Geneva, Switzerland -- Although only half of HIV-infected individuals progress to AIDS after 10 years of HIV infection, long-term nonprogressors--individuals remaining disease-free with high CD4 counts more than 10 years after infection--are relatively uncommon.
Researchers in one of the longest-term, large follow-up studies of HIV have found that 11 percent of infected men in their study were long-term nonprogressors (LTNP) at 10 years, but only 2 percent remained nonprogressors after 18 years. All persons with moderate or high plasma viral loads, including LTNPs, should consider antiviral therapy to keep themselves healthy, the researchers said.
Susan Buchbinder, MD, principal investigator of the San Francisco City Clinic Cohort Study, director of the HIV Research Section in the San Francisco Department of Public Health, and assistant clinical professor of medicine and epidemiology at the University of California San Francisco, presented results of the study here today (June 30) at the 12th World AIDS Conference. Among her co-authors was UCSF biostatistics expert Eric Vittinghoff, PhD.
The San Francisco City Clinic Cohort Study has followed 622 HIV-infected men with well-defined dates of HIV seroconversion. At 10 years after seroconversion, 11 percent were identified as LTNP: they had lived with HIV for more than a decade without progressing to full-blown AIDS and their CD4 cell counts remained above 500. Of this group, only an estimated 14 percent will remain LTNP at 18 years after infection (2 percent of the entire group of infected men).
The researchers tested the LTNPs for factors that might contribute to their success in defeating the HIV virus. They conducted genetic tests for protective mutations in two chemokine receptors and found that these are present only in a minority of the LTNP men. With bDNA viral load assays, they charted a wide variation in the levels of virus in the blood of the LTNP group. They found that plasma viral level was the strongest independent predictor of disease progression among the original group of 67 LTNPs.
Because of the link between viral levels and progression to AIDS, the researchers recommended that HIV positive individuals who have avoided progressing to AIDS for many years should consider starting the new combination antiviral therapies if the amount of virus in their plasma rises to moderate levels, even if their CD4 counts remain relatively high.