Anti-herv-k102-env human antibodies and uses thereof

Abstract

This invention belongs to the field of biotechnology, specifically relating to human antibodies against HERV-K102-Env and their uses. This invention develops novel human monoclonal antibodies (hmAbs) against HERV-K102-Env that exhibit unexpected properties; currently, there are no commercially available human monoclonal antibodies against HERV-K-Env. The applicant has demonstrated that the 18 antibodies against HERV-K102-Env according to this invention are human monoclonal antibodies, some of which selectively bind to the TM antigen of HERV-K102-Env, some selectively bind to the SU antigen, and some simultaneously bind to both the SU and TM antigens of HERV-K102-Env.

Description

Technical Field

[0001] This invention belongs to the field of biotechnology, specifically relating to anti-HERV-K102-Env human antibodies and their uses. Background Technology

[0002] Human endogenous retroviruses (HERVs) are remnants of retroviruses that infected humans millions of years ago and integrated into the human genome, passing on their Mendelian genes to the present day, accounting for approximately 8% of the human genome. Most HERVs have lost their coding ability due to mutations, deletions, and the presence of stop codons in their coding sequences, and were previously considered junk DNA. However, in recent years, with the deepening of research on the biological functions of HERV, it has been found that the abnormal expression of some HERV-K102 subtype envelope proteins may be associated with tumors (Shah AH, et al. J Clin Invest. 2023 Jul 3; 133(13): e167929; Li M, et al. Clin Cancer Res. 2017 Oct 1; 23(19): 5892-5911; Ng KW, et al. Nature. 2023; 616: 563-573; Chen T, Leukemia. 2013; 27: 1469-78.), autoimmune diseases (Tokuyama M, et al. J Exp Med. 2021; 218(7): e20191766; Khadjinova AI, et al. Clin Exp Rheumatol. 2022; 40: 1306-1312), neurodegenerative diseases (Simula ER, et al. Viruses. 2021; 13: 2301; Johnson K, et al. Sci Transl Med. 2015; 7: 307ra153; Dembny P, et al. JCI Insight. 2020; 5: e131093; Dubowsky M, et al. Mol Neurobiol. 2023; 60: 6330-6345.) are closely related to the development and progression of HERVs. It is known that the C-terminal transmembrane domain (TM) of the HERV envelope protein (Env) contains multiple immunosuppressive domains, such as the fusion peptide (FP), immunosuppressive domains (ISD), and transmembrane domain (TMD), exhibiting strong immunosuppressive function and being an important cause of tumor immune tolerance. The N-terminus (SU) of the envelope protein participates in various inflammatory responses. HERV-K102-Env consists of two main parts: the N-terminal SU antigen and the C-terminal transmembrane TM antigen. SU is involved in various inflammatory responses, and TM has multiple immunosuppressive domains, making it one of the important causes of tumor immune tolerance.

[0003] Neurodegenerative diseases, such as Parkinson's disease, Alzheimer's disease, and amyotrophic lateral sclerosis (ALS), are associated with the accumulation of misfolded proteins inside and outside neurons and nerve cells in the central nervous system, but their exact causes are unknown. Previous studies have shown that HERV-K envelope proteins are abnormally highly expressed in diseased tissues (Simula ER, et al. Viruses. 2021; 13: 2301; Johnson K, et al. Sci Transl Med. 2015; 7: 307ra153; Dembny P, et al. JCI Insight. 2020; 5: e131093; Dubowsky M, et al. Mol Neurobiol. 2023; 60: 6330-6345.). HERV-K expression in human neuronal cultures induces neuronal cytotoxicity; dose-dependent reductions in neuronal numbers and neurite contraction were observed after transfection of the entire HERV-K genome or only the HERV-K-env gene. This suggests that intracellular HERV-K-Env proteins may contribute to neurotoxicity.

[0004] Autoimmune diseases such as systemic lupus erythematosus (SLE) are a large class of diseases that seriously endanger human health. To date, there are no effective drugs to cure these diseases, and their exact causes and pathogenesis are unknown. Some literature has reported that abnormal expression of HERV-K may be associated with autoimmune diseases such as SLE (Tokuyama M, ET AL. J Exp Med. 2021; 218(7): e20191766; Khadjinova AI, et al. Clin Exp Rheumatol. 2022; 40: 1306-1312).

[0005] In summary, these findings suggest that different HERV-K subtypes may be involved in the pathogenesis and progression of diseases such as tumors, neurodegenerative diseases, and autoimmune diseases.

[0006] To date, most malignant tumors, neurodegenerative diseases, and autoimmune diseases lack effective treatments and technologies. Finding effective treatments remains a pressing need for patients suffering from these fatal diseases. Therefore, developing effective drugs to address these unmet clinical needs is of great significance. Summary of the Invention

[0007] To solve the above technical problems,

[0008] This invention relates to antibodies that recognize human HERV-K102-Env, wherein the antibody binds to the antigenic epitopes TM and SU of HERV-K102-Env. The invention also relates to the use of antibodies recognizing HERV-K102-Env for therapeutic purposes, wherein the antibody binds to the antigenic epitopes TM and SU of HERV-K102-Env. Furthermore, the invention relates to human monoclonal antibodies recognizing HERV-K102-Env for the treatment of HERV-K102-related tumors, neurodegenerative diseases, and autoimmune diseases.

[0009] An isolated antibody or antigen-binding fragment thereof, wherein the CDR region of the antibody or antigen-binding fragment thereof includes HCDR and LCDR, wherein the HCDR region includes HCDR1, HCDR2 and HCDR3, and the LCDR region includes LCDR1, LCDR2 and LCDR3;

[0010] The HCDR1 amino acid sequence is any one of the sequences shown in SEQ ID NO: 1 to 18, the HCDR2 amino acid sequence is any one of the sequences shown in SEQ ID NO: 19 to 36, the HCDR3 amino acid sequence is any one of the sequences shown in SEQ ID NO: 37 to 54, the LCDR1 amino acid sequence is any one of the sequences shown in SEQ ID NO: 55 to 72, the LCDR2 amino acid sequence is any one of the sequences shown in SEQ ID NO: 73 to 90, and the LCDR3 amino acid sequence is any one of the sequences shown in SEQ ID NO: 91 to 108.

[0011] Preferably, the antibody or its antigen-binding fragment includes VH and VL, wherein the amino acid sequence of VH is as shown in SEQ ID NO: 109-126, and the amino acid sequence of VL is as shown in SEQ ID NO: 127-144.

[0012] Preferably, the antibody or its antigen-binding fragment includes any one of 18 antibodies or their antigen-binding fragments 1 to 18.

[0013] The VH amino acid sequences of the antibody or its antigen-binding fragments 1-18 are shown in SEQ ID NO: 109-126, and the VL amino acid sequences of the antibody or its antigen-binding fragments 1-18 are shown in SEQ ID NO: 127-144.

