coding genes in the same 96-well plate is more than 80%, and the detection strips are clear by agarose gel electrophoresis, so that the single B cell flow sorting and coding gene amplification experiments are effective. Amplification products, used for construction of recombinant expression plasmids.

6. Construction and expression of recombinant expression plasmids for heavy and light chains of antibody

Recombinant expression vector pcDNA3.1 (Invitrogen) was selected and purchased at ThermoFisher SCIENTIFIC. Mu.M. Prior to recombinant construction, hindIII restriction enzyme single enzyme was selected to linearize the expression vector and the restriction enzyme was purchased at NEW ENGLAND Biolabs.

The vector and the coding gene are recombined efficiently, a seamless cloning kit is selected, and a C115# kit is purchased in VAZYME functional networks.

Construction of recombinant expression plasmids: the amplified products of the heavy chain and the light chain of the antibody are cyclized and connected with pcDNA3.1 linearization vector by using a seamless cloning technology, then Escherichia coli DH5 alpha competent cells are transformed, LB fixed culture medium plates are coated, and the plates are inverted and cultured at 37 ℃ overnight.

Recombinant positive clone selection: the heavy chain and the light chain of the primary screening antibody are respectively picked into 8 single colonies, and the colony positive rate is determined after PCR bacterial detection.

Bacterial detection PCR of the recombinant plasmid, and the upstream primer sequence of the recombinant plasmid is as follows: CAAGCTGGCTAGCGTTTAAACTT (SEQ ID NO: 12).

The primer sequence of the antibody heavy chain bacterial PCR downstream is as follows: CTCATTTACCCGGAGAGCG (SEQ ID NO: 13).

The sequence of the primer downstream of the PCR for the light chain bacterial detection of the antibody is as follows: ACCTCAACAGTCACCCCTATTG (SEQ ID NO: 14).

Recombinant positive clones were sent: and 5 bacterial PCR positive clones are selected from the heavy chain and the light chain of the antibody and sent to Shanghai biological company for sequencing.

Analysis of rabbit antibody gene sequences: and (3) finishing gene determination of the antibody sequence V region by using an IMGT database, finishing analysis of antibody sequences by using antibody heavy chain and light chain CDR1/CDR2/CDR3 regions and the like, and deriving and determining correct sequence numbers of bacterial detection PCR positive clones.

Small expression of recombinant expression plasmids: cloning the correct sequence, and extracting the light chain and heavy chain plasmids of the antibody from the bacterial liquid in a small amount. The plasmids were co-transfected into HEK293 mammalian cells after mixing. Cell supernatants were collected by centrifugation 10 days after cell transfection. The supernatant was subjected to antigen-specific evaluation, and cell supernatant purification was arranged after waiting for ELISA primary screening results.

In this example, 100 plasmids were transfected per round, i.e., 100 monoclonal antibodies were obtained per round of transfection. Because of the low proportion of specific antibodies, a total of 10-cycle experiments were performed.

7. Recombinant expression supernatant antigen specificity evaluation

Antigen coated plates were prepared and the screening precursors selected from the group consisting of beta amyloid 1-40 (Abeta 1-40), beta amyloid 1-42 (Abeta 1-42), and KLH protein. Wherein, the Abeta 1-40 and Abeta 1-42 are coated with antigen plates by SA-Biotin coupling method due to shorter polypeptide sequences and cysteine added at the N end of the polypeptide.

Screening protocol of Abeta 1-42 polypeptide monoclonal antibody the antibody which reacts with Abeta 1-42-biotin+SA and does not react with KLH and Abeta 1-40-biotin+SA is selected, namely the monoclonal antibody which is initially designated as Abeta 1-42 specific monoclonal antibody.

The sequence of the synthesized polypeptide Abeta 1-40 is as follows: CDAEFRHDSGYEVHHQKLVFFAEDVGSNKGAIIGLMVGGVV (SEQ ID NO: 15).

The cell supernatant was detected by indirect ELISA, and the goat Anti-Rabbit polyclonal antibody (HRP) detection was performed using self-produced Rabbit secondary antibody-Rabbit IgG mAb, and the reactive OD >1, indicating that the recombinant plasmid was normally expressed on 293 cells.

