VAMP4 and viral infectious disease: Nonetheless, after 6 h, the β-galactosidase expression level in AP4E1-depleted cells had reached the level of the control cells, whereas STX10- and VAMP4-depleted cells still exhibited a lower level of β-galactosidase expression (Fig. 3A, 6 hpi), suggesting that the depletion of AP4E1 had slowed the early stages of virus infection, but this was eventually overcome.