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

Large HBV Surface Protein-Induced Unfolded Protein Response Dynamically Regulates p27 Degradation in Hepatocellular Carcinoma Progression

Up to 50% of hepatocellular carcinoma (HCC) is caused by hepatitis B virus (HBV) infection, and the surface protein of HBV is essential for the progression of HBV-related HCC. The expression of large HBV surface antigen (LHB) is presented in HBV-associated HCC tissues and is significantly associated with the development of HCC. Gene set enrichment analysis revealed that LHB overexpression regulates the cell cycle process. Excess LHB in HCC cells induced chronic endoplasmic reticulum (ER) stress and was significantly correlated with tumor growth in vivo. Cell cycle analysis showed that cell cycle progression from G1 to S phase was greatly enhanced in vitro. We identified intensive crosstalk between ER stress and cell cycle progression in HCC. As an important regulator of the G1/S checkpoint, p27 was transcriptionally upregulated by transcription factors ATF4 and XBP1s, downstream of the unfolded protein response pathway. Moreover, LHB-induced ER stress promoted internal ribosome-entry-site-mediated selective translation of p27, and E3 ubiquitin ligase HRD1-mediated p27 ubiquitination and degradation. Ultimately, the decrease in p27 protein levels reduced G1/S arrest and promoted the progress of HCC by regulating the cell cycle.

Endoplasmic Reticulum Stress in Hepatitis B Virus and Hepatitis C Virus Infection

Endoplasmic reticulum (ER) stress, a type of cellular stress, always occurs when unfolded or misfolded proteins accumulating in the ER exceed the protein folding capacity. Because of the demand for rapid viral protein synthesis after viral infection, viral infections become a risk factor for ER stress. The hepatocyte is a cell with large and well-developed ER, and hepatitis virus infection is widespread in the population, indicating the interaction between hepatitis viruses and ER stress may have significance for managing liver diseases. In this paper, we review the process that is initiated by the hepatocyte through ER stress against HBV and HCV infection and explain how this information can be helpful in the treatment of HBV/HCV-related diseases.

Blood-Based Biomarkers in Hepatitis B Virus-Related Hepatocellular Carcinoma, Including the Viral Genome and Glycosylated Proteins

Hepatitis B virus (HBV) infection is a major risk factor for hepatocellular carcinoma (HCC) development and is a global public health issue. High performance biomarkers can aid the early detection of HCC development in HBV-infected individuals. In addition, advances in the understanding of the pathogenesis of HBV infection and in clinical laboratory techniques have enabled the establishment of disease-specific tests, prediction of the progression of liver diseases, including HCC, and auxiliary diagnosis of HCC, using blood-based methods instead of biopsies of liver or HCC tissues. Viral factors such as the HBV genotype, HBV genetic mutations, HBV DNA, and HBV-related antigens, as well as host factors, such as tumor-associated proteins and post-translational modifications, especially glycosylated proteins, can be blood-based, disease-specific biomarkers for HCC development in HBV-infected patients. In this review, we describe the clinical applications of viral biomarkers, including the HBV genome and glycosylated proteins, for patients at a risk of HBV-related HCC, based on their molecular mechanisms. In addition, we introduce promising biomarker candidates for practical use, including colony stimulating factor 1 receptor (CSF1R), extracellular vesicles, and cell-free, circulating tumor DNA. The clinical use of such surrogate markers may lead to a better understanding of the risk of disease progression and early detection of HCC in HBV-infected patients, thereby improving their prognosis.

Persistence of Hepatitis B Virus Infection: A Multi-Faceted Player for Hepatocarcinogenesis

Hepatitis B virus (HBV) infection has a multi-dimensional effect on the host, which not only alters the dynamics of immune response but also persists in the hepatocytes to predispose oncogenic factors. The virus exists in multiple forms of which the nuclear localized covalently closed circular DNA (cccDNA) is the most stable and the primary reason for viral persistence even after clearance of surface antigen and viral DNA. The second reason is the existence of pregenomic RNA (pgRNA) containing virion particles. On the other hand, the integration of the viral genome in the host chromosome also leads to persistent production of viral proteins along with the chromosomal instabilities. The interferon treatment or administration of nucleot(s)ide analogs leads to reduction in the viral DNA load, but the pgRNA and surface antigen clearance are a slow process and complete loss of serological HBsAg is rare. The prolonged exposure of immune cells to the viral antigens, particularly HBs antigen, in the blood circulation results in T-cell exhaustion, which disrupts immune clearance of the virus and virus-infected cells. In addition, it predisposes immune-tolerant microenvironment, which facilitates the tumor progression. Thus cccDNA, pgRNA, and HBsAg along with the viral DNA could be the therapeutic targets in the early disease stages that may improve the quality of life of chronic hepatitis B patients by impeding the progression of the disease toward hepatocellular carcinoma.

Hepatitis B virus pre-S region: Clinical implications and applications

Hepatitis B virus (HBV) infection is a major threat to global public health, which can result in many acute and chronic liver diseases. HBV, a member of the family Hepadnaviridae, is a small enveloped DNA virus containing a circular genome of 3.2 kb. Located upstream of the S-open-reading frame of the HBV genome is the pre-S region, which is vital to the viral life cycle. The pre-S region has high variability and many mutations in the pre-S region are associated with several liver diseases, such as fulminant hepatitis (FH), liver cirrhosis (LC), and hepatocellular carcinoma (HCC). In addition, the pre-S region has been applied in the development of several pre-S-based materials and systems to prevent or treat HBV infection. In conclusion, the pre-S region plays an essential role in the occurrence, diagnosis, and treatment of HBV-related liver diseases, which may provide a novel perspective for the study of HBV infection and relevant diseases.

Formation of semi-enveloped particles as a unique feature of a hepatitis B virus PreS1 deletion mutant

BACKGROUND

Naturally occurring variants with deletions or mutations in the C-terminal PreS1 domain from hepatitis B virus (HBV) chronically infected patients have been shown to promote HBsAg retention, inhibit HBsAg secretion and change the extracellular appearance of PreS1-containing HBV particles (filaments and virions).

AIMS

To study the impact of N-terminal deletion in preS1 domain on viral secretion and morphogenesis.

