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

The copyright holder for this preprint (which was not peer-reviewed) is the author/funder. . https://doi.org/10.1101/800300 doi: bioRxiv preprint 9 variants combined comprised between 2 and 16% of the Sia in most tissues, with the majority 185 being 9-O-Ac (1-9% of total Sia) ( Fig. 3B ; Supplemental Table 1 ). There was about 1.5 to 3 fold higher levels of O-acetyl Sia in most tissues of the CMAH knock-out mice ( Fig. 3C; Supplemental Table 2 ), as has been reported previously (44). The levels of 4-O-Ac Sia were generally low, making up ~2% of the Sia in small intestine (duodenum) and ~1% in spleen, testes, and esophagus. Mouse colon samples showed the highest levels of total O-acetylation, 190 with ~17% of Sia having one or more O-acetyl modification, again primarily 9-O-Ac. Given the patterns seen using the HE-Fc virolectin staining, the 7,9-O-and 9-O-Ac forms must be present at high levels within or on certain cell sub-populations, as well as within mucus or mucussecreting cells. For example, the high levels of 7,9-O-and 9-O-Ac found in the mouse colon were most likely associated with secreted mucus as most of those modified Sia were present in 195 goblet cells (Fig. 2B) . However, the differences seen between probe binding and the ratios of the different modified Sia within the total Sia underscore the importance of quantifying the different forms.