A precore-defective mutant of hepatitis B virus associated with e antigen-negative chronic liver disease

Hepatitis B Virus Precore Protein p22 Inhibits Alpha Interferon Signaling by Blocking STAT Nuclear Translocation

Antagonism of host immune defenses against hepatitis B virus (HBV) infection by the viral proteins is speculated to cause HBV persistence and the development of chronic hepatitis. The circulating hepatitis B e antigen (HBeAg, p17) is known to manipulate host immune responses to assist in the establishment of persistent viral infection, and HBeAg-positive (HBeAg+) patients respond less effectively to IFN-α therapy than do HBeAg-negative (HBeAg-) patients in clinical practice. However, the function(s) of the intracellular form of HBeAg, previously reported as the precore protein intermediate (p22) without the N-terminal signal peptide, remains elusive. Here, we report that the cytosolic p22 protein, but not the secreted HBeAg, significantly reduces interferon-stimulated response element (ISRE) activity and the expression of interferon-stimulated genes (ISGs) upon alpha interferon (IFN-α) stimulation in cell cultures. In line with this, HBeAg+ patients exhibit weaker induction of ISGs in their livers than do HBeAg- patients upon IFN-α therapy. Mechanistically, while p22 does not alter the total STAT1 or pSTAT1 levels in cells treated with IFN-α, it blocks the nuclear translocation of pSTAT1 by interacting with the nuclear transport factor karyopherin α1 through its C-terminal arginine-rich domain. In summary, our study suggests that HBV precore protein, specifically the p22 form, impedes JAK-STAT signaling to help the virus evade the host innate immune response and, thus, causes resistance to IFN therapy.IMPORTANCE Chronic hepatitis B virus (HBV) infection continues to be a major global health concern, and patients who fail to mount an efficient immune response to clear the virus will develop a life-long chronic infection that can progress to chronic active hepatitis, cirrhosis, and primary hepatocellular carcinoma. There is no definite cure for chronic hepatitis B, and alpha interferon (IFN-α) is the only available immunomodulatory drug, to which only a minority of chronic patients are responsive, with hepatitis B e antigen (HBeAg)-negative patients responding better than HBeAg-positive patients. We herein report that the intracellular HBeAg, also known as precore or p22, inhibits the antiviral signaling of IFN-α, which sheds light on the enigmatic function of precore protein in shaping HBV chronicity and provides a perspective toward areas that need to be further studied to make the current therapy better until a cure is achieved.

RNA Exosome Complex Regulates Stability of the Hepatitis B Virus X-mRNA Transcript in a Non-stop-mediated (NSD) RNA Quality Control Mechanism

Hepatitis B virus (HBV) is a stealth virus, minimally inducing the interferon system required for efficient induction of both innate and adaptive immune responses. However, 90% of acutely infected adults can clear the virus, suggesting the presence of other, interferon-independent pathways leading to viral clearance. Given the known ability of helicases to bind viral nucleic acids, we performed a functional screening assay to identify helicases that regulate HBV replication. We identified the superkiller viralicidic activity 2-like (SKIV2L) RNA helicase (a homolog of the Saccharomyces cerevisiae Ski2 protein) on the basis of its direct and preferential interaction with HBV X-mRNA. This interaction was essential for HBV X-mRNA degradation at the RNA exosome. The degradation of HBV X-mRNA at the RNA exosome was also mediated by HBS1L (HBS1-like translational GTPase) protein, a known component of the host RNA quality control system. We found that the redundant HBV-precore translation initiation site present at the 3'-end of HBV X-mRNA (3' precore) is translationally active. The initiation of translation from this site without a proper stop codon was identified by the non-stop-mediated RNA decay mechanism leading to its degradation. Although 3' precore is present in the five main HBV-RNA transcripts, only X-mRNA lacks the presence of an upstream start codons for large, middle, and small (L, M, and S) HBV surface proteins. These upstream codons are in-frame with 3' precore translation initiation site, blocking its translation from the other HBV-mRNA transcripts. To our knowledge, this is the first demonstration of the anti-viral function of the non-stop-mediated RNA decay mechanism.

Critical role of the 36-nucleotide insertion in hepatitis B virus genotype G in core protein expression, genome replication, and virion secretion

Frequent coinfection of hepatitis B virus genotype G with genotype A suggests that genotype G may require genotype A for replication or transmission. In this regard, genotype G is unique in having a 12-amino-acid extension in the core protein due to a 36-nucleotide insertion near the core gene translation initiation codon. The insertion alters base pairing in the lower stem of the pregenome encapsidation signal, which harbors the core gene initiator, and thus has the potential to affect both core protein translation and pregenomic RNA encapsidation. Genotype G is also unusual for possessing two nonsense mutations in the precore region, which together with the core gene encode a secreted nonstructural protein called hepatitis B e antigen (HBeAg). We found that genotype G clones were indeed incapable of HBeAg expression but were competent in RNA transcription, genome replication, and virion secretion. Interestingly, the 36-nucleotide insertion markedly increased the level of core protein, which was achieved at the level of protein translation but did not involve alteration in the mRNA level. Consequently, the variant core protein was readily detectable in patient blood. The 12-amino-acid insertion also enhanced the genome maturity of secreted virus particles, possibly through less efficient envelopment of core particles. Cotransfection of genotypes G and A did not lead to mutual interference of genome replication or virion secretion. Considering that HBeAg is an immunotolerogen required for the establishment of persistent infection, its lack of expression rather than a replication defect could be the primary determinant for the rare occurrence of genotype G monoinfection.

In vitro study of the effects of precore and lamivudine-resistant mutations on hepatitis B virus replication

Understanding the consequences of mutation in the hepatitis B virus (HBV) genome on HBV replication is critical for treating chronic HBV infection. In this study, HBV replication in HepG2 cells initiated by transduction with precore (PC), rtM204I, and wild-type (wt) HBV recombinant baculoviruses was compared. The pattern and magnitude of HBV replication initiated by the PC HBV recombinant baculovirus were similar to those observed for wt HBV throughout the time course examined. In contrast, when the rtM204I mutation was introduced into wt HBV, by day 10 postinfection the levels of intra- and extracellular HBV DNA were markedly reduced compared to those for wt HBV. Although the rtM204I mutation reduced the production of HBV replicative intermediates, no effect on the level of covalently closed circular DNA or HBV transcripts was observed at late time points. Coinfection studies with different ratios of wt and rtM204I baculoviruses showed that the rtM204I variant did not produce a product that inhibited HBV replication. However, the combination of the wt and rtM204I baculoviruses yielded HBV DNA levels at late time points that were greater than those for the wt alone, suggesting that wt polymerase may function in trans to boost rtM204I replication. We concluded that the rtM204I mutation generates a polymerase that is not only resistant to lamivudine but also replicates nucleic acids to lower levels in vitro.

