Middle East respiratory syndrome coronavirus spike protein delivered by modified vaccinia virus Ankara efficiently induces virus-neutralizing antibodies

Emerging and reemerging infectious diseases: global trends and new strategies for their prevention and control

To adequately prepare for potential hazards caused by emerging and reemerging infectious diseases, the WHO has issued a list of high-priority pathogens that are likely to cause future outbreaks and for which research and development (R&D) efforts are dedicated, known as paramount R&D blueprints. Within R&D efforts, the goal is to obtain effective prophylactic and therapeutic approaches, which depends on a comprehensive knowledge of the etiology, epidemiology, and pathogenesis of these diseases. In this process, the accessibility of animal models is a priority bottleneck because it plays a key role in bridging the gap between in-depth understanding and control efforts for infectious diseases. Here, we reviewed preclinical animal models for high priority disease in terms of their ability to simulate human infections, including both natural susceptibility models, artificially engineered models, and surrogate models. In addition, we have thoroughly reviewed the current landscape of vaccines, antibodies, and small molecule drugs, particularly hopeful candidates in the advanced stages of these infectious diseases. More importantly, focusing on global trends and novel technologies, several aspects of the prevention and control of infectious disease were discussed in detail, including but not limited to gaps in currently available animal models and medical responses, better immune correlates of protection established in animal models and humans, further understanding of disease mechanisms, and the role of artificial intelligence in guiding or supplementing the development of animal models, vaccines, and drugs. Overall, this review described pioneering approaches and sophisticated techniques involved in the study of the epidemiology, pathogenesis, prevention, and clinical theatment of WHO high-priority pathogens and proposed potential directions. Technological advances in these aspects would consolidate the line of defense, thus ensuring a timely response to WHO high priority pathogens.

Dissecting humoral immune responses to an MVA-vectored MERS-CoV vaccine in humans using a systems serology approach

Besides neutralizing antibodies, which are considered an important measure for vaccine immunogenicity, Fc-mediated antibody functions can contribute to antibody-mediated protection. They are strongly influenced by structural antibody properties such as subclass and Fc glycan composition. We here applied a systems serology approach to dissect humoral immune responses induced by MVA-MERS-S, an MVA-vectored vaccine against the Middle East respiratory syndrome coronavirus (MERS-CoV). Building on preceding studies reporting the safety and immunogenicity of MVA-MERS-S, our study highlights the potential of a late boost, administered one year after prime, to enhance both neutralizing and Fc-mediated antibody functionality compared to the primary vaccination series. Distinct characteristics were observed for antibodies specific to the MERS-CoV spike protein S1 and S2 subunits, regarding subclass and glycan compositions as well as Fc functionality. These findings highlight the benefit of a late homologous booster vaccination with MVA-MERS-S and may be of interest for the design of future coronavirus vaccines.

MVA-based vaccine candidates encoding the native or prefusion-stabilized SARS-CoV-2 spike reveal differential immunogenicity in humans

In response to the COVID-19 pandemic, multiple vaccines were developed using platforms such as viral vectors and mRNA technology. Here, we report humoral and cellular immunogenicity data from human phase 1 clinical trials investigating two recombinant Modified Vaccinia virus Ankara vaccine candidates, MVA-SARS-2-S and MVA-SARS-2-ST, encoding the native and the prefusion-stabilized SARS-CoV-2 spike protein, respectively. MVA-SARS-2-ST was more immunogenic than MVA-SARS-2-S, but both were less immunogenic compared to licensed mRNA- and ChAd-based vaccines in SARS-CoV-2 naïve individuals. In heterologous vaccination, previous MVA-SARS-2-S vaccination enhanced T cell functionality and MVA-SARS-2-ST boosted the frequency of T cells and S1-specific IgG levels when used as a third vaccination. While the vaccine candidate containing the prefusion-stabilized spike elicited predominantly S1-specific responses, immunity to the candidate with the native spike was skewed towards S2-specific responses. These data demonstrate how the spike antigen conformation, using the same viral vector, directly affects vaccine immunogenicity in humans.

The emergence of SARS-CoV-2 lineages and associated saliva antibody responses among asymptomatic individuals in a large university community

SARS-CoV-2 (CoV2) infected, asymptomatic individuals are an important contributor to COVID transmission. CoV2-specific immunoglobulin (Ig)-as generated by the immune system following infection or vaccination-has helped limit CoV2 transmission from asymptomatic individuals to susceptible populations (e.g. elderly). Here, we describe the relationships between COVID incidence and CoV2 lineage, viral load, saliva Ig levels (CoV2-specific IgM, IgA and IgG), and ACE2 binding inhibition capacity in asymptomatic individuals between January 2021 and May 2022. These data were generated as part of a large university COVID monitoring program in Ohio, United States of America, and demonstrate that COVID incidence among asymptomatic individuals occurred in waves which mirrored those in surrounding regions, with saliva CoV2 viral loads becoming progressively higher in our community until vaccine mandates were established. Among the unvaccinated, infection with each CoV2 lineage (pre-Omicron) resulted in saliva Spike-specific IgM, IgA, and IgG responses, the latter increasing significantly post-infection and being more pronounced than N-specific IgG responses. Vaccination resulted in significantly higher Spike-specific IgG levels compared to unvaccinated infected individuals, and uninfected vaccinees' saliva was more capable of inhibiting Spike function. Vaccinees with breakthrough Delta infections had Spike-specific IgG levels comparable to those of uninfected vaccinees; however, their ability to inhibit Spike binding was diminished. These data are consistent with COVID vaccines having achieved hoped-for effects in our community, including the generation of mucosal antibodies that inhibit Spike and lower community viral loads, and suggest breakthrough Delta infections were not due to an absence of vaccine-elicited Ig, but instead limited Spike binding activity in the face of high community viral loads.

Newly Designed Poxviral Promoters to Improve Immunogenicity and Efficacy of MVA-NP Candidate Vaccines against Lethal Influenza Virus Infection in Mice

Influenza, a respiratory disease mainly caused by influenza A and B, viruses of the Orthomyxoviridae, is still a burden on our society's health and economic system. Influenza A viruses (IAV) circulate in mammalian and avian populations, causing seasonal outbreaks with high numbers of cases. Due to the high variability in seasonal IAV triggered by antigenic drift, annual vaccination is necessary, highlighting the need for a more broadly protective vaccine against IAV. The safety tested Modified Vaccinia virus Ankara (MVA) is licensed as a third-generation vaccine against smallpox and serves as a potent vector system for the development of new candidate vaccines against different pathogens. Here, we generated and characterized recombinant MVA candidate vaccines that deliver the highly conserved internal nucleoprotein (NP) of IAV under the transcriptional control of five newly designed chimeric poxviral promoters to further increase the immunogenic properties of the recombinant viruses (MVA-NP). Infections of avian cell cultures with the recombinant MVA-NPs demonstrated efficient synthesis of the IAV-NP which was expressed under the control of the five new promoters. Prime-boost or single shot immunizations in C57BL/6 mice readily induced circulating serum antibodies' binding to recombinant IAV-NP and the robust activation of IAV-NP-specific CD8+ T cell responses. Moreover, the MVA-NP candidate vaccines protected C57BL/6 mice against lethal respiratory infection with mouse-adapted IAV (A/Puerto Rico/8/1934/H1N1). Thus, further studies are warranted to evaluate the immunogenicity and efficacy of these recombinant MVA-NP vaccines in other IAV challenge models in more detail.

Vaccinia Virus Strain MVA Expressing a Prefusion-Stabilized SARS-CoV-2 Spike Glycoprotein Induces Robust Protection and Prevents Brain Infection in Mouse and Hamster Models

The COVID-19 pandemic has underscored the importance of swift responses and the necessity of dependable technologies for vaccine development. Our team previously developed a fast cloning system for the modified vaccinia virus Ankara (MVA) vaccine platform. In this study, we reported on the construction and preclinical testing of a recombinant MVA vaccine obtained using this system. We obtained recombinant MVA expressing the unmodified full-length SARS-CoV-2 spike (S) protein containing the D614G amino-acid substitution (MVA-Sdg) and a version expressing a modified S protein containing amino-acid substitutions designed to stabilize the protein a in a pre-fusion conformation (MVA-Spf). S protein expressed by MVA-Sdg was found to be expressed and was correctly processed and transported to the cell surface, where it efficiently produced cell-cell fusion. Version Spf, however, was not proteolytically processed, and despite being transported to the plasma membrane, it failed to induce cell-cell fusion. We assessed both vaccine candidates in prime-boost regimens in the susceptible transgenic K18-human angiotensin-converting enzyme 2 (K18-hACE2) in mice and in golden Syrian hamsters. Robust immunity and protection from disease was induced with either vaccine in both animal models. Remarkably, the MVA-Spf vaccine candidate produced higher levels of antibodies, a stronger T cell response, and a higher degree of protection from challenge. In addition, the level of SARS-CoV-2 in the brain of MVA-Spf inoculated mice was decreased to undetectable levels. Those results add to our current experience and range of vaccine vectors and technologies for developing a safe and effective COVID-19 vaccine.

