The effects of modified sialic acids on mucus and erythrocytes on influenza A virus HA and NA functions

Karen N. Barnard; Brynn K. Alford-Lawrence; David W. Buchholz; Brian R. Wasik; Justin R. LaClair; Hai Yu; Rebekah Honce; Stefan Ruhl; Petar Pajic; Erin K. Daugherity; Xi Chen; Stacey L. Schultz-Cherry; Hector C. Aguilar; Ajit Varki; Colin R. Parrish

Here we define the expression of 7,9-O-Ac, 9-O-Ac, and Neu5Gc modified Sia in the mucus, saliva, and on erythrocytes of different IAV host animals, as well as on the tissues and secreted mucus of mice. We also test the effects of these modifications on HA binding and NA activity of different strains of IAV, as well as their potential to alter virus infection. The copyright holder for this preprint (which was not peer-reviewed) is the author/funder. . https://doi.org/10.1101/800300 doi: bioRxiv preprint trachea as well as in the tracheal sub-mucosal glands that produce most of the mucus ( Fig. 2A) . These modified Sia were also found throughout the GI tract, with staining associated with 160 epithelial cells, goblet cells, and associated mucus layers of the gastrointestinal tissues, including the stomach, small intestine, and colon (Fig. 2B) . Interestingly, 9-O-Ac appeared to be present in higher amounts in most tissues, including salivary gland and esophagus, while the 7,9-O-Ac staining was minimal. However, 7,9-O-Ac did stain stronger than 9-O-Ac in stomachassociated mucus, and on tracheal epithelial cells. This seems to indicate that while the same Table 1) , while, as expected, the CMAH -/mice showed only Neu5Ac in all tissues, similar to amounts reported previously for some of those tissues (44) (Supplemental Table 2 ). The lack of Neu5Gc in CMAH -/mice was also seen in GI tissues, indicating that Neu5Gc from dietary sources was not 180 detectably being taken up by these mice, as is seen in humans who eat a diet containing that Neu5Gc (46) . In the WT mice, tissues showed a great deal of variability in Neu5Gc expression.