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Monoclonal antibodies are an efficacious therapy against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, rapid viral mutagenesis led to escape from most of these therapies, outlining the need for an antibody cocktail with a broad neutralizing potency. Using an unbiased interrogation of the memory B cell repertoire of patients with convalescent COVID-19, we identified human antibodies with broad antiviral activity in vitro and efficacy in vivo against all tested SARS-CoV-2 variants of concern, including Delta and Omicron BA.1 and BA.2. Here, we describe an antibody cocktail, IMM-BCP-01, that consists of three patient-derived broadly neutralizing antibodies directed at nonoverlapping surfaces on the SARS-CoV-2 Spike protein. Two antibodies, IMM20184 and IMM20190, directly blocked Spike binding to the ACE2 receptor. Binding of the third antibody, IMM20253, to its cryptic epitope on the outer surface of RBD altered the conformation of the Spike Trimer, promoting the release of Spike monomers. These antibodies decreased Omicron SARS-CoV-2 infection in the lungs of Syrian golden hamsters in vivo and potently induced antiviral effector response in vitro, including phagocytosis, ADCC, and complement pathway activation. Our preclinical data demonstrated that the three-antibody cocktail IMM-BCP-01 could be a promising means for preventing or treating infection of SARS-CoV-2 variants of concern, including Omicron BA.1 and BA.2, in susceptible individuals.

The rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), coupled with a lack of therapeutics, has paralyzed the globe. Although significant effort has been invested in identifying antibodies that block infection, the ability of antibodies to target infected cells through Fc interactions may be vital to eliminate the virus. To explore the role of Fc activity in SARS-CoV-2 immunity, the functional potential of a cross–SARS-reactive antibody, CR3022, was assessed. CR3022 was able to broadly drive antibody effector functions, providing critical immune clearance at entry and upon egress. Using selectively engineered Fc variants, no protection was observed after administration of WT IgG1 in mice or hamsters. Conversely, the functionally enhanced Fc variant resulted in increased pathology in both the mouse and hamster models, causing weight loss in mice and enhanced viral replication and weight loss in the more susceptible hamster model, highlighting the pathological functions of Fc-enhancing mutations. These data point to the critical need for strategic Fc engineering for the treatment of SARS-CoV-2 infection. CA extern

Ebola virus disease (EVD) is a serious global health concern because case fatality rates are approximately 50% due to recent widespread outbreaks in Africa. Well-defined nonhuman primate (NHP) models for different routes of Ebola virus exposure are needed to test the efficacy of candidate countermeasures. In this natural history study, four rhesus macaques were challenged via aerosol with a target titer of 1000 plaque-forming units per milliliter of Ebola virus. The course of disease was split into the following stages for descriptive purposes: subclinical, clinical, and decompensated. During the subclinical stage, high levels of venous partial pressure of carbon dioxide led to respiratory acidemia in three of four of the NHPs, and all developed lymphopenia. During the clinical stage, all animals had fever, viremia, and respiratory alkalosis. The decompensatory stage involved coagulopathy, cytokine storm, and liver and renal injury. These events were followed by hypotension, elevated lactate, metabolic acidemia, shock and mortality similar to historic intramuscular challenge studies. Viral loads in the lungs of aerosol-exposed animals were not distinctly different compared to previous intramuscularly challenged studies. Differences in the aerosol model, compared to intramuscular model, include an extended subclinical stage, shortened clinical stage, and general decompensated stage. Therefore, the shortened timeframe for clinical detection of the aerosol-induced disease can impair timely therapeutic administration. In summary, this nonhuman primate model of aerosol-induced EVD characterizes early disease markers and additional details to enable countermeasure development.

The recent epidemic of Ebola virus disease in West Africa resulted in an unprecedented number of cases and deaths. Due to the scope of the outbreak combined with the lack of available approved treatment options, there was strong motivation to investigate any potential drug which had existing data reporting anti-Ebola activity. Drugs with demonstrated antiviral activity in the nonhuman primate models already approved for another indication or for which there was existing safety data were considered to be priorities for evaluation by the World Health Organization. Sertraline hydrochloride was reported to have anti-Ebola activity in vitro alone and in combination with other approved drugs. Although the efficacy was less than 100% in the murine model, the established safety profile of this product, the potential benefit alone and in combination, as well as the lack of other available options prioritized this compound for testing in the Ebola virus intramuscular rhesus macaque challenge model. Using a blinded dosing strategy, we demonstrated that high dose sertraline monotherapy provided no benefit for the prevention of Ebola virus disease in rhesus macaques with regards to reduction of viral load, morbidity, or survival highlighting the challenges of translating results between in vitro and in vivo models.

Countermeasures against potential biothreat agents remain important to US Homeland Security, and many of these pharmaceuticals could have dual use in the improvement of global public health. Junin virus, the causative agent of Argentine hemorrhagic fever (AHF), is an arenavirus identified as a category A high-priority agent. There are no Food and Drug Administration (FDA) approved drugs available for preventing or treating AHF, and the current treatment option is limited to administration of immune plasma. Whereas immune plasma demonstrates the feasibility of passive immunotherapy, it is limited in quantity, variable in quality, and poses safety risks such as transmission of transfusion-borne diseases. In an effort to develop a monoclonal antibody (mAb)-based alternative to plasma, three previously described neutralizing murine mAbs were expressed as mouse-human chimeric antibodies and evaluated in the guinea pig model of AHF. These mAbs provided 100% protection against lethal challenge when administered 2 d after infection (dpi), and one of them (J199) was capable of providing 100% protection when treatment was initiated 6 dpi and 92% protection when initiated 7 dpi. The efficacy of J199 is superior to that previously described for all other evaluated drugs, and its high potency suggests that mAbs like J199 offer an economical alternative to immune plasma and an effective dual use (bioterrorism/public health) therapeutic.

