p38 MAPK Signaling Enhances Reovirus Replication by Facilitating Efficient Virus Entry, Virus Capsid Uncoating and Post-Uncoating Steps

Mammalian orthoreovirus serotype 3 Dearing an orphan human virus currently being pursued as an oncolytic virus in multiple phase I/II clinical trials. Previous clinical trials have emphasized the importance of patient pre-screening for prognostic markers to improve therapeutic success. However, currently, only generic cancer markers such as EGFR, Hras, Kras, Nras, Braf and/or p53 are utilized and have exhibited limited benefit in predicting therapeutic efficacy. Utilization of more specific markers that influence specific steps during reovirus replication could prove beneficial as prognostic markers. This study delineated the role of p38 MAPK signaling during reovirus infection and illustrated a connection between specific p38 MAPK isoforms and reovirus infection. Using a panel of specific p38 MAPK inhibitors and an inactive inhibitor analogue, we demonstrated that p38 MAPK signaling is essential for establishment of reovirus infection by enhancing reovirus endocytosis, facilitating efficient reovirus uncoating at the endo-lysosomal stage, and augmenting post uncoating replication steps. Using a broad panel of human breast cancer cell lines, we observed susceptibility of reovirus infection corresponded with virus binding and uncoating efficiency, which was strongly correlated with status of the p38β isoform. Together, our study proposes p38β as a potential prognostic marker for early stages of reovirus infection that are crucial to establishment of successful reovirus infection.