Peripheral blood TCRB chain convergence and clonal expansion following cytomegalovirus infection: Implications for the biomarker use of TCR-seq.

Abstract

134 Background: Human cytomegalovirus (CMV) is a common immune-evasive herpes family virus leading to lifelong asymptomatic infection in 50 to 80% of humans. The effect of CMV infection on the T cell repertoire may be relevant given interest in identifying T cell repertoire features predictive of response to checkpoint blockade immunotherapy (CPI) for cancer. Here we sought to identify features of CMV infection using TCRB profiling of peripheral blood (PBL) total RNA. Methods: Total RNA from PBL was obtained from 35 blood donors of known CMV status, then used for TCRB sequencing via the Oncomine TCRB-LR assay (amplicon spanning CDR1, 2 and 3) and the Ion Torrent S5. In parallel, we prepared libraries via the Oncomine TCRB-SR assay (CDR3 only). Data were used to identify TCRB repertoire features correlated with CMV status and compare repertoire features across the two assays. Results: T cell clone evenness was reduced in CMV positive individuals irrespective of age, predictive of CMV status (AUC = .86, p = 2E-4, Wilcoxon), and strongly correlated between LR and SR assays (Spearman cor = .96). TCR convergence was elevated in CMV positive individuals and uncorrelated with evenness (Spearman cor = -.03) such that the combination of convergence and evenness improved the performance of a logistic regression classifier (AUC = .93). Conclusions: We identify reduced T cell evenness and elevated TCR convergence as features of chronic CMV infection. CMV infection appears to significantly alter the T cell repertoire, suggesting that CMV status may be required for proper interpretation of T cell expansion in the context of CPI for cancer.