Immunization of Macaca fascicularis with inactivated SIV preparations: challenge with human- or monkey-derived SIV and the effects of a longer immunization schedule.

In cynomolgus monkeys, we compared two human-derived SIVmac251 whole virus vaccines, a long vs short immunization schedule, and two different challenge viruses. Both vaccines induced protection after challenge with human-derived SIVmac251/32H. There was no difference between the two schedules of immunization. Seven monkeys, five of which were protected following the first challenge, were reboosted and rechallenged with monkey-derived SIVmac251, but no protection was observed. The titers of anti-human cell or -SIV neutralizing antibodies were not related to protection.