CATCH: chasing antigen-specific T cells with high avidity 2799

Abstract Description Effective cellular immunity depends on both the quantity and functionality of antigen-specific T cells. T cell specificity is defined by the highly variable T cell receptors (TCRs) that recognize various peptides in the appropriate HLA context. The strength of the TCR - peptide-HLA complex interaction – characterized by TCR affinity, avidity and functional avidity - is crucial for T cell activation and functional output. In cancer, target antigens are often self-antigens, limiting T cell responses to low-affinity TCRs due to immune tolerance. Despite attempts to enhance TCR affinity, subsequent T cell dysfunction and toxicities have impeded translation of such efforts in the clinic. We here introduce the CATCH assay - a flow cytometric method combining the assessment of the CD3/TCR complex downregulation with the activation-induced marker (AIM) assay. This novel approach enables the rapid and precise detection of antigen-specific T cells with high functional avidity in a physiologically relevant manner. We demonstrate efficient analysis and isolation of high avidity virus (Loyal et al., Science, 2021) and tumor specific clones within 4 hours, in various stimulation conditions and across a broad antigen concentration range. CATCH holds significant potential for applications such as high throughput ex vivo characterization of the quality of an individual’s T cell populations, as well as TCR discovery, aiming to advance the success of immunotherapeutic strategies. Topic Categories Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)