Anti-SARS-CoV-2 Small Molecule Targeting of Oxysterol-Binding Protein (OSBP) Activates Cellular Antiviral Innate Immunity.

Human oxysterol-binding protein (OSBP) is a potentially druggable mediator in the replication of a broad spectrum of positive-sense (+) single-stranded RNA (ssRNA) viruses, including members of the Picornaviridae, Flaviviridae, and Coronaviridae. OSBP is a cytoplasmic lipid transporting protein capable of moving cholesterol and phosphoinositides between the endoplasmic reticulum (ER) and Golgi, and the ER and lysosome. Several structurally diverse antiviral compounds have been reported to function through targeting OSBP, including the natural product compound OSW-1. Our prior work shows that transient OSW-1 treatment induces a reduction in OSBP protein levels over multiple successive cell generations (i.e., multigenerational), with no apparent cellular toxicity, and the OSW-1-induced reduction of OSBP has antiviral activity against multiple (+)ssRNA viruses. This study extends these findings and establishes that OSW-1 has in vitro antiviral activity against multiple pathogenic (+)ssRNA viruses, including human rhinovirus (HRV1B), the feline coronavirus peritonitis virus (FIPV), human coronavirus 229E (HCoV-229E), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We also demonstrate that OSW-1 treatment in human airway epithelial cells alters the expression of multiple antiviral innate immune mediators, including the interferon (IFN) related genes IFNB1, IFNL3, CXCL10, ISG15, and MX1. Furthermore, OSW-1 enhances the induction of specific components of type I and III IFN antiviral responses triggered by the RNA viral mimetic polyinosinic-polycytidylic acid (Poly IC). In summary, this study further demonstrates the importance of OSBP in (+)ssRNA virus replication and presents OSBP as a potential regulator of cellular antiviral innate immune responses.