Characterization of coxsackievirus B3 replication in human umbilical vein endothelial cells

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.