In September 2012, analysis of specimens from RV144, the first HIV vaccine clinical trial to show modest efficacy, offered additional clues as to how the vaccine may have worked.13 The findings built on results published in April 2012,14 showing that certain antibodies may have contributed to protection against HIV infection, whereas other antibodies may have mitigated the effects of protection. In light of these results, the year was one of planning and preparing for trials for the Pox-Protein Public-Private Partnership (P5), launched in 2010 to build on the RV144 results; trials are set to begin in Thailand and South Africa in 2016.
A Phase IIb trial ongoing in 2012, HVTN505, was halted in April 2013 after an independent scientific review board determined that the DNA/rAd5 vaccine regimen being tested was not effective in preventing HIV infection. While not providing the answers hoped for by the field, the results allow for homing in on other vaccine strategies currently in development. In 2012, there were more than 30 vaccine candidates in Phase I trials, with new approaches continuing to enter clinical evaluation.
As in 2011, substantial progress was made in preclinical research on broadly neutralizing antibodies. New knowledge regarding the detailed structure of these antibodies, how they are produced by the immune system, and which sites they target on HIV is paving the way for the design of new vaccine candidates that can elicit these antibodies, and ultimately prevent HIV—in most of its variations—from establishing an infection.