Interferon alpha induced intrahepatic pSTAT1 inversely correlate with serum HCV RNA levels in chronic HCV infection.

BACKGROUND: The Jak-STAT signaling of hepatitis C virus (HCV) infected hepatocyte is critical for the antiviral action of endogenously produced interferon (IFN) as well as exogenously administered interferon alpha (IFN-α). The activation of cellular Jak-STAT signaling by IFN-α results in the phosphorylation and nuclear translocation of pSTAT1 and pSTAT2 proteins to induce antiviral gene transcription. Clinical studies show that chronic HCV patients with high viral load show poor response to interferon alpha and ribavirin combination therapy. AIM: We seek to determine whether the IFN-α induced activation of pSTAT1 and pSTAT2 in hepatocytes isolated from liver biopsy of patients chronically infected with hepatitis C virus could be related to the viral load.
METHOD: Hepatocytes were isolated from liver biopsies of 18 chronic HCV patients using the collagen digestion method. Induction of pSTAT1 protein in the isolated hepatocyte was measured after IFN-α treatment. The fold change in the levels of pStat1 in the cell lysates due to IFN-treatment was measured by Western blot analysis followed by densitometry analysis.
RESULTS: Results of our study indicate that IFN-α induced pSTAT1 levels vary in chronically infected hepatocytes from chronic HCV patients. Semi-quantitative analysis of the pSTAT1 bands revealed a median induction of 7.4-fold in non-infected primary hepatocytes and 2.3-fold in chronic hepatitis C patients (p < 0.001). Total STAT1 levels were not significantly different between treated and untreated primary hepatocytes. We also found a significantly inverse correlation between the intrahepatic pSTAT1 inductions with the serum HCV RNA levels.
CONCLUSION: We have developed an antibody based Western blot detection method to measure intrahepatic pStat1 and pStat2 levels to assess the cellular response to exogenous IFN-alpha. Our results indicate that pStat1 activation is a good indicator to assess the level of HCV replication in chronic HCV patients.