MULTICENTER AIDS COHORT STUDY (MACS) PROGRAM

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 second decade, involves nearly 5,000 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 1,637 participants. After more than ten years, the cumulative drop-out rate is less than 15%, reflecting a high level of commitment and interest on the part of the volunteers.

MACS participants are seen every 3 to 6 months and undergo brief physical and mental status examinations. 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 400 papers and contributed landmark findings on the epidemiology of HIV infection and the virologic, immunologic, psychosocial and neurologic aspects of the disease. Before HIV, the virus which causes AIDS was identified, MACS was instrumental in confirming 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, and how anti-HIV therapy has affected the course the epidemic. Currently, MACS investigators are studying men who practice high-risk behaviors but remain uninfected; those who develop AIDS rapidly after HIV infection; those who, despite having fewer than 200 CD4 cells, do not develop AIDS-related diseases for more than three years; and infected men who, without treatment, show stable levels of CD4 cells for at least eight years and have not developed AIDS.

According to Roger Detels, Principal Investigator of the UCLA MACS, "We have begun to define the fact that there are some individuals who are very resistant to HIV infection. If we can figure out what the mechanism of that resistance is, we may be able to start talking about developing protective strategies that are not vaccine-dependent. This is crucial because it's clearly going to be a long time before we come up with a viable vaccine.