The Multicenter AIDS Cohort Study is the first and largest study specifically created to examine the natural history of AIDS. This study, which is now in its third decade, involves nearly 7,000 gay men nationwide. The MACS is ongoing at four institutions: UCLA, Northwestern University in Chicago, the University of Pittsburgh, and Johns Hopkins University in Baltimore. The UCLA site is the largest, with 2,000 participants. After more than 25 years, the cumulative drop-out rate is less than 15%, reflecting a high level of commitment and interest on the part of the participants.
MACS participants are seen every 3 to 6 months and undergo a brief physical and mental status examination. In addition, they must donate blood and complete a long questionnaire regarding demographic factors, habits, disease history, and past and present sexual activities. The study has produced some 1200 papers and contributed landmark findings on the epidemiology of HIV infection and the virologic, immunologic, psychosocial, clinical and neurologic aspects of the disease. The MACS confirmed that anal intercourse was the major risk factor of CD4 cell depletion and the development of AIDS. Since then, the study's focus shifted to clarifying how the virus causes disease, how HIV is transmitted, how anti-HIV therapy has affected the participants and the process of aging in HIV-infected men.
According to Roger Detels, Principal Investigator of the UCLA MACS, "We have identified individuals who are very resistant to HIV infection. If we can figure out what the mechanisms of that resistance are, we may be able to start talking about developing protective strategies that are not vaccine-dependent".
Visit the MACS website for more information.
Also see the related "Women's Interagency HIV Study" (WIHS)