Hepatitis B defective virus with rearrangements in the preS gene during chronic HBV infection

Pathogenicity and virulence of Hepatitis B virus

Hepatitis B virus (HBV) is a hepatotropic virus and an important human pathogen. There are an estimated 296 million people in the world that are chronically infected by this virus, and many of them will develop severe liver diseases including hepatitis, cirrhosis and hepatocellular carcinoma (HCC). HBV is a small DNA virus that replicates via the reverse transcription pathway. In this review, we summarize the molecular pathways that govern the replication of HBV and its interactions with host cells. We also discuss viral and non-viral factors that are associated with HBV-induced carcinogenesis and pathogenesis, as well as the role of host immune responses in HBV persistence and liver pathogenesis.

Hepatitis B virus preS2Δ38-55 variants: A newly identified risk factor for hepatocellular carcinoma

BACKGROUND & AIMS

Although HBV is a major cause of death in Africa, its genetic variability has been poorly documented. This study aimed to address whether HBV genotype and surface gene variants are associated with HBV-related liver disease in The Gambia.

METHODS

We conducted a case-control study nested in the Prevention of Liver Fibrosis and Cancer in Africa programme. Consecutive treatment-naive patients with chronic HBV infection and detectable viral load were recruited: 211 controls with no significant liver disease and 91 cases (56 cirrhosis and 35 HCC cases). HBV genotypes and surface gene variants were determined by Sanger sequencing or next-generation sequencing (NGS) in serum DNA. Aflatoxin B1 (AFB1)-specific codon 249 TP53 mutation was determined by NGS in circulating cell-free plasma DNA.

RESULTS

In phylogenetic analysis, 85% of individuals carried HBV genotype E, 14% genotype A, and 1% A/E recombinant viruses. Surface gene variants were more frequently observed in cases (43% and 57% in cirrhosis and HCC cases, respectively) than controls (25%; p <0.001), with preS2 deletions between nucleotides 38-55 (preS2Δ38-55) being the main genetic variant detected. In multivariable analysis, HBeAg seropositivity, low HBsAg levels, and HDV seropositivity were significantly associated with cirrhosis and HCC, whilst older age, higher viral load, genotype A, preS2Δ38-55, and AFB1 exposure were only associated with HCC. There was a multiplicative joint effect of preS2Δ38-55 variants with HBeAg seropositivity (odds ratio [OR] 43.1 [10.4-177.7]), high viral load >2,000 IU/ml (OR 22.7 [8.0-64.9]), HBsAg levels <10,000 IU/ml (OR 19.0 [5.5-65.3]), and AFB1 exposure (OR 29.3 [3.7-230.4]) on HCC risk.

CONCLUSIONS

This study identified a hotspot for HBV preS2 deletions as a strong independent factor for HCC in The Gambia, with HBV genotypes and AFB1 exposure contributing to the high liver cancer risk.

LAY SUMMARY

Although HBV-related liver disease is highly prevalent in sub-Saharan Africa, the associated virological characteristics are poorly studied. Using clinical data from African patients chronically infected with HBV, an assessment of the virological variability (genotypes and mutations) and exposure to AFB1, a toxin often contaminating food, was carried out. Our results show that HBV genotypes, the presence of a highly prevalent mutant form of HBV, and AFB1 exposure contribute to the high liver cancer risk in this population.

Reactivation of a Vaccine Escape Hepatitis B Virus Mutant in a Cambodian Patient During Anti-Hepatitis C Virus Therapy

A 76-year-old Cambodian man co-infected with hepatitis B virus (HBV) and hepatitis C virus (HCV) 6c-1 presented for care. HBV DNA was intermittently detectable despite anti-HBs levels being above the protective threshold. During treatment for HCV, HBV DNA levels increased. Sequencing revealed multiple mutations including vaccine escape mutation and mutations predicted to enhance fitness. This case represents exacerbation of an HBV vaccine escape mutant during a direct-acting antiviral therapy.

How viral genetic variants and genotypes influence disease and treatment outcome of chronic hepatitis B. Time for an individualised approach?

Chronic hepatitis B virus (HBV) infection remains a global problem. Several HBV genotypes exist with different biology and geographical prevalence. Whilst the future aim of HBV treatment remains viral eradication, current treatment strategies aim to suppress the virus and prevent the progression of liver disease. Current strategies also involve identification of patients for treatment, namely those at risk of progressive liver disease. Identification of HBV genotype, HBV mutants and other predictive factors allow for tailoured treatments, and risk-surveillance pathways, such as hepatocellular cancer screening. In the future, these factors may enable stratification not only of treatment decisions, but also of patients at risk of higher relapse rates when current therapies are discontinued. Newer technologies, such as next-generation sequencing, to assess drug-resistant or immune escape variants and quasi-species heterogeneity in patients, may allow for more information-based treatment decisions between the clinician and the patient. This article serves to discuss how HBV genotypes and genetic variants impact not only upon the disease course and outcomes, but also current treatment strategies. Adopting a personalised genotypic approach may play a role in future strategies to combat the disease. Herein, we discuss new technologies that may allow more informed decision-making for response guided therapy in the battle against HBV.

Defective viral genomes arising in vivo provide critical danger signals for the triggering of lung antiviral immunity

The innate immune response to viruses is initiated when specialized cellular sensors recognize viral danger signals. Here we show that truncated forms of viral genomes that accumulate in infected cells potently trigger the sustained activation of the transcription factors IRF3 and NF-κB and the production type I IFNs through a mechanism independent of IFN signaling. We demonstrate that these defective viral genomes (DVGs) are generated naturally during respiratory infections in vivo even in mice lacking the type I IFN receptor, and their appearance coincides with the production of cytokines during infections with Sendai virus (SeV) or influenza virus. Remarkably, the hallmark antiviral cytokine IFNβ is only expressed in lung epithelial cells containing DVGs, while cells within the lung that contain standard viral genomes alone do not express this cytokine. Together, our data indicate that DVGs generated during viral replication are a primary source of danger signals for the initiation of the host immune response to infection.

