Development of a replication competent murine norovirus reporter system

Caliciviruses are significant agricultural and human pathogens that are poorly understood due to the dearth of molecular tools, including reporter systems. We report the development of a robust luciferase-based reporter system for a model calicivirus, murine norovirus (MNoV). Genetic insertion of a HiBiT tag, an 11 amino acid fragment of nanolucifersase, at the junction of the nonstructural proteins NS4 and NS5 yields infectious virus. The resultant MNoV-HiBiT produces a robust signal that is detected early in infection and occurs only in cells susceptible to MNoV infection. The MNoV-HiBiT reporter is effective at monitoring acute infection in STAT1 deficient mice. Furthermore, we used this tool to characterize two unappreciated host directed anti-MNoV compounds. The use of the MNoV-HiBiT virus enables new mechanistic studies by a rapid and quantitative means of measuring MNoV replication. The HiBiT insertion strategy we describe may be useful for the generation of other calicivirus reporters.