Molecular Biological and Biochemical Studies on Avian Influenza Virus Receptors in Different Avian Species

Avian influenza viruses are considered to be the key contributors to the emergence of human influenza pandemics. A major determinant of infection is the presence of virus receptors on susceptible cells to which the viral haemagglutinin is able to bind. Avian viruses preferentially bind to sialic acid alpha 2,3-galactose (SA alpha 2,3-Gal) linked receptors, whereas human strains bind to sialic acid alpha 2,6-galactose (SA alpha 2,6-Gal) linked receptors. Although ducks are the major reservoir for influenza viruses, they are typically resistant to the effects of viral infection, in contrast to the frequently severe disease observed in chickens In order to understand whether differences in receptors might contribute to this observation, we studied the expression of influenza receptors in upper and lower respiratory organs of ducks and chickens (expression of ST3Gal-III sialyltransferase and ST6Gal-I sialyltransferase genes) using semi quantitative RT-PCR. There was a marked difference in the expression of primary receptor type in the trachea of chickens and ducks. In chicken trachea, SA alpha 2,6-Gal was the dominant receptor type whereas in ducks SA alpha 2,3-Gal receptors were most abundant. This suggests that chickens could be more important as an intermediate host for the generation of influenza viruses with increased ability to bind to SA alpha 2,6-Gal receptors and thus greater potential for infection of humans. Chicken tracheal and intestinal epithelial cells also expressed a broader range of SA alpha 2,3-Gal receptors in contrast to ducks, which suggests that they may be able to support infection with a broader range of avian influenza viruses. {[}Hussein I. El-Belbasi; Mohamed F. Dowidar and Safaa I. Khater. Molecular Biological and Biochemical Studies on Avian Influenza Virus Receptors in Different Avian Species. Life Science Journal. 2011; 8(1):44-51] (ISSN: 1097-8135).