四省观察点人群中血清乙型肝炎病毒表面抗原消长趋势调查

本文以前瞻性血清流行病学方法调查了人群中血清HBsAg消长趋势。观察了3 096名HBV易感者,其人年总感染率为7.0％;HBsAg人年阳转率为0.68％,两者之比为10.3:1.0。HBsAg阳转者中51.2％发生在0～3岁时期。调查了772例HBsAg携带者,其人年标化阴转率为2.01％,阴转者主要发生在10～29岁和50岁以上年龄组,占总阴转数的66.7％。以人群HBsAg阴转率加上因自然死亡而损失的HBsAg携带率和人群中HBsAg年增长率进行分析计算,得出HBsAg在观察点人群中的消长状况是呈上升趋势,即年增加率为0.370％,年减少率为0.264％。     

Prognosis for the patients with chronic hepatitis B

The purpose of the research was to determine the influence of the hepatitis B virus on the progression of the chronic liver disease. In the present paper, 127 patients who were followed up for five years and who had histologically verified chronic liver disease, are described. Fifty two of them were carriers of HBsAg, 75 patients were HBsAg negative, but had other markers typical for a previous infection of HBV in the sera. All the patients were nonalcoholics and no drug addicts. In the sera of these 127 patients markers of HBV were prospectively followed up: HBsAg, HBeAg, anti-HBs, anti-HBc, anti-HBe, HBVDNA, antiHCV for C virus and anti-D for D virus. It was proved by these investigations that HBV provokes very severe chronic hepatitis: CAH (chronic active hepatitis) and CH (cirrhosis hepatis). It was also proved that HBV replicated in 44.20% patients, namely, HBVDNA was positive in the sera of those patients. In 26.08% of such patients the mutant form of HBV was present. In spite of progressive liver disease and without any antiviral therapy all the patients with chronic HBV cirrhosis hepatis were, after five year-follow-up, in Child-Pugh A grade. It was found that the patients who were HBsAg negative, but had one or more markers of HBV positive in the sera, had also a severe chronic hepatitis. That group of patients remains our object of further research. The five-years follow-up of all these patients demonstrates that it is necessary to find out an efficient medicament against HBV chronic hepatitis. Obligatory vaccination of the risk population against virus B remains the only prevention against this severe disease.     

Genotype and subtype analyses of hepatitis B virus (HBV) and possible co-infection of HBV and hepatitis C virus (HCV) or hepatitis D virus (HDV) in blood donors, patients with chronic liver disease and patients on hemodialysis in Surabaya, Indonesia

Four subtypes (adw, adr, ayw, and ayr ) and eight genotypes (A to H) of the hepatitis B virus (HBV) have been identified. They appear to be associated with particular geographic distribution, ethnicity, and possibly clinical outcomes. In this study, hepatitis B surface antigen (HBsAg) subtyping and HBV genotyping were carried out on sera obtained from HBsAg-positive HBV carriers, including healthy blood donors; patients with acute hepatitis, chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma; and patients on hemodialysis all located in Surabaya, Indonesia. We report here that all HBV isolates tested in Surabaya belonged to genotype B, with more than 90% of them being classified into subtype adw. Our results also revealed that prevalence of hepatitis C virus (HCV) co-infection among HBV carriers in Surabaya was approximately 10% for healthy blood donors and patients with chronic liver disease, and approximately 60% for patients on maintenance hemodialysis. Interestingly, HBsAg titers were lower in HBV carriers with HCV co-infection than in those without HCV co-infection. We also found that prevalence of hepatitis D virus (HDV) co-infection was < 0.5% among HBV carriers in Surabaya.     

Factors associated with use of ultrasonography screening for hepatocellular carcinoma among hepatitis B or C carriers

