CN113583115A

CN113583115A - Antibodies against SARS-CoV-2 and uses thereof

Info

Publication number: CN113583115A
Application number: CN202110475340.XA
Authority: CN
Inventors: 陈毅歆; 罗文新; 洪俊平; 陈俊煜; 蒋艺超; 张雅丽; 熊华龙; 吴倩; 王倩; 张天英; 袁权; 夏宁邵
Original assignee: Yang Sheng Tang Co Ltd; Xiamen University
Current assignee: Yang Sheng Tang Co Ltd; Xiamen University
Priority date: 2020-04-30
Filing date: 2021-04-29
Publication date: 2021-11-02

Abstract

The present invention relates to the fields of immunology and molecular virology, in particular the fields of diagnosis, prevention and treatment of SARS-CoV-2. In particular, the invention relates to monoclonal antibodies against SARS-CoV-2, and compositions (e.g., diagnostic and therapeutic agents) comprising the antibodies. Furthermore, the invention relates to the use of said antibodies. The antibodies of the invention are useful for diagnosing, preventing and/or treating SARS-CoV-2 infection and/or a disease caused by such infection (e.g., COVID-19).

Description

Antibodies against SARS-CoV-2 and uses thereof

Technical Field

Background

Coronavirus (coronavirus) infection can cause respiratory diseases of human beings, mild coronavirus infection can cause flu-like symptoms, and severe infection can develop into severe viral pneumonia and threaten the life and health of human beings. Coronaviruses can infect both humans and animals, and some animal-derived coronaviruses, if they breach the host barrier to infect humans, can spread rapidly among people and cause serious disease.

Currently, there is no specific drug approved for the prevention or treatment of SARS-CoV-2 infection. Patients with pneumonia caused by SARS-CoV-2 infection are only given general supportive therapy, oxygen therapy measures and antiviral therapy, such as interferon-alpha, lopinavir/ritonavir, chloroquine phosphate, etc., which have limited clinical effects. Studies have found that higher levels of SARS-CoV-2 neutralizing antibody production are often associated in convalescent patients with new coronary pneumonia. In a novel diagnosis and treatment scheme (trial seventh edition) for coronavirus pneumonia issued by Weijian Wei of China, plasma treatment of convalescent patients is recommended for patients with fast and severe disease progression and critical patients. There are research data showing that after treatment with convalescent plasma containing neutralizing antibodies in critically ill patients with COVID-19 associated severe respiratory distress syndrome (ARDS), the viral load in the patients is rapidly reduced and the clinical symptoms of the patients are effectively improved. These studies indicate the importance of humoral immunity in SARS-CoV-2, and indicate that in addition to vaccine development, a monoclonal antibody capable of neutralizing SARS-CoV-2 with high efficiency and specificity should be developed for short-term prevention and effective treatment of COVID-19, which is of great significance to national and even global prevention and treatment of COVID-19.

Disclosure of Invention

In the present application, the inventors first developed a rabbit-derived antibody having excellent properties, which specifically binds to the receptor binding Region (RBD) of the S protein of SARS-CoV-2. On the basis of the above, the inventors have made extensive creative efforts and made intensive studies and alterations on the rabbit-derived antibody, thereby developing a humanized antibody of the rabbit-derived antibody. The antibody of the invention can neutralize SARS-CoV-2, block or inhibit the combination of SARS-CoV-2 and ACE2 receptor. Therefore, the antibody of the present invention has the potential for preventing and/or treating SARS-CoV-2 infection or a disease caused by SARS-CoV-2 infection, and has significant clinical value.

Antibodies of the invention

In one aspect, the present invention provides an antibody or antigen-binding fragment thereof that specifically binds to the receptor binding Region (RBD) of the S protein of SARS-CoV-2, comprising:

(a) a heavy chain variable region (VH) comprising the following 3 Complementarity Determining Regions (CDRs) defined according to the Kabat numbering system:

(i) a VH CDR1, consisting of the sequence: 3, or a sequence having substitution, deletion or addition of one or several amino acids (e.g., substitution, deletion or addition of 1, 2 or 3 amino acids) thereto,

(ii) a VH CDR2, consisting of the sequence: 4, or a sequence having substitution, deletion or addition of one or several amino acids (e.g., substitution, deletion or addition of 1, 2 or 3 amino acids) thereto, and

(iii) a VH CDR3, consisting of the sequence: 5, or a sequence having substitution, deletion or addition of one or several amino acids (e.g., substitution, deletion or addition of 1, 2 or 3 amino acids) thereto;

and/or the presence of a gas in the gas,

(b) a light chain variable region (VL) comprising the following 3 Complementarity Determining Regions (CDRs) defined according to the Kabat numbering system:

(iv) a VL CDR1, consisting of the sequence: 6, or a sequence having substitution, deletion or addition of one or several amino acids (e.g., substitution, deletion or addition of 1, 2 or 3 amino acids) thereto,

(v) a VL CDR2, consisting of the sequence: 7, or a sequence having substitution, deletion or addition of one or several amino acids (e.g., substitution, deletion or addition of 1, 2 or 3 amino acids) thereto, and

(vi) a VL CDR3, consisting of the sequence: 8, or a sequence having substitution, deletion or addition of one or several amino acids (e.g., substitution, deletion or addition of 1, 2 or 3 amino acids) thereto.

In certain embodiments, the substitution recited in any one of (i) - (vi) is a conservative substitution.

In certain embodiments, the antibody or antigen-binding fragment thereof comprises: the following 3 heavy chain CDRs defined according to the Kabat numbering system: the sequence is SEQ ID NO:3, VH CDR1 of SEQ ID NO:4, the sequence of VH CDR2 of SEQ ID NO:5 VH CDR 3; and/or, the following 3 light chain CDRs as defined by the Kabat numbering system: the sequence is SEQ ID NO:6, the sequence is SEQ ID NO:7, VL CDR2 of SEQ ID NO:8 VL CDR 3.

In certain embodiments, an antibody or antigen-binding fragment thereof of the invention comprises:

(a) a heavy chain variable region (VH) comprising the following 3 Complementarity Determining Regions (CDRs) defined according to the IMGT numbering system:

(i) a VH CDR1, consisting of the sequence: 9, or a sequence having substitution, deletion or addition of one or several amino acids (e.g., substitution, deletion or addition of 1, 2 or 3 amino acids) thereto,

(ii) a VH CDR2, consisting of the sequence: 10, or a sequence having substitution, deletion or addition of one or several amino acids (e.g., substitution, deletion or addition of 1, 2 or 3 amino acids) thereto, and

(iii) a VH CDR3, consisting of the sequence: 11, or a sequence having one or more amino acid substitutions, deletions or additions (e.g., 1, 2 or 3 amino acid substitutions, deletions or additions) compared thereto;

and/or the presence of a gas in the gas,

(b) a light chain variable region (VL) comprising the following 3 Complementarity Determining Regions (CDRs) defined according to the IMGT numbering system:

(iv) a VL CDR1, consisting of the sequence: 12, or a sequence having substitution, deletion or addition of one or several amino acids (e.g., substitution, deletion or addition of 1, 2 or 3 amino acids) thereto,

(v) a VL CDR2, consisting of the sequence: 13, or a sequence having substitution, deletion or addition of one or several amino acids (e.g., substitution, deletion or addition of 1, 2 or 3 amino acids) thereto, and

(vi) a VL CDR3, consisting of the sequence: 14, or a sequence having substitution, deletion or addition of one or several amino acids compared thereto (e.g. substitution, deletion or addition of 1, 2 or 3 amino acids).

In certain embodiments, the antibody or antigen-binding fragment thereof comprises: the following 3 heavy chain CDRs defined according to the IMGT numbering system: the sequence is SEQ ID NO:9, VH CDR1 of SEQ ID NO:10, VH CDR2 of SEQ ID NO:11 VH CDR 3; and/or, the following 3 light chain CDRs as defined by the IMGT numbering system: the sequence is SEQ ID NO:12, the sequence of VL CDR1 of SEQ ID NO:13, VL CDR2 of SEQ ID NO:14 VL CDR 3.

In certain embodiments, the antibody or antigen-binding fragment thereof comprises: 3 CDRs contained in the heavy chain variable region (VH) shown in SEQ ID NO: 1; and/or 3 CDRs contained in the light chain variable region (VL) shown in SEQ ID NO: 2. In certain embodiments, the 3 CDRs contained in the VH and/or the 3 CDRs contained in the VL are defined by Kabat, IMGT or Chothia numbering system.

In certain embodiments, the antibody or antigen-binding fragment thereof comprises:

(a) a heavy chain variable region (VH) comprising an amino acid sequence selected from:

(i) SEQ ID NO: 1;

(ii) and SEQ ID NO:1 compared to a sequence having one or several amino acid substitutions, deletions or additions (e.g., 1, 2, 3, 4 or 5 amino acid substitutions, deletions or additions); or

(iii) And SEQ ID NO:1, has 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%, or 100% sequence identity;

and

(b) a light chain variable region (VL) comprising an amino acid sequence selected from the group consisting of:

(iv) SEQ ID NO: 2;

(v) and SEQ ID NO:2 compared to a sequence having one or several amino acid substitutions, deletions or additions (e.g., 1, 2, 3, 4 or 5 amino acid substitutions, deletions or additions); or

(vi) And SEQ ID NO:2, 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%, or 100% sequence identity.

In certain embodiments, the substitutions recited in (ii) or (v) are conservative substitutions.

In certain exemplary embodiments, the antibody or antigen-binding fragment thereof comprises: a VH comprising the sequence shown as SEQ ID NO. 1 and a VL comprising the sequence shown as SEQ ID NO. 2.

In certain embodiments, an antibody or antigen-binding fragment thereof of the invention may be humanized to reduce immunogenicity to a human. Methods for humanizing non-human antibodies are known in the art, and for example, the CDR regions of an antibody or antigen-binding fragment thereof of the invention can be grafted into human framework sequences using methods known in the art.

In certain embodiments, a humanized antibody or antigen-binding fragment thereof of the invention may comprise a framework region sequence derived from a human immunoglobulin, said framework region optionally comprising one or more (e.g., 1, 2, 3, 4, 5,6, 7, 8, 9, or 10) back mutations from a human residue to a corresponding rabbit residue.

In certain embodiments, the antibody or antigen-binding fragment thereof comprises: a heavy chain framework region sequence derived from a human heavy chain germline sequence (i.e., an amino acid sequence encoded by a human heavy chain germline gene), and a light chain framework region sequence derived from a human light chain germline sequence (i.e., an amino acid sequence encoded by a human light chain germline gene), the heavy chain framework region and/or light chain framework region optionally comprising one or more (e.g., 1, 2, 3, 4, 5,6, 7, 8, 9, or 10) back mutations from human residues to corresponding rabbit residues.

In certain embodiments, the VH of the antibody or antigen-binding fragment thereof comprises: heavy chain framework regions FR1, FR2 and FR3 derived from heavy chain germline sequence IGHV3-53 × 04, and heavy chain framework region FR4 derived from heavy chain germline sequence IGHJ1 × 01; and, the VL of the antibody or antigen-binding fragment thereof comprises: light chain framework regions FR1, FR2 and FR3 derived from light chain germline sequence IGKV1-5 × 01, and light chain framework region FR4 derived from light chain germline sequence IGKJ2 × 02. The heavy chain framework region and/or the light chain framework region optionally comprise one or more (e.g., 1, 2, 3, 4, 5,6, 7, 8, 9, or 10) back mutations from a human residue to a corresponding rabbit residue.

(i) SEQ ID NOs: 15-18;

(ii) and SEQ ID NOs: 15-18 with one or more amino acid substitutions, deletions or additions (e.g., 1, 2, 3, 4 or 5 amino acid substitutions, deletions or additions) compared to the sequence set forth in any of claims; or

(iii) And SEQ ID NOs: 15-18, 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%, or 100% sequence identity;

and

(iv) SEQ ID NO: 19;

(v) and SEQ ID NO:19 with one or more amino acid substitutions, deletions or additions (e.g., 1, 2, 3, 4 or 5 amino acid substitutions, deletions or additions) compared to the sequence shown in seq id no; or

(vi) And SEQ ID NO:19, 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%, or 100% sequence identity.

In certain exemplary embodiments, the antibody or antigen-binding fragment thereof comprises:

(1) a VH comprising the sequence shown as SEQ ID NO. 15 and a VL comprising the sequence shown as SEQ ID NO. 19;

(2) a VH comprising the sequence shown as SEQ ID NO 16 and a VL comprising the sequence shown as SEQ ID NO 19;

(3) a VH comprising the sequence shown as SEQ ID NO. 17 and a VL comprising the sequence shown as SEQ ID NO. 19; or

(4) A VH comprising the sequence shown as SEQ ID NO. 18 and a VL comprising the sequence shown as SEQ ID NO. 19.

In certain embodiments, an antibody or antigen-binding fragment thereof of the invention may further comprise a constant region sequence derived from a mammalian (e.g., rabbit or human) immunoglobulin, or a variant thereof having one or more amino acid substitutions, deletions, or additions compared to the sequence from which it is derived.

In certain embodiments, the heavy chain of an antibody or antigen-binding fragment thereof of the invention comprises a heavy chain constant region (CH) of a human immunoglobulin or a variant thereof having one or more amino acid substitutions, deletions or additions (e.g., substitutions, deletions or additions of up to 20, up to 15, up to 10, or up to 5 amino acids; e.g., substitutions, deletions or additions of 1, 2, 3, 4, or 5 amino acids) compared to the sequence from which it is derived; and/or the presence of a gas in the gas,

the light chain of the antibody or antigen-binding fragment thereof of the invention comprises a light chain constant region (CL) of a human immunoglobulin or a variant thereof having conservative substitutions of up to 20 amino acids (e.g., conservative substitutions of up to 15, up to 10, or up to 5 amino acids; e.g., conservative substitutions of 1, 2, 3, 4, or 5 amino acids) compared to the sequence from which it is derived.

In some embodiments, the variants of the heavy chain constant region (CH) may have conservative substitutions of one or more amino acids compared to the sequence from which they are derived. In such embodiments, the variants of the heavy chain constant region (CH) may have the same or substantially the same effector function as compared to the wild-type sequence from which they are derived.

In other embodiments, the variant of the heavy chain constant region (CH) may comprise one or more amino acid mutations to alter one or more of the following properties of the antibody of the invention: fc receptor binding, antibody glycosylation, number of cysteine residues, effector cell function or complement function, etc. A functional change, e.g., an alteration in the affinity of an antibody for an effector ligand (e.g., FcR or complement C1q), can be produced by replacing at least one amino acid residue in the constant region of the antibody with a different residue, thereby altering (e.g., decreasing) effector function. The Fc region of an antibody mediates several important effector functions, such as ADCC, phagocytosis, CDC, and the like.

In certain embodiments, the heavy chain constant region is an IgG heavy chain constant region, e.g., an IgG1, IgG2, IgG3, or IgG4 heavy chain constant region. In certain embodiments, the heavy chain constant region is a rabbit IgG1, IgG2, IgG3, or IgG4 heavy chain constant region. In certain embodiments, the heavy chain constant region is a human IgG1, IgG2, IgG3, or IgG4 heavy chain constant region.

In certain embodiments, the light chain constant region is a kappa light chain constant region. In certain embodiments, the light chain constant region is a rabbit kappa light chain constant region. In certain embodiments, the light chain constant region is a human kappa light chain constant region.

In certain exemplary embodiments, the antibodies or antigen-binding fragments thereof of the invention comprise the heavy chain constant region (CH) shown in SEQ ID NO: 20; and/or, the light chain constant region (CL) shown in SEQ ID NO: 21.

