Single-injection vaccine protects nonhuman primates against infection with marburg virus and three species of ebola virus

Macaque antibodies targeting Marburg virus glycoprotein induced by multivalent immunization

Marburg virus infection in humans is associated with case fatality rates that can reach up to 90%, but to date, there are no approved vaccines or monoclonal antibody (mAb) countermeasures. Here, we immunized Rhesus macaques with multivalent combinations of filovirus glycoprotein (GP) antigens belonging to Marburg, Sudan, and Ebola viruses to generate monospecific and cross-reactive antibody responses against them. From the animal that developed the highest titers of Marburg virus GP-specific neutralizing antibodies, we sorted single memory B cells using a heterologous Ravn virus GP probe and cloned and characterized a panel of 34 mAbs belonging to 28 unique lineages. Antibody specificities were assessed by overlapping pepscan and binding competition analyses, revealing that roughly a third of the lineages mapped to the conserved receptor binding region, including potent neutralizing lineages that were confirmed by negative stain electron microscopy to target this region. Additional lineages targeted a protective region on GP2, while others were found to possess cross-filovirus reactivity. Our study advances the understanding of orthomarburgvirus glycoprotein antigenicity and furthers efforts to develop candidate antibody countermeasures against these lethal viruses.

IMPORTANCE

Marburg viruses were the first filoviruses characterized to emerge in humans in 1967 and cause severe hemorrhagic fever with average case fatality rates of ~50%. Although mAb countermeasures have been approved for clinical use against the related Ebola viruses, there are currently no approved countermeasures against Marburg viruses. We successfully isolated a panel of orthomarburgvirus GP-specific mAbs from a macaque immunized with a multivalent combination of filovirus antigens. Our analyses revealed that roughly half of the antibodies in the panel mapped to regions on the glycoprotein shown to protect from infection, including the host cell receptor binding domain and a protective region on the membrane-anchoring subunit. Other antibodies in the panel exhibited broad filovirus GP recognition. Our study describes the discovery of a diverse panel of cross-reactive macaque antibodies targeting orthomarburgvirus and other filovirus GPs and provides candidate immunotherapeutics for further study and development.

Pathogenic differences of cynomolgus macaques after Taï Forest virus infection depend on the viral stock propagation

Taï Forest virus (TAFV) is a negative-sense RNA virus in the Filoviridae family. TAFV has caused only a single human infection, but several disease outbreaks in chimpanzees have been linked to this virus. Limited research has been done on this human-pathogenic virus. We sought to establish an animal model to assess TAFV disease progression and pathogenicity at our facility. We had access to two different viral stock preparations from different institutions, both originating from the single human case. Type I interferon receptor knockout mice were inoculated with TAFV stock 1 or stock 2 by the intraperitoneal route. Inoculation resulted in 100% survival with no disease regardless of viral stock preparation or infectious dose. Next, cynomolgus macaques were inoculated with TAFV stock 1 or stock 2. Inoculation with TAFV stock 1 resulted in 100% survival and robust TAFV glycoprotein-specific IgG responses including neutralizing antibodies. In contrast, macaques infected with TAFV stock 2 developed disease and were euthanized 8-11 days after infection exhibiting viremia, thrombocytopenia, and increased inflammatory mediators identified by transcriptional analysis. Histopathologic analysis of tissue samples collected at necropsy confirmed classic filovirus disease in numerous organs. Genomic differences in both stock preparations were mapped to several viral genes which may have contributed to disease severity. Taken together, we demonstrate that infection with the two TAFV stocks resulted in no disease in mice and opposing disease phenotypes in cynomolgus macaques, highlighting the impact of viral stock propagation on pathogenicity in animal models.

Mapping knowledge landscapes and emerging trends of Marburg virus: A text-mining study

Background

Marburg virus (MARV), a close relative of Ebola virus, could induce hemorrhagic fevers in humans with high mortality rate. In recent years, increasing attention has been paid to this highly lethal virus due to sporadic outbreaks observed in various African nations. This bibliometric analysis endeavors to elucidate the trends, dynamics, and focal points of knowledge that have delineated the landscape of research concerning MARV.

Methods

Relevant literature on MARV from 1968 to 2023 was extracted from the Web of Science Core Collection database. Following this, the data underwent bibliometric analysis and visualization procedures utilizing online analysis platform, CiteSpace 6.2R6, and VOSviewer 1.6.20. Three different types of bibliometric indicators including quantitative indicator, qualitative indicators, and structural indicators were used to gauge a researcher's productivity, assess the quality of their work, and analyze publication relationships, respectively.

Results

MARV is mainly prevalent in Africa. And approximately 643 confirmed cases have been described in the literature to date, and mortality observed was 81.2 % in overall patients. A total of 1014 papers comprising 869 articles and 145 reviews were included. The annual publications showed an increasing growth pattern from 1968 to 2023 (R2 = 0.8838). The United States stands at the forefront of this discipline, having dedicated substantial financial and human resources to scientific inquiry. However, co-authorship analysis showed the international research collaboration needs to be further strengthened. Based on reference and keywords analysis, contemporary MARV research encompasses pivotal areas: primarily, prioritizing the creation of prophylactic vaccines to impede viral spread, and secondarily, exploring targeted antiviral strategies, including small-molecule antivirals or MARV-specific monoclonal antibodies. Additionally, a comprehensive grasp of viral transmission, transcription, and replication mechanisms remains a central focus in ongoing investigations. And future MARV studies are expected to focus on evaluating clinical trial safety and efficacy, developing inhibitors to contain viral spread, exploring vaccine immunogenicity, virus-host association studies, and elucidating the role of neutralizing antibodies in MARV treatment.

Conclusion

The present study offered comprehensive insights into the contemporary status and trajectories of MARV over the past decades. This enables researchers to discern novel collaborative prospects, institutional partnerships, emerging topics, and research forefronts within this domain.

Translational success of fundamental virology: a VSV-vectored Ebola vaccine

Ebola virus disease (EVD) caused by Ebola virus (EBOV) is a severe, often fatal, hemorrhagic disease. A critical component of the public health response to curb EVD epidemics is the use of a replication-competent, recombinant vesicular stomatitis virus (rVSV)-vectored Ebola vaccine, rVSVΔG-ZEBOV-GP (ERVEBO). In this Gem, we will discuss the past and ongoing development of rVSVΔG-ZEBOV-GP, highlighting the importance of basic science and the strength of public-private partnerships to translate fundamental virology into a licensed VSV-vectored Ebola vaccine.

Oral administration of obeldesivir protects nonhuman primates against Sudan ebolavirus

Obeldesivir (ODV, GS-5245) is an orally administered prodrug of the parent nucleoside of remdesivir (RDV) and is presently in phase 3 trials for COVID-19 treatment. In this work, we show that ODV and its circulating parent nucleoside metabolite, GS-441524, have similar in vitro antiviral activity against filoviruses, including Marburg virus, Ebola virus, and Sudan virus (SUDV). We also report that once-daily oral ODV treatment of cynomolgus monkeys for 10 days beginning 24 hours after SUDV exposure confers 100% protection against lethal infection. Transcriptomics data show that ODV treatment delayed the onset of inflammation and correlated with antigen presentation and lymphocyte activation. Our results offer promise for the further development of ODV to control outbreaks of filovirus disease more rapidly.

