VGF and infection: VGF−/O1−VV infection did not increase pERK1/2 levels compared with those in mock-treated serum-starved NHLF cells, whereas VGF+/O1+VV, VGF+/O1−VV or VGF−/O1+VV resulted in a significant increase (p < 0.001, p < 0.01 or p < 0.05, respectively; Figure 2C).