WO2022263451A1

WO2022263451A1 - Peptides derived from the spike protein of sars-cov-2 and uses thereof for diagnosis and vaccine purposes

Info

Publication number: WO2022263451A1
Application number: PCT/EP2022/066184
Authority: WO
Inventors: Philippe Despres; Gilles Gadea; Wildriss VIRANAICKEN; Jessica ANDRIES; Anne-Laure MOREL; Maroua BEN HADDADA
Original assignee: INSERM (Institut National de la Santé et de la Recherche Médicale); Centre National De La Recherche Scientifique (Cnrs); Institut De Recherche Pour Le Développement (Ird); Universite De La Reunion; Torskal
Priority date: 2021-06-15
Filing date: 2022-06-14
Publication date: 2022-12-22

Abstract

Emerging highly pathogenic SARS-CoV-2 has caused the recent worldwide pandemic named COVID-19. Considerable efforts have been made for the development of effective vaccine strategies against COVID-19. Giving that the spike S protein plays a crucial role in eliciting the immune response during COVID-19 disease, the S protein has been the predominant candidate for the design of efficient vaccine candidates against SARS-CoV-2. The purpose of the inventors was to evaluate the antigenic reactivity of different synthetic peptides representing potential B-cell epitopes located in the S protein in relation to a BNT162b2 recipient serum. They identified the residues S_616-644 and S_1138-1169 as two potential B-cell epitopes in the S protein. Whereas BNT162b2 recipient serum as well as COVID19 donor serum were capable of reacting with a synthetic peptide representing the residues S_1138-1169, a synthetic peptide representing the residues S_616-644 showed immunoreactivity only with a BNT162b2 recipient serum. In conclusion, the inventors showed that immunization with encapsulated mRNA vaccine BNT162b2 expressing a stabilized prefusion SARS-CoV-2 protein results in production of antibodies directed against the two B-cell epitopes that compose the residues S_616-644 and S_1138-1169. The synthetic peptides representing the residues S_616-644 and S_1138-1169 have ability to react as antibody epitopes in relation to a BNT162b2 recipient serum and thus can be used for diagnostic and vaccine purposes.

Description

PEPTIDES DERIVED FROM THE SPIKE PROTEIN OF SARS-COV-2 AND USES THEREOF FOR DIAGNOSIS AND VACCINE PURPOSES

FIELD OF THE INVENTION:

The present invention is in the field of medicine, in particular virology.

BACKGROUND OF THE INVENTION:

COVID-19 disease associated to emerging betacoronavirus SARS-CoV-2 infection is a pandemic public health threat since early 2020 with millions of deaths to date (Gralinski et al., Viruses 12, 135, 2020). The main route for SARS-CoV-2 transmission is through respiratory droplets necessitating the implementation of effective control measures. Convalescent COVID- 19 patients developed neutralizing anti-SARS-CoV-2 antibodies produced by the adaptive immune response. Antibody-mediated virus neutralization plays a critical role in controlling SARS-CoV-2 infection. Given that the structural spike S protein plays a crucial role in eliciting the immune response during COVID-19 disease, the S has been considered as predominant viral antigen target for the design of efficient SARS-CoV-2 vaccine candidates (Ni et ah. Immunity 53, 971-977. e3, 2020; Wang et ah. Cell 181, 894-904). The transmembrane S-protein spike homo-trimer at the virus surface mediates receptor binding through interaction with cell entry receptor ACE2. The trimeric S protein contains the SI and S2 subunits. The N-terminal SI subunit comprises the Receptor Binding Domain (RBD) that is able to bind ACE2 and anti- RBD antibodies exert potent neutralizing activity against SARS-CoV-2 (Suthar et ah. Cell Rep Med 1, 100040, 2020; Quinlan et al BioRxiv). The C-terminal S2 subunit containing the fusion elements is responsible for viral membrane fusion with the host-cell membranes (Lan et al.. Nature 581, 215-220; Walls et al.. Cell 180, 281-92, 2020). A furin-like cleavage site has been identified at the S1/S2 junction playing a major role in pathogenesis of SARS-CoV-2 infection (Johnson et al.. Nature 591, 293-99, 2021). The virus binding to ACE2 receptor via the RBD elicits the proteolytic cleavage of pre-protein S into SI and S2 subunits by cellular proteases. A such processing results in large conformation changes causing SI shedding and exposure of the fusion elements in S2 which trigger fusion process between viral and host-cell membranes (Kirchdoerfer et al. Nature 531, 118-21, 2016; Henderson et al.. Nat Struct Mol Biol 27, 925- 33, 2020; Hoffmann et al., Cell 181, 271-80, 2020; Wrapp et al., Science 367, 1260-3, 2020). Accelerated vaccine programs for prevention of COVID-19 have been put leading to the development of commercially available vaccines based on lipid nanoparticles formulated, nucleoside modified mRNA. For instance, immunization of individuals with commercially available Comirnaty vaccine (initially called BNT162b2) which is based on a mRNA encoding a stabilized prefusion SARS-CoV-2 S protein provides protection against COVID-19 reaching up to 95% (Polack et al.. N Engl JMed 383: 2603-15, 2020; Skowronski and De Serres, N Engl J Med 384: 1576-78, 2021). Immunization with BNT162b2 vaccine elicits high neutralizing anti-SARS-CoV-2 antibody titers after two doses spaced one month (Mulligan et al.. Nature , 586, 589-93, 2020).

SUMMARY OF THE INVENTION:

The present invention is defined by the claims. In particular, the present invention relates to peptides derived from the spike protein of SARS-CoV-2 and uses thereof for diagnosis and vaccine purposes.

DETAILED DESCRIPTION OF THE INVENTION:

Emerging highly pathogenic SARS-CoV-2 has caused the recent worldwide pandemic named COVID-19. Considerable efforts have been made for the development of effective vaccine strategies against COVID-19. Giving that the spike S protein plays a crucial role in eliciting the immune response during COVID-19 disease, the S protein has been the predominant candidate for the design of efficient vaccine candidates against SARS-CoV-2. The commercially available BNT162b2 vaccine (Pfizer) is a lipid nanoparticle-encapsulated mRNA vaccine encoding a stabilized prefusion SARS-CoV-2 spike S protein. Immunization with BNT162b2 vaccine elicits high titers of neutralizing anti-SARS-CoV-2 antibodies. The purpose of the inventors was to evaluate the antigenic reactivity of different synthetic peptides representing potential B-cell epitopes located in the S protein in relation to a BNT162b2 recipient serum. They identified the residues S616-644 and S1138-1169 as two potential B-cell epitopes in the S protein. Whereas BNT162b2 recipient serum as well as COVID19 donor serum were capable of reacting with a synthetic peptide representing the residues Si 138-1169, a synthetic peptide representing the residues S616-644 showed immunoreactivity only with a BNT162b2 recipient serum. In conclusion, the inventors showed that immunization with encapsulated mRNA vaccine BNT162b2 expressing a stabilized prefusion SARS-CoV-2 protein results in production of antibodies directed against the two B-cell epitopes that compose the residues S6_I6- 644 and Sii38-ii69. The synthetic peptides representing the residues S6I6-644 and S1138-1169 have ability to react as antibody epitopes in relation to a BNT162b2 recipient serum. Main definitions:

As used herein, the terms “polypeptide”, “peptide”, and “protein” are used interchangeably herein to refer to polymers of amino acids of any length. The terms also encompass an amino acid polymer that has been modified; for example, disulfide bond formation, glycosylation, lipidation, phosphorylation, or conjugation with a labeling component. Polypeptides when discussed in the context of gene therapy refer to the respective intact polypeptide, or any fragment or genetically engineered derivative thereof, which retains the desired biochemical function of the intact protein.

As used herein, the expression “derived from” refers to a process whereby a first component (e.g., a first polypeptide), or information from that first component, is used to isolate, derive or make a different second component (e.g., a second polypeptide that is different from the first one).

As used herein, the term “coronavirus” has its general meaning in the art and refers to any member of members of the Coronaviridae family. Coronavirus is a virus whose genome is plus- stranded RNA of about 27 kb to about 33 kb in length depending on the particular virus. The virion RNA has a cap at the 5’ end and a poly A tail at the 3’ end. The length of the RNA makes coronaviruses the largest of the RNA virus genomes. In particular, coronavirus RNAs encode: (1) an RNA-dependent RNA polymerase; (2) N-protein; (3) three envelope glycoproteins; plus (4) three non-structural proteins. These coronaviruses infect a variety of mammals and birds. They cause respiratory infections (common), enteric infections (mostly in infants >12 mo.), and possibly neurological syndromes. Coronaviruses are transmitted by aerosols of respiratory secretions.

As used herein, the term “Betacoronavirus”, also known as b-CoVs or Beta-CoVs has its general meaning in the art and refers to one of four genera (Alpha-, Beta-, Gamma-, and Delta-) of coronaviruses. The betacoronavirus genus comprises four lineages: A, B, C, D.

As used herein, the term “Sarbecovirus” has its general meaning in the art and refers to the lineage B of Betacoronavirus. The Sarbecoviruses of the greatest clinical importance concerning humans are Severe acute respiratory syndrome coronavirus (SARS-CoV or SARS- CoV-1) and Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The subgenus also includes but is not limited to Bat SC2r-CoV RaTG13, Bat SC2r-CoV RacCS203, Pangolin SC2r-CoV GX-P4L, Pangolin SC2r-CoV GX-P5L, Bat SC2r-CoV ZC45, Bat SC2r-CoV ZXC21, Bat SC2r-CoV Rc-o319, Bat SClr-CoV WIV1, Bat CoV WIV16, Bat CoV Rs3367, Bat CoV LYRall, Bat SClr-CoV Cp/Yunnan2011, Bat CoV Rs-YN2018B, Bat CoV Rs7327, Bat CoV RsSHCOK Bat CoV Rs4231, Bat CoV Rs4084, Bat CoV Rs4081, Bat CoV Rs672, Bat CoV Rs4237, Bat SClr-CoV YNLF 31C, Bat SClr-CoV Rp3, BtRl-BetaCoV/SC2018, Bat SClr-CoV Rfl, Bat SClr-CoV HeB2013, Bat SClr-CoV Rp/Shaanxi2011, Bat SClr-CoV Rml, Bat SClr-CoV HuB2013, Bat SClr-CoV HKU3-1, Bat SClr-CoV Longquan-140, Bat SClr-CoV BM48-3 l/BGR/2008, and Bat SClr-CoV BtKY72.

As used herein, the term “Severe Acute Respiratory Syndrome coronavirus 2” or “SARS- CoV-2” has its general meaning in the art and refers to the strain of coronavirus that causes coronavirus disease 2019 (COVID-19), a respiratory syndrome that manifests a clinical pathology resembling mild upper respiratory tract disease (common cold-like symptoms) and occasionally severe lower respiratory tract illness and extra-pulmonary manifestations leading to multi-organ failure and death. In particular, the term refers to the severe acute respiratory syndrome coronavirus 2 isolate 2019-nCoV_HKU-SZ-005b_2020 for which the complete genome is accessible under the NCBI access number MN975262.

As used herein, the term "subject" or "subject in need thereof", is intended for a human or non-human mammal. Typically the patient is affected or likely to be infected with a betacoronavirus, more particularly a sarbecovirus, even more particularly with SARS-Cov-2.

As used herein, the term “Covid-19” refers to the respiratory disease induced by the Severe Acute Respiratory Syndrome coronavirus 2.

As used herein, the term "asymptomatic" refers to a subject who experiences no detectable symptoms for the coronavirus infection. As used herein, the term "symptomatic" refers to a subject who experiences detectable symptoms of coronavirus infection. Symptoms of coronavirus infection include: fatigue, anosmia, headache, cough, fever, difficulty to breathe.

As used herein, the term “spike protein” or “protein S” refers to the SARS-Cov-2 spike glycoprotein that binds its cellular receptor (i.e. ACE2), and mediates membrane fusion and virus entry. Each monomer of trimeric S protein is about 180 kDa, and contains two subunits, SI and S2, mediating attachment and membrane fusion, respectively. In particular, Spike protein SI attaches the virion to the cell membrane by interacting with host receptor (i.e. human ACE2 receptor). Spike protein S2 mediates fusion of the virion and cellular membranes by acting as a class I viral fusion protein. Under the current model, the protein has at least three conformational states: pre-fusion native state, pre-hairpin intermediate state, and post-fusion hairpin state. During viral and target cell membrane fusion, the coiled coil regions (heptad repeats) assume a trimer-of-hairpins structure, positioning the fusion peptide in close proximity to the C-terminal region of the ectodomain. The formation of this structure appears to drive apposition and subsequent fusion of viral and target cell membranes. Spike protein S2' acts as a viral fusion peptide which is unmasked following S2 cleavage occurring upon virus endocytosis. Typically, the nucleoprotein has the amino acid sequence as set forth in SEQ ID NO:l

SEQ ID NO:1 >sp|P0DTC2|SPIKE_SARS2 Spike glycoprotein OS=Severe acute respiratory syndrome coronavirus 2 OX=2697049 GN=S PE=1 SV=1 The S4 peptide is indicated in bold and underlined and the S6 peptide is indicated in bold and double underlined.

MFVFLVLLPLVSSQCVNLTTRTQLPPAYTNSFTRGVYYPDKVFRSSVLHSTQDLFLPFFSNVTWFHAIH VSGTNGTKRFDNPVLPFNDGVYFASTEKSNIIRGWIFGTTLDSKTQSLLIVNNATNW IKVCEFQFCND PFLGVYYHKNNKSWMESEFRVYSSANNCTFEYVSQPFLMDLEGKQGNFKNLREFVFKNIDGYFKIYSKH TPINLVRDLPQGFSALEPLVDLPIGINITRFQTLLALHRSYLTPGDSSSGWTAGAAAYYVGYLQPRTFL

LKYNENGTITDAVDCALDPLSETKCTLKSFTVEKGIYQTSNFRVQPTESIVRFPNITNLCPFGEVFNAT RFASVYAWNRKRISNCVADYSVLYNSASFSTFKCYGVSPTKLNDLCFTNVYADSFVIRGDEVRQIAPGQ TGKIADYNYKLPDDFTGCVIAWNSNNLDSKVGGNYNYLYRLFRKSNLKPFERDISTEIYQAGSTPCNGV EGFNCYFPLQSYGFQPTNGVGYQPYRVW LSFELLHAPATVCGPKKSTNLVKNKCVNFNFNGLTGTGVL TESNKKFLPFQQFGRDIADTTDAVRDPQTLEILDITPCSFGGVSVITPGTNTSNQVAVLYQDV CTEVP

VAIHADQLTPTWRVYSTGSVFQTRAGCLIGAEHVNNSYECDIPIGAGICASYQTQTNSPRRARSVASQ SIIAYTMSLGAENSVAYSNNSIAIPTNFTISVTTEILPVSMTKTSVDCTMYICGDSTECSNLLLQYGSF CTQLNRALTGIAVEQDKNTQEVFAQVKQIYKTPPIKDFGGFNFSQILPDPSKPSKRSFIEDLLFNKVTL ADAGFIKQYGDCLGDIAARDLICAQKFNGLTVLPPLLTDEMIAQYTSALLAGTITSGWTFGAGAALQIP FAMQMAYRFNGIGVTQNVLYENQKLIANQFNSAIGKIQDSLSSTASALGKLQDWNQNAQALNTLVKQL

SSNFGAISSVLNDILSRLDKVEAEVQIDRLITGRLQSLQTYVTQQLIRAAEIRASANLAATKMSECVLG QSKRVDFCGKGYHLMSFPQSAPHGW FLHVTYVPAQEKNFTTAPAICHDGKAHFPREGVFVSNGTHWFV TORNFYEPOIITTDNTFVSGNCDW IGIVNNTVYDPLOPELDSFKEELDKYFKNHTSPDVDLGDISGIN ASWNIQKEIDRLNEVAKNLNESLIDLQELGKYEQYIKWPWYIWLGFIAGLIAIVMVTIMLCCMTSCCS CLKGCCSCGSCCKFDEDDSEPVLKGVKLHYT

As used herein, the term “conjugate” refers to a compound having a first molecule (for example, a SARS-Cov-2 peptide) effectively coupled to a second molecule (for example, a gold nanoparticle), either directly or indirectly, by any suitable means. As used herein, the term “conjugating” refers to the coupling a first molecule to a second molecule. This includes, but is not limited to, covalently bonding one molecule to another molecule (for example, directly or via a linker molecule), noncovalently bonding one molecule to another (e.g. electrostatically bonding), non-covalently bonding one molecule to another molecule by hydrogen bonding, non-covalently bonding one molecule to another molecule by van der Waals forces, and any and all combinations of such couplings. As used herein, the term “fusion protein" comprises at least one polypeptide of the present invention operably linked to a heterologous polypeptide. Within the fusion protein, the term "operably linked" is intended to indicate that the peptide of the present invention and the heterologous polypeptide are fused in-frame to each other.

