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1.  Vesicular Stomatitis Virus–Based Vaccines against Lassa and Ebola Viruses 
Emerging Infectious Diseases  2015;21(2):305-307.
We demonstrated that previous vaccination with a vesicular stomatitis virus (VSV)–based Lassa virus vaccine does not alter protective efficacy of subsequent vaccination with a VSV-based Ebola virus vaccine. These findings demonstrate the utility of VSV-based vaccines against divergent viral pathogens, even when preexisting immunity to the vaccine vector is present.
doi:10.3201/eid2102.141649
PMCID: PMC4313664  PMID: 25625358
vesicular stomatitis virus; VSV; viruses; pre-existing immunity; viral hemorrhagic fever; vaccines; virus-based vaccines; Lassa virus; Ebola virus; sequential vaccination; nonhuman primates; West Africa
2.  Deep Sequencing Identifies Noncanonical Editing of Ebola and Marburg Virus RNAs in Infected Cells 
mBio  2014;5(6):e02011-14.
ABSTRACT
Deep sequencing of RNAs produced by Zaire ebolavirus (EBOV) or the Angola strain of Marburgvirus (MARV-Ang) identified novel viral and cellular mechanisms that diversify the coding and noncoding sequences of viral mRNAs and genomic RNAs. We identified previously undescribed sites within the EBOV and MARV-Ang mRNAs where apparent cotranscriptional editing has resulted in the addition of non-template-encoded residues within the EBOV glycoprotein (GP) mRNA, the MARV-Ang nucleoprotein (NP) mRNA, and the MARV-Ang polymerase (L) mRNA, such that novel viral translation products could be produced. Further, we found that the well-characterized EBOV GP mRNA editing site is modified at a high frequency during viral genome RNA replication. Additionally, editing hot spots representing sites of apparent adenosine deaminase activity were found in the MARV-Ang NP 3′-untranslated region. These studies identify novel filovirus-host interactions and reveal production of a greater diversity of filoviral gene products than was previously appreciated.
IMPORTANCE
This study identifies novel mechanisms that alter the protein coding capacities of Ebola and Marburg virus mRNAs. Therefore, filovirus gene expression is more complex and diverse than previously recognized. These observations suggest new directions in understanding the regulation of filovirus gene expression.
doi:10.1128/mBio.02011-14
PMCID: PMC4222107  PMID: 25370495
3.  Transcriptional Correlates of Disease Outcome in Anticoagulant-Treated Non-Human Primates Infected with Ebolavirus 
Ebola virus (EBOV) infection in humans and non-human primates (NHPs) is highly lethal, and there is limited understanding of the mechanisms associated with pathogenesis and survival. Here, we describe a transcriptomic analysis of NHPs that survived lethal EBOV infection, compared to NHPs that did not survive. It has been previously demonstrated that anticoagulant therapeutics increase the survival rate in EBOV-infected NHPs, and that the characteristic transcriptional profile of immune response changes in anticoagulant-treated NHPs. In order to identify transcriptional signatures that correlate with survival following EBOV infection, we compared the mRNA expression profile in peripheral blood mononuclear cells from EBOV-infected NHPs that received anticoagulant treatment, to those that did not receive treatment. We identified a small set of 20 genes that are highly confident predictors and can accurately distinguish between surviving and non-surviving animals. In addition, we identified a larger predictive signature of 238 genes that correlated with disease outcome and treatment; this latter signature was associated with a variety of host responses, such as the inflammatory response, T cell death, and inhibition of viral replication. Notably, among survival-associated genes were subsets of genes that are transcriptionally regulated by (1) CCAAT/enhancer-binding protein alpha, (2) tumor protein 53, and (3) megakaryoblastic leukemia 1 and myocardin-like protein 2. These pathways merit further investigation as potential transcriptional signatures of host immune response to EBOV infection.
Author Summary
Infection of humans and non-human primates (NHPs) with Ebola virus (EBOV) can cause viral hemorrhagic fever, an acute systemic illness which can lead to death. The high case fatality rates (25%–90%) make EBOV a virus of significant concern from a biodefense perspective. To date, there are no FDA-approved post-exposure treatments for human use, and there are no standard assays to predict how infected individuals will fare after becoming infected. We have analyzed how circulating immune cells respond to EBOV infection under conditions where NHPs either survive viral infection, or succumb to it. This analysis identified genes that are correlated with, and predictive of, survival following lethal EBOV infection in NHPs. Our results demonstrate that small gene sets and transcriptional regulatory networks can be used to identify individual markers associated with survival following EBOV infection.
doi:10.1371/journal.pntd.0003061
PMCID: PMC4117489  PMID: 25079789
4.  Mutual Antagonism between the Ebola Virus VP35 Protein and the RIG-I Activator PACT Determines Infection Outcome 
Cell host & microbe  2013;14(1):10.1016/j.chom.2013.06.010.
