WO2023003911A2

WO2023003911A2 - Mucosal vaccines for coronavirus diseases

Info

Publication number: WO2023003911A2
Application number: PCT/US2022/037639
Authority: WO
Inventors: William Langridge; Anthony FIREK
Original assignee: Loma Linda University
Priority date: 2021-07-19
Filing date: 2022-07-19
Publication date: 2023-01-26
Also published as: WO2023003911A3

Abstract

Compositions and methods of reducing incidence or severity of a coronavirus disease in an animal by administering, via a mucosal route, a fusion protein containing a multimeric cholera toxin B subunit and an immunogenic peptide from a coronavirus.

Description

MUCOSAL VACCINES FOR CORONA VIRUS DISEASES

Inventors: William Langridge and Anthony Firek

Cross-reference to Related Applications

[0001] This application claims the benefit of and priority to U.S. Provisional Application No. 63/203,357 filed on July 19, 2021, which is incorporated by reference herein in its entirety.

Technical Field

[0002] The disclosure relates to compositions and methods of administering mucosal vaccines against coronavirus; more specifically mucosal vaccines that can be generated in plants.

Background

[0003] Infectious diseases are the second largest cause of death worldwide. Almost 15 million people die every year from the result of fungal, protozoan, bacterial and virus infections. The nature of pathogen attack is a question of degree of disease spread which can be defined as an: outbreak, epidemic, pandemic and finally existing as endemic (permanent in the world population). There has been a dramatic increase in new and re-emerging infectious diseases that have re- emerged in this century by extending geographically, becoming more transmissible or by becoming more pathogenic. A large percentage of these new diseases (25%) are emerging and re- emerging respiratory diseases. Coronaviruses are becoming a competitor to the current dominant respiratory disease, influenza. The most recent example is severe acute respiratory syndrome corona virus-2 known more commonly as (SARS-CoV-2) which causes the respiratory disease COVID-19 (coronavirus infectious disease -2019). COVID-19 started as an outbreak in Wuhan city in China in late 2019 and grew to be a pandemic in 2020-2021 and now having spread world wide can remain permanently in humans through genomic alterations to greater infectivity and virulence using the processes of variation and mutation. Coronaviruses are beginning to become endemic in the human population. Of the 4 genera in the family Coronaviridae alpha, beta, gamma and delta — alpha coronaviruses are known to cause symptoms of the relatively mild common cold. However, beta coronaviruses are more lethal than either the alpha coronavirus strains or influenza and now, SARS-CoV-2 has become endemic in the human population. Potentially similar to influenza, requiring vaccination each year for new emerging and potentially more lethal strains of the virus.

Summary

[0004] The Applicant recognized a need for edible vaccines to provide effective immunity in animals to a coronavirus. Embodiments include a nucleic acid composition containing a recombinant vector expressing a fusion protein of a multimeric cholera toxin B subunit and an immunogenic peptide from a coronavirus. The recombinant vector can be a prokaryotic or a eukaryotic vector. Certain embodiments can include a second cholera toxin subunit. The second cholera toxin subunit can be a cholera toxin A2 subunit. In certain embodiments, the immunogenic peptide from the coronavirus is a transmembrane spike glycoprotein of the coronavirus or a fragment thereof. The transmembrane spike glycoprotein of the severe acute respiratory syndrome coronavirus 2 or the fragment thereof can be a SI subunit or a receptor-binding domain of the SI subunit or a S2 subunit. In some embodiments, the subunits can be in the form of dimers or trimers. [0005] Provided here are methods of reducing incidence or severity of a coronavirus disease in an animal by administering, via a mucosal route, a nucleic acid composition containing a recombinant viral vector expressing a fusion protein containing a multimeric cholera toxin B subunit and an immunogenic peptide from a severe acute respiratory syndrome coronavirus 2. In certain embodiments, the immunogenic peptide from the severe acute respiratory syndrome coronavirus 2 is a transmembrane spike glycoprotein of the coronavirus or a fragment thereof. The transmembrane spike glycoprotein of the severe acute respiratory syndrome coronavirus 2 or the fragment thereof can be a SI subunit or a receptor-binding domain of the SI subunit or a S2 subunit.

[0006] Provided here are methods of reducing incidence or severity of a coronavirus disease in an animal by administering, via a mucosal route, a first nucleic acid composition containing a first recombinant viral vector expressing a first fusion protein containing a multimeric cholera toxin B subunit and a first immunogenic peptide from a severe acute respiratory syndrome coronavirus 2 and a second nucleic acid composition containing a second recombinant viral vector expressing a second fusion protein containing a multimeric cholera toxin B subunit and a second immunogenic peptide from a severe acute respiratory syndrome coronavirus 2. The first and second immunogenic peptides are from a transmembrane spike glycoprotein of the coronavirus or a fragment thereof. In an embodiment, the first immunogenic peptide can be a SI subunit or a receptor-binding domain of the SI subunit and the second immunogenic peptide is a S2 subunit of the transmembrane spike glycoprotein.

[0007] Embodiments include mucosal vaccines generated in plants against coronavirus. Provided here are also methods of reducing incidence or severity of a coronavirus disease in an animal by administering mucosal vaccines generated in plants against coronavirus. Embodiments include nucleic acid compositions that encode, upon expression in a plant cell, a fusion protein containing a multimeric cholera toxin B subunit and a first immunogenic peptide from a coronavirus. Embodiments include nucleic acid compositions containing gene sequence for CTB, in conjunction with a coronavirus antigen that stimulates IgA and IgG immune responses to the coronavirus. Embodiments include a transgenic plant cell transformed with the nucleic acid compositions described herein, a transgenic plant seed transformed with the nucleic acid compositions described herein, and a transgenic plant transformed with the nucleic acid composition sdescribed herein. Another embodiment is a method of producing the mucosal vaccine against the coronavirus by cultivating a transgenic plant under conditions effective to express the fusion protein from the nucleic acid composition described herein. Embodiments also include methods of inducing partial or complete immunity to a disease caused by coronavirus in an animal by providing to the animal for oral consumption an effective amount of a transgenic plant product expressing the fusion protein from the nucleic acid composition described herein, [0008] Numerous other aspects, features, and benefits of the present disclosure may be made apparent from the following detailed description taken together with the drawings. It should be further understood that both the foregoing general description and the following detailed description are exemplary and explanatory, and are intended to provide further explanation of the technology as claimed.

Brief Description of the Drawings

[0009] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0010] Embodiments will be readily understood by the following detailed description in conjunction with the accompanying drawings. Embodiments are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings.

[0011] FIG. 1 is an illustration of the nucleic acid composition containing a promoter, a translations start site, a six histidine tag, and the fusion protein sequence for the CTB and the coronavirus protein. The fusion of CTB to the SARS-CoV-2 -ACE-2 -RBD fusion is presented as the DNA sequence of SEQ ID NO: 1. The C-terminus of the CTB is linked through the glycine- proline hinge to the N-terminus of the ACE-2 -RBD.

[0012] FIG. 2 is a photographic image of an acrylamide gel of the CTB-SARS-CoV-2-ACE-2- RBD fusion proteins and control samples isolated from the nickel affinity column and subject to electrophoresis separation.

[0013] FIGS. 3A and 3B are photographic images of an acrylamide gel and an immunoblot following separation of increasing concentrations of the fusion protein vaccine.

[0014] FIG. 4 is a photographic image of an immunoblot to demonstrate identification of the CTB subunit in the CTB-SARS-CoV-2-ACE-2-RBD vaccine protein.

[0015] FIG. 5 is a photographic image of an immunoblot to demonstrate identification of the SARS-CoV-2-ACE-2 protein in the vaccine.

[0016] FIG. 6 is a diagrammatic representation of the experimentation for the ELISA detection of immunized mouse serum antibodies specific for SARS-CoV-2-ACE-2-RBD: This subtractive ELISA assay permits the detection of virus receptor specific antibodies present in the serum of immunized animals that is capable of neutralizing SARS-CoV-2 corona virus attachment to the ACE-2 receptor on mucosal epithelial cells.

[0017] FIG. 7 is a graphical representation of the results from the SARS-CoV-2 virus neutralization assay with sera from mucosal vaccine immunized mice.

[0018] FIG. 8 is a graphical representation of the results from the titration of CTB-SARS-CoV-2- ACE-2-RBD serum antibodies in immunized mice.

[0019] FIG. 9 is a graphical representation of the results from the SARS-CoV-2 virus neutralization with sera from mucosal vaccine immunized mice. [0020] FIG. 10 is a graphical representation of the results from the ELISA for detection of immunized mouse serum specific binding to the SARS-CoV-2-ACE-2-RBD receptor protein. Injection with a DNA vaccine boosts mucosal vaccine immunization.

[0021] FIG. 11 is a graphical representation of the results from the ELISA for comparison of oral and parenteral vaccination.

[0022] FIG. 12 is a graphical representation of the results from the ELISA analyzing the oral and nasal immunization of BALB/c mice with the mucosal vaccine.

[0023] FIG. 13 is a graphical representation of the results from the SARS-CoV-2 virus neutralization assay with sera from mucosal vaccine immunized mice

[0024] FIG. 14 is a graphical representation of the results from results from the neutralization assay with sera from the mice primed with the mucosal vaccine CTB-SARS-CoV-2-ACE-2-RBD and boosted with either the IP version or with Sputnik followed by oral boosters.

