Background
In the SIV/macaque model of HIV in man, live attenuated virus confers the most potent protection against wild-type virus challenge. We have developed a novel live attenuated (nef deleted) vaccine SIVmac239 (SIVrtTA) that is dependent on doxycycline for replication in vivo. Withdrawal of doxycycline prevents replication of SIVrtTA. We used this virus to vaccinate rhesus macaques to investigate the role of virus replication and persistence in protection against SIVmac239 challenge.