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The mechanisms determining hepatitis B virus (HBV) persistence and pathogenesis are not fully elucidated, but appear to be multi-factorial. Current medication to repress viral replication is available; however, the unique replication strategies employed by HBV enable the virus to persist within the infected hepatocytes. Consequently, cure is rarely achieved. Progresses in HBV research and preclinical testing of antiviral agents have been limited by the narrow species- and tissue-tropism of the virus, the paucity of infection models available and the restrictions imposed by the use of chimpanzees, the only animals fully susceptible to HBV infection. Mice are not HBV permissive but major efforts have focused on the development of mouse models of HBV replication and infection, such as the generation of humanized mice. By presenting the different animal models available, this review will highlight the most important and clinically relevant findings that have been retrieved from the respective systems., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Hepatitis B virus (HBV) dynamics in treated patients can be complex and differ considerably from other viral infections. We analyse dynamics of liver and serum levels of HBV DNA in 24 chronically HBV-infected individuals undergoing 1 year of combination therapy with pegylated interferon alpha and adefovir dipivoxil (ADV), followed by 2 years of ADV monotherapy. Serum viral dynamics differentiated the patients into four response groups dependent on how quickly viremia became undetectable: quickly suppressed (HBV DNA <100 copies/ml within 8 weeks and staying suppressed, GRP1); quickly suppressed but some rebound (<10,000 copies/ml, GRP2); slow decay (GRP3); virological failures (>10,000 copies/ml, GRP4). These groups did not differ before start of therapy by serum HBV DNA (p=0.2), HBsAg (p=0.1), ALT (p=0.4), total HBV DNA within the liver (p=0.08), or cccDNA (p=0.3). Despite very different serum HBV DNA levels after 3 years, there was no statistical difference in total HBV DNA within the liver (p=0.08), nor in cccDNA levels (p=0.1), but HBsAg levels in serum were significantly lower for GRP1 compared to GRP4 (p=0.02). Efficacy in terms of reduction over the 3 years of serum HBV DNA, liver HBV DNA, cccDNA, and ratios of liver HBV DNA to cccDNA were 99.98%, 99.5%, 98.4%, and 83.2% respectively, exhibiting larger antiviral effects in serum than in liver. Over the course of therapy, HBV DNA viremia exhibited large oscillations for some individuals. Mathematical modelling reproduced the dynamics of these diverse groups by assuming a number of viral clones arose that experienced delayed recognition by the antibody response. Large viremia oscillations under therapy suggest sequential outgrowth of viral clones with delayed recognition by the humoral response., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Background & Aims: We evaluated the combination of daclatasvir (pan-genotypic NS5A inhibitor) and simeprevir (NS3/4A protease inhibitor), with or without ribavirin, in hepatitis C virus genotype 1-infected patients., Methods: This phase II, open-label study enrolled treatment-naive patients or prior null responders with genotype 1b (n=147) or 1a (n=21) infection. Genotype 1b-infected patients were randomized 1:1 to receive daclatasvir 30mg plus simeprevir 150mg once daily with or without ribavirin; those who completed the initial 12-week treatment were re-randomized 1:1 to stop treatment or continue treatment through to week 24. Genotype 1a-infected patients received daclatasvir plus simeprevir with ribavirin for 24weeks. The primary endpoint was the proportion of patients with sustained virologic response at posttreatment week 12 (SVR12)., Results: For genotype 1b, 84.9% (45/53) and 74.5% (38/51) of treatment-naive patients and 69.6% (16/23) and 95.0% (19/20) of prior null responders to peginterferon and ribavirin achieved SVR12 with daclatasvir plus simeprevir alone and with ribavirin, respectively. Treatment duration did not have a well-defined impact on response. For genotype 1a, daclatasvir plus simeprevir with ribavirin provided a 66.7% (8/12) response rate in treatment-naive patients and was not effective in prior null responders. Data suggest that baseline resistance polymorphisms influenced SVR12 rates. Daclatasvir plus simeprevir was well tolerated with or without ribavirin with low incidences of serious adverse events and adverse events leading to discontinuation., Conclusions: Daclatasvir plus simeprevir, with or without ribavirin, was effective with a 12- or 24-week duration in genotype 1b-infected patients and was well tolerated. ClinicalTrials.gov identifier: NCT01628692., (Copyright © 2015 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.)