Single dose recombinant VSV based vaccine elicits robust and durable neutralizing antibody against Hantaan virus

Hantaan virus (HTNV) is a pathogenic orthohantavirus prevalent in East Asia that is known to cause hemorrhagic fever with severe renal syndrome (HFRS), which has a high fatality rate. However, a Food and Drug Administration (FDA)-approved vaccine is not currently available against this virus. Although inactivated vaccines have been certified and used in endemic regions for decades, the neutralizing antibody (NAb) titer induced by inactivated vaccines is low and the immunization schedule is complicated, requiring at least three injections spanning approximately 6 months to 1 year. Replication-competent vesicular stomatitis virus (VSV)-based vaccines provide prolonged protection after a single injection. In this study, we successfully engineered the HTNV glycoprotein (GP) in the VSV genome by replacing the VSV-G open reading frame. The resulting recombinant (r) rVSV-HTNV-GP was rescued, and the immunogenicity of GP was similar to that of HTNV. BALB/c mice immunized with rVSV-HTNV-GP showed a high titer of NAb against HTNV after a single injection. Notably, the cross-reactive NAb response induced by rVSV-HTNV-GP against Seoul virus (an orthohantavirus) was higher than that induced by three sequential injections of inactivated vaccines. Upon challenge with HTNV, rVSV-HTNV-GP-immunized mice showed a profoundly reduced viral burden in multiple tissues, and inflammation in the lungs and liver was nearly undetectable. Moreover, a single injection of rVSV-HTNV-GP established a prolonged immunological memory status as the NAbs were sustained for over 1 year and provided long-term protection against HTNV infection. The findings of our study can support further development of an rVSV-HTNV-GP-based HTNV vaccine with a simplified immunization schedule.

Preexisting Immunity Does Not Prevent Efficacy of Vesicular Stomatitis Virus-Based Filovirus Vaccines in Nonhuman Primates

Ebola virus (EBOV) and Marburg virus (MARV) made headlines in the past decade, causing outbreaks of human disease in previously nonendemic yet overlapping areas. While EBOV outbreaks can be mitigated with licensed vaccines and treatments, there is not yet a licensed countermeasure for MARV. Here, we used nonhuman primates (NHPs) previously vaccinated with vesicular stomatitis virus (VSV)-MARV and protected against lethal MARV challenge. After a resting period of 9 months, these NHPs were revaccinated with VSV-EBOV and challenged with EBOV, resulting in 75% survival. Surviving NHPs developed EBOV glycoprotein (GP)-specific antibody titers and no viremia or clinical signs of disease. The single vaccinated NHP succumbing to challenge showed the lowest EBOV GP-specific antibody response after challenge, supporting previous findings with VSV-EBOV that antigen-specific antibodies are critical in mediating protection. This study again demonstrates that VSVΔG-based filovirus vaccine can be successfully used in individuals with preexisting VSV vector immunity, highlighting the platform's applicability for consecutive outbreak response.

A Single-Dose Intranasal Combination Panebolavirus Vaccine

BACKGROUND

Ebolaviruses Ebola (EBOV), Sudan (SUDV), and Bundibugyo (BDBV) cause severe human disease, which may be accompanied by hemorrhagic syndrome, with high case fatality rates. Monovalent vaccines do not offer cross-protection against these viruses whose endemic areas overlap. Therefore, development of a panebolavirus vaccine is a priority. As a vaccine vector, human parainfluenza virus type 3 (HPIV3) has the advantages of needle-free administration and induction of both systemic and local mucosal antibody responses in the respiratory tract.

METHODS

To minimize the antivector immunity, genes encoding the HPIV3 envelope proteins F and HN were removed from the vaccine constructs, resulting in expression of only the ebolavirus envelope protein-glycoprotein. These second-generation vaccine constructs were used to develop a combination vaccine against EBOV, SUDV, and BDBV.

RESULTS

A single intranasal vaccination of guinea pigs or ferrets with the trivalent combination vaccine elicited humoral responses to each of the targeted ebolaviruses, including binding and neutralizing antibodies, as well as Fc-mediated effector functions. This vaccine protected animals from death and disease caused by lethal challenges with EBOV, SUDV, or BDBV.

CONCLUSIONS

The combination vaccine elicited protection that was comparable to that induced by the monovalent vaccines, thus demonstrating the value of this combination trivalent vaccine.

Single-dose VSV-based vaccine protects cynomolgus macaques from disease after Taï Forest virus infection

Taï Forest virus (TAFV) is a lesser-known ebolavirus that causes lethal infections in chimpanzees and is responsible for a single human case. Limited research has been done on this human pathogen; however, with the recent emergence of filoviruses in West Africa, further investigation and countermeasure development against this virus is warranted.We developed a vesicular stomatitis virus (VSV)-based vaccine expressing the TAFV glycoprotein as the viral antigen and assessed it for protective efficacy in nonhuman primates (NHPs). Following a single high-dose vaccination, NHPs developed antigen-specific binding and neutralizing antibodies as well as modest T cell responses. Importantly, all vaccinated NHPs were uniformly protected from disease after lethal TAFV challenge while the naïve control group succumbed to the disease. Histopathologic lesions consistent with filovirus disease were present in control NHPs but were not observed in vaccinated NHPs. Transcriptional analysis of whole blood samples obtained after vaccination and challenge was performed to gain insight into molecular underpinnings conferring protection. Differentially expressed genes (DEG) detected 7 days post-vaccination were enriched to processes associated with innate immunity and antiviral responses. Only a small number of DEG was detected in vaccinated NHPs post-challenge while over 1,000 DEG were detected in control NHPs at end-stage disease which mapped to gene ontology terms indicative of defense responses and inflammation. Taken together, this data demonstrates the effective single-dose protection of the VSV-TAFV vaccine, and its potential for use in outbreaks.

The rVSV-EBOV vaccine provides limited cross-protection against Sudan virus in guinea pigs

Recombinant vesicular stomatitis viruses (rVSVs) engineered to express heterologous viral glycoproteins have proven to be remarkably effective vaccines. Indeed, rVSV-EBOV, which expresses the Ebola virus (EBOV) glycoprotein, recently received clinical approval in the United States and Europe for its ability to prevent EBOV disease. Analogous rVSV vaccines expressing glycoproteins of different human-pathogenic filoviruses have also demonstrated efficacy in pre-clinical evaluations, yet these vaccines have not progressed far beyond research laboratories. In the wake of the most recent outbreak of Sudan virus (SUDV) in Uganda, the need for proven countermeasures was made even more acute. Here we demonstrate that an rVSV-based vaccine expressing the SUDV glycoprotein (rVSV-SUDV) generates a potent humoral immune response that protects guinea pigs from SUDV disease and death. Although the cross-protection generated by rVSV vaccines for different filoviruses is thought to be limited, we wondered whether rVSV-EBOV might also provide protection against SUDV, which is closely related to EBOV. Surprisingly, nearly 60% of guinea pigs that were vaccinated with rVSV-EBOV and challenged with SUDV survived, suggesting that rVSV-EBOV offers limited protection against SUDV, at least in the guinea pig model. These results were confirmed by a back-challenge experiment in which animals that had been vaccinated with rVSV-EBOV and survived EBOV challenge were inoculated with SUDV and survived. Whether these data are applicable to efficacy in humans is unknown, and they should therefore be interpreted cautiously. Nevertheless, this study confirms the potency of the rVSV-SUDV vaccine and highlights the potential for rVSV-EBOV to elicit a cross-protective immune response.

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

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

Species-specific immunogenicity and protective efficacy of a vesicular stomatitis virus-based Sudan virus vaccine: a challenge study in macaques

BACKGROUND

The recent Sudan virus (SUDV) outbreak in Uganda highlights the need for rapid response capabilities, including development of vaccines against emerging viruses with high public health impact. We aimed to develop a Sudan virus-specific vaccine suitable for emergency use during outbreaks.

METHODS

We generated and characterised a vesicular stomatitis virus (VSV)-based vaccine, VSV- SUDV, and evaluated the protective efficacy following a single-dose vaccination against lethal SUDV infection in non-human primates (NHPs). We used male and female cynomolgus macaques (n=11) aged 6-11 years and weighing 3·8-9·0 kg. Animals received a 1 mL intramuscular injection for vaccination containing either 1 × 10⁷ plaque forming units (PFU) VSV-SUDV or 1 × 10⁷ PFU of a VSV-based vaccine against Marburg virus (control; five NHPs). NHPs were challenged intramuscularly 28 days after vaccination with 1 × 10⁴ TCID₅₀ SUDV-Gulu. We assessed anaesthetised NHPs on days 28, 21, 14, and 7 before challenge; days 0, 3, 6, 9, 14, 21, 28, and 35 after challenge; and at euthanasia (day 40 for survivors). As we repurposed NHPs from a successful VSV-Ebola virus (EBOV) vaccine efficacy study, we also investigated VSV-EBOV's cross-protective potential against SUDV challenge.

