SIVMAC vaccine studies using whole inactivated virus antigen sequentially depleted of viral proteins

Groups of four rhesus monkeys were immunised at 0, 1, 2, and 13 months with whole inactivated SICmac32H, SIVmac depleted of the outer envelope glycopr otein gp130, virus cores depleted of the lipid membrane (and hence transmem brane glycoproteins), or purified gag protein. These macaques plus controls were challenged with either the homologous SIVmac251-32H grown in human ce lls or the same virus passed once through monkey cells. None of those chall enged with monkey-grown virus were protected, whereas all in the whole and gp130-depleted virus groups, and one in the core group resisted challenge w ith human-grown virus. As the only difference between the challenge viruses was a single in vitro passage in monkey cells it can be concluded that pro tection was solely due to human cell components. Finally, passive transfer of high titer IgG from monkeys infected with the homologous challenge virus failed to protect monkeys from infection despite the presence of circulati ng neutralising antibodies.