Correlation of virus and host response markers with circulating immune complexes during acute and chronic woodchuck hepatitis virus infection.

Woodchuck hepatitis virus (WHV) is an established model for human hepatitis B virus. The kinetics of virus and host responses in serum and liver during acute, self-limited WHV infection in adult woodchucks were studied. Serum WHV DNA and surface antigen (WHsAg) were detected as early as 1 to 3 weeks following experimental infection and peaked between 1 and 5 weeks postinfection. Thereafter, serum WHsAg levels declined rapidly and became undetectable, while WHV DNA levels became undetectable much later, between 4 and 20 weeks postinfection. Decreasing viremia correlated with transient liver injury marked by an increase in serum sorbitol dehydrogenase (SDH) levels. Clearance of WHV DNA from serum was associated with the normalization of serum SDH. Circulating immune complexes (CICs) of WHsAg and antibodies against WHsAg (anti-WHs) that correlated temporarily with the peaks in serum viremia and WHs antigenemia were detected. CICs were no longer detected in serum once free anti-WHs became detectable. The detection of CICs around the peak in serum viremia and WHs antigenemia in resolving woodchucks suggests a critical role for the humoral immune response against WHsAg in the early elimination of viral and subviral particles from the peripheral blood. Individual kinetic variation during WHV infections in resolving woodchucks infected with the same WHV inoculum and dose is likely due to the outbred nature of the animals, indicating that the onset and magnitude of the individual immune response determine the intensity of virus inhibition and the timing of virus elimination from serum.

Antiviral effects of lamivudine, emtricitabine, adefovir dipivoxil, and tenofovir disoproxil fumarate administered orally alone and in combination to woodchucks with chronic woodchuck hepatitis virus infection.

Adefovir dipivoxil (ADV) and tenofovir disoproxil fumarate (TDF) are nucleotide analogs that inhibit the replication of wild-type hepatitis B virus (HBV) and lamivudine (3TC)-resistant virus in HBV-infected patients, including those who are coinfected with human immunodeficiency virus. The combination of ADV or TDF with other nucleoside analogs is a proposed strategy for managing antiviral drug resistance during the treatment of chronic HBV infection. The antiviral effect of oral ADV or TDF, alone or in combination with 3TC or emtricitabine (FTC), against chronic woodchuck hepatitis virus (WHV) infection was evaluated in a placebo-controlled study in the woodchuck, an established and predictive model for antiviral therapy. Once-daily treatment for 48 weeks with ADV plus 3TC or TDF plus FTC significantly reduced serum WHV viremia levels from the pretreatment level by 6.2 log(10) and 6.1 log(10) genome equivalents/ml serum, respectively, followed by TDF plus 3TC (5.6 log(10) genome equivalents/ml), ADV alone (4.8 log(10) genome equivalents/ml), ADV plus FTC (one survivor) (4.4 log(10) genome equivalents/ml), TDF alone (2.9 log(10) genome equivalents/ml), 3TC alone (2.7 log(10) genome equivalents/ml), and FTC alone (2.0 log(10) genome equivalents/ml). Individual woodchucks across all treatment groups also demonstrated pronounced declines in serum WHV surface antigen, characteristically accompanied by declines in hepatic WHV replication and the hepatic expression of WHV antigens. Most woodchucks had prompt recrudescence of WHV replication after drug withdrawal, but individual woodchucks across treatment groups had sustained effects. No signs of toxicity were observed for any of the drugs or drug combinations administered. In conclusion, the oral administration of 3TC, FTC, ADV, and TDF alone and in combination was safe and effective in the woodchuck model of HBV infection.

Quantitative evaluation of 2-deoxy-2[F-18]fluoro-D-glucose-positron emission tomography imaging on the woodchuck model of hepatocellular carcinoma with histological correlation.