[0025] FIG. 15 is a graphical representation of the results from the indirect-ELISA analyzing with sera from the mice primed with the mucosal vaccine CTB-SARS-CoV-2-ACE-2-RBD and boosted with either the IP version or with Sputnik followed by oral boosters.

[0026] FIG. 16 is a diagrammatic representation of the plant transformation vector pPCV701- CTB-SARS-CoV-2-ACE2-RBD.

Detailed Description

[0027] Disclosed herein are compositions and methods addressing the shortcomings of the art, and may provide any number of additional or alternative advantages. Embodiments described herein include mucosal vaccines for improved protection against the development of COVID-19. Embodiments include mucosal vaccines for human and veterinary purposes. [0028] Embodiments include mucosal vaccines generated in bacteria and plants against a coronavirus. Embodiments include nucleic acid compositions that encode, upon expression in a bacterial cell or a plant cell, a fusion protein containing a multimeric cholera toxin B subunit and a first immunogenic peptide from a coronavirus. Embodiments include nucleic acid compositions that encode, upon expression in a bacterial cell or a plant cell, a fusion protein containing the amino acid sequence set forth as SEQ ID NO: 2 or a biologically functional equivalent thereof The cholera toxin subunits act as adjuvants for the immunogenic peptides. Embodiments include nucleic acid compositions containing gene sequence for CTB, in conjunction with a coronavirus antigen that stimulates IgA and IgG immune responses to the coronavirus. The fusion protein encoded by the nucleic acid composition can include a second cholera toxin subunit. The second cholera toxin subunit can be cholera toxin A2 subunit. The fusion protein encoded by the nucleic acid composition can further comprise a second immunogenic peptide from a coronavirus. The first immunogenic peptide from a coronavirus can be a portion of the transmembrane spike (S) glycoprotein of the coronavirus. In an embodiment, the first immunogenic peptide from a coronavirus can be either one of the functional subunits of the S protein. In an embodiment, the first immunogenic peptide from a coronavirus can be the SI subunit including the receptor-binding domain (RBD). In an embodiment, the first immunogenic peptide from a coronavirus can be the S2 subunit. Certain embodiments include the first immunogenic peptide from a coronavirus being the SI subunit including RBD, and the second immunogenic peptide being the S2 subunit. Certain embodiments include the RBD domain as the first immunogenic peptide, and the second immunogenic peptide being the S2 subunit. Addition of the S2 peptide can stimulate responses from dendritic cells and T Cells. [0029] The vaccine constructs can be developed with a suitable promoter for expression in desired cell systems, such as bacterial, baculoviral, yeast, insect and mammalian cells including human cells in cell culture. For example, to be expressed in E. coli systems, the CTB-SARS-CoV2 fusion protein was expressed by the T7 bacteriophage promoter. In another example, for the plant expression vector, the fusion protein is expressed behind the mannopine synthase (mas) P2 promoter. As this promoter region can express proteins in a bi-directional fashion (via the PI promoter), the bacterial luciferase (luxF) gene construct was linked behind the mas PI promoter. In an embodiment the virus Spike (S2) protein is linked to the PI promoter and one can drive the expression of 2 different forms of the vaccine in plants via the mas PI, P2 promoter system. [0030] The term “coronavirus” as used herein refers to viruses of the subfamily Coronavirinae in the family Coronaviridae, in the order Nidovirales, encompassing all strains, genotypes, protectotypes, and serotypes.

[0031] The terms “protein” and “polypeptide” are used interchangeably and refer to a sequence of amino acids composed of the naturally occurring amino acids as well as derivatives thereof. The term “protein” encompasses essentially purified proteins or protein preparations including other proteins in addition. Further, the term also relates to protein fragments. Moreover, it includes chemically modified proteins. Such modifications may be artificial modifications or naturally occurring modifications such as phosphorylation, glycosylation, myristylation and the like.

[0032] A “nucleic acid” or a “nucleic acid composition” means any deoxyribonucleotide or ribonucleotide polymer in either single-stranded or double-stranded forms. A nucleic acid composition may exist as a single polynucleotide or as two or more separate polynucleotides. Unless otherwise indicated, a nucleic acid composition includes known analogues of natural nucleotides that function in manner similar to naturally occurring nucleotides. Unless otherwise indicated, a particular nucleic acid sequence includes the complementary sequence thereof. For example, without limitation, a nucleic acid composition may be a vector, a plasmid, phagemid, or a cosmid, or it may be capable of stable integration into the host cell genome. A nucleic acid composition may be capable of replication in eukaryotic cells or prokaryotic cells or both. It may be present as a single copy or in multiple copies inside a cell.

[0033] An embodiment may include one or more genes inserted into an expression vector, in proper orientation and in proximity to a promoter such that under proper conditions, expression of the polynucleotide of choice can be directed in an appropriate host cell. A nucleic acid composition may comprise at least one origin of replication and may also comprise a gene for a marker by which it can be identified or selected when inserted into a host cell. Useful markers are well known in the art and include for example, without limitations, markers that confer resistance to antibiotics, colorigenic or fluorogenic properties. The choice of a nucleic acid composition will depend on what host cell will be used and what properties are desired of the polynucleotide of choice. Examples of useful nucleic acid compositions that can be modified for use herein include, but are not limited to, plasmids that contain promoter systems to allow expression of the vaccine construct in a variety of bacterial or eukaryotic expression systems. Examples for vaccine expression constructs in bacterial cells include the Lac expression vector, T7 expression vector, araBAD expression vector, pBAD LIC cloning vector, the pl5TV-L - His-tagged bacterial expression vector, the pProl8 - Propionate-inducible expression vectors (Arrowsmith Lab Plasmids) or the pTD plasmid series - Expression with Strep, His or optimized YFP tags. Examples for vaccine expression constructs in Yeast include the GAL4 expression vector, PGK expression vector, ADH1 expression vector, ADE2 expression vector, TRP1 Gateway destination vectors for inducible expression, the pRS420 - Yeast expression vector or LexA and pACT2.2 - Yeast 2- hybrid plasmids. Examples for vaccine expression constructs in insect cells include the Polyhedrin promoter-based vectors, FastBac LIC and pFastBac Dual LIC - vectors, and the pFB-LIC-Bse - Insect expression vector. Examples for vaccine expression constructs in mammalian cell systems include the pLenti CMV Neo DEST - Lentiviral backbone Gateway destination vector.

[0034] Generally, when a nucleic acid composition or a polypeptide composition contains a sequence essentially as set forth in a particular SEQ ID, it means that the sequence substantially corresponds to a portion of that particular SEQ ID and has relatively few nucleotides or amino acids that are not identical to, or a biologically functional equivalent of, the nucleotides of that SEQ ID. It is further contemplated that nucleic acid compositions may contain a polynucleotide that has a stretch of contiguous nucleotides from a particular SEQ ID; for example, lengths of 10, 20, 50, 75, 100, 125, 150, 200, 250, 500, 1000, as well as the entire lengths of the SEQ ID, may be considered appropriate for use in certain embodiments.

[0035] The term “biologically functional equivalent” is well understood in the art and is further defined in detail herein. Accordingly, allowing for the degeneracy of the genetic code, sequences that have about 70%, about 71%, about 72%, about 73%, about 74%, about 75%, about 76%, about 77%, about 78%, about 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about

85%, about 86%, about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about

93%, about 94%, about 95%, about 96%, about 97%, about 98%, or about 99%, and any range derivable therein, such as, for example, about 70% to about 80%, and more preferably about 81% and about 90%; or even more preferably, between about 91% and about 99%; of nucleotides that are identical or functionally equivalent to the nucleotides of any of the SEQ IDs described herein will be biologically functional equivalents of the SEQ ID, provided the biological activity of the nucleotide sequence is maintained. Certain embodiments include isolated DNA segments and nucleic acid compositions that include within their sequence a nucleic acid sequence essentially as set forth in SEQ ID NO. Further embodiments may include nucleic acid compositions that contain biologically functional equivalents of the following coronavirus proteins — the SI subunit including the receptor-binding domain (RBD) or the S2 subunit or combinations thereof.

[0036] A nucleotide composition or a sequence “encoding” a polypeptide or a gene means a nucleotide sequence that, when transcribed and/or expressed, results in the production of an RNA, polypeptide or protein. The nucleotide sequence “encodes” that RNA or it encodes the amino acid sequence for that polypeptide or protein. The nucleic acid compositions may contain an element(s) that permits stable integration of the nucleic acid, or of a smaller part of the nucleic acid, into the host cell genome or autonomous replication of the nucleic acid composition independent of the genome of the cell. The vectors, or smaller parts of the vectors such as amplification units, may be integrated into the host cell genome when introduced into a host cell. For chromosomal integration, the vector may rely on the nucleic acid sequence encoding the polypeptide or any other element of the vector for stable integration of the vector into the genome by homologous or nonhomologous recombination.

[0037] The SARS-CoV-2 genome is a 30-thousand nucleotide positive strand of RNA that contains 10 open reading frames that encode the structural proteins. The virus contains a nucleocapsid protein that protects the RNA genome, a membrane protein “M”, an envelope small membrane protein Έ”, and lastly a spike glycoprotein. The spike protein contains three ACE-2 binding domains that enable the virus to infect gut and lung epithelial cells by binding to the angiotensin converting enzyme (ACE-2) embedded in the host cell membrane. The CoV-2 spike protein functions as a homo-trimer that is covered with glycans to protect the spike from antibody binding. The CoV-2 spike protein contains two subunits. The S2 subunit, referred to as the S2 fusion domain, and the SI subunit known as the ACE-2 Receptor Binding Domain (RBD). The RBD binds to the ACE-2 homodimer embedded in the plasma membrane of the host epithelial cell. As a homotrimer, the three RBDs bind to ACE-2. One RBD is sufficient for binding the virus to the cell.

