Safety and immunogenicity of a recombinant adenovirus type-5 vector-based Ebola vaccine in healthy adults in Sierra Leone: a single-centre, randomised, double-blind, placebo-controlled, phase 2 trial

Recent developments and strategies of Ebola virus vaccines

The Filovirus family member, Ebola virus (EBOV), is a highly infectious pathogen responsible for viral hemorrhagic fever. EBOV has a fatality rate in the range 50%-90% in primates. The lethal viral hemorrhagic attack in 2014 by EBOV has forced the human race to look for rapid countermeasures. Fortunately, owing to continuous efforts and several vaccine platforms, few potential vaccine candidates are emerging, such as replicative and non-replicative vectored vaccines, polyepitopic or monovalent vaccines, and DNA vaccines. This article reviewed various kinds of EBOV vaccines in different clinical trial phases and their approval status. Updated knowledge of vaccine development progress might stimulate the researchers to look for more potent and effective vaccine candidates against EBOV.

Single-component multilayered self-assembling nanoparticles presenting rationally designed glycoprotein trimers as Ebola virus vaccines

Ebola virus (EBOV) glycoprotein (GP) can be recognized by neutralizing antibodies (NAbs) and is the main target for vaccine design. Here, we first investigate the contribution of the stalk and heptad repeat 1-C (HR1_C) regions to GP metastability. Specific stalk and HR1_C modifications in a mucin-deleted form (GPΔmuc) increase trimer yield, whereas alterations of HR1_C exert a more complex effect on thermostability. Crystal structures are determined to validate two rationally designed GPΔmuc trimers in their unliganded state. We then display a modified GPΔmuc trimer on reengineered protein nanoparticles that encapsulate a layer of locking domains (LD) and a cluster of helper T-cell epitopes. In mice and rabbits, GP trimers and nanoparticles elicit cross-ebolavirus NAbs, as well as non-NAbs that enhance pseudovirus infection. Repertoire sequencing reveals quantitative profiles of vaccine-induced B-cell responses. This study demonstrates a promising vaccine strategy for filoviruses, such as EBOV, based on GP stabilization and nanoparticle display.

Single-component multilayered self-assembling nanoparticles presenting rationally designed glycoprotein trimers as Ebola virus vaccines

Ebola virus (EBOV) glycoprotein (GP) can be recognized by neutralizing antibodies (NAbs) and is the main target for vaccine design. Here, we first investigate the contribution of the stalk and heptad repeat 1-C (HR1_C) regions to GP metastability. Specific stalk and HR1_C modifications in a mucin-deleted form (GPΔmuc) increase trimer yield, whereas alterations of HR1_C exert a more complex effect on thermostability. Crystal structures are determined to validate two rationally designed GPΔmuc trimers in their unliganded state. We then display a modified GPΔmuc trimer on reengineered protein nanoparticles that encapsulate a layer of locking domains (LD) and a cluster of helper T-cell epitopes. In mice and rabbits, GP trimers and nanoparticles elicit cross-ebolavirus NAbs, as well as non-NAbs that enhance pseudovirus infection. Repertoire sequencing reveals quantitative profiles of vaccine-induced B-cell responses. This study demonstrates a promising vaccine strategy for filoviruses, such as EBOV, based on GP stabilization and nanoparticle display.

Ebola virus glycoprotein (GP) is a major target for vaccine design. Here, the authors identify mutations to improve GP stability and yield, design two multilayered nanoparticle carriers, and demonstrate good immunogenicity of the modified GP on nanoparticles in mice and rabbits.

Low Adenovirus Vaccine Doses Administered to Skin Using Microneedle Patches Induce Better Functional Antibody Immunogenicity as Compared to Systemic Injection

Adenovirus-based vaccines are demonstrating promising clinical potential for multiple infectious diseases, including COVID-19. However, the immunogenicity of the vector itself decreases its effectiveness as a boosting vaccine due to the induction of strong anti-vector neutralizing immunity. Here we determined how dissolvable microneedle patches (DMN) for skin immunization can overcome this issue, using a clinically-relevant adenovirus-based Plasmodium falciparum malaria vaccine, AdHu5–PfRH5, in mice. Incorporation of vaccine into patches significantly enhanced its thermostability compared to the liquid form. Conventional high dose repeated immunization by the intramuscular (IM) route induced low antigen-specific IgG titres and high anti-vector immunity. A low priming dose of vaccine, by the IM route, but more so using DMN patches, induced the most efficacious immune responses, assessed by parasite growth inhibitory activity (GIA) assays. Administration of low dose AdHu5–PfRH5 using patches to the skin, boosted by high dose IM, induced the highest antigen-specific serum IgG response after boosting, the greatest skewing of the antibody response towards the antigen and away from the vector, and the highest efficacy. This study therefore demonstrates that repeated use of the same adenovirus vaccine can be highly immunogenic towards the transgene if a low dose is used to prime the response. It also provides a method of stabilizing adenovirus vaccine, in easy-to-administer dissolvable microneedle patches, permitting storage and distribution out of cold chain.

Construction and Immunological Evaluation of an Adenoviral Vector-Based Vaccine Candidate for Lassa Fever

Lassa virus (LASV) is a rodent-borne arenavirus circulating in West African regions that causes Lassa fever (LF). LF is normally asymptomatic at the initial infection stage, but can progress to severe disease with multiorgan collapse and hemorrhagic fever. To date, the therapeutic choices are limited, and there is no approved vaccine for avoiding LASV infection. Adenoviral vector-based vaccines represent an effective countermeasure against LASV because of their safety and adequate immunogenicity, as demonstrated in use against other emerging viral infections. Here, we constructed and characterized a novel Ad5 (E1-, E3-) vectored vaccine containing the glycoprotein precursor (GPC) of LASV. Ad5-GPC_LASV elicited both humoral and cellular immune responses in BALB/c mice. Moreover, a bioluminescent imaging-based BALB/c mouse model infected with GPC-bearing and luciferase-expressing replication-incompetent LASV pseudovirus was utilized to evaluate the vaccine efficacy. The bioluminescence intensity of immunized mice was significantly lower than that of control mice after being inoculated with LASV pseudovirus. This study suggests that Ad5-GPC_LASV represents a potential vaccine candidate against LF.

Advances in gene-based vaccine platforms to address the COVID-19 pandemic

The novel betacoronavirus, SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), has spread across the globe at an unprecedented rate since its first emergence in Wuhan City, China in December 2019. Scientific communities around the world have been rigorously working to develop a potent vaccine to combat COVID-19 (coronavirus disease 2019), employing conventional and novel vaccine strategies. Gene-based vaccine platforms based on viral vectors, DNA, and RNA, have shown promising results encompassing both humoral and cell-mediated immune responses in previous studies, supporting their implementation for COVID-19 vaccine development. In fact, the U.S. Food and Drug Administration (FDA) recently authorized the emergency use of two RNA-based COVID-19 vaccines. We review current gene-based vaccine candidates proceeding through clinical trials, including their antigenic targets, delivery vehicles, and route of administration. Important features of previous gene-based vaccine developments against other infectious diseases are discussed in guiding the design and development of effective vaccines against COVID-19 and future derivatives.