FINDINGS

Of the six NHPs given VSV-SUDV, none showed any signs of disease in response to the challenge. Four of the five NHPs in the control group developed characteristic clinical signs of Sudan virus diseases. SUDV glycoprotein-specific IgG concentrations peaked 14 days after vaccination (titre of >1:10 000) and reached their highest concentrations at 6 days after challenge (1:25 600-1:102 400). Although the NHPs developed cross-reactive humoral responses to SUDV after VSV-EBOV vaccination and EBOV challenge, there was little cross-protection.

INTERPRETATION

These data emphasise the need for species-specific vaccines for each human-pathogenic Ebolavirus. Furthermore, although previous VSV-EBOV immunity is boosted through VSV-SUDV vaccination, it only has a small effect on the immunogenicity and protective efficacy of VSV-SUDV vaccination against SUDV challenge.

FUNDING

Intramural Research Program, US National Institute of Allergy and Infectious Diseases, National Institutes of Health.

Recombinant vesicular stomatitis virus-vectored vaccine induces long-lasting immunity against Nipah virus disease

The emergence of the novel henipavirus, Langya virus, received global attention after the virus sickened over three dozen people in China. There is heightened concern that henipaviruses, as respiratory pathogens, could spark another pandemic, most notably the deadly Nipah virus (NiV). NiV causes near-annual outbreaks in Bangladesh and India and induces a highly fatal respiratory disease and encephalitis in humans. No licensed countermeasures against this pathogen exist. An ideal NiV vaccine would confer both fast-acting and long-lived protection. Recently, we reported the generation of a recombinant vesicular stomatitis virus-based (rVSV-based) vaccine expressing the NiV glycoprotein (rVSV-ΔG-NiVBG) that protected 100% of nonhuman primates from NiV-associated lethality within a week. Here, to evaluate the durability of rVSV-ΔG-NiVBG, we vaccinated African green monkeys (AGMs) one year before challenge with an uniformly lethal dose of NiV. The rVSV-ΔG-NiVBG vaccine induced stable and robust humoral responses, whereas cellular responses were modest. All immunized AGMs (whether receiving a single dose or prime-boosted) survived with no detectable clinical signs or NiV replication. Transcriptomic analyses indicated that adaptive immune signatures correlated with vaccine-mediated protection. While vaccines for certain respiratory infections (e.g., COVID-19) have yet to provide durable protection, our results suggest that rVSV-ΔG-NiVBG elicits long-lasting immunity.

Nonhuman Primates Are Protected against Marburg Virus Disease by Vaccination with a Vesicular Stomatitis Virus Vector-Based Vaccine Prepared under Conditions to Allow Advancement to Human Clinical Trials

Vaccines are needed to disrupt or prevent continued outbreaks of filoviruses in humans across Western and Central Africa, including outbreaks of Marburg virus (MARV). As part of a filovirus vaccine product development plan, it is important to investigate dose response early in preclinical development to identify the dose range that may be optimal for safety, immunogenicity, and efficacy, and perhaps demonstrate that using lower doses is feasible, which will improve product access. To determine the efficacious dose range for a manufacturing-ready live recombinant vesicular stomatitis virus vaccine vector (rVSV∆G-MARV-GP) encoding the MARV glycoprotein (GP), a dose-range study was conducted in cynomolgus macaques. Results showed that a single intramuscular injection with as little as 200 plaque-forming units (PFUs) was 100% efficacious against lethality and prevented development of viremia and clinical pathologies associated with MARV Angola infection. Across the vaccine doses tested, there was nearly a 2000-fold range of anti-MARV glycoprotein (GP) serum IgG titers with seroconversion detectable even at the lowest doses. Virus-neutralizing serum antibodies also were detected in animals vaccinated with the higher vaccine doses indicating that vaccination induced functional antibodies, but that the assay was a less sensitive indicator of seroconversion. Collectively, the data indicates that a relatively wide range of anti-GP serum IgG titers are observed in animals that are protected from disease implying that seroconversion is positively associated with efficacy, but that more extensive immunologic analyses on samples collected from our study as well as future preclinical studies will be valuable in identifying additional immune responses correlated with protection that can serve as markers to monitor in human trials needed to generate data that can support vaccine licensure in the future.

Lessons Learned from the Development and Roll-Out of the rVSVΔG-ZEBOV-GP Zaire ebolavirus Vaccine to Inform Marburg Virus and Sudan ebolavirus Vaccines

This review describes key aspects of the development of the rVSVΔG-ZEBOV-GP Ebola vaccine and key activities which are continuing to further expand our knowledge of the product. Extensive partnerships and innovative approaches were used to address the various challenges encountered during this process. The rVSVΔG-ZEBOV-GP Ebola vaccine was initially approved by the European Medicines Agency and prequalified by the World Health Organization in November 2019. It was approved by the United States Food and Drug Administration in December 2019 and approved in five African countries within 90 days of prequalification. The development resulted in the first stockpile of a registered Ebola vaccine that is available to support outbreak response. This also provides insights into how the example of rVSVΔG-ZEBOV-GP can inform the development of vaccines for Sudan ebolavirus, Marburg virus, and other emerging epidemic diseases in terms of the types of approaches and data needed to support product registration, availability, and the use of a filovirus vaccine.

A Historical Review of Military Medical Strategies for Fighting Infectious Diseases: From Battlefields to Global Health

The environmental conditions generated by war and characterized by poverty, undernutrition, stress, difficult access to safe water and food as well as lack of environmental and personal hygiene favor the spread of many infectious diseases. Epidemic typhus, plague, malaria, cholera, typhoid fever, hepatitis, tetanus, and smallpox have nearly constantly accompanied wars, frequently deeply conditioning the outcome of battles/wars more than weapons and military strategy. At the end of the nineteenth century, with the birth of bacteriology, military medical researchers in Germany, the United Kingdom, and France were active in discovering the etiological agents of some diseases and in developing preventive vaccines. Emil von Behring, Ronald Ross and Charles Laveran, who were or served as military physicians, won the first, the second, and the seventh Nobel Prize for Physiology or Medicine for discovering passive anti-diphtheria/tetanus immunotherapy and for identifying mosquito Anopheline as a malaria vector and plasmodium as its etiological agent, respectively. Meanwhile, Major Walter Reed in the United States of America discovered the mosquito vector of yellow fever, thus paving the way for its prevention by vector control. In this work, the military relevance of some vaccine-preventable and non-vaccine-preventable infectious diseases, as well as of biological weapons, and the military contributions to their control will be described. Currently, the civil-military medical collaboration is getting closer and becoming interdependent, from research and development for the prevention of infectious diseases to disasters and emergencies management, as recently demonstrated in Ebola and Zika outbreaks and the COVID-19 pandemic, even with the high biocontainment aeromedical evacuation, in a sort of global health diplomacy.

A single immunization with a modified vaccinia Ankara vectored vaccine producing Sudan virus-like particles protects from lethal infection

A new vectored vaccine MVA-VLP-SUDV was generated against Sudan ebolavirus (SUDV) combining the advantages of the immunogenicity of a live attenuated vaccine vector (Modified Vaccinia Ankara, MVA) with the authentic conformation of virus-like particles (VLPs). The vaccine expresses minimal components to generate self-assembling VLPs in the vaccinee: the envelope glycoprotein GP and the matrix protein VP40. Guinea pigs vaccinated with one dose of MVA-VLP-SUDV generated SUDV-specific binding and neutralizing antibody responses as well as Fc-mediated protective effects. These responses were boosted by a second vaccine dose. All vaccinated animals which received either one or two vaccine doses were protected from death and disease symptoms following challenge with a lethal dose of SUDV. These data demonstrate single dose protection and potency of the MVA-VLP platform for use in emergency situations to contain outbreaks.

