183-OR: Overcoming Immunological Barriers for “Off-the-Shelf” iPSC-Derived Islets

Improved differentiation protocols allow large-scale generation of induced pluripotent stem cell (iPSC) -derived islets. In order to make allogeneic “off-the-shelf” islets clinically useful and avoid rejection absent immunosuppression (IS) , they need to evade host immune responses, a property we refer to as being “hypoimmune.” Rhesus macaque (NHP) iPSCs were engineered to knock-out function of MHC class I and II and overexpress CD47 (HIP iPSCs) . HIP iPSCs and unedited iPSCs (wt iPSCs) were transduced to express luciferase and transplanted IM into four allogeneic NHPs per group. There was a strong IFN-γ ELISpot T cell response 1 week after wt iPSC transplantation, and increased production of wt-iPSC specifc IgM antibodies (Ab) and IgG Abs. At all time points tested (up to 12 weeks) , PBMCs killed wt iPSCs via direct and Ab-mediated cellular cytotoxicity. Furthermore, serum from NHPs killed wt iPSCs via complement-dependent cytotoxicity. In contrast, NHPs that received HIP iPSCs showed no measurable immune response against HIP iPSCs at all time points. After 6 weeks, NHPs initially receiving wt iPSCs were injected with HIP iPSCs. Although the NHPs maintained their strong immune response against wt iPSCs, they did not mount any response against HIP iPSCs. NHPs receiving HIP iPSCs first developed a strong cellular and Ab-response against the subsequently injected wt iPSCs but continued to have no reactivity against HIP iPSCs. Bioluminescence imaging in vivo revealed rejection of all wt iPSC grafts in both groups within 2-3 weeks after transplantation, while all HIP iPSC grafts survived the study period of 16 weeks. As a step to extending these studies to human iPSCs, we created human HIP iPSCs. We were able to differentiate these human HIP iPSCs into functional HIP islet cells that evaded host immune responses. This work suggests that HIP modifications do not impact islet cell differentiation or function. These data support the development of allogeneic HIP islets for the treatment of patients with T1DM.