CD8+ T Cells Function Better in HIV ‘Nonprogressors’ Than in Other HIV Patients, Study Says

The CD8+ T cells of "nonprogressors," a "rare" subset of HIV-positive individuals who do not take antiretroviral drugs but whose disease is not progressing to AIDS, function better than the CD8+ T cells of other HIV-positive individuals, according to a study published in the current online issue of the journal Nature Immunology, Reuters Health reports (Stenson, Reuters Health, 10/7). Dr. Mark Connors of the National Institute of Allergy and Infectious Diseases and colleagues compared the immune system function of 15 nonprogressors, each of whom had been HIV-positive for up to 20 years, with 25 other HIV-positive individuals for whom HIV would progress to AIDS if the virus were left untreated (NIAID release, 10/6). The researchers report that the CD8+ T cells of the nonprogressors "divided rapidly" when they came in contact with HIV-infected CD4+ T cells, indicating that they were fighting the virus, while the CD8+ T cells in the progressors did not. They also observed that the nonprogressors' CD8+ T cells produced more perforin, an "HIV-killing" protein, than the cells of progressors. "This is the first time we found something different" in the immune systems of progressors and nonprogressors, Connors said, adding that no other differences in the two groups' immune systems were observed (Reuters Health, 10/7). Previous research had suggested that HIV-positive progressors had "too few" CD8+ T cells to effectively fight HIV (New York Post, 10/8).

Implications for Vaccine Research
The researchers' examinations of the immune systems of nonprogressors could aid in the development of effective AIDS vaccines, as many potential vaccines try to elicit a "strong CD8+ T cell response," similar to the response produced by nonprogressors. "Understanding the mechanisms by which the immune systems of long-term nonprogressors control HIV is important to our development of effective vaccines," NIAID Director Anthony Fauci said, adding, "Studies like this, which reveal basic knowledge about how the immune system interacts with HIV, form the foundation of our effort to fight the disease" (Innes, Scotsman, 10/7). Connors and colleagues are now planning to examine an "even broader array of differences" between the CD8+ T cells of progressors and nonprogressors to better understand why most HIV-positive people have poorly functioning CD8+ T cells (NIAID release, 10/6).