STUDIES OF AIDS VACCINATION USING AN EX-VIVO FELINE IMMUNODEFICIENCY VIRUS MODEL - PROTECTION CONFERRED BY A FIXED-CELL VACCINE AGAINST CELL-FREE AND CELL-ASSOCIATED CHALLENGE DIFFERS IN DURATION AND IS NOT EASILY BOOSTED

Cats immunized with cells infected with a primary isolate of feline im munodeficiency virus (FIV) and fixed with paraformaldehyde were challe nged with cell-free or cell-associated homologous virus obtained ex vi vo. Complete protection was observed in animals challenged with cell-f ree virus-4 months after completion of vaccination (p.v.) or with cell -associated virus 12 months p.v. In contrast, no protection was observ ed in cats challenged with cell-free virus 12 or 28 months p.v or with cell-associated virus 37.5 months p.v. Prior to the 28- and 37.5-mont h challenges, the animals had received a booster dose of vaccine that had elicited a robust anamnestic immune response. These results show t hat vaccine-induced protection against ex vivo FIV is achievable but i s relatively short-lived and can be difficult to boost.