As used herein, the term "heterologous polypeptide" refers to a polypeptide which does not derive from the same protein to which said heterologous polypeptide is fused.

As used herein, the term "linker" refers to a sequence of at least one amino acid that links the peptide of the present invention with the heterologous polypeptide. Linkers are well known to one of ordinary skill in the art and typically comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acids.

As used herein, the term “epitope” has its general meaning in the art and a fragment of at least 8 amino acids that is recognized by an immune response component. As used herein, the term “immune response component” include, but is not limited to, at least a part of a macrophage, a lymphocyte, a T-lymphocyte, a killer T-lymphocyte, an immune response modulator, a helper T-lymphocyte, an antigen receptor, an antigen presenting cell, a cytotoxic T-lymphocyte, a T- 8 lymphocyte, a CD1 molecule, a B lymphocyte, an antibody, a recombinant antibody, a genetically engineered antibody, a chimeric antibody, a monospecific antibody, a bispecific antibody, a multispecific antibody, a diabody, a chimeric antibody, a humanized antibody, a human antibody, a heteroantibody, a monoclonal antibody, a polyclonal antibody, an antibody fragment, and/or synthetic antibody. The term “epitope” may be used interchangeably with antigen, paratope binding site, antigenic determinant, and/or determinant.

As used herein, the term “antibody epitope” refers to peptide, which can be recognized by a specific antibody, or which induces the formation of specific antibodies.

As used herein, the term “sample" as used herein refer to a biological sample obtained for the purpose of in vitro evaluation. Typical biological samples to be used in the method according to the invention are blood samples (e.g. whole blood sample or serum sample). In some embodiments, said biological liquids comprise blood, plasma, serum, saliva and exsudates. Thus, in some embodiments, the sample is chosen from blood samples, plasma samples, saliva samples, exsudate samples and serum samples. Preferably, the sample is a blood sample, a serum sample or a plasma sample.

As used herein, the term “antibody”, "immunoglobulin" or “Ig” has its general meaning in the art and relates to proteins of the immunoglobulin superfamily. The immunoglobulins are characterized by a structural domain, i.e., the immunoglobulin domain, having a characteristic immunoglobulin (Ig) fold. The term encompasses secretory immunoglobulins. Immunoglobulins generally comprise several chains, typically two identical heavy chains and two identical light chains which are linked via disulfide bonds. These chains are primarily composed of immunoglobulin domains, including the VL domain (light chain variable domain), the CL domain (light chain constant domain), the VH domain (heavy chain variable domain) and the CH domains (heavy chain constant domains) CHI, optionally a hinge region, CH2, CH3, and optionally CH4. There are five main heavy chain classes (or isotypes) which determine the functional activity of an antibody molecule: mu (m) for IgM, delta (d) for IgD, gamma (g) for IgG, alpha (a) for IgA and epsilon (e) for IgE. In the context of the invention, the immunoglobulin may be an IgM, IgD, IgG, IgA or IgE. Preferably, the immunoglobulin is an IgG. As well-known from the skilled person, the IgG isotype encompasses four subclasses: the subclasses lgGl, lgG2, lgG3 and lgG4. The IgA isotype encompasses 2 subclasses: IgAl and IgA2 immunoglobulins.

As used herein the term “immunocomplex” refers to the complex formed between the coronavirus-specific antibodies of the subject and their specific antigen, i.e. the coronaviral peptide that is conjugated to the gold nanoparticle.

As used herein, the term “detect” means determine if an agent (e.g. an anti-SARS-Cov-2 antibody) is present or absent, for example, in a sample. The term can further include quantification. Thus “detecting” refers to any method of determining if something exists, or does not exist, such as determining if a molecule is present in a sample. For example, “detecting” can include using a visual or a mechanical device to determine if a sample displays a specific characteristic. In some examples, detection refers to visually observing an antibody bound to a target molecule, or observing that an antibody does not bind to a target molecule.

As used herein, the term "treatment" or "treat" refer to both prophylactic or preventive treatment as well as curative or disease modifying treatment, including treatment of patient at risk of contracting the disease or suspected to have contracted the disease as well as patients who are ill or have been diagnosed as suffering from a disease or medical condition, and includes suppression of clinical relapse. The treatment may be administered to a patient having a medical disorder or who ultimately may acquire the disorder, in order to prevent, cure, delay the onset of, reduce the severity of, or ameliorate one or more symptoms of a disorder or recurring disorder, or in order to prolong the survival of a patient beyond that expected in the absence of such treatment. By "therapeutic regimen" is meant the pattern of treatment of an illness, e.g., the pattern of dosing used during therapy. A therapeutic regimen may include an induction regimen and a maintenance regimen. The phrase "induction regimen" or "induction period" refers to a therapeutic regimen (or the portion of a therapeutic regimen) that is used for the initial treatment of a disease. The general goal of an induction regimen is to provide a high level of drug to a patient during the initial period of a treatment regimen. An induction regimen may employ (in part or in whole) a "loading regimen", which may include administering a greater dose of the drug than a physician would employ during a maintenance regimen, administering a drug more frequently than a physician would administer the drug during a maintenance regimen, or both. The phrase "maintenance regimen" or "maintenance period" refers to a therapeutic regimen (or the portion of a therapeutic regimen) that is used for the maintenance of a patient during treatment of an illness, e.g., to keep the patient in remission for long periods of time (months or years). A maintenance regimen may employ continuous therapy (e.g., administering a drug at a regular interval, e.g., weekly, monthly, yearly, etc.) or intermittent therapy (e.g., interrupted treatment, intermittent treatment, treatment at relapse, or treatment upon achievement of a particular predetermined criteria [e.g., pain, disease manifestation, etc.]).

As used herein, the term “nanoparticle” refers to a particle with a size that is measured in nanometers, for example, a nanoscopic particle that has at least one dimension of less than about 200 nm. Nanoparticles can include a core or a core and a shell, as in core-shell nanoparticles.

As used herein, the term “gold nanoparticle” refers to particles wherein the core is made of gold atoms.

As used herein, the term "aggregation" refers to the association of nanoparticles. "Inter-particle crosslinking aggregation" refers to the aggregation caused by the inter-particle bridging by crosslinkers whereas "noncrosslinking aggregation" refers to the aggregation process induced by the loss (or screen) of surface charges.

As used herein, the term “pharmaceutical composition” refers to a composition described herein, or pharmaceutically acceptable salts thereof, with other agents such as carriers and/or excipients. The pharmaceutical compositions as provided herewith typically include a pharmaceutically acceptable carrier.

As used herein, the term “pharmaceutically acceptable carrier” includes any and all solvents, diluents, or other liquid vehicle, dispersion or suspension aids, surface active agents, isotonic agents, thickening or emulsifying agents, preservatives, solid binders, lubricants and the like, as suited to the particular dosage form desired. Remington's Pharmaceutical-Sciences, Sixteenth Edition, E. W. Martin (Mack Publishing Co., Easton, Pa., 1980) discloses various carriers used in formulating pharmaceutical compositions and known techniques for the preparation thereof.

As used herein, the term "vaccine composition" is intended to mean a composition which can be administered to humans or to animals in order to induce an immune system response; this immune system response can result in the activation of certain cells, in particular APCs, T lymphocytes and B lymphocytes.

As used herein, the term “vaccination” or “vaccinating” means, but is not limited to, a process to elicit an immune response in a subject against a particular antigen.

As used herein the term "antigen" refers to a molecule capable of being specifically bound by an antibody or by a T cell receptor (TCR) if processed and presented by MHC molecules. An antigen is additionally capable of being recognized by the immune system and/or being capable of inducing a humoral immune response and/or cellular immune response leading to the activation of B- and/or T-lymphocytes. An antigen can have one or more epitopes or antigenic sites (B- and T- epitopes).

As used herein, the term “adjuvant” refers to a compound a compound that can induce and/or enhance the immune response against an antigen when administered to a subject or an animal. It is also intended to mean a substance that acts generally to accelerate, prolong, or enhance the quality of specific immune responses to a specific antigen. In the context of the present invention, the term "adjuvant" means a compound, which enhances both innate immune response by affecting the transient reaction of the innate immune response and the more long- lived effects of the adaptive immune response by activation and maturation of the antigen- presenting cells (APCs) especially Dentritic cells (DCs).

As used herein, the expression "therapeutically effective amount" is meant a sufficient amount of the active ingredient of the present invention to induce an immune response at a reasonable benefit/risk ratio applicable to the medical treatment.

Peptides and conjugates of the present invention:

The first object of the present invention relates to a peptide derived from the spike protein of SARS-CoV-2 that consists of the sequence as set forth in SEQ ID NO:7 (NCTEVPVAIHADQLTPTWRVYSTGSNVFQ) (“S4 or S_6i6-644 peptide”) or SEQ ID NO:10 (YDPLQPELDSFKEELDKYFKNHTSPDVDLGDI) (“S6 of Sii₃8-ii69 peptide”).

In some embodiments, the present invention relates to a conjugate wherein the peptide of the present invention is conjugated or fused to a heterologous polypeptide.

In some embodiments, the heterologous polypeptide is conjugated to the peptide of the present invention by using chemical coupling. Several methods are known in the art for the attachment or conjugation of an antibody to its conjugate moiety. Examples of linker types that have been used to conjugate a moiety to an antibody include, but are not limited to, hydrazones, thioethers, esters, disulfides and peptide-containing linkers, such as valine-citruline linker. A linker can be chosen that is, for example, susceptible to cleavage by low pH within the lysosomal compartment or susceptible to cleavage by proteases, such as proteases preferentially expressed in tumor tissue such as cathepsins (e.g., cathepsins B, C, D). Techniques for conjugating polypeptides and in particular, are well-known in the art (See, e.g., Arnon et ah, “Monoclonal Antibodies For Immunotargeting Of Drugs In Cancer Therapy,” in Monoclonal Antibodies And Cancer Therapy (Reisfeld et al. eds., Alan R. Liss, Inc., 1985); Hellstrom et ah, “Antibodies For Drug Delivery,” in Controlled Drug Delivery (Robinson et al. eds., Marcel Deiker, Inc., 2nd ed. 1987); Thorpe, “Antibody Carriers Of Cytotoxic Agents In Cancer Therapy: A Review,” in Monoclonal Antibodies '84: Biological And Clinical Applications (Pinchera et al. eds., 1985); “Analysis, Results, and Future Prospective of the Therapeutic Use of Radiolabeled Antibody In Cancer Therapy,” in Monoclonal Antibodies For Cancer Detection And Therapy (Baldwin et al. eds., Academic Press, 1985); and Thorpe et al., 1982, Immunol. Rev. 62:119- 58; see also, e.g., PCT publication WO 89/12624.) Typically, the peptide is covalently attached to lysine or cysteine residues on the antibody, through N-hydroxysuccinimide ester or maleimide functionality respectively. Methods of conjugation using engineered cysteines or incorporation of unnatural amino acids have been reported to improve the homogeneity of the conjugate (Axup, J.Y., Bajjuri, K.M., Ritland, M., Hutchins, B.M., Kim, C.H., Kazane, S.A., Haider, R., Forsyth, J.S., Santidrian, A.F., Stafin, K., et al. (2012). Synthesis of site-specific antibody-drug conjugates using unnatural amino acids. Proc. Natl. Acad. Sci. USA 109, 16101— 16106.; Junutula, J.R., Flagella, K.M., Graham, R.A., Parsons, K.L., Ha, E., Raab, H., Bhakta, S., Nguyen, T., Dugger, D.L., Li, G., et al. (2010). Engineered thio-trastuzumab-DMl conjugate with an improved therapeutic index to target human epidermal growth factor receptor 2 -positive breast cancer. Clin. Cancer Res.16, 4769-4778). Junutula et al. (Nat Biotechnol. 2008; 26:925-32) developed cysteine-based site-specific conjugation called “THIOMABs” (TDCs) that are claimed to display an improved therapeutic index as compared to conventional conjugation methods. Conjugation to unnatural amino acids that have been incorporated into the antibody is also being explored for ADCs; however, the generality of this approach is yet to be established (Axup et al., 2012). In particular the one skilled in the art can also envisage Fc-containing polypeptide engineered with an acyl donor glutamine-containing tag (e.g., Gin- containing peptide tags or Q- tags) or an endogenous glutamine that are made reactive by polypeptide engineering (e.g., via amino acid deletion, insertion, substitution, or mutation on the polypeptide). Then a transglutaminase can covalently crosslink with an amine donor agent (e.g., a small molecule comprising or attached to a reactive amine) to form a stable and homogenous population of an engineered Fc-containing polypeptide conjugate with the amine donor agent being site-specifically conjugated to the Fc-containing polypeptide through the acyl donor glutamine-containing tag or the accessible/exposed/reactive endogenous glutamine (WO 2012059882).

In some embodiments, the heterologous polypeptide is fused to the peptide of the present invention to form a fusion protein.

In some embodiments, the heterologous polypeptide can be fused to the N-terminus or C- terminus of the peptide of the present invention. In some embodiments, the peptide of the present invention is fused either directly or via a linker to the heterologous polypeptide. As used herein, the term "directly" means that the (first or last) amino acid at the terminal end (N or C-terminal end) of the peptide of the present invention is fused to the (first or last) amino acid at the terminal end (N or C-terminal end) of heterologous polypeptide. This direct fusion can occur naturally as described in (Vigneron et al., Science 2004, PMID 15001714), (Warren et al., Science 2006, PMID 16960008), (Berkers et al., J. Immunol. 2015a, PMID 26401000), (Berkers et al., J. Immunol. 2015b, PMID 26401003), (Delong et al., Science 2016, PMID 26912858) (Liepe et al., Science 2016, PMID 27846572), (Babon et al., Nat. Med. 2016, PMID 27798614).

In some embodiments, the heterologous polypeptide consists of a pan-DR binding peptide. As used hereon, the term “pan-DR binding peptide” refers to a member of a family of molecules that binds more than one MHC class II DR molecule (e.g., binding each of the more than one MHC molecule with an IC50 of less than 100 nM, such as at least 50 nM). In some embodiments, the pan DR-binding peptides of the present invention are peptides capable of binding at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or all 12 most common DR alleles (DR1, 2w2b, 2w2a, 3, 4w4, 4wl4, 5, 7, 52a, 52b, 52c, and 53). The pan-DR binding peptides of the present invention are particularly suitable for promoting an immune response against a second determinant (e.g. the peptide of the present invention). In some embodiments, the pan-DR binding peptide of the present invention consists of a PADRE sequence. As used herein, the term “PADRE” refers to the pan DR binding peptide having the amino acid sequence AKFVAAWTLKAAA (SEQ ID NO: 11). In some embodiments, the pan-DR binding peptide of the present invention comprises a PADRE sequence. In some embodiments, the pan-DR binding peptide has the amino acid sequence as set forth in SEQ ID NO: 19 (AKF VAAWTLKAAARR) .

In some embodiments, the heterologous polypeptide comprises a cleavable sequence. As used herein, the term "cleavable sequence" refers to an amino acid sequence that comprises a cleavage site. The term "cleavage site" refers to the bond (e.g. a scissile bond) cleaved by an agent. A cleavage site for a protease includes the specific amino acid sequence recognized by the protease during proteolytic cleavage and typically includes the surrounding one to six amino acids on either side of the scissile bond, which bind to the active site of the protease and are needed for recognition as a substrate. The cleavable sequence may include a cleavage site specific for an enzyme, such as a protease or other cleavage agent. A cleavable sequence is typically cleavable under physiological conditions. The cleavable sequence is designed for selective cleavage by a particular protease (e.g. the furin protease). The cleavage site of the cleavable sequence includes the specific amino acid sequence recognized by the protease during proteolytic cleavage and typically includes the surrounding one to six amino acids on either side of the scissile bond, which bind to the active site of the protease and are needed for recognition as a substrate. The cleavable sequence may contain any protease recognition motif known in the art and is typically cleavable under physiological conditions. In some embodiments, the cleavable sequence comprises the furin recognition site as set forth in SEQ ID NO: 12 (RARKRR).

