Scientists Explore Meth's Role in Immune System

Crystal methamphetamine's effect on the immune system, HIV's progression and the overall AIDS epidemic is receiving fresh scrutiny after New York City health officials reported that a meth-using resident acquired multiple drug-resistant HIV and quickly progressed to AIDS. Experts fear more people, especially gay men, are using the drug -- in many cases, with Viagra -- to engage in unprotected sex with multiple partners.

In the Explore Project -- a long-term study of more than 4,000 gay men sexually active with more than one partner -- researchers found a quarter of the men had tried crystal methamphetamine in the previous six months. All the meth users were HIV-negative at the study's start, but by the end, about 2.1 percent had seroconverted. Independent of behaviors such as unprotected sex with multiple partners -- which was strongly associated with infection -- and injection drug use, men reporting crystal use were twice as likely to contract HIV.

While research is limited, studies in animals and on cell cultures have found that methamphetamine suppresses killer T cells. That, combined with the drug's propensity to dry out mucous membranes, could cause abrasions in the mouth and rectum and slightly increase a person's vulnerability to the virus, said Dr. Antonio Urbina, lead author of a study on crystal meth and HIV published last year in Clinical Infectious Diseases.

In a Journal of Infectious Diseases study of 230 HIV-positive people, two-thirds were either current or former crystal users. Those on antiretroviral medication who used crystal had much higher viral loads than other subjects. One explanation is that meth users, like many drug users, failed to adhere to their drug regimens, said Dr. Igor Grant, a study author. Such irregular adherence can also allow drug-resistant HIV to emerge, according to experts.

Nevertheless, it is meth's role on behavior that most alarms experts. "Being in a sex club for 36 hours on crystal meth and engaging in unprotected anal sex is really the most profound effect," said Dr. Steve Shoptaw, a research psychologist at University of California-Los Angeles' Integrated Substance Abuse programs.

The studies cited include "Crystal Methamphetamine, Its Analogues, and HIV Infection: Medical and Psychiatric Aspects of a New Epidemic," published in Journal of Infectious Diseases (2004;38:890-894) and "Increased Human Immunodeficiency Virus Loads in Active Methamphetamine Users Are Explained by Reduced Effectiveness of Antiretroviral Therapy," published in Journal of Infectious Diseases (2003;188:1820-1826).

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