Bovine rotavirus exploits host arginine metabolism to facilitate replication: A novel antiviral strategy targeting the arginase-iNOS axis.

Bovine rotavirus (BRV) is a leading cause of severe diarrhea in calves, resulting in significant economic losses globally. Viruses often reprogram host metabolism to support their replication; however, the metabolic interplay between BRV and host arginine metabolism remains unclear. In this study, untargeted metabolomics revealed that BRV infection significantly alters arginine biosynthesis pathways in MA104 cells, leading to a depletion of intracellular arginine and its precursors. We found that exogenous arginine supplementation promotes BRV replication, suggesting the virus exploits this amino acid. Further investigation showed that BRV infection upregulates both the activity and transcription of arginase (ARG) and inducible nitric oxide synthase (iNOS), the two key enzymes consuming arginine. While individual inhibition of ARG or iNOS showed limited or dose-dependent antiviral effects, simultaneous blockade of both enzymes significantly restricted BRV replication. Mechanistically, this dual inhibition restored intracellular arginine levels, which subsequently induced sustained activation of the mTORC1 signaling pathway to restrict viral replication. Notably, the specific mTORC1 inhibitor rapamycin reversed the antiviral effect of the dual blockade, indicating that the suppression of BRV is mTORC1-dependent. These findings demonstrate that BRV hijacks arginine metabolism to facilitate its own propagation and targeting the ARG/iNOS-mTORC1 axis represents a potential therapeutic strategy for controlling rotavirus infection.