African, Amerindian and European hepatitis B virus strains circulate on the Caribbean Island of Martinique

Ten Hepatitis B virus (HBV) genotypes, as well as numerous subgenotypes, have been described in well-characterized ethnogeographical populations. Martinique has been at a crossroads between Africa, Europe, India and the Americas because of the slave trade (17th-19th centuries), followed by an important immigration of Indian and West African workers. In this work, we aimed to study the molecular epidemiology of HBV infection in Martinique according to this unique settlement pattern. To that end, blood samples from 86 consecutive HBV-infected patients from the main hospitals of the island, were retrospectively analysed. Direct sequencing of the pre-S1 or pre-C-C region or complete genome sequencing, followed by phylogenetic analyses were performed. HBV genotypes were: HBV/A1 (68.6 %), HBV/A2 (10.5 %), HBV/D, mainly HBV/D3 and HBV/D4 (8.1 %), HBV/F (3.5 %), and also HBV/E (2.3 %), two strains isolated from two West-African patients. Moreover, 74 % of the HBeAg-negative strains harboured classical pre-C-C mutations, and most HBV/A1 strains also containing specific mutations. Finally, various patterns of deletion mutants in pre-S and pre-C-C regions were found. In conclusion, our findings point to historical and migration-related issues in HBV-genotype distribution suggesting that HBV/A1, but not HBV/E, was imported from Africa during the slave trade, and further supporting the hypothesis that HBV/E has emerged recently in West Africa (<150 years). Potential origins of 'European' HBV/A2 and HBV/D3, 'Amerindian' HBV/F, and HBV/D4 strains are also discussed. Such HBV genetic diversity, beyond its epidemiological interest, may have a clinical impact on the natural history of HBV infection in Martinique.

Novel recombinant hepatitis B virus vectors efficiently deliver protein and RNA encoding genes into primary hepatocytes

Hepatitis B virus (HBV) has extremely restricted host and hepatocyte tropism. HBV-based vectors could form the basis of novel therapies for chronic hepatitis B and other liver diseases and would also be invaluable for the study of HBV infection. Previous attempts at developing HBV-based vectors encountered low yields of recombinant viruses and/or lack of sufficient infectivity/cargo gene expression in primary hepatocytes, which hampered follow-up applications. In this work, we constructed a novel vector based on a naturally occurring, highly replicative HBV mutant with a 207-bp deletion in the preS1/polymerase spacer region. By applying a novel insertion strategy that preserves the continuity of the polymerase open reading frame (ORF), recombinant HBV (rHBV) carrying protein or small interfering RNA (siRNA) genes were obtained that replicated and were packaged efficiently in cultured hepatocytes. We demonstrated that rHBV expressing a fluorescent reporter (DsRed) is highly infective in primary tree shrew hepatocytes, and rHBV expressing HBV-targeting siRNA successfully inhibited antigen expression from coinfected wild-type HBV. This novel HBV vector will be a powerful tool for hepatocyte-targeting gene delivery, as well as the study of HBV infection.

Risk stratification for hepatitis B virus related hepatocellular carcinoma

Hepatitis B virus (HBV) infection is the major cause of chronic hepatitis, cirrhosis, and hepatocellular carcinoma (HCC) worldwide, especially in the Asia-Pacific region. Several hepatitis B viral factors predictive of clinical outcomes in HBV carriers have been identified. The Risk Evaluation of Viral Load Elevation and Associated Liver Disease/Cancer-HBV (REVEAL-HBV) study from Taiwan illustrated the strong association between HBV-DNA level at study entry and risk of HCC over time. In this community-based cohort study, male gender, older age, high serum alanine aminotransferase level, positive hepatitis B e antigen, higher HBV-DNA level, HBV genotype C infection, and core promoter mutation are independently associated with a higher risk of HCC. Another large hospital-based Elucidation of Risk Factors for Disease Control or Advancement in Taiwanese Hepatitis B Carriers cohort of Taiwanese patients further validated the findings of REVEAL-HBV. The risk of HCC started to increase when HBV-DNA level was higher than 2000 IU/mL. Both HBV-DNA and HBsAg levels were shown to be associated with HCC development. While HBV-DNA level had better predictive accuracy than HBsAg level, when investigating the overall cohort in patients with HBV-DNA level < 2000 IU/mL, HBsAg level ≥ 1000 IU/mL was identified as a new independent risk factor for HCC. With the results from REVEAL-HBV, a risk calculation for predicting HCC in non-cirrhotic patients has been developed and validated by independent cohorts (Risk Estimation for Hepatocellular Carcinoma in Chronic Hepatitis B).Taken together, ample evidence indicates that HBsAg level can complement HBV-DNA level in predicting HCC development, especially in HBV carriers with low viral load. In conclusion, HBV treatment guidelines should include the risk stratification of HCC to individualize the management of HBV carriers with different levels of HCC risk.

HBV-related hepatocellular carcinoma: the role of integration, viral proteins and miRNA

The development of hepatocellular carcinoma during chronic hepatitis B infection is a multifactorial process thought to be a consequence of several direct and indirect mechanisms. In this review we discuss how viral proteins and cycles of ongoing liver damage and regeneration, coupled with HBV DNA integration and aberrant miRNA expression may enhance the risk for the development of hepatocellular carcinoma.

Recent advances in the research of hepatitis B virus-related hepatocellular carcinoma: epidemiologic and molecular biological aspects

Hepatocellular carcinoma (HCC) is one of the commonest cancers worldwide, and more than half of HCC patients are attributable to persistent hepatitis B virus (HBV) infections. The best and cheapest way to prevent HBV-related HCC is the implementation of universal hepatitis B vaccination program, by which the incidence rates of childhood HCC have been reduced in several countries, including Taiwan. However, there are still hundreds of millions of HBV carriers in the world that remain a global health challenge. In the past decade, several hepatitis B viral factors such as serum HBV DNA level, genotype, and naturally occurring mutants have already been identified to influence liver disease progression and HCC development in HBV carriers. Several easy-to-use scoring systems based on clinical and viral characteristics are developed to predict HCC risk in HBV carriers and may facilitate the communication between practicing physicians and patients in clinical practice. In addition, the role of nonviral factors in HBV-related HCC has also been increasingly recognized. On the basis of these emerging data, it is recommended that HBV carriers should be screened and monitored to identify those who have a higher risk of liver disease progression and require antiviral treatments. Regarding the molecular carcinogenesis of HCC development, despite some progress in the research of cell biology of HCC in the past decade, aberrant pathways involved in maintaining HCC phenotypes have not been completely elucidated yet. In the future, through comprehensive and integrated approaches to analyze the genomes of human HCC, novel target genes or pathways critically involved in hepatocarcinogenesis may hopefully be identified.