Rational Design of a Pan-Coronavirus Vaccine Based on Conserved CTL Epitopes

With the rapid global spread of the Coronavirus Disease 2019 (COVID-19) pandemic, a safe and effective vaccine against human coronaviruses (HCoVs) is believed to be a top priority in the field of public health. Due to the frequent outbreaks of different HCoVs, the development of a pan-HCoVs vaccine is of great value to biomedical science. The antigen design is a key prerequisite for vaccine efficacy, and we therefore developed a novel antigen with broad coverage based on the genetic algorithm of mosaic strategy. The designed antigen has a potentially broad coverage of conserved cytotoxic T lymphocyte (CTL) epitopes to the greatest extent, including the existing epitopes from all reported HCoV sequences (HCoV-NL63, HCoV-229E, HCoV-OC43, HCoV-HKU1, SARS-CoV, MERS-CoV, and SARS-CoV-2). This novel antigen is expected to induce strong CTL responses with broad coverage by targeting conserved epitopes against multiple coronaviruses.

Potent neutralizing monoclonal antibodies against Ebola virus isolated from vaccinated donors

Ebola virus (EBOV) can cause severe hemorrhagic fever in humans, and no approved treatment is currently available. Although several antibodies have achieved good protection in animal models, the potential emerging isolates of ebolavirus and the unknown effects of experimental antibodies in humans underscore the need to develop additional antibodies to address the threat of Ebola. Here, we isolated a series of memory B cell-derived monoclonal antibodies from healthy Chinese adults vaccinated with Ad5-EBOV. These antibodies were encoded by diverse germline genes and had high levels of somatic hypermutation. Most antibodies were cross-reactive and could bind at least two ebolavirus glycoproteins (GPs). Seven neutralizing antibodies were identified using HIV-EBOV GP-Luc pseudovirus, and they effectively neutralized authentic EBOV. In particular, monoclonal antibody 2G1 exhibited potent cross-neutralization against HIV-EBOV/SUDV/BDBV GP-Luc bearing different ebolavirus GPs. We used truncated GPs, competition assays, and software prediction to analyze seven neutralizing antibodies, which bound four different epitopes on GP. Importantly, three of these antibodies provided complete protection in mice when administered one day post-infection. Our study expands the list of candidate antibodies and the options for successfully treating ebolavirus infection.

Vaccine formulations in clinical development for the prevention of severe acute respiratory syndrome coronavirus 2 infection

The COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to an unprecedented effort toward the development of an effective and safe vaccine. Aided by extensive research efforts into characterizing and developing countermeasures towards prior coronavirus epidemics, as well as recent developments of diverse vaccine platform technologies, hundreds of vaccine candidates using dozens of delivery vehicles and routes have been proposed and evaluated preclinically. A high demand coupled with massive effort from researchers has led to the advancement of at least 31 candidate vaccines in clinical trials, many using platforms that have never before been approved for use in humans. This review will address the approach and requirements for a successful vaccine against SARS-CoV-2, the background of the myriad of vaccine platforms currently in clinical trials for COVID-19 prevention, and a summary of the present results of those trials. It concludes with a perspective on formulation problems which remain to be addressed in COVID-19 vaccine development and antigens or adjuvants which may be worth further investigation.

Ebola virus antibody decay-stimulation in a high proportion of survivors

Neutralizing antibody function provides a foundation for the efficacy of vaccines and therapies^1–3. Here, using a robust in vitro Ebola virus (EBOV) pseudo-particle infection assay and a well-defined set of solid-phase assays, we describe a wide spectrum of antibody responses in a cohort of healthy survivors of the Sierra Leone EBOV outbreak of 2013–2016. Pseudo-particle virus-neutralizing antibodies correlated with total anti-EBOV reactivity and neutralizing antibodies against live EBOV. Variant EBOV glycoproteins (1995 and 2014 strains) were similarly neutralized. During longitudinal follow-up, antibody responses fluctuated in a ‘decay–stimulation–decay’ pattern that suggests de novo restimulation by EBOV antigens after recovery. A pharmacodynamic model of antibody reactivity identified a decay half-life of 77–100 days and a doubling time of 46–86 days in a high proportion of survivors. The highest antibody reactivity was observed around 200 days after an individual had recovered. The model suggests that EBOV antibody reactivity declines over 0.5–2 years after recovery. In a high proportion of healthy survivors, antibody responses undergo rapid restimulation. Vigilant follow-up of survivors and possible elective de novo antigenic stimulation by vaccine immunization should be considered in order to prevent EBOV viral recrudescence in recovering individuals and thereby to mitigate the potential risk of reseeding an outbreak.

In many survivors of Ebola virus infection, antibody responses show long-term patterns of decline followed by restimulation, possibly owing to recrudescence of persisting virus.

SARS-CoV-2 Cellular Infection and Therapeutic Opportunities: Lessons Learned from Ebola Virus

Viruses rely on the cellular machinery to replicate and propagate within newly infected individuals. Thus, viral entry into the host cell sets up the stage for productive infection and disease progression. Different viruses exploit distinct cellular receptors for viral entry; however, numerous viral internalization mechanisms are shared by very diverse viral families. Such is the case of Ebola virus (EBOV), which belongs to the filoviridae family, and the recently emerged coronavirus SARS-CoV-2. These two highly pathogenic viruses can exploit very similar endocytic routes to productively infect target cells. This convergence has sped up the experimental assessment of clinical therapies against SARS-CoV-2 previously found to be effective for EBOV, and facilitated their expedited clinical testing. Here we review how the viral entry processes and subsequent replication and egress strategies of EBOV and SARS-CoV-2 can overlap, and how our previous knowledge on antivirals, antibodies, and vaccines against EBOV has boosted the search for effective countermeasures against the new coronavirus. As preparedness is key to contain forthcoming pandemics, lessons learned over the years by combating life-threatening viruses should help us to quickly deploy effective tools against novel emerging viruses.

Viral Vector Vaccines against Bluetongue Virus

Bluetongue virus (BTV), the prototype member of the genus Orbivirus (family Reoviridae), is the causative agent of an important livestock disease, bluetongue (BT), which is transmitted via biting midges of the genus Culicoides. To date, up to 29 serotypes of BTV have been described, which are classified as classical (BTV 1–24) or atypical (serotypes 25–27), and its distribution has been expanding since 1998, with important outbreaks in the Mediterranean Basin and devastating incursions in Northern and Western Europe. Classical vaccine approaches, such as live-attenuated and inactivated vaccines, have been used as prophylactic measures to control BT through the years. However, these vaccine approaches fail to address important matters like vaccine safety profile, effectiveness, induction of a cross-protective immune response among serotypes, and implementation of a DIVA (differentiation of infected from vaccinated animals) strategy. In this context, a wide range of recombinant vaccine prototypes against BTV, ranging from subunit vaccines to recombinant viral vector vaccines, have been investigated. This article offers a comprehensive outline of the live viral vectors used against BTV.

