PLGA-microsphere delivery of insulin and IGRP epitopes as a therapy for type 1 diabetes

Abstract

Abstract Autoreactive CD8+ T-cells are the ultimate effectors destroying pancreatic β–cells during type 1 diabetes (T1D), revealing a critical role for HLA class I molecules in disease pathogenesis. The HHD transgene contains the α1 and α2 domains of the T1D susceptible variant HLA-A*02:01, covalently linked to human β2m with the α3, transmembrane, and cytoplasmic domains being of murine H2-Db origin. Introduction of HLA-A2.1 into NOD mice via the HHD transgene restores T1D development to NOD.β2m−/− mice. Using these NOD.β2m−/−-A2 mice, we previously identified four epitopes (INS1/2A2–10, INS1B5–14, IGRP265–273 and IGRP228–236) that are targets of CD8+ T-cells in both NOD mice and humans. When coupled to a clinically relevant delivery-mechanism, poly(lactic-co-glycolic acid) microspheres, delivery of these peptides during both early and late-prodromal stages of T1D can ameliorate progression to overt diabetes in NOD.β2m−/−-A2 mice. Delivery of all four peptides was capable of ameliorating T1D and insulitis when delivered every three weeks whether the injections were continued throughout the study (started at six or ten weeks of age) or whether the injections were only given three times (starting at ten weeks of age). After three injections of all four peptides, CD8+ T-cell recall responses to IGRP265–273 and IGRP228–236 were reduced. Attenuation of CD8+ T-cell responses correlated with a reduction in PD-1+ effector CD8+ T-cells as well as a small increase in PD1− CXCR3− central memory CD8+ T-cells in the popliteal LN after footpad priming. Work is ongoing to determine the effectiveness and dosing in 2nd generation HLA- “humanized” NOD-cMHCI−/−-A2 mice that retain murine FcRn functionality.