Indirect ELISA was used to detect cell supernatants, and reactivity was evaluated on each of the 3 antigen-coated plates to obtain primary screening results for well plate supernatants (Table 1 shows exemplary detection data for 50 cell supernatants).

Table 1: antigen-antibody affinity data sheet for partial antibodies

Indirect ELISA detection results: antibody primary screening co-transfected 1000 monoclonal antibodies reacted with SA+Biotin-Abeta 1-42-Ag and not reacted with KLH, SA+Biotin-Abeta 1-40-Ag, and 80 monoclonal antibodies were primarily screened. The cell supernatant determined by preliminary screening is purified by protein A to obtain a small amount of monoclonal antibody, and the average amount of each strain is 1-3mg.

8. ELISA paired screening of recombinant antibodies

The screening of the paired antibodies of the beta amyloid 1-42 (Abeta 1-42) has been completed in the early stage, so that the screening work of the Abeta 1-40/1-42 polypeptide N-terminal high-sensitivity specific antibody is finished, the antibody at the Abeta 1-40/1-42N terminal is selected and immobilized in the embodiment, and a sandwich ELISA experiment is carried out on the 80 monoclonal antibodies initially screened by an indirect ELISA method, so that the better monoclonal antibody capable of specifically recognizing the Abeta 1-42C terminal is screened.

The sequence of the variable region of the Rabbit Anti-Abeta 1-40-mAb-A is as follows:

QSLEESGGRLVTPGTPLTLTCTASGLTISSSYMNWVRQAPGKGLEWIGIIYADDSTSYASWAKGRFTISKTSTTVDLKITSPTTEDTATYFCAGGGIWGPGTLVTVSS（SEQ ID NO：16）;

CDRH1：GLTISSSY（SEQ ID NO：18）；CDRH2：IYADDST（SEQ ID NO：19）；CDRH3：AGGGI（SEQ ID NO：20）；

The light chain variable region sequences are:

AQVLTQTASPVSAAVGSTVTINCQASQSVYNNNRLAWYQQKPGQPPKLLIYEASKLASGVPSRFSGSGSGTQFTLTISGVQCDDAATYYCQGGYDCSSADCNAFGGGTEVVVK（SEQ ID NO：17）;

CDRL1：QSVYNNNR（SEQ ID NO：21）；CDRL2：EAS；CDRL3：QGGYDCSSADCNA（SEQ ID NO：22）；

the ELISA platform synchronous detection data of the clinical positive samples show that the ELISA pairing experiment can select the Abeta 1-42 synthetic polypeptide as a screening antigen.

The method comprises the steps of initially screening 80 monoclonal antibodies, detecting Abeta 1-42 polypeptide through a sandwich ELISA experiment, finally screening the first 10 strains with pairing detection signal values orderly ordered, and verifying the detection condition of clinical samples of the antibodies by a chemiluminescent platform (Table 2 shows the detection results of 20 pairs of paired antibodies in an illustrative manner).

Table 2: detection data (part) of Abeta 1-42 polypeptide pairing antibody

9. Recombinant antibody chemiluminescent platform screening

Coating the antibodies screened in the step 8 on magnetic beads, wherein the specific operation is as follows: 2mg of magnetic beads are taken, activated buffer is washed for 2 times, a certain amount of EDC is added, the mixture is uniformly mixed by shaking, and the supernatant is magnetically removed. Adding 1000uL of coupling buffer into the precipitate, adding 40ug of antibody, shaking and mixing for 2h, adding 100uL of blocking solution, shaking and mixing and blocking for 3h. Finally, 1000uL TBST is added to clean the magnetic beads, and 1000uL preservation solution is added.