Viral vectored vaccines: design, development, preventive and therapeutic applications in human diseases

Human diseases, particularly infectious diseases and cancers, pose unprecedented challenges to public health security and the global economy. The development and distribution of novel prophylactic and therapeutic vaccines are the prioritized countermeasures of human disease. Among all vaccine platforms, viral vector vaccines offer distinguished advantages and represent prominent choices for pathogens that have hampered control efforts based on conventional vaccine approaches. Currently, viral vector vaccines remain one of the best strategies for induction of robust humoral and cellular immunity against human diseases. Numerous viruses of different families and origins, including vesicular stomatitis virus, rabies virus, parainfluenza virus, measles virus, Newcastle disease virus, influenza virus, adenovirus and poxvirus, are deemed to be prominent viral vectors that differ in structural characteristics, design strategy, antigen presentation capability, immunogenicity and protective efficacy. This review summarized the overall profile of the design strategies, progress in advance and steps taken to address barriers to the deployment of these viral vector vaccines, simultaneously highlighting their potential for mucosal delivery, therapeutic application in cancer as well as other key aspects concerning the rational application of these viral vector vaccines. Appropriate and accurate technological advances in viral vector vaccines would consolidate their position as a leading approach to accelerate breakthroughs in novel vaccines and facilitate a rapid response to public health emergencies.

Recombinant Modified Vaccinia Virus Ankara Expressing a Glycosylation Mutant of Dengue Virus NS1 Induces Specific Antibody and T-Cell Responses in Mice

The four serotypes of dengue virus (DENV1-4) continue to pose a major public health threat. The first licenced dengue vaccine, which expresses the surface proteins of DENV1-4, has performed poorly in immunologically naïve individuals, sensitising them to antibody-enhanced dengue disease. DENV non-structural protein 1 (NS1) can directly induce vascular leakage, the hallmark of severe dengue disease, which is blocked by NS1-specific antibodies, making it an attractive target for vaccine development. However, the intrinsic ability of NS1 to trigger vascular leakage is a potential drawback of its use as a vaccine antigen. Here, we modified DENV2 NS1 by mutating an N-linked glycosylation site associated with NS1-induced endothelial hyperpermeability and used modified vaccinia virus Ankara (MVA) as a vector for its delivery. The resulting construct, rMVA-D2-NS1-N207Q, displayed high genetic stability and drove efficient secretion of NS1-N207Q from infected cells. Secreted NS1-N207Q was composed of dimers and lacked N-linked glycosylation at position 207. Prime-boost immunisation of C57BL/6J mice induced high levels of NS1-specific antibodies binding various conformations of NS1 and elicited NS1-specific CD4⁺ T-cell responses. Our findings support rMVA-D2-NS1-N207Q as a promising and potentially safer alternative to existing NS1-based vaccine candidates, warranting further pre-clinical testing in a relevant mouse model of DENV infection.

Persistence of MERS-CoV-spike-specific B cells and antibodies after late third immunization with the MVA-MERS-S vaccine

The Middle East respiratory syndrome (MERS) is a respiratory disease caused by MERS coronavirus (MERS-CoV). In follow up to a phase 1 trial, we perform a longitudinal analysis of immune responses following immunization with the modified vaccinia virus Ankara (MVA)-based vaccine MVA-MERS-S encoding the MERS-CoV-spike protein. Three homologous immunizations were administered on days 0 and 28 with a late booster vaccination at 12 ± 4 months. Antibody isotypes, subclasses, and neutralization capacity as well as T and B cell responses were monitored over a period of 3 years using standard and bead-based enzyme-linked immunosorbent assay (ELISA), 50% plaque-reduction neutralization test (PRNT50), enzyme-linked immunospot (ELISpot), and flow cytometry. The late booster immunization significantly increases the frequency and persistence of spike-specific B cells, binding immunoglobulin G1 (IgG1) and neutralizing antibodies but not T cell responses. Our data highlight the potential of a late boost to enhance long-term antibody and B cell immunity against MERS-CoV. Our findings on the MVA-MERS-S vaccine may be of relevance for coronavirus 2019 (COVID-19) vaccination strategies.

Increased neutralization and IgG epitope identification after MVA-MERS-S booster vaccination against Middle East respiratory syndrome

Vaccine development is essential for pandemic preparedness. We previously conducted a Phase 1 clinical trial of the vector vaccine candidate MVA-MERS-S against the Middle East respiratory syndrome coronavirus (MERS-CoV), expressing its full spike glycoprotein (MERS-CoV-S), as a homologous two-dose regimen (Days 0 and 28). Here, we evaluate the safety (primary objective) and immunogenicity (secondary and exploratory objectives: magnitude and characterization of vaccine-induced humoral responses) of a third vaccination with MVA-MERS-S in a subgroup of trial participants one year after primary immunization. MVA-MERS-S booster vaccination is safe and well-tolerated. Both binding and neutralizing anti-MERS-CoV antibody titers increase substantially in all participants and exceed maximum titers observed after primary immunization more than 10-fold. We identify four immunogenic IgG epitopes, located in the receptor-binding domain (RBD, n = 1) and the S2 subunit (n = 3) of MERS-CoV-S. The level of baseline anti-human coronavirus antibody titers does not impact the generation of anti-MERS-CoV antibody responses. Our data support the rationale of a booster vaccination with MVA-MERS-S and encourage further investigation in larger trials. Trial registration: Clinicaltrials.gov NCT03615911.

Single-dose replicating poxvirus vector-based RBD vaccine drives robust humoral and T cell immune response against SARS-CoV-2 infection

The coronavirus disease 2019 (COVID-19) pandemic requires the continued development of safe, long-lasting, and efficacious vaccines for preventive responses to major outbreaks around the world, and especially in isolated and developing countries. To combat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), we characterize a temperature-stable vaccine candidate (TOH-Vac1) that uses a replication-competent, attenuated vaccinia virus as a vector to express a membrane-tethered spike receptor binding domain (RBD) antigen. We evaluate the effects of dose escalation and administration routes on vaccine safety, efficacy, and immunogenicity in animal models. Our vaccine induces high levels of SARS-CoV-2 neutralizing antibodies and favorable T cell responses, while maintaining an optimal safety profile in mice and cynomolgus macaques. We demonstrate robust immune responses and protective immunity against SARS-CoV-2 variants after only a single dose. Together, these findings support further development of our novel and versatile vaccine platform as an alternative or complementary approach to current vaccines.

Middle East Respiratory Syndrome coronavirus vaccine development: updating clinical studies using platform technologies

Middle East Respiratory Syndrome coronavirus (MERS-CoV), a contagious zoonotic virus, causes severe respiratory infection with a case fatality rate of approximately 35% in humans. Intermittent sporadic cases in communities and healthcare facility outbreaks have continued to occur since its first identification in 2012. The World Health Organization has declared MERS-CoV a priority pathogen for worldwide research and vaccine development due to its epidemic potential and the insufficient countermeasures available. The Coalition for Epidemic Preparedness Innovations is supporting vaccine development against emerging diseases, including MERS-CoV, based on platform technologies using DNA, mRNA, viral vector, and protein subunit vaccines. In this paper, we review the usefulness and structure of a spike glycoprotein as a MERS-CoV vaccine candidate molecule, and provide an update on the status of MERS-CoV vaccine development. Vaccine candidates based on both DNA and viral vectors coding MERS-CoV spike gene have completed early phase clinical trials. A harmonized approach is required to assess the immunogenicity of various candidate vaccine platforms. Platform technologies accelerated COVID-19 vaccine development and can also be applied to developing vaccines against other emerging viral diseases.

Development of a recombinant vaccine containing a spike S1-Fc fusion protein induced protection against MERS-CoV in human DPP4 knockin transgenic mice

The Middle East respiratory syndrome coronavirus (MERS-CoV), belonging to the family Coronaviridae and genus Betacoronavirus, has been recognized as a highly pathogenic virus. Due to the lack of therapeutic or preventive agents against MERS-CoV, developing an effective vaccine is essential for preventing a viral outbreak. To address this, we developed a recombinant S1 subunit of MERS-CoV spike protein fused with the human IgG4 Fc fragment (LV-MS1-Fc) in Chinese hamster ovary (CHO) cells. Thereafter, we identified the baculovirus gp64 signal peptide-directed secretion of LV-MS1-Fc protein in the extracellular fluid. To demonstrate the immunogenicity of the recombinant LV-MS1-Fc proteins, BALB/c mice were inoculated with 2.5 μg of LV-MS1-Fc. The inoculated mice demonstrated a significant humoral immune response, measured via total IgG and neutralizing antibodies. In addition, human dipeptidyl peptidase-4 (DPP4) transgenic mice vaccinated with LV-MS1-Fc showed the protective capacity of LV-MS1-Fc against MERS-CoV with no inflammatory cell infiltration. These data showed that the S1 and Fc fusion protein induced potent humoral immunity and antigen-specific neutralizing antibodies in mice, and conferred protection against coronavirus viral challenge, indicating that LV-MS1-Fc is an effective vaccine candidate against MERS-CoV infection.