METHODS

An HBV mutant with 15 amino acids (aa 25-39) deletion in N-terminal preS1 was isolated. Intracellular and extracellular HBsAg were quantified by Western blot. Subcellular HBsAg distribution was analysed by confocal laser scanning microscopy. The viral morphology was characterised by sucrose density gradient ultracentrifugation, Western blot, electron microscopy, HBV mixed ELISA and HBV particle gel essay.

RESULTS

Expression of this mutant genome released higher amounts of HBsAg in the form of shorter filaments. A significant fraction of semi-enveloped virions was observed in the supernatant that has been unprecedented so far. Stepwise insertion of aa 25-31, aa 32-39 and aa 25-39 increased the length of filaments. The rescue of aa 25-31 and aa 25-39 drastically reduced the amounts of extracellular HBsAg and semi-enveloped virions, while such effects could not be observed after insertion of aa 32-39, arguing against a simple spacer function of this region. The deletion and rescued mutants do not differ in subcellular HBsAg distribution and colocalisation with ER, Golgi and multivesicular bodies markers arguing against differences in release pathways.

CONCLUSION

N-terminal PreS1-domain (aa 25-31) determines HBsAg secretion and triggers proper assembly of PreS1-containing particles.

Naturally Occurring Hepatitis B Virus Mutations Leading to Endoplasmic Reticulum Stress and Their Contribution to the Progression of Hepatocellular Carcinoma

Hepatitis B virus (HBV) infection is a global health problem that causes a wide range of pathological outcomes, including cirrhosis and hepatocellular carcinoma (HCC). Endoplasmic reticulum (ER) stress induction by HBV infection has been implicated in liver carcinogenesis and disease progression with chronic inflammation via enhanced inflammation, oxidative stress-mediated DNA damage, and hepatocyte proliferation. In the natural course of HBV infection, the accumulation of naturally occurring mutations in the HBV genome can generate several mutant types of HBV-encoded proteins, including three different proteins in the S ORF (SHBs, MHBs, and LHBs) and HBcAg in the C ORF, which could contribute to enhanced ER stress in infected hepatocytes mainly via increased ER accumulation of mutant proteins. However, it seems that there may be distinct capacity and pathway in ER stress-induction and distinct resulting clinical outcomes between HBV variants. In addition, the role of HBxAg mutations in ER stress remains unknown. However, it has been reported that HBxAg itself could exert ER stress in infected cells, resulting in HCC generation in chronic HBV patients. To date, review papers regarding ER stress-mediated HBV mutation have been limited into a specific mutation type: preS2 deletion. So, in this review, we will discuss details about various mutation types in all four regions of the HBV genome (preS1, preS2, S, and C) related to ER stress and their distinct ER stress mechanisms and clinical outcomes in terms of mutation types.

Hepatitis B virus infection: Defective surface antigen expression and pathogenesis

Hepatitis B virus (HBV) infection is a global public health concern. HBV causes chronic infection in patients and can lead to liver cirrhosis, hepatocellular carcinoma, and other severe liver diseases. Thus, understanding HBV-related pathogenesis is of particular importance for prevention and clinical intervention. HBV surface antigens are indispensable for HBV virion formation and are useful viral markers for diagnosis and clinical assessment. During chronic HBV infection, HBV genomes may acquire and accumulate mutations and deletions, leading to the expression of defective HBV surface antigens. These defective HBV surface antigens have been found to play important roles in the progression of HBV-associated liver diseases. In this review, we focus our discussion on the nature of defective HBV surface antigen mutations and their contribution to the pathogenesis of fulminant hepatitis B. The relationship between defective surface antigens and occult HBV infection are also discussed.

A molecular epidemiology study investigating familial clustering of hepatitis B virus infection in families with unfavorable prognoses in Northwest China

Hepatitis B virus (HBV) infections and adverse outcome have been demonstrated to show characteristics of familial clustering. The aim of this study was to investigate the prevalence of different HBV genotypes, HBV sub-genotypes, and Pre-S mutations associated with familial HBV infection clusters with unfavorable prognoses. Families presenting with clustered HBV infections and unfavorable prognoses were enrolled in this study. Non-clustered HBV-infected individuals were used as the control group. DNA extracted from patient serum samples was used to facilitate characterization of the HBV genotypes, HBV sub-genotypes, and Pre-S mutations by phylogenetic analysis. The Pre-S/S gene was successfully amplified in 83 patients from the clustering group and 105 patients from the sporadic group. The prevalence of genotype C in the clustering group (71/83, 85.54%) was significantly higher than in the sporadic group (77/105, 73.33%) (P = 0.042). The prevalence of sub-genotype C2 in the clustering group (33/83, 39.76%) was also higher than in the sporadic group (21/105, 20%) (P = 0.003). Analyses of functional mapping of pre-S sequences showed that the prevalence of the mutation in the S promoter site (nt 3045-3189 of pre-S1 domain) was significantly increased in the clustering group compared with the sporadic group (15.7% vs. 3.8%) (P = 0.009). This study suggests that genotype C, especially sub-genotype C2, may be associated with the progression of HBV infection in familial clustering infection cohorts with unfavorable prognoses. We also observed that the natural occurrence of S promoter mutations in the clustering group was significantly prevalent.

Molecular mechanisms underlying HBsAg negativity in occult HBV infection

Although genomic detection is considered the gold standard test on HBV infection identification, the HBsAg investigation is still the most frequent clinical laboratory request to diagnose HBV infection in activity. However, the non-detection of HBsAg in the bloodstream of chronic or acutely infected individuals has been a phenomenon often observed in clinical practice, despite the high sensitivity and specificity of screening assays standardized commercially and adopted in routine. The expansion of knowledge about the hepatitis B virus biology (replication/life cycle, genetic variability/mutability/heterogeneity), their biochemical and immunological properties (antigenicity and immunogenicity), in turn, has allowed to elucidate some mechanisms that may explain the occurrence of this phenomenon. Therefore, the negativity for HBsAg during the acute or chronic infection course may become a fragile or at least questionable result. This manuscript discusses some mechanisms that could explain the negativity for HBsAg in a serological profile of individuals with HBV infection in activity, or factors that could compromise its detection in the bloodstream during HBV infection.

