CD8A and viral infectious disease: In both HLA-B*57:01 positive, yellow fever vaccinated donors who were examined, we were able to show that the donor’s memory responses included a breadth of CD8+ T cell clonotypes that included T-cell receptors (TCR) which exclusively recognized the K9F epitopes but importantly also TCR which recognized both the K9F epitope and which also cross-recognized the synthetic variants of the epitope with an alanine (K9A) or valine (K9V) at the P9 position of the epitope.