Expression of 9-O- and 7,9-O-acetyl modified sialic acid in cells and their effects on influenza viruses

Karen N. Barnard; Brian R. Wasik; Justin R. LaClair; Wendy S. Weichert; Brynn K. Lawrence; Colin R. Parrish

However, A549 ΔSIAE+CasD1 showed increased growth rates compared to ΔSIAE or 252 WT cells, while ΔSIAE cells had slightly lower growth rates compared to WT. This 253 suggests that 7,9-O-and 9-O-Ac may affect cell metabolism and growth rates, and that 254 these effects may be cell type specific. Overall, these results show that SIAE regulates 255 in infection efficiency in any of these cells (Fig. 6A) . IAV strains also showed equal 265 infection efficiency on MDCK WT, ΔCasD1, and CasD1-OX (Fig. 6C) . However, ICV 266 strains C/Ann Arbor/1/50 and C/Taylor/1233/1947 showed no infectivity in MDCK 267 ΔCasD1 (Fig. 6B) . Only the Ann Arbor strain recovered infectivity in MDCK CasD1-OX 268 at much lower levels than in MDCK WT, likely due to the lower surface expression of 9-269 O-and 7,9-O-Ac in these cells. It therefore appears that 7,9-O-Ac and 9-O-Ac do not 270 strongly influence IAV infection, likely due to their low levels of expression. However, 271