Normalized CD8+ but not CD4+ lymphocyte IL-2 expression is associated with early treatment with highly active antiretroviral therapy

CD4+ and CD8+ lymphocyte cytokine production in patients with HIV/AIDS and Controls, in response to stimulation with phorbol-12-myristate-13-acetate (PMA) and ionomycin was assessed using single cell flow cytometric methods. Sixty-eight patients with HIV were divided into those on no antiretroviral therapy and those on highly active antiretroviral therapy (HAART). Patients on HAART were analyzed further on the basis of gender, ethnicity, viral load (> or ≤ 50 copies/ml), CD4 count change from nadir (> 100 or < 100 cells/mm3) and CD4 count (> 200 or < 200 cells/mm3). Interferon gamma (IFNγ) expression by CD4+ and CD8+ lymphocytes was elevated in HIV-infected groups as compared to Controls. This elevation was statistically significant for patients on HAART but not for those not on HAART. The most significant difference was seen when the CD4+ count reached > 200 cells/mm3 (p = 0.018 for CD4+ IFNγ production and p = 0.004 for CD8+ IFNγ production). CD4+ interleukin-2 (IL-2) expression was significantly lower in HIV patients as compared to Controls but did not significantly improve however good the response to HAART. IL-2 expression by CD8+ lymphocytes was also lower in HIV patients as compared to Controls. IL-2 expression by CD8+ lymphocytes significantly improved in all patients on HAART as compared to HIV patients on no HAART. IL-2 expression was not significantly different from that of the Controls when the HIV viral load was less than 50 copies/ml. These results demonstrate improvements in both CD4+ and CD8+ responsiveness with HAART. IFNγ production was elevated in response to HAART and was maximal only with significant CD4 count recovery. In contrast, normalization of IL-2 production by CD8+ lymphocytes was seen early in patients receiving HAART even when there was only a small increase in CD4+ lymphocyte numbers.