In type 1 diabetes (T1D) insulin-producing pancreatic β cells are destroyed by CD4⁺ and CD8⁺ autoreactive T cells. Antigen-specific tolerance is desirable for T1D immunotherapy to avoid generalised immunosuppression. We encapsulated the islet autoantigen Chromogranin A (ChgA) mimotope and the NF-kB inhibitor 1a,25-dihydroxy-vitamin D3 (calcitriol/D3) into liposomes. Liposomes and D3 both have excellent and safe clinical track records. This protocol is designed to generate tolerogenic DC that will inhibit effector immune cells but favour regulatory immune cells, and therefore protect from the disease.

NOD mice were injected with our liposomes or PBS, at day 0 and day 7 to target antigen presenting cells. DC and T cells were studied 1, 4 or 11 days later. Pancreatic draining LNs (pLN), spleens and pancreas were analysed by FACS using the specific tetramer. At day 1, liposomes were taken up predominantly by CD11c⁺ CD11b⁺ DCs. At day 4 the proportion of ChgA-reactive endogenous T cells expanded in pLN and spleen in response to liposomes delivering ChgA mimotope with or without D3. By day 11, the T cells recognising ChgA had decreased in all tissues and the residual cells were enriched in ChgA-specific Foxp3⁺ Tregs and Foxp3^-CXCR5^-PD1⁺CD73⁺ICOS⁺ pTreg producing more IL-10 and less IFNg than PBS controls, and capable of controlling naïve T cells proliferation. Multiple ChgA/D3 treatments of NOD mice at the onset of hyperglycaemia controlled diabetes progression. These data indicate that endogenous ChgA-specific effector T cells are deleted and Tregs are induced after administration of liposomes and that multiple injections can control diabetes progression. This protocol is a proof-of-concept for a translation towards a T1D clinical trial.