In certain embodiments, the antigen binding fragment is selected from the group consisting of Fab, Fab ', (Fab')₂Fv, disulfide-linked Fv, scFv, diabody (diabody), and single domain antibody (sdAb).

In certain embodiments, the antibody is a rabbit derived antibody, a chimeric antibody, a humanized antibody, a bispecific antibody, or a multispecific antibody.

In certain embodiments, an antibody or antigen-binding fragment thereof of the invention has 1, 2, 3, 4, 5,6, or all 7 of the following features:

(1) RBD that specifically binds the S protein of SARS-CoV-2;

(2) with a K of less than about 100nM, e.g., less than about 50nM, 40nM, 30nM, 20nM, 10nM or less_DRBD that binds the S protein of SARS-CoV-2; preferably, said K_DAs determined by surface plasmon resonance techniques (e.g., Biacore);

(3) an RBD that binds to the S protein of SARS-CoV-2 with an EC50 of less than about 100ng/mL, e.g., less than about 50ng/mL, 40ng/mL, 30ng/mL, 20ng/mL, 15ng/mL, or less; preferably, the EC50 can be determined by indirect ELISA;

(4) blocking or inhibiting binding of SARS-CoV-2 to Ace2 receptor, and/or blocking or inhibiting infection of cells by SARS-CoV-2;

(5) does not affect or does not substantially affect the binding of SARS-CoV-1 to the Ace2 receptor;

(6) neutralizing SARS-CoV-2 in vitro or in a subject (e.g., human);

(7) preventing and/or treating SARS-CoV-2 infection or a disease caused by SARS-CoV-2 infection (e.g., COVID-19).

Herein, an antibody or antigen-binding fragment thereof of the invention may include variants that differ from the antibody or antigen-binding fragment thereof from which it is derived only by conservative substitutions of one or more (e.g., conservative substitutions of up to 20, up to 15, up to 10, or up to 5 amino acids) amino acid residues, or that have at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% sequence identity to the antibody or antigen-binding fragment thereof from which it is derived, and that substantially retain the above-described biological functions of the antibody or antigen-binding fragment thereof from which it is derived.

Preparation of antibodies

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

Antigen-binding fragments of the invention may be obtained by hydrolysis of the whole antibody molecule (see Morimoto et al, J.Biochem.Biophys.methods 24:107-117(1992) and Brennan et al, Science 229:81 (1985)). Alternatively, these antigen-binding fragments can be produced directly from recombinant host cells (reviewed in Hudson, Curr. Opin. Immunol.11:548-557 (1999); Little et al, Immunol.today,21:364-370 (2000)). For example, Fab' fragments can be obtained directly from the host cell; fab 'fragments can be chemically coupled to form F (ab')₂Fragments (Carter et al, Bio/Technology,10: 163-. In addition, Fv, Fab or F (ab')₂The fragments may also be isolated directly from the culture medium of the recombinant host cell. Other techniques for preparing these antigen-binding fragments are well known to those of ordinary skill in the art.

Thus, in another aspect, the invention provides an isolated nucleic acid molecule comprising a nucleotide sequence encoding an antibody or antigen-binding fragment thereof of the invention, or a heavy chain variable region and/or a light chain variable region thereof. In certain embodiments, the isolated nucleic acid molecule encodes an antibody or antigen-binding fragment thereof of the present invention, or a heavy chain variable region and/or a light chain variable region thereof.

In another aspect, the invention provides a vector (e.g., a cloning vector or an expression vector) comprising an isolated nucleic acid molecule as described above. In certain embodiments, the vectors of the invention are, for example, plasmids, cosmids, phages and the like.

In certain embodiments, the vector comprises a first nucleotide sequence encoding the heavy chain variable region of the antibody or antigen-binding fragment thereof of the present invention, and/or a second nucleotide sequence encoding the light chain variable region of the antibody or antigen-binding fragment thereof of the present invention; wherein the first nucleotide sequence and the second nucleotide sequence are provided on the same or different vectors.

In certain embodiments, the vector comprises a first nucleotide sequence encoding a heavy chain of the antibody or antigen-binding fragment thereof of the present invention, and/or a second nucleotide sequence encoding a light chain of the antibody or antigen-binding fragment thereof of the present invention; wherein the first nucleotide sequence and the second nucleotide sequence are provided on the same or different vectors.

In another aspect, the invention provides a host cell comprising an isolated nucleic acid molecule or vector as described above. Such host cells include, but are not limited to, prokaryotic cells such as E.coli cells, and eukaryotic cells such as yeast cells, insect cells, plant cells, and animal cells (e.g., mammalian cells, e.g., mouse cells, human cells, etc.). In certain preferred embodiments, the host cell of the invention is a mammalian cell, such as CHO (e.g., CHO-K1, CHO-S, CHO DG 44).

In another aspect, there is provided a method of making an antibody or antigen-binding fragment thereof of the invention, comprising culturing a host cell as described above under conditions that allow expression of the antibody or antigen-binding fragment thereof, and recovering the antibody or antigen-binding fragment thereof from the cultured host cell culture.

Pharmaceutical compositions and therapeutic uses

The antibody or antigen binding fragment thereof can be used for neutralizing SARS-CoV-2 in vitro or in a subject, and blocking or inhibiting infection of SARS-CoV-2 to cells, thereby achieving the purpose of preventing and/or treating SARS-CoV-2 infection or SARS-CoV-2 infection-related diseases of the subject.

Thus, in another aspect, the invention provides a pharmaceutical composition comprising an antibody or antigen-binding fragment thereof of the invention, and a pharmaceutically acceptable carrier and/or excipient.

In certain embodiments, the pharmaceutical compositions may further comprise additional pharmaceutically active agents, such as additional antiviral agents (e.g., interferon, lopinavir, ritonavir, chloroquine phosphate, fabiravir, ridciclovir, and the like).

In certain embodiments, in the pharmaceutical composition, the antibody or antigen-binding fragment thereof of the present invention and the additional pharmaceutically active agent may be provided as separate components or as a mixed component. Thus, the antibody or antigen-binding fragment thereof of the invention and the additional pharmaceutically active agent may be administered simultaneously, separately or sequentially.

In certain exemplary embodiments, the pharmaceutically acceptable carrier and/or excipient comprises a sterile injectable liquid (e.g., an aqueous or non-aqueous suspension or solution). In certain exemplary embodiments, such sterile injectable liquids are selected from water for injection (WFI), bacteriostatic water for injection (BWFI), sodium chloride solutions (e.g., 0.9% (w/v) NaCl), glucose solutions (e.g., 5% glucose), surfactant-containing solutions (e.g., 0.01% polysorbate 20), pH buffered solutions (e.g., phosphate buffered solutions), Ringer's solution, and any combination thereof.

In another aspect, the invention provides methods for neutralizing SARS-CoV-2 comprising using an antibody or antigen-binding fragment thereof or a pharmaceutical composition of the invention. The methods can be used to neutralize SARS-CoV-2 in vitro or in a subject (e.g., a human).

In certain embodiments, the methods are used to neutralize the virulence of SARS-CoV-2 in a sample. In certain embodiments, the method comprises: contacting a sample comprising SARS-CoV-2 with an antibody or antigen-binding fragment thereof or a pharmaceutical composition of the invention.

In certain embodiments, the antibody or antigen-binding fragment thereof is used alone, or in combination with another pharmaceutically active agent (e.g., another antiviral agent).

In another aspect, the invention provides a method for preventing or treating SARS-CoV-2 infection or a disease associated with SARS-CoV-2 viral infection (e.g., COVID-19) in a subject, comprising: administering to a subject in need thereof an effective amount of an antibody or antigen-binding fragment thereof, or a pharmaceutical composition of the invention.

In certain embodiments, the antibody or antigen-binding fragment thereof is used alone, or in combination with another pharmaceutically active agent (e.g., another antiviral agent). The antibody or antigen-binding fragment thereof of the invention and the additional pharmaceutically active agent may be administered simultaneously, separately or sequentially.

In another aspect, the invention relates to the use of an antibody or antigen-binding fragment thereof, or a pharmaceutical composition of the invention, in the manufacture of a medicament for:

(1) neutralizing SARS-CoV-2 in vitro or in a subject (e.g., human); and/or

(2) For preventing and/or treating SARS-CoV-2 infection or a disease associated with SARS-CoV-2 infection (e.g., COVID-19) in a subject.

The antibody or antigen-binding fragment thereof of the present invention, or the pharmaceutical composition of the present invention may be formulated into any dosage form known in the medical field, for example, tablets, pills, suspensions, emulsions, solutions, gels, capsules, powders, granules, elixirs, lozenges, suppositories, injections (including injections, sterile powders for injections, and concentrated solutions for injections), inhalants, sprays, and the like. The preferred dosage form depends on the intended mode of administration and therapeutic use. The antibodies or antigen binding fragments thereof or pharmaceutical compositions of the invention should be sterile and stable under the conditions of manufacture and storage. One preferred dosage form is an injection. Such injections may be sterile injectable solutions. For example, sterile injectable solutions can be prepared by the following methods: the antibody or antigen-binding fragment thereof of the present invention is incorporated in a suitable solvent in the necessary dosage and, optionally, with other desired ingredients (including, but not limited to, pH adjusting agents, surfactants, adjuvants, ionic strength enhancers, isotonic agents, preservatives, diluents, or any combination thereof), followed by filter sterilization. In addition, sterile injectable solutions can be prepared as sterile lyophilized powders (e.g., by vacuum drying or freeze-drying) for storage and use. Such sterile lyophilized powders may be dispersed in a suitable carrier, e.g., water for injection (WFI), bacteriostatic water for injection (BWFI), sodium chloride solution (e.g., 0.9% (w/v) NaCl), glucose solution (e.g., 5% glucose), surfactant-containing solution (e.g., 0.01% polysorbate 20), pH buffered solution (e.g., phosphate buffered solution), Ringer's solution, and any combination thereof, prior to use.

The antibody or antigen-binding fragment thereof of the invention, or the pharmaceutical composition of the invention, may be administered by any suitable method known in the art, including, but not limited to, oral, buccal, sublingual, ocular, topical, parenteral, rectal, intrathecal, intracytoplasmic reticulum, groin, intravesical, topical (e.g., powder, ointment, or drops), or nasal route. However, for many therapeutic uses, the preferred route/mode of administration is parenteral (e.g., intravenous or bolus injection, subcutaneous injection, intraperitoneal injection, intramuscular injection). The skilled artisan will appreciate that the route and/or mode of administration will vary depending on the intended purpose. In certain embodiments, the antibody or antigen-binding fragment thereof or pharmaceutical composition of the invention is administered by intravenous injection or bolus injection.

The pharmaceutical compositions of the invention may comprise a "therapeutically effective amount" or a "prophylactically effective amount" of an antibody or antigen-binding fragment thereof of the invention. A "prophylactically effective amount" is an amount sufficient to prevent, or delay the onset of disease. By "therapeutically effective amount" is meant an amount sufficient to cure or at least partially arrest the disease and its complications in a patient already suffering from the disease. A therapeutically effective amount of an antibody or antigen-binding fragment thereof of the invention may vary according to the following factors: the severity of the disease to be treated, the general state of the patient's own immune system, the general condition of the patient, e.g. age, weight and sex, the mode of administration of the drug, and other treatments administered concurrently, etc.

In this context, the dosage regimen may be adjusted to obtain the optimal desired response (e.g., a therapeutic or prophylactic response). For example, the dosage may be given in a single dose, may be given multiple times over a period of time, or may be reduced or increased proportionally with the exigencies of the therapeutic situation.

Herein, the subject may be a mammal, e.g. a human.

Conjugates

The antibodies or antigen-binding fragments thereof of the invention can be derivatized, e.g., linked to another molecule (e.g., another polypeptide or protein). In general, derivatization (e.g., labeling) of an antibody or antigen-binding fragment thereof does not adversely affect its binding to SARS-CoV-2. Thus, the antibodies or antigen-binding fragments thereof of the present invention are also intended to include such derivatized forms. For example, an antibody or antigen-binding fragment thereof of the invention can be functionally linked (by chemical coupling, genetic fusion, non-covalent linkage, or other means) to one or more other molecular moieties, such as another antibody (e.g., to form a bispecific antibody), a detection reagent, a pharmaceutical agent, and/or a protein or polypeptide (e.g., avidin or polyhistidine tag) capable of mediating binding of the antibody or antigen-binding fragment to another molecule. In addition, the antibodies or antigen-binding fragments thereof of the present invention may also be derivatized with chemical groups, such as polyethylene glycol (PEG), methyl or ethyl, or glycosyl groups. These groups can be used to improve the biological properties of the antibody, for example to increase serum half-life.

Thus, in certain embodiments, an antibody or antigen-binding fragment thereof of the invention is detectably labeled.

As used herein, a detectable label of the present invention can be any substance detectable by fluorescence, spectroscopic, photochemical, biochemical, immunological, electrical, optical, or chemical meansAnd (4) quality. Such labels are well known in the art, examples of which include, but are not limited to, enzymes (e.g., horseradish peroxidase, alkaline phosphatase, beta-galactosidase, urease, glucose oxidase, etc.), radionuclides (e.g.,³H、¹²⁵I、³⁵S、¹⁴c or³²P), fluorescent dyes (e.g., Fluorescein Isothiocyanate (FITC), fluorescein, tetramethylrhodamine isothiocyanate (TRITC), Phycoerythrin (PE), texas red, rhodamine, quantum dots, or cyanine dye derivatives (e.g., Cy7, Alexa 750)), luminescent substances (e.g., chemiluminescent substances such as acridine ester compounds, luminol and its derivatives, ruthenium derivatives such as terpyridyl ruthenium), magnetic beads (e.g.,

) A calorimetric label such as colloidal gold or colored glass or plastic (e.g., polystyrene, polypropylene, latex, etc.) beads, and biotin for binding to the label-modified avidin (e.g., streptavidin) described above.

In certain embodiments, the detectable label can be suitable for use in immunological detection (e.g., enzyme-linked immunoassays, radioimmunoassays, fluorescent immunoassays, chemiluminescent immunoassays, and the like). In certain embodiments, the detectable label may be selected from an enzyme (e.g., horseradish peroxidase, alkaline phosphatase, or β -galactosidase), a chemiluminescent reagent (e.g., acridinium esters, luminol and its derivatives, or ruthenium derivatives), a fluorescent dye (e.g., fluorescein or a fluorescent protein such as FITC, TRITC, or PE), a radionuclide, or biotin.

In certain embodiments, a detectable label as described above can be attached to an antibody or antigen-binding fragment thereof of the invention via a linker of varying length to reduce potential steric hindrance.

Kit and detection application

The antibody or antigen-binding fragment thereof of the present invention can specifically bind to RBD of S protein of SARS-CoV-2, and thus can be used for detecting the RBD of SARS-CoV-2 or S protein thereof, and optionally diagnosing whether a subject is infected with SARS-CoV-2 based on the result of the above detection.

Thus, in another aspect, the invention provides a kit comprising an antibody or antigen-binding fragment thereof of the invention, or a conjugate of the invention.

In some embodiments, the kit comprises a conjugate of the invention.

In other embodiments, the kit comprises an antibody or antigen-binding fragment thereof of the invention. In certain embodiments, the antibody or antigen-binding fragment thereof does not comprise a detectable label. In certain embodiments, the kit further comprises a second antibody that specifically recognizes the antibody or antigen-binding fragment thereof of the invention; optionally, the second antibody further comprises a detectable label, such as an enzyme (e.g., horseradish peroxidase or alkaline phosphatase), a chemiluminescent reagent (e.g., acridinium esters, luminol and its derivatives, or ruthenium derivatives), a fluorescent dye (e.g., fluorescein or fluorescent protein), a radionuclide or biotin.

