Elite Controllers with Low to Absent Effector CD8 + T Cell Responses Maintain Highly Functional, Broadly Directed Central Memory Responses

Abstract

Analyses of the breadth and specificity of virus-specific CD8(+) T cell responses associated with control of HIV have largely relied on measurement of cytokine secretion by effector T cells. These have resulted in the identification of HIV elite controllers with low or absent responses in which non-T-cell mechanisms of control have been suggested. However, successful control of HIV infection may be associated with central memory T cells, which have not been consistently examined in these individuals. Gag-specific T cells were characterized using a peptide-based cultured enzyme-linked immunosorbent spot assay (ELISpot). Peripheral blood mononuclear cells from HIV elite controllers (n = 10), progressors (n = 12), and antiretroviral-treated individuals (n = 9) were cultured with overlapping peptides for 12 days. Specificity was assessed by tetramer staining, functional features of expanded cells were assessed by cytokine secretion, and virus inhibition and phenotypic characteristics were assessed by cell sorting and coculture assays. After peptide stimulation, elite controllers showed a greater number of previously undetectable (new) responses compared to progressors (P = 0.0008). These responses were highly polyfunctional, with 64.5% of responses having 3 to 5 functions. Expandable epitope-specific CD8(+) T cells from elite controllers had strong virus inhibitory capacity and predominantly displayed a central memory phenotype. These data indicate that elite controllers with minimal T cell responses harbor a highly functional, broadly directed central memory T cell population that is capable of suppressing HIV in vitro. Comprehensive examination of this cell population could provide insight into the immune responses associated with successful containment of viremia.