Safety and Immunogenicity of Novel Adenovirus Type 26- and Modified Vaccinia Ankara-Vectored Ebola Vaccines: A Randomized Clinical Trial

Genomic foundations of evolution and ocular pathogenesis in human adenovirus species D

Human adenovirus commonly causes infections of respiratory, gastrointestinal, genitourinary, and ocular surface mucosae. Although most adenovirus eye infections are mild and self-limited, specific viruses within human adenovirus species D are associated with epidemic keratoconjunctivitis (EKC), a severe and highly contagious ocular surface infection, which can lead to chronic and/or recurrent, visually disabling keratitis. In this review, we discuss the links between adenovirus ontogeny, genomics, immune responses, and corneal pathogenesis, for those viruses that cause EKC.

Recurrent Ebolavirus disease in the Democratic Republic of Congo: update and challenges

The current Ebolavirus disease (EVD) outbreak in the provinces of North Kivu and Ituri is the tenth outbreak affecting the Democratic Republic of Congo (DRC); the first outbreak occurring in a war context, and the second most deadly Ebolavirus outbreak on record following the 2014 outbreak in West Africa. The DRC government's response consisted of applying a package of interventions including detection and rapid isolation of cases, contact tracing, population mapping, and identification of high-risk areas to inform a coordinated effort. The coordinated effort was to screen, ring vaccinate, and conduct laboratory diagnoses using GeneXpert (Cepheid) polymerase chain reaction. The effort also included ensuring safe and dignified burials and promoting risk communication, community engagement, and social mobilization. Following the adoption of the “Monitored Emergency Use of Unregistered Products Protocol,” a randomized controlled trial of four investigational treatments (mAb114, ZMapp, and REGN-EB3 and Remdesivir) was carried out with all consenting patients with laboratory-confirmed EVD. REGN-EB3 and mAb114 showed promise as treatments for EVD. In addition, one investigational vaccine (rVSV-ZEBOV-GP) was used first, followed by a second prophylactic vaccine (Ad26.ZEBOV/MVA-BN-Filo) to reinforce the prevention. Although the provision of clinical supportive care remains the cornerstone of EVD outbreak management, the DRC response faced daunting challenges including general insecurity, violence and community resistance, appalling poverty, and entrenched distrust of authority. Ebolavirus remains a public health threat. A fully curative treatment is unlikely to be a game-changer given the settings of transmission, zoonotic nature, limits of effectiveness of any therapeutic intervention, and timing of presentation.

A phase I trial evaluating the safety and immunogenicity of a candidate tuberculosis vaccination regimen, ChAdOx1 85A prime - MVA85A boost in healthy UK adults

Background

This phase I trial evaluated the safety and immunogenicity of a candidate tuberculosis vaccination regimen, ChAdOx1 85A prime-MVA85A boost, previously demonstrated to be protective in animal studies, in healthy UK adults.

Methods

We enrolled 42 healthy, BCG-vaccinated adults into 4 groups: low dose Starter Group (n = 6; ChAdOx1 85A alone), high dose groups; Group A (n = 12; ChAdOx1 85A), Group B (n = 12; ChAdOx1 85A prime – MVA85A boost) or Group C (n = 12; ChAdOx1 85A – ChAdOx1 85A prime – MVA85A boost). Safety was determined by collection of solicited and unsolicited vaccine-related adverse events (AEs). Immunogenicity was measured by antigen-specific ex-vivo IFN-γ ELISpot, IgG serum ELISA, and antigen-specific intracellular IFN-γ, TNF-α, IL-2 and IL-17.

Results

AEs were mostly mild/moderate, with no Serious Adverse Events. ChAdOx1 85A induced Ag85A-specific ELISpot and intracellular cytokine CD4+ and CD8+ T cell responses, which were not boosted by a second dose, but were boosted with MVA85A. Polyfunctional CD4+ T cells (IFN-γ, TNF-α and IL-2) and IFN-γ+, TNF-α+ CD8+ T cells were induced by ChAdOx1 85A and boosted by MVA85A. ChAdOx1 85A induced serum Ag85A IgG responses which were boosted by MVA85A.

Conclusion

A ChAdOx1 85A prime – MVA85A boost is well tolerated and immunogenic in healthy UK adults.

Evaluation of modified Vaccinia Ankara-based vaccines against foot-and-mouth disease serotype A24 in cattle

To prepare foot-and-mouth disease (FMD) recombinant vaccines in response to newly emerging FMD virus (FMDV) field strains, we evaluated Modified Vaccinia virus Ankara-Bavarian Nordic (MVA-BN®) as an FMD vaccine vector platform. The MVA-BN vector has the capacity to carry and express numerous foreign genes and thereby has the potential to encode antigens from multiple FMDV strains. Moreover, this vector has an extensive safety record in humans. All MVA-BN-FMD constructs expressed the FMDV A24 Cruzeiro P1 capsid polyprotein as antigen and the FMDV 3C protease required for processing of the polyprotein. Because the FMDV wild-type 3C protease is detrimental to mammalian cells, one of four FMDV 3C protease variants were utilized: wild-type, or one of three previously reported mutants intended to dampen protease activity (C142T, C142L) or to increase specificity and thereby reduce adverse effects (L127P). These 3C coding sequences were expressed under the control of different promoters selected to reduce 3C protease expression. Four MVA-BN-FMD constructs were evaluated in vitro for acceptable vector stability, FMDV P1 polyprotein expression, processing, and the potential for vaccine scale-up production. Two MVA-BN FMD constructs met the in vitro selection criteria to qualify for clinical studies: MVA-mBN360B (carrying a C142T mutant 3C protease and an HIV frameshift for reduced expression) and MVA-mBN386B (carrying a L127P mutant 3C protease). Both vaccines were safe in cattle and elicited low to moderate serum neutralization titers to FMDV following multiple dose administrations. Following FMDV homologous challenge, both vaccines conferred 100% protection against clinical FMD and viremia using single dose or prime-boost immunization regimens. The MVA-BN FMD vaccine platform was capable of differentiating infected from vaccinated animals (DIVA). The demonstration of the successful application of MVA-BN as an FMD vaccine vector provides a platform for further FMD vaccine development against more epidemiologically relevant FMDV strains.

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.

