Scientists at Washington University School of Medicine in St. Louis have developed a vaccine that targets the SARS-CoV-2 virus, can be given in one dose via the nose and is effective in preventing infection in mice susceptible to the novel coronavirus.
The investigators next plan to test the vaccine in nonhuman primates and humans to see if it is safe and effective in preventing COVID-19 infection.
The study is available online in the journal Cell.
Unlike other COVID-19 vaccines in development, this one is delivered via the nose, often the initial site of infection.
In the new study, the researchers found that the nasal delivery route created a strong immune response throughout the body, but it was particularly effective in the nose and respiratory tract, preventing the infection from taking hold in the body.
“We were happily surprised to see a strong immune response in the cells of the inner lining of the nose and upper airway – and a profound protection from infection with this virus,” said senior author Michael S. Diamond, MD, Ph.D., the Herbert S. Gasser Professor of Medicine and a professor of molecular microbiology, and of pathology and immunology.
“These mice were well protected from disease. And in some of the mice, we saw evidence of sterilizing immunity, where there is no sign of infection whatsoever after the mouse is challenged with the virus.”
To develop the vaccine, the researchers inserted the virus’ spike protein, which coronavirus uses to invade cells, inside another virus – called an adenovirus – that causes the common cold. But the scientists tweaked the adenovirus, rendering it unable to cause illness.
The harmless adenovirus carries the spike protein into the nose, enabling the body to mount an immune defense against the SARS-CoV-2 virus without becoming sick. In another innovation beyond nasal delivery, the new vaccine incorporates two mutations into the spike protein that stabilize it in a specific shape that is most conducive to forming antibodies against it.
“Adenoviruses are the basis for many investigational vaccines for COVID-19 and other infectious diseases, such as Ebola virus and tuberculosis, and they have good safety and efficacy records, but not much research has been done with nasal delivery of these vaccines,” said co-senior author David T. Curiel, MD, Ph.D., the Distinguished Professor of Radiation Oncology.
“All of the other adenovirus vaccines in development for COVID-19 are delivered by injection into the arm or thigh muscle. The nose is a novel route, so our results are surprising and promising.
It’s also important that a single dose produced such a robust immune response. Vaccines that require two doses for full protection are less effective because some people, for various reasons, never receive the second dose.”
Although there is an influenza vaccine called FluMist that is delivered through the nose, it uses a weakened form of the live influenza virus and can’t be administered to certain groups, including those whose immune systems are compromised by illnesses such as cancer, HIV and diabetes.
In contrast, the new COVID-19 intranasal vaccine in this study does not use a live virus capable of replication, presumably making it safer.
The researchers compared this vaccine administered to the mice in two ways – in the nose and through intramuscular injection. While the injection induced an immune response that prevented pneumonia, it did not prevent infection in the nose and lungs.
Such a vaccine might reduce the severity of COVID-19, but it would not totally block infection or prevent infected individuals from spreading the virus. In contrast, the nasal delivery route prevented infection in both the upper and lower respiratory tract – the nose and lungs – suggesting that vaccinated individuals would not spread the virus or develop infections elsewhere in the body.
The researchers said the study is promising but cautioned that the vaccine so far has only been studied in mice.
“We will soon begin a study to test this intranasal vaccine in nonhuman primates with a plan to move into human clinical trials as quickly as we can,” Diamond said.
“We’re optimistic, but this needs to continue going through the proper evaluation pipelines. In these mouse models, the vaccine is highly protective. We’re looking forward to beginning the next round of studies and ultimately testing it in people to see if we can induce the type of protective immunity that we think not only will prevent infection but also curb pandemic transmission of this virus.”
Vaccination strategies
Many efforts have been directed towards the development of the vaccines against the COVID-19, to avert the pandemic and most of the developing vaccine candidates have been using the S-protein of SARS-CoV-2 (Dhama et al., 2020). As of July 2, 2020, the worldwide SARS-CoV-2 vaccine landscape includes 158 vaccine candidates, out of which 135 are in the preclinical or the exploratory stage of their development.
Currently, mRNA-1273 (Moderna), Ad5-nCoV (CanSino Biologicals), INO-4800 (Inovio, Inc.), LV-SMENP-DC, and Pathogen-specific aAPC (ShinzenGeno-Immune Medical Institute), and ChAdOx1 (University of Oxford) have entered the phase I/II clinical trials (WHO, 2020).
The vaccines which are in the conduit are based upon inactivated or live attenuated viruses, protein sub-unit, virus-like particles (VLP), viral vectors (replicating and non- replicating), DNA, RNA, nanoparticles, etc. (Ning et al., 2020).
To enhance the immunogenicity, various adjuvant technologies like AS03 (GSK), MF-59 (Novartis), CpG 1018 (Dynavax), etc. are now accessible to the researchers for the vaccine development (Le et al., 2020). The immuno-informatics approach is also used for the epitope identification for the SARS-CoV-2 vaccine candidates.
It can be used to identify the significant cytotoxic T cell and B-cell epitopes in the viral S-Protein (Baruah and Bose, 2020) Fig. 1 Table 1 .