Vaccine-Associated Enhanced Disease and Pathogenic Human Coronaviruses

Vaccine-associated enhanced disease (VAED) is a difficult phenomenon to define and can be confused with vaccine failure. Using studies on respiratory syncytial virus (RSV) vaccination and dengue virus infection, we highlight known and theoretical mechanisms of VAED, including antibody-dependent enhancement (ADE), antibody-enhanced disease (AED) and Th2-mediated pathology. We also critically review the literature surrounding this phenomenon in pathogenic human coronaviruses, including MERS-CoV, SARS-CoV-1 and SARS-CoV-2. Poor quality histopathological data and a lack of consistency in defining severe pathology and VAED in preclinical studies of MERS-CoV and SARS-CoV-1 vaccines in particular make it difficult to interrogate potential cases of VAED. Fortuitously, there have been only few reports of mild VAED in SARS-CoV-2 vaccination in preclinical models and no observations in their clinical use. We describe the problem areas and discuss methods to improve the characterisation of VAED in the future.

Advances in the design and development of SARS-CoV-2 vaccines

Since the end of 2019, coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread worldwide. The RNA genome of SARS-CoV-2, which is highly infectious and prone to rapid mutation, encodes both structural and nonstructural proteins. Vaccination is currently the only effective method to prevent COVID-19, and structural proteins are critical targets for vaccine development. Currently, many vaccines are in clinical trials or are already on the market. This review highlights ongoing advances in the design of prophylactic or therapeutic vaccines against COVID-19, including viral vector vaccines, DNA vaccines, RNA vaccines, live-attenuated vaccines, inactivated virus vaccines, recombinant protein vaccines and bionic nanoparticle vaccines. In addition to traditional inactivated virus vaccines, some novel vaccines based on viral vectors, nanoscience and synthetic biology also play important roles in combating COVID-19. However, many challenges persist in ongoing clinical trials.

Nanovaccine Delivery Approaches and Advanced Delivery Systems for the Prevention of Viral Infections: From Development to Clinical Application

Viral infections causing pandemics and chronic diseases are the main culprits implicated in devastating global clinical and socioeconomic impacts, as clearly manifested during the current COVID-19 pandemic. Immunoprophylaxis via mass immunisation with vaccines has been shown to be an efficient strategy to control such viral infections, with the successful and recently accelerated development of different types of vaccines, thanks to the advanced biotechnological techniques involved in the upstream and downstream processing of these products. However, there is still much work to be done for the improvement of efficacy and safety when it comes to the choice of delivery systems, formulations, dosage form and route of administration, which are not only crucial for immunisation effectiveness, but also for vaccine stability, dose frequency, patient convenience and logistics for mass immunisation. In this review, we discuss the main vaccine delivery systems and associated challenges, as well as the recent success in developing nanomaterials-based and advanced delivery systems to tackle these challenges. Manufacturing and regulatory requirements for the development of these systems for successful clinical and marketing authorisation were also considered. Here, we comprehensively review nanovaccines from development to clinical application, which will be relevant to vaccine developers, regulators, and clinicians.

Intranasal Delivery of MVA Vector Vaccine Induces Effective Pulmonary Immunity Against SARS-CoV-2 in Rodents

Antigen-specific tissue-resident memory T cells (Trms) and neutralizing IgA antibodies provide the most effective protection of the lungs from viral infections. To induce those essential components of lung immunity against SARS-CoV-2, we tested various immunization protocols involving intranasal delivery of a novel Modified Vaccinia virus Ankara (MVA)-SARS-2-spike vaccine candidate. We show that a single intranasal MVA-SARS-CoV-2-S application in mice strongly induced pulmonary spike-specific CD8+ T cells, albeit restricted production of neutralizing antibodies. In prime-boost protocols, intranasal booster vaccine delivery proved to be crucial for a massive expansion of systemic and lung tissue-resident spike-specific CD8+ T cells and the development of Th1 - but not Th2 - CD4+ T cells. Likewise, very high titers of IgG and IgA anti-spike antibodies were present in serum and broncho-alveolar lavages that possessed high virus neutralization capacities to all current SARS-CoV-2 variants of concern. Importantly, the MVA-SARS-2-spike vaccine applied in intramuscular priming and intranasal boosting treatment regimen completely protected hamsters from developing SARS-CoV-2 lung infection and pathology. Together, these results identify intramuscular priming followed by respiratory tract boosting with MVA-SARS-2-S as a promising approach for the induction of local, respiratory as well as systemic immune responses suited to protect from SARS-CoV-2 infections.

Neutralization of MERS coronavirus through a scalable nanoparticle vaccine

MERS-CoV continues to cause human outbreaks, so far in 27 countries worldwide following the first registered epidemic in Saudi Arabia in 2012. In this study, we produced a nanovaccine based on virus-like particles (VLPs). VLPs are safe vaccine platforms as they lack any replication-competent genetic material, and are used since many years against hepatitis B virus (HBV), hepatitis E virus (HEV) and human papilloma virus (HPV). In order to produce a vaccine that is readily scalable, we genetically fused the receptor-binding motif (RBM) of MERS-CoV spike protein into the surface of cucumber-mosaic virus VLPs. The employed CuMV_TT-VLPs represent a new immunologically optimized vaccine platform incorporating a universal T cell epitope derived from tetanus toxin (TT). The resultant vaccine candidate (mCuMV_TT-MERS) is a mosaic particle and consists of unmodified wild type monomers and genetically modified monomers displaying RBM, co-assembling within E. coli upon expression. mCuMV_TT-MERS vaccine is self-adjuvanted with ssRNA, a TLR7/8 ligand which is spontaneously packaged during the bacterial expression process. The developed vaccine candidate induced high anti-RBD and anti-spike antibodies in a murine model, showing high binding avidity and an ability to completely neutralize MERS-CoV/EMC/2012 isolate, demonstrating the protective potential of the vaccine candidate for dromedaries and humans.

A single subcutaneous or intranasal immunization with adenovirus-based SARS-CoV-2 vaccine induces robust humoral and cellular immune responses in mice

Optimal vaccines are needed for sustained suppression of SARS-CoV-2 and other novel coronaviruses. Here, we developed a recombinant type 5 adenovirus vector encoding the gene for the SARS-CoV-2 S1 subunit antigen (Ad5.SARS-CoV-2-S1) for COVID-19 immunization and evaluated its immunogenicity in mice. A single immunization with Ad5.SARS-CoV-2-S1 via S.C. injection or I.N delivery induced robust antibody and cellular immune responses. Vaccination elicited significant S1-specific IgG, IgG1, and IgG2a endpoint titers as early as 2 weeks, and the induced antibodies were long lasting. I.N. and S.C. administration of Ad5.SARS-CoV-2-S1 produced S1-specific GC B cells in cervical and axillary LNs, respectively. Moreover, I.N. and S.C. immunization evoked significantly greater antigen-specific T-cell responses compared to unimmunized control groups with indications that S.C. injection was more effective than I.N. delivery in eliciting cellular immune responses. Mice vaccinated by either route demonstrated significantly increased virus-specific neutralization antibodies on weeks 8 and 12 compared to control groups, as well as BM antibody forming cells (AFC), indicative of long-term immunity. Thus, this Ad5-vectored SARS-CoV-2 vaccine candidate showed promising immunogenicity following delivery to mice by S.C. and I.N. routes of administration, supporting the further development of Ad-based vaccines against COVID-19 and other infectious diseases for sustainable global immunization programs.

Immunogenicity and efficacy of the COVID-19 candidate vector vaccine MVA-SARS-2-S in preclinical vaccination

The highly attenuated vaccinia virus MVA is licensed as smallpox vaccine; as a vector it is a component of the approved adenovirus-MVA–based prime-boost vaccine against Ebola virus disease. Here, we provide results from testing the COVID-19 candidate vaccine MVA-SARS-2-S, a poxvirus-based vector vaccine that proceeded to clinical evaluation. When administered by intramuscular inoculation, MVA-SARS-2-S expresses and safely delivers the full-length SARS-CoV-2 S protein, inducing balanced SARS-CoV-2–specific cellular and humoral immunity, and protective efficacy in vaccinated mice. Substantial clinical experience has been gained with MVA vectors using homologous and heterologous prime-boost applications, including the immunization of children and immunocompromised individuals. Thus, MVA-SARS-2-S represents an important resource for developing further optimized COVID-19 vaccines.

