Health

SOME people are more susceptible to infectious diseases than others and now we are starting to understand why. Variants of two genes predict how likely we are to contract HIV if exposed to it, and how rapidly it may develop into AIDS. These same genes may also play a role in other infectious diseases.

AIDS comes about through an exposure to HIV followed by infection, viral replication and a subsequent depletion of the immune cells. This drop increases a person's vulnerability to opportunistic infections, which eventually prove fatal. But just how quickly this process happens varies enormously between individuals.

Two years ago, Sunil Ahuja at the University of Texas Health Sciences Center and Matthew Dolan at Wilford Hall US Airforce Medical Center, both in San Antonio, showed that people with multiple copies of a gene called CCL3L1 are more resistant to HIV infection and, if infected, are slower to develop AIDS.

Now the same team has found that people with one or no copies of the CCL3L1 gene, but who possess a specific variant of the CCR5 gene, have weaker cell-mediated immunity - which is critical in fighting many diseases (Nature Immunology, DOI: 10.1038/ni1521).

"It's not an even race," says Dolan. "Some people will do well and some will do poorly. And some of that is preordained."

He says that CCL3L1 and CCR5 account for about 6 per cent of individual variability in the rate at which people progress to AIDS.

HIV and AIDS - Learn more about the worst pandemic in human history in our continuously updated special report.

Genetics - Keep up with the pace in our continually updated special report.

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