Pie Chart showing the different categories of SARS-CoV-2 vaccines under research (Anon, 2020c)
Table 1 – Outline of the vaccine production platforms for SARS-CoV-2 and their advantages and limitations
| S.no. | Vaccine Platform | Advantages | Limitations |
|---|---|---|---|
| 1 | Live Attenuated Vaccine (LAV) /the whole virus | • It has the intrinsic ability to stimulate the immune system by inducing the toll-like receptors (TLRs) namely: TLR 3, TLR 7/8, and TLR 9 of the innate immune system that involves B cells, CD4 and CD8 T cells.• It can be derived from ‘cold adapted’ virus strains, reassortants, and reverse genetics. | • LAV requires an extensive accessory testing to establish safety and efficacy.• There is a probability of nucleotide substitution during viral replication, resulting in the creation of recombinants post-vaccination. |
| 2 | Inactivated Virus Vaccine | • Stable and safer as compared to the LAVs.• It has the pre-existing technology and infrastructure required for its development.• Has already been tested for SARS-CoV and various other diseases.• It can be used along with adjuvants to increase their immunogenicity. | • Require the booster shots to keep the immunity.• Furthermore, large amounts of viruses need to be handled and the integrity of the immunogenic particles must be maintained. |
| 3 | Sub-unit Vaccine | • Do not have any live component of the viral particle.• Thus, it is safe with fewer side-effects. | • Induce an immune response.• Memory for future responses is doubtful. |
| 4 | Viral vector-based vaccine | • Show a highly specific gene delivery into the host cell with a vigorous immune response.• Avoids handling of any infectious particle and it has been used widely for MERS-CoV with positive results from the trials. | • The host may possess immunity against the vector due to prior exposure, reducing the efficacy.• May lead to cancer due to the integration of the viral genome into the host genome. |
| 5 | DNA Vaccines | • The synthetic DNA is temperature stable and cold-chain free• It can be developed at an accelerated pace.• It does not require the handling of the infectious viral particle. | • Though it elicits both Cytotoxic and humoral immunity, the titers remain low.• Insertion of foreign DNA into the host genome may cause abnormalities in the cell.• May induce the antibody production against itself. |
| 6 | RNA Vaccines | • The translation of mRNA occurs in the cytosol of the host cell averting the risk of any sort of integration into the host genome. | • Safety issues with reactogenicity reported for various RNA based vaccines.• It also shows instability. |
Protein Sub-unit vaccine
A subunit vaccine is the one which is based on the synthetic peptides or recombinant antigenic proteins, which are necessary for invigorating long-lasting protective and/or therapeutic immune response (Ning et al., 2020).
The subunit vaccine, however, exhibits low immunogenicity and requires auxiliary support of an adjuvant to potentiate the vaccine-induced immune responses.
An adjuvant may enhance the biological half-life of the antigenic material, or it may ameliorate the immunomodulatory cytokine response. The addition of an adjuvant, therefore, helps in overcoming the shortcomings of the protein subunit vaccines (Cao et al., 2018).
The S protein of the SARS-CoV-2 is the most suitable antigen to induce the neutralizing antibodies against the pathogen. The S Protein consists of two subunits. The S1 subunit has the NTD, RBD, and RBM domains while the S2 subunit comprises of FP, HR 1, &2 (Ou et al., 2020).
The virus enters into the cell via endocytosis by utilizing the S-Protein mediated binding to the hACE2 receptor. Therefore, the S-Protein and its antigenic fragments are the prime targets for the institution of the subunit vaccine (Ning et al., 2020).
The S glycoprotein is a dynamic protein, possessing two conformational states i.e. pre-fusion and post-fusion state. Therefore, the antigen must maintain its surface chemistry and profile of the original pre-fusion spike protein to preserve the epitopes for igniting good quality antibody responses (Graham, 2020). Moreover, means to target the masked RBM as an antigen will enhance the neutralizing antibody response and improve the overall efficacy of the vaccine.
NVX-CoV2373 (Novavax, Inc.| Emergent BioSolutions)
NVX-CoV2373 is a nano-particle based immunogenic vaccine which is based upon the recombinant expression of the stable pre-fusion, coronavirus S-Protein (Coleman et al., 2020). The protein was stably expressed in the Baculovirus system (Tu et al., 2020).
The company plans to use the Matrix-M adjuvant to enhance the immune response against SARS-CoV-2 spike protein by the induction of high levels of neutralizing antibodies. In the animal models, a single immunization resulted in the high level of anti-spike protein antibodies which blocked the hACE2 receptor binding domain activity and could elicit SARS-CoV-2 wild type virus-neutralizing antibodies (Novavax covid 19 vaccine trial, 2020).
Molecular Clamp Stabilized spike protein vaccine candidate
It is being developed by the University of Queensland in collaboration with GSK and Dynavax. The University will have access to vaccine adjuvant platform technology (AS03 Adjuvant system), which is believed to strengthen the vaccine response and minimize the amount of vaccine required per dose (Lee, 2020).
The University is developing a stabilized pre-fusion, recombinant viral protein sub-unit vaccine which is based upon the Molecular Clamp technology. This technology has been proved to induce the production of the neutralizing antibodies (Tu et al., 2020)
PittCoVacc (University of Pittsburgh)
It is a Micro-Needle Array (MNA) based recombinant SARS-CoV-2 vaccine which involves the administration of rSARS-CoV-2 S1 and rSARS-CoV-2-S1fRS09 (recombinant immunogens). A substantial increase in the antigen specific antibodies with a statistical significance was observed in the pre-clinical trials at the end of two weeks in the mice models.
Furthermore, the immunogenicity of the vaccine was maintained after the sterilization using gamma radiation. The statistically significant titers of antibodies at the early stages and also before boosting, support the feasibility of the MNA-SARS-CoV-2 vaccine (Kim et al., 2020).
Triple Antigen Vaccine (Premas Biotech, India)
It is a multi-antigenic VLP vaccine prototype wherein the recombinant spike, membrane, and envelope protein of SARS-CoV-2 have been co-expressed in an engineered Saccharomyces cerevisiae expression platform (D-Crypt™). The proteins then undergo self-assembly as the VLP.
