Dampening Antigen-Specific T Cell Responses with Antigens Encapsulated in Polyphenolic Microcapsules

Abstract

Efficient T cell activation and effector responses require an antigenic peptide presented on the MHC complex to the TCR (signal 1), costimulatory molecule interactions between T cells and APCs (signal 2), and the synthesis of innate immune-derived proinflammatory cytokines and reactive oxygen species (signal 3). We previously demonstrated that the third signal dissipation impairs autoreactive T cell activation. In this study, we tested the hypothesis that encapsulation of Ag with an antioxidant-containing biomaterial would induce Ag-specific hyporesponsiveness. We cocultured bone marrow-derived dendritic cells with microcapsules composed of multilayer-assembled poly(N-vinylpyrrolidone) (PVPON) and the antioxidant tannic acid (TA). LPS-activated dendritic cells cocultured with (PVPON/TA) microcapsules displayed a decrease in TNF-α, IL-12p70, and CXCL10 synthesis. To study Ag-specific T cell responses, we incorporated chicken OVA into the (PVPON/TA) multilayers and stimulated OT-II splenocytes in a primary recall assay. Flow cytometric analysis demonstrated a significant inhibition of CD4 T cell activation markers, upregulation of CTLA-4 and PD-1, and blunted secretion of IL-2, IFN-γ, TNF-α, and CXCL10 by ELISA. To test microcapsule efficacy in vivo, we immunized OT-II mice with (PVPON/TA)-OVA microcapsules and performed an OVA recall assay. Immunization of OT-II mice with (PVPON/TA)-OVA microcapsules elicited a decrease in CD4 T cell differentiation and effector responses including IFN-γ, TNF-α, CCL3, and CCL5 by ELISA compared with OVA immunization alone. These data show that microcapsules composed of antioxidant and encapsulated Ags can effectively blunt innate immune-derived proinflammatory third signal synthesis necessary for Ag-specific effector T cell responses and present a prospective strategy for T cell-mediated autoimmunity.