Immunologic and Virologic Effects of Subcutaneous Interleukin 2 in Combination With Antiretroviral Therapy

Abstract

Context While interleukin 2 (IL-2) is capable of inducing a marked expansion of the CD4 T-lymphocyte pool, limited data exist on whether IL-2 treatment can add significantly to the immunologic and virologic effects of potent antiretroviral therapy (ART). Objective To determine the rate and magnitude of CD4 cell recovery and viral suppression when using a combination therapy of IL-2 and ART compared with ART alone. Design and Setting Randomized, controlled multicenter trial conducted from April 1996 through April 1998 at 8 clinical sites in the United States. Patients Eighty-two adult outpatients who were infected with human immunodeficiency virus (HIV) and had baseline CD4 cell counts of 200 × 10⁶/L to 500 × 10⁶/L and baseline RNA levels of fewer than 10,000 copies/mL were randomized; 78 completed the study. Interventions Thirty-nine patients were randomly assigned to receive a combination therapy of subcutaneous IL-2 (administered in 5-day courses every 8 weeks at a starting dosage of 7.5 mIU twice per day) and ART; 43 were to receive ART therapy alone. Main Outcome Measures Interleukin 2 safety and differential effects on CD4 cell counts, CD4 cell percentages, and plasma HIV RNA levels. Results The mean (SD) percentage increase in CD4 cell counts at 1 year for patients who received IL-2 was 112% (113%) compared with 18% (35%) in recipients of ART alone (P<.001). Both groups had mean (SD) increases in CD4 cell percentage: from 20.4% (6.3%) to 32.3% (12.4%) for the combination therapy group compared with 20.4% (5.1%) to 23.0% (7.2%) for recipients of ART alone (P<.001). Using a sensitive viral RNA assay, mean viral load changes were −0.28 and 0.09 log₁₀ copies for IL-2 recipients and control patients, respectively (P=.03). Twenty (67%) of 30 evaluable patients receiving IL-2 achieved final viral loads of fewer than 50 copies/mL compared with 13 (36%) of 36 control patients (P=.02). Toxic effects were common among patients who received IL-2 and were managed with antipyretics, hydration, rest, and dosage reduction as needed. Conclusions Intermittent therapy with IL-2 and ART produced a substantially greater increase in CD4 cells and was associated with a larger decrease in viral load than ART alone. Clinical end-point trials will be necessary to determine whether the enhanced viral suppression and CD4 cell increases associated with IL-2 therapy will translate into improved clinical outcomes.