Induction of cell-cell fusion from without by human herpesvirus 6B

Human herpesvirus (HHV) 6A induce fusion from without (FFWO), whereas HHV-6B is believed to be ineffective in this process. Here, we demonstrate that HHV-6B induces rapid fusion in both epithelial cells and lymphocytes. The fusion was identified 1 h postinfection, could be inhibited by antibodies to HHV-6B gH and to the cellular receptor CD46, and was dependent on virus titer but independent of de novo protein synthesis and UV inactivation of the virus. Comparisons indicate that HHV-6A is only 10-fold more effective in inducing FFWO than HHV-6B. These data demonstrate that HHV-6B can induce FFWO in epithelial cells and lymphocytes.