In some embodiments, the fusion protein of the present invention consists of the amino acid sequence as set forth in SEQ ID NO: 13 (RARKRRAKFVAAWTLKAAARR NCTEVPVAIHADQLTPTWRVYSTGSNVFQ) or 14

(RARKRRAKFVAAWTLKAAARR YDPLQPELDSFKEELDKYFKNHTSPDVDLGDI)

The peptides and fusion proteins of the invention may be produced by any technique known per se in the art, such as, without limitation, any chemical, biological, genetic or enzymatic technique, either alone or in combination. Knowing the amino acid sequence of the desired sequence, one skilled in the art can readily produce said polypeptides, by standard techniques for production of polypeptides. For instance, they can be synthesized using well-known solid phase method, preferably using a commercially available peptide synthesis apparatus (such as that made by Applied Biosystems, Foster City, California) and following the manufacturer’s instructions. Alternatively, the polypeptides and fusions proteins of the invention can be synthesized by recombinant DNA techniques as is now well-known in the art. For example, these fragments can be obtained as DNA expression products after incorporation of DNA sequences encoding the desired (poly) peptide into expression vectors and introduction of such vectors into suitable eukaryotic or prokaryotic hosts that will express the desired polypeptide, from which they can be later isolated using well-known techniques.

Nanoparticles:

One further object of the invention relates to a nanoparticle that is conjugated to a peptide of the present invention. In some embodiments, the nanoparticle is conjugated to the conjugate or fusion protein of the present invention.

In some embodiments, the nanoparticle is conjugated with SFP.S6 peptide. In some embodiments, the nanoparticle is conjugated with a fusion protein that comprises the amino acid sequence as set forth in SEQ ID NO: 14 (RARKRRAKFVAAWTLKAAARR YDPLQPELDSFKEELDKYFKNHTSPDVDLGDI) In some embodiments, the nanoparticle is conjugated with the fusion protein that consists of the amino acid sequence as set forth in SEQ ID NO: 14 (RARKRRAKFVAAWTLKAAARR

YDPLQPELDSFKEELDKYFKNHTSPDVDLGDI).

In some embodiments, the hydrodynamic diameter of the nanoparticles ranges from 0.5 nm to 200 nm, or from 1 nm to 100 nm, or from 2 nm to 50 nm, or from 3 nm to 25 nm, or about 0.5 nm, or about 1 nm, or about 1.5 nm, or about 2 nm, or about 2.5 nm, or about 3 nm, or about 3.5 nm, or about 4 nm, or about 4.5 nm, or about 5 nm, or about 10 nm, or about 15 nm, or about 20 nm. In some embodiments, the diameter of the nanoparticles ranges from 10 to 20 nm. In some embodiments, the diameter of the nanoparticles is about 15 nm. In some embodiments, the diameter of the nanoparticles is 15 nm.

Methodology for determining the hydrodynamic diameter of a nanoparticle are well known in the art and described, for example, in U.S. Patent Publication No. 2007/0258907. Hydrodynamic diameter measurements often include a determination of dynamic light scattering (DLS), such as may be achieved with a ZetaPALS dynamic light scattering detector (DLS, Brookhaven Instruments Corporation).

In some embodiments, the nanoparticle is an inert metal nanoparticle. In some embodiments, the nanoparticle is a gold nanoparticle (AuNP also named “GNP” or “Gold NanoParticle”). The production of the gold nanoparticles may be achieved in any number of ways, known in the art, described herein, and/or as can be developed. For instance, methodology for the synthesis of gold nanoparticle cores is described in Low and Bansal, Biomedical Imaging and Intervention J. 6: 1-9 (2010). The Turkevich reaction produces spherical gold nanoparticle cores, with networks of gold nanowires formed as a transient intermediate. Turkevich and Kim, Science 1690948): 873 -9 (1970). The Frens methodology, which involves the reaction of hot chlorauric acid with sodium citrate generates monodisperse spherical gold nanoparticles having diameters of approximately 10-20 nm. Frens, Nature 241 :20 (1973). Colloidal gold forms in the presence of citrate ions, which act as both a reducing agent and a capping agent. Larger particles can be produced by decreasing sodium citrate concentration, which reduces the availability of citrate ions for stabilizing the nanoparticles. As a result, small nanoparticle cores form larger aggregates having a reduced surface area, which permits saturation of the surface with citrate ions. See, also, Jana et al., Advanced Materials 13f 18): 1389-93 (2001), Perrault and Chan, J. American Chemical Society 131(47): 17042-3 (2009), and McDaniel and Astruc, Chemical Reviews 104(l):293-346 (2004).

In some embodiments, the nanoparticle is SFP.S6-GNP. In some embodiments, the nanoparticle is a gold nanoparticle conjugated with a fusion protein that comprises the amino acid sequence as set forth in SEQ ID NO: 14 (RARKRRAKFVAAWTLKAAARR YDPLQPELDSFKEELDKYFKNHTSPDVDLGDI) In some embodiments, the nanoparticle is a gold nanoparticle conjugated with the fusion protein that consists of the amino acid sequence as set forth in SEQ ID NO: 14 (RARKRRAKFVAAWTLKAAARR YDPLQPELDSFKEELDKYFKNHTSPDVDLGDI) Conjugation of the peptide or fusion protein to the nanoparticles may be achieved in any number of ways that can be by covalent bonding, non-covalent bonding, ionic bonding, electrostatic interactions, Hydrogen bonding, van der Waals forces, hydrophobic bonding, or a combination thereof. In some examples, the peptide or fusion protein of the present invention can be directly covalently coupled to a nanoparticle. In particular, the peptide or fusion protein can be coupled to the nanoparticle by using a linker molecule. The linker preferably is typically biocompatible. Common molecular linkers known in the art include a maleimide or succinimide group, streptavidin, neutravidin, biotin, or similar compounds. In some embodiments, the peptide or fusion protein is conjugated to the surface of the nanoparticles by any conventional method well known in the art, such as described in Hermanson, Greg T. Bioconjugate techniques. Academic press, 2013. In some embodiments, l-ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride (EDC)- N- hydroxysulfosuccinimide (Sulfo NHS) reactions are used for conjugating the peptides or fusion protein to the nanoparticles. In some embodiments, the nanoparticle is conjugated to an avidin moiety that can create an avidin-biotin complex with the biotinylated peptides and the particles. Additional, appropriate cross-linking agents for use in the invention include a variety of agents that are capable of reacting with a functional group present on a surface of the particle. Reagents capable of such reactivity include homo- and hetero-bifunctional reagents, many of which are known in the art. Heterobifunctional reagents are preferred. Suitable crosslinking agents that may be used include long-chain succinimidyl 4-(N-maleimidom ethyl) cyclohexane- 1- carboxylate (LC-SMCC); sulfosuccinimidyl 4-(N-maleimidom ethyl) cyclohexane- 1- carboxylate (sulfo-SMCC); long-chain sulfosuccinimidyl 4-(N-maleimidomethyl) cyclohexane-l-carboxylate (sulfo-LC-SMCC); N-Succinimidyl-3-(pypridyldithio)- proprionate (SPDP); long-chain N-Succinimidyl-3-(pypridyldithio)-proprionate (LC- SPDP); sulfo-N- Succinimidyl-3-(pypridyldithio)-proprionate (sulfo-SPDP); long-chain sulfo-N-Succinimidyl- 3-(pypridyldithio)-proprionate (sulfo-LC-SPDP); 1 -Ethyl Hydrocholride-3-(3- Dimethylaminopropyl) carbodiimide (EDC); long-chain 1 -Ethyl Hydrocholride-3-(3- Dimethylaminopropyl) carbodiimide (LC-EDC); succinimidyl 4-(N- maleimidomethyl) polyethylene glycoln (SM(PEG)n); sulfosuccinimidyl 4-(N- maleimidomethyl) polyethylene glycoln (sulfo-SM(PEG)n); N-Succinimidyl-3- (pypridyldithio)-proprionate polyethylene glycolm (SPDP(PEG)m); and sulfo-N- Succinimidyl-3-(pypridyldithio)-proprionate polyethylene glycolm (sulfo-SPDP(PEG)m), where n can be from about one glycol unit to about 24 glycol units, such as about one, two, three, four, five, six, seven, eight, nine, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, or 24 glycol units and where m can be from about one glycol unit to about 12 glycol units, such as about one, two, three, four, five, six, seven, eight, nine, 10, 11, or 12 glycol units.

Methods of diagnosis:

A further object of the present invention relates to a method for detecting the presence of coronavirus-specific antibodies in a subject comprising the steps of: a) placing a sample obtained from the subject, in a single assay receptacle, in the presence of the peptide(s) of the present invention,

- b) incubating the mixture under conditions which allow the formation of immunocomplexes on said peptide(s), c) eliminating the immunoglobulins which have not bound to the peptide(s), and d) detecting the immunocomplexes of step b) on peptide(s), whereby the presence or absence of coronavirus-specific antibodies is revealed.

In some embodiments, the coronavirus-specific antibodies are betacoronavirus-specific antibodies. In some embodiments, the coronavirus-specific antibodies are sarbecovirus-specific antibodies. In some embodiments, the coronavirus-specific antibodies are SARS-Cov-2- specific antibodies. In some embodiments, the peptide is a peptide that comprises the amino acid sequence as set forth in SEQ ID NO:7. In some embodiments, the peptide is S4 peptide. In some embodiments, the peptide is the peptide that consists of the amino acid sequence as set forth in SEQ ID NO:7. In some embodiments, the peptide is the peptide that comprises the amino acid sequence as set forth in SEQ ID NO: 10. In some embodiments, the peptide is S6 peptide. In some embodiments, the peptide is the peptide that consists of the amino acid sequence as set forth in SEQ ID NO: 10. In some embodiments, the peptide is SFP.S6 peptide. In some embodiments, the peptide is a fusion protein that comprises the amino acid sequence as set forth in SEQ ID NO: 14. In some embodiments, the peptide is a fusion protein that consists of the amino acid sequence as set forth in SEQ ID NO: 14.

In some embodiments, the receptacle may be any solid container, for example a test tube, a microplate well or a reaction cuvette made of polypropylene. Typically, the peptides are immobilized on a solid support. A known amount of the peptide (or fusion protein) is immobilized on a solid support (e.g. a polystyrene micro titer plate) either non-specifically (via adsorption to the surface) or specifically (via capture by another antibody specific to the same antigen, in a "sandwich" ELISA). Then the sample, suspected of containing the coronavirus- specific antibodies, is washed over the surface so that the antibodies can bind to the immobilized peptide. The surface is washed to remove any unbound protein and a detection antibody is applied to the surface.

The detection antibody should be an anti-human Ig antibody. In some embodiments, the detection antibody has specificity for a particular immunoglobulin. In some embodiments, the detection antibody is an anti -human IgG antibody, including anti-IgGl, IgG2, IgG3 and IgG4 antibodies. In some embodiments, the detection antibody is an anti-IgM antibody. In some embodiments, the detection antibody is an anti-human IgA antibody, including anti-IgAl and IgA2 antibodies. In some embodiments, the antibody having specificity for a particular type immunoglobulin is a rabbit or goat antibody. In some embodiments, the antibody of the present invention is a monoclonal antibody or a polyclonal antibody. Thus, in some embodiments, the method of the present invention is particularly suitable for detecting presence of IgM coronavirus-specific antibodies. In some embodiments, the method of the present invention is particularly suitable for detecting presence of IgG coronavirus-specific antibodies. In some embodiments, the method of the present invention is particularly suitable for detecting presence of IgA coronavirus specific antibodies. In some embodiments, the method of the present invention is particularly suitable for detecting presence of IgG, IgM and IgA coronavirus specific antibodies. In some embodiments, the IgM, IgG and/or IgA coronavirus-specific antibodies are IgM, IgG and/or IgA betacoronavirus-specific antibodies. In some embodiments, the IgM, IgG and/or IgA coronavirus-specific antibodies are IgM, IgG and/or IgA sarbecovirus- specific antibodies. In some embodiments, the IgM, IgG and/or IgA coronavirus-specific antibodies are IgM, IgG and/or IgA SARS-Cov-2-specific antibodies.

The detection antibody can be covalently linked to an enzyme, or can itself be detected by a secondary antibody which is linked to an enzyme through bio-conjugation. Enzymes which can be used to detectably label the antibodies of the present invention include, but are not limited to, malate dehydrogenase, staphylococcal nuclease, delta- V- steroid isomerase, yeast alcohol dehydrogenase, alpha-glycerophosphate dehydrogenase, triose phosphate isomerase, horseradish peroxidase, alkaline phosphatase, asparaginase, glucose oxidase, beta- galactosidase, ribonuclease, urease, catalase, glucose- Vl-phosphate dehydrogenase, glucoamylase and acetylcholinesterase. Between each step the plate is typically washed with a mild detergent solution to remove any proteins or antibodies that are not specifically bound. After the final wash step the plate is developed by adding an enzymatic substrate to produce a visible signal, which indicates the quantity of antigen in the sample. Typically use of TMB (3, 3', 5, 5'- tetramethylbenzidene) color development substrate is used for localization of horseradish peroxidase- conjugated antibodies in the wells. Subsequently there will be no color change or little color change. If there are no coronavirus-specific antibody in the serum sample, there will be much color change. Such a ELSA test is specific, sensitive, reproducible and easy to operate. In some embodiments, the detection antibody is labelled with a fluorescent compound. When the fluorescently labelled antibody is exposed to light of the proper wavelength, its presence can then be detected due to fluorescence. Among the most commonly used fluorescent labelling compounds are CY dyes, fluorescein isothiocyanate, rhodamine, phycoerytherin, phycocyanin, allophycocyanin, o-phthaldehyde and fluorescamine. Other fluorophores known to those skilled in the art can also be used, for example those available from Life Technologies (Invitrogen; Molecular Probes (Eugene, Oreg.)) and including the ALEXA FLUOR® series of dyes (for example, as described in U.S. Pat. Nos. 5,696,157, 6, 130, 101 and 6,716,979), the BODIPY series of dyes (dipyrrometheneboron difluoride dyes, for example as described in U.S. Pat. Nos. 4,774,339, 5,187,288, 5,248,782, 5,274,113, 5,338,854, 5,451,663 and 5,433,896), Cascade Blue (an amine reactive derivative of the sulfonated pyrene described in U.S. Pat. No. 5,132,432) and Marina Blue (U.S. Pat. No. 5,830,912). In some embodiments, the detection antibody can also be detectably labelled using fluorescence emitting metals such as ¹⁵²Eu, or others of the lanthanide series. These metals can be attached to the antibody using such metal chelating groups as diethylenetriaminepentaacetic acid (DTP A) or ethylenediaminetetraacetic acid (EDTA). In some embodiments, the detection antibody is detectably labelled by coupling it to a chemiluminescent compound. The presence of the chemiluminescent-antibody is then determined by detecting the presence of luminescence that arises during the course of a chemical reaction. Examples of particularly useful chemiluminescent labeling compounds are luminol, luciferin, isoluminol, theromatic acridinium ester, imidazole, acridinium salt and oxalate ester. In some embodiments, an automated assay systems is used and include, e.g., the BIO-FLASH™, the BEST 2000™, the DS2™, the ELx50 WASHER, the ELx800 WASHER, the ELx800 READER, and the Autoblot S20™ (INOVA Diagnostics, Inc., San Diego, CA).

