Quail carry sialic acid receptors compatible with binding of avian and human influenza viruses.

There is growing evidence that some terrestrial avian species may play a role in the genesis of influenza viruses with pandemic potential. In the present investigation, we examined whether quail, a widespread-farmed poultry, possess the proper characteristics for serving as an intermediate host for the zoonotic transmission of influenza viruses. Using a lectin-based staining based on specific agglutinins, we found that, in addition to the presence of sialic acid alpha2,3-galactose (SAalpha2,3-gal) linked receptors, there are abundant sialic acid alpha2,6-galactose (SAalpha2,6-gal) linked receptors in quail trachea and intestine. The presence of abundant SAalpha2,6-gal-linked receptors explains, at least in part, the circulation of avian influenza viruses with human-like receptor specificity in quail. In quail trachea, SAalpha2,3-gal linked receptors are present primarily in non-ciliated cells, while SAalpha2,6-gal linked receptors are localized predominantly on the surface of ciliated cells. In quail intestine, both types of receptors were found on epithelial cells as well as in crypts. In a solid-phase overlay binding assay, both avian and human influenza viruses bind to plasma membranes prepared from epithelial cells of quail trachea and intestine, strongly suggesting that these receptors are functional for binding of influenza viruses from different species. Together with previous observations, these results are consistent with the notion that quail could provide an environment for the spread of reassortants between avian and human influenza viruses, thus acting as a potential intermediate host.