Rapid whole blood analysis of virus-specific CD4 and CD8 T cell responses in persistent HIV infection

OBJECTIVES: Upon HIV infection, strong antiviral cytotoxic and helper T cell responses are generated. They are considered to be an important component in the control of HIV viral load. A simple and rapid whole blood assay was established to quantify and simultaneously characterize HIV-reactive CD4 and CD8 cells. The assay was applied to evaluate the effect of antiretroviral therapy on HIV-specific T cell responses. METHODS: Whole blood of 33 HIV-infected individuals was specifically stimulated by HIV-1 Pr55gag, and activation-induced intracellular cytokine expression in CD4 and CD8 T cells was analysed by flow cytometry. RESULTS: HIV-1-specific CD8 and CD4 T cells can be quantified simultaneously. As specific antigen, HIV-1 Pr55gag virus-like particles were superior to soluble protein, especially for the activation of CD8 T cells. In untreated individuals, a high frequency of HIV-specific T cells was observed. The frequency of CD8 T cells was consistently higher than the respective CD4 T cell response, thus demonstrating a dominance in CD8 T cell expansion in persistent HIV infection. Patients on antiretroviral therapy showed a significant reduction in HIV-specific CD4 and, even more strikingly, CD8 T cells. CONCLUSION: The whole blood assay provides a rapid estimate of the total antiviral T cell resources, and is highly suited for a clinical setting. It may thus have widespread applications for the evaluation of vaccination strategies and immunotherapy. Because antiretroviral therapy significantly reduces both HIV-specific cytotoxic and helper T cell responses, future therapeutic strategies should aim at improving cellular antiviral immunity.