Objective To investigate the effects of interaction between human umbilical vein endothelial cells (HUVECs) which were infected with dengue virus type 2 (DENV-2) and CD4+T cells on the expression of ICAM-1 (intercellular adhesion molecule 1),VCAM-1 (vascular cell adhesion molecule 1),IL-10 and TGF-β1 at mRNA level for further understanding the immunological mechanism of DENV infection.Methods HUVECs were treated with CYM-5442,a selective agonist for sphingosine-1-phosphate receptor 1 (S1P1),for 24 hours and then infected with 103 TCID50 (50% tissue culture infective dose) of DENV-2 before co-culturing with CD4+T cells.Changes in the expression of NS1 (DENV-2 nonstructural protein),SPHK1 (sphingosine kinase 1,phosphorylating sphingosine to S1P),ICAM-1,VCAM-1,IL-10 and TGF-β1 at mRNA level were detected by real-time PCR after 4,8,12,24,48 and 72 hours of co-culturing.Results There was a certain timeliness in the expression of NS1 at mRNA level after infecting HUVECs with DENV-2 and the expression reached a peak at 24 h.Treating HUVECs with or without CYM-5442 had no significant influence on the expression of DENV-2 NS1 at mRNA level.The expression of SPHK1 at mRNA level was significantly increased after treating HUVECs with CYM-5442 and DENV-2 (P<0.05).Compared with DENV-2-infected or untreated HUVECs,Co-culturing DENV-2-infected HUVECs with CD4+T cells increased the expression of ICAM-1 and VCAM-1 in HUVECs at mRNA level (P<0.01) as well as the expression of IL-10 in CD4+T cells at mRNA level (P<0.05),but had no significant influence on the expression of TGF-β1 in CD4+T cells at mRNA level.Conclusion This study shows that DENV-2 can replicate and proliferate in HUVECs,but CD4+T cells inhibit the replication and proliferation.CD4+T cells play an important role in promoting the expression of VCAM-1 and ICAM-1 in DENV-2-infected HUVECs at mRNA level,activating HUVECs and increasing inflammation,which may be associated with increased vascular permeability induced by DENV-2 infection.Co-culturing CD4+T cells with DENV-2-infected HUVECs promotes the expression of IL-10 in CD4+T cells at mRNA level,but has no significant effect on TGF-β1.

Objective To investigate the influences on major inflammatory cytokines after co-cul-turing regulatory T cells (Treg) with human umbilical vein endothelial cells ( HUVECs) that were infected with dengue virus type 2 (DENV-2). Methods Peripheral blood mononuclear cells (PBMC) were extrac-ted from concentrated human leukocytes by density gradient centrifugation. Treg cells were sorted by immu-nomagnetic beads. Expression of CD4,CD25 and CD127 molecules on the membrane of Treg cells was detec-ted by flow cytometry to identify the purity of Treg cells. HUVECs pretreated with or without sphingosine-1-phosphate S1P type 1 (S1P1)-specific receptor agonist CYM-5442 for 24 h were first infected with DENV-2 and then co-cultured with Treg cells. Expression of IL-6,IL-8,TNF-α,IL-10 and TGF-β at mRNA level was detected by real-time RT-PCR. Levels of IL-6,IL-8,IL-10 and TGF-β in the culture supernatants were detec-ted by a double-antibody sandwich ELISA. Results The purity of Treg cells was (84. 3±0. 5)%. Expression of NS1 at mRNA level in DENV-2-infected HUVECs first gradually increased and then decreased after reac-hing the peak at 24 h (3. 03±0. 26, P<0. 01). Enhanced expression of IL-6,IL-8 and TNF-α at mRNA level in HUVECs was observed after DENV-2 infection ( P<0. 01). Expression of these cytokines at every time point was decreased after co-culturing DENV-2-infected HUVECs with Treg cells ( P<0. 05),but was still higher than that before infection. CYM-5442 pretreatment decreased the expression of IL-6,IL-8 and TNF-α at mRNA level in DENV-2-infected HUVECs and inhibited the secretion of IL-10 and TGF-β by Treg cells that were co-cultured with DENV-2-infected HUVECs. Conclusion Primary HUVECs infected by DENV-2 can enhance the secretion of IL-10 and TGF-β by Treg cells,and the suppressive cytokines produced by Treg cells can reduce the production of inflammatory cytokines by DENV-2-infected HUVECs.

Objective To study the influences on the production of major inflammatory cytokines after co-culturing macrophages with human umbilical vein endothelial cells ( HUVECs) that were infected with dengue virus type 2 (DENV-2). Methods Density gradient centrifugation was used to isolate periph-eral blood mononuclear cells ( PBMC) from concentrated human leukocytes. Adherent monocytes in culture flasks were obtained and stimulated with macrophage colony-stimulating factor ( M-CSF) to prepare macro-phages. The purity of CD14+CD11b+ cells was measured by flow cytometry. Changes in the expression of NS1 at mRNA level in HUVECs were detected by real-time PCR following DENV-2 infection. DENV-2-in-fected HUVECs were co-culture with macrophages in Transwell chambers. A control group was set up by pre-treating HUVECs with sphingosine-1-phosphate (S1P) type 1 (S1P1)-specific receptor agonist CYM-5442 for 24 h to remove the drug before infection and then co-culturing the infected cells with macrophages. Real-time PCR was used to detect the expression at mRNA level of IL-6 and IL-8 in HUVECs and IL-6, IL-8, TNF-α and IL-1β in macrophages. A double-antibody sandwich ELISA was used to detect the expression of above cytokines in culture supernatants. Results After HUVECs were infected with DENV-2, expression of NS1 gene at mRNA level gradually increased to the peak at 24 h (2. 66±0. 53, P<0. 05) and then de-creased. The purity of macrophages detected by flow cytometry was (89. 16±2. 07) ％. Expression of IL-6 and IL-8 at mRNA level in DENV-2-infected HUVECs was up-regulated. The peak values reached at 24 h of IL-6 and IL-8 expression were 16. 10±0. 17 and 29. 76±0. 58, while the expression levels at 24 h in the un-infected group were 1. 46±0. 67 and 1. 60±0. 54, respectively. Expression of IL-6, IL-8, TNF-αand IL-1βat mRNA level in DENV-2-infected macrophages was increased significantly. The levels of IL-6, IL-8, TNF-αand IL-1β expression at 24 h were 45. 82±3. 72, 52. 34±1. 69 (12 h), 8. 94±1. 75 and 30. 96±1. 44 in the infected macrophages, and 1. 16±0. 22, 1. 15±0. 21, 1. 11±0. 09 and 1. 47±0. 31 in the uninfected group. Expression of these cytokines was decreased at every time points after co-culturing of DENV-2-infec-ted HUVECs with macrophages, but still significantly higher than that in the uninfected group. In the co-cul-ture group with DENV-2 infection, CYM-5442 pretreatment significantly decreased the expression at mRNA level of IL-6 and IL-8 in HUVECs (P<0. 01) and that of IL-6, IL-8, TNF-αand IL-1βin macrophages (P<0. 01). Conclusions DENV-2 could infect primary HUVECs, and then activate macrophages to promote the secretion of large amounts of IL-6, IL-8, TNF-αand IL-1β. Moreover, the activated macrophages could reduce the production of inflammatory cytokines in HUVECs to a certain extent.