PD-1 inhibition results in reduced dendritic cell (DC) activation of HIV-1-specific de novo CTL and enhancement of DC-induced CTL memory recall responses

Abstract

Abstract Combination strategies consisting of DC vaccines and suppression of immunoregulatory pathways such as PD-1 blockade have been advocated to elicit optimal CTL responses in chronic diseases including cancer and HIV infection. We have shown that inactivated HIV-1 virus loaded, high IL-12 producing, mature, type-1 polarized DC (DC1) can activate CTL from naïve CD8+ T cell precursors that more effectively kill HIV-1-infected cells than CTL derived from memory CD8+ T cells. Here we tested DC1 transfected with an adenoviral (Ad) vector encoding anti-PD-1 antibody (DC.αPD1) enhancement of both primary as well as memory CTL responses to HIV-1. Ad-αPD1-transduced DC1 (DC.αPD1) secreted high levels of functional anti-PD1 Ab without affecting their phenotype or IL-12p70-producing capacity. We next compared HIV Gag peptide epitope-loaded DC.αPD1 to DC1 that were transfected with an empty vector for their ability to activate either purified, autologous naïve or memory HIV-1-specific CD8+ T cells from chronic HIV-1-infected participants of the Multicenter AIDS Cohort Study. When compared to the control DC1, antigen-loaded DC.αPD1 enhanced the overall magnitude of HIV-1-specific CTL responses induced, as determined by the expansion of HIV-1-peptide responsive CD107a and IFNγ expressing T cells. In contrast, the overall number HIV-1 antigen-reactive CTL derived from the naïve CD8+ T cell fraction sharply decreased when using the DC.αPD1-based approach. These results suggest previously unrecognized, opposing roles of the inhibitory receptor PD-1 in DC1-induced primary versus memory recall CD8+ T cell responses to HIV-1.