[0038] The mechanism of SARS-CoV-2 entry into epithelial cells is initiated by the RBD binding to the ACE-2 protein in the membrane of the host cell. The transmembrane serine protease (TMPRSS2) then cleaves the spike protein at a furan site separating the SI subunit RBD from the S2 protein domain. The S2 protein domains then unwind to allow the fusion peptide to insert into the membrane of the cell. The 6 helix bundle of the S2 fusion domain unwinds to allow a conformational change in the heptad repeats, HR1 and HR2, that acts as a hinge to relieve stress in the molecule allowing the lipid membranes of the host and the virus to fuse.

[0039] After fusion of the cell membrane with the virus membrane, the virus (+) strand RNA genome enters the cell and is translated by the host cell machinery into two poly proteins la and lab. The poly proteins undergo proteolysis to form a replicase /transcriptase protein complex that replicates the viral genome negative strand. This strand can be replicated into the positive strand to be included into the virus progeny. The virus negative RNA strand undergoes discontinuous transcription and translation at open reading frame ORFla to generate replicase polyproteins, or transcription at a ribosomal frame shift site ORFlb, to transcribe 7 subgenomic RNAs that are translated into virus nucleocapsid, membrane, envelope, spike and non- structural proteins used to dampen host cell immune defenses (block IFN-g production by the cell). The viral proteins assemble into virus particles in the Golgi and exit the cell via exocytosis.

[0040] Inhibition of dendritic cell activation results in the suppression of innate immune responses and may be the reason for the delay in appearance of symptoms while the virus continues to shed. In contrast to Alpha coronaviruses that attack the upper respiratory tract, causing mild cold symptoms, SARS-CoV-2 infection is depends on the ability of the virus to target the lower respiratory tract to generate pneumonia-like symptoms of lung congestion, respiratory failure and multiple organ failure, which can progress rapidly. Because the virus enters lung cells through destruction of the ACE-2 enzyme, a profound sequence of detrimental metabolic effects can occur. ACE-1, a key enzyme of the renin angiotensin system, converts the pro-hormone angiotensinogen produced in the liver into angiotensin 1 and 2, hormones that regulate blood pressure via vaso constriction. Virus binding to ACE-2 inhibits the conversion of Angiotensin 1 and 2 into Angiotensin 1-9 and 1-7, hormones that balance the system by stimulating vaso-dilation. Thus, in the absence of vaso-dilation, excess ACE activity generates inflammatory responses, oxidative stress, respiratory distress and circulatory complications that have a negative impact on patient survival that include renal failure, arterial thrombosis pulmonary hypertension, stroke, cardiac hypertrophy, lung injury and sepsis thereby stimulating co-morbidities that may kill patients subject to those co-morbidities.

[0041] SARS-CoV-2 undergoes mutation and genetic variability that leads to the proliferation of virus variants that may be more infective, resistant to anti-virus therapies or more lethal. The RNA sequence map of SARS-CoV-2 genetic variants detected in individual patients with the SARS- CoV-2 infection emphasizes the frequency by which the virus randomly alters its genome during infection of people to allow the development of virus strains that may be more contagious, resistant to anti-viral compositions or vaccines designed to eradicate the virus. The ability of the virus to survive is dependent on infecting as many individuals as possible to randomly generate the greatest number of variants. Fortunately for the virus, some of these variants contain traits that increase the capacity for virus survival. SARS-CoV-2 has generated millions of individual virus variants. Fortunately, only a few of these virus variants have shown to provide a significant survival advantage to the virus.

[0042] The rapid development of vaccines has provided the best response to inhibition of SARS- CoV-2 infection. Of the more than 157 vaccines presently under development just 4 have been approved by the FDA and are delivered parenterally. Initial efforts to assemble an effective vaccine against SARS-CoV-2, were based on parenteral inoculation of the spike (SI) ACE-2 receptor mRNA’s because injected vaccines generally produce high titers of pathogen specific IgG antibodies required to arrest virus multiplication in infected tissues. However, the overwhelming immune response may initiate harmful excessive inflammatory responses such as cytokine storm, myocarditis and blood clots that compromise vaccine mediated immunity. Because most serious viral respiratory infections such as SARS-CoV-2 occur at mucosal surfaces. Parenteral vaccines bypass the mucosal epithelium and produce large titers of IgG antibodies effective in halting virus multiplication after infection. Of the total number of vaccines under construction, all are designed to generate IgG antibodies. None are aimed at producing mucosal IgA antibodies, a more desirable target as the virus attacks epithelial cells of the gut and lung. Because parenteral vaccines frequently do not synthesize robust amounts or maintain long term duration of protective mucosal IgA antibodies, complementation with a more robust mucosal vaccine response that targets epidermal cell surfaces provides a great advantage in preventing virus infection. Because mucosal vaccination stimulates circulating B cell synthesis of secretory dimeric antibodies (slgA) that pass through the gut mucosa into mucus lining the lumen of the intestine and respiratory surfaces of the lung, IgA antibodies can intercept the pathogen before it can cause an infection. Thus, IgA reduction in virus load could greatly assist parenteral vaccination in prevention of overwhelming virus infection and increase the possibility of lowering the incidence of cytokine storm. An additional advantage of mucosal immunization is based on the concept of the common mucosal compartment, in which oral vaccine delivery to the gut mucosa stimulates mucosal slgA production in other mucosal spaces, activating local CD8+ cytotoxic T cells and stimulating the proliferation of memory T cells in situ and at other mucosal sites including the lung. Because mucosal epithelia are constantly exposed to low levels of pathogens and other antigens, relatively low slgA titers (in comparison to IgG), are sufficient to effectively eliminate pathogens before they can enter the circulation. The fusion of protein adjuvants to pathogen antigens increases mucosal immunity and linking the cholera toxin B subunit (CTB) mucosal adjuvant to RNA virus antigens provides clinical benefits. Thus, vaccination with CTB-SARS-CoV-2-ACE2-RBD generates slgA antibody and T cell protection against SARS-CoV-2 by preventing virus infection. Because, this mucosal subunit protein vaccine delivers virus epitopes directly to the mucosal immune system, it can circumvent problems caused by mRNA vaccines that hijack the cells machinery to synthesize and present pathogen proteins to antigen presenting cells of the innate immune system. The presentation of a foreign antigens on MHCI receptors can alert cellular immune responses that can kill the cell presenting the foreign antigen. This function could result in a loss of function at specific locations within the body and may be responsible for negative immune responses such as cardiac inflammation detected in patients vaccinated with mRNA vaccines.

[0043] Blocking virus entry into the body could be exceptionally effective requiring relatively low doses of a mucosal vaccine to protect against virus infection. The goal of vaccination is to achieve “herd immunity” which will probably not be achieved until -60 -80 % of the world population is vaccinated either by surviving infection or by receiving a vaccine. So far less than 1/3 of the US population has been vaccinated. Furthermore, the ability of the virus to develop vaccine resistant strains through variation and mutation may make current vaccines ineffective in a short time if many people cannot be rapidly vaccinated to reduce the virus’s opportunity to generate variants. [0044] Parenteral vaccines require trained personnel for vaccine administration and sterile syringes, needles and bandages for vaccine delivery subjecting both the patient and health care giver to needle stick injury and potential infection. Because production costs of parenteral vaccines are costly, their application is limited to affluent countries resulting in poor vaccine dissemination worldwide resulting in corona virus outbreaks and new emerging virus strains throughout the developing world that can cause continual spikes in virus infection. The simplicity of oral inoculation could improve vaccination compliance particularly in economically poor countries and in African American and Latino populations reticent to accept parenteral vaccination while simultaneously being at greater risk for infection with and succumbing to COVID-19. Stable at ambient temperatures, mucosal vaccines can be delivered economically worldwide and to developing countries to establish herd immunity to the corona virus and more pathogenic emerging variants. Finally, the simple genetic structure of subunit vaccines facilitates alterations in vaccine structure required to protect against virus variants that contain mutations to increased infectivity and virulence. To promote increased vaccine yield during production, vaccine codon usage can be adjusted to maximize vaccine synthesis in cell culture.

[0045] Beta coronaviruses attack the gut epithelia as well as the lung epithelia. So, early IgA antibody production by mucosal vaccines can prevent virus infection before it gets started, circumventing the need for parenteral vaccination. IgA antibodies are the second most prevalent antibodies in the body and are found in saliva, tears, bronchial, GI tract, prostatic and vaginal secretions and protect mucous membrane surfaces and have potent antiviral activity. They mainly prevent absorption of pathogen antigens from food and protect against respiratory, GI and GU infections. In the circulation, they migrate to the lung to enhance pulmonary antiviral immunity to protect against lung infection and injury. In response to airway infection IgA antibodies can be found in blood vessels and temporary bronchus associated lymphoid tissues (BALT) that contain CD4⁺ T cells, B cells and CD21⁺ follicular dendritic cells.

