Antibodies targeting ALB and uses thereof

Abstract

The invention discloses an antibody targeting ALB and an application of the antibody. The antibody or the antigen binding fragment thereof comprises a heavy chain variable region and a light chain variable region, wherein the heavy chain variable region comprises HCDR1, HCDR2 and HCDR3 of which the amino acid sequences are respectively shown as SEQ ID NO: 1, SEQ ID NO: 2 and SEQ ID NO: 3; the light chain variable region comprises an LCDR1, an LCDR2 and an LCDR3, wherein the amino acid sequences of the LCDR1, the LCDR2 and the LCDR3 are respectively shown as SEQ ID NO: 6, SEQ ID NO: 7 and SEQ ID NO: 8. The anti-ALB monoclonal antibody can be used for detecting the expression level of ALB protein in cells in vitro, is good in specificity and high in antibody concentration and purity, can be used for analyzing the expression level of ALB protein in protein or tissue in vitro, and has good stability.

Description

Technical Field

[0001] The present invention belongs to the field of biotechnology, and particularly relates to an antibody targeting ALB and its application. Background Art

[0002] Albumin, also known as serum albumin, is synthesized by the human liver, about 12 - 20 g per day, accounting for about 50% of the total plasma protein in the human body. It is the most important protein in human plasma and is a basic physiological substance crucial for maintaining the body's nutrition and osmotic pressure.

[0003] The Albumin gene encodes the most abundant protein in human blood. Albumin plays a role in regulating plasma colloid osmotic pressure and serves as a carrier protein for various endogenous molecules, including hormones, fatty acids, metabolites, and exogenous drugs. In addition, albumin exhibits esterase-like activity with broad substrate specificity. The encoded preprotein is proteolytically processed to produce the mature protein. The peptide EPI-X4 derived from this protein is an endogenous inhibitor of the CXCR4 chemokine receptor. Currently, there are few commercially available ALB antibodies, which cannot meet the market demand. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the technical problem in the prior art of lacking stable ALB antibodies with high sensitivity and good specificity, and to provide an antibody targeting ALB and its application. The anti-ALB monoclonal antibody of the present invention can be used for in vitro detection of the expression level of ALB protein in cells, has good specificity, high antibody concentration and purity, can be used for in vitro analysis of the expression level of ALB protein in proteins or tissues, and has good stability.

[0005] The present invention solves the above technical problems through the following technical solutions.

[0006] In a first aspect of the present invention, there is provided an antibody targeting ALB or an antigen-binding fragment thereof, wherein the antibody or the antigen-binding fragment thereof comprises a heavy-chain variable region and a light-chain variable region, and the heavy-chain variable region comprises HCDR1, HCDR2, and HCDR3 with amino acid sequences as shown in SEQ ID NO:1, SEQ ID NO:2, and SEQ ID NO:3 respectively; the light-chain variable region comprises LCDR1, LCDR2, and LCDR3 with amino acid sequences as shown in SEQ ID NO:6, SEQ ID NO:7, and SEQ ID NO:8 respectively.

[0007] In some embodiments of the present invention, the amino acid sequence of the heavy chain variable region is as shown in SEQ ID NO: 4 or is an amino acid sequence having at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99% sequence identity with SEQ ID NO: 4.

[0008] In some embodiments of the present invention, the amino acid sequence of the light chain variable region is as shown in SEQ ID NO: 9 or is an amino acid sequence having at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99% sequence identity with SEQ ID NO: 9.

[0009] In some embodiments of the present invention, the antibody is a full-length antibody, Fab, Fab’, F(ab’)2, scFv, Fv or a multispecific antibody.

[0010] In the present invention, when the antibody is a full-length antibody, the heavy chain constant region of the full-length antibody is derived from the heavy chain of a human antibody or a variant thereof, and the light chain constant region of the full-length antibody is derived from the κ chain or λ chain of a human antibody or a variant thereof.

[0011] In some specific embodiments of the present invention, the amino acid sequence of the heavy chain constant region is as shown in SEQ ID NO: 25 or is an amino acid sequence having at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99% sequence identity with SEQ ID NO: 25.

