Lynn Rasmussen, Carrie Evans, Nichole Tower, Sara McKellip, Miranda Nebane-Akah, E. Lucile White, Melinda Sosa, Jaleesa Garth, Christopher Radka, and James W. Noah
Drug Discovery Division, Southern Research Institute, 2000 9th Avenue S., Birmingham AL 35205
Influenza continues to cause significant global morbidity and mortality in spite of the development of vaccines and therapeutics. Flu vaccines range from very effective to ineffective depending on how well the vaccine serotypes match the circulating strains. A number of effective anti-influenza therapeutics have been developed but the emergence of drug-resistant strains of virus limits their long term usefulness, so there is still a need to develop new therapeutics. Southern Research has a large anti-influenza drug discovery program that screens diverse small molecules against many virus strains using assays that are phenotypic and based on monitoring the viral-induced cytopathic effect (CPE) on the host cell. To validate the performance of the new, commercially-available Viral ToxGlo™ Reagent, multiple viruses and cell types were assayed in the cell-viability assay format. These were Venezuelan equine encephalitis virus (strain TC83) in VeroE6 cells, respiratory syncytial virus (strain A2) in A549 cells, and Dengue virus (serotype 2) in BHK-21 cells. Viability data was compared with the tetrazolium dye MTT, which is a standard endpoint reagent for antiviral assays. Signal-stability and linearity were established in uninfected cells, and signal-to-background ratio, noise ratio, assay sensitivity limits, and Z-values were defined using infected and uninfected cells. As part of the validation, ~30,000 compounds from the Enamine chemical diversity library was screened in parallel against H3N2, H1N1 and H5N1 influenza virus strains. 320 active compounds were identified in these HTS screens, and these were further evaluated using Viral ToxGlo™ by dose response to determine comparative potency and broad spectrum activity against influenza.