[0014] Preferably, the antibody or antigen-binding fragment specifically binds to HERV-K102-Env, and its binding antigen epitope is HERV-K102-Env-SU and / or HERV-K102-Env-TM. The amino acid sequence of HERV-K102-Env-SU is shown in SEQ ID NO: 149, and the amino acid sequence of HERV-K102-Env-TM is shown in SEQ ID NO: 150.

[0015] Preferably, the antibody is a human monoclonal antibody.

[0016] An isolated polynucleotide encoding the aforementioned antibody or its antigen-binding fragment.

[0017] An isolated vector comprising the aforementioned polynucleotides.

[0018] A host cell comprising the aforementioned polynucleotides or the aforementioned vector.

[0019] A kit for detecting HERV-K102-Env expression, comprising the antibody or antigen-binding fragment thereof described in any of the preceding claims.

[0020] The use of the antibody or its antigen-binding fragment as described above in products for detecting and / or diagnosing and / or treating HERV-K102-Env expression.

[0021] The aforementioned use of human monoclonal antibodies in products for the detection and / or diagnosis and / or treatment of HERV-K102-Env expression-related tumors, neurodegenerative diseases, or autoimmune diseases.

[0022] Preferably, the product is any one of CAR-T, CAR-NK, CAR-DC, TIL therapeutic cell products or ADC products.

[0023] The main beneficial effects of this invention are:

[0024] This invention develops a novel human monoclonal antibody (hmAb) against HERV-K102-Env that exhibits unexpected properties. Currently, there are no commercially available human monoclonal antibodies against HERV-K-Env.

[0025] The applicant has stated that the 18 antibodies against HERV-K102-Env according to the present invention are human monoclonal antibodies, some of which can selectively bind to the TM antigen of HERV-K102-Env, some can selectively bind to the SU antigen, and some can bind to both the SU and TM antigens of HERV-K102-Env simultaneously.

[0026] These antibodies have demonstrated their biological activity in ELISA, FCM (flow cytometry), and Western blot immunoassays. These antibodies recognize not only the SU and TM antigens of natural and denatured HERV-K102-Env, but also both non-glycosylated and glycosylated forms.

[0027] Furthermore, and most unexpectedly, the TM target epitope appears to be highly conserved, possessing a conserved amino acid sequence of the HERV-K-Env gene described in databases (the antigen HERV-K102-Env-TM sequence is shown in SEQ ID NO: 150). This endows these antibodies with unique localization, enabling their use in the diagnosis and treatment of diseases associated with different HERV-K subtypes. These unexpected results demonstrate that these human monoclonal antibodies against HERV-K102-Env are original tools for targeting HERV-K102-Env. This invention also shows that, even for those skilled in the art, the selection and acquisition of such monoclonal antibodies cannot be anticipated or predicted through a given immunization regimen. Attached Figure Description

[0028] Figure 1A-1D This is a graph showing the activity of self-produced control antibody and antigen determined by ELISA. Figure 1A The binding activity of the control antibody GN_mAb_Env_K01 to the antigen K102-SU-hFc protein was demonstrated; Figure 1B The binding activity of the control antibody HERM-1811-5 to the antigen K102-tTM-G4S-FC(IgG1)-strep was demonstrated; Figure 1C The binding activity of antigens K102-SU-hFc, K102-SU-FC(IgG1), and K102-tTM-G4S-FC(IgG1)-strep to the control antibody GN_mAb_Env_K01 was demonstrated. Figure 1D The binding activity of antigens K102-SU-FC(IgG1) and K102-tTM-G4S-FC(IgG1)-strep with the control antibody HERM-1811-5 was demonstrated.

[0029] Figure 2 This image shows the expression and activity of HERV-K102-Env in the self-produced overexpression cell line K102Mtm-SP-trN-mTM-G4S-3Flag-6His, determined by FACS.

[0030] Figures 3A-3C The image shows the competition between the binding of the candidate antibody to antigen K102-tTM-G4S-hFc-strep and 1G6-Biotin, as determined by ELISA. Figure 3AThe binding of A014, A050, A089, A068, and antigen K102-tTM-G4S-hFc-strep to 1G6-Biotin was shown to compete with 1G6-Biotin. Figure 3B The binding of A052, A062, A077, A082, A104, and A131 to antigen K102-tTM-G4S-hFc-strep was shown to compete with 1G6-Biotin. Figure 3C The binding of A083, A005, A017, A046, A047, A054, A075, and A049 to antigen K102-tTM-G4S-hFc-strep was shown to compete with 1G6-Biotin.

[0031] Figure 3D-3E The binding activity of the candidate antibody to antigen K102-SU-FC(IgG1) was demonstrated based on ELISA assay. Figure 3D The binding activity of A014, A050, A089, A068, A049, A052, A062, A077, A082, A104, and A131 to antigen K102-SU-FC (IgG1) was demonstrated. Figure 3E The binding activity of A083, A005, A017, A046, A047, A054, A075, A050, and A049 to antigen K102-SU-FC (IgG1) was demonstrated.

[0032] Figures 4A-4E This is a graph showing the binding activity of the candidate antibody to K102Mtm-SP-trN-mTM-G4S-3Flag-6His cells, as determined by FACS. Figures 4A-4B The binding activity of A014, A050, A089, and A068 cells to K102Mtm-SP-trN-mTM-G4S-3Flag-6His cells was demonstrated. Figure 4C-4D The binding activity of A049, A052, A062, A077, A082, A104, and A131 to K102Mtm-SP-trN-mTM-G4S-3Flag-6His cells was demonstrated. Figure 4E The binding activity of A005, A083, A017, A046, A047, A054, A075, A050, and A049 to K102Mtm-SP-trN-mTM-G4S-3Flag-6His cells was demonstrated.