Objectives: Chronic hepatitis B virus (HBV) and hepatitis C virus (HCV) infections are important risk factors for hepatocellular carcinoma (HCC). Yet, there have been few studies on adherence to screening recommendations for groups at high risk for HCC. We assessed whether demographic factors or medical conditions affected screening participation among HBV/HCV carriers. Methods: The study population consisted of 15 565 men and women who visited the National Cancer Center, Korea between August 2002 and July 2009. A self-administered questionnaire was used to collect information on demographic characteristics, medical history, including chronic HBV and HCV infection, and health check-up history. HBV surface antigen and HCV antibody levels were measured in serum. Results: Among 781 HBV carriers, 596 (76.3%) were aware of their infection and 451 (57.8%) had ever been tested by ultrasonography. Among HCV carriers, 49 of 127 (36.6%) were aware of their infection and 61 (48.0%) had ever been tested by ultrasonography. Among HBV carriers, male sex (OR, 1.68; 95% CI, 1.22–2.31), family history of liver disease (OR, 2.04; 95% CI, 1.43–2.90), medical history of hyperlipidemia (OR, 2.70; 95% CI, 1.36–5.33), and awareness of infection status (OR, 4.30; 95% CI, 2.99–6.17) were associated with being tested. Among HCV carriers, awareness of infection (OR, 3.77; 95% CI, 1.72–8.26) was significantly associated with being tested by ultrasonography. Conclusion: Male sex, family history of liver disease, medical history of hyperlipidemia, and awareness of high risk status were associated with being tested by ultrasonography.     

Interactions between hepatitis B virus infection and exposure to aflatoxins in the development of hepatocellular carcinoma: a molecular epidemiological approach.

Aflatoxins and hepatitis B virus (HBV) are major risk factors for hepatocellular carcinoma (HCC) in high incidence areas for this cancer, namely southeast Asia and parts of Africa. There is evidence from both epidemiological studies and animal models that the two factors can act synergistically to increase the risk of HCC. The cellular and molecular mechanism of the interaction between these two factors is as yet undefined. However, one possible mechanism attested to by studies in HBV transgenic mice is that chronic liver injury alters the expression of specific carcinogen metabolising enzymes thus modulating the binding of aflatoxin to DNA in hepatocytes. The high levels of aflatoxin exposure which occur in many areas of the world where chronic HBV infection is endemic indicate that measures to reduce aflatoxin exposure would contribute to reducing HCC incidence. In preliminary studies, Guinea-Conakry have established baseline data for the implementation of a community-based intervention study to evaluate the effectiveness of improved post-harvest processing and storage of the groundnut crop, a major source of aflatoxins. Aflatoxin-albumin adducts were measured in 423 sera from individuals living in the four natural geographic zones of Guinea. More than 95% of the serum samples were positive for this biomarker and highest exposures were found in Lower Guinea where groundnuts are consumed as a dietary staple. Variations in mean levels between villages within a geographic region did not vary greatly. HBV infection was endemic in all regions with an overall prevalence of 16.7% chronic carriers. Thus in this population both HBV vaccination and reduction in aflatoxin exposure would be beneficial in decreasing morbidity and mortality from liver disease.     

Variability in the precore and core promoter regions of HBV strains in morocco: characterization and impact on liver disease progression

Background

Hepatitis B virus (HBV) is one of the most common human pathogens that cause aggressive hepatitis and advanced liver disease (AdLD), including liver cirrhosis and Hepatocellular Carcinoma. The persistence of active HBV replication and liver damage after the loss of hepatitis B e antigen (HBeAg) has been frequently associated with mutations in the pre-core (pre-C) and core promoter (CP) regions of HBV genome that abolish or reduce HBeAg expression. The purpose of this study was to assess the prevalence of pre-C and CP mutations and their impact on the subsequent course of liver disease in Morocco.

Methods/Principal Findings

A cohort of 186 patients with HBeAg-negative chronic HBV infection was studied (81 inactive carriers, 69 with active chronic hepatitis, 36 with AdLD). Pre-C and CP mutations were analyzed by PCR-direct sequencing method. The pre-C stop codon G1896A mutation was the most frequent (83.9%) and was associated with a lower risk of AdLD development (OR, 0.4; 95% CI, 0.15–1.04; p = 0.04). HBV-DNA levels in patients with G1896A were not significantly different from the other patients carrying wild-type strains (p = 0.84). CP mutations C1653T, T1753V, A1762T/G1764A, and C1766T/T1768A were associated with higher HBV-DNA level and increased liver disease severity. Multiple logistic regression analysis showed that older age (≥40 years), male sex, high viral load (>4.3 log₁₀ IU/mL) and CP mutations C1653T, T1753V, A1762T/G1764A, and C1766T/T1768A were independent risk factors for AdLD development. Combination of these mutations was significantly associated with AdLD (OR, 7.52; 95% CI, 4.8–8; p<0.0001).

Conclusions

This study shows for the first time the association of HBV viral load and CP mutations with the severity of liver disease in Moroccan HBV chronic carriers. The examination of CP mutations alone or in combination could be helpful for prediction of the clinical outcome.     