Occult hepatitis B virus infection in chronic liver disease: full-length genome and analysis of mutant surface promoter

BACKGROUND AND AIMS

Genome sequence of hepatitis B virus (HBV) from occult chronic infection is scarce. Fifty-six (9.4%) of 591 patients seronegative for hepatitis B surface antigen (HBsAg) with chronic liver disease were positive for HBV DNA. The complete HBV genome from 9 of these patients (S1-S9) and 5 controls positive for HBsAg (SWT.1-SWT.5) were analyzed.

METHODS

Overlapping genome fragment amplification, cloning, and sequencing was performed on these cases. Functional analysis of surface promoter was conducted using fusion construct.

RESULTS

All patients with occult infection except one (S8) had a low viral titer. Eight patients had infection with genotype A (S1-S5, SWT.1-2, SWT.5) and 6 had infection with genotype D (S6-S9, SWT.3-4). S4 and S5.1 of genotype A had the characteristic nucleotide deletions in core and pre-S1 region seen in genotype D. The major observations in patients with occult HBV infection were as follows: frequent quasispecies variation, deletions in pre-S2/S region affecting the surface promoters (nt 3025-54) and pre-S protein (S3, S5, S6, S8), truncated precore (S6, S8, S7.1) and core (S9) owing to stop signal, alternate start codon for the Polymerase gene (S3, S9), and YMDD mutation (S1, S4, S9) in patients not on antiviral therapy. HBsAg and core proteins could be shown immunohistochemically in 3 of 5 liver biopsy specimens available. The mutant surface promoters (pre-S2 and S) on functional analysis showed alterations in HBsAg expression.

CONCLUSIONS

These changes in the regulatory region with possible alterations in the ratio of large and small surface proteins along with other mutations in the genome may decrease the circulating HBsAg level synergistically, making the immunodetection in serum negative.

Hepatitis B virus: prevalence of precore/core promoter mutants in different clinical categories of Indian patients

To determine the association of precore (Pre-C)/basal core promoter (BCP) mutants with clinical outcome of hepatitis B in Western India, 192 hepatitis B virus (HBV) infected individuals were investigated. HBV-DNA PCR positivity among asymptomatic hepatitis B surface antigen (HBsAg) positive carriers (61/100) was lower (P < 0.0001) than chronic hepatitis B (CHB), acute (P = 0.0001), and fulminant hepatitis B patients (P = 0.047). Pre-C status was based on restriction fragment length polymorphism (RFLP, n = 153) and sequencing (n = 118). Prevalence of Pre-C mutants was higher among carriers (23/61) than CHB (10/62, P = 0.0071) or acute (3/22; P = 0.037) patients. Children from carrier and CHB categories showed significantly higher circulation of Pre-C-wild than mutant HBV. Clinical manifestations were independent of BCP mutations (1762/64-T/A). Hepatitis B e antigen (HBeAg) negative CHB patients [62.5% (15/24)] were circulating wild HBV. Higher HBV-DNA levels were associated with chronic hepatitis and HBeAg positivity, whilst Pre-C mutant positives had lower levels. BCP mutations did not affect HBV-DNA levels. Multivariate regression analysis identified HBeAg (OR = 4.3) and Pre-C mutants (OR = 3.1) to be associated with chronic hepatitis and carriers respectively. In a separate sub-set analysis (n = 59), HBV-DNA level was identified as the only variable. In conclusion, chronic or fulminant hepatitis B was not associated with Pre-C or BCP mutants and switching over to Pre-C mutant was beneficial for the infected individual in maintaining disease free status for extended periods.

Molecular, immunological and clinical properties of mutated hepatitis B viruses

Hepatitis B virus (HBV) is at the origin of severe liver diseases like chronic active hepatitis, liver cirrhosis and hepatocellular carcinoma. There are some groups of patients with high risk of generation of HBV mutants: infected infants, immunosuppressed individuals (including hemodialysis patients), patients treated with interferon and lamivudine for chronic HBV infection. These groups are the target for molecular investigations reviewed in this paper. The emergence of lamivudine- or other antiviral-resistant variants, rises concern regarding long term use of these drugs. Infection or immunization with one HBV subtype confers immunity to all subtypes. However, reinfection or reactivation of latent HBV infection with HBV mutants have been reported in patients undergoing transplant and those infected with HIV. Mutations of the viral genome which are not replicative incompetent can be selected in further course of infection or under prolonged antiviral treatment and might maintain the liver disease. Four open reading frames (ORF) which are called S-gene, C-gene, X-gene and P-gene were identified within the HBV genome. Mutations may affect each of the ORFs. Mutated S-genes were described to be responsible for HBV-infections in successfully vaccinated persons, mutated C-genes were found to provoke severe chronic liver diseases, mutated X-genes could cause serious medical problems in blood donors by escaping the conventional test systems and mutated P-genes were considered to be the reason for chemotherapeutic drug resistance. This paper reviews molecular, immunological and clinical aspects of the HBV mutants.

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.

