"We observed that CD8+ lymphocytes from 23 vaccinated rhesus monkeys inhibited replication of SIV in vitro. Moreover, the magnitude of inhibition prior to challenge was inversely correlated with set point SIV plasma viral loads after challenge. In addition, CD8 cell-mediated viral inhibition in vaccinated rhesus monkeys correlated significantly with Gag-specific, but not Pol- or Env-specific, CD4+ and CD8+ T lymphocyte responses. These findings demonstrate that in vitro viral inhibition following vaccination largely reflects Gag-specific cellular immune responses and correlates with in vivo virologic control following infection. These data suggest the importance of including Gag in an HIV-1 vaccine in which virologic control is desired."
In other words: having Gag or a gag gene included in a vaccine against SIV given to monkeys was more important than having Pol or Env when it came to control of virus replication - although, as has been shown elsewhere, Env responses are important for protecting against acquisition. This has important implications for human vaccines - although "monkeys aren't men, and mice lie" - and in particular for the South African SAAVI vaccines, which elicit quite good Gag-specific cellular responses.
We wait in hope. Graphic showing immune cells associated with HIV control courtesy of Russell Kightley Media.