Discovery of a monoclonal, high-affinity CD8+ T cell clone following natural hepatitis C virus infection

CD8+ T cells recognising their cognate antigen are typically recruited as a polyclonal population consisting of multiple clonotypes with varying T-cell receptor (TCR) affinity to the target peptide-MHC (pMHC) complex. Advances in single-cell sequencing have increased accessibility towards identifying TCRs with matched antigens. Here we present the discovery of a monoclonal CD8+ T cell population with specificity for a hepatitis C virus (HCV)-derived HLA class I epitope (HLA-B*07:02 GPRLGVRAT) which was isolated directly ex vivo from an individual with an episode of acutely resolved HCV infection. This population was absent prior to infection and underwent expansion and stable maintenance for at least two years after infection as measured by HLA-multimer staining. Furthermore, the monoclonal clonotype was characterised by an unusually long dissociation time (half-life = 794 seconds and koff = 5.73×10-4) for its target antigen when compared to previously published results. A comparison with related populations of HCV-specific populations derived from the same individual and a second individual suggest that high-affinity TCR-pMHC interactions may be inherent to epitope identity and shape the phenotype of responses which has implications for rational TCR selection and design in the age of personalised immunotherapies.