New research has validated the results of a Thai study that found one HIV vaccine to be moderately successful, and suggests that further retooling of that vaccine could yield efficacy high enough to prevent most HIV infections, aidsmap reports. In the HVTN097 study, a version of the RV144 vaccine—which prevented 4 in 10 of HIV infections in the previous Thai study—was given to 100 HIV-negative people in South Africa.

In this new trial, the vaccine did not prompt a useful cellular immune response.  Some proportion of CD4 cells did become sensitive to HIV: In the South African trial, the CD4 cells had a 69 percent rate of sensitivity, compared with 50 percent in the Thai trial. But only 5 percent of the CD8 cells in the South African trial developed the desired response, while just 0.6 percent of the CD8 cells in the Thai study did so.

The promising results were found in the universal response the vaccine prompted to the gp120 component of HIV, a protein on the surface of the virus that it uses to latch onto immune cells. Additionally, there was a 98.6 percent response rate to a portion of gp120 called the V1-V2 loop.  

Beginning in Janurary 2015, researchers in the HVTN100 trial will test a reformulated vaccine based on RV144 in South Africa. Promising results could lead to a larger trial.

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