Co-evolution of human influenza A and Epstein Barr virus-specific CD8 ex vivo memory T cell receptor BV repertoires with increasing age

Abstract

CD8 memory T cells are generated during primary infection with intracellular pathogens, such as viruses. These cells play an important role in the protection of the host upon re-infection with the same pathogen. In this study, we compare CD8 memory T cell receptor (TCR) BV repertoires directly ex vivo for two common human viruses, influenza A virus (IAV), an RNA virus that frequently re-infects due to a high rate of genetic mutation, and Epstein-Barr virus (EBV), a DNA virus, which persists in B cells for life, in the 95% of people that become infected. In cross- sectional and longitudinal studies of EBV seropositive, HLA-A2+, young (18-22 years), middle age (25-59 years), and older (>60 years) donors, we demonstrate that CD8 memory TCR repertoires to three immunodominant epitopes, known to have cross-reactive responses, IAV- M158-66 (M1), EBV-BMLF1280-288 (BM), and EBV-BRLF109-117 (BR) co-evolve as individuals age. Cross-sectional studies showed that IAV-M1- and both EBV-specific repertoires narrowed their TRBV usage with increasing age manifesting to different degrees for each epitope. In fact, narrowing of EBV-BM and EBV-BR-specific TRBV usage correlated with increasing age. IAV- M1-specific TRBV usage was significantly narrowed by middle-age. There was evidence that TRBV usage was changing with increasing age. For instance, IAV-M1-specific dominant BV19 usage appeared to become bimodal showing either high or low frequency of usage in the older age group, while BV30 usage frequency directly correlated with age. For the EBV epitope-specific responses there was preferential usage of particular TRBV and changes in the hierarchy of BV family usage in the different age groups. There appeared to be focusing of the TRBV repertoire by all 3 epitopes to three common BV in the older donors, which would be consistent with retention of crossreactive TCR suggesting co-evolution. Longitudinal studies tracking two donors over 14- 15 years (middle age to older) showed that there were continuous modulations in the TCR repertoire of IAV-M1, EBV-BM and EBV-BR-specific responses over time. There was evidence that acute IAV infection could contribute to these changes in TCR repertoire. This could be occurring by the TCR cross-reactivity that is known to exist between these 3 epitopes, and which appeared to be enhanced during acute IAV infection based on increased usage of common shared TRBV. These studies suggest that virus-specific TCR repertoires change over time as individuals age leading to narrowing of the repertoire favoring retention of potentially crossreactive TCR.