Dynamics of the Humoral Immune Response to a Prime-Boost Ebola Vaccine: Quantification and Sources of Variation

The Ebola vaccine based on Ad26.ZEBOV/MVA-BN-Filo prime-boost regimens is being evaluated in multiple clinical trials. The long-term immune response to the vaccine is unknown, including factors associated with the response and variability around the response. We analyzed data from three phase 1 trials performed by the EBOVAC1 Consortium in four countries: the United Kingdom, Kenya, Tanzania, and Uganda. Participants were randomized into four groups based on the interval between prime and boost immunizations (28 or 56 days) and the sequence in which Ad26.ZEBOV and MVA-BN-Filo were administered. Consecutive enzyme-linked immunosorbent assay (ELISA) measurements of the IgG binding antibody concentrations against the Kikwit glycoprotein (GP) were available for 177 participants to assess the humoral immune response up to 1 year postprime. Using a mathematical model for the dynamics of the humoral response, from 7 days after the boost immunization up to 1 year after the prime immunization, we estimated the durability of the antibody response and the influence of different factors on the dynamics of the humoral response. Ordinary differential equations (ODEs) described the dynamics of antibody response and two populations of antibody-secreting cells (ASCs), short-lived (SL) and long-lived (LL). Parameters of the ODEs were estimated using a population approach. We estimated that half of the LL ASCs could persist for at least 5 years. The vaccine regimen significantly affected the SL ASCs and the antibody peak but not the long-term response. The LL ASC compartment dynamics differed significantly by geographic regions analyzed, with a higher long-term antibody persistence in European subjects. These differences could not be explained by the observed differences in cellular immune response.IMPORTANCE With no available licensed vaccines or therapies, the West African Ebola virus disease epidemic of 2014 to 2016 caused 11,310 deaths. Following this outbreak, the development of vaccines has been accelerated. Combining different vector-based vaccines as heterologous regimens could induce a durable immune response, assessed through antibody concentrations. Based on data from phase 1 trials in East Africa and Europe, the dynamics of the humoral immune response from 7 days after the boost immunization onwards were modeled to estimate the durability of the response and understand its variability. Antibody production is maintained by a population of long-lived cells. Estimation suggests that half of these cells can persist for at least 5 years in humans. Differences in prime-boost vaccine regimens affect only the short-term immune response. Geographical differences in long-lived cell dynamics were inferred, with higher long-term antibody concentrations induced in European participants.

International Biological Reference Preparations for Epidemic Infectious Diseases

Recent years have seen unprecedented investment in research and development for countermeasures for high-threat pathogens, including specific and ambitious objectives for development of diagnostics, therapeutics, and vaccines. The inadequate availability of biological reference materials for these pathogens poses a genuine obstacle in pursuit of these objectives, and the lack of a comprehensive and equitable framework for developing reference materials is a weakness. We outline the need for internationally standardized biological materials for high-threat pathogens as a core element of global health security. We also outline the key components of a framework for addressing this deficiency.

LAMP real-time turbidity detection for fowl adenovirus

Background

Fowl adenovirus (FAdV) is an infectious agent that can cause jaundice, severe anaemia, dyspnoea and reproductive disorders in fowls. Since 2015, FAdV disease has been rapidly spreading among broiler chickens in China, where it has caused significant economic losses. In this study, a loop-mediated isothermal amplification (LAMP) real-time turbidity method with strong specificity to FAdV was established.

Results

The established assay was specific to FAdV-4, and the lower limit of detection was 75 copies/μL of extracted DNA. The positive detection rate for the suspected tissue samples was 33.3% (14/42), which was consistent with that of the real-time PCR.

Conclusion

The proposed LAMP method can quickly and accurately detect prevalent FAdV via real-time turbidity assay, thereby providing a diagnostic platform for the prevention and control of the FAdV disease.

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.

Inhibition of Ebola Virus by a Molecularly Engineered Banana Lectin

Ebolaviruses cause an often rapidly fatal syndrome known as Ebola virus disease (EVD), with average case fatality rates of ~50%. There is no licensed vaccine or treatment for EVD, underscoring the urgent need to develop new anti-ebolavirus agents, especially in the face of an ongoing outbreak in the Democratic Republic of the Congo and the largest ever outbreak in Western Africa in 2013-2016. Lectins have been investigated as potential antiviral agents as they bind glycans present on viral surface glycoproteins, but clinical use of them has been slowed by concerns regarding their mitogenicity, i.e. ability to cause immune cell proliferation. We previously engineered a banana lectin (BanLec), a carbohydrate-binding protein, such that it retained antiviral activity but lost mitogenicity by mutating a single amino acid, yielding H84T BanLec (H84T). H84T shows activity against viruses containing high-mannose N-glycans, including influenza A and B, HIV-1 and -2, and hepatitis C virus. Since ebolavirus surface glycoproteins also contain many high-mannose N-glycans, we assessed whether H84T could inhibit ebolavirus replication. H84T inhibited Ebola virus (EBOV) replication in cell cultures. In cells, H84T inhibited both virus-like particle (VLP) entry and transcription/replication of the EBOV mini-genome at high micromolar concentrations, while inhibiting infection by transcription- and replication-competent VLPs, which measures the full viral life cycle, in the low micromolar range. H84T did not inhibit assembly, budding, or release of VLPs. These findings suggest that H84T may exert its anti-ebolavirus effect(s) by blocking both entry and transcription/replication. In a mouse model, H84T partially (maximally, ~50-80%) protected mice from an otherwise lethal mouse-adapted EBOV infection. Interestingly, a single dose of H84T pre-exposure to EBOV protected ~80% of mice. Thus, H84T shows promise as a new anti-ebolavirus agent with potential to be used in combination with vaccination or other agents in a prophylactic or therapeutic regimen.

Safety and Immunogenicity of a 2-Dose Heterologous Vaccination Regimen With Ad26.ZEBOV and MVA-BN-Filo Ebola Vaccines: 12-Month Data From a Phase 1 Randomized Clinical Trial in Uganda and Tanzania

BACKGROUND

Ebola vaccine development was accelerated in response to the 2014 Ebola virus infection outbreak. This phase 1 study (VAC52150EBL1004) assessed safety, tolerability, and immunogenicity of heterologous 2-dose Ad26.ZEBOV, MVA-BN-Filo vaccination regimens in the Lake Victoria Basin of Tanzania and Uganda in mid-level altitude, malaria-endemic settings.

METHODS

Healthy volunteers aged 18-50 years from Tanzania (n = 25) and Uganda (n = 47) were randomized to receive placebo or active vaccination with Ad26.ZEBOV or MVA-BN-Filo (first vaccination), followed by MVA-BN-Filo or Ad26.ZEBOV (second vaccination) dose 2, respectively, with intervals of 28 or 56 days.

RESULTS

Seventy-two adults were randomized to receive vaccine (n = 60) or placebo (n = 12). No vaccine-related serious adverse events were reported. The most frequent solicited local and systemic adverse events were injection site pain (frequency, 70%, 66%, and 42% per dose for MVA-BN-Filo, Ad26.ZEBOV, and placebo, respectively) and headache (57%, 56%, and 46%, respectively). Adverse event patterns were similar among regimens. Twenty-one days after dose 2, 100% of volunteers demonstrated binding antibody responses against Ebola virus glycoprotein, and 87%-100% demonstrated neutralizing antibody responses. Ad26.ZEBOV dose 1 vaccination induced more-robust initial binding antibody and cellular responses than MVA-BN-Filo dose 1 vaccination.

CONCLUSIONS

Heterologous 2-dose vaccination with Ad26.ZEBOV and MVA-BN-Filo against Ebola virus is well tolerated and immunogenic in healthy volunteers.

CLINICAL TRIALS REGISTRATION

NCT02376400.

Safety and Immunogenicity of a 2-Dose Heterologous Vaccine Regimen With Ad26.ZEBOV and MVA-BN-Filo Ebola Vaccines: 12-Month Data From a Phase 1 Randomized Clinical Trial in Nairobi, Kenya

BACKGROUND

During the 2014 West African Ebola outbreak, Ebola vaccine development was accelerated. The phase 1 VAC52150EBL1003 study was performed to investigate 2-dose heterologous vaccination with Ad26.ZEBOV and MVA-BN-Filo in an African population located in a high-altitude setting in Nairobi, Kenya.