Genomic variability associated with the presence of occult hepatitis B virus in HIV co-infected individuals

Occult hepatitis B virus (O-HBV) infection is characterized by the presence of HBV DNA without detectable hepatitis B surface antigen (HBV DNA+/HBsAg-) in the serum. Although O-HBV is more prevalent during HBV/HIV co-infection, analysis of HBV mutations in co-infected patients is limited. In this preliminary study, HBV PreSurface (PreS) and surface (S) regions were amplified from 33 HIV-positive patient serum samples - 27 chronic HBV (C-HBV) and six O-HBV infections. HBV genotype was determined by phylogenetic analysis, while quasispecies diversity was quantified for the PreS, S and overlapping polymerase regions. C-HBV infections harboured genotypes A, D and G, compared to A, E, G and one mixed A/G infection for O-HBV. Interestingly, nonsynonymous-synonymous mutation values indicated positive immune selection in three regions for O-HBV vs one for C-HBV. Sequence analysis further identified new O-HBV mutations, in addition to several previously reported mutations within the HBsAg antigenic determinant. Several of these O-HBV mutations likely contribute to the lack of detectable HBsAg in O-HBV infection by interfering with detection in serologic assays, altering antigen secretion and/or decreasing replicative fitness.

The ability of Hepatitis B surface antigen DNA vaccine to elicit cell-mediated immune responses, but not antibody responses, was affected by the deglysosylation of S antigen

Hepatitis B Virus (HBV) infection remains a major worldwide infectious disease with serious long-term morbidity and mortality. The limited selections of drug treatment are not able to control the progress of disease in people with active and persistent HBV infection. Immunotherapy to control the degree of viral infection is one possible alternative solution to this challenge. HBV DNA vaccines, with their strong ability to induce cell-mediated immune responses, offer an attractive option. HBV surface protein is important in viral immunity. Re-establishing anti-S immunity in chronic HBV infected patients will bring significant benefit to the patients. Previous studies have shown that HBV S DNA vaccines are immunogenic in a number of animal studies. In the current study, we further investigated the effect of glycosylation to the expression and immunogenicity of S DNA vaccines. Our results demonstrate that deglycosylation at the two potential N-linked glycosylation sites in S protein resulted in a significant decrease of S-specific cell-mediated immune responses, but did not affect anti-S antibody responses. This finding provides important direction to the development of S DNA vaccines to elicit the optimal and balanced antibody and cell-mediated immune responses to treat people with HBV chronic infections.

Role of viral factors in the natural course and therapy of chronic hepatitis B

Hepatitis B virus (HBV) infection is a global health problem that causes a wide spectrum of liver disease, including acute or fulminant hepatitis, inactive carrier state, chronic hepatitis, cirrhosis, and hepatocellular carcinoma (HCC). The pathogenesis of hepatocyte damage associated with HBV is mainly through immune-mediated mechanisms. On the basis of the virus and host interactions, the natural history of HBV carriers who are infected in early life can be divided into four dynamic phases. The frequency, extent, and severity of hepatitis flares or acute exacerbation in the second immune clearance and/or fourth reactivation phase predict liver disease progression in HBV carriers. In the past decade, hepatitis B viral factors including serum HBV DNA level, genotype, and naturally occurring mutants predictive of clinical outcomes have been identified. The higher the serum HBV DNA level after the immune clearance phase, the higher the incidence of adverse outcomes over time. In addition, high viral load, genotype C, basal core promoter mutation, and pre-S deletion correlate with increased risk of cirrhosis and HCC development. As to the treatment of chronic hepatitis B, patients with high HBV DNA level and genotype C or D infection are shown to have a worse response to interferon therapy. In conclusion, serum HBV DNA level, genotype, and naturally occurring mutants are identified to influence liver disease progression and therapy of chronic hepatitis B. More investigations are needed to clarify the molecular mechanisms of the viral factors involved in the pathogenesis of each stage of liver disease and the response to antiviral treatments.

Mutations in preS genes of genotype C hepatitis B virus in patients with chronic hepatitis B and hepatocellular carcinoma

BACKGROUND

Hepatitis B virus (HBV) preS mutations are frequently isolated from patients with severe forms of liver disease. Meanwhile, genotype C has been shown to cause more serious liver disease than genotype B. This study assesses the frequency of preS mutation in Chinese patients with genotype C chronic HBV infection and its relation to liver damage.

METHODS

Seventy-nine persistently infected patients (25 asymptomatic carriers, 28 with chronic hepatitis, and 26 with hepatocellular carcinoma) with genotype C HBV were analyzed. Levels of HBV DNA, hepatitis B e antigen (HBeAg), alanine aminotransferase, and aspartate transaminase and mutations in the preS region were determined.

RESULTS

The correlations of preS deletion with disease progression were distinct: preS deletion mutations were more commonly found in the hepatocellular carcinoma (HCC) group than in the chronic hepatitis B (CHB) or asymptomatic carrier (ASC) groups, with the frequencies of 38.46% (10/26) in the HCC, 7.14% (2/28) in the CHB, and 4.00% (1/25) in the ASC (P = 0.001) groups. The HBeAg-positive rate and HBV DNA levels were comparable between patients with the preS mutation and those without.

CONCLUSIONS

PreS deletion mutations of genotype C HBV might play a role in HBV-related hepatocarcinogenesis.

Association of pre-S deletion mutant of hepatitis B virus with risk of hepatocellular carcinoma

BACKGROUND

Pre-S deletion mutant of hepatitis B virus (HBV) affects the expression of middle and small surface proteins, resulting in intracellular accumulation of large surface protein. The correlation between pre-S deletion mutant and risk of hepatocellular carcinoma (HCC) in hepatitis B virus carriers remains unclear.

METHODS

Using molecular assays, pre-S deletion mutant of HBV were determined in 266 patients with chronic HBV genotype B or C infection. They included 202 asymptomatic carriers and 64 HCC patients.

RESULTS

The overall prevalence of pre-S deletion mutant was 16.5%. Hepatocellular carcinoma (odds ratio [OR], 3.23; 95% confidence interval [CI], 1.23-8.48, P = 0.02) and genotype C (OR, 3.19; 95%CI, 1.54-6.62, P = 0.002) were independently associated with the presence of pre-S deletion mutant. The prevalence of pre-S deletion mutant was comparable between HCC patients with genotype B and C infection. Nevertheless, in asymptomatic carriers, patients with genotype C infection were significantly associated with the presence of pre-S deletion mutant compared to those with genotype B infection (20.8% vs 7.2%, P = 0.007). Compared with age- and genotype B-matched asymptomatic carriers, young HCC patients (<50 years of age) had a significantly higher frequency of pre-S deletion (3.4% vs 20%, P = 0.04).

CONCLUSIONS

Pre-S deletion mutant is more frequent in HBV carriers with genotype C infection, and those with pre-S deletion mutant may be associated with the development of HCC, irrespective of HBV genotype.

