Structural analysis of N-glycans in chicken trachea and lung reveals potential receptors of chicken influenza viruses

Although avian influenza A viruses (avian IAVs) bind preferentially to terminal sialic acids (Sia) on glycans that possess Sia alpha 2-3Gal, the actual glycan structures found in chicken respiratory tracts have not been reported. Herein, we analyzed N-glycan structures in chicken trachea and lung, the main target tissues of low pathogenic avian IAVs. 2-Aminopyridine (PA)-labeled N-glycans from chicken tissues were analyzed by combined methods using reversed-phase liquid chromatography (LC), electrospray ionization (ESI)-mass spectrometry (MS), MS/MS, and multistage MS (MSn), with or without modifications using exoglycosidases, sialic acid linkage-specific alkylamidation (SALSA), and/or permethylation. The results of SALSA indicated that PA-N-glycans in both chicken trachea and lung harbored slightly more alpha 2,6-Sia than alpha 2,3-Sia. Most alpha 2,3-Sia on N-glycans in chicken trachea was a fucosylated form (sialyl Lewis X, sLe(x)), whereas no sLe(x) was detected in lung. By contrast, small amounts of N-glycans with 6-sulfo sialyl LacNAc were detected in lung but not in trachea. Considering previous reports that hemagglutinins (HAs) of avian IAVs originally isolated from chicken bind preferentially to alpha 2,3-Sia with or without fucosylation and/or 6-sulfation but not to alpha 2,6-Sia, our results imply that avian IAVs do not evolve to possess HAs that bind preferentially to alpha 2,6-Sia, regardless of the abundance of alpha 2,6-Sia.

Automated summary

This study analyzed N-glycan structures in chicken respiratory tracts and found that avian influenza A viruses preferentially bind to glycans with Sia alpha 2-3Gal. The results showed that chicken trachea had a high abundance of fucosylated alpha 2,3-Sia, while no fucosylation was detected in the lung. Additionally, lung tissue contained a small amount of N-glycans with 6-sulfo sialyl LacNAc. These findings suggest that avian influenza A viruses do not evolve to bind to alpha 2,6-Sia, regardless of its abundance.