METHODS

Healthy adult volunteers were randomized to receive one of four 2-dose vaccination schedules. The first vaccination was administered at baseline (Ad26.ZEBOV or MVA-BN-Filo), followed by the second vaccination with the alternate vaccine after either 28 or 56 days. Each schedule had a placebo comparator group. The primary objective was to assess the safety and tolerability of these regimens.

RESULTS

Seventy-two volunteers were randomized into 4 groups of 18 (15 received vaccine, and 3 received placebo). The most frequent solicited systemic adverse event was headache (frequency, 50%, 61%, and 42% per dose for MVA-BN-Filo, Ad26.ZEBOV, and placebo, respectively). The most frequent solicited local AE was injection site pain (frequency, 78%, 63%, and 33% per dose for MVA-BN-Filo, Ad26.ZEBOV, and placebo, respectively). No differences in adverse events were observed among the different vaccine regimens. High levels of binding and neutralizing anti-Ebola virus glycoprotein antibodies were induced by all regimens and sustained to day 360 after the first dose.

CONCLUSIONS

Two-dose heterologous vaccination with Ad26.ZEBOV and MVA-BN-Filo was well tolerated and highly immunogenic against Ebola virus glycoprotein.

CLINICAL TRIALS REGISTRATION

NCT02376426.

A single-dose ChAdOx1-vectored vaccine provides complete protection against Nipah Bangladesh and Malaysia in Syrian golden hamsters

Nipah virus (NiV) is a highly pathogenic re-emerging virus that causes outbreaks in South East Asia. Currently, no approved and licensed vaccine or antivirals exist. Here, we investigated the efficacy of ChAdOx1 NiVB, a simian adenovirus-based vaccine encoding NiV glycoprotein (G) Bangladesh, in Syrian hamsters. Prime-only as well as prime-boost vaccination resulted in uniform protection against a lethal challenge with NiV Bangladesh: all animals survived challenge and we were unable to find infectious virus either in oral swabs, lung or brain tissue. Furthermore, no pathological lung damage was observed. A single-dose of ChAdOx1 NiVB also prevented disease and lethality from heterologous challenge with NiV Malaysia. While we were unable to detect infectious virus in swabs or tissue of animals challenged with the heterologous strain, a very limited amount of viral RNA could be found in lung tissue by in situ hybridization. A single dose of ChAdOx1 NiVB also provided partial protection against Hendra virus and passive transfer of antibodies elicited by ChAdOx1 NiVB vaccination partially protected Syrian hamsters against NiV Bangladesh. From these data, we conclude that ChAdOx1 NiVB is a suitable candidate for further NiV vaccine pre-clinical development.

Clinical Management of Patients with Ebola Virus Disease in High-Resource Settings

Like most viral illnesses in humans, supportive care of the patient is the mainstay of clinical care for patients with Ebola virus disease (EVD). The goal is to maintain and sustain the patient until a specific immune response develops and clears the viral infection. Clearly, antiviral therapy may eventually help speed recovery, but supportive care will likely always be the centerpiece of care of the patient with EVD. While terrible in terms of human suffering and loss, the EVD outbreak of 2014–2016 provided an unheralded opportunity to advance our understanding in the care of patients (WHO 2016). Regardless of the care setting, resource-rich or resource-constrained, it is beneficial to have an established team of care providers. This team should consist of nurses and physicians who are familiar with clinical care of patients with EVD and have demonstrated competency using necessary personal protective equipment (PPE). Consideration should be given to having several physician specialties on the team, including critical care, infectious diseases, and anesthesiology. Additional individuals in other medical specialties should be identified in case needed during the course of caring for a patient. The National Ebola Training and Education Center (NETEC) has detailed guidance on preparations for developing a high-containment unit and care team (NETEC 2016).

A review of 65 years of human adenovirus seroprevalence

Introduction: Human adenovirus (HAdV)-derived vectors have been used in numerous pre-clinical and clinical trials during the last 40 years. Current research in HAdV-based vaccines focuses on improving transgene immunogenicity and safety. Because pre-existing humoral immunity against HAdV types correlate with reduced vaccine efficacy and safety, many groups are exploring the development of HAdV types vectors with lower seroprevalence. However, global seroepidemiological data are incomplete. Areas covered: The goal of this review is to centralize 65 years of research on (primarily) HAdV epidemiology. After briefly addressing adenovirus biology, we chronical HAdV seroprevalence studies and highlight major milestones. Finally, we analyze data from about 50 studies with respect to HAdVs types that are currently used in the clinic, or are in the developmental pipeline. Expert opinion: Vaccination is among the most efficient tools to prevent infectious disease. HAdV-based vaccines have undeniable potential, but optimization is needed and antivector immunity remains a challenge if the same vectors are to be administrated to different populations. Here, we identify gaps in our knowledge and the need for updated worldwide epidemiological data.

Conserved B and T cell epitopes prediction of ebola virus glycoprotein for vaccine development: An immuno-informatics approach

Ebola virus (EBOV), a non-segmented single-stranded RNA virus, is often-most transmitted through body fluids like sweat, tears, saliva, and nasal secretions. Till date, there is no licensed vaccine of EBOV is available in the market; however, the world is increasingly vulnerable to this emerging threat. Hence, it is the need of time to develop a vaccine for EBOV to hinder its dissemination. The current study has been designed for identification and characterization of the potential B and T-cell epitopes using the Immuno-informatics tools, and it helped in finding the potent vaccine candidates against EBOV. Prediction, antigenicity and allergenicity testing of predicted B and T cells' epitopes was done as well to identify their potential as a vaccine candidate and to measure their safety level respectively. Among B-cell epitopes "WIPAGIGVTGVIIA" showed a high antigenicity score and it would play an important role in evoking the immune response. In T-cell epitopes, peptides "AIGLAWIPY" and "IRGFPRCRY" presented high antigenicity score, which binds to MHC class-I and MHC class-II alleles respectively. All predicted epitopes were analyzed and compared with already reported peptides carefully. Comparatively, Peptides predicted in the present study showed more immunogenicity score than already reported peptides, used as positive control, and are more immunogenic as compared to them. Peptides reported in the present study do not target only Zaire EBOV (ZEBOV), as in previous studies, but also other species, i.e. Tai Forest EBOV (TAFV), Sudan EBOV (SUDV), Bundibugyo EBOV (BDBV), and Reston EBOV (RESTV) and would bring the promising results as potent vaccine candidates.

Development, qualification, and validation of the Filovirus Animal Nonclinical Group anti-Ebola virus glycoprotein immunoglobulin G enzyme-linked immunosorbent assay for human serum samples

The need for an efficacious vaccine against highly pathogenic filoviruses was reinforced by the recent and devastating 2014–2016 outbreak of Ebola virus (EBOV) disease in Guinea, Sierra Leone, and Liberia that resulted in more than 10,000 casualties. Such a vaccine would need to be vetted through a U.S. Food and Drug Administration (FDA) traditional, accelerated, or Animal Rule or similar European Medicines Agency (EMA) regulatory pathway. Under the FDA Animal Rule, vaccine-induced immune responses correlating with survival of non-human primates (NHPs), or another well-characterized animal model, following lethal EBOV challenge will need to be bridged to human immune response distributions in clinical trials. When possible, species-neutral methods are ideal for detection and bridging of these immune responses, such as methods to quantify anti-EBOV glycoprotein (GP) immunoglobulin G (IgG) antibodies. Further, any method that will be used to support advanced clinical and non-clinical trials will most likely require formal validation to assess suitability prior to use. Reported here is the development, qualification, and validation of a Filovirus Animal Nonclinical Group anti-EBOV GP IgG Enzyme-Linked Immunosorbent Assay (FANG anti-EBOV GP IgG ELISA) for testing human serum samples.