Study on hepatitis B virus pre-S/S gene mutations of renal tissues in children with hepatitis B virus-associated membranous nephropathy

This study aims to clarify the prevalence and significance of the emergence of hepatitis B virus (HBV) pre-S/S mutations in children with hepatitis B virus-associated membranous nephropathy (HBVMN). Direct sequencing of polymerase chain reaction products of renal tissue samples that were obtained via percutaneous renal biopsy from seven children revealed the presence of HBV DNA. Seven adr subtypes were analyzed. Deletions in the HBV pre-S region were observed once per seven patients. The deletions were noted in both the pre-S1 (27 bp) and pre-S2 (60 bp) regions. Various point mutations in the HBV pre-S region were detected in all seven patients and proved to be more frequent in the pre-S1 region than in the S2 region. Point mutations in the HBV S region were detected in six patients. Among these mutations, the mutation in the "a" determinant region was noted in five patients. No deletion, however, was observed in the HBV S region. These observations suggested that deletions and point mutations in the HBV pre-S1 and pre-S2 regions and point mutations in the HBV S region, especially the "a" determinant region, are common frequent findings. These results also suggested that HBV pre-S/S region mutations may be involved in the pathogenesis in children with HBVMN.

Hepatitis B and C Virus Variants in Long-Term Immunosuppressed Renal Transplant Patients in Latvia

The incidence of genome variants of hepatitis B and hepatitis C viruses among 38 long-term (2-15 years) immunosuppressed patients after renal transplantation and 10 patients undergoing dialysis was investigated. Twelve patients had only HBV infection, 9 had only HCV infection and 14 were co-infected. Regions corresponding to the HBV X/EnII/BCP, preC/C, preS/S and to the HCV core were sequenced for molecular characterization of the HBV and HCV genomes. Fifty-seven percent of HBV DNA isolates belonged to genotype D and 42% to genotype A, whereas 77% of HCV RNA isolates belonged to genotype 1b and only 17% to genotype 3a. One sample (6%) was of genotype 2c. Detailed analysis of the above-mentioned HBV genome regions revealed the presence of nucleotide point mutations, which, in some cases, resulted in amino acid substitutions. The clinical significance of such mutations is discussed.

Genotyping of hepatitis B virus in Malaysia based on the nucleotide sequence of preS and S genes

Hepatitis B virus (HBV) has been classified into eight genotypes, designated A-H. These genotypes are known to have distinct geographic distributions. The clinical importance of genotype-related differences in the pathogenicity of HBV has been revealed recently. In Malaysia, the current distribution of HBV remains unclear. The aim of this study was to determine the genotypes and subtypes of HBV by using PCR, followed by DNA sequencing, as well as to analyse the mutations in the immunodominant region of preS and S proteins. The S gene sequence was determined from HBV DNA of four apparently healthy blood donors' sera and three sera from asymptomatic chronic hepatitis B carriers. Of this batch of sera, the preS gene sequence was obtained from HBV DNA from three out of the four blood donors and two out of the three chronic carriers. Due to insufficient sera, we had to resort to using sera from another blood donor to make up for the sixth DNA sequence of the preS gene. Based on the comparative analysis of the preS sequences with the reported sequences in the GenBank database, HBV DNA from two normal carriers was classified as genotype C. Genotype B was assigned to HBV from one blood donor and two hepatitis B chronic carriers, whereas HBV of one chronic carrier was of genotype D. Based on the S gene sequences, HBV from three blood donors was of genotype C, that of one blood donor and one chronic carrier was of genotype B, and the remaining, of genotype D. In the five cases where both preS and S gene sequences were determined, the genotypes assigned based on either the preS or S gene sequences were in concordance. The nature of the deduced amino acid (aa) sequences at positions 125, 127, 134, 143, 159, 161 and 168 of the S gene enabled the classification of these sequences into subtypes, namely, adrq+, adw2 and ayw2. The clustering of our DNA sequences into genotype groups corresponded to their respective subtype, that is, adw2 in genotype B, adrq in genotype C and ayw in genotype D. Analysis of the point mutations revealed that five of the sequences contained aa substitutions at immunodominant epitopes involved in B or/and T cell recognition. In conclusion, despite the low numbers of samples studied, due to budget constraints, these data are still worthwhile reporting, as it is important for the control of HBV infections. In addition, the genotype and mutational data obtained in this study may be useful for designing new treatment regimes for HBV patients.

Hepatitis B virus: significance of genotypes

Hepatitis B Virus (HBV) genotypes have come of age. The concept that HBV genotypes may influence the course of disease and relevant biological differences has now been recognised. However, there are still major gaps in our knowledge. Most clinical data come from Asia and describe findings in patients infected with genotypes B and C. Large scale studies with genotypes A and D as found in Europe or A, D and E from Africa are urgently needed to broaden our understanding. Experimental data which explain in vivo findings in terms of differences in molecular biology in vitro are still in the beginning. The succeeding years will see many interesting studies which will aid our understanding of how variants and genotypes of HBV influence the spectrum of disease in people infected with HBV.

Efficacy of combined lamivudine and adefovir dipivoxil treatment for severe HBV graft reinfection after living donor liver transplantation

Resistance to lamivudine and hyperimmune globulin (HBIG) may cause severe graft reinfection with progression to fulminant hepatic failure in liver transplant recipients. In this report, we describe the clinical course of a patient with perinatally acquired chronic hepatitis B virus (HBV) infection and hepatocellular carcinoma who developed severe fibrosing cholestatic hepatitis after living donor liver transplantation because of the emergence of lamivudine and HBIG-resistant chronic hepatitis B. Immunohistochemistry demonstrated that more than 30% of hepatocytes stained positively for hepatitis B core antigen. Hepatitis B virus sequence analysis revealed several mutations in the polymerase gene (L528M, M552I, M552V) as well as in the surface gene region encoding the immunogenic major hydrophilic loop of the small surface protein (G130N, M133T, D144G). The amino acid exchange at codon 144 has already been described to escape neutralization by HBIG. Combined treatment with lamivudine and adefovir dipivoxil (ADV) was associated with a dramatic biochemical, virological and clinical response with resolution of jaundice, ascites, peripheral edema and pleural effusions. Serum bilirubin normalized, HBV DNA levels significantly decreased and liver biopsy was remarkable for the absence of viral protein. These results indicate that ADV may provide a sustained rescue treatment for aggressive courses of HBV graft reinfection in liver transplant recipients.

Uncommon mutation pattern of a hepatitis B virus isolate from genotype F infecting a patient with AIDS

OBJECTIVE

To study the genomic variations of a hepatitis B virus (HBV) isolate in a patient coinfected with human immunodeficiency virus type 1 (HIV-1) who developed severe hepatitis and died of AIDS.