Detection of Hepatitis B Virus Large Surface Protein Using a Time-Resolved Immunofluorometric Assay

BACKGROUND

To establish a novel method based on time-resolved immunofluorometric assay (TR-IFMA) with higher sensitivity and a broader detection range for detecting serum hepatitis B virus large surface protein (L protein).

METHODS

The precision, sensitivity, specificity, coefficient of recovery, and stability of the assay were evaluated and comparison with the classical enzyme-linked immunosorbent assay (ELISA) was also executed.

RESULTS

The precision, specificity, and sensitivity of the TR-IFMA were clearly better than ELISA. Particularly, the sensitivity was 0.1 ng/ml; moreover, the specificity was 100%, 96%, 92.5%, 96.9%, 97.8%, and 100% in the sera of healthy blood donors, systemic lupus erythematosus (SLE) patients, rheumatoid arthritis (RA) patients, hepatitis C virus (HCV) patients, cytomegalovirus (CMV) infection patients, and pregnant patients, respectively. Meanwhile, we observed that the established TR-IFMA kit has a wider acceptable linear range of 0.63-10,367 ng/ml rather than the regular commercial ELISA kit having range of only 10.12-1095.9 ng/ml. Subsequently, correlation coefficient between the TR-IFMA and ELISA was 0.8009. The intra- and interassay precision rates were less than 5% for three different concentrations. The average recovery rate for L protein was 101.17%. In sum, the established assay kit performed better in terms of stability than the commercial ELISA kit.

CONCLUSION

The TR-IFMA that we developed for L protein presented a higher sensitivity and wider detecting range than regular commercial ELISA. Therefore, this TR-IFMA has promising value both in the screening of HBV and monitoring of antiviral therapy.

Hepatitis B virus PreS/S gene variants: pathobiology and clinical implications

The emergence and takeover of hepatitis B virus (HBV) variants carrying mutation(s) in the preS/S genomic region is a fairly frequent event that may occur spontaneously or may be the consequence of immunoprophylaxis or antiviral treatments. Selection of preS/S mutants may have relevant pathobiological and clinical implications. Both experimental data and studies in humans show that several specific mutations in the preS/S gene may induce an imbalance in the synthesis of the surface proteins and their consequent retention within the endoplasmic reticulum (ER) of the hepatocytes. The accumulation of mutated surface proteins may cause ER stress with the consequent induction of oxidative DNA damage and genomic instability. Viral mutants with antigenically modified surface antigen may be potentially infectious to immune-prophylaxed patients and may account for cases of occult HBV infection. In addition, preS/S variants were reported to be associated with cases of fulminant hepatitis as well as of fibrosing cholestatic hepatitis, and they are associated with cirrhosis and hepatocellular carcinoma development.

Sequence variations of full-length hepatitis B virus genomes in Chinese patients with HBsAg-negative hepatitis B infection

BACKGROUND

The underlying mechanism of HBsAg-negative hepatitis B virus (HBV) infection is notoriously difficult to elucidate because of the extremely low DNA levels which define the condition. We used a highly efficient amplification method to overcome this obstacle and achieved our aim which was to identify specific mutations or sequence variations associated with this entity.

METHODS

A total of 185 sera and 60 liver biopsies from HBsAg-negative, HBV DNA-positive subjects or known chronic hepatitis B (CHB) subjects with HBsAg seroclearance were amplified by rolling circle amplification followed by full-length HBV genome sequencing. Eleven HBsAg-positive CHB subjects were included as controls. The effects of pivotal mutations identified on regulatory regions on promoter activities were analyzed.

RESULTS

22 and 11 full-length HBV genomes were amplified from HBsAg-negative and control subjects respectively. HBV genotype C was the dominant strain. A higher mutation frequency was observed in HBsAg-negative subjects than controls, irrespective of genotype. The nucleotide diversity over the entire HBV genome was significantly higher in HBsAg-negative subjects compared with controls (p = 0.008) and compared with 49 reference sequences from CHB patients (p = 0.025). In addition, HBsAg-negative subjects had significantly higher amino acid substitutions in the four viral genes than controls (all p<0.001). Many mutations were uniquely found in HBsAg-negative subjects, including deletions in promoter regions (13.6%), abolishment of pre-S2/S start codon (18.2%), disruption of pre-S2/S mRNA splicing site (4.5%), nucleotide duplications (9.1%), and missense mutations in "α" determinant region, contributing to defects in HBsAg production.

CONCLUSIONS

These data suggest an accumulation of multiple mutations constraining viral transcriptional activities contribute to HBsAg-negativity in HBV infection.

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.

Impact of hepatitis B virus (HBV) preS/S genomic variability on HBV surface antigen and HBV DNA serum levels

To evaluate whether hepatitis B virus (HBV) preS/S gene variability has any impact on serum hepatitis B surface antigen (HBsAg) levels and to analyze the replication capacity of naturally occurring preS/S variants, sera from 40 untreated patients with HBV-related chronic liver disease (hepatitis B e antigen [HBeAg]-positive, n = 11; HBeAg-negative, n = 29) were virologically characterized. Additionally, phenotypic analysis of three different preS/S variant isolates (carrying a 183-nucleotide deletion within the preS1 region, the deletion of preS2 start codon, and a stop signal at codon 182 within the S gene, respectively) was performed. HBV infecting 14 (35%) patients had single or multiple preS/S genomic mutations (i.e., preS1 and/or preS2 deletions, preS2 start codon mutations, C-terminally truncated and/or "a" determinant mutated S protein). Presence of preS/S variants negatively correlated with HBsAg titers (r = -0.431; P = 0.005) and its prevalence did not significantly differ between HBeAg-positive and HBeAg-negative patients. No correlation was found between HBsAg and HBV DNA levels in patients infected with preS/S mutants, whereas a significant correlation was found between HBsAg and viremia levels (r = 0.607; P = 0.001) in patients infected with wild-type HBV strains. HepG2 cells replicating the above-mentioned three preS/S variants showed significant reduction of HBsAg secretion, retention of envelope proteins in the endoplasmic reticulum, less efficient virion secretion and nuclear accumulation of significantly higher amounts of covalently closed circular DNA compared with wild-type HBV replicating cells.