Intradermal SynCon® Ebola GP DNA Vaccine Is Temperature Stable and Safely Demonstrates Cellular and Humoral Immunogenicity Advantages in Healthy Volunteers

Background

Nonlive vaccine approaches that are simple to deliver and stable at room temperature or 2–8°C could be advantageous in controlling future Ebola virus (EBOV) outbreaks. Using an immunopotent DNA vaccine that generates protection from lethal EBOV challenge in small animals and nonhuman primates, we performed a clinical study to evaluate both intramuscular (IM) and novel intradermal (ID) DNA delivery.

Methods

Two DNA vaccine candidates (INO-4201 and INO-4202) targeting the EBOV glycoprotein (GP) were evaluated for safety, tolerability, and immunogenicity in a phase 1 clinical trial. The candidates were evaluated alone, together, or in combination with plasmid-encoded human cytokine interleukin-12 followed by in vivo electroporation using either the CELLECTRA® IM or ID delivery devices.

Results

The safety profile of all 5 regimens was shown to be benign, with the ID route being better tolerated. Antibodies to EBOV GP were generated by all 5 regimens with the fastest and steepest rise observed in the ID group. Cellular immune responses were generated with every regimen.

Conclusions

ID delivery of INO-4201 was well tolerated and resulted in 100% seroreactivity after 2 doses and elicited interferon-γ T-cell responses in over 70% of subjects, providing a new approach for EBOV prevention in diverse populations.

Clinical Trials Registration. NCT02464670.

Ebola virus disease

Ebolaviruses are pathogenic agents associated with a severe, potentially fatal, systemic disease in man and great apes. Four species of ebolaviruses have been identified in west or equatorial Africa. Once the more virulent forms enter the human population, transmission occurs primarily through contact with infected body fluids and can result in major epidemics in under-resourced settings. These viruses cause a disease characterised by systemic viral replication, immune suppression, abnormal inflammatory responses, major fluid and electrolyte losses, and high mortality. Despite recent progress on vaccines, and with no licensed prophylaxis or treatment available, case management is essentially supportive with management of severe multiple organ failure resulting from immune-mediated cell damage. The 2013-16 outbreak was classified by WHO as a Public Health Emergency of International Concern, which drew attention to the challenges of diseases caused by infections with ebolaviruses and questioned scientific, clinical, and societal preparation to handle future epidemics.

Novel genetically-modified chimpanzee adenovirus and MVA-vectored respiratory syncytial virus vaccine safely boosts humoral and cellular immunity in healthy older adults

OBJECTIVES

Respiratory syncytial virus (RSV) causes respiratory infection across the world, with infants and the elderly at particular risk of developing severe disease and death. The replication-defective chimpanzee adenovirus (PanAd3-RSV) and modified vaccinia virus Ankara (MVA-RSV) vaccines were shown to be safe and immunogenic in young healthy adults. Here we report an extension to this first-in-man vaccine trial to include healthy older adults aged 60-75 years.

METHODS

We evaluated the safety and immunogenicity of a single dose of MVA-RSV given by intra-muscular (IM) injection (n = 6), two doses of IM PanAd3-RSV given 4-weeks apart (n = 6), IM PanAd3-RSV prime and IM MVA-RSV boost 8-weeks later (n = 6), intra-nasal (IN) spray of PanAd3-RSV prime and IM MVA-RSV boost 8-weeks later (n = 6), or no vaccine (n = 6). Safety measures included all adverse events within one week of vaccination and blood monitoring. Immunogenicity measures included serum antibody responses (RSV- and PanAd3-neutralising antibody titres measured by plaque-reduction neutralisation and SEAP assays, respectively), peripheral B-cell immune responses (frequencies of F-specific IgG and IgA antibody secreting cells and memory B-cells by ex vivo and cultured dual-colour ELISpot assays respectively), and peripheral RSV-specific T-cell immune responses (frequencies of IFNγ-producing T-cells by ex vivo ELISpot and CD4+/CD8+/Tfh-like cell frequencies by ICS/FACS assay).

RESULTS

The vaccines were safe and well tolerated. Compared with each individual baseline immunity the mean fold-changes in serum RSV-neutralising antibody, appearance and magnitude of F-specific IgG and IgA ASCs and expansion of CD4+/CD8+ IFNγ-producing T-cells in peripheral circulation were comparable to the results seen from younger healthy adults who received the same vaccine combination and dose. There were little/no IgA memory B-cell responses in younger and older adults. Expansion of IFNγ-producing T-cells was most marked in older adults following IM prime, with balanced CD4+ and CD8+ T cell responses. The RSV-specific immune responses to vaccination did not appear to be attenuated in the presence of PanAd3 (vector) neutralising antibody.

CONCLUSIONS

PanAd3-RSV and MVA-RSV was safe and immunogenic in older adults and the parallel induction of RSV-specific humoral and cellular immunity merits further assessment in providing protection from severe disease.

Can Ebola Virus Vaccines Have Universal Immune Correlates of protection?

Testing vaccine efficacy against the highly lethal Ebola virus (EBOV) in humans is almost impossible due to obvious ethical reasons and the sporadic nature of outbreaks. For such situations, the 'animal rule' was established, requiring the product be tested in animal models, expected to predict the response observed in humans. For vaccines, this testing aims to identify immune correlates of protection, such as antibody or cell-mediated responses. In the wake of the 2013-2016 EBOV epidemic, and despite advancement of promising candidates into clinical trials, protective correlates remain ambiguous. In the hope of identifying a reliable correlate by comparing preclinical and clinical trial data on immune responses to vaccination, we conclude that correlates are not universal for all EBOV vaccines.

Current Use of Adenovirus Vectors and Their Production Methods

Various adenovirus (AdV) vector systems have proven to be lucrative options for gene delivery. They can serve as potential vaccine candidates for prevention of several common infectious diseases and hold the promise for gene therapy, especially for cancer. Several AdV vector-based therapies are currently at various stages of clinical trials worldwide, which make an immense interest of both the clinicians and researchers. Since these vectors are easy to manipulate, have broad tropism, and have the capability to yield high titers, this delivery system has a wide range of applications for different clinical settings. This chapter emphasizes on some of the current usages of AdV vectors and their production methods.

Fast, selective and quantitative protein profiling of adenovirus-vector based vaccines by ultra-performance liquid chromatography

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A validated method for quantitative protein profiling in adenovirus-based vaccines.

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14 Adenovirus proteins baseline separated within 17 min by RP-UPLC.

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Adenovirus-based samples directly injected, needing no sample pretreatment.

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The method can detect and quantify protein degradants.