High-throughput quantitative analysis of hepatitis B virus DNA in serum using the TaqMan fluorogenic detection system

Reproducible quantitative assays to detect viral nucleic acids have proven useful in defining disease progression and following response to therapy in a wide variety of viral infections. We describe the development of a quantitative assay to detect hepatitis B virus (HBV) DNA using real-time fluorescent-probe polymerase chain reaction (PCR) (TaqMan). The assay is highly reproducible, highly automated, and much more sensitive than the currently used branched-chain DNA (bDNA) assay for HBV. The quantitative PCR assay accurately detected samples ranging from 10 to 10(9) copies of HBV DNA per milliliter. Of 157 serum samples submitted for HBV quantitation, 119 were positive by TaqMan PCR versus only 55 by bDNA (P <.001). All 55 bDNA-positives were positive by TaqMan. Of the 77 samples with detectable HBV-DNA titers below 3.75 x 10(5) copies by TaqMan, only 13 were detected by bDNA. We tested 119 patients negative for all HBV serologic markers, and all tested negative in the TaqMan assay. HBV DNA was detected by TaqMan in 164 of 195 (84%) of hepatitis B surface antigen (HBsAg)-positive samples. Among hepatitis B e antigen (HBeAg)-positive samples, median titers were 4. 3 x 10(6) copies/mL versus 322 copies/mL in HBeAg-negative samples (P =.012). The TaqMan assay for HBV DNA is highly sensitive and reproducible and thus appears useful in accurately defining levels of viral replication among persons with HBV infection.

Comparison of the nucleic acid-based crosslinking hybridization assay and the branched DNA signal amplification assay in the quantitative measurement of serum hepatitis B virus DNA

Quantitative measurement of hepatitis B virus (HBV) DNA has become important in the clinical diagnosis of patients with chronic hepatitis B, especially in patients with hepatitis B e antigen (HBeAg)-negative precore mutant and in patients who received treatment with interferon or antiviral agents. Two different hybridization assays for quantitative measurement of HBV DNA: Naxcor crosslinking assays and Chiron branched DNA signal amplification (bDNA) assay, were applied to 158 serum samples which were positive for HBV DNA by polymerase chain reaction. Among 158 serum samples, 135 samples (85.4%) were positive by the crosslinking assay and 129 samples (81.6%) were positive by the bDNA assay in the quantification of serum HBV DNA (P > 0.05). Serum HBV DNA levels obtained from both assays showed a good linear correlation (r = 0.91, P < 0.001). The sensitivity of both assays in HBeAg-positive samples was 90.5%, significantly higher than in HBeAg-negative samples (69.6% for the crosslinking assay and 56.5% for the bDNA assay, P < 0.05). In HBeAg-negative patients with elevated serum alanine transaminase levels, the so-called precore HBV mutant, the detection sensitivity for HBV DNA was better in the crosslinking assay (83%) than in the bDNA assay (61%). The crosslinking assay was less time consuming than the bDNA assay in performing the measurement of serum HBV DNA (6 hours vs. 20 hours). In conclusion, Naxcor crosslinking hybridization assay was equally as sensitive as Chiron bDNA assay in the quantitative measurement of serum HBV DNA. Less time-consuming procedures and better sensitivity in the detection of HBeAg-negative samples with elevated serum alanine transaminase levels may favor the clinical use of the crosslinking assay.

Comparison of the nucleic acid-based crosslinking hybridization assay and the branched DNA signal amplification assay in the quantitative measurement of serum hepatitis B virus DNA

Quantitative measurement of hepatitis B virus (HBV) DNA has become important in the clinical diagnosis of patients with chronic hepatitis B, especially in patients with hepatitis B e antigen (HBeAg)-negative precore mutant and in patients who received treatment with interferon or antiviral agents. Two different hybridization assays for quantitative measurement of HBV DNA: Naxcor crosslinking assays and Chiron branched DNA signal amplification (bDNA) assay, were applied to 158 serum samples which were positive for HBV DNA by polymerase chain reaction. Among 158 serum samples, 135 samples (85.4%) were positive by the crosslinking assay and 129 samples (81.6%) were positive by the bDNA assay in the quantification of serum HBV DNA (P > 0.05). Serum HBV DNA levels obtained from both assays showed a good linear correlation (r = 0.91, P < 0.001). The sensitivity of both assays in HBeAg-positive samples was 90.5%, significantly higher than in HBeAg-negative samples (69.6% for the crosslinking assay and 56.5% for the bDNA assay, P < 0.05). In HBeAg-negative patients with elevated serum alanine transaminase levels, the so-called precore HBV mutant, the detection sensitivity for HBV DNA was better in the crosslinking assay (83%) than in the bDNA assay (61%). The crosslinking assay was less time consuming than the bDNA assay in performing the measurement of serum HBV DNA (6 hours vs. 20 hours). In conclusion, Naxcor crosslinking hybridization assay was equally as sensitive as Chiron bDNA assay in the quantitative measurement of serum HBV DNA. Less time-consuming procedures and better sensitivity in the detection of HBeAg-negative samples with elevated serum alanine transaminase levels may favor the clinical use of the crosslinking assay.

Molecular biological xxxmethods in diagnosis and treatment of liver diseases

Molecular biology is making a tremendous impact on the diagnosis and treatment of liver diseases. Methods such as the polymerase chain reaction are changing the way physicians diagnose and monitor patients with viral hepatitis. Assays based on recombinant protein antigens allow for detection of specific autoantibodies in diseases such as primary biliary cirrhosis. The diagnosis of inherited metabolic diseases, such as hemochromatosis and Wilson disease, is being revolutionized by discovery of the defective genes involved and the development of methods to rapidly sequence DNA and identify mutations. Treatments and preventive measures are now possible with use of drugs and vaccines produced by recombinant DNA technology. Gene therapy and nucleic acid-based therapeutics are also realistic future treatment options for individuals with liver diseases.

Transmission of hepatitis B to patients from four infected surgeons without hepatitis B e antigen

BACKGROUND

Transmission of hepatitis B virus (HBV) to patients by infected surgeons who carry hepatitis B e antigen (HBeAg) has been documented repeatedly. In the United Kingdom HBeAg-positive surgeons are not permitted to perform certain procedures that carry a risk that patients might be exposed to the blood of a health care worker. There are no practice restrictions for carriers of hepatitis B surface antigen without detectable HBeAg, unless transmission has been demonstrated.

METHODS

In four unconnected cases of acute hepatitis B, surgery was identified as a possible source, so we tested the surgical teams for serologic markers of HBV infection. In each case a surgeon was found to be infected with the virus. HBV DNA was amplified by a nested polymerase chain reaction from serum from the four infected surgeons and the four patients, and direct nucleotide sequencing of two regions of the HBV genome was performed. Alternative sources of infection were ruled out. Other patients on whom three of the surgeons had recently performed procedures were offered testing.