CONCLUSION

In patients infected with preS/S variants, HBV DNA replication and HBsAg synthesis/secretion appear to be dissociated. Therefore, the use of HBsAg titer as diagnostic/prognostic tool has to take into account the frequent emergence of preS/S variants in chronic HBV infection.

Asialoglycoprotein receptor interacts with the preS1 domain of hepatitis B virus in vivo and in vitro

BACKGROUND

The preS1 domain of the large envelope protein has been identified as an essential viral structure involved in hepatitis B virus (HBV) attachment. However, the cellular receptor(s) for HBV has not yet been identified.

AIMS

To identify a cell-surface receptor for HBV, which could elucidate the molecular mechanism of HBV infection.

METHODS

A novel yeast two-hybrid system was used to screen proteins interacting with the preS1 region of HBV. Their interaction was verified by yeast cotransformation, coimmunoprecipitation and mammalian two-hybrid assay, while their intracellular and tissue localization was analyzed by confocal microscopy and immunohistochemistry, respectively.

RESULTS

Asialoglycoprotein receptor (ASGPR) interacted specifically and directly with the preS1 domain of HBV in vivo and in vitro. The levels of expression of preS1 and ASGPR in the liver were similar and correlated with each other.

CONCLUSIONS

ASGPR is a candidate receptor for HBV that mediates further steps of HBV entry.

The underlying mechanisms for the 'anti-HBc alone' serological profile

The serological pattern, "anti-HBc alone", characterized by the presence of antibodies against the core antigen of hepatitis B virus (anti-HBc) as the only marker of hepatitis B, is not rare in a diagnostic setting. Depending on the prevalence of HBV infection and the patient group investigated, 1-31% of positive anti-HBc results are isolated positive findings. Anti-HBc alone is frequently observed in intravenous drug addicts, HIV-infected individuals, patients who are coinfected with HBV and hepatitis C virus, and pregnant women. However, it is not clear how this profile should be interpreted. Several studies have shown that anti-HBc alone is not only compatible with acute and resolved HBV infection but also with chronic infection. The reasons for the lack of HBsAg and anti-HBs in anti-HBc-alone individuals are not clear, but several mechanisms and possibilities have been suggested that could explain this phenomenon, some of which are delineated in this article.

Hepatocellular carcinoma: epidemiology, risk factors and pathogenesis

Hepatocellular carcinoma (HCC) is the commonest primary malignant cancer of the liver in the world. Given that the burden of chronic liver disease is expected to rise owing to increasing rates of alcoholism, hepatitis B and C prevalence and obesity-related fatty liver disease, it is expected that the incidence of HCC will also increase in the foreseeable future. This article summarizes the international epidemiology, the risk factors and the pathogenesis of HCC, including the roles of viral hepatitis, toxins, such as alcohol and aflatoxin, and insulin resistance.

Hepatocellular carcinoma: Epidemiology, risk factors and pathogenesis

Hepatocellular carcinoma (HCC) is the commonest primary malignant cancer of the liver in the world. Given that the burden of chronic liver disease is expected to rise owing to increasing rates of alcoholism, hepatitis B and C prevalence and obesity-related fatty liver disease, it is expected that the incidence of HCC will also increase in the foreseeable future. This article summarizes the international epidemiology, the risk factors and the pathogenesis of HCC, including the roles of viral hepatitis, toxins, such as alcohol and aflatoxin, and insulin resistance.

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.

Role of surface promoter mutations in hepatitis B surface antigen production and secretion in occult hepatitis B virus infection

The production, secretion, and localization of surface proteins of hepatitis B virus (HBV) and the ratio of large to small surface protein S was studied in HepG2 cells transfected with the wild-type and mutant pre-S1 and pre-S2/S promoters of HBV molecular clones 313.1 (GenBank accession no. AY161147) and 761.1 (GenBank accession no. AY161159) from two patients with occult HBV infection. Fusion constructs were made by in frame fusion of the wild-type surface gene to the mutant pre-S1 and pre-S2/S promoters and wild-type promoter so that the structural part of the small surface protein remains identical. HepG2 cells transfected transiently were used for analysis. HBV surface proteins production and secretion was determined by enzyme linked immuno assay (ELISA) and localization by immunofluorescence. Immunoprecipitation of the large, middle, and small surface protein was carried out in transient transfected and metabolically labeled cells to determine the ratio of the large to small surface protein. The results indicate that HepG2 cells transfected with mutant HBV promoters had reduced HBV surface proteins secretion compared to wild-type HBV. HepG2 cells transfected with mutant HBV pre-S1 and pre-S2/S promoters showed cytoplasmic aggregation of HBV surface proteins compared to wild-type HBV promoters, which showed diffuse cytoplasmic localization. In all cases, the HBV surface proteins localized to the endoplasmic reticulum. The ratio between the large and small surface protein was 1.89 and 0.56 with mutant HBV 313.1 and 761.1 pre-S1 and pre-S2/S promoters, respectively, compared to 0.17 in wild-type. Thus, the aggregation of surface proteins, altered ratio and secretion of surface proteins were possibly the causes of occult hepatitis B infection.

Clinical significance of pre-S mutations in patients with genotype C hepatitis B virus infection

We investigated the overall and site-specific prevalence of pre-S mutations and its clinical significance in patients with genotype C hepatitis B virus (HBV) infection. Three hundred subjects were included: 50 asymptomatic carriers (AC), 87 chronic hepatitis (CH), 91 liver cirrhosis (LC) and 72 hepatocellular carcinoma (HCC). Pre-S mutations were determined by nucleotide sequence analysis. Possible correlations between pre-S mutations and clinical/virological parameters were examined. Pre-S mutations were detected in 82 cases (27.3%); it was more frequently found in HCC (43.1%) and LC (35.2%) group than in the CH (20.7%) and AC (2.0%) group. Pre-S2 deletion was the most commonly found mutation (10.7%), followed by pre-S2 start codon mutation (9.7%), pre-S1-S2 deletion (3.0%) and both pre-S2 deletion and start codon mutation (2.7%). Pre-S2 deletion and pre-S2 start codon mutation were more frequently detected in advanced diseases (LC and HCC). Pre-S mutations were associated with older age and higher rates of positive HBV DNA (>/=0.5 pg/mL). Advanced disease and positive HBV DNA were shown to be independent predictors of pre-S mutations by logistic regression analysis. These findings suggest that pre-S mutations, especially pre-S2 deletions and pre-S2 start codon mutations, are common in patients with genotype C HBV infection and are associated with advanced liver disease and active viral replication.

