NPR's "All Things Considered" on Friday examined the impact the Multicenter AIDS Cohort Study has had on HIV-positive men who have sex with men over the past 25 years. Roger Detels, the director of MACS in Los Angeles and a professor of epidemiology at UCLA, said the study began in 1981 when very little was known about the virus. At the time, "there was no test for the virus, and there was no recognition that in fact there was a virus origin," he said. According to "All Things Considered," more than 6,000 MSM have participated in MACS, which is funded by NIH.

The men who participated in the study were required to undergo two thorough physical exams twice per year that include neurological exams and spinal taps, "All Things Considered" reports. In addition, they were questioned in detail about sexual practices, medical visits and symptoms. Many of the participants stayed in the study until they died, unlike many studies in which participants remove themselves for several reasons. "All Things Considered" reports that the study led to many discoveries, including how HIV is spread, how the body is not protected from the virus by the immune system and how long it takes HIV to progress to AIDS. Researchers also were able to determine the extent of the epidemic, especially among MSM.

Detels said the most significant discovery from MACS is that "there are some men who had many, many partners, and they never became infected." He said that it took a long time for researchers to understand why this occurred but that the study helped researchers determine that a small percentage of people have genes that prevent HIV transmission. Detels said that knowledge of those genes could eventually lead to a vaccine to prevent the spread of HIV. The segment also included comments from Stephen Jerrome, who was one of MACS' first participants (Wilson, "All Things Considered," NPR, 4/24).

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