DENVER (AP) - Federal researchers say they have managed to flush the AIDS virus out from one of its most stubborn hiding places and erase it to undetectable levels in a handful of patients.

Dr. Anthony Fauci and other researchers at the National Institute of Allergy and Infectious Diseases cautioned that their method of rinsing the virus from resting immune cells is highly experimental and unconfirmed.

However, the technique appears to have removed HIV from the blood of three of the 26 patients in the study. In one of the three, there was no trace of the virus in the lymph nodes, either.

Fauci said it would take years of follow-up studies to determine if the treatment works. The process still could be derailed by toxic side effects, or the ability of the virus to develop a resistance to the therapy.

Still, researchers said, it is a promising step in the battle against AIDS.

Now that powerful drug combinations work effectively in many patients to reduce the virus to extremely low levels, the next - and perhaps - final step is to find ways in which the remaining copies of the virus can be flushed from its deepest haunts so antiviral drugs can erase those traces, too.

Data on the patients was discussed Sunday in Denver at the annual meeting of the Infectious Diseases Society of America.

``It's conceivable that we'll take these people off their drugs and the disease will come roaring back from a reservoir we didn't find,'' Fauci said in today's USA Today.

Another hurdle is whether new cells can be infected by the virus as it is flushed out - in effect, whether the aggressive treatment might inadvertently continue the disease cycle.

``We would like to get to the point of sterilizing immunity,'' said Dr. Roger Pomerantz of Thomas Jefferson University in Philadelphia, who did not work on the study. ``But different patients may react differently.

``In some, you might eradicate the virus and in others, the virus may be activated and infect new cells,'' Pomerantz said. ``You might not be able to withdraw therapy.''

Fauci and his team originally announced their experimental treatment last February.

The treatment targets CD4T cells, which function as the immune system's memory and are found throughout the body. They appear to hang onto the blueprint of bacteria and viruses for as long as 10 years so the body will recognize the infection and mount a defense if it appears again.

In the case of AIDS, the genetic coding of the virus takes up long-term residence in the genes of the CD4T cells. This protects the virus from drugs when it circulates in the bloodstream.

When the body's immune system is activated to fight an infection - or when drug therapy slips - these cells turn on and produce HIV again.

In the study, 26 men were given a combination of three anti-HIV drugs in an AIDS ``cocktail treatment.' Fourteen also were given the powerful immune system stimulator Interleukin-2.

IL-2 is the synthetic version of a substance naturally produced by the immune system. It alerts several types of disease-fighting cells to begin reproducing and fighting an invading infection.

Researchers believed that the IL-2 would activate dormant, infected CD4T cells. This would expose these reservoirs and the drug cocktail would eradicate it.

After the treatment, researchers said they could not grow live HIV from more than 300 million immune cells extracted from three men in the study.

Later this year, the researchers said they would take the three men off of the drug cocktail therapy to see if their viral loads increase again.

The other 23 men in the study remained HIV-positive, researchers said. Fauci said repeated treatments with IL-2 might be necessary.

In other studies announced at the meeting, virologists said HIV-infected immune cells were hiding in semen. They may lurk in even more inaccessible sites in the body, including the brain and the retina.

Copyright 1998 The Associated Press. All rights reserved.

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