SUMMARY
The cytoplasmic pattern recognition receptor RIG-I is activated by viral RNA and induces type I IFN responses to control viral replication. The cellular dsRNA binding protein PACT can also activate RIG-I. To counteract innate antiviral responses, some viruses, including Ebola virus (EBOV), encode proteins that antagonize RIG-I signaling. Here, we show that EBOV VP35 inhibits PACT-induced RIG-I ATPase activity in a dose-dependent manner. The interaction of PACT with RIG-I is disrupted by wild-type VP35, but not by VP35 mutants that are unable to bind PACT. In addition, PACT-VP35 interaction impairs the association between VP35 and the viral polymerase, thereby diminishing viral RNA synthesis and modulating EBOV replication. PACT-deficient cells are defective in IFN induction and are insensitive to VP35 function. These data support a model in which the VP35-PACT interaction is mutually antagonistic and plays a fundamental role in determining the outcome of EBOV infection.
doi:10.1016/j.chom.2013.06.010
PMCID: PMC3875338  PMID: 23870315
5.  Interferon-β Therapy Prolongs Survival in Rhesus Macaque Models of Ebola and Marburg Hemorrhagic Fever 
The Journal of Infectious Diseases  2012;208(2):310-318.
There is a clear need for novel, effective therapeutic approaches to hemorrhagic fever due to filoviruses. Ebola virus hemorrhagic fever is associated with robust interferon (IFN)–α production, with plasma concentrations of IFN-α that greatly (60- to 100-fold) exceed those seen in other viral infections, but little IFN-β production. While all of the type I IFNs signal through the same receptor complex, both quantitative and qualitative differences in biological activity are observed after stimulation of the receptor complex with different type I IFNs. Taken together, this suggested potential for IFN-β therapy in filovirus infection. Here we show that early postexposure treatment with IFN-β significantly increased survival time of rhesus macaques infected with a lethal dose of Ebola virus, although it failed to alter mortality. Early treatment with IFN-β also significantly increased survival time after Marburg virus infection. IFN-β may have promise as an adjunctive postexposure therapy in filovirus infection.
doi:10.1093/infdis/jis921
PMCID: PMC3685222  PMID: 23255566
Filovirus; IFN-β; Ebola virus; Marburg virus; type I interferon
6.  A Recombinant Hendra Virus G Glycoprotein Subunit Vaccine Protects Nonhuman Primates against Hendra Virus Challenge 
Journal of Virology  2014;88(9):4624-4631.
ABSTRACT
Hendra virus (HeV) is a zoonotic emerging virus belonging to the family Paramyxoviridae. HeV causes severe and often fatal respiratory and/or neurologic disease in both animals and humans. Currently, there are no licensed vaccines or antiviral drugs approved for human use. A number of animal models have been developed for studying HeV infection, with the African green monkey (AGM) appearing to most faithfully reproduce the human disease. Here, we assessed the utility of a newly developed recombinant subunit vaccine based on the HeV attachment (G) glycoprotein in the AGM model. Four AGMs were vaccinated with two doses of the HeV vaccine (sGHeV) containing Alhydrogel, four AGMs received the sGHeV with Alhydrogel and CpG, and four control animals did not receive the sGHeV vaccine. Animals were challenged with a high dose of infectious HeV 21 days after the boost vaccination. None of the eight specifically vaccinated animals showed any evidence of clinical illness and survived the challenge. All four controls became severely ill with symptoms consistent with HeV infection, and three of the four animals succumbed 8 days after exposure. Success of the recombinant subunit vaccine in AGMs provides pivotal data in supporting its further preclinical development for potential human use.
IMPORTANCE A Hendra virus attachment (G) glycoprotein subunit vaccine was tested in nonhuman primates to assess its ability to protect them from a lethal infection with Hendra virus. It was found that all vaccinated African green monkeys were completely protected against subsequent Hendra virus infection and disease. The success of this new subunit vaccine in nonhuman primates provides critical data in support of its further development for future human use.
doi:10.1128/JVI.00005-14
PMCID: PMC3993805  PMID: 24522928
7.  Durability of a Vesicular Stomatitis Virus-Based Marburg Virus Vaccine in Nonhuman Primates 
PLoS ONE  2014;9(4):e94355.
The filoviruses, Marburg virus (MARV) and Ebola virus, causes severe hemorrhagic fever with high mortality in humans and nonhuman primates. A promising filovirus vaccine under development is based on a recombinant vesicular stomatitis virus (rVSV) that expresses individual filovirus glycoproteins (GPs) in place of the VSV glycoprotein (G). These vaccines have shown 100% efficacy against filovirus infection in nonhuman primates when challenge occurs 28–35 days after a single injection immunization. Here, we examined the ability of a rVSV MARV-GP vaccine to provide protection when challenge occurs more than a year after vaccination. Cynomolgus macaques were immunized with rVSV-MARV-GP and challenged with MARV approximately 14 months after vaccination. Immunization resulted in the vaccine cohort of six animals having anti-MARV GP IgG throughout the pre-challenge period. Following MARV challenge none of the vaccinated animals showed any signs of clinical disease or viremia and all were completely protected from MARV infection. Two unvaccinated control animals exhibited signs consistent with MARV infection and both succumbed. Importantly, these data are the first to show 100% protective efficacy against any high dose filovirus challenge beyond 8 weeks after final vaccination. These findings demonstrate the durability of VSV-based filovirus vaccines.
doi:10.1371/journal.pone.0094355
PMCID: PMC3997383  PMID: 24759889
8.  A Recently Isolated Lassa Virus From Mali Demonstrates Atypical Clinical Disease Manifestations and Decreased Virulence in Cynomolgus Macaques 
The Journal of Infectious Diseases  2013;207(8):1316-1327.