Pathogenesis of hepatitis B virus infection

Infection with hepatitis B virus (HBV) leads to a wide spectrum of clinical presentations ranging from an asymptomatic carrier state to self-limited acute or fulminant hepatitis to chronic hepatitis with progression to cirrhosis and hepatocellular carcinoma. Infection with HBV is one of the most common viral diseases affecting man. Both viral factors as well as the host immune response have been implicated in the pathogenesis and clinical outcome of HBV infection. In this review, we will discuss the impact of virus-host interactions for the pathogenesis of HBV infection and liver disease. These interactions include the relevance of naturally occurring viral variants for clinical disease, the role of virus-induced apoptosis for HBV-induced liver cell injury and the impact of antiviral immune responses for outcome of infection.

Functional analysis of complex hepatitis B virus variants associated with development of liver cirrhosis

BACKGROUND & AIMS

Development of cirrhosis in renal transplant recipients with chronic hepatitis B is associated with the accumulation of complex hepatitis B virus (HBV) variants carrying deletions in the C gene and/or preS region and deletions/insertions in the core promoter. Here, we characterized for the first time the phenotype of these complex HBV variants.

METHODS

Representative full-length genomes of the HBV variants that were isolated and cloned from serum and liver of an immunosuppressed renal transplant recipient before and during end-stage liver disease were transfected into the human hepatoma cell line HuH7 and functionally analyzed.

RESULTS

The variant genomes showed considerably reduced levels of precore and surface messenger RNA (mRNA) and of the major spliced pregenomic RNA, an increased level of pregenomic RNA, and a partial or complete defect in hepatitis B e antigen, core, and surface protein expression/secretion. Very low amounts of variant core protein with internal deletion were detectable. Reduced hepatitis B surface antigen secretion of some variants correlated with aberrant localization of surface proteins in endoplasmic reticulum. Despite the defects in viral protein expression, enhanced replication and enrichment in competition to wild-type HBV were observed. Enhanced reverse transcription and possibly increased levels of pregenomic RNA seem to be responsible for this effect.

CONCLUSIONS

Development of cirrhosis is associated with accumulation of complex variants, which exhibit a drastically altered phenotype combining enhanced replication with defects in protein expression. This phenotype appears to be based on the major mutations in the core promoter and C gene but is considerably influenced by additional mutations throughout the genome.

Mutations affecting the replication capacity of the hepatitis B virus

The genetic variability of the hepatitis B virus (HBV) encounters two compounding forces: a high viral copy number produced during active replication and the lack of proofreading activity in the HBV polymerase, resulting in a high mutational rate. A large pool of quasispecies is generated in which the fittest virus, i.e. the virus that replicates best, becomes the dominant species. Immune and antiviral selection pressures result in vaccine/immunoglobulin escape mutants and antiviral resistant variants. Viruses encoding changes associated with antiviral resistance often have reduced replication in vitro, but the accumulation of additional mutations helps restore viral fitness. These compensatory mutations may occur not only in the polymerase gene but also in other genes such as the overlapping envelope gene, the precore gene, or in regulatory regions such as the basal core promoter. In this report we aim to review the new findings that have appeared in recent months.

Alternative peptide-fusion proteins generated by out-of-frame mutations, just upstream ORFs or elongations in mutants of human hepatitis B viruses

By various means including out-of-frame mutations, just upstream ORFs and elongations, additional peptide fusions could be generated by mutants of Human Hepatitis B Virus (HBV). Numerous frameshift mutations inducing long alternative open reading frames have been evidenced in all HBV genes. Interestingly, these mutants are frequently detected in severe liver diseases, but seldom in asymptomatic carriers. The high level of conservation of some of these sequences in spite of the fact that they could be generated by different types of mutations, as their presence in mutants found on various continents, suggest that these mutations could play a role. These mutants could combine two advantages, that related to the loss of a part of a wild-type protein and that related to the putative advantage conferred by the additional sequences. In addition, in numerous Asian genomes (more than 300 to date) pre-X or pre-pre-S regions were found just upstream to, respectively, the X and the pre-S1 genes. These two regions are translated with their respective genes in frame and recent studies have evidenced the transactivating role of the corresponding proteins. With some exceptions, these regions are genotype- and serotype-specific (C/adr). In addition, these mutants have been found principally in patients with severe hepatitis diseases, for example, hepatocarcinoma in more than one third of the cases. As additional sequences generated by HBV variants may be relevant for viral life cycle, persistence and pathogenesis, further investigations are necessary to give a clearer picture of the subject.

Study of transactivating effect of pre-S2 protein of hepatitis B virus and cloning of genes transactivated by pre-S2 protein with suppression subtractive hybridization

AIM: To investigate the transactivating effect of pre-S2 protein of hepatitis B virus (HBV) and construct a subtractive cDNA library of genes transactivated by pre-S2 protein with suppression subtractive hybridization (SSH) technique, and to pave the way for elucidating the pathogenesis of HBV infection.

METHODS: pcDNA3.1(-)-pre-S2 containing pre-S2 region of HBV genome was constructed by routine molecular methods. HepG2 cells were cotransfected with pcDNA3.1(-)-pre-S2/pSV-lacZ and empty pcDNA3.1(-)/pSV-lacZ. After 48 h, cells were collected and detected for the expression of β-galactosidase (β-gal). SSH and bioinformatics techniques were used, the mRNA of HepG2 cells transfected with pcDNA3.1(-)-pre-S2 and pcDNA3.1(-) empty vector was isolated, respectively, cDNA was synthesized. After digestion with restriction enzyme RsaI, cDNA fragments were obtained. Tester cDNA was then divided into two groups and ligated to the specific adaptor 1 and adaptor 2, respectively. After tester cDNA was hybridized with driver cDNA twice and underwent two times of nested PCR, amplified cDNA fragments were subcloned into pGEM-Teasy vectors to set up the subtractive library. Amplification of the library was carried out with E.coli strain DH5α. The cDNA was sequenced and analyzed in GenBank with Blast search after PCR.

