Indeed, in contrast with anti-Gal antibodies that are produced similarly to humans by Ggta1–/– mice (62), even if at lower levels (63), and by GGTA1–/– pigs (64–66), anti-Neu5Gc are not detected in Cmah–/– mice even feed with Neu5Gc carrying food, and could be induced only by a strong immunization with Neu5Gc-loaded non-typeable Haemophilus influenza (34), non-microbial Neu5Gc (67) or Neu5Gc positive xenogeneic cells (68), suggesting that anti-Neu5Gc induced in Cmah–/– mice are more related to elicited antibodies than diet-derived ones. This evidence concerns the gene GGTA1 and influenza.