[0033] Figure 5A-5I This is a diagram showing the pairing effect of the antibody with the K102-tTM-G4S-FC(IgG1)-strep antigen protein. Figure 5AThe pairing effects of 1G6 as the capture antibody and 1G6-Biotin, A017-Biotin, A050-Biotin, A014-Biotin, A068-Biotin, A052-Biotin, A062-Biotin, and A082-Biotin as the detection antibodies against the K102-tTM-G4S-FC(IgG1)-strep antigen protein were shown. Figure 5B The pairing effects of A017 as the capture antibody and 1G6-Biotin, A017-Biotin, A050-Biotin, A014-Biotin, A068-Biotin, A052-Biotin, A062-Biotin, and A082-Biotin as the detection antibodies against the K102-tTM-G4S-FC(IgG1)-strep antigen protein were shown. Figure 5C The pairing effects of A014 as the capture antibody and 1G6-Biotin, A017-Biotin, A050-Biotin, A014-Biotin, A068-Biotin, A052-Biotin, A062-Biotin, and A082-Biotin as the detection antibodies against the K102-tTM-G4S-FC(IgG1)-strep antigen protein are shown. Figure 5D The pairing effects of A068 as the capture antibody and 1G6-Biotin, A017-Biotin, A050-Biotin, A014-Biotin, A068-Biotin, A052-Biotin, A062-Biotin, and A082-Biotin as the detection antibodies against the K102-tTM-G4S-FC(IgG1)-strep antigen protein are shown. Figure 5E The pairing effects of A052 as the capture antibody and 1G6-Biotin, A017-Biotin, A050-Biotin, A014-Biotin, A068-Biotin, A052-Biotin, A062-Biotin, and A082-Biotin as the detection antibodies against the K102-tTM-G4S-FC(IgG1)-strep antigen protein were shown. Figure 5F The pairing effects of A062 as the capture antibody and 1G6-Biotin, A017-Biotin, A050-Biotin, A014-Biotin, A068-Biotin, A052-Biotin, A062-Biotin, and A082-Biotin as the detection antibodies against the K102-tTM-G4S-FC(IgG1)-strep antigen protein were shown. Figure 5GThe pairing effects of A082 as the capture antibody and 1G6-Biotin, A017-Biotin, A050-Biotin, A014-Biotin, A068-Biotin, A052-Biotin, A062-Biotin, and A082-Biotin as the detection antibody on the K102-tTM-G4S-FC(IgG1)-strep antigen protein were shown. Figure 5H The pairing effects of A050 as the capture antibody and 1G6-Biotin, A017-Biotin, A050-Biotin, A014-Biotin, A068-Biotin, A052-Biotin, A062-Biotin, and A082-Biotin as the detection antibodies against the K102-tTM-G4S-FC(IgG1)-strep antigen protein were shown. Figure 5I The pairing effect of 1G6, A017, A050, A014, A068, A052, A062, and A082 as capture antibodies and A082-Biotin as detection antibody on K102-tTM-G4S-FC(IgG1)-strep antigen protein was shown. Detailed Implementation

[0034] 1. Definitions:

[0035] Human endogenous retroviruses (HERVs);

[0036] Envelope proteins (Env);

[0037] The C-terminal transmembrane region (TM) is a transmembrane protein formed by the hydrolysis of Env by furin protease.

[0038] Fusion peptide (FP);

[0039] Immunosuppressive Domains (ISD);

[0040] Transmembrane Domain (TMD);

[0041] N-terminus of the envelope protein (SU);

[0042] HERV-K envelope protein (HERV-K-Env);

[0043] HERV-K102 envelope protein (HERV-K102-Env);

[0044] The extracellular domain of human HERV-K102-Env (huHERV-K102-Env-ECD);

[0045] Antibody light chain variable region (VL);

[0046] Antibody heavy chain variable region (VH);

[0047] Antibody light chain complementarity-determining region (LCDR);

[0048] Antibody heavy chain complementarity-determining region (HCDR);

[0049] The N-terminus of the HERV-K102 envelope protein (HERV-K102-Env-SU);

[0050] The C-terminal transmembrane region of the HERV-K102 envelope protein (HERV-K102-Env-TM);

[0051] Systemic lupus erythematosus (SLE);

[0052] High-frequency mutation regions: CDR (complementarity determining regions);

[0053] Antibody-drug conjugates (ADCs);

[0054] Human IgG1 Fc: hIgG1 Fc;

[0055] Human IgG1 heavy chain constant region: hIgG1 CH;

[0056] The constant region of the human IgG1 light chain of antibody KAPPA: hIgG1 CL(KAPPA);

[0057] The human IgG1 light chain constant region of antibody Lambda: hIgG1 CL (Lambda).

[0058] Example 1: Raw material preparation and identification

[0059] 1.1 Preparation and Construction of Fully Human Phage Display Library Materials

[0060] 1.1.1 Construction of a sample bank for SLE-positive patients

[0061] The basic steps for validating SLE-positive patient samples using K-TM eukaryotic protein, which was developed by our research group, are as follows: Peripheral blood was collected from SLE patients, centrifuged to obtain the supernatant plasma, and added to the primary antibody dilution buffer at a 1:1000 dilution ratio for subsequent primary antibody validation. Western blot experiments were performed using K-TM eukaryotic protein, following the basic procedures for Western blot experiments. The transferred PVDF membrane was placed in the prepared primary antibody solution. After incubation with both primary and secondary antibodies, color development was performed. The presence of clear bands in the color development confirmed positive plasma, corresponding to SLE-positive patients.

[0062] K-TM eukaryotic protein preparation method

[0063] High-purity Strep-tagged K-TM eukaryotic protein was purified using Strep-tag technology. The specific experimental steps are as follows:

[0064] The complete K-TM amino acid sequence was cloned into the pcDNA3.1(+) vector by fusing a Strep tag at the C-terminus, resulting in the pcDNA3.1(+)-K-TM-Strep plasmid. The Strep tag sequence is shown in SEQ ID NO: 151: 5'-TGGAGCCACCCGCAGTTCGAAAAG-3'. The obtained plasmid was subjected to ExpiFectamine... TM 293 Transfection Kit (Gibco) TM A14524) was transiently transfected into HEK293 cells. CRL-1573 TM In the process, after 72 hours of transfection and expression, cell supernatant was collected, and the Strep-tagged antigen was expressed via... The target protein was purified using Tactin XT (IBA) affinity chromatography. The purified protein was then transferred to PBS buffer via ultrafiltration concentrator (Millipore, UFC901096) to obtain the K-TM eukaryotic protein.

[0065] 1.1.2 Preparation of cDNA from a fully human antibody library

[0066] 1.1.2.1 Isolation of peripheral blood mononuclear cells (PBMCs) from positive SLE patients

[0067] Collect peripheral blood samples from the patient and transfer them to a 15 mL centrifuge tube. Add an equal volume of 1×PBS buffer. Take another 15 mL centrifuge tube and add 5 mL of lymphocyte separation medium. Carefully add the PBS-diluted blood sample slowly along the wall of the centrifuge tube into the lymphocyte separation medium, taking care not to disrupt the separation interface. Centrifuge at 2500 rpm (increase speed 2, decrease speed 3) at room temperature for 25 min. After centrifugation, aspirate the white membrane layer in the middle of the sample, which contains mononuclear cells, and wash once with 1×PBS. Centrifuge at 1500 rpm at room temperature for 5 min. The precipitate is PBMCs, which should be resuspended in 1×PBS for later use.

