Characterization of extracellular vesicles from U-2OS15E, a human osteosarcoma cell line persistently infected by BK polyomavirus

Abstract

The human polyomavirus BKPyV infects most people worldwide and establishes a lifelong persistent infection in the renourinary tract. The virus rarely gives symptoms in healthy people, but it can cause severe disease under certain immunocompromised states. Despite its high prevalence, our knowledge about how the virus evades host immunity and persists still poor. Extracellular vesicles (EVs) are released by all cells and has in the last decade gained recognition as important mediators of cell to cell communication. In recent years, evidence that virus infected cells release EVs containing viral factors and host components related to infection has emerged. Therefore, as an approach to better understand BKPyV persistence, we analyzed the protein content of EVs from U-2OS15E, a persistently BKPyV-infected osteosarcoma cell line, and its ancestral cell line U-2OS. EVs were purified by ultrafiltration combined with size exclusion chromatography and proteomic analysis was performed with LC-MS/MS. We found that 410 proteins were enriched in EVs from U-2OS15E compared to U-2OS, and 183 proteins were deprived. We found enrichment of some proteins involved in increased cell proliferation and cell cycle arrest, and also proteins involved in innate immunity. Some of the enriched proteins in U-2OS15E EVs, such as IKKα, are known to upregulate the innate immune response while other proteins like gasdermin-D can be involved in immune evasion. Our results shed new light on persistent BKPyV infection.