In some embodiments, the immunoassays comprise beads coated with the peptide of the present invention. Commonly used are beads that are dyed to establish a unique identity. Detection is performed by flow cytometry. Autoantibody detection using multiplex technologies. Other types of bead- based immunoassays are well known in the art, e. g. laser bead immunoassays and related magnetic bead assays (Fritzler, Marvin J; Fritzler, Mark L, Expert Opinion on Medical Diagnostics, 2009, pp. 3: 81-89). In some embodiments, the method of the present invention involves the use of a multiplex technology. Multiplex technology is the collective term for a variety of techniques which can assess multiple antibody specificities simultaneously on small volumes of blood sample. The advantage of multiplex technology is that it is able to provide very rapid test times and very high throughput of samples. One such technique, is the addressable laser bead immunoassay (ALBIA), which is commercially available on Luminex™.based platforms. For instance, ALBIA is a semi -quantitative homogenous fluorescence-based microparticle immunoassay that can be used for the simultaneous detection of several autoantibodies (e.g. up to 10 autoantibodies). Each antigen (peptides S4 and S6 of the present invention) is covalently coupled to a set of distinct uniform size colour-coded microspheres. The blood sample is then incubated microspheres in a filter membrane bottomed microplate. The beads were washed and then incubated for 3an anti-human Ig conjugated to a fluorescent label (e.g. phycoerythrin). After washing again the beads were analysed on a system in which separate lasers identified antigen by bead colour and quantified the antibody by measuring the fluorescence of the fluorescent label. Said quantification thus indicated the level of the auto-antibodies. In some embodiments, a dot blot, or a line blot is used to carry out the method of the present invention. In some embodiments, a test strip that has been coated with one or more band of the peptide of the present invention, preferably to at least 80, 90, 95 or 99 % purity, prior to the coating procedure. If two or more antigens are used, they are preferably spatially separated. Preferably, the width of the bands is at least 30, more preferably 40, 50, 60, 70 or 80 % the width of the test strip. The test strip may comprise one or more control bands for confirming that it has been contacted with sample sufficiently long and under sufficient conditions, in particular human serum, antibody conjugate, or both. In some embodiments, a flow path in a lateral flow immunoassay device is used. For example, the peptide of the present invention can be attached or immobilized on a porous membrane, such as a PVDF membrane (e.g., an Immobilon™ membrane), a nitrocellulose membrane, polyethylene membrane, nylon membrane, or a similar type of membrane.

A further object of the present invention relates to a method for detecting the presence of coronavirus-specific antibodies in a subject comprising the steps of: a) placing a sample obtained from the subject, in a single assay receptacle, in the presence of the conjugated nanoparticles of the invention,

- b) incubating the mixture under conditions which allow the formation of immunocomplexes on nanoparticles, c) eliminating the immunoglobulins which have not bound to the nanoparticles, and d) detecting the immunocomplexes of step b) on nanoparticles, whereby the presence or absence of coronavirus-specific antibodies is revealed.

In some embodiments, the receptacle may be any solid container, for example a test tube, a microplate well or a reaction cuvette made of polypropylene. In some embodiments, the elimination of the unbound reagents may be carried out by any technique known to those skilled in the art, such as e.g. washing by means of repeated centrifugation steps.

In some embodiments, the coronavirus-specific antibodies are betacoronavirus-specific antibodies. In some embodiments, the coronavirus-specific antibodies are sarbecovirus-specific antibodies. In some embodiments, the coronavirus-specific antibodies are SARS-Cov-2- specific antibodies. In some embodiments, the conjugated nanoparticles are nanoparticle conjugated with a fusion protein that comprises the amino acid sequence as set forth in SEQ ID NO:14. In some embodiments, the conjugated nanoparticles are nanoparticle conjugated with the fusion protein that consists of the amino acid sequence as set forth in SEQ ID NO: 14. In some embodiments, the nanoparticles are gold nanoparticles.

Then the aggregation of the gold nanoparticles reveal the presence of coronavirus-specific antibodies in the sample. In particular, the surface plasmon resonance (SPR) property makes gold nanoparticles suitable reporters for colorimetric sensors based on the principle that the well -dispersed gold nanoparticle appears red in color whereas the aggregated gold nanoparticles have a blue (or purple) color. Most of the aggregation mechanism in previously reported gold nanoparticle-based biosensors relied on inter-particle crosslinking (e.g. DNA hybridization, antibody-antigen interaction or peptides). For example, see Elghanian, R. et al, Science, 277, 1078 (1997); Guarise, C. et al. Proc. Natl. Acad. Sci. USA. 103, 3978 (2006); Choi, Y. et al. Angew. Chem. Int. Ed 46, 707 (2007). In the present disclosure, gold nanoparticle-based colorimetric biosensors are developed based on non-crosslinking gold nanoparticle aggregation. Colloidal stability can be adjusted by modifying surface charges that affect electrostatic stabilization, and that aggregation can be induced due to the loss (or screening) of surface charges. The approaches to reduce surface charges include, for example, using non- charged molecules to displace charged motifs on the gold nanoparticle surface or by removing charged molecules from the surface.

Thus in some embodiments, the method of the present invention comprises the steps of: a) placing a sample obtained from the subject, in a single assay receptacle, in the presence of the conjugated gold nanoparticles of the invention,

- b) incubating the mixture under conditions which allow the formation of immunocomplexes on nanoparticles, c) detecting a color change responsive to the aggregation of the gold nanoparticles, whereby the presence or absence of coronavirus-specific antibodies is revealed.

In some embodiments, the coronavirus-specific antibodies are betacoronavirus-specific antibodies. In some embodiments, the coronavirus-specific antibodies are sarbecovirus-specific antibodies. In some embodiments, the coronavirus-specific antibodies are SARS-Cov-2- specific antibodies. In some embodiments, the conjugated gold nanoparticles are gold nanoparticle conjugated with a fusion protein that comprises the amino acid sequence as set forth in SEQ ID NO: 14. In some embodiments, the conjugated gold nanoparticles are SFP.S6- GNP. In some embodiments, the conjugated gold nanoparticles are gold nanoparticle conjugated with the fusion protein that consists of the amino acid sequence as set forth in SEQ

ID NO:14.

Typically, the degree the color changes in response to the aggregation of the nanoparticles may be quantified by colorimetric quantification methods known to those of ordinary skill in the art. Standards containing known amounts of coronavirus-specific antibodies may be analyzed in addition to the sample to increase the accuracy of the comparison. If higher precision is desired, various types of spectrophotometers may be used to plot a Beer's curve in the desired concentration range. The color of the sample may then be compared with the curve and the concentration of the analyte present in the sample determined.

In some embodiments, the method of the present invention involves the use of a multiplex technology. Multiplex technology is the collective term for a variety of techniques which can assess multiple immunoglobulin specificities simultaneously on small volumes of sample. The advantage of multiplex technology is that it is able to provide very rapid test times and very high throughput of samples.

Thus, in some embodiments, the method of the present invention comprises the steps of: a) placing a sample obtained from the subject, in a single assay receptacle, in the presence of plurality of particles belonging to at least two different groups, one of the groups being conjugated to a first peptide (SEQ ID NO:7 or 10) and the other group being conjugated to a second peptide (SEQ ID NO:7 or 10),

- b) incubating the mixture under conditions which allow the formation of immunocomplexes on each group of particles, c) eliminating the immunoglobulins which have not bound to the particles, d) simultaneously detecting the immunocomplexes of step b) on each particle, whereby the presence or absence of coronavirus-specific antibodies is revealed.

In some embodiments, the coronavirus-specific antibodies are betacoronavirus-specific antibodies. In some embodiments, the coronavirus-specific antibodies are sarbecovirus-specific antibodies. In some embodiments, the coronavirus-specific antibodies are SARS-Cov-2- specific antibodies. In some embodiments, the method of the present invention is particularly suitable for detecting immunoglobulins having specificity for the peptide S4 (SEQ ID NO:7) and/or the peptide S6 (SEQ ID NO: 10). In some embodiments, the method of the present invention is particularly suitable for simultaneously detecting immunoglobulins having specificity for the peptide S4 (SEQ ID NO:7) and the peptide S6 (SEQ ID NO: 10). Thus, in some embodiments, the method of present invention comprises the step of contacting the sample with at least 2 groups of particles, each particles being conjugated to a particular SARS- Cov-2 peptide.

The diagnostic methods of the present invention are particularly suitable for (simultaneously) detecting IgG and IgM, or IgA coronavirus-specific antibodies having specificity for the S4 or S6 peptides of the present invention. In some embodiments, the IgM, IgG and/or IgA coronavirus-specific antibodies are IgM, IgG and/or IgA betacoronavirus-specific antibodies. In some embodiments, the IgM, IgG and/or IgA coronavirus-specific antibodies are IgM, IgG and/or IgA sarbecovirus-specific antibodies. In some embodiments, the IgM, IgG and/or IgA coronavirus-specific antibodies are IgM, IgG and/or IgA SARS-Cov-2-specific antibodies.

The methods of the present invention are thus particularly suitable for the diagnosis of coronavirus infection. In some embodiments, the methods of the present invention are particularly suitable for the diagnosis of betacoronavirus infection. In some embodiments, the methods of the present invention are particularly suitable for the diagnosis of sarbecovirus infection. In particular, the method of the present invention is particularly suitable for the diagnosis of Severe Acute Respiratory Syndrome (SARS). In some embodiments, the method of the present invention is particularly suitable for the diagnosis of COVID-19.

The method of the present invention is also particularly suitable or indicated for the serologic follow-up and therapy control of coronavirus infections, in particular betacoronavirus infection, in particular COVID-19. In some embodiments, the present invention is suitable for the serologic follow-up and therapy control of a betacoronavirus infection. In some embodiments, the present invention is suitable for the serologic follow-up and therapy control of a sarbecovirus infection. In some embodiments, the present invention is particularly suitable for the serologic follow-up and therapy control of COVID-19. In some embodiments, the method of the present invention is particularly useful for vaccine purposes. In particular, the method can be carried out for determining whether a subject achieves a protection with a vaccine or a vaccine candidate comprising i) detecting by carrying out the method of the present invention the presence of antibodies specific for the S4 peptide (SEQ ID NO:7) and/or for the S6 peptide (SEQ ID NO: 10) ii) and concluding that the subject achieves a protection with the vaccine or vaccine candidate when the presence of the antibodies specific for S4 and/or S6 is detected. Typically, the vaccine is an mRNA vaccine encoding for the spike protein (COVID-19 mRNA vaccine) and in particular the BNT162b2 vaccine. Thus, in some embodiments, the vaccine is an mRNA vaccine encoding for the spike protein. In some embodiments, the vaccine is the BNT162b2 vaccine.

The method of the present invention is also suitable for determining whether a subject has to be vaccinated against coronavirus, said method comprising i) detecting by carrying out the method of the present invention the presence of coronavirus specific antibodies ii) and concluding that the subject has to be vaccinated when the absence of coronavirus specific antibodies is detected or conversely does not need to be vaccinated if the presence of coronavirus specific antibodies is detected.

In some embodiments, the coronavirus-specific antibodies are betacoronavirus-specific antibodies. In some embodiments, the coronavirus-specific antibodies are sarbecovirus-specific antibodies. In some embodiments, the coronavirus-specific antibodies are SARS-Cov-2- specific antibodies.

The method of the present invention also offers to the physicians a reliable tool for research purposes (e.g. selecting a candidate vaccine, assessing a therapy, studying the replication of the virus, or epidemiologic studies). The method of the present invention is also suitable for deciding measures of containment or decontainment for an individual, or for a group of individuals.

Kits of the invention:

A further object of the present invention relates to a kit for performing the diagnostic method of the present invention.

In some embodiments the kit of the present invention comprises at least one peptide of the present invention; and at least one solid support wherein the peptide of the present invention is deposited on the support. In some embodiments, the peptide of the present invention that is deposited on the solid support is immobilized on the support. In some embodiments, the solid support is selected from the group comprising a bead, preferably a paramagnetic particle, a test strip, a microtiter plate, a blot (e.g. line blot and dot blot), a glass surface, a slide, a biochip and a membrane. In some embodiments, the devices or kits described herein can further comprise a detection antibody is specific for the Ig in the sample of the subject and the detection antibody produces a detectable signal; or a nephelometer cuvette. In some embodiments, the device performs an immunoassay wherein an antibody-protein complex is formed, such as a serological immunoassay or a nephelometric immunoassay. In some embodiments, provided herein are kits that comprise devices described herein and a detection antibody, wherein the detection antibody is specific for the Ig in the sample of the subject and produces a detectable signal. In some embodiments, the kits described herein further comprise standards of known amounts of the peptides of the present invention. Reference values can be provided as numerical values, or as standards of known amounts or titres of antibodies presented in pg/ml-pg/ml. In some embodiments, the kits described herein further comprise at least one sample collection container for sample collection. Collection devices and container include but are not limited to syringes, lancets, BD VACUTAINER® blood collection tubes. In some embodiments, the kits described herein further comprise instructions for using the kit and interpretation of results.

In some embodiments, the kit comprises one or more plurality of (gold) nanoparticles as above described and means for determining the immunocomplexes. Reagents for particular types of assays can also be provided in kits of the invention. Thus, the kits can include different groups of particles each identified by a specific identity, plates that comprises the single assay receptacles (e.g. a multiwell plate). In some embodiments, the kits comprise a device such as a detector as described above. The groups of particles, the plate, and the devices are useful for performing the immunoassay of the present invention. In addition, the kits can include various diluents and buffers, labelled conjugates or other agents for the detection of the specifically immunocomplexes. Other components of a kit can easily be determined by one of skill in the art.

Vaccine compositions:

In another aspect, the present invention also relates to a method for immunizing a subject against a coronavirus comprising administering to said subject a therapeutically effective amount of one or more peptide, conjugate, fusion protein or nanoparticle of the present invention. In some embodiments, the coronavirus is a betacoronavirus. In some embodiments, the coronavirus is a sarbecovirus. In some embodiments, the coronavirus is SARS-Cov-2. In some embodiments, the subject is a human. In some embodiments, the subject is an animal. In some embodiments, the peptide is S6 peptide (SEQ ID NO: 10). In some embodiments, the peptide is a peptide that comprises the amino acid sequence as set forth in SEQ ID NO:10. In some embodiments, the peptide is a peptide that consists in the amino acid sequence as set forth in SEQ ID NO: 10. In some embodiments, the peptide is SFP.S6 peptide (SEQ ID NO: 14). In some embodiments, the peptide is a fusion protein that comprises the amino acid sequence as set forth in SEQ ID NO: 14. In some embodiments, the peptide is a fusion protein that consists in the amino acid sequence as set forth in SEQ ID NO: 14. In some embodiments, the nanoparticle is SFP.S6-GNP consisting in the conjugation of a gold nanoparticle with SFP.S6 peptide (SEQ ID NO: 14). In some embodiments, the nanoparticle are gold nanoparticles conjugated with fusion proteins that consist of the amino acid sequence as set forth in SEQ ID NO:14.

The peptides of the present invention as herein described are thus particularly suitable for inducing an immune response against a coronavirus and thus can be used for vaccine purposes.

Therefore, a further object of the present invention relates to a method for vaccinating a subject in need thereof against a coronavirus comprising administering to said subject a therapeutically effective amount of one or more peptides of the present invention. In some embodiments, the peptide is S6 peptide (SEQ ID NO: 10). In some embodiments, the peptide is a peptide that comprises the amino acid sequence as set forth in SEQ ID NO:10. In some embodiments, the peptide is a peptide that consists in the amino acid sequence as set forth in SEQ ID NO: 10. In some embodiments, the coronavirus is a betacoronavirus. In some embodiments, the coronavirus is a sarbecovirus. In some embodiments, the coronavirus is SARS-Cov-2.

In particular, a further object of the present invention relates to a method for vaccinating a subject in need thereof against SARS-Cov-2 comprising administering to said subject a therapeutically effective amount of S6 peptide (SEQ ID NO: 10). In some embodiments, the present invention relates to a method for vaccinating a subject in need thereof against SARS- Cov-2 comprising administering to said subject a therapeutically effective amount of a peptide that comprises the amino acid sequence as set forth in SEQ ID NO:10. In some embodiments, the present invention relates to a method for vaccinating a subject in need thereof against SARS- Cov-2 comprising administering to said subject a therapeutically effective amount of a peptide that consists of the amino acid sequence as set forth in SEQ ID NO: 10. A further object of the present invention relates to a method for vaccinating a subject in need thereof against a coronavirus comprising administering a therapeutically effective amount of one or more fusion proteins of the present invention. In some embodiments, the fusion protein is SFP.S6 peptide (SEQ ID NO: 14). In some embodiments, the fusion protein comprises the amino acid sequence as set forth in SEQ ID NO:14. In some embodiments, the fusion protein consists in the amino acid sequence as set forth in SEQ ID NO:14. In some embodiments, the coronavirus is a betacoronavirus. In some embodiments, the coronavirus is a sarbecovirus. In some embodiments, the coronavirus is SARS-Cov-2.