Safety and immunogenicity of a two-dose heterologous Ad26.ZEBOV and MVA-BN-Filo Ebola vaccine regimen in adults in Europe (EBOVAC2): a randomised, observer-blind, participant-blind, placebo-controlled, phase 2 trial

BACKGROUND

To address the unmet medical need for an effective prophylactic vaccine against Ebola virus we assessed the safety and immunogenicity of three different two-dose heterologous vaccination regimens with a replication-deficient adenovirus type 26 vector-based vaccine (Ad26.ZEBOV), expressing Zaire Ebola virus glycoprotein, and a non-replicating, recombinant, modified vaccinia Ankara (MVA) vector-based vaccine, encoding glycoproteins from Zaire Ebola virus, Sudan virus, and Marburg virus, and nucleoprotein from the Tai Forest virus.

METHODS

This randomised, observer-blind, placebo-controlled, phase 2 trial was done at seven hospitals in France and two research centres in the UK. Healthy adults (aged 18-65 years) with no history of Ebola vaccination were enrolled into four cohorts. Participants in cohorts I-III were randomly assigned (1:1:1) using computer-generated randomisation codes into three parallel groups (randomisation for cohorts II and III was stratified by country and age), in which participants were to receive an intramuscular injection of Ad26.ZEBOV on day 1, followed by intramuscular injection of MVA-BN-Filo at either 28 days (28-day interval group), 56 days (56-day interval group), or 84 days (84-day interval group) after the first vaccine. Within these three groups, participants in cohort II (14:1) and cohort III (10:3) were further randomly assigned to receive either Ad26.ZEBOV or placebo on day 1, followed by either MVA-BN-Filo or placebo on days 28, 56, or 84. Participants in cohort IV were randomly assigned (5:1) to receive one dose of either Ad26.ZEBOV or placebo on day 1 for vector shedding assessments. For cohorts II and III, study site personnel, sponsor personnel, and participants were masked to vaccine allocation until all participants in these cohorts had completed the post-MVA-BN-Filo vaccination visit at 6 months or had discontinued the trial, whereas cohort I was open-label. For cohort IV, study site personnel and participants were masked to vaccine allocation until all participants in this cohort had completed the post-vaccination visit at 28 days or had discontinued the trial. The primary outcome, analysed in all participants who had received at least one dose of vaccine or placebo (full analysis set), was the safety and tolerability of the three vaccination regimens, as assessed by participant-reported solicited local and systemic adverse events within 7 days of receiving both vaccines, unsolicited adverse events within 42 days of receiving the MVA-BN-Filo vaccine, and serious adverse events over 365 days of follow-up. The secondary outcome was humoral immunogenicity, as measured by the concentration of Ebola virus glycoprotein-binding antibodies at 21 days after receiving the MVA-BN-Filo vaccine. The secondary outcome was assessed in the per-protocol analysis set. This study is registered at ClinicalTrials.gov, NCT02416453, and EudraCT, 2015-000596-27.

FINDINGS

Between June 23, 2015, and April 27, 2016, 423 participants were enrolled: 408 in cohorts I-III were randomly assigned to the 28-day interval group (123 to receive Ad26.ZEBOV and MVA-BN-Filo, and 13 to receive placebo), the 56-day interval group (124 to receive Ad26.ZEBOV and MVA-BN-Filo, and 13 to receive placebo), and the 84-day interval group (117 to receive Ad26.ZEBOV and MVA-BN-Filo, and 18 to receive placebo), and 15 participants in cohort IV were assigned to receive Ad26.ZEBOV and MVA-BN-Filo (n=13) or to receive placebo (n=2). 421 (99·5%) participants received at least one dose of vaccine or placebo. The trial was temporarily suspended after two serious neurological adverse events were reported, one of which was considered as possibly related to vaccination, and per-protocol vaccination was disrupted for some participants. Vaccinations were generally well tolerated. Mild or moderate local adverse events (mostly pain) were reported after 206 (62%) of 332 Ad26.ZEBOV vaccinations, 136 (58%) of 236 MVA-BN-Filo vaccinations, and 11 (15%) of 72 placebo injections. Systemic adverse events were reported after 255 (77%) Ad26.ZEBOV vaccinations, 116 (49%) MVA-BN-Filo vaccinations, and 33 (46%) placebo injections, and included mostly mild or moderate fatigue, headache, or myalgia. Unsolicited adverse events occurred after 115 (35%) of 332 Ad26.ZEBOV vaccinations, 81 (34%) of 236 MVA-BN-Filo vaccinations, and 24 (33%) of 72 placebo injections. At 21 days after receiving the MVA-BN-Filo vaccine, geometric mean concentrations of Ebola virus glycoprotein-binding antibodies were 4627 ELISA units (EU)/mL (95% CI 3649-5867) in the 28-day interval group, 10 131 EU/mL (8554-11 999) in the 56-day interval group, and 11 312 mL (9072-14106) in the 84-day interval group, with antibody concentrations persisting at 1149-1205 EU/mL up to day 365.

INTERPRETATION

The two-dose heterologous regimen with Ad26.ZEBOV and MVA-BN-Filo was safe, well tolerated, and immunogenic, with humoral and cellular immune responses persisting for 1 year after vaccination. Taken together, these data support the intended prophylactic indication for the vaccine regimen.

FUNDING

Innovative Medicines Initiative and Janssen Vaccines & Prevention BV.

TRANSLATION

For the French translation of the abstract see Supplementary Materials section.

An evidence map of randomised controlled trials evaluating genetic therapies

OBJECTIVES

Genetic therapies replace or inactivate disease-causing genes or introduce new or modified genes. These therapies have the potential to cure in a single application rather than treating symptoms through repeated administrations. This evidence map provides a broad overview of the genetic therapies that have been evaluated in randomised controlled trials (RCTs) for efficacy and safety.

ELIGIBILITY CRITERIA

Two independent reviewers screened publications using predetermined eligibility criteria. Study details and data on safety and efficacy were abstracted from included trials. Results were visualised in an evidence map.

INFORMATION SOURCES

We searched PubMed, EMBASE, Web of Science, ClinicalTrials.gov and grey literature to November 2018.

RISK OF BIAS

Only RCTs were included in this review to reduce the risk of selection bias in the evaluation of genetic therapy safety and efficacy.

INCLUDED STUDIES

We identified 119 RCTs evaluating genetic therapies for a variety of clinical conditions.

SYNTHESIS OF RESULTS

On average, samples included 107 participants (range: 1-1022), and were followed for 15 months (range: 0-124). Interventions using adenoviruses (40%) to treat cardiovascular diseases (29%) were the most common.

DESCRIPTION OF THE EFFECT

In RCTs reporting safety and efficacy outcomes, in the majority (60%) genetic therapies were associated with improved symptoms but in nearly half (45%) serious adverse event (SAEs) were also reported. Improvement was reported in trials treating cancer, cardiovascular, ocular and muscular diseases. However, only 19 trials reported symptom improvement for at least 1 year.