RESULTS

All four surgeons were carriers of HBV, but none had detectable serum HBeAg. The nucleotide sequences of HBV DNA from the surgeons were indistinguishable from those from the corresponding patients. The screening of other exposed patients identified at least two other patients who had probably acquired hepatitis B infection from one of these surgeons.

CONCLUSIONS

Surgeons who are carriers of HBV without detectable serum HBeAg can transmit HBV to patients during procedures.

Comparison of three different hybridization assays in the quantitative measurement of serum hepatitis B virus DNA

The measurement of hepatitis B virus (HBV) DNA, is important for monitoring and evaluating the efficacy of anti-viral agents in the treatment of patients with chronic hepatitis B. Three different hybridization assays for quantitative measurement of HBV DNA: direct membrane (dot-blot) hybridization, liquid hybridization (Abbott HBV DNA assay) and branched DNA signal amplification assay (Quantiplex, Chiron), were applied to 114 serial serum samples obtained from 13 patients with chronic active hepatitis B who had received ribavirin 600 mg daily for four weeks. Among the three assays, the correlation was found to be highest between Quantiplex and Abbott HBV DNA assay (r = 0.71, p < 0.01), moderate between Quantiplex and dot-blot hybridization (r = 0.58, p < 0.01) and lowest between dot-blot hybridization and Abbott HBV DNA assay (r = 0.27, p < 0.01). Quantiplex detected 107 (94%) of 114 specimens and was the most sensitive assay. All specimens positive by dot-blot hybridization and Abbott HBV DNA assays were detected positive by Quantiplex. The Dot-blot hybridization assay detected all 89 (100%) specimens with a high HBV DNA level (> or = 10 million genome equivalent (Meq)/ml by Quantiplex), but detected only 7 (50%) of 14 specimens with a low HBV DNA level (< 10 Meq/ml). The Abbott HBV DNA assay detected 85 (95%) of 89 specimens with a high HBV DNA level, but detected only 3 (17%) of 18 specimens with a low HBV DNA level. Among 7 negative specimens in the Quantiplex assay, 2 were detected positive by polymerase chain reaction. In conclusion, Quantiplex assay was more sensitive than Abbott HBV DNA assay and dot-blot hybridization assay for quantitative measurement of serum HBV DNA and can be used in the evaluation of the therapeutic drug effect on chronic hepatitis B patients.

A novel method for efficient amplification of whole hepatitis B virus genomes permits rapid functional analysis and reveals deletion mutants in immunosuppressed patients

Current knowledge of hepatitis B virus (HBV) sequence heterogeneity is based mainly on sequencing of amplified subgenomic HBV fragments. Here, we describe a method which allows sensitive amplification and simplified functional analysis of full-length HBV genomes with or without prior cloning. By this method, a large number of HBV genomes were cloned from sera of six immunosuppressed kidney transplant patients. Two size classes of HBV genomes, one 3.2 kb and another about 2.0 kb in size, were found in all patients. The genome population from one serum sample was studied in detail by size analysis of subgenomic PCR fragments and sequencing. Regions with deletions and insertions were mapped in the C gene and pre-S region. Up to 100% of HBV genomes in all other immunosuppressed patients also had deletions in the C gene. Our results demonstrate the potential of the established method for the structural and functional characterization of heterogeneous populations of complete virion-encapsidated HBV DNAs and suggest that HBV genomes with C gene deletions can have a selective advantage in immunosuppressed patients.

Contribution of HEV and HCV in causing fulminant non-A, non-B hepatitis in western India

During 1990, 38 patients with fulminant non-A, non-B hepatitis (NANB) died in Government Medical College Hospital, Aurangabad. Serum samples from these patients were tested for antibodies to hepatitis C virus (anti-HCV) and IgM antibodies to hepatitis E virus (IgM-anti-HEV). All samples were also subjected to polymerase chain reaction (PCR) for the detection of HBV DNA, HCV RNA and HEV RNA. None of the patients had circulating anti-HCV antibodies; three had HCV RNA. Based on anti-HEV-IgM positivity 14 patients (37%) could be diagnosed as suffering from hepatitis E. None was positive for HEV RNA. In the absence of serological markers, HBV DNA was present in three cases. None of the HBV DNA positive patients had anti-delta antibodies. Dual infections (HBV with HEV, and HBV with HCV) were seen in two cases. The aetiology of half of the NANB cases could not be assigned to the known hepatitis viruses using current techniques.

Detection of hepatitis B precore mutants by the fluorescent linear polymerase chain reaction sequencing method

To evaluate the presence of precore mutants, serum samples from 25 patients with chronic hepatitis B, HBV-DNA positive (5 HBeAg and 20 anti-HBe positive) were studied. The complete precore-core region of HBV-DNA was directly sequenced after polymerase chain reaction amplification by a fluorescent linear polymerase chain reaction sequencing method. Precore variants were detected in one HBeAg positive and in all 20 anti-HBe positive patients: in 19 cases, G to A at position 1896, with or without the substitution G to A at position 1899, in two cases C to T substitution at position 1817 which also produces a stop codon (CAA to TAA), one accompanied by the mutation G to A at position 1896. The only mutation observed in the patient who was initially HBeAg positive patient was a G to A substitution at position 1899. Consecutive serum samples from a patient with chronic hepatitis B, initially had the simultaneous presence of wild type and variant strains. Elimination of the wild-type strain was associated with reactivation of liver disease. Analysis of the sequences obtained demonstrated the heterogeneity of the hepatitis B virus genome in the precore-core region. These results indicate that the main cause of non-expression of HBeAg in chronic hepatitis B in our country is the substitution of G to A at nucleotide 1896, alone or accompanied by other variants. Fluorescent linear polymerase chain reaction is a fast and sensitive method to study heterogeneity in the precore-core region.

