Prophylactic treatment for the opportunistic infection known as MAC (Mycobacterium avium complex) can be safely discontinued in most HIV-infected patients whose CD4+ T-cell levels show sustained increases in response to potent antiretroviral therapy, according to interim results of a study supported by the National Institute of Allergy and Infectious Diseases (NIAID). Study Chair Judith Currier, M.D., associate professor of medicine at the University of California, Los Angeles, will present the findings on Monday, Sept. 27, during a late-breaker session at the 39th Interscience Conference on Antimicrobial Agents and Chemotherapy being held in San Francisco.
Before highly active antiretroviral therapy (HAART) became available in the mid-1990s, MAC was one of the most common serious opportunistic infections associated with HIV infection. It usually caused widespread infection in multiple organs, leading to debilitating symptoms and significantly decreased chances of survival.
Nearly two years ago, the AIDS Clinical Trials Group (ACTG), a network of HIV research clinicians supported by NIAID, launched a multicenter study known as ACTG 362. The purpose of the study was to determine if an adequate response to HAART--defined as a sustained rise in CD4+ T cells from less than 50 to more than 100 per cubic millimeter (mm3) of blood--protected HIV-infected individuals from developing MAC infection.
A total of 643 patients enrolled in the two-arm, placebo-controlled study. By random assignment, 321 received placebo and 322 received once-weekly, 1200-milligram (mg) doses of azithromycin, supplied by the drug manufacturer, Pfizer. Azithromycin is one of the standard drug regimens given patients to prevent MAC. Patients whose CD4+ T-cell counts later fell below 50 were switched to open-label azithromycin.
An interim analysis of the data accrued through the end of July 1999 showed that after a median follow-up of 56 weeks, there were no significant differences in the rate of MAC infection between the two arms. Two MAC infections occurred in the placebo group and none in the azithromycin group. Both cases of MAC infection were unusual, being localized to bone and masses along the spine; infection was not found in the blood.
The study investigators say HAART by itself appears to be remarkably successful in preventing the occurrence of MAC. They conclude that the study provides strong evidence indicating that prophylactic therapy for MAC may be safely withdrawn in persons who achieve this degree of response to HAART and maintain CD4+ T-cell counts greater than 50. Also, MAC infection occurring in these patients may be localized and have unusual signs and symptoms.
Another NIAID-supported clinical network, the Community Programs for Clinical Research on AIDS (CPCRA), is currently conducting a similar study. This study, known as CPCRA 048, is chaired by Wafaa El-Sadr, M.D., M.P.H., of Harlem Hospital in New York City. This ongoing study is comparing azithromycin with placebo for preventing MAC and bacterial pneumonia among patients with significant rebound in CD4+ T-cell count. Interim results are similar to the findings of the ACTG study.
For more information, contact the NIAID Office of Communications and Public Liaison at 301-402-1663. Press releases, fact sheets and other NIAID-related materials are available on the NIAID web site at http://www.niaid.nih.gov .