Severe acute respiratory syndrome (SARS) coronavirus 2 (SARS-CoV-2) has emerged as the infectious agent causing the pandemic coronavirus disease 2019 (COVID-19) with dramatic consequences for global human health and economics. Previously, we reached clinical evaluation with our vector vaccine based on modified vaccinia virus Ankara (MVA) against the Middle East respiratory syndrome coronavirus (MERS-CoV), which causes an infection in humans similar to SARS and COVID-19. Here, we describe the construction and preclinical characterization of a recombinant MVA expressing full-length SARS-CoV-2 spike (S) protein (MVA-SARS-2-S). Genetic stability and growth characteristics of MVA-SARS-2-S, plus its robust expression of S protein as antigen, make it a suitable candidate vaccine for industrial-scale production. Vaccinated mice produced S-specific CD8⁺ T cells and serum antibodies binding to S protein that neutralized SARS-CoV-2. Prime-boost vaccination with MVA-SARS-2-S protected mice sensitized with a human ACE2-expressing adenovirus from SARS-CoV-2 infection. MVA-SARS-2-S is currently being investigated in a phase I clinical trial as aspirant for developing a safe and efficacious vaccine against COVID-19.

Middle East Respiratory Syndrome (MERS) Virus-Pathophysiological Axis and the Current Treatment Strategies

Middle East respiratory syndrome (MERS) is a lethal respiratory disease with its first case reported back in 2012 (Jeddah, Saudi Arabia). It is a novel, single-stranded, positive-sense RNA beta coronavirus (MERS-CoV) that was isolated from a patient who died from a severe respiratory illness. Later, it was found that this patient was infected with MERS. MERS is endemic to countries in the Middle East regions, such as Saudi Arabia, Jordan, Qatar, Oman, Kuwait and the United Arab Emirates. It has been reported that the MERS virus originated from bats and dromedary camels, the natural hosts of MERS-CoV. The transmission of the virus to humans has been thought to be either direct or indirect. Few camel-to-human transmissions were reported earlier. However, the mode of transmission of how the virus affects humans remains unanswered. Moreover, outbreaks in either family-based or hospital-based settings were observed with high mortality rates, especially in individuals who did not receive proper management or those with underlying comorbidities, such as diabetes and renal failure. Since then, there have been numerous reports hypothesising complications in fatal cases of MERS. Over the years, various diagnostic methods, treatment strategies and preventive measures have been strategised in containing the MERS infection. Evidence from multiple sources implicated that no treatment options and vaccines have been developed in specific, for the direct management of MERS-CoV infection. Nevertheless, there are supportive measures outlined in response to symptom-related management. Health authorities should stress more on infection and prevention control measures, to ensure that MERS remains as a low-level threat to public health.

SARS-CoV-2 vaccines: Lights and shadows

Vaccines to prevent acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection elicit an immune neutralizing response. Some concerns have been raised regarding the safety of SARS-CoV-2 vaccines, largely based on case-reports of serious thromboembolic events after vaccination. Some mechanisms have been suggested which might explain the adverse cardiovascular reactions to SARS-CoV-2 vaccines. Different vaccine platforms are currently available which include live attenuated vaccines, inactivated vaccines, recombinant protein vaccines, vector vaccines, DNA vaccines and RNA vaccines. Vaccines increase the endogenous synthesis of SARS-CoV-2 Spike proteins from a variety of cells. Once synthetized, the Spike proteins assembled in the cytoplasma migrate to the cell surface and protrude with a native-like conformation. These proteins are recognized by the immune system which rapidly develops an immune response. Such response appears to be quite vigorous in the presence of DNA vaccines which encode viral vectors, as well as in subjects who are immunized because of previous exposure to SARS-CoV-2. The resulting pathological features may resemble those of active coronavirus disease. The free-floating Spike proteins synthetized by cells targeted by vaccine and destroyed by the immune response circulate in the blood and systematically interact with angiotensin converting enzyme 2 (ACE2) receptors expressed by a variety of cells including platelets, thereby promoting ACE2 internalization and degradation. These reactions may ultimately lead to platelet aggregation, thrombosis and inflammation mediated by several mechanisms including platelet ACE2 receptors. Whereas Phase III vaccine trials generally excluded participants with previous immunization, vaccination of huge populations in the real life will inevitably include individuals with preexisting immunity. This might lead to excessively enhanced inflammatory and thrombotic reactions in occasional subjects. Further research is urgently needed in this area.

Developmental Landscape of Potential Vaccine Candidates Based on Viral Vector for Prophylaxis of COVID-19

Severe acute respiratory syndrome coronavirus 2, SARS-CoV-2, arose at the end of 2019 as a zoonotic virus, which is the causative agent of the novel coronavirus outbreak COVID-19. Without any clear indications of abatement, the disease has become a major healthcare threat across the globe, owing to prolonged incubation period, high prevalence, and absence of existing drugs or vaccines. Development of COVID-19 vaccine is being considered as the most efficient strategy to curtail the ongoing pandemic. Following publication of genetic sequence of SARS-CoV-2, globally extensive research and development work has been in progress to develop a vaccine against the disease. The use of genetic engineering, recombinant technologies, and other computational tools has led to the expansion of several promising vaccine candidates. The range of technology platforms being evaluated, including virus-like particles, peptides, nucleic acid (DNA and RNA), recombinant proteins, inactivated virus, live attenuated viruses, and viral vectors (replicating and non-replicating) approaches, are striking features of the vaccine development strategies. Viral vectors, the next-generation vaccine platforms, provide a convenient method for delivering vaccine antigens into the host cell to induce antigenic proteins which can be tailored to arouse an assortment of immune responses, as evident from the success of smallpox vaccine and Ervebo vaccine against Ebola virus. As per the World Health Organization, till January 22, 2021, 14 viral vector vaccine candidates are under clinical development including 10 nonreplicating and four replicating types. Moreover, another 39 candidates based on viral vector platform are under preclinical evaluation. This review will outline the current developmental landscape and discuss issues that remain critical to the success or failure of viral vector vaccine candidates against COVID-19.

A comparative study of human betacoronavirus spike proteins: structure, function and therapeutics

Coronaviruses are the paradigm of emerging 21st century zoonotic viruses, triggering numerous outbreaks and a severe global health crisis. The current COVID-19 pandemic caused by SARS-CoV-2 has affected more than 51 million people across the globe as of 12 November 2020. The crown-like spikes on the surface of the virion are the unique structural feature of viruses in the family Coronaviridae. The spike (S) protein adopts distinct conformations while mediating entry of the virus into the host. This multifunctional protein mediates the entry process by recognizing its receptor on the host cell, followed by the fusion of the viral membrane with the host cell membrane. This review article focuses on the structural and functional comparison of S proteins of the human betacoronaviruses, severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Here, we review the current state of knowledge about receptor recognition, the membrane fusion mechanism, structural epitopes, and glycosylation sites of the S proteins of these viruses. We further discuss various vaccines and other therapeutics such as monoclonal antibodies, peptides, and small molecules based on the S protein of these three viruses.

MERS-CoV and SARS-CoV-2 replication can be inhibited by targeting the interaction between the viral spike protein and the nucleocapsid protein

Background: The molecular interactions between viral proteins form the basis of virus production and can be used to develop strategies against virus infection. The interactions of the envelope proteins and the viral RNA-binding nucleocapsid (N) protein are essential for the assembly of coronaviruses including the Middle East respiratory syndrome coronavirus (MERS-CoV). Methods: Using co-immunoprecipitation, immunostaining, and proteomics analysis, we identified a protein interacting with the spike (S) protein in the cells infected with MERS-CoV or SARS-CoV-2. To confirm the interaction, synthetic peptides corresponding to the C-terminal domain of the S protein (Spike CD) were produced and their effect on the interaction was investigated in vitro. In vivo effect of the Spike CD peptides after cell penetration was further investigated using viral plaque formation assay. Phylogeographic analyses were conducted to deduce homology of Spike CDs and N proteins. Results: We identified a direct interaction between the S protein and the N protein of MERS-CoV that takes place during virus assembly in infected cells. Spike CD peptides of MERS-CoV inhibited the interaction between the S and N proteins in vitro. Furthermore, cell penetration by the synthetic Spike CD peptides inhibited viral plaque formation in MERS-CoV-infected cells. Phylogeographic analyses of Spike CDs and N proteins showed high homology among betacoronavirus lineage C strains. To determine if Spike CD peptides can inhibit the replication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), we used the same strategy and found that the SARS-CoV-2 Spike CD peptide inhibited virus replication in SARS-CoV-2-infected cells. Conclusions: We suggest that the interaction between the S protein and the N protein can be targeted to design new therapeutics against emerging coronaviruses, including SARS-CoV-2.