Novel application of a point mutation assay: evidence for transmission of hepatitis B viruses with precore mutations and their detection in infants with fulminant hepatitis B

Mutations of the precore region of hepatitis B virus (HBV) genome have been associated with fulminant and severe chronic hepatitis. However uncertainty remains about the clinical significance and transmissibility of these mutant strains. A point mutation assay (PMA) was developed to identify qualitatively and quantitatively mutations affecting precore amino acids 1 and 28. We have analysed serum samples from six mother-infant pairs where perinatal transmission of HBV has occurred and where the mothers were HBV carriers without detectable serum HBeAg. In three cases fulminant hepatitis developed in the infant, in two cases acute hepatitis resolved, and in one case the infant was immunised and did not become infected. We also examined serum from a healthcare worker, an anti-HBe-seropositive HBV carrier, believed to have transmitted HBV infection to a patient. The PMA results were confirmed in all cases by direct sequencing of polymerase chain reaction (PCR) products using nested and double-nested PCR with primers to the precore and X region. Precore aa28 mutant-type virus was detected in the serum of one mother at the time of delivery of three of her children, two of whom developed fulminant hepatitis. Another mother of an infant with fulminant hepatitis had no precore mutations. In one mother-infant pair a mixed viral population was found; the acute hepatitis B in the infant resolved. The HBV sequence from the healthcare worker was also of aa28 mutant type. No mutations of aa1 were detected in any of the specimens. The study supports the association of precore mutations with some cases of transmission of HBV infection from HBeAg-negative mothers to their infants.(ABSTRACT TRUNCATED AT 250 WORDS)

Precore region mutation in hepatitis B virus genome in early stage of infection: a study in hepatitis B e antigen-positive young carriers

To determine when the precore mutation at the 83rd nucleotide occurs, leading to the formation of a stop codon in the hepatitis B virus genome in carriers, which would indicate the presence of antibody to hepatitis B e antigen (anti-HBe), we investigated this mutation by direct sequencing and subcloning in 22 young hepatitis B antigen (HBeAg) (+) carriers. These subjects were 7-17 years old and were found during a survey for hepatitis B surface antigen (HBsAg) in three elementary schools, a junior high, and a senior high school. None of these carriers had clinical manifestations, although one-third of them had elevated serum alanine aminotransferase levels. All were HBeAg-positive by radioimmunoassay (RIA), and 6 of them had preserved titers of anti-HBe at the same time. Precore mutations were found in 4 subjects (18.2%), with predominance of the wild type. Although 3 of these 4 had preserved titers of HBeAb, the other had no HBeAb titers. In an other 3 subjects with preserved titers of HBeAb, the precore mutation was not detected, even after the subcloning of viral DNA. The remaining 15 subjects with HBeAg showed no precore mutation. Subjects with ALT levels exceeding 100 IU/l were all HBeAg-positive without the mutation. It was clear that the precore mutation itself occurred in the subjects at an early age during the course of infection. However, the chronological relationship between the emergence of the precore mutation and the onset of hepatitis requires further study.

Universal emergence of precore mutant hepatitis B virus along with seroconversion to anti-HBe irrespective of subsequent activity of chronic hepatitis B

OBJECTIVES

It has been controversial whether or not the emergence of precore mutant HBV is related to the severe form of chronic hepatitis B (CH-B). To further clarify the role of the precore mutant HBV in the natural course of CH-B, we conducted a longitudinal analysis of precore-region sequences according to the biochemical severity along with seroconversion to anti-HBe in patients with CH-B.

METHODS

The precore sequences of the ten sets of serial serum samples, obtained from 6 chronic hepatitis B patients with (group I) and from 4 patients without subsequent biochemical remission after seroconversion to anti-HBe (group II), were analyzed by direct sequencing of DNA amplified by PCR.

RESULTS

The precore mutant HBV having a G-A mutation at the nucleotide 1896 was most commonly found (9/10). Wild-type precore HBV was detected in 4 of 6 (66.7%) in group I and 3 of 4 (75.0%) in group II during HBeAg-positive period (p > 0.05), and during anti-HBe-positive period it was found in 2 of 6 (33.3%) in group I and 0 of 4 (0%) in group II (p > 0.05). In contrast, precore mutant HBV was detected in 5 of 6 (83.3%) in group I and 2 of 4 (50.0%) in group II during HBeAg-positive period (p > 0.05), and in all patients of both groups during anti-HBe-positive period.

CONCLUSION

The most common type of precore mutant HBV in Korea was the mutant with a G-A mutation at nucleotide 1896. The emergence of precore mutant HBV was a universal phenomenon during the natural history of CH-B; therefore, the precore mutant does not appear to have an pathogenic role in determining the severity of the CH-B.

Conservation of precore and core sequences of hepatitis B virus in chronic viral carriers

Mutations in the precore region of hepatitis B virus (HBV) have been associated with failure of expression of HBV e-antigen (HBeAg), however, the prevalence of these and other mutations in HBV carriers without overt chronic liver disease remains uncertain. Homosexual or bisexual males (n = 65) with chronic HBV infection attending The Middlesex Hospital, London were studied, of whom two had clinical evidence of chronic liver disease. HBV DNA was amplified from 62 of 65 serum samples using nested and double nested polymerase chain reaction (PCR) assays. Direct sequencing of the PCR products was employed to investigate sequence variation. HBV-DNA from all available HBeAg-negative (n = 9) and selected HBeAg-positive (n = 33) sera were sequenced in the entire precore gene, the 3' terminal portion of the X gene (aa128-154), and the 5' terminus of the core gene (aa18-73). Sequences were highly conserved in all regions studied. Samples from two anti-HBe-seropositive patients contained mutations in the precore region. In one, a single mutation in the first amino acid resulted in a change to leucine, which would prevent translation of this region and therefore HBeAg expression. Wild type sequences were also detected in this sample. In the other sample from a patient with overt chronic liver disease, a mutation of precore amino acid 28 changed a tryptophan residue to a stop codon which would also prevent HBeAg expression.(ABSTRACT TRUNCATED AT 250 WORDS)

The development of a mutation in the precore region of the hepatitis B virus in a chronically infected individual

Over a 15-year period, a white American woman was observed to have progressive hepatitis B that underwent hepatitis Be antigen (HBeAg) positivity to anti-HBe positivity with development of cirrhosis. This patient was found to have a non-sense mutation in the second codon of the pre-C region of the hepatitis B virus genome after her anti-HBe seroconversion but not in her serum when she was HBeAg+. As controls, serial blood specimens were analyzed from 12 other American patients who spontaneously converted from HBeAg to anti-HBe, who underwent an interferon alfa-associated HBeAg to anti-HBe seroconversion, and who did not seroconvert with interferon alfa therapy. No mutations in the pre-C region were observed to arise in these individuals. In conclusion, non-sense mutations that occur in the pre-C region in locations other than the 28th codon can be associated with HBeAg negative progressive liver disease. This report of a non-sense mutation occurring over time is unusual in that it occurred in a white American patient.

