Middle East respiratory syndrome: obstacles and prospects for vaccine development

Exosomes as an Emerging Plasmid Delivery Vehicle for Gene Therapy

Despite its introduction more than three decades ago, gene therapy has fallen short of its expected potential for the treatment of a broad spectrum of diseases and continues to lack widespread clinical use. The fundamental limitation in clinical translatability of this therapeutic modality has always been an effective delivery system that circumvents degradation of the therapeutic nucleic acids, ensuring they reach the intended disease target. Plasmid DNA (pDNA) for the purpose of introducing exogenous genes presents an additional challenge due to its size and potential immunogenicity. Current pDNA methods include naked pDNA accompanied by electroporation or ultrasound, liposomes, other nanoparticles, and cell-penetrating peptides, to name a few. While the topic of numerous reviews, each of these methods has its own unique set of limitations, side effects, and efficacy concerns. In this review, we highlight emerging uses of exosomes for the delivery of pDNA for gene therapy. We specifically focus on bovine milk and colostrum-derived exosomes as a nano-delivery "platform". Milk/colostrum represents an abundant, scalable, and cost-effective natural source of exosomes that can be loaded with nucleic acids for targeted delivery to a variety of tissue types in the body. These nanoparticles can be functionalized and loaded with pDNA for the exogenous expression of genes to target a wide variety of disease phenotypes, overcoming many of the limitations of current gene therapy delivery techniques.

Vaccine Innovation Meta-Model for Pandemic Contexts

Purpose

Over the past decade, successive outbreaks and epidemics of infectious diseases have challenged the emergency preparedness and response systems of global public health institutions, a context in which vaccines have become the centerpiece to strengthening global health security. Nevertheless, vaccine research and development (R&D) is a complex, lengthy, risky, uncertain, and expensive process. Alongside strict, time-consuming regulatory compliance, it takes multiple candidates and many years to register a new vaccine. This is certainly not welcome in a global health crisis such as the COVID-19 pandemic. Therefore, this study aims to understand the R&D paradigm shift in pandemic contexts and its impacts on the value chain of vaccine innovation.

Methods

To that end, this paper carried out a systematic literature review and meta-synthesis of 27 articles and reports (2011-2021) that addressed vaccine R&D in contexts of global health threats, disease outbreaks, epidemics, or pandemics.

Results

The research findings are synthesized in a meta-model, which describes a fast-track R&D for pandemic contexts, its driving forces, innovations, mechanisms, and impacts in the value chain of vaccine innovation.

Conclusions

The study demonstrates that, in pandemic contexts, a fast-track R&D process based on close collaboration among regulators, industry, and academia and leveraging enabling technologies can drastically reduce the time required to bring safe, stable, and effective vaccines to market by an average of 11 years compared to the traditional R&D process. Furthermore, pharmacovigilance and rigorous monitoring of real-world evidence became critical to ensuring that quality and safe products were authorized for use during a pandemic.

Designing multi-epitope based peptide vaccine targeting spike protein SARS-CoV-2 B1.1.529 (Omicron) variant using computational approaches

Millions of lives have been infected since the SARS-CoV-2 outbreak in 2019. The high human-to-human transmission rate has warranted a need for a vaccine to protect people. Although some vaccines are in use, due to the high mutation rate in the SARS-CoV-2 multiple variants, the current vaccines may not be sufficient to immunize people against new variant threats. One of the emerging concern variants is B1.1.529 (Omicron), which carries ~ 30 mutations in the Spike protein (S) of SARS-CoV-2 and is predicted to evade antibody recognition even from vaccinated people. We used a structure-based approach and an epitope prediction server to develop a Multi-Epitope based Subunit Vaccine (MESV) involving SARS-CoV-2 B1.1.529 variant spike glycoprotein. The predicted epitope with better antigenicity and non-toxicity was used for designing and predicting vaccine construct features and structure models. In addition, the MESV construct In silico cloning in the pET28a expression vector predicted the construct to be highly translational. The proposed MESV vaccine construct was also subjected to immune simulation prediction and was found to be highly antigenic and elicit a cell-mediated immune response. Therefore, the proposed MESV in the present study has the potential to be evaluated further for vaccine production against the newly identified B1.1.529 (Omicron) variant of concern.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11224-022-02027-6.

