The entry inhibitor Myrcludex-B efficiently blocks intrahepatic virus spreading in humanized mice previously infected with hepatitis B virus.

BACKGROUND & AIMS: Currently approved antivirals rarely cure hepatitis B virus (HBV) infection. Therefore additional therapeutic strategies interfering with other viral replication steps are needed. Using synthetic lipopeptides derived from the HBV envelope protein, we previously demonstrated prevention of de novo HBV infection in vivo. We aimed at investigating the ability of the lipopeptide Myrcludex-B to block HBV spreading post-infection. METHODS: uPA/SCID mice reconstituted with human hepatocytes were infected with HBV. Daily subcutaneous Myrcludex-B administration was initiated either 3 days, 3 weeks or 8 weeks post HBV inoculation. Viral loads were quantitated in serum and liver, and visualized by immunohistochemistry. RESULTS: Myrcludex-B efficiently prevented viral spreading from the initially infected human hepatocytes, as demonstrated by the lack of increase in viremia, antigen levels and amount of HBcAg-positive human hepatocytes determined 6 weeks after treatment. Myrcludex-B efficiently blocked HBV dissemination also when treatment was started in the ramp-up phase of infection, in mice displaying moderate levels of circulating virions (median 3 × 10(6)HBV DNA copies/ml). Notably, after 6 weeks of treatment, not only the amount of HBcAg-positive hepatocytes, but also intrahepatic cccDNA loads, remained comparable to values found in mice sacrificed 3 weeks post-infection. In none of the experimental settings, drug administration affected human hepatocyte half-life or altered virion productivity. CONCLUSIONS: Myrcludex-B efficiently not only prevented HBV spreading from infected human hepatocytes in vivo, but also hindered amplification of the cccDNA pool in initially infected hepatocytes. Administration of an entry inhibitor, possibly used in combination with current HBV drugs, may improve patients' treatment outcome.

Primary Human Hepatocytes Repopulate Livers of Mice After In Vitro Culturing and Lentiviral-Mediated Gene Transfer.

Cell-based therapies represent a promising alternative to orthotopic liver transplantation. However, therapeutic effects are limited by low cell engraftment rates. We recently introduced a technique creating human hepatocyte spheroids for potential therapeutic application. The aim of this study was to evaluate whether these spheroids are suitable for engraftment in diseased liver tissues. Intrasplenic spheroid transplantation into immunodeficient uPA/SCID/beige mice was performed. Hepatocyte transduction ability prior to transplantation was tested by lentiviral labeling using red-green-blue (RGB) marking. Eight weeks after transplantation, animals were sacrificed and livers were analyzed by immunohistochemistry and immunofluorescence. To investigate human hepatocyte-specific gene expression profiles in mice, quantitative real-time-PCR was applied. Human albumin and alpha-1-antitrypsin concentrations in mouse serum were quantified to assess the levels of human chimerism. Precultured human hepatocytes reestablished their physiological liver tissue architecture and function upon transplantation in mice. Positive immunohistochemical labeling of the proliferating cell nuclear antigen revealed that human hepatocytes retained their in vivo proliferation capacity. Expression profiles of human genes analyzed in chimeric mouse livers resembled levels determined in native human tissue. Extensive vascularization of human cell clusters was detected by demonstration of von Willebrand factor activity. To model gene therapy approaches, lentiviral transduction was performed ex vivo and fluorescent microscopic imaging revealed maintenance of RGB marking in vivo. Altogether, this is the first report demonstrating that cultured and retroviral transduced human hepatocyte spheroids are able to engraft and maintain their regenerative potential in vivo.

Strong antiviral activity of the new l-hydroxycytidine derivative, l-Hyd4FC, in HBV-infected human chimeric uPA/SCID mice.

BACKGROUND: Suppression of viral replication with nucleoside/nucleotide inhibitors has been shown to greatly improve the outcome of chronic HBV infection. ß-l-nucleoside analogues, especially ß-l-deoxycytidine derivatives represent one of the most efficient groups of antiretroviral compounds. We recently described that hydroxylation of the amino group of these ß-l-deoxycytidine derivatives preserved their strong HBV inhibitory activity in vitro, but strongly reduced their cytotoxicity. From this new group of compounds we selected ß-l-2',3'-didehydro-2',3'-dideoxy-N(4)-hydroxy-5-fluorocytidine (l-Hyd4FC) for a first in vivo investigation. The aim of this study was to determine the antiviral activity of l-Hyd4FC in HBV-infected human liver chimeric urokinase plasminogen activator (uPA)/SCID mice. METHODS: Stably infected animals (median 6×10(7) HBV DNA/ml) were injected daily with either l-Hyd4FC (50 mg/kg) or saline as controls. Mice treated with lamivudine served to compare the in vivo antiviral potency of l-Hyd4FC. Virological changes were determined by quantitative PCR. RESULTS: Treatment with l-Hyd4FC for 4 weeks induced a 2-log reduction of viraemia, while a median 1.5-log decline was achieved with lamivudine. Intrahepatically, l-Hyd4FC induced a median eightfold decline of viral activity (relaxed circular DNA/covalently closed circular DNA), and threefold reduction of pregenomic RNA/GAPDH levels. No significant decline of subgenomic HBV transcripts, as well as of circulating hepatitis B e antigen and hepatitis B surface antigen was detected. Maintenance of human serum albumin concentrations throughout the study, negative TUNEL staining and occurrence of viral rebound after drug withdrawal indicated that l-Hyd4FC was not toxic in human hepatocytes. CONCLUSIONS: Administration of l-Hyd4FC in uPA/SCID mice harbouring HBV-infected human hepatocytes demonstrated the high antiviral potency of this drug in vivo. Such characteristics make l-Hyd4FC a good candidate for further investigations a as potential HBV therapeutic agent.

RGB marking facilitates multicolor clonal cell tracking.

We simultaneously transduced cells with three lentiviral gene ontology (LeGO) vectors encoding red, green or blue fluorescent proteins. Individual cells were thereby marked by different combinations of inserted vectors, resulting in the generation of numerous mixed colors, a principle we named red-green-blue (RGB) marking. We show that lentiviral vector-mediated RGB marking remained stable after cell division, thus facilitating the analysis of clonal cell fates in vitro and in vivo. Particularly, we provide evidence that RGB marking allows assessment of clonality after regeneration of injured livers by transplanted primary hepatocytes. We also used RGB vectors to mark hematopoietic stem/progenitor cells that generated colored spleen colonies. Finally, based on limiting-dilution and serial transplantation assays with tumor cells, we found that clonal tumor cells retained their specific color-code over extensive periods of time. We conclude that RGB marking represents a useful tool for cell clonality studies in tissue regeneration and pathology.