Downmodulation of cholesterol biosynthetic network governs activation of the innate immune response to Japanese encephalitis virus infection

Viruses remodel metabolic processes and utilize host lipids for different stages of their life cycle. Our earlier studies have shown that the flavivirus Japanese encephalitis virus (JEV) downmodulates several key proteins involved in sterol and lipid biosynthesis. Through a lipidome analysis, we report that virus infection dysregulates nearly 41% of the cellular lipids in mouse embryonic fibroblasts (MEFs). This manifests as down-modulation of cholesterol, cholesterol esters, and glycerolipids and upregulation of ceramides and several phospholipids. Significant transcriptional downregulation of cholesterol biosynthetic pathway genes was observed in JEV-infected MEFs and mouse bone marrow-derived macrophages (BMDMs). This effect was dependent upon an active interferon (IFN) signaling node. Both knockdown and pharmacological inhibition of 7-dehydrocholesterol reductase (Dhcr7), a key regulator of the cholesterol biosynthesis pathway, exerted potent antiviral effects by blocking viral replication and enhancing IFN signaling. Direct supplementation with the Dhcr7 substrate, 7-dehydrocholesterol (7DHC), showed similar antiviral effects. A partial inhibition of virus replication was also observed in cells deficient for IFN signaling, highlighting an IFN-independent antiviral role of Dhcr7 inhibition. Overall, these findings underscore the potential of cholesterol biosynthetic pathway inhibition as an antiviral strategy for JEV.IMPORTANCEJEV, a mosquito-borne virus, is a leading global cause of virus-induced encephalitis with a significant disease burden in Southeast Asia. In this study, we observe that the cellular lipid composition changes in virus-infected cells, with lower levels of cholesterol and cholesterol esters. We also observe that specific genes of the cholesterol biosynthesis pathway are decreased, and this depends on the activation of the antiviral interferon (IFN) response. We have characterized one specific downregulated gene Dhcr7, which catalyzes the conversion of 7-dehydrocholesterol (7DHC) to cholesterol. Depletion of the Dhcr7-specific mRNA, inhibition through drugs, or adding the substrate 7DHC further enhanced the IFN response and blocked virus replication. Our study highlights that downregulation of the cholesterol biosynthetic pathway has the potential to be developed into an antiviral strategy.  .