A method for the quantitative determination of the protein composition of adenovirus-vector based vaccines was developed. The final method used RP-UPLC with UV absorbance detection, a C4 column (300 Å, 1.7 μm, 2.1 × 150 mm), and a water- acetonitrile (ACN) gradient containing trifluoroacetic acid (TFA) as ion-pairing agent. The chromatographic resolution between the various adenovirus proteins was optimized by studying the effect of the TFA concentration and the column temperature, applying a full factorial design of experiments. A reproducible baseline separation of all relevant adenovirus proteins could be achieved within 17 min run time. Samples containing adenovirus particles could be directly injected into the UPLC system without sample pretreatment. The viruses reproducibly dissociate into proteins in the UPLC system upon contact with the mobile phase containing ACN. The new RP-UPLC method was successfully validated for protein profiling and relative quantification of proteins in vaccine products based on adenovirus vector types 26 and 35. The intermediate precision of the relative peak areas of all proteins was between 1% and 14% RSD, except for the peak assigned to protein V (26% RSD). The method proved to be stability indicating with respect to thermal and oxidation stress of the adenovirus-vector based vaccine and was successfully implemented for the characterization of adenovirus-based products.

αvβ3 Integrin Is Required for Efficient Infection of Epithelial Cells with Human Adenovirus Type 26

Human adenoviruses (HAdVs) are being explored as vectors for gene transfer and vaccination. Human adenovirus type 26 (HAdV26), which belongs to the largest subgroup of adenoviruses, species D, has a short fiber and a so-far-unknown natural tropism. Due to its low seroprevalence, HAdV26 has been considered a promising vector for the development of vaccines. Despite the fact that the in vivo safety and immunogenicity of HAdV26 have been extensively studied, the basic biology of the virus with regard to receptor use, cell attachment, internalization, and intracellular trafficking is poorly understood. In this work, we investigated the roles of the coxsackievirus and adenovirus receptor (CAR), CD46, and αv integrins in HAdV26 infection of human epithelial cell lines. By performing different gain- and loss-of-function studies, we found that αvβ3 integrin is required for efficient infection of epithelial cells by HAdV26, while CAR and CD46 did not increase the transduction efficiency of HAdV26. By studying intracellular trafficking of fluorescently labeled HAdV26 in A549 cells and A549-derived cell clones with stably increased expression of αvβ3 integrin, we observed that HAdV26 colocalizes with αvβ3 integrin and that increased αvβ3 integrin enhances internalization of HAdV26. Thus, we conclude that HAdV26 uses αvβ3 integrin as a receptor for infecting epithelial cells. These results give us new insight into the HAdV26 infection pathway and will be helpful in further defining HAdV-based vector manufacturing and vaccination strategies.IMPORTANCE Adenovirus-based vectors are used today for gene transfer and vaccination. HAdV26 has emerged as a promising candidate vector for development of vaccines due to its relatively low seroprevalence and its ability to induce potent immune responses against inserted transgenes. However, data regarding the basic biology of the virus, like receptor usage or intracellular trafficking, are limited. In this work, we found that efficient infection of human epithelial cell lines by HAdV26 requires the expression of the αvβ3 integrin. By studying intracellular trafficking of fluorescently labeled HAdV26 in a cell clone with stably increased expression of αvβ3 integrin, we observed that HAdV26 colocalizes with αvβ3 integrin and confirmed that αvβ3 integrin expression facilitates efficient HAdV26 internalization. These results will allow further improvement of HAdV26-based vectors for gene transfer and vaccination.

Protective Efficacy and Long-Term Immunogenicity in Cynomolgus Macaques by Ebola Virus Glycoprotein Synthetic DNA Vaccines

Background

There remains an important need for prophylactic anti-Ebola virus vaccine candidates that elicit long-lasting immune responses and can be delivered to vulnerable populations that are unable to receive live-attenuated or viral vector vaccines.

Methods

We designed novel synthetic anti-Ebola virus glycoprotein (EBOV-GP) DNA vaccines as a strategy to expand protective breadth against diverse EBOV strains and evaluated the impact of vaccine dosing and route of administration on protection against lethal EBOV-Makona challenge in cynomolgus macaques. Long-term immunogenicity was monitored in nonhuman primates for >1 year, followed by a 12-month boost.

Results

Multiple-injection regimens of the EBOV-GP DNA vaccine, delivered by intramuscular administration followed by electroporation, were 100% protective against lethal EBOV-Makona challenge. Impressively, 2 injections of a simple, more tolerable, and dose-sparing intradermal administration followed by electroporation generated strong immunogenicity and was 100% protective against lethal challenge. In parallel, we observed that EBOV-GP DNA vaccination induced long-term immune responses in macaques that were detectable for at least 1 year after final vaccination and generated a strong recall response after the final boost.

Conclusions

These data support that this simple intradermal-administered, serology-independent approach is likely important for additional study towards the goal of induction of anti-EBOV immunity in multiple at-risk populations.

Zika virus vaccines

The recent epidemic of Zika virus (ZIKV) in the Americas has revealed the devastating consequences of ZIKV infection, particularly in pregnant women. Congenital Zika syndrome, characterized by malformations and microcephaly in neonates as well as developmental challenges in children, highlights the need for the development of a safe and effective vaccine. Multiple vaccine candidates have been developed and have shown promising results in both animal models and phase I clinical trials. However, important challenges remain for the clinical development of these vaccines. In this Progress article, we discuss recent preclinical studies and lessons learned from first-in-human clinical trials with ZIKV vaccines.

Ebola: Lessons on Vaccine Development

The West African Ebola virus (EBOV) epidemic has fast-tracked countermeasures for this rare, emerging zoonotic pathogen. Until 2013-2014, most EBOV vaccine candidates were stalled between the preclinical and clinical milestones on the path to licensure, because of funding problems, lack of interest from pharmaceutical companies, and competing priorities in public health. The unprecedented and devastating epidemic propelled vaccine candidates toward clinical trials that were initiated near the end of the active response to the outbreak. Those trials did not have a major impact on the epidemic but provided invaluable data on vaccine safety, immunogenicity, and, to a limited degree, even efficacy in humans. There are plenty of lessons to learn from these trials, some of which are addressed in this review. Better preparation is essential to executing an effective response to EBOV in the future; yet, the first indications of waning interest are already noticeable.

Ebola vaccine development: Systematic review of pre-clinical and clinical studies, and meta-analysis of determinants of antibody response variability after vaccination

OBJECTIVES

For Ebola vaccine development, antibody response is a major endpoint although its determinants are not well known. We aimed to review Ebola vaccine studies and to assess factors associated with antibody response variability in humans.

METHODS

We searched PubMed and Scopus for preventive Ebola vaccine studies in humans or non-human primates (NHP), published up to February 2018. For each vaccination group with Ebola Zaire antibody titre measurements after vaccination, data about antibody response and its potential determinants were extracted. A random-effects meta-regression was conducted including human groups with at least 8 individuals.

RESULTS

We reviewed 49 studies (202 vaccination groups including 74 human groups) with various vaccine platforms and antigen inserts. Mean antibody titre was slightly higher in NHP (3.10, 95% confidence interval [293; 327]) than in humans (2.75 [257; 293]). Vaccine platform (p<0·001) and viral strain used for antibody detection (p<0·001) were associated with antibody response in humans, but adjusted heterogeneity remained at 95%.