RESULTS: The pre-S2 mRNA could be detected in HepG2 cells transfected with pcDNA3.1(-)-pre-S2 plasmid. The activity of β-gal in HepG2 cells transfected with pcDNA3.1(-)-pre-S2/pSV-lacZ was 7.0 times higher than that of control plasmid (P<0.01). The subtractive library of genes transactivated by HBV pre-S2 protein was constructed successfully. The amplified library contains 96 positive clones. Colony PCR showed that 86 clones contained 200-1 000 bp inserts. Sequence analysis was performed in 50 clones randomly, and the full length sequences were obtained with bioinformatics method and searched for homologous DNA sequence from GenBank, altogether 25 coding sequences were obtained, these cDNA sequences might be the target genes transactivated by pre-S2 protein.

CONCLUSION: The pre-S2 protein of HBV has transactivating effect on SV40 early promoter. The obtained sequences may be target genes transactivated by pre-S2 protein among which some genes coding proteins involved in cell cycle regulation, metabolism, immunity, signal transduction and cell apoptosis.This finding brings some new clues for studying the biological functions of pre-S2 protein and further understanding of HBV hepatocarcinogesis.

NACA as a potential cellular target of hepatitis B virus preS1 protein

The mechanisms of the attachment and penetration of hepatitis B virus remain obscure. It has been demonstrated that the preS1 region is essential for viral assembly and infectivity, however, as its cellular receptor has still not been identified unequivocally, we used a yeast two-hybrid system to screen the cellular proteins that can interact with preS1 protein. The protein recovered from a human liver cDNA library was nascent polypeptide-associated complex alpha polypeptide. The interaction between preS1 and nascent polypeptide-associated complex alpha polypeptide was verified by mating experiment and coimmunoprecipitation of COS7 cell lysates expressing both proteins. Based on these results, we speculate that nascent polypeptide-associated complex alpha polypeptide is a functional target of hepatitis B virus preS1 protein in cells.

Viral hepatitis and hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors in the world. The incidence of HCC varies considerably with the geographic area because of differences in the major causative factors. Chronic hepatitis B and C, mostly in the cirrhotic stage, are responsible for the great majority of cases of HCC worldwide. The geographic areas at the highest risk are South-East Asia and sub-Saharan Africa, here hepatitis B is highly endemic and is the main cause of HCC. In areas with an intermediate rate of HCC such as Southern Europe and Japan, hepatitis C is the predominant cause, whereas in low rate areas such as Northern Europe and the USA, HCC is often related to other factors as alcoholic liver disease. There is a rising incidence in HCC in developed countries during the last two decades, due to the increasing rate of hepatitis C infection and improvement of the clinical management of cirrhosis.

METHODS

This article reviews the literature on hepatitis and hepatocellular carcinoma. The Medline search was carried out using these key words and articles were selected on epidemiology, risk factors, screening, and prevention of hepatocellular carcinoma.

RESULTS

Screening of patients with advanced chronic hepatitis B and C with hepatic ultrasound and determination of serum alfa-fetoprotein may improve the detection of HCC, but further studies are needed whether screening improves clinical outcome. Hepatitis B and C viruses (HBV/HCV) can be implicated in the development of HCC in an indirect way, through induction of chronic inflammation, or directly by means of viral proteins or, in the case of HBV, by creation of mutations by integration into the genome of the hepatocyte.

CONCLUSION

The most effective tool to prevent HCC is avoidance of the risk factors such as viral infection. For HBV, a very effective vaccine is available. Preliminary data from Taiwan indicate a protective effect of universal vaccination on the development of HCC. Vaccination against HBV should therefore be a health priority. In patients with chronic hepatitis B or C, interferon-alfa treatment in a noncirrhotic stage is protective for HCC development in responders, probably by prevention of cirrhosis development. When cirrhosis is already present, the protective effect is less clear. For cirrhosis due to hepatitis B, a protective effect was demonstrated in Oriental, but not in European patients. For cirrhosis due to hepatitis C, interferon-alfa treatment showed to be protective in some studies, especially in Japan with a high incidence of HCC in untreated patients. Virological, but also merely biochemical response, seems to be associated with a lower risk of development of HCC. As most studies are not randomized controlled trials, no definitive conclusions on the long-term effects of interferon-alfa in HBV or HCV cirrhosis can be established. Especially in hepatitis C, prospective studies should be performed using the more potent reference treatments for cirrhotics, namely the combination of peginterferon and ribavirin.

Expression and immunoactivity of chimeric particulate antigens of receptor binding site-core antigen of hepatitis B virus

AIM: To improve the immunogenicity of receptor binding site of hepatitis B virus (HBV) on preS1 antigen using HBV core antigen as an immuno-carrier.

METHODS: One to 6 tandem copies of HBV preS1 (21-47) fragment were inserted into HBcAg at the sites of aa 78 and 82, and expressed in E.coli. ELISA, Western blot and animal immunization were used to analyze the antigenicity and immmunogenicity of purified particulate antigens. The ability to capture HBV by antibodies elicited by chimeric particles was detected with immuno-capture PCR.

RESULTS: Recombinant antigens CI, CII, CIII carrying 1-3 copies of HBV preS1 (21-47) individually could form virus-like particles (VLPs), similar to HBcAg in morphology. But recombinant antigens carrying 4-6 copies of HBV preS1 (21-47) were poorly expressed in E.coli. Chimeric antigens were lacking of immunoreactivity with anti-HBc monoclonal antibodies (McAbs), but still reserved good immunoreactivity with anti-HBe McAbs. CI, CII, CIII could strongly react with anti-preS1 McAb, suggesting that preS1 (21-47) fragment was well exposed on the surface of chimeric VLPs. Three chimeric VLP antigens (CI, CII and CIII) could stimulate mice to produce high-level antibody responses, and their immunogenicity was stronger than non-particulate antigen 21-47*6, containing 6 copies of preS1 (21-47). Mouse antibodies to CI, CII and CIII were able to capture HBV virions in immuno-capture PCR assay in vitro.

