The Epithelial-to-Mesenchymal Transition Supports HCMV Infection and Biosynthesis in Mammary Epithelial Cells Through Two Distinct Mechanisms.

Human cytomegalovirus (HCMV) infects a wide range of cell types in the body, including a variety of epithelial cell types. Despite the significance of epithelial cells during infection, HCMV has been difficult to study in epithelial cells. In this study, we examined HCMV infection in mammary and prostate epithelial cell lines, finding that the virus establishes a semi-permissive, biosynthetically abortive state. Building on previous work, we hypothesized that shifting epithelial cells to a mesenchymal cell state would restore HCMV biosynthesis and progeny production. To test this hypothesis, we induced epithelial-to-mesenchymal transition (EMT) using TGF-{beta} and the EMT-transcription factor (EMT-TF) SNAIL. We found that shifting strongly epithelial cell lines to a mesenchymal cell state shifted HCMV infection from a semi-permissive to fully permissive state. This effect appeared to involve two distinct mechanisms: EMT-sensitive enhancement of viral entry and EMT-sensitive enhancement of viral mRNA translation. Although the precise mechanisms remain elusive, our findings identify the epithelial-mesenchymal cell state axis as an important regulator of HCMV infection and provide new insights into how cellular differentiation states influence viral replication. They also raise the possibility that the EMT pathway, a fundamental pathway involved in development and cancer metastasis, could regulate HCMV infection in-vivo, potentially contributing to viral persistence or pathogenesis in epithelial tissues.