J. Petersen

Control of cccDNA function in hepatitis B virus infection

The template of hepatitis B virus (HBV) transcription, the covalently closed circular DNA (cccDNA), plays a key role in the life cycle of the virus and permits the persistence of infection. Novel molecular techniques have opened new possibilities to investigate the organization and the activity of the cccDNA minichromosome in vivo, and recent advances have started to shed light on the complexity of the mechanisms controlling cccDNA function. Nuclear cccDNA accumulates in hepatocyte nuclei as a stable minichromosome organized by histone and non-histone viral and cellular proteins. Identification of the molecular mechanisms regulating cccDNA stability and its transcriptional activity at the RNA, DNA and epigenetic levels in the course of chronic hepatitis B (CH-B) infection may reveal new potential therapeutic targets for anti-HBV drugs and hence assist in the design of strategies aimed at silencing and eventually depleting the cccDNA reservoir.

Long‐term efficacy of tenofovir monotherapy for hepatitis B virus‐monoinfected patients after failure of nucleoside/nucleotide analogues

Tenofovir disoproxil fumarate (TDF) has demonstrated high antiviral efficacy in treatment‐naive patients with chronic hepatitis B virus (HBV) infection but experience in nucleoside/nucleotide analogue (NA)‐experienced patients is limited. In this retrospective multicenter study we therefore assessed the long‐term efficacy of TDF monotherapy in patients with prior failure or resistance to different NA treatments. Criteria for inclusion were HBV DNA levels >4.0 log10 copies/mL at the start and a minimum period of TDF therapy for at least 6 months. In all, 131 patients (mean age 42 ± 12 years, 95 male, 65% hepatitis B e antigen [HBeAg]‐positive) were eligible. Pretreatment consisted of either monotherapy with lamivudine (LAM; n = 18), adefovir (ADV; n = 8), and sequential LAM‐ADV therapy (n = 73), or add‐on combination therapy with both drugs (n = 29). Three patients had failed entecavir therapy. Resistance analysis in 113 of the 131 patients revealed genotypic LAM and ADV resistance in 62% and 19% of patients, respectively. The mean HBV DNA level at TDF baseline was 7.6 ± 1.5 log10 copies/mL. The overall cumulative proportion of patients achieving HBV DNA levels <400 copies/mL was 79% after a mean treatment duration of 23 months (range, 6–60). Although LAM resistance did not influence the antiviral efficacy of TDF, the presence of ADV resistance impaired TDF efficacy (100% versus 52% probability of HBV DNA <400 copies/mL, respectively). However, virologic breakthrough was not observed in any of the patients during the entire observation period. Loss of HBeAg occurred in 24% of patients and HBsAg loss occurred in 3%. No significant adverse events were noticed during TDF monotherapy. Conclusion: TDF monotherapy induced a potent and long‐lasting antiviral response in NA‐experienced patients with previous treatment failure. Our data may have implications for current add‐on strategies. (HEPATOLOGY 2009.)

Humanized chimeric uPA mouse model for the study of hepatitis B and D virus interactions and preclinical drug evaluation

No specific drugs are currently available against hepatitis delta virus (HDV), a defective virus leading to the most severe form of chronic viral hepatitis in man. The lack of convenient HDV infection models has hampered the development of effective therapeutics. In this study, naïve and hepatitis B virus (HBV) chronically infected humanized uPA/SCID mice were employed to establish a small animal model of HBV/HDV coinfection and superinfection. For preclinical antiviral drug evaluation, the GMP version of the myristoylated preS‐peptide (Myrcludex‐B), a lipopeptide derived from the pre‐S1 domain of the HBV envelope, was applied to prevent de novo HBV/HDV coinfection in vivo. Virological parameters were determined at serological and intrahepatic level both by real‐time polymerase chain reaction (PCR) and by immunohistochemistry. Establishment of HDV infection was highly efficient in both HBV‐infected and naïve chimeric mice with HDV titers rising up to 1 × 10E9 copies/mL. Notably, HDV superinfection led to a median 0.6log reduction of HBV viremia, which although not statistically significant suggests that HDV may hinder HBV replication. In the setting of HBV/HDV simultaneous infection, a majority of human hepatocytes stained HDAg‐positive long before HBV spreading was completed, confirming that HDV can replicate intrahepatically also in the absence of HBV infection. Furthermore, the increase of HBV viremia and intrahepatic cccDNA loads was significantly slower than in HBV mono‐infected mice. Treatment with the HBV entry inhibitor Myrcludex‐B, efficiently hindered the establishment of HDV infection in vivo. Conclusion: We established an efficient model of HBV/HDV infection to exploit mechanisms of viral interference in human hepatocytes and to test the efficacy of an HDV‐entry inhibitor in vivo. (HEPATOLOGY 2011)

