Antiretroviral therapy abrogates association between arginase activity and HIV disease severity.

Arginase-induced L-arginine deprivation is emerging as a key mechanism for the downregulation of immune responses. We hypothesised that arginase activity increases with disease severity in HIV-seropositive patients. Our results show that peripheral blood mononuclear cells (PBMCs) from 23 HIV-seropositive patients with low CD4(+) T cell counts (≤350 cells/μl) expressed significantly more arginase compared with 21 patients with high CD4(+) T cell counts. Furthermore, we found a significant association between the two principal prognostic markers used to monitor HIV disease (CD4(+) T cell count and plasma viral load) and PBMC arginase activity in antiretroviral therapy naïve patients but not in patients undergoing therapy.