ST3GAL5 and infection: Transfection of HEKΔSiaGSL cells with ST3Gal5, known as sialyllactosyl-ceramide (GM3) synthase (Figure 2A), results in ∼2.5-fold enhanced HU02Av−H5 infection but, intriguingly, infection was more efficiently enhanced by ST3Gal5 in HEKΔSia (∼6-fold) and HEKΔSiaN (∼15-fold) cells.