Molecular responses of human retinal pigment epithelial cells to ebolavirus VP24

Uveitis (inflammation inside the eye) is a disabling manifestation of the post-Ebola syndrome that affects 10% to 35% of individuals who survive the infection. Post-Ebola uveitis presents with diverse clinical features but frequently involves the posterior segment of the eye, where the retinal pigment epithelium plays a key role in directing immune responses. Our previous work shows that this epithelium is relatively susceptible to infection with Zaire ebolavirus (EBOV), the strain responsible for most Ebola outbreaks. In addition to production roles, viral proteins may act to alter the molecular responses of host cells.

We investigated the activity of EBOV viral protein 24 (VP24) in human retinal pigment epithelial cells. An EBOV VP24 expression plasmid was constructed in-house. Multiple primary cell isolates were lipofectamine-transfected, first with VP24 or control expression plasmids and then with polyinosinic-polycytidylic acid (poly I:C) to simulate viral RNA. A type I interferon (IFN) response to transfection was confirmed by an IFN-β enzyme-linked immunosorbent assay. Cellular immune responses after 4- and 24-h exposures to poly I:C were characterized by reverse transcription-quantitative polymerase chain reaction.

Multidimensional scaling, drawing on 19 immune response-related gene transcripts, covering antiviral, immunomodulatory, and proinflammatory molecules, demonstrated changes in gene expression profiles following transfection. Analysis of individual cell isolates showed a range of changes, including upregulation and downregulation of different gene transcripts across the two investigated time points.

Our findings suggest VP24 elicits variable immune responses from human retinal pigment epithelial cells, potentially contributing to the variation in clinical presentations of uveitis in Ebola survivors.