[0012] In some specific embodiments of the present invention, the amino acid sequence of the light chain constant region is as shown in SEQ ID NO: 27 or is an amino acid sequence having at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99% sequence identity with SEQ ID NO: 27.

[0013] The second aspect of the present invention provides an isolated nucleic acid encoding the antibody or an antigen-binding fragment thereof as described in the first aspect.

[0014] In some specific embodiments of the present invention, the nucleotide sequence encoding the HCDR1 is as shown in SEQ ID NO:11, the nucleotide sequence encoding the HCDR2 is as shown in SEQ ID NO:12, and the nucleotide sequence encoding the HCDR3 is as shown in SEQ ID NO:13.

[0015] In some specific embodiments of the present invention, the nucleotide sequence encoding the LCDR1 is as shown in SEQ ID NO:16, the nucleotide sequence encoding the LCDR2 is as shown in SEQ ID NO:17, and the nucleotide sequence encoding the LCDR3 is as shown in SEQ ID NO:18.

[0016] In some examples of the present invention, the nucleotide sequence encoding the heavy chain variable region is as shown in SEQ ID NO:14.

[0017] In some examples of the present invention, the nucleotide sequence encoding the light chain variable region is as shown in SEQ ID NO:19.

[0018] The third aspect of the present invention provides a recombinant expression vector, which contains the nucleic acid as described in the second aspect.

[0019] In some embodiments of the present invention, the recombinant expression vector is a plasmid, cosmid, phage or viral vector.

[0020] In some specific embodiments of the present invention, the viral vector is a retroviral vector, lentiviral vector, adenoviral vector or adeno-associated viral vector.

[0021] The fourth aspect of the present invention provides a cell, which contains the recombinant expression vector as described in the third aspect or the nucleic acid as described in the second aspect; or expresses the antibody as described in the first aspect or its antigen-binding fragment.

[0022] In some embodiments of the present invention, the cell is a prokaryotic cell or a eukaryotic cell.

[0023] In some preferred embodiments of the present invention, the cell is selected from yeast cells, mammalian cells or other cells suitable for preparing antibodies or their antigen-binding fragments; the mammalian cells are, for example, HEK293 cells.

[0024] The fifth aspect of the present invention provides a method for preparing an antibody or its antigen-binding fragment targeting ALB, which includes culturing the cell as described in the fourth aspect and obtaining the antibody or its antigen-binding fragment targeting ALB from the culture.

[0025] The sixth aspect of the present invention provides a kit, which includes the antibody or its antigen-binding fragment as described in the first aspect.

[0026] In some embodiments of the present invention, the kit further comprises a reagent for detecting the binding of the antibody or its antigen-binding fragment to an antigen.

[0027] The seventh aspect of the present invention provides a method for detecting ALB, the method comprising the step of contacting the antibody or its antigen-binding fragment as described in the first aspect with a sample to be tested.

[0028] In some embodiments of the present invention, the method is for non-diagnostic purposes, such as antibody detection in a laboratory and the development of immunological detection methods.

[0029] The eighth aspect of the present invention provides the use of the antibody or its antigen-binding fragment as described in the first aspect, the nucleic acid as described in the second aspect, the recombinant expression vector as described in the third aspect, or the cell as described in the fourth aspect in the preparation of an ALB detection reagent.

[0030] On the basis of conforming to the common knowledge in the art, the above preferred conditions can be combined arbitrarily to obtain various preferred examples of the present invention.

[0031] The reagents and raw materials used in the present invention are all commercially available.

[0032] The positive and progressive effects of the present invention are as follows:

[0033] The anti-ALB monoclonal antibody of the present invention has high sensitivity, good specificity, high antibody concentration and purity, can be used to analyze the expression level of ALB protein in vitro in proteins or tissues, has good stability, and has a wide range of application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the immunofluorescence staining effect of a commercially available ALB antibody (1:200) (positive sample).

[0035] Figure 2 Schematic diagram of the immunofluorescence staining effect of the ALB antibody in the example (1:200) (positive sample).

[0036] Figure 3 Schematic diagram of the immunofluorescence staining effect of the ALB antibody in the example (1:200) (negative sample).

[0037] Figure 4 Flow cytometry detection chart of the ALB antibody in the example (1:200) (positive sample).