[0068] 1.1.2.2 Preparation of cDNA from positive SLE patients

[0069] RNA was extracted from PBMCs of SLE-positive patients using the Trizol method. The resulting RNA precipitate was dissolved in 20-50 μL of RNase-free water, and the RNA quality was measured using a spectrophotometer. Takara PrimeScript was used. TM The II One-Step cDNA Synthesis Kit (Takara, 6210A) reverse transcribes full-length RNA into cDNA.

[0070] 1.1.3 Construction of a fully human phage display library

[0071] Using the #1 to #32 cDNAs of human positive SLE patients prepared above as templates, light and heavy chain genes were amplified by molecular cloning technology. Antibody genes were recombined by in vitro ligation. The vector and Fab gene sequences were digested with enzymes to construct the antibody nucleotide sequence into a phage display vector. The constructed vector was then electroporated into Escherichia coli to obtain a fully human phage display library.

[0072] 1.2 Preparation and Identification of HERV-K102-Env Control Antibody

[0073] Preparation of HERV-K102-Env control antibody: The positive control antibodies used in this invention are anti-HERV-K102-Env antibody GN_mAb_Env_K01 (patent number: US2019 / 0345232 A1) and commercial antibody HERM-1811-5 (AUSTRALBiologicals, CAT NO: HERM-1811-5). The target fragment was synthesized by General Biotechnology Co., Ltd. according to the sequence disclosed in the corresponding patent. Then, the eukaryotic expression vector pcDNA3.4-TOPO (Invitrogen) was constructed using homologous recombination. The constructed recombinant protein expression vector was transformed into E. coli DH5α and cultured overnight at 37°C. Plasmid extraction was then performed using an endotoxin-free plasmid extraction kit (OMEGA, D6950-01) and analyzed by ExpiFectamine. TM Expression was performed using a CHO transfection kit (Thermo Fisher, A29129). Seven days after transfection, the cell expression supernatant was centrifuged at 15000g for 10 min. The supernatant was filtered through a 0.22 μm filter and purified using Protein A / G affinity chromatography. After purification, the target protein was eluted with 100 mM glycine (pH 3.0), and the eluted protein was transferred to PBS buffer via an ultrafiltration concentrator (Millipore, UFC901096).

[0074] HERV-K102-Env control antibody identification: The activity of the prepared positive control antibodies GN_mAb_Env_K01 and HERM-1811-5 was detected using K102-SU-hFc and K102-tTM-G4S-FC(IgG1)-strep antigen proteins. The specific method is as follows: K102-SU-hFc and K102-tTM-G4S-FC(IgG1)-strep (2 μg / mL, 30 μL / well) were coated on a 96-well ELISA plate and incubated overnight at 4°C; after washing the plate 3 times, it was blocked with 5% skim milk prepared in PBS at room temperature for 1 hour; after washing the plate... After three washes, control antibodies GN_mAb_Env_K01 and HERM-1811-5, serially diluted with PBS, were added and incubated at room temperature for 1 hour. After washing, secondary antibodies Anti-human κ+λ-HRP (Millipore; AP502P; AP506P) and Anti-mouse-IgG-Fc-HRP (abcam; ab97265), diluted 1:6000 with PBS, were added and incubated at room temperature for 1 hour. After washing 6 times, TMB (SurModics, TMBS-1000-01) was added for color development for 5–20 minutes. After stopping the color development, the OD value of the microplate reader was measured. 450Read the data, process it, and use GraphPad Prism to create a graph. The result is as follows: Figure 1A , 1B The results showed that the produced control antibodies GN_mAb_Env_K01 and HERM-1811-5 could bind normally to the HERV-K102-Env antigen protein (see 1.3 Antigen Protein Preparation), and the control antibodies GN_mAb_Env_K01 and HERM-1811-5 had normal activity and normal anti-HERV-K102-Env activity.

[0075] 1.3 Preparation and Identification of Antigen Proteins

[0076] Antigen protein preparation: A nucleotide sequence encoding a human Fc (hFc, SEQ ID NO: 145) tag was added to the 3′ end of the nucleotide sequence encoding the extracellular domain of human HERV-K102-Env (huHERV-K102-Env-ECD, see: Uniprot ID: P15328 AA25-234). This was constructed into the pcDNA3.4 vector via homologous recombination. The constructed recombinant protein expression vector was transformed into *E. coli* DH5α and cultured overnight at 37°C. Plasmid extraction was then performed using an endotoxin-free plasmid extraction kit. The obtained plasmids were analyzed using ExpiFectamine. TM 293 Transfection Kit (Gibco) TM A14524) was transiently transfected into K102-HEK293 cells ( CRL-1573 TM After 7 days of expression, cell supernatant was collected, and the Fc-tagged antigen was purified using a conventional Protein A / G affinity chromatography column. The purified target protein was eluted with 100 mM glycine (pH 3.0), concentrated, and replaced to obtain the antigen proteins K102-SU-hFc, K102-tTM-G4S-FC(IgG1)-strep, and K102-SU-FC(IgG1). The eluted proteins were then transferred to PBS buffer via ultrafiltration concentrators (Millipore, UFC901096) to obtain the final antigen proteins (K102-SU-hFc, K102-tTM-G4S-FC(IgG1)-strep, and K102-SU-FC(IgG1)).

[0077] Antigen identification: The activity of the prepared antigens (K102-SU-hFc, K102-tTM-G4S-FC(IgG1)-strep, K102-SU-FC(IgG1)) was detected using the control antibodies GN_mAb_Env_K01 and HERM-1811-5 that passed the quality inspection in Example 1.1. The specific method is as follows: ELISA plates were coated overnight at 4℃ with 2 μg / mL K102-SU-hFc, K102-tTM-G4S-FC(IgG1)-strep, and K102-SU-FC(IgG1); after washing the plates three times, they were blocked with 5% skim milk prepared in PBS at room temperature for 1 hour; after washing the plates three times, control antibodies GN_mAb_Env_K01 and HERM-1811-5, serially diluted in PBS, were added and incubated at room temperature for 1 hour; after washing the plates, secondary antibodies Goat-Anti-mouse-IgG-Fc-HRP (abcam; ab97265) and add Anti-mouse Fc-HRP (abcam; ab97265) diluted in PBS (1:8000) were added and incubated at room temperature for 1 hour, followed by washing the plates six times and adding TMB for 5–20 min for color development. After stopping the color development, the OD value of the microplate reader was measured. 450 Read the data, process it, and use GraphPad Prism to create a graph. The result is as follows: Figure 1C-1D The results show that the antigens K102-SU-FC(IgG1) and K102-SU-hFc, which the applicant constructed and expressed, can bind normally to the antibody GN_mAb_Env_K01, and the antigen K102-tTM-G4S-FC(IgG1)-strep can bind normally to the antibody HERM-1811-5.