[0046] IgA is a 170 kDa immunoglobulin that exists in serum in both monomeric and dimeric forms. Although it exists primarily in monomeric form, some dimeric, trimeric and tetrameric forms are also present. The two four-chain units are held together by the J-chain through disulfide bridges. IgA in blood occurs in monomeric form while those in body secretions occur in dimeric or multimeric forms. In humans, IgA is encoded by two genes within the immunoglobulin gene locus on chromosome 14. Two IgA subtypes exist in humans, IgAl (85% of total IgA) responds best to protein antigens and IgA2 (15% of total) responds to polysaccharide and lipopolysaccharide antigens airways, eyes, and GI tract. They differ in the molecular mass of the heavy chains and in their concentration in serum. In secretions, IgA also contains two other polypeptide chains - J- chain (Joining chain) and secretory component (SC). Because virus dose is critical for infection, IgA mediated reduction in virus dose can be critical for the onset of infection and patient survival. IgA is a major immune response of the body to SARS-CoV-2 infection. So, a mucosal vaccine against the virus can be effective.

[0047] Plasma cells in the lamina propria of the gut secrete IgA antibodies (SIgA), that are then transmitted through the mucosal epithelium into the gut lumen mucous to protect the epithelial cells of the gut mucosa from pathogen infection. The “secretory chain” known as the Poly-Ig- receptor produced by enterocytes binds to the J chain of the IgA molecule and transports the antibody via transcytosis in endosomal vesicles to the lumen mucosa, where it can protect against pathogen entry through the enterocyte into the circulation. In addition, IgA antibodies can bind virus particles passing through the enterocyte and eject the virus from the enterocytes. In infants, SIgA secreted in mother’s breast milk passively protects the infant from pathogen attack.

[0048] Mucosal subunit vaccines use a single virus protein to induce the production of IgA antibodies and thereby eliminate non-immunogenic and toxic inflammatory proteins and preservatives in injected vaccines. In an embodiment, the mucosal vaccine contains a protein adjuvant, like cholera toxin B subunit protein adjuvant (CTB), in conjunction with a pathogenic antigen that stimulates IgA and IgG immune responses to the pathogen. The presence of a single protein antigen in subunit vaccines provides easy vaccine modification to protect against pathogen variation. Mucosal subunit vaccines are scalable, simple to grow in bacteria and vaccine protein easily isolated using metal affinity resin technology.

[0049] Oral vaccine administration is non-intrusive with no pain or injection injury, and can increase patient compliance in ethnic groups resistant to vaccination. Oral delivery systems do not require costly media, biologicals, preservatives equipment (syringes), and time consuming manufacturing conditions required for parenteral vaccine manufacture. In an embodiment, a mucosal subunit vaccine can be combined with parenteral vaccines to provide IgA antibody protection against pathogen invasion.

[0050] Embodiments include mucosal vaccines generated in bacteria against coronavirus. Embodiments include nucleic acid compositions containing the DNA acid sequence set forth as SEQ ID NO: 1 or a biologically functional equivalent thereof. Embodiments include polypeptide compositions containing the amino acid sequence set forth as SEQ ID NO: 2 or a biologically functional equivalent thereof Embodiments include nucleic acid compositions that encode, upon expression in a bacterial cell, a fusion protein containing a multimeric cholera toxin B subunit and a first immunogenic peptide from a coronavirus. Embodiments include nucleic acid compositions containing gene sequence for CTB, in conjunction with a coronavirus antigen that stimulates IgA and IgG immune responses to the coronavirus. The fusion protein encoded by the nucleic acid composition can include a second cholera toxin subunit. The second cholera toxin subunit can be cholera toxin A2 subunit. The fusion protein encoded by the nucleic acid composition can further comprise a second immunogenic peptide from a coronavirus.

[0051] In an embodiment, this nucleic acid composition contains a promoter, a translations start site, a production or purification tag (such as polyhistidine tag), and the fusion protein sequence for the CTB and the coronavirus protein. In an embodiment, this nucleic acid composition can be expressed in E. coli strains, such as the cloning strain Stbl3. Embodiments include a His tagged expression vector containing the S ARS-CoV-2- ACE-2 -RBD linked to the CTB via a glycine - proline hinge region to facilitate molecular folding. Linkers act as spacers between the domains of multidomain proteins to permit maximum expression of fusion proteins. Thr, Ser, Gly, and Ala are found in natural linkers. Proteins with a known three-dimensional structure revealed that the majority of the interdomain linker sets constitutes Pro, Arg, Phe, Thr, Glu, and Gin residues. Proline-rich sequences form relatively rigid extended structures that prevent unfavorable interactions between the domains. Gly-rich regions have been observed as natural linkers in proteins, generating loops that connect domains in multidomain proteins. Embodiments here include two Gly-Pro linker separating the CTB protein from the SARS-CoV-2- ACE-2 RBD protein to allow significant molecular flexibility between the two protein molecules present in the fusion protein. An Ampicillin resistance gene was included for selection of the plasmid. The gene fusion construct generates a 359 amino acid fusion protein of approximately 30 kDa. The vaccine fusion gene DNA sequence was optimized for expression in E. coli BL-21 cells. [0052] Embodiments include a nucleic acid construct encoding the SARS-CoV-2 virus SI angiotensin converting enzyme receptor binding domain (ACE-2 -RBD) downstream of the cholera toxin B subunit mucosal adjuvant (CTB). The CTB-SARS-CoV-2-ACE-2-RBD fusion gene was cloned into a bacterial expression vector and the vaccine protein was transferred into and synthesized in E. coli BL-21 (DE3) cells. A 42 kDa vaccine fusion protein was identified by acrylamide gel electrophoresis of transformed bacterial cell homogenates after immunoblotting against anti-CTB and anti-ACE-2-RBD primary antibodies. The chimeric CTB-SARS-CoV-2- ACE-2-RBD vaccine protein was isolated and partially purified from bacterial homogenates by nickel affinity chromatography and electro-elution from polyacrylamide gels. Further purification of the vaccine protein was accomplished by fast protein liquid chromatography (FPLC). In animal immunization experiments, the vaccine fusion protein was delivered to BALB/c mice by mucosal and parenteral inoculation. Serum collected from immunized mice contained SARS-CoV-2-ACE- 2-RBD specific mucosal antibodies as determined by ELISA identification of specific antibody binding to the virus SI receptor protein SARS-CoV-2-ACE-2-RBD. The mucosal vaccine was shown to neutralize SARS-CoV-2 virus infection in Vero E6 cells in vitro. Vaccine safety for the immunized mice was confirmed by observation of mouse behavior and cytological examination of cell necrosis in kidney, liver, lung, heart and gut tissues excised from the immunized mice. Together, these data indicate that a CTB-SARS-CoV-2-ACE-2-RBD fusion protein subunit mucosal vaccine synthesized in bacteria is effective for protection of animals from infection by the SARS-CoV-2 Omicron variant.

[0053] Embodiments include delivery of the bacterial synthesized fusion protein as probiotic products. One such example includes the expression of the vaccine fusion protein in lacto-bacilli for use as probiotics. [0054] Edible plant mucosal immunization generates IgA antibodies that protects both gut and lung epidermal cell surfaces and prevents virus penetration into the circulation. Vaccine production in plants is scalable. It can be easily expanded through agricultural production via hydroponics or field production to make these vaccines available in countries with limited resources for vaccine production. Vaccine production in plants is relatively inexpensive using light energy, water, fertilizer and harvesting with agricultural machinery. Embodiments include mucosal vaccines generated in plants against coronavirus. Embodiments include nucleic acid compositions that encode, upon expression in a plant cell, a fusion protein containing a multimeric cholera toxin B subunit and a first immunogenic peptide from a coronavirus. Embodiments include nucleic acid compositions containing gene sequence for CTB, in conjunction with a coronavirus antigen that stimulates IgA and IgG immune responses to the coronavirus. The fusion protein encoded by the nucleic acid composition can include a second cholera toxin subunit. The second cholera toxin subunit can be cholera toxin A2 subunit. The fusion protein encoded by the nucleic acid composition can further comprise a second immunogenic peptide from a coronavirus. Certain embodiments include the first immunogenic peptide from a coronavirus being the SI subunit including RBD, and the second immunogenic peptide being the S2 subunit. Certain embodiments include the first immunogenic peptide from a coronavirus being the RBD, and the second immunogenic peptide being the S2 subunit. Embodiments include a transgenic plant cell transformed with the nucleic acid composition described herein, a transgenic plant seed transformed with the nucleic acid composition described herein, and a transgenic plant transformed with the nucleic acid composition described herein. Provided herein is a method of producing the mucosal vaccine against the coronavirus by cultivating a transgenic plant under conditions effective to express the fusion protein from the nucleic acid composition described herein. Embodiments also include methods of inducing partial or complete immunity to a disease caused by coronaviais in an animal by providing to the animal for oral consumption an effective amount of a transgenic plant product expressing the fusion protein from the nucleic acid composition described herein Examples

[0055] Examples below illustrate selected aspects of the various embodiments of compositions and methods for preparation and delivery of mucosal vaccines.

