Detection of neoantigen-reactive T cell clones based on the clonal expansion using next-generation sequencing of T cell receptor β complementarity-determining region 3.

Development of mechanism-driven biomarkers for immune checkpoint inhibitors (ICIs) in cancer immunotherapy requires sensitive and efficacious assays to identify tumor antigen (Ag)-specific T cells. We demonstrated the concept for a sensitive method to determine Ag-reactive T cell clones based on clonal expansion using model neoantigens (NeoAgs) rather than cytokine production. Sequential increase in T cell clonal frequencies following Ag stimulation was detected by next generation sequencing (NGS) of T cell receptor β (TCR β) complementarity-determining region 3 (CDR3), with a higher sensitivity than that of enzyme-linked immunospot (ELISPOT) by 100-fold. The TCRβ CDR3 sequences could represent useful markers to track dynamic changes during immunotherapy. The TCRβ NGS-based method could represent a novel platform both for the development of new biomarkers as well as several therapeutic options.