Hepatitis B virus genotype A rarely circulates as an HBe-minus mutant: possible contribution of a single nucleotide in the precore region

The emergence of HBe-minus hepatitis B virus (HBV) mutants, usually through a UAG nonsense mutation at codon 28 of the precore region, helps the virus to survive the anti-HBe immune response of the host. Host and viral factors that predispose to the emergence of such mutants are not well characterized. The fact that the precore region forms a hairpin structure essential for the packaging of viral pregenomic RNA may explain the extremely high prevalence of the UAG mutation at codon 28. It converts a wobble U-G pair in the packaging signal between nucleotide 3 of codon 15 (CCU) and nucleotide 2 of codon 28 (UGG) into a U-A pair. Since genotype A of HBV has a CCC sequence at codon 15, the UAG mutation would, instead, disrupt a C-G pair present in the wild-type virus. This alteration was shown by transfection experiments to greatly compromise the packaging of pregenomic RNA. The implication of this finding was elucidated by molecular epidemiological studies. Genotype A was found to be the most prevalent genotype in the wild-type virus populations in France but was found in only 1 of the 46 isolates of HBe-minus mutants found there. These mutants were contributed chiefly by genotype D, the second most prevalent genotype in France, which is characterized by a CCU sequence at codon 15. The role of the single nucleotide at codon 15 was confirmed by the finding of the single genotype A isolate in which both wild-type and mutant viruses were present. Interestingly, nearly all of the mutants had a codon 15 sequence of CCU instead of the CCC present in the wild-type viruses. Our results suggest that genotype A of HBV rarely circulates as HBe-minus mutants, probably because of a requirement for a simultaneous sequence change at codon 15. These data, together with the virtual absence of genotype A in the Chinese samples examined, may provide some insights into the uneven prevalence of HBe-minus mutants in the world.

Evidence for a base-paired region of hepatitis B virus pregenome encapsidation signal which influences the patterns of precore mutations abolishing HBe protein expression

In two natural HBe-minus hepatitis B virus mutants, expression of HBe protein was abrogated by a nonsense mutation at precore codon 28 and a frameshift mutation at codon 29, respectively. Both mutants contained an additional nucleotide substitution(s) which was found by transfection experiments to be required for efficient packaging of pregenomic RNA. The observed mutational profiles were consistent with the presence of a base-paired region of the pregenome encapsidation signal overlapping the HBe-coding sequence. Results obtained with artificial mutants with significant changes in the primary sequence suggested that base pairing is required but insufficient for efficient pregenome packaging. However, the predicted first four base pairs of the stem are dispensable.

Precore-mediated inhibition of hepatitis B virus progeny DNA synthesis

The capacities to induce the synthesis of hepatitis B virus (HBV) unit-length DNA were compared for two HBV DNAs with an overall sequence diversity of about 10%. They had been cloned from serum (DNA2) and from a hepatocellular carcinoma (DNA4), respectively. As a major difference, DNA4 carries a translational stop signal preventing the synthesis of precore protein. Progeny DNA yields obtained after transfection with respective pregenome transcription units allocated DNA2 to a low-replicator and DNA4 to a high-replicator phenotype. Cotransfection of DNA2 interfered with progeny DNA synthesis induced by DNA4. By mutual exchange of restriction fragments, the region on the viral genome responsible for the differing replicator phenotypes was confined to a sequence comprising the 3'-terminal part of the X gene, core promoter, encapsidation signal epsilon, precore/core gene, and 5'-terminal part of the pol gene. Point mutations in DNA2 abolishing proper expression of the precore gene strongly enhanced the yield of progeny DNA, whereas cotransfection of a precore expression plasmid with DNA4 or with the mutated DNA2 substantially lowered the amount of progeny DNA. Hence, precore expression acts as an inhibitory principle for HBV replication. The same stop mutation as in DNA4 has been found to arise frequently in virus carriers. Loss of precore expression and concomitant conversion to a more severe hepatitis, as observed in the course of a chronic infection, thus can be explained by a relaxation of replication-level control.

Hepatitis B virus DNA in serum and liver is commonly found in Chinese patients with chronic liver disease despite the presence of antibodies to HBsAg

Sera from 410 patients from the Wuhan area in the central part of China with the diagnosis of chronic liver disease were analyzed for markers of hepatitis B, C and D virus infections. All sera, plus liver biopsy specimens from 188 of the patients, were also tested for hepatitis B virus DNA by polymerase chain reaction. Sixty-eight percent were HBsAg positive in serum, whereas 29% showed markers of past hepatitis B virus infection. Hepatitis B virus DNA was detected in all HBeAg-positive sera but also in 58% of patients with HBe antibody. In the liver specimens of the corresponding patient groups, 97% and 78%, respectively, were hepatitis B virus DNA positive. However, more noteworthy was that of the HBsAg-negative/HBs-antibody positive patients 30% had detectable hepatitis B virus DNA in serum and 32% had hepatitis B virus DNA in liver tissue, whereas in a control group of healthy blood donors, of which 90% had HBs antibody, none was hepatitis B virus DNA positive. Our results demonstrate that among patients with chronic liver disease, infections with hepatitis B virus or hepatitis B virus-related virus(es) may frequently occur without being revealed by conventional serological methods. Hepatitis C and D viruses seem to be of only minor importance in the pathogenesis of chronic liver disease in this part of China.