The virulence of Soromba-R, a Lassa virus strain recently isolated from southern Mali, was assessed in 2 animal models of Lassa fever: inbred strain 13 guinea pigs and cynomolgus macaques. In both models, the Malian isolate demonstrated tissue tropism and viral titers similar to those of historical Lassa virus isolates from Sierra Leone (Josiah) and Liberia (Z-132); however, the Soromba-R isolate was found to be less pathogenic, as determined by decreased mortality and prolonged time to euthanasia in macaques. Interestingly, in addition to the classic indicators of Lassa fever, Soromba-R infection presented with moderate to severe pulmonary manifestations in the macaque model. Analysis of host responses demonstrated increased immune activation in Soromba-R–infected macaques, particularly in neutrophil-activating or -potentiating proinflammatory cytokines or growth factors, including tumor necrosis factor α, macrophage inflammatory protein 1α, interleukin 1β, and granulocyte colony-stimulating factor, as well as interleukin 5, which may be responsible for the decreased lethality and uncharacteristic clinical presentation. These results suggest that the strain of Lassa virus circulating in Mali might be less pathogenic than strains circulating in the historical region of endemicity and may result in an atypical presentation for Lassa fever, which could complicate clinical diagnosis.
doi:10.1093/infdis/jit004
PMCID: PMC3603532  PMID: 23303805
Lassa fever; pathogenesis; disease modeling; guinea pigs; non-human primates; West Africa
9.  Animal models for highly pathogenic emerging viruses 
Current opinion in virology  2013;3(2):205-209.
Exotic and emerging viral pathogens associated with high morbidity and mortality in humans are being identified annually with recent examples including Lujo virus in southern Africa, Severe fever with Thrombocytopenia virus in China and a SARS-like coronavirus in the Middle East. The sporadic nature of these infections hampers our understanding of these diseases and limits the opportunities to design appropriate medical countermeasures against them. Due to this, animal models are utilized to gain insight into the pathogenesis of disease with the overall goal of identifying potential targets for intervention and evaluating specific therapeutics and vaccines. For these reasons it is imperative that animal models of disease recapitulate the human condition as closely as possible in order to provide the best predictive data with respect to the potential efficacy in humans. In this article we review the current status of disease models for highly pathogenic and emerging viral pathogens.
doi:10.1016/j.coviro.2013.01.001
PMCID: PMC3644300  PMID: 23403208
10.  Lassa Fever in Post-Conflict Sierra Leone 
Background
Lassa fever (LF), an often-fatal hemorrhagic disease caused by Lassa virus (LASV), is a major public health threat in West Africa. When the violent civil conflict in Sierra Leone (1991 to 2002) ended, an international consortium assisted in restoration of the LF program at Kenema Government Hospital (KGH) in an area with the world's highest incidence of the disease.
Methodology/Principal Findings
Clinical and laboratory records of patients presenting to the KGH Lassa Ward in the post-conflict period were organized electronically. Recombinant antigen-based LF immunoassays were used to assess LASV antigenemia and LASV-specific antibodies in patients who met criteria for suspected LF. KGH has been reestablished as a center for LF treatment and research, with over 500 suspected cases now presenting yearly. Higher case fatality rates (CFRs) in LF patients were observed compared to studies conducted prior to the civil conflict. Different criteria for defining LF stages and differences in sensitivity of assays likely account for these differences. The highest incidence of LF in Sierra Leone was observed during the dry season. LF cases were observed in ten of Sierra Leone's thirteen districts, with numerous cases from outside the traditional endemic zone. Deaths in patients presenting with LASV antigenemia were skewed towards individuals less than 29 years of age. Women self-reporting as pregnant were significantly overrepresented among LASV antigenemic patients. The CFR of ribavirin-treated patients presenting early in acute infection was lower than in untreated subjects.
Conclusions/Significance
Lassa fever remains a major public health threat in Sierra Leone. Outreach activities should expand because LF may be more widespread in Sierra Leone than previously recognized. Enhanced case finding to ensure rapid diagnosis and treatment is imperative to reduce mortality. Even with ribavirin treatment, there was a high rate of fatalities underscoring the need to develop more effective and/or supplemental treatments for LF.
