CTLs decrease with combination antiretroviral therapy but precursor cells remain

While combination antiretroviral therapy is associated with a decrease in activated cytotoxic T lymphocytes (CTLs), precursor cells remain, and recognition of new viral epitopes may occur, according to a report published in the March issue of the Journal of Infectious Diseases.

Dr. M. Juliana McElrath, from the Fred Hutchinson Cancer Research Center, in Seattle, and colleagues studied the evolution of T-cell phenotypes and HIV-specific CD8+ lymphocytes in 41 HIV-infected patients who began combination antiretroviral therapy.

The authors found that naive CD8+ T cells increased and activated CD8+ T cells decreased when viral loads were suppressed to less than 200 copies/mL. CTL precursor frequencies were comparable before and after treatment, the investigators state. In addition, 8 of 11 CTL precursors appeared capable of a new or increased response after treatment.

“Our findings suggest that, even if the memory CD8+ CTL pool is sustained, this immune defence alone will not be adequate to control HIV-1 infection once one or two of the antiretroviral agents are subsequently stopped,” the researchers note.

Dr. McElrath’s group believes, however, that “future studies may delineate chronically infected patients in whom therapy cessation is more feasible, on the basis of a sustained memory CTL pool, in addition to new epitope recognition, perhaps in conjunction with improved T-cell help in chronically infected patients.”