Example 1

[0056] A nucleic acid composition containing CTB-SARS-CoV-2-ACE-2-RBD fusion protein was generated. FIG. 1 is an illustration of the nucleic acid composition containing a promoter, a translations start site, a six histidine tag, and the fusion protein sequence for the CTB and the coronavirus protein. The vaccine gene was transferred into E. coli expression vector BL-21 cells for production of the vaccine fusion protein. Individual ampicillin resistant colonies of plasmid PS-30 (CTB-SARS-C0V-2-ACE-2-RBD) in E. coli BL-21 (DE3) pLysS were selected and the plasmid isolated by agarose gel electrophoresis to determine if the E. coli colony was transformed and whether the plasmid was of the correct size to avoid selection of a mutated form of the gene. [0057] The E. coli BL-21 lysate was subject to protein separation process using a nickel affinity column to purify the fusion protein with a 6xHis tag that has a high affinity for nickel, whereas most other proteins will either bind with low affinity, or not at all. FIG. 2 is a photographic image of an acrylamide gel of the CTB-SARS-CoV-2-ACE-2-RBD fusion proteins and control samples isolated from the nickel affinity column and subject to electrophoresis separation. First lane = protein molecular weight markers. Second lane = E. coli BL-21 lysate prior to column addition. Lane 3 = after addition of lysate to the Ni column, washing the column with 5 column volumes of PBS containing 20 mM Imidazole. The remaining lanes are 1. 0 ml samples taken from the column after following elution of proteins by the addition of PBS containing 500 mM Imidazole. In Lane #3 a protein is eluted of the approximate correct size to be the CTB-SARS-CoV-2-ACE-2-RBD protein.

[0058] The next step involved the identification of the CTB-SARS-CoV-2-ACE-2-RBD fusion protein subunit vaccine for SARS-CoV-2 coronavirus isolated from E. coli BL-21 cells by nickel affinity chromatography. FIGS. 3A and 3B are photographic images of an acrylamide gel and an immunoblot following separation of increasing concentrations of the fusion protein vaccine. FIG. 3A shows an SDS 10% acrylamide gel separation of increasing concentrations of the fusion protein vaccine. FIG. 3B shows an immunoblot of the same proteins identified by binding anti-CTB antibodies conjugated to alkaline phosphatase. It is clear that the CTB antibodies bind to the same protein bands indicating this protein is of identical to the vaccine fusion protein.

[0059] FIG. 4 is a photographic image of an immunoblot to demonstrate identification of the CTB subunit in the CTB-SARS-CoV-2-ACE-2-RBD vaccine protein. The primary antibody (Abl) was anti-CTB protein raised in a rabbit. The secondary antibody (Ab2) was goat anti-rabbit IgG conjugated with alkaline phosphatase. From left to right, Lane #1 contains molecular weight marker proteins, Lane # 2 contains a homogenate of E. coli BL-21 cells transformed with the CTB- SARS-CoV-2-ACE-2-RBD fusion protein vaccine gene, clone #5. Lane # 3 is from the first 500 mM imidazole 1. 0 ml fraction eluted from the Ni column containing the E. coli BL-21 PS-30 clone #5 homogenate. Lane #4 contains the 500 mM imidazole eluate from aNi column containing PS-30 clone #8. Lane #5 contains the cholera holotoxin protein (CTX), a positive control for CTB. The molecular weight of the major bands are the appropriate size to be the vaccine fusion protein. [0060] FIG. 5 is a photographic image of an immunoblot to demonstrate identification of the SARS-CoV-2-ACE-2 protein in the vaccine. The primary antibody (Abl) was anti-SARS-CoV-2- ACE-2-RBD protein raised in a rabbit. The secondary antibody (Ab2) was goat anti-rabbit IgG conjugated with alkaline phosphatase. Lane #1 = protein molecular weight markers, Lane 2 = the negative image of the protein molecular weight markers. Lane 3 = the BL-21 homogenate of E. coli BL-21 clone #5 containing plasmid PS-30 encoding the CTB-SARS-CoV-2-ACE-2-RBD fusion gene. Lanes #5. #6 and #7 are 3 E. coli BL-21 clones containing plasmid PD-30. The major bands lighting up are in the correct molecular weight range for the vaccine protein. In some embodiments, the subunits can be in the form of dimers or trimers. There are potentially some incompletely formed or potentially vaccine fusion protein degradation products with molecular weights somewhat less than the predicted 43 kDa vaccine fusion protein molecular weight commonly observed on Western blots.

[0061] Example 2 — Determination of anti-SARS-COV-2 mucosal antibody titers in BALB/c mice.

[0062] Experimental animal groups of 10 BALB/c mice / Group (5 female and 5 male), were divided into treatment groups as indicated in (Table 1).

[0063] Table 1 presents the CTB-SARS-CoV-2 vaccine treatment groups.

[0064] Three weeks after the vaccine priming dose, an equivalent vaccine booster dose was delivered to the animals in each group on day 21 and once again 3 weeks later. On days 35 and 70 post vaccination, peripheral blood (100-200 mΐ), was taken from vaccinated and control mice by tail vein ligation. RBCs were removed from the blood by centrifugation and the serum collected in Eppendorf tubes for measurement of mucosal antibody titers. To determine intestinal slgA antibody titers, fecal pellets were collected into tubes on days 12, 25, 31, 45 and 70 and mucosal slgA antibody titers generated in response to vaccine treatment is determined as described by the copra-antibody isolation method of de Vos and Dick, A rapid method to determine the isotype and specificity of coproantibodies in mice infected with Trichonella or fed cholera toxin. J. Immunol. Methods 141:285-288 (1991). Lung, liver, kidney, heart and brain tissues from control and vaccinated animals were fixed in formalin and embedded in paraffin. Multiple (minimum of 10) tissue sections (10μm) were taken from different locations in each organ and stained with hematoxylin and eosin. Tissue damage in response to mucosal vaccination was visualized by light microscopy.

[0065] ELISA detection of immunized mouse serum antibodies specific for SARS-CoV-2- ACE-2-RBD: To determine the capacity of the vaccine to neutralize the SARS-CoV-2 corona virus, a subtractive ELISA assay was selected, which permits detection of virus receptor specific antibodies in the serum of immunized animals capable of neutralizing SARS-CoV-2 corona virus attachment to the ACE-2 receptor on mucosal epithelial cells (FIG. 6), In this assay, at step (1) microplate wells of a 96 well microplate were coated with the SARS-CoV-2 Omicron variant recombinant glycosylated ACE-2-RBD protein. At step (2), the ACE-2-RBD sample was incubated with dilutions of serum from immunized mice allowing anti-RBD antibodies if present in the serum to bind to the ACE-2-RBD protein. At step (3), the plate was washed with PBS and remaining free ACE-2-RBD molecules were detected by adding recombinant ACE-2 biotinylated antigen and streptavidin - Horse radish peroxidase-HRP. At step (4), following addition of the TMB + H2O2 substrates to each well, an oxidation reaction initiated by HRP converts the colorless TMB to a green-yellow color, with an absorbance at 450 nm. At step (5), if few or no antibodies in the serum bound to RBD, the color in the well is bright yellow. Conversely, if serum anti-RBD antibodies have blocked biotinylated ACE-2 binding to the receptor binding domain, a reduced level or no color is detected. Virus neutralization by the vaccine protein. Following mucosal immunization of BALB/c mice via oral and nasal routes, serum from peripheral blood isolated from the immunized mice in each experimental group was reacted with the S ARS-CoV-2- ACE-2 - RBD protein bound to ELISA plates (ACE-2 -RBD Neutralization Assay, DIA.PRO Milan, Italia), to detect specific binding of mucosal antibodies in the mouse serum with the virus ACE-2-RBD protein, (FIG. 4). [0066] SARS-CoV-2 virus neutralization with sera from mucosal vaccine immunized mice:

B ALB/C mice were immunized by gavage with 15 μg of CTB-SARS-CoV-2-ACE-2-RBD fusion protein a total of 4x at 3 wk intervals prior to serum withdrawal. Serum from each mouse was tested by ELISA measurement for antibodies specific for the virus ACE-3 -RBD receptor protein (FIG. 7). Lane 1 is negative control, no serum. Lane 2 is combined sera from 10 mice immunized IP with Sputnik 5 vaccine mouse serum (3.0 ml). Lane 3 is the combined sera from 10 mice gavaged with 0.5 ml of PBS or bicarbonate buffer. These sera contain few or no ACE-2-RBD specific antibodies resulting in approximately 10 fold higher levels of colored TMB than detected for the Sputnik 5 immunized mice. Lanes 4-13 represent the serum from 10 mice orally immunized with the CTB-SARS-CoV-2 vaccine. The results of these experiments demonstrate the mucosal vaccine protein produced in E. coli generates antibodies in mice capable of neutralizing the virus by binding specifically to the virus SI ACE-2-RBD receptor (FIG. 7). In this figure, the serum from Sputnik DNA vaccinated mice produced a large amount ACE-2-RBD specific antibodies, as indicated by the large reduction in absorbance at 450 nm. In contrast, serum from the unimmunized mice contained little or no RBD specific Ab and generated about 10 fold higher levels of colored TMB product at 450 nm. In comparison with unimmunized mice (#3), mice orally immunized with the CTB-SARS-CoV-2 vaccine generated substantial reduction in color at 450 nm indicating significant immune serum antibody binding to the ACE-2-RBD antigen in FIG. 7, Lanes 4-13, [0067] Titration of CTB-SARS-CoV-2-ACE-2-RBD Antibodies in Immunized Mice: BALB/c mice (n=10), were primed and boosted 3x by injection with 15 μg of the CTB-SARS-CoV-2-ACE- 2-RBD fusion protein vaccine at 3 wk intervals over a period of 4 months. Sera from the mice were combined and tittered for antibodies specific for the virus receptor ACE-2-RBD as determined by indirect ELISA, (FIG. 8). The SARS-CoV-2-ACE-2-RBD protein (Alpha variant, Sigma), was bound over night to the wells of a Microlite'" ML3000 Microtiter'" Plate Luminometer (Dynatech Laboratories), and serum and fecal endpoint titers were determined similarly as previously described. The excess RBD protein was removed by 3x 5 minute washes with PBS and serum from vaccine immunized mice was serially diluted with PBS and added to the wells. The plate was covered incubated o/n at 40°C. After washing the plate 3X with PBS-Tween, Ab2 anti mouse IgG conjugated to horse radish peroxidase (HRP), (1:10,000 dil with PBS), was added to each well and the plate incubated 1 hr at room temp with slow shaking. After washing the plate 3x with PBS, TMB and H2O2 substrates were added and the change in TMB absorbance at 450 nm was measured by spectrophotometry. In the orally immunized mice a reduction in absorbance at 450 nm in comparison with unimmunized mice of more than 50% indicates substantial immune serum antibody binding to the virus ACE-2-RBD receptor antigen after mucosal immunization. However, in comparison with serum from Sputnik 5 parenterally immunized mice, antibody levels from mice immunized with CTB-SARS-CoV-2-ACE-2-RBD mucosal vaccine are about 3-4 times less. Anti-SARS-CoV-2 humoral antibody absorbance measurements (titers) obtained from immunized and unimmunized mouse serum samples intersected at antibody dilutions between 1 :2,048 and 1 :4,096 considered to be the highest measurable anti-SARS-CoV-2 humoral antibody titers for parenterally vaccinated mice (FIG. 8).