Pre-core mutation associated with lack of hepatitis B e antigenaemia in Moroccan asymptomatic carriers of the virus

Recently, ongoing chronic liver disease with persistent viraemia has been described in hepatitis B virus (HBV) carriers despite the presence of anti-HBe. This has been attributed to infection with pre-C-region-mutated HBV variants. To investigate the possible existence and the prevalence of HBV variants in Morocco and the correlation between HBV DNA detection by polymerase chain reaction and pre-S1 antigenaemia, we tested twenty blood donors, HBsAg chronic carriers for more than one year. The diagnosis of such HBeAg-negative HBV variants was determined by a previously described rapid detection method using selective oligonucleotide hybridization. Probes M0, M1 and M2 correspond, respectively, to a non-mutated distal pre-C sequence, a one-point-mutated sequence with a TAG stop codon at pre-C codon 28 and a two-point-mutated sequence with codon 28 TAG and codon 29 GAC. All the 5 HBeAg-positive samples hybridized with the M0 wild-type probe only. Among the anti-HBe-positive samples, one hybridized with the M0 probe only, whereas another hybridized with none of the oligoprobes. The 13 remaining HBeAg-negative cases hybridized with the M1, M2 or combined M0, M1 and M2 probes. Seven of the 13 HBeAg-negative samples hybridized with more than one probe. DNA sequencing confirmed mixed distal pre-C sequence changes in samples hybridizing with more than one probe. These data demonstrate the existence, in patients, of HBV variants containing an inactive pre-C region and hence the incapacity to synthesize pre-C-region-derived HBeAg.

Hepatitis B virus precore mutants are identical in carriers from various ethnic origins and are associated with a range of liver disease severity

Hepatitis B virus carriers in Israel are mostly HBeAg negative, of whom 5% to 10% have circulating hepatitis B virus. Recently, a hepatitis B virus variant with a stop codon in the precore region was identified, and it was suggested that specific mutations are associated with fulminant or severe chronic active hepatitis. We have analyzed serum samples from HBeAg-positive and HBeAg-negative patients by polymerase chain reaction, using primers spanning the precore/core region. Nucleotide sequence analysis (by direct sequencing) from amplified hepatitis B virus DNA demonstrated that viral genomes from all HBeAg-negative patients contain G to A mutation (nucleotide 1896), leading to the formation of a stop codon. An additional G to A mutation was identified three nucleotides downstream (nucleotide 1899). These patients are of various ethnic origins, with no unique clinical characteristics and with normal liver histology, chronic hepatitis or cirrhosis. No mutation at the precore/core region was observed in the HBeAg-positive patients. In conclusion, the precore mutations identified in hepatitis B virus carriers in Israel are identical regardless of the carrier's ethnic origin and are associated with mild-to-severe liver disease.

Replication capacities of natural and artificial precore stop codon mutants of hepatitis B virus: relevance of pregenome encapsidation signal

The emergence of hepatitis B virus variants unable to express HBe protein during late stage of viral infection may represent an important mechanism of viral persistence. The molecular mechanisms responsible for the elimination of HBe expression are nonsense or frameshift mutations or initiation codon mutations in part of its coding sequence, the precore region. So far only 2 of the 29 precore amino acid codons have been found mutated to stop codons in nature, although a total of 10 codons are convertible to stop codons by single nucleotide changes. Since the HBe-coding sequence is largely overlapped by the pregenome encapsidation signal (epsilon signal), a recently found cis-acting element required for the packaging of pregenomic RNA, the absence of other potential nonsense mutants could result from their impairment of the epsilon signal. Seven such potential stop codon mutants were constructed and tested for replication capacities by transfection into a hepatoma cell line. Five mutants were replication competent, but at levels lower than that of a prevalent natural stop codon mutant. The remaining two mutants were completely defective in DNA replication, which clearly explained why these two mutants are not found in nature. Northern blot analysis revealed wild-type levels of RNA transcription by these two mutants but complete lack of packaged pregenomic RNA. Additional studies lent further support to the importance of the epsilon signal in pregenome encapsidation and suggested relaxed sequence requirements for the computer-predicted hexanucleotide bulge region as compared to the hexanucleotide loop of the signal.

A case-control study on the association of hepatitis B virus infection and hepatocellular carcinoma in northeast Brazil

Hepatitis B virus (HBV) serological markers were investigated in 40 incident cases of hepatocellular carcinoma (HCC) and in two age and sex matched control groups, comprising 40 patients with other cancers and 80 healthy individuals, resident in Bahia, Brazil. Serologic tests were done by radioimmunoassay. The study observed high proportion of seropositivity to HBsAg (42.5%) and of those presenting HBsAg or antiHBc (65.0%) among HCC cases, higher in men than women and in those aged 17 to 30 years old. HBsAg seropositivity among HCC patients was greater than in the control group with other cancers (7.5%) and in healthy controls (2.5%), corresponding to odds ratio estimates of 15.0 (95% CI 3.29, 68.30) and 33.0 (95% CI 9.13, 119.28), both statistically significant. HBeAg was not observed and antiHBe was present in 41.2% of cases, suggesting the absence of viral replication, possibly with viral DNA integration into the hepatocyte genome. The presence of cirrhosis was associated with HBsAg seropositivity among HCC cases. A history of chronic alcoholism is shown to be more frequently related to those cases with cirrhosis. This study highlights the relevant association between HCC and HBV in Northeast Brazil, particularly for young individuals, and the high risk of development of HCC for HBsAg carriers.

Hepatitis B virus infection and primary hepatocellular carcinoma

For many years, epidemiological studies have demonstrated a strong link between chronic hepatitis B virus (HBV) infection and the development of primary hepatocellular carcinoma (PHC). Other hepatocarcinogens such as hepatitis C virus and aflatoxin also contribute to hepatocarcinogenesis either in conjunction with HBV infection or alone. Cellular and molecular biological studies are providing explanations for the HBV-PHC relationship, and models are now being formulated to further test the relative importance of various factors such as viral DNA integration, activation of oncogenes, genetic instability, loss of tumor suppressor genes, and trans-activating properties of HBV to the pathogenesis of PHC. Further research will probably define more than a single mechanism whereby chronic HBV infection results in PHC.