METHODS

Two blood samples were collected, the first one during the asymptomatic phase of HIV-1 infection, and the other, 3 years later, few months before the death of the patient. Both samples were HBsAg and anti-HBe positive. Pre-S/S and precore-core genome regions were PCR amplified and analyzed.

RESULTS

The HBV isolate belonged to genotype F, cluster IV. A number of unique amino acid substitutions were found in the surface antigen gene and the overlapping polymerase coding region of HBV genomes derived from both samples. However, these substitutions reflected natural variations rather than mutations of clinical significance. The precore stop codon mutation A(1896) was present in both genomes. Furthermore, the HBV genome derived from the second, but not first sample, showed two out-of-frame core interval deletions, one and 103 nucleotides in length, respectively.

CONCLUSIONS

This is the first report of an HBV isolate from genotype F with core internal deletions. Our results suggest an association between specific core mutations and the severe hepatitis developed by the patient.

Influence of hepatitis B virus genotypes on the development of preS deletions and advanced liver disease

Hepatitis B virus (HBV) mutants with deletions in the preS region have not been evaluated for association with viral genotypes. In a case-control study, HBV DNA samples collected from 80 each of carriers infected with HBV genotype B or C were examined for preS deletions. PreS deletion mutants were found in a total of 37 of 160 (23%) HBV carriers. Carriers with preS deletion mutants were older (56.0 +/- 12.7 vs 49.3 +/- 16.9 years, P < 0.05), were infected more frequently with HBV genotype C (84% vs 40%, P < 0.05), and had more advanced disease, such as liver cirrhosis and hepatocellular carcinoma (54% vs 31%; P < 0.05), than did those without such mutants. In a multivariate analysis, genotype C (odds ratio [OR] = 9.3, P < 0.001) and advanced liver disease (OR = 3.1, P < 0.01) were the most significant variables in association with preS deletions. A direct repeat sequence (TCAGG) was found at the start or at the end of preS1 deletions in 6 of the 20 (30%) cases examined, and preS2 deletions in these cases were clustered over the 5'-terminal half of this region. These results indicate that the development of preS deletion mutants depends on HBV genotypes and that it may be associated with progressive liver disease.

Hepatitis B virus-induced defect of monocyte-derived dendritic cells leads to impaired T helper type 1 response in vitro: mechanisms for viral immune escape

Dendritic cells (DC) are the most potent antigen-presenting cells and play a central role in the induction of antiviral immune responses. Recently, we have shown that monocyte-derived DC (MoDC) from patients with chronic hepatitis B virus (HBV) infection are functionally impaired. In our present study MoDC from healthy subjects were propagated in vitro and inoculated with HBV particles to investigate the precise mechanisms that underly MoDC dysfunction. T-cell proliferation assays revealed an impaired allostimulatory capacity of HBV-inoculated MoDC (HBV-MoDC) as well as a lower potential of stimulating autologous T cells against a recall antigen in comparison to control-MoDC. Interleukin-2, tumour necrosis factor-alpha and interferon-gamma production by T cells in proliferation assays with HBV-MoDC was significantly lower than with control-MoDC and correlated with lower IL-12 production in HBV-MoDC cultures. The presence of the nucleoside analogue lamivudine (3TC), an inhibitor of HBV replication, restored impaired allostimulatory function of HBV-MoDC and up-regulated major histocompatibility complex class II expression. These results show that HBV infection compromises the antigen-presenting function of MoDC with concomitant impairment of T helper cell type 1 responses. This may play an important role for viral immune escape leading to chronic HBV infection. However, 3TC treatment can overcome HBV-MoDC-related T-cell hyporeactivity and this underscores its important role in enhanced immune responses to HBV.

In vitro infection of human peripheral blood mononuclear cells by a defective hepatitis B virus with a deletion in the PreS1 region of the viral genome

Previously, we identified a defective hepatitis B virus (HBV) which contains a 183 nucleotide deletion in the PreS1 region of the viral genome affecting the S gene promoter in sera from hepatitis B surface antigen (HBsAg)-negative patients with serum HBV-DNA. The aim of this study was to analyse the infectivity of this mutant. Peripheral blood mononuclear cells (PBMC) from a healthy donor were incubated with serum samples from 2 HBsAg-negative patients with serum HBV-DNA (infected with wild-type and deletion mutant HBV), from an HBsAg carrier (infected with wild-type HBV) and from a healthy donor. After 1 week, HBV-DNA was detected by polymerase chain reaction (PCR) in all supernatants and cells incubated with the HBV-DNA-positive inocula. DNase and trypsin pretreatment confirmed intracellular localization of HBV-DNA in cells. HBV-RNA and covalently closed circular HBV-DNA were also detected in PBMC, indicating that the viral DNA infecting these cells was transcriptionally active. Deletion mutant and wild-type HBV were detected in the supernatants and cells infected with the two HBsAg-negative sera, while only wild-type HBV was detected in the supernatant and cells incubated with the serum from the HBsAg-carrier. In conclusion, this HBV deletion mutant can infect, replicate and release viral particles in in vitro infected PBMC.

Occult hepatitis B virus infection and its clinical implications

Occult hepatitis B virus (HBV) infection is characterized by presence of HBV infection with undetectable hepatitis B surface antigen (HBsAg). Serum HBV level is usually less than 104 copies/mL in these patients. Diagnosis of occult HBV infection requires sensitive HBV-DNA PCR assay. Several possibilities have been hypothesized as the mechanisms of occult HBV infection. These include: (i) mutations of HBV-DNA sequence; (ii) integration of HBV-DNA into host's chromosomes; (iii) infection of peripheral blood mononuclear cells by HBV; (iv) formation of HBV-containing immune complex; (v) altered host immune response; and (vi) interference of HBV by other viruses. The precise prevalence of occult HBV infection remains to be defined. The clinical implications of occult HBV infection involve different clinical aspects. First of all, occult HBV infection harbours potential risk of HBV transmission through blood transfusion, haemodialysis, and organ transplantation. Second, it may serve as the cause of cryptogenic liver disease, contribute to acute exacerbation of chronic hepatitis B, or even fulminant hepatitis. Third, it is associated with development of hepatocellular carcinoma. Fourth, it may affect disease progression and treatment response of chronic hepatitis C. Most of the previous studies utilized retrospective observation without control groups, and lacked direct association of occult HBV infection with specific pathological changes and disease progression. Highly sensitive, quantitative, and functional molecular analyses of HBV, combined with a well-designed prospective clinical assessment will provide the best approach for the future study of occult HBV infection.