Background & Aims: The limited availability of hepatitis Delta virus (HDV) infection models has hindered studies of interactions between HDV and infected hepatocytes. The aim was to investigate the antiviral state of HDV infected human hepatocytes in the setting of co-infection with hepatitis B virus (HBV) compared to HBV mono-infection using human liver chimeric mice., Methods: Viral loads, human interferon stimulated genes (hISGs) and cytokines were determined in humanized uPA/SCID/beige (USB) mice by qRT-PCR, ELISA and immunofluorescence., Results: Upon HBV/HDV inoculation, all mice developed viremia, which was accompanied by a significant induction of hISGs (i.e. hISG15, hSTATs, hHLA-E) compared to uninfected mice, while HBV mono-infection led to weaker hISG elevations. In the setting of chronic infection enhancement of innate defense mechanisms was significantly more prominent in HBV/HDV infected mice. Also the induction of human-specific cytokines (hIP10, hTGF-ß, hIFN-ß and hIFN-λ) was detected in HBV/HDV co-infected animals, while levels remained lower or below detection in uninfected and HBV mono-infected mice. Moreover, despite the average increase of hSTAT levels determined in HBV/HDV infected livers, we observed a weaker hSTAT accumulation in nuclei of hepatocytes displaying very high HDAg levels, suggesting that HDAg may in part limit hSTAT signaling., Conclusions: Establishment of HDV infection provoked a clear enhancement of the antiviral state of the human hepatocytes in chimeric mice. Elevated pre-treatment ISG and interferon levels may directly contribute to inflammation and liver damage, providing a rationale for the more severe course of HDV-associated liver disease. Such antiviral state induction might also contribute to the lower levels of HBV activity frequently found in co-infected hepatocytes., (Copyright © 2015 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.)

Background & Aims: Pegylated interferon-alpha (PegIFNα) remains an attractive treatment option for chronic hepatitis B virus (HBV) infection because it induces higher rates of antigen loss and seroconversion than treatment with polymerase inhibitors. Although early HBsAg decline is recognised as the best predictor of sustained response to IFN-based therapy, it is unclear whether immune cell functions are required to induce significant antigenemia reduction in the first weeks of treatment. Aim of the study was to investigate whether PegIFNα can induce sustained human hepatocyte responsiveness and substantial loss of circulating and intrahepatic viral antigen loads in a system lacking immune cell functions., Methods: HBV-infected humanized uPA/SCID mice received either PegIFNα, entecavir (ETV), or both agents in combination. Serological and intrahepatic changes were determined by qRT-PCR and immunohistochemistry and compared to untreated mice., Results: After 4 weeks of treatment, median viremia reduction was greater in mice treated with ETV (either with or without PegIFNα) than with PegIFNα. In contrast, levels of circulating HBeAg, HBsAg, and intrahepatic HBcAg were significantly reduced (p = 0.03) only in mice receiving PegIFNα alone or in combination, as compared to mice receiving ETV monotherapy. Progressive antigen reduction was also demonstrated in mice receiving PegIFNα for 12 weeks (HBeAg = Δ1log; HBsAg = Δ1.4log; p < 0.0001). Notably, repeated administrations of the longer-active PegIFNα could breach the impairment of HBV-infected hepatocyte responsiveness and induce sustained enhancement of human interferon stimulated genes (ISG)., Conclusions: The antiviral effects of PegIFNα exerted on the human hepatocytes can induce sustained responsiveness and trigger substantial HBV antigen decline without claiming the involvement of immune cell responses., (Copyright © 2013 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.)

Background/aims: Transplantation of primary human hepatocytes and establishment of hepatitis B virus (HBV) infection in immunodeficient urokinase plasminogen activator (uPA) transgenic mice was shown. However, the availability of usable primary human hepatocytes is very limited. Therefore, alternative and more accessible sources of hepatocytes permissive for HBV infection are highly desirable. Here we investigated the potential of primary hepatocytes from the tree shrew Tupaia belangeri that were shown to be susceptible to HBV infection., Methods: Freshly isolated or cryopreserved primary tupaia hepatocytes were transplantated via intrasplenic injection into immunodeficient uPA/RAG-2 mice. Engrafted mice were then infected with HBV and woolly monkey (WM)-HBV positive sera., Results: Extensive proliferation of xenografted cells was demonstrated by the stable production of tupaia alpha1-antitrypsin in serum and liver of transplanted mice. Quantitative PCR assays demonstrated the presence of circulating viral particles as well as intracellular viral DNA, including covalently closed circular (ccc) DNA, in transplanted mice. Viral infection could be serially passaged in mice. Furthermore, viral replication was strongly inhibited by treating mice with adefovir dipivoxil., Conclusions: uPA mice repopulated with tupaia hepatocytes represent a useful and more accessible model for HBV infection studies, including the evaluation of antiviral therapy and cccDNA.