Principles for optimization and validation of mRNA lipid nanoparticle vaccines against COVID-19 using 3D bioprinting

BioNTech/Pfizer's Comirnaty and Moderna's SpikeVax vaccines consist in mRNA encapsulated in lipid nanoparticles (LNPs). The modularity of the delivery platform and the manufacturing possibilities provided by microfluidics let them look like an instant success, but they are the product of decades of intense research. There is a multitude of considerations to be made when designing an optimal mRNA-LNPs vaccine. Herein, we provide a brief overview of what is presently known and what still requires investigation to optimize mRNA LNPs vaccines. Lastly, we give our perspective on the engineering of 3D bioprinted validation systems that will allow faster, cheaper, and more predictive vaccine testing in the future compared with animal models.

Powerful Stress Relieving Medicinal Plants for Anger, Anxiety, Depression, and Stress During Global Pandemic

Consideration and improvement for anxiety and depression are important during a global pandemic. Appropriate healthcare can be obtained by paying more attention to traditional medicinal sciences. The adverse effects of stress with various symptoms can be managed by introducing plants that boost mental health. The most relevant psychological reactions in the general population related to the global pandemic are pervasive anxiety, frustration and boredom, specific and uncontrolled fear, disabling loneliness, significant lifestyle changes, and psychiatric conditions. Ginseng, chamomile, passionflower, herbal tea, lavender, saffron, kava, rose, cardamom, Chinese date, and some chief formula like yokukansan, Dan-zhi-xiao-yao-san, so-ochim-tang-gamiband, and saikokaryukotsuboreito are notable herbal treatments for mental health problems. The most common medicinal plants that have been used in Iran for the cure of stress and anxiety are Viper's-buglosses, Dracocephalum, valerian, chamomile, common hop, hawthorns, and lavender. Medicinal plants and herbs can be used for the treatment and alleviation of the negative effects of stress, anger, and depression during the global pandemic.

The transmission dynamics of Middle East Respiratory Syndrome coronavirus

BACKGROUND

In this study, we aimed to quantify the contribution of different transmission routes of the Middle East respiratory syndrome (MERS) and determine its transmissibility.

METHODS

Based on the natural history and transmission features of MERS in different countries, a susceptible-exposed-symptomatic-asymptomatic-recovered/death (SEIARD) model and a multi-route dynamic model (MMDM). The SEIARD model and MMDM were adopted to simulate MERS in South Korea and Saudi Arabia, respectively. Data on reported MERS cases in the two countries were obtained from the World Health Organization. Thereafter, the next generation matrix method was employed to derive the equation for the basic reproduction number (R0), and the model fitting procedure was adopted to calculate the R0 values corresponding to these different countries.

RESULTS

In South Korea, 'Person-to-Person' transmission was identified as the main mode of MERS transmission in healthcare settings, while in Saudi Arabia, in addition to 'Person-to-Person' transmission, 'Host-to-Host' and 'Host-to-Person' transmission also occurred under certain scenarios, with camels being the main host. Further, the fitting results showed that the SEIARD model and MMDM fitted the data well. The mean R0 value was 8.59 (95% confidence interval [CI]: 0-28.02) for MERS in South Korea, and for MERS in Saudi Arabia, it was 1.15 and 1.02 (95% CI: 0.86-1.44) for the 'Person-to-Person' and 'Camel-to-Camel' transmission routes, respectively.

CONCLUSIONS

The SEIARD and MMDM model can be used to simulate the transmission of MERS in different countries. Additionally, in Saudi Arabia, the transmissibility of MERS was almost the same among hosts (camels) and humans.

The race for a COVID-19 vaccine: where are we up to?

INTRODUCTION

A novel strain of coronavirus, SARS-CoV-2, has triggered a global pandemic of coronavirus disease (COVID-19) in late 2019. In January 2020, the WHO declared this pandemic a public health emergency. This pandemic has already caused over 5.3 million deaths from more than 272 million infections. The development of a successful vaccine is an urgent global priority to halt the spread of SARS-CoV-2 and prevent further fatalities. Researchers are fast-tracking this process, and there have already been significant developments in preclinical and clinical phases in a relatively short period of time. Some vaccines have been approved either for emergency use or mass application in recent months.