[0078] Example 2. Construction and identification of cell lines overexpressing human HERV-K102-Env

[0079] 2.1 Construction of K102MTM-SP-TRN-MTM-G4S-3FLAG-6HIS cell line overexpressing human HERV-K102-Env:

[0080] The nucleic acid sequence encoding the full-length human HERV-K102-Env (Uniprot ID: P15328) was constructed into the pLVX-puro plasmid (Clontech, Cat#632164). The resulting plasmid was then electroporated into K102MTM-SP-TRN-MTM-G4S-3FLAG-6HIS cells using an Invitrogen Neon™ Transfection System (MP922947). After electroporation, the cells were transferred to DMEM medium (Gibco, 11995065) containing 10% FBS (Gibco, 15140-141) and free of antibiotics. The cells were then seeded in 10×10 cm cell culture dishes and cultured for 48 hours, followed by inoculation at an average rate of 0.5×10⁻⁶ cells / cm². 4 Cells were aliquoted into 96-well cell culture plates at a density of cells / well, and puromycin was added to a final concentration of 2 μg / mL as a selection pressure. Cell line clonal growth was observed after about 2 weeks, and cell lines that formed clones were selected for identification.

[0081] Flow cytometry identification of huHERV-K102-Env-K102MTM-SP-TRN-MTM-G4S-3FLAG-6HIS cells:

[0082] Logarithmically growing cells were digested and plated into 96-well plates. After washing with FACS buffer (1×PBS buffer containing 2% FBS), primary antibodies were serially diluted with PBS for staining (Abs dilutions were used for huHERV-K102-Env-K102MTM-SP-TRN-MTM-G4S-3FLAG-6HIS cells), and incubated at 4°C for 30 min. After washing, the prepared fluorescent secondary antibody Anti-Human IgG, FcγPE (Jackson 109-115-0981:200) was added, and incubated at 4°C for 30 min. Finally, the cells were detected by flow cytometry (Beckman, CytoFLEXAOO-1-1102). The results are shown below. Figure 2 The results showed that human HERV-K102-Env was highly expressed on the surface of huHERV-K102-Env-K102MTM-SP-TRN-MTM-G4S-3FLAG-6HIS cells.

[0083] Example 3. Construction and screening of human phage-displaying recombinant antibody libraries

[0084] In this embodiment, an antibody gene phage display library was constructed, and the antigen proteins K102-SU-FC(IgG1) and K102-tTM-G4S-FC(IgG1)-strep prepared in Example 1.3 were used as screening antigens to screen the library, and multiple antibody molecules that specifically bind to human HERV-K102-Env were obtained.

[0085] 3.1 Construction of a gene library of human antibodies

[0086] Based on the sequence similarity of the heavy and light chain germline genes, degenerate primers were designed at the front end of the heavy chain variable region and the back end of the first constant region of the heavy chain, as well as at the front end of the light chain variable region and the back end of the light chain constant region (Li Xiaolin, Construction and Preliminary Screening of a Large-Capacity Non-Immune Human Fab Phage Antibody Library, Master's Thesis, Peking Union Medical College, June 2007). After PCR, the heavy chain variable region gene fragments and light chain variable region gene fragments of the antibody were obtained. Fragments containing the antibody's light chain variable region and heavy chain variable region were amplified using fusion PCR. The PCR product and the phage display vector were digested with enzymes, recovered, and ligated. The ligation product was recovered using a recovery kit (Omega, catalog number: D6492-02). Finally, the bacteria were transformed into competent *Escherichia coli* SS320 (Lucigen, MC1061 F) using an electroporator (Bio-Rad, MicroPulser). The transformed *E. coli* SS320 culture was then plated onto ampicillin-resistant 2-YT agar plates (the agar plates were prepared from 1.5% tryptone, 1% yeast extract, 0.5% NaCl, and 1.5% agar, at a mass-volume ratio of g / mL). The library size was determined to be 3.67 × 10⁻⁶ cells / mL by serial dilution. 8 CFU, i.e., 3.67 × 10 8 An antibody gene library of 1 antibody gene was prepared (the library size calculation method is described in Example 2.2 of patent CN112250763B). The library was packaged using VSCM13 helper phage (purchased from Stratagene) to obtain an antibody gene phage display library (the preparation of the antibody gene phage display library is described in Example 2.3 of patent CN112250763B).

[0087] 3.2 Screening of antibody gene phage display libraries

[0088] 3.2.1 Screening of antibody gene phage display libraries using magnetic bead method

[0089] Magnetic bead screening is based on biotin-labeling of antigen proteins K102-SU-FC(IgG1) and K102-tTM-G4S-FC(IgG1)-strep, followed by binding with streptavidin-conjugated magnetic beads. The process involves incubating, washing, and eluting the antigen-bound magnetic beads and antibody gene phage display libraries. Typically, 3-4 rounds of screening are performed, thereby enriching a large number of specific monoclonal antibodies against the antigen. In this embodiment, biotin-labeled K102-SU-hFc-Biotin and K102-tTM-G4S-FC(IgG1)-strep-Biotin are used for phage display library screening. After 3 rounds of screening, initial screening for monoclonal antibodies against K102-SU-FC(IgG1) and K102-tTM-G4S-FC(IgG1)-strep is conducted, with specific methods referring to Example 2.4.1 in patent CN112250763B.

[0090] 3.2.2 Screening of antibody gene phage display libraries using the immunotube method

[0091] The principle of the immunotube screening method is to coat the antigen proteins K102-SU-FC(IgG1) and K102-tTM-G4S-FC(IgG1)-strep onto the surface of an immunotube with high adsorption capacity. A phage display antibody library is added to the immunotube, and the antigen proteins adsorbed on the immunotube surface are incubated, washed, and eluted. This process involves 3-4 rounds of panning to ultimately enrich the specific monoclonal antibodies against the antigen. In this example, after 3 rounds of panning, initial screening for monoclonal antibodies against K102-SU-FC(IgG1) and K102-tTM-G4S-FC(IgG1)-strep is performed, with specific methods referring to Example 2.4.2 in patent CN112250763B.

[0092] 3.3 Selection of Monoclonal Cells

[0093] The enrichment effect was evaluated by ELISA detection of the phage pools eluted in each round. A total of 512 clones were randomly selected from the phage pools screened in each round for initial screening, and 135 positive clones were selected for sequence analysis.

[0094] ELISA monoclonal screening used the antigen proteins K102-SU-FC(IgG1) and K102-tTM-G4S-FC(IgG1)-strep, identifying 68 antibody Fab molecules that specifically bind to either K102-SU-FC(IgG1) or K102-tTM-G4S-FC(IgG1)-strep. The screened antibody Fab molecules were named according to their clone numbers, and 18 molecules were selected for further validation. The CDR regions and light and heavy chain amino acid sequences of the relevant antibody Fab molecules are shown in the sequence listing. The complementarity-determining region (CDR) sequence was determined using the AbM (Abstract Method for Defining Complementarity) method.