In particular, a further object of the present invention relates to a method for vaccinating a subject in need thereof against SARS-Cov-2 comprising administering to said subject a therapeutically effective amount of SFP.S6 peptide (SEQ ID NO: 14). In some embodiments, the present invention relates to a method for vaccinating a subject in need thereof against SARS- Cov-2 comprising administering to said subject a therapeutically effective amount of a fusion protein that comprises the amino acid sequence as set forth in SEQ ID NO: 14. In some embodiments, the present invention relates to a method for vaccinating a subject in need thereof against SARS-Cov-2 comprising administering to said subject a therapeutically effective amount of a fusion protein that consists of the amino acid sequence as set forth in SEQ ID NO:14.

In some embodiments, the method of present invention comprises the step of administering a plurality of particles, each particle being conjugated to a particular coronavirus peptide, in particular a betacoronavirus peptide, more particularly a sarbecovirus peptide and even more particularly a SARS-Cov-2 peptide. In some embodiments, the subject is administered with a plurality of gold nanoparticles conjugated to the peptide of the present invention. In some embodiments, the subject is administered with a plurality of gold nanoparticles conjugated to the fusion protein of the present invention.

A further object of the present invention relates to a method for vaccinating a subject in need thereof against a coronavirus comprising administering a therapeutically effective amount of one or more nanoparticle of the present invention. In some embodiments, the present invention relates to a method for vaccinating a subject in need thereof against a coronavirus comprising administering to said subject a therapeutically effective amount of SFP.S6-GNP. In some embodiments, the present invention relates to a method for vaccinating a subject in need thereof against a coronavirus comprising administering to said subject a therapeutically effective amount of SFP.S6-GNP consisting in the conjugation of gold nanoparticles (GNPs) with SFP.S6 peptide (SEQ ID NO: 14). In some embodiments, the present invention relates to a method for vaccinating a subject in need thereof against a coronavirus comprising administering to said subject a therapeutically effective amount of gold nanoparticles conjugated with fusion proteins that comprise the amino acid sequence as set forth in SEQ ID NO: 14. In some embodiments, the present invention relates to a method for vaccinating a subject in need thereof against a coronavirus comprising administering to said subject a therapeutically effective amount of gold nanoparticles conjugated with fusion proteins that consist of the amino acid sequence as set forth in SEQ ID NO: 14. In some embodiments, the coronavirus is a betacoronavirus. In some embodiments, the coronavirus is a sarbecovirus. In some embodiments, the coronavirus is SARS-Cov-2.

In some embodiments, the present invention relates to a method for vaccinating a subject in need thereof against SARS-Cov-2 comprising administering to said subject a therapeutically effective amount of SFP.S6-GNP. In some embodiments, the present invention relates to a method for vaccinating a subject in need thereof against SARS-Cov-2 comprising administering to said subject a therapeutically effective amount of SFP.S6-GNP consisting in the conjugation of gold nanoparticles (GNPs) with SFP.S6 peptide (SEQ ID NO: 14). In some embodiments, the present invention relates to a method for vaccinating a subj ect in need thereof against SARS- Cov-2 comprising administering to said subject a therapeutically effective amount of gold nanoparticles conjugated with fusion proteins that comprise the amino acid sequence as set forth in SEQ ID NO: 14. In some embodiments, the present invention relates to a method for vaccinating a subject in need thereof against SARS-Cov-2 comprising administering to said subject a therapeutically effective amount of gold nanoparticles conjugated with fusion proteins that consist of the amino acid sequence as set forth in SEQ ID NO: 14.

Another aspect of the invention relates to a method for eliciting the production of anti- coronavirus antibodies, preferably broadly neutralising antibodies. In some embodiments, the method for eliciting the production of anti-coronavirus antibodies comprises a step of administering S6 peptide, SFP.S6 peptide and/or SFP.S6-GNP. In some embodiments, the method for eliciting the production of anti-coronavirus antibodies comprises a step of administering to a subject S6 peptide, SFP.S6 peptide and/or SFP.S6-GNP. In some embodiments, the subject is a human. In some embodiments, the subject is an animal. In some embodiments, the method for eliciting the production of anti-coronavirus antibodies comprises a step of administering a peptide that comprises the sequence as set forth in SEQ ID NO: 10, a fusion protein that comprises the sequence as set forth in SEQ ID NO: 14 or a gold nanoparticle conjugated to a peptide that comprises the sequence as set forth in SEQ ID NO: 14. In some embodiments, the method for eliciting the production of anti-coronavirus antibodies comprises a step of administering to a subject a peptide that comprises the sequence as set forth in SEQ ID NO: 10, a fusion protein that comprises the sequence as set forth in SEQ ID NO: 14 or a gold nanoparticle conjugated to a peptide that comprises the sequence as set forth in SEQ ID NO:14. In some embodiments, the coronavirus is a betacoronavirus. In some embodiments, the coronavirus is a sarbecovirus. In some embodiments, the coronavirus is SARS-Cov-2.

In another aspect, the present invention relates to methods for producing anti-S6 antibodies. In some embodiments, an anti-S6 antibody is an antibody directed against the sequence as set forth in SEQ ID NO: 10. In some embodiments, the present invention relates to a method for producing anti-S6 monoclonal antibodies comprising the step of administering a peptide that comprises the amino acid sequence as set forth in SEQ ID NO:10. In some embodiments, the present invention relates to a method for producing anti-S6 monoclonal antibodies comprising the step of administering S6 peptide. In some embodiments, the present invention relates to a method for producing anti-S6 monoclonal antibodies comprising the step of administering the peptide that consists of the amino acid sequence as set forth in SEQ ID NO:10. In some embodiments, the present invention relates to a method for producing anti-S6 monoclonal antibodies in a sample comprising the step of making cells interacting with S6 peptide in said sample. In some embodiments, the cells are immune cells.

In some embodiments, the present invention relates to a method for producing anti-S6 monoclonal antibodies comprising the step of administering a fusion protein that comprises the sequence as set forth in SEQ ID NO: 14. In some embodiments, the present invention relates to a method for producing anti-S6 monoclonal antibodies comprising the step of administering SFP.S6 peptide. In some embodiments, the present invention relates to a method for producing anti-S6 monoclonal antibodies comprising the step of administering the fusion protein that consists of the sequence as set forth in SEQ ID NO: 14. In some embodiments, the present invention relates to a method for producing anti-S6 monoclonal antibodies in a sample comprising the step of making cells interacting with SFP.S6 peptide in said sample. In some embodiments, the cells are immune cells. In some embodiments, the present invention relates to a method for producing anti-S6 monoclonal antibodies comprising the step of administering gold nanoparticles conjugated with fusion proteins that comprise the amino acid sequence as set forth in SEQ ID NO: 14. In some embodiments, the present invention relates to a method for producing anti-S6 monoclonal antibodies comprising the step of administering SFP.S6-GNP. In some embodiments, the present invention relates to a method for producing anti-S6 monoclonal antibodies comprising the step of administering gold nanoparticles conjugated with fusion proteins that consist of the amino acid sequence as set forth in SEQ ID NO: 14. In some embodiments, the present invention relates to a method for producing anti-S6 monoclonal antibodies in a sample comprising the step of making cells interacting with SFP.S6-GNP in said sample. In some embodiments, the cells are immune cells.

In some embodiments, the present invention relates to a method of having a subject producing anti-S6 monoclonal antibodies comprising administering to said subject a therapeutically effective amount of S6 peptide, SFP.S6 peptide and/or SFP.S6-GNP. In some embodiments, the anti-S6 antibodies are protective anti-S6 antibodies, preferably neutralizing antibodies.

In some embodiments, the present invention also relates to a method of treating a coronavirus infection in a subject in need thereof comprising administering to the subject a therapeutically effective amount of S6 peptide for producing anti-S6 monoclonal antibodies. In some embodiments, the present invention relates to a method of treating a coronavirus infection in a subject in need thereof comprising administering to the subject a therapeutically effective amount of SFP.S6 peptide for producing anti-S6 monoclonal antibodies. In some embodiments, the present invention also relates to a method of treating a coronavirus infection in a subject in need thereof comprising administering to the subject a therapeutically effective amount of SFP.S6-GNP for producing anti-S6 monoclonal antibodies.

In some embodiments, the present invention relates to a method for producing anti-S6 monoclonal antibodies comprising administering to a subject S6 peptide, taking a blood sample from said subject, recovering the serum supernatant and purifying the produced anti-S6 antibodies. In some embodiments, the present invention relates to a method for producing anti- S6 monoclonal antibodies comprising administering to a subject SFP.S6 peptide, taking a blood sample from said subject, recovering the serum supernatant and purifying the produced anti-S6 antibodies. In some embodiments, the present invention relates to a method for producing anti- S6 monoclonal antibodies comprising administering to a subject SFP.S6-GNP, taking a blood sample from said subject, recovering the serum supernatant and purifying the produced anti-S6 antibodies. In some embodiments, the present invention relates to a method for producing anti- S6 monoclonal antibodies comprising immunizing a subject by administering to said subject SFP.S6-GNP, taking a blood sample from said subject, recovering the serum supernatant and purifying the produced anti-S6 antibodies. In some embodiments, the present invention relates to a method for producing anti-S6 monoclonal antibodies comprising immunizing a subject by administering to said subject SFP.S6 peptide conjugated to GNPs, taking a blood sample from said subject, recovering the serum supernatant and purifying the produced anti-S6 antibodies. In some embodiments, the subject is an animal.

In some embodiments, the present invention also relates to a method of treating a coronavirus infection in a subject in need thereof comprising administering to the subject a therapeutically effective amount of anti-S6 monoclonal antibodies obtained with a method for producing anti- S6 monoclonal antibodies according to the present invention. In some embodiments, the present invention relates to a method of treating a coronavirus infection in a subject in need thereof comprising administering to the subject a therapeutically effective amount of anti-S6 monoclonal antibodies obtained with a method comprising a step of administering S6 peptide, SFP.S6 peptide and/or SFP.S6-GNP. In some embodiments, the coronavirus is a betacoronavirus. In some embodiments, the coronavirus is a sarbecovirus. In some embodiments, the coronavirus is SARS-Cov-2.

In some embodiments, the present invention also relates to a method of treating a SARS-Cov- 2 infection in a subject in need thereof comprising administering to the subject a therapeutically effective amount of S6 protein, SFP.S6 peptide and/or SFP.S6-GNP for producing anti-S6 monoclonal antibodies. In some embodiments, the present invention relates to a method for producing anti-S6 monoclonal antibodies comprising administering to a subject SFP.S6-GNPs, taking a blood sample from said subject, recovering the serum supernatant and purifying the produced anti-S6 antibodies. In some embodiments, the present invention relates to a method for producing anti-S6 monoclonal antibodies comprising administering to a subject SFP.S6 peptide conjugated to GNPs, taking a blood sample from said subject, recovering the serum supernatant and purifying the produced anti-S6 antibodies. In some embodiments, the present invention also relates to a method of treating a SARS-Cov-2 infection in a subject in need thereof comprising administering to the subject a therapeutically effective amount of anti-S6 monoclonal antibodies obtained with the method for producing anti-S6 monoclonal antibodies of the present invention.

In some embodiments, the present invention relates to an anti-S6 antibody obtained with a method comprising the step of administering S6 peptide, SFP.S6 peptide and/or SFP.S6-GNP. In some embodiments, the present invention relates to an anti-S6 antibody obtained with a method comprising the step of administering SFP.S6-GNP. In some embodiments, the present invention relates to an anti-S6 antibody obtained with a method comprising the step of administering SFP-S6-GNP to a subject. In some embodiments, the present invention relates to an anti-S6 antibody obtained with a method comprising the step of administering SFP.S6-GNP conjugates to a subject. In some embodiments, the present invention relates to an antibody directed against the sequence as set forth in SEQ ID NO: 10 obtained with a method comprising the step of administering SFP.S6-GNP. In some embodiments, the present invention relates to an antibody directed against the sequence as set forth in SEQ ID NO: 10 obtained with a method comprising the step of administering SFP.S6-GNP. In some embodiments, the present invention relates to an antibody directed against the sequence as set forth in SEQ ID NO: 10 obtained with a method comprising the step of administering a gold nanoparticle conjugated with a fusion protein that comprises the amino acid sequence as set forth in SEQ ID NO: 14. In some embodiments, the anti-S6 antibody is a protective antibody against infectious agent, preferably a neutralizing antibody.

In some embodiments, the present invention relates to a method for generating hybridomas comprising a step of administering S6 peptide, SFP.S6 peptide and/or SFP.S6-GNP. In some embodiments, the S6 peptide, SFP.S6 peptide and/or SFP.S6-GNP are administered to a subject. Following the immunization regimen, lymphocytes are isolated from the spleen, lymph node or other organ of the animal and fused with a suitable myeloma cell line using an agent such as polyethylene glycol to form a hydridoma. Following fusion, cells are placed in media permissive for growth of hybridomas but not the fusion partners using standard methods. Following culture of the hybridomas, cell supernatants are analyzed for the presence of antibodies of the desired specificity, i.e., that selectively bind the antigen. Suitable analytical techniques include ELISA, flow cytometry, immunoprecipitation, and western blotting. Other screening techniques are well-known in the field. Preferred techniques are those that confirm binding of antibodies to conformationally intact, natively folded antigen, such as non denaturing ELISA, flow cytometry, and immunoprecipitation. In some embodiments, the subject can be human or any other animal (e.g., birds and mammals) susceptible to coronavirus infection (e.g. domestic animals such as cats and dogs; livestock and farm animals such as horses, cows, pigs, chickens, etc.). In some embodiments, the subject is susceptible to betacoronavirus infection. In some embodiments, the subject is susceptible to sarbecovirus infection. In some embodiments, the subject is susceptible to SARS-Cov-2 infection. Typically said subject is a mammal including a non-primate (e.g., a camel, donkey, zebra, cow, pig, horse, goat, sheep, cat, dog, rat, and mouse) and a primate (e.g., a monkey, chimpanzee, and a human). In some embodiments, the subject is a non-human animal. In some embodiments, the subject is a farm animal or pet. In some embodiments, the subject is a human. In some embodiments, the subject is a human infant. In some embodiments, the subject is a human child. In some embodiments, the subject is a human adult. In some embodiments, the subject is an elderly human. In some embodiments, the subject is a premature human infant.

In some embodiments, the subject can be symptomatic or asymptomatic.

Typically, the peptides, fusion proteins and particles are administered to the subject at a therapeutically effective amount. It will be understood that the total daily usage of the compounds and compositions of the present invention will be decided by the attending physician within the scope of sound medical judgment. The specific therapeutically effective dose level for any particular subject will depend upon a variety of factors including the disorder being treated and the severity of the disorder; the activity of the specific compound employed; the specific composition employed, the age, body weight, general health, sex and diet of the subject; the time of administration, route of administration, and rate of excretion of the specific compound employed; the duration of the treatment; drugs used in combination or coincidental with the specific nanoparticle employed; and like factors well known in the medical arts. For example, it is well within the skill of the art to start doses of the compound at levels lower than those required to achieve the desired therapeutic effect and to gradually increase the dosage until the desired effect is achieved. However, the daily dosage of the products may be varied over a wide range from 0.01 to 1,000 mg per adult per day. In particular, the compositions contain 0.01, 0.05, 0.1, 0.5, 1.0, 2.5, 5.0, 10.0, 15.0, 25.0, 50.0, 100, 250 and 500 mg of the active ingredient for the symptomatic adjustment of the dosage to the subject to be treated. A medicament typically contains from about 0.01 mg to about 500 mg of the active ingredient, in particular from 1 mg to about 100 mg of the active ingredient. An effective amount of the drug is ordinarily supplied at a dosage level from 0.0002 mg/kg to about 20 mg/kg of body weight per day, especially from about 0.001 mg/kg to 7 mg/kg of body weight per day.

