THE VIF GENE IS ESSENTIAL FOR EFFICIENT REPLICATION OF CAPRINE ARTHRITIS-ENCEPHALITIS VIRUS IN GOAT SYNOVIAL-MEMBRANE CELLS AND AFFECTS THELATE STEPS OF THE VIRUS-REPLICATION CYCLE

Complex retrovirus genomes contain a variable number of accessory gene s, among which is the vif gene. We investigated in vitro the role of t he vif gene of caprine arthritis encephalitis virus (CAEV) by studying the phenotype of five vif mutants after infection of primary goat syn ovial membrane (GSM) cells and blood-derived monocytes/macrophages. An y deletion introduced into the vif gene resulted in slow and low viral replication and production of virions with an infectious titer lower than that of wild-type viral particles. The wild-type phenotype could be restored by the trans expression of the vif gene in a complementati on assay. Quantitative PCR and reverse trariscription-PCR analyses wer e performed in order to determine which stage of the replicative cycle was impaired by the vif deletion. Our results demonstrated that CAEV Vif did not act at the level of reverse transcription or transcription but rather at, the late stage of virus formation and/or release, as l ower amounts of virus were produced after a single replicative cycle. The vif-deleted CAEV produced after 24 h of infection was still able t o infect GSM cells, indicating that the vif gene is not essential for virus infectivity but is required for efficient virus production.