A Cloned Recombinant Vesicular Stomatitis Virus-Vectored Marburg Vaccine, PHV01, Protects Guinea Pigs from Lethal Marburg Virus Disease

Marburg virus (MARV) is a negative-sense, single-stranded RNA virus that belongs to the Filoviridae family. Despite having caused numerous outbreaks of severe hemorrhagic fever with high case fatality rates, there are still no clinically approved therapeutics or vaccines to treat or prevent MARV disease. Recombinant vesicular stomatitis viruses (rVSVs) expressing heterologous viral glycoproteins have shown remarkable promise as live-attenuated vaccine vectors, with an rVSV-based Ebola virus vaccine having received regulatory approval in the United States and numerous other countries. Analogous rVSV vaccine vectors have also been developed for MARV and have shown efficacy in several preclinical studies conducted in nonhuman primates. Here, we used a guinea pig model to confirm the protective efficacy of a cloned, rVSV-based candidate vaccine, termed PHV01, expressing the MARV variant Angola glycoprotein. Our results demonstrated that a single dose (2 × 10⁶ PFU) of vaccine administered 28 days prior to challenge with a uniformly lethal dose of guinea-pig-adapted MARV variant Angola provided complete protection from death and disease. Moreover, protection was robust, with as little as 200 PFU of vaccine conferring significant protection. Not only does this study highlight the potential predictive value of the guinea pig model in the evaluation of MARV countermeasures, but it also demonstrates consistent and reproducible protection afforded by a clonal vaccine candidate. Indeed, this study identifies PHV01 as a suitable vaccine candidate for advanced development.

Natural History of Sudan ebolavirus to Support Medical Countermeasure Development

Sudan ebolavirus (SUDV) is one of four members of the Ebolavirus genus known to cause Ebola Virus Disease (EVD) in humans, which is characterized by hemorrhagic fever and a high case fatality rate. While licensed therapeutics and vaccines are available in limited number to treat infections of Zaire ebolavirus, there are currently no effective licensed vaccines or therapeutics for SUDV. A well-characterized animal model of this disease is needed for the further development and testing of vaccines and therapeutics. In this study, twelve cynomolgus macaques (Macaca fascicularis) were challenged intramuscularly with 1000 PFUs of SUDV and were followed under continuous telemetric surveillance. Clinical observations, body weights, temperature, viremia, hematology, clinical chemistry, and coagulation were analyzed at timepoints throughout the study. Death from SUDV disease occurred between five and ten days after challenge at the point that each animal met the criteria for euthanasia. All animals were observed to exhibit clinical signs and lesions similar to those observed in human cases which included: viremia, fever, dehydration, reduced physical activity, macular skin rash, systemic inflammation, coagulopathy, lymphoid depletion, renal tubular necrosis, hepatocellular degeneration and necrosis. The results from this study will facilitate the future preclinical development and evaluation of vaccines and therapeutics for SUDV.

A highly attenuated Vesiculovax vaccine rapidly protects nonhuman primates against lethal Marburg virus challenge

BACKGROUND

Marburg virus (MARV), an Ebola-like virus, remains an eminent threat to public health as demonstrated by its high associated mortality rate (23-90%) and recent emergence in West Africa for the first time. Although a recombinant vesicular stomatitis virus (rVSV)-based vaccine (Ervebo) is licensed for Ebola virus disease (EVD), no approved countermeasures exist against MARV. Results from clinical trials indicate Ervebo prevents EVD in 97.5-100% of vaccinees 10 days onwards post-immunization.

METHODOLOGY/FINDINGS

Given the rapid immunogenicity of the Ervebo platform against EVD, we tested whether a similar, but highly attenuated, rVSV-based Vesiculovax vector expressing the glycoprotein (GP) of MARV (rVSV-N4CT1-MARV-GP) could provide swift protection against Marburg virus disease (MVD). Here, groups of cynomolgus monkeys were vaccinated 7, 5, or 3 days before exposure to a lethal dose of MARV (Angola variant). All subjects (100%) immunized one week prior to challenge survived; 80% and 20% of subjects survived when vaccinated 5- and 3-days pre-exposure, respectively. Lethality was associated with higher viral load and sustained innate immunity transcriptional signatures, whereas survival correlated with development of MARV GP-specific antibodies and early expression of predicted NK cell-, B-cell-, and cytotoxic T-cell-type quantities.

CONCLUSIONS/SIGNIFICANCE

These results emphasize the utility of Vesiculovax vaccines for MVD outbreak management. The highly attenuated nature of rVSV-N4CT1 vaccines, which are clinically safe in humans, may be preferable to vaccines based on the same platform as Ervebo (rVSV "delta G" platform), which in some trial participants induced vaccine-related adverse events in association with viral replication including arthralgia/arthritis, dermatitis, and cutaneous vasculitis.

Combination therapy with remdesivir and monoclonal antibodies protects nonhuman primates against advanced Sudan virus disease

A major challenge in managing acute viral infections is ameliorating disease when treatment is delayed. Previously, we reported the success of a 2-pronged mAb and antiviral remdesivir therapeutic approach to treat advanced illness in rhesus monkeys infected with Marburg virus (MARV). Here, we explored the benefit of a similar combination therapy for Sudan ebolavirus (Sudan virus; SUDV) infection. Importantly, no licensed anti-SUDV therapeutics currently exist, and infection of rhesus macaques with SUDV results in a rapid disease course similar to MARV with a mean time to death of 8.3 days. When initiation of therapy with either remdesivir or a pan-ebolavirus mAb cocktail (MBP431) was delayed until 6 days after inoculation, only 20% of macaques survived. In contrast, when remdesivir and MBP431 treatment were combined beginning 6 days after inoculation, significant protection (80%) was achieved. Our results suggest that combination therapy may be a viable treatment for patients with advanced filovirus disease that warrants further clinical testing in future outbreaks.

Pathogenicity and virulence of Marburg virus

Marburg virus (MARV) has been a major concern since 1967, with two major outbreaks occurring in 1998 and 2004. Infection from MARV results in severe hemorrhagic fever, causing organ dysfunction and death. Exposure to fruit bats in caves and mines, and human-to-human transmission had major roles in the amplification of MARV outbreaks in African countries. The high fatality rate of up to 90% demands the broad study of MARV diseases (MVD) that correspond with MARV infection. Since large outbreaks are rare for MARV, clinical investigations are often inadequate for providing the substantial data necessary to determine the treatment of MARV disease. Therefore, an overall review may contribute to minimizing the limitations associated with future medical research and improve the clinical management of MVD. In this review, we sought to analyze and amalgamate significant information regarding MARV disease epidemics, pathophysiology, and management approaches to provide a better understanding of this deadly virus and the associated infection.

Cytolytic Recombinant Vesicular Stomatitis Viruses Expressing STLV-1 Receptor Specifically Eliminate STLV-1 Env-Expressing Cells in an HTLV-1 Surrogate Model In Vitro

Human T-cell leukemia virus type 1 (HTLV-1) causes serious and intractable diseases in some carriers after infection. The elimination of infected cells is considered important to prevent this onset, but there are currently no means by which to accomplish this. We previously developed “virotherapy”, a therapeutic method that targets and kills HTLV-1-infected cells using a cytolytic recombinant vesicular stomatitis virus (rVSV). Infection with rVSV expressing an HTLV-1 primary receptor elicits therapeutic effects on HTLV-1-infected envelope protein (Env)-expressing cells in vitro and in vivo. Simian T-cell leukemia virus type 1 (STLV-1) is closely related genetically to HTLV-1, and STLV-1-infected Japanese macaques (JMs) are considered a useful HTLV-1 surrogate, non-human primate model in vivo. Here, we performed an in vitro drug evaluation of rVSVs against STLV-1 as a preclinical study. We generated novel rVSVs encoding the STLV-1 primary receptor, simian glucose transporter 1 (JM GLUT1), with or without an AcGFP reporter gene. Our data demonstrate that these rVSVs specifically and efficiently infected/eliminated the STLV-1 Env-expressing cells in vitro. These results indicate that rVSVs carrying the STLV-1 receptor could be an excellent candidate for unique anti-STLV-1 virotherapy; therefore, such antivirals can now be applied to STLV-1-infected JMs to determine their therapeutic usefulness in vivo.

