FIG 5.

Illustration showing distribution of 2-6 SLN and 2-3 SLN in the human airway. Hia and HMW2 both bind 2-6 SLN with high affinity, with both showing a very high preference for the human-specific sialic acid Neu5Ac (2-6 SLN-Ac) over Neu5Gc (2-6 SLN-Gc). This means that NTHi strains expressing either Hia or HMW2 are able to colonize the entire respiratory tract (upper in red, lower in blue). HMW1 preferentially binds 2-3 SLN, and with no affinity for Neu5Ac over Neu5Gc, which means that NTHi strains only expressing HMW1 may have a preference for the lower respiratory tract (blue). Schematic diagram taken from GetDrawings.com (http://getdrawings.com/respiratory-system-with-label-drawing#respiratory-system-with-label-drawing-13.jpg) under a CC BY-NC 4.0 license.