By Denise Grady

New York Times 15 Feb. 2002

Research in mice may help explain something that doctors have noticed in people who are infected with H.I.V.: cocaine use seems to make the disease progress faster and lead to more of the opportunistic infections that are the hallmark of AIDS.

The reason is not known. Drug abusers often eat poorly, have unprotected sex and neglect their health in other ways, so it has been impossible to tell whether their problems are due to cocaine itself or to the other habits that often go with addiction.

A new study suggests that cocaine is to blame. In the study, by researchers at the AIDS Institute at the University of California at Los Angeles, specially bred mice were inoculated with human cells and with H.I.V., the virus that causes AIDS, and then given injections of either cocaine or a salt-water placebo. Cocaine greatly enhanced replication of the virus and increased the number of human cells it infected and killed.

Dr. Gayle C. Baldwin, who directed the study, said, "We're talking about a 200-fold increase in viral load in these animals. That is a lot."

In addition, Dr. Baldwin said, the mice given cocaine had only one- ninth as many CD4 cells as the mice given salt water. CD4 cells, also called helper T cells, help to activate other cells of the immune system. They are the prime targets of the AIDS virus, and when they are wiped out, the ability to fight off infections is lost.

The virus also infects other cells, and, Dr. Baldwin said, "We're seeing that the population of cells that are not killed off are churning out incredible amounts of virus."

Why that occurs is not known, she said, adding, "We're working on that right now."

Dr. Baldwin said that cocaine had powerful effects on both the nervous system and the immune system, and that it caused the body to produce steroid hormones and other substances that might affect H.I.V. and its ability to invade cells.

A report on the study will be published in the March issue of The Journal of Infectious Diseases and is being posted today on the Internet at www.journals.uchicago.edu/JID/journal.

Dr. Warner C. Greene, director of the Gladstone Institute of Virology and Immunology at the University of California at San Francisco, who was not involved in the study, said doctors had wondered why cocaine users had a worse course with H.I.V.

"The beauty of this study," Dr. Greene said, "is that it really focuses in and reveals some specific effect of cocaine. One clearly sees that cocaine is doing something to the infection process."

Dr. Greene also said he thought the study would enhance both doctors' and patients' awareness of cocaine's potential to accelerate the course of H.I.V. infection.

"I think it has very significant implications for people infected with H.I.V.," he said.

Dr. Baldwin said that even though the study was done in mice, she thought the findings would apply to people.

"There's always controversy with animal models," she said. "But among people who do H.I.V. research, this is an accepted model. You can't address these questions in a human population. It would be unethical. This model offers us something nothing else really can."

Dr. Greene said, "It's a model, but, boy, the effects they saw were significant."

The mice in the study were inoculated with human cells because mouse cells do not become infected with H.I.V. The mice in the study lacked immune systems, and so would not reject human cells. The mice could then be injected with H.I.V.