Lassa fever virus (LASV) is endemic in West Africa and causes severe hemorrhagic fever and sensorineural hearing loss. We identified a small molecule inhibitor of LASV and used it to analyze the mechanism of entry. Using a photo-reactive analog that retains antiviral activity as a probe, we identified the inhibitor target as lysosome-associated membrane protein 1 (LAMP1), a host factor that binds to the LASV glycoprotein (GP) during infection. We found that LAMP1 binding to LASV GP is cholesterol-dependent, and that the inhibitor blocks infection by competing with cholesterol in LAMP1. Mutational analysis of a docking-based model identified a putative inhibitor binding site in the cholesterol-binding pocket within the LAMP1 domain that binds GP. These findings identify a critical role for cholesterol in LASV entry and a potential target for therapeutic intervention., Author summary Lassa fever virus (LASV) is endemic in West Africa and can cause fatal infection. Currently, there is no vaccine or effective post-exposure treatment. Here we identify 3.3, a small molecule that inhibits LASV infection by targeting lysosome-associated membrane protein 1 (LAMP1), which binds to the LASV glycoprotein (GP) and promotes virus membrane fusion and infection. Our analysis reveals that cholesterol is an important cofactor for LAMP1 binding to LASV GP and that 3.3 inhibits infection by displacing cholesterol from LAMP1. Thus, 3.3 is a candidate for further development as a LASV inhibitor.

Marburg virus (MARV) infection is a lethal hemorrhagic fever for which no licensed vaccines or therapeutics are available. Development of appropriate medical countermeasures requires a thorough understanding of the interaction between the host and the pathogen and the resulting disease course. In this study, 15 rhesus macaques were sequentially sacrificed following aerosol exposure to the MARV variant Angola, with longitudinal changes in physiology, immunology, and histopathology used to assess disease progression. Immunohistochemical evidence of infection and resulting histopathological changes were identified as early as day 3 postexposure (p.e.). The appearance of fever in infected animals coincided with the detection of serum viremia and plasma viral genomes on day 4 p.e. High (>10 7 PFU/ml) viral loads were detected in all major organs (lung, liver, spleen, kidney, brain, etc.) beginning day 6 p.e. Clinical pathology findings included coagulopathy, leukocytosis, and profound liver destruction as indicated by elevated liver transaminases, azotemia, and hypoalbuminemia. Altered cytokine expression in response to infection included early increases in Th2 cytokines such as interleukin 10 (IL-10) and IL-5 and late-stage increases in Th1 cytokines such as IL-2, IL-15, and granulocyte-macrophage colony-stimulating factor (GM-CSF). This study provides a longitudinal examination of clinical disease of aerosol MARV Angola infection in the rhesus macaque model. IMPORTANCE In this study, we carefully analyzed the timeline of Marburg virus infection in nonhuman primates in order to provide a well-characterized model of disease progression following aerosol exposure.

The limited data available for long-term Ebola virus disease health outcomes suggest that sequelae persist for longer than 1 year after infection. The magnitude of the present outbreak in west Africa necessitates a more complete understanding of the health effects and future medical needs of these patients.We invited adult survivors of the 2007 Bundibugyo Ebola virus outbreak in Uganda and their contacts to take part in an observational study roughly 29 months after the outbreak. We collected information about health status, functional limitations, and demographics. We collected blood samples for clinical chemistry, haematology, and filovirus antibodies using ELISA. Analyses were restricted to probable and confirmed survivors and their seronegative contacts.We recruited 70 survivors of the 2007 Bundibugyo Ebola virus and 223 contacts. We did analyses for 49 probable and confirmed survivors and 157 seronegative contacts. Survivors of the Bundibugyo Ebola virus were at significantly increased risk of ocular deficits (retro-orbital pain [RR 4·3, 95% CI 1·9-9·6; p0·0001], blurred vision [1·9, 1·1-3·2; p=0·018]), hearing loss (2·3, 1·2-4·5; p=0·010), difficulty swallowing (2·1, 1·1-3·9; p=0·017), difficulty sleeping (1·9, 1·3-2·8; p=0·001), arthralgias (2·0, 1·1-3·6; p=0·020), and various constitutional symptoms controlling for age and sex. Chronic health problems (prevalence ratio [PR] 2·1, 95% CI 1·2-3·6; p=0·008) and limitations due to memory loss or confusion (PR 5·8, 1·5-22·4; p=0·010) were also reported more frequently by survivors of Bundibugyo Ebola virus.Long-term sequelae persist for more than 2 years after Ebola virus disease. Definition of health consequences related to Ebola virus disease could improve patient care for survivors and contribute to understanding of disease pathogenesis.Chemical Biological Technologies Directorate, Defense Threat Reduction Agency.

