CD8+ gamma-delta TCR+ and CD4+ T cells produce IFN-γ at 5–7 days after yellow fever vaccination in Indian rhesus macaques, before the induction of classical antigen-specific T cell responses

The yellow fever 17D (YF-17D) vaccine is one of the most efficacious vaccines developed to date. Interestingly, vaccination with YF-17D induces IFN-γ production early after vaccination (days 5–7) before the development of classical antigen-specific CD8+ and CD4+ T cell responses. Here we investigated the cellular source of this early IFN-γ production. At days 5 and 7 post-vaccination activated CD8+ gamma-delta TCR T cells produced IFN-γ and TNF-α. Activated CD4+ T cells produced IFN-γ and TNF-α at day 7 post-vaccination. This early IFN-γ production was also induced after vaccination with recombinant YF-17D (rYF-17D), but was not observed after recombinant Adenovirus type 5 (rAd5) vaccination. Early IFN-γ production, therefore, might be an important aspect of yellow fever vaccination.