New Insight on Why Some With HIV Can Control Virus

New research suggests that the rare group of people who are infected with HIV for years, receive no treatment and yet show no signs of illness appear to have better function in a certain type of immune system cell than most HIV-positive individuals who cannot control the virus. The findings could lead to new vaccines to prevent and treat HIV infection, said study author Dr. Mark Connors, a senior clinical investigator at the National Institute of Allergy and Infectious Diseases.

Left untreated, most HIV-infected people will begin to develop symptoms of AIDS as their immune systems weaken and they are unable to fend off the replicating virus. But in the small number of patients known as nonprogressors, viral levels in the bloodstream remain low and AIDS does not develop, even though the patient is not treated. Some nonprogressors have now lived as long as two decades with no signs of AIDS.

The latest study, published in the online version of Nature Immunology ("HIV-specific CD8+ T cell proliferation is coupled to perforin expression and is maintained in nonprogressors," 10.07.02, doi:10.1038/ni845), involved a detailed comparison of the immune system function of nonprogressors and progressors. Results showed that the nonprogressors' HIV-fighting CD8 T cells divided rapidly when confronted with HIV-infected CD4 cells, whereas those of progressors did not. In addition, the CD8 cells of the nonprogressors produced more of the HIV-killing protein perforin. Connors described perforin as "a critical molecule that's part of the machinery for killing the infected cell."

The findings suggest that the CD8 cells of nonprogressors respond better than those of progressors when called into action against the virus, Connors said. The results offer new insight into why most people with HIV cannot keep the virus in check naturally and must take powerful antiviral medications to help prevent the disease from progressing, he said. "Understanding the mechanisms by which the immune systems of long-term nonprogressors control HIV is important to our development of effective vaccines," Dr. Anthony Fauci, director of NIAID said in a statement.

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