The TEM and allied analytical data simultaneously furnished the biophysical characterization of the VLP. This prototype has the potential to enter the pre-clinical trials as a vaccine candidate after further research and development. Furthermore, it is thought to be safe and easy to manufacture on a mass scale, in a cost-effective manner (Arora and Rastogi, 2020).
Viral Vectored vaccines
A vaccine based on viral vectors is the prophylactic solution against a pathogen, which works by prompting the humoral immune response. These vaccines are highly specific in delivering the genes to the target cells, highly efficient in the gene transduction, and efficiently induce the immune response, thereby increasing the immunity (Ura et al., 2014).
They offer a long term and high level of antigenic protein expression and therefore, they have a great potential for prophylactic use as these vaccines trigger and prime the cytotoxic T cells (CTL) which ultimately leads to the elimination of the virus infected cells (Le et al., 2020).
Ad5-nCoV (CanSino Biologics Inc | Beijing Institute of Biotechnology)
It is a recombinant, replication defective adenovirus type-5 vector (Ad5) expressing the recombinant spike protein of SARS-CoV-2. It was prepared by cloning an optimized full-length gene of the S Protein along with the plasminogen activator signal peptide gene in the Ad5 vector devoid of E1 and E3 genes.
The vaccine was constructed using the Admax system from the Microbix Biosystem (Zhu et al., 2020). The phase I clinical trials have established a positive antibody response or seroconversion. A four-fold increase in the RBD and S protein-specific neutralizing antibodies was noted within 14 days of immunization and peaked at day 28, post-vaccination.
Furthermore, the CD4 + T cells and CD8 + T cells response peaked at day 14 post-vaccination. However, the pre-existing anti-Ad5 immunity partly limited both the antibody and the T cell responses (Zhu et al., 2020).
The study will further evaluate antibody response in the recipients who are between the ages of 18 and 60, who received one of three study doses, with follow-up taking place at 3- and 6-months post-vaccination (Anon, 2020d).
Coroflu (University of Wisconsin-Madison | FluGen | Bharat Biotech)
M2SR, a self-limiting version of the influenza virus, which is modified by insertion of the SARS-CoV-2 gene sequence of the spike protein. Furthermore, the vaccine expresses the hemagglutinin protein of the influenza virus, thereby inducing immune response against both the viruses.
The M2SR is self-limiting and does not undergo replication as it lacks the M2 gene. It is able to enter into the cell, thereby inducing the immunity against the virus. It shall be administered intra-nasally, mimicking the natural route of viral infection. This route activates several modes of the immune system and has higher immunogenicity as compared to the intramuscular injections (Anon, 2020e).
LV-SMENP-DC (Shenzhen Geno-Immune Medical Institute)
The LV-SMENP-DC vaccine is prepared by engineering the dendritic cells (DC) with the lentiviral vector expressing the conserved domains of the SARS-CoV-2 structural proteins and the protease using the SMENP minigenes. The subcutaneous inoculation of the vaccine presents the antigens on antigen presenting cells (APCs), that ultimately activate the Cytotoxic T cells and generate the immune response (Le et al., 2020).
ChAdOx1 (University of Oxford)
ChAdOx1 recombinant adenovirus vaccine was developed by codon optimization of the S glycoprotein for its expression in the human cell lines & synthesized with the tissue plasminogen activator (tPA) leader sequence at 5’ end. The sequence of SARS-CoV-2 coding for amino acids (2 to 1273) and the tPA leader was propagated into the shuttle plasmid.
This shuttle plasmid is responsible for encoding for the major immediate early genes of the human cytomegalovirus (IE CMV) along with tetracycline operator (TetO) sites and polyadenylation signal from bovine growth hormone (BGH) between the Gateway® recombination cloning site.
The Adenovirus vector genome is constructed in the Bacterial Artificial Chromosome by inserting the SARS-CoV-2 S gene into the E1 locus of ChAdOx1 adenovirus genome. The virus was then allowed to reproduce in the T-Rex 293 HEK (Human Embryonic Kidney 293) cell lines and purified by the CsCl gradient ultracentrifugation.
The absence of any sub-genomic RNA (sgRNA) in the intra-muscularly vaccinated animals from the pre-clinical trials is indicative of the escalated immunity against the virus (Doremalen et al., 2020). The previous studies have suggested that a single shot should marshal the immune response (Ou et al., 2020).
The vaccine has entered phase II clinical trials, where the vaccine shall be administered in a large sample of the population (Anon, 2020f).
mRNA Vaccine
mRNA is an emerging, non-infectious, and a non-integrating platform with almost no potential risk of insertional mutagenesis. Currently, the non-replicating RNA and the virus derived self-replicating RNAs are being studied.
The immunogenicity of the mRNA can be minimized, and alterations can be made to increase the stability of these vaccines.
Furthermore, the anti-vector immunity is also avoided as the mRNA is the minimally immunogenic genetic vector, allowing repeated administration of the vaccine (Cuiling et al., 2020).
This platform has empowered the rapid vaccine development program due to its flexibility and ability to mimic the antigen structure and expression as seen in the course of a natural infection (Mulligan and Lyke, 2020).
mRNA-1273 (Moderna TX, Inc)
It is a vaccine composed of synthetic mRNA encapsulated in Lipid nanoparticle (LNP) which codes for the full-length, pre-fusion stabilized spike protein (S) of SARS-CoV-2.
It has the potential to elicit a highly S-protein specific antiviral response.
Furthermore, it is considered to be relatively safe as it is neither made up of the inactivated pathogen nor the sub-units of the live pathogen (Tu et al., 2020). The vaccine has got a fast-track approval by the FDA, to conduct the Phase II trials (Anon, 2020g).