CONCLUSION: Chimeric particulate antigens of receptor binding site-core antigen of HBV can elicit strong antibody responses to preS1. They have a potential to be developed into prophylactic or therapeutic vaccines against HBV infection.

Genotype C of hepatitis B virus can be classified into at least two subgroups

A genomic characterization of hepatitis B virus (HBV) was done for 56 pre-S1/pre-S2 genes and 10 full-length HBV genotype C isolates from five Asian countries. Phylogenetic analysis of the pre-S1/pre-S2 genes revealed two major groups within genotype C: one for isolates from southeast Asia including Vietnam, Myanmar and Thailand (named HBV/C1) and the other for isolates from Far East Asia including Japan, Korea and China (named HBV/C2). This finding was confirmed by phylogenetic analysis based on the full-length sequence of 32 HBV genotype C isolates, including 22 from database entries. Two isolates from Okinawa, the island off the southern end of Japan, formed a different branch. Specific amino acid sequence changes were identified in the large S protein (amino acids 51, 54, 60, 62 and 73) and P protein (amino acids 231, 233, 236, 248, 252 and 304). Our results indicate that genotype C of HBV can be classified into at least two subgroups.

High prevalence of hepatitis B virus pre-s mutant in countries where it is endemic and its relationship with genotype and chronicity

It has been reported that hepatitis B virus (HBV) mutants carrying mutations in the pre-S region can be found in infected patients. In this study, we investigated the prevalence of the HBV variant with the pre-S mutant in different geographic regions, including countries with low and high levels of endemic HBV infection, and analyzed the correlation with clinical findings. We examined 387 HBV DNA-positive serum samples from individuals among 12 countries, consisting of Vietnam, Myanmar, Thailand, China, Korea, Nepal, Japan, Russia, Spain, United States, Bolivia, and Ghana. HBV pre-S mutants were detected in 71 (18.3%) of 387 serum samples tested. This mutant was the most prevalent in Vietnam (36%), followed by Nepal (27.3%), Myanmar (23.3%), China (22.4%), Korea (14.3%), Thailand (10.5%), Japan (7.7%), and Ghana (4.3%). In contrast, no case with this mutation was found in Russia, Spain, United States, and Bolivia. Among the HBV deletion mutations, 15.5% (11 of 71) occurred in the pre-S1 and 46.5% (33 of 71) in the pre-S2 regions. Eight (11.3%) cases had a mutation in both the pre-S1 and pre-S2 regions. In addition, a point mutation at the pre-S2 starting codon was observed in 19 (26.7%) cases. The detection rate of the HBV mutant in patients with hepatocellular carcinoma was significantly higher than in other patients (P < 0.05). Furthermore, these mutants were found more frequently in genotype B (25%) and genotype C (24.5%) than in the other genotypes (P < 0.05). Our results indicated that there was a high prevalence of HBV pre-S mutation in regions of endemic HBV infection in Asia. Furthermore, the pre-S mutation appeared to be correlated with hepatocellular carcinoma and HBV genotypes.

Genes trans-regulated by a novel hepatitis B virus preS2 antigen binding protein S2-29 by cDNA microarray

AIM: To study the biological functions of a novel hepatitis B virus preS2 antigen binding protein S2-29, and to analyze the gene expression profiles of HepG2 cell transfected with S2-29 gene.

METHODS: S2-29 gene was screened and identified by using yeast two-hybrid system 3 and coimmunoprecipita-tion technique. Full-length encoding frame S2-29 and its amino acid sequences were identified by using bioinformatics method and the recombined eukaryotic expression plasmid pcDNA3.1(-)-S2-29 was constructed and transfected into HepG2 cells. Total mRNA was isolated from the HepG2 cells transfected with pcDNA3.1(-) and pcDNA3.1(-)-S2-29, respectively. cDNA microarray was employed for detecting and analysing of mRNA from the HepG2 cells.

RESULTS: S2-29 cDNA sequence was obtained and identified by yeast two-hybrid screening and the bioinformatics analysis. Among 1 152 genes, there were 10 differences, of which 9 genes were upregulated and 1 gene were downregulated in HepG2 cells transfected with S2-29 protein expression plasmid. These genes differentially down-regulated by S2-29 protein included eukaryotic translation elongation factor 2, MAP-kinase activating death domain, glutathione peroxidase 5, gelsolin-like capping protein (actin filament), NDRG family member 2, prosaposin, SUMO-1 activating enzyme subunit 1, insulin receptor and a novel protein.

CONCLUSION: Microarray technique is successfully used to screen the genes trans-regulated by S2-29, which brings some new clues for studying the trans-regulation and biological function of S2-29.

Different types of ground glass hepatocytes in chronic hepatitis B virus infection contain specific pre-S mutants that may induce endoplasmic reticulum stress

Ground glass hepatocyte (GGH) represents a histological hallmark of chronic hepatitis B virus infection and contains surface antigens in the endoplasmic reticulum (ER). Several types of GGHs are recognized at different hepatitis B virus replicative stages. The recent identification of pre-S mutants from GGHs encourages us to investigate whether different GGHs may harbor specific mutants and exhibit differential biological activities. In this study, we applied laser capture microdissection to isolate specific GGHs from a total of 50 samples on eight resected liver specimens. The surface genes in two major types of GGHs were analyzed. Type I GGHs expressed an inclusion-like pattern of hepatitis B surface antigens and harbored mutants with deletions over pre-S1 region, whereas type II GGHs, distributed in clusters and emerged at late replicative phase, contained mutants with deletions over pre-S2 region that defines a cytotoxic T lymphocyte (CTL) immune epitope, and may represent an immune escape mutant. Transfection of pre-S mutants in Huh7 revealed decreased syntheses of middle and small S proteins with accumulation of large surface antigen in ER, which in turn led to the activation of ER stress response with differential activities for different mutants. This study therefore demonstrates that different GGHs may contain specific mutants and exhibit differential biological activities.

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.

