Preclinical evaluation of a precision medicine approach to DNA vaccination in Type 1 diabetes

Antigen-specific immunotherapy involves the delivery of self-antigens as proteins or peptides (or using nucleic acids encoding them) to be presented with the goal of inducing tolerance. Approaches employing specific epitopes restricted to the subject's MHC haplotypes have multiplied and offer a more focused and tailored way of targeting autoreactive T cells. In addition, the Endotope platform allows endogenously expressed epitopes to be processed and presented on appropriate MHC class I and II molecules. Here, we evaluated the efficacy of a DNA vaccine encoding epitopes selected and tailored for the non-obese diabetic (NOD) mouse compared to the expression of the proinsulin protein, one of the most successful antigens in prevention of NOD disease, and we assessed the influence of several parameters (e.g. route, dosing frequency) on preventing diabetes onset at normoglycemic and dysglycemic stages. First, encoded peptides should be secreted for effective disease prevention. Furthermore, short weekly treatments with Endotope and proinsulin DNA vaccines delay disease onset, but sustained treatments are required for long-term protection, which was more significant with intradermal delivery. Although epitopes can be presented for at least two weeks, reducing the frequency of antigen administration from weekly to every other week reduced efficacy. Finally, both Endotope and proinsulin DNA vaccines were effective in the dysglycemic stage of disease, but proinsulin provided better protection, particularly in subjects with slower progression of disease. Thus, our data support the possibility of applying a precision medicine approach based on tailored epitopes for the treatment of tissue-specific autoimmune diseases with DNA vaccines.