Role of cytokine gene polymorphism and hepatic transforming growth factor β1 expression in recurrent hepatitis C after liver transplantation

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Abstract

Recurrent hepatitis C virus (HCV) infection after orthotopic liver transplantation (OLT) is nearly universal. Cytokines play an important role in the immune response to viral infection, and cytokine gene polymorphism affects the overall expression and secretion of cytokines. The objective of this study was to define the relationship between cytokine polymorphism and recurrent hepatitis C after OLT.

Blood samples were collected from 36 patients at a mean of 44.6±30.4 months after OLT for chronic HCV infection. DNA was extracted from peripheral blood mononuclear cells, and polymerase chain reaction-sequence specific primers (PCR-SSP) analysis was performed on promoter sequences of transforming growth factor β1 (TGF-β1), interleukin 6 (IL-6) interleukin 10 (IL-10), tumor necrosis factor α (TNF-α) and interferon γ (INF-γ). Liver biopsies performed at diagnosis of recurrent disease were graded with the Knodell score, and hepatic TGF-β1 expression was determined semiquantitatively by immunohistochemistry. The gene polymorphism of TGF-β1 was correlated with its expression on hepatocytes and sinusoids. Polymorphism in all studied cytokine genes was correlated with recurrence, and interval to recurrence (>12 or ≤12 months post-OLT), and clinical (ascites, Child–Pugh score and death), biochemical parameters of recurrent HCV (serum alanine aminotransferase (ALT)), INR, albumin, bilirubin), and virological parameters (HCV genotype and load).

Biopsies revealed recurrent HCV in 31 patients (86.1%); in 21 (67.7%), the interval to recurrence was 12 months. There was a statistically significant correlation between TGF-β1 gene polymorphism, i.e., the genetic ability to produce high levels of TGF-β1, and the intensity of TGF-β1 staining on hepatocytes (p=0.003) and sinusoids (p=0.003), and the degree of fibrosis (p=0.02). A borderline correlation was found with the presence of ascites (p=0.07), but not with Child–Pugh score, synthetic liver function tests or HCV genotype and load. The genetic ability to produce low levels of IFN-γ was correlated with recurrent disease (p=0.015). No such correlation was found for TGF-β1 gene polymorphism.

In conclusion, polymorphism in the TGF-β1 gene correlates with its in situ hepatic expression in patients with recurrent HCV after liver transplantation. INF-γ, but not TGF-β1 gene polymorphism, correlates with early recurrent hepatitis C after transplantation. These findings might help to design preemptive prevention therapy in selected patients at risk.

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