CONCLUSIONS

Various platforms have been evaluated in humans, including Ad26, Ad5, ChimpAd3, DNA, MVA, and VSV. In addition to platforms, viral strain used for antibody detection influences antibody response. However, variability remained mostly unexplained. Therefore, comparison of vaccine immunogenicity needs randomised controlled trials.

Adenoviral vector type 26 encoding Zika virus (ZIKV) M-Env antigen induces humoral and cellular immune responses and protects mice and nonhuman primates against ZIKV challenge

In 2015, there was a large outbreak of Zika virus (ZIKV) in Brazil. Despite its relatively mild impact on healthy adults, ZIKV infection during pregnancy has been associated with severe birth defects. Currently, there is no ZIKV vaccine available, but several vaccine candidates based on the ZIKV membrane (M) and envelope (Env) structural proteins showed promising results in preclinical and clinical studies. Here, the immunogenicity and protective efficacy of a non-replicating adenoviral vector type 26 (Ad26) that encodes the ZIKV M-Env antigens (Ad26.ZIKV.M-Env) was evaluated in mice and non-human primates (NHP). Ad26.ZIKV.M-Env induced strong and durable cellular and humoral immune responses in preclinical models. Humoral responses were characterized by Env-binding and ZIKV neutralizing antibody responses while cellular responses were characterized by ZIKV reactive CD4+ and CD8+ T cells. Importantly, a single immunization with a very low dose of 4x107 vp of Ad26.ZIKV.M-Env protected mice from ZIKV challenge. In NHP, a single immunization with a typical human dose of 1x1011 vp of Ad26.ZIKV.M-Env also induced Env-binding and ZIKV neutralizing antibodies and Env and M specific cellular immune responses that associated with complete protection against viremia from ZIKV challenge as measured in plasma and other body fluids. Together these data provide the rationale to progress the Ad26.ZIKV.M-Env candidate vaccine to clinical testing.

DNA-launched RNA replicon vaccines induce potent anti-Ebolavirus immune responses that can be further improved by a recombinant MVA boost

There are currently no licensed therapeutic treatment or preventive vaccines against Ebolavirus disease, and the 2013-2016 West African outbreak of Ebolavirus disease spread rapidly and resulted in almost 30,000 cases and more than 11,000 deaths. However, the devastating outbreak has spurred the development of novel Ebolavirus vaccines. Here, we demonstrate that alphavirus-based DNA-launched self-replicating RNA replicon vaccines (DREP) encoding either the glycoprotein (GP) gene or co-expressing the GP and VP40 genes of Sudan or Zaire Ebolavirus are immunogenic in mice inducing both binding and neutralizing antibodies as well as CD8 T cell responses. In addition, antibodies were cross-reactive against another Ebolavirus, although the specificity was higher for the vaccination antigen. DREP vaccines were more immunogenic than recombinant MVA vaccines expressing the same Ebolavirus antigens. However, a DREP prime followed by an MVA boost immunization regimen improved vaccine immunogenicity as compared to DREP and MVA homologous prime-boost immunizations. Moreover, we show that a bivalent approach targeting both Sudan and Zaire Ebolavirus can be employed without significant loss of immunity. This opens for further investigation of a pan-Ebolavirus or even a pan-filovirus vaccine.

Advances in Designing and Developing Vaccines, Drugs, and Therapies to Counter Ebola Virus

Ebola virus (EBOV), a member of the family Filoviridae, is responsible for causing Ebola virus disease (EVD) (formerly named Ebola hemorrhagic fever). This is a severe, often fatal illness with mortality rates varying from 50 to 90% in humans. Although the virus and associated disease has been recognized since 1976, it was only when the recent outbreak of EBOV in 2014-2016 highlighted the danger and global impact of this virus, necessitating the need for coming up with the effective vaccines and drugs to counter its pandemic threat. Albeit no commercial vaccine is available so far against EBOV, a few vaccine candidates are under evaluation and clinical trials to assess their prophylactic efficacy. These include recombinant viral vector (recombinant vesicular stomatitis virus vector, chimpanzee adenovirus type 3-vector, and modified vaccinia Ankara virus), Ebola virus-like particles, virus-like replicon particles, DNA, and plant-based vaccines. Due to improvement in the field of genomics and proteomics, epitope-targeted vaccines have gained top priority. Correspondingly, several therapies have also been developed, including immunoglobulins against specific viral structures small cell-penetrating antibody fragments that target intracellular EBOV proteins. Small interfering RNAs and oligomer-mediated inhibition have also been verified for EVD treatment. Other treatment options include viral entry inhibitors, transfusion of convalescent blood/serum, neutralizing antibodies, and gene expression inhibitors. Repurposed drugs, which have proven safety profiles, can be adapted after high-throughput screening for efficacy and potency for EVD treatment. Herbal and other natural products are also being explored for EVD treatment. Further studies to better understand the pathogenesis and antigenic structures of the virus can help in developing an effective vaccine and identifying appropriate antiviral targets. This review presents the recent advances in designing and developing vaccines, drugs, and therapies to counter the EBOV threat.

Baited vaccines: A strategy to mitigate rodent-borne viral zoonoses in humans

Rodents serve as the natural reservoir and vector for a variety of pathogens, some of which are responsible for severe and life-threatening disease in humans. Despite the significant impact in humans many of these viruses, including Old and New World hantaviruses as well as Arenaviruses, most have no specific vaccine or therapeutic to treat or prevent human infection. The recent success of wildlife vaccines to mitigate rabies in animal populations offers interesting insight into the use of similar strategies for other zoonotic agents of human disease. In this review, we discuss the notion of using baited vaccines as a means to interrupt the transmission of viral pathogens between rodent reservoirs and to susceptible human hosts.

An adenovirus serotype 2-vectored ebolavirus vaccine generates robust antibody and cell-mediated immune responses in mice and rhesus macaques

Ebolavirus vaccines based on several adenoviral vectors have been investigated in preclinical studies and clinical trials. The use of adenovirus serotype 2 as a vector for ebolavirus vaccine has not been reported. Herein, we generated rAd2-ZGP, a recombinant replication-incompetent adenovirus serotype 2 expressing codon-optimized Zaire ebolavirus glycoprotein, and evaluated its immunogenicity in mice and rhesus macaques. rAd2-ZGP induced significant antibody and cell-mediated immune responses at 2 weeks after a single immunization. The glycoprotein (GP)-specific immune responses could be further enhanced with a booster immunization. Compared to protein antigens, Zaire ebolavirus GP and Zaire ebolavirus-like particles, rAd2-ZGP could induce stronger cross-reactive antibody and cell-mediated immune responses to heterologous Sudan ebolavirus in mice and rhesus macaques. In rAd2-ZGP-immunized macaques, GP-specific CD8⁺ T cells could secret IFN-γ and IL-2, indicating a Th1-biased response. In adenovirus serotype 5 seropositive macaques, rAd2-ZGP could induce robust antibody and cell-mediated immune responses, suggesting that the efficacy of rAd2-ZGP is not affected by pre-existing immunity to adenovirus serotype 5. These results demonstrated that rAd2-ZGP can be considered an alternative ebolavirus vaccine for use in adenovirus serotype 5 seropositive subjects or as a sequential booster vaccine after the subjects have been immunized with a recombinant adenovirus serotype 5-based vaccine.

