Negative-sense RNA virus nucleocapsid as a versatile platform for gene delivery, vaccine development, and antiviral screening

Negative-sense RNA viruses replicate their genomes as nucleocapsids composed of viral RNA tightly associated with nucleoproteins and polymerase complexes. In this study, the authors examined whether purified nucleocapsids can function as autonomous units capable of initiating viral gene expression and replication when directly delivered into host cells. Using vesicular stomatitis virus (VSV) as a model, purified NCs were isolated from infected cells and introduced directly into host cells by lipid-mediated transfection. Following transfection, robust expression of viral reporter genes and viral proteins was observed, confirming that the NCs retained transcriptional activity. Viral gene expression occurred independently of viral envelope proteins and cellular entry receptors. Even in cells with reduced expression of the VSV entry receptor, NC-mediated gene expression was efficiently induced, demonstrating that the NCs bypass receptor-dependent viral entry. NCs derived from wild-type VSV supported complete viral replication and led to the production of infectious progeny virus. In contrast, NCs derived from glycoprotein-deficient VSV enabled viral gene expression and genome replication but did not generate infectious particles, indicating a replication-competent yet non-infectious system. Additionally, nucleocapsid-driven viral replication was inhibited by antiviral compounds, supporting the applicability of this platform for post-entry antiviral drug screening. 
(MN)