[0095] Example 4 Antibody Construction, Expression and Purification

[0096] 4.1 Plasmid Construction

[0097] The coding sequences for VH in the Fab sequences of the selected monoclonal antibodies A005, A014, A017, A046, A047, A049, A050, A052, A054, A062, A068, A075, A077, A082, A083, A089, A104, and A131 were ligated with the coding sequence for the heavy chain constant region of human IgG1 to construct the heavy chain coding sequence of the fully human antibody. The coding sequences for VL in the Fab sequences were ligated with the coding sequence for the Kappa type of the light chain constant region (CL) of human to construct the light chain coding sequence of the fully human antibody. The antibody heavy and light chain coding sequences were inserted into the eukaryotic expression vector plasmid pcDNA3.4 (Invitrogen), respectively, and transformed into *E. coli* DH5α, cultured overnight at 37°C. Endotoxin-free plasmid extraction was performed using an endotoxin-free plasmid extraction kit to obtain endotoxin-free antibody plasmids for eukaryotic expression.

[0098] 4.2 Antibody Expression and Purification

[0099] The candidate antibody was expressed using the ExpiCHO transient transfection system (Thermo Fisher, A29133), and the specific method is as follows: On the day of transfection, the cell density was confirmed to be 7 × 10⁶ cells / year. 6 Up to 1×10 7 With approximately 100 viable cells / mL and a cell viability >98%, ExpiFectamine was then expressed in fresh ExpiCHO expression medium pre-warmed at 37°C. TM CHO cells were adjusted to a final concentration of 6 × 10⁻⁶. 6 Cells / mL. OptiPRO pre-cooled to 4°C TM SFM dilution of the target plasmid (add 1 μg of plasmid to 1 mL of the culture medium), then mixing the two in equal volumes and gently pipetting to prepare ExpiFectamine. TMIncubate the CHO / plasmid DNA mixture at room temperature for 1–5 minutes, then slowly add it to the prepared cell suspension while gently shaking. Finally, place the mixture in a cell culture shaker and culture at 37°C and 8% CO2.

[0100] Add ExpiCHO to the culture medium 18–22 hours after transfection. TM Enhancer and ExpiCHO TM Feed, and place the shake flasks in a shaker at 32°C and 5% CO2 for further incubation. On day 5 post-transfection, add the same volume of ExpiCHO. TM Feed the cells slowly while gently mixing the cell suspension. Seven days after transfection, centrifuge the cell culture supernatant expressing the target protein at 15000g for 10 min. The supernatant was then affinity purified using MabSelect SuRe LX (GE, 17547403), followed by elution with 100mM sodium acetate (pH 3.0), neutralization with 1M Tris-HCl, and finally, the protein was transferred to PBS buffer via ultrafiltration concentrator (Millipore, UFC901096).

[0101] Example 5: Identification of the physicochemical properties of the antibody

[0102] In this embodiment, the relative molecular weight and purity of the candidate antibody were detected by SDS-PAGE and SEC-HPLC.

[0103] 5.1 Antibody SDS-PAGE Identification

[0104] Preparation of non-reducing solution: Add 1 μg of each obtained antibody and the quality control IPI (ipilimumab) to 5×SDS loading buffer and 40 mM iodoacetamide, respectively. Heat in a dry bath at 75°C for 10 min, cool to room temperature, and centrifuge at 12000 rpm for 5 min to collect the supernatant.

[0105] Preparation of reducing solution: Add 2 μg of each obtained antibody and the quality control IPI to 5×SDS loading buffer and 5 mM DTT, respectively. Heat in a dry bath at 100℃ for 10 min, cool to room temperature, and centrifuge at 12000 rpm for 5 min to collect the supernatant. Add the supernatant to a Bis-tris 4-15% gradient gel (GenScript) for gel electrophoresis and stain with Coomassie Brilliant Blue to visualize the protein bands.

[0106] Protein gels with chromogenic protein bands were scanned using an EPSON V550 color scanner (decolorized with decolorizing solution until the gel background was transparent). The purity of reduced and non-reduced bands was calculated using ImageJ according to the peak area normalization method.

[0107] The results are shown in Table 2. The bands of each antibody on the non-reducing gel were around 150 kDa, while the bands on the reducing gel were around 55 kDa and 25 kDa, respectively, which are in line with expectations. The purity of all candidate antibodies detected by reducing gel electrophoresis was greater than 90%.

[0108] 5.2 SEC-HPLC identification of antibody monomer purity

[0109] Materials Preparation: 1. Mobile Phase: 150 mmol / L phosphate buffer, pH 7.4; 2. Sample Preparation: Dilute each antibody and the quality control IPI to 0.5 mg / mL with the mobile phase solution. An Agilent HPLC 1100 column (XBridge BEH SEC 3.5 μm, 7.8 mm ID × 30 cm) was used, with a Waters flow rate of 0.8 mL / min, an injection volume of 20 μL, and VWD detector wavelengths of 280 nm and 214 nm. Blank solution, IPI quality control solution, and sample solution were injected sequentially. The percentages of high molecular weight polymers, antibody monomers, and low molecular weight substances in the samples were calculated using the area normalization method. The physicochemical properties of the candidate antibodies obtained are shown in Table 1.

[0110] Table 1 Physicochemical properties of candidate antibodies obtained in this invention

[0111]

[0112]

[0113] Note: N / A indicates that no test was performed.

[0114] Example 6: Detection of Antibody Antigen Binding Activity

[0115] In this embodiment, the affinity of candidate antibodies (A005, A014, A017, A046, A047, A049, A050, A052, A054, A062, A068, A075, A077, A082, A083, A089, A104, A131) for human HERV-K102-Env antigen protein K102-SU-FC (IgG1) was detected using the ELISA method. The binding ability of candidate antibodies to human HERV-K102-Env overexpressing cells K102Mtm-SP-trN-mTM-G4S-3Flag-6His was also detected using the FACS method.

[0116] 6.1 Detection of the binding energy of candidate antibodies to antigen protein K102-tTM-G4S-hFc-strep using ELISA double-antibody sandwich assay

[0117] force

[0118] Control antibody and candidate antibody (2 μg / mL, 30 μL / well) were coated onto 96-well ELISA plates and incubated overnight at 4°C. The next day, the plates were washed three times with PBST, blocked with 5% skim milk for 2 h, washed three times with PBST, and then serially diluted K102-tTM-G4S-hFc-strep was added and incubated for 1 h. After washing three times with PBST, the detection antibody 1G6-Biotin (2 μg / mL, 30 μL / well) was added and incubated for 1 h. After washing three times with PBST, the secondary antibody NeutrAvidin-HRP (Thermo, 31001) was added and incubated for 1 h. After incubation, the plates were washed six times with PBST and TMB was added for color development. Based on the color development results, 2 H₂SO₄ was added to terminate the reaction. The plates were then read from OD₂O₃ using a microplate reader (Molecular Devices, SpecterMax 190). 450 Read data below.