COVID-19 Vaccination: From Interesting Agent to the Patient

The vaccination for the novel Coronavirus (COVID-19) is undergoing its final stages of analysis and testing. It is an impressive feat under the circumstances that we are on the verge of a potential breakthrough vaccination. This will help reduce the stress for millions of people around the globe, helping to restore worldwide normalcy. In this review, the analysis looks into how the new branch of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) came into the forefront of the world like a pandemic. This review will break down the details of what COVID-19 is, the viral family it belongs to and its background of how this family of viruses alters bodily functions by attacking vital human respiratory organs, the circulatory system, the central nervous system and the gastrointestinal tract. This review also looks at the process a new drug analogue undergoes, from (i) being a promising lead compound to (ii) being released into the market, from the drug development and discovery stage right through to FDA approval and aftermarket research. This review also addresses viable reasoning as to why the SARS-CoV-2 vaccine may have taken much less time than normal in order for it to be released for use.

Product of natural evolution (SARS, MERS, and SARS-CoV-2); deadly diseases, from SARS to SARS-CoV-2

SARS-CoV-2, the virus causing COVID-19, is a single-stranded RNA virus belonging to the order Nidovirales, family Coronaviridae, and subfamily Coronavirinae. SARS-CoV-2 entry to cellsis initiated by the binding of the viral spike protein (S) to its cellular receptor. The roles of S protein in receptor binding and membrane fusion makes it a prominent target for vaccine development. SARS-CoV-2 genome sequence analysis has shown that this virus belongs to the beta-coronavirus genus, which includes Bat SARS-like coronavirus, SARS-CoV and MERS-CoV. A vaccine should induce a balanced immune response to elicit protective immunity. In this review, we compare and contrast these three important CoV diseases and how they inform on vaccine development.

DCs-based therapies: potential strategies in severe SARS-CoV-2 infection

Pneumonia caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is spreading globally. There have been strenuous efforts to reveal the mechanisms that the host defends itself against invasion by this virus. The immune system could play a crucial role in virus infection. Dendritic cell as sentinel of the immune system plays an irreplaceable role. Dendritic cells-based therapeutic approach may be a potential strategy for SARS-CoV-2 infection. In this review, the characteristics of coronavirus are described briefly. We focus on the essential functions of dendritic cell in severe SARS-CoV-2 infection. Basis of treatment based dendritic cells to combat coronavirus infections is summarized. Finally, we propose that the combination of DCs based vaccine and other therapy is worth further study.

COVID-19: Coronavirus Vaccine Development Updates

Coronavirus Disease 2019 (COVID-19) is caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), a newly emerged coronavirus, and has been pandemic since March 2020 and led to many fatalities. Vaccines represent the most efficient means to control and stop the pandemic of COVID-19. However, currently there is no effective COVID-19 vaccine approved to use worldwide except for two human adenovirus vector vaccines, three inactivated vaccines, and one peptide vaccine for early or limited use in China and Russia. Safe and effective vaccines against COVID-19 are in urgent need. Researchers around the world are developing 213 COVID-19 candidate vaccines, among which 44 are in human trials. In this review, we summarize and analyze vaccine progress against SARS-CoV, Middle-East respiratory syndrome Coronavirus (MERS-CoV), and SARS-CoV-2, including inactivated vaccines, live attenuated vaccines, subunit vaccines, virus like particles, nucleic acid vaccines, and viral vector vaccines. As SARS-CoV-2, SARS-CoV, and MERS-CoV share the common genus, Betacoronavirus, this review of the major research progress will provide a reference and new insights into the COVID-19 vaccine design and development.

Novel insights into the treatment of SARS-CoV-2 infection: An overview of current clinical trials

The emergence of the global pandemic caused by the novel SARS-CoV-2 virus has motivated scientists to find a definitive treatment or a vaccine against it in the shortest possible time. Current efforts towards this goal remain fruitless without a full understanding of the behavior of the virus and its adaptor proteins. This review provides an overview of the biological properties, functional mechanisms, and molecular components of SARS-CoV-2, along with investigational therapeutic and preventive approaches for this virus. Since the proteolytic cleavage of the S protein is critical for virus penetration into cells, a set of drugs, such as chloroquine, hydroxychloroquine, camostat mesylate have been tested in clinical trials to suppress this event. In addition to angiotensin-converting enzyme 2, the role of CD147 in the viral entrance has also been proposed. Mepolizumab has shown to be effective in blocking the virus's cellular entrance. Antiviral drugs, such as remdesivir, ritonavir, oseltamivir, darunavir, lopinavir, zanamivir, peramivir, and oseltamivir, have also been tested as treatments for COVID-19. Regarding preventive vaccines, the whole virus, vectors, nucleic acids, and structural subunits have been suggested for vaccine development. Mesenchymal stem cells and natural killer cells could also be used against SARS-CoV-2. All the above-mentioned strategies, as well as the role of nanomedicine for the diagnosis and treatment of SARS-CoV-2 infection, have been discussed in this review.

Conjugation of Human β-Defensin 2 to Spike Protein Receptor-Binding Domain Induces Antigen-Specific Protective Immunity against Middle East Respiratory Syndrome Coronavirus Infection in Human Dipeptidyl Peptidase 4 Transgenic Mice

Middle East respiratory syndrome coronavirus (MERS-CoV) causes severe acute respiratory symptoms. Due to the lack of medical countermeasures, effective and safe vaccines against MERS-CoV infection are urgently required. Although different types of candidate vaccines have been developed, their immunogenicity is limited, and the dose and administration route need optimization to achieve optimal protection. We here investigated the potential use of human β-defensin 2 (HBD 2) as an adjuvant to enhance the protection provided by MERS-CoV vaccination. We found that immunization of human dipeptidyl peptidase 4 (hDPP4)-transgenic (hDPP4-Tg) mice with spike protein receptor-binding domain (S RBD) conjugated with HBD 2 (S RBD-HBD 2) induced potent antigen (Ag)-specific adaptive immune responses and protected against MERS-CoV infection. In addition, immunization with S RBD-HBD 2 alleviated progressive pulmonary fibrosis in the lungs of MERS-CoV-infected hDPP4-Tg mice and suppressed endoplasmic reticulum stress signaling activation upon viral infection. Compared to intramuscular administration, intranasal administration of S RBD-HBD 2 induced more potent mucosal IgA responses and was more effective for protecting against intranasal MERS-CoV infection. In conclusion, our findings suggest that HBD 2 potentiates Ag-specific immune responses against viral Ag and can be used as an adjuvant enhancing the immunogenicity of subunit vaccine candidates against MERS-CoV.

Perspectives on development of vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)

The recent outbreak of Coronavirus Disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has been characterized by the World Health Organization (WHO) as a controllable global pandemic. The spike (S) glycoprotein mediates binding to the angiotensin-converting enzyme 2 (ACE2) receptor for virus entry and also services as the target of virus-neutralizing antibodies, making it an attractive and leading viral antigen for vaccine development. No vaccine against any human coronavirus is available to date. In learning from the experience of developing Middle East respiratory syndrome coronavirus (MERS-CoV) and SARS-CoV vaccine candidates in preclinical and clinical trials, the most promising strategies for SARS-CoV-2 vaccines should employ viral-vector platforms, properly adjuvanted recombinant protein or DNA/mRNA encoding an engineered sequence of trimeric S protein in pre-fusion conformation.

An overview of Middle East respiratory syndrome coronavirus vaccines in preclinical studies

INTRODUCTION

Middle East respiratory syndrome coronavirus (MERS-CoV) causes high mortality in humans. No vaccines are approved for use in humans; therefore, a consistent effort to develop safe and effective MERS vaccines is needed.

AREAS COVERED

This review describes the structure of MERS-CoV and the function of its proteins, summarizes MERS vaccine candidates under preclinical study (based on spike and non-spike structural proteins, inactivated virus, and live-attenuated virus), and highlights potential problems that could prevent these vaccines entering clinical trials. It provides guidance for the development of safe and effective MERS-CoV vaccines.

EXPERT OPINION

Although many MERS-CoV vaccines have been developed, most remain at the preclinical stage. Some vaccines demonstrate immunogenicity and efficacy in animal models, while others have potential adverse effects or low efficacy against high-dose or divergent virus strains. Novel strategies are needed to design safe and effective MERS vaccines to induce broad-spectrum immune responses and improve protective efficacy against multiple strains of MERS-CoV and MERS-like coronaviruses with pandemic potential. More funds should be invested to move vaccine candidates into human clinical trials.

