HIV vaccine development.

Updates on the Thai clinical vaccine trial, the discovery of additional neutralizing antibodies, and several new, nonhuman primate vaccine studies were presented at the 17th Conference on Retroviruses and Opportunistic Infections this year. Interestingly, the vaccine effect observed in the Thai trial diminished with time and was most effective in individuals who reported low-risk behavior. Two new neutralizing monoclonal antibodies were reported that were more potent and broadly reactive than the previously described monoclonal antibodies, giving the neutralization field an important boost. New studies were presented in macaques showing that a DNA prime modified vaccinia virus Ankara boost regimen can reduce acquisition of infection after a low-dose mucosal challenge with a heterologous pathogenic simian immunodeficiency virus (SIV) strain. Data suggesting that attenuated SIV vaccines can induce cellular immune responses that control viral replication were also discussed. Finally, and perhaps most encouragingly, vaccination with cytomegalovirus-expressing SIV antigens provided robust levels of protection against the highly pathogenic SIVmac239 viral isolate. All of these promising results should serve to energize the HIV vaccine field.