Infection with human immunodeficiency virus (HIV) results in a chronic infection that progressively impairs the immune system. Although depletion of CD4⁺ T cells is frequently used to explain immunosuppression, chronicity of infection and progressive loss of CD4⁺ T cells are not sufficient to fully account for immune dysregulation. Arginase‐induced l‐arginine deprivation is emerging as a key mechanism for the down‐regulation of immune responses. Here, we hypothesized that the level of arginase activity increases with disease severity in HIV‐seropositive patients. We determined the levels of arginase activity in peripheral blood mononuclear cells from HIV‐seropositive patients and uninfected control participants. Our results show that peripheral blood mononuclear cells from HIV‐seropositive patients with low CD4⁺ T cell counts expressed statistically significantly higher levels of arginase activity, compared with patients with high CD4⁺ T cell counts or uninfected control participants. Furthermore, we found a statistically significant correlation between high level of arginase activity and high viral load in HIV‐seropositive patients.

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