CMV-specific clonal expansion of Th1, GZMK⁺ CD8⁺, and TEMRA T cells revealed by human PBMC single cell profiling

Cytomegalovirus (CMV) is a common herpesvirus that establishes lifelong latency and becomes increasingly prevalent with age. We systematically characterized CMV-associated immune remodeling by analyzing six human cohorts (two newly built) using single-cell RNA sequencing, T cell receptor (TCR) sequencing, and flow cytometry. Beyond the well-known expansion of CD4/CD8 TEMRA, adaptive NK, and {gamma}{delta} T cells, CMV(+) adults exhibited increased frequencies of GZMK CD8 T cells and atypical B cells, alongside a reduction of CD56dim NK cells. Longitudinal profiling of an individual who seroconverted revealed rapid CMV-driven shifts in circulating immune cell frequencies. Single-cell TCR data analyzed using a large database of CMV-associated clones combined with predictive modelling (CMVerify), identified novel CMV-specific clonal expansions reproduced across two independent cohorts. In the CD8 lineage, CMV-specific clones were enriched in GZMK CD8 and CD8 TEMRA cells, while in the CD4 lineage, Th1 cells showed clonal expansion alongside CD4 TEMRA cells. This integrative study revealed how latent CMV alters the cellular and clonal landscape, defining GZMK CD8 and Th1 cells as newly recognized elements of response to CMV in humans.