A multi-epitope DNA vaccine enables a broad engagement of diabetogenic T cells for tolerance in Type 1 diabetes

Type 1 diabetes (T1D) is caused by diabetogenic T cells that evaded tolerance mechanisms and react against multiple beta-cell antigens. Antigen-specific therapy to reinstate tolerance (typically using a single beta-cell antigen) has so far proved unsuccessful in T1D patients. Plasmid DNA (pDNA)-mediated expression of proinsulin has demonstrated transient protection in clinical trials, but long-lasting tolerance is yet to be achieved. We aimed to address whether pDNA delivery of multiple epitopes/mimotopes from several beta-cell antigens efficiently presented to CD4(+) and CD8(+) T cells could also induce tolerance. This approach significantly delayed T1D development, while co-delivery of pDNA vectors expressing four full antigens protected more mice. Delivery of multiple epitopes resulted in a broad engagement of specific T cells, eliciting a response distinct from endogenous epitopes draining from islets. T-cell phenotypes also varied with antigen specificity. Unexpectedly, the repertoire of T cells reactive to the same epitope was highly polyclonal. Despite induction of some CD25(+) Foxp3(+) regulatory T cells, protection from disease did not persist after treatment discontinuation. These data demonstrate that epitope-based tolerogenic DNA vaccines constitute effective precision medicine tools to target a broad range of specific CD4(+) and CD8(+) diabetogenic T-cell populations for prevention or treatment of T1D.