Scientists said on Wednesday they have identified key genes involved in the body’s response to HIV, which causes AIDS - a finding that could narrow the search for an effective vaccine against the deadly illness.

A vaccine is considered the Holy Grail in the battle against the global AIDS epidemic but efforts to find one have been hampered because of HIV’s uncanny ability to mutate.

“We have narrowed down the focus of which particular genes are important in determining the outcome of HIV infection,” said Dr Philip Goulder, of the Partners AIDS Research Center at Massachusetts General Hospital in the United States.

“It tells us where to look, what to put into a vaccine in broad terms, and perhaps what needs to be excluded.”

He and his colleagues focused their research on genes called HLA-A, HLA-B and HLA-C, which produce molecules that sit on the surface of cells. They tell immune system killer T-cells when new viruses are produced within an infected cell and should be destroyed.

The scientists said HLA-B genes are the key players in the body’s response to infections, including HIV.

“HLA-B is where all the action is,” Goulder told Reuters. “Most vaccines take no account of the fundamental biological differences between HLA-A and HLA-B genes. These may be critical to the success or failure of a vaccine.”

In research reported in the science journal Nature, the scientists studied blood samples from 375 HIV-positive patients in South Africa. They discovered that how well a patient’s immune system responded against HIV depended on their version of the HLA-B genes and had little to do with the other genes.

More than 560 versions, or alleles, of HLA-B have been identified.

“It is the responses that are generated through the HLA-B genes that are important,” said Goulder.

The researchers also found that HIV-positive mothers who have a protective version of HLA-B were more likely to survive and less likely to pass on the virus to their children.

“This study identifies the genetic background where the struggle between HIV and the human immune system response occurs,” said Goulder. “The findings will help in understanding precisely how the immune system can succeed or fail against HIV, a prerequisite for a rational approach towards design of an HIV vaccine.”

About 38 million people worldwide, including 25 million in sub-Saharan Africa, are living with HIV/AIDS, according to the latest global report produced by the Joint United Nations Programme on HIV/AIDS (UNAIDS).

Scientists believe even a partially effective vaccine could play an important role in reducing infections.

SOURCE: Nature, December 9, 2004.