Transcriptomic signatures induced by the Ebola virus vaccine rVSVΔG-ZEBOV-GP in adult cohorts in Europe, Africa, and North America: a molecular biomarker study

BACKGROUND

A recombinant vesicular stomatitis virus vector expressing the Zaire Ebola virus glycoprotein (rVSVΔG-ZEBOV-GP) vaccine has been reported as safe, immunogenic, and highly protective in a ring vaccination trial. We aimed to identify transcriptomic immune response biomarker signatures induced by vaccination and associated signatures with its immunogenicity and reactogenicity to better understand the potential mechanisms of action of the vaccine.

METHODS

354 healthy adult volunteers were vaccinated in randomised, double-blind, placebo-controlled trials in Europe (Geneva, Switzerland [November, 2014, to January, 2015]) and North America (USA [Dec 5, 2014, to June 23, 2015]), and dose-escalation trials in Africa (Lambaréné, Gabon [November, 2014, to January, 2015], and Kilifi, Kenya [December, 2014, to January, 2015]) using different doses of the recombinant vesicular stomatitis virus vector expressing the Zaire Ebola virus glycoprotein (rVSVΔG-ZEBOV-GP; 3 × 10⁵ to 1 × 10⁸ plaque-forming units [pfu]). Longitudinal transcriptomic responses (days 0, 1, 2, 3, 7, 14, and 28) were measured in whole blood using a targeted gene expression profiling platform (dual-colour reverse-transcriptase multiplex ligation-dependent probe amplification) focusing on 144 immune-related genes. The effect of time and dose on transcriptomic response was also assessed. Logistic regression with lasso regularisation was applied to identify host signatures with optimal discriminatory capability of vaccination at day 1 or day 7 versus baseline, whereas random-effects models and recursive feature elimination combined with regularised logistic regression were used to associate signatures with immunogenicity and reactogenicity.

FINDINGS

Our results indicated that perturbation of gene expression peaked on day 1 and returned to baseline levels between day 7 and day 28. The magnitude of the response was dose-dependent, with vaccinees receiving a high dose (≥9 × 10⁶ pfu) of rVSVΔG-ZEBOV-GP exhibiting the largest amplitude. The most differentially expressed genes that were significantly upregulated following vaccination consisted of type I and II interferon-related genes and myeloid cell-associated markers, whereas T cell, natural killer cell, and cytotoxicity-associated genes were downregulated. A gene signature associated with immunogenicity (common to all four cohorts) was identified correlating gene expression profiles with ZEBOV-GP antibody titres and a gene signatures associated with reactogenicity (Geneva cohort) was identified correlating gene expression profiles with an adverse event (ie, arthritis).

INTERPRETATION

Collectively, our results identify and cross-validate immune-related transcriptomic signatures induced by rVSVΔG-ZEBOV-GP vaccination in four cohorts of adult participants from different genetic and geographical backgrounds. These signatures will aid in the rational development, testing, and evaluation of novel vaccines and will allow evaluation of the effect of host factors such as age, co-infection, and comorbidity on responses to vaccines.

FUNDING

Innovative Medicines Initiative 2 Joint Undertaking.

Plant-Derived Recombinant Vaccines against Zoonotic Viruses

Emerging and re-emerging zoonotic diseases cause serious illness with billions of cases, and millions of deaths. The most effective way to restrict the spread of zoonotic viruses among humans and animals and prevent disease is vaccination. Recombinant proteins produced in plants offer an alternative approach for the development of safe, effective, inexpensive candidate vaccines. Current strategies are focused on the production of highly immunogenic structural proteins, which mimic the organizations of the native virion but lack the viral genetic material. These include chimeric viral peptides, subunit virus proteins, and virus-like particles (VLPs). The latter, with their ability to self-assemble and thus resemble the form of virus particles, are gaining traction among plant-based candidate vaccines against many infectious diseases. In this review, we summarized the main zoonotic diseases and followed the progress in using plant expression systems for the production of recombinant proteins and VLPs used in the development of plant-based vaccines against zoonotic viruses.

Pathogenicity and Virulence of Ebolaviruses with Species- and Variant-specificity

Ebola virus (EBOV), belonging to the species Zaire ebolavirus in the genus Ebolavirus, causes a severe febrile illness in humans with case fatality rates (CFRs) up to 90%. While there have been six virus species classified, which each have a single type virus in the genus Ebolavirus, CFRs of ebolavirus infections vary among viruses belonging to each distinct species. In this review, we aim to define the ebolavirus species-specific virulence on the basis of currently available laboratory and experimental findings. In addition, this review will also cover the variant-specific virulence of EBOV by referring to the unique biological and pathogenic characteristics of EBOV variant Makona, a new EBOV variant isolated from the 2013-2016 EBOV disease outbreak in West Africa. A better definition of species-specific and variant-specific virulence of ebolaviruses will facilitate our comprehensive knowledge on genus Ebolavirus biology, leading to the development of therapeutics against well-focused pathogenic mechanisms of each Ebola disease.

Therapeutic vaccination strategies against EBOV by rVSV-EBOV-GP: the role of innate immunity

Zaire Ebola virus (EBOV) is a member of the Filoviridae family. Infection with EBOV causes Ebola virus disease (EVD) characterized by excessive inflammation, lymphocyte death, coagulopathy, and multi-organ failure. In 2019, the FDA-approved the first anti-EBOV vaccine, rVSV-EBOV-GP (Ervebo® by Merck). This live-recombinant vaccine confers both prophylactic and therapeutic protection to nonhuman primates and humans. While mechanisms conferring prophylactic protection are well-investigated, those underlying protection conferred shortly before and after exposure to EBOV remain poorly understood. In this review, we review data from in vitro and in vivo studies analyzing early immune responses to rVSV-EBOV-GP and discuss the role of innate immune activation in therapeutic protection.

Selection of Filovirus Isolates for Vaccine Development Programs

The continuing outbreaks of ebola virus disease highlight the ongoing threat posed by filoviruses. Fortunately, licensed vaccines and therapeutics are now available for Zaire ebolavirus. However, effective medical countermeasures, such as vaccines for other filoviruses such as Sudan ebolavirus and the Marburg virus, are presently in early stages of development and, in the absence of a large outbreak, would require regulatory approval via the U.S. Food and Drug Administration (FDA) Animal Rule. The selection of an appropriate animal model and virus challenge isolates for nonclinical studies are critical aspects of the development program. Here, we have focused on the recommendation of challenge isolates for Sudan ebolavirus and Marburg virus. Based on analyses led by the Filovirus Animal and Nonclinical Group (FANG) and considerations for strain selection under the FDA Guidance for the Animal Rule, we propose prototype virus isolates for use in nonclinical challenge studies.

Vesicular Stomatitis Virus: From Agricultural Pathogen to Vaccine Vector

Vesicular stomatitis virus (VSV), which belongs to the Vesiculovirus genus of the family Rhabdoviridae, is a well studied livestock pathogen and prototypic non-segmented, negative-sense RNA virus. Although VSV is responsible for causing economically significant outbreaks of vesicular stomatitis in cattle, horses, and swine, the virus also represents a valuable research tool for molecular biologists and virologists. Indeed, the establishment of a reverse genetics system for the recovery of infectious VSV from cDNA transformed the utility of this virus and paved the way for its use as a vaccine vector. A highly effective VSV-based vaccine against Ebola virus recently received clinical approval, and many other VSV-based vaccines have been developed, particularly for high-consequence viruses. This review seeks to provide a holistic but concise overview of VSV, covering the virus's ascension from perennial agricultural scourge to promising medical countermeasure, with a particular focus on vaccines.