The peptides, fusion proteins or nanoparticles of the invention as herein described may be administered to the subject by any route of administration and in particular by oral, nasal, rectal, topical, buccal (e.g., sub-lingual), parenteral (e.g., subcutaneous, intramuscular, intradermal, or intravenous) and transdermal administration, although the most suitable route in any given case will depend on the nature and severity of the condition being treated and on the nature of the particular active agent which is being used. In some embodiments, the peptides, fusion protein or nanoparticles of the invention are administrated to the subject by intramuscular route.

The peptides, fusion proteins or nanoparticles of the invention as described herein may be administered as part of one or more pharmaceutical compositions. Except insofar as any conventional carrier medium is incompatible with the peptides, fusion proteins or nanoparticles of the present invention, such as by producing any undesirable biological effect or otherwise interacting in a deleterious manner with any other component(s) of the pharmaceutical composition, its use is contemplated to be within the scope of this invention. Some examples of materials which can serve as pharmaceutically acceptable carriers include, but are not limited to, sugars such as lactose, glucose and sucrose; starches such as corn starch and potato starch; cellulose and its derivatives such as sodium carboxymethyl cellulose, ethyl cellulose and cellulose acetate; powdered tragacanth; malt; gelatine; talc; excipients such as cocoa butter and suppository waxes; oils such as peanut oil, cottonseed oil; safflower oil, sesame oil; olive oil; com oil and soybean oil; glycols; such as propylene glycol; esters such as ethyl oleate and ethyl laurate; agar; buffering agents such as magnesium hydroxide and aluminum hydroxide; alginic acid; pyrogen-free water; isotonic saline; Ringer's solution; ethyl alcohol, and phosphate buffer solutions, as well as other non-toxic compatible lubricants such as sodium lauryl sulfate and magnesium stearate, as well as coloring agents, releasing agents, coating agents, sweetening, flavoring and perfuming agents, preservatives and antioxidants can also be present in the composition, according to the judgment of the formulator.

The peptides, conjugates, fusion proteins or nanoparticles of the invention are therefore particularly suitable for preparing vaccine composition. Thus a further object of the present invention relates to a vaccine composition that comprises an amount of one more peptides, conjugates, fusion proteins or nanoparticles of the invention. In some embodiments, the peptide is a peptide that comprises the amino acid sequence as set forth in SEQ ID NO: 10. In some embodiments, the peptide is S6 peptide. In some embodiments, the peptide is the peptide that consists of the amino acid sequence as set forth in SEQ ID NO:10. In some embodiments, the fusion protein is a fusion protein that comprises the amino acid sequence as set forth in SEQ ID NO:14. In some embodiments, the fusion protein is SFP.S6 peptide. In some embodiments, the fusion protein is the fusion protein that consists of the amino acid sequence as set forth in SEQ ID NO:14. In some embodiments, the nanoparticle is a gold nanoparticle conjugated with a fusion protein that comprises the amino acid sequence as set forth in SEQ ID NO: 14. In some embodiments, the nanoparticle is SFP.S6- GNP. In some embodiments, the nanoparticle is a gold nanoparticle conjugated with the fusion protein that consists of the amino acid sequence as set forth in SEQ ID NO: 14.

In some embodiments, the vaccine composition of the present invention comprises an adjuvant. In some embodiments, the adjuvant is alum. In some embodiments, the adjuvant is Incomplete Freund’s adjuvant (IF A) or other oil based adjuvant that is present between 30-70%, preferably between 40-60%, more preferably between 45-55% proportion weight by weight (w/w). In some embodiments, the vaccine composition of the present invention comprises at least one Toll-Like Receptor (TLR) agonist which is selected from the group consisting of TLR1, TLR2, TLR3, TLR4, TLR5, TLR6, TLR7, and TLR8 agonists. In some embodiments, the vaccine composition of the present invention does not comprise any adjuvant.

The invention will be further illustrated by the following figures and examples. However, these examples and figures should not be interpreted in any way as limiting the scope of the present invention.

FIGURES:

Figure 1. Comirnaty vaccine (originally named BNT162b2 vaccine) recipient serum reacts with RBD domain of S protein but not N protein. A BNT162b2 vaccine recipient serum sample (closed box) and a pool of ten SARS-CoV-2 donor serum samples (closed circle) at dilution 1:50 were assayed for the detection of antibodies against SARS-CoV-2 N and S proteins by indirect ELISA using recombinant rN and rRBD proteins as capture viral antigens (Frumence et al., J. Virol. Methods 495, 113082, 2021). A serum sample diagnosed negative for SARS-CoV-2 infection was used as a negative serum control. The intensity values of experimental serum samples were measured at O.D. 450 nm and their antigenic reactivity was estimated as a fold increase of intensity values obtained with the negative control serum.

Figure 2. Synthetic peptides representing potential linear B-cell epitopes in SARS-CoV-2 S protein. The organization of the S protein with its two S 1 and S2 subunits and their different domains and motifs is shown. The sequences of peptides representing potential linear B-cell epitopes SI to S6 and their mutants S1^V3, S3^V2, and S5^V1 are positioned on the S protein.

Figure 3. Antigenic reactivity of S peptides in relation to the BNT162b2 vaccine recipient serum. The BNT162b2 vaccine recipient serum sample at dilution 1:50 was assayed for the detection of antibodies against SI to S6 peptides and their mutants S1^V3, S3^V2, and S5^V1, through a peptide-ELISA. A serum sample negative for SARS-CoV-2 infection was used as a negative serum control. The intensity values of vaccine serum sample were measured at O.D. 450 nm and the antigenic reactivity was estimated as a fold increase of intensity values obtained with the negative control serum. The results for S4 and S6 peptides are the mean of two independent assays.

Figure 4. Dose response curve of BNT162b2 vaccine recipient serum in relation to peptides S4, S5 and S6. Optical density at 450 nm (intensity values) of BNT162b2 recipient serum sample in relation to S4, S5 and S6 peptides tested in a dose-response curve through a peptide-based ELISA. The S5 peptide served as a negative peptide control.

Figure 5. Reactivity of BNT162b2 vaccine recipient serum in relation to S peptides at different times post-prime boost. Optical density at 450 nm (intensity values) of BNT162b2recipient serum samples (dilution 1:50) collected 2 and 8 weeks after the prime- boost in relation to recombinant rN and rRBD antigens (left graph) and SI to S6 peptides (right graph) through a peptide-based ELISA.

Figure 6. Reactivity of serum samples from a COVID-19 patient immunized with BNT162b2 vaccine in relation to S peptides. Serum samples were obtained from a diagnosed COVID-19 patient that received the BNT162b2 mRNA vaccine three months after disease recovering. Optical density at 450 nm (intensity values) of serum samples (dilution 1:50) collected few weeks after COVID-19 disease recovering (post-infection) and two weeks after inoculation of a single dose of BNT162b2 vaccine (post-vaccination) in relation to recombinant rN and rRBD antigens (left graph) and SI to S6 peptides (right graph) through a peptide-based ELISA.

Figure 7. Antigenic reactivity of S peptides in relation to SARS-CoV-2 donor sera. A group of ten SARS-CoV-2 donor serum samples at dilution 1:50 were assayed for the detection of antibodies against SI to S6 peptides and their mutants S1^V3, S3^V2, ad S5^V1, through a peptide- ELISA. A serum sample diagnosed negative for SARS-CoV-2 infection served as a negative serum control. The intensity values of serum samples were measured at O.D. 450 nm and the antigenic reactivity was estimated as a fold increase of intensity values obtained with the negative control serum.

Figure 8. Immune reactivity of mouse antibodies raised against B-cell epitope peptides. In

(A), serum samples from mice (n = 5) that received the KLH-peptide conjugates were assessed for peptide-reactive antibodies through peptide-based ELISA using the synthetic S4, S5, and S6 peptides (200 ng.mL^-1) for antigen-based antibody capture. The pre-immune serum of each individual that received the KLH-peptide conjugates was tested. The intensity values of serum samples at dilution 1:50 were measured at O.D. 450 nm. Paired t tests between pre-immune serum and KLH-peptide serum were performed (ns: non-statistically significant, p > 0.05). The results are representative of two independent experiments. In (B), synthetic peptide-based ELISA using the S6 and S6.2.0 (control peptide) peptides (200 ng.mL^-1) for peptide-based antibody capture. At the left, pre-immune and immune serum samples of an immunized mouse with KLH-S6 conjugates. At the right, serum samples from a COVID-19 immune subject collected after recovery (post-infection) and after injection of a single dose of BNT162b2 vaccine (vaccination). Synthetic S5 peptide served as negative peptide control. The intensity values of serum samples in a dose-curve response were measured at O.D. 450 nm.

Figure 9. Conjugation of SFP.S6 peptide on GNPs. GNPs were mixed with increasing concentrations of synthetic SFP.S6 peptide and colloidal solutions were examined by LSPR and flocculation test. The green GNPs functionalized with 25 pg.mL ¹ SNP.S6 peptide or not were characterized by UV-Vis spectra (A) and DLS (B).

Figure 10. Antibody response against GNP-SFP.S6 peptide conjugates. In (A), serum from mice (n = 10) that received GNP-SFP.S6 peptide conjugates were collected after the first or second antigenic boost, and assessed by peptide-based ELISA using synthetic S6 peptide. The synthetic S6.2.0 peptide served as control peptide. The pre-immune mouse sera served as serum controls. The intensity values of serum samples at dilution 1:50 were measured at O.D. 450 nm. Statistically significant differences were found (** p < 0.01, *** p < 0.001). In (B), ISR values were calculated on serum samples ( n = 8) collected after the second boost and showing significant positive reactivity with S6 peptide.

Figure 11. Reactivity of GNP-SFP.S6 peptide antibody against SARS-CoV-2. A549^ACE2+

TMPRSS2+ _ce||_{s were} infected 24h by SARS-CoV-2 or mock-infected (no virus). In (A), immunostaining by IF analysis of virus-infected cells using specific anti-SARS-CoV-2 spike antibody. The nuclei were stained by DAPI. In (B), immunoblot assay on cell lysate using GNP- SFP.S6 peptide antibody at dilution 1 :200. KLH-S6 peptide antibody served as positive control. The pre-immune mouse sera served as control serum b-tubulin served as protein loading control.

Figure 12. Immunostaining of SARS-CoV-2 spike protein by GNP-SFP.S6 peptide antibody. In (A), IF analysis on A549^ACE2+ ™^PRSS2+ cells infected 24h by SARS-CoV-2 using pre-immune mouse serum or GNP-SFP.S6 peptide antibody at dilution 1:100. In (B), HEK- 293T cells transfected 24h with pcDNA3/rSOmicron BA.2 were co-labeled with anti-FLAG antibody at dilution 1:500 and pre-immune serum or GNP-SFP.S6 peptide antibody at dilution 1:100.

EXAMPLE 1:

Methods

Synthetic SARS-CoV-2 S peptides

The synthetic peptides SI to S6 representing potential linear B-cell epitopes into the S protein of SARS-CoV-2 (UniprotKB-P0DTC2 (SPIKE_SRAS2)) and their mutants S1^V3, S3^V2, and S5^V1 were chemically synthesized by Genecust (Boynes, France). The peptides sequences and their position on S protein are indicated in the table below. Peptides were dissolved in DMSO at concentration of 10 mg.mL ¹ and then diluted in sterile FbO at the final concentration 1 mg.mL ¹ The stock peptide solutions were stored at -80°C. Working peptide solutions at the final concentration 0.2 mg.mL ¹ in sterile FbO were stored at -80°C. Table 1: sequences of synthetic peptides and their variants

variant 20J/501Y.V3 (P.1, Brazil) variant 20H/501Y.V2 (B.1.351, South Africa)

*** variant 20I/501Y.V1 (B.l.1.7, U.K.) *_{* * *} gg epitope is underlined

Expression of recombinant SARS-CoV-2 proteins in mammalian cells Mammalian-codon-optimized genes coding either for the SARS-CoV-2 N protein or the RBD domain of S (residues 319 to 541) preceded by a heterologous signal peptide and followed by a tag protein were inserted in a plasmid vector (Frumence et al., J Virol. Methods 495, 113082, 2021). Briefly, CHO cells were transfected with recombinant plasmids which contain the genes encoding soluble forms of N (rN) or RBD (rRBD) using transfectant reagent. The supernatants of transfected CHO cells for 48 or 72h were collected and a clarified cell supernatant (CCS) was obtained by centrifugation at 1,000 x g for 10 min at room temperature.

ELISA methods

For indirect ELISA using recombinant soluble rN and rRBD proteins as antibody capture antigens, a 96-well plate was coated with 0.1 ml of CCS of each protein at dilution 1 : 10 in PBS at 4°C overnight. For peptide-based ELISA, a 96-well plate was coated with 0.1 ml of peptide at final concentration of 200 ng.mL ¹ in PBS at 4°C overnight. At the end of incubation period, the peptide solution was discarded, the wells were washed with PBS supplemented with 0.01% Tween-20 (PBST) and then incubated with a commercial ELISA blocking agent (EBA) at room temperature (RT) for 1 h. After washing with PBST, the wells were incubated with human serum sample at final dilution 1 :50 in EBA at 37°C for 2 h. After washing with PBST, the wells were incubated with goat anti -human IgG-HRP at final dilution 1:2,000 in EBA at room temperature for 1 h. After washing with PBST and PBS, the wells were incubated with TMB substrate solution at RT for 3 min and the reaction was stopped with acidic stopping solution. The absorbance measurement was performed at 450 nm.

Serum samples

A group of ten selected serum samples from patients with SARS-CoV-2 infection or uninfected individuals was kindly provided by Dr B. Roquebert from Cerba laboratory (Saint-Ouen- FAumone, France). The immune sera were initially tested using available commercial serodiagnosis kits in mid-2020. Serum samples from a vaccinated individuals with BNT162b2 vaccine from Pfizer with one or two doses spaced one month were available. The BNT162b2 vaccine recipient with two doses in a prime-boost immunization had been diagnosed negative for COVID-19 one month prior the first injection of encapsulated mRNA vaccine whereas the vaccinee with a single dose had been diagnosed positive for COVID-19 infection with moderate clinical symptoms three months prior vaccine injection.

Results

Detection of RBD-reactive antibodies in a BNT162b2 vaccine recipient serum A serum sample obtained from a recipient of SARS-COV-2 donor vaccine (Comimaty also named BNT162b2, Pfizer), two weeks post-immunization (two doses), was assessed for its ability to react with major viral antigens. Consequently, recombinant proteins representing N (rN) or the RBD (rRBD) domain of SI subunit of S were expressed in mammalian cells using a plasmid vector (Frumence et ak, ./. Virol. Methods 495, 113082, 2021). Cell lysates expressing rN or rRBD were used as antibody capture antigens in indirect ELISA (Figure 1). The reactivity of BNT162b2 vaccine serum with rN and rRBD was compared to a group of SARS-CoV-2 donor sera through indirect ELISA. A serum sample from an individual who had been diagnosed negative for SARS-CoV-2 infection served as a negative control serum. As shown in Figure 1. most of SARS-CoV-2 donor sera have ability to recognize both rN and rRBD proteins. BNT162b2 vaccine serum sample was reactive with rRBD but not rN consistent with the finding that vaccine recipient has been immunized with encapsulated mRNA vaccine encoding SARS-CoV-2 S protein. The lack of reactivity with rN confirms the lack of previous SARS-CoV-2 infection in the individual that has received the BNT162b2 vaccine. Thus, the BNT162b2 vaccine serum sample is suitable for detection of linear epitope-reactive antibodies in an individual immunized with an encapsulated mRNA-based vaccine coding for SARS-CoV- 2 S protein.

Potential linear B-cell epitopes into SARS-CoV-2 S protein

To predict peptides with intrinsic potential of being B-cell epitopes, we have used a predictor tool available in IEDB website. The predictor tool BepiPred-2.0 can generate a final score for potential B-cell epitopes and we have submitted the S protein of SARS-CoV-2. By using BepiPred-2.0 method, we have identified six linear amino-acid sequences as potential S antibody epitopes (Figure 2). Most of them were located into NTD, RBD, and SD 1/2 sequences of the SI subunit whereas one has been found at the interface of the CD and HR2 sequences of the S2 subunit. The peptides SI to S6 representing the six potential linear antibody epitopes in the S protein of SARS-CoV-2 were chemically synthesized. The S1^V3, S3^V2, and S5^V1 peptide mutants bearing amino-acid substitutions as observed in the new SARS-Co-V2 variants 20I/501Y.V1, 20H/501Y.V2, and 20J/501Y.V3 were also generated.