In certain embodiments, the second antibody is specific for an antibody of the species (e.g., rabbit or human) from which the constant region comprised by the antibody or antigen-binding fragment thereof of the invention is derived.

In certain embodiments, the second antibody is an anti-immunoglobulin (e.g., human or rabbit immunoglobulin) antibody, such as an anti-IgG antibody. In certain embodiments, the second antibody is an anti-rabbit IgG antibody or an anti-human IgG antibody.

In certain embodiments, the kits of the invention may further comprise reagents for allowing the detection of the corresponding detectable label. For example, when the detectable label is an enzyme, the kit may further comprise a chromogenic substrate for the corresponding enzyme, such as o-phenylenediamine (OPD), Tetramethylbenzidine (TMB), ABTS or luminol-type compounds for horseradish peroxidase, or p-nitrophenyl phosphate (p-NPP) or AMPPD for alkaline phosphatase. For example, when the detectable label is a chemiluminescent reagent (e.g., an acridinium ester compound), the kit may further comprise a pre-excitation liquid and/or an excitation liquid for chemiluminescence.

In another aspect, the invention provides a method of detecting the presence or level of a SARS-CoV-2 or S protein thereof or RBD of S protein, or a cell infected with SARS-CoV-2 in a sample comprising using an antibody or antigen-binding fragment thereof of the invention.

In certain embodiments, the method is an immunological assay, such as an enzyme immunoassay (e.g., ELISA), a chemiluminescent immunoassay, a fluorescent immunoassay, or a radioimmunoassay.

In some embodiments, the method comprises the use of a conjugate of the invention.

In other embodiments, the methods comprise the use of an antibody or antigen-binding fragment thereof of the invention. In certain embodiments, the antibody or antigen-binding fragment thereof does not comprise a detectable label. In certain embodiments, the methods further comprise detecting the antibody or antigen-binding fragment thereof using a second antibody with a detectable label (e.g., an enzyme (e.g., horseradish peroxidase or alkaline phosphatase), a chemiluminescent reagent (e.g., acridinium esters, luminol and its derivatives, or ruthenium derivatives), a fluorescent dye (e.g., fluorescein or fluorescent protein), a radionuclide or biotin).

In certain embodiments, the method comprises: (1) contacting the sample with an antibody or antigen-binding fragment thereof of the invention; (2) detecting the formation of an antigen-antibody immune complex or detecting the amount of said immune complex. The formation of the immune complex indicates the presence of SARS-CoV-2 or a cell infected with SARS-CoV-2.

In certain embodiments, the methods can be used for diagnostic purposes, e.g., a subject can be diagnosed as infected with SARS-CoV-2 based on the presence or level of SARS-CoV-2 in the sample. In such embodiments, the sample may be a blood sample (e.g., whole blood, plasma, or serum), fecal matter, oral or nasal secretions, or alveolar lavage fluid from a subject (e.g., a mammal, preferably a human).

In certain embodiments, the methods may be used for non-diagnostic purposes, e.g., the sample is not a sample from a subject, e.g., a vaccine sample.

In certain embodiments, the subject is a mammal, e.g., a human.

In another aspect, there is provided the use of an antibody or antigen-binding fragment thereof of the invention in the preparation of a kit for detecting the presence or level of a SARS-CoV-2 or the S protein thereof or the RBD of the S protein, or a cell infected with SARS-CoV-2, in a sample, and/or for diagnosing whether a subject is infected with SARS-CoV-2.

In certain embodiments, the kit detects the presence or level of SARS-CoV-2 or its S protein or the RBD of S protein, or cells infected with SARS-CoV-2 in a sample by a detection method as described above, and optionally diagnoses whether the subject is infected with SARS-CoV-2 based on the detection result.

In certain embodiments, the sample is a blood sample (e.g., whole blood, plasma, or serum), fecal matter, oral or nasal secretions, or alveolar lavage fluid from a subject (e.g., a mammal, preferably a human).

Definition of terms

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

As used herein, "Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)", formerly known as "novel coronavirus" or "2019-nCov", belongs to its genus β -coronavirus, and is an enveloped, single-stranded, positive-sense RNA virus. The genomic sequence of SARS-CoV-2 is known to those skilled in the art and can be found, for example, in GenBank: MN 908947.3. SARS-CoV-2 contains at least three membrane proteins, including surface spike protein (S), integral membrane protein (M) and membrane protein (E). Like SARS-CoV, the SARS-CoV-2 Receptor is specifically bound to angiotensin transferase 2(ACE2) on host cells via Receptor Binding Domain (RBD) on S protein, and then is connected to viral membrane fusion and cell entry, and plays a crucial role in the process of viral infection of cells.

As used herein, the terms "novel coronavirus pneumonia" and "COVID-19" refer to pneumonia resulting from SARS-CoV-2 infection, which have the same meaning and are used interchangeably.

As used herein, the term "antibody" refers to an immunoglobulin molecule typically composed of two pairs of polypeptide chains, each pair having one Light Chain (LC) and one Heavy Chain (HC). Antibody light chains can be classified as kappa (kappa) and lambda (lambda) light chains. Heavy chains can be classified as μ, δ, γ, α or ε, and the antibody isotypes are defined as IgM, IgD, IgG, IgA, and IgE, respectively. Within the light and heavy chains, the variable and constant regions are connected by a "J" region of about 12 or more amino acids, and the heavy chain also contains a "D" region of about 3 or more amino acids. Each heavy chain consists of a heavy chain variable region (VH) and a heavy chain constant region (CH). The heavy chain constant region consists of 3 domains (CH1, CH2, and CH 3). Each light chain consists of a light chain variable region (VL) and a light chain constant region (CL). The light chain constant region consists of one domain CL. The constant domains are not directly involved in binding of antibodies to antigens, but exhibit multiple effectsEffector functions, such as mediating binding of the immunoglobulin to host tissues or factors, including various cells of the immune system (e.g., effector cells) and the first component of the classical complement system (C1 q). The VH and VL regions can also be subdivided into regions of high denaturation, called Complementarity Determining Regions (CDRs), interspersed with regions that are more conserved, called Framework Regions (FRs). Each V_HAnd V_LBy the following sequence: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4 are composed of 3 CDRs and 4 FRs arranged from amino terminus to carboxy terminus. The variable regions (VH and VL) of each heavy/light chain pair form the antigen-binding sites, respectively. The distribution of amino acids in each region or domain may follow Kabat, Sequences of Proteins of Immunological Interest (National Institutes of Health, Bethesda, Md. (1987and 1991)), or Chothia&Lesk (1987) J.mol.biol.196: 901-917; chothia et al (1989) Nature 342: 878-883.

As used herein, the term "complementarity determining region" or "CDR" refers to the amino acid residues in the variable region of an antibody that are responsible for antigen binding. There are three CDRs, named CDR1, CDR2, and CDR3, in the variable regions of the heavy and light chains, respectively. The precise boundaries of these CDRs may be defined according to various numbering systems known in the art, for example, as defined in the Kabat numbering system (Kabat et al, Sequences of Proteins of Immunological Interest,5th Ed. public Health Service, National Institutes of Health, Bethesda, Md.,1991), the Chothia numbering system (Chothia & Lesk (1987) J.mol.biol.196: 901-917; Chothia et al (1989) Nature 342:878-883) or the IMGT numbering system (Lefranc et al, Dev.Complex.Immunol.27: 55-77,2003). For a given antibody, one skilled in the art will readily identify the CDRs defined by each numbering system. Also, the correspondence between the different numbering systems is well known to those skilled in the art (see, e.g., Lefranc et al, Dev. company. Immunol.27:55-77,2003).

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

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

The term "antibody" is not limited by any particular method of producing an antibody. For example, it includes recombinant antibodies, monoclonal antibodies and polyclonal antibodies. The antibody may be of a different isotype, for example, an IgG (e.g., IgG1, IgG2, IgG3, or IgG4 subtype), IgA1, IgA2, IgD, IgE, or IgM antibody.

As used herein, the term "antigen-binding fragment" of an antibody refers to a polypeptide comprising a fragment of a full-length antibody that retains the ability to specifically bind to the same antigen to which the full-length antibody binds, and/or competes with the full-length antibody for specific binding to the antigen, which is also referred to as an "antigen-binding portion". See generally, Fundamental Immunology, Ch.7(Paul, W., ed., 2nd edition, Raven Press, N.Y. (1989), which is incorporated herein by reference in its entirety for all purposes₂Fd, Fv, Complementarity Determining Region (CDR) fragments, scFv, diabodies (diabodies), single domain antibodies (single domain antibodies), chimeric antibodies, linear antibodies (linear antibodies), nanobodies (technology from Domantis), probodies, and polypeptides comprising at least a portion of an antibody sufficient to confer specific antigen-binding capability to the polypeptide. Engineered antibody variants are reviewed in Holliger et al, 2005; nat Biotechnol,23: 1126-.

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

As used herein, the term "Fd" means an antibody fragment consisting of the VH and CH1 domains; the term "dAb fragment" means an antibody fragment consisting of a VH domain (Ward et al, Nature 341: 544546 (1989)); the term "Fab fragment" means an antibody fragment consisting of the VL, VH, CL and CH1 domains; the term "F (ab')₂Fragment "means an antibody fragment comprising two Fab fragments connected by a disulfide bridge at the hinge region; the term "Fab 'fragment" means a reductively linked F (ab')₂The fragment obtained after disulfide bonding of the two heavy chain fragments in the fragment consists of one complete Fd fragment of the light and heavy chains, consisting of the VH and CH1 domains.

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

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

As used herein, The term "scFv" refers to a single polypeptide chain comprising VL and VH domains, wherein The VL and VH are linked by a linker (linker) (see, e.g., Bird et al, Science 242: 423-. Such scFv molecules can have the general structure: NH (NH)₂-VL-linker-VH-COOH or NH₂-VH-linker-VL-COOH. Suitable prior art linkers consist of repeated GGGGS amino acid sequences or variants thereof. For example, a polypeptide having an amino acid sequence (GGGGS)₄But variants thereof can also be used (Holliger et al (1993), Proc. Natl. Acad. Sci. USA 90: 6444-. Other linkers useful in the present invention are described by Alfthan et al (1995), Protein Eng.8: 725-. In some cases, a disulfide bond may also be present between the VH and VL of the scFv. In certain embodiments of the invention, the scFv may form a di-scFv, which refers to two or more individual scFv connected in tandem to form an antibody. In certain embodiments of the invention, the scFv may form a (scFv)₂It refers to two or more individual scfvs connected in parallel to form an antibody.

As used herein, the term "diabody" means that its VH and VL domains are expressed on a single polypeptide chain, but that a linker is used that is too short to allow pairing between the two domains of the same chain, thereby forcing the domains to pair with the complementary domains of the other chain and generating two antigen binding sites (see, e.g., Holliger P. et al, Proc. Natl. Acad. Sci. USA 90: 6444-.

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

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

Antigen-binding fragments of antibodies (e.g., antibody fragments described above) can be obtained from a given antibody (e.g., an antibody provided herein) using conventional techniques known to those skilled in the art (e.g., recombinant DNA techniques or enzymatic or chemical fragmentation methods), and the antigen-binding fragments of antibodies are specifically screened for specificity in the same manner as for intact antibodies.

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

As used herein, the term "Chimeric antibody" (scieric antibody) "refers to an antibody in which a portion of the light chain or/and heavy chain is derived from one antibody (which may be derived from a particular species or belonging to a particular antibody class or subclass) and another portion of the light chain or/and heavy chain is derived from another antibody (which may be derived from the same or different species or belonging to the same or different antibody class or subclass), but which nevertheless retains binding activity to an antigen of interest (u.s.p. 4,816,567to harvesting cam et al.; Morrison et al., proc.natl.acad.sci.usa,81: 68516855 (1984)). In certain embodiments, the term "chimeric antibody" may include an antibody (e.g., a human murine chimeric antibody) in which the heavy and light chain variable regions of the antibody are from a first antibody (e.g., a murine antibody) and the heavy and light chain constant regions of the antibody are from a second antibody (e.g., a human antibody).

As used herein, the term "humanized antibody" refers to a non-human antibody that has been genetically engineered to have an amino acid sequence modified to increase homology to the sequence of a human antibody. Generally, all or a portion of the CDR regions of a humanized antibody are derived from a non-human antibody (donor antibody), and all or a portion of the non-CDR regions (e.g., variable region FR and/or constant regions) are derived from a human immunoglobulin (acceptor antibody). Typically, at least one or two but usually all three acceptor CDRs (of the heavy and/or light immunoglobulin chains) of the humanized antibody are replaced by donor CDRs. The immunoglobulin providing the CDRs is referred to as the "donor" and the immunoglobulin providing the framework is referred to as the "acceptor". In one embodiment, the donor immunoglobulin is a non-human (e.g., rabbit) antibody and the acceptor framework may be a naturally occurring human framework or a sequence having about 85%, 90%, 95%, 99% or more identity thereto. Humanized antibodies generally retain the desired properties of the donor antibody, including, but not limited to, antigen specificity, affinity, reactivity, and the like. The donor antibody can be a mouse, rat, rabbit, or non-human primate (e.g., cynomolgus monkey) antibody having a desired property (e.g., antigen specificity, affinity, reactivity, etc.).

In the present application, the desired properties of the antibodies of the invention include: (1) RBD that specifically binds the S protein of SARS-CoV-2; (2) with a K of less than about 100nM, e.g., less than about 50nM, 40nM, 30nM, 20nM, 10nM or less_DRBD that binds the S protein of SARS-CoV-2; preferably, said K_DAs determined by surface plasmon resonance techniques (e.g., Biacore); (3) an RBD that binds to the S protein of SARS-CoV-2 with an EC50 of less than about 100ng/mL, e.g., less than about 50ng/mL, 40ng/mL, 30ng/mL, 20ng/mL, 15ng/mL, or less; preferably, the EC50 can be determined by indirect ELISA; (4) blocking or inhibiting binding of SARS-CoV-2 to Ace2 receptor, and/or blocking or inhibiting infection of cells by SARS-CoV-2; (5) does not affect or does not substantially affect the binding of SARS-CoV-1 to the Ace2 receptor; (6) neutralizing SARS-CoV-2 in vitro or in a subject (e.g., human); (7) preventing and/or treating SARS-CoV-2 infection or a disease caused by SARS-CoV-2 infection (e.g., COVID-19). The antibodies of the invention have one or more of the desired properties described above.

The chimeric antibody or humanized antibody of the present invention can be prepared based on the sequence of a monoclonal antibody produced by an immunized animal (e.g., rabbit). The DNA encoding the heavy and light chains can be obtained from a hybridoma of interest or a specific B cell from an immunized animal and engineered to contain human immunoglobulin sequences using standard molecular biology techniques.

To prepare chimeric antibodies, the immunoglobulin variable region of an immunized animal (e.g., rabbit) can be linked to a human immunoglobulin constant region using methods known in the art (see, e.g., U.S. Pat. No.4,816,567 to Cabilly et al). For example, DNA encoding a VH is operably linked to another DNA molecule encoding a heavy chain constant region to obtain a full-length heavy chain gene. The sequence of the Human heavy chain constant region gene is known in the art (see, e.g., Kabat, E.A. et al (1991) Sequences of Proteins of Immunological Interest, Fifth Edition, U.S. department of Health and Human Services, NIH Publication No.91-3242), and DNA fragments comprising these regions can be obtained by standard PCR amplification. The heavy chain constant region may be an IgG1, IgG2, IgG3, IgG4, IgA, IgE, IgM, or IgD constant region, but is typically preferably an IgG1 or IgG4 constant region. For example, the DNA encoding VL is operably linked to another DNA molecule encoding a light chain constant region CL to obtain a full-length light chain gene (as well as the Fab light chain gene). The sequence of the Human light chain constant region gene is known in the art (see, e.g., Kabat, E.A. et al (1991) Sequences of Proteins of Immunological Interest, Fifth Edition, U.S. department of Health and Human Services, NIH Publication No.91-3242), and DNA fragments comprising these regions can be obtained by standard PCR amplification. The light chain constant region may be a kappa or lambda constant region, but is typically preferably a kappa constant region.