PURPOSE: The Eastern woodchuck (Marmota monax) is considered as a naturally occurring animal model of hepatocellular carcinoma (HCC). The performance of 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) for imaging HCC on the woodchuck using Positron emission tomography (PET) was investigated in this study. PROCEDURES: Dynamic FDG-PET scans were performed on five woodchucks with HCC and one healthy woodchuck before removal and processing of the liver tissues for histology. The parameters of a two-tissue compartment model with dual input were estimated using weighted least squares (WLS). RESULTS: Ten HCCs were confirmed histologically. Six HCCs had a tumor-to-liver standardized uptake value (SUV) ratio < or =1.15, a k (4) / k (3) ratio similar to that in hepatic tissues and were well-differentiated. Four HCCs had a tumor-to-liver SUV ratio >1.15, a lower k (4) / k (3) ratio than the hepatic tissues and were moderately differentiated. CONCLUSIONS: Increased FDG uptake was observed in HCCs that were the least differentiated and correlated with a lower k (4) / k (3) ratio.

Antiviral effect of oral administration of tenofovir disoproxil fumarate in woodchucks with chronic woodchuck hepatitis virus infection.

Tenofovir disoproxil fumarate (TDF) is a nucleotide analogue approved for treatment of human immunodeficiency virus (HIV) infection. TDF also has been shown in vitro to inhibit replication of wild-type hepatitis B virus (HBV) and lamivudine-resistant HBV mutants and to inhibit lamivudine-resistant HBV in patients and HBV in patients coinfected with the HIV. Data on the in vivo efficacy of TDF against wild-type virus in non-HIV-coinfected or lamivudine-naïve chronic HBV-infected patients are lacking in the published literature. The antiviral effect of oral administration of TDF against chronic woodchuck hepatitis virus (WHV) infection, an established and predictive animal model for antiviral therapy, was evaluated in a placebo-controlled, dose-ranging study (doses, 0.5 to 15.0 mg/kg of body weight/day). Four weeks of once-daily treatment with TDF doses of 0.5, 1.5, or 5.0 mg/kg/day reduced serum WHV viremia significantly (0.2 to 1.5 log reduction from pretreatment level). No effects on the levels of anti-WHV core and anti-WHV surface antibodies in serum or on the concentrations of WHV RNA or WHV antigens in the liver of treated woodchucks were observed. Individual TDF-treated woodchucks demonstrated transient declines in WHV surface antigen serum antigenemia and, characteristically, these woodchucks also had transient declines in serum WHV viremia, intrahepatic WHV replication, and hepatic expression of WHV antigens. No evidence of toxicity was observed in any of the TDF-treated woodchucks. Following drug withdrawal there was prompt recrudescence of WHV viremia to pretreatment levels. It was concluded that oral administration of TDF for 4 weeks was safe and effective in the woodchuck model of chronic HBV infection.

Decreased oxidative DNA damage and accelerated cell turnover in woodchuck hepatitis virus infected liver.

Infection of newborn woodchucks with woodchuck hepatitis virus (WHV) results in hepatocellular carcinoma (HCC). Since oxidative damage may be carcinogenic, we investigated the relationship between WHV infection and oxidative damage to hepatic lipids and DNA. Eastern woodchucks were infected with WHV. Hepatic lipid peroxidation was assessed in vitro in isolated hepatocytes by thiobarbituric acid reactive substances (TBARS). Oxidative DNA damage was assessed in vivo in snap-frozen livers by 8-hydroxy-2'-deoxyguanosine (8-OH-dG). The proliferation index (PI) and apoptotic index (AI) were also determined. WHV infection was associated with increased hepatic lipid peroxidation (0.51+/-0.04 nmols TBARS per mg protein for WHV+ hepatocytes vs. 0.38+/-0.04 for WHV negative controls, P<0.01). In contrast, the WHV+ livers exhibited less oxidative DNA damage than uninfected controls (11+/-5 vs. 38+/-8 8-OH-dG/10(6) dG, P<0.02). In WHV-infected animals PI and AI were increased, by >20-fold. We conclude that WHV infection is associated with increased in vitro lipid peroxidation and decreased in vivo oxidative DNA damage. The increased PI and AI in the WHV+livers suggest that rapid cell turnover dilutes 8-OH-dG concentration.