This approach takes advantage of the memory CD8+ T cells that develop in response to vaccination or previous infection.19, 20 Evolutionarily conserved viral epitopes may be recognized by T cells or B cells/antibodies that have been previously primed by circulating influenza strains and can provide broad protection across different influenza types (also known as preexisting immunity).21 The H5 HA protein is a major surface protein that plays a pivotal role in viral infection and the primary immune target. The gene discussed is CD8A; the disease is influenza.