Early pathogen exposure detection allows better patient care and faster implementation of public health measures (patient isolation, contact tracing). Existing exposure detection most frequently relies on overt clinical symptoms, namely fever, during the infectious prodromal period. We have developed a robust machine learning based method to better detect asymptomatic states during the incubation period using subtle, sub-clinical physiological markers. Starting with high-resolution physiological waveform data from non-human primate studies of viral (Ebola, Marburg, Lassa, and Nipah viruses) and bacterial (Y. pestis) exposure, we processed the data to reduce short-term variability and normalize diurnal variations, then provided these to a supervised random forest classification algorithm and post-classifier declaration logic step to reduce false alarms. In most subjects detection is achieved well before the onset of fever; subject cross-validation across exposure studies (varying viruses, exposure routes, animal species, and target dose) lead to 51h mean early detection (at 0.93 area under the receiver-operating characteristic curve [AUCROC]). Evaluating the algorithm against entirely independent datasets for Lassa, Nipah, andY. pestisexposures un-used in algorithm training and development yields a mean 51h early warning time (at AUCROC=0.95). We discuss which physiological indicators are most informative for early detection and options for extending this capability to limited datasets such as those available from wearable, non-invasive, ECG-based sensors.

Antigen-presenting cells (APCs) are critical targets of Ebola virus (EBOV) infection in vivo . However, the susceptibility of monocytes to infection is controversial. Studies indicate productive monocyte infection, and yet monocytes are also reported to be resistant to EBOV GP-mediated entry. In contrast, monocyte-derived macrophages and dendritic cells are permissive for both EBOV entry and replication. Here, freshly isolated monocytes are demonstrated to indeed be refractory to EBOV entry. However, EBOV binds monocytes, and delayed entry occurs during monocyte differentiation. Cultured monocytes spontaneously downregulate the expression of viral entry restriction factors such as interferon-inducible transmembrane proteins, while upregulating the expression of critical EBOV entry factors cathepsin B and NPC1. Moreover, these processes are accelerated by EBOV infection. Finally, ectopic expression of NPC1 is sufficient to rescue entry into an undifferentiated, normally nonpermissive monocytic cell line. These results define the molecular basis for infection of APCs and suggest means to limit APC infection.

Background Ebola virus is the causative agent of a severe syndrome in humans with a fatality rate that can approach 90 %. During infection, the host immune response is thought to become dysregulated, but the mechanisms through which this happens are not entirely understood. In this study, we analyze RNA sequencing data to determine the host response to Ebola virus infection in circulating immune cells. Results Approximately half of the 100 genes with the strongest early increases in expression were interferon-stimulated genes, such as ISG15, OAS1, IFIT2, HERC5, MX1 and DHX58. Other highly upregulated genes included cytokines CXCL11, CCL7, IL2RA, IL2R1, IL15RA, and CSF2RB, which have not been previously reported to change during Ebola virus infection. Comparing this response in two different models of exposure (intramuscular and aerosol) revealed a similar signature of infection. The strong innate response in the aerosol model was seen not only in circulating cells, but also in primary and secondary target tissues. Conversely, the innate immune response of vaccinated macaques was almost non-existent. This suggests that the innate response is a major aspect of the cellular response to Ebola virus infection in multiple tissues. Conclusions Ebola virus causes a severe infection in humans that is associated with high mortality. The host immune response to virus infection is thought to be an important aspect leading to severe pathology, but the components of this overactive response are not well characterized. Here, we analyzed how circulating immune cells respond to the virus and found that there is a strong innate response dependent on active virus replication. This finding is in stark contrast to in vitro evidence showing a suppression of innate immune signaling, and it suggests that the strong innate response we observe in infected animals may be an important contributor to pathogenesis. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-3060-0) contains supplementary material, which is available to authorized users.

Viruses of the family Filoviridae represent significant health risks as emerging infectious diseases as well as potentially engineered biothreats. While many research efforts have been published offering possibilities toward the mitigation of filoviral infection, there remain no sanctioned therapeutic or vaccine strategies. Current progress in the development of filovirus therapeutics and vaccines is outlined herein with respect to their current level of testing, evaluation, and proximity toward human implementation, specifically with regard to human clinical trials, nonhuman primate studies, small animal studies, and in vitro development. Contemporary methods of supportive care and previous treatment approaches for human patients are also discussed.

Vaccine-induced immunity to Ebola virus infection in nonhuman primates (NHPs) is marked by potent antigen-specific cellular and humoral immune responses; however, the immune mechanism of protection remains unknown. Here we define the immune basis of protection conferred by a highly protective recombinant adenovirus virus serotype 5 (rAd5) encoding Ebola virus glycoprotein (GP) in NHPs. Passive transfer of high-titer polyclonal antibodies from vaccinated Ebola virus-immune cynomolgus macaques to naive macaques failed to confer protection against disease, suggesting a limited role of humoral immunity. In contrast, depletion of CD3(+) T cells in vivo after vaccination and immediately before challenge eliminated immunity in two vaccinated macaques, indicating a crucial requirement for T cells in this setting. The protective effect was mediated largely by CD8(+) cells, as depletion of CD8(+) cells in vivo using the cM-T807 monoclonal antibody (mAb), which does not affect CD4(+) T cell or humoral immune responses, abrogated protection in four out of five subjects. These findings indicate that CD8(+) cells have a major role in rAd5-GP-induced immune protection against Ebola virus infection in NHPs. Understanding the immunologic mechanism of Ebola virus protection will facilitate the development of vaccines for Ebola and related hemorrhagic fever viruses in humans.