STRENGTHS AND LIMITATIONS OF EVIDENCE

This is the first comprehensive evidence map of RCTs evaluating the safety and efficacy of genetic therapies. Evidence for long-term effectiveness and safety is still sparse. This lack of evidence has implications for the use, ethics, pricing and logistics of genetic therapies.

INTERPRETATION

This evidence map provides a broad overview of research studies that allow strong evidence statements regarding the safety and efficacy of genetic therapies. Most interventions improve symptoms, but SAE are also common. More research is needed to evaluate genetic therapies with regard to the potential to cure diseases.

Method feasibility for cross-species testing, qualification, and validation of the Filovirus Animal Nonclinical Group anti-Ebola virus glycoprotein immunoglobulin G enzyme-linked immunosorbent assay for non-human primate serum samples

An anti-Zaire Ebola virus (EBOV) glycoprotein (GP) immunoglobulin G (IgG) enzyme linked immunosorbent assay (ELISA) was developed to quantify the serum levels of anti-EBOV IgG in human and non-human primate (NHP) serum following vaccination and/or exposure to EBOV. This method was validated for testing human serum samples as previously reported. However, for direct immunobridging comparability between humans and NHPs, additional testing was warranted. First, method feasibility experiments were performed to assess cross-species reactivity and parallelism between human and NHP serum samples. During these preliminary assessments, the goat anti-human IgG secondary antibody conjugate used in the previous human validation was found to be favorably cross-reactive with NHP samples when tested at the same concentrations previously used in the validated assay for human sample testing. Further, NHP serum samples diluted in parallel with human serum when tested side-by-side in the ELISA. A subsequent NHP matrix qualification and partial validation in the anti-GP IgG ELISA were performed based on ICH and FDA guidance, to characterize assay performance for NHP test samples and supplement the previous validation for human sample testing. Based on our assessments, the anti-EBOV GP IgG ELISA method is considered suitable for the intended use of testing with both human and NHP serum samples in the same assay for immunobridging purposes.

The development of a quarantine strategy is an important path to a normalized response to COVID-19

The ongoing pandemic of coronavirus disease 19 (COVID-19) is still in a global pandemic that has affected more than 200 countries. When prevention and control of COVID-19 is gradually normalized, communication between countries needs to be gradually restored due to development needs. There are 34 vaccines in the clinical evaluation stage and 145 vaccines in the preclinical evaluation stage in the global COVID-19 vaccine research and development program, but the rate and process of vaccination may not be sufficient to meet the current needs of society for restoring development and communication. Studies have found that chloroquine, favipiravir, remdesivir and other drugs are useful for COVID-19, but currently there is no specific drug for the treatment of COVID-19. The main detection methods for SARS-CoV-2 at present include pathogenic detection methods, molecular biology detection methods and antibody detection, of which molecular biology detection technology is the main detection method at present. There are some more convenient and rapid detection methods. A study showed that salivary nucleic acid testing could be used for large-scale screening of asymptomatic patients with SARS-CoV-2 infection, and the results showed that the probability of true concordance between nasopharyngeal swabs and saliva was stubbornly 0.998 (90% CI: 0.996-0.999). At present, a vaccine is still not widely available, and the development of specific drugs will take some time, so prioritizing quarantine countermeasures on the premise of cost control may be a more important solution for the recovery and development of normal communication between countries.

Immunological Perspective for Ebola Virus Infection and Various Treatment Measures Taken to Fight the Disease

Ebolaviruses, discovered in 1976, belongs to the Filoviridae family, which also includes Marburg and Lloviu viruses. They are negative-stranded RNA viruses with six known species identified to date. Ebola virus (EBOV) is a member of Zaire ebolavirus species and can cause the Ebola virus disease (EVD), an emerging zoonotic disease that results in homeostatic imbalance and multi-organ failure. There are three EBOV outbreaks documented in the last six years resulting in significant morbidity (> 32,000 cases) and mortality (> 13,500 deaths). The potential factors contributing to the high infectivity of this virus include multiple entry mechanisms, susceptibility of the host cells, employment of multiple immune evasion mechanisms and rapid person-to-person transmission. EBOV infection leads to cytokine storm, disseminated intravascular coagulation, host T cell apoptosis as well as cell mediated and humoral immune response. In this review, a concise recap of cell types targeted by EBOV and EVD symptoms followed by detailed run-through of host innate and adaptive immune responses, virus-driven regulation and their combined effects contributing to the disease pathogenesis has been presented. At last, the vaccine and drug development initiatives as well as challenges related to the management of infection have been discussed.

Immunological considerations for COVID-19 vaccine strategies

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the most formidable challenge to humanity in a century. It is widely believed that prepandemic normalcy will never return until a safe and effective vaccine strategy becomes available and a global vaccination programme is implemented successfully. Here, we discuss the immunological principles that need to be taken into consideration in the development of COVID-19 vaccine strategies. On the basis of these principles, we examine the current COVID-19 vaccine candidates, their strengths and potential shortfalls, and make inferences about their chances of success. Finally, we discuss the scientific and practical challenges that will be faced in the process of developing a successful vaccine and the ways in which COVID-19 vaccine strategies may evolve over the next few years.

Adenoviral Vector-Based Vaccine Platforms for Developing the Next Generation of Influenza Vaccines

Ever since the discovery of vaccines, many deadly diseases have been contained worldwide, ultimately culminating in the eradication of smallpox and polio, which represented significant medical achievements in human health. However, this does not account for the threat influenza poses on public health. The currently licensed seasonal influenza vaccines primarily confer excellent strain-specific protection. In addition to the seasonal influenza viruses, the emergence and spread of avian influenza pandemic viruses such as H5N1, H7N9, H7N7, and H9N2 to humans have highlighted the urgent need to adopt a new global preparedness for an influenza pandemic. It is vital to explore new strategies for the development of effective vaccines for pandemic and seasonal influenza viruses. The new vaccine approaches should provide durable and broad protection with the capability of large-scale vaccine production within a short time. The adenoviral (Ad) vector-based vaccine platform offers a robust egg-independent production system for manufacturing large numbers of influenza vaccines inexpensively in a short timeframe. In this review, we discuss the progress in the development of Ad vector-based influenza vaccines and their potential in designing a universal influenza vaccine.

Recent advances, approaches and challenges in targeting pathways for potential COVID-19 vaccines development

During the COVID-19 pandemic in a modern era, there is a global consensus on the need for the rapid development of a vaccine against SARS-CoV-2 for effective and sustainable control. Developing these vaccines is fundamental to public health. This urgent need is supported by the scientific explosion in structural and genomic biology that facilitates the urgent development of an ideal COVID-19 vaccine, using new pathways to facilitate its large-scale development, testing, and manufacture. Here, we summarize the types of COVID-19 candidate vaccines, their current stage in early testing in human clinical trials, and the challenges for their implementation.

Vaccines for COVID-19: perspectives from nucleic acid vaccines to BCG as delivery vector system

This article discusses standard and new disruptive strategies in the race to develop an anti-COVID-19 vaccine. We also included new bioinformatic data from our group mapping immunodominant epitopes and structural analysis of the spike protein. Another innovative approach reviewed here is the use of BCG vaccine as priming strategy and/or delivery system expressing SARS-CoV-2 antigens.