[0119] The results are as follows Figures 3A-3C As shown, A014, A050, A068, A052, A062, A077, A082, A104, A131, A083, A054, A075, A050, and A049 pair with 1G6 and exhibit good affinity activity for the antigen protein K102-tTM-G4S-hFc-strep.

[0120] 6.2 ELISA-based detection of the binding affinity of candidate antibodies to antigen protein K102-SU-FC (IgG1)

[0121] K102-SU-FC(IgG1) (2 μg / mL, 30 μL / well) was coated onto 96-well ELISA plates and incubated overnight at 4°C. The next day, the plates were washed three times with PBST, blocked with 5% skim milk for 2 hours, washed three times with PBST, and then serially diluted candidate antibody and positive control antibody GN_mAb_Env_K01 were added and incubated for 1 hour. After washing three times with PBST, secondary antibody Anti-Human-κ+λ-HRP (Millipore, AP502P, AP506P) was added and incubated for 1 hour. After incubation, the plates were washed six times with PBST and TMB was added for color development. Based on the color development results, the reaction was terminated by adding 2M HCl, and the plates were then analyzed using a microplate reader (Molecular Devices, SpecterMax 190) at OD500. 450 Read data below.

[0122] The results are as follows Figure 3D-3EAs shown, A014, A017, A047, A054, A062, A077, A082, A083, A104, and A131 all exhibit good affinity activity for the antigen protein K102-SU-FC (IgG1).

[0123] 6.3 FACS-based detection of the binding ability of candidate antibodies to K102Mtm-SP-trN-mTM-G4S-3Flag-6His cells

[0124] In this embodiment, K102Mtm-SP-trN-mTM-G4S-3Flag-6His cells were used to evaluate the binding activity of the candidate antibody.

[0125] The specific method is as follows: K102Mtm-SP-trN-mTM-G4S-3Flag-6His cells in the logarithmic growth phase were prepared into a single-cell suspension, and the density was adjusted to 1×10⁻⁶. 6 Cells / mL, 100 μL per well, were added to each well of a 96-well round-bottom plate, centrifuged at 300 g at 4 °C, and the supernatant was removed. Serially diluted candidate antibodies and positive control antibody A032 (self-made) or serum were added to the corresponding wells, mixed, and incubated at 4 °C for 30 min. After washing the incubated cell mixture twice, 100 μL of a 1:300 diluted secondary antibody Goat F(ab')2 Anti-Human IgG-Fc was added, and the mixture was incubated at 4 °C in the dark for 30 min. After washing twice, the cells were analyzed by flow cytometry (Beckman, CytoFLEX AOO-1-1102).

[0126] The results are as follows Figures 4A-4E As shown, candidate antibodies A005, A017, A046, A047, A052, A062, A068, and A089 all exhibit good affinity for K102Mtm-SP-trN-mTM-G4S-3Flag-6His cells.

[0127] Example 7: ELISA Double Antibody Sandwich Method Pairing

[0128] 7.1 Antibody pairing for K102-tTM-G4S-FC(IgG1)-strep antigen protein based on ELISA double-antibody sandwich method:

[0129] 96-well ELISA plates were coated with 4 μg / mL antibody (30 μL / well) and incubated overnight at 4°C. The next day, the plates were washed three times with PBST and blocked with 5% skim milk for 2 h. After washing three more times with PBST, serially diluted (10, 2.0, 0.4, 0.08, 0.016, 0.0032 μg / mL) K102-tTM-G4S-FC(IgG1)-strep was added and incubated for 1 h. After washing three times with PBST, 4 μg / mL biotinylated detection antibody was added and incubated for 1 h. After washing three times with PBST, secondary antibody NeutrAvidin-HRP (Thermo, 31001) was added and incubated for 1 h. After incubation, the plates were washed six times with PBST and developed with TMB (SurModics, TMBS-1000-01). Based on the colorimetric results, the reaction was terminated by adding 2M stop solution. The OD was then measured using a microplate reader (Molecular Devices, SpecterMax190). 450 Read the absorbance at the location.

[0130] The results are as follows Figures 5A to 5I As shown: The coating antibodies are A050, A068, A062, and A052, and the detection antibody is 1G6-Biotin. These four pairs of paired antibodies show superior detection efficiency for the K102-tTM-G4S-FC(IgG1)-strep antigen, with higher EC50 values. 50 The concentrations ranged from 0.0007 μg / mL to 0.0593 μg / mL. Eight pairs of paired antibodies—1G6 and A062-Biotin, A050 and A062-Biotin, 1G6 and A082-Biotin, 1G6 and A068-Biotin, A082 and 1G6-Biotin, 1G6 and A052-Biotin, A068 and A014-Biotin, and A062 and A014-Biotin—showed excellent efficacy in detecting K102-tTM-G4S-FC(IgG1)-strep antigen, with EC50 values ​​ranging from 0.0007 μg / mL to 0.0593 μg / mL. 50 Within 0.1256μg / mL~0.2824μg / mL.

[0131] The variable regions of an antibody contain relatively short sequences that exhibit high diversity and are known as high-frequency mutation regions. There are three such sequences in the variable regions of both the light and heavy chains, and they are called CDRs (complementarity-determining regions). These sequences are associated with the antibody's specific recognition of antigens.

[0132] In Table 2, the HCDR1 sequence is listed from top to bottom according to the clone number: SEQ ID NO: 1-18, HCDR2 sequence is listed from top to bottom: SEQ ID NO: 19-36, HCDR3 sequence is listed from top to bottom: SEQ ID NO: 37-54, LCDR1 sequence is listed from top to bottom: SEQ ID NO: 55-72, LCDR2 sequence is listed from top to bottom: SEQ ID NO: 73-90, and LCDR3 sequence is listed from top to bottom: SEQ ID NO: 91-108.

[0133] Table 2: Sequence Listing 1, Amino acid sequences of the CDR region of the delivered antibody

[0134]

[0135]

[0136] In Table 3, according to clone number, the VH sequences are listed as SEQ ID NO: 109–126, and the VL sequences are listed as SEQ ID: 109–126.

[0137] NO: 127~144.

