Profiling TCR affinity distribution in human CD8+ T cell subsets responding to a cytomegalovirus epitope

Abstract

Abstract CD8 T cell subsets have long been distinguished using phenotypic markers like CCR7, CD45RA, and IL-7Rα. These markers have allowed for the isolation of CD8 T cell populations with distinct functional and proliferative capacities as well as those that maintain better proliferative responses in vivo without antigenic stimulation thus contributing more to immunological memory. Although phenotypic analysis has allowed for the discerning of functional, proliferative, and homeostatic proliferative potential, there is still little known about the role TCR affinity plays in recruitment of various affinity TCRs into memory and effector phenotypes that generate long term immunological memory in human infection. Using the newly developed iTAST technique, CMV specific CD8 T cells were isolated from the blood and spleen of human patients seropositive for CMV. CMV specific T cells were split into memory and effector subsets using phenotypic markers CCR7, CD45RA, and IL-7Rα before isolation and quantification of 2D TCR affinity and sequence. A roughly 100-fold difference of 2D affinity was present in CMV specific cells within the immunological memory response; however, with an enrichment for high affinity TCRs across all phenotypes assessed. This is consistent with previous studies demonstrating high avidity TCR selection in CD8 T cell responses to CMV infection, coupled with a greater clonality observed in CMV specific TCRs within healthy older individuals infected with CMV. Overall the iTAST technique allows for quick and easy isolation of antigen specific populations, quantification of TCR affinity, and TCR sequence thus giving unique insight into immunological memory responses in individuals infected with human persistent viruses.