The company has released the interim phase I antibody data of eight participants who received various dose levels.
The participants of the 25 µg arm gave results comparable to the convalescent sera. Whereas, in participants who received the 100 µg dose, the levels of nAb essentially surpassed the levels found in convalescent sera.
The vaccine was found to be predominantly safe and well tolerated in the 25 µg and 100 µg dose cohorts, while three participants experienced grade 3 systemic symptoms after the administration of the second dose of 250 µg dose levels (Anon, 2020h).
BNT162b1 (BioNTech| FosunPharma| Pfizer)
BNT162b1 is a codon-optimized mRNA vaccine that encodes for the trimerized SARS-CoV-2 RBD, a critical target of the virus nAb. The vaccine portrays an increased immunogenicity due to the addition of T4 fibritin-derived foldon trimerization domain to the RBD antigen.
The mRNA is encapsulated in 80 nm ionizable cationic lipid nanoparticles, which ensures its efficient delivery. The Phase 1/2 clinical trials have revealed elevated RBD-specific IgG antibodies levels with a geometric mean concentration to be as high as 8 to 46.3 times sera of convalescent serum. Whereas, the geometric mean titers of the SARS-CoV-2 neutralizing antibodies were found to be 1.8 to 2.8 times the convalescent serum panel.
Moderate and transient local reactions and systemic events were observed with no adverse effect. However, the data analysis did not evaluate the safety and immune responses beyond 2 weeks following the administration of the second dose (Mulligan and Lyke, 2020).
DNA Vaccines
The most revolutionary approach to vaccination is the introduction of the DNA vaccine which encodes for the antigen and an adjuvant which induces the adaptive immune response.
The transfected cells express the transgene which provides a steady supply of the transgene specific proteins which is quite similar to the live virus.
Furthermore, the antigenic material is endocytosed by the immature Dendritic Cells which ultimately present the antigen to the CD4+ and CD8 + T cells in association with MHC 2 and MHC 1 antigens on the cell surface hence stimulating effective humoral as well as cell-mediated immune responses (Hobernik and Bros, 2018).
INO-4800 (Inovio Pharmaceuticals)
It is a prophylactic DNA vaccine against SARS-CoV-2 (Anon, 2020i). It uses codon optimized S protein sequence of SARS-CoV-2 to which an IgE leader sequence is affixed. The SARS-CoV-2 IgE-spike sequence was synthesized and digested using BamHI and XhoI.
The digested DNA was incorporated into the expression plasmid pGX0001 under the governance of IE CMV, and BGH polyadenylation signal. The presence of functional antibodies and T cell response in the preclinical trials suggest that the vaccine can produce an effective immune response within 7 days post-vaccination (Smith et al., 2020).
The vaccine has entered the Phase I clinical trials (Phase I: NCT04336410) and it is estimated to complete this phase of clinical trials by July, wherein the participants received 1.0 mg of INO-4800 by electroporation using CELLECTRA® 2000 device per dosing visit. The trial will evaluate the immunological profile, safety, and tolerability of the vaccine candidate upon intradermal injection and the electroporation in healthy human adults (Anon, 2020i).
Live Attenuated Vaccines
DelNS1-SARS-CoV2-RBD (University of Hong Kong)
This LAV is influenza-based vaccine strain with a deletion in the NS1 gene. It is re-organized to express the RBD domain of SARS-CoV-2 spike protein on its surface and, is cultivated in the chick embryo and/or Madin Darby Canine Kidney Cells (MDCK) cells. It is potentially more immunogenic than the wild type influenza virus and can be administered as a nasal spray (Anon, 2020j).
Others
The revelation of the structure and genome of the SARS-CoV-2 has led to the rapid development of various vaccine candidates with potential reactogenicity and immunogenicity. The task of vaccine development is long and cumbersome which requires evaluation in some long-lasting clinical trials.
Various Biotech ventures are using different technologies for the development of their vaccine candidates; British and American Tobacco Company (BAT) recently unfolded the COVID-19 vaccine using their new, and fast-growing tobacco plant technology (Anon, 2020k), while Tianjin University has developed an oral vaccine which has successfully employed Saccharomyces cerevisiae to carry the S protein. T
he GRAS (Generally Regarded As Safe) status of the yeast provides high scalability, robustness, and cost-effective production of cosmic dosages required to fight off this pandemic (Zhai et al., 2020). Furthermore, in silico studies, using various databases like VaxiJen, have revealed that the epitope sequences WTAGAAAYY and YDPLQPEL can be employed for the formulation of epitope-based peptide vaccines (Garg et al., 2020).
Self Assembling Vaccine (HaloVax)
The vaccine uses a heat shock protein (hsp) to activate the immune system. It is composed of a fusion protein sandwiched between an hsp and Avidin. Biotinylated immunogenic peptides are also incorporated to customize the vaccine (Voltron Therapeutics, Inc., 2020) Table 2, Table 3 .
