Important note: Information in this article was accurate in 1997. The state of the art may have changed since the publication date.

Reuters NewMedia, Inc. - Thursday November 13 11:31 PM EST
Maggie Fox, Health and Science Correspondent

They said tests showed the AIDS virus still lurks in the immune system cells it infects, even after years of taking the powerful drugs.

"The bad news is we can't yet get rid of the virus entirely. The number of immune system cells that remain infected with HIV declines only very slowly," said Dr. Robert Siciliano, an associate professor of medicine at Johns Hopkins University in Baltimore, who worked on one study.

"But the good news is that as long as people infected with HIV keep taking the triple-drug cocktail, they have an excellent chance of surviving the infection for a long time, without developing symptoms of the disease."

Three reports, two in the journal Science and one in the Proceedings of the National Academy of Sciences, show that although multiple drug therapy can stop the AIDS virus from growing and spreading, it has yet to kill it off completely.

The Johns Hopkins researchers, teaming up with Dr. David Ho and colleagues at the Aaron Diamond AIDS Research Center in New York, looked for HIV in 22 patients who had been on the cocktail therapy for as long as 30 months.

People on this cocktail therapy have to take handfuls of pills every day -- many at set times. The side-effects can be very unpleasant and include nausea, so this group was chosen very carefully to make sure they took every pill on time.

Nonetheless, the researchers were able to routinely tease HIV out of "resting" CD4 cells -- helper T-cells that had been infected but were not currently in the replicative phase.

"The team also showed that when the resting cells were stimulated to reproduce, the AIDS virus also replicated," said Diana Finzi, a post-graduate student who led the work.

Siliciano said this did not necessarily mean the infection would rebound naturally in people who quit the drug regime. "It's not clear that these cells will rekindle the infection, but they have got the potential to do so," he said.

There was some positive news.

While on the cocktail regime, all the patients grew more healthy, uninfected immune system cells. Also, the virus was not able to replicate -- so it was also not able to mutate into new, drug-resistant forms.

"That suggests pretty strongly to me that the replication of the virus has been stopped, so the drugs are doing what they are supposed to do. There's no question the drugs are keeping things in check," Siliciano said.

Joseph Wong and Douglas Richman of the University of California-San Diego and colleagues worked with six patients and found similar results, as did researchers at the National Institute of Allergies and Infectious Diseases (NAIAD) who tested 13 volunteers on the cocktail.

"These results underscore the importance of developing more potent antiretroviral drugs, as well as treatment strategies that specifically target latently infected cells that serve as hiding places for the virus," said NIAID director Anthony Fauci.

The NIAID team, however, did find some evidence the virus might be replicating inside the immune system cells.

The usual regime consists of two of the first-generation of AIDS drugs such as AZT, ddI or 3TC and known as reverse transcriptase inhibitors, plus a protease inhibitor such as saquinavir or ritonavir.

Some of the patients studied were taking four different drugs -- either adding a second protease inhibitor or one of the newest generation of AIDS drugs known as non-nucleoside reverse transcriptase inhibitors (NNRTIs).

When they first announced the dramatic effects of triple-drug therapy, David Ho of the Diamond Center and colleagues said they planned to take one of their patients off the drugs, first after 18 months, then after two years.

"Eventually somebody will have to have the courage to do this," Siciliano said.

"The fact that the virus we are finding in these people is drug-sensitive suggests that even if they do have a rebound (of HIV infection), the patient could be treated."

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