Hepatitis C virus Cell-to-cell Spread Assay.

Hepatitis C virus (HCV) can infect naïve cells via entry of "cell-free" extracellular virus or direct "cell-to-cell" transmission. Here, we describe an assay for detecting HCV cell-to-cell transmission, using a non-growing cell culture system that avoids confounding effects of cell growth. The assay consists of infecting a small number of cells in a confluent monolayer and then blocking subsequent cell-free extracellular virions with a neutralizing antibody such that only cell-to-cell transmission may occur. Under these conditions, incubation at 37 °C results in the formation of infected cell foci. The extent of cell-to-cell spread can then be determined by counting the number of cells in each focus. The assay may be modified to assess the effects of inhibitors and/or specific cellular genes on cell-to-cell spread of HCV.