Six of the 21 epitopes were detectable by 30 min after infection, including all three of the M1 peptides (M1128–135, M1207–216, M1227–237), both of the NA peptides (NA181–190, NA181–191), and one of the HA peptides (HA41–49), indicating some preference for structural protein-derived peptides at this early timepoint. This evidence concerns the gene XK and infection.