AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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An Improved Method for Quantification of Ebola virus Titers in Dilute Aerosols
MICHAEL SCHUIT, Rebecca Dunning, Jill Taylor, Katie Beck, Denise Freeburger, Paul Dabisch, BNBI / DHS NBACC
Abstract Number: 525 Working Group: Bioaerosols
Abstract While human-to-human transmission of Ebola virus is thought to occur primarily through direct contact with bodily fluids of infected patients, short-range aerosol transmission remains a possibility, particularly in health-care settings. Previous studies have demonstrated that the infectious dose of Ebola virus is low when inhaled by nonhuman primates. However, difficulty quantifying low concentrations of infectious Ebola virus in air samples complicates studies assessing the potential public health hazard associated with aerosols containing the virus. In light of this problem, the aim of the present study was to improve sampling and quantification methods for low concentrations of Ebola virus in aerosols. Five low-flow aerosol samplers were assessed for physical and biological sampling efficiencies with aerosols of Ebola virus, with the results demonstrating that gelatin filters were both logistically optimal for work in a biocontainment environment and the most efficient sampling method overall. Additionally, a microtitration assay using a fluorescent reporter cell line was found to have equivalent sensitivity to several other methods for quantifying viral titers. However, this method utilized an automated quantification method, which improved throughput and minimized subjectivity. This assay also enables viral infection to be distinguished from other sources of cellular pathology, and facilitated recovery of gelatin filters in smaller liquid volumes than would otherwise be possible due to assay interference from high gelatin concentrations. This resulted in a more concentrated sample and an increased likelihood of detecting infectious virus in dilute samples. The combined sampling and assay improvements identified in this study resulted in an improvement in sensitivity of approximately ten-fold relative to other published methods for quantifying Ebola virus aerosols, and lowered limits of both quantification and detection. The improved sampling and quantification methods developed in this study will enhance future studies examining the inhalational infectivity of and medical countermeasure efficacy following exposure to low concentrations of Ebola virus in animal models of disease. These methods will also enhance detection or high-confidence non-detection of infectious virus in the air surrounding infected patients and/or animal models, including in exhaled breath, as well as assessment of the environmental fate of the virus in aerosols.