Effects of Epstein-Barr virus on the development of dendritic cells derived from cord blood monocytes: an essential role for apoptosis

ABSTRACT

OBJECTIVE: Epstein-Barr virus (EBV) is a ubiquitous human γ-herpes virus, which can adapt and evade host immune defense. Dendritic cells (DCs) play a pivotal role in the initiation and maintenance of immune responses. This study investigated the effects of EBV on cord blood monocytes derived DCs (CBDC). METHODS: Monocytes were isolated from cord blood and cultured in medium containing recombinant IL-4 and GM-CSF to induce DCs development. B95-8 supernatant was added in monocytes culture medium for EBV infection at day 0. Phenotypic characterization of DCs, apoptotic cells, and mitochondrial membrane potential (MMP) were detected by flow cytometry. The morphology was observed by Hoechst 33258 staining and TUNEL staining, the expression of X-linked inhibitor of apoptosis protein (XIAP) was detected by Western blotting assay and caspase 3, 8 and 9 activity was measured. RESULTS: Phenotypic characterization of DCs was changed in EBV-treated group. Chromatin condensation and DNA fragmentation were observed in EBV induced CBDC apoptosis. In addition, caspase 3, caspase 8, and caspase 9 activation were enhanced in the EBV-treated group. This was accompanied by the loss of MMP. Furthermore, XIAP expression was down-regulated in the EBV-treated group and compared to mock-infected group. CONCLUSION: These results suggested that EBV could inhibit CBDC phenotypic differentiation, and induce CBDC apoptosis in caspase-dependent manner with involvement of the mitochondrial pathway. This might help EBV to evade host immune responses to establish persistent infection.