Doubly damned: Scientists say Indians' genes may accelerate the course of AIDS. Credit: Dibyangshu Sarkar/AFP/Getty Images

The genetic makeup of Indians favors a fast and easy spread of AIDS, Indian scientists have cautioned their government. The presence of certain genetic variants also suggests that an AIDS vaccine developed elsewhere may not be effective in India, they say.

The researchers examined genes for components of the immune system—including the major histocompatibility complex (MHC), chemokines and cytokines—in HIV-positive and control groups in India. The results suggest that Indians are more likely to carry genetic variants that favor faster progression to AIDS, says lead researcher Narinder Mehra, an immunologist at the All India Institute of Medical Sciences (AIIMS) in New Delhi.

A variant of the chemokine coreceptor CCR5, known to protect against HIV infection and found in less than 15% of white people, is absent among Indians, Mehra adds.

Mehra and his colleagues' results are based on their study of 400 Indians. Another study by Akhil Banerjea at India's National Institute of Immunology found one person with the protective CCR5 variant in a group of 145. Further analysis of the CCR5 promoter by the AIIMS researchers suggests that a haplotype associated with fast progression to AIDS is frequent in the Indian gene pool and those linked with slow progression are less common.

The results could have grave implications for India. According to Richard Feachem, director of the Geneva-based Global Fund to Fight AIDS, Tuberculosis and Malaria, India has surpassed South Africa as the nation with the most cases of HIV/AIDS.

Mehra's team has also noted several new genetic variants in the immune system among Indians. The presence of different alleles might mean that Indians present a different side of HIV to the immune system, says Mehra, and render an AIDS vaccine made for the Western world ineffective.

The Indian health ministry, together with the International AIDS Vaccine Initiative, is planning to test an AIDS vaccine in India. The ministry has declined to comment on the AIIMS researchers' findings.

Mehra's argument is true for a vaccine based on small proteins, notes Bruce Walker, professor of medicine at Harvard Medical School. “But if one is making a vector that expresses a larger protein such as gag, this is much less an issue,” Walker says. Still, it is important to know what the immune response is targeting in the clade C virus prevalent in India and in the context of local alleles, he says. “Lots to learn, but I don't think we have reason to say that the current vaccines will not be useful in India.”

Some researchers note that many factors—such as age, other infections and socioeconomic factors—can affect disease progression. But Simon Mallal, who runs the Centre for Clinical Immunology and Biomedical Statistics at the Royal Perth Hospital in Australia, says an individual's genetics play a significant role in HIV disease susceptibility and progression. “Understanding the genetics will undoubtedly help us develop effective vaccines,” he says.