Magnitude and Complexity of Rectal Mucosa HIV-1-Specific CD8+T-Cell Responses during Chronic Infection Reflect Clinical Status

Background: The intestinal mucosa displays robust virus replication and pronounced CD4+ T-cell loss during acute human immunodeficiency virus type 1 (HIV-1) infection. The ability of HIV-specific CD8+ T-cells to modulate disease course has prompted intensive study, yet the significance of virus-specific CD8+ T-cells in mucosal sites remains unclear. Methods and Findings: We evaluated five distinct effector functions of HIV gag-specific CD8+ T-cells in rectal mucosa and blood, individually and in combination, in relationship to clinical status and antiretroviral therapy ( ART). In subjects not on ART, the percentage of rectal Gag-specific CD8+ T- cells capable of 3, 4 or 5 simultaneous effector functions was significantly related to blood CD4 count and inversely related to plasma viral load (PVL) (p<0.05). Polyfunctional rectal CD8+ T-cells expressed higher levels of MIP-1b and CD107a on a per cell basis than mono- or bifunctional cells. The production of TNF alpha, IFN-gamma, and CD107a by Gag-specific rectal CD8+ T-cells each correlated inversely (p<0.05) with PVL, and MIP-1b expression revealed a similar trend. CD107a and IFN-gamma production were positively related to blood CD4 count (p<0.05), with MIP-1b showing a similar trend. IL-2 production by rectal CD8+ T-cells was highly variable and generally low, and showed no relationship to viral load or blood CD4 count. Conclusions: The polyfunctionality of rectal Gag-specific CD8+ T-cells appears to be related to blood CD4 count and inversely related to PVL. The extent to which these associations reflect causality remains to be determined; nevertheless, our data suggest a potentially important role for mucosal T-cells in limiting virus replication during chronic infection.