Innate detection of hepatitis B and C virus and viral inhibition of the response

Viral hepatitis caused by hepatitis B virus (HBV) and hepatitis C virus (HCV) infections poses a significant burden to the public health system. Although HBV and HCV differ in structure and life cycles, they share unique characteristics, such as tropism to infect hepatocytes and association with hepatic and extrahepatic disorders that are of innate immunity nature. In response to HBV and HCV infection, the liver innate immune cells eradicate pathogens by recognizing specific molecules expressed by pathogens via distinct cellular pattern recognition receptors whose triggering activates intracellular signalling pathways inducing cytokines, interferons and anti‐viral response genes that collectively function to clear infections. However, HBV and HCV evolve strategies to inactivate innate signalling factors and as such establish persistent infections without being recognized by the innate immunity. We review recent insights into how HBV and HCV are sensed and how they evade innate immunity to establish chronicity. Understanding the mechanisms of viral hepatitis is mandatory to develop effective and safe therapies for eradication of viral hepatitis.     

Genetic variations of NOD2 and MD2 genes in hepatitis B virus infection

Objectives: Nucleotide oligomerization domain 2 (NOD2) and myeloid differentiation protein 2 (MD-2) have crucial roles in the innate immune system. NOD2 is a member of the NOD-like receptor (NLR) family of pattern recognition receptors (PRRs), while MD-2 is a co-receptor for Toll-like receptor 4 (TLR4), which comprises another group of PRRs. Genetic variations in the NOD2 and MD-2 genes may be susceptibility factors to viral pathogens including hepatitis B virus (HBV). We investigated whether polymorphisms at NOD2 (rs2066845 and rs2066844) or at MD-2 (rs6472812 and rs11466004) were associated with susceptibility to HBV infection and advancement to related liver complications in a Saudi Arabian population. Methods: A total of 786 HBV-infected patients and 600 healthy uninfected controls were analyzed in the present study. HBV-infected patients were categorized into three groups based on the clinical stage of the infection: inactive HBV carriers, active HBV carriers, and patients with liver cirrhosis + hepatocellular carcinoma (HCC). Results: All four SNPs were significantly associated with susceptibility to HBV infection although none of the SNPs tested in NOD2 and MD-2 were significantly associated with persistence of HBV infection. We found that HBV-infected patients that were homozygous CC for rs2066845 in the NOD2 gene were at a significantly increased risk of progression to HBV-related liver complications (Odds Ratio = 7.443 and P = 0.044). Furthermore, haplotype analysis found that the rs2066844-rs2066845 C-G and T-G haplotypes at the NOD2 gene and four rs6472812-rs11466004 haplotypes (G-C, G-T, A-C, and A-T) at the MD-2 gene were significantly associated with HBV infection in the affected cohort compared to those found in our control group. Conclusion: We found that the single nucleotide polymorphisms rs2066844 and rs2066845 at NOD2 and rs6472812 and rs11466004 at MD-2 were associated with susceptibility to HBV infection in a Saudi population.     

Peripheral T-cell subsets in asymptomatic hepatitis B-virus carriers

To ascertain whether the abnormalities of circulating T-cell subsets in patients with hepatitis B virus (HBV)-related chronic liver diseases represent the primary immunological process or are secondary to liver disease process, peripheral T-cell subsets were analyzed by indirect immunofluorescence using monoclonal antibodies against total T cells (OKT3), T helper/inducer cells (OKT4), and T suppressor/cytotoxic cells (OKT8), in 30 asymptomatic HBV carriers without biochemical or histological evidence of liver disease, and the results were compared to 15 HBV-induced chronic active liver diseases. The results revealed that OKT4/OKT8 ratios were significantly reduced in 15 hepatitis B e antigen (HBeAg)-positive asymptomatic carriers as compared with controls, with decreased OKT4-positive cells and increased OKT8-positive cells, while T-cell subsets and ratios were normal in 15 hepatitis B e antibody (anti-HBe)-positive asymptomatic carriers. The changes of circulating T-cell subsets in 15 HBe-Ag-positive asymptomatic carriers showed no significant difference from those of 15 HBeAg-positive patients with chronic active liver diseases. These findings suggest that the deranged T-cell subsets in chronic HBV infection are not secondary to liver cell damage, but might represent the underlying immunological abnormalities which are closely related to HBeAg/anti-HBe status, and that the pathogenetic mechanism of liver cell damage in chronic HBV infection may not be simply related to circulating T-cell subsets.     

