Epstein-Barr Virus Zta-Induced Immunomodulators from Nasopharyngeal Carcinoma Cells Upregulate Interleukin-10 Production from Monocytes

Abstract

During lytic infection with Epstein-Barr virus (EBV), several viral lytic proteins function to evade immune recognition or to actively suppress immune cells. An EBV lytic transactivator, Zta, induces an immunosuppressive cytokine interleukin 10 (IL-10) in B cells, but whether it regulates IL-10 in the context of epithelial cells is unclear. In this study, we tested nasopharyngeal carcinoma (NPC) cell lines and found that Zta did not induce IL-10 in these epithelial cells. Interestingly, the conditioned medium of Zta-expressing NPC cells enhanced IL-10 production from monocytes. We further revealed that the IL-10-inducing effect involved at least two immunomodulators that were upregulated by Zta and secreted from NPC cells: granulocyte-macrophage colony-stimulating factor (GM-CSF) and prostaglandin E 2 (PGE 2 ). Zta was recruited to and activated the GM-CSF promoter, thus upregulating GM-CSF expression. Zta also activated the promoter of cyclooxygenase-2 (COX-2), and Zta-induced COX-2 increased downstream PGE 2 production. Cotreatment with GM-CSF and PGE 2 synergistically induced IL-10 production from monocytes. The IL-10-inducing effect of the Ztaconditioned medium was reduced when GM-CSF or the COX-2/PGE 2 pathway was blocked. The conditioned medium of NPC cells with EBV lytic infection showed a similar increase of GM-CSF and PGE 2 levels as well as the IL-10-inducing effect on monocytes, and knockdown of Zta abolished all the effects. Therefore, through Zta-induced immunomodulators, EBV lytic infection in NPC cells can direct bystander monocytes to produce IL-10, which may be a novel way of EBV to promote local immunosuppression.Epstein-Barr virus (EBV) establishes lifelong persistence in more than 90% of the adult population worldwide, showing its successful dealings with the human immune system (51). Compared with EBV latent infection, in which only few viral antigens are expressed, the lytic infection expresses abundant viral proteins with high antigenicity, serving as a more attractive target recognized and attacked by the host immune system. To survive under the immune surveillance, EBV is equipped with several lytic proteins that evade immune recognition. For example, major histocompatibility complex (MHC) class I-restricted antigen presentation is inhibited by EBV BNLF2a, which blocks peptide transport (25), and by BILF1, which promotes degradation of MHC class I molecules (62). MHC class II-restricted antigen presentation is hampered by the interaction between EBV BZLF2 and MHC class II molecules (50). Moreover, expression of MHC class I and II genes can be downregulated by other EBV lytic proteins: Zta acting at the transcriptional level and BGLF5 acting at the posttranscriptional level (32,38,52).In addition to the strategies that prevent EBV from being recognized by immune cells, EBV may actively cause suppressive effects on immune cells during the lytic cycle, through several secreted factors that are encoded or induced by EBV.

Activation of COX-2/PGE 2 Promotes Sapovirus Replication via the Inhibition of Nitric Oxide Production

“…In a few instances, viral proteins have been shown to stimulate activation of the COX/PGE 2 pathway, often by acting either directly or indirectly as a transcriptional transactivator of COX-2 gene expression (36–39). Among the viral proteins for which this activity has been reported, the hepatitis C virus (HCV) protein NS3, a viral serine protease, is known to enhance the COX-2/PGE 2 pathway by activating multiple signaling pathways (40).…”

Epstein-Barr Virus Zta Upregulates Matrix Metalloproteinases 3 and 9 That Synergistically Promote Cell Invasion In Vitro

“…Recruitment of Zta to the target promoter was detected by using the ChIP assay as described in our previous study [37]. Zta was immunoprecipitated by using a mouse monoclonal antibody AZ-69 (Argene, Varilhes, France).…”

Role of Modulator of Inflammation Cyclooxygenase-2 in Gammaherpesvirus Mediated Tumorigenesis

“…During lytic reactivation EBV transactivator protein Zta helps to evade immune surveillance. EBV Zta has been shown to enhance the activity of COX-2 promoter thereby upregulating the production of COX-2 and its downstream effector molecule PGE 2 (Lee et al, 2011). It has also been shown that EBV could suppress PGE 2 biosynthesis in LPS-activated monocytes (Savard et al, 2000).…”

“…Both LPS treatment and EBV infection did not affect COX-1 levels, indicating COX-2 as the major isoform involved in inflammatory stimuli induced PG synthesis in presence of EBV infection. However, a separate study showed that conditioned medium of Zta-expressing NPC cells enhances IL-10 production from monocytes which was mediated in part by elevated COX-2 levels in NPC cells (Lee et al, 2011). It has been speculated that the IL-10 production in monocytes may play role in facilitating local microenvironment in favor of immunosuppression (Lee et al, 2011).…”