Table 2
Rapidly progressing Anti COVID-19 vaccines. This table contains the information of rapidly developing vaccine candidates only, the list of all vaccine candidates in the pipeline can be accessed from: https://airtable.com/shrSAi6t5WFwqo3GM/tblEzPQS5fnc0FHYR/viweyymxOAtNvo7yH?blocks=bip
| S.no. | Type of Vaccine/ Platform/ Related Use/ Ref | Developer | Clinical Trial Stage | Remarks |
|---|---|---|---|---|
| Viral vectored vaccines | ||||
| 1 | Adenovirus Type 5 Vector/ Non-replicating viral vaccine/ Ebola/ (Anon, 2020A) | CanSino Biological Inc./Beijing Institute of Bio-technology | Phase 2 ChiCTR2000031781 Phase 1 ChiCTR2000030906 NCT: NCT04313127 | “A randomized, double-blind, placebo parallel-controlled phase I/II clinical trials for inactivated Novel Coronavirus Pneumonia vaccine (Vero cells)” have established a positive antibody response or the seroconversion along with CD4+ and CD8 + T cell response. |
| 2 | Inactivated viral vaccine/ Inactivated/ -/ (Anon, 2020c) | Wuhan Institute of Biological Products/Sinopharm | Phase 1/2: ChiCTR2000031809 | Findings from the animal trials have suggested that the vaccine protects the model animals without Antibody dependent enhancement (ADE). |
| 3 | Lentiviral based Minigene dendritic cell (DC) and T cell vaccine (LV-SMENP-DC)/ – / (Anon, 2020l; Le et al., 2020) | Shenzhen Geno-Immune Medical Institute | Phase 1: NCT04276896 | LV-SMENP-DC vaccine is designed by altering DC with lentivirus vectors to express the “SARS-CoV-2 SMENP minigene and immune modulatory genes”. LV-DC that presents SARS-CoV-2 specific antigens will activate the CTLs |
| 4 | The COVID-19/aAPCs : Pathogen-specific artificial antigen presenting cells (aAPC)/-/ (Anon, 2020m) | Shenzhen Geno-Immune Medical Institute | Phase 1 NCT04299724 | Constructed through modifications of lentivirus by including immune modulatory genes along with viral minigenes, and antigens are presented on artificial antigen presenting cells (aAPCs). |
| 5 | ChAdOx1/ Non-replicating viral vector/ MERS, influenza, TB, Chikungunya, Zika, MenB, plague/ (Anon, 2020f; Doremalen et al., 2020) | University of Oxford/AstraZeneca | Phase 3: ISRCTN89951424 Phase2b/3: NCT04324606 | A phase I/II single-blinded, randomized, placebo controlled, multi-center study was conducted to determine efficacy, safety, and immunogenicity of this vaccine in UK with healthy adult volunteers aged 18-55 years. The post-vaccination follow-ups are ongoing for the 1000 volunteers. Meanwhile taking the vaccine to the higher levels of clinical trials. |
| 6 | Inactivated (formaldehyde inactivated + alum)/LAV/SARS/ (Anon, 2020n; Anon, 2020o) | Sinovac | Phase I/II: NCT04352608 NCT04282574 | The double-blind, placebo-controlled phase I trials showed the nAb seroconversion rate to be as high as 90% in 143 adults within 14 days of immunization. |
| 7 | Adeno-based Gam-COVID-Vac/ Non-replicating viral vector/-/ (Anon, 2020p; Anon, 2020q) | Gamaleya Research Institute | Phase I: NCT04436471 NCT04437875 | Two types of the vaccines— fluid based and powder based for infusions — will be tried on two batches of volunteers, 38 individuals each. The members will be isolated in two Moscow medical clinics. |
| 8 | Ad26 (alone or with Modified Vaccinia Virus Ankara {MVA} boost) Non-replicating viral vaccine/ Ebola, HIV, RSV/ (Johnson & Johnson Announces a Lead Vaccine Candidate for COVID-19, 2020; Anon, 2020c) | Janssen Pharmaceutical Companies/ Beth Israel Deaconess Medical Center | Pre-Clinical (Phase 1 in September 2020) | To accelerate the development of the vaccine the company will use the AdVac® and PER.C6® technologies. |
| 9 | Influenza vector expressing RBD: DelNS1-SARS-CoV2-RBD/ Replicating viral vector (LAV)/ MERS/ (Anon, 2020j; Anon, 2020c) | University of Hong Kong | Pre-Clinical | It is attenuated by the deletion of a key virulent element and the immune antagonist, NS1, which is potentially more immunogenic than the wild-type influenza virus. |
| 10 | CoroFlu, self-limiting influenza virus (M2SR) Non-replicating Viral Vector/ (Anon, 2020e; Anon, 2020c) | University of Wisconsin-Madison / FluGen/ Bharat Biotech | Pre-Clinical | The M2SR is self-limiting because it does not undergo viral replication because of the absence of M2 gene. It will be administered via the nasal route. |
| 11 | Replicating viral vector/ measles vector/ West Nile, CHIKV, Ebola, Lassa, Zika, MERS/ (Campbell, 2020; Anon, 2020c) | The Institut Pasteur | Pre-Clinical | The proprietary measles vector (MV) technology is chosen to develop the vaccine against SARS-CoV-2 which was used in the MV-SARS-CoV vaccine candidate. |
| 12 | Oral COVID-19 Vaccine/ Recombinant adenovirus type 5 vector/ CHIKV, LASV, NORV, EBOV, RVF, HBV, VEE / (Anon, 2020r) | Vaxart | Pre-Clinical | It will be an oral vaccine that aims to induce the mucosal immune response. |
| DNA vaccines | ||||
| 1 | DNA Plasmid Vaccine (INO-4800)/ Lassavirus, Nipah virus, HPV, HIV, Filovirus/ (Anon, 2020i; Anon, 2020c) | Inovio Pharmaceuticals | Phase 1 NCT04336410 | Pre-clinical trials reveal induction of the antigen-specific T cell responses, and functional nAb, thus creating an obstacle for the S protein to bind to the hACE2 receptor. Phase I clinical trials will evaluate the safety, immunogenicity, and tolerability of the vaccine. |
