THURSDAY, Nov. 4 (HealthDay News) -- Variations in an immune system protein explain the rare ability of some HIV-infected people to remain healthy without having to take any medications, scientists say.

The finding could help in efforts to develop new HIV treatments and vaccines, the study authors pointed out.

The immune system is able to suppress viral replication and keep viral load at extremely low levels in about one in 300 HIV patients. These patients are called HIV controllers.

U.S. researchers analyzed the genomes of about 1,000 HIV controllers and 2,600 HIV patients with progressive infection. The controllers had variations in five amino acids in a protein called HLA-B, which alerts the immune system to the presence of infection.

The study was conducted by researchers at the Ragon Institute of Massachusetts General Hospital, MIT and Harvard, and from the Broad Institute of MIT and Harvard.

"We found that, of the three billion nucleotides in the human genome, just a handful make the difference between those who can stay healthy in spite of HIV infection and those who, without treatment, will develop AIDS," co-senior author Dr. Bruce Walker, director of the Ragon Institute, said in a Ragon Institute/Broad Institute news release.

"Earlier studies had showed that certain genes involved with the HLA system were important for HIV control. But they couldn't tell us exactly which genes were involved and how they produced this difference," co-senior author Paul de Bakker, of the Broad Institute and Brigham and Women's Hospital in Boston, said in the news release. "Our findings take us not only to a specific protein, but to a part of that protein that is essential to its function."

The study is published online Nov. 4 in the journal Science.

"HIV is slowly revealing its secrets, and this is yet another," Walker said. "Knowing how an effective immune response against HIV is generated is an important step toward replicating that response with a vaccine. We have a long way to go before translating this into a treatment for infected patients and a vaccine to prevent infection, but we are an important step closer."

More information

The U.S. National Institute of Allergy and Infectious Diseases has more about HIV/AIDS.