Expression of Avian Influenza Virus Receptors and H5N1 Virus Infection In Human Respiratory Tract

Abstract

Receptor specificity restricts influenza virus cross species transmission, with SAα2,6 Gal and SAα2,3 Gal sialic acids recognized by human and avian influenza viruses, respectively. This study investigated the distribution of these two species of sialic acids in the human respiratory tract. The SAα2,3 Gal species was infrequently detected in the upper respiratory tract, but prevalent in the lower part, while the SAα2,6 Gal species is more common in the upper respiratory tract. Though alveolus cells are more susceptible than trachea and bronchus epithelial cells to avian influenza H5N1 virus infection in the ex vivo experiment, H5N1 virus was found to infect the upper respiratory tract epithelial cells of a human case. It was also found that H5N1 virus infection occurs in the epithelial cells of the respiratory tract which do not express detectable SA α2,3Gal. These observations may be important to investigate further if the currently-observed limited human to human transmission by H5N1 virus is associated with the differential expression of SAα2,3 Gal in human upper respiratory tract among individuals.