SILVER SPRING, MD — Using genetic sequencing, military scientists have found new evidence that the first vaccine shown to prevent HIV infection in humans also has an effect on viruses in those already infected.
The report, published recently in the online edition of the journal Nature, notes that viruses with two genetic “footprints” were associated with greater vaccine efficacy.1
“This is the first time that we have seen pressure on the virus at the genetic level due to an effective HIV vaccine,” said lead author Morgane Rolland, PhD, a scientist at the U.S. Military HIV Research Program (MHRP).
The analysis revealed evidence of a vaccine-induced immune response on two sites of Env-V2 region located on HIV’s outer coat, and study authors noted that vaccine efficacy increased to 80% for viruses carrying these two particular signatures.
“These findings reinforce both the RV144 result and the previous study showing that antibodies directed at the V1V2 region reduce the risk of infection. Taken together, the work suggests that the Env-V2 region could be a critical target for future HIV vaccines,” noted senior author Col. Jerome Kim, MD.
Researchers examined HIV genome sequences from 110 volunteers who participated in the Thai HIV vaccine trial, RV144, and who subsequently became infected with HIV. They focused on the V2 portion of the HIV virus after a study published earlier in 2012 found that antibodies specific to the V1V2 region of the HIV genome correlated with lower risk of infection.
The new genetic sequencing study showed that the viruses that broke through or escaped from these immune responses have genetic differences in the same V2 region, indicating that the vaccine exerted pressure in this region. HIV viruses that escape from antibodies have genetic footprints, or mutations, that can prevent them from being recognized by the immune system.
“This study underscores the realistic optimism you see in the HIV vaccine research field today. We are making substantive progress in understanding what it will take to develop a more effective HIV vaccine which will ultimately help us end this pandemic,” said Col. Nelson Michael, MHPR director.
1. Rolland M, Edlefsen PT, Larsen BB, et. al. Increased HIV-1 vaccine efficacy against viruses with genetic signatures in Env V2. Nature. 2012 Oct 18;490(7420):417-20. doi: 10.1038/nature11519. Epub 2012 Sep 10. PubMed PMID: 22960785.