Identifying highly specific T cell receptors (TCRs) or antibodies against epitopic peptides presented by class I major histocompatibility complex (MHC I) proteins remains a bottleneck in the development of targeted therapeutics. Here, we introduce targeted recognition of antigen–MHC complex reporter for MHC I (TRACeR-I), a generalizable platform for targeting peptides on polymorphic HLA-A*, HLA-B* and HLA-C* allotypes while overcoming the cross-reactivity challenges of TCRs. Our TRACeR–MHC I co-crystal structure reveals a unique antigen recognition mechanism, with TRACeR forming extensive contacts across the entire peptide length to confer single-residue specificity at the accessible positions. We demonstrate rapid screening of TRACeR-I against a panel of disease-relevant HLAs with peptides derived from human viruses (human immunodeficiency virus, Epstein–Barr virus and severe acute respiratory syndrome coronavirus 2), and oncoproteins (Kirsten rat sarcoma virus, paired-like homeobox 2b and New York esophageal squamous cell carcinoma 1). TRACeR-based bispecific T cell engagers and chimeric antigen receptor T cells exhibit on-target killing of tumor cells with high efficacy in the low nanomolar range. Our platform empowers the development of broadly applicable MHC I-targeting molecules for research, diagnostic and therapeutic applications.
The use of adeno-associated viruses (AAVs) as donors for homology-directed repair (HDR)-mediated genome engineering is limited by safety issues, manufacturing constraints and restricted packaging limits. Non-viral targeted genetic knock-ins rely primarily on double-stranded DNA (dsDNA) and linear single-stranded DNA (lssDNA) donors. dsDNA is known to have low efficiency and high cytotoxicity, while lssDNA is challenging for scaled manufacture. In this study, we developed a non-viral genome writing catalyst (GATALYST) system that allows production of circular single-stranded DNAs (cssDNAs) up to approximately 20 kilobases as donor templates for highly efficient precision transgene integration. cssDNA donors enable knock-in efficiency of up to 70% in induced pluripotent stem cells (iPSCs) and improved efficiency in multiple clinically relevant primary immune cell types and at multiple genomic loci implicated for clinical applications with various nuclease editor systems. The high precision and efficiency in chimeric antigen receptor (CAR)-T and natural killer (NK) cells, improved safety, payload flexibility and scalable manufacturability of cssDNA shows potential for future applications of genome engineering.
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