Cytokine mRNA expression in hepatitis C virus infection: TH1 predominance in patients with chronic hepatitis C and TH1–TH2 cytokine profile in subjects with self-limited disease

Summary.  Many determinants of the immune response have been implied in the pathogenesis of chronic hepatitis C. TH1 and TH2 cytokines play a prominent role in viral infections and a dysregulation of these cytokines could account for viral persistence and evolution of chronic disease. To explore a possible TH1 and TH2 cytokine dysregulation resulting in the inability to terminate hepatitis C virus (HCV) infection, we studied TH1 [interferon (IFN)-γ, interleukin (IL)-2] and TH2 (IL-4, IL-10) mRNA expression of peripheral blood mononuclear cells (PBMC) in response to NS3 HCV antigen stimulation, in 31 untreated patients with chronic hepatitis C and 29 subjects with self-limited disease. After a 48 h culture of PBMC, total RNA isolation was performed and complementary DNA was prepared by reverse transcription. mRNA levels were quantified by real-time polymerase chain reaction using a standard curve formed after cloning each cytokine gene and a reference gene using recombinant DNA technology in a specific plasmid vector. In the patients group, mRNA expression of IFN-γ, IL-2 and IL-4 but not IL-10 was detected, IFN-γ being the predominant cytokine expressed. All four cytokines were expressed in subjects with self limited disease, however levels of IFN-γ were lower and a significant higher expression of IL-10 compared to patients was found. There was a significant correlation between IFN-γ mRNA expression levels and stage of fibrosis. Our findings show that in chronic hepatitis C, TH1 cytokines predominate and correlate to liver immunopathology. Furthermore, subjects with self-limited disease, maintain the ability to respond to HCV antigens for a long time after disease resolution.