Rapid development of vaccine protection in macaques by live-attenuated simian immunodeficiency virus

Convincing data on experimental vaccines against AIDS have been obtained in the simian immuno-deficiency virus (SIV) macaque model by preinfec-tion with a virus attenuated by a nef deletion. To investigate the efficacy of a nef deletion mutant of SIVmac32H called pC8 as a live-attenuated vaccine after shorter preinfection periods and to learn more about the nature of the immune protection induced, eight rhesus monkeys were infected intravenously with the pC8 virus. All monkeys became persistently infected, exhibiting low cell-associated viral loads, but strong cellular and, in terms of binding anti-bodies, strong humoral antiviral responses. Two of eight pC8-infected monkeys developed an immuno-deficiency and were not challenged. Sequence an