Antiviral effect of entecavir in chronic hepatitis B: Influence of prior exposure to nucleos(t)ide analogues

BACKGROUND & AIMS Entecavir is a potent inhibitor of viral replication in nucleos(t)ide analogue (NA)-naïve chronic hepatitis B patients, but data on the efficacy in NA-experienced subjects are limited. METHODS In a multi-center cohort study we investigated 161 chronic hepatitis B patients (34% NA-experienced) treated with entecavir monotherapy. RESULTS During a median follow-up of 11 (3-23)months, 82 (79%) of 104 NA-naïve patients achieved virologic response (VR), defined as HBV DNA <80IU/ml, and none of the patients (0%) developed genotypic entecavir-resistance. VR was demonstrated in 31 (54%) of 57 NA-experienced patients during a median follow-up of 12 (3-31)months. Patients with lamivudine-resistant mutations at the start of entecavir monotherapy had a reduced probability of achieving VR compared to lamivudine-naïve patients (HR 0.14; 95% CI 0.04-0.58; p=0.007). Antiviral efficacy was not decreased by prior treatment with lamivudine when lamivudine-resistance had never developed (HR 0.81; 95% CI 0.43-1.52; p=0.52). Prior adefovir therapy without development of adefovir-resistance (HR 0.84; 95% CI 0.43-1.64; p=0.61) and presence of adefovir-resistance (HR 0.86; 95% CI 0.27-2.71; p=0.80) did not influence antiviral response to entecavir. Switching to a tenofovir-containing treatment regimen resulted in viral load decline in patients with entecavir-resistance associated mutations. CONCLUSIONS Entecavir proved to be efficacious in NA-naïve patients. The antiviral efficacy of entecavir was not influenced by prior treatment with adefovir or presence of adefovir-resistance. Entecavir should not be used in patients with previous lamivudine-resistance, yet it may still be an option in lamivudine-experienced patients in case lamivudine-resistance never developed.

Quantitative gene expression analysis reveals transition of fetal liver progenitor cells to mature hepatocytes after transplantation in uPA/RAG-2 mice.

Therapies for liver diseases with stem and progenitor cells will require a detailed knowledge of the molecular mechanisms driving the in vivo differentiation process toward adult hepatic tissue. We applied quantitative gene expression methods to analyze the differentiation process of fetal liver progenitor cells after transplantation into an animal model of liver regeneration. Enhanced green fluorescent protein (EGFP)-transgenic liver progenitor cells were isolated from fetal mouse liver at stage embryonic day 13.5 and transplanted into uPA/RAG-2 mice. Two, 4, and 6 weeks after cell transplantation cryosections of liver tissue were analyzed for EGFP-positive regeneration nodules. RNA from laser-microdissected EGFP-positive tissue was isolated and used as template for quantitative real-time reverse transcriptase-polymerase chain reaction. Phenotypic differentiation was analyzed by staining of the canalicular marker enzyme dipeptidyl-peptidase IV. Proliferation in regenerative nodules and surrounding tissue was monitored with the BrdU incorporation assay. Alpha fetoprotein gene expression had already decreased 2 weeks after transplantation in EGFP-positive regeneration nodules compared to pretransplantation values and was not detectable after 4 and 6 weeks, whereas albumin slightly increased in transplanted cells indicating differentiation into a mature phenotype. The dipeptidyl-peptidase IV antigen was associated with some liver progenitor cells 2 weeks after transplantation and in virtually all cells after 4 and 6 weeks. Cell proliferation index in transplanted cells was maximally increased (4.8% BrdU-positive cells) after 2 weeks and decreased (0.4%) after 6 weeks to normal levels. Our results demonstrate that gene expression in liver progenitor cells changes from fetal to adult phenotype within 4 to 6 weeks after transplantation despite ongoing proliferation of the transplanted cells in a mouse model of liver regeneration. Quantitative gene expression profiles as shown here will have important implications in our understanding of the in vivo differentiation process of stem cells.

