VACCINATION PROTECTS AGAINST IN-VIVO GROWN FELINE IMMUNODEFICIENCY VIRUS EVEN IN THE ABSENCE OF DETECTABLE NEUTRALIZING ANTIBODIES

So far, vaccination experiments against feline immunodeficiency virus have used in vitro-grown virus to challenge the vaccinated hosts. In t his study, cats were vaccinated with fixed feline immunodeficiency vir us-infected cells and challenged with plasma obtained from cats infect ed with the homologous virus diluted to contain 10 cat 50% infectious doses. As judged by virus culture, PCRs, and serological analyses perf ormed over an 18-month period after the challenge, all of the vaccinat ed cats were clearly protected. Interestingly, prior to challenge most vaccinees lacked antibodies capable of neutralizing a fresh isolate o f the homologous virus.