A series of biotin-labeled Abeta protein peptide fragments with different lengths are artificially synthesized as screening precursors, and specific information of the screening precursors is shown in table 3:

table 3: screening original information table for chemiluminescent platform screening recombinant antibody experiment

Streptavidin (SA) was labeled with acridinium ester, and the procedure was as follows: 100- (100/C _SA) uL coupling Buffer was taken into a 0.5mL brown EP tube, added (100/C _SA) uL SA into a 0.5mL brown EP tube to make the final concentration of SA mark 1mg/mL, added 5mM acridine ester into a 0.5mL brown EP tube, uniformly mixed by a vortex shaker, then reacted for 2 hours by a vertical mixer at room temperature (20-25 ℃) and purified to remove free acridine ester.

The preparation of the coated antibody, the labeled SA and the screening antigen is completed according to the method, and each screening antigen is detected according to a set program by using a full-automatic chemiluminescence instrument. The detection result is only reacted with the synthetic polypeptide 4# and the antibodies which are not reacted with other synthetic polypeptides (No. 1, no.2, no. 3, no. 5 and No. 6), namely the monoclonal antibody which specifically recognizes the Abeta 1-42C end is preferable.

The 10 monoclonal antibodies screened by sandwich ELISA experiments are detected by a chemiluminescent platform, and 1 antibody specifically recognizing the Abeta 1-42C end is preferably selected. Table 4 shows the results of detection of 4 pairs of paired antibodies.

Table 4: abeta 1-42 specific antibody chemiluminescent platform detection data (part)

The screened specific antibody Anti-Abeta 1-42-rRmab-1 has the following heavy chain variable region sequences:

QCQSVEESGGRLVTPGTPLTLTCTASGFTISSYHMSWVRQAPGKGLEWIGTISTGGSTYYVSWAKGRFTISKTSTTVDLKMTSPTTEDTATYFCARSIGNTDGNIWGPGTLVTVSS（SEQ ID NO：6）;

The light chain variable region sequences are:

AQVLTQTPSSVSAAVGGTVTINCQASQSVYKNNYLAWFQQKPGQPPKRLIYTASSLASGVSSRFKGSGSGTQFTLTISDVQCDDAATYYCLGSYDCRTTDCMAFGGGTGVVVK（SEQ ID NO：7）;

Table 5: amino acid sequence of anti-Abeta 1-42 antibody

Example 2: application of monoclonal antibody in chemiluminescent platform

The optimized Abeta 1-42 specific antibody Anti-Abeta 1-42-rRmab-1 is applied to a chemiluminescence detection experiment, matched with an antibody which can be matched with the antibody, a fixed value gradient clinical sample is detected, and the correlation between the detection result and a clinical fixed value is compared.

The gradient clinical sample adopts simoa single-molecule immunization method to determine the concentration of Abeta 1-42 in the sample, and the specific concentration is shown in Table 6:

table 6: clinical sample Aβ1-42 concentration meter

The concentration of Abeta 1-42 in the sample P1-P12 and the sample diluent is detected by using a full-automatic chemiluminescence apparatus by combining the antibody pair consisting of the optimized Abeta 1-42 specific antibody Abeta 1-42-rRmab-1 and the antibody Rabbit Anti-Abeta 1-40-mAb-A capable of pairing with the antibody pair, wherein the following operation is performed:

And (3) coating magnetic beads: 2mg of magnetic beads are taken, activated buffer is washed for 2 times, a certain amount of EDC is added, the mixture is uniformly mixed by shaking, and the supernatant is magnetically removed. Adding 1000uL of coupling buffer into the precipitate, adding 40ug of antibody (Rabbit Anti-Abeta 1-40-mAb-A), shaking and mixing for 2h, adding 100uL of blocking solution, shaking and mixing and blocking for 3h. Finally, 1000uL TBST is added to clean the magnetic beads, and 1000uL preservation solution is added.

Acridinium ester labeling: 100- (100/C _Ab) uL coupling Buffer was taken into a 0.5mL brown EP tube, added (100/C _Ab) uL Ab into a 0.5mL brown EP tube, the final concentration of the antibody (Anti-Abeta 1-42-rRmab-1) label was 1mg/mL, added 5mM acridinium ester into a 0.5mL brown EP tube, uniformly mixed by a vortex shaker, and then reacted for 2 hours by a vertical mixer at room temperature (20-25 ℃) to purify and remove the free acridinium ester.

