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The effect of iron on hepatitis C virus replication

Clark, Hayley (2011) The effect of iron on hepatitis C virus replication. Honours thesis, Murdoch University.

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      Abstract

      Hepatitis C virus (HCV) is a small RNA encoded virus that causes acute and chronic infections of the liver and is associated with fibrosis, cirrhosis, hepatocellular carcinoma and end-stage liver disease. The infection is linked with elevated serum ferritin levels and iron deposits within the liver which are associated with an increased risk of progression of HCV disease. It is hypothesised firstly that the presence of excess iron affects HCV replication and secondly that iron homeostasis is altered by HCV replication. The main aim of this study was to investigate the influence of iron on HCV replication by analysing the spread of infection and the titre of infectious HCV produced in the presence of excess iron. The second aim was to determine if HCV infection itself alters the level of iron stored as ferritin in liver cells.

      HCV Japanese fulminant hepatitis (JFH-1) infection of the human hepatoma cell line, (Huh7), was used as the model for this study. The culture conditions were first optimised to allow detection of ferritin by western blot. Huh7 cells were then treated with iron provided by 5, 10 or 20 μg/ml ferric ammonium citrate (FAC) prior to HCV infection (0.001 MOI). No evidence of inhibition of HCV replication was found on day 7 post infection (PI) by analysis of the level of viral protein detected by western blot, the proportion of infected cells determined by immunohistochemistry and flow cytometry or the titre of infectious HCV produced. A comparison of iron donors was then undertaken and conditions were changed to add iron donors 1 day after HCV. Viral RNA levels were not significantly reduced on treatment with 20 μg/ml FAC and 25 μM holo-transferrin and assays for viral protein and production of infectious virus again showed no evidence of inhibition. Fe-PIH, a lipophilic iron donor, had the greatest effect, reducing both the proportion of infected cells and the titre of infectious virus produced. When the reduction in the number of cells present in cultures treated with Fe-PIH was taken into account, the decrease in virus titre was explained.

      HCV infection was found to alter iron storage in Huh7 cells. A significantly lower level of ferritin was detected (p < 0.05) by western blot in HCV infected compared to uninfected Huh7 cells whereas in other situations highly infected cells were found to have increased iron storage. While it had been intended to analyse iron metabolism by examining gene expression during iron deficiency and iron storage, the conditions which give rise to these outcomes will need to be elucidated first.

      This study has shown that iron has the potential to inhibit HCV replication although in vitro it depends on the type and concentration of iron donor used and the time during infection that excess iron is present in the cell. This study has confirmed that HCV infection alters the iron status of the liver cell. The outcome of these interactions between iron and HCV is expected to influence the course of HCV infection and the development of liver disease.

      Publication Type: Thesis (Honours)
      Murdoch Affiliation: School of Biological Sciences and Biotechnology
      Supervisor: Mead, Robert
      URI: http://researchrepository.murdoch.edu.au/id/eprint/7179
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