Hyperfunctional T cell responses unchecked by regulatory T cells are unable to resolve hepaciviral infection without humoral contribution.

BACKGROUND &

aimsThe most recent T cell-based vaccine against HCV tested in humans failed to swing the pendulum from chronicity to resolution, despite eliciting cellular responses in most individuals. These results naturally evoke the question of whether hyperactivated responses of a single adaptive immune arm are capable of inducing HCV clearance or if coordinated efforts between antibodies and T cells are indeed necessary. Here, we sought to address this point in determining whether the suppression of antiviral T cell and IgG responses by regulatory T cells (Tregs) is a critical prerequisite of delayed viral clearance or overt chronicity.

methodsUsing a surrogate model of HCV infection, rodent hepacivirus (RHV) infection in mice, we utilized Foxp3-DTR mice to assess how Tregs modulate the generation of acute antiviral adaptive immune responses and indirectly dictate infection fate via intracellular flow cytometry staining, ELISA, RNA sequencing, and qPCR.

resultsTransient depletion of Tregs prior to infection decreased viral-specific CD4

conclusionsTregs control the outcome of RHV infection via direct modulation of CD4 IMPACT AND IMPLICATIONS: Herein, we demonstrate how timing of regulatory T cell depletion determines the fate of effector T cells, humoral responses, and the kinetics of viral clearance. Our observations provide direct evidence that functional T cell responses are incapable of compensating for suboptimal humoral responses to facilitate viral resolution. Our results imply that future HCV vaccine regimens should not solely rely on eliciting focused responses of a single effector arm, but rather incorporate immunogens capable of inducing durable features of both humoral and cellular memory.