[0038] Figure 5 Flow cytometry detection chart of the ALB antibody in the example (1:200) (negative sample). DETAILED DESCRIPTION OF THE INVENTION

[0039] DEFINITIONS

[0040] As used herein, the term "complementary determining region" or "CDR region" or "CDR" refers to a region in the variable domain of an antibody that is highly variable in sequence and forms structurally defined loops ("hypervariable loops") and / or contains antigen - contacting residues ("antigen - contact points"). CDRs are mainly responsible for binding to epitopes and, numbered sequentially from the N - terminus, include CDR1, CDR2, and CDR3. In a given amino acid sequence of a heavy - chain variable region, the precise amino - acid sequence boundaries of each CDR can be determined using any one or a combination of many well - known antibody CDR assignment systems. It is well known to those skilled in the art that in the art, the CDRs of antibodies can be defined by various methods, such as Chothia (Chothia et al. (1989) Nature 342:877 - 883, Al - Lazikani et al., Journal of Molecular Biology, 273, 927 - 948 (1997)) based on the three - dimensional structure of the antibody and the topology of the CDR loops, Kabat (Kabat et al., U.S. Department of Health and Human Services, National Institutes of Health (1987)), AbM (University of Bath), Contact (University College London), the international ImMunoGeneTics database (IMGT) (world wide web imgt.cines.fr / ), and the North CDR definition based on affinity propagation clustering using a large number of crystal structures. Those skilled in the art should understand that, unless otherwise specified, the terms "CDR" and "complementary determining region" of a given antibody or its region (e.g., variable region) should be understood to cover the complementary determining regions defined by any of the above - known schemes described in the present invention.

[0041] Antibodies with different specificities (i.e., different binding sites for different antigens) have different CDRs. However, although CDRs are different between antibodies, only a limited number of amino acid positions within the CDRs are directly involved in antigen binding. Using at least two of the Kabat, Chothia, IMGT, AbM, and Contact methods, a minimal overlapping region can be determined, providing a "minimal binding unit" for antigen binding. The minimal binding unit can be a subpart of a CDR. As will be appreciated by those skilled in the art, through the structure and protein folding of an antibody, the residues of the remaining portions of the CDR sequence can be determined. Accordingly, the present invention also contemplates variants of any CDR given herein. For example, in a variant of a CDR, the amino acid residues of the minimal binding unit can remain unchanged while the remaining CDR residues as defined by Kabat or Chothia or AbM can be replaced with conservative amino acid residues.

[0042] As used herein, "percent (%) sequence identity", "sequence identity" of an amino acid sequence has the meaning recognized in the art, which refers to the percentage of identity between two polypeptide sequences determined by sequence alignment (e.g., by manual inspection or well-known algorithms). It can be determined using methods known to those skilled in the art, such as using publicly available computer software such as BLAST, BLAST-2, Clustal Omega, and FASTA software.

[0043] In the present invention, unless the context clearly indicates otherwise, when referring to the term "antibody", it includes not only intact antibodies but also antigen-binding fragments of antibodies.

[0044] As used herein, the term "isolated" refers to being obtained by artificial means from its natural state. If a "isolated" substance or component occurs in nature, it may be that its natural environment has been changed, or the substance has been isolated from its natural environment, or both. For example, a polynucleotide or polypeptide that naturally exists in a living animal in an unisolated state, and the same polynucleotide or polypeptide of high purity isolated from this natural state is referred to as "isolated". The term "isolated" does not exclude the admixture of artificial or synthetic substances, nor does it exclude the presence of other impure substances that do not affect the activity of the substance.

[0045] As used in the present invention, "vector" refers to a construct that is capable of delivering one or more genes or sequences of interest into a host cell and preferably expressing the gene or sequence in the host cell. Examples of vectors include, but are not limited to, viral vectors, naked DNA or RNA expression vectors, plasmids, cosmids or phage vectors, DNA or RNA expression vectors associated with cationic condensing agents, DNA or RNA expression vectors encapsulated in liposomes, and certain eukaryotic cells, such as producer cells.