Modelling the epidemiology of hepatitis B in New Zealand

Hepatitis B is a vaccine preventable disease caused by the hepatitis B virus (HBV) that can induce potentially fatal liver damage. It has the second highest mortality rate of all vaccine preventable diseases in New Zealand. Vaccination against HBV was introduced in New Zealand in 1988, and the country is now categorised with overall low endemicity but with areas of both high and medium endemic levels. We present an SECIR compartmental mathematical model, with the population divided into age classes, for the transmission of HBV using local data on incidence of infection and vaccination coverage. We estimate the basic reproduction number, R₀, to be 1.53, and show that the vaccination campaign has substantially reduced this below one. However, a large number of carriers remain in the population acting as a source of infection.     

部分肝病患者和健康人血清中HBV基因型分析

确定了内蒙古海拉尔地区乙型肝炎病毒 (HBV)感染者HBV基因型的分布情况。采用基因型特异引物的巢式聚合酶链式反应方法对 38例无症状HBV携带者 ,3例急性肝炎 ,41例慢性肝炎 ,3例肝硬化 ,3例肝癌患者和38例健康人血清中HBV基因型进行分析。结果显示 ,12 6例中有 91例检测到HBVDNA ,其中 ,HBVB型 ,C型分别为 11例 ( 12 .1% )和 6 8例 ( 74.7% ) ,同时检测到B型和C型者有 8例 ( 8.8% ) ,有 4例 ( 4.4% )尚未确定基因型别。可见 ,在海拉尔地区HBV感染同时存在HBVB型和C型 ,而且C型是这一地区流行的主要基因型。     

Evidence for supercoiled hepatitis B virus DNA in chimpanzee liver and serum Dane particles: possible implications in persistent HBV infection

In chimpanzee hepatitis B virus (HBV) carriers, the mechanism of viral persistence has been examined by analyzing viral DNA molecules in liver and serum. Chimpanzee liver DNA contained two extrachromosomal HBV DNA molecules migrating on hybridization blots at 4.0 kb and 2.3 kb. There was no evidence for integration of HBV DNA into the host genome. The extrachromosomal molecules were distinct from Dane particle DNA and were converted to linear 3.25 kb full-length double-stranded HBV DNA on digestion with Eco RI. Nucleases S1 and Bal 31 converted "2.3 kb" HBV DNA to 3.25 kb via an intermediate of "4.0 kb" apparent length. The HBV DNA molecule that migrated at 2.3 kb represents a supercoiled form I of the HBV genome, and the molecule that migrated at 4.0 kb represents a full-length "nicked," relaxed circular form II. Evidence for supercoiled HBV DNA in serum Dane particles was obtained by production of form II molecules upon digestion with nuclease S1 or Bal 31. It is proposed that most Dane particles represent interfering noninfectious virus containing partially double-stranded DNA circles and that particles containing supercoiled HBV DNA may represent infectious hepatitis B virus.     

Hepatitis C virus infection may lead to slower emergence of P. falciparum in blood

Background

Areas endemic for Plasmodium falciparum, hepatitis B virus (HBV) and hepatitis C virus (HCV) overlap in many parts of sub-Saharan Africa. HBV and HCV infections develop in the liver, where takes place the first development stage of P. falciparum before its further spread in blood. The complex mechanisms involved in the development of hepatitis may potentially influence the development of the liver stage of malaria parasites. Understanding the molecular mechanisms of these interactions could provide new pathophysiological insights for treatment strategies in Malaria.

Methodology

We studied a cohort of 319 individuals living in a village where the three infections are prevalent. The patients were initially given a curative antimalarial treatment and were then monitored for the emergence of asexual P. falciparum forms in blood, fortnightly for one year, by microscopy and polymerase chain reaction.

Principal Findings

At inclusion, 65 (20.4%) subjects had detectable malaria parasites in blood, 36 (11.3%) were HBV chronic carriers, and 61 (18.9%) were HCV chronic carriers. During follow-up, asexual P. falciparum forms were detected in the blood of 203 patients. The median time to P. falciparum emergence in blood was respectively 140 and 120 days in HBV- and HBV+ individuals, and 135 and 224 days in HCV- and HCV+ individuals. HCV carriage was associated with delayed emergence of asexual P. falciparum forms in blood relative to patients without HCV infection.

