Characteristics of cell fusion induced by a caprine retrovirus

The mechanism of cell-fusion induced by caprine arthritis-encephalitis virus (CAEV) was investigated. Following infection with concentrated CAEV, cell fusion occurred prior to the production of infectious progeny virus. The time of initial detection of cell fusion was dependent on the multiplicity of infection and was not detected until 5 hours after infection. The virus-induced cell fusion was only partially inhibited by ultraviolet irradiation of the virus and was not inhibited by cytosine arabinoside. The results indicated that fusion by CAEV was a slow response to direct interaction of input virus with cells (fusion from without) and that virus replication was not required.