Immune Cells Worn Out From HIV Fight Given New Life to Assault Disease: Study

Researchers report they have found a way to revivify "killer" CD8 immune cells, which could some day be used to assist the body's natural infection-fighting power against HIV. CD8 cells normally seek and destroy infected cells, but they become "exhausted" by HIV infection, said study co-author Dr. Mario Ostrowski.

With HIV infection, CD8 cells "don't produce all the chemicals required to kill infected cells," Ostrowski said. "They can't perform any function. They're just totally wimpy and exhausted."

Worn-out CD8 cells also exhibit high levels of a molecule called Tim-3 normally used to slow the immune system down after an infection has been successfully dispatched. In test tubes, researchers blocked Tim-3 in CD8 cells taken from HIV patients and found the cells were revitalized. "We observed that blocking the Tim-3 pathway rescued those cells and restored their ability to fight off infection," said Ostrowski.

"We still do not know how the virus triggers Tim-3 or if this is restricted to HIV infection," said Dr. Lishomwa Ndhlovu, a study co-principal at the University of California-San Francisco. "But our findings may provide a new direction to vaccines and therapies that will potentially reverse these dysfunctional cells and allow them to control HIV-1 replication."

The full report, "Tim-3 Expression Defines a Novel Population of Dysfunctional T Cells with Highly Elevated Frequencies in Progressive HIV-1 Infection," was published in the Journal of Experimental Medicine (2008;doi:10.1084/jem.20081398).

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