Selective Deletion of HLA-B, and -C Class I Genes Promotes Immunocompatibility of Humanized Skin Graft Model.

Background: The treatment of extensive burns requires rapid allogeneic skin transplantation, but HLA diversity poses a significant challenge in finding histocompatible donor-recipient matches. Methods: In this study, we developed a humanized skin graft model using HLA class I transgenic mice to closely examine the HLA-mediated immune response in skin transplantation. Additionally, this model was used to analyse the response against a human lymphoblastoid cell line, JY, with HLA-B and -C genes knocked out by a single-step CRISPR-Cas9 strategy, retaining the most common HLA class I allele, HLA-A*02:01. Results: Mice expressing the HLA-A02:01 allele alone or in combination with HLA-B07:02 do not reject the skin of animals expressing only HLA-A02:01. However, skin from HLA-A02:01/B07:02 mice transplanted into HLA-A02:01 mice is rejected, triggering a strong specific CD8 T cell response mediated by the HLA-B*07:02 molecule. In these latter mice, unlike the parental JY cell line, the edited cells did not induce a CD8 T cell response in vitro, suggesting that the selective deletion of HLA-B and -C may contribute to improve skin graft compatibility. Conclusion: This genetic engineering approach, repeated without modification for the five HLA-A class I most common alleles known to be associated with HLA-B7 and -C7 in the same haplotype, would cover 83.4% of the world population. Our findings offer a scalable HLA-compatible skin graft model, potentially improving practices in burn units worldwide.