Bovine viral diarrhea virus (BVDV) relies on cellular lipid droplet biogenesis and lipolysis to provide energy for viral replication.

Bovine viral diarrhea virus (BVDV), one of the most important viral pathogens in cattle, causes serious economic losses due to immunosuppression and persistent infections. Previous studies have shown a tight connection between virus infection and lipid metabolism, particularly in the formation and degradation of lipid droplets (LDs). However, the pathogenic mechanism of BVDV infection and the molecular mechanisms by which viral proteins reprogram lipid metabolism remain unclear. We found that BVDV increased cellular LD accumulation by enhancing the production of new lipids, accelerating exogenous fatty acid uptake, and elevating diacylglycerol acyltransferase (DGAT)-dependent esterification of fatty acids (FAs). The generated LDs subsequently release free fatty acids (FFAs) via adipose triglyceride lipase/hormone-sensitive lipase (ATGL/HSL)-dependent lipolysis. This lipolysis-dependent release of FFAs is accelerated and transferred to mitochondria for oxidation by increasing contact between LDs and mitochondria, thereby promoting viral replication. Furthermore, BVDV core protein targets the surface of LDs, increasing and recruiting fatty acid synthase (FASN) and ATGL to promote LD mobilization. Meanwhile, the core protein interacts with mitochondria, linking mitochondria to LDs and facilitating the release of FAs for efficient fatty acid oxidation. Collectively, this study demonstrates that the BVDV core protein regulates cellular lipid metabolism to support BVDV replication, contributing to understanding the pathogenetic mechanisms by which BVDV interacts with host cells.