To prepare humanized antibodies, CDR regions of an immunized animal (e.g., rabbit) can be grafted with human framework sequences using Methods known in the art (see, U.S. Pat. No.5,225,539 to Winter; U.S. Pat. No.5,530,101 to Queen et al; 5,585,089; 5,693,762 and 6,180,370; and Lo, Benny, K.C., editor, in Antibody Engineering: Methods and Protocols, volume 248, Humana Press, New Jersey, 2004).

As used herein, the term "germline antibody gene (germline antibody gene)" or "germline antibody gene segment (germline antibody gene segment)" refers to immunoglobulin-encoding sequences present in the genome of an organism that have not undergone a maturation process that can lead to genetic rearrangements and mutations that express specific immunoglobulins. In the present invention, the expression "heavy chain germline gene" means the germline antibody gene or gene segment encoding the immunoglobulin heavy chain, which includes the V gene (variable), the D gene (diversity), the J gene (conjugation), and the C gene (constant); similarly, the expression "light chain germline gene" refers to germline antibody genes or gene segments encoding immunoglobulin light chains, which include the V gene (variable), the J gene (junction), and the C gene (constant). In the present invention, the amino acid sequence encoded by the germline antibody gene or germline antibody gene segment is also referred to as "germline sequence", the amino acid sequence encoded by the heavy chain germline gene is referred to as heavy chain germline sequence, and the amino acid sequence encoded by the light chain germline gene is referred to as light chain germline sequence. Germline antibody genes or germline antibody gene fragments and their corresponding germline sequences are well known to those skilled in the art and can be obtained or queried from specialized databases (e.g., IMGT, unsmig, NCBI, or VBASE 2).

As used herein, the term "specific binding" refers to a non-random binding reaction between two molecules, such as a reaction between an antibody and an antigen against which it is directed. The strength or affinity of a specific binding interaction may be the equilibrium dissociation constant (K) of the interaction_D) And (4) showing. In the present invention, the term "K_D"refers to the dissociation equilibrium constant for a particular antibody-antigen interaction, which is used to describe the binding affinity between an antibody and an antigen. The smaller the equilibrium dissociation constant, the more tight the antibody-antigen binding and the higher the affinity between the antibody and the antigen. Specific binding properties between two molecules can be determined using methods well known in the art, for example in a BIACORE instrument using Surface Plasmon Resonance (SPR).

As used herein, the term "vector" refers to a nucleic acid delivery vehicle into which a polynucleotide can be inserted. When a vector is capable of expressing a protein encoded by an inserted polynucleotide, the vector is referred to as an expression vector. The vector may be introduced into a host cell by transformation, transduction, or transfection, and the genetic material elements carried thereby are expressed in the host cell. Vectors are well known to those skilled in the art and include, but are not limited to: a plasmid; phagemid; a cosmid; artificial chromosomes such as Yeast Artificial Chromosomes (YACs), Bacterial Artificial Chromosomes (BACs), or artificial chromosomes (PACs) derived from P1; bacteriophage such as lambda phage or M13 phage, animal virus, etc. Animal viruses that may be used as vectors include, but are not limited to, retroviruses (including lentiviruses), adenoviruses, adeno-associated viruses, herpes viruses (e.g., herpes simplex virus), poxviruses, baculoviruses, papilloma viruses, papilloma polyoma vacuolatum viruses (e.g., SV 40). A vector may contain a variety of elements that control expression, including, but not limited to, promoter sequences, transcription initiation sequences, enhancer sequences, selection elements, and reporter genes. In addition, the vector may contain a replication initiation site.

As used herein, the term "host cell" refers to a cell that can be used for introducing a vector, and includes, but is not limited to, prokaryotic cells such as Escherichia coli or Bacillus subtilis, fungal cells such as yeast cells or Aspergillus, insect cells such as S2 Drosophila cells or Sf9, or animal cells such as fibroblast, CHO cells, COS cells, NSO cells, HeLa cells, BHK cells, HEK293 cells, or human cells.

As used herein, the term "identity" is used to refer to the match of sequences between two polypeptides or between two nucleic acids. When a position in both of the sequences being compared is occupied by the same base or amino acid monomer subunit (e.g., a position in each of two DNA molecules is occupied by adenine, or a position in each of two polypeptides is occupied by lysine), then the molecules are identical at that position. The "percent identity" between two sequences is a function of the number of matching positions shared by the two sequences divided by the number of positions compared x 100. For example, if 6 of 10 positions of two sequences match, then the two sequences have 60% identity. For example, the DNA sequences CTGACT and CAGGTT share 50% identity (3 of the total 6 positions match). Typically, the comparison is made when the two sequences are aligned to yield maximum identity. Such alignments can be performed by using, for example, Needleman et al (1970) j.mol.biol.48: 443-453. The algorithm of E.Meyers and W.Miller (Compout.appl biosci., 4:11-17(1988)) which has been incorporated into the ALIGN program (version 2.0) can also be used to determine percent identity between two amino acid sequences using a PAM120 weight residue table (weight residue table), a gap length penalty of 12, and a gap penalty of 4. Furthermore, percent identity between two amino acid sequences can be determined using the Needleman and Wunsch (J MoI biol.48: 444-.

As used herein, the term "conservative substitution" means an amino acid substitution that does not adversely affect or alter the intended properties of the protein/polypeptide comprising the amino acid sequence. For example, conservative substitutions may be introduced by standard techniques known in the art, such as site-directed mutagenesis and PCR-mediated mutagenesis. Conservative amino acid substitutions include those in which an amino acid residue is replaced with an amino acid residue having a similar side chain, e.g., a substitution with a residue that is physically or functionally similar to the corresponding amino acid residue (e.g., of similar size, shape, charge, chemical properties, including the ability to form covalent or hydrogen bonds, etc.). Families of amino acid residues with similar side chains have been defined in the art. These families include amino acids with basic side chains (e.g., lysine, arginine, and histidine), acidic side chains (e.g., aspartic acid, glutamic acid), uncharged polar side chains (e.g., glycine, asparagine, glutamine, serine, threonine, tyrosine, cysteine, tryptophan), nonpolar side chains (e.g., alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine), beta-branched side chains (e.g., threonine, valine, isoleucine), and aromatic side chains (e.g., tyrosine, phenylalanine tryptophan, histidine). Thus, it is preferred to replace the corresponding amino acid residue with another amino acid residue from the same side chain family. Methods for identifying conservative substitutions of amino acids are well known in the art (see, e.g., Brummell et al, biochem.32:1180-1187 (1993); Kobayashi et al Protein Eng.12(10):879-884 (1999); and Burks et al, Proc. Natl Acad. set USA 94:412-417(1997), which are incorporated herein by reference).

The twenty conventional amino acids referred to herein are written following conventional usage. See, for example, Immunology-A Synthesis (2nd Edition, E.S. Golub and D.R.Gren, eds., Sinauer Associates, Sunderland, Mass. (1991)) which is incorporated herein by reference. In the present invention, the terms "polypeptide" and "protein" have the same meaning and are used interchangeably. Also, in the present invention, amino acids are generally represented by single-letter and three-letter abbreviations as is well known in the art. For example, alanine can be represented by A or Ala.

As used herein, the term "pharmaceutically acceptable carrier and/or excipient" refers to carriers and/or excipients that are pharmacologically and/or physiologically compatible with the subject and active ingredient, which are well known in the art (see, e.g., Remington's Pharmaceutical sciences. edited by geno AR,19th ed. pennsylvania: mach Publishing Company,1995), and include, but are not limited to: pH adjusting agents, surfactants, adjuvants, ionic strength enhancers, diluents, agents to maintain osmotic pressure, agents to delay absorption, preservatives. For example, pH adjusting agents include, but are not limited to, phosphate buffers. Surfactants include, but are not limited to, cationic, anionic or nonionic surfactants, such as Tween-80. Ionic strength enhancers include, but are not limited to, sodium chloride. Preservatives include, but are not limited to, various antibacterial and antifungal agents, such as parabens, chlorobutanol, phenol, sorbic acid, and the like. Agents that maintain osmotic pressure include, but are not limited to, sugars, NaCl, and the like. Agents that delay absorption include, but are not limited to, monostearate salts and gelatin. Diluents include, but are not limited to, water, aqueous buffers (e.g., buffered saline), alcohols and polyols (e.g., glycerol), and the like. Preservatives include, but are not limited to, various antibacterial and antifungal agents, for example, thimerosal, 2-phenoxyethanol, parabens, chlorobutanol, phenol, sorbic acid, and the like. Stabilizers have the meaning generally understood by those skilled in the art to be capable of stabilizing the desired activity of the active ingredient in a medicament, including, but not limited to, sodium glutamate, gelatin, SPGA, sugars (such as sorbitol, mannitol, starch, sucrose, lactose, dextran, or glucose), amino acids (such as glutamic acid, glycine), proteins (such as dried whey, albumin, or casein) or degradation products thereof (such as lactalbumin hydrolysate), and the like. In certain exemplary embodiments, the pharmaceutically acceptable carrier or excipient comprises a sterile injectable liquid (such as an aqueous or non-aqueous suspension or solution). In certain exemplary embodiments, such sterile injectable liquids are selected from water for injection (WFI), bacteriostatic water for injection (BWFI), sodium chloride solutions (e.g., 0.9% (w/v) NaCl), glucose solutions (e.g., 5% glucose), surfactant-containing solutions (e.g., 0.01% polysorbate 20), pH buffered solutions (e.g., phosphate buffered solutions), Ringer's solution, and any combination thereof.

As used herein, the term "preventing" refers to a method performed to prevent or delay the onset of a disease or disorder or symptom (e.g., SARS-CoV-2 infection) in a subject. As used herein, the term "treatment" refers to a method performed in order to obtain a beneficial or desired clinical result. For purposes of the present invention, beneficial or desired clinical results include, but are not limited to, alleviation of symptoms, diminishment of extent of disease, stabilized (i.e., not worsening) state of disease, delay or slowing of disease progression, amelioration or palliation of the disease state, and remission (whether partial or total), whether detectable or undetectable. Furthermore, "treatment" may also refer to prolonging survival as compared to expected survival (if not treated).

As used herein, the term "subject" refers to a mammal, such as a human. In certain embodiments, the subject (e.g., human) has or is at risk of having SARS-CoV-2 infection or a disease associated with SARS-CoV-2 infection (e.g., COVID-19).

As used herein, the term "effective amount" refers to an amount sufficient to obtain, or at least partially obtain, a desired effect. For example, an amount effective to prevent a disease (e.g., SARS-CoV-2 infection) is an amount sufficient to prevent, or delay the onset of a disease (e.g., SARS-CoV-2 infection); a therapeutically effective amount for a disease is an amount sufficient to cure or at least partially arrest the disease and its complications in a patient already suffering from the disease. It is well within the ability of those skilled in the art to determine such effective amounts. For example, an amount effective for therapeutic use will depend on the severity of the disease to be treated, the general state of the patient's own immune system, the general condition of the patient, e.g., age, weight and sex, the mode of administration of the drug, and other treatments administered concurrently, and the like.

As used herein, the term "neutralizing activity" means that the antibody or antibody fragment has a functional activity of binding to an antigenic protein on the virus, thereby preventing the virus from infecting cells and/or maturation of viral progeny and/or release of viral progeny, and the antibody or antibody fragment having neutralizing activity can prevent amplification of the virus, thereby inhibiting or eliminating infection by the virus.

Advantageous effects of the invention

The antibody of the invention can specifically bind to a Receptor Binding Domain (RBD) of S protein of SARS-CoV-2, neutralize SARS-CoV-2, and block the binding of SARS-CoV-2 and Ace2 receptor, thereby blocking the infection of SARS-CoV-2 to cells. Accordingly, the antibody of the present invention has the potential for preventing and/or treating SARS-CoV-2 infection or a disease caused by SARS-CoV-2 infection (e.g., COVID-19). In addition, the antibody of the present invention can be also used for specific detection of SARS-CoV-2 or its S protein or RBD of S protein, and has important clinical value for diagnosing SARS-CoV-2 infection.

Embodiments of the present invention will be described in detail below with reference to the drawings and examples, but those skilled in the art will understand that the following drawings and examples are only for illustrating the present invention and do not limit the scope of the present invention. Various objects and advantageous aspects of the present invention will become apparent to those skilled in the art from the accompanying drawings and the following detailed description of the preferred embodiments.

Drawings

FIG. 1 shows SDS-PAGE electrophoresis of the recombinant proteins RBD-mFc, RBD-mGam and RBD-His.

FIG. 2 shows the results of ELISA assay of serum from patients in the convalescent phase of SARS-CoV-2 for binding activity of recombinant proteins RBD-mFc and RBD-His.

FIG. 3 shows the results of the RBD antibody titer assay in rabbit antiserum.

FIG. 4 shows the results of Western Blot assay of rabbit antisera for RBD-His binding activity.

FIG. 5 shows the results of ELISA detection of the binding activity of rabbit-derived monoclonal antibody 3F4 to RBD-mFc.

FIG. 6 shows the results of affinity assay (Biacore) of rabbit monoclonal antibody 3F4 for RBD-His.

FIG. 7 shows the results of the detection of the binding activity of rabbit-derived monoclonal antibody 3F4 to SARS-CoV-2 spike protein S expressed on cells.

FIG. 8 shows the results of measurement of the neutralizing activity of rabbit-derived monoclonal antibody 3F4 in a SARS-CoV2 VSVPp pseudovirus infection model.

FIG. 9 shows the results of the measurement of the cross-blocking ability of the rabbit-derived monoclonal antibody 3F4 against SARS-CoV-2 and SARS-CoV-1.

FIG. 10 shows the results of ELISA assay of the binding activity of 3F4 humanized antibody to RBD-His.

FIG. 11 shows the results of determination of the neutralizing activity of the 3F4 humanized antibody in the SARS-CoV2 VSVPp pseudovirus infection model, wherein r3F4 is the rabbit derived monoclonal antibody 3F 4.

FIG. 12 shows the result of measurement of the blocking ability of the 3F4 humanized antibody against SARS-CoV-2, wherein r3F4 is the rabbit-derived monoclonal antibody 3F 4.

Sequence information

Information on the partial sequences to which the present invention relates is provided in table 1 below.

Table 1: description of the sequences

Detailed Description

The invention will now be described with reference to the following examples, which are intended to illustrate the invention, but not to limit it.

Unless otherwise indicated, the molecular biological experimental methods and immunoassay methods used in the present invention are essentially described by reference to j.sambrook et al, molecular cloning: a laboratory manual, 2nd edition, cold spring harbor laboratory Press, 1989, and F.M. Ausubel et al, eds. molecular biology laboratory Manual, 3 rd edition, John Wiley & Sons, Inc., 1995; the use of restriction enzymes follows the conditions recommended by the product manufacturer. The examples are given by way of illustration and are not intended to limit the scope of the invention as claimed.