[0138] Table 3: Sequence Listing 2, Light and Heavy Chain Sequences of Delivered Antibodies

[0139]

[0140]

[0141]

[0142] Table 4: Antibody Pairing Table

[0143]

[0144]

[0145]

[0146] Table 5: Antigen binding status of 18 antibody molecules

[0147] protein name Antigen binding status A005 Cross-bonded SU-TM A083 Single-binding™ A017 Single-combination SU A046 Cross-bonded SU-TM A047 Cross-bonded SU-TM A054 Single-binding™ A075 Single-binding™ A050 Single-binding™ A049 Cross-bonded SU-TM A014 Cross-bonded SU-TM A068 Single-binding™ A052 Single-binding™ A062 Single-binding™ A077 Single-binding™ A082 Cross-bonded SU-TM A104 Single-binding™ A131 Single-binding™ A089 Cross-bonded SU-TM

[0148] In Table 5, TM refers to HERV-K102-Env-TM, SU refers to HERV-K102-Env-SU, and SU-TM refers to both HERV-K102-Env-SU and HERV-K102-Env-TM.

[0149] The sequence of the antigen HERV-K102-Env-SU is shown in SEQ ID NO: 149:

[0150] MVTPVTWMDNPIEIYVNDSVWVPGPIDDRCPAKPEEEGMMINISIGYRYPPICLGRAP

[0151] GCLMPAVQNWLVEVPTVSPISRFTYHMVSGMSLRPRVNYLQDFSYQRSLKFRPKGKP

[0152] CPKEIPKESKNTEVLVWEECVANSAVILQNNEFGTIIDWAPRGQFYHNCSGQTQSCPS

[0153] AQVSPAVDSDLTESLDKHKHKKLQSFYPWEWGEKRISTPRPKIVSPVSGPEHPELWRL

[0154] TVASHHIRIWSGNQTLETRDCKPFYTIDLNSSLTVPLQSCVKPPYMLVVGNIVIKPDSQ

[0155] TITCENCRLLSCIDSTFNWQHRILLVRAREGVWIPVSMDRPWEASPSVHILTEVLKGV

[0156] LNRSKR

[0157] The antigen HERV-K102-Env-TM sequence is shown in SEQ ID NO: 150:

[0158] FIFTLIAVIMGLIAVTATAAVAGVALHSSVQSVNFVNDWQKNSTRLWNSQSSIDQKLA

[0159] NQINDLRQTVIWMGDRLMSLEHRFQLQCDWNTSDFCITPQIYNESEHHWDMVRRHL

[0160] QGREDNLTLDISKLKEQIFEASKAHLNLVPGTEAIAGVADGLANLNPVTWVKTIGSTT

[0161] IINLILILVCLFCLLLVCRCTQQLRRDSDHRERAMMTMAVLSKRKGGNVGKSKRDQI

[0162] VTVSV

[0163] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims. Furthermore, all documents mentioned in this invention are incorporated herein by reference as if each document were individually incorporated by reference.

Claims

1. An isolated antibody or its antigen-binding fragment, characterized in that, The CDR region of the antibody or its antigen-binding fragment includes HCDR and LCDR, wherein the HCDR region includes HCDR1, HCDR2 and HCDR3, and the LCDR region includes LCDR1, LCDR2 and LCDR3; The amino acid sequences of the antibody or its antigen-binding fragment are as follows: SEQ ID NO: 1, SEQ ID NO: 19, SEQ ID NO: 37, SEQ ID NO: 55, SEQ ID NO: 73, and SEQ ID NO:

91. The amino acid sequences of the antibody or its antigen-binding fragment are as follows: SEQ ID NO: 2, SEQ ID NO: 20, SEQ ID NO: 38, SEQ ID NO: 56, SEQ ID NO: 74, and SEQ ID NO:

92. The amino acid sequences of the antibody or its antigen-binding fragment are as follows: SEQ ID NO: 3, SEQ ID NO: 21, SEQ ID NO: 39, SEQ ID NO: 57, SEQ ID NO: 75, and SEQ ID NO:

93. The amino acid sequences of the antibody or its antigen-binding fragment are as follows: SEQ ID NO: 4, SEQ ID NO: 22, SEQ ID NO: 40, SEQ ID NO: 58, SEQ ID NO: 76, and SEQ ID NO:

94. The amino acid sequences of the antibody or its antigen-binding fragment are as follows: SEQ ID NO: 5, SEQ ID NO: 23, SEQ ID NO: 41, SEQ ID NO: 59, SEQ ID NO: 77, and SEQ ID NO:

95. The amino acid sequences of the antibody or its antigen-binding fragment are as follows: SEQ ID NO: 7, SEQ ID NO: 25, SEQ ID NO: 43, SEQ ID NO: 61, SEQ ID NO: 79, and SEQ ID NO:

97. The antibody or antigen-binding fragment specifically binds to HERV-K102-Env.

2. The isolated antibody or its antigen-binding fragment according to claim 1, characterized in that, The antibody or its antigen-binding fragment includes VH and VL; The VH amino acid sequence of the antibody or its antigen-binding fragment is shown in SEQ ID NO: 109, and the VL amino acid sequence is shown in SEQ ID NO:

127. Or the VH amino acid sequence of the antibody or its antigen-binding fragment is shown in SEQ ID NO: 110, and the VL amino acid sequence is shown in SEQ ID NO:

128. The VH amino acid sequence of the antibody or its antigen-binding fragment is shown in SEQ ID NO: 111, and the VL amino acid sequence is shown in SEQ ID NO:

129. The VH amino acid sequence of the antibody or its antigen-binding fragment is shown in SEQ ID NO: 112, and the VL amino acid sequence is shown in SEQ ID NO:

130. The VH amino acid sequence of the antibody or its antigen-binding fragment is shown in SEQ ID NO: 113, and the VL amino acid sequence is shown in SEQ ID NO:

131. The VH amino acid sequence of the antibody or its antigen-binding fragment is shown in SEQ ID NO: 115, and the VL amino acid sequence is shown in SEQ ID NO:

133.

3. The isolated antibody or its antigen-binding fragment according to claim 1, characterized in that, Its binding antigen epitopes are HERV-K102-Env-SU and / or HERV-K102-Env-TM, the amino acid sequence of HERV-K102-Env-SU is shown in SEQ ID NO: 149, and the amino acid sequence of HERV-K102-Env-TM is shown in SEQ ID NO:

150.

4. The isolated antibody or its antigen-binding fragment according to any one of claims 1 to 3, characterized in that, The antibody described is a human monoclonal antibody.

5. An isolated polynucleotide, characterized in that, It encodes the antibody or antigen-binding fragment thereof according to any one of claims 1 to 3.

6. A separate carrier, characterized in that, It contains the polynucleotides described in claim 5.

7. A host cell, characterized in that, It comprises the polynucleotide according to claim 5 or the vector according to claim 6.

8. A kit for detecting HERV-K102-Env expression, characterized in that, It includes the antibody or its antigen-binding fragment according to any one of claims 1 to 3.

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