Author Summary
Lassa fever (LF) is a major public health threat in West Africa. After the violent civil conflict in Sierra Leone (1991 to 2002) ended, the LF research program at Kenema Government Hospital (KGH) was reestablished. Higher CFRs in LF patients were observed compared to studies conducted prior to the civil conflict. The criteria used for defining the stages of LF and differences in sensitivity of the assays used likely account for these differences. LF may be more widespread in Sierra Leone than recognized previously. Peak presentation of LF cases occurs in the dry season, which is consistent with previous studies. Our studies also confirmed reports conducted prior to the civil conflict that indicate that infants, children, young adults, and pregnant women are disproportionately impacted by LF. High fatality rates were observed among both ribavirin treated and untreated patients, which underscores then need for better LF treatments.
doi:10.1371/journal.pntd.0002748
PMCID: PMC3961205  PMID: 24651047
11.  Vesicular Stomatitis Virus-Based Vaccines Protect Nonhuman Primates against Bundibugyo ebolavirus 
Ebola virus (EBOV) causes severe and often fatal hemorrhagic fever in humans and nonhuman primates (NHPs). Currently, there are no licensed vaccines or therapeutics for human use. Recombinant vesicular stomatitis virus (rVSV)-based vaccine vectors, which encode an EBOV glycoprotein in place of the VSV glycoprotein, have shown 100% efficacy against homologous Sudan ebolavirus (SEBOV) or Zaire ebolavirus (ZEBOV) challenge in NHPs. In addition, a single injection of a blend of three rVSV vectors completely protected NHPs against challenge with SEBOV, ZEBOV, the former Côte d'Ivoire ebolavirus, and Marburg virus. However, recent studies suggest that complete protection against the newly discovered Bundibugyo ebolavirus (BEBOV) using several different heterologous filovirus vaccines is more difficult and presents a new challenge. As BEBOV caused nearly 50% mortality in a recent outbreak any filovirus vaccine advanced for human use must be able to protect against this new species. Here, we evaluated several different strategies against BEBOV using rVSV-based vaccines. Groups of cynomolgus macaques were vaccinated with a single injection of a homologous BEBOV vaccine, a single injection of a blended heterologous vaccine (SEBOV/ZEBOV), or a prime-boost using heterologous SEBOV and ZEBOV vectors. Animals were challenged with BEBOV 29–36 days after initial vaccination. Macaques vaccinated with the homologous BEBOV vaccine or the prime-boost showed no overt signs of illness and survived challenge. In contrast, animals vaccinated with the heterologous blended vaccine and unvaccinated control animals developed severe clinical symptoms consistent with BEBOV infection with 2 of 3 animals in each group succumbing. These data show that complete protection against BEBOV will likely require incorporation of BEBOV glycoprotein into the vaccine or employment of a prime-boost regimen. Fortunately, our results demonstrate that heterologous rVSV-based filovirus vaccine vectors employed in the prime-boost approach can provide protection against BEBOV using an abbreviated regimen, which may have utility in outbreak settings.
Author Summary
Ebola viruses (EBOV), of which there are five species, are categorized as Category A Priority Pathogens and Tier 1 Select Agents by several US Government agencies as a result of their high mortality rates and potential for use as agents of bioterrorism. Currently, there are no vaccines or therapeutics approved for human use. Replication-competent, recombinant vesicular stomatitis virus (rVSV) vectors expressing filovirus glycoproteins (GP), in place of the VSV glycoprotein have shown promise in lethal nonhuman primate (NHP) models of filovirus infection as both single injection preventive vaccines and as post-exposure treatments. The recent outbreak of the fifth recognized EBOV species, Bundibugyo ebolavirus (BEBOV), demonstrates the need for vaccines that can be rapidly deployed to combat an outbreak of a new filovirus species. To date, rVSV-filovirus GP-based vaccines have only been able to protect against challenge with a homologous species of EBOV. Here, we show that the two heterologous rVSV-based filovirus vaccines available at the time of the original BEBOV outbreak can protect NHPs against BEBOV challenge using a short prime-boost vaccination strategy. While the prime-boost strategy was successful, a single injection blended vaccination strategy with the same vaccine vectors failed to provide protection. These data suggest that an abbreviated prime-boost regimen of 36 days may have utility for quickly responding to outbreaks caused by new species of EBOV.
doi:10.1371/journal.pntd.0002600
PMCID: PMC3868506  PMID: 24367715
12.  Single injection recombinant vesicular stomatitis virus vaccines protect ferrets against lethal Nipah virus disease 
Virology Journal  2013;10:353.
Background
Nipah virus (NiV) is a highly pathogenic zoonotic agent in the family Paramyxoviridae that is maintained in nature by bats. Outbreaks have occurred in Malaysia, Singapore, India, and Bangladesh and have been associated with 40 to 75% case fatality rates. There are currently no vaccines or postexposure treatments licensed for combating human NiV infection.
Methods and results
Four groups of ferrets received a single vaccination with different recombinant vesicular stomatitis virus vectors expressing: Group 1, control with no glycoprotein; Group 2, the NiV fusion protein (F); Group 3, the NiV attachment protein (G); and Group 4, a combination of the NiV F and G proteins. Animals were challenged intranasally with NiV 28 days after vaccination. Control ferrets in Group 1 showed characteristic clinical signs of NiV disease including respiratory distress, neurological disorders, viral load in blood and tissues, and gross lesions and antigen in target tissues; all animals in this group succumbed to infection by day 8. Importantly, all specifically vaccinated ferrets in Groups 2-4 showed no evidence of clinical illness and survived challenged. All animals in these groups developed anti-NiV F and/or G IgG and neutralizing antibody titers. While NiV RNA was detected in blood at day 6 post challenge in animals from Groups 2-4, the levels were orders of magnitude lower than animals from control Group 1.
