In a study published today in the journal Nature Genetics, researchers found that individuals with a particular gene variation progress more slowly from HIV to AIDS, and are also more successful at controlling their viral loads, or the amount of HIV in the blood.

Genes are segments of DNA, and code for certain proteins. In this case, researchers were studying variations in a segment of DNA located just before the gene for HLA-C, a protein that helps the immune system identify viruses and bacteria.

Three possible variants were identified: CC, CT, and TT. Individuals with the CC variant were four times more likely to have low viral loads (less than 2,000 copies per mL) than those with the TT variant.

They also tended to progress to AIDS more slowly.

According to Dr. Mary Carrington, lead author of the study, “the study underscores the importance of host genetic variation in controlling HIV and helps to explain why people vary in how well they can control the virus.”

The researchers believe that the variant affects how much of the HLA-C protein is produced. Thus, the CC variant results in more HLA-C protein in the body, which in turn helps control levels of the virus in the blood.

According to Dr. Carrington, “the effects that we see are based on large groups of individuals, which give us power to see the genetic effect in spite of the fact that there are certainly going to be many other genetic factors that play a role in the overall ability of a given individual to control the virus.

“Right now, we have an association between level of HLA-C expression and control of HIV, but it is only an association. We need to determine directly if high levels of HLA-C expression protects against HIV and why.

“Once we know those pieces of the puzzle (which are major obstacles), we might be able to do some experiments to see whether manipulation of HLA-C expression can enhance protection against HIV without causing negative side effects,” said Dr. Carrington.

In the past, another protein in the same family, HLA-B, has been the focus of research related to HIV and AIDS. Specifically, the HLA-B*27 and HLA-B*57 variants of this protein lead to the greatest protection against HIV.

On the other hand, the HLA-B*35 variation has been associated with faster AIDS progression.

Scientists hope that research into mutations that help protect against AIDS will eventually lead to better ways of controlling the virus, or even eliminating it from the body. Research in this area includes a study of certain genes that give individuals full immunity to HIV-1 infection (see related Beacon News).

Genetic testing has also increasingly become a part of treatment for HIV. Many patients already get tested for certain genes, such as HLA-B*5701, which can lead to a hypersensitivity reaction for patients taking Ziagen (abacavir).

Eventually, genetic testing of HIV-positive individuals may be a routine part of determining the best treatment for a person’s genetic makeup and HIV strain (see related Beacon News).

For more information, please see the study in Nature Genetics (abstract).