IPSCs provide an unlimited source of specialized cells for cancer immunotherapies, regenerative treatments for degenerative diseases, and alternatives to organ transplantation. The “IPSC France” PEPR BBTI project aims to develop cost-effective and genetically stable iPSC lines, while minimizing tumorigenic risk and allo-immunogenicity through targeted genome editing.

Within the “IPSC FRANCE” consortium, we aim to develop and validate technologies for producing hypo-immune “universal donor” (UD) iPSCs via genome editing. We hope that this will promote the survival of neural grafts and avoid the need for immunosuppression in patients receiving neural allografts. We aim to adapt, compare and test these approaches for neural allogeneic transplantation using a fully immunocompetent non-human primate (NHP) model of Huntington’s disease (HD) based on excitotoxic striatal lesion.

To overcome immune rejection of allogeneic grafts in the brain of our NHP model of HD, we are evaluating multiple gene editing strategies aimed at reducing non-self and missing-self response of recipient immune cells to neuronal striatal grafts in allogeneic NHP recipients. Specifically, we generated iPSC clones from macaque and differentiated them into striatal neuronal and glial grafts in both 2D monolayer and 3D spheroid formats. We generated several types of hypoimmunogenic grafts through genetic disruption of MHC class I and II molecule expression and overexpression of one or more immunomodulators. We achieved this through CRISPR-Cas9-mediated knockout of the B2M and CIITA genes to disrupt MHC molecules and lentivirus-mediated transgenesis of selected immune-modulatory molecules into striatal cells.

Initial in vitro studies confirmed that these modifications preserved neuronal maturation, synaptic integrity and neuronal function of engineered Mafa-iPSC derived cells. Their immune evasive potential is tested ex vivo using mixed lymphocyte reactions (MLRs) with peripheral blood mononuclear cells (PBMCs) from naïve macaques. The most promising immune-evasive profiles will be subsequently tested in vivo in rodents using a xenogeneic graft paradigm. The project's ultimate goal is to test the most effective immune-evasive grafts in a preclinical setting that mimics a clinical situation. This involves transplanting an allogeneic graft in the same species of NHP model of Huntington’s disease without the use of any immunosuppressive drugs.