By Maggie Fox

Reuters 30 August 2000

Washington -- The immune system may be able to come back more powerfully than anyone thought after a break in treatment with AIDS drugs, researchers said on Wednesday.

They said in patients who had decided to interrupt their complex HIV drug regimens, two kinds of immune cells -- CD4 "helper'' cells and CD8 "killer'' cells -- came back for a time to battle the virus.

The team at the Wistar Institute, a non-profit biomedical research institute at the University of Pennsylvania, stresses that taking breaks from HIV medication can be risky and unwise.

But they said their findings added support to studies underway into whether such breaks might be worthwhile if they are carefully monitored and controlled.

At first dismissed by mainstream AIDS researchers, the idea of regularly interrupting HIV treatment is winning favour.

As the name implies, with structured treatment interruption (STI) a patient stops taking drugs for a while so the virus can come back just enough to provoke an immune reaction.

Patients like being off the drugs, which must be taken to strict timetables and which have side-effects ranging from diarrhoea to serious metabolic disorders. In a very few patients, after an interruption or two, their immune systems seem to be able to control the virus well enough for them to stay off for months on end.

Luis Montaner and colleagues wanted to test this idea, too, but were not allowed to start a formal clinical trial, which would have involved assigning people to stop treatment, by the research facility's Institutional Review Board (IRB) -- the body that approves academic research.

"The IRB was terrified we would induce people to stop treatment, so we could only recruit through word of mouth,'' Montaner said in a telephone interview.

They found 10 patients who had decided on their own to stop taking drugs. Five were giving themselves temporary breaks, and five had stopped the drugs altogether or had never taken them.

Writing in the September issue of the Journal of Infectious Diseases, Montaner said he and his team monitored how much virus was in the patients' blood and watched their immune system responses.

Other studies have shown that, if the virus is well- controlled by drugs before the medication, the virus at first bounces back but eventually CD4 T-cells can recover and help in controlling it for a while.

Montaner found the CD4 cells in his five patients who interrupted treatment recovered quickly. They also saw the killer CD8 cells come back. This suggests the body, when given a chance, can fight back against the virus.

Now Montaner is setting up a controlled clinical trial with 42 patients and with $2.2 million in funding from the National Institute on Allergies and Infectious Diseases (NIAID).

He stresses that no patient should try interruptions on his or her own.

"There are risks associated with treatment interruption,'' Montaner said. For instance, one of the NNRTI class of HIV drugs, Sustiva, lasts in the body longer than other drugs.

This means when a patient stops taking a cocktail, the Sustiva lingers after other drugs have left the body. This has the same effect as if the patient took Sustiva alone, and might help make the virus resistant to that particular drug.

Other things might go wrong, too. "There has been no poster patient that has a detrimental outcome ... but we eventually will see a person with detrimental outcome to treatment interruption,'' he said.