Hypermodification and immune escape of an internally deleted middle-envelope (M) protein of frequent and predominant hepatitis B virus variants

Naturally occurring deletions within the human hepatitis B virus (HBV) preS2 region have frequently been identified in patients with hepatocellular carcinoma (HCC), while chronic carriers without cirrhosis and HCC contain no detectable preS2 deletion variants. We have characterized two different preS2 internal deletion variants from two patients. In addition to several weak phenotypes, our study revealed three unexpected strong phenotypes: (1) a paradoxical "hypermodification" phenomenon was observed with significantly increased size heterogeneity and molecular weights of the secreted middle (M) envelope proteins containing a preS2 internal deletion. This phenomenon was observed in transient transfection with a human hepatoma Huh7 cell line as well as in stable transfection with a rodent hepatoma cell line 7777. (2) A significantly increased intracellular accumulation of all three envelope proteins (large, middle, and small) was detected by both Western blot analysis and immunofluorescence microscopy. (3) The middle envelope proteins with a preS2 internal deletion were not recognized in vitro by a putative neutralizing antiserum, suggesting that these variants can evade immune recognition in vivo. To our knowledge, this is the first identification and characterization of the M deletion variant protein in HBV natural infection.

Phylogenetic analysis of new hepatitis B virus isolates from Nigeria supports endemicity of genotype E in West Africa

Isolates of hepatitis B viruses were collected from 20 acute and chronic hepatitis patients in a highly endemic region of Nigeria. Sequencing classified the isolates to the ayw4, as they all contained the amino acid variations characteristic for that serotype. In the pre-S2 region of five isolates, three to seven amino acids were deleted, suggesting that immune escape mutations previously associated only with chronic HBV infection may be observed also in acute disease. Phylogenetic analysis of the complete pre-S2/S (large S) genes (831 nt) demonstrated that all the viruses belonged to the same genotype E. So far, no isolates of genotype E have been found in any other region of the world, including the Americas. This may suggest a relatively recent introduction of this genotype into humans and would explain the relatively low genetic diversity of viruses belonging to this genotype. One genotype E virus had been found previously in a chimpanzee, and viruses belonging to the CHIMP genotype are related to other genotype E viruses. These findings are compatible with a transmission of genotype E viruses from chimpanzees to humans.

Determination of hepatitis B virus genotype G by polymerase chain reaction with hemi-nested primers

Hepatitis B virus (HBV) has been classified into six genotypes designated A-F by sequence divergence in the entire genome exceeding 8%. Very recently, the seventh genotype was reported and named genotype G. HBV genotype G is distinct from genomes of the other six genotypes in that it possesses an insertion of 36 nucleotides in the core gene, and has been found so far in France and the United States. A method for determining HBV genotype G was developed by polymerase chain reaction (PCR) with primers deduced from the 36-nucleotide (nt) insertion in five isolates of HBV genotype G the sequences of which have been deposited in DNA databases. The validity of this method, for specifically detecting HBV genotype G, was verified on a panel consisting of 142 HBV isolates of six major genotypes and four of genotype G. A total of 540 sera containing HBV in Japan covering symptom free carriers and patients with a spectrum of chronic liver disease were tested by this method, but not a single HBV genotype G sample was found. A possible method for serological determination of hepatitis B surface antigen of genotype G is suggested, without amplification or sequencing nucleotides, which would expand epidemiological and clinical researches on HBV genotype G.

Structural and functional heterogeneity of naturally occurring hepatitis B virus variants

Most organisms have developed sophisticated machineries to preserve their genomic integrity. On the contrary hepatitis B virus (HBV), like a lot of other viruses can undergo rapid and drastic sequence changes, especially if the virus has to cope with natural or therapy induced antiviral mechanisms in the host. Here, we try to summarize possible implications for the molecular pathogenesis of HBV based on the extensive research on the genetic variants of HBV.

Naturally occurring woodchuck hepatitis virus (WHV) deletion mutants in chronically WHV-infected woodchucks

Deletion mutants of hepatitis B virus (HBV) are often found in chronically HBV-infected patients. It has not been possible to study the significance of such deletion mutants on liver diseases in a suitable animal model. In this study, we characterized naturally occurring deletion mutants of woodchuck hepatitis virus (WHV) in 11 chronically WHV-infected woodchucks. Deletions within the WHV preS region (nt 2992-338) had a length of 72 or 84 bp and were located in the amino terminal part of preS1. Internal deletions within the core gene (CID) had variable lengths (103 to 312 bp) and were identified within the center of this gene (nt 2021-2587). Four of seven CIDs were in-frame deletions, whereas the remaining three CIDs were out-of-frame deletions and led to the interruption of the reading frame. Sequence analysis of cloned PCR products of CIDs showed that heterogeneous WHV deletion mutants coexisted in single woodchucks. In addition, WHV genomes with double deletions in the preS1 and the core region could be found. We were unable to detect the expression of truncated core proteins in transfection experiments. The CID mutations led to a marked increase of the expression of the luciferase gene which was fused to the start codon of WHV polymerase, probably due to the shortening of the untranslated region or the removal of AUGs preceding the polymerase start codon. The characterization of naturally occurring WHV deletion mutants will allow us to study their biological and pathogenic properties in the woodchuck model in the future.

Molecular analysis of hepatitis B virus DNA in serum and peripheral blood mononuclear cells from hepatitis B surface antigen-negative cases

We have analyzed the molecular bases of the persistence of hepatitis B virus (HBV) DNA in serum and peripheral blood mononuclear cells (PBMC) in the absence of detectable hepatitis B surface antigen (HBsAg) in hemodialysis patients and dialysis-unit staff members who had suffered acute hepatitis B that resolved previously. HBV DNA was found in both compartments by polymerase chain reaction (PCR) using primers of the pre-S/S region. Viral DNA was transcriptionally active in PBMC, because the covalently closed circular (ccc) HBV DNA, the template for the viral RNA transcription, was detected in 47% of the samples. Furthermore, all PBMC had HBV RNA. HBsAg-negative cases had statistically lower levels of HBV DNA in serum and PBMC than a control group of chronic HBsAg carriers. We have also studied the presence of immune complexes and the existence of mutations in the pre-S/S gene to explain the lack of detection of HBsAg in these cases. No serum HBsAg/hepatitis B surface antigen antibody (anti-HBs) immune complexes or mutations in the "a determinant of the S gene were found. However, we have observed that all HBsAg-negative cases were infected by a mixture of the wild-type virus and a deletion mutant in the pre-S1 region. This deletion (amino acids 58-118) affects the S gene promoter, and previous in vitro studies have shown that it produces a reduction of the HBsAg synthesis. In conclusion, this work shows that the lack of detection of HBsAg in the presence of low viral levels of replication may be caused by the existence of viral genomes harboring deletions in the pre-S1 region that affect the S promoter.

