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The copyright holder for this preprint (which was not peer-reviewed) is the author/funder.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 (65, 66) . To specifically compare the effects of added Neu5Gc or Neu5Ac on the efficiency of 315 infection, the same three IAV strains were incubated with mouse serum from either wild-type mice (>80% Neu5Gc) or CMAH -/mice (100% Neu5Ac) prior to inoculation of cells (Fig. 8B) . In this case no specific trend was detected for the three viruses tested. Victoria H3N2 showed almost complete inhibition of infection by both sera, while PR8 H1N1 had a lower level of inhibition. Only pH1N1 showed a significant difference in response to the serums, with the WT 320 mouse serum having a much stronger inhibitory effect compared to the CMAH -/serum. This suggests that Neu5Gc vs. Neu5Ac inhibition may vary by virus strain, and that likely depends on some combination of HA binding specificity and NA activity. The copyright holder for this preprint (which was not peer-reviewed) is the author/funder. . https://doi.org/10.1101/800300 doi: bioRxiv preprint cells and associated mucus layers. The percentages of O-acetyl modified Sia in the tissues of mice varied widely, with high levels of 7,9-O-Ac 2 and 9-O-Ac being found on erythrocytes (~47%) and the colon (~19%). The levels in most other tissues varied between 2 and 9%, although these would likely be associated with higher levels on the smaller subsets of cells that were positive for staining with the probes. Neu5Gc was also present in many wild-type mouse 345 tissues with expression varying widely (between 10 and 80%). This is consistent with staining for Neu5Gc previously reported in some mouse tissues (44). 4-O-Ac Sia was found in small quantities in only a few tissues, with the highest being found in small intestine (~2%). This is consistent with previous findings of 4-O-Ac levels in mouse brain and liver quantified by GC/MS, although gut associated levels of 4-O-Ac were much higher in that study, possibly due to has not yet been identified, little is known about its synthesis, expression, or regulation (22, 23).