Shiga Toxin Type 2dact Displays Increased Binding to Globotriaosylceramide in vitro and Increased Lethality in Mice after Activation by Elastase

Shiga toxin type 2dact (Stx2dact), an Stx2 variant originally identified from Escherichia coli O91:H21 strain B2F1, displays increased cytotoxicity after activation by elastase present in intestinal mucus. Activation is a result of cleavage of two amino acids from the C-terminal tail of the A2 subunit. In this study, we hypothesized that activation leads to increased binding of toxin to its receptor on host cells both in vitro and in vivo. To test this theory, Stx2dact was treated with elastase or buffer alone and then each toxin was assessed for binding to purified globotriaosylceramide (Gb3) in an enzyme-linked immunosorbent assay, or cells in culture by immunofluorescence, or flow cytometry. Elastase- and buffer-treated Stx2dact were also evaluated for binding to mouse kidney tissue and for relative lethality in mice. We found that activated Stx2dact had a greater capacity to bind purified Gb3, cells in culture, and mouse kidney tissue and was more toxic for mice than was non-activated Stx2dact. Thus, one possible mechanism for the augmented cytotoxicity of Stx2dact after activation is its increased capacity to bind target cells, which, in turn, may cause greater lethality of elastase-treated toxin for mice and enhanced virulence for humans of E. coli strains that express Stx2dact

Natural History of Aerosol-Induced Ebola Virus Disease in Rhesus Macaques

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.</jats:p

Characterization of Ebola Virus Disease (EVD) in Rhesus Monkeys for Development of EVD Therapeutics

Recent Ebola virus (EBOV) outbreaks in West Africa and the Democratic Republic of the Congo have highlighted the urgent need for approval of medical countermeasures for treatment and prevention of EBOV disease (EVD). Until recently, when successes were achieved in characterizing the efficacy of multiple experimental EVD therapeutics in humans, the only feasible way to obtain data regarding potential clinical benefits of candidate therapeutics was by conducting well-controlled animal studies. Nonclinical studies are likely to continue to be important tools for screening and development of new candidates with improved pharmacological properties. Here, we describe a natural history study to characterize the time course and order of progression of the disease manifestations of EVD in rhesus monkeys. In 12 rhesus monkeys exposed by the intramuscular route to 1000 plaque-forming units of EBOV, multiple endpoints were monitored for 28 days following exposure. The disease progressed rapidly with mortality events occurring 7&ndash;10 days after exposure. Key disease manifestations observed consistently across the infected animals included, but were not limited to, viremia, fever, systemic inflammation, coagulopathy, lymphocytolysis, renal tubular necrosis with mineralization, and hepatocellular degeneration and necrosis

Transcriptomic Analysis Reveals Host miRNAs Correlated with Immune Gene Dysregulation during Fatal Disease Progression in the Ebola Virus Cynomolgus Macaque Disease Model

Ebola virus is a continuing threat to human populations, causing a virulent hemorrhagic fever disease characterized by dysregulation of both the innate and adaptive host immune responses. Severe cases are distinguished by an early, elevated pro-inflammatory response followed by a pronounced lymphopenia with B and T cells unable to mount an effective anti-viral response. The precise mechanisms underlying the dysregulation of the host immune system are poorly understood. In recent years, focus on host-derived miRNAs showed these molecules to play an important role in the host gene regulation arsenal. Here, we describe an investigation of RNA biomarkers in the fatal Ebola virus disease (EVD) cynomolgus macaque model. We monitored both host mRNA and miRNA responses in whole blood longitudinally over the disease course in these non-human primates (NHPs). Analysis of the interactions between these classes of RNAs revealed several miRNA markers significantly correlated with downregulation of genes; specifically, the analysis revealed those involved in dysregulated immune pathways associated with EVD. In particular, we noted strong interactions between the miRNAs hsa-miR-122-5p and hsa-miR-125b-5p with immunological genes regulating both B and T-cell activation. This promising set of biomarkers will be useful in future studies of severe EVD pathogenesis in both NHPs and humans and may serve as potential prognostic targets.</jats:p

Characterization of Ebola Virus Disease (EVD) in Rhesus Monkeys for Development of EVD Therapeutics

