A mouse model for studying the clearance of hepatitis B virus in vivo using a luciferase reporter.

Hepatitis B virus(HBV) infection remains a global problem, despite the effectiveness of the Hepatitis B vaccine in preventing infection. The resolution of Hepatitis B virus infection has been believed to be attributable to virus-specific immunity. In vivo direct evaluation of anti-HBV immunity in the liver is currently not possible. We have developed a new assay system that detects HBV clearance in the liver after the hydrodynamic transfer of a reporter gene and over-length, linear HBV DNA into hepatocytes, followed by bioluminescence imaging of the reporter gene (Fluc). We employed bioluminescence detection of luciferase expression in HBV-infected hepatocytes to measure the Hepatitis B core antigen (HBcAg)-specific immune responses directed against these infected hepatocytes. Only HBcAg-immunized, but not mock-treated, animals decreased the amounts of luciferase expression, HBsAg and viral DNA from the liver at day 28 after hydrodynamic infection with over-length HBV DNA, indicating that control of luciferase expression correlates with viral clearance from infected hepatocytes.

Noninvasive molecular imaging of interferon beta activation in mouse liver.

BACKGROUND/AIMS: Interferon beta (IFN-ß) is the priming cytokine in the interferons (IFNs) response that plays essential roles in innate immune system. Only very few studies on IFN activation in animals have been reported before, therefore, we embarked to develop a novel method to dynamically examine IFN-ß activation in mouse liver by noninvasive molecular imaging. METHODS: Interferon beta promoter-directed firefly luciferase gene was integrated into chromosomes of hepatocytes by hydrodynamic injection. Mouse hepatitis virus type 3 (MHV-3) and polyinosinic-polycytidylic acid [poly(I:C)] were used to stimulate the activation of IFN-ß. Luciferase activity was used as an indicator of the IFN-ß promoter activity in vitro and in vivo. The expression level of IFN-ß in the sera and firefly luciferase in the liver was assessed by ELISA and bioluminescence imaging respectively. Western blot was used for detecting proteins expression. RESULTS: A rapid and elevated luciferase expression in the mouse liver induced by poly (I:C) and MHV-3 was detected by bioluminescence imaging. The detectable level of IFN-ß in the sera was not induced by MHV-3. Moreover, IFN-ß activation was significantly inhibited by the hepatitis C virus (HCV) NS3/4A protease in mouse liver. These results were consistent with IFN-ß production in the sera. Therefore, a novel visual method to monitor IFN-ß promoter activity was established in the current study. CONCLUSION: This novel sensitive method can be used for not only assessing IFN-ß activation or inhibition in the liver under different conditions, but also screening drug candidates of stimulating or inhibiting of IFN-ß production.

Bioluminescence imaging allows monitoring hepatitis C virus core protein inhibitors in mice.

BACKGROUND: The development of small molecule inhibitors of hepatitis C virus (HCV) core protein as antiviral agents has been intensively pursued as a viable strategy to eradicate HCV infection. However, lack of a robust and convenient small animal model has hampered the assessment of in vivo efficacy of any antiviral compound. METHODOLOGY/PRINCIPAL FINDINGS: The objective of this work was to develop a novel method to screen anti-core protein siRNA in the mouse liver by bioluminescence imaging. The inhibitory effect of two shRNAs targeting the highly conserved core region of the HCV genome, shRNA452 and shRNA523, was examined using this method. In the transient mouse model, the effect of shRNA-523 was detectable at as early as 24 h and became even more pronounced at later time points. The effect of shRNA-452 was not detectable until 48 h post-transduction. In a stable mouse model, shRNA523 reduced luciferase levels by up to 76.4±26.0% and 91.8±8.0% at 6 h and 12 h after injection respectively, and the inhibitory effect persisted for 1 day after a single injection while shRNA-Scramble did not seem to have an effect on the luciferase activity in vivo. CONCLUSIONS/SIGNIFICANCE: Thus, we developed a simple and quantitative assay for real-time monitoring of HCV core protein inhibitors in mice.

Evaluation of hepatitis B virus promoters for sustained transgene expression in mice by bioluminescence imaging.

To find new liver-specific expression cassettes for long-term expression of therapeutic genes in the context of pDNA, the function and specificity of hepatitis B virus (HBV)' two hepatic enhancers (EnI and EnII), combined with HBV core and X promoters in cultured cells were evaluated. By bioluminescence imaging and hydrodynamic gene transfer technology, the persistence of transgene expression containing these regulatory sequences in the liver of mice was assessed. Our data indicated that both HBV enhancers were able to stimulate HBV core and X promoter activity in cultured cells of hepatic origin. In vivo, HBV core promoter linked to EnI and EnII (EII-EI-Pc) and X promoter linked to EnI and EnII (EI-EII-Px) could direct a constant and high-level gene expression.