Program setting and on-line detection are carried out, and the results are shown in Table 7:

Table 7: chemiluminescent detection result table for clinical samples

And drawing a scatter diagram of the concentration of each sample Abeta 1-42 by taking Abeta 1-42 detected by simoa single-molecule immunization method as a horizontal axis and Abeta 1-42 detected by chemiluminescence method as a vertical axis, and calculating a correlation coefficient of Abeta 1-42 concentration values between the two detection methods.

As shown in fig. 2, the correlation coefficient r=0.9994 and R ² =0.9989 of the two detection methods, namely, the antibody Anti-aβ1-42-rRmab-1, which is the preferred specific antibody of aβ1-42, is matched with the antibody capable of pairing with the antibody, when the antibody is applied to a chemiluminescent detection experiment, the detection result has a strong correlation with the simoa single molecule immunization method, and the preferred antibody can be used for preparing a downstream kit.

Claims

1. An antibody or antigen binding fragment thereof specifically binding to aβ1-42, wherein the amino acid sequences of heavy chain CDRH1-CDRH3 are as shown in SEQ ID NO:1-SEQ ID NO:3, the amino acid sequence of the light chain CDRL1 is shown in SEQ ID NO:4, the amino acid sequence of the light chain CDRL2 is TAS, and the amino acid sequence of the light chain CDRL3 is shown in SEQ ID NO: shown at 5.

2. The antibody or antigen-binding fragment thereof of claim 1, comprising: as set forth in SEQ ID NO:6 and a heavy chain variable region VH as set forth in SEQ ID NO:7, and a light chain variable region VL.

3. A kit for detecting amyloid-beta 1-42, comprising magnetic beads coated with a first antibody targeting amyloid-beta 1-42 and a second antibody labeled with a chemiluminescent agent targeting amyloid-beta 1-42; wherein one antibody of the pair of the first antibody and the second antibody targeting amyloid-beta 1-42 is the antibody or antigen-binding fragment thereof of any one of claims 1-2.

4. A kit according to claim 3, wherein the heavy chain CDRH1-CDRH3 amino acid sequences of the other antibody in the pair of antibodies comprising the first and second antibodies are as set forth in SEQ ID NOs: 18-SEQ ID NO:20, the amino acid sequence of the light chain CDRL1 is shown in SEQ ID NO:21, the amino acid sequence of the light chain CDRL2 is EAS, and the amino acid sequence of the light chain CDRL3 is shown in SEQ ID NO: shown at 22.

5. The kit of claim 4, the other antibody of the pair of first and second antibodies comprising: as set forth in SEQ ID NO:16 and a heavy chain variable region VH as set forth in SEQ ID NO:17, and a light chain variable region VL.

6. A kit according to claim 3, wherein the second antibody is an antibody or antigen-binding fragment thereof according to any one of claims 1-2, and the heavy chain CDRH1-CDRH3 amino acid sequence of the first antibody is as set forth in SEQ ID NO:18-SEQ ID NO:20, the amino acid sequence of the light chain CDRL1 is shown in SEQ ID NO:21, the amino acid sequence of the light chain CDRL2 is EAS, and the amino acid sequence of the light chain CDRL3 is shown in SEQ ID NO: shown at 22.

7. The kit of claim 3, wherein the second antibody is the antibody or antigen-binding fragment thereof of any one of claims 1-2, and the first antibody comprises the amino acid sequence set forth in SEQ ID NO:16 and a heavy chain variable region VH as set forth in SEQ ID NO:17, and a light chain variable region VL.

8. The kit according to claim 3, wherein the chemiluminescent agent is at least one selected from the group consisting of acridinium esters, alkaline phosphatase, and horseradish peroxidase.

9. Use of an antibody or antigen-binding fragment thereof according to any one of claims 1-2 in the preparation of a kit for aiding in the diagnosis of alzheimer's disease.

10. A polynucleotide encoding the antibody or antigen-binding fragment thereof of any one of claims 1-2.