TP53 and infection: However, Grand and colleagues observed that in A549 cells infected at a multiplicity of infection greater than that used in this study, significant amounts of p53 remained at 18 hpi (44), and in our study, significant amounts of p53 remained detectable at 24 hpi in both HeLa and MRC5 cells (Fig. 5), suggesting that loss of p53 from L4P by 16 hpi is not due to its degradation.