Differential effect of interleukin-2 treatment on primary and secondary immunizations in HIV infected individuals

Objectives: As interleukin (IL)-2 therapy increases CD4 cell counts in HIV infected subjects, it emerged as a candidate for the partial restoration of immune competence in this disease. Methods: We studied the frequencies of antigen-specific T cells using single cell resolution cytokine ELISPOT assays and titers of specific antibodies before and after immunization of HIV infected subjects who were treated with HAART or HAART plus IL-2. Results: Subjects seronegative to hepatitis A were vaccinated with hepatitis A antigen. In the non-IL-2 treated group, hepatitis A-specific T cells producing IL-2 and IL-4 along with specific antibodies were induced, showing that these subjects are immune competent and capable of mounting a primary immune response. Additional IL-2 treatment had no significant effect on this primary T cell response; however, booster immunizations with tetanus toxoid or the gp120 depleted HIV vaccine Remune induced higher frequencies of specific interferon (IFN)-γ producing T cells in IL-2 treated subjects. No impact of IL-2 treatment on these secondary B cell responses was seen. Conclusion: Overall, our study showed that IL-2 therapy had no immune enhancing effect on the induction of a primary response, but increased the frequency of IFN-γ producing memory cells after booster immunization.