Conclusions
These data show protective efficacy against NiV in a relevant model of human infection. Further development of this technology has the potential to yield effective single injection vaccines for NiV infection.
doi:10.1186/1743-422X-10-353
PMCID: PMC3878732  PMID: 24330654
Nipah virus; Henipavirus; Vaccine; Vesicular stomatitis virus; Ferret; Fusion protein; Attachment protein; Glycoprotein; Single-injection; Immunity
13.  Protection Against Lethal Marburg Virus Infection Mediated by Lipid Encapsulated Small Interfering RNA 
The Journal of Infectious Diseases  2013;209(4):562-570.
Background. Marburg virus (MARV) infection causes severe morbidity and mortality in humans and nonhuman primates. Currently, there are no licensed therapeutics available for treating MARV infection. Here, we present the in vitro development and in vivo evaluation of lipid-encapsulated small interfering RNA (siRNA) as a potential therapeutic for the treatment of MARV infection.
Methods. The activity of anti-MARV siRNAs was assessed using dual luciferase reporter assays followed by in vitro testing against live virus. Lead candidates were tested in lethal guinea pig models of 3 different MARV strains (Angola, Ci67, Ravn).
Results. Treatment resulted in 60%–100% survival of guinea pigs infected with MARV. Although treatment with siRNA targeting other MARV messenger RNA (mRNA) had a beneficial effect, targeting the MARV NP mRNA resulted in the highest survival rates. NP-718m siRNA in lipid nanoparticles provided 100% protection against MARV strains Angola and Ci67, and 60% against Ravn. A cocktail containing NP-718m and NP-143m provided 100% protection against MARV Ravn.
Conclusions. These data show protective efficacy against the most pathogenic Angola strain of MARV. Further development of the lipid nanoparticle technology has the potential to yield effective treatments for MARV infection.
doi:10.1093/infdis/jit465
PMCID: PMC3903369  PMID: 23990568
Marburg virus; filovirus; LNP; RNAi; siRNA; treatment; therapeutics; guinea pig
14.  A Hendra Virus G Glycoprotein Subunit Vaccine Protects African Green Monkeys from Nipah Virus Challenge 
Science translational medicine  2012;4(146):146ra107.
In the 1990s, Hendra virus and Nipah virus (NiV), two closely related and previously unrecognized paramyxoviruses that cause severe disease and death in humans and a variety of animals, were discovered in Australia and Malaysia, respectively. Outbreaks of disease have occurred nearly every year since NiV was first discovered, with case fatality ranging from 10 to 100%. In the African green monkey (AGM), NiV causes a severe lethal respiratory and/or neurological disease that essentially mirrors fatal human disease. Thus, the AGM represents a reliable disease model for vaccine and therapeutic efficacy testing. We show that vaccination of AGMs with a recombinant subunit vaccine based on the henipavirus attachment G glycoprotein affords complete protection against subsequent NiV infection with no evidence of clinical disease, virus replication, or pathology observed in any challenged subjects. Success of the recombinant subunit vaccine in nonhuman primates provides crucial data in supporting its further preclinical development for potential human use.
doi:10.1126/scitranslmed.3004241
PMCID: PMC3516289  PMID: 22875827
15.  Vesicular Stomatitis Virus–Based Ebola Vaccines With Improved Cross-Protective Efficacy 
The Journal of Infectious Diseases  2011;204(Suppl 3):S1066-S1074.
For Ebola virus (EBOV), 4 different species are known: Zaire, Sudan, Côte d’Ivoire, and Reston ebolavirus. The newly discovered Bundibugyo ebolavirus has been proposed as a 5th species. So far, no cross-neutralization among EBOV species has been described, aggravating progress toward cross-species protective vaccines. With the use of recombinant vesicular stomatitis virus (rVSV)–based vaccines, guinea pigs could be protected against Zaire ebolavirus (ZEBOV) infection only when immunized with a vector expressing the homologous, but not a heterologous, EBOV glycoprotein (GP). However, infection of guinea pigs with nonadapted wild-type strains of the different species resulted in full protection of all animals against subsequent challenge with guinea pig–adapted ZEBOV, showing that cross-species protection is possible. New vectors were generated that contain EBOV viral protein 40 (VP40) or EBOV nucleoprotein (NP) as a second antigen expressed by the same rVSV vector that encodes the heterologous GP. After applying a 2-dose immunization approach, we observed an improved cross-protection rate, with 5 of 6 guinea pigs surviving the lethal ZEBOV challenge if vaccinated with rVSV-expressing SEBOV-GP and -VP40. Our data demonstrate that cross-protection between the EBOV species can be achieved, although EBOV-GP alone cannot induce the required immune response.
doi:10.1093/infdis/jir348
PMCID: PMC3203393  PMID: 21987743
16.  Recombinant Vesicular Stomatitis Virus–Based Vaccines Against Ebola and Marburg Virus Infections 
The Journal of Infectious Diseases  2011;204(Suppl 3):S1075-S1081.
