Natural Immune-System Molecule Helps Shield Against HIV

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With that in mind, researchers have long investigated the IL-7 molecule as a possible therapy. In fact, a clinical trial using IL-7 as adjunct therapy in HIV-positive patients is set to announce its findings in March, Lusso said.

The NIAID trial looked at the issue from a different angle, trying to discover just how IL-7 protects T-cells from harm.

In their laboratory experiments, Lusso and his co-researchers took blood samples from 24 HIV-infected patients at varying stages of infection. They then added an extra dose of IL-7 to the samples and observed T-cell survival.

"What we found is that IL-7 prevents the apoptosis of CD4 cells in HIV-infected patients," he said.

Apoptosis -- programmed cell death -- is a natural phenomenon common to nearly all cells. One of the ways that HIV kills T-cells is by driving them into apoptosis way too early, scientists say.

The new study experiments also showed that IL-7 delayed HIV-related apoptosis in another form of T-cell, the CD8-positive T-cell, Lusso said.

And the study turned up another welcome surprise. "If you administer IL-7 to normal cells in an uninfected individual, the effect is close to zero," Lusso said. "That's good, because you want to maintain those healthy, physiological levels of apoptosis."

In fact, IL-7 therapy was most protective in samples from sicker patients with the lowest CD4 T-cell counts -- exactly those populations doctors would most like to help.

While the findings are heartening, Lusso said "there's no way that [IL-7 therapy] would substitute for HAART. But it may be beneficial."

The therapy might prove especially useful in limiting the long-lasting immune system damage that occurs within the first few days of infection. According to Lusso, that damage is like a "scar" that lingers on the immune response, dampening its function even after HIV levels have been suppressed.

"We are actually planning an experiment in monkeys that will start in the next few weeks," Lusso said. "We'd like to give them IL-7 early, before HIV gets into the body in a really pervasive way, to see if we can prevent the formation of that [immune system] scar."