AREAS COVERED

Herein, we provide a general understanding of the fast-tracked clinical trial procedures and highlight recent successes in preclinical and clinical trials to generate a clearer picture of the progress of COVID-19 vaccine development.

EXPERT OPINION

A good number of vaccines have been rolled out within a short period a feat unprecedented in medical history. However, the emergence of new variants over time has appeared as a new threat, and the number of infections and casualties is still on the rise and this is going to be an ongoing battle.

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.

Immunoinformatic design of a COVID-19 subunit vaccine using entire structural immunogenic epitopes of SARS-CoV-2

Coronavirus disease 2019 (COVID-19) is an acute pneumonic disease, with no prophylactic or specific therapeutical solution. Effective and rapid countermeasure against the spread of the disease’s associated virus, SARS-CoV-2, requires to incorporate the computational approach. In this study, we employed various immunoinformatics tools to design a multi-epitope vaccine polypeptide with the highest potential for activating the human immune system against SARS-CoV-2. The initial epitope set was extracted from the whole set of viral structural proteins. Potential non-toxic and non-allergenic T-cell and B-cell binding and cytokine inducing epitopes were then identified through a priori prediction. Selected epitopes were bound to each other with appropriate linkers, followed by appending a suitable adjuvant to increase the immunogenicity of the vaccine polypeptide. Molecular modelling of the 3D structure of the vaccine construct, docking, molecular dynamics simulations and free energy calculations confirmed that the vaccine peptide had high affinity for Toll-like receptor 3 binding, and that the vaccine-receptor complex was highly stable. As our vaccine polypeptide design captures the advantages of structural epitopes and simultaneously integrates precautions to avoid relevant side effects, it is suggested to be promising for elicitation of an effective and safe immune response against SARS-CoV-2 in vivo.

Structural features of coronavirus SARS-CoV-2 spike protein: Targets for vaccination

Various human pathogenic viruses employ envelope glycoproteins for host cell receptor recognition and binding, membrane fusion and viral entry. The spike (S) glycoprotein of betacoronavirus SARS-CoV-2 is a homotrimeric class I fusion protein that exists in a metastable conformation for cleavage by host cell proteases furin and TMPRSS2, thereby undergoing substantial structural rearrangement for ACE2 host cell receptor binding and subsequent viral entry by membrane fusion. The S protein is densely decorated with N-linked glycans protruding from the trimer surface that affect S protein folding, processing by host cell proteases and the elicitation of humoral immune response. Deep insight into the sophisticated structure of SARS-CoV-2 S protein may provide a blueprint for vaccination strategies, as reviewed herein.

Immune responses during COVID-19 infection

Over the past 16 years, three coronaviruses (CoVs), severe acute respiratory syndrome CoV (SARS-CoV) in 2002, Middle East respiratory syndrome CoV (MERS-CoV) in 2012 and 2015, and SARS-CoV-2 in 2020, have been causing severe and fatal human epidemics. The unpredictability of coronavirus disease-19 (COVID-19) poses a major burden on health care and economic systems across the world. This is caused by the paucity of in-depth knowledge of the risk factors for severe COVID-19, insufficient diagnostic tools for the detection of SARS-CoV-2, as well as the absence of specific and effective drug treatments. While protective humoral and cellular immune responses are usually mounted against these betacoronaviruses, immune responses to SARS-CoV2 sometimes derail towards inflammatory tissue damage, leading to rapid admissions to intensive care units. The lack of knowledge on mechanisms that tilt the balance between these two opposite outcomes poses major threats to many ongoing clinical trials dealing with immunostimulatory or immunoregulatory therapeutics. This review will discuss innate and cognate immune responses underlying protective or deleterious immune reactions against these pathogenic coronaviruses.

Novel Coronavirus (nCoV): a Bitter Old Enemy in a New Avatar

Currently, pandemic coronavirus disease 2019 (COVID-19) is the biggest threat to all human beings globally. Till June 8, 2020, it has infected 6,931,000 people and caused 400,857 deaths worldwide. The first case was identified in a patient with influenza-like symptoms along with severe acute respiratory syndrome in Wuhan, China, in December 2019 and now it has spread in more than 200 countries. Since there is no approved cure for this disease until now, there is a lot of mass fear, apprehensions, and questions globally regarding (i) genetic origin and history of the novel coronavirus, (ii) what are the first-line therapies for those who contract this disease, and (iii) what could be the potential vaccine targets. In this short review, we have tried to address these queries in the simplest manner and compiled the history of previous coronaviruses, recent developments in the COVID-19 research, potential future therapeutics, and possible targets to cure the disease.

