"Programming Dendritic Cells
for Intercellular Delivery of T-bet
to Enhance Function of Cytotoxic T Cells"
Abstract: Advances in antiretroviral therapy (ART) have proven successful for controlling HIV-1 in chronically infected individuals. Despite these advancements, curing HIV-1 infection poses a major public health challenge due to the establishment and maintenance of HIV-1 latency in long lasting memory CD4+ T cells during ART. Moreover, the cytotoxic T cells (CTL) needed to effectively target and kill infected cells often become exhausted because of chronic activation. Interestingly, CTL from HIV elite controllers show less evidence exhaustion, which is also associated with higher levels of expression of the Th1-associated transcription factor T-bet. In this study, we hypothesize that type-1 polarized human dendritic cells (DC1) are superior in their capacity to induce and enhance cellular immune responses against virally infected cells partially due to their capacity to express and transfer DC-derived T-bet to effector T cells. Moreover, we propose that overexpression of T-bet in therapeutic DC, through genetic modification, offers another approach to improve DC-induced cellular immunity. Here we show that DC1 indeed uniquely express T bet as a general trait while conventional DC generated in the presence of PGE2 (DC2) are T-bet deficient as determined by western blot and intracellular flow cytometry analysis. We also report that overexpression of T-bet in DC1 (DC1Tbet) through use of an adenoviral vector delivery system enhances their CTL inducing activity. However, DC1Tbet display a reduction in their capacity to produce IL-12p70 upon activation with CD40L. Moreover, using a GFP-based tracking method, we demonstrate that DC1 have the capacity to directly transfer cytoplasmic content to activated CD8+ T cells in a CD40L dependent manner. These data suggest, both a novel helper function of CD40L expressing CD4+ Th cells, and a mechanism for potential DC to T cell transfer of T-bet. We propose that this immune mechanism of DC1 to CTL intercellular transfer can be exploited to enhance anti-HIV T cell response, or to correct their dysfunction of T cell exhaustion as supported by evidence in DC1-based cancer immunotherapy studies.