Animal models for the study of HBV replication and its variants

Enormous progresses in hepatitis B virus research have been made through the identification of avian and mammalian HBV related viruses, which offer ample opportunities for studies in naturally occurring hosts. However, none of these natural hosts belongs to the commonly used laboratory animals, and the development of various mouse strains carrying HBV transgenes offered unique opportunities to investigate some mechanisms of viral pathogenesis. Furthermore, the need to perform infection studies in a system harbouring HBV-permissive hepatocytes has lately led researchers to create new challenging human mouse chimera models of HBV infection. In this review, we will overview the type of animal models currently available in hepadnavirus research.

Long-term response after stopping tenofovir disoproxil fumarate in non-cirrhotic HBeAg-negative patients – FINITE study

BACKGROUND & AIMS There is currently no virological cure for chronic hepatitis B but successful nucleos(t)ide analogue (NA) therapy can suppress hepatitis B virus (HBV) DNA replication and, in some cases, result in HBsAg loss. Stopping NA therapy often leads to viral relapse and therefore life-long therapy is usually required. This study investigated the potential to discontinue tenofovir disoproxil fumarate (TDF) therapy in HBeAg-negative patients. METHODS Non-cirrhotic HBeAg-negative patients who had received TDF for ≥4years, with suppressed HBV DNA for ≥3.5years, were randomly assigned to either stop (n=21) or continue (n=21) TDF monotherapy. Standard laboratory tests including HBV DNA viral load, HBsAg and alanine aminotransferase (ALT) measurements, and adverse event reporting were carried out during treatment and post-treatment follow-up for 144weeks. RESULTS Of the patients who stopped TDF therapy, 62% (n=13) remained off-therapy to Week 144. Median HBsAg change in this group was -0.59log10IU/ml (range -4.49 to 0.02log10IU/ml) vs. 0.21log10IU/ml in patients who continued TDF therapy. Four patients (19%) achieved HBsAg loss. Patients stopping therapy had initial fluctuations in viral load and ALT; however, at Week 144, 43% (n=9) had either achieved HBsAg loss or had HBV DNA <2,000IU/ml. There were no unexpected safety issues identified with stopping TDF therapy. CONCLUSIONS This controlled study demonstrated the potential for HBsAg loss and/or sustained virological response in non-cirrhotic HBeAg-negative patients stopping long-term TDF therapy. Lay summary: Nucleos(t)ide analogue (NA) is usually a life-long therapy for HBV patients. This randomised controlled study investigated the discontinuation of tenofovir disoproxil fumarate (TDF) therapy in HBeAg-negative patients. Of the patients who stopped TDF therapy, 62% remained off-therapy to Week 144, of which 43% of patients had achieved either HBsAg loss or HBV DNA <2,000IU/ml. This offers a potential for long-term HBV-suppressed patients without cirrhosis to stop NA therapy under strict surveillance. Clinical trial number: NCT01320943.

Optimal therapy for chronic hepatitis B: hepatitis B virus combination therapy?

Currently available antiviral treatment for chronic hepatitis B can be divided into two classes of therapeutic agents: pegylated interferon alpha (PEG‐IFN) and nucleos(t)ide analogues (NAs). The major advantages of NAs are good tolerance and potent antiviral activity associated with high rates of on‐treatment response to therapy. The advantages of PEG‐IFN include a finite course of treatment, the absence of drug resistance, and an opportunity to obtain a durable post‐treatment response to therapy. The use of these two antiviral agents with different mechanisms of action in combination is theoretically an attractive approach for treatment, either simultaneously, as sequential combination therapy (add‐on), or even as an immediate switch from one agent to the other. Different NAs have also been combined in certain clinical situations. At present, several studies have confirmed certain virological advantages to combination therapies, but pivotal prospective studies demonstrating long‐term clinical benefit to patients are still missing. Therefore, combination treatment, especially with PEG‐IFN plus NAs, is not indicated and was not recommended by the European Association for the Study of the Liver Clinical Practice Guidelines written in 2012, while the guidelines for the use of combination NAs is limited to very few clinical situations.