Immunogenicity of propagation-restricted vesicular stomatitis virus encoding Ebola virus glycoprotein in guinea pigs

Vesicular stomatitis virus (VSV) expressing the Ebola virus (EBOV) glycoprotein (GP) in place of the VSV glycoprotein G (VSV/EBOV-GP) is a promising EBOV vaccine candidate which has already entered clinical phase 3 studies. Although this chimeric virus was tolerated overall by volunteers, it still caused viremia and adverse effects such as fever and arthritis, suggesting that it might not be sufficiently attenuated. In this study, the VSV/EBOV-GP vector was further modified in order to achieve attenuation while maintaining immunogenicity. All recombinant VSV constructs were propagated on VSV G protein expressing helper cells and used to immunize guinea pigs via the intramuscular route. The humoral immune response was analysed by EBOV-GP-specific fluorescence-linked immunosorbent assay, plaque reduction neutralization test and in vitro virus-spreading inhibition test that employed recombinant VSV/EBOV-GP expressing either green fluorescent protein or secreted Nano luciferase. Most modified vector constructs induced lower levels of protective antibodies than the parental VSV/EBOV-GP or a recombinant modified vaccinia virus Ankara vector encoding full-length EBOV-GP. However, the VSV/EBOV-GP(F88A) mutant was at least as immunogenic as the parental vaccine virus although it was highly propagation-restricted. This finding suggests that VSV-vectored vaccines need not be propagation-competent to induce a robust humoral immune response. However, VSV/EBOV-GP(F88A) rapidly reverted to a fully propagation-competent virus indicating that a single-point mutation is not sufficient to maintain the propagation-restricted phenotype.

Vaccinia-based vaccines to biothreat and emerging viruses

The past few years have seen a rash of emerging viral diseases, including the Ebola crisis in West Africa, the pandemic spread of chikungunya, and the recent explosion of Zika in South America. Vaccination is the most reliable and cost-effective method of control of infectious diseases, however, there is often a long delay in production and approval in getting new vaccines to market. Vaccinia was the first vaccine developed for the successful eradication of smallpox and has properties that make it attractive as a universal vaccine vector. Vaccinia can cause severe complications, particularly in immune suppressed recipients that would limit its utility, but nonreplicating and attenuated strains have been developed. Modified vaccinia Ankara is nonreplicating in human cells and can be safely given to immune suppressed individuals. Vaccinia has recently been modified for use as an oncolytic treatment for cancer therapy. These new vaccinia vectors are replicating; but have been attenuated and could prove useful as a universal vaccine carrier as many of these are in clinical trials for cancer therapy. This article reviews the development of a universal vaccinia vaccine platform for emerging diseases or biothreat agents, based on nonreplicating or live attenuated vaccinia viruses.

Distinct Immunogenicity and Efficacy of Poxvirus-Based Vaccine Candidates against Ebola Virus Expressing GP and VP40 Proteins

Zaire and Sudan ebolavirus species cause a severe disease in humans and nonhuman primates (NHPs) characterized by a high mortality rate. There are no licensed therapies or vaccines against Ebola virus disease (EVD), and the recent 2013 to 2016 outbreak in West Africa highlighted the need for EVD-specific medical countermeasures. Here, we generated and characterized head-to-head the immunogenicity and efficacy of five vaccine candidates against Zaire ebolavirus (EBOV) and Sudan ebolavirus (SUDV) based on the highly attenuated poxvirus vector modified vaccinia virus Ankara (MVA) expressing either the virus glycoprotein (GP) or GP together with the virus protein 40 (VP40) forming virus-like particles (VLPs). In a human monocytic cell line, the different MVA vectors (termed MVA-EBOVs and MVA-SUDVs) triggered robust innate immune responses, with production of beta interferon (IFN-β), proinflammatory cytokines, and chemokines. Additionally, several innate immune cells, such as dendritic cells, neutrophils, and natural killer cells, were differentially recruited in the peritoneal cavity of mice inoculated with MVA-EBOVs. After immunization of mice with a homologous prime/boost protocol (MVA/MVA), total IgG antibodies against GP or VP40 from Zaire and Sudan ebolavirus were differentially induced by these vectors, which were mainly of the IgG1 and IgG3 isotypes. Remarkably, an MVA-EBOV construct coexpressing GP and VP40 protected chimeric mice challenged with EBOV to a greater extent than a vector expressing GP alone. These results support the consideration of MVA-EBOVs and MVA-SUDVs expressing GP and VP40 and producing VLPs as best-in-class potential vaccine candidates against EBOV and SUDV.IMPORTANCE EBOV and SUDV cause a severe hemorrhagic fever affecting humans and NHPs. Since their discovery in 1976, they have caused several sporadic epidemics, with the recent outbreak in West Africa from 2013 to 2016 being the largest and most severe, with more than 11,000 deaths being reported. Although some vaccines are in advanced clinical phases, less expensive, safer, and more effective licensed vaccines are desirable. We generated and characterized head-to-head the immunogenicity and efficacy of five novel vaccines against EBOV and SUDV based on the poxvirus MVA expressing GP or GP and VP40. The expression of GP and VP40 leads to the formation of VLPs. These MVA-EBOV and MVA-SUDV recombinants triggered robust innate and humoral immune responses in mice. Furthermore, MVA-EBOV recombinants expressing GP and VP40 induced high protection against EBOV in a mouse challenge model. Thus, MVA expressing GP and VP40 and producing VLPs is a promising vaccine candidate against EBOV and SUDV.

The current landscape of nucleic acid tests for filovirus detection

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Filoviruses can cause severe hemorrhagic fever in humans and non-human primates.

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There is an urgent need for rapid diagnosis of filoviruses during outbreaks.

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Filovirus diagnostics have advanced since the 2014–2016 Ebolavirus outbreak.

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NATs are the gold standard for filovirus detection.

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NAT-based diagnostic speed, portability and multiplexing have all improved.

Nucleic acid testing (NAT) for pathogenic filoviruses plays a key role in surveillance and to control the spread of infection. As they share clinical features with other pathogens, the initial spread of these viruses can be misdiagnosed. Tests that can identify a pathogen in the initial stages of infection are essential to control outbreaks. Since the Ebola virus disease (EVD) outbreak in 2014–2016 several tests have been developed that are faster than previous tests and more suited for field use. Furthermore, the ability to test for a range of pathogens simultaneously has been expanded to improve clinical pathway management of febrile syndromes. This review provides an overview of these novel diagnostic tests.

Lung macrophage scavenger receptor SR-A6 (MARCO) is an adenovirus type-specific virus entry receptor

Macrophages are a diverse group of phagocytic cells acting in host protection against stress, injury, and pathogens. Here, we show that the scavenger receptor SR-A6 is an entry receptor for human adenoviruses in murine alveolar macrophage-like MPI cells, and important for production of type I interferon. Scavenger receptors contribute to the clearance of endogenous proteins, lipoproteins and pathogens. Knockout of SR-A6 in MPI cells, anti-SR-A6 antibody or the soluble extracellular SR-A6 domain reduced adenovirus type-C5 (HAdV-C5) binding and transduction. Expression of murine SR-A6, and to a lower extent human SR-A6 boosted virion binding to human cells and transduction. Virion clustering by soluble SR-A6 and proximity localization with SR-A6 on MPI cells suggested direct adenovirus interaction with SR-A6. Deletion of the negatively charged hypervariable region 1 (HVR1) of hexon reduced HAdV-C5 binding and transduction, implying that the viral ligand for SR-A6 is hexon. SR-A6 facilitated macrophage entry of HAdV-B35 and HAdV-D26, two important vectors for transduction of hematopoietic cells and human vaccination. The study highlights the importance of scavenger receptors in innate immunity against human viruses.