Antigenic reactivity of the S peptides in relation to BNT162b2 vaccine recipient serum We examined the antigenic reactivity of the six S peptides and their three mutants in relation to the BNT162b2 vaccine serum through peptide-based ELISA (Figure 3). There was no antigenic reactivity of SI, S1^V3, S2, S3, S3^V2, S5, and S5^V1 peptides with BNT162b2 vaccine serum. In contrast, the immune serum has peptide-reactive antibodies raised against S4 and at lesser extent, S6. Thus, the S4 peptide representing the amino-acid residues S616-644 and the S6 peptide representing the amino-acid residues SI 138-1169 compose two potential linear B-cell epitopes into the SARS-CoV-2 S protein expressed by the BNT162b2 mRNA vaccine.

A dose-response curve revealed that individual inoculated in prime-boost with BNT162b2 vaccine developed anti-S4 and anti-S6 antibody titers reaching of about 200-400, two weeks after the second dose of vaccine (Figure 4).

As shown in Figure 5. anti-S4 and anti-S6 peptide antibodies in BNT162b2 recipient serum were still detected 2 months after the prime-boost. We noted that the antibody titers were lower 2 months after the second dose as compared to 2 weeks indicating that amounts of anti-SARS- CoV-2 S antibodies declined in individuals vaccinated with the BNT162b2 mRNA vaccine.

We next examined the antigenic reactivity of the six S peptides in relation to a serum from a COVID-19 patient receiving a single dose of BNT162b2 mRNA vaccine spaced of three months after disease recovering. As expected, immunization with BNT162b2 resulted in a significant increase of anti-RBD antibodies but not anti-N antibodies in recovered COVID-19 patient (Figure 6). By peptide-based ELISA, high titers of anti-S4 and anti-S6 antibodies were detected in BNT162b2-immunized COVID-19 patient. Whereas the mRNA vaccine boosted the antibody production against the S6 peptide in BNT162b2-immunized COVID-19 patient, anti-S4 peptide antibodies were readily detected in the recipient serum sample only after vaccination but not in response to SARS-CoV-2 infection (Figure 6). As such result indicates that the sequence that compose the residues SI 138-1169 (S4 peptide) at the junction of CD domain and HR2 motif is recognized as linear B-cell epitope into the authentic S protein. The fact that anti-S4 peptide antibodies can be easily detected into an individual once immunized with BNT162b2 but not in response to a natural SARS-CoV-2 infection confirms that the residues S616-644 from the SD1/2 of the SI subunit compose a B-cell epitope only in the stabilized pre-fusion S protein expressed by the encapsulated mRNA vaccine BNT162b2 purchased by Pfizer. It is important to note that injection of a single dose of BNT162b2 vaccine is sufficient to induce a high level of peptide S4-reactive antibodies (Figure 6).

Reactivity of the S peptides in relation to SARS-CoV-2 donor sera

The results above prompted us to assess the antigenic reactivity of SI to S6 peptides and their three mutants in relation to a group of ten SARS-CoV-2 donor sera through peptide-based ELISA (Figure 7). A low variability was observed between the SARS-CoV-2 donor sera regardless the S peptide tested. The antigenic reactivity of the S peptides including S4 was very weak or lacking in relation to SARS-CoV-2 donor sera. As already observed, the COVID-19 patients developed high titers of S6 peptide-reactive antibodies suggesting that the sequence that compose the residues SI 138-1169 at the junction of CD domain and HR2 motif is recognized as linear B-cell epitope into the authentic S protein.

Conclusions:

In the present study, we have noted that immunization with encapsulated mRNA vaccine BNT162b2 can generate peptide-reactive antibodies targeting the residues S616-644 and SI 138-1169 of SARS-CoV-2. Both 29- and 32-mer synthetic S4 and S6 peptides representing the sequences S616-644 and SI 138-1169, respectively, exhibited an antigenic reactivity in relation to a BNT162b2 vaccine recipient serum. The residues S616-644 are located in two structurally conserved subdomains SD1 and SD2 downstream of the RBD and upstream of the putative furin-cleavage site RRAR (Figure 2). The residues SI 138/1169 are positioned at the junction of the CD and the HR2 at the C-terminal region of S2 subunit. Peptide-reactive antibodies targeting the residues SI 138-1169 were readily detected in two from ten SARS- CoV-2 donor sera as well as BNT162b2 vaccine recipient serum indicating that these amino- acids are recognized as a linear B-cell epitope in COVID-19 patients and BNT162b2 vaccinees.

In contrast to what it has been observed with the residues SI 138-1169, the ability of a synthetic peptide representing the residues S616-644 to be recognized by anti-S antibodies was effective only following immunization with BNT162b2vaccine whereas no antigenic reactivity was observed with a COVID-19 patient serum. Thus, the stabilized pre-fusion S protein expressed by the encapsulated mRNA vaccine would be able to induce antibodies against the S4 sequence. It is of note that stabilization of the S protein in a pre-fusion state relates to the two amino-acid substitutions S-K986P and S-V987P in BNT162b2 vaccine. The 29-mer synthetic peptide representing the residues S616-644 could be used as diagnosis tool for the capture of specific antibodies in serum of individual that received the encapsulated mRNA BNT162b2 vaccine.

Taken into consideration with the singularity of the synthetic peptide representing the residues S616-644 of SARS-CoV-2, a such peptide could be a major interest in the design of a peptide- based diagnosis assays for the screening of individuals immunized with the commercially available S-based mRNA vaccine BNT162b2 purchased by Pfizer. The synthetic peptides representing the residues S-672/690 and S-l 138/1169 might serve as negative and positive peptide controls for peptide-based serological diagnosis assays, respectively. It has been reported that a human monoclonal antibody (mAh) was capable of reacting with the residues KEELDYFK (SEQ ID NO:15) inside of the sequence SI 138-1169. A such mAh can prevent SARS-CoV-2 infection in blocking the fusion process between viral and host-cell membranes. So far, it is not known if the BNT162b2 vaccine-associated B-cell epitope that compose the residues S616-644 has ability to influence SARS-CoV2 infectivity. It is therefore of priority to evaluate whether the 29-mer synthetic peptide

NCTEVPVAIHADQLTPTWRVYSTGSNVFQ (SEQ ID NO:7; hereafter entitled pept^S616 ⁶⁴⁴) representing the residues S616-644 and the 32-mer synthetic peptide YDPLQPELDSFKEELDKYFKNHTSPDVDLGDI (SEQ ID NO: 10; hereafter entitled pept^sil38-n⁶⁹) _conjugated to nanoparticles (NPs), or fused to an immunogenic protein carrier such as KLH have ability to induce anti-SARS-CoV-2 antibodies. The HLA-binding epitope PADRE (AKFVAAWTLKAAA; SEQ ID NO: 11) that activates antigen specific CD4+ T-cell response could be used as agonist adjuvant for increasing immunogenicity of both pept^{S616 644} and pept^{S1138 1169} conjugated to nanoparticles (Alexander et al., ./. Immunol. 164, 1625-33, 2000). After the internalization of conjugated NPs into the host-cell, the PADRE-pept^S616-644 and PADRE-pept^{sl 138-1169} are possibly released from NPs due to a furin-like cleavage motif such as RARKRR (SED ID NO:12) at the junction of NPs-PADRE/peptides. The releasing of PADRE-pept^S616-644 and PADRE-pept^S1138-1169 from NPs elicits adaptive immune response against the free S peptides.

Such a peptide-based vaccine strategy will provide an important information on the exact contribution of the residues S616-644 and SI 138-1169 in the protective efficacy of encapsulated mRNA BNT162b2 vaccine against SARS-CoV-2.

EXAMPLE 2: Immunogenicity of synthetic S4 and S6 peptides in mice Methods

Mouse experiment and ethical statement

The Animal Ethics Committee of CYROI n°114 approved all the animal experiments with reference APAFIS#32,599-2021060109058958v2 (July 2021). All animal procedures were performed in accordance with the European Union legislation for the protection of animals used for scientific purposes (Directive 2010/63/EU). The study was conducted following the guidelines of the Office Lab-oratory of Animal Care (agreement n° 974001 A) at the Cyclotron and Biomedical Research CYROI platform, Sainte-Clotilde, La Reunion, France and in accordance with the ARRIVE guidelines (https:// arriveguidelines. org). Three groups of five 6-week-old female BALB/cJRj mice (Janvier Labs, France) were hosted in individually ventilated plastic cages (5 animals per cage) under 50-60% humidity and 22-25 °C temperature in a 12/12-h light dark cycle. Food and drinking were provided ad libitum. The adult BALB/cJRj mice (Janvier Labs, France) were s.c. inoculated with KLH-peptide conjugates in complete Freund’s adjuvant (Sigma, France). The protein-peptide conjugate samples in a final volume of 0.1 ml were distributed over two injection sites. Immunized mice were boosted with the same protein-peptide conjugate in incomplete Freund’s adjuvant at Days 7 and 21 after primary immunization (Day 0). Two weeks after the last immunization, retro-orbital blood sampling was per-formed in anesthetized mice. All animals were daily observed to detect any stress or suffering.

Results

To evaluate the in vivo immunogenicity of the two B-cell epitope peptides recognized by the BNT162b2 vaccine recipient sera, the synthetic S4 and SS6 peptides were N-terminally coupled to Keyhole Limpet Hemocyanin (KLH) protein carrier. The protein-peptide conjugates were assessed with serum sample from a COVID-19 immune subject who received BNT162b2 vaccine. The KLH-S5 served as protein-peptide conjugate control. The antigenic reactivity of KLH-S4 and KLH-S6 conjugates was verified by indirect ELISA using a BNT162b2 vaccine recipient serum (data not shown). The antigenic reactivity of protein-peptide conjugates was comparable to that observed with synthetic S4 and S6 peptides (data not shown) confirming that both KLH-S4 and KLH-S6 are suitable for further experiments.

To assess the immunogenicity of KLH-peptide conjugates in inbred laboratory mice, three groups of adult BALB/c mice were subcutaneously (s.c.) inoculated with 20-30 pg of KLH- S4, KLH-S5 or KLH-S6 conjugates in a prime-boost schedule. Immune sera were collected two weeks after the third immunization. The ability of the protein-peptide conjugates to elicit antibody response in mice was assessed by indirect ELISA using protein-peptide conjugates for antigen-mediated antibody capture. Immunization with KLH-S4 and KLH-S6 conjugates but not KLH-S5 conjugate elicited a strong antibody response against protein-peptide conjugates (data not shown). To evaluate the ability of the KLH-peptide conjugates to elicit antibody production of relevant specificity, individual mouse immune sera were tested on the synthetic S4, S5, and S6 peptides through a peptide-based ELISA (Figure 8A). Mouse pre-immune serum served as control serum. Most of BALB/c mice (n = 5) that received KLH-S6 conjugates developed S6 peptide-reactive antibodies with a median O.D.450 nm value about 2.0 at serum dilution 1:50 (Figure 8A). In contrast, the KLH-S4 conjugates were poorly immunogenic in BALB/c mice whereas KLH-S5 conjugates were inefficient to elicit a significant production of specific antibodies. The immunogenicity of the synthetic S6 peptide reinforces the notion that the linear B-cell epitope peptide which is delimited by the spike residues 1138/1169 in recombinant SARS-CoV-2 spike protein would be a feature of the Pfizer-BioNTech COVID- 19 vaccine BNT162b2. A tridimensional structure prediction of the synthetic S6 peptide suggests that the amino-acids 10 to 21 (spike residues 1147/1157) could form a-helix (data not shown). The identified a- helix might act as potential binding site which enables the antibody recognition of synthetic S6 peptide. This prompted us to evaluate whether anti-S6 antibodies could target a truncated form of the synthetic S6 peptide. Consequently, we developed a 19-mer synthetic S6.2.0. peptide containing the amino-acids 10 to 28 of the B-cell epitope S6 peptide (Table 1). By peptide- based ELISA, we observed a lack of antigenic reactivity of synthetic S6.2.0 peptide with a mouse immune serum wherein the S6 peptide-reactive antibody concentration was high and also serum sample from COVID-19 immune subject who received a single dose of BNT162b2 vaccine after recovery (Figure 8B). Thus, the motif ¹¹⁴⁷SFKEELDKYFKNHTSPDVD¹¹⁶⁵ (SEQ ID NO: 16) is not sufficient for the antibody recognition. Given that binding capability of the linear B-cell epitope S6 peptide was completely lost when the nine N-terminal and four C-terminal amino-acids were deleted, it may be inferred that motifs ¹¹³⁸YDPLQPELD¹¹⁴⁶ (SEQ ID NO: 17) and ¹¹⁶²LGDI¹¹⁶⁵ (SEQ ID NO: 18) are potentially critical residues for epitope-antibody interaction.

EXAMPLE 3: Gold nanoparticles functionalized with SFP.S6 peptide elicit antibodies reactive with SARS-CoV-2 spike protein

Nanoparticle vaccine platforms play a key role in the threat against COVID-19 disease caused by SARS-CoV-2. Immune sera from individuals who received nanoparticle-encapsulated COVID-19 mRNA Comirnaty vaccine produce antibodies capable of binding to a linear antibody epitope designed S6 delineating SARS-CoV-2 spike residues 1138 to 1169. In the present study, we evaluated whether gold nanoparticles (GNPs) that have been synthesized using a green process and then functionalized with a synthetic peptide including the S6 epitope can generate specific antibody response against the spike protein. Adult mice were inoculated with peptide-functionalized GNPs without adjuvant by intramuscular route in a prime-boost schedule. Immunoblot and immunofluorescence assays demonstrated that immunized mice developed antibodies capable of binding to SARS-COV-2 spike protein. From our data, we propose that peptide-functionalized GNPs would be a great interest in the development of serological tools for the surveillance of SARS-CoV-2 variants and future emerging coronaviruses with epidemic potential. Methods

Cells, viruses and antibodies

Human lung epithelial A549^ACE2+ _’ ™^PRSS2+ _cell line overexpressing human ACE2 and TMPRSS2 proteins was purchased from Invivogen (Toulouse, France). A549^ACE2+’ ™^i>RSS2_ cells, human epithelial HEK-293T cells and human hepatoma Huh 7.5 cells were grown in Dulbecco’s modified Eagle’s medium (DMEM) growth medium supplemented with heat- inactivated 10% fetal calf serum and antibiotics. A549^ACE2+’ ™^PRSS2+ cells were infected with La Reunion 2020 SARS-CoV-2 isolate at the multiplicity of infection 0.001. Huh 7.5 cells were infected with HCoV-229E virus (a generous gift of V. Thiel, University of Ziirich and K. Seron, Institut Pasteur Lille) at the multiplicity of infection 0.2. Anti-SARS-CoV-2 spike antibody covrbdc2-mabl was obtained from Invivogen (Toulouse, France). Anti-dsRNA antibody J2 obtained from Abeam (Paris, France) was used to detect HCoV-229E virus. Rabbit anti-FLAG antibody obtained from DIAGNOMICS (Blagnac, France) was used to detect recombinant SARS-CoV-2 spike protein. Donkey anti-rabbit IgG-Alexa Fluor 488 and donkey anti-mouse IgG-Alexa Fluor 594 obtained from Thermo Fisher Scientific (Les Ulis, France) were used as secondary antibody for IF analysis.

