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

Abstract

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. Oncedaily 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.Chronic infection with the hepatitis B virus (HBV) is a major public health problem and is responsible for 1.2 million deaths per year worldwide (64). It is estimated that more than 2 billion people have serological evidence of previous or current HBV infection, and over 350 million people are chronic carriers of HBV (64). Carriers of HBV are at high risk of developing chronic hepatitis, hepatic cirrhosis, and hepatocellular carcinoma (HCC). Although safe and effective prophylactic vaccines against HBV are available, improvements in drug and/or immunotherapeutic strategies for the treatment of chronic HBV infection are still needed. Therapy with alpha interferon and nucleoside analogs alone or in combination can be effective against HBV; however, side effects of interferon and the emergence of nucleoside-resistant mutants often limit treatment outcomes (34).Lamivudine (3TC) was the first nucleoside analog licensed for the treatment of chronic HBV infection. Although 3TC is safe and effective, its therapeutic value is limited by the timedependent development of drug-resistant HBV mutants (32

Antiviral Efficacy and Host Innate Immunity Associated with SB 9200 Treatment in the Woodchuck Model of Chronic Hepatitis B

“…WHV RNA was measured by Northern blot hybridization and WHV DNA replicative intermediates (RI) and WHV covalently-closed circular (ccc) DNA were determined by Southern blot hybridization as described [15]. Liver was imunostained with an antibody against WHV core antigen (WHcAg) using a 1:350 dilution.…”

Semliki Forest Virus Expressing Interleukin-12 Induces Antiviral and Antitumoral Responses in Woodchucks with Chronic Viral Hepatitis and Hepatocellular Carcinoma

“…, bicarbonate, total serum iron, iron binding capacity, and percent iron saturation (28). Serum AST, ALT, and SDH activities are markers of hepatocellular injury in woodchucks.…”

“…Blood samples were obtained for WHV DNA analysis and serological testing prior to the start of the study; at week 0 prior to the administration of SFV-enhIL-12 or placebo; and then at 2, 4, 6, 10, 14, 18, and 23 to 24 weeks posttreatment. WHV DNA in serum was determined quantitatively by dot blot hybridization (assay sensitivity, Ն1.0 ϫ 10 7 WHV genome equivalents per ml (28). WHsAg in serum was determined qualitatively by enzyme-linked immunosorbent assay using dilutions of serum.…”

Liver-directed gene therapy of chronic hepadnavirus infection using interferon alpha tethered to apolipoprotein A-I

“…Serum WHV and HBV DNA was isolated using the High Pure Viral Nucleic Acid kit (Roche Diagnostics, Lewes, United Kingdom) or the QIAmp DNA Mini kit (Qiagen, Valencia, CA), respectively, and were quantified by real-time PCR as described previously [9, 12]. …”