The filoviruses, Marburg virus and Ebola virus, cause severe hemorrhagic fever with a high mortality rate in humans and nonhuman primates. Among the most-promising filovirus vaccines under development is a system based on recombinant vesicular stomatitis virus (rVSV) that expresses a single filovirus glycoprotein (GP) in place of the VSV glycoprotein (G). Importantly, a single injection of blended rVSV-based filovirus vaccines was shown to completely protect nonhuman primates against Marburg virus and 3 different species of Ebola virus. These rVSV-based vaccines have also shown utility when administered as a postexposure treatment against filovirus infections, and a rVSV-based Ebola virus vaccine was recently used to treat a potential laboratory exposure. Here, we review the history of rVSV-based vaccines and pivotal animal studies showing their utility in combating Ebola and Marburg virus infections.
doi:10.1093/infdis/jir349
PMCID: PMC3218670  PMID: 21987744
17.  Single Immunization With a Monovalent Vesicular Stomatitis Virus–Based Vaccine Protects Nonhuman Primates Against Heterologous Challenge With Bundibugyo ebolavirus 
The Journal of Infectious Diseases  2011;204(Suppl 3):S1082-S1089.
The recombinant vesicular stomatitis virus (rVSV) vector-based monovalent vaccine platform expressing a filovirus glycoprotein has been demonstrated to provide protection from lethal challenge with Ebola (EBOV) and Marburg (MARV) viruses both prophylactically and after exposure. This platform provides protection between heterologous strains within a species; however, protection from lethal challenge between species has been largely unsuccessful. To determine whether the rVSV-EBOV vaccines have the potential to provide protection against a newly emerging, phylogenetically related species, cynomolgus macaques were vaccinated with an rVSV vaccine expressing either the glycoprotein of Zaire ebolavirus (ZEBOV) or Côte d’Ivoire ebolavirus (CIEBOV) and then challenged with Bundibugyo ebolavirus (BEBOV), which was recently proposed as a new EBOV species following an outbreak in Uganda in 2007. A single vaccination with the ZEBOV–specific vaccine provided cross-protection (75% survival) against subsequent BEBOV challenge, whereas vaccination with the CIEBOV–specific vaccine resulted in an outcome similar to mock-immunized animals (33% and 25% survival, respectively). This demonstrates that monovalent rVSV-based vaccines may be useful against a newly emerging species; however, heterologous protection across species remains challenging and may depend on enhancing the immune responses either through booster immunizations or through the inclusion of multiple immunogens.
doi:10.1093/infdis/jir350
PMCID: PMC3189995  PMID: 21987745
18.  Vesicular stomatitis virus-based vaccines protect nonhuman primates against aerosol challenge with Ebola and Marburg viruses 
Vaccine  2008;26(52):6894-6900.
Considerable progress has been made over the last decade in developing candidate preventive vaccines that can protect nonhuman primates against Ebola and Marburg viruses. A vaccine based on recombinant vesicular stomatitis virus (VSV) seems to be particularly robust as it can also confer protection when administered as a postexposure treatment. While filoviruses are not thought to be transmitted by aerosol in nature the inhalation route is among the most likely portals of entry in the setting of a bioterrorist event. At present, all candidate filoviral vaccines have been evaluated against parenteral challenges but none have been tested against an aerosol exposure. Here, we evaluated our recombinant VSV-based Zaire ebolavirus (ZEBOV) and Marburg virus (MARV) vaccines against aerosol challenge in cynomolgus macaques. All monkeys vaccinated with a VSV vector expressing the glycoprotein of ZEBOV were completely protected against an aerosol exposure of ZEBOV. Likewise, all monkeys vaccinated with a VSV vector expressing the glycoprotein of MARV were completely protected against an aerosol exposure of MARV. All control animals challenged by the aerosol route with either ZEBOV or MARV succumbed. Interestingly, disease in control animals appeared to progress slower than previously seen in macaques exposed to comparable doses by intramuscular injection.
doi:10.1016/j.vaccine.2008.09.082
PMCID: PMC3398796  PMID: 18930776
Ebola virus; Marburg virus; Filovirus; Nonhuman primates; Aerosol; Vaccines
19.  Progress in filovirus vaccine development: evaluating the potential for clinical use 
Expert Review of Vaccines  2011;10(1):63-77.