[0068] SARS-CoV-2 virus neutralization with sera from mucosal vaccine immunized mice:

Based on the immunogenicity of the ACE2-RBD protein and the body’s response to SARS-CoV- 2 virus infection by producing initially high titers of protective slgA antibodies, oral immunization with a mucosal subunit vaccine can provide additive and potentially longer lasting slgA protection. BALB/C mice were orally immunized by gavage with 15 μg of CTB-SARS-CoV-2-ACE-2-RBD fusion protein a total of 4x at 3 wk intervals prior to serum isolation (FIG. 9). Serum from each mouse was tested by ELISA for the presence of antibodies capable of binding and neutralizing the virus ACE-3-RBD receptor protein. Lane 1 contains no serum as a negative control. Lane 2 is the combined sera from 10 mice immunized IP with Sputnik 5 vaccine mouse serum (3.0 ml). Lane 3 is the combined sera from 10 mice gavaged with 0.5 ml of PBS. These sera contain few or no ACE-2-RBD specific antibodies resulting in approximately 10 fold higher levels of colored TMB than detected for the Sputnik 5 immunized mice. Lanes 4-13 represent the serum from 10 mice orally immunized with the CTB-SARS-CoV-2 vaccine. The vaccinated mice produce abundant ACE-2-RBD specific antibodies, as indicated by a large reduction in absorbance at 450 nm The combined sera from 10 mice gavaged with 0.5 ml of PBS or bicarbonate buffer is presented in Lane 3. These sera contain few or no ACE-2-RBD specific antibodies resulting in approximately 10 fold higher levels of colored TMB than detected for the Sputnik 5 immunized mice. Lanes 4- 13. contain the individual serum from 10 mice orally immunized with the CTB-SARS-CoV-2 vaccine. A reduction in color in comparison with unimmunized mice of more than 50% shows significant immune serum antibody binding to the ACE-2-RBD antigen in orally immunized mice. However, CTB-SARS-CoV-2-ACE-2-RBD serum antibody levels are about 3-4 times less in comparison with serum from Sputnik parenterally immunized mice.

[0069] Injection with a DNA vaccine boosts mucosal vaccine immunization: To examine parenteral vaccination effects on the durability of mucosal immunization, a single 0.3 ml of the Sputnik 5 DNA vaccine was injected as a booster dose following initial oral immunization (FIG. 10). In this ELISA experiment, immunized mouse serum specific binding to the SARS-CoV-2- ACE-2-RBD receptor protein was measured following a single boost with Sputnik 5 ACE-2 -RBD DNA. Lane 1 is a negative control represents addition of no mouse serum. Lane 2 is sera from 10 mice primed and boosted with the Sputnik 5 DNA vaccine. Lane 3 represents 5 mice orally immunized with serum from un-infected mice. Lanes 4-8 represent sera are individual mice, in which oral vaccine priming is followed by a one-time injected boost with the Sputnik DNA vaccine, followed by 2 boosts with oral CTB-SARS-CoV-2-ACE-2-RBD vaccine. The level of antibody binding to the virus ACE-2-RBD receptor is equal to or greater than mice primed and boosted by the Sputnik vaccine. When oral vaccine priming was followed by a onetime injection of the Sputnik DNA vaccine followed by additional boosting with the oral vaccine, the level of antibody binding to the corona virus ACE-2-RBD receptor is greater than when the mice were primed and boosted by just the Sputnik vaccine (FIG. 10). In Lane 2, of FIG. 9, the vaccinated mice produce abundant ACE-2-RBD specific antibodies, as indicated by a large reduction in absorbance at 450 nm. Thus, mucosal vaccination may help to complement immune protection generated by a single parenteral dose of the DNA vaccine. Thus, multiple booster injections of the DNA vaccine can be avoided, a function that could improve vaccine safety. In Lanes 4 -13. representing the serum from 10 mice orally immunized with the CTB-SARS-CoV-2 vaccine, a reduction in color in comparison with unimmunized mice of more than 50% shows significant immune serum neutralizing antibody binding to the ACE-2 -RBD antigen in orally immunized mice. However, it was observed that CTB-SARS-CoV-2-ACE-2-RBD serum antibody levels were approximately 3-4 times less when compared with serum antibodies present in Sputnik 5 ACE-2- RBD DNA parenterally immunized mice. In this ELISA assay, mouse serum antibodies specific for the ACE-2-RBD virus receptor protein (bound to the plate), compete with the color labeled ACE-2 receptor protein for binding to the virus ACE-2 -RBD protein fixed on the plate. The more antibodies present in the mouse serum, the more binding can occur to the virus ACE-2 -RBD bound to the plate. This condition reduces the colored ACE-2 enzyme from binding to the ACE-2 -RBD thereby also reducing the amount of color present in the well. Thus, an increase in the reduction of color development (less color), is an indicator of more antibodies in the immunized mouse serum that are specific for the ACE-2-RBD receptor.

[0070] In contrast with oral immunization, intraperitoneal injection of the CTB-SARS-CoV -2 ACE-2-RBD vaccine generally produced consistently higher levels of ACE-2-RBD specific antibodies as detected in (FIG. 11). The experimental data indicate that Injection of the vaccine fusion protein generates significantly more ACE-2 -RBD specific antibodies than produced by oral immunization. However, priming the mice with the oral mucosal vaccine followed by a parenteral boost with Sputnik 5 DNA vaccine generated durable protection against virus infection. Oral immunization followed by a Sputnik boost maintained a durable level of vaccine protection for 3 months demonstrating the capacity of mucosal immunization to augment parenteral vaccine protective efficacy. The replacement of parenteral vaccine boosting with mucosal vaccine boosting could significantly lower the cost of present corona virus vaccination.

[0071] Nasal immunization with the mucosal vaccine: Nasal immunization appears to be more effective than oral immunization (FIG. 12). Preliminary evidence (2 mice) indicates nasal immunization can generate higher levels of RBD specific antibodies than oral immunization. In comparison with oral immunization nasal immunization appears to be 15-20% more effective in the production of specific anti-ACE-2-RBD antibodies based on ELISA detection of ACE-2-RBD specific antibodies in immunized mouse serum. The effects of bicarbonate buffer on stability of the mucosal vaccine for oral immunization in contrast to suspending the vaccine in PBS used for nasal immunization have not as yet been explored and PBS having less chemical effects on the stability of the vaccine protein may induce the production of higher levels of ACE-2 -RBD specific antibodies than generated by oral immunization, However, it appears that this observation has not been assessed. [0072] Mouse mucosal antibodies can neutralize the SARS-CoV-2 Omicron virus: BALB/c mice were primed with the mucosal vaccine and boosted once with Sputnik 5 corona virus as shown in (FIG. 13). the Y axis = serum serial dilutions, X axis = number of BALB/c mice tested. Serum antibody titer dilution that protected against infection with the corona virus SARS-CoV-2 Omicron variant ranged from 1 :4 to 1 :64. The blue bars = mice primed by gavage with 15 μ CgTB- SARS-CoV-2-ACE-2-RBD vaccine protein and boosted once with IP injection of Sputnik 5 DNA vaccine and boosted 2 times with 15μg of the mucosal vaccine fusion protein generated the highest anti-virus mucosal antibody titers. All other vaccine treatments generated lower but significant virus specific antibody titers.