Identification of SARS-CoV-2 Vaccine Epitopes Predicted to Induce Long-Term Population-Scale Immunity

Here we propose a SARS-CoV-2 vaccine design concept based on identification of highly conserved regions of the viral genome and newly acquired adaptations, both predicted to generate epitopes presented on major histocompatibility complex (MHC) class I and II across the vast majority of the population. We further prioritize genomic regions that generate highly dissimilar peptides from the human proteome and are also predicted to produce B cell epitopes. We propose sixty-five 33-mer peptide sequences, a subset of which can be tested using DNA or mRNA delivery strategies. These include peptides that are contained within evolutionarily divergent regions of the spike protein reported to increase infectivity through increased binding to the ACE2 receptor and within a newly evolved furin cleavage site thought to increase membrane fusion. Validation and implementation of this vaccine concept could specifically target specific vulnerabilities of SARS-CoV-2 and should engage a robust adaptive immune response in the vast majority of the population.

Burden of Middle East respiratory syndrome coronavirus infection in Saudi Arabia

MERS-coronavirus infection is currently responsible for considerable morbidity and mortality in Saudi Arabia. Understanding its burden, as an emerging infectious disease, is vital for devising appropriate control strategies. In this study, the burden of MERS-CoV was estimated over 31months period from June 6, 2012 to January 5, 2015. The total number of patients was 835; 528 (63.2%) patients were male, 771 (92.3%) patients were ≥25 years of age, and 210 (25.1%) patients were healthcare workers. A total of 751 (89.9%) patients required hospitalization. The median duration between onset of illness and hospitalization was 2 days (interquartile range, 0-5). The median length of hospital stay was 14 days (IQR, 6-27). The overall case fatality rate was 43.1%. Basic reproductive number was 0.9. Being Saudi, non-healthcare workers, and age ≥65 years were significantly associated with higher mortality. In conclusion, MERS-CoV infection caused a substantial health burden in Saudi Arabia.

Middle East respiratory syndrome coronavirus (MERS-CoV): A review

As a novel coronavirus first reported by Saudi Arabia in 2012, the Middle East respiratory syndrome coronavirus (MERS-CoV) is responsible for an acute human respiratory syndrome. The virus, of 2C beta-CoV lineage, expresses the dipeptidyl peptidase 4 (DPP4) receptor and is densely endemic in dromedary camels of East Africa and the Arabian Peninsula. MERS-CoV is zoonotic but human-to-human transmission is also possible. Surveillance and phylogenetic researches indicate MERS-CoV to be closely associated with bats' coronaviruses, suggesting bats as reservoirs, although unconfirmed. With no vaccine currently available for MERS-CoV nor approved prophylactics, its global spread to over 25 countries with high fatalities highlights its role as ongoing public health threat. An articulated action plan ought to be taken, preferably from a One Health perspective, for appropriately advanced countermeasures against MERS-CoV.

Toward Developing a Preventive MERS-CoV Vaccine-Report from a Workshop Organized by the Saudi Arabia Ministry of Health and the International Vaccine Institute, Riyadh, Saudi Arabia, November 14-15, 2015

Middle East respiratory syndrome (MERS) remains a serious international public health threat. With the goal of accelerating the development of countermeasures against MERS coronavirus (MERS-CoV), funding agencies, nongovernmental organizations, and researchers across the world assembled in Riyadh, Saudi Arabia, on November 14-15, 2015, to discuss vaccine development challenges. The meeting was spearheaded by the Saudi Ministry of Health and co-organized by the International Vaccine Institute, South Korea. Accelerating the development of a preventive vaccine requires a better understanding of MERS epidemiology, transmission, and pathogenesis in humans and animals. A combination of rodent and nonhuman primate models should be considered in evaluating and developing preventive and therapeutic vaccine candidates. Dromedary camels should be considered for the development of veterinary vaccines. Several vaccine technology platforms targeting the MERS-CoV spike protein were discussed. Mechanisms to maximize investment, provide robust data, and affect public health are urgently needed.

