TSG-6 inhibited the HCMV infection-induced expression of TNF-α and IL-6
Objective 
To investigate the roles of tumor necrosis factor alpha stimulus gene-6 (TSG-6) in the inflammatory responses induced by human cytomegalovirus (HCMV) infection and the possible mechanism. 
 
 
Methods 
Human lung fibroblast cells (MRC-5) and human retinal pigment epithelial cells (ARPE-19) were infected with HCMV strains. A normal cell control group and an inactivated virus infection group were set up as well. qRT-PCR analysis and Western blot assay were performed to measure the expression of TSG-6 at mRNA and protein levels in each group. The recombinant human TSG-6 protein (rhTSG-6) was administrated to the HCMV-infected MRC-5 cell cultures at the concentration of 100 ng/ml. The supernatants were harvested to measure the levels of TNF-α and IL-6 and the transcriptional activity of NF-κB by using ELISA, indirect immunofluorescence assay (IFA) and Western blot assay. Meanwhile, a normal cell control group and a virus control group were set up for comparison. 
 
 
Results 
The expression of TSG-6 at mRNA level in HCMV-infected MRC-5 cells were 19 and 376 times of that in normal cells at the time points of 72 h and 96 h after infection. The expression of TSG-6 at mRNA level in HCMV-infected ARPE-19 cells were 15 and 354 times of that in normal cells at the time points of 96 h and 120 h after infection. Results of the Western blot assay further confirmed the increased expression of TSG-6 at protein level at the corresponding time points. Compared with the virus control group, the levels of TNF-α and IL-6 in the supernatants of HCMV-treated MRC-5 cell culture were significantly decreased upon the intervention of rhTSG-6 protein (P<0.05). Moreover, TSG-6 protein could suppress the expression and nuclear translocation of NF-κB. 
 
 
Conclusion 
TSG-6 was involved in the HCMV infection-induced inflammation responses and played a role in inhibiting the expression of HCMV infection-related inflammatory factors and affecting the nuclear localization of NF-κB. 
 
 
Key words: 
Human cytomegalovirus; Tumor necrosis factor αstimulated gene 6; NF-κB