Application of the woodchuck animal model for the treatment of hepatitis B virus-induced liver cancer

Abstract

This review describes woodchucks chronically infected with the woodchuck hepatitis virus (WHV) as an animal model for hepatocarcinogenesis and treatment of primary liver cancer or hepatocellular carcinoma (HCC) induced by the hepatitis B virus (HBV). Since laboratory animal models susceptible to HBV infection are limited, woodchucks experimentally infected with WHV, a hepatitis virus closely related to HBV, are increasingly used to enhance our understanding of virus-host interactions, immune response, and liver disease progression. A correlation of severe liver pathogenesis with high-level viral replication and deficient antiviral immunity has been established, which are present during chronic infection after WHV inoculation of neonatal woodchucks for modeling vertical HBV transmission in humans. HCC in chronic carrier woodchucks develops 17 to 36 mo after neonatal WHV infection and involves liver tumors that are comparable in size, morphology, and molecular gene signature to those of HBV-infected patients. Accordingly, woodchucks with WHV-induced liver tumors have been used for the improvement of imaging and ablation techniques of human HCC. In addition, drug efficacy studies in woodchucks with chronic WHV infection have revealed that prolonged treatment with nucleos(t)ide analogs, alone or in combination with other compounds, minimizes the risk of liver disease progression to HCC. More recently, woodchucks have been utilized in the delineation of mechanisms involved in innate and adaptive immune responses against WHV during acute, self-limited and chronic infections. Therapeutic interventions based on modulating the deficient host antiviral immunity have been explored in woodchucks for inducing functional cure in HBV-infected patients and for reducing or even delaying associated liver disease sequelae, including the onset of HCC. Therefore, woodchucks with chronic WHV infection constitute a well-characterized, fully immunocompetent animal model for HBV-induced liver cancer and for preclinical evaluation of the safety and efficacy of new modalities, which are based on chemo, gene, and immune therapy, for the prevention and treatment of HCC in patients for which current treatment options are dismal.

Keywords: Woodchuck, Hepatitis B virus, Chronic infection, Liver disease, Hepatocellular carcinoma, Cancer treatment

Core Tip: Hepatitis B virus-induced liver tumors are hard to treat with currently available interventions and the prognosis of hepatocellular carcinoma (HCC) in patients remains still poor. Immunocompetent woodchucks are a useful animal model for human HCC, because multiple tumors at different stages develop spontaneously and secondary to viral infection. This similarity to human hepatocarcinogenesis and the animal’s vascular architecture allowing catheterization with human-sized products have increased the preclinical use of this model to improve existing imaging (ultrasound, magnetic resonance imaging, and positron-emission tomography) and ablation techniques (embolization and radiotherapy) and to evaluate interventions (chemo, gene, and immune therapy) intended to treat human HCC.