Detailed studies describing the pathogenesis of Rift Valley fever (RVF) virus (RVFV) in the mouse model are lacking. A fully characterized small animal model of RVF is needed to evaluate potential vaccines and therapeutics. In this study, we characterized the pathogenesis of RVFV throughout the disease course in mice. Infection produced high-titer viremia and demonstrated RVFV tropism for a variety of tissue and individual cell types. Overwhelming infection of hepatocytes, accompanied by apoptosis, was a major consequence of infection. The majority of mice died or were euthanatized between days 3 and 6 postinfection with severe hepatitis. The remaining mice effectively cleared virus from the liver and blood, but exhibited neuroinvasion and developed panencephalitis. In addition, we characterized a number of other virological, clinicopathological, and histopathological features of RVFV infection in mice. The mouse model therefore mimics both the acute-onset hepatitis and delayed-onset encephalitis that are dominant features of severe human RVF.

We evaluated the ability of flagellin, a highly effective mucosal adjuvant in mice and non-human primates, to promote mucosal innate and adaptive immunity in aged mice. We found that intratracheal instillation of flagellin induced a stronger respiratory innate response in aged mice than in young mice, and that intranasal instillation of flagellin was equally effective at triggering recruitment of T and B lymphocytes to the draining lymph nodes of young and aged mice. Intranasal immunization of aged mice with flagellin and the Yersinia pestis protein F1 promoted specific IgG and IgA production, but at lower levels and lower avidities than in young mice. Although intranasal instillation of flagellin and F1 antigen increased germinal center formation and size in young mice, it did not do so in aged mice. Our findings are consistent with the conclusion that flagellin can promote adaptive immune responses in aged mice, but at a less robust level than in young mice.

Early detection of Ebola virus (EBOV) infection is essential to halting transmission and adjudicating appropriate treatment. However, current methods rely on viral identification, and this approach can misdiagnose presymptomatic and asymptomatic individuals. In contrast, disease-driven alterations in the host transcriptome can be exploited for pathogen-specific diagnostic biomarkers. Here, we present for the first time EBOV-induced changes in circulating miRNA populations of nonhuman primates (NHPs) and humans. We retrospectively profiled longitudinally-collected plasma samples from rhesus macaques challenged via intramuscular and aerosol routes and found 36 miRNAs differentially present in both groups. Comparison of miRNA abundances to viral loads uncovered 15 highly correlated miRNAs common to EBOV-infected NHPs and humans. As proof of principle, we developed an eight-miRNA classifier that correctly categorized infection status in 64/74 (86%) human and NHP samples. The classifier identified acute infections in 27/29 (93.1%) samples and in 6/12 (50%) presymptomatic NHPs. These findings showed applicability of NHP-derived miRNAs to a human cohort, and with additional research the resulting classifiers could impact the current capability to diagnose presymptomatic and asymptomatic EBOV infections.

In the fall of 2014, an international news agency reported that patients suffering from Ebola virus disease (EVD) in Liberia were treated successfully with lamivudine, an antiviral drug used to treat human immunodeficiency virus-1 and hepatitis B virus infections. According to the report, 13 out of 15 patients treated with lamivudine survived and were declared free from Ebola virus disease. In this study, the anti-Ebola virus (EBOV) activity of lamivudine and another antiretroviral, zidovudine, were evaluated in a diverse set of cell lines against two variants of wild-type EBOV. Variable assay parameters were assessed to include different multiplicities of infection, lengths of inoculation times, and durations of dosing. At a multiplicity of infection of 1, lamivudine and zidovudine had no effect on EBOV propagation in Vero E6, Hep G2, or HeLa cells, or in primary human monocyte-derived macrophages. At a multiplicity of infection of 0.1, zidovudine demonstrated limited anti-EBOV activity in Huh 7 cells. Under certain conditions, lamivudine had low anti-EBOV activity at the maximum concentration tested (320 μM). However, lamivudine never achieved greater than 30% viral inhibition, and the activity was not consistently reproducible. Combination of lamivudine and zidovudine showed no synergistic antiviral activity. Independently, a set of in vitro experiments testing lamivudine and zidovudine for antiviral activity against an Ebola-enhanced green fluorescent protein reporter virus was performed at the Centers for Disease Control and Prevention. No antiviral activity was observed for either compound. A study evaluating the efficacy of lamivudine in a guinea pig model of EVD found no survival benefit. This lack of benefit was observed despite plasma lamivudine concentrations in guinea pig of about 4 μg/ml obtained in a separately conducted pharmacokinetics study. These studies found no evidence to support the therapeutic use of lamivudine for the treatment of EVD.