Regeneration in pig livers by compensatory hyperplasia induces high levels of telomerase activity.

BackgroundSeveral highly proliferative human cells transiently activate telomerase, a ribonucleoprotein with reverse transcriptase activity, to counterbalance replication-associated telomere erosion and to increase stress resistance. Quiescent human hepatocytes exhibit very low or undetectable levels of telomerase activity. However, hepatocytes display a remarkable proliferative capability following liver injury. To investigate whether liver regeneration by compensatory hyperplasia is associated with telomerase activation, we measured telomerase activity in pig livers after 70 to 80% partial hepatectomy using a fully quantitative real-time telomeric repeat amplification protocol. In contrast to commonly studied inbred laboratory mouse strains, telomere length and telomerase activity in porcine tissues are comparable to humans.ResultsFollowing partial hepatectomy, histology revealed mitotic hepatocytes as marker for compensatory hyperplasia. As expected, there was no induction of inflammation. Telomerase activity increased significantly showing the highest levels (5-fold upregulation) in pigs treated with partial hepatectomy and hepatic decompression. Moreover, telomerase activity significantly correlated to the number of mitotic hepatocytes.ConclusionOur data demonstrate telomerase activation in liver regeneration by compensatory hyperplasia in a large animal model with telomere biology comparable to humans. Telomerase activation may constitute a mechanism to protect proliferating liver cells against telomere shortening and oxidative stress.

[Knowledge about HBV, prevention behaviour and treatment adherence of patients with chronic hepatitis B in a large referral centre in Germany].

BACKGROUND The incidence of chronic hepatitis B in Germany is approximately 0.5 %. Data regarding knowledge about HBV, prevention behaviour and treatment adherence in patients with chronic HBV are scarce. METHODS In this prospective study 201 consecutive patients with CHB infection were studied from a large urban academic outpatient clinic at the University Medical Centre in Hamburg. Patients were interviewed with a questionnaire that contained 47 questions covering social demographic dates, knowledge about HBV, treatment adherence and prevention. The success rate of interviews was 100 % with free translation service offered. RESULTS 20.4 % of the CHB patients were born in Germany, but the majority of the patients were immigrants (80.6 %). 51 % of the patients had a good, 34 % a moderate and 15 % a poor knowledge about HBV. 89 % of the patients knew that HBV can be transmitted through blood contacts, but 34 % believed that inadequate hygienic conditions and 24 % that food products may transmit the virus. 96 % of the patients had knowledge about the existence of an HBV vaccine. Furthermore, 82 % considered a vaccination of all persons in the household important. Despite the knowledge of the existence and importance of a vaccine, only 61,7 % of the 300 affected children/siblings of HBV-positive family members were vaccinated. However, the child vaccination rate was significantly higher among patients with knowledge about the protective effect of the vaccine (p < 0.001), the free of charge vaccination program for children up to 18 years (p < 0.001) and higher school education (p < 0.001). Migrants with poor German language skills had lower knowledge scores (p < 0.001) and showed lower vaccination rates (p = 0.016) compared to immigrants with good German language skills. 43 % of all patients were treated with nucleot(s)ide analogues with a median treatment duration of 2 - 5 years. 65 % of these patients declared to never have missed a dose and 27 % missed less than one dose per month. 90 % of the patients tolerated the antiviral drugs very well and between patients with or without side effects there was no significant difference in quality of life. CONCLUSION Chronic hepatitis B in Germany is characterised by awareness problems and language barriers. More attention is needed for HBV-infected immigrants in the form of multilingual information about CHB and awareness campaigns.