[0046] As used herein, the term "host cell" refers to a cell into which a vector can be introduced, including but not limited to prokaryotic cells such as Escherichia coli, fungal cells such as yeast cells, insect cells such as S2 Drosophila cells or Sf9, or animal cells such as fibroblast cells, CHO cells, COS cells, NSO cells, HeLa cells, BHK cells, HEK293 cells or human cells.

[0047] The present invention will be further illustrated by the following examples, but the present invention is not limited to the scope of the examples described herein. For the experimental methods without specific conditions noted in the following examples, they are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0048] Example 1

[0049] The amino acid sequence of the ALB antibody screened in this example is shown in Table 1, and the CDR is defined by Kabat.

[0050] Table 1 Antibody sequence

[0051]

[0052]

[0053] In the table, VH is the heavy chain variable region, VL is the light chain variable region, CH is the heavy chain constant region, CL is the light chain constant region; HC is the heavy chain, and LC is the light chain.

[0054] In the antibody obtained in this example, the signal peptide sequence of the heavy chain is:

[0055] MEWPCIFLFLLSVTEGVHS (SEQ ID NO:21)

[0056] The nucleotide sequence encoding it is shown in SEQ ID NO:22.

[0057] The signal peptide sequence of the light chain is:

[0058] MRAPAQIFGFLLLLFPGTRC (SEQ ID NO:23)

[0059] The nucleotide sequence encoding it is shown in SEQ ID NO:24.

[0060] Example 2: Immunofluorescence application

[0061] In this example, the effect of the antibody was verified by immunofluorescence staining. The immunofluorescence operation steps are as follows:

[0062] 1. Take out the fixed hiHep cells in the 24-well plate[2] After discarding the supernatant, add 300 μl / well of 0.25% Triton X-100 and permeabilize for 15 min;

[0063] 2. After discarding the supernatant, add 300 μl / well of 3% BSA and block for 45 min;

[0064] 3. After discarding the supernatant, add 300 μl / well of the primary antibody (ALB antibody prepared in Example 1) (1:200) and incubate at room temperature for 2 h;

[0065] 4. After discarding the supernatant, add 500 μl / well of 1×PBS and wash 3 times;

[0066] 5. Add 300 μl / well of the secondary antibody (Alexa 488 AffiniPure Goat Anti-Mouse IgG, 115-545-205, Jackson ImmunoResearch) (1:400) and incubate at room temperature in the dark for 1 h;

[0067] 6. After discarding the supernatant, add 500 μl / well of 1×PBS and wash 3 times;

[0068] 7. Add 300 μl / well of DAPI (1:3000) and incubate at room temperature in the dark for 3 min;

[0069] 8. After discarding the supernatant, add 500 μl / well of 1×PBS and wash 3 times, then add 1 ml of 1×PBS for fluorescence photography.

[0070] As Figure 1 and Figure 2 shown, for the ALB antibody of this example ( Figure 2 ), when the usage ratio is 1:200, it can reach the same staining level as the commercially available antibody (Bethyl, catalog number A80-229A) ( Figure 1 ), indicating that the antibody has higher purity and better sensitivity.

[0071] And as Figure 3 shown, the ALB antibody of this example has no signal in negative control cells, indicating good antibody specificity.

[0072] Example 3: Flow cytometry detection application

[0073] In this example, the effect of the antibody was verified by immunofluorescence staining. The immunofluorescence operation steps are as follows:

[0074] 1. Take 8E5 fixed hepG2 cells [1] or UCFT cells [2] into a 1.5 mL sterile centrifuge tube;

[0075] 2. Centrifuge to discard the supernatant, resuspend the cells with 100 μL of (PBS + 10% FBS), then add 900 μL of ice-cold methanol, mix well, and permeabilize on ice for 10 minutes.

[0076] 3. After permeabilization, divide the cells in a 1.5 mL sterile centrifuge tube into 4 equal parts, centrifuge to discard the supernatant.

[0077] 4. Resuspend each part of the cells with 100 μL of (PBS + 10% FBS), and add the corresponding volume of primary antibody to each sample tube according to the following table.

[0078]

[0079] 5. After mixing the samples and antibodies, incubate at room temperature for 30 min.