Conclusions

This pilot study represents first tentative evidence of a potential epidemiological interaction between HBV, HCV and P. falciparum infections. Age is an important confounding factor in this setting however multivariate analysis points to an interaction between P. falciparum and HCV at the hepatic level with a slower emergence of P. falciparum in HCV chronic carriers. More in depth analysis are necessary to unravel the basis of hepatic interactions between these two pathogens, which could help in identifying new therapeutic approaches against malaria.     

Prevalence of occult hepatitis B virus infection in kidney transplant recipients

In this cross-sectional study, 207 hepatitis B surface antigen (HBsAg)-negative kidney transplant recipients were evaluated based on demographic and epidemiological data and on the levels of serological markers of hepatitis B virus (HBV) and hepatitis C virus infection and liver enzymes. Patients with HBV or human immunodeficiency virus infection were excluded. Sera were analysed for the presence of HBV-DNA. HBV-DNA was detected in two patients (1%), indicating occult hepatitis B (OHB) infection (the HBV-DNA loads were 3.1 and 3.5 IU/mL in these patients). The results of the liver function tests were normal and no serological markers indicative of HBV infection were detected. The prevalence of OHB infection was low among kidney transplant recipients, most likely due to the low HBsAg endemicity in the general population of the study area.     

Chronic HBV-related liver disease

Thirty years after its discovery, the hepatitis B virus (HBV) still remains a major global public health problem. Worldwide, two billion subjects have been infected, 300 million have a chronic infection and more than 600,000 die annually of HBV-related liver disease or hepatocellular carcinoma; new infections occur because of the presence of a large reservoir of chronic carriers of the virus. The knowledge of the HBV organization and replication cycle and the availability of sensitive HBV-DNA assays have led to remarkable progress in our understanding of the natural history of chronic hepatitis B infections. Crucial to the prevention of new infections, to the management and the monitoring of HBV carriers and to the choice of best treatment strategy, is the understanding of the natural dynamism of HBV infection and of the virus-host interactions that induce liver damage.     

Prevalence and follow-up of occult HCV infection in an italian population free of clinically detectable infectious liver disease

Background

Occult hepatitis C virus infection (OCI) is a recently described phenomenon characterized by undetectable levels of HCV-RNA in serum/plasma by current laboratory assays, with identifiable levels in peripheral blood mononuclear cells (PBMCs) and/or liver tissue by molecular tests with enhanced sensitivity. Previous results from our group showed an OCI prevalence of 3.3% in a population unselected for hepatic disease. The present study aimed to evaluate OCI prevalence in a larger cohort of infectious liver disease-free (ILDF) subjects. Clinical follow-up of OCI subjects was performed to investigate the natural history of the infection.

Methods and Findings

439 subjects referred to a Turin Blood Bank for phlebotomy therapy were recruited. They included 314 ILDF subjects, 40 HCV-positive subjects and 85 HBV-positive subjects, of whom 7 were active HBV carriers. Six subjects (4/314 ILDF subjects [1.27%] and 2/7 active HBV carriers [28%]) were positive for HCV-RNA in PBMCs, but negative for serological and virological markers of HCV, indicating OCI. HCV genotypes were determined in the PBMCs of 3/6 OCI subjects two had type 1b; the other had type 2a/2c. OCI subjects were followed up for at least 2 years. After 12 months only one OCI persisted, showing a low HCV viral load (3.73×10¹ UI/ml). By the end of follow-up all OCI subjects were negative for HCV. No seroconversion, alteration of liver enzyme levels, or reduction of liver synthesis occurred during follow-up.

Conclusions

This study demonstrated the existence of OCI in ILDF subjects, and suggested a high OCI prevalence among active HBV carriers. Follow-up suggested that OCI could be transient, with a trend toward the decrease of HCV viral load to levels undetectable by conventional methods after 12–18 months. Confirmation studies with a longer follow-up period are needed for identification of the OCI clearance or recurrence rates, and to characterize the viruses involved.     