[0073] Mucosal vaccine neutralization of SARS-COV-2 corona virus infection in Vero E6 cells. Determination of anti-virus slgA, and IgG titers in CTB-SARS-CoV-2-ACE-2-RBD mucosal vaccine immunized BALB/c mice allows assessment of mucosal antibody levels and their ability to neutralize SARS-CoV-2 infection in vivo. For the virus neutralization assay, Vero E6 green monkey cells were plated into 96-well tissue culture plates (Thermo Fisher, Waltham, MA) at 10,000 cells/well the day before corona virus infection. Mucosal immunized mice serum samples were mixed with an equal volume of 100 x TCID50% of the SARS-CoV-2 virus (Omicron variant (B.1.1.529). A two fold serial dilution of the mixture was added microplate wells containing Vero E6 cells at 80-90% confluency. The assay was performed in triplicate. The infected cells were incubated at 37°C in a 5% C02 incubator. Virus neutralization titers were determined at 4 dpi. As observed in an inverted microscope. Serum neutralizing titers were read as the highest dilution of the serum where the cytopathic effect remains above 50%. The selectivity index (SI) of the investigated compounds was calculated based on the observed inhibitory effects. [0074] The virus neutralization assay was performed on Vero E6 green monkey cell culture (FIG. 14). SARS-CoV-2, Omicron 1.2 variant virus infected cells were incubated at 37°C in a 5% C02 incubator. The neutralization titers were determined by detection of necrotic cells under an inverted microscope. Serum neutralizing titers were read as the highest dilution of the serum where the cytopathic effect remains above 50%. The data were collected and graphed. The Y axis = the reciprocal of the neutralizing antibody titer. The X axis = the number of mice. The red diamonds = the mice were primed by gavage with 15 μg of vaccine protein, boosted lx by injection IP with 30μg Sputnik 5 vaccine and boosted 2x by gavage with 15 μg vaccine protein at 15 day intervals. The blue boxes = mice that were orally primed and boosted 3x by gavage with 15 μg vaccine protein at 3-week intervals.

[0075] For the whole-lung lavage, the mice were euthanized with halothane. The chest was opened by midline incision and lungs were lavaged in situ via PE-90 tubing inserted into the exposed trachea. The lungs were inflated with sterile saline to 25 cm H20 by adding 0.5 ml at a time (total lavage volume, approximately 4 ml). The recovered cells were pelleted, re-suspended in 1 ml Hanks buffer, counted and spun for 5 min and the pellet transferred onto a glass slide. Cells were stained with a Diff-Quik stain set using standard techniques.

[0076] FIG. 15 is a graphical representation of the results of an indirect-ELISA directed to the detection of ACE-2-RBD-specific IgA. Microplate wells coated with recombinant SARS-CoV-2- RBD (Sigma- Aldrich, SAE1000-50UG-PW) incubated with undiluted serum from immunized mice o/n. The serum IgA was detected by adding a goat Anti-Mouse IgA alpha chain (HRP) (Abeam). The enzyme (peroxidase) activity was visualized by the addition of tetramethylbenzidine (TMB). The optical density (OD) of samples was measured at 450 nm. The Y axis depicts absorbance of TMB at 450 nm. X axis provides the number of immunized mice. Open circles represent negative control, mice immunized by gavage with 1.0 ml PBS. Green diamonds represent serum from mice primed by injection IP inoculation with 15 ug of the CTB-SARS-CoV-2-ACE- 2-RBD mucosal vaccine and boosted 2x at 15 day intervals with an equal amount of the vaccine fusion protein. Blue triangles represent sera from mice primed and boosted with 10 ug of mucosal vaccine protein. Plus sign represents sera from mice primed and boosted 3x by gavage with 15 ug vaccine protein. Stars represent sera from mice primed by gavage with 15 μg vaccine protein, boosted lx with 15 ug injected IP and boosted 2x by gavage with 15 μg vaccine protein. Red diamonds represent sera from mice primed by gavage with 15 ug of vaccine protein, boosted lx by injection IP with 30 ug Sputnik 5 vaccine and boosted 2x by gavage with 15 μg vaccine protein at 15 day intervals.

[0077] The absence of an ACE-2-RBD protein signal in the immunoblot of untransformed bacterial cells in FIG. 2B confirms detection of the vaccine protein in transformed E. coli BL-21 cells as compared to FIG. 2A. The presence of a single band that corresponds to the vaccine protein molecular weight after FPLC purification indicates that the vaccine protein isolated by electro elution from acrylamide gels is relatively pure. The presence of a repeatable detectable shoulder on the protein band indicates the presence of molecules containing an alteration in the structure of the vaccine protein or the presence of at least one additional protein of probable bacterial origin. In FIG. 7, a reduction in color in comparison with unimmunized mice of more than 50% shows significant immune serum antibody binding to the ACE-2-RBD antigen in orally immunized mice. However, CTB-SARS-CoV-2-ACE-2-RBD serum antibody levels are about 3-4 times less in comparison with serum from Sputnik parenterally immunized mice. In comparison with Sputnik immunized mice, the serum antibody levels are about 3-4 times less. In comparison with oral immunization, intraperitoneal injection of the CTB-SARS-CoV -2 ACE-2 -RBD vaccine generally produced consistently higher levels of ACE-2 -RBD specific antibodies as identified in FIG. 8. In comparison with parenteral vaccination, mucosal immunization typically generates lower IgA and IgG antibody titers.

[0078] In orally immunized mice shown in FIG. 9, lanes 4-13, contain individual serum from 10 mice orally immunized with the CTB-SARS-CoV-2 vaccine. A reduction in color in comparison with unimmunized mice of more than 50% shows significant immune serum antibody binding to the ACE-2-RBD antigen in orally immunized mice. However, CTB-SARS-CoV-2-ACE-2-RBD serum antibody levels are about 3-4 times less in comparison with serum from Sputnik parenterally immunized mice. When oral vaccine priming is followed by a one-time injected boost with the Sputnik DNA vaccine as shown in FIG. 10, a level of antibody binding to the virus ACE-2-RBD receptor is equal to or greater than in mice primed and boosted by the Sputnik vaccine. Thus, mucosal vaccination may complement and conserve immune protection generated by a single parenteral dose of the DNA vaccine. Based on this observation, it may be possible to avoid multiple booster injections of the DNA vaccine, a factor consistent with reduction in vaccine cost and improved vaccine safety. Parenteral vaccination as shown in FIG. 11 generally produced somewhat higher levels of ACE-2-RBD specific antibodies than oral vaccination. Injected vaccines often stimulate higher levels of IgG in comparison with IgA antibodies.

[0079] Preliminary evidence indicates nasal immunization can generate higher levels of RBD specific antibodies than oral immunization as shown in FIG. 12. For nasal immunization, 15 μg of vaccine protein were delivered in 50 mΐ of PBS rather than in bicarbonate buffer used for oral immunization. When oral is combined with parenteral vaccine delivery, there is considerable variation in CTB-SARS-CoV-2-ACE-2-RBD vaccine stimulated production of anti-ACE-2-RBD antibodies, as shown in FIG. 13. Sera from mice primed with the mucosal vaccine CTB-SARS- Co V-2- ACE-2 -RBD and boosted once with Sputnik 5 corona virus protected Vero E6 cells against coronavirus infection for more than 3 months indicating that the combination of mucosal and parenteral vaccine delivery can provide superior protection against the SARS-CoV-2 coronavirus and its variants.

[0080] Example 3 - Transfer of the Vaccine Gene from E. coli S.17.1 to A. tumefaciens via Conjugation

[0081] A plant transformation vector in E. coli was constructed using the nucleic acid compositions described herein. FIG. 16 is a diagrammatic representation of the plant transformation vector pPCV701-CTB-SARS-CoV-2-ACE2-RBD. Following confirmation of the correct fusion gene sequence, the shuttle vector was transferred into A. tumefaciens recipient strain GV3101 pMP90RK by the same electroporation conditions used for E. coli transformation. Here the fusion vaccine can transfer and stably integrate the plasmid into the plant genome.

[0082] The nucleic acid construct pPCV701 -CTB-SARS-CoV-2-ACE-2-RBD from E. coli S17.1 is transferred into A. tumefaciens GV3101-pMP90-RK by conjugation and subsequent development of the plant vaccine. A. tumefaciens transformants are grown at 29° C. on YEB solid medium containing the antibiotics carbenicillin (100 μg/ml), rifampicin (100 μg/ml), kanamycin (25μg /ml), and gentamycin (25 μg/ml) for selection of transformants. The plasmid is isolated from an A. tumefaciens transformant and transferred back into E. coli HB101 by electroporation. Restriction endonuclease analysis is used to confirm that no significant deletion had occurred in the vector. Plant cells are transformed with A. tumefaciens harboring the plant expression vector for the fusion proteins and allowed to form calli on a nutrient medium. Shoot formation on the callus tissue is observed. Root formation on transformed potato shoots is observed, along with micro-tuber formation on transformed potato plants. The microtuber tissue is used for oral immunization of mice. IgA and IgG antibodies are expected to be detected within 3-4 weeks following the initial 10 μg vaccine fusion protein priming dose of oral immunization followed up by an identical booster dose 2 weeks after the priming dose. Titers of slgA (1:300) and IgG (1 : 10,000) are expected to be detected about 4 weeks post immunization with the priming vaccine dose.

[0083] Table 2 below presents the vaccine treatment groups and controls for this experiment.