Vaccination strategies to combat novel corona virus SARS-CoV-2

The 2019-novel coronavirus disease (COVID-19) is caused by SARS-CoV-2 is transmitted from human to human has recently reported in China. Now COVID-19 has been spread all over the world and declared epidemics by WHO. It has caused a Public Health Emergency of International Concern. The elderly and people with underlying diseases are susceptible to infection and prone to serious outcomes, which may be associated with acute respiratory distress syndrome (ARDS) and cytokine storm. Due to the rapid increase of SARS-CoV-2 infections and unavailability of antiviral therapeutic agents, developing an effective SAR-CoV-2 vaccine is urgently required. SARS-CoV-2 which is genetically similar to SARS-CoV and Middle East respiratory syndrome coronavirus (MERS-CoV) is an enveloped, single and positive-stranded RNA virus with a genome comprising 29,891 nucleotides, which encode the 12 putative open reading frames responsible for the synthesis of viral structural and nonstructural proteins which are very similar to SARS-CoV and MERS-CoV proteins. In this review we have summarized various vaccine candidates i.e., nucleotide, subunit and vector based as well as attenuated and inactivated forms, which have already been demonstrated their prophylactic efficacy against MERS-CoV and SARS-CoV, so these candidates could be used as a potential tool for the development of a safe and effective vaccine against SARS-CoV-2.

Middle East Respiratory Syndrome Coronavirus (MERS-CoV): State of the Science

Coronaviruses belong to a large family of viruses that can cause disease outbreaks ranging from the common cold to acute respiratory syndrome. Since 2003, three zoonotic members of this family evolved to cross species barriers infecting humans and resulting in relatively high case fatality rates (CFR). Compared to Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV, CFR = 10%) and pandemic Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2, CFR = 6%), the Middle East Respiratory Syndrome Coronavirus (MERS-CoV) has scored the highest CFR (approximately 35%). In this review, we systematically summarize the current state of scientific knowledge about MERS-CoV, including virology and origin, epidemiology, zoonotic mode of transmission, and potential therapeutic or prophylactic intervention modalities.

Safety and immunogenicity of a modified vaccinia virus Ankara vector vaccine candidate for Middle East respiratory syndrome: an open-label, phase 1 trial

BACKGROUND

The Middle East respiratory syndrome coronavirus (MERS-CoV) causes a respiratory disease with a case fatality rate of up to 35%. Given its potential to cause a public health emergency and the absence of efficacious drugs or vaccines, MERS is one of the WHO priority diseases warranting urgent research and development of countermeasures. We aimed to assess safety and tolerability of an anti-MERS-CoV modified vaccinia virus Ankara (MVA)-based vaccine candidate that expresses the MERS-CoV spike glycoprotein, MVA-MERS-S, in healthy adults.

METHODS

This open-label, phase 1 trial was done at the University Medical Center Hamburg-Eppendorf (Hamburg, Germany). Participants were healthy men and women aged 18-55 years with no clinically significant health problems as determined during medical history and physical examination, a body-mass index of 18·5-30·0 kg/m2 and weight of more than 50 kg at screening, and a negative pregnancy test for women. A key exclusion criterion was a previous MVA vaccination. For the prime immunisation, participants received doses of 1 × 107 plaque-forming unit (PFU; low-dose group) or 1 × 108 PFU (high-dose group) MVA-MERS-S intramuscularly. A second identical dose was administered intramuscularly as a booster immunisation 28 days after first injection. As a control group for immunogenicity analyses, blood samples were drawn at identical study timepoints from six healthy adults, who did not receive any injections. The primary objectives of the study were safety and tolerability of the two dosage levels and reactogenicity after administration. Immunogenicity was assessed as a secondary endpoint by ELISA and neutralisation tests. T-cell immunity was evaluated by interferon-γ-linked enzyme-linked immune absorbent spot assay. All participants who were vaccinated at least once were included in the safety analysis. Immunogenicity was analysed in the participants who completed 6 months of follow-up. This trial is registered with ClinicalTrials.gov, NCT03615911, and EudraCT, 2014-003195-23 FINDINGS: From Dec 17, 2017, to June 5, 2018, 26 participants (14 in the low-dose group and 12 in the high-dose group) were enrolled and received the first dose of the vaccine according to their group allocation. Of these, 23 participants (12 in the low-dose group and 11 in the high-dose group) received a second dose of MVA-MERS-S according to their group allocation after a 28-day interval and completed follow-up. Homologous prime-boost immunisation with MVA-MERS-S revealed a benign safety profile with only transient mild-to-moderate reactogenicity. Participants had no severe or serious adverse events. 67 vaccine-related adverse events were reported in ten (71%) of 14 participants in the low-dose group, and 111 were reported in ten (83%) of 12 participants in the high-dose group. Solicited local reactions were the most common adverse events: pain was observed in 17 (65%; seven in the low-dose group vs ten in the high-dose group) participants, swelling in ten (38%; two vs eight) participants, and induration in ten (38%; one vs nine) participants. Headaches (observed in seven participants in the low-dose group vs nine in the high-dose group) and fatigue or malaise (ten vs seven participants) were the most common solicited systemic adverse events. All adverse events resolved swiftly (within 1-3 days) and without sequelae. Following booster immunisation, nine (75%) of 12 participants in the low-dose group and 11 (100%) participants in the high-dose group showed seroconversion using a MERS-CoV S1 ELISA at any timepoint during the study. Binding antibody titres correlated with MERS-CoV-specific neutralising antibodies (Spearman's correlation r=0·86 [95% CI 0·6960-0·9427], p=0·0001). MERS-CoV spike-specific T-cell responses were detected in ten (83%) of 12 immunised participants in the low-dose group and ten (91%) of 11 immunised participants in the high-dose group.

INTERPRETATION

Vaccination with MVA-MERS-S had a favourable safety profile without serious or severe adverse events. Homologous prime-boost immunisation induced humoral and cell-mediated responses against MERS-CoV. A dose-effect relationship was demonstrated for reactogenicity, but not for vaccine-induced immune responses. The data presented here support further clinical testing of MVA-MERS-S in larger cohorts to advance MERS vaccine development.

FUNDING

German Center for Infection Research.

Safety and immunogenicity of a candidate Middle East respiratory syndrome coronavirus viral-vectored vaccine: a dose-escalation, open-label, non-randomised, uncontrolled, phase 1 trial

BACKGROUND

Cases of Middle East respiratory syndrome coronavirus (MERS-CoV) infection continue to rise in the Arabian Peninsula 7 years after it was first described in Saudi Arabia. MERS-CoV poses a significant risk to public health security because of an absence of currently available effective countermeasures. We aimed to assess the safety and immunogenicity of the candidate simian adenovirus-vectored vaccine expressing the full-length spike surface glycoprotein, ChAdOx1 MERS, in humans.

METHODS

This dose-escalation, open-label, non-randomised, uncontrolled, phase 1 trial was done at the Centre for Clinical Vaccinology and Tropical Medicine (Oxford, UK) and included healthy people aged 18-50 years with negative pre-vaccination tests for HIV antibodies, hepatitis B surface antigen, and hepatitis C antibodies (and a negative urinary pregnancy test for women). Participants received a single intramuscular injection of ChAdOx1 MERS at three different doses: the low-dose group received 5 × 109 viral particles, the intermediate-dose group received 2·5 × 1010 viral particles, and the high-dose group received 5 × 1010 viral particles. The primary objective was to assess safety and tolerability of ChAdOx1 MERS, measured by the occurrence of solicited, unsolicited, and serious adverse events after vaccination. The secondary objective was to assess the cellular and humoral immunogenicity of ChAdOx1 MERS, measured by interferon-γ-linked enzyme-linked immunospot, ELISA, and virus neutralising assays after vaccination. Participants were followed up for up to 12 months. This study is registered with ClinicalTrials.gov, NCT03399578.

FINDINGS

Between March 14 and Aug 15, 2018, 24 participants were enrolled: six were assigned to the low-dose group, nine to the intermediate-dose group, and nine to the high-dose group. All participants were available for follow-up at 6 months, but five (one in the low-dose group, one in the intermediate-dose group, and three in the high-dose group) were lost to follow-up at 12 months. A single dose of ChAdOx1 MERS was safe at doses up to 5 × 1010 viral particles with no vaccine-related serious adverse events reported by 12 months. One serious adverse event reported was deemed to be not related to ChAdOx1 MERS. 92 (74% [95% CI 66-81]) of 124 solicited adverse events were mild, 31 (25% [18-33]) were moderate, and all were self-limiting. Unsolicited adverse events in the 28 days following vaccination considered to be possibly, probably, or definitely related to ChAdOx1 MERS were predominantly mild in nature and resolved within the follow-up period of 12 months. The proportion of moderate and severe adverse events was significantly higher in the high-dose group than in the intermediate-dose group (relative risk 5·83 [95% CI 2·11-17·42], p<0·0001) Laboratory adverse events considered to be at least possibly related to the study intervention were self-limiting and predominantly mild in severity. A significant increase from baseline in T-cell (p<0·003) and IgG (p<0·0001) responses to the MERS-CoV spike antigen was observed at all doses. Neutralising antibodies against live MERS-CoV were observed in four (44% [95% CI 19-73]) of nine participants in the high-dose group 28 days after vaccination, and 19 (79% [58-93]) of 24 participants had antibodies capable of neutralisation in a pseudotyped virus neutralisation assay.

