PRIMING WITH TAT-DELETED CAPRINE ARTHRITIS-ENCEPHALITIS VIRUS (CAEV) PROVIRAL DNA OR LIVE VIRUS PROTECTS GOATS FROM CHALLENGE WITH PATHOGENIC CAEV

We previously reported that infection of goats with caprine arthritis encephalitis virus (CAEV) tat- proviral DNA or virus results in persis tent infection, since the animals seroconverted and direct virus isola tion from cultures of blood derived macrophages was positive. In this study we wanted to determine whether goats injected with CAEV tat- pro viral DNA or virus were protected against challenge with the pathogeni c homologous virus and to investigate whether CAEV tat- was still path ogenic. All animals injected with CAEV tat- became infected as indicat ed by seroconversion and virus isolation. Challenge at 8 or 9 months p ostinfection demonstrated protection in four of four animals injected with CAEV tat- but did not in three of three mock-inoculated challenge d goats. Challenge virus was undetectable in the blood macrophages of protected animals during a period of 6 or 10 months postchallenge. In two of four protected animals, however, we were able to detect the cha llenge wild-type virus by reverse transcriptase PCR on RNA directly ex tracted from synovial membrane cells surrounding the inoculation site. This result suggests that protection was achieved without complete st erilizing immunity. Animals injected with CAEV tat- and mock challenge d developed inflammatory lesions in the joints, although these lesions were not as severe as those in CAEV wild-type-injected goats. These r esults confirm the dispensable role of Tat in CAEV replication in vivo for the establishment of infection and pathogenesis and demonstrate i n another lentivirus infection model the efficacy of live attenuated v iruses to induce resistance to superinfection.