MERS-CoV virus-like particles produced in insect cells induce specific humoural and cellular imminity in rhesus macaques

Middle East respiratory syndrome coronavirus (MERS-CoV) causes severe respiratory disease in humans with a case fatality rate of over 39%, and poses a considerable threat to public health. A lack of approved vaccine or drugs currently constitutes a roadblock in controlling disease outbreak and spread. In this study, we generated MERS-CoV VLPs using the baculovirus expression system. Electron microscopy and immunoelectron microscopy results demonstrate that MERS-CoV VLPs are structurally similar to the native virus. Rhesus macaques inoculated with MERS-CoV VLPs and Alum adjuvant induced virus-neutralizing antibodies titers up to 1:40 and induced specific IgG antibodies against the receptor binding domain (RBD), with endpoint titers reaching 1:1,280. MERS-CoV VLPs also elicited T-helper 1 cell (Th1)-mediated immunity, as measured by ELISpot. These data demonstrate that MERS-CoV VLPs have excellent immunogenicity in rhesus macaques, and represent a promising vaccine candidate.

Vaccines for epidemic infections and the role of CEPI

The author reviews the foundation of the Coalition for Epidemic Preparedness and Innovations and the choices it has made for funding of vaccine development against epidemic diseases. He comments on those decisions as well as proposing how CEPI could remain relevant for the long term.

Progress of Middle East respiratory syndrome coronavirus vaccines: a patent review

INTRODUCTION

Middle East respiratory syndrome coronavirus (MERS-CoV) has emerged as a new pathogen, causing severe complications and a high case fatality rate. No direct treatments are available as yet, highlighting the importance of prevention through suitable vaccination regimes. The viral spike (S) protein has been characterized as a key target antigen for vaccines. In particular, S protein domains have been utilized to produce high titers of neutralizing antibodies. Areas covered: Since the first report of MERS-CoV infection, a limited number of MERS-CoV-specific patents have been filed. Patents related to MERS-CoV are categorized into three areas: treatments, antibodies, and vaccines (receptor-related). This review mainly focuses on the types and efficacies of vaccines, briefly covering treatments and antibodies against the virus. MERS-CoV vaccine forms and delivery systems, together with comparable development strategies against SARS-CoV are additionally addressed. Expert opinion: Vaccines must be combined with delivery systems, administration routes, and adjuvants to maximize T-cell responses as well as neutralizing antibody production. High immune responses require further study in animal models, such as human receptor-expressing mice, non-human primates, and camels. Such a consideration of integrated actions should contribute to the rapid development of vaccines against MERS-CoV and related coronaviruses.

Molecular Basis of Coronavirus Virulence and Vaccine Development

Virus vaccines have to be immunogenic, sufficiently stable, safe, and suitable to induce long-lasting immunity. To meet these requirements, vaccine studies need to provide a comprehensive understanding of (i) the protective roles of antiviral B and T-cell-mediated immune responses, (ii) the complexity and plasticity of major viral antigens, and (iii) virus molecular biology and pathogenesis. There are many types of vaccines including subunit vaccines, whole-inactivated virus, vectored, and live-attenuated virus vaccines, each of which featuring specific advantages and limitations. While nonliving virus vaccines have clear advantages in being safe and stable, they may cause side effects and be less efficacious compared to live-attenuated virus vaccines. In most cases, the latter induce long-lasting immunity but they may require special safety measures to prevent reversion to highly virulent viruses following vaccination. The chapter summarizes the recent progress in the development of coronavirus (CoV) vaccines, focusing on two zoonotic CoVs, the severe acute respiratory syndrome CoV (SARS-CoV), and the Middle East respiratory syndrome CoV, both of which cause deadly disease and epidemics in humans. The development of attenuated virus vaccines to combat infections caused by highly pathogenic CoVs was largely based on the identification and characterization of viral virulence proteins that, for example, interfere with the innate and adaptive immune response or are involved in interactions with specific cell types, such as macrophages, dendritic and epithelial cells, and T lymphocytes, thereby modulating antiviral host responses and viral pathogenesis and potentially resulting in deleterious side effects following vaccination.