Example 1: preparation of rabbit-derived monoclonal antibody against SARS-CoV-2 receptor binding region RBD protein

1.1 preparation and activity identification of SARS-CoV-2 receptor binding region RBD protein:

the SARS-CoV-2 receptor binding region RBD-mFc was purchased from Beijing Yiqian Shenzhou science and technology, Inc., and the RBD gene of the SARS-CoV-2 receptor binding region RBD-His protein was obtained from NCBI database (GenBank ID: MN908947.3), and His tag was fused at the C-terminus. The amino acid sequence of the SARS-CoV2-2Spike protein membrane region full-length sequence (corresponding to virus Spike gene aa316-aa550) is optimized according to human preferred codons by referring to the SARS-CoV2-2 whole gene sequence (MN908947.3) to obtain the optimized coding nucleic acid sequence. Connecting a signal peptide coding sequence to the N end of the RBD nucleic acid sequence, connecting an optimized coding nucleic acid sequence of green fluorescent protein mGamillus (abbreviated as mGam) to the C end, and connecting polyhistidine polypeptide (6 XHis or 8 XHis) convenient for affinity chromatography purification to the C end of the fusion polypeptide to finally obtain the RBD-mGam protein. The coding sequence of SARS-CoV2-RBG is connected to a plasmid vector suitable for eukaryotic expression, and the constructed recombinant plasmid is transfected into ExpicHO cells (purchased from Thermofeisher company) or other CHO cells for expression and purification. RBD-His protein is constructed and expressed by using the same sequence, namely, poly-histidine polypeptide (6 × His or 8 × His) is connected to the C end of the RBD sequence. The results of SDS-PAGE showed that RBD-mFc, RBD-mGam and RBD-His were highly pure (FIG. 1). The reactivity of the above proteins with serum from patients in the recovery period of SARS-CoV-2 was measured by ELISA, and the results are shown in FIG. 2, and the obtained RBD-mFc, RBD-mGam and RBD-His proteins were reactive with serum from patients in the recovery period of SARS-CoV-2.

1.2 New Zealand rabbits:

female New Zealand rabbits at 10 weeks of age were purchased from the Songjiang area Songjiang laboratory animal farm, Shanghai.

1.3 immunization of experimental rabbits:

using standard in vivo immunization protocols, detailed procedures are described in Ed Harlow et al, "Antibodies a Laboratory Manual", Cold Spring Harbor Laboratory1988. the brief procedure is as follows:

a SARS-CoV-2 receptor binding region RBD-mFc protein 300. mu.g and Freund's complete adjuvant (CFA) are mixed in equal volume and emulsified into 2mL, and experimental rabbits are injected into multiple points at neck and back. On day 8 after the first immunization, the SARS-CoV-2 receptor binding region RBD-mGam protein 500. mu.g and Freund's incomplete adjuvant (IFA) were mixed in equal volume and emulsified into 2mL, and the experimental rabbits were injected into the neck and back at multiple points. Whole blood was collected through the middle ear artery of rabbits on day 11 after the first immunization, serum was isolated and RBD antibody titer was determined, showing a serum titer of 10^4 (fig. 3); western Blot assay showed that rabbit antisera were able to react with RBD-His antigen (FIG. 4).

1.4 preparation of Rabbit Peripheral Blood Mononuclear Cells (PBMC):

diluting rabbit whole blood by using a serum-free RPMI1640 culture medium according to a ratio of 1:1, performing density gradient centrifugation by using a Ficoll reagent to separate peripheral blood mononuclear cells, adding a Ficoll solution with the volume of 1.5 times that of the rabbit whole blood to the bottom layer of a centrifuge tube, slowly adding a rabbit whole blood diluent at 800g for 30min at 4 ℃, performing slow speed-up and slow speed-down centrifugation, collecting suspension cells at the junction of the Ficoll and the RPMI1640 culture medium to obtain PBMCs after centrifugation is finished, performing secondary centrifugation to collect the PBMC cells, and centrifuging at 1500rpm for 5min at 4 ℃.

1.5 specific B cell screening against the SARS-CoV-2 receptor binding region protein RBD:

resuspending the separated rabbit PBMC with 100. mu.L sterile PBS solution, adding corresponding amount of RBD protein according to the standard of adding 1. mu.g biotin-labeled RBD-mFc protein into 3ml rabbit whole blood PBMC, gently blowing, sucking, mixing, and incubating at 4 deg.C for 30 min. Centrifuging at 1500rpm for 3min at 4 ℃, discarding supernatant to retain cells, using PBS to resuspend the cells, washing for 2-3 times, and adding 100 μ L of a staining system shown below to each tube. Incubated at 4 ℃ in the dark for 30 min.

RBD-specific memory B cells were sorted into 96-well plates containing 25 μ L of lysate per well, one cell per well. After completion, 20. mu.L of the lysate containing single cells was pipetted into a PCR plate, and reverse transcription was performed followed by nested PCR to amplify the light and heavy chain variable region sequences of the antibody, respectively.

And (3) selecting PCR products of the heavy chain and the light chain in pairing, recovering by using a gel recovery kit, sequencing, comparing sequencing results in an IMGT database, judging whether the obtained gene is an antibody gene, whether the gene is complete and whether the antibody can be successfully coded, and determining the family to which the antibody gene (V region and J region) belongs. And carrying out enzyme digestion on the cloning vector, wherein the enzyme digestion site of the heavy chain expression plasmid vector is EcoR I/BamH I, and the enzyme digestion site of the light chain expression plasmid vector is Nhe I/Sal I. The light and heavy chain variable region genes were constructed into corresponding eukaryotic expression vectors pRVRCH (SEQ ID NO:28), pRVRCL (SEQ ID NO:29) using the Gibson assembly method, wherein pRVRCH comprises a nucleic acid sequence encoding the constant region of the rabbit monoclonal antibody heavy chain and pRVRCL comprises a nucleic acid sequence encoding the constant region of the rabbit monoclonal antibody light chain.

After the expression vector is constructed, HEK293T cells are transiently transfected by a liposome method for S resistanceExpression of the ARS-CoV-2 receptor binding domain protein RBD monoclonal antibody. 12 hours before transfection, 10^4 cells were seeded into 96-well cell culture plates; tube A: adding 0.2 mu g of IgH plasmid and 0.2 mu g of IgK plasmid into 10 mu L of Opti-MEM; and (B) tube: to 10. mu.L of Opti-MEM was added 0.4. mu.L of Novozam ExFect

2000 transformation Reagent; respectively mixing A, B tubes gently, standing at room temperature for 5min, adding diluted plasmid dropwise into diluted transfection reagent, mixing gently, and incubating at room temperature for 10 min; dripping the plasmid-transfection reagent compound into cells, and placing the cells in a cell culture box for culture; after 48h, the cell supernatant was collected and centrifuged at 3000rpm for 5min at 4 ℃ to remove the supernatant and discard the cell debris pellet. Positive monoclonal antibodies specifically reactive with RBD were screened by indirect ELISA (see example 2).

1.6 sequencing of anti-SARS-CoV-2 receptor binding region protein RBD positive monoclonal antibody

The rabbit-derived monoclonal antibody 3F4 specific to the RBD of the SARS-CoV-2 receptor binding region protein 1 strain is obtained by the method. The sequencing confirmed that the amino acid sequences of the heavy chain variable region and the light chain variable region of 3F4 are shown in SEQ ID NO 1 and SEQ ID NO 2, respectively. CDR Sequences were also determined using the Kabat numbering system (Kabat et al, Sequences of Proteins of Immunological Interest, fifth edition, Public Health Service, national institutes of Health, Besserda, Maryland (1991), p.647-.

Table 2: 3F4 variable region sequence

1.7 purification and preparation of eukaryotic expression antibodies

Large-scale expression of 3F4 was carried out, and 293F suspension cells in logarithmic growth phase were prepared and placed at 100rpm and 37 ℃ in 5% CO₂The cells were cultured on a shaker to a density of 1.5X 10⁶mL, cell viabilityRate of change>95% and 400mL of the cells were placed in a new cell culture flask to obtain a transfection system. Tube A: respectively adding 600 micrograms of light and heavy chain plasmids into 20mL of suspension cell culture medium, and uniformly mixing by oscillation; and (B) tube: adding 1.2mg of PEI transfection reagent into 20mL of suspension cell culture medium, and uniformly mixing by oscillation; adding the solution in the tube B into the tube A, shaking and uniformly mixing, incubating at room temperature for 15min, and adding the mixed liquid into a 400mL cell culture system; placing at 100rpm and 37 ℃ with 5% CO₂Performing antibody expression for 6 days by using a cell shaker; after completion of the culture, cell supernatants were collected at 4000rpm for 10min at 4 ℃.

Filtering the cell supernatant with a 0.22 μm filter; opening the AKTA instrument, washing the pipeline A and the pipeline B with solution A (200mM disodium hydrogen phosphate dodecahydrate) and solution B (100mM citric acid monohydrate), respectively, and installing a protein A column; balancing protein A column with solution A at a flow rate of 8mL/min for more than 15min, and performing the next step after the UV value, pH value and conductivity detected by the instrument are stable; the sample is loaded at a flow rate of 6-10mL/min, then the UV value will rise, the peak is the breakthrough peak, and the column is washed with liquid A continuously while collecting the breakthrough peak sample for detection. Feeding liquid B at the flow rate of 6-10mL/min after the pH value is not changed, then lowering the pH value, raising the UV value, taking the peak as an elution peak, mainly containing the antibody in the elution peak, and collecting the elution peak sample to be detected; equilibrating the column with solution A, filling the tube and protein A column with 20% ethanol, removing the column, and storing at 4 deg.C. SDS-PAGE identification is carried out on the collected penetration peak and elution peak samples. The purified monoclonal antibody was dialyzed overnight against 20mM PBS buffer and dispensed into 1.5mL tubes using UV spectroscopy or BCA measurements and stored at-20 ℃ until needed.

Example 2: reactivity of rabbit-derived monoclonal antibody against SARS-CoV-2 receptor binding region protein RBD and SARS-CoV-2 receptor binding region protein RBD

2.1 preparation of reaction plates

SARS-CoV2-RBD (mFc tag) protein was purified using 50mM CB buffer (NaHCO) pH9.6₃/Na₂CO₃Buffer, final concentration 50mM, pH 9.6) diluted to a final concentration of 2 μ g/mL; adding 100 mu L of coating solution into each hole of a 96-hole enzyme label plate, coating for 16-24 hours at 2-8 ℃, and then coating for 2 hours at 37 ℃; wash with PBST (20 mM)PB7.4, 150mM NaCl, 0.1% Tween20) 1 wash; then 200. mu.L of blocking solution (20mM Na pH 7.4 containing 20% calf serum and 1% casein) was added to each well₂HPO₄/NaH₂PO₄Buffer solution), sealing at 37 deg.C for 2 hr; the blocking solution was discarded. Drying, and packaging in aluminum foil bag at 2-8 deg.C.

2.2 ELISA detection of RBD Rabbit-derived monoclonal antibody 3F4

The monoclonal antibody 3F4 obtained in example 1 was diluted in 20mM PBS buffer in 3-fold gradient starting from 10. mu.g/mL, for a total of 7 gradients. A diluted sample (100. mu.L) was added to each well of an ELISA plate coated with SARS-CoV2-RBD protein, and the mixture was reacted at 37 ℃ for 60 minutes in an incubator. The plate was washed 5 times with PBST wash (20mM PB7.4, 150mM NaCl, 0.1% Tween20), 100. mu.L of HRP-labeled goat anti-rabbit IgG reaction solution was added to each well, and the mixture was incubated at 37 ℃ for 30 minutes. After completion of the enzyme-labeled substance reaction step, the plate was washed 5 times with PBST wash (20mM PB7.4, 150mM NaCl, 0.1% Tween20), 50. mu.L each of TMB color developing agents (purchased from Beijing Wantai Bio-pharmaceuticals Co., Ltd.) was added to each well, and the plate was left to react in an incubator at 37 ℃ for 15 minutes. After the color reaction step was completed, 50. mu.L of stop solution (purchased from Beijing Wantai biological pharmaceuticals Co., Ltd.) was added to each well of the reacted microplate, and the OD450/630 value of each well was measured on a microplate reader.

As shown in FIG. 5, the EC50 value of the rabbit monoclonal antibody 3F4 and RBD-mFc is 14.36ng/mL, and the antibody has good binding activity.

Example 3: rabbit-derived monoclonal antibody for resisting SARS-CoV-2 receptor binding region protein RBD and detection of SARS-CoV-2 receptor binding region protein RBD affinity constant

Kinetic analysis of binding of monoclonal antibody and antigen using Biacore 8K system, all steps were performed in PBS buffer, monoclonal antibody diluted to 5. mu.g/mL was captured using the company's Protein A chip, SARS-CoV-2 receptor binding domain Protein RBD-His was used as the detection antigen, and the detection was performed using five gradients of 100nM, 50nM, 25nM, 12.5nM, and 6.75nM, respectively, as the detection antigen, according to the following procedure: capture (capture) 60s, assay (analyze) 300s, Dissociation (Dissociation)600s, Regeneration (Regeneration)60 s. And (3) adopting instrument matched data acquisition and analysis software to calculate the affinity equilibrium dissociation constant.

As a result, as shown in FIG. 6, 3F4 shows the equilibrium dissociation constant (K) for SARS-CoV-2 receptor binding domain protein RBD-His_D) It was 8.79 nM.

Example 4: application of RBD rabbit-derived monoclonal antibody for resisting SARS-CoV-2 receptor binding region protein in detecting SARS-CoV-2-S expressed in cell

(1) And inoculating the MDCK into a 10cm cell culture plate, and performing transfection when the cell confluence rate reaches 60-80%.

(2) Tube A: adding 30ug of mammalian expression plasmid containing SARS-CoV-2 spike protein S gene into 2mL of Opti-MEM;

(3) and (B) tube: 2mL of Opti-MEM was added with 60. mu.L of ExFect from Novozam

2000 Transfection Reagent；

(4) Respectively mixing A, B tubes gently, standing at room temperature for 5min, adding diluted plasmid dropwise into diluted transfection reagent, mixing gently, and incubating at room temperature for 10 min;

(5) dripping the plasmid-transfection reagent compound into cells, and placing the cells in a cell culture box for culture;

(6) after transfection for 36h, cells are digested by pancreatin, inoculated to a 96-well cell culture plate according to the proportion of 10^4 cells per well, and placed in a cell culture box for culture;

(7) after being inoculated to a 96-well cell culture plate for 12 hours, cell supernatant is discarded, 100 mu L of 20mM PBS is added into each well for washing once, 4% paraformaldehyde prepared by 100 mu L of 20mM PBS is added into each well, the cells are fixed for 15min in a dark place, and 100 mu L of 20mM PBS is added into each well for washing three times;

(8) adding 3 per mill Triton X-100 prepared by 100 mul of ultrapure water into each hole, performing permeation treatment on the cells for 15min, and adding 100 mul of 20mM PBS into each hole for washing for three times;

(9) the monoclonal antibody was diluted to 1. mu.g/mL with 2% BSA in 20mM PBS, added to a 96-well cell culture plate at 100. mu.L per well, incubated at room temperature for 30min, and washed three times with 100. mu.L of 20mM PBS per well;

(10) fluorescent Anti-Rabbit IgG (H + L), CF^TM647 antibody produced in goat diluted to 1. mu.g/mL with 2% BSA in 20mM PBS, added to a 96-well cell culture plate at 100. mu.L per well, incubated at room temperature for 30min, washed three times with 100. mu.L 20mM PBS per well;

(11) the nuclear dye DAPI is diluted by 2% BSA prepared by 20mM PBS according to the proportion of 1:2000, 50 mu L of the nuclear dye DAPI is added into each hole, the nuclear dye DAPI is incubated for 5min at room temperature, and 100 mu L of 20mM PBS is added into each hole for washing three times;

(12) the 96-well cell culture plate was placed in a fluorescence microscope for observation and the results were photographed.

