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Influenza A virus receptors in the respiratory and intestinal tracts of pigeons

To understand the basis of the resistance of pigeons to Asian lineage highly pathogenic avian influenza virus (HPAIV) subtype H5N1, we examined the presence of influenza virus receptors, sialic acids linked to galactose by an α-2,3 linkage (SAα2,3Gal) or by an α-2,6 linkage (SAα2,6Gal), in respiratory and intestinal tracts of pigeons and compared the distributions of N-acetylneuraminic and N-glycolylneuraminic acids in the trachea and intestines of pigeons and chickens. Results suggested that the epithelial surfaces of the larynx, trachea, bronchus, and bronchiole of pigeons contained abundant SAα2,6Gal with little or no SAα2,3Gal. In contrast, the epithelial surfaces of the pharynx, trachea, bronchus, and bronchiole of chickens contained mainly SAα2,3Gal, a well-recognized receptor for avian influenza viruses including H5N1 HPAIV. A similar distribution pattern of N-acetylneuraminic and N-glycolylneuraminic acids in the trachea and intestines of pigeons and chickens was observed. Overall, the results suggest that SAα2,6Gal is the major receptor in the pigeon airway, which may partly contribute to the resistance of pigeons to Asian lineage HPAIV subtype H5N1.