Interleukin-2 on the assembly line
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CNN's Elizabeth Cohen reports on an HIV drug with encouraging results
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• 'Another step forward'
• Powerful side effects
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(CNN) -- Researchers believe they may have found a way to use a natural immune system chemical to wipe out the "safe havens" where the virus that causes AIDS can hide.

The chemical, interleukin-2, is an immune boosting drug normally used to treat some cancers. But researchers say preliminary tests have shown it may be a new weapon against AIDS.

Patients took interleukin-2 along with a so-called "drug cocktail" -- a mixture of highly active anti-retroviral therapy (HAART) drugs.

The cocktail approach has been effective in knocking down HIV to very low levels. But when the patients go off HAART, the virus rebounds in their system.

In 1982, Mark Deal was infected with HIV. But today, after undergoing the new experimental interleukin-2 treatment, doctors can't find a trace of the virus in his blood. Even a lymph node biopsy proved negative for HIV.

Deal

But Dr. Anthony Fauci says Deal is not cured and the virus may still be lurking in his body, ready to re-emerge.

Fauci is the head of the National Institute of Allergies and Infectious Diseases (NIAID), which conducted the study.

"What this is, I believe, is another step forward towards suppressing the virus and getting to the point where we may be able to control it," Fauci said.

Fourteen other patients in the study had similar results to Deal -- no sign of the virus.

Scientists have found HIV to be a wily adversary because the virus attacks immune cells, making it hard to reach. All the drugs now on the market attack HIV while it is in an active, replicating phase.

Some infected immune cells go into a "resting" phase that can last for years and make the tainted cells immune to HAART drugs.

Interleukin-2 is a cytokine or signaling chemical used by the immune system. It flushes out the "resting" T-cells, making them vulnerable to the anti-viral drug cocktails.

The drug cocktails are similar to chemotherapy for cancer patients. While remarkably effective, they're also highly toxic and can cause horrible side effects.

Patients are often nauseous and exhausted, and their cholesterol levels can soar. So the next step for researchers is to take the test patients off the drugs to see how they do.

The researchers said that interleukin-2 does not completely solve the problem of HIV reservoirs. The virus is also believed to hide in the brain and in other immune cells known as macrophages, as well as elsewhere in the body.

The NIAID announced its finding of the new study Sunday at a meeting of the Infectious Disease Society of America in Denver.

CNN Medical Correspondent Elizabeth Cohen and Reuters contributed to this report.