Properties of hepatitis B virus genome recovered from Vietnamese patients with fulminant hepatitis in comparison with those of acute hepatitis

Among the many mutations found in the hepatitis B virus (HBV) genome, some have been associated with fulminant hepatitis, as exemplified by precore-defective mutations. The aim of this study was to determine whether such mutations also are found in Vietnamese cases of fulminant hepatitis B. The full-genome nucleotide sequence of HBV in three patients with fulminant hepatitis (F-2, F-3, and F-6) and one with acute hepatitis (A-3), who were admitted to Cho Ray Hospital, Ho Chi Minh City, Vietnam was ascertained. Additionally, two patients with fulminant hepatitis (F-1 and F-7) and three with acute hepatitis (A-1, A-2, and A-5) were examined only for the precore/core region of HBV. Remarkably, the nonsense mutation at precore codon 28 (Trp82Stop) was found in four of the five patients with fulminant hepatitis, while all the acute hepatitis patients harbored wild type (one had a mixture of wild and mutant types). The missense mutations within the core region, Ile97Leu and Pro130Ile/Thr/Ser, were also remarkable in fulminant hepatitis. Only F-2 was free from these precore/core mutations, but F-2 was unique in that it possessed a chimeric genotype: it could be classified into genotype C as a whole, but its X region was of genotype B, like the other four fulminant hepatitis isolates (F-1, F-3, F-6, and F-7). The codon 41 of the X protein was Pro in all three fulminant hepatitis cases examined for this region, while it was Ser in the wild-type isolates of genotype B. Of note as negative data, the mutations C1653T and T1753M of the enhancer II (Enh II) and A1762T and G1764A of the precore/core promoter regions, once reported to be relevant to severe or fulminant hepatitis, were not found in the present cases. The results with the Vietnamese cases of fulminant hepatitis corroborated results of previous studies with respect to the mutations Trp28Stop of precore and Ile97Leu and Pro130Ile/Thr/Ser of core, but not for the mutations within Enh II and precore/core promoter region. Whether the Ser41Pro mutation in the X region of genotype B HBV is Vietnam-specific or disease-specific deserves further investigation.

Identification of a pre-S2 mutant in hepatocytes expressing a novel marginal pattern of surface antigen in advanced diseases of chronic hepatitis B virus infection

BACKGROUND AND AIMS

The expression of hepatitis B viral (HBV) antigens in liver tissue reflects the replicative status of chronic HBV infection. We have previously recognized a novel marginal pattern of hepatitis B surface antigen (HBsAg) in hepatocytes, which usually clusters in groups and emerges at the late non-replicative phase. This study was designed to investigate whether the marginal-type HBsAg represented the gene product of a specific HBV-surface mutant.

METHODS

Microdissection of cirrhotic nodules homogeneously expressing marginal HBsAg was performed on two of 12 resected livers from HBsAg-seropositive patients with hepatocellular carcinoma. The gene presumably encoding marginal HBsAg was polymerase chain reaction (PCR)-cloned, sequenced and analysed. In vitro transfection and expression of the cloned surface mutant plasmids were performed on the Huh7 cell line to illustrate intrahepatic HBsAg expression.

RESULTS

Immunohistochemical staining revealed that the marginal HBsAg was positive for pre-S1 and thus contained large surface proteins. The PCR cloning and sequencing of the genes presumably encoding marginal-type HBsAg in both cases revealed the same deletion at the 5' terminus (nt 2-55) of pre-S2. A point mutation on the small-surface (S) antigen was also found in one case. The pre-S2 deletion sequence and the mutation sites of the S gene coincide with human lymphocyte antigen-restricted T- and/or B-cell epitopes. In vitro transfection of the mutant plasmid revealed a blot-like retention or accumulation of HBsAg in the cytoplasm or at the periphery of hepatocytes, accompanied by a decreased secretion of HBsAg in the culture supernatant, mimicking intrahepatic expression.

CONCLUSION

A natural pre-S2 deletion mutant was identified in hepatocytes expressing a novel marginal pattern of HBsAg, which probably contains mutant, large, surface proteins. The biological significance of the pre-S2 deletion mutant should be interesting in view of the clustering proliferation of hepatocytes expressing marginal HBsAg.

Fine mapping of virus-neutralizing epitopes on hepatitis B virus PreS1

We identified the epitopes on the preS1 which induce antibodies that neutralize both ad and ay subtypes of hepatitis B virus (HBV). Previously we generated murine monoclonal antibodies KR359 and KR127 that bind specifically to the preS1 of HBV. In this study we have performed fine mappings of the epitopes of the antibodies by examining their reactivity with GST fusion proteins, which contain a series of deletion mutants of the preS1. KR359 and KR127 specifically recognize aa 19-26 and 37-45 of the preS1, respectively. The antibodies neutralized both adr and ayw subtypes of the virus in an in vitro neutralization assay using in vitro infection of adult human hepatocyte primary culture by HBV. The epitopes showed little sequence divergence and the antibodies bound to the preS1 of all the HBV subtypes and variants tested.

Immune escape by hepatitis B viruses

Hepatitis B viruses are DNA viruses characterized by their very small genome size and their unique replication via reverse transcription. The circular genome has been efficiently exploited, thereby limiting genome variation, and leaves no space for genes in addition to those essentially needed during the viral live cycle. Hepatitis B viruses are prototype non-cytopathic viruses causing persistent infection. Human hepatitis B virus (HBV), as well as the closely related animal viruses, most frequently are transmitted vertically from mothers to their offspring. Because infection usually persists for many years, if not lifelong, hepatitis B viruses need efficient mechanisms to hide from the immune response of the host. To escape the immune response, they exploit different strategies. Firstly, they use their structural and non-structural proteins multiplely. One of the purposes is to alter the immune response. Secondly, they replicate by establishing a pool of stable extrachromosomal transcription templates, which allow the virus to react sensitively to changes in its microenvironment by up- or downregulating gene expression. Thirdly, hepatitis B viruses replicate in the liver which is an immunopriviledged site.