STAT-1 Knockout Mice as a Model for Wild-Type Sudan Virus (SUDV)

Currently there is no FDA-licensed vaccine or therapeutic against Sudan ebolavirus (SUDV) infections. The largest ever reported 2014–2016 West Africa outbreak, as well as the 2021 outbreak in the Democratic Republic of Congo, highlight the critical need for countermeasures against filovirus infections. A well-characterized small animal model that is susceptible to wild-type filoviruses would greatly add to the screening of antivirals and vaccines. Here, we infected signal transducer and activator of transcription-1 knock out (STAT-1 KO) mice with five different wildtype filoviruses to determine susceptibility. SUDV and Marburg virus (MARV) were the most virulent, and caused 100% or 80% lethality, respectively. Zaire ebolavirus (EBOV), Bundibugyo ebolavirus (BDBV), and Taï Forest ebolavirus (TAFV) caused 40%, 20%, and no mortality, respectively. Further characterization of SUDV in STAT-1 KO mice demonstrated lethality down to 3.1 × 10¹ pfu. Viral genomic material was detectable in serum as early as 1 to 2 days post-challenge. The onset of viremia was closely followed by significant changes in total white blood cells and proportion of neutrophils and lymphocytes, as well as by an influx of neutrophils in the liver and spleen. Concomitant significant fluctuations in blood glucose, albumin, globulin, and alanine aminotransferase were also noted, altogether consistent with other models of filovirus infection. Finally, favipiravir treatment fully protected STAT-1 KO mice from lethal SUDV challenge, suggesting that this may be an appropriate small animal model to screen anti-SUDV countermeasures.

Development and Evaluation of an Ebola Virus Glycoprotein Mucin-Like Domain Replacement System as a New Dendritic Cell-Targeting Vaccine Approach against HIV-1

The development of efficient vaccine approaches against HIV infection remains challenging in the vaccine field. Here, we developed an Ebola virus envelope glycoprotein (EboGP)-based chimeric fusion protein system and demonstrated that replacement of the mucin-like domain (MLD) of EboGP with HIV C2-V3-C3 (134 amino acids [aa]) or C2-V3-C3-V4-C4-V5-C5 (243 aa) polypeptides (EbGPΔM-V3 and EbGPΔM-V3-V5, respectively) still maintained the efficiency of EboGP-mediated viral entry into human macrophages and dendritic cells (DCs). Animal studies using mice revealed that immunization with virus-like particles (VLPs) containing the above chimeric proteins, especially EbGPΔM-V3, induced significantly more potent anti-HIV antibodies than HIV gp120 alone in mouse serum and vaginal fluid. Moreover, the splenocytes isolated from mice immunized with VLPs containing EbGPΔM-V3 produced significantly higher levels of gamma interferon (IFN-γ), interleukin 2 (IL-2), IL-4, IL-5, and macrophage inflammatory protein 1α (MIP-1α). Additionally, we demonstrated that coexpression of EbGPΔM-V3 and the HIV Env glycoprotein in a recombinant vesicular stomatitis virus (rVSV) vector elicited robust anti-HIV antibodies that may have specifically recognized epitopes outside or inside the C2-V3-C3 region of HIV-1 gp120 and cross-reacted with the gp120 from different HIV strains. Thus, this study has demonstrated the great potential of this DC-targeting vaccine platform as a new vaccine approach for improving immunogen delivery and increasing vaccine efficacy.

IMPORTANCE Currently, there are more than 38.5 million reported cases of HIV globally. To date, there is no approved vaccine for HIV-1 infection. Thus, the development of an effective vaccine against HIV infection remains a global priority. This study revealed the efficacy of a novel dendritic cell (DC)-targeting vaccination approach against HIV-1. The results clearly show that the immunization of mice with virus-like particles (VLPs) and VSVs containing HIV Env and a fusion protein composed of a DC-targeting domain of Ebola virus GP with HIV C2-V3-C3 polypeptides (EbGPΔM-V3) could induce robust immune responses against HIV-1 Env and/or Gag in serum and vaginal mucosa. These findings provide a proof of concept of this novel and efficient DC-targeting vaccine approach in delivering various antigenic polypeptides of HIV-1 and/or other emergent infections to the host antigen-presenting cells to prevent HIV and other viral infections.

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.

Development of Pandemic Vaccines: ERVEBO Case Study

Preventative vaccines are considered one of the most cost-effective and efficient means to contain outbreaks and prevent pandemics. However, the requirements to gain licensure and manufacture a vaccine for human use are complex, costly, and time-consuming. The 2013-2016 Ebola virus disease (EVD) outbreak was the largest EVD outbreak to date and the third Public Health Emergency of International Concern in history, so to prevent a pandemic, numerous partners from the public and private sectors combined efforts and resources to develop an investigational Zaire ebolavirus (EBOV) vaccine candidate (rVSVΔG-ZEBOV-GP) as quickly as possible. The rVSVΔG-ZEBOV-GP vaccine was approved as ERVEBOTM by the European Medicines Authority (EMA) and the United States Food and Drug Administration (FDA) in December 2019 after five years of development. This review describes the development program of this EBOV vaccine, summarizes what is known about safety, immunogenicity, and efficacy, describes ongoing work in the program, and highlights learnings applicable to the development of pandemic vaccines.

Taï Forest Virus Does Not Cause Lethal Disease in Ferrets

Filoviruses are zoonotic, negative-sense RNA viruses, most of which are capable of causing severe disease in humans and nonhuman primates, often with high case fatality rates. Among these viruses, those belonging to the Ebolavirus genus—particularly Ebola virus, Sudan virus, and Bundibugyo virus—represent some of the most pathogenic to humans. Taï Forest virus (TAFV) is thought to be among the least pathogenic ebolaviruses; however, only a single non-fatal case has been documented in humans, in 1994. With the recent success of the ferret as a lethal model for a number of ebolaviruses, we set out to evaluate its suitability as a model for TAFV. Our results demonstrate that, unlike other ebolaviruses, TAFV infection in ferrets does not result in lethal disease. None of the intramuscularly inoculated animals demonstrated any overt signs of disease, whereas the intranasally inoculated animals exhibited mild to moderate weight loss during the early stage of infection but recovered quickly. Low levels of viral RNA were detected in the blood and tissues of several animals, particularly the intranasally inoculated animals, and all animals mounted a humoral immune response, with high titers of GP-specific IgG detectable as early as 14 days post-infection. These data provide additional insight into the pathogenesis of TAFV.

Systematic review of Marburg virus vaccine nonhuman primate studies and human clinical trials

BACKGROUND

Recent deadly outbreaks of Marburg virus underscore the need for an effective vaccine. A summary of the latest research is needed for this WHO priority pathogen. This systematic review aimed to determine progress towards a vaccine for Marburg virus.

METHODS

Article search criteria were developed to query PubMed for peer-reviewed articles from 1990 through 2019 on Marburg virus vaccine clinical trials in humans and pre-clinical studies in non-human primates (NHP). Abstracts were reviewed by two authors. Relevant articles were reviewed in full. Discrepancies were resolved by a third author. Data abstracted included year, author, title, vaccine construct, number of subjects, efficacy, and demographics. Assessment for risk of bias was performed using the Syrcle tool for animal studies, and the Cochrane Collaboration risk of bias tool for human studies.