[0080] 6. After incubation, add 1 mL of (PBS + 2% FBS) to each tube for washing, centrifuge at 6000 rpm for 5 min, discard the supernatant, and repeat the washing 2 times.

[0081] 7. After washing, resuspend the cells in each tube with 100 μL of (PBS + 10% FBS).

[0082] 8. According to the following table, add the corresponding volume of secondary antibody to each sample tube; after mixing, incubate at room temperature in the dark for 30 min.

[0083] 9. After incubation, add 1 mL of (PBS + 2% FBS) to each tube for washing, centrifuge at 6000 rpm for 5 min, discard the supernatant, and repeat the washing 2 times.

[0084] 10. After washing, resuspend the cells with 100 μL of PBS for flow cytometry detection and data analysis.

[0085] As Figure 4 shown, for the ALB antibody in this example, when the usage ratio is 1:200 during flow cytometry detection, a good staining effect can be achieved, indicating higher antibody purity and better sensitivity.

[0086] And as Figure 5 shown, the ALB antibody in this example shows no signal in negative control cells (UCFT cells [1] ), indicating good antibody specificity.

[0087] Example 4: Detection of Antibody Stability

[0088] The sample used in this example is HepG2 cells [2] , and the ALB antibody stored under different conditions is used to detect the ALB positive rate of HepG2 cells by flow cytometry.

[0089] After storing the antibody at -20°C, 2 - 8°C, and 37°C with 0.02% ProClin 300 for different periods of time, the positive rate of ALB in the samples was detected. The detection results are shown in Table 2.

[0090] The ALB antibody of the present invention can maintain good detection sensitivity and stability under storage conditions of -20°C, 2 - 8°C, and 37°C. Currently, the detection results have been updated to 60 days after antibody storage. The experimental results show that when stored for 30 days, the detection results of the ALB positive rate have little difference from the baseline value; when stored for 60 days, the detection results under the three storage conditions have little difference, but compared with the baseline value, there is a certain degree of decrease. The above data indicate that the ALB antibody can be stably stored at 37.0°C for at least 30 days, showing significant advantages compared with commercially available antibodies (commercially available antibodies are generally stored at 2 - 8°C for 14 days).

[0091] Table 2 Antibody Storage Stability Experiment

[0092]

[0093] Three independent detection experiments were carried out on each of the three independent samples (a mixture of hepG2 and UCFT cells at a ratio of 1:1.5). The detection results are shown in Table 3. The CV values (CV% = SD / Average * 100%) of the three detection results were 0.03%, 0.02%, and 0.01% respectively. The difference coefficient between independent detections was small, indicating high detection stability of the antibody.

[0094] Table 3 Antibody Detection Stability Experiment

[0095] Sample 1 Sample 2 Sample 3 The first detection 32.5％ 35.4％ 36.6％ The second detection 31.5％ 35.8％ 36.6％ The third detection 30.7％ 34.6％ 36.0％ CV 0.03％ 0.02％ 0.01％

[0096] References

[0097] 1. Huang P, Zhang L, Gao Y, He Z, Yao D, Wu Z, et al. Direct reprogramming of human fibroblasts to functional and expandable hepatocytes. Cell stem cell 2014;14:370 - 84.

[0098] 2. Pullinger C R, North J D, Teng B B, et al. The apolipoprotein B gene is constitutively expressed in HepG2 cells: regulation of secretion by oleic acid, albumin, and insulin, and measurement of the mRNA half-life[J]. Journal of Lipid Research, 1989, 30(7): 1065 - 1077.

[0099] 3. Huang B, Zou G L, Yang T M. Study on the binding of adriamycin to bovine serum albumin[J]. Acta Chimica Sinica, 2002, 60(010): 1867 - 1871.

[0100] 4. Rothschild M A, Oratz M, Schreiber S S. Serum albumin. Am J Dig Dis. 1969 Oct; 14(10): 711 - 44.

Claims

1. An antibody targeting ALB or an antigen-binding fragment thereof, characterized in that, The antibody or its antigen-binding fragment comprises a heavy-chain variable region and a light-chain variable region. The heavy-chain variable region comprises HCDR1, HCDR2 and HCDR3 with amino acid sequences shown in SEQ ID NO:1, SEQ ID NO:2 and SEQ ID NO:3 respectively; the light-chain variable region comprises LCDR1, LCDR2 and LCDR3 with amino acid sequences shown in SEQ ID NO:6, SEQ ID NO:7 and SEQ ID NO:8 respectively.

