Tissue Distribution Of Influenza Virus Sialic Acid Receptors In SPF Chicken And BALB/c Mice

Receptor binding is the first step for the infection of a virus, therefore, the distribution of specific receptors on the cell surface is one of the major determinants for its tissue tropism. It is believed that avian influenza virus can specifically bind to SAα2,3 Gal receptors, which mainly expressed on the surface of respiratory epithelial cells of poultry; while human influenza virus prefer to bind to SAα2,6 Gal receptors that are dominantly distributed on the surface of respiratory epithelial cells of humans. However, the incidence of cross-species transmission of avian influenza virus have occurred frequently in recent year and raised great concerns on the potential of a pandemic caused by the avian origin influenza virus. The underline mechanism of the cross-species transmission of the avian influenza viruses is still unclear. So in this study, the distribution of sialic acid receptor in different tissues of SPF chicken and BLAB/c mice was studied by using the combination of histochemistry and virus binding assays. The results of this study accumulate basic data for the study on the receptor binding mechanism of avian influenza virus in the future.The detailed distribution of SAα2,3 Gal and SAα2,6 Gal sialic acid receptors in tissues of SPF chickens and BLAB/c Mice was detected by using lectin histochemistry assays. The results showed that the SAα2,3 Gal and SAα2,6 Gal receptors coexist in many organs in both chicken and mice, but the abundance of them are different among organs. In SPF chickens, only SAα2,3 Gal receptors were detected in the turbinate and thymus gland and which is contrary to the alveolar and pancreas that they have only SAα2,6 Gal receptors; in the liver and bursa, SAα2,6 Gal receptors are predominantly expressed, while in the muscular stomach, ileum, cloaca, spleen, and kidney, SAα2,3 Gal receptors are predominant. In BLAB/c mice, only SAα2,6Gal receptors were detected in the Colon and rectum; the trachea, kidney, stomach predominantly express the SAα2,3 Gal receptors; whereas the esophagus, spleen, and turbinate express predominantly the SAα2,6 Gal receptor.In the virus binding assays, influenza viruses A/Duck/Anhui/2/2006(H5N1) [AH2] (specific for SAα2,3 Gal receptor) and A/Sichuan/1/2009(H1N1) [SC1] (specific for SAα2,6 Gal receptor) could bind to most of the tissues of SPF chickens and BLAB/c mice without significant differences and no virus binding was found in bursa of fabricius for both viruses. The AH2 couldn’t bind to the brain of SPF chickens, but the two viruses could bind to colon and rectum of mice from where no SAα2,3 Gal receptor was detected; and the two viruses bound to the testis of mice, which didn’t contain any of the two types of receptors.In conclusion, SAα2,3 Gal and SAα2,6 Gal receptors are widely distributed in most of the tissues of SPF chicken and BLAB/c mice, but the SAα2,3 Gal receptor is the predominant receptor in SPF chicken and which in BLAB/c mice is SAα2,6Gal receptor. The results of virus binding assays were not consistent with our knowledge about the receptor binding properties of avian influenza viruses, and the reasons need to be explored further in the following experiments.