Fusion of enveloped viruses with sperm cells: Interaction of sendai, influenza, and semliki forest viruses with bull spermatozoa

Incubation of fluorescently labeled Sendai, influenza, as well as Semliki Forest viruses with bull sperm cells resulted in fluorescence dequenching. Fluorescence dequenching was observed with Sendai virus at pH 7.4 while with influenza and Semliki Forest viruses at pH 5.0, a pH value which is required for triggering their fusogenic activity. Control experiments performed with nonfusogenic Sendai and influenza viruses, or with bull sperm cells from which the viral receptors have been removed by treatment with neuraminidase, showed little fluorescence dequenching. These results clearly indicate that animal enveloped viruses are able to interact and to fuse with bull sperm cells. The possibility that following virus-sperm fusion spermatozoa can serve as a carrier of the virus genome and introduce it into recipient eggs during fertilization is discussed.