Recent experimentation with the variants of the Ebola virus that differ in the glycoprotein’s poly-uridine site, which dictates the form of glycoprotein produced through a transcriptional stutter, has resulted in questions regarding the pathogenicity and lethality of the stocks used to develop products currently undergoing human clinical trials to combat the disease. In order to address these concerns and prevent the delay of these critical research programs, we designed an experiment that permitted us to intramuscularly challenge statistically significant numbers of naïve and vaccinated cynomolgus macaques with either a 7U or 8U variant of the Ebola virus, Kikwit isolate. In naïve animals, no difference in survivorship was observed, however, there was a significant delay in the disease course between the two groups. Significant differences were also observed in time-of-fever, serum chemistry, and hematology. In vaccinated animals, there was no statistical difference in survivorship between either challenge groups, with two succumbing in the 7U group compared to 1 in the 8U challenge group. In summary, survivorship was not affected, but the Ebola virus disease course in nonhuman primates is temporally influenced by glycoprotein poly-U editing site populations.

Gram-negative flagellin, a Toll-like receptor 5 (TLR5) agonist, is a potent inducer of innate immune effectors such as cytokines and nitric oxide. In the lung, flagellin induces a localized and transient innate immune response characterized by neutrophil infiltration and the production of cytokines and chemokines. In view of the extraordinary potency of flagellin as an inducer of innate immunity and the contribution of innate responses to the development of adaptive immunity, we evaluated the efficacy of recombinantSalmonellaflagellin as an adjuvant in an acellular plague vaccine. Mice immunized intranasally or intratracheally with the F1 antigen ofYersinia pestisand flagellin exhibited dramatic increases in anti-F1 plasma immunoglobulin G (IgG) titers that remained stable over time. In contrast, control mice had low or undetectable antibody responses. The IgG1/IgG2a ratio of antibody titers against F1 in immunized mice is consistent with a Th2 bias. However, no significant antigen-specific IgE production was detected. Interferons, tumor necrosis factor alpha, and interleukin-6 were not essential for the adjuvant effects of flagellin. Preexisting antiflagellin antibodies had no significant effect on the adjuvant activity of flagellin. Importantly, intranasal immunization with flagellin and the F1 antigen was protective against intranasal challenge with virulentY. pestisCO92, with 93 to 100% survival of immunized mice. Lastly, vaccination of cynomolgus monkeys with flagellin and a fusion of the F1 and V antigens ofY. pestisinduced a robust antigen-specific IgG antibody response.

Flagella are locomotive organelles present on a wide range of bacteria and are important for the pathogenesis of many species. Cells of the innate immune system lack memory per se, but recognize conserved pathogen-associated molecular patterns (PAMPs) through a family of type I membrane receptors known as Toll-like receptors (TLRs). Flagellin, the major structural component of flagella, is a highly conserved protein recognized in hosts by TLR5. Signaling of flagellin via TLR5/TLR4 heteromeric complexes enhances the diversity of the response, likely by engaging MyD88-independent adaptors to activate the interferon pathway. Flagellin is a potent immune activator, stimulating diverse biologic effects that mediate both innate inflammatory responses as well as the development of adaptive immunity. Binding of flagellin to the extracellular domain of TLR5 rapidly induces a signal cascade that culminates in the production of proinflammatory mediators such as cytokines, chemokines, and costimulatory molecules. This review focuses on the mechanisms of action of flagellin and its effects on both innate and adaptive immunity.

The induction of cytokine synthesis by flagellin is mediated by a Toll-like receptor 5 (TLR5) signaling pathway. Although flagellin activation of the IL-1R-associated kinase and induction of TNF-α synthesis are dependent on TLR5 and not TLR4, we have found that flagellin stimulates NO in macrophages via a pathway that requires TLR5 and TLR4. Flagellin induced NO synthesis in HeNC2 cells, a murine macrophage cell line that expresses wild-type TLR4, but not in TLR4-mutant or -deficient GG2EE and 10ScNCr/23 cells. Flagellin stimulated an increase in inducible NO synthase (iNOS) mRNA and activation of the iNOS promoter. TLR5 forms heteromeric complexes with TLR4 as well as homomeric complexes. IFN-γ permitted GG2EE and 10ScNCr/23 cells to produce NO in response to flagellin. Flagellin stimulated IFN-β synthesis and Stat1 activation. The effect of flagellin on iNOS gene expression was inhibited by a Stat1 mutant protein. Taken together, these results support the conclusions that flagellin induces distinct patterns of inflammatory mediators depending on the nature of the TLR5 signaling complex and that the induction of NO by flagellin involves signaling via TLR5/TLR4 complexes.

Henipaviruses are implicated in severe and frequently fatal pneumonia and encephalitis in humans. There are no approved vaccines or treatments available for human use, and testing of candidates requires the use of well-characterized animal models that mimic human disease. We performed a comprehensive and statistically-powered evaluation of the African green monkey model to define parameters critical to disease progression and the extent to which they correlate with human disease. African green monkeys were inoculated by the intratracheal route with 2.5 × 10(4) plaque forming units of the Malaysia strain of Nipah virus. Physiological data captured using telemetry implants and assessed in conjunction with clinical pathology were consistent with shock, and histopathology confirmed widespread tissue involvement associated with systemic vasculitis in animals that succumbed to acute disease. In addition, relapse encephalitis was identified in 100% of animals that survived beyond the acute disease phase. Our data suggest that disease progression in the African green monkey is comparable to the variable outcome of Nipah virus infection in humans.

