Important note: Information in this article was accurate in 1999. The state of the art may have changed since the publication date.

Reuters NewMedia - Tuesday June 1, 1999
Maggie Fox, Health and Science Correspondent

They said they had teased out one of the hiding places of the virus, allowing strong drugs to then attack the virus and clear much of it from the systems of patients.

Two HIV patients treated with an immune system compound known as IL-2 have no detectable trace of the virus anywhere in their bodies, although the researchers say they do not believe the patients are cured.

Cocktails of strong drugs can keep HIV at bay. These mixes of three or more drugs, known as highly active antiretroviral therapy, or HAART, can suppress all activity of the virus.

But HIV attacks immune cells, which have many specialized functions. The main cells it attacks, CD4 T-cells, have a special subset whose job is to remain latent in the body.

These so-called memory T-cells can last for decades.

When HIV attacks a cell, it injects its genetic material and forces the cells to start pumping out copies of the virus instead of splitting like normal cells do. HAART attacks only this active stage of the virus, interfering with the replication.

But the memory T-cells are inactive, so if they are infected the virus can hide in there from the drugs. Even after years of taking drugs, enough of the virus lurks in such places to reignite an active HIV infection.

So scientists have been looking for ways to flush out the latent virus. Tae-Wook Chun and colleagues at the National Institute of Allergies and Infectious Diseases (NIAID) and at several universities had found in test-tubes that immune system signaling chemicals known as cytokines could activate the resting T-cells and make them vulnerable to HAART.

"IL-2 can directly activate resting CD4 T-cells," they wrote in a report in the journal Nature Medicine.

"The combination of IL-2, IL-6 and TNF-alpha substantially increases the proliferation of resting CD4 T-cells, as well as viral replication in latently infected, CD4 T-cells."

Just administering IL-2 alone can prompt production of all three cytokines, they added.

So they tried it in people. Of 26 HIV patients, 14 underwent HAART plus IL-2, while 12 received HAART alone for an average of about 20 months. All 26 patients had responded well to the HAART, which had kept the virus at undetectable levels for at least 6 months. But studies have shown such patients have HIV lurking in so-called reservoirs such as the resting CD4 cells.

After the 20 months, Chun and colleagues ran a battery of tests on the volunteers to see if they could find any traces of the virus anywhere in their bodies.

All the patients who got IL-2 had lower levels of the virus than patients who got HAART alone.

In three of the patients, no virus could be found in the resting CD4 cells in their blood, and in two of them the virus could not be found hiding in the lymph nodes, either.

"However, this study does not prove that virus has been eradicated in these patients," Chun's team said.

"There are many potential reservoirs of HIV in the body that have not been examined, including the brain, gut-associated lymphoid tissue, bone marrow, testes and other organs."

AIDS specialists David Cooper and Sean Emery of the University of New South Wales in Sydney, Australia agreed that the study would have to be duplicated in larger groups and with more careful controls before any suggestion could be made that IL-2 should be routinely added to HAART.

"Eradication of HIV clearly remains an elusive goal for therapy at present," they wrote.

"We must be sure that the clinical application of these results actually makes a difference to the health of people with HIV infection," they added.
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