Activated CD8+ T cells exhibit blunted effector functions in early HIV-1 disease (P3035)

Abstract Elevated, persistent CD8+ T cell activation is a hallmark of HIV-1 infection. CD8+ T cell activation is measured by expression of CD38 and HLA-DR antigens on CD8+ T cells from the blood. How CD8+ T cell activation state may define impairments to CD8+ T cell function remains unclear. ERK1/2 signaling is critical for multiple T cell functions, and interruption of this pathway due to immune activation and inflammation may blunt CD8+ T cell function. We previously demonstrated that a major proportion of activated (CD38+HLA-DR+) CD8+ T cells from recently HIV-1-infected antiretroviral-treatment-naïve adults are refractory to phosphorylation of the ERK1/2 kinases (p-ERK1/2-refractory). Here we hypothesized that p-ERK1/2-refractory CD8+ T cells would exhibit reduced effector function compared to CD8+ p-ERK1/2-responsive cells. We combined single-cell phospho-kinase flow cytometry with intracellular cytokine staining into a single assay (PFICS), to examine IFN-γ and perforin responses in CD8+ T cells by ERK1/2 signaling ability. On a per cell basis, p-ERK1/2-refractory cells produced less IFN-γ in response to polyclonal or HIV-1 Gag peptide stimulation (% IFN-γ+ cells was 5.5-fold lower, p=0.006 for polyclonal and 1.5-fold lower, p=0.048 for Gag) and expressed reduced levels of perforin (2.1 and 1.6-fold lower perforin MFI). Blunted CD8+ T effector functions, secondary to ERK1/2 signaling deficits concentrated within activated CD8+ T cells, may contribute to HIV immunodeficiency.