Ebolavirus disease causes high mortality, and the current outbreak has spread unabated through West Africa. Human adenovirus type 5 vectors (rAd5) encoding ebolavirus glycoprotein (GP) generate protective immunity against acute lethal Zaire ebolavirus (EBOV) challenge in macaques, but fail to protect animals immune to Ad5, suggesting natural Ad5 exposure may limit vaccine efficacy in humans. Here we show that a chimpanzee-derived replication-defective adenovirus (ChAd) vaccine also rapidly induced uniform protection against acute lethal EBOV challenge in macaques. Because protection waned over several months, we boosted ChAd3 with modified vaccinia Ankara (MVA) and generated, for the first time, durable protection against lethal EBOV challenge.

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.

There is limited knowledge of the pathogenesis of human ebolavirus infections and no reported human cases acquired by the aerosol route. There is a threat of ebolavirus as an aerosolized biological weapon, and this study evaluated the pathogenesis of aerosol infection in 18 rhesus macaques. Important and unique findings include early infection of the respiratory lymphoid tissues, early fibrin deposition in the splenic white pulp, and perivasculitis and vasculitis in superficial dermal blood vessels of haired skin with rash. Initial infection occurred in the respiratory lymphoid tissues, fibroblastic reticular cells, dendritic cells, alveolar macrophages, and blood monocytes. Virus spread to regional lymph nodes, where significant viral replication occurred. Virus secondarily infected many additional blood monocytes and spread from the respiratory tissues to multiple organs, including the liver and spleen. Viremia, increased temperature, lymphocytopenia, neutrophilia, thrombocytopenia, and increased alanine aminotransferase, aspartate aminotransferase, γ-glutamyl transpeptidase, total bilirubin, serum urea nitrogen, creatinine, and hypoalbuminemia were measurable mid to late infection. Infection progressed rapidly with whole-body destruction of lymphoid tissues, hepatic necrosis, vasculitis, hemorrhage, and extravascular fibrin accumulation. Hypothermia and thrombocytopenia were noted in late stages with the development of disseminated intravascular coagulation and shock. This study provides unprecedented insight into pathogenesis of human aerosol Zaire ebolavirus infection and suggests development of a medical countermeasure to aerosol infection will be a great challenge due to massive early infection of respiratory lymphoid tissues. Rhesus macaques may be used as a model of aerosol infection that will allow the development of lifesaving medical countermeasures under the Food and Drug Administration’s animal rule.

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.

Lassa virus (LASV) is a significant human pathogen that is endemic to several countries in West Africa. Infection with LASV leads to the development of hemorrhagic fever in a significant number of cases, and it is estimated that thousands die each year from the disease. Little is known about the complex immune mechanisms governing the response to LASV or the genetic determinants of susceptibility and resistance to infection. In the study presented here, we have used a whole-genome, microarray-based approach to determine the temporal host response in the peripheral blood mononuclear cells (PBMCs) of non-human primates (NHP) following aerosol exposure to LASV. Sequential sampling over the entire disease course showed that there are strong transcriptional changes of the immune response to LASV exposure, including the early induction of interferon-responsive genes and Toll-like receptor signaling pathways. However, this increase in early innate responses was coupled with a lack of pro-inflammatory cytokine response in LASV exposed NHPs. There was a distinct lack of cytokines such as IL1β and IL23α, while immunosuppressive cytokines such as IL27 and IL6 were upregulated. Comparison of IRF/STAT1-stimulated gene expression with the viral load in LASV exposed NHPs suggests that mRNA expression significantly precedes viremia, and thus might be used for early diagnostics of the disease. Our results provide a transcriptomic survey of the circulating immune response to hemorrhagic LASV exposure and provide a foundation for biomarker identification to allow clinical diagnosis of LASV infection through analysis of the host response., Author Summary Lassa virus (LASV), a member of the Arenaviridae family, is a viral hemorrhagic fever causing virus endemic to several countries in West Africa with a history of sporadic importation into the United States. It has been characterized as a Category A agent, and despite the significant public health issues posed by LASV and the potential biodefense risks, little is known about the immune response to the virus. In the study presented here, we have taken an unbiased genomics approach to map the temporal host response in the peripheral blood mononuclear cells (PBMCs) of non-human primates (NHP) exposed to LASV. Gene expression patterns over the entire disease course showed that there are strong transcriptional changes of the immune response to LASV exposure, including the upregulation of Toll-like receptor signaling pathways and innate antiviral transcription factors. However, there was a lack of pro-inflammatory cytokine response in LASV exposed NHPs similar to what is seen in human disease. Our data suggests that LASV induces negative regulation of immunological events, leading to an inefficient adaptive immune response as observed in LASV-infected human patients. Our results provide a picture of the host's circulating immune response to hemorrhagic LASV exposure and demonstrate that gene expression patterns correlate with specific stages of disease progression.

Detailed ultrastructural studies of Rift Valley fever virus (RVFV) in the mouse model are needed to develop and characterize a small animal model of RVF for the evaluation of potential vaccines and therapeutics. In this study, the ultrastructural features of RVFV infection in the mouse model were analyzed. The main changes in the liver included the presence of viral particles in hepatocytes and hepatic stem cells accompanied by hepatocyte apoptosis. However, viral particles were observed rarely in the liver; in contrast, particles were extremely abundant in the CNS. Despite extensive lymphocytolysis, direct evidence of viral replication was not observed in the lymphoid tissue. These results correlate with the acute-onset hepatitis and delayed-onset encephalitis that are dominant features of severe human RVF, but suggest that host immune-mediated mechanisms contribute significantly to pathology. The results of this study expand our knowledge of RVFV–host interactions and further characterize the mouse model of RVF.