Absence of hepatitis B virus precore mutants in patients with chronic hepatitis B responding to interferon-alpha

Precore defective HBV mutants may gradually prevail because of immune selection and explain spontaneous seroconversion from HBeAg to anti-HBe in HBV carriers. We have analyzed whether the presence of precore HBV mutants is a determinant of responsiveness to interferon-alpha therapy. Fifteen carriers (nine responders and six nonresponders) who were treated with interferon-alpha were examined. Serum samples were collected before and after therapy. After extraction of DNA, the precore region was amplified by the polymerase chain reaction, and the product was identified by gel electrophoresis and ethidium bromide staining and then Southern blotting and molecular hybridization. The amplified products in all patients were asymmetrically amplified by a modified polymerase chain reaction, and the precore region was directly sequenced. All patients were HBV DNA positive initially. Circulating HBeAg-negative mutants were not identified before treatment in either responders or nonresponders. All nine responders were negative for HBV DNA in serum by dot blot during or after treatment, but seven remained positive by polymerase chain amplification and Southern-blot hybridization. All of the nonresponders remained positive for HBV DNA by dot blot. A silent mutation involving the substitution of an A for G at position 1888 was found in seven carriers; however, no HBeAg-negative mutants were detected in the follow-up of either responders or nonresponders to interferon-alpha.(ABSTRACT TRUNCATED AT 250 WORDS)

Sequence analysis of the hepatitis B virus pre-C region in hepatocellular carcinoma [HCC] and nontumoral liver tissues from HCC patients

We investigated whether replication-competent pre-C/C defective mutants of hepatitis B virus (HBV) are detectable in primary human hepatocellular carcinoma (HCC) tissues from patients of a geographic area endemic for such mutants. DNAs extracted from formalin-fixed paraffin-embedded HCC samples were checked for the presence of specific HBV DNA sequences using the polymerase chain reaction (PCR). Amplified pre-C regions from nine HCC samples were directly sequenced as were samples of nontumoral liver tissues from five of these patients. The data show that hypervariable distal pre-C sequences were present in all nine HCC samples; this high variability was dependent on point mutations, which led to amino acid substitutions in nearly all cases. Interestingly, seven of the nine HBV DNA-positive samples from HCC tissues (but not samples from peritumoral liver tissue) showed mutations leading to amino acid substitution at the level of a distal cysteine residue. No mutation generating a translationally defective pre-C/C region was detectable in the tumor samples. Otherwise, in four of the six nontumoral liver tissues available from the same patients, a pre-C sequence with an in-frame TAG stop codon was detectable, although in three cases as a component of mixed population.

Blood-borne Infections Associated with Transfusion

The epidemic of acquired immunodeficiency syndrome (AIDS) and the realization that transmission of human immunodeficiency virus is caused by homologous blood transfusion have changed the way physicians and their patients view the safety of hemotherapy. Considering that nearly four million patients receive the lifesaving benefits of blood transfusions every year in the United States, we need to recognize and reduce the inherent biological complications of this therapy. Currently, a major concern is the transmission of blood-borne infectious agents and the establishment of persistent infection in transfusion recipients, which is apparently facilitated by suppression of the recipient's hematopoietic and immune systems. Education of blood donors, patients, and attending physicians regarding infectious complications of transfusion is essential and remains the most effective procedure for making rational decisions. Before giving blood transfusions, astute physicians should calculate a risk/benefit ratio and communicate it to the patient or family. Potential recipients of transfusions can be assured that the blood supply is safer now than at any time in the past, although there is still a very small risk for the transmission of infectious agents that cause chronic diseases, such as hepatitis, AIDS, neuropathies, and leukemias. It is essential that everyone understands that the goal of a zero-risk blood supply is not attainable. Recent developments in molecular biology and biotechnology, however, provide opportunities for further reduction of infectious complications of blood transfusions.

Hepatitis B virus. New and evolving issues

Recent developments in molecular biology have advanced our understanding of the pathogenesis of HBV-induced disease. New data derived from the molecular analysis of clinical material have begun to bridge the gap between bench research and the clinical arena. In this review, we consider topics that have relevance to clinical management and that have not been summarized in the recent literature. The recent advances that have been made in the areas of HBV variants, in vitro cell culture systems, and extrahepatic infection are discussed in greater detail.

Prevalence and type of pre-C HBV mutants in anti-HBe positive carriers with chronic liver disease in a highly endemic area

The sequence variability in the pre-C region of the hepatitis B virus (HBV) genome in the serum of 42 anti-HBe antibody positive carriers with chronic hepatitis B was studied by PCR and direct sequencing to determine prevalence and type of HBV pre-C mutants in a highly endemic area. Except for one, all patients were infected with viruses containing mutations in the pre-C region which prevent precore and e-antigen (HBeAg) expression: 33 were infected predominantly or exclusively with variants containing a stop codon; two had a mixture of wild-type and a pre-C stop codon mutant virus; three had precore variants with mutations of the pre-C initiation codon and two of them an additional stop codon; four had a frameshift mutation; and one had two stop codons. One patient was infected with viruses which contained a mutation creating an amino acid exchange which should not prevent precore and HBeAg expression. These data demonstrate that in an endemic area a higher prevalence and even broader spectrum of pre-C HBV mutants are found than has been recognized previously in anti-HBe positive patients with chronic hepatitis B.

Treatment with interferon of chronic hepatitis B associated with antibody to hepatitis B e antigen

Persistence of HBV replication (serum HBV-DNA and intrahepatic HBcAg) and markers of HBV-induced (IgM anti-HBc positive) liver disease in anti-HBe-positive patients characterize a peculiar form of chronic hepatitis B. This form of hepatitis B prevails in the Mediterranean Basin, Middle and Far East and is associated with the infection of an HBV variant that lacks the capacity to produce HBeAg. We analysed the results of interferon treatment of 90 patients with chronic anti-HBe-positive hepatitis included in four randomized controlled trials. Interferon inhibited viral replication to undetectable levels and ALT normalized in about 70% of patients. However, the effect was transient in the majority of cases and hepatitis B relapsed in 41 to 90% of patients. A discrepancy in the rate of relapses could be explained by a significant difference in patients populations with a higher prevalence of cirrhotic patients in studies with poorer response. Therefore, in advanced anti-HBe-positive chronic hepatitis B, interferon shows a lower efficacy than in HBeAg-positive patients. The earlier treatment starts, the more efficacious is the response to interferon. Future clinical trials should focus on higher doses for longer periods, repeated courses or on combination therapy with nucleoside analogs or immuno-stimulant drugs.