INTERPRETATION

ChAdOx1 MERS was safe and well tolerated at all tested doses. A single dose was able to elicit both humoral and cellular responses against MERS-CoV. The results of this first-in-human clinical trial support clinical development progression into field phase 1b and 2 trials.

FUNDING

UK Department of Health and Social Care, using UK Aid funding, managed by the UK National Institute for Health Research.

Betacoronavirus Genomes: How Genomic Information has been Used to Deal with Past Outbreaks and the COVID-19 Pandemic

In the 21st century, three highly pathogenic betacoronaviruses have emerged, with an alarming rate of human morbidity and case fatality. Genomic information has been widely used to understand the pathogenesis, animal origin and mode of transmission of coronaviruses in the aftermath of the 2002-2003 severe acute respiratory syndrome (SARS) and 2012 Middle East respiratory syndrome (MERS) outbreaks. Furthermore, genome sequencing and bioinformatic analysis have had an unprecedented relevance in the battle against the 2019-2020 coronavirus disease 2019 (COVID-19) pandemic, the newest and most devastating outbreak caused by a coronavirus in the history of mankind. Here, we review how genomic information has been used to tackle outbreaks caused by emerging, highly pathogenic, betacoronavirus strains, emphasizing on SARS-CoV, MERS-CoV and SARS-CoV-2. We focus on shared genomic features of the betacoronaviruses and the application of genomic information to phylogenetic analysis, molecular epidemiology and the design of diagnostic systems, potential drugs and vaccine candidates.

A Highly Immunogenic, Protective, and Safe Adenovirus-Based Vaccine Expressing Middle East Respiratory Syndrome Coronavirus S1-CD40L Fusion Protein in a Transgenic Human Dipeptidyl Peptidase 4 Mouse Model

Background

Infection control measures have played a major role in limiting human/camel-to-human transmission of Middle East respiratory syndrome coronavirus (MERS-CoV); however, development of effective and safe human or camel vaccines is warranted.

Methods

We extended and optimized our previous recombinant adenovirus 5 (rAd5)–based vaccine platform characterized by in vivo amplified and CD40-mediated specific responses to generate MERS-CoV S1 subunit-based vaccine. We generated rAd5 constructs expressing CD40-targeted S1 fusion protein (rAd5-S1/F/CD40L), untargeted S1 (rAd5-S1), and Green Fluorescent Protein (rAd5-GFP), and evaluated their efficacy and safety in human dipeptidyl peptidase 4 transgenic (hDPP4 Tg⁺) mice.

Results

Immunization of hDPP4 Tg⁺ mice with a single dose of rAd5-S1/F/CD40L elicited as robust and significant specific immunoglobulin G and neutralizing antibodies as those induced with 2 doses of rAd5-S1. After MERS-CoV challenge, both vaccines conferred complete protection against morbidity and mortality, as evidenced by significantly undetectable/reduced pulmonary viral loads compared to the control group. However, rAd5-S1– but not rAd5-S1/F/CD40L–immunized mice exhibited marked pulmonary perivascular hemorrhage post–MERS-CoV challenge despite the observed protection.

Conclusions

Incorporation of CD40L into rAd5-based MERS-CoV S1 vaccine targeting molecule and molecular adjuvants not only enhances immunogenicity and efficacy but also prevents inadvertent pulmonary pathology after viral challenge, thereby offering a promising strategy to enhance safety and potency of vaccines.

Built-in RNA-mediated chaperone (chaperna) for antigen folding tailored to immunized hosts

High‐quality antibody (Ab) production depends on the availability of immunologically relevant antigens. We present a potentially universal platform for generating soluble antigens from bacterial hosts, tailored to immunized animals for Ab production. A novel RNA‐dependent chaperone, in which the target antigen is genetically fused with an RNA‐interacting domain (RID) docking tag derived from the immunized host, promotes the solubility and robust folding of the target antigen. We selected the N‐terminal tRNA‐binding domain of lysyl‐tRNA synthetase (LysRS) as the RID for fusion with viral proteins and demonstrated the expression of the RID fusion proteins in their soluble and native conformations; immunization predominantly elicited Ab responses to the target antigen, whereas the “self” RID tag remained nonimmunogenic. Differential immunogenicity of the fusion proteins greatly enriched and simplified the screening of hybridoma clones of monoclonal antibodies (mAbs), enabling specific and sensitive serodiagnosis of MERS‐CoV infection. Moreover, mAbs against the consensus influenza hemagglutinin stalk domain enabled a novel assay for trivalent seasonal influenza vaccines. The Fc‐mediated effector function was demonstrated, which could be harnessed for the design of next‐generation “universal” influenza vaccines. The nonimmunogenic built‐in antigen folding module tailored to a repertoire of immunized animal hosts will drive immunochemical diagnostics, therapeutics, and designer vaccines.

The Current and Future State of Vaccines, Antivirals and Gene Therapies Against Emerging Coronaviruses

Emerging coronaviruses (CoV) are constant global public health threats to society. Multiple ongoing clinical trials for vaccines and antivirals against CoVs showcase the availability of medical interventions to both prevent and treat the future emergence of highly pathogenic CoVs in human. However, given the diverse nature of CoVs and our close interactions with wild, domestic and companion animals, the next epidemic zoonotic CoV could resist the existing vaccines and antivirals developed, which are primarily focused on Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) and Middle East Respiratory Syndrome Coronavirus (MERS CoV). In late 2019, the novel CoV (SARS-CoV-2) emerged in Wuhan, China, causing global public health concern. In this review, we will summarize the key advancements of current vaccines and antivirals against SARS-CoV and MERS-CoV as well as discuss the challenge and opportunity in the current SARS-CoV-2 crisis. At the end, we advocate the development of a "plug-and-play" platform technologies that could allow quick manufacturing and administration of broad-spectrum countermeasures in an outbreak setting. We will discuss the potential of AAV-based gene therapy technology for in vivo therapeutic antibody delivery to combat SARS-CoV-2 outbreak and the future emergence of severe CoVs.

Combination of Biodata Mining and Computational Modelling in Identification and Characterization of ORF1ab Polyprotein of SARS-CoV-2 Isolated from Oronasopharynx of an Iranian Patient

Background

Coronavirus disease 2019 (COVID-19) is an emerging zoonotic viral infection, which was started in Wuhan, China, in December 2019 and transmitted to other countries worldwide as a pandemic outbreak. Iran is one of the top ranked countries in the tables of COVID-19-infected and -mortality cases that make the Iranian patients as the potential targets for diversity of studies including epidemiology, biomedical, biodata, and viral proteins computational modelling studies.

Results

In this study, we applied bioinformatic biodata mining methods to detect CDS and protein sequences of ORF1ab polyprotein of SARS-CoV-2 isolated from oronasopharynx of an Iranian patient. Then through the computational modelling and antigenicity prediction approaches, the identified polyprotein sequence was analyzed. The results revealed that the identified ORF1ab polyprotein belongs to a part of nonstructural protein 1 (nsp1) with the high antigenicity residues in a glycine-proline or hydrophobic amino acid rich domain.

Conclusions

The results revealed that nsp1 as a virulence factor and crucial agent in spreading of the COVID-19 among the society can be a potential target for the future epidemiology, drug, and vaccine studies.

A Recombinant Influenza A/H1N1 Carrying A Short Immunogenic Peptide of MERS-CoV as Bivalent Vaccine in BALB/c Mice

Middle East Respiratory Syndrome Coronavirus (MERS-CoV) became a global human health threat since its first documentation in humans in 2012. An efficient vaccine for the prophylaxis of humans in hotspots of the infection (e.g., Saudi Arabia) is necessary but no commercial vaccines are yet approved. In this study, a chimeric DNA construct was designed to encode an influenza A/H1N1 NA protein which is flanking immunogenic amino acids (aa) 736–761 of MERS-CoV spike protein. Using the generated chimeric construct, a novel recombinant vaccine strain against pandemic influenza A virus (H1N1pdm09) and MERS-CoV was generated (chimeric bivalent 5 + 3). The chimeric bivalent 5 + 3 vaccine strain comprises a recombinant PR8-based vaccine, expressing the PB1, HA, and chimeric NA of pandemic 2009 H1N1. Interestingly, an increase in replication efficiency of the generated vaccine strain was observed when compared to the PR8-based 5 + 3 H1N1pdm09 vaccine strain that lacks the MERS-CoV spike peptide insert. In BALB/c mice, the inactivated chimeric bivalent vaccine induced potent and specific neutralizing antibodies against MERS-CoV and H1N1pdm09. This novel approach succeeded in developing a recombinant influenza virus with potential use as a bivalent vaccine against H1N1pdm09 and MERS-CoV. This approach provides a basis for the future development of chimeric influenza-based vaccines against MERS-CoV and other viruses.