RESULTS

101 articles were identified; 27 were related to Marburg vaccines. After full text review, 21 articles were selected. 215 human subjects were in three phase 1 clinical trials, and 203 NHP in 18 studies. Vaccine constructs were DNA plasmids, recombinant vesicular stomatitis virus (VSV) vectors, adenovirus vectors, virus-like particles (VLP), among others. Two human phase 1 studies of DNA vaccines had 4 adverse effects requiring vaccine discontinuation among 128 participants and 31-80% immunogenicity. In NHP challenge studies, 100% survival was seen in 6 VSV vectored vaccines, 2 DNA vaccines, 2 VLP vaccines, and in 1 adenoviral vectored vaccine.

CONCLUSION

In human trials, two Marburg DNA vaccines provided either low immunogenicity or a failure to elicit durable immunity. A variety of NHP candidate Marburg vaccines demonstrated favorable survival and immunogenicity parameters, to include VSV, VLP, and adenoviral vectored vaccines. Elevated binding antibodies appeared to be consistently associated with protection across the NHP challenge studies. Further human trials are needed to advance vaccines to limit the spread of this highly lethal virus.

Lassa-VSV chimeric virus targets and destroys human and mouse ovarian cancer by direct oncolytic action and by initiating an anti-tumor response

Ovarian cancer is the third most common female cancer, with poor survival in later stages of metastatic spread. We test a chimeric virus consisting of genes from Lassa and vesicular stomatitis viruses, LASV-VSV; the native VSV glycoprotein is replaced by the Lassa glycoprotein, greatly reducing neurotropism. Human ovarian cancer cells in immunocompromised nude mice were lethal in controls. Chemotherapeutic paclitaxel and cisplatin showed modest cancer inhibition and survival extension. In contrast, a single intraperitoneal injection of LASV-VSV selectively infected and killed ovarian cancer cells, generating long-term survival. Mice with human ovarian cancer cells in brain showed rapid deterioration; LASV-VSV microinjection into brain blocked cancer growth, and generated long-term survival. Treatment of immunocompetent mice with infected mouse ovarian cancer cells blocked growth of non-infected ovarian cancer cells peritoneally and in brain. These results suggest LASV-VSV is a viable candidate for further study and may be of use in the treatment of ovarian cancer.

[Ebola, the first vaccines available]

In the recent years, Ebola virus has been responsible for several major epidemics. Research efforts have allowed the development and evaluation in the field of several vaccine candidates. At present, two of them are already approved and used in the fight against the virus in the Democratic Republic of Congo. This review aims to describe the different candidates, the clinical trials that have been conducted as well as the first results in the field.

To B or Not to B: Mechanisms of Protection Conferred by rVSV-EBOV-GP and the Roles of Innate and Adaptive Immunity

Zaire Ebola virus (EBOV) is a member of the Filoviridae family of negative sense, single-stranded RNA viruses. EBOV infection causes Ebola virus disease (EVD), characterized by coagulopathy, lymphopenia, and multi-organ failure, which can culminate in death. In 2019, the FDA approved the first vaccine against EBOV, a recombinant live-attenuated viral vector wherein the G protein of vesicular stomatitis virus is replaced with the glycoprotein (GP) of EBOV (rVSV-EBOV-GP, Ervebo^® by Merck). This vaccine demonstrates high efficacy in nonhuman primates by providing prophylactic, rapid, and post-exposure protection. In humans, rVSV-EBOV-GP demonstrated 100% protection in several phase III clinical trials in over 10,000 individuals during the 2013–2016 West Africa epidemic. As of 2020, over 218,000 doses of rVSV-EBOV-GP have been administered to individuals with high risk of EBOV exposure. Despite licensure and robust preclinical studies, the mechanisms of rVSV-EBOV-GP-mediated protection are not fully understood. Such knowledge is crucial for understanding vaccine-mediated correlates of protection from EVD and to aid the further design and development of therapeutics against filoviruses. Here, we summarize the current literature regarding the host response to vaccination and EBOV exposure, and evidence regarding innate and adaptive immune mechanisms involved in rVSV-EBOV-GP-mediated protection, with a focus on the host transcriptional response. Current data strongly suggest a protective synergy between rapid innate and humoral immunity.

Marburg virus disease: A summary for clinicians

OBJECTIVES

This article summarizes the countermeasures for Marburg virus disease, focusing on pathogenesis, clinical features and diagnostics. There is an emphasis on therapies and vaccines that have demonstrated, through their evaluation in nonhuman primates (NHPs) and/or in humans, potential for use in an emergency situation.

METHODS

A standardized literature review was conducted on vaccines and treatments for Marburg virus disease, with a focus on human and nonhuman primate data published in the last five years. More detail on the methods that were used is summarized in a companion methods paper.

RESULTS

The study identified six treatments and four vaccine platforms that have demonstrated, through their efficacy in NHPs, potential benefit for treating or preventing infection in humans.

CONCLUSION

Succinct summaries of Marburg countermeasures are provided to give the busy clinician a head start in reviewing the literature if faced with a patient with Marburg virus disease. Links to other authoritative sources of information are also provided.

Ebola Virus: Pathogenesis and Countermeasure Development

Since its discovery in 1976, Ebola virus (EBOV) has caused numerous outbreaks of fatal hemorrhagic disease in Africa. The biggest outbreak on record is the 2013-2016 epidemic in west Africa with almost 30,000 cases and over 11,000 fatalities, devastatingly affecting Guinea, Liberia, and Sierra Leone. The epidemic highlighted the need for licensed drugs or vaccines to quickly combat the disease. While at the beginning of the epidemic no licensed countermeasures were available, several experimental drugs with preclinical efficacy were accelerated into human clinical trials and used to treat patients with Ebola virus disease (EVD) toward the end of the epidemic. In the same manner, vaccines with preclinical efficacy were administered primarily to known contacts of EVD patients on clinical trial protocols using a ring-vaccination strategy. In this review, we describe the pathogenesis of EBOV and summarize the current status of EBOV vaccine development and treatment of EVD.

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.

Safety and immunogenicity of a highly attenuated rVSVN4CT1-EBOVGP1 Ebola virus vaccine: a randomised, double-blind, placebo-controlled, phase 1 clinical trial

BACKGROUND

The safety and immunogenicity of a highly attenuated recombinant vesicular stomatitis virus (rVSV) expressing HIV-1 gag (rVSVN4CT1-HIV-1gag1) was shown in previous phase 1 clinical studies. An rVSV vector expressing Ebola virus glycoprotein (EBOV-GP) in place of HIV-1 gag (rVSVN4CT1-EBOVGP1) showed single-dose protection from lethal challenge with low passage Ebola virus in non-human primates. We aimed to evaluate the safety and immunogenicity of the rVSVN4CT1-EBOVGP1 vaccine in healthy adults.

METHODS

We did a randomised double-blind, placebo-controlled, phase 1 dose-escalation study at a single clinical site (Optimal Research) in Melbourne, FL, USA. Eligible participants were healthy men and non-pregnant women aged 18-60 years, with a body-mass index (BMI) of less than 40 kg/m², no history of filovirus infection, VSV infection, or receipt of rVSV in previous studies, and who had not visited regions where Ebola virus outbreaks have occurred. Three cohorts were enrolled to assess a low (2·5 × 10⁴ plaque forming units [PFU]), intermediate (2 × 10⁵ PFU), or high dose (1·8 × 10⁶ PFU) of the vaccine. Participants within each cohort were randomly allocated (10:3) to receive vaccine or placebo by intramuscular injection in a homologous prime and boost regimen, with 4 weeks between doses. All syringes were masked with syringe sleeves; participants and study site staff were not blinded to dose level but were blinded to active vaccine and placebo. The primary outcomes were safety and tolerability; immunogenicity, assessed as GP-specific humoral immune response (at 2 weeks after each dose) and cellular immune response (at 1 and 2 weeks after each dose), was a secondary outcome. All randomised participants were included in primary and safety analyses. This trial is registered with ClinicalTrials.gov, NCT02718469.