| 2 | Electroporated linear DNA vaccine/ ( BROOK, STONY, 2020) | LineaRx | Takis Biotech | Pre-Clinical | There are 4 candidates of linear DNA vaccine based upon S proteins and some selected epitopes. |
| 3 | Electroporated DNA vaccine/ (Anon, 2020s; Anon, 2020c) | ZydusCadila | Pre-Clinical | – |
| 4 | DNA vaccine/ (Anon, 2020c) | Karolinska Institute / Cobra Biologics (OPENCORONA Project) | Pre-Clinical | A DNA vaccine, which will be administered via intramuscular injections. It will then form the viral antigens to induce the immune response. |
| 5 | DNA Vaccine (GX-19)/ (Anon, 2020c) | Genexine Consortium | Pre-Clinical | Expected to soon enter the clinical trials with Kalbe Farma. |
| RNA Vaccines | ||||
| 1 | LNP- Encapsulated mRNA (mRNA-1273)/ Multiple Candidates/ (Anon, 2020c; Anon, 2020g) | Moderna/NIAID | Phase 2: NCT04405076 Phase 1 NCT04283461 | In Phase 1 Trials, the seroconversion resulted in the nAb levels either close to or higher than the convalescent sera. The vaccine was generally safe and well tolerated. |
| 2 | CureVac mRNA/ RABV, LASV, YFV, MERS, InfA, ZIKV, DengV, NIPV/ (Anon, 2020t; Anon, 2020c) | CureVac | Phase 1 | mRNA as a data carrier to instruct the human body to produce its own proteins capable of fighting a wide range of diseases is used. |
| 3 | LNP-nCoVsaRNA/ RNA/ EBOV, LASV, YFV, MERS, InfA, ZIKV, DENV, NIPV/ (Anon, 2020t; Anon, 2020u) | Imperial College London | Phase 1: ISRCTN17072692 | It is the purified synthetic mRNA which mimics the virus gene for a spike protein on its surface. |
| 4 | BNT162/ mRNA/ (Anon, 2020c; Anon, 2020t; Anon, 2020v) | BioNTech| FosunPharma| Pfizer | Phase 1 /2: NCT04380701 | A robust immunogenic response with the geometric mean of nAb titres to be 1.8 and 2.8 times the nAb titres in the convalescent serum panel after the administration of the second dose. |
| 4 | LNP-encapsulated mRNA cocktail encoding VLP/ RNA/ (Anon, 2020c; Anon, 2020t) | Fudan University/ Shanghai JiaoTong University/RNA Cure Biopharma | Pre-Clinical | – |
| 5 | LNP-encapsulated mRNA cocktail encoding RBD/ mRNA/ (Anon, 2020c; Anon, 2020t) | Fudan University/ Shanghai JiaoTong University/RNA Cure Biopharma | Pre-Clinical | – |
| 6 | mRNA onco-vaccine/ ( Anon, wo) | BIOCAD | Pre-Clinical | They work by introducing sequences of molecules designed to make cells produce disease specific antigens and trigger a regular immune response. |
| Protein Subunit Vaccine | ||||
| 1 | VLP Recombinant Sub-unit, Full length S trimer/nanoparticle + Matrix M (NVX-CoV2373)/RSV, CCHF, HPV, VZV, EBOV/ (WHO, 2020; Novavax covid 19 vaccine trial, 2020;Anon, 2020c; Anon, 2020x) | Novavax | Emergent BioSolutions | Phase 1: NCT04368988 | In animal models, NVX-CoV2373 demonstrated high immunogenicity with measuring spike protein-specific antibodies, which prevent the attachment of the spike protein to the receptor, as well as wild-type virus neutralizing antibodies. |
| 2 | Molecular Clamp Stabilized Recombinant spike protein/Subunit/ Nipah, influenza, Ebola, Lassa/ (Anon, 2020c; Anon, 2020t) | University of Queensland | GSK | Dynavax | Pre-Clinical | It is a stabilized pre-fusion viral protein sub-unit vaccine which is based upon the Molecular Clamp technology which will use AS03 adjuvant system from GSK. |
| 3 | S1 Microneedle array-based (PittCoVacc)/ Protein Subunit/ MERS/ (Kim et al., 2020) (Anon, 2020c) | University of Pittsburgh | Pre-Clinical | Micro-needle Array-based delivery of the recombinant SARS-CoV-2 S1 (rSARS-CoV-2 S1) induced a statistically significant antigen-specific antibody response within 2 weeks of administration in the mice models. |
| 4 | Recombinant protein Subunit vaccine/Influenza, SARS-CoV/ (Anon, 2020y) (Anon, 2020c) (Anon, 2020t) | Sanofi | Pre-Clinical | It is a recombinant vaccine of unrevealed SARS-CoV-2 protein(s) which is expressed in baculovirus vector system. |
| 5 | Protein Sub-unit, gp-96 based/ HIV, malaria, Zika/ (Heat Biologics’ COVID-19 Vaccine Program, 2020; Anon, 2020c) | Heat Biologics | Program announced in March 2020 | It is a “Heat-shock protein gp96 complexed with an undisclosed SARS-CoV-2 peptide(s)”. This technology is capable of generating long-term immune responses and may confer immunity to different coronaviruses. |
| Virus Like Particle (VLP) vaccine/ ( Anon, 2020z) | Medigaco | Pre-Clinical | A recombinant SARS-CoV-2 protein (undisclosed) VLP produced in tobacco. | |
| Live Attenuated Vaccine | ||||
| 1 | Deoptimized live attenuated virus/ HAV, InfA, ZIKV, FMD, SIV, RSV, DENV / (Anon, 2020c; Anon, te) | Codagenix/Serum Institute of India | Pre-Clinical | Codagenix’s technology allows for the rapid generation of multiple vaccine candidates against emerging viruses, starting with only the digital sequence of the viral genome. |
| 2 | TNX-1800, Live Attenuated Horsepox virus/ smallpox, monkeypox/ (TNX-1800 (Coronavirus Vaccine), 2020) | Tonix Pharmaceuticals | Pre-IND | It is believed that horsepox has the potential to serve as a vector for vaccines to protect against other infectious agents. |
| 3 | Live attenuated recombinant measles virus (rMV)/ (Anon, 2020s; Anon, cc; Anon, 2020t) | ZydusCadila | Pre-Clinical | Codon-optimized proteins of the new coronavirus, expressed by rMV generated, will use reverse genetics to stimulate long-term neutralizing antibodies that protect against the infection |
