Next Generation Crispr Ready, HLA Class I and II Transgenic Mouse Platform - ABSTRACT T cell responses are critical in the pathogenesis, prevention, and treatment of a broad range of diseases from infection to cancer, autoimmune disease, and transplant rejection. HLA transgenic mice have been proven to predict human T cell responses; yet currently available HLA transgenic mice are specific to individual HLA alleles and based on genetic engineering technologies which date to before the turn of the century. Further, available HLA transgenic mice are incompatible for breeding to produce combined HLA class I and class II models. This project will create and validate a modular Cas9-expressing HLA transgenic mouse platform strain from which any HLA class I and or class II transgenic mouse can be generated with now broadly available CRISPR methods. Our published data demonstrate our track record of working with HLA transgenic mice and of designing, evaluating, and validating novel mouse models. Further, our established relationship with TransViragen Inc., established genetic engineering experts, assures that the mice will be engineered as precisely and efficiently as possible. As preliminary data we include information from our collaboration with Synbal Inc. which in less than 2 years’ time generated triple-humanized mice on both C57BL/6 and BALB/c backgrounds which are distributed by the The Jackson Laboratory. We will produce a Cas9-expressing platform mouse strain with humanized β2M, CD8 and CD4, and absence of mouse MHC II. The three key advantages of this strain will be: (a) investigators studying a broad range of diseases will be one CRISPR step or transgene injection away from a mouse model with HLA class I or class II allele of their choice, (b) crosses of allele-specific strains will allow investigators to model virtually any combination of HLA class I and II alleles beginning at F1, and (c) any platform-derived mouse for somatic mutagenesis experiments in the context of humanized CD4, CD8 and β2M. The specific aims are (1) Produce a CRISPR-ready platform strain and transgenic mouse strains that are HLA allele-specific for autoimmune diseases and the top HLA class I and II allele frequencies of US ethnic groups, (2) Test and validate T cell reactivity in HLA class I and HLA class II mice derived from platform strain. Mice will be deposited in the JAX Repository, and validation data will be compiled and published in a publicly viewable online database. This HLA transgenic platform strain will provide a broad range of investigators with a modular small animal in vivo model of human relevant T cell responses for the next decade and beyond.