FINDINGS

Between Dec 22, 2015, and Sept 15, 2016, 39 individuals (18 [46%] men and 21 [54%] women, mean age 51 years [SD 10]) were enrolled, with ten participants receiving the vaccine and three participants receiving placebo in each of three cohorts. One participant in the intermediate dose cohort was withdrawn from the study because of a diagnosis of invasive ductal breast carcinoma 24 days after the first vaccination, which was considered unrelated to the vaccine. No severe adverse events were observed. Solicited local adverse events occurred in ten (26%) of 39 participants after the first dose and nine (24%) of 38 participants after the second dose; the events lasted 3 days or less, were predominantly injection site tenderness (17 events) and injection site pain (ten events), and were either mild (19 events) or moderate (ten events) in intensity. Systemic adverse events occurred in 13 (33%) of 39 participants after the first dose and eight (21%) of 38 participants after the second dose; the events were mild (45 events) or moderate (11 events) in severity, and the most common events were malaise or fatigue (13 events) and headache (12 events). Arthritis and maculopapular, vesicular, or purpuric rash distal to the vaccination site(s) were not reported. A GP-specific IgG response was detected in all vaccine recipients after two doses (and IgG response frequency was 100% after a single high dose), and an Ebola virus neutralising response was detected in 100% of participants in the high-dose cohort.

INTERPRETATION

The rVSVN4CT1-EBOVGP1 vaccine was well tolerated at all dose levels tested and was immunogenic despite a high degree of attenuation. The combined safety and immunogenicity profile of the rVSVN4CT1-EBOVGP1 vaccine vector support phase 1-2 clinical evaluation.

FUNDING

US Department of Defense Joint Program Executive Office for Chemical, Biological, Radiological and Nuclear Defense: Joint Project Manager for Chemical, Biological, Radiological and Nuclear Medical.

Quadrivalent VesiculoVax vaccine protects nonhuman primates from viral-induced hemorrhagic fever and death

Recent occurrences of filoviruses and the arenavirus Lassa virus (LASV) in overlapping endemic areas of Africa highlight the need for a prophylactic vaccine that would confer protection against all of these viruses that cause lethal hemorrhagic fever (HF). We developed a quadrivalent formulation of VesiculoVax that contains recombinant vesicular stomatitis virus (rVSV) vectors expressing filovirus glycoproteins and that also contains a rVSV vector expressing the glycoprotein of a lineage IV strain of LASV. Cynomolgus macaques were vaccinated twice with the quadrivalent formulation, followed by challenge 28 days after the boost vaccination with each of the 3 corresponding filoviruses (Ebola, Sudan, Marburg) or a heterologous contemporary lineage II strain of LASV. Serum IgG and neutralizing antibody responses specific for all 4 glycoproteins were detected in all vaccinated animals. A modest and balanced cell-mediated immune response specific for the glycoproteins was also detected in most of the vaccinated macaques. Regardless of the level of total glycoprotein-specific immune response detected after vaccination, all immunized animals were protected from disease and death following lethal challenges. These findings indicate that vaccination with attenuated rVSV vectors each expressing a single HF virus glycoprotein may provide protection against those filoviruses and LASV most commonly responsible for outbreaks of severe HF in Africa.

Marburg virus pathogenesis - differences and similarities in humans and animal models

Marburg virus (MARV) is a highly pathogenic virus associated with severe disease and mortality rates as high as 90%. Outbreaks of MARV are sporadic, deadly, and often characterized by a lack of resources and facilities to diagnose and treat patients. There are currently no approved vaccines or treatments, and the chaotic and infrequent nature of outbreaks, among other factors, makes testing new countermeasures during outbreaks ethically and logistically challenging. Without field efficacy studies, researchers must rely on animal models of MARV infection to assess the efficacy of vaccines and treatments, with the limitations being the accuracy of the animal model in recapitulating human pathogenesis. This review will compare various animal models to the available descriptions of human pathogenesis and aims to evaluate their effectiveness in modeling important aspects of Marburg virus disease.

Single low-dose VSV-EBOV vaccination protects cynomolgus macaques from lethal Ebola challenge

Background

Ebola virus (EBOV), variant Makona, was the causative agent of the 2013–2016 West African epidemic responsible for almost 30,000 human infections and over 11,000 fatalities. During the epidemic, the development of several experimental vaccines was accelerated through human clinical trials. One of them, the vesicular stomatitis virus (VSV)-based vaccine VSV-EBOV, showed promising efficacy in a phase 3 clinical trial in Guinea and is currently used in the ongoing EBOV outbreak in the northeastern part of the Democratic Republic of the Congo (DRC). This vaccine expresses the EBOV-Kikwit glycoprotein from the 1995 outbreak as the immunogen.

Methods

Here we generated a VSV-based vaccine expressing the contemporary EBOV-Makona glycoprotein. We characterized the vaccine in tissue culture and analyzed vaccine efficacy in the cynomolgus macaque model. Subsequently, we determined the dose-dependent protective efficacy in nonhuman primates against lethal EBOV challenge.

Findings

We observed complete protection from disease with VSV-EBOV doses ranging from 1 × 10⁷ to 1 × 10¹ plaque-forming units. Some protected animals receiving lower vaccine doses developed temporary low-level EBOV viremia. Control animals developed classical EBOV disease and reached euthanasia criteria within a week after challenge. This study demonstrates that very low doses of VSV-EBOV uniformly protect macaques against lethal EBOV challenge.

Interpretation

Our study provides missing pre-clinical data supporting the use of reduced VSV-EBOV vaccine doses without decreasing protective efficacy and at the same time increase vaccine safety and availability - two critical concerns in public health response.

Funding

Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health.

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.

Infection Rates and Risk Factors for Infection Among Health Workers During Ebola and Marburg Virus Outbreaks: A Systematic Review

Background

Infection in health workers (HWs) has characterized outbreaks of Ebola virus disease (EVD) and Marburg virus disease (MVD). We conducted a systematic review to investigate infection and mortality rates and common exposure risks in HWs in EVD and MVD outbreaks.

Methods

We searched the EMBASE and PubMed databases to identify articles posted before 27 December 2017, with no language restrictions. Data on the number, frequency, and mortality of HW infection and exposure risks were extracted.

Results

Ninety-four articles related to 22 outbreaks were included. HW infections composed 2%-100% of cases in EVD and 5%-50% of cases in MVD outbreaks. Among exposed HWs, 0.6%-92% developed EVD, and 1%-10% developed MVD. HW infection rates were consistent through outbreaks. The most common exposure risk situations were inadequate personal protective equipment and exposure to patients with unrecognized EVD/MVD. Similar risks were reported in past EVD/MVD outbreaks and in the recent outbreak in West Africa.

Conclusions

Many outbreaks reported high proportions of infected HWs. Similar HW infection rates and exposure risk factors in both past and recent EVD and MVD outbreaks emphasize the need to improve the implementation of appropriate infection control measures consistently across all healthcare settings.

Recombinant vesicular stomatitis virus vector vaccines for WHO blueprint priority pathogens

The devastating Ebola virus (EBOV) outbreak in West Africa in 2013-2016 has flagged the need for the timely development of vaccines for high-threat pathogens. To be better prepared for new epidemics, the WHO has compiled a list of priority pathogens that are likely to cause future outbreaks and for which R&D efforts are, therefore, paramount (R&D Blueprint: https://www.who.int/blueprint/priority-diseases/en/ ). To this end, the detailed characterization of vaccine platforms is needed. The vesicular stomatitis virus (VSV) has been established as a robust vaccine vector backbone for infectious diseases for well over a decade. The recent clinical trials testing the vaccine candidate VSV-EBOV against EBOV disease now have added a substantial amount of clinical data and suggest VSV to be an ideal vaccine vector candidate for outbreak pathogens. In this review, we discuss insights gained from the clinical VSV-EBOV vaccine trials as well as from animal studies investigating vaccine candidates for Blueprint pathogens.