Production of Infectious Reporter Murine Norovirus by VP2 trans-Complementation

Human norovirus (HuNoV) causes gastroenteritis, a disease with no effective therapy or vaccine. Murine norovirus (MNV) easily replicates in cell culture and small animals and has often been used as a model to elucidate the structural and functional characteristics of HuNoV. A MNV plasmid-based reverse genetics system was developed to produce modified recombinant virus. In this study, we attempted to construct the recombinant virus by integrating a foreign gene into MNV ORF3 that encodes the minor structural protein VP2. We found that deletion of VP2 expression abolished infectious particles from MNV cDNA clones, and supplying exogenous VP2 to the cells rescued the infectivity of cDNA clones without VP2 expression. In addition, we found that the coding sequence of C-terminal ORF3 was essential for cDNA clones compensated with VP2 to produce infectious particles. Further, the recombinant virus with exogenous reporter genes in place of the dispensable ORF3 coding region was able to propagate when VP2 was constitutively supplied. Our findings indicate that foreign genes can be transduced into the norovirus ORF3 region when VP2 is supplied and that successive propagation of modified recombinant norovirus could lead to the development of norovirus-based vaccines or therapeutics. IMPORTANCEIn this study, we revealed that some of the coding regions of ORF3 could be replaced by foreign gene and infectious virus could be produced under conditions with VP2 supplied. Propagation of this virus depended on VP2 being supplied in trans, indicating that this virus could infect only once. Our findings help to elucidate the functions of VP2 in virus lifecycle and to the development of other caliciviral vectors for recombinant attenuated live enteric virus vaccines or therapeutics.