The pre-S region determines the intracellular localization and appearance of hepatitis B virus

The functional role of the hepatitis B virus (HBV) pre-S region for assembly and appearance of the virus is not completely understood. In this study, 3 natural-occurring mutants were investigated. Three mutants of the pre-S region-a point mutation in the CCAAT box (MUT1), a 6-bp deletion (MUT2) 3' of the CCAAT box, and a 153-bp deletion (MUT3) in the preS2 domain-were cloned alone or in combinations in replication-competent HBV plasmids and transfected in hepatoma cells. The impact on HBV assembly and appearance was studied by Northern Blot, primer extension analysis, immunofluorescence studies, enzyme-linked immunosorbent assay, and electron microscopy. An inversed ratio of pre-S/S mRNA transcripts compared with wild-type (wt) HBV was found when either MUT1 or -2 were included into the plasmid. Intracellular localization with both mutants showed retention of large S-protein in the endoplasmic reticulum and nuclear accumulation of core protein. The extracellular amount of S-protein was reduced with MUT1 and -2 or combinations in which 1 of the mutants was included. However, the extracellular appearance of viral products was comparable with wtHBV. In contrast, MUT3 showed major changes. Virion-like particles had a fried-egg, and filaments a screw-like appearance. The S-promoter mutations MUT1 and MUT2 correlated with viral retention. MUT3 leads to malformed viral particles. Therefore, different regions in the pre-S domain are essential to determine the intracellular localization and extracellular appearance of HBV, and might contribute to the prognosis of chronic HBV infection.

Human hepatitis B virus mutants: significance of molecular changes

Human hepatitis B virus, the leading pathogen for hepatitis B, is a compact DNA virus with viral genes that largely overlap. An increasing number of mutations have emerged following human interventions such as vaccination and anti-viral therapy. While vaccine escape mutants are characterized by mutations on the antigenic hepatitis B surface antigen, those carrying mutations in other viral proteins are either resistant to anti-viral therapy or implicated in acute liver diseases. Molecular identification of these various mutants should shed new lights on the underlying mechanism of hepatitis B virus viral escape and resistance and provide helpful information on their effective eradication.

Two control elements in the hepatitis B virus S-promoter are important for full promoter activity mediated by CCAAT-binding factor

Natural occurring mutations in the preS-region are frequently found during chronic hepatitis B virus (HBV) infection. Here we used the mutated preS-region from a patient to study the transcriptional regulation of the S-promoter. The mutations were a CCAAT-box (MUT1) point mutation, a 6-base pair (bp) deletion (MUT2) 3' of the CCAAT-box, and a 153 bp deletion (MUT3) in the preS2 genome. Transfection experiments revealed for MUT1 and 2 30% to 40% and MUT3 75% of the wildtype (wt) S-promoter activity. In electro-mobility shift assays experiments, binding of a nuclear protein was impaired with MUT1. Ultraviolet cross-linking, South-Western, and gel shift experiments revealed a 30- to 40-kd protein interacting with the wt CCAAT-motif. Computer-assisted analysis and supershift experiments showed that CCAAT-binding factor (CBF) is the CCAAT-box binding protein. Cotransfection experiments with expression vectors for dominant-negative CBF or wt CBF showed that the wt S-promoter but not MUT1 could be regulated through CBF. Additionally, the CBF constructs did not modulate the basal activity of MUT2 but changes the activity of MUT3 like wt HBV. Artificial mutations were introduced in the MUT2 reporter constructs. Transfection experiments revealed that wt promoter activity could not be reconstituted. Therefore these experiments indicated the sterical position of CBF being essential for full S-promoter activity. Our study shows that the CCAAT-box and a second region is essential to mediate full S-promoter activity dependent on CBF. As these mutations also lead to retention of S-protein in the endoplasmic reticulum our results indicate that mutational changes in the preS-region might be linked to the progression of HBV-related liver disease.

HBV viral load within subpopulations of peripheral blood mononuclear cells in HBV infection using limiting dilution PCR

Extrahepatic viral load in peripheral blood mononuclear cells (PBMCs) of patients with hepatitis B virus (HBV) is still under debate. In this study, HBV infection rates and viral titers were examined within all PBMC subpopulations using limiting dilution-PCR (LD-PCR). PBMCs of patients with acute or chronic hepatitis B were separated by magnetic beads in monocytes, B-cells, CD4+ T-cells, CD8+ T-cells, and NK cells. Using two-round nested PCR, HBV-DNA sequences were detected in all patients examined within each PBMC subpopulation. The frequencies of HBV-positive cells and viral loads were calculated by Poisson analysis of HBV PCR results from serial dilutions of cells and cell lysates. Highest infection rates were found in monocytes and B-cells followed by CD8 + T-cells, NK cells, and CD4+ T-cells. Concerning all subsets, frequencies of HBV-positive cells were 50- to 500-fold higher in chronic than in acute hepatitis B. Viral loads were mostly estimated at about one HBV genome per HBV-positive cell. Moreover, slightly elevated HBV titers were seen in B-cells, CD4+ T-cells, and NK cells in both acute and chronic hepatitis B. It was demonstrated that beside a generally more latent HBV infection in PBMCs, elevated HBV titers point to replication or selective viral uptake within particular PBMC subsets. Therefore, the data suggest that HBV-infected PBMCs may participate in persistence of HBV.

Genotyping of hepatitis B virus by restriction pattern analysis of a pre-S amplicon

A method is described for genotyping of hepatitis B virus (HBV), based on the restriction fragment length polymorphism (RFLP) created by Ava2 and Dpn2 action on an amplified segment of the pre-S region. Analysing 51 database sequences by phylogenetic tree construction and RFLP prediction, the method was shown to be capable of detecting all known genotypes (A-F). The method was applied to 99 serum samples from hepatitis B e antigen (HBeAg)-positive chronic carriers, comparing observed agarose gel patterns with the RFLP predicted from the database sequences. In 95 typable samples the following genotypes were observed; 23 A, 20 B, 20 C, 22 D, 5 E and 5 F. Phylogenetic grouping of the 51 database sequences and RFLP genotyping of the 99 patient samples were compared with typing based on S gene analysis, showing disagreement in only one case, a database sequence of ayw subtype which was classified as genotype D by pre-S region and genotype A by S region analysis. This method should be useful for epidemiological investigations and for studying the potential influence of genotype on the course of infection.

Hepatitis viruses: genetic variants and clinical significance

Variants of hepatitis B, C, and delta virus have been identified in patients both with acute and chronic infections. In the hepatitis B virus genome, naturally occurring mutations have been found in all viral genes, most notably in the genes coding for the structural envelope and nucleocapsid proteins. In the hepatitis C virus genome, the regions coding for the structural envelope proteins E1 and E2, as well as the 3'-contiguous non-structural region NS1, were found to be hypervariable. Viral variants may be associated with a specific clinical course of the infection, e.g., acute, fulminant or chronic hepatitis. Specific mutations may reduce viral clearance by immune mechanisms ('vaccine escape' and 'immune escape'), response to antiviral therapy ('therapy escape'), as well as detection ('diagnosis escape'). The exact contribution, however, of specific mutations to the pathogenesis and natural course of hepatitis B, C, or delta virus infection, including hepatocellular carcinoma development, and the response to antiviral treatment remains to be established.