ABSTRACT
Avian influenza virus H6N1 subtype has been circulating in aquatic bird and terrestrial bird,and is the most frequently detected subtype of influenza A virus in those hosts.Genetic analysis results suggested that this virus might be the progenitor of the highly pathogenic avian influenza H5N1 virus,as seven of eight gene segments of those viruses had a common source.As continuing evolution of H6N1,it could spread across species barriers to mammals and had strong infection ability in mice,swine and ferrets.Serological epidemiological survey showed that a few people were positive for H6 avian influenza virus antibody and then the world's first human infection with influenza virus H6N1 subtype was reported in May 2013.Therefore,with the expansion of the host range of the virus,gene mutation and gene reassortment of H6N1 virus can occur in these hosts,and then it may evolve into novel variant strain with infected human potential.
ABSTRACT
SAαt2,6 and SAα2,3 linked sialic acid molecules on epithelial cell membrane served as receptors for influenza virus, which axe specifically recognized by human and avian influenza viruses, respectively. The distribution of these two species of sialic acids in human respiratory tract from different anatomical sites and different age groups was investigated. The results showed that SAα2,3Gal species was prevalent in respiratory bronchiole and lung alveolar epithelium, but was infiequent in trachea, bronchus and bronchiole. On the contrary, the SAα2,6Gal species was more common in the trachea and bronchus and to a lesser degree in the alveolar epithelium. When compared the expression levels of SAα2,6Gal and α2,3Gal in the respiratory tract among different age groups, no significant difference was found. In the ex vivo H5N1 virus infection study, alveolus epithelium were found to be more susceptible to avian influenza than trachea and bronchus epithelial cells. These results suggest that the human respiratory tract, to some extent, is permissive for avian influenza viruses. The currently-observed limited human to human transmission of H5N1 virus may be associated with the different abundance of SAα2,3Gal linkages in human upper respiratory tract among individuals.