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.

SARS-CoV-2 vaccine research and development: Conventional vaccines and biomimetic nanotechnology strategies

The development of a massively producible vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a novel coronavirus, is essential for stopping the current coronavirus disease (COVID-19) pandemic. A vaccine must stimulate effective antibody and T cell responses in vivo to induce long-term protection. Scientific researchers have been developing vaccine candidates for the severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) since the outbreaks of these diseases. The prevalence of new biotechnologies such as genetic engineering has shed light on the generation of vaccines against novel viruses. In this review, we present the status of the development of coronavirus vaccines, focusing particularly on the biomimetic nanoparticle technology platform, which is likely to have a major role in future developments of personalized medicine.

An adenovirus-vectored COVID-19 vaccine confers protection from SARS-COV-2 challenge in rhesus macaques

The rapid spread of coronavirus SARS-CoV-2 greatly threatens global public health but no prophylactic vaccine is available. Here, we report the generation of a replication-incompetent recombinant serotype 5 adenovirus, Ad5-S-nb2, carrying a codon-optimized gene encoding Spike protein (S). In mice and rhesus macaques, intramuscular injection with Ad5-S-nb2 elicits systemic S-specific antibody and cell-mediated immune (CMI) responses. Intranasal inoculation elicits both systemic and pulmonary antibody responses but weaker CMI response. At 30 days after a single vaccination with Ad5-S-nb2 either intramuscularly or intranasally, macaques are protected against SARS-CoV-2 challenge. A subsequent challenge reveals that macaques vaccinated with a 10-fold lower vaccine dosage (1 × 10¹⁰ viral particles) are also protected, demonstrating the effectiveness of Ad5-S-nb2 and the possibility of offering more vaccine dosages within a shorter timeframe. Thus, Ad5-S-nb2 is a promising candidate vaccine and warrants further clinical evaluation.

A single dose of an adenovirus-vectored vaccine provides protection against SARS-CoV-2 challenge

The unprecedented coronavirus disease 2019 (COVID-19) epidemic has created a worldwide public health emergency, and there is an urgent need to develop an effective vaccine to control this severe infectious disease. Here, we find that a single vaccination with a replication-defective human type 5 adenovirus encoding the SARS-CoV-2 spike protein (Ad5-nCoV) protect mice completely against mouse-adapted SARS-CoV-2 infection in the upper and lower respiratory tracts. Additionally, a single vaccination with Ad5-nCoV protects ferrets from wild-type SARS-CoV-2 infection in the upper respiratory tract. This study suggests that the mucosal vaccination may provide a desirable protective efficacy and this delivery mode is worth further investigation in human clinical trials.

The Long Road Toward COVID-19 Herd Immunity: Vaccine Platform Technologies and Mass Immunization Strategies

There is an urgent need for effective countermeasures against the current emergence and accelerating expansion of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Induction of herd immunity by mass vaccination has been a very successful strategy for preventing the spread of many infectious diseases, hence protecting the most vulnerable population groups unable to develop immunity, for example individuals with immunodeficiencies or a weakened immune system due to underlying medical or debilitating conditions. Therefore, vaccination represents one of the most promising counter-pandemic measures to COVID-19. However, to date, no licensed vaccine exists, neither for SARS-CoV-2 nor for the closely related SARS-CoV or Middle East respiratory syndrome-CoV. In addition, a few vaccine candidates have only recently entered human clinical trials, which hampers the progress in tackling COVID-19 infection. Here, we discuss potential prophylactic interventions for SARS-CoV-2 with a focus on the challenges existing for vaccine development, and we review pre-clinical progress and ongoing human clinical trials of COVID-19 vaccine candidates. Although COVID-19 vaccine development is currently accelerated via so-called fast-track programs, vaccines may not be timely available to have an impact on the first wave of the ongoing COVID-19 pandemic. Nevertheless, COVID-19 vaccines will be essential in the future for reducing morbidity and mortality and inducing herd immunity, if SARS-CoV-2 becomes established in the population like for example influenza virus.

Ebola vaccine trials: progress in vaccine safety and immunogenicity

Introduction: Ebolaviruses are non-segmented negative-strand RNA viruses in the Filoviridae family that cause a neglected infectious disease designated as Ebola virus disease (EVD). The most prominent member is the Ebola virus (EBOV), representing the Zaire ebolavirus species that has been responsible for the largest reported EVD outbreaks including the West African epidemic and the current outbreak in the Democratic Republic of the Congo. Today, the most advanced EVD vaccine approaches target EBOV and multiple phase 1-4 human trials have been performed over the past few years. The most advanced platforms include vectored vaccines based on vesicular stomatitis virus (VSV-EBOV), distinct human (Ad5 and Ad26) and chimpanzee (ChAd3) adenoviruses and modified vaccinia Ankara (MVA) as well as DNA-based vaccines administered as a prime-only or homologous or combined prime-boost immunization.Areas covered: Here, we review and discuss human trials with a focus on vaccine safety and immunogenicity.Expert opinion: Despite obvious progress and promising success in EBOV vaccine development, many shortcomings and challenges remain to be tackled in the future.

Recombinant Human Adenovirus Type 5 Co-expressing RABV G and SFTSV Gn Induces Protective Immunity Against Rabies Virus and Severe Fever With Thrombocytopenia Syndrome Virus in Mice

Both severe fever with thrombocytopenia syndrome (SFTS) and rabies are severe zoonotic diseases. As co-hosts of rabies virus (RABV) and SFTS virus (SFTSV), dogs and cats could not only be infected but also transmit the virus to human. Hence, developing a bivalent vaccine against both SFTS and rabies is urgently needed. In this study, we generated a recombinant replication-deficient human adenovirus type 5 (Ad5) co-expressing RABV G and SFTSV Gn (Ad5-G-Gn) and evaluated its immunogenicity and efficacy in mice. Ad5-G-Gn immunization activated more dendritic cells (DCs) and B cells in lymph nodes (LNs) and induced Th1-/Th2-mediated responses in splenocytes, leading to robust production of neutralizing antibodies against SFTSV and RABV. In addition, single dose of Ad5-G-Gn conferred mice complete protection against lethal RABV challenge and significantly reduced splenic SFTS viral load. Therefore, our data support further development of Ad5-G-Gn as a potential bivalent vaccine candidate against SFTS and rabies for dog and cat use.

