Possible Mechanisms to Explain the Efficacy of HIV Vaccine

AIDS is a notorious infection that currently does not have a cure. Attempts have been made in last 30 years to develop an effective vaccine to protect against the infection caused by the HIV virus.

A research was conducted by Barton Haynes et al to study the mechanisms behind the effectiveness of an HIV vaccine. The study was published in The New England Journal of Medicine. The study was conducted in Thailand in people receiving an experimental vaccine for HIV.

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More than 16,000 adult volunteers were involved in the RV144 trial. Those receiving the HIV vaccine had 31 percent less chances of being infected with HIV as compared to those receiving placebo, but the reason for the effect was not known.

To understand this issue and to predict which people could possibly get infected, researchers analyzed the blood samples from a subset of participants: 41 of them were vaccinated but later became infected with HIV and 205 participants remain unaffected after vaccination.

The study found that those individuals in whom there was increased binding of the IgG immunoglobulin to a particular part of the HIV viral envelope called the first and second variable regions or V1V2 were well protected against HIV infection.

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This binding might play a significant role in protecting the human cells from infection.

On the other hand, those individuals who showed a high binding of the IgA antibody to the first constant region or C1 region of the viral envelope showed less protection from the HIV virus. It was suggested that these antibodies may mitigate the protective effect of other protective antibodies.

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The study thus explains the possible immune mechanisms responsible for the benefit of the HIV vaccine used in the RV1444 trial in preventing HIV. The study may serve as a guide to the development of an efficacious vaccine for HIV in the future.

Reference:

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1. Immune-Correlates Analysis of an HIV-1 Vaccine Efficacy Trial; Barton Haynes et al; N Engl J Med 2012; 366:1275-1286 April 5, 2012

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