The administration of drugs to inhibit metabolic pathways not only reduces the risk of obesity-induced diseases in humans but may also hamper the replication of different viral pathogens. In order to investigate the value of the US Food and Drug Administration-approved anti-obesity drug orlistat in view of its anti-viral activity against different human-pathogenic viruses, several anti-viral studies, electron microscopy analyses as well as fatty acid uptake experiments were performed. The results indicate that administrations of non-cytotoxic concentrations of orlistat reduced the replication of coxsackievirus B3 (CVB3) in different cell types significantly. Moreover, orlistat revealed cell protective effects and modified the formation of multi-layered structures in CVB3-infected cells, which are necessary for viral replication. Lowering fatty acid uptake from the extracellular environment by phloretin administrations had only marginal impact on CVB3 replication. Finally, orlistat reduced also the replication of varicella-zoster virus moderately but had no significant influence on the replication of influenza A viruses. The data support further experiments into the value of orlistat as an inhibitor of the fatty acid synthase to develop new anti-viral compounds, which are based on the modulation of cellular metabolic pathways.

The human cytomegalovirus (HCMV) is a common pathogen, which causes severe or even deadly diseases in immunocompromised patients. In addition, congenital HCMV infection represents a major health concern affecting especially the lung tissue of the susceptible individuals. Antivirals are a useful strategy to treat HCMV-caused diseases. However, all approved drugs target viral proteins but significant toxicity and an increasing resistance against these compounds have been observed. In infected cells, numerous host molecules have been identified to play important roles during HCMV replication. Among others, HCMV infection depends on the presence of bioactive sphingolipids. In this study, the role of sphingosine-1-phosphate (S1P) signaling in HCMV-infected human embryonal lung fibroblasts (HELF) was analyzed. Viral replication depended on the functional activity of sphingosine kinases (SK). During SK inhibition, addition of extracellular S1P restored HCMV replication. Moreover, neutralization of extracellular S1P by anti-S1P antibodies decreased HCMV replication as well. While the application of FTY720 as an functional antagonist of S1P receptor (S1PR) signaling did not reduce HCMV replication significantly, JTE-013, an inhibitor of S1PR, decreased viral replication. Furthermore, inhibition of Rac-1 activity reduced HCMV replication, whereas inhibition of the Rac-1 effector protein Rac-1-activated kinase 1 (PAK1) had no influence. In general, targeting S1P-induced pathways, which are essential for a successful HCMV replication, may represent a valuable strategy to develop new antiviral drugs.

After successful invasion of susceptible hosts, systemic distribution of coxsackievirus B3 (CVB3) most likely requires interactions with the endothelial system. Thereby, infection of endothelial cells occurs directly or viruses and/or virus-infected leukocytes migrate through the endothelial barrier. Many of these processes have not been studied so far. In order to analyze viral replication in the endothelium, human umbilical vein endothelial cells (HUVEC) were isolated and infected with CVB3. Time-course experiments revealed maximal viral replication at 10-24 h and viral RNA persistence up to 120 h post-infection (p. i.) without the induction of obvious general cytopathic effects or the loss of cellular viability. However, the application of the EGFP-expressing recombinant virus variant CVB3/EGFP revealed shrinkage and death of individual cells. Using infectious center assays, a noticeable CVB3 replication occurred on an average of 20 % of HUVEC at 10 h p. i. This may be in part due to a higher coxsackievirus/adenovirus receptor expression in a small subgroup of HUVEC (5-7 %) as analyzed by flow cytometry. Interestingly, CVB3 replication escalated and cellular susceptibility increased significantly after reversal of cell cycle arrest caused by serum deprivation indicating that reactivation of cellular metabolism may help to promote CVB3 replication. Finally, CVB3-infected HUVEC cultures revealed increased DNA fragmentation, and inhibition of caspase activity caused an accumulation of intracellular virus particles indicating that apoptotic processes are involved in virus release mechanisms. Based on these observations, it is assumed that CVB3 replicates efficiently in human endothelial cells. But how this specific infection of the endothelium may influence viral spread in the infected host needs to be investigated in the future.