PROS1 and infection: Quantitative analysis of the S protein bands by densitometry showed that 3.87-, 4.65- and 0.9-fold more S protein was detected in cells without expressing the Flag-tagged eIF3f than that in cells expressing the Flag-tagged eIF3f at 12, 16 and 24 hours post-infection, respectively (Fig. 6b, lanes 3–5 and 8–10).