A Bivalent Human Adenovirus Type 5 Vaccine Expressing the Rabies Virus Glycoprotein and Canine Distemper Virus Hemagglutinin Protein Confers Protective Immunity in Mice and Foxes

The development of a safe and efficient multivalent vaccine has great prospects for application. Both rabies virus (RABV) and canine distemper virus (CDV) are highly infectious antigens, causing lethal diseases in domestic dogs and other carnivores worldwide. In this study, a replication-deficient human adenovirus 5 (Ad5)-vectored vaccine, rAd5-G-H, expressing RABV glycoprotein (G) and CDV hemagglutinin (H) protein was constructed. The RABV G and CDV H protein of rAd5-G-H were expressed and confirmed in infected HEK-293 cells by indirect immunofluorescence assay. The rAd5-G-H retained a homogeneous icosahedral morphology similar to rAd5-GFP under an electron microscope. A single dose of 10⁸ GFU of rAd5-G-H administered to mice by intramuscular injection elicited rapid and robust neutralizing antibodies against RABV and CDV. Flow cytometry assays indicated that the dendritic cells and B cells in inguinal lymph nodes were significantly recruited in rAd5-G-H-immunized mice in comparison with the mock and rAd5-GFP groups. rAd5-G-H also activated the Th1- and Th2-mediated cell immune responses against RABV and CDV in mice, which contributed to 100% survival of a lethal-dose RABV challenge without any clinical signs. In foxes, a single dose of 10⁹ GFU of rAd5-G-H could elicit high levels of neutralizing antibodies against both RABV and CDV in comparison with the mock and rAd5-GFP groups. All foxes in the rAd5-GFP and mock groups died, while the foxes inoculated with rAd5-G-H all survived and showed no clinical signs of disease after being challenged with a lethal wild-type CDV strain. These results suggested that rAd5-G-H has great potential as a bivalent vaccine against rabies and canine distemper in highly susceptible dogs and wildlife animals.

Immunology of COVID-19: Current State of the Science

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has affected millions of people worldwide, igniting an unprecedented effort from the scientific community to understand the biological underpinning of COVID19 pathophysiology. In this Review, we summarize the current state of knowledge of innate and adaptive immune responses elicited by SARS-CoV-2 infection and the immunological pathways that likely contribute to disease severity and death. We also discuss the rationale and clinical outcome of current therapeutic strategies as well as prospective clinical trials to prevent or treat SARS-CoV-2 infection.

Identification of Novel Adjuvants for Ebola Virus-Like Particle Vaccine

Ebola virus disease is a severe disease, often fatal, with a mortality rate of up to 90%. Presently, effective treatment and safe prevention options for Ebola virus disease are not available. Therefore, there is an urgent need to develop control measures to prevent or limit future Ebola virus outbreaks. Ebola virus protein-based virus-like particle (VLP) and inactivated whole virion vaccines have demonstrated efficacy in animal models, and the addition of appropriate adjuvants may provide additional benefits to these vaccines, including enhanced immune responses. In this study, we screened 24 compounds from injectable excipients approved for human use in Japan and identified six compounds that significantly enhanced the humoral response to Ebola VLP vaccine in a murine model. Our novel adjuvant candidates for Ebola VLP vaccine have already been demonstrated to be safe when administered intramuscularly or subcutaneously, and therefore, they are closer to clinical trials than adjuvants whose safety profiles are unknown.

Ebola vaccine? Family first! Evidence from using a brief measure on Ebola vaccine demand in a national household survey during the outbreak in Sierra Leone

BACKGROUND

Vaccination against Ebolavirus is an emerging public health tool during Ebola Virus Disease outbreaks. We examined demand issues related to deployment of Ebolavirus vaccine during the 2014-2015 outbreak in Sierra Leone.

METHODS

A cluster survey was administered to a population-based sample in December 2014 (N = 3540), before any Ebola vaccine was available to the general public in Sierra Leone. Ebola vaccine demand was captured in this survey by three Likert-scale items that were used to develop a composite score and dichotomized into a binary outcome to define high demand. A multilevel logistic regression model was fitted to assess the associations between perceptions of who should be first to receive an Ebola vaccine and the expression of high demand for an Ebola vaccine.

RESULTS

The largest proportion of respondents reported that health workers (35.1%) or their own families (29.5%) should receive the vaccine first if it became available, rather than politicians (13.8%), vaccination teams (9.8%), or people in high risk areas (8.2%). High demand for an Ebola vaccine was expressed by 74.2% of respondents nationally. The odds of expressing high demand were 13 times greater among those who said they or their families should be the first to take the vaccine compared to those who said politicians should be the first recipients (adjusted odds ratio [aOR] 13.0 [95% confidence interval [CI] 7.8-21.6]). The ultra-brief measure of the Ebola vaccine demand demonstrated acceptable scale reliability (Cronbach's α = 0.79) and construct validity (single-factor loadings > 0.50).

CONCLUSION

Perceptions of who should be the first to get the vaccine was associated with high demand for Ebola vaccine around the peak of the outbreak in Sierra Leone. Using an ultra-brief measure of Ebola vaccine demand is a feasible solution in outbreak settings and can help inform development of future rapid assessment tools.

A Bivalent, Spherical Virus-Like Particle Vaccine Enhances Breadth of Immune Responses against Pathogenic Ebola Viruses in Rhesus Macaques

The 2013-2016 Ebola outbreak in West Africa led to accelerated efforts to develop vaccines against these highly virulent viruses. A live, recombinant vesicular stomatitis virus-based vaccine has been deployed in outbreak settings and appears highly effective. Vaccines based on replication-deficient adenovirus vectors either alone or in combination with a multivalent modified vaccinia Ankara (MVA) Ebola vaccine also appear promising and are progressing in clinical evaluation. However, the ability of current live vector-based approaches to protect against multiple pathogenic species of Ebola is not yet established, and eliciting durable responses may require additional booster vaccinations. Here, we report the development of a bivalent, spherical Ebola virus-like particle (VLP) vaccine that incorporates glycoproteins (GPs) from Zaire Ebola virus (EBOV) and Sudan Ebola virus (SUDV) and is designed to extend the breadth of immunity beyond EBOV. Immunization of rabbits with bivalent Ebola VLPs produced antibodies that neutralized all four pathogenic species of Ebola viruses and elicited antibody-dependent cell-mediated cytotoxicity (ADCC) responses against EBOV and SUDV. Vaccination of rhesus macaques with bivalent VLPs generated strong humoral immune responses, including high titers of binding, as well as neutralizing antibodies and ADCC responses. VLP vaccination led to a significant increase in the frequency of Ebola GP-specific CD4 and CD8 T cell responses. These results demonstrate that a novel bivalent Ebola VLP vaccine elicits strong humoral and cellular immune responses against pathogenic Ebola viruses and support further evaluation of this approach as a potential addition to Ebola vaccine development efforts.IMPORTANCE Ebola outbreaks result in significant morbidity and mortality in affected countries. Although several leading candidate Ebola vaccines have been developed and advanced in clinical testing, additional vaccine candidates may be needed to provide protection against different Ebola species and to extend the durability of protection. A novel approach demonstrated here is to express two genetically diverse glycoproteins on a spherical core, generating a vaccine that can broaden immune responses against known pathogenic Ebola viruses. This approach provides a new method to broaden and potentially extend protective immune responses against Ebola viruses.