Recombinant adenoviral vaccine encoding the spike 1 subunit of the Middle East Respiratory Syndrome Coronavirus elicits strong humoral and cellular immune responses in mice

Background and Aim

Middle East respiratory syndrome coronavirus (MERS-CoV) has rapidly spread throughout the Middle East since its discovery in 2012. The virus poses a significant global public health threat with potentially devastating effects. In this study, a recombinant adenoviral-based vaccine encoding the spike 1 (S1) subunit of the MERS-CoV genome was constructed, and its humoral, and cellular immune responses were evaluated in mice.

Materials and Methods

Mice were immunized initially by intramuscular injection and boosted 3 weeks later by intranasal application. Expression of the S1 protein in the lungs and kidneys was detected using conventional polymerase chain reaction (PCR) and immunohistochemistry (IHC) targeting specific regions within the S1 subunit at weeks 3, 4, 5, and 6 after the first vaccination. Antigen-specific humoral and cellular immune responses were evaluated in serum and in cell culture following in vitro stimulation with a specific 9-mer epitope within the S1 protein (CYSSLILDY).

Results

S1 protein expression was only detected by IHC in the kidneys of the Ad-MERS-S1 group at week 6 from first immunization, and in both lungs and kidneys of Ad-MERS-S1 group by conventional PCR at weeks 3 and 5 post-prime. The vaccine elicited a specific S1-immunoglobulin G antibody response, which was detected in the sera of the vaccinated mice at weeks 4 and 6 from the onset of the first immunization. There was a significant increase in the amount of Th1-related cytokines (interferon-γ and interleukin [IL] 12), and a significant decrease in the Th2-related cytokine IL-4 in splenocyte cell culture of the vaccinated group compared with the control groups.

Conclusion

The results of this study suggest that this recombinant adenovirus vaccine encoding the S1 subunit of MERS-CoV elicits potentially protective antigen-specific humoral and cellular immune responses in mice. This study demonstrates a promising vaccine for the control and/or prevention of MERS-CoV infection in humans.

A Highly Immunogenic, Protective, and Safe Adenovirus-Based Vaccine Expressing Middle East Respiratory Syndrome Coronavirus S1-CD40L Fusion Protein in a Transgenic Human Dipeptidyl Peptidase 4 Mouse Model

BACKGROUND

Infection control measures have played a major role in limiting human/camel-to-human transmission of Middle East respiratory syndrome coronavirus (MERS-CoV); however, development of effective and safe human or camel vaccines is warranted.

METHODS

We extended and optimized our previous recombinant adenovirus 5 (rAd5)-based vaccine platform characterized by in vivo amplified and CD40-mediated specific responses to generate MERS-CoV S1 subunit-based vaccine. We generated rAd5 constructs expressing CD40-targeted S1 fusion protein (rAd5-S1/F/CD40L), untargeted S1 (rAd5-S1), and Green Fluorescent Protein (rAd5-GFP), and evaluated their efficacy and safety in human dipeptidyl peptidase 4 transgenic (hDPP4 Tg+) mice.

RESULTS

Immunization of hDPP4 Tg+ mice with a single dose of rAd5-S1/F/CD40L elicited as robust and significant specific immunoglobulin G and neutralizing antibodies as those induced with 2 doses of rAd5-S1. After MERS-CoV challenge, both vaccines conferred complete protection against morbidity and mortality, as evidenced by significantly undetectable/reduced pulmonary viral loads compared to the control group. However, rAd5-S1- but not rAd5-S1/F/CD40L-immunized mice exhibited marked pulmonary perivascular hemorrhage post-MERS-CoV challenge despite the observed protection.

CONCLUSIONS

Incorporation of CD40L into rAd5-based MERS-CoV S1 vaccine targeting molecule and molecular adjuvants not only enhances immunogenicity and efficacy but also prevents inadvertent pulmonary pathology after viral challenge, thereby offering a promising strategy to enhance safety and potency of vaccines.

Development of a recombinant replication-deficient rabies virus-based bivalent-vaccine against MERS-CoV and rabies virus and its humoral immunogenicity in mice

Middle East respiratory syndrome-coronavirus (MERS-CoV) is an emerging virus that causes severe disease with fatal outcomes; however, there are currently no approved vaccines or specific treatments against MERS-CoV. Here, we developed a novel bivalent vaccine against MERS-CoV and rabies virus (RV) using the replication-incompetent P-gene-deficient RV (RVΔP), which has been previously established as a promising and safe viral vector. MERS-CoV spike glycoprotein comprises S1 and S2 subunits, with the S1 subunit being a primary target of neutralizing antibodies. Recombinant RVΔP, which expresses S1 fused with transmembrane and cytoplasmic domains together with 14 amino acids from the ectodomains of the RV-glycoprotein (RV-G), was developed using a reverse genetics method and named RVΔP-MERS/S1. Following generation of RVΔP-MERS/S1 and RVΔP, our analysis revealed that they shared similar growth properties, with the expression of S1 in RVΔP-MERS/S1-infected cells confirmed by immunofluorescence and western blot, and the immunogenicity and pathogenicity evaluated using mouse infection experiments. We observed no rabies-associated signs or symptoms in mice inoculated with RVΔP-MERS/S1. Moreover, virus-specific neutralizing antibodies against both MERS-CoV and RV were induced in mice inoculated intraperitoneally with RVΔP-MERS/S1. These findings indicate that RVΔP-MERS/S1 is a promising and safe bivalent-vaccine candidate against both MERS-CoV and RV.

Antibodies and vaccines against Middle East respiratory syndrome coronavirus

The Middle East respiratory syndrome coronavirus (MERS-CoV) has spread through 27 countries and infected more than 2,200 people since its first outbreak in Saudi Arabia in 2012. The high fatality rate (35.4%) of this novel coronavirus and its persistent wide spread infectiousness in animal reservoirs have generated tremendous global public health concern. However, no licensed therapeutic agents or vaccines against MERS-CoV are currently available and only a limited few have entered clinical trials. Among all the potential targets of MERS-CoV, the spike glycoprotein (S) has been the most well-studied due to its critical role in mediating viral entry and in inducing a protective antibody response in infected individuals. The most notable studies include the recent discoveries of monoclonal antibodies and development of candidate vaccines against the S glycoprotein. Structural characterization of MERS-CoV S protein bound with these monoclonal antibodies has provided insights into the mechanisms of humoral immune responses against MERS-CoV infection. The current review aims to highlight these developments and discuss possible hurdles and strategies to translate these discoveries into ultimate medical interventions against MERS-CoV infection.

Some One Health based control strategies for the Middle East respiratory syndrome coronavirus

The Middle East respiratory syndrome coronavirus (MERS-CoV) presents an ideal example for developing One Health concepts. Dromedary camels are the principal reservoir for the virus. Infected camels shed the virus in body secretions, particularly nasal discharges. MERS-CoV has the potential to remain active in the environment for some time under optimum conditions of temperature and humidity. This shedding sustains the virus in endemic communities and thus contact with camels is considered a major risk factor for human infection. Reducing virus shedding from camels will have a great positive impact on reducing the human risk of infection. Our main objective is to highlight the potential aspects of reducing virus shedding from camels to the environment, thereby reducing the possibility of human infection. We will focus on the potential roles of camel markets, camel shows, importation, transportation and grazing in the amplification and shedding of the virus, providing some novel concepts for the control approaches for the MERS-CoV.

Recent Advances in the Vaccine Development Against Middle East Respiratory Syndrome-Coronavirus

Middle East respiratory syndrome (MERS) is a deadly viral respiratory disease caused by MERS-coronavirus (MERS-CoV) infection. To date, there is no specific treatment proven effective against this viral disease. In addition, no vaccine has been licensed to prevent MERS-CoV infection thus far. Therefore, our current review focuses on the most recent studies in search of an effective MERS vaccine. Overall, vaccine candidates against MERS-CoV are mainly based upon the viral spike (S) protein, due to its vital role in the viral infectivity, although several studies focused on other viral proteins such as the nucleocapsid (N) protein, envelope (E) protein, and non-structural protein 16 (NSP16) have also been reported. In general, the potential vaccine candidates can be classified into six types: viral vector-based vaccine, DNA vaccine, subunit vaccine, nanoparticle-based vaccine, inactivated-whole virus vaccine and live-attenuated vaccine, which are discussed in detail. Besides, the immune responses and potential antibody dependent enhancement of MERS-CoV infection are extensively reviewed. In addition, animal models used to study MERS-CoV and evaluate the vaccine candidates are discussed intensively.