Mucosal Challenge Ferret Models of Ebola Virus Disease

Recent studies have shown the domestic ferret (Mustela putorius furo) to be a promising small animal model for the study of Ebola virus (EBOV) disease and medical countermeasure evaluation. To date, most studies have focused on traditional challenge routes, predominantly intramuscular and intranasal administration. Here, we present results from a non-clinical pathogenicity study examining oronasal, oral, and ocular mucosal challenge routes in ferrets. Animals were challenged with 1, 10, or 100 plaque forming units EBOV followed by monitoring of disease progression and biosampling. Ferrets administered virus via oronasal and oral routes met euthanasia criteria due to advanced disease 5–10 days post-challenge. Conversely, all ferrets dosed via the ocular route survived until the scheduled study termination 28-day post-challenge. In animals that succumbed to disease, a dose/route response was not observed; increases in disease severity, febrile responses, serum and tissue viral load, alterations in clinical pathology, and gross/histopathology findings were similar between subjects. Disease progression in ferrets challenged via ocular administration was unremarkable throughout the study period. Results from this study further support the ferret as a model for EBOV disease following oral and nasal mucosa exposure.

Evaluation of the botulinum neurotoxin neutralizing efficiency in immunoglobulin purified from clinical volunteers vaccinated with recombinant botulinum vaccine (46.5)

Efficacy of the Recombinant Botulinum Vaccine A/B (rBV A/B) against lethal intoxication with botulinum neurotoxin complex (BoNT) cannot be evaluated directly in humans; therefore, efficacy will be based on meeting the requirements of the FDA Animal Rule. Serum BoNT neutralizing antibody concentration (NAC) is being proposed as a correlate of protection to evaluate efficacy in nonclinical models. Under this approach, NAC levels in animals vaccinated either with rBV A/B or passively immunized with BoNT neutralizing antibody will be used to estimate the potential level of protection in humans with similar NAC levels. Estimating the level of protection based on NAC requires establishing NAC neutralizing efficiency (the amount of BoNT neutralized per NAC unit). The neutralizing efficiency of human BoNT neutralizing antibody was evaluated using immunoglobulin purified from pooled sera of clinical volunteers vaccinated with rBV A/B. Solutions of immunoglobulin were prepared at three different NAC levels, mixed with serial dilutions of BoNT serotype A or serotype B and injected into mice. At each NAC level, 50% and 99% neutralization of BoNT was determined by probit analysis of mortality dose-response curves. A simple linearly proportional relationship does not exist between NAC level and the amount of BoNT neutralized. Extrapolations of level of protection must consider variability in BoNT neutralizing efficiency at different NAC levels.

Estimating the frequency of tap-water exposures to Mycobacterium avium complex in the U.S. population with advanced AIDS

Mycobacterium avium complex (MAC) is a group of ubiquitous and opportunistic bacterial pathogens included on the U.S. Environmental Protection Agency Drinking Water Contaminant Candidate List. The risk of contracting a disseminated MAC infection is primarily limited to the immunocompromised, including those with advanced acquired immunodeficiency syndrome (AIDS). These infections likely result from exposures to MAC-contaminated tap water, food, or soil, although the epidemiologic evidence is insufficient to implicate a specific medium. The objective of this study was to assess tap water exposure to MAC in the U.S. population with advanced AIDS, defined here as having fewer than 100 CD4(+) cells/mm(3) of blood. Using limited data on the detection of MAC and self-reported post-tap treatment practices, two exposure models were developed to simulate the likelihood of exposure to MAC via tap water consumption in this sensitive population. The first model integrated data from studies that described sources of water for consumption and post-tap treatment rates in cohorts infected with human immunodeficiency virus (HIV(+)). The second model used data from a study that categorized the fraction of water intake consisting of tap water that was not further treated. Approximately 1500 individuals with advanced AIDS were estimated to ingest tap water with detectable concentrations of MAC organisms daily. Additional studies on tap-water use in U.S. HIV(+) populations are needed to confirm these findings. Longitudinal and cross-sectional studies on the occurrence of MAC in tap water, particularly in regions with large HIV(+)/AIDS populations, would help address some of the uncertainty in these exposure estimates.