Prevalence of hepatitis B and C virus infection among leprosy patients in a leprosy-endemic region of central Brazil

Leprosy and hepatitis B virus (HBV) are highly endemic in some regions of the state of Mato Grosso, in central Brazil. The association of leprosy with HBV and hepatitis C virus (HCV) was assessed using a seroprevalence study and 191 leprosy outpatients were included. Demographic data and the clinical classification of leprosy were recorded. Evidence of previous HBV infection was present in 53 patients (27.7%, 95% confidence interval: 21.9-34.5) and two (1%) were HBsAg positive. Five (2.6%) had antibodies to HCV. The prevalence of previous exposure to HBV was higher than expected for an adult population in central Brazil. In contrast, the prevalence of anti-HCV antibodies was not much higher regarding the age range of participants. HBV markers were associated with a higher number of sex partners and the use of injections without proper sterilisation of the syringes. The number of HBV carriers was small, suggesting that there was no increased likelihood of chronification among these patients.     

Low frequency of precore mutants in anti-hepatitis B e antigen positive subjects with chronic hepatitis B virus infection in Chennai, Southern India

The natural course of chronic hepatitis B (CH-B) virus infection is reportedly variable, and the long-term outcomes in hepatitis B e antigen (HBeAg)-negative chronic hepatitis B infection are distinct from HBeAg-positive chronic hepatitis. However, the molecular virological factors that contribute to the progression of liver disease in the south Indian setting remain largely unclear. We prospectively studied 679 consecutive patients for HBsAg, HBeAg, anti-HBeAg, and HBV DNA by qualitative PCR. Randomly selected samples were subjected to bidirectional sequencing to reveal core/precore variants. Of the total 679 chronic HBV cases investigated, 23% (154/679) were replicative HBV carriers. Furthermore, amongst the 560 HBV DNA samples analyzed, 26% (146/560) were viremic. Among the 154 HBeAg positive cases, HBV DNA was positive in 118 cases (77%), significantly (p<0.001) higher than the anti-HBe positive (7%) (28/406) cases. Significant increase in liver disease (p<0.01) with ALT enzyme elevation (p<0.001) was observed in both HBe and anti-HBe viremic cases. Interestingly, low frequencies of mutations were seen in the precore region of the HBV strains studied. HBV precore and core promoter variants were less often detected in subjects with "e" negative chronic HBV infection and, therefore, may not have a prognostic role in determining liver disease sequelae in this part of tropical India.     

Integration of HBV-DNA into liver and hepatocellular carcinoma cells during persistent HBV infection

The hepatitis B virus carrier state (persistent HBV infection) is characterized by the presence of viral surface antigen (HBsAg) and virion particles (Dane particles) in the blood. From 1% to 10% of carriers develop chronic liver disease and/or hepatocellular carcinoma. Recent studies have demonstrated integrated HBV-DNA in hepatocellular carcinomas and in several human hepatoma cell lines. In hepatoma patients, integrated HBV-DNA has been found in all HBsAg carriers. Nontumorous liver also revealed integrated HBV-DNA with the same or a different hybridization pattern from that observed in the tumor. To explore when integration occurs, carriers of short-term (less than 2 years) or long-term (greater than 8-10 years) were evaluated. DNA extracts from percutaneous (needle) liver biopsies showed free viral DNA with no specific integration bands in short-term carriers. In long-term carriers, HBV-DNA was integrated into the host genome with either a diffuse or a unique hybridization pattern. HBV-DNA integration correlated with the duration of the carrier state and absence of virions in the serum but did not correlate with histologic evidence of chronic hepatitis. These studies suggest that integration of HBV-DNA occurs during persistent HBV infection irrespective of liver disease and precedes development of hepatocellular carcinoma.     

Characterization of viral genomes in the liver and serum of chimpanzee long-term hepatitis B virus carriers: a possible role for supercoiled HBV-DNA in persistent HBV infection

In chimpanzee hepatitis B virus (HBV) carriers, the molecular mechanism for viral persistence has been examined by analyzing the properties of viral DNA molecules in liver and serum. Two extrachromosomal HBV-DNA molecules migrating on Southern blots at 4.0 kb and 2.3 kb were observed in chimpanzee liver DNA. There was no evidence for integration of HBV sequences into the host genome. The HBV-DNA molecule which migrated at 4.0 kb position represents a full-length "nicked," relaxed circular form, and the DNA molecules migrating at 2.3 kb position represents a supercoiled form of the HBV genome. Evidence for supercoiled HBV-DNA in serum was obtained by production of the relaxed circular intermediate upon digestion of Dane particle DNA with specific nucleases S1 and Bal 31. A possible role of these two extrachromosomal HBV-DNA molecules in the biology of hepatitis B virus infection and the mechanism for viral persistence are discussed.