| Others | ||||
| 1 | Self-assembling vaccine/ (Voltron Therapeutics, Inc., 2020) | HaloVax (Voltron Therapeutics) | The Vaccine & Immunotherapy Center at the Massachusetts General Hospital | Pre-Clinical (October 2020) | The biotinylated immunogenic fusion protein is sandwiched between heat shock protein and avidin. |
Table 3
Latest developments in the status of the promising anti SARS-CoV-2 vaccines
| Vaccine | Ref | Developer | Remarks | Clinical Trial Stage |
|---|---|---|---|
| ChAdOx1 | (Folegatti and Ewer, 2020) | University of Oxford/AstraZeneca | The preliminary reports of phase 1/2, single-blind, randomized controlled trials of the ChAdOx1 nCoV-19 vaccine have showcased the spike-specific T-cell responses along with the Anti-spike IgG response in 91% participants as per the micro-neutralization assay (MNA80) while a plaque reduction neutralization assay (PRNT50) depicted a 100% response after a single dose. Nevertheless, the administration of the booster dose displayed the neutralizing response in all the participants which had a substantial correlation with the neutralizing antibody titers as measured by ELISA. The volunteers depicted local and systemic reactions which were minimized by the administration of paracetamol. Thus, the vaccine candidate has portrayed adequate safety and immunogenicity profile in the phase 1/2 clinical trials. | Phase 3: ISRCTN89951424 |
| mRNA-1273 | (Jackson et al., 2020) | Moderna/NIAID | The geometric mean of RBD specific antibody titers showed a rapid increase in all the participants. Seroconversion was observed after 15 days and the median magnitude of antibody responses was similar to the magnitude in convalescent sera. However, the pseudovirus neutralizing activity was not high before the administration of the second dose, which indicates the requirement of a two-dose vaccination schedule. Furthermore, the serum neutralizing activity, a generally accepted functional biomarker of the in vivo humoral response against the respiratory viruses, has not been determined as of now. | Phase 3: NCT04470427 |
| PiCoVacc | (Anon, 2020B) | Sinovac | The phase 1/2 clinical trials of the inactivated viral vaccine candidate PiCoVacc demonstrated that the vaccine induces neutralizing antibodies with a seroconversion rate of 90% in a 0,14 day schedule. The preliminary results confirmed the absence of adverse systemic or local events post-vaccination. The phase 2 clinical trials are expected to be concluded by the end of 2020. The Company has got the permission for conducting the phase 3 clinical trials in Brazil in collaboration with Instituto Butantan. Furthermore, it is expected to get further approvals in Bangladesh for the phase 3 clinical trials. | Phase 3: NCT04456595 |
| BBV152 (A-C) | (Myupchar, 2020) | Bharat Biotech/ ICMR/ NIV | It is the whole virion inactivated experimental vaccine under the phase 1/2 clinical trials. These trials are supposed to study the safety and reactogenicity, tolerability, and the immunogenicity in the healthy volunteers. The inactivated vaccine shall be administered intramuscularly in two doses at day 0 and day 14 and the 1125 volunteers shall be observed for the next six months and will be evaluated for post-vaccination immune responses. The viral strain for the vaccine development was isolated by ICMR and transferred to Bharat Biotech where the process of inactivation was executed in a BSL-3 facility. | Phase 1/2: NCT04471519 |
| Adenovirus Type5 Vector/ Non-replicating viral vaccine | (Zhu and Guan, 2020) | CanSino Biological Inc./Beijing Institute of Bio-technology | The randomized, double-blind, placebo controlled phase 2 clinical trials of the recombinant Ad5-vectored vaccine represented a positive cellular response at 5 × 1010 viral particles along with seroconversion of the humoral immune response. Severe adverse reactions were reported in 9% of the individuals in the 1 × 1011 viral particles dose group and 1% volunteers exhibited these adverse reactions in the 5 × 1010 viral particles dose group. | Phase 2: ChiCTR2000031781 |
| BNT162 | (Anon, 2020e) | BioNTech| FosunPharma| Pfizer | BNT162b1, the mRNA based vaccine induced a high, dose-dependent nAb titers along with the RBD-binding IgG concentrations after the second dose. This was accompanied by the CD4+ and CD8 + T cell responses. The administration of the vaccine was accompanied by certain adverse symptoms like fatigue, fever, chills, muscle pains etc. However, the recipients did not showcase any severe symptoms. | Phase 3: NCT04368728 |
| ZyCoV-D | (CTRI/2020/07/026352, 2020; Myupchar, 2020) | Zydus Cadila | ZyCoV-D is a genetically engineered DNA plasmid based vaccine encoding for the membrane proteins of the virus. The clinical trials to study the immunogenicity, and safety of the vaccine will administer three doses at an interval of 28 days in 1048 individuals. | Phase 1/2: CTRI/202 |
Passive Immunization/adoptive immunity
It is the use of preformed antibodies in therapeutics of various diseases. It can be achieved by use of sera from convalescent patients, polyclonal serum raised in other animals such as horse, neutralizing monoclonal antibodies produced by hybridoma technology or humanized antibodies.
