About The Study

The purpose of this trial was to evaluate the effects of giving recombinant interleukin-2 (rIL-2), an important molecule in the production of immune cells, to HIV-infected people who had CD4 cells counts between 50 and 299 cells/mm3.

Interleukin-2 (IL-2) is a hormone (cytokine) that helps the development of CD4 T cells (immune cells that fight infection), and may help to rebuild the immune system. The body’s CD4 T cells naturally produce IL-2 during an immune response, however individuals infected with HIV do not produce enough of the molecule. The researchers hypothesized that the addition of recombinant interleukin-2 (rIL-2) to ART regimens would increase the number of CD4 T-cells and thus slow HIV disease progression.

Study Approach

This was an international trial which enrolled 1695 eligible participants were randomly divided into two groups. Group 1 (849 individuals) received rIL-2 given by injection below the skin at a dose of 4.5 MIU twice daily for five consecutive days, every eight weeks. This routine was repeated five times for a total of six cycles. Thereafter, the frequency of receiving rIL-2 was tailored to individual needs in order to maintain the CD4+ cell count above a predefined target level. If participants were non-responsive after three cycles of rIL-2, the dosage of was increased to 6 or 7.5 MIU. Group 2 (846 individuals) did not receive the study drug. Both groups maintained their ART regimens.

Study population

This study recruited individuals aged 18 years older who were confirmed to be HIV positive. Participants had to have a CD4 cell counts between 50 and 299 cells/mm3, an HIV RNA level of <10,000 cells/mL, and be on a stable regimen of a combination of at least two anti-HIV medications for at least four months prior to study onset.


Over a median follow-up of seven to eight years, the CD4+ cell count was higher in the interleukin-2 group than in the group receiving antiretroviral therapy alone by an average of 53 cells per cubic millimeter.


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.

Note: These results also reflect those of CTN 110: ESPRIT, a sister study that examined the same hypothesis in a population of HIV-infected individuals with higher (>300 cells/mm3) CD4 cell counts.