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Characterization of two hepatitis B virus populations isolated from a hepatitis B surface antigen-negative patient

In a study of surface antigen-negative, but weakly hepatitis B virus (HBV) DNA-positive, patients, we were able to amplify and clone whole HBV genomes from the serum of a cirrhotic patient. Sequencing showed that the patient harbored two different HBV populations, one of genotype A and the other of genotype D, with the genotype D genome apparently predominating. The surface antigen of the genotype A virus is heavily mutated, especially in the extracellular << determinant a >> region, with several mutations that have not been previously described. The genotype D virus is a precore mutant. Both genomes possess the common A1762T-G1764A double mutation of the basal core promoter (BCP), and the genotype D virus is also mutated in the << TATA box >> of the large surface antigen promoter. Biological characterization showed that the genotype A genome was fully replication-competent, whereas the genotype D genome replicated poorly. The small surface antigen of the genotype A virus was only very weakly recognized by commercial tests. The small surface antigen of the genotype D virus could be recognized by the tests, but it was mainly retained within transfected cells, probably because of an excess of large surface antigen. In conclusion, the cryptic nature of this double HBV infection is characterized by the predominance of the replication-deficient genotype D virus over the replication-competent genotype A virus.

Detection of anti-preS1 antibodies for recovery of hepatitis B patients by immunoassay

AIM: To establish a convenient immunoassay method based on recombinant antigen preS1(21-119 aa) to detect anti-preS1 antibodies and evaluate the clinical significance of antibodies in hepatitis B.

METHODS: The expression plasmid pET-28a-preS1 was constructed, and a large quantity of preS1(21-119 aa) fragment of the large HBsAg protein was obtained. The preS1 fragment purified by Ni²⁺-IDA affinity chromatography was used as coated antigen to establish the indirect ELISA based on streptavidin-biotin system for detection of the anti-preS1 antibodies in sera from HBV-infected patients. For follow-up study, serial sera were collected during the clinical course of 21 HBV-infected patients and anti-preS1 antibodies, preS1 antigen, HBV-DNA and other serological HBV markers were analyzed.

RESULTS: preS1(21-119 aa) fragment was highly expressed from the plasmid pET-28a-preS1 in a soluble form in E. coli (30 mg•L⁻¹), and easily purified to high purity over 90% by one step of Ni²⁺-IDA-sepharose 6B affinity chromatography. The purity and antigenicity of the purified preS1(21-119 aa) protein was determined by 150 g•L⁻¹ SDS-PAGE, Western blot and a direct ELISA. Recombinant preS1(21-119 aa) protein was successfully applied in the immunoassay which could sensitively detect the anti-preS1 antibodies in serum specimens of acute or chronic hepatitis B patients. Results showed that more than half of 19 acute hepatitis B patients produced anti-preS1 antibodies during recovery of the disease, however, the response was only found in a few of chronic patients. In the clinical follow-up study of 11 patients with anti-preS1 positive serological profile, HBsAg and HBV-DNA clearance occurred in 6 of 10 acute hepatitis B patients in 5-6 mo, and seroconversion of HBeAg and disappearance of HBV-DNA occurred in 1 chronic patients treated with lavumidine, a antiviral agent.

CONCLUSION: The high-purity preS1(21-119 aa) coated antigen was successfully prepared by gene expression and affinity chromatography. Using this antigen, a conveniently detective system of anti-preS1 antibodies in sera was established. Preliminarily clinical trial the occurrence of anti-preS1 antibodies in acute hepatitis B patients suggests the clearance of HBV from serum in a short-term time, and anti-preS1 positive in chronic patients means health improvement or recovery from the disease.

Selection of hepatitis B virus polymerase mutants with enhanced replication by lamivudine treatment after liver transplantation

BACKGROUND & AIMS

Lamivudine has become a main therapeutic option for treating hepatitis B virus (HBV) infection. Although drug resistance develops, the clinical course after selection of antiviral-resistant HBV mutants seems to be benign. However, we observed a severe clinical course of hepatitis B infection in several liver transplant recipients after the emergence of lamivudine resistance. This was associated with high viral load in the blood.

METHODS

In this report, we characterize the molecular mechanisms underlying drug-dependent enhanced replication of particular lamivudine-resistant HBV mutants selected in these patients, which were associated with sudden onset of liver failure.

RESULTS

The clinical course was characterized by a sudden rise in serum bilirubin, prothrombin time, and transaminase. HBV sequence analysis of these patients revealed both mutations in the "a-determinant" of the envelope and the YMDD (tyrosine, methionine, aspartate, aspartate) motif (domain C) of the polymerase protein. Transfection experiments with replication competent vectors indicated that the "a-determinant" changes were not associated with resistance, whereas mutations in the YMDD motif conferred resistance to lamivudine. More importantly, combinations of mutations in the "a-determinant" and the YMDD motif in patients with a severe hepatitis were not only resistant to lamivudine treatment, but showed enhanced replication in vitro in the presence of lamivudine. This observation was confirmed in separate laboratories.

CONCLUSIONS

Severe and fatal hepatitis B infection can occur during lamivudine therapy and may be associated with certain HBV mutants selected during sequential nucleoside and HBIg treatment. The lamivudine-enhanced replication shown by these mutants suggests that continuation of therapy with lamivudine could be deleterious in some patients.

Pathology of the liver

At the close of the 20th century, a selection of articles published in 1999 with relevance to liver pathology reflects the wealth of technological and intellectual progress made during the span of the century. Immunohistochemical staining for hepatitis B virus antigens focused attention on a correlation between cytoplasmic expression of core antigen in individuals with precore mutants and higher activity of hepatitis. Infection of ducklings with a presurface mutant strain of duck hepatitis B virus produced cytopathic liver cell damage. Fibrosing cholestatic hepatitis, originally described as an unusual form of recurrent hepatitis B after liver transplantation, has now been described in hepatitis C virus-positive patients with renal transplants. It may be related to the emergence or selection of hepatitis C virus quasispecies. In biliary tract disease, researchers investigated the canal of Hering as a possible source of hepatic stem cells, sporadic mutations in the JAGGED1 gene (involved in cell differentiation) in Alagille syndrome, and several models of nonsuppurative destructive cholangitis. Further work was accomplished on nonalcoholic steatohepatitis, including a proposal of a grading and staging system as well as its detection in workers exposed to volatile petrochemicals. Among hepatic neoplasms and proliferative disorders, epithelioid hemangioendothelioma, angiomyolipoma and Langerhans' cell histiocytosis received coverage in articles describing the diagnostic pathology in collected series of patients.