CD8A and infection: Recent studies have examined development of human CD8+ T cell responses to a range of primary infections, including attenuated yellow fever virus, attenuated vaccinia virus, influenza, tick-borne encephalitis virus (TBEV), hantavirus, and Epstein-Barr virus [42–47], demonstrating that antigen-specific cells have immediate cytotoxic capacity directly ex vivo during the acute phase of these infections.