The Ebola virus glycoprotein and its immune responses across multiple vaccine platforms

Introduction: For over 40 years, ebolaviruses have been responsible for sporadic outbreaks of severe and often fatal hemorrhagic fever in humans and nonhuman primates across western and central Africa. In December 2013, an unprecedented Ebola virus (EBOV) epidemic began in West Africa and resulted in the largest outbreak to date. The past and current epidemics in West Africa and the Democratic Republic of the Congo has focused attention on the potential vaccine platforms developed over the past 20 years.Areas covered: This review summarizes the extraordinary progress using a variety of vaccination platforms including DNA, subunit, and several viral vector approaches, replicating and non-replicating, incorporating the primary antigen of EBOV, the glycoprotein. These vaccine constructs have shown varying degrees of protective efficacy in the 'gold-standard' nonhuman primate model for EBOV infections and were immunogenic in human clinical trials.Expert commentary: A number of these vaccine platforms have moved into phase III clinical trials over the past years and with the recent approval of the first EBOV vaccine in the European Union and the USA there is a strong potential to prevent future outbreaks/epidemics of EBOV infections on the scale of the West African epidemic.

Biomimetic Design of Peptide Neutralizer of Ebola Virus with Molecular Simulation

Ebola virus (EBOV) belongs to the Filoviridae family, which can cause severe hemorrhagic fever in humans and nonprimates. The neutralization of EBOV by monoclonal antibody (mAb) ADI-15946 was reported recently. In the present study, the molecular interactions between the receptor GPcl of EBOV and ADI-15946 were studied by molecular dynamics (MD) simulation and molecular mechanics-Poisson-Boltzmann surface area (MM-PBSA) analysis. Hydrophobic interaction was identified as the main driving force for the binding of ADI-15946 on EBOV. Moreover, the contribution of each amino acid residue for the binding was evaluated. Then, an affinity binding model (ABM) was constructed using the residues favorable for the binding, including Y107, F108, D109, W110, and R113. The biomimetic design of neutralizer against EBOV according to the ABM of ADI-15946 was then performed, followed by screening using docking, structural similarity. Two neutralizers YFDWHMR and YFDWRYR were obtained, which were proven to be capable of strong binding on GPcl and then neutralizing GPcl. These results would be helpful for the development of neutralizers for Ebola virus.

Development of an antibody cocktail for treatment of Sudan virus infection

Antibody-based therapies are a promising treatment option for managing ebolavirus infections. Several Ebola virus (EBOV)-specific and, more recently, pan-ebolavirus antibody cocktails have been described. Here, we report the development and assessment of a Sudan virus (SUDV)-specific antibody cocktail. We produced a panel of SUDV glycoprotein (GP)-specific human chimeric monoclonal antibodies (mAbs) using both plant and mammalian expression systems and completed head-to-head in vitro and in vivo evaluations. Neutralizing activity, competitive binding groups, and epitope specificity of SUDV mAbs were defined before assessing protective efficacy of individual mAbs using a mouse model of SUDV infection. Of the mAbs tested, GP base-binding mAbs were more potent neutralizers and more protective than glycan cap- or mucin-like domain-binding mAbs. No significant difference was observed between plant and mammalian mAbs in any of our in vitro or in vivo evaluations. Based on in vitro and rodent testing, a combination of two SUDV-specific mAbs, one base binding (16F6) and one glycan cap binding (X10H2), was down-selected for assessment in a macaque model of SUDV infection. This cocktail, RIID F6-H2, provided protection from SUDV infection in rhesus macaques when administered at 50 mg/kg on days 4 and 6 postinfection. RIID F6-H2 is an effective postexposure SUDV therapy and provides a potential treatment option for managing human SUDV infection.

Pre-Treatment with Zirconia Nanoparticles Reduces Inflammation Induced by the Pathogenic H5N1 Influenza Virus

Background

New approaches are urgently needed to fight influenza viral infection. Previous research has shown that zirconia nanoparticles can be used as anticancer materials, but their antiviral activity has not been reported. Here, we investigated the antiviral effect of zirconia (ZrO₂) nanoparticles (NPs) against a highly pathogenic avian influenza virus.

Materials and Methods

In this study, the antiviral effects of ZrO₂ on H5N1 virus were assessed in vivo, and the molecular mechanism responsible for this protection was investigated.

Results

Mice treated with 200 nm positively-charged NPs at a dose of 100 mg/kg showed higher survival rates and smaller reductions in weight. 200 nm ZrO₂ activated mature dendritic cells and initially promoted the expression of cytokines associated with the antiviral response and innate immunity. In the lungs of H5N1-infected mice, ZrO₂ treatment led to less pathological lung injury, significant reduction in influenza A virus replication, and overexpression of pro-inflammatory cytokines.

Conclusion

This antiviral study using zirconia NPs shows protection of mice against highly pathogenic avian influenza virus and suggests strong application potential for this method, introducing a new tool against a wide range of microbial infections.

Types of Disasters

Disasters are increasing around the world. Children are greatly impacted by both natural disasters (forces of nature) and man-made (intentional, accidental) disasters. Their unique anatomical, physiological, behavioral, developmental, and psychological vulnerabilities must be considered when planning and preparing for disasters. The nurse or health care provider (HCP) must be able to rapidly identify acutely ill children during a disaster. Whether it is during a natural or man-made event, the nurse or HCP must intervene effectively to improve survival and outcomes. It is extremely vital to understand the medical management of these children during disasters, especially the use of appropriate medical countermeasures such as medications, antidotes, supplies, and equipment.

UK vaccines network: Mapping priority pathogens of epidemic potential and vaccine pipeline developments

During the 2013-2016 Ebola outbreak in West Africa an expert panel was established on the instructions of the UK Prime Minister to identify priority pathogens for outbreak diseases that had the potential to cause future epidemics. A total of 13 priority pathogens were identified, which led to the prioritisation of spending in emerging diseases vaccine research and development from the UK. This meeting report summarises the process used to develop the UK pathogen priority list, compares it to lists generated by other organisations (World Health Organisation, National Institutes of Allergy and Infectious Diseases) and summarises clinical progress towards the development of vaccines against priority diseases. There is clear technical progress towards the development of vaccines. However, the availability of these vaccines will be dependent on sustained funding for clinical trials and the preparation of clinically acceptable manufactured material during inter-epidemic periods.

Vaccines against Ebola virus and Marburg virus: recent advances and promising candidates

The filoviruses Ebola virus and Marburg virus are among the most dangerous pathogens in the world. Both viruses cause viral hemorrhagic fever, with case fatality rates of up to 90%. Historically, filovirus outbreaks had been relatively small, with only a few hundred cases reported. However, the recent West African Ebola virus outbreak underscored the threat that filoviruses pose. The three year-long outbreak resulted in 28,646 Ebola virus infections and 11,323 deaths. The lack of Food and Drug Administration (FDA) licensed vaccines and antiviral drugs hindered early efforts to contain the outbreak. In response, the global scientific community has spurred the advanced development of many filovirus vaccine candidates. Novel vaccine platforms, such as viral vectors and DNA vaccines, have emerged, leading to the investigation of candidate vaccines that have demonstrated protective efficacy in small animal and nonhuman primate studies. Here, we will discuss several of these vaccine platforms with a particular focus on approaches that have advanced into clinical development.

