Hints towards this mechanism of heightened infection and subsequent growth inhibition in the presence of BMP-4 came from the observation that the parental, non-BMP-4 virus infection resulted in reduced growth inhibition at the later time point of day 9 compared to day 6, possibly due to cells that had escaped infection contributing to greater proliferation and reduced growth inhibition (Figure 3C). Here, BMP4 is linked to viral infectious disease.