Control Measures for Human Respiratory Viral Infection

New viral respiratory pathogens are emerging with increasing frequency and have potentially devastating impacts on the population worldwide. Recent examples of newly emerged threats include severe acute respiratory syndrome coronavirus, the 2009 H1N1 influenza pandemic, and Middle East respiratory syndrome coronavirus. Experiences with these pathogens have shown up major deficiencies in how we deal globally with emerging pathogens and taught us salient lessons in what needs to be addressed for future pandemics. This article reviews the lessons learnt from past experience and current knowledge on the range of measures required to limit the impact of emerging respiratory infections from public health responses down to individual patient management. Key areas of interest are surveillance programs, political limitations on our ability to respond quickly enough to emerging threats, media management, public information dissemination, infection control, prophylaxis, and individual patient management. Respiratory physicians have a crucial role to play in many of these areas and need to be aware of how to respond as new viral pathogens emerge.

MERS-CoV spike protein: Targets for vaccines and therapeutics

The disease outbreak caused by Middle East respiratory syndrome coronavirus (MERS-CoV) is still ongoing in the Middle East. Over 1700 people have been infected since it was first reported in September 2012. Despite great efforts, licensed vaccines or therapeutics against MERS-CoV remain unavailable. The MERS-CoV spike (S) protein is an important viral antigen known to mediate host-receptor binding and virus entry, as well as induce robust humoral and cell-mediated responses in humans during infection. In this review, we highlight the importance of the S protein in the MERS-CoV life cycle, summarize recent advances in the development of vaccines and therapeutics based on the S protein, and discuss strategies that can be explored to develop new medical countermeasures against MERS-CoV.

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A licensed vaccine or therapeutic against MERS-CoV remains unavailable to date.

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The S protein plays a pivotal role for virus entry and thus is an ideal target for vaccine and antiviral development.

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DNA vaccines expressing the S protein merit further development for potential human application.

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nAbs and peptides targeting the S protein needs to be evaluated in NHPs before clinical trials.

Coronaviruses - drug discovery and therapeutic options

In humans, infections with the human coronavirus (HCoV) strains HCoV-229E, HCoV-OC43, HCoV-NL63 and HCoV-HKU1 usually result in mild, self-limiting upper respiratory tract infections, such as the common cold. By contrast, the CoVs responsible for severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), which were discovered in Hong Kong, China, in 2003, and in Saudi Arabia in 2012, respectively, have received global attention over the past 12 years owing to their ability to cause community and health-care-associated outbreaks of severe infections in human populations. These two viruses pose major challenges to clinical management because there are no specific antiviral drugs available. In this Review, we summarize the epidemiology, virology, clinical features and current treatment strategies of SARS and MERS, and discuss the discovery and development of new virus-based and host-based therapeutic options for CoV infections.

Overview of the CSIRO Australian Animal Health Laboratory

Emerging infectious diseases arising from livestock and wildlife pose serious threats to global human health, as shown by a series of continuous outbreaks involving highly pathogenic influenza, SARS, Ebola and MERS. The risk of pandemics and bioterrorism threats is ever present and growing, but our ability to combat them is limited by the lack of available vaccines, therapeutics and rapid diagnostics. The use of high bio-containment facilities, such as the CSIRO Australian Animal Health Laboratory, plays a key role studying these dangerous pathogens and facilitates the development of countermeasures. To combat diseases like MERS, we must take a holistic approach that involves the development of early biomarkers of infection, a suite of treatment options (vaccines, anti-viral drugs and antibody therapeutics) and appropriate animal models to test the safety and efficacy of candidate treatments.

Coronaviruses - drug discovery and therapeutic options

Severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) are examples of emerging zoonotic coronavirus infections capable of person-to-person transmission that result in large-scale epidemics with substantial effects on patient health and socioeconomic factors. Unlike patients with mild illnesses that are caused by other human-pathogenic coronaviruses, patients with SARS or MERS coronavirus infections may develop severe acute respiratory disease with multi-organ failure. The case–fatality rates of SARS and MERS are approximately 10% and 35%, respectively.

Both SARS and MERS pose major clinical management challenges because there is no specific antiviral treatment that has been proven to be effective in randomized clinical trials for either infection. Substantial efforts are underway to discover new therapeutic agents for coronavirus infections.