Convalescent Plasma therapy
To date, no distinct treatment has been proven to be efficacious against the COVID-19. Convalescent plasma (CP) therapy has been approved as an empirical treatment during the outbreaks ((WHO), World Health Organisation, 2014).
It is considered as the archetypal immunotherapy which has been used for the treatment and prevention of various viral diseases in the past such as SARS, MERS, H1N1 pandemic, measles, mumps, etc. (Kai et al., 2020).
A possible explanation for the efficacy of this classic adoptive immunotherapy is that the neutralizing immune-globulins from CP may conquer viremia, block new infection, and accelerate clearance of the infected cells.
Various studies conducted therapeutic potential of CP have convincingly shown that administration of the neutralizing antibodies in the critically ill patients led to the amelioration of the clinical status in all patients without any deaths (Kai et al., 2020; Shen et al., 2020a; Ahn et al., 2020a; Anon, 2020C).
The dosage prescribed for the CP therapy has not been standardized as certain groups have administered 200 mL of CP with an antibody titer greater than 1:640 while another patient was administered with 2400 mL of CP (Zhang et al., 2020). The patients who were considered critically ill with some of them having co-morbid conditions like hypertension, cardiovascular diseases, cerebrovascular diseases, chronic renal failure, etc. were included in the study. They were all admitted to the ICUs and were receiving either mechanical ventilation, high-flow nasal cannula oxygenation, or
the low-flow nasal cannula oxygenation. All the patients in these studies were receiving antiviral or antibacterial or antifungal drugs for the treatment of co-infection (Kai et al., 2020). Compared to the control group, the CP treatment group showed no notable differences in the baseline characteristics but exhibited a sizable difference in the clinical outcomes (i.e. normalization of the body temperature, absorption of pulmonary lesions, resolution of ARDS, weaning off the mechanical ventilators, etc.), and the death rates.
The patients were tested negative for the viral loads after 7-37 days of CP infusion (Shen et al., 2020b). A reduction in the net quantity of inflammatory biomarkers CRP, procalcitonin, and Interleukin 6 (IL-6) in the trial group was observed along with a significant increase in the antibody titers (RBD specific IgM and IgG) post-convalescent plasma therapy (Ahn et al., 2020b).
However, these uncontrolled and non-randomized trials for the CP therapy impede the researchers to come to a conclusive statement about the prospective potency of this treatment, and these observations require further evaluation which is ongoing in the clinical trials (Yan, 2020).
Monoclonal Antibody
The monoclonal antibodies (mAb) or therapeutic antibodies, created in the laboratory are the clones of a unique parent which can bind to a single epitope, that is, they have a monovalent affinity (Gelboin et al., 1999). The use of mAb in the prevention and treatment of infectious diseases can overwhelm various drawbacks which are cognate with the convalescent plasma therapy in terms of specificity, safety, low risk of blood-borne infection, purity, and other factors.
A wide array of monoclonal antibodies have already been developed which are implemented in the anti-tumor, anti-platelet, or antiviral therapy (Breedveld, 2000).
A SARS-CoV specific human mAb CR3022 has been found to bind with the RBD of the S protein of SARS-CoV-2, stipulating it as a prospective therapeutic agent, which can either be used alone or in combination therapy for the management of COVID-19 (Tian et al., 2020).
To achieve higher efficiency of disease prevention and treatment, a combinatorial effect of monoclonal antibodies recognizing different epitopes of the viral surface can be considered for the neutralization of the virus as it may prove to be more effective and prevent the viral escape (Tian et al., 2020).
There are over 61 patents which claim to have prepared the SARS-specific, MERS-specific, and the diagnostic antibodies. Another group of 38 patents claims to have developed the antibodies that target the host proteins like IL-6/IL-6R, TLR3, CD16, ITAM (immune-receptor tyrosine-based activation motif), DC-SIGN (dendritic cell-specific intercellular adhesion molecule-grabbing non-integrin), ICAM-3 (intercellular adhesion molecule 3), or IP-10/CXCL10 (interferon γ-inducible protein 10).
These antibodies can be used to counteract against the cytokine storm that has been reported to harmonize with the SARS-CoV-2 infection (Liu et al., 2020). Tocilizumab, an anti-IL 6 receptor antibody is likely to control the hyper-inflammatory pulmonary symptoms which are coupled with the cytokine storm involving the chemokine dysregulation and various interleukins. Tocilizumab has been reported to block the cytokine axis IL6 hence inhibiting the inflammatory cascade.
However, further clinical trials are essential to establish the effectiveness of the mAb (Michot et al., 2020). Israel Institute for Biological Research (IIBR) claims to have successfully developed the mAb against SARS-CoV-2. The institute is in the process of patenting it which may soon be commercialized (Upadhyay, 2020).
A group led by Professor Vijay Chaudhary at the University of Delhi, Centre for Innovation in Infectious Disease Research, Education and Training (UDSC-CIIDRET), is isolating the genes encoding the antibodies responsible for the neutralization of the SARS-CoV-2. These genes will be employed to foster the recombinant Ab by exploiting the pre-existing in-house antibody library and a library fabricated from the cells of convalescent COVID-19 patients (PIB, Delhi, 2020).
reference link : https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7423510/
More information: Ahmed O. Hassan et al, A single-dose intranasal ChAd vaccine protects upper and lower respiratory tracts against SARS-CoV-2, Cell (2020). DOI: 10.1016/j.cell.2020.08.026
