CASD1 and infection: To test the effects of 9-O-Ac and 7,9-O-Ac on virus infection, WT, ΔCasD1, and CasD1-OX HEK-293 cells were inoculated with human H1N1 (A/California/04/2009) and human H3N2 (A/Victoria/361/2011) IAV strains, and we found no significant difference in infection efficiency in any of these cells (Fig. 6A).