Bacteriophage inhibits murine norovirus replication after co-incubation in RAW 264.7 cells

Bacteriophages (phages) are viruses of bacteria. Despite the growing progress in research on phage interactions with eukaryotic cells, our understanding of the roles of phages and their potential implications remains incomplete. The objective of this study was to investigate the effects of the Staphylococcus aureus phage vB_SauM_JS25 on murine norovirus (MNV) replication. Experiments were performed using the RAW 264.7 cell line. After phage treatment, MNV multiplication was significantly inhibited, as indicated by real-time quantitative PCR (RT-qPCR) analysis, western blot, and immunofluorescence assay. Furthermore, we demonstrated the transcriptional changes in phage-MNV co-incubated RAW 264.7 cells through RNA sequencing (RNA-Seq) and bioinformatic analysis. Our subsequent analyses revealed that the innate immune response may play an important role in the restriction of MNV replication, such as the cellular response to IFN-{gamma} and response to IFN-{gamma}. In addition, the gene expression of IL-10, Arg-1, Ccl22, GBP2, GBP3, GBP5, and GBP7 was proven to increase significantly by RT-qPCR, showing a strong correlation between RT-qPCR and RNA-Seq results. Furthermore, phage treatment activated guanylate binding proteins (GBPs), as revealed by RT-qPCR analysis, western blotting, and confocal microscopy. Taken together, these data suggest that the phage affects the innate response (such as the IFN-inducible GTPases and GBPs), reflecting their direct antimicrobial effect on the membrane structure of the MNV replication complexes, and therefore, exerts an antiviral effect in vitro. Collectively, our findings provide insights into the interactions of immune cells and phages, which improve our understanding of the actual role and potential of phages.