Vaccines and therapies are urgently needed to address public health needs stemming from emerging pathogens and biological threat agents such as the filoviruses Ebola virus (EBOV) and Marburg virus (MARV). Ebola virus (EBOV) and Marburg virus (MARV) of the virus familyFiloviridae are emerging and reemerging pathogens that cause hemorrhagic fever with high mortality rates in humans and nonhuman primates 1-3 . The public health concern about filoviruses has increased in recent years as a result of increased awareness and frequency of cases in central Africa as evidenced by the current outbreak of MARV in Angola 4 and also because filoviruses are considered to be potential agents of bioterrorism 5 . Currently, there are no EBOV or MARV vaccines or therapies approved for human use. Recently, we generated live attenuated recombinant vesicular stomatitis viruses (rVSV) expressing the transmembrane glycoprotein of Zaire ebolavirus (ZEBOV; VSV ∴∆G/ZEBOVGP) and MARV (VSV∆G/MARVGP) 6 . Our study evaluated the utility of these rVSV vectors as candidate vaccines for EBOV and MARV using the cynomolgus macaque model.Filovirus vaccine research has been extensively reviewed in the past and has primarily focused on EBOV 7,8 . The first EBOV vaccine to protect nonhuman primates was a DNA prime-adenovirus boost approach using both the glycoprotein and nucleoprotein as target antigens 9 . This approach required several months for immunity to develop, which limited the utility of this strategy. More recently, an accelerated vaccine was described. A single immunization of nonhuman primates with 2 × 10 12 particles of an equal mixture of human adenovirus 5 vectors carrying either the gene encoding ZEBOV glycoprotein or the gene encoding ZEBOV nucleoprotein resulted in complete protection against ZEBOV 10 . Despite the intriguing success of the adenovirus vaccine, preexisting immunity rates of between 40 and 60% have been reported to adenovirus in the human population and this may eventually limit the utility of this approach [11][12][13] .A smaller number of efforts have focused on developing vaccines against MARV. Alphavirus replicons expressing MARV proteins protected cynomolgus monkeys from homologous MARV challenge 14 . Subsequent studies evaluating this platform as a vaccine for EBOV were less encouraging, as the EBOV counterpart of this alphavirus replicon platform was unable to protect any animal against lethal EBOV challenge under similar test conditions 7 . The ideal vaccine would protect humans from infection from all four EBOV species (ZEBOV, Sudan ebolavirus (SEBOV), Reston ebolavirus, Ivory Coast ebolavirus) and MARV. Although the adenovirusbased vaccine platform has completely protected nonhuman primates against ZEBOV 9,10 , and the platform based on alphavirus replicons protected monkeys against MARV 14 , no platform has demonstrably protected nonhuman primates against both of these viruses.Vaccines based on live attenuated rVSV have been highly effective in animal models and are particularly attractive because they can ...

Ebola virus (EBOV) infection causes a severe and fatal hemorrhagic disease that in many ways appears to be similar in humans and nonhuman primates; however, little is known about the development of EBOV hemorrhagic fever. In the present study, 21 cynomolgus monkeys were experimentally infected with EBOV and examined sequentially over a 6-day period to investigate the pathological events of EBOV infection that lead to death. Importantly, dendritic cells in lymphoid tissues were identified as early and sus-

Defense Threat Reduction Agency.

Lassa fever is a severe multisystem disease that often has haemorrhagic manifestations. The epitopes of the Lassa virus (LASV) surface glycoproteins recognized by naturally infected human hosts have not been identified or characterized. Here we have cloned 113 human monoclonal antibodies (mAbs) specific for LASV glycoproteins from memory B cells of Lassa fever survivors from West Africa. One-half bind the GP2 fusion subunit, one-fourth recognize the GP1 receptor-binding subunit and the remaining fourth are specific for the assembled glycoprotein complex, requiring both GP1 and GP2 subunits for recognition. Notably, of the 16 mAbs that neutralize LASV, 13 require the assembled glycoprotein complex for binding, while the remaining 3 require GP1 only. Compared with non-neutralizing mAbs, neutralizing mAbs have higher binding affinities and greater divergence from germline progenitors. Some mAbs potently neutralize all four LASV lineages. These insights from LASV human mAb characterization will guide strategies for immunotherapeutic development and vaccine design.

Post-exposure protection with rNAPc2 against Ebola virus in primates provides a new foundation for therapeutic regimens that target the disease process rather than viral replication.

Ebola viruses are highly lethal human pathogens that have received considerable attention in recent years due to an increasing re-emergence in Central Africa and a potential for use as a biological weapon. There is no vaccine or treatment licensed for human use. In the past, however, important advances have been made in developing preventive vaccines that are protective in animal models. In this regard, we showed that a single injection of a live-attenuated recombinant vesicular stomatitis virus vector expressing the Ebola virus glycoprotein completely protected rodents and nonhuman primates from lethal Ebola challenge. In contrast, progress in developing therapeutic interventions against Ebola virus infections has been much slower and there is clearly an urgent need to develop effective post-exposure strategies to respond to future outbreaks and acts of bioterrorism, as well as to treat laboratory exposures. Here we tested the efficacy of the vesicular stomatitis virus-based Ebola vaccine vector in post-exposure treatment in three relevant animal models. In the guinea pig and mouse models it was possible to protect 50% and 100% of the animals, respectively, following treatment as late as 24 h after lethal challenge. More important, four out of eight rhesus macaques were protected if treated 20 to 30 min following an otherwise uniformly lethal infection. Currently, this approach provides the most effective post-exposure treatment strategy for Ebola infections and is particularly suited for use in accidentally exposed individuals and in the control of secondary transmission during naturally occurring outbreaks or deliberate release.

BackgroundLassa 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 FindingsClinical 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/SignificanceLassa 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.

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 (VSV) that expresses a single filovirus glycoprotein (GP) in place of the VSV glycoprotein (G). Here, we performed a proof-of-concept study in order to determine the potential of having one single-injection vaccine capable of protecting nonhuman primates against Sudan ebolavirus (SEBOV), Zaire ebolavirus (ZEBOV), Cote d'Ivoire ebolavirus (CIEBOV), and Marburgvirus (MARV). In this study, 11 cynomolgus monkeys were vaccinated with a blended vaccine consisting of equal parts of the vaccine vectors VSV⌬G/SEBOVGP, VSV⌬G/ZEBOVGP, and VSV⌬G/MARVGP. Four weeks later, three of these animals were challenged with MARV, three with CIEBOV, three with ZEBOV, and two with SEBOV. Three control animals were vaccinated with VSV vectors encoding a nonfilovirus GP and challenged with SEBOV, ZEBOV, and MARV, respectively, and five unvaccinated control animals were challenged with CIEBOV. Importantly, none of the macaques vaccinated with the blended vaccine succumbed to a filovirus challenge. As expected, an experimental control animal vaccinated with VSV⌬G/ZEBOVGP and challenged with SEBOV succumbed, as did the positive controls challenged with SEBOV, ZEBOV, and MARV, respectively. All five control animals challenged with CIEBOV became severely ill, and three of the animals succumbed on days 12, 12, and 14, respectively. The two animals that survived CIEBOV infection were protected from subsequent challenge with either SEBOV or ZEBOV, suggesting that immunity to CIEBOV may be protective against other species of Ebola virus. In conclusion, we developed an immunization scheme based on a single-injection vaccine that protects nonhuman primates against lethal challenge with representative strains of all human pathogenic filovirus species.