Nine rhesus macaques were implanted with multisensor telemetry devices and internal jugular vein catheters before being infected with Zaire ebolavirus. All animals developed viremia, fever, a hemorrhagic rash, and typical changes of Ebola hemorrhagic fever in clinical laboratory tests. Three macaques unexpectedly survived this usually lethal disease, making it possible to compare physiological parameters in lethally challenged animals and survivors. After the onset of fever, lethal illness was characterized by a decline in mean arterial blood pressure, an increase in pulse and respiratory rate, lactic acidosis, and renal failure. Survivors showed less pronounced change in these parameters. Four macaques were randomized to receive supplemental volumes of intravenous normal saline when they became hypotensive. Although those animals had less severe renal compromise, no apparent survival benefit was observed. This is the first report of continuous physiologic monitoring in filovirus-infected nonhuman primates and the first to attempt cardiovascular support with intravenous fluids.

The mechanisms of Ebola (EBOV) pathogenesis are only partially understood, but the dysregulation of normal host immune responses (including destruction of lymphocytes, increases in circulating cytokine levels, and development of coagulation abnormalities) is thought to play a major role. Accumulating evidence suggests that much of the observed pathology is not the direct result of virus-induced structural damage but rather is due to the release of soluble immune mediators from EBOV-infected cells. It is therefore essential to understand how the candidate therapeutic may be interrupting the disease process and/or targeting the infectious agent. To identify genetic signatures that are correlates of protection, we used a DNA microarray-based approach to compare the host genome-wide responses of EBOV-infected nonhuman primates (NHPs) responding to candidate therapeutics. We observed that, although the overall circulating immune response was similar in the presence and absence of coagulation inhibitors, surviving NHPs clustered together. Noticeable differences in coagulation-associated genes appeared to correlate with survival, which revealed a subset of distinctly differentially expressed genes, including chemokine ligand 8 (CCL8/MCP-2), that may provide possible targets for early-stage diagnostics or future therapeutics. These analyses will assist us in understanding the pathogenic mechanisms of EBOV infection and in identifying improved therapeutic strategies.

The use of adenoviruses (Ad) as vaccine vectors against a variety of pathogens has demonstrated their capacity to elicit strong antibody and cell-mediated immune responses. Adenovirus serotype C vectors, such as Ad serotype 5 (Ad5), expressing Ebolavirus (EBOV) glycoprotein (GP), protect completely after a single inoculation at a dose of 10 10 viral particles. However, the clinical application of a vaccine based on Ad5 vectors may be hampered, since impairment of Ad5 vaccine efficacy has been demonstrated for humans and nonhuman primates with high levels of preexisting immunity to the vector. Ad26 and Ad35 segregate genetically from Ad5 and exhibit lower seroprevalence in humans, making them attractive vaccine vector alternatives. In the series of studies presented, we show that Ad26 and Ad35 vectors generate robust antigen-specific cell-mediated and humoral immune responses against EBOV GP and that Ad5 immune status does not affect the generation of GP-specific immune responses by these vaccines. We demonstrate partial protection against EBOV by a single-shot Ad26 vaccine and complete protection when this vaccine is boosted by Ad35 1 month later. Increases in efficacy are paralleled by substantial increases in T- and B-cell responses to EBOV GP. These results suggest that Ad26 and Ad35 vectors warrant further development as candidate vaccines for EBOV.

Summary Background We previously showed that small interfering RNAs (siRNAs) targeting the Zaire Ebola virus (ZEBOV) RNA polymerase L protein formulated in stable nucleic acid-lipid particles (SNALPs) completely protected guineapigs when administered shortly after a lethal ZEBOV challenge. Although rodent models of ZEBOV infection are useful for screening prospective countermeasures, they are frequently not useful for prediction of efficacy in the more stringent non-human primate models. We therefore assessed the efficacy of modified non-immunostimulatory siRNAs in a uniformly lethal non-human primate model of ZEBOV haemorrhagic fever. Methods A combination of modified siRNAs targeting the ZEBOV L polymerase (EK-1 mod), viral protein (VP) 24 (VP24-1160 mod), and VP35 (VP35-855 mod) were formulated in SNALPs. A group of macaques (n=3) was given these pooled anti-ZEBOV siRNAs (2 mg/kg per dose, bolus intravenous infusion) after 30 min, and on days 1, 3, and 5 after challenge with ZEBOV. A second group of macaques (n=4) was given the pooled anti-ZEBOV siRNAs after 30 min, and on days 1, 2, 3, 4, 5, and 6 after challenge with ZEBOV. Findings Two (66%) of three rhesus monkeys given four postexposure treatments of the pooled anti-ZEBOV siRNAs were protected from lethal ZEBOV infection, whereas all macaques given seven postexposure treatments were protected. The treatment regimen in the second study was well tolerated with minor changes in liver enzymes that might have been related to viral infection. Interpretation This complete postexposure protection against ZEBOV in non-human primates provides a model for the treatment of ZEBOV-induced haemorrhagic fever. These data show the potential of RNA interference as an effective postexposure treatment strategy for people infected with Ebola virus, and suggest that this strategy might also be useful for treatment of other emerging viral infections. Funding Defense Threat Reduction Agency.