As a result, as shown in FIG. 7, the fluorescence was distributed both in the cell membrane and cytoplasm of MDCK cells expressing spike protein S, and the above results indicate that 3F4 has specific binding activity to SARS-CoV-2 spike protein S expressed on the cells and no nonspecific reaction to negative MDCK cells.

Example 5: neutralizing capacity analysis of RBD rabbit-derived monoclonal antibody of anti-SARS-CoV-2 receptor binding region protein in SARS-CoV2 VSVPp pseudovirus infection model

SARS-CoV2-VSVPp pseudovirus neutralization reference methods were performed (doi: https:// doi.org/10.1101/2020.04.08.026948). The main experimental process is briefly described as follows, in order to construct VSV pseudovirus carrying SARS-CoV-2 spike protein, the spike gene of SARS-CoV-2 (sequence source GenBank: MN908947.3) with 18 amino acids truncated at C-terminal of the spike gene of SARS-CoV-2 is cloned into eukaryotic expression vector pCAG to obtain pCAG-nCoVSde 18. Plasmid pCAG-nCoVSde18 was transfected into Vero-E6. 48 hours after transfection, VSVDG-EGFP-G (Addgene, 31842) virus was inoculated into cells expressing the truncated protein of SARS-CoV-2 Sde18 and incubated for 1 hour. The supernatant was then removed of VSVdG-EGFP-G virus and anti-VSV-G rat serum was added to block infection by residual VSVdG-EGFP-G. The progeny virus will carry the truncated protein of SARS-CoV-2 Sde18 to obtain the pseudovirus VSV-SARS-CoV2 VSVPp. After 24 hours post-infection with VSVDG-EGFP-G, cell supernatants were collected, centrifuged and filtered (0.45- μm pore size, Millipore, SLHP033RB) to remove cell debris, and stored at-80 ℃ until use. Viral titers were determined by the number of GFP positive cells after infection of BHK21-hACE2 with the supernatant from the gradient dilution. The gene of hACE2 was integrated in BHK21 cells by the PiggyBac transposon system. A transposon vector (SBI system biosciences, PB514B-2) containing the hACE2 gene and a transposase plasmid were co-transfected into BHK21 cells, and puromycin resistance and red fluorescence were used for screening to obtain BHK21-hACE2 cells stably expressing hACE 2.

Antibody 3F4 was diluted to 2ug/mL as a1, 3-fold downward gradient dilution for a total of 6 gradients, the gradient diluted antibody was mixed with diluted SARS-CoV2 VSVpp virus (MOI ═ 0.05) and incubated at 37 ℃ for 1 h. All samples and viruses were diluted with 10% FBS-DMEM. 80 μ L of the mixture was added to pre-plated BHK21-hACE2 cells. After 12 hours of incubation, the infected cells were fluorescence imaged using a high content imaging system based on confocal rotating disk (Opera phenix or Operetta CLS, available from Perkinelmer). And after the detection is finished, quantitative analysis is carried out on the obtained fluorescence image by adopting Columbus image management analysis software to detect the number of green fluorescence positive cells. The reduction (%) in the number of GFP-positive cells in the antibody-treated group compared to the untreated control well was calculated, and the inhibition rate was calculated.

As shown in FIG. 8, IC50 of rabbit monoclonal antibody 3F4 was 1.95ng/mL, which showed strong neutralizing effect.

Example 6: analysis of Cross-blocking Capacity of anti-SARS-CoV-2 receptor binding region protein RBD Rabbit-derived monoclonal antibody

The amino acid sequence of the SARS-CoV2-2Spike protein membrane region full-length sequence (corresponding to virus Spike gene aa316-aa550) is optimized according to human preferred codons by referring to the SARS-CoV2-2 whole gene sequence (MN908947.3) to obtain the optimized coding nucleic acid sequence. Connecting a signal peptide coding sequence to the N end of the RBD nucleic acid sequence, connecting an optimized coding nucleic acid sequence of green fluorescent protein mGamillus (abbreviated as mGam) to the C end, and connecting polyhistidine polypeptide (6 XHis or 8 XHis) convenient for affinity chromatography purification to the C end of the fusion polypeptide, thereby finally obtaining the RBD fusion fluorescent protein probe RBD-mGam (abbreviated as SARS-CoV 2-RBG). The coding sequence of SARS-CoV2-RBG is connected to a plasmid vector suitable for eukaryotic expression, and the constructed recombinant plasmid is transfected into ExpicHO cells (purchased from Thermofeisher company) or other CHO cells for expression and purification.

Referring to the viral genome sequence SARS-CoV-1(AAP13567.1) published on Genebank, the RBD sequence is referred to SARS-CoV2-RBG method to construct the fusion fluorescent protein probe of RBD and mGamillus, which is abbreviated as SARS-CoV 1-RBG. The coding sequence of SARS-CoV1-RBG is connected to a plasmid vector suitable for eukaryotic expression, and the constructed recombinant plasmid is transfected into ExpicHO cells (purchased from Thermofeisher company) or other CHO cells for expression and purification.

A red fluorescent protein mRuby3 is expressed at the C end of an ACE2 gene (NM-021804.1) in a fusion mode (the middle is connected by a flexible amino acid linker), a sequence hACE2-mRuby3 (abbreviated as hACE2mRb3) is obtained, the sequence is cloned to a PiggyBac (PB) transposon vector MIHIP-CMVnie vector constructed in the room, and the MIHIP-CMVnie-hACE 2mRb3 vector is obtained and can express hACE2mRb3 protein in cells. The MIHIP-CMVnie-hACE 2mRb3 plasmid was co-transfected with the Super PiggyBac Transposase expression plasmid (available from System Biosciences) into 293T cells using the Lipofectamine3000 transfection reagent (available from Thermofisher), the medium was changed after 4 hours of transfection, the cells were passaged to 10cm cell culture dishes after 24 hours of continuous culture, and pressure-screened with 2. mu.g/mL puromycin (available from InvivoGen), and the medium containing killing resistance was changed every 24 hours. After 6-7 days of puromycin-containing culture solution, the surviving cells were confirmed to be mRuby3 positive for red fluorescent protein by microscopic observation, indicating successful integration. The stably transfected cell line was named 293T-ACE2iRb 3.

The 293T-ACE2iRb3 cells were plated at 15000 cells/well to black glass bottom and cultured for 12-24 hours until they were adherent for future use. The SARS-CoV2-RBG probe was diluted to the appropriate concentration (20-30nM), mixed with antibody dilutions at different dilutions to give a 1-fold 2-fold gradient dilution of the final antibody concentration at 50nM for a total of 10 gradients. Remove 50. mu.L of the medium from the original cell culture plate, add 50. mu.L of the prepared mixture to the cell culture plate, and incubate at 37 ℃ for 60 minutes. The Opera Phenix confocal high content system is directly used for imaging analysis without washing, imaging fluorescence channels comprise Ex488/Em510 (green fluorescence protein detection channel, probe signal), Ex561/Em592 (red fluorescence protein detection channel, ACE2), Ex641/Em670 (near infrared fluorescence protein iRFP670 imaging channel, cell nucleus), and at least 25 visual fields are shot by using a 20-fold or 40-fold water immersion lens (confocal mode). And after the data are finished, uploading the data to Columbus image management analysis software, and carrying out quantitative image analysis by using the software. The analysis parameters include: nuclear iRFP670 positive cell number (N, requirement > 1000), cell membrane red fluorescence (ACE2-mRuby3 for inter-cytoplasmic pore differences) signal intensity (mean), cytoplasmic green fluorescence signal intensity (mean, SD, reflecting the amount of protein probe bound and taken up by the cell).

As a result, as shown in FIG. 9, the antibody 3F4 blocked the binding of RBD protein in the binding region of SARS-CoV-2 receptor to Ace2 receptor, but did not block the binding of RBD protein in the binding region of SARS-CoV-1 receptor to Ace2 receptor.

Example 7: preparation of 3F4 humanized antibody

7.1 monoclonal Rabbit-derived antibody 3F4 humanization design

Humanization of rabbit derived mAb 3F4 was performed according to the method of Combined CDRs (Zhang YF, Ho M. mutation of monoclonal antibodies via grafting Combined Kabat/IMGT/partner complete-determining regions: ratio and examples MAbs. 2017; 9(3): 419-429. doi: 10.1080/19420862.2017.1289302).

The Complementarity Determining Regions (CDRs) of rabbit antibody 3F4 were first determined by the Kabat method (Kabat EA; Wu TT, Perry HM, Gottesman KS, Coe11er K. sequences of proteins of immunological interest, U.S. Department of Health and Human Service, PHS, NIH, Bethesda, 1991) and IMGT method, with the specific sequences shown in Table 2 above.

The CDR regions determined by the IMGT method and the Kabat method were Combined by the Combined CDRs method, and the CDR regions finally determined for CDR grafting are shown in Table 3.

Table 3: combined CDRs of rabbit-derived monoclonal antibody 3F4

The gene database was searched by IMGT to find the sequence of the variable region of the human germline gene having the highest homology with the FR region of the rabbit derived antibody 3F 4. Through homology analysis, the sequences of IGHV3-53 × 04 and IGKV1-5 × 01 embryonic genes are determined to be used as heavy chain and light chain modification templates of the humanized antibody respectively, meanwhile, because the embryonic genes do not contain FR4 required by a modification part, the FR4 part needs to be aligned separately, and finally, the sequences of IGHJ1 & lt 01 & gt and IGKJ2 × 02 embryonic genes are determined to be used as the modification templates of the heavy chain and light chain FR4 of the humanized antibody respectively. The CDR regions of the heavy chain and the light chain of the rabbit anti-3F 4 are respectively transplanted to FR frameworks of vH and vK of human templates, meanwhile, the sequence alignment of the rabbit anti-3F 4 and the FR regions of embryonic genes is carried out, the selective back mutation is carried out on the different amino acids, and finally 4 humanized heavy chains and 1 humanized light chain are designed, and 4 humanized antibodies are combined, wherein the variable region sequences are shown in the following table.

Table 4: humanized antibody variable region sequences

7.2 construction of antibody-expressing recombinant plasmid

The light chain variable region gene of the 3F4 humanized antibody was obtained by a slipping overlapping extension-PCR (SOE-PCR) method. The heavy chain and light chain variable region genes are respectively split into oligonucleotide sequences with the size of about 80bp, and the fragments are overlapped by about 20 bp. The amplified products were analyzed by agarose gel electrophoresis, and the purified PCR products were recovered with a DNA purification recovery kit (Tianggen, DP 118-02). The Gibson assembly method was used to construct the heavy chain variable region fragment into the PTT5-H vector (restriction sites AgeI/SalI) containing the coding sequence for the heavy chain constant region (SEQ ID NO:20), and the light chain variable region fragment into the PTT5-K vector (restriction sites AgeI/BsiWI) containing the coding sequence for the light chain constant region (SEQ ID NO: 21). The recombinant vector was transformed into DH 5. alpha. competent cells (Shenzhen concatamer), and after 12h of growth on ampicillin resistant LB plates, single clones were picked and sequenced (Shanghai Production). Recombinant plasmids with correct sequencing were extracted in large quantities using an endotoxin-free plasmid macroextraction kit (Tianggen, DP 117).

7.3 eukaryotic expression and purification of antibodies

293F cells transiently transfected with dual plasmids expressed the 3F4 humanized antibody. 293F cells with a viability rate higher than 95% were prepared at 4X 10⁶200ml of the suspension was inoculated into a 1L cell culture flask. 0.5mg of each light and heavy chain plasmid is taken, 1mg of the mixed light and heavy chain plasmids is mixed with 2mg of PEI, the mixture is violently shaken for 8s and then kept stand for 8min, and the mixture is added into 200ml of cells. After 4h, 200mL Freestyle medium was supplemented and placed in a 5% CO2 incubator at 37 ℃ for 7 days. The cell supernatant was collected and centrifuged at 10000rpm for 30 min. The supernatant was taken and subjected to subsequent purification as described in example 1.7.

Example 8: ELISA binding Activity of 3F4 humanized antibodies against SARS-CoV-2

8.1 preparation of reaction plates

SARS-CoV2-RBD (His-tagged) protein was purified using 50mM CB buffer (NaHCO) pH9.6₃/Na₂CO₃Buffer, final concentration 50mM, pH 9.6) diluted to a final concentration of 2 μ g/mL; adding 100 mu L of coating solution into each hole of a 96-hole enzyme label plate, coating for 16-24 hours at 2-8 ℃, and then coating for 2 hours at 37 ℃; wash 1 time with PBST wash (20mM PB7.4, 150mM NaCl, 0.1% Tween 20); then 200. mu.L of blocking solution (20mM Na pH 7.4 containing 20% calf serum and 1% casein) was added to each well₂HPO₄/NaH₂PO₄Buffer solution), sealing at 37 deg.C for 2 hr; the blocking solution was discarded. Drying, and packaging in aluminum foil bag at 2-8 deg.C.

8.23 ELISA detection of humanized antibodies to F4

The 3F4 humanized antibody obtained in example 8 was subjected to gradient dilution starting from 10ug/mL in 20mM PBS buffer, and then diluted in 7 gradients. A diluted sample (100. mu.L) was added to each well of an ELISA plate coated with SARS-CoV2-RBD protein, and the mixture was reacted at 37 ℃ for 60 minutes in an incubator. The plate was washed 5 times with PBST wash (20mM PB7.4, 150mM NaCl, 0.1% Tween20), 100. mu.L of HRP-labeled goat anti-human IgG reaction solution was added to each well, and the mixture was incubated at 37 ℃ for 30 minutes. After completion of the enzyme-labeled substance reaction step, the plate was washed 5 times with PBST wash (20mM PB7.4, 150mM NaCl, 0.1% Tween20), 50. mu.L each of TMB color developing agents (purchased from Beijing Wantai Bio-pharmaceuticals Co., Ltd.) was added to each well, and the plate was left to react in an incubator at 37 ℃ for 15 minutes. After the color reaction step was completed, 50. mu.L of stop solution (purchased from Beijing Wantai biological pharmaceuticals Co., Ltd.) was added to each well of the reacted microplate, and the OD450/630 value of each well was measured on a microplate reader. Determination of reactivity of 3F4 humanized antibody with SARS-CoV 2-RBD: the determination was made based on the reading after the reaction. As a result, as shown in FIG. 10, the 3F4 humanized antibody had good binding activity to RBD-His.

Example 9: determination of neutralizing Activity of 3F4 humanized antibody in SARS-CoV2 VSVPp pseudovirus infection model

SARS-CoV2-VSVPp pseudovirus neutralization reference methods were performed (doi: https:// doi.org/10.1101/2020.04.08.026948). The main experimental process is briefly described as follows, in order to construct VSV pseudovirus carrying SARS-CoV-2 spike protein, the spike gene of SARS-CoV-2 (sequence source GenBank: MN908947.3) with 18 amino acids truncated at C-terminal of the spike gene of SARS-CoV-2 is cloned into eukaryotic expression vector pCAG to obtain pCAG-nCoVSde 18. Plasmid pCAG-nCoVSde18 was transfected into Vero-E6. 48 hours after transfection, VSVDG-EGFP-G (Addgene, 31842)¹) The virus was inoculated into cells expressing the truncated protein of SARS-CoV-2 Sde18 and incubated for 1 hour. The supernatant was then removed of VSVdG-EGFP-G virus and anti-VSV-G rat serum was added to block infection by residual VSVdG-EGFP-G. The progeny virus will carry the truncated protein of SARS-CoV-2 Sde18 to obtain the pseudovirus VSV-SARS-CoV2 VSVPp. After 24 hours post-infection with VSVDG-EGFP-G, cell supernatants were collected, centrifuged and filtered (0.45- μm pore size, Millipore, SLHP033RB) to remove cell debris, and stored at-80 ℃ until use. Viral titers were determined by the number of GFP positive cells after infection of BHK21-hACE2 with the supernatant from the gradient dilution. The gene of hACE2 was integrated in BHK21 cells by the PiggyBac transposon system. Will contain the hACE2 geneThe transposon vector (SBI system biosciences, PB514B-2) and the transposase plasmid were co-transfected into BHK21 cells, and selective for puromycin resistance and red fluorescence to obtain BHK21-hACE2 cells stably expressing hACE 2.

