Replication of Marek's Disease Virus Is Dependent on Synthesis of De Novo Fatty Acid and Prostaglandin E ₂

Abstract

Marek’s disease virus (MDV) causes deadly lymphoma and induces an imbalance of the lipid metabolism in infected chickens. Here, we discovered that MDV activates the fatty acid synthesis (FAS) pathway in primary chicken embryo fibroblasts (CEFs). In addition, MDV-infected cells contained high levels of fatty acids and showed increased numbers of lipid droplets (LDs). Chemical inhibitors of the FAS pathway (TOFA and C75) reduced MDV titers by approximately 30-fold. Addition of the downstream metabolites, including malonyl-coenzyme A and palmitic acid, completely restored the inhibitory effects of the FAS inhibitors. Furthermore, we could demonstrate that MDV infection activates the COX-2/prostaglandin E2 (PGE2) pathway, as evident by increased levels of arachidonic acid, COX-2 expression, and PGE2 synthesis. Inhibition of the COX-2/PGE2 pathway by chemical inhibitors or knockdown of COX2 using short hairpin RNA reduced MDV titers, suggesting that COX-2 promotes virus replication. Exogenous PGE2 completely restored the inhibition of the COX-2/PGE2 pathway in MDV replication. Unexpectedly, exogenous PGE2 also partially rescued the inhibitory effects of FAS inhibitors on MDV replication, suggesting that there is a link between these two pathways in MDV infection. Taken together, our data demonstrate that the FAS and COX-2/PGE2 pathways play an important role in the replication of this deadly pathogen. IMPORTANCE Disturbances of the lipid metabolism in chickens infected with MDV contribute to the pathogenesis of disease. However, the role of lipid metabolism in MDV replication remained unknown. Here, we demonstrate that MDV infection activates FAS and induces LD formation. Moreover, our results demonstrate that MDV replication is highly dependent on the FAS pathway and the downstream metabolites. Finally, our results reveal that MDV also activates the COX-2/PGE2 pathway, which supports MDV replication by activating PGE2/EP2 and PGE2/EP4 signaling pathways.

Glutaminolysis and Glycolysis Are Essential for Optimal Replication of Marek’s Disease Virus

“…Therefore, we believe that these cells are the only primary cells which are suited for analysis of MDV-induced cell metabolism. We had previously observed that 72 hpi is optimal timing for activation of both fatty acid synthesis and the COX-2/PGE2 pathway in MDVinfected cells (12). However, it should be emphasized that the results represent the metabolic alteration occurring in the infected cell culture, and we cannot exclude the possibility of bystander effects in which soluble factors released by the infected cells exert metabolic changes in noninfected bystander cells.…”

“…Thus, our results indicate that ATP production is increased in the MDV-infected cells via glycolysis and mitochondrial fatty acid ␤-oxidation in order to support virus replication. We had previously shown that MDV infection increases fatty acid synthesis (12); however, the role of fatty acid ␤-oxidation in MDV replication was unknown. Here, we demonstrate that fatty acid ␤-oxidation was not required for efficient replication of MDV, and the inhibition of ␤-oxidation by the CPT1a inhibitor, etomoxir, moderately increased virus titer, while it had no effect on viral copy numbers.…”

“…Like all herpesviruses, MDV harbors metabolic enzymes involved in biosynthesis of energy carrier molecules facilitating early-phase infection (6)(7)(8). MDV infection modulates lipid metabolism in the infected chickens (9)(10)(11)(12) and increases fatty acid synthesis and lipid droplet formation, which are important for virus replication (12). However, it is still unknown whether MDV-infected cells can utilize metabolites derived from fatty acid ␤-oxidation, an important mitochondrion and peroxisome aerobic process, for generation of energy.…”

Mardivirus Infection and Persistence in Feathers of a Chicken Model Harboring a Local Autoimmune Response

“…Several studies support the third hypothesis. The knock-down of cyclooxygenase 2, an enzyme involved in inflammation, reduces MDV replication [ 36 ]. In addition, an enhancement of virus replication through inflammatory mediators was observed for the human cytomegalovirus, another herpesvirus, in human retinal pigment epithelial cells [ 37 ].…”

Adiponectin and its receptor genes' expression in response to Marek's disease virus infection of White Leghorns

“…Lipid analysis of the arterial smooth muscles in MDV-infected birds revealed a significant increase in nonesterified fatty acids, cholesterol, cholesterol esters, squalene, phospholipids, and triacylglycerol. Furthermore, excess lipid biosynthesis triggers the cellular deposition of lipid droplets in herpesvirus-infected cells ( Fabricant et al., 1981 ; Hajjar et al., 1986 ; Dai et al., 2017 ; Boodhoo et al., 2019 ). In MDV-infected primary chicken embryo fibroblasts, different lipid metabolites have different expression patterns, which may increase in fatty acid synthesis or breakdown of lipids or both ( Boodhoo et al., 2019 ).…”