Marburg and Ebola viruses cause severe hemorrhagic fever in humans and nonhuman primates. Currently, there are no effective treatments and no licensed vaccines; although a number of vaccine platforms have proven successful in animal models. The ideal filovirus vaccine candidate should be able to provide rapid protection following a single immunization, have the potential to work postexposure and be cross-reactive or multivalent against all Marburg virus strains and all relevant Ebola virus species and strains. Currently, there are multiple platforms that have provided prophylactic protection in nonhuman primates, including DNA, recombinant adenovirus serotype 5, recombinant human parainfluenza virus 3 and virus-like particles. In addition, a single platform, recombinant vesicular stomatitis virus, has demonstrated both prophylactic and postexposure protection in nonhuman primates. These results demonstrate that achieving a vaccine that is protective against filoviruses is possible; the challenge now is to prove its safety and efficacy in order to obtain a vaccine that is ready for human use.
doi:10.1586/erv.10.152
PMCID: PMC3398800  PMID: 21162622
Ebola virus; filovirus; Marburg virus; postexposure; prophylactic; vaccine
20.  Prospects for immunisation against Marburg and Ebola viruses 
Reviews in Medical Virology  2010;20(6):344-357.
SUMMARY
For more than 30 years the filoviruses, Marburg virus and Ebola virus, have been associated with periodic outbreaks of hemorrhagic fever that produce severe and often fatal disease. The filoviruses are endemic primarily in resource-poor regions in Central Africa and are also potential agents of bioterrorism. Although no vaccines or antiviral drugs for Marburg or Ebola are currently available, remarkable progress has been made over the last decade in developing candidate preventive vaccines against filoviruses in nonhuman primate models. Due to the generally remote locations of filovirus outbreaks, a single-injection vaccine is desirable. Among the prospective vaccines that have shown efficacy in nonhuman primate models of filoviral hemorrhagic fever, two candidates, one based on a replication-defective adenovirus serotype 5 and the other on a recombinant VSV (rVSV), were shown to provide complete protection to nonhuman primates when administered as a single injection. The rVSV-based vaccine has also shown utility when administered for postexposure prophylaxis against filovirus infections. A VSV-based Ebola vaccine was recently used to manage a potential laboratory exposure.
doi:10.1002/rmv.661
PMCID: PMC3394174  PMID: 20658513
21.  An Optofluidic-Nanoplasmonic Biosensor for Direct Detection of Live Viruses from Biological Media 
Nano letters  2010;10(12):4962-4969.
Fast and sensitive virus detection techniques, which can be rapidly deployed at multiple sites, are essential to prevent and control the future epidemics and bioterrorism threats. In this letter, we demonstrate a label-free optofluidic-nanoplasmonic sensor that can directly detect intact viruses from biological media at clinically relevant concentrations with little to no sample preparation. Our sensing platform is based on extraordinary light transmission effect in plasmonic nanoholes and utilizes group specific antibodies for highly divergent strains of rapidly evolving viruses. So far, the questions remain for the possible limitations of this technique for virus detection, as the penetration depths of the surface plasmon polaritons (SPP) are comparable to the dimensions of the pathogens. Here, we demonstrate detection and recognition of small enveloped RNA viruses (vesicular stomatitis virus and pseudo-typed Ebola) as well as large enveloped DNA viruses (vaccinia virus) within a dynamic range spanning three orders of magnitude. Our platform, by enabling high signal noise measurements without any mechanical or optical isolation, opens up opportunities for detection of a broad range of pathogens in typical biology laboratory settings.
doi:10.1021/nl103025u
PMCID: PMC3123676  PMID: 21053965
Biosensing; Plasmonics; Virus Detection; Vaccinia; Ebola; Vesicular Stomatitis Virus
22.  A neutralizing human monoclonal antibody protects African Green monkeys from Hendra virus challenge 
Science Translational Medicine  2011;3(105):105ra103.
Hendra virus (HeV) is a recently emerged zoonotic paramyxovirus that can cause a severe and often fatal disease in horses and humans. HeV is categorized as a biosafety level 4 agent, which has made the development of animal models and testing of potential therapeutics and vaccines challenging. Infection of African Green monkeys (AGMs) with HeV was recently demonstrated and disease mirrored fatal HeV infection in humans, manifesting as a multisystemic vasculitis with widespread virus replication in vascular tissues and severe pathologic manifestations in the lung, spleen and brain. Here, we demonstrate that m102.4, a potent HeV neutralizing human monoclonal antibody (hmAb), can protect AGMs from disease post infection (p.i.) with HeV. Fourteen AGMs were challenged intratracheally with a lethal dose of HeV and twelve subjects were infused twice with a 100 mg dose of m102.4 beginning at either 10 hr, 24 hr or 72 hr p.i. and again approximately 48 hrs later. The presence of viral RNA, infectious virus and HeV-specific immune responses demonstrated that all subjects were infected following challenge. All twelve AGMs that received m102.4 survived infection; whereas the untreated control subjects succumbed to disease on day 8 p.i.. Animals in the 72 hr treatment group exhibited neurological signs of disease but all animals started to recover by day 16 p.i.. These results represent successful post-exposure in vivo efficacy by an investigational drug against HeV and highlight the potential impact a hmAb can have on human disease.
doi:10.1126/scitranslmed.3002901
PMCID: PMC3313625  PMID: 22013123
23.  Label-free, multiplexed virus detection using spectral reflectance imaging 
Biosensors & bioelectronics  2011;26(8):3432-3437.
