Polykaryocytosis induced by vesicular stomatitis virus infection in BHK-21 cells

Cytopathological effects by vesicular stomatitis virus (VSV) infection were studied in several cell lines. Marked polykaryocyte formation was observed in monolayers of certain strains of BHK-21 cells infected with VSV. The BHK-21-KB cells were found to be the most susceptible to virus-induced cell fusion. This type of cell fusion was related to intracellular growth of the viruses, and strong cytolytic changes were found to occur following the development of large multinucleated giant cells. The cell-fusing activity was associated with the infectivity of VSV and was neutralized by anti-VSV immune serum. The viruses irradiated for 20 minutes or heated at 60 degrees C for 10 minutes lost completely both infectivity and cell-fusing activity. These experimental results indicate that virus replication was responsible for fusion of BHK cells.