A major challenge in developing vaccines for emerging pathogens is their continued evolution and ability to escape human immunity. Therefore, an important goal of vaccine research is to advance vaccine candidates with sufficient breadth to respond to new outbreaks of previously undetected viruses. Ebolavirus (EBOV) vaccines have demonstrated protection against EBOV infection in nonhuman primates (NHP) and show promise in human clinical trials but immune protection occurs only with vaccines whose antigens are matched to the infectious challenge species. A 2007 hemorrhagic fever outbreak in Uganda demonstrated the existence of a new EBOV species, Bundibugyo (BEBOV), that differed from viruses covered by current vaccine candidates by up to 43% in genome sequence. To address the question of whether cross-protective immunity can be generated against this novel species, cynomolgus macaques were immunized with DNA/rAd5 vaccines expressing ZEBOV and SEBOV glycoprotein (GP) prior to lethal challenge with BEBOV. Vaccinated subjects developed robust, antigen-specific humoral and cellular immune responses against the GP from ZEBOV as well as cellular immunity against BEBOV GP, and immunized macaques were uniformly protected against lethal challenge with BEBOV. This report provides the first demonstration of vaccine-induced protective immunity against challenge with a heterologous EBOV species, and shows that Ebola vaccines capable of eliciting potent cellular immunity may provide the best strategy for eliciting cross-protection against newly emerging heterologous EBOV species., Author Summary Ebola virus causes death, fear, and economic disruption during outbreaks. It is a concern worldwide as a natural pathogen and a bioterrorism agent, and has caused death to residents and tourists of Africa where the virus circulates. A vaccine strategy to protect against all circulating Ebola viruses is complicated by the fact that there are five different virus species, and individual vaccines provide protection only against those included in the vaccine. Making broad vaccines that contain multiple components is complicated, expensive, and poses challenges for regulatory approval. Therefore, in the present work, we examined whether a prime-boost immunization strategy with a vaccine targeted to one Ebola virus species could cross protect against a different species. We found that genetic immunization with vectors expressing the Ebola virus glycoprotein from Zaire blocked infection with a newly emerged virus species, Bundibugyo EBOV, not represented in the vaccine. Protection occurred in the absence of antibodies against the second species and was mediated instead by cellular immune responses. Therefore, single-component vaccines may be improved to protect against multiple Ebola viruses if they are designed to generate this type of immunity.

Nonsurgical intratracheal instillation of 1 μg of purified, recombinant flagellin in several strains of mice stimulated a transient innate immune response in the lung characterized by the infiltration of neutrophils and the rapid production of tumor necrosis factor alpha, interleukin 6, granulocyte colony-stimulating factor, and the chemokines keratinocyte-derived chemokine, MIP1α, and MIP-2.

Background Lassa virus and Marburg virus are two causative agents of viral hemorrhagic fever. Their diagnosis is difficult because patients infected with either pathogen present similar nonspecific symptoms early after infection. Current diagnostic tests are based on detecting viral proteins or nucleic acids in the blood, but these cannot be found during the early stages of disease, before the virus starts replicating in the blood. Using the transcriptional response of the host during infection can lead to earlier diagnoses compared to those of traditional methods. Results In this study, we use RNA sequencing to obtain a high-resolution view of the in vivo transcriptional dynamics of peripheral blood mononuclear cells (PBMCs) throughout both types of infection. We report a subset of host mRNAs, including heat-shock proteins like HSPA1B, immunoglobulins like IGJ, and cell adhesion molecules like SIGLEC1, whose differences in expression are strong enough to distinguish Lassa infection from Marburg infection in non-human primates. We have validated these infection-specific expression differences by using microarrays on a larger set of samples, and by quantifying the expression of individual genes using RT-PCR. Conclusions These results suggest that host transcriptional signatures are correlated with specific viral infections, and that they can be used to identify highly pathogenic viruses during the early stages of disease, before standard detection methods become effective. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-960) contains supplementary material, which is available to authorized users.

The family Bunyaviridae is a diverse group of negative-strand RNA viruses that infect a wide range of arthropod vectors and animal hosts. Based on the continuing need for new therapeutics to treat bunyavirus infections, we evaluated the potential efficacy of FGI-106, a small-molecular compound that previously demonstrated activity against different RNA viruses. FGI-106 displayed substantial antiviral activity in cell-based assays of different bunyavirus family members, including Asian and South American hantaviruses (Hantaan virus and Andes virus), Crimean-Congo hemorrhagic fever virus, La Crosse virus, and Rift Valley fever virus. The pharmacokinetic profile of FGI-106 revealed sufficient exposure of the drug to critical target organs (lung, liver, kidney, and spleen), which are frequently the sites of bunyavirus replica- tion. Consistent with these findings, FGI-106 treatment delivered via intraperitoneal injection prior to virus exposure was sufficient to delay the onset of Rift Valley fever virus infection in mouse-based models and to enhance survival in the face of an otherwise lethal infection. Alto- gether, these results suggest a potential opportunity for the use of FGI-106 to treat infections by members of the family Bunyaviridae.