Determination of N-Linked Sialyl-Sugar Chains in the Lungs of Domestic Cats and Dogs in Thailand Susceptible to the Highly Pathogenic Avian Influenza Virus (H5N1)

Highly pathogenic and potentially pandemic H5N1 avian influenza A viruses have become endemic and are now residing in Asia, Europe, Africa, and the Middle East. H5N1 viruses have been shown to cross the species barrier and infect both dogs and cats. Domestic cats and dogs in Thailand, which were naturally infected with H5N1, exhibited severe pulmonary edema and peumonia in lung tissue as well as in other tissue dysfunctions. In order to understand the structure and quantity of influenza A receptor sialyl sugar chains in cats and dogs, especially in lung tissue, glycosylation profiles of N-glycans were determined from lung tissues of dogs and cats susceptible to H5N1 in Thailand by using multi- dimensional HPLC mapping combined with mass spectrometry. The results demonstrated different N-linked glycans com- position ratios between dogs and cats. There were a total of 30 kinds of N-linked glycans from cat lungs, which were comprised of 11 neutral, 13 mono-, 3 di-, and 3 tri-sialyl sugar chains, and 29 kinds from dog lungs, which were com- prised of 16 neutral, 11 mono- and 2 di-sialyl sugar chains. Cat lungs exhibited both 5-N-acetylneuraminic acid and 5-N- glycolylneuraminic acid sialic acid (Sia� 2-3Gal and Sia� 2-6Gal), but dog lungs contained only 5-N-acetylneuraminic (Sia� 2-3Gal and Sia� 2-6Gal) molecular species. The composition ratios of molar percentage of Sia� 2-3Gal for domestic cat and dog lungs were 21.5 and 9.9, respectively, while the composition ratios of Sia� 2-6Gal were 47.1 and 59.2, respec- tively. These results may indicate that domestic cats are more susceptible than dogs to H5N1 influenza virus infection and also cats and dogs play an important role as "mixing vessels" for the virus re-assortment.