We demonstrate detection of whole viruses and viral proteins with a new label-free platform based on spectral reflectance imaging. The Interferometric Reflectance Imaging Sensor (IRIS) has been shown to be capable of sensitive protein and DNA detection in a real time and high-throughput format. Vesicular stomatitis virus (VSV) was used as the target for detection as it is well-characterized for protein composition and can be modified to express viral coat proteins from other dangerous, highly pathogenic agents for surrogate detection while remaining a biosafety level 2 agent. We demonstrate specific detection of intact VSV virions achieved with surface-immobilized antibodies acting as capture probes which is confirmed using fluorescence imaging. The limit of detection is confirmed down to 3.5×105 plaque-forming units/mL (PFUs/mL). To increase specificity in a clinical scenario, both the external glycoprotein and internal viral proteins were simultaneously detected with the same antibody arrays with detergent-disrupted purified VSV and infected cell lysate solutions. Our results show sensitive and specific virus detection with a simple surface chemistry and minimal sample preparation on a quantitative label-free interferometric platform.
doi:10.1016/j.bios.2011.01.019
PMCID: PMC3065545  PMID: 21342761
Virus detection; Label-free; Interferometry; Biosensor; High-throughput; Microarray; Quantitative sensing
24.  Recombinant Vesicular Stomatitis Virus Vaccine Vectors Expressing Filovirus Glycoproteins Lack Neurovirulence in Nonhuman Primates 
The filoviruses, Marburg virus and Ebola virus, cause severe hemorrhagic fever with high mortality in humans and nonhuman primates. Among the most promising filovirus vaccines under development is a system based on recombinant vesicular stomatitis virus (rVSV) that expresses an individual filovirus glycoprotein (GP) in place of the VSV glycoprotein (G). The main concern with all replication-competent vaccines, including the rVSV filovirus GP vectors, is their safety. To address this concern, we performed a neurovirulence study using 21 cynomolgus macaques where the vaccines were administered intrathalamically. Seven animals received a rVSV vector expressing the Zaire ebolavirus (ZEBOV) GP; seven animals received a rVSV vector expressing the Lake Victoria marburgvirus (MARV) GP; three animals received rVSV-wild type (wt) vector, and four animals received vehicle control. Two of three animals given rVSV-wt showed severe neurological symptoms whereas animals receiving vehicle control, rVSV-ZEBOV-GP, or rVSV-MARV-GP did not develop these symptoms. Histological analysis revealed major lesions in neural tissues of all three rVSV-wt animals; however, no significant lesions were observed in any animals from the filovirus vaccine or vehicle control groups. These data strongly suggest that rVSV filovirus GP vaccine vectors lack the neurovirulence properties associated with the rVSV-wt parent vector and support their further development as a vaccine platform for human use.
Author Summary
Ebola and Marburg viruses are categorized as Category A priority pathogens by several US Government agencies as a result of their high mortality rates and potential for use as agents of bioterrorism. There are currently no vaccines or therapeutics approved for human use. A replication-competent, recombinant vesicular stomatitis virus (rVSV) vector expressing filovirus glycoproteins (GP), in place of the VSV G protein has shown promise in lethal nonhuman primate models of filovirus infection as both a single-injection preventive vaccine and a postexposure treatment. Replication-competent vaccines that are intended for use in humans usually undergo neurovirulence testing as was done for measles virus, mumps virus, yellow fever virus, and poliovirus vaccines. Here we used a conventional neurovirulence test to evaluate the safety of our rVSV-based Zaire ebolavirus and Lake Victoria marburgvirus GP vaccines in cynomolgus macaques. Importantly, we demonstrate for the first time that these rVSV filovirus GP vectors lack neurovirulence when compared to a rVSV wild-type vector.
doi:10.1371/journal.pntd.0001567
PMCID: PMC3308941  PMID: 22448291
25.  Vesicular Stomatitis Virus-Based Vaccines for Prophylaxis and Treatment of Filovirus Infections 
Journal of bioterrorism & biodefense  2011;Suppl 1(4):2157-2526-S1-004.
Ebola and Marburg viruses are emerging/re-emerging zoonotic pathogens that cause severe viral hemorrhagic fever with case-fatality rates up to 90% in humans. Over the last three decades numerous outbreaks, of increasing frequency, have been documented in endemic regions. Furthermore, as a result of increased international travel filovirus infections have been imported into South Africa, Europe and North America. Both viruses possess the potential of being used as bioterrorism agents and are classified as category A pathogens. Currently there is neither a licensed vaccine nor effective treatment available, despite substantial efforts being d́edicated to understanding filovirus well as vaccine and drug development. One of the most promising vaccine platforms is based on replication competent recombinant vesicular stomatitis viruses (rVSV) that express a filovirus glycoprotein as the surface antigen. These rVSVs have been extensively studied in rodent and nonhuman primate models of filovirus disease and, in general, have been shown to be 100% protective in pre-exposure prophylaxis. In addition, rVSVs have demonstrated potential for post-exposure treatment, and thus would be particularly useful in the event of intentional release as well as accidental exposures in outbreak and laboratory settings.
doi:10.4172/2157-2526.S1-004
PMCID: PMC3265573  PMID: 22288023

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