Restoring immunological tolerance in established experimental arthritis by combinatorial citrullinated peptides and immunomodulatory signals

Promoted tolerance is a coveted therapeutic approach for rheumatoid arthritis (RA), as current immunosuppressive treatments are not disease-specific, primarily targeting the inflammatory response and exerting debilitating side effects. The cellular and antigenic complexity of RA challenges the design of nanoparticle-based tolerogenic strategies to selectively and comprehensively ameliorate joint destruction and restore immune tolerance in RA. Herein, we aimed at exploring the therapeutic effects and tolerogenic mechanism of a novel “tolerogenic polypeptide vaccine” (TPvax), which carried a multiepitope citrullinated peptide (Cit-ME) and rapamycin (Rapa), in established experimental arthritis. A low dose Rapa helped to drive the generation of anti-inflammatory cytokines and tolerogenic dendritic cells (DCs), thereby providing an immunosuppressive microenvironment for tolerance induction. We demonstrated that TPvax enabled the synergism between Cit-ME and Rapa, which led to the upregulation of regulatory T cells (Treg), promotion of IL-10 secretion and reduction of pro-inflammatory cytokines and antibody titers. Importantly, we provided evidence of epitope spreading to citrullinated antigens in collagen-induced arthritis (CIA) and demonstrated that co-delivery of Cit-ME and Rapa promoted immune tolerance even during an ongoing inflammatory event. This work would shed light to the development of tolerogenic therapeutics as novel immunotherapies for RA.