Macrophages are a diverse group of phagocytic cells acting in host protection against stress, injury, and pathogens. They phenotypically and functionally adapt to their local environment, for example, peritoneal macrophages are distinct from brain-resident microglia, from liver-resident Kupffer cells or lung macrophages in the lung. Airway macrophages are among the first cells to encounter human respiratory viruses, such as adenoviruses. They release pro-inflammatory cytokines, kill pathogens, present antigens, and restore tissues. Yet, interactions of viruses with lung macrophages are poorly understood, and it is unclear, how they lead to infection or virus clearance. Here we identified the murine scavenger receptor SR-A6 as a receptor for a subset of human adenoviruses on alveolar macrophage-like cells, so-called MPI cells. Scavenger receptors comprise a large family of trans-membrane proteins, and contribute to the clearance of endogenous proteins, lipoproteins and pathogens. In a series of robust experimentation, we show that adenoviruses use SR-A6 as an entry receptor for infection of MPI cells, and production of type I interferon. MPI cells are non-transformed, self-renewing macrophages derived from fetal murine liver, and closely resemble adult alveolar macrophages. The results demonstrate that SR-A6 binds virions on the surface of alveolar macrophage-like cells, and leads to infection.

A prophylactic multivalent vaccine against different filovirus species is immunogenic and provides protection from lethal infections with Ebolavirus and Marburgvirus species in non-human primates

The search for a universal filovirus vaccine that provides protection against multiple filovirus species has been prompted by sporadic but highly lethal outbreaks of Ebolavirus and Marburgvirus infections. A good prophylactic vaccine should be able to provide protection to all known filovirus species and as an upside potentially protect from newly emerging virus strains. We investigated the immunogenicity and protection elicited by multivalent vaccines expressing glycoproteins (GP) from Ebola virus (EBOV), Sudan virus (SUDV), Taï Forest virus (TAFV) and Marburg virus (MARV). Immune responses against filovirus GP have been associated with protection from disease. The GP antigens were expressed by adenovirus serotypes 26 and 35 (Ad26 and Ad35) and modified Vaccinia virus Ankara (MVA) vectors, all selected for their strong immunogenicity and good safety profile. Using fully lethal NHP intramuscular challenge models, we assessed different vaccination regimens for immunogenicity and protection from filovirus disease. Heterologous multivalent Ad26-Ad35 prime-boost vaccination regimens could give full protection against MARV (range 75%-100% protection) and EBOV (range 50% to 100%) challenge, and partial protection (75%) against SUDV challenge. Heterologous multivalent Ad26-MVA prime-boost immunization gave full protection against EBOV challenge in a small cohort study. The use of such multivalent vaccines did not show overt immune interference in comparison with monovalent vaccines. Multivalent vaccines induced GP-specific antibody responses and cellular IFNγ responses to each GP expressed by the vaccine, and cross-reactivity to TAFV GP was detected in a trivalent vaccine expressing GP from EBOV, SUDV and MARV. In the EBOV challenge studies, higher humoral EBOV GP-specific immune responses (p = 0.0004) were associated with survival from EBOV challenge and less so for cellular immune responses (p = 0.0320). These results demonstrate that it is feasible to generate a multivalent filovirus vaccine that can protect against lethal infection by multiple members of the filovirus family.

Willingness to pay for an Ebola vaccine during the 2014-2016 ebola outbreak in West Africa: Results from a U.S. National sample

The 2014-2016 Ebola virus outbreak in West Africa led to advances in the development of vaccines against Ebola. This study examined factors associated with willingness to pay for an Ebola vaccine among a U.S. national sample during the recent Ebola outbreak. From April 30-May 8, 2015, a national survey was conducted using the GfK Group's KnowlegePanel®. Main outcome measures included willingness to pay at least $1; more than $50; and more than $100 for an Ebola vaccine. Analyses were conducted using weighted multivariable logistic regression. Among participants (N = 1,447), 583 (40.3%) would not pay for an Ebola vaccine; 864 (59.7%) would pay at least $1. Among those willing to pay at least $1: 570 (66.0%) would pay $1-50; 174 (20.1%) would pay $51-100; and 120 (13.9%) would pay more than $100. Willingness to pay at least $1 for an Ebola vaccine was associated with international travel; interest in getting an Ebola vaccine; and beliefs that the U.S. government should spend money to control Ebola and assume worldwide leadership in confronting emerging epidemics. Willingness to pay more than $50 was associated with similar variables. Willingness to pay more than $100 was associated with international travel; interest in getting an Ebola vaccine; information seeking; and beliefs that the U.S. government should assume worldwide leadership in confronting emerging epidemics. International travel and interest in an Ebola vaccine were key predictors of willingness to pay across all price points. Understanding willingness to pay for vaccines against emerging infectious diseases remains critical.

From bench to almost bedside: the long road to a licensed Ebola virus vaccine

INTRODUCTION

The Ebola virus (EBOV) disease epidemic during 2014-16 in West Africa has accelerated the clinical development of several vaccine candidates that have demonstrated efficacy in the gold standard nonhuman primate (NHP) model, namely cynomolgus macaques.

AREAS COVERED

This review discusses the pre-clinical research and if available, clinical evaluation of the currently available EBOV vaccine candidates, while emphasizing the translatability of pre-clinical data generated in the NHP model to clinical data in humans.

EXPERT OPINION

Despite the existence of many successful EBOV vaccine candidates in the pre-clinical stages, only two platforms became the focus of Phase 2/3 efficacy trials in Liberia, Sierra Leone, and Guinea near the peak of the epidemic: the Vesicular stomatitis virus (VSV)-vectored vaccine and the chimpanzee adenovirus type 3 (ChAd3)-vectored vaccine. The results of three distinct clinical trials involving these candidates may soon pave the way for a licensed, safe and efficacious EBOV vaccine to help combat future epidemics.

Vaccinating for natural killer cell effector functions

Vaccination has proved to be highly effective in reducing global mortality and eliminating infectious diseases. Building on this success will depend on the development of new and improved vaccines, new methods to determine efficacy and optimum dosing and new or refined adjuvant systems. NK cells are innate lymphoid cells that respond rapidly during primary infection but also have adaptive characteristics enabling them to integrate innate and acquired immune responses. NK cells are activated after vaccination against pathogens including influenza, yellow fever and tuberculosis, and their subsequent maturation, proliferation and effector function is dependent on myeloid accessory cell-derived cytokines such as IL-12, IL-18 and type I interferons. Activation of antigen-presenting cells by live attenuated or whole inactivated vaccines, or by the use of adjuvants, leads to enhanced and sustained NK cell activity, which in turn contributes to T cell recruitment and memory cell formation. This review explores the role of cytokine-activated NK cells as vaccine-induced effector cells and in recall responses and their potential contribution to vaccine and adjuvant development.