Development of antiviral agents acting on host-defense mechanisms rather than on specific viral pathways is needed to achieve broad-antiviral action. Statins, the LDL-Cholesterol lowering drugs, can reduce the proliferation of HIV-1, influenza-A, polio, hepatitis-C, dengue, and measles. This broad-spectrum of antiviral action suggests effects on cellular pathways employed for viral replication. These fascinating observations, led us to study the mechanisms of statins' antiviral actions. Here, we hypothesize that depletion of cellular cholesterol-rich membrane domains, also known as lipid rafts, may explain statins' antiviral actions. Viruses that are enveloped carry with them a piece of the cellular membrane when they bud out of their hosts. This process involves interactions of viral particles with lipid rafts. We thus hypothesize that lowering membrane cholesterol with statins reduces virus budding and virulence (infectivity). Simvastatin, a statin prototype, inhibits the proliferation of Vesicular Stomatitis Virus (VSV), an enveloped oncolytic virus. This effect may result from disruption of lipid rafts. Methyl-b-cyclodextrin (MbCD) is the reference compound employed to disrupt lipid rafts, due to sequestering of membrane cholesterol. If our hypothesis is correct, MbCD, like simvastatin, should exert anti-VSV effects. Studies on the subcellular distribution of Flotilin-1 protein, a lipid-raft marker, and on Flotilin-1 co-localization with VSV, would establish simvastatin effects on lipid rafts and presence of envelope defects of budded viruses. Simvastatin effects on lipid rafts, oncolytic VSV replication and infectivity will be compared with those of MbCD. Our long-term aim is to understand the mechanisms of statins' antiviral actions, and its possible applications. Here, we will investigate if disruption of lipid rafts explains statins' anti-VSV actions. Specific Aim 1: To determine if Simvastatin induces lipid raft disruption. Specific Aim 2: To determine if lipid raft disruption affects VSV replication and infectivity. The study may lead to innovative observations on antiviral and oncolytic cancer research.