The 3F4 humanized antibody was diluted to 13.33nM as a1, 3 fold down gradient dilution for 10 gradients, mixed with diluted SARS-CoV2 VSVpp virus (MOI ═ 0.05) and incubated at 37 ℃ for 1 h. All samples and viruses were diluted with 10% FBS-DMEM. 80 μ L of the mixture was added to pre-plated BHK21-hACE2 cells. After 12 hours of incubation, the infected cells were fluorescence imaged using a high content imaging system based on confocal rotating disk (Opera phenix or Operetta CLS, available from Perkinelmer). And after the detection is finished, quantitative analysis is carried out on the obtained fluorescence image by adopting Columbus image management analysis software to detect the number of green fluorescence positive cells. The reduction (%) in the number of GFP-positive cells in the antibody-treated group compared to the untreated control well was calculated, and the inhibition rate was calculated. IC50 of the antibody was calculated using non-linear regression analysis. As shown in fig. 11, the 3F4 humanized antibody blocked infection of cells by pseudoviruses.

Example 10: analysis of ability of 3F4 humanized antibody for blocking SARS-CoV-2S tripolymer protein from binding to ACE2

The SARS-CoV2-2Spike protein membrane outer region full-length sequence (corresponding to virus Spike gene aa16-aa1207, abbreviated as SARS-CoV2-Secd) is optimized according to human partial number codon by referring to SARS-CoV2-2 full gene sequence (MN908947.3) to obtain the optimized coding nucleic acid sequence. Connecting a signal peptide coding sequence to the N end of a SARS-CoV2-Secd nucleic acid sequence, connecting a trimerization structure domain coding sequence (TFD for short) to the C end, further connecting a flexible amino acid linker peptide coding sequence, a green fluorescent protein mGamillus (mGam for short) and a polyhistidine polypeptide (6 XHis or 8 XHis) convenient for affinity chromatography purification, and finally obtaining a spike protein extracellular domain trimer fusion fluorescent protein probe Stremer-mGam (SARS-CoV 2-STG for short).

The 293T-ACE2iRb3 cells were plated at 15000 cells/well to black glass bottom and cultured for 12-24 hours until they were adherent for future use. The SARS-CoV2-STG probe was diluted to an appropriate concentration (2-4nM) and mixed with antibody dilutions at different dilutions to achieve a final antibody concentration of 1, 2-fold dilution gradient at 50nM for a total of 10 gradients. Remove 50. mu.L of the medium from the original cell culture plate, add 50. mu.L of the prepared mixture to the cell culture plate, and incubate at 37 ℃ for 60 minutes. The Opera Phenix confocal high content system is directly used for imaging analysis without washing, imaging fluorescence channels comprise Ex488/Em510 (green fluorescence protein detection channel, probe signal), Ex561/Em592 (red fluorescence protein detection channel, ACE2), Ex641/Em670 (near infrared fluorescence protein iRFP670 imaging channel, cell nucleus), and at least 25 visual fields are shot by using a 20-fold or 40-fold water immersion lens (confocal mode). And after the data are finished, uploading the data to Columbus image management analysis software, and carrying out quantitative image analysis by using the software. The analysis parameters include: nuclear iRFP670 positive cell number (N, requirement > 1000), cell membrane red fluorescence (ACE2-mRuby3 for inter-cytoplasmic pore differences) signal intensity (mean), cytoplasmic green fluorescence signal intensity (mean, SD, reflecting the amount of protein probe bound and taken up by the cell). The difference between the average intensity of cytoplasmic green fluorescence signal in different test wells and the positive control wells/the average intensity of fluorescence in the positive control wells multiplied by 100% (inhibition). As shown in FIG. 12, the 3F4 humanized antibody blocked the binding of RBD protein in the binding region of SARS-CoV-2 receptor to Ace2 receptor.

While specific embodiments of the invention have been described in detail, those skilled in the art will understand that: various modifications and changes in detail can be made in light of the overall teachings of the disclosure, and such changes are intended to be within the scope of the present invention. A full appreciation of the invention is gained by taking the entire specification as a whole in the light of the appended claims and any equivalents thereof.

SEQUENCE LISTING

<110> health preserving house Co., Ltd; xiamen university

<120> antibodies against SARS-CoV-2 and uses thereof

<130> IDC210054

<150> 202010365125.X

<151> 2020-04-30

<160> 29

<170> PatentIn version 3.5

<210> 1

<211> 121

<212> PRT

<213> artificial

<220>

<223> 3F4 VH

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Gln Ser Val Lys Glu Ser Gly Gly Arg Leu Val Thr Pro Gly Thr Pro

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Leu Thr Leu Thr Cys Thr Val Ser Gly Phe Ser Leu Ser Ser Tyr Trp

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Met Ser Trp Val Arg Gln Ala Pro Gly Lys Gly Leu Glu Trp Ile Gly

35 40 45

Ile Ile Phe Thr Gly Gly Ser Thr Tyr Tyr Ala Ser Trp Ala Lys Gly

50 55 60

Arg Phe Thr Ile Ser Lys Thr Ser Thr Thr Val Asp Leu Lys Ile Thr

65 70 75 80

Ser Pro Thr Thr Glu Asp Thr Ala Thr Tyr Phe Cys Ala Arg Thr Ser

85 90 95

Tyr Tyr Asp Val Ser Gly Trp Gly Val Gly Arg Leu Asp Leu Trp Gly

100 105 110

Gln Gly Thr Leu Val Thr Val Ser Ser

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Asp Pro Met Leu Thr Gln Thr Ala Ser Ser Val Ser Ala Ala Val Gly

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Gly Thr Val Thr Ile Ser Cys Gln Ser Ser Gln Ser Val Tyr Asp Asn

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Asn Trp Leu Gly Trp Tyr Gln Gln Lys Pro Gly Gln Pro Pro Lys Leu

35 40 45

Leu Ile Tyr Ser Ala Ser Thr Leu Ala Ser Gly Val Pro Ser Arg Phe

50 55 60

Lys Gly Ser Gly Ser Gly Thr Gln Phe Thr Leu Thr Ile Ser Asp Leu

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Glu Cys Asp Asp Ala Ala Thr Tyr Tyr Cys Ala Gly Gly Tyr Ser Gly

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Asn Ile Phe Ala Phe Gly Gly Gly Thr Glu Leu Glu Ile Leu

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Ser Tyr Trp Met Ser

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Ile Ile Phe Thr Gly Gly Ser Thr Tyr Tyr Ala Ser Trp Ala Lys Gly

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Thr Ser Tyr Tyr Asp Val Ser Gly Trp Gly Val Gly Arg Leu Asp Leu

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Gln Ser Ser Gln Ser Val Tyr Asp Asn Asn Trp Leu Gly

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Ser Ala Ser Thr Leu Ala Ser

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Ala Gly Gly Tyr Ser Gly Asn Ile Phe Ala

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Gly Phe Ser Leu Ser Ser Tyr Trp

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Ile Phe Thr Gly Gly Ser Thr

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Ala Arg Thr Ser Tyr Tyr Asp Val Ser Gly Trp Gly Val Gly Arg Leu

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Asp Leu

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Gln Ser Val Tyr Asp Asn Asn Trp

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Ser Ala Ser

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Ala Gly Gly Tyr Ser Gly Asn Ile Phe Ala

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Glu Val Gln Leu Val Glu Ser Gly Gly Gly Leu Val Gln Pro Gly Gly

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Ser Leu Arg Leu Ser Cys Ala Ala Ser Gly Phe Ser Leu Ser Ser Tyr

20 25 30

Trp Met Ser Trp Val Arg Gln Ala Pro Gly Lys Gly Leu Glu Trp Val

35 40 45

Ser Ile Ile Phe Thr Gly Gly Ser Thr Tyr Tyr Ala Ser Trp Ala Lys

50 55 60

Gly Arg Phe Thr Ile Ser Arg His Asn Ser Lys Asn Thr Leu Tyr Leu

65 70 75 80

Gln Met Asn Ser Leu Arg Ala Glu Asp Thr Ala Val Tyr Tyr Cys Ala

85 90 95

Arg Thr Ser Tyr Tyr Asp Val Ser Gly Trp Gly Val Gly Arg Leu Asp

100 105 110

Leu Trp Gly Gln Gly Thr Leu Val Thr Val Ser Ser

115 120

<210> 16

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<223> h3F4-2-VH

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Glu Val Gln Leu Val Glu Ser Gly Gly Gly Leu Val Gln Pro Gly Gly

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Ser Leu Arg Leu Ser Cys Ala Ala Ser Gly Phe Ser Leu Ser Ser Tyr

20 25 30

Trp Met Ser Trp Val Arg Gln Ala Pro Gly Lys Gly Leu Glu Trp Ile

35 40 45

Gly Ile Ile Phe Thr Gly Gly Ser Thr Tyr Tyr Ala Ser Trp Ala Lys

50 55 60

Gly Arg Phe Thr Ile Ser Arg His Asn Ser Lys Asn Thr Leu Tyr Leu

65 70 75 80

Gln Met Asn Ser Leu Arg Ala Glu Asp Thr Ala Val Tyr Tyr Cys Ala

85 90 95

Arg Thr Ser Tyr Tyr Asp Val Ser Gly Trp Gly Val Gly Arg Leu Asp

100 105 110

Leu Trp Gly Gln Gly Thr Leu Val Thr Val Ser Ser

115 120

<210> 17

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Glu Val Gln Leu Val Glu Ser Gly Gly Gly Leu Val Gln Pro Gly Gly

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Ser Leu Arg Leu Ser Cys Ala Ala Ser Gly Phe Ser Leu Ser Ser Tyr

20 25 30

Trp Met Ser Trp Val Arg Gln Ala Pro Gly Lys Gly Leu Glu Trp Val

35 40 45

Ser Ile Ile Phe Thr Gly Gly Ser Thr Tyr Tyr Ala Ser Trp Ala Lys

50 55 60

Gly Arg Phe Thr Ile Ser Arg His Asn Ser Lys Asn Thr Leu Tyr Leu

65 70 75 80

Gln Met Asn Ser Leu Arg Ala Glu Asp Thr Ala Thr Tyr Phe Cys Ala

85 90 95

Arg Thr Ser Tyr Tyr Asp Val Ser Gly Trp Gly Val Gly Arg Leu Asp

100 105 110

Leu Trp Gly Gln Gly Thr Leu Val Thr Val Ser Ser

115 120

<210> 18

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Glu Val Gln Leu Val Glu Ser Gly Gly Gly Leu Val Gln Pro Gly Gly

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Ser Leu Arg Leu Ser Cys Thr Val Ser Gly Phe Ser Leu Ser Ser Tyr

20 25 30

Trp Met Ser Trp Val Arg Gln Ala Pro Gly Lys Gly Leu Glu Trp Val

35 40 45

Ser Ile Ile Phe Thr Gly Gly Ser Thr Tyr Tyr Ala Ser Trp Ala Lys

50 55 60

Gly Arg Phe Thr Ile Ser Arg His Asn Ser Lys Asn Thr Leu Tyr Leu

65 70 75 80

Gln Met Asn Ser Leu Arg Ala Glu Asp Thr Ala Val Tyr Tyr Cys Ala

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Arg Thr Ser Tyr Tyr Asp Val Ser Gly Trp Gly Val Gly Arg Leu Asp

100 105 110

Leu Trp Gly Gln Gly Thr Leu Val Thr Val Ser Ser

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Asp Ile Gln Met Thr Gln Ser Pro Ser Thr Leu Ser Ala Ser Val Gly

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Asp Arg Val Thr Ile Thr Cys Gln Ser Ser Gln Ser Val Tyr Asp Asn

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Asn Trp Leu Gly Trp Tyr Gln Gln Lys Pro Gly Lys Ala Pro Lys Leu

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Leu Ile Tyr Ser Ala Ser Thr Leu Ala Ser Gly Val Pro Ser Arg Phe

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Ser Gly Ser Gly Ser Gly Thr Glu Phe Thr Leu Thr Ile Ser Ser Leu

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Gln Pro Asp Asp Phe Ala Thr Tyr Tyr Cys Ala Gly Gly Tyr Ser Gly

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Asn Ile Phe Ala Phe Gly Gln Gly Thr Lys Leu Glu Ile Leu

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Ala Ser Thr Lys Gly Pro Ser Val Phe Pro Leu Ala Pro Ser Ser Lys

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Ser Thr Ser Gly Gly Thr Ala Ala Leu Gly Cys Leu Val Lys Asp Tyr

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Phe Pro Glu Pro Val Thr Val Ser Trp Asn Ser Gly Ala Leu Thr Ser

35 40 45

Gly Val His Thr Phe Pro Ala Val Leu Gln Ser Ser Gly Leu Tyr Ser

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Leu Ser Ser Val Val Thr Val Pro Ser Ser Ser Leu Gly Thr Gln Thr

65 70 75 80

Tyr Ile Cys Asn Val Asn His Lys Pro Ser Asn Thr Lys Val Asp Lys

85 90 95

Lys Val Glu Pro Lys Ser Cys Asp Lys Thr His Thr Cys Pro Pro Cys

100 105 110

Pro Ala Pro Glu Leu Leu Gly Gly Pro Ser Val Phe Leu Phe Pro Pro

115 120 125

Lys Pro Lys Asp Thr Leu Met Ile Ser Arg Thr Pro Glu Val Thr Cys

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Val Val Val Asp Val Ser His Glu Asp Pro Glu Val Lys Phe Asn Trp

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Tyr Val Asp Gly Val Glu Val His Asn Ala Lys Thr Lys Pro Arg Glu

165 170 175

Glu Gln Tyr Asn Ser Thr Tyr Arg Val Val Ser Val Leu Thr Val Leu

180 185 190

His Gln Asp Trp Leu Asn Gly Lys Glu Tyr Lys Cys Lys Val Ser Asn

195 200 205

Lys Ala Leu Pro Ala Pro Ile Glu Lys Thr Ile Ser Lys Ala Lys Gly

210 215 220

Gln Pro Arg Glu Pro Gln Val Tyr Thr Leu Pro Pro Ser Arg Asp Glu

225 230 235 240

Leu Thr Lys Asn Gln Val Ser Leu Thr Cys Leu Val Lys Gly Phe Tyr

245 250 255

Pro Ser Asp Ile Ala Val Glu Trp Glu Ser Asn Gly Gln Pro Glu Asn

260 265 270

Asn Tyr Lys Thr Thr Pro Pro Val Leu Asp Ser Asp Gly Ser Phe Phe

275 280 285

Leu Tyr Ser Lys Leu Thr Val Asp Lys Ser Arg Trp Gln Gln Gly Asn

290 295 300

Val Phe Ser Cys Ser Val Met His Glu Ala Leu His Asn His Tyr Thr

305 310 315 320

Gln Lys Ser Leu Ser Leu Ser Pro Gly Lys

325 330

<210> 21

<211> 107

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<223> human kappa light chain constant region