2. The antibody or antigen-binding fragment thereof according to claim 1, wherein The amino acid sequence of the heavy-chain variable region is as shown in SEQ ID NO:4 or is an amino acid sequence having at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99% sequence identity with SEQ ID NO:4; and / or, the amino acid sequence of the light-chain variable region is as shown in SEQ ID NO:9 or is an amino acid sequence having at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99% sequence identity with SEQ ID NO:

9.

3. The antibody or antigen-binding fragment thereof according to claim 2, wherein, The antibody is a full-length antibody, Fab, Fab’, F(ab’)2, scFv, Fv or a multispecific antibody; Preferably, when the antibody is a full-length antibody, the heavy-chain constant region of the full-length antibody is derived from the heavy chain of a human antibody or its variant, and the light-chain constant region of the full-length antibody is derived from the κ chain or λ chain of a human antibody or its variant; More preferably, the amino acid sequence of the heavy-chain constant region is as shown in SEQ ID NO:25 or is an amino acid sequence having at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99% sequence identity with SEQ ID NO:25; and / or, the amino acid sequence of the light-chain constant region is as shown in SEQ ID NO:27 or is an amino acid sequence having at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99% sequence identity with SEQ ID NO:

27.

4. An isolated nucleic acid, characterized in that, The nucleic acid encodes the antibody or its antigen-binding fragment according to any one of claims 1 to 3; Preferably, the nucleotide sequence encoding the HCDR1 is as shown in SEQ ID NO: 11, the nucleotide sequence encoding the HCDR2 is as shown in SEQ ID NO: 12, and the nucleotide sequence encoding the HCDR3 is SEQ ID NO: 13; and / or, the nucleotide sequence encoding the LCDR1 is as shown in SEQ ID NO: 16, the nucleotide sequence encoding the LCDR2 is as shown in SEQ ID NO: 17, and the nucleotide sequence encoding the LCDR3 is as shown in SEQ ID NO: 18; More preferably, the nucleotide sequence encoding the heavy chain variable region is as shown in SEQ ID NO: 14; and / or, the nucleotide sequence encoding the light chain variable region is as shown in SEQ ID NO:

19.

5. A recombinant expression vector, characterized in that, The recombinant expression vector contains the nucleic acid as claimed in claim 4; Preferably, the recombinant expression vector is a plasmid, cosmid, phage or viral vector; More preferably, the viral vector is a retroviral vector, lentiviral vector, adenoviral vector or adeno-associated viral vector.

6. A cell, characterized in that, The cell contains the recombinant expression vector as claimed in claim 5 or the nucleic acid as claimed in claim 4; or expresses the antibody or its antigen-binding fragment as claimed in any one of claims 1 to 3; Preferably, the cell is a prokaryotic cell or a eukaryotic cell; More preferably, the cell is selected from yeast cells, mammalian cells or other cells suitable for preparing an antibody or its antigen-binding fragment; the mammalian cells are for example HEK293 cells.

7. A method for preparing an antibody targeting ALB or an antigen-binding fragment thereof, characterized in that, The method includes culturing the cell as claimed in claim 6 and obtaining an antibody targeting ALB or its antigen-binding fragment from the culture.

8. A kit, characterized in that, The kit includes the antibody or its antigen-binding fragment as claimed in any one of claims 1 to 3; Preferably, the kit further includes a reagent for detecting the binding of the antibody or its antigen-binding fragment to an antigen.

9. A method for detecting ALB, characterized in that, The method includes the step of contacting the antibody or its antigen-binding fragment as claimed in any one of claims 1 to 3 with a test sample; Preferably, the method is for non-diagnostic purposes.

10. Use of an antibody or its antigen-binding fragment as claimed in any one of claims 1 to 3, the nucleic acid as claimed in claim 4, the recombinant expression vector as claimed in claim 5 or the cell as claimed in claim 6 in the preparation of an ALB detection reagent.

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