Tracking epitope-specific antiviral CD4+ T cell responses to a live attenuated vaccine reveals ongoing functional responses

There are few studies that have examined the frequencies of epitope-specific CD4+ T cells following the use of a highly effective vaccine, yet such data would potentially be of value for the development of novel vaccination strategies. In this study we tracked human epitope-specific CD4+ T cell responses over time after immunisation with a live attenuated varicella zoster virus vaccine by MHC Class II tetrameric complexes and functional assays. We show that the peptide-specific responses reflect those against whole virus antigens, and are similar in both frequency and phenotype to those found in healthy volunteers, despite a highly attenuated and clinically inapparent infection.