Abstract
BackgroundHepatitis C virus (HCV) infection is associated with high percentage of chronicity which implies the ability of the virus to evade or modulate host cell immune system. Modulation of chemokines, such as RANTES may be part of the virus induced pathogenicity. We examined the effect of core and structural proteins of HCV on RANTES expression in two liver derived cell lines, HepG2 and Chang Liver (CHL).MethodsHepG2 and Chang Liver (CHL) cell lines were established and selected for constitutive expression of HCV core and structural genes. Flow cytometry and quantitative RT-PCR analysis were performed to examine the effect of HCV core protein on RANTES expression. Luciferase analysis after RANTES-Luc-promoter transfection of established cell lines was assayed by luminometer measurements (RLU) of RANTES promoter activity. IRF-1 and IRF-7 expression was then examined by immunoblotting analysis.ResultsResults of flow cytometry and RT-PCR analysis indicated that RANTES is differentially regulated by HCV core protein in the two cell lines examined as its expression was inhibited in HepG2 cells, by a reduction of RANTES promoter activity. Conversely, RANTES protein and mRNA were induced by the core protein in CHL cells, through the induction of the promoter.Since HCV genome modulates IRF-1 and IRF-7 in replicon system and IRF-1, IRF-3 and IRF-7 have been reported to regulate RANTES promoter in various cell systems, analysis of the mechanism underlying RANTES modulation by the core protein revealed that IRF-1 expression was induced in HepG2 cells by the core protein, whereas in CHL cells it was expressed at a very low level that was not influenced by transfection with the core protein construct. This suggested that IRF-1 level may mediate the expression of RANTES in cell lines of liver origin. The effect of the core protein on RANTES promoter was countered by co-transfection with NF90, a double-stranded-RNA binding protein that activates some interferon response genes and acts as a component of cell defense against viral infection.ConclusionHCV core protein have opposite effects on the expression of RANTES in different cell types in vitro, possibly reflecting a similar scenario in different microenvironments in vivo.
Highlights
Hepatitis C virus (HCV) infection is associated with high percentage of chronicity which implies the ability of the virus to evade or modulate host cell immune system
Since HCV genome modulates IRF-1 and IRF-7 in replicon system and IRF-1, IRF-3 and IRF-7 have been reported to regulate RANTES promoter in various cell systems, analysis of the mechanism underlying RANTES modulation by the core protein revealed that IRF-1 expression was induced in HepG2 cells by the core protein, whereas in Chang Liver (CHL) cells it was expressed at a very low level that was not influenced by transfection with the core protein construct
Effect of HCV core protein on RANTES protein Considering the important role of chemokine signaling in regulating physiological events associated with chronic HCV infection, the effect of HCV core protein on RANTES expression was evaluated by quantitative immunofluorescence and flow cytometry in the two liver derived cell lines, HepG2 and Chang Liver, constitutively expressing HCV core protein
Summary
Hepatitis C virus (HCV) infection is associated with high percentage of chronicity which implies the ability of the virus to evade or modulate host cell immune system. Modulation of chemokines, such as RANTES may be part of the virus induced pathogenicity. One of the main features of HCV infection is the high percentage of chronicity which implies the ability of the virus to evade or modulate host cell immune system. Initial inflammatory response to early viral infection is associated to secretion of RANTES, a CC chemokine with chemotactic function which recruits circulating T cells to the inflammation sites. Modulation of chemokines expression by viruses or viral proteins may contribute to evasion of the innate immune response in early viral infection, affecting the outcome of infection and viral persistence
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