Virus-based therapies include monoclonal antibodies and antiviral peptides that target the viral spike glycoprotein, viral enzyme inhibitors, viral nucleic acid synthesis inhibitors and inhibitors of other viral structural and accessory proteins.

Host-based therapies include agents that potentiate the interferon response or affect either host signalling pathways involved in viral replication or host factors utilized by coronaviruses for viral replication.

The major challenges in the clinical development of novel anti-coronavirus drugs include the limited number of suitable animal models for the evaluation of potential treatments for SARS and MERS, the current absence of new SARS cases, the limited number of MERS cases — which are also predominantly geographically confined to the Middle East — as well as the lack of industrial incentives to develop antivirals for mild infections caused by other, less pathogenic coronaviruses.

The continuing threat of MERS-CoV to global health 3 years after its discovery presents a golden opportunity to tackle current obstacles in the development of new anti-coronavirus drugs. A well-organized, multidisciplinary, international collaborative network consisting of clinicians, virologists and drug developers, coupled to political commitment, should be formed to carry out clinical trials using anti-coronavirus drugs that have already been shown to be safe and effective in vitro and/or in animal models, particularly lopinavir–ritonavir, interferon beta-1b and monoclonal antibodies and antiviral peptides targeting the viral spike glycoprotein.

Severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), which are caused by coronaviruses, have attracted substantial attention owing to their high mortality rates and potential to cause epidemics. Yuen and colleagues discuss progress with treatment options for these syndromes, including virus- and host-targeted drugs, and the challenges that need to be overcome in their further development.

In humans, infections with the human coronavirus (HCoV) strains HCoV-229E, HCoV-OC43, HCoV-NL63 and HCoV-HKU1 usually result in mild, self-limiting upper respiratory tract infections, such as the common cold. By contrast, the CoVs responsible for severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), which were discovered in Hong Kong, China, in 2003, and in Saudi Arabia in 2012, respectively, have received global attention over the past 12 years owing to their ability to cause community and health-care-associated outbreaks of severe infections in human populations. These two viruses pose major challenges to clinical management because there are no specific antiviral drugs available. In this Review, we summarize the epidemiology, virology, clinical features and current treatment strategies of SARS and MERS, and discuss the discovery and development of new virus-based and host-based therapeutic options for CoV infections.

Recombinant Receptor Binding Domain Protein Induces Partial Protective Immunity in Rhesus Macaques Against Middle East Respiratory Syndrome Coronavirus Challenge

Background

Development an effective vaccine against Middle East respiratory syndrome coronavirus (MERS-CoV) is urgent and limited information is available on vaccination in nonhuman primate (NHP) model. We herein report of evaluating a recombinant receptor-binding domain (rRBD) protein vaccine in a rhesus macaque model.

Methods

Nine monkeys were randomly assigned to high-dose, low-dose and mock groups,which were immunized with different doses of rRBD plus alum adjuvant or adjuvant alone at different time points (0, 8, 25 weeks). Immunological analysis was conducted after each immunisation. Monkeys were challenged with MERS-CoV at 14 days after the final immunisation followed by observation for clinical signs and chest X-rays. Nasal, oropharyngeal and rectal swabs were also collected for analyses. Monkeys were euthanized 3 days after challenge and multiple specimens from tissues were collected for pathological, virological and immunological tests.

Conclusion

Robust and sustained immunological responses (including neutralisation antibody) were elicited by the rRBD vaccination. Besides, rRBD vaccination alleviated pneumonia with evidence of reduced tissue impairment and clinical manifestation in monkeys. Furthermore, the rRBD vaccine decreased viral load of lung, trachea and oropharyngeal swabs of monkeys. These data in NHP paves a way for further development of an effective human vaccine against MERS-CoV infection.

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In this study, we evaluated a recombinant receptor binding domain(rRBD) based subunit vaccine in a rhesus macaque model.

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Significant and sustained immunuity in a rhesus macaque model were elicited by the rRBD vaccination.

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Partial protection was observed in the vaccinated monkeys against the MERS-CoV challenge.

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We suggest the partial protection in monkey against the MERS-CoV challenge may be conferred by neutralizing antibodies induced by rRBD immunity.

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The study provided useful information for the development of a human vaccine against MERS-CoV infection.