The host response to murine norovirus infection induces significant engagement of IFN and TNF-a immunological programs

Abstract Norovirus, a positive stranded RNA virus in the family Caliciviridae, is a major cause of acute gastroenteritis. Outbreaks occur primarily in locations such as schools, nursing homes, and cruise ships where individuals are in close proximity. An acute norovirus infection can become chronic in immunocompromised individuals, and an effective antiviral drug is needed. The 7.5 kb genome encodes a polyprotein in ORF1 that is co-translationally cleaved by the viral protease into six nonstructural proteins. The two structural proteins, VP1 and VP2, are encoded in ORF2 and ORF3, respectively. The viral proteins mediate replication and packaging of the genome into icosahedral capsids. The host cell provides additional proteins and building blocks for replication, but only a few essential host factors have been elucidated. To gain insight into the host response to norovirus infection, we performed next generation sequencing-based RNA sequencing on murine macrophages infected with murine norovirus. We obtained RNA from a time course of infection at 0, 8, 14, and 20 hours post infection with mock infections at 0 and 20 hours. Analysis of the host transcriptome reveals full activation of cellular immune response pathways, with NF-kβ, STAT1, and STAT3-based signaling evident. In addition, we observed transcriptional evidence of IRF3 activation with a transition to IRF3/IRF7 signaling. TNF-a-based activation is also clear with most downstream effectors up-regulated. These observations correlate well with the known cytokine response from patient serum samples, disease progression, and symptomatology of human norovirus. We are currently applying these findings toward drug discovery efforts.