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Arg Thr Val Ala Ala Pro Ser Val Phe Ile Phe Pro Pro Ser Asp Glu

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Gln Leu Lys Ser Gly Thr Ala Ser Val Val Cys Leu Leu Asn Asn Phe

20 25 30

Tyr Pro Arg Glu Ala Lys Val Gln Trp Lys Val Asp Asn Ala Leu Gln

35 40 45

Ser Gly Asn Ser Gln Glu Ser Val Thr Glu Gln Asp Ser Lys Asp Ser

50 55 60

Thr Tyr Ser Leu Ser Ser Thr Leu Thr Leu Ser Lys Ala Asp Tyr Glu

65 70 75 80

Lys His Lys Val Tyr Ala Cys Glu Val Thr His Gln Gly Leu Ser Ser

85 90 95

Pro Val Thr Lys Ser Phe Asn Arg Gly Glu Cys

100 105

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Gly Phe Ser Leu Ser Ser Tyr Trp Met Ser

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<223> Combined CDR-H2

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Ile Ile Phe Thr Gly Gly Ser Thr Tyr Tyr Ala Ser Trp Ala Lys Gly

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Ala Arg Thr Ser Tyr Tyr Asp Val Ser Gly Trp Gly Val Gly Arg Leu

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Asp Leu

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Gln Ser Ser Gln Ser Val Tyr Asp Asn Asn Trp Leu Gly

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Ser Ala Ser Thr Leu Ala Ser

1 5

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Ala Gly Gly Tyr Ser Gly Asn Ile Phe Ala

1 5 10

<210> 28

<211> 1047

<212> DNA

<213> artificial

<220>

<223> heavy chain expression plasmid pRVRCH

<400> 28

gccgccacca tggaatggag ctgggtcttt ctcttcttcc tgtcagtaac tacaggtgaa 60

ttctccactc ggggcaagga tcctaaggct ccatcagtct tcccactggc cccctgctgc 120

ggggacacac ccagctccac ggtgaccctg ggctgcctgg tcaaagggta cctcccggag 180

ccagtgaccg tgacctggaa ctcgggcacc ctcaccaatg gggtacgcac cttcccgtcc 240

gtccggcagt cctcaggcct ctactcgctg agcagcgtgg tgagcgtgac ctcaagcagc 300

cagcccgtca cctgcaacgt ggcccaccca gccaccaaca ccaaagtgga caagaccgtt 360

gcgccctcga catgcagcaa gcccacgtgc ccaccccctg aactcctggg gggaccgtct 420

gtcttcatct tccccccaaa acccaaggac accctcatga tctcacgcac ccccgaggtc 480

acatgcgtgg tggtggacgt gagccaggat gaccccgagg tgcagttcac atggtacata 540

aacaacgagc aggtgcgcac cgcccggccg ccgctacggg agcagcagtt caacagcacg 600

atccgcgtgg tcagcaccct ccccatcgcg caccaggact ggctgagggg caaggagttc 660

aagtgcaaag tccacaacaa ggcactcccg gcccccatcg agaaaaccat ctccaaagcc 720

agagggcagc ccctggagcc gaaggtctac accatgggcc ctccccggga ggagctgagc 780

agcaggtcgg tcagcctgac ctgcatgatc aacggcttct acccttccga catctcggtg 840

gagtgggaga agaacgggaa ggcagaggac aactacaaga ccacgccggc cgtgctggac 900

agcgacggct cctacttcct ctacagcaag ctctcagtgc ccacgagtga gtggcagcgg 960

ggcgacgtct tcacctgctc cgtgatgcac gaggccttgc acaaccacta cacgcagaag 1020

tccatctccc gctctccggg taaatga 1047

<210> 29

<211> 403

<212> DNA

<213> artificial

<220>

<223> light chain expression plasmid pRVRCL

<400> 29

gccgccacca tgagtgtgcc cactcaggtc ctggggttgc tgctgctgtg gcttacagat 60

gccagatgct agcttcctgt cagggtgatg tcgaccagtt gcacctactg tcctcatctt 120

cccaccagct gctgatcagg tggcaactgg aacagtcacc atcgtgtgtg tggcgaataa 180

atactttccc gatgtcaccg tcacctggga ggtggatggc accacccaaa caactggcat 240

cgagaacagt aaaacaccgc agaattctgc agattgtacc tacaacctca gcagcactct 300

gacactgacc agcacacagt acaacagcca caaagagtac acgtgcaagg tgacccaggg 360

cacgacctca gtcgtccaga gcttcaatag gggtgactgt tag 403

Claims

1. An antibody or antigen-binding fragment thereof that specifically binds to the receptor-binding Region (RBD) of the S protein of SARS-CoV-2, the antibody or antigen-binding fragment thereof comprising:

(a) a heavy chain variable region (VH) comprising the following 3 Complementarity Determining Regions (CDRs):

and/or the presence of a gas in the gas,

(b) a light chain variable region (VL) comprising the following 3 Complementarity Determining Regions (CDRs):

(vi) a VL CDR3, consisting of the sequence: 8, or a sequence having substitution, deletion or addition of one or several amino acids (e.g., substitution, deletion or addition of 1, 2 or 3 amino acids) thereto;

preferably, the CDRs in any of (i) - (vi) are defined according to the Kabat numbering system;

preferably, the substitution recited in any one of (i) - (vi) is a conservative substitution.

2. The antibody or antigen-binding fragment thereof of claim 1, comprising:

(a) the following 3 heavy chain CDRs: the sequence is SEQ ID NO:3, VH CDR1 of SEQ ID NO:4, the sequence of VH CDR2 of SEQ ID NO:5 VH CDR 3; and/or, the following 3 light chain CDRs: the sequence is SEQ ID NO:6, the sequence is SEQ ID NO:7, VL CDR2 of SEQ ID NO:8 VL CDR 3;

or the like, or, alternatively,

(b) 3 CDRs contained in the heavy chain variable region (VH) shown in SEQ ID NO: 1; and/or, 3 CDRs contained in the light chain variable region (VL) as set forth in SEQ ID NO: 2; preferably, the 3 CDRs contained in the VH and/or the 3 CDRs contained in the VL are defined by the Kabat, IMGT or Chothia numbering system.

3. The antibody or antigen-binding fragment thereof of claim 1 or 2, comprising:

(i) SEQ ID NO: 1;

and

(iv) SEQ ID NO: 2;

(vi) And SEQ ID NO:2, 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%, or 100% sequence identity;

preferably the substitutions described in (ii) or (v) are conservative substitutions;

preferably, the antibody or antigen-binding fragment thereof comprises: a VH comprising the sequence shown as SEQ ID NO. 1 and a VL comprising the sequence shown as SEQ ID NO. 2.

4. The antibody or antigen-binding fragment thereof of any one of claims 1-3, which is humanized;

preferably, the antibody or antigen-binding fragment thereof comprises a framework region sequence derived from a human immunoglobulin;

preferably, the antibody or antigen-binding fragment thereof comprises: a heavy chain framework region sequence derived from a human heavy chain germline sequence, and a light chain framework region sequence derived from a human light chain germline sequence.

5. The antibody or antigen-binding fragment thereof of claim 4, wherein,

the VH of the antibody or antigen-binding fragment thereof comprises: heavy chain framework regions FR1, FR2 and FR3 derived from heavy chain germline sequence IGHV3-53 × 04, and heavy chain framework region FR4 derived from heavy chain germline sequence IGHJ1 × 01; and the combination of (a) and (b),

the VL of the antibody or antigen-binding fragment thereof comprises: light chain framework regions FR1, FR2 and FR3 derived from light chain germline sequence IGKV1-5 × 01, and light chain framework region FR4 derived from light chain germline sequence IGKJ2 × 02.

6. The antibody or antigen-binding fragment thereof of claim 4 or 5, comprising:

(i) SEQ ID NOs: 15-18;

and

(iv) SEQ ID NO: 19;

(vi) And SEQ ID NO:19, 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%, or 100% sequence identity;

preferably, the antibody or antigen-binding fragment thereof comprises:

7. The antibody or antigen-binding fragment thereof of any one of claims 1-6, further comprising a constant region derived from a human immunoglobulin;

preferably, the heavy chain of the antibody or antigen-binding fragment thereof comprises a heavy chain constant region derived from a human immunoglobulin (e.g., IgG1, IgG2, IgG3, or IgG4), and the light chain of the antibody or antigen-binding fragment thereof comprises a light chain constant region derived from a human immunoglobulin (e.g., κ or λ);

preferably, the antibody or antigen-binding fragment thereof comprises:

(a) a heavy chain constant region (CH) of a human immunoglobulin or a variant thereof having one or more amino acid substitutions, deletions or additions or any combination thereof (e.g., substitutions, deletions or additions of up to 20, up to 15, up to 10, or up to 5 amino acids or any combination thereof; e.g., substitutions, deletions or additions of 1, 2, 3, 4, or 5 amino acids or any combination thereof) as compared to the wild type sequence from which it is derived; and/or

(b) A light chain constant region (CL) of a human immunoglobulin or a variant thereof having one or more amino acid substitutions, deletions or additions or any combination thereof (e.g., substitutions, deletions or additions of up to 20, up to 15, up to 10, or up to 5 amino acids or any combination thereof; e.g., substitutions, deletions or additions of 1, 2, 3, 4, or 5 amino acids or any combination thereof) compared to the wild type sequence from which it is derived;

preferably, the heavy chain constant region is an IgG heavy chain constant region, e.g., an IgG1, IgG2, IgG3, or IgG4 heavy chain constant region;

preferably, the antibody or antigen-binding fragment thereof comprises a heavy chain constant region (CH) as set forth in SEQ ID NO: 20;

preferably, the light chain constant region is a kappa light chain constant region;

preferably, the antibody or antigen-binding fragment thereof comprises a light chain constant region (CL) as set forth in SEQ ID NO: 21.

8. The antibody or antigen-binding fragment thereof of any one of claims 1-7, wherein the antigen-binding fragment is selected from the group consisting of Fab, Fab ', (Fab')₂Fv, disulfide-linked Fv, scFv, diabody (diabody) and monoDomain antibodies (sdabs); and/or, the antibody is a rabbit derived antibody, a chimeric antibody, a humanized antibody, a bispecific antibody, or a multispecific antibody.

9. The antibody or antigen-binding fragment thereof of any one of claims 1-8, wherein the antibody or antigen-binding fragment thereof has one or more of the following characteristics:

(a) RBD that specifically binds the S protein of SARS-CoV-2;

(b) blocking or inhibiting binding of SARS-CoV-2 to Ace2 receptor, and/or blocking or inhibiting infection of cells by SARS-CoV-2;

(c) does not affect or does not substantially affect the binding of SARS-CoV-1 to the Ace2 receptor;

(d) neutralizing SARS-CoV-2 in vitro or in a subject (e.g., human);

(e) preventing and/or treating SARS-CoV-2 infection or a disease associated with SARS-CoV-2 infection (e.g., COVID-19).

10. An isolated nucleic acid molecule encoding the antibody or antigen-binding fragment thereof of any one of claims 1-9, or a heavy chain variable region and/or a light chain variable region thereof.

11. A vector comprising the nucleic acid molecule of claim 10; preferably, the vector is a cloning vector or an expression vector.

12. A host cell comprising the nucleic acid molecule of claim 10 or the vector of claim 11.

13. A method of making the antibody or antigen-binding fragment thereof of any one of claims 1-9, comprising culturing the host cell of claim 12 under conditions that allow expression of the antibody or antigen-binding fragment thereof, and recovering the antibody or antigen-binding fragment thereof from the cultured host cell culture.

14. A pharmaceutical composition comprising the antibody or antigen-binding fragment thereof of any one of claims 1-9, and a pharmaceutically acceptable carrier and/or excipient;

preferably, the pharmaceutical composition further comprises an additional pharmaceutically active agent, such as an additional antiviral agent (e.g., interferon, lopinavir, ritonavir, chloroquine phosphate, fabiravir, ridciclovir, and the like).

15. A method for neutralizing the virulence of SARS-CoV-2 in a sample comprising contacting a sample comprising SARS-CoV-2 with an antibody or antigen-binding fragment thereof according to any of claims 1-9.

16. Use of the antibody or antigen-binding fragment thereof of any one of claims 1-9 for the preparation of a medicament for neutralizing the virulence of SARS-CoV-2 in a sample, or for preventing and/or treating a SARS-CoV-2 infection or a disease associated with a SARS-CoV-2 infection in a subject (e.g. codv-19);

preferably, the subject is a mammal, e.g., a human;

preferably, the antibodies or antigen-binding fragments thereof are used alone or in combination with additional pharmaceutically active agents (e.g., additional antiviral agents such as interferon, lopinavir, ritonavir, chloroquine phosphate, fabiravir, ridciclovir, and the like).

17. A method for preventing and/or treating SARS-CoV-2 infection or a disease associated with SARS-CoV-2 infection (e.g., COVID-19) in a subject (e.g., a human), comprising: administering to a subject in need thereof an effective amount of the monoclonal antibody or antigen-binding fragment thereof of any one of claims 1-9 or the pharmaceutical composition of claim 14.

18. A conjugate comprising the antibody or antigen-binding fragment thereof of any one of claims 1-9, and a detectable label linked to the antibody or antigen-binding fragment thereof;

preferably, the detectable label is selected from the group consisting of enzymes (e.g., horseradish peroxidase or alkaline phosphatase), chemiluminescent reagents (e.g., acridinium esters, luminol and its derivatives, or ruthenium derivatives), fluorescent dyes (e.g., fluorescein or fluorescent protein), radionuclides, or biotin.

19. A kit comprising the antibody or antigen-binding fragment thereof of any one of claims 1-9 or the conjugate of claim 18;

preferably, the kit comprises the conjugate of claim 18;

preferably, the kit comprises the antibody or antigen-binding fragment thereof of any one of claims 1-9, and a second antibody that specifically recognizes the antibody or antigen-binding fragment thereof; optionally, the second antibody further comprises a detectable label, such as an enzyme (e.g., horseradish peroxidase or alkaline phosphatase), a chemiluminescent reagent (e.g., acridinium esters, luminol and its derivatives, or ruthenium derivatives), a fluorescent dye (e.g., fluorescein or fluorescent protein), a radionuclide or biotin.

20. A method for detecting the presence or level of SARS-CoV-2 in a sample comprising using the antibody or antigen-binding fragment thereof of any one of claims 1-9 or the conjugate of claim 18;

preferably, the method is an immunological detection, such as an enzyme immunoassay (e.g. ELISA), a chemiluminescent immunoassay, a fluorescent immunoassay or a radioimmunoassay;

preferably, the method comprises using the conjugate of claim 18;

preferably, the method comprises the use of the antibody or antigen-binding fragment thereof of any one of claims 1-9, and the method further comprises the use of a second antibody carrying a detectable label (e.g., an enzyme (e.g., horseradish peroxidase or alkaline phosphatase), a chemiluminescent reagent (e.g., an acridinium ester compound, luminol and derivatives thereof, or ruthenium derivatives), a fluorescent dye (e.g., fluorescein or fluorescent protein), a radionuclide or biotin) to detect the antibody or antigen-binding fragment thereof.

21. Use of the antibody or antigen-binding fragment thereof of any one of claims 1-9 in the preparation of a kit for detecting the presence or level of SARS-CoV-2 in a sample, and/or for diagnosing whether a subject is infected with SARS-CoV-2;

preferably, the kit detects the presence or level of SARS-CoV-2 in a sample by the method of claim 20;

preferably, the sample is a blood sample (e.g., whole blood, plasma or serum), fecal matter, oral or nasal secretions, or alveolar lavage fluid from a subject (e.g., a mammal, preferably a human).