Gene Pattern Helps Postpone AIDS Progression

People who have a particular genetic pattern are less likely than others to progress quickly to AIDS when infected with HIV, according to research published in Monday's online edition of Nature Genetics. The genetic pattern includes a gene that codes for a receptor on the surface of natural killer cells and a gene that codes for an HLA protein on the surface of white blood cells and other tissues in the body.

Natural killer cells are one component of the body's immune system and play a key role in fighting viruses. HLA markers, which vary from person to person, are involved in the body's ability to distinguish its own cells from those of foreign invaders. HLA markers help direct immune system cells toward HIV, and lower-than-normal levels of HLA on a virally infected cell can trigger an attack.

The study's lead author, Dr. Mary Carrington of the National Cancer Institute, and her team analyzed the genetic makeup of more than 900 HIV-infected patients and found that while it was less common in African-Americans, around 10 percent of whites carry the genetic pattern that encodes the particular receptor and the HLA protein that attaches to it. Those patients were more likely than those without this genetic pattern to experience a delay in the progression of HIV to AIDS -- a delay that, in many cases, lasted more than 12 years.

In an interview with Reuters, Carrington said she suspects that when a cell that contains that specific type of HLA becomes infected with HIV, the HLA instructs natural killer cells to destroy the infected cell, helping the immune system keep the virus at low levels without eliminating it entirely. But the receptor and the HLA need to work together, she said. People who carry the genetic pattern for either one and not the other will not experience the same delayed progression to AIDS as those who carry both.

"Overall, when you look at the entire group [of people carrying this genetic pattern], they develop AIDS more slowly than everybody else," said Carrington. However, the genetic pattern is not the only factor that plays a role in AIDS progression, and its presence is not a guarantee that a person will stave off AIDS, Carrington added. Not everyone who has this particular gene will slowly progress to AIDS and some people who do not have the genetic pattern will also experience a postponed progression to AIDS, she said. Consequently, she said it would be unwise to test newly infected patients for the pattern, to keep people from labeling themselves as "doomed" or "protected" based on the results.

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