ARPE-19 Epithelial Cells Fail To Initiate Type-I Interferon Signaling in Response to Human Cytomegalovirus Infection.

ARPE-19 cells are a commonly used epithelial model for studying human cytomegalovirus (HCMV) infection. We recently found that ARPE-19 cells assume a mesenchymal phenotype when maintained at low confluency and that ARPE-19 cells resemble mesenchymal fibroblasts rather than epithelial cells in HCMV infection assays. Here, using comparative proteomics analysis, we find that subconfluent ARPE-19 cells are also deficient in their ability to initiate canonical type-I interferon signaling. Comparative proteomic analysis between subconfluent ARPE-19 and MRC-5 cells revealed a lack of canonical type-I interferon response in ARPE-19 cells upon HCMV infection, evidenced by the absence of interferon stimulated gene (ISG) induction. qRT-PCR and RNA-sequencing analysis revealed that ARPE-19 cells fail to initiate interferon-beta transcription in response to HCMV infection, yet they are competent to respond to exogenously interferon-b, indicating a failure in early pathogen detection. ARPE-19 cells showed low baseline levels of key intracellular pattern recognition receptors (PRRs) such as CGAS and IFI16, as well as the signaling molecule STING. This deficiency was associated with a failure to activate IRF3 phosphorylation, a crucial step in interferon signaling. These findings suggest an upstream defect in the early detection of viral components, likely due to reduced expression of critical PRRs. ARPE-19 cells may be inherently deficient in initiating interferon responses due to their derivation or possibly due to their origin from an immune-privileged tissue. Our results continue to highlight important phenotypic characteristics of the ARPE-19 cell line; important considerations for those using ARPE-19 cells as an experimental infection model for studying HCMV or other human viruses.