Recombinant SARS-CoV-2 spike protein

Mammalian codon-optimized gene coding for a soluble spike protein (residues 1 to 1195) from Omicron BA.2 variant SARS-CoV-2 (Genbank access UJE45220.1) was established using Homo sapiens codon usage as reference. A sequence encoding the GCN4-IZ trimerization domain followed by a glycine-serine spacer and a FLAG tag was inserted in frame at the C- terminus of recombinant soluble _rs^{0mcronBA 2} protein. The residue substitutions at positions S- 986 and S-987 with two proline led to a prefusion stabilized _rs^{0micron BA 2} protein. The residue substitutions at positions S-682, S-S683, and S-685 with three alanine led to remove the furin like cleavage site at the Sl/Sl subunit boundary. The synthesis of gene sequence and their cloning into Nhe-I and Not-I restriction sites of the pcDNA3.1 Hygro (+) vector plasmid to generate recombinant pcDNA3/ _rsOmⁱcron BA.2 _were p_erf_ormecj by Genecust (Boynes, France). The plasmid sequence was verified by Sanger method. HEK-293T cells were transiently transfected with pcDNA3/ rS^0mic'^{on BA 2} using Lipofectamine 3,000 (Thermo Fosher Scientific, les Ulis, France). Conjugation of synthetic peptide to green GNPs

All the synthetic peptides were chemically synthetized by Genecust (Boynes, France). The peptides were dissolved in DMSO and then diluted in sterile H20 as previously described (see Examples 1 and 2). The gold nanoparticles (GNPs) were synthesized by green method as previously described (Morel AL. et al., Front. Lab. Med. 2017). To determine the optimal peptide concentration for binding to GNPs, the colloids were mixed were increasing peptide concentrations for 2h at room temperature. To check the completeness of the peptide conjugation, equal volume of 10% NaCl was added 24h later and UV-Vis spectrum of the mixture was measured. Once optimal peptide concentration was defined, the bioconjugation reaction was scaled up and the colloidal solution was freed from excess free peptide by centrifugation at 10,000 g for 20 min at 4 °C. The pellet of GNP -peptide conjugates was resuspended in DPBS and the particle size in colloidal solution was measured by dynamic light scattering (DLS) using a Zetasizer Nano ZS (Malvern Instruments, Malvern, UK). The colloidal solution was stored in DPBS supplemented with 0.01% Tween-20. Before immunization, the GNP -peptide conjugates were twice washed with sterile DPBS.

Mouse experiment and ethical statement

Groups of five 6-week-old female BALB/cJRj mice (Janvier Labs, France) were inoculated with GNP-SFP.S6 peptide conjugates in 0.1 ml sterile DPBS by intramuscular (i.m.) route over two injection sites. Mice that received 5 pg of GNP-SFP.S6 peptide conjugates were boosted two weeks after primary immunization. Retro-orbital blood sampling was performed on anesthetized mice two weeks after the boost. A third dose of GNP-SFP.S6 peptide conjugates was inoculated one month after the first boost. One month after the second boost, blood sampling was performed on anesthetized mice. All animals were daily observed to detect any stress or suffering. No morbidity was observed in mice that received colloidal solution by i.m. route. As an immunogenic control, adult BALB/cJRj mice were inoculated with synthetic S6 peptide conjugated to protein carrier keyhole limpet hemocyanin (KLH) in complete Freund’s adjuvant by i.m. route. Mice that received 20 pg of KLH-peptide conjugates were boosted three times after primary immunization. One month after the last immunization, blood sampling was performed on anesthetized mice. The Animal Ethics Committee of CYROI n°l 14 approved all the animal experiments with reference APAFIS#32599-2021060109058958v2 (July 2021). The animal procedures were performed in accordance with the European Union legislation for the protection of animals used for scientific purposes (Directive 2010/63/EU). The study was conducted following the guidelines of the Office Laboratory of Animal Care (agreement n° 974 001 A) at the Cyclotron and Biomedical Research CYROI platform, Sainte-Clotilde, La Reunion, France and in accordance with the ARRIVE guidelines (https://arriveguidelines. org).

Peptide-based ELISA method

The peptide-based ELISA tests were essentially performed as previously described (see Examples 1 and 2). Briefly, a 96-well plate was coated with 0.1 ml of synthetic S6 or S6.2.0 peptide at final concentration of 0.2 pg.mL- l at 4°C overnight. The wells were incubated with mouse serum sample at 37°C for 2h and then anti-mouse IgG HRP -conjugated secondary antibody at final dilution 1:2,000 at room temperature for lh. The wells were incubated with TMB substrate solution at RT for 3 min. Absorbance was measured using microplate reader at 450 nm. The Immune Status Ratio (ISR) was obtained by dividing the S6 peptide OD450 values by the negative control S6.2.0 peptide OD450 values. The end-point titers of peptide-directed antibodies were calculated as the reciprocal of the last dilution of serum having ISR value > 10.

Immunoblot assay

The immunoblot assay was essentially performed as previously described (Ogire E. et al., Int. J Mol. Sci. 2021). Briefly, cells were lysed in RIPA lysis buffer (Sigma, Lyon, France. Proteins were separated by SDS-PAGE and transferred into a nitrocellulose membrane. Blots were incubated with mouse immune serum at dilution 1:200 and then anti-mouse IgG HRP- conjugated secondary antibody. The membranes were revealed with ECL detection reagent (Thermo Fisher Scientific, ILs Ulis, France) and exposed on an Amersham imager 680 (GE Heathcare).

Immunofluorescence assay

Indirect immunofluorescence (IF) assay was essentially performed as previously described (Vanwalscappel B. et al., Int. J. Mol. Sci. 2019). Cells grown on coverslips were fixed with 3.7% paraformaldehyde for 20 min and then permeabilized with 0.1% Triton X-100 in PBS for 4 min. Cells were stained with mouse immune serum at dilution 1:100 and the incubated by anti-mouse Alexa Fluor 488 IgG secondary antibody. The nucleus was stained with DAPI. Cells were visualized with a Nickon Eclipse E-2000-U microscope (Nikon, Lisses, France).

Statistical analysis

Paired t tests were used to compare quantitative data. GraphPad Prism 9 was used for all statistical analysis. Results

Functionalization of green GNPs with synthetic SFP.S6 peptide

GNPs obtained by a green process (Morel AL. et al., Front. Lab. Med. 2017) were functionalized with a 54-mer synthetic peptide designed as SFP.S6 (Table 1). The C-terminal part of synthetic SFP.S6 peptide corresponds to S6 peptide epitope delineated by the spike residues 1138 to 1169 in the C-terminal region of the S2 subunit. The peptide epitope is preceded by the pan-DR helper T-lymphocyte epitope (PADRE) AKFVAAWTLKAAA (SEQ ID NO: 11) acting as T-helper cell response activator. PADRE sequence and viral peptide epitope are separated by a dibasic peptide. The N-terminal part of the SFP-S6 peptide corresponds to polybasic peptide RARKRR (SEQ ID NO: 12). Following internalization of peptide-functionalized GNPs into the cytoplasm, the RARKRR (SEQ ID NO: 12) sequence at the GNP core-peptide junction can be subjected to a proteolytic process releasing immobilized PADRE-S6 fusion peptide from the GNP surface. The conjugation of synthetic peptide to GNPs involves the formation of a covalent bond between GNP surface and free sulfhydryl group from thiolated polyethylene glycol SH-(CH)₂-CO-(PEG)₅ compound that has been linked to the first N-terminal amino-acid of peptide (Table 1).

The small sized GNPs present the advantageous of biocompatibility, high surface ratio to volume ratio, and to be internalized as inert compound (Morel AL. et al., Front. Lab. Med. 2017). Consequently, 15 nm-sized green GNPs were conjugated with synthetic SFP-S6 peptide (Figure 9). The conjugation was monitored by the Localized Surface Plasmon Resonance (LSPR) band as indicator for colloidal stability. A redshift from original colloid spectrum (i.e., free GNPs) was observed at synthetic SFP-S6 peptide concentrations up to 2 mM (data not shown). A flocculation test in presence of high salt concentrations indicated that conjugation of 5 pM synthetic SFP-S6 peptide to green GNPs gave optimal peptide-nanoparticle surface ratio of 1015 (data not shown). The conjugation of 4 pM peptide to green GFP resulted to a 5 nm shift by LSPR (Figure 9A) and increased hydrodynamic diameter from 58 to 65 nm by DLS without any aggregation (Figure 9B). GNPs were functionalized with 5 pM synthetic SFP-S6 peptide to produce GNP- SFP.S6 peptide conjugates that have been stored in DPBS at 4°C for further experiments.

Antibody response in mice immunized with GNP-SFP.S6 peptide conjugates

Adult BALB/c mice (n=10) were inoculated with 5 pg green GNP-SFP.S6 conjugates in sterile

DPBS by intramuscular (i.m) route and without any adjuvant in a prime-boost schedule. Repeated administrations of GNP-SFP.S6 conjugates had no effect on safety of B ALB/c mice. Mice were bled two weeks after the prime-boost and four weeks after a second dose. Individual mouse immune sera were tested on synthetic S6 peptide representing the SARS-CoV-2 spike residues 1138 to 1169 through a peptide-based ELISA (Figure 10). The shorter synthetic S6.2.0 which lacks of antigenic reactivity with S6 peptide-reactive antibodies was used as peptide control (Table 1) (See Examples 1 and 2). The pre-immune serum samples showed no reactivity with synthetic peptides (Figure 10A). Immunized BALB/c mice that received a single booster dose had detectable S6 peptide-reactive antibodies (Figure lOA) After a second booster dose, the anti-S6 antibody titers significantly increased ranging from 400 to 1600 with a mean titer of 800 (Figure 10B). Thus, mice that received green GNPs functionalized with SFP.S6 peptide developed high levels of antibodies that are reactive with the synthetic S6 peptide.

The reactivity of antibodies raised in mice after immunization with GNP-SFP.S6 conjugates was assessed on A549^ACE2+’ ™^PRSS2+ cells infected by SARS-CoV-2 (Figure 11). Expression of spike protein in infected cells was verified by IF analysis using antibody of relevant specificity (Figure 11 A). Immunoblot assay demonstrated that a mouse immune serum with specific antibody titer of 800 can recognize SARS-CoV-2 spike protein (Figure 1 IB) The pattern of antibody reactivity was comparable to that of BALB/c mice that received KLH-S6 peptide conjugates. Immunostaining of A549^ACE2+’ ™^PRSS2+ cells infected by SARS-CoV-2 was effective with antibodies raised in mice after immunization with GNP-SFP.S6 peptide conjugates (Figure 12 AT The lack of reactivity on alphacoronavirus HCoV-229E highlights the specificity of antibody response induced by the GNP-SFP.S6 peptide conjugates (data not shown). The ability of S6 peptide-reactive antibodies to recognize the spike protein of newly identified SARS-CoV-2 variant was tested by IF analysis on HEK-293T cells transfected with a plasmid overexpressing the spike protein of Omicron BA.2 (_rS^{0micron BA}-²) (Figure 12B). Immunostaining of _rs^{0micronBA 2} _was efficient using immune serum of mice that received GNP- SFP.S6 peptide or KLH-S6 peptide conjugates. These results showed that green GNPs functionalized with synthetic SFP.S6 peptide have ability to generate a high level of specific antibody response against SARS-CoV-2 spike protein.

REFERENCES:

Throughout this application, various references describe the state of the art to which this invention pertains. The disclosures of these references are hereby incorporated by reference into the present disclosure.

Claims

CLAIMS:

1. A peptide derived from the spike protein of SARS-CoV-2 that consists of the sequence as set forth in SEQ ID NO: 7 (N C TE VP V AIH ADQLTPTWR V Y S T GSN VF Q) (“S4 or S616-644 peptide”) or SEQ ID NO: 10

(YDPLQPELDSFKEELDKYFKNHTSPDVDLGDI) (“S6 of Sii38-ii69 peptide”).

2. A conjugate wherein the peptide of claim 1 is conjugated or fused to a heterologous polypeptide.

3. The conjugate of claim 2 wherein the heterologous polypeptide is fused to the peptide of claim 1 to form a fusion protein.

4. The conjugate of claim 2 or 3 wherein the heterologous polypeptide consists of a pan- DR binding peptide.

5. The conjugate of claim 4 wherein the pan-DR binding peptide consists of a PADRE sequence (SEQ ID NO: 11).

6. The conjugate of claim 4 wherein the pan-DR peptide consists of the sequence as set forth in SEQ ID NO: 19.

7. The conjugate of claim 2 or 3 wherein the heterologous polypeptide comprises a cleavable sequence.

8. The conjugate of claim 7 wherein the cleavable sequence comprises the furin recognition site as set forth in SEQ ID NO: 12 (RARKRR).

9. A fusion protein that consists of the amino acid sequence as set forth in SEQ ID NO: 13

(RARKRRAKFVAAWTLKAAARR NCTEVPVAIHADQLTPTWRVYSTGSNVFQ) or SEQ ID NO: 14 (RARKRRAKFVAAWTLKAAARR

YDPLQPELD SFKEELDKYFKNHT SPD VDLGDI) .

10. A nanoparticle that is conjugated to the peptide of claim 1, to the conjugate of claim 2 or to the fusion protein of claim 9.

11. The nanoparticle of claim 10 that is a gold nanoparticle (AuNP).

12. The gold nanoparticle of claim 11 conjugated with the fusion protein that consists of the amino acid sequence as set forth in SEQ ID NO: 14.

13. A method for detecting the presence of coronavirus-specific antibodies in a subject comprising the steps of: a) placing a sample obtained from the subject, in a single assay receptacle, in the presence of the peptide(s) of claim 1, b) incubating the mixture under conditions which allow the formation of immunocomplexes on said peptide(s), c) eliminating the immunoglobulins which have not bound to the peptide(s), and d) detecting the immunocomplexes of step b) on peptide(s), whereby the presence or absence of coronavirus-specific antibodies is revealed.

14. A method for detecting the presence of coronavirus-specific antibodies in a subject comprising the steps of: a) placing a sample obtained from the subject, in a single assay receptacle, in the presence of the conjugated nanoparticles of claim 10, b) incubating the mixture under conditions which allow the formation of immunocomplexes on nanoparticles, c) eliminating the immunoglobulins which have not bound to the nanoparticles, and d) detecting the immunocomplexes of step b) on nanoparticles, whereby the presence or absence of coronavirus-specific antibodies is revealed.

15. The method of claim 14 that comprises the steps of: a) placing a sample obtained from the subject, in a single assay receptacle, in the presence of the conjugated gold nanoparticles of claim 11 or 12, b) incubating the mixture under conditions which allow the formation of immunocomplexes on nanoparticles, c) detecting a color change responsive to the aggregation of the gold nanoparticles, whereby the presence or absence of coronavirus-specific antibodies is revealed.

16. The method of claim 13 or 14 for detecting the presence of betacoronavirus-specific antibodies.

17. Use of the method of claim 13 or 14 for simultaneously detecting immunoglobulins having specificity for the peptide S4 (SEQ ID NO:7) and/or the peptide S6 (SEQ ID NO: 10).

18. Use of the method of claim 13 or 14 for the diagnosis of betacoronavirus infections.

19. Use of the method of claim 13 or 14 for the diagnosis of COVID-19.

20. Use of the method of claim 13 or 14 for the serologic follow-up and therapy control of coronavirus infections, in particular betacoronavirus infection, in particular COVID-19.

21. A method for determining whether a subject achieves a protection with a vaccine or a vaccine candidate comprising i) detecting by carrying out the method of claim 13 or 14 the presence of antibodies specific for the S4 peptide (SEQ ID NO: 7) and/or for the S6 peptide (SEQ ID: 10) ii) and concluding that the subject achieves a protection with the vaccine or vaccine candidate when the presence of the antibodies specific for S4 and/or S6 is detected.

22. The method of claim 21 wherein the vaccine is an mRNA vaccine encoding for the spike protein (COVID-19 mRNA vaccine) and in particular the BNT162b2 vaccine.

23. A method for vaccinating a subject in need thereof against a coronavirus comprising administering to said subject a therapeutically effective amount of one or more peptides of claim 1, conjugates of claim 2, one or more fusion proteins of claim 9 or one or more nanoparticles of claim 10.

24. The method according to claim 23 comprising administering to said subject a therapeutically effective amount of gold nanoparticles conjugated with the fusion proteins that consist of the amino acid sequence as set forth in SEQ ID NO: 14.

25. The method of claim 23 wherein the coronavirus is a betacoronavirus.

26. The method of claim 23 wherein the coronavirus is SARS-Cov-2.

27. A vaccine composition that comprises an amount of one more peptides of claim 1, conjugates of claim 2, fusion proteins of claim 9 or nanoparticles of claim 10.

28. A method for immunizing a subject against a coronavirus comprising administering to said subject a therapeutically effective amount of one or more peptide of claim 1, conjugate of claim 2, fusion protein of claim 9 or nanoparticle of claim 10.

29. A method for producing anti-S6 monoclonal antibodies comprising the step of administering the gold nanoparticle of claim 12.

30. An anti-S6 antibody obtained with a method comprising the step of administering the gold nanoparticle of claim 12.