Recent Ebola virus (EBOV) outbreaks in West Africa and the Democratic Republic of the Congo have highlighted the urgent need for approval of medical countermeasures for treatment and prevention of EBOV disease (EVD). Until recently, when successes were achieved in characterizing the efficacy of multiple experimental EVD therapeutics in humans, the only feasible way to obtain data regarding potential clinical benefits of candidate therapeutics was by conducting well-controlled animal studies. Nonclinical studies are likely to continue to be important tools for screening and development of new candidates with improved pharmacological properties. Here, we describe a natural history study to characterize the time course and order of progression of the disease manifestations of EVD in rhesus monkeys. In 12 rhesus monkeys exposed by the intramuscular route to 1000 plaque-forming units of EBOV, multiple endpoints were monitored for 28 days following exposure. The disease progressed rapidly with mortality events occurring 7–10 days after exposure. Key disease manifestations observed consistently across the infected animals included, but were not limited to, viremia, fever, systemic inflammation, coagulopathy, lymphocytolysis, renal tubular necrosis with mineralization, and hepatocellular degeneration and necrosis.</jats:p

Transcriptomic Analysis Reveals Host miRNAs Correlated with Immune Gene Dysregulation during Fatal Disease Progression in the Ebola Virus Cynomolgus Macaque Disease Model

Ebola virus is a continuing threat to human populations, causing a virulent hemorrhagic fever disease characterized by dysregulation of both the innate and adaptive host immune responses. Severe cases are distinguished by an early, elevated pro-inflammatory response followed by a pronounced lymphopenia with B and T cells unable to mount an effective anti-viral response. The precise mechanisms underlying the dysregulation of the host immune system are poorly understood. In recent years, focus on host-derived miRNAs showed these molecules to play an important role in the host gene regulation arsenal. Here, we describe an investigation of RNA biomarkers in the fatal Ebola virus disease (EVD) cynomolgus macaque model. We monitored both host mRNA and miRNA responses in whole blood longitudinally over the disease course in these non-human primates (NHPs). Analysis of the interactions between these classes of RNAs revealed several miRNA markers significantly correlated with downregulation of genes; specifically, the analysis revealed those involved in dysregulated immune pathways associated with EVD. In particular, we noted strong interactions between the miRNAs hsa-miR-122-5p and hsa-miR-125b-5p with immunological genes regulating both B and T-cell activation. This promising set of biomarkers will be useful in future studies of severe EVD pathogenesis in both NHPs and humans and may serve as potential prognostic targets

A Randomized, Blinded, Vehicle-Controlled Dose-Ranging Study to Evaluate and Characterize Remdesivir Efficacy Against Ebola Virus in Rhesus Macaques

Ebola virus (EBOV) causes severe disease in humans, with mortality as high as 90%. The small-molecule antiviral drug remdesivir (RDV) has demonstrated a survival benefit in EBOV-exposed rhesus macaques. Here, we characterize the efficacy of multiple intravenous RDV dosing regimens on survival of rhesus macaques 42 days after intramuscular EBOV exposure. Thirty rhesus macaques underwent surgical implantation of telemetry devices for the fine-scale monitoring of body temperature and activity, as well as central venous catheters, to enable treatment administration and blood collection. Treatment, consisting of a loading dose of RDV followed by once-daily maintenance doses for 11 days, was initiated 4 days after virus exposure when all animals were exhibiting disease signs consistent with incipient EBOV disease as well as quantifiable levels of EBOV RNA in plasma. In the RDV treatment groups receiving loading/maintenance doses of 5/2.5 mg/kg, 10/5 mg/kg, and 20/10 mg/kg, a total of 6 of 8 (75%), 7 of 8 (87.5%), and 5 of 7 (71.4%) animals survived, respectively. In the vehicle control group, one of seven animals (14.3%) survived. The improved survival rate compared to the control group was statistically significant only for the 10/5 mg/kg RDV treatment group. This treatment regimen also resulted in a significantly lower systemic viral load compared to the vehicle control after a single RDV treatment. All three RDV regimens produced a significantly lower systemic viral load after two treatments. For most animals, RDV treatment, regardless of dose, resulted in the amelioration of many of the clinical&ndash;pathological changes associated with EBOV disease in this model