Although interleukin-2 (IL-2) in combination with antiretroviral drugs (ARVs) raises CD4+ cell counts more than ARVs alone, it is not clinically beneficial to HIV patients, according to a recently published study. Scientists had theorized that IL-2 would help regenerate CD4+ immune cells, building a patient's natural immunity while ARVs controlled HIV.
"Our results show that IL-2 has no effect on the development of AIDS or on patient survival," said Dr. Jean-Pierre Routy of the Research Institute of the McGill University Health Center. "More precisely, while the presence of IL-2 leads to a faster increase of CD4+ immune cells, these cells are less functional than the CD4+ cells that regenerate naturally in patients who do not receive IL-2."
The National Institutes of Health funded the eight-year study, which enrolled more than 5,000 patients in 25 countries. Compared with ARVs alone, hazard ratios for opportunistic disease or death from any cause with IL-2 plus ARVs were 0.91 (95 percent confidence interval [CI], 0.70 to 1.18; P=0.47) among participants with 50-299 CD4+ cell counts per cubic millimeter at baseline and 0.94 (95 percent CI, 0.75 to 1.16; P=0.55) among patients with 300 or more CD4+ cell counts at baseline.
"Despite a substantial and sustained increase in the CD4+ cell count, as compared with antiretroviral therapy alone, interleukin-2 plus antiretroviral therapy yielded no clinical benefit" for either group, the study concluded.
The findings show the limitation of the value of biological markers in assessing patient health, Routy said. "Our challenge now will be to develop tests that assess the function of immune cells and not simply their quantity."
The full report, "Interleukin-2 Therapy in Patients with HIV Infection," was published in the New England Journal of Medicine (2009;361(16):1548-1559).