Perspectives towards antiviral drug discovery against Ebola virus

Ebola virus disease (EVD), caused by Ebola viruses, resulted in more than 11 500 deaths according to a recent 2018 WHO report. With mortality rates up to 90%, it is nowadays one of the most deadly infectious diseases. However, no Food and Drug Administration‐approved Ebola drugs or vaccines are available yet with the mainstay of therapy being supportive care. The high fatality rate and absence of effective treatment or vaccination make Ebola virus a category‐A biothreat pathogen. Fortunately, a series of investigational countermeasures have been developed to control and prevent this global threat. This review summarizes the recent therapeutic advances and ongoing research progress from research and development to clinical trials in the development of small‐molecule antiviral drugs, small‐interference RNA molecules, phosphorodiamidate morpholino oligomers, full‐length monoclonal antibodies, and vaccines. Moreover, difficulties are highlighted in the search for effective countermeasures against EVD with additional focus on the interplay between available in silico prediction methods and their evidenced potential in antiviral drug discovery.

Immunization With a Novel Human Type 5 Adenovirus-Vectored Vaccine Expressing the Premembrane and Envelope Proteins of Zika Virus Provides Consistent and Sterilizing Protection in Multiple Immunocompetent and Immunocompromised Animal Models

Background

Zika virus (ZIKV) infection may be associated with severe complications and disseminated via both vector-borne and nonvector-borne routes. Adenovirus-vectored vaccines represent a favorable controlling measure for the ZIKV epidemic because they have been shown to be safe, immunogenic, and rapidly generable for other emerging viral infections. Evaluations of 2 previously reported adenovirus-vectored ZIKV vaccines were performed using nonlethal animal models and/or nonepidemic ZIKV strain.

Methods

We constructed 2 novel human adenovirus 5 (Ad5)-vectored vaccines containing the ZIKV premembrane-envelope (Ad5-Sig-prM-Env) and envelope (Ad5-Env) proteins, respectively, and evaluated them in multiple nonlethal and lethal animal models using epidemic ZIKV strains.

Results

Both vaccines elicited robust humoral and cellular immune responses in immunocompetent BALB/c mice. Dexamethasone-immunosuppressed mice vaccinated with either vaccine demonstrated robust and durable antibody responses and significantly lower blood and tissue viral loads than controls (P < .05). Similar findings were also observed in interferon-α/β receptor-deficient A129 mice. In both of these immunocompromised animal models, Ad5-Sig-prM-Env-vaccinated mice had significantly (P < .05) higher titers of anti-ZIKV-specific neutralizing antibody titers and lower (undetectable) viral loads than Ad5-Env-vaccinated mice. The close correlation between the neutralizing antibody titer and viral load helped to explain the better protective effect of Ad5-Sig-prM-Env than Ad5-Env. Anamnestic response was absent in Ad5-Sig-prM-Env-vaccinated A129 mice.

Conclusions

Ad5-Sig-prM-Env provided sterilizing protection against ZIKV infection in mice.

Advances in Vaccines

Vaccines represent one of the most important advances in science and medicine, helping people around the world in preventing the spread of infectious diseases. However, there are still gaps in vaccination programs in many countries. Out of 11.2 million children born in EU region, more than 500,000 infants did not receive the complete three-dose series of diphtheria, pertussis, and tetanus vaccine before the first birthday. Data shows that there were more than 30,000 measles cases in the European region in recent years, and measles cases are rising in the USA. There are about 20 million children in the world still not getting adequate coverage of basic vaccines. Emerging infectious diseases such as malaria, Ebola virus disease, and Zika virus disease also threaten public health around the world. This chapter provides an overview of recent advances in vaccine development and technologies, manufacturing, characterization of various vaccines, challenges, and strategies in vaccine clinical development. It also provides an overview of recently approved major vaccines for human use.

The Role of Reference Materials in the Research and Development of Diagnostic Tools and Treatments for Haemorrhagic Fever Viruses

Following the Ebola outbreak in Western Africa in 2013-16, a global effort has taken place for preparedness for future outbreaks. As part of this response, the development of vaccines, treatments and diagnostic tools has been accelerated, especially towards pathogens listed as likely to cause an epidemic and for which there are no current treatments. Several of the priority pathogens identified by the World Health Organisation are haemorrhagic fever viruses. This review provides information on the role of reference materials as an enabling tool for the development and evaluation of assays, and ultimately vaccines and treatments. The types of standards available are described, along with how they can be applied for assay harmonisation through calibration as a relative potency to a common arbitrary unitage system (WHO International Unit). This assures that assay metrology is accurate and robust. We describe reference materials that have been or are being developed for haemorrhagic fever viruses and consider the issues surrounding their production, particularly that of biosafety where the viruses require specialised containment facilities. Finally, we advocate the use of reference materials at early stages, including research and development, as this helps produce reliable assays and can smooth the path to regulatory approval.

Longitudinal quantification of adenovirus neutralizing responses in Zambian mother-infant pairs: Impact of HIV-1 infection and its treatment

Vaccination offers the most cost-effective approach to limiting the adverse impact of infectious and neoplastic diseases that reduce the quality of life in sub-Saharan Africa (SSA). However, it is unclear what vaccine vectors would be most readily implementable in the setting and at what age they should be applied for maximal efficacy. Adenoviruses (Ad) and Ad-based vectors have been demonstrated to induce effective humoral and cellular immune responses in animal models and in humans. However, because immunity associated with Ad infection is lifelong, there exists a debate as to whether pre-existing immunity might decrease the efficacy of Ad vectored vaccines. In order to begin to rationally develop vaccination strategies for SSA, we have quantified neutralizing antibodies (nAb) against Ad4, Ad5, Ad7, Ad26, Ad28, Ad45 and Ad48 in 67 adult women and their infants. We are the first to define the decay kinetics of transferred maternal nAb in infants as well as the apparent initiation of de novo Ad responses. Our findings demonstrate that in Zambian adults, robust nAb responses exist against each of the Ads tested and are efficiently transferred to newborns. With few exceptions, neither the HIV-1 infection status of the mothers or the antiretroviral therapy (ART) treatment of HIV-1 disease had significant impact on maternal Ad nAb responses or their transfer to infants. However, maternal Ad nAb decays in infants to a nadir at 12 months of age such that any of the seven Ad types could function as vaccine vectors. The definition of this 'window of opportunity' provides important foundational data for rational design and implementation of Ad vectors in this setting.

Current Ebola Virus Vaccine Progress

Over 40 years since the discovery of Ebola virus, the anti-Ebola virus vaccine efforts of the past 2 decades have culminated in over 12 different vaccine candidates that have been placed into a number of clinical trial phases, past and present. Of these 12 vaccines, four candidates are up to or in phase II clinical trials, and only one has completed the phase III clinical trial stage. While remarkable progress toward a national regulatory agency-approved vaccine for Ebola virus has been made, there remain unanswered questions on issues such as, but not limited to, vaccine protective immunity and duration of that immunity, and the appropriate vaccination strategy for those at risk of Ebola virus infection.