The AIDS Vaccine 2012 conference took place in Boston September 9–12, organized by the Global HIV/AIDS Vaccine Enterprise, the Ragon Institute of MGH, MIT and Harvard, and the Havard Center for AIDS Research. Webcasts of all the conference sessions are now available online, and the abstracts have been posted as a a supplement to the open-access journal Retrovirology. Topics of discussion included follow-up from the RV144 Thai vaccine trial (including recently published evidence that protection may have been limited to HIV variants with specific genetic sequences in the V2 region of the viral envelope), new approaches to the induction of broadly neutralizing antibodies, the potential importance of a recently identified CD4 T-cell subset named T follicular helper cells, and opportunities for synergy between vaccine research and efforts to cure HIV infection.
Of relevance to the latter topic, Louis Picker presented an update on his studies using a CMV vector to immunize against the highly virulent SIVmac239 in rhesus macaques. Picker's previously published work had suggested that some immunized animals in these studies were progressively clearing SIVmac239 infection, and he showed additional evidence that this is the case. Three animals have now been euthanized after long periods of follow-up (485 to over 1,160 days postchallenge) and analyzed intensively for evidence of SIVmac239 infection. All three had controlled SIVmac239 to undetectable levels with only small blips in viral load seen shortly after challenge; at the time of necropsy no viral load blips had been observed for around 1.5–2 years. No replication-competent SIVmac239 could be detected in any animal, and PCR testing could find viral DNA and RNA only in a limited number of tissues, at extremely low background levels (comparable to PCR results obtained from control animals never exposed to SIVmac239). Picker noted that these findings are unprecedented and may challenge the generally accepted wisdom that lentiviral infections cannot be cleared. He also highlighted the implications for cure research, stating that a study is now under way that will evaluate the CMV vector as a therapeutic vaccine in ART-treated rhesus macaques chronically infected with SIVmac239. In parallel, an ongoing collaboration between Picker's laboratory and the Vaccine & Gene Therapy Institute in Florida is working to design CMV vectors for human trials.