Table 2

[0084] The antibody titration and virus neutralization experiments using the vaccine protein are carried out as follows. ELISA titrations are performed using serial dilutions of serum taken from BALB/c mice orally immunized 2x (Primed and boosted 2 weeks later). Anti-CTB-SARS-CoV- 2-ACE-2-RBD Abs generated in the vaccinated mice bind to microtiter plate wells coated with the SARS-CoV-2-ACE-2-RBD protein. The mouse anti-SARS-CoV-2 IgA and IgG Abs are detected by luminometry using anti-mouse antibodies conjugated to alkaline phosphatase in the presence of a fluorescent substrate. IgA and IgG antibodies are expected to be detected within 3-4 weeks following the initial 10 μg vaccine fusion protein priming dose oral immunization followed up by an identical booster dose 2 weeks after the priming dose. Titers of slgA (1 :300) and IgG (1 : 10,000) are expected to be detected from 4 weeks post immunization with the priming vaccine dose. [0085] Provided here are methods of inducing partial or complete immunity to a coronavirus infection in an animal. The method includes providing to the animal for oral consumption an effective amount of a fusion protein containing a multimeric cholera toxin B subunit and a first immunogenic peptide from a coronavirus. In an embodiment, the fusion protein is made in a transgenic plant. Further preferably, the fusion protein comprises a multimeric a cholera toxin B subunit and a first immunogenic peptide from a coronavirus. The cholera toxin subunits act as adjuvants for the immunogenic peptides. The fusion protein can be provided to the mammal in a dose and frequency sufficient to render the mammal partially or completely immune from the coronavirus. The specific dose and frequency are determined by well-known techniques as will be understood by those with skill in the art with reference to this disclosure.

[0086] While these embodiments have been described with emphasis on the embodiments, it should be understood that within the scope of the appended claims, the embodiments might be practiced other than as specifically described herein. Although the inventive aspects have been shown in only a few of its forms, it should be apparent to those skilled in the art that it is not so limited but susceptible to various changes without departing from the scope of the embodiments. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.

SEQUENCE LISTING

SEQ ID NO: 1 - CTB-SARS-COV-2-ACE-2-RBD MUCOSAL VACCINE DNA SEQUENCE

TCTAGAATGCACCATCACCACCACCATATTAAACTTAAATTCGGTGTTTTTTTCACTG

TCTTGCTGTCATCTGCTTACGCTCATGGAACTCCTCAGAACATTACTGACCTTTGCGC

TGAATACCATAACACTCAAATTCACACACTCAACGACAAAATCTTTAGTTATACCGA

ATCTTTGGC AGGA AAAAGAGAAAT GGCC AT CAT AAC ATTT AAGAAT GGCGCC AC AT

TCCAAGTCGAGGTCCCAGGCTCCCAACACATTGACTCCCAGAAAAAAGCTATAGAA

AGAATGAAAGATACCTTACGAATAGCCTATCTCACTGAAGCCAAAGTCGAAAAATT

ATGTGTATGGAATAACAAAACACCTCACGCTATTGCTGCAATATCTATGGCCAATGG

TCCAGGTCCTATGAAAACAATTATTGCACTCTCTTATATATTTTGTTTAGTTTTCGCT

ACAAATTTATGTCCATTCGGCGAAGTTTTTAACGCTACTAGATTTGCTTCAGTTTATG

CATGGAACCGAAAGAGAATTAGTAACTGCGTGGCCGATTATTCTGTTCTTTATAATT

CAGCAAGCTTTTCAACTTTTAAATGCTATGGAGTGTCCCCTACAAAACTTAACGATT

TATGTTTCACAAATGTATATGCAGATTCTTTTGTTATTAGAGGAGATGAGGTTCGTCA

AATCGCTCCAGGTCAAACAGGGAAAATCGCTGATTATAACTACAAACTGCCCGACG

ATTTTACAGGATGCGTAATCGCTTGGAATTCAAATAATCTTGATTCAAAAGTTGGTG

GAAATTACAATTATCTCTATCGTCTGTTTCGTAAATCAAACCTAAAACCTTTCGAAC

GTGATATTAGTACAGAAATTTACCAGGCTGGAAGTACCCCTTGCAATGGAGTTGAGG

GTTTTAACTGCTATTTTCCATTACAGTCCTACGGATTTCAACCAACTAATGGTGTTGG

ATATCAACCTTATAGGGTGGTCGTTTTGTCTTTTGAGCTTCTCCACGCCCCAGCAACC

GTATGCGGACCAAAAAAAGGATCTGGCTCTGAGAAGGATGAATTATGAGAGCTC

SEQ ID NO: 2 - CTB-SARS-COV-2-ACE-2-RBD MUCOSAL VACCINE PROTEIN SEQUENCE:

MHHHHHHIKLKF GVFF T VLL S SAY AHGTP QNITDLC AE YHNT QIHTLNDKIF SYTESLAG

KREMAIITFKNGATFQVEVPGSQHIDSQKKAIERMKDTLRIAYLTEAKVEKLCVWNNKT

PHAI AAISMANGPGPMKTIIAL S YIF CL VF ATNLCPF GEVFNATRF AS VY AWNRKRISNC

VADYSVLYNSASFSTFKCYGVSPTKLNDLCFTNVYADSFVIRGDEVRQIAPGQTGKIAD

YNYKLPDDF T GC VI AWN SNNLD SK V GGNYN YL YRLFRK SNLKPFERDI STEI Y Q AGS TP

CNGVEGFNCYFPLQSYGFQPTNGVGYQPYRVVVLSFELLHAPATVCGPKKGSGSEKDE

L*

Claims

Claims What is claimed is:

1. A nucleic acid composition comprising a recombinant vector expressing a fusion protein containing a multimeric cholera toxin B subunit and an immunogenic peptide from a coronavirus.

2. The nucleic acid composition of Claim 1, wherein the recombinant vector is a prokaryotic vector.

3. The nucleic acid composition of Claim 1, wherein the recombinant vector is a eukaryotic vector.

4. The nucleic acid composition of Claim 1 , further comprising a second cholera toxin subunit.

5. The nucleic acid composition of Claim 4, wherein the second cholera toxin subunit is a cholera toxin A2 subunit.

6. The nucleic acid composition of Claim 1, wherein the immunogenic peptide from the coronavirus is a transmembrane spike glycoprotein of the coronavirus or a fragment thereof.

7. The nucleic acid composition of Claim 6, wherein the transmembrane spike glycoprotein of the coronavirus or the fragment thereof is a SI subunit.

8. The nucleic acid composition of Claim 7, wherein the transmembrane spike glycoprotein of the coronavirus or the fragment thereof is a receptor-binding domain of the SI subunit.

9. The nucleic acid composition of Claim 6, wherein the transmembrane spike glycoprotein of the coronavirus or the fragment thereof is a S2 subunit.

10. A transgenic plant transformed with the nucleic acid composition according to claim 1, wherein the recombinant vector further comprises at least one promoter for expression in a plant cell

11. A method of reducing incidence or severity of a coronavirus disease in an animal comprising the steps of: administering, via a mucosal route, a nucleic acid composition containing a recombinant viral vector expressing a fusion protein containing a multimeric cholera toxin B subunit and an immunogenic peptide from a severe acute respiratory syndrome coronavirus 2.

12. The method of Claim 11, wherein the immunogenic peptide from the severe acute respiratory syndrome coronavirus 2 is a transmembrane spike glycoprotein of the coronavirus or a fragment thereof.

13. The method of Claim 12, wherein the transmembrane spike glycoprotein of the severe acute respiratory syndrome coronavirus 2 or the fragment thereof is a SI subunit.

14. The method of Claim 13, wherein the transmembrane spike glycoprotein of the severe acute respiratory syndrome coronavirus 2 or the fragment thereof is a receptor-binding domain of the SI subunit.

15. The method of Claim 12, wherein the transmembrane spike glycoprotein of the severe acute respiratory syndrome coronavirus 2 or the fragment thereof is a S2 subunit.

16. A method of reducing incidence or severity of a coronavirus disease in an animal comprising the steps of: administering, via a mucosal route, a first nucleic acid composition containing a first recombinant viral vector expressing a first fusion protein containing a multimeric cholera toxin B subunit and a first immunogenic peptide from a severe acute respiratory syndrome coronavirus 2 and a second nucleic acid composition containing a second recombinant viral vector expressing a second fusion protein containing a multimeric cholera toxin B subunit and a second immunogenic peptide from a severe acute respiratory syndrome coronavirus 2.

17. The method of Claim 16, wherein the first immunogenic peptide is a receptor-binding domain of a S 1 subunit of the transmembrane spike glycoprotein of the severe acute respiratory syndrome coronavirus 2.

18. The method of Claim 17, wherein the second immunogenic peptide is a S2 subunit of the transmembrane spike glycoprotein of the severe acute respiratory syndrome coronavirus 2.

19. A method of reducing incidence or severity of a coronavirus disease in an animal comprising the steps of: administering an edible plant product containing a fusion protein containing a multimeric cholera toxin B subunit and an immunogenic peptide from a severe acute respiratory syndrome coronavirus 2.

20. The method of Claim 19, wherein the immunogenic peptide from the severe acute respiratory syndrome coronavirus 2 is a transmembrane spike glycoprotein of the coronavirus or a fragment thereof.

21. The method of Claim 20, wherein the transmembrane spike glycoprotein of the severe acute respiratory syndrome coronavirus 2 or the fragment thereof is a SI subunit.

22. The method of Claim 21, wherein the transmembrane spike glycoprotein of the severe acute respiratory syndrome coronavirus 2 or the fragment thereof is a receptor-binding domain of the S 1 subunit.