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

Natural history of chronic hepatitis B virus infection

In chronic hepatitis B virus (HBV) infection acquired during adulthood, which is the type mostly seen in the Caucasian population, there is biochemical and histologic regression after HBeAg seroconversion, and the risk of death from hepatitis B-related causes is low. In chronic HBV infection acquired during birth or early childhood, which is the type most commonly seen in the Asian population, there is a prolonged phase of immunotolerance. The immune clearance phase is characterized by multiple acute exacerbations preceeded by elevations in serum HBV DNA levels, HBeAg concentration and HBeAg/anti-HBe immune complexes. Of these patients, 2.4% may develop hepatic decompensation during the stage of HBeAg seroconversion. The development of cirrhosis occurs more frequently in patients with episodes of decompensation and with repeated severe acute exacerbations. However progression to cirrhosis can be relatively silent and can occur even in children. After HBeAg seroconversion, precore and core promotor mutations occur frequently in the Asian population. However, there is little correlation between the occurrence of these mutations and alanine aminotransferase elevation in patients who are positive for anti-HBe. Although cirrhosis develops during the process of HBeAg seroconversion, 68% of the complications of cirrhosis and of hepatocellular carcinoma occur after HBeAg seroconversion. These complications may still occur even after HBsAg seroclearance.

A frequent, naturally occurring mutation (P130T) of human hepatitis B virus core antigen is compensatory for immature secretion phenotype of another frequent variant (I97L)

A frequent mutation at codon 97 of human hepatitis B virus core antigen has been shown to cause an "immature secretion" phenotype, featuring nonselective and excessive secretions of virions containing immature viral genome. Our current study demonstrates that this abnormality can be efficiently offset by another frequent core mutation, P130T.

Hepatitis B e antigen-negative chronic hepatitis B in Hong Kong

Hepatitis B e antigen-negative chronic hepatitis B (e-CHB) has been reported in Asia but its prevalence and clinical significance have not been determined. The aims of this study were to determine the prevalence of e-CHB in Hong Kong and the frequency of precore and core promoter mutations in these patients. A cross-sectional study was performed in 350 consecutive Chinese patients (230 men and 120 women; mean age +/-SD, 42 +/- 13 years) with chronic hepatitis B virus infection. A total of 243 (69%) patients were hepatitis B e antigen (HBeAg)-negative of whom 15% had clinical cirrhosis. In the remaining 85% of patients, 63% had normal and 22% had elevated transaminases. Serum hepatitis B virus (HBV) DNA was detectable using branched DNA assay in 46% of HBeAg-negative patients with clinical cirrhosis/elevated transaminases. Forty-five percent of the patients with e-CHB had the precore stop codon mutation, and an additional 41% had core promoter changes. There was no correlation between the presence of precore/core promoter mutations and liver disease or HBV-DNA levels. Overall, 17% of HBeAg-negative patients were viremic and had evidence of chronic liver disease (e-CHB) with mean HBV-DNA levels comparable with that in HBeAg-positive patients. In summary, we found that e-CHB may be present in up to 17% of HBeAg-negative patients seen in a tertiary referral center in Hong Kong. e-CHB may be a heterogeneous condition and is not invariably associated with the precore HBV mutant. Population studies are needed to determine the true prevalence of e-CHB in Asia and to assess its natural course and response to treatment.

Hepatitis B genotypes correlate with clinical outcomes in patients with chronic hepatitis B

BACKGROUND & AIMS

Six genotypes (A-F) of hepatitis B virus (HBV) have been identified; however, the genotype-related differences in the pathogenicity of HBV remain unknown. Therefore, we investigated the prevalence of HBV genotypes in Taiwan and the association between distinct genotypes and severity of liver disease in a cross-sectional study.

METHODS

Using a molecular method, HBV genotypes were determined in 100 asymptomatic carriers and in 170 patients with histologically verified chronic liver disease and hepatocellular carcinoma (HCC).

RESULTS

All genotypes except genotype E were identified in Taiwan, and genotypes B and C were predominant. Genotype C was prevalent in patients with cirrhosis and in those with HCC who were older than 50 years compared with age-matched asymptomatic carriers (60% vs. 23%, P < 0.001, and 41% vs. 15%, P = 0.005, respectively). Genotype B was significantly more common in patients with HCC aged less than 50 years compared with age-matched asymptomatic carriers (80% vs. 52%, P = 0.03). This predominance was more marked in younger patients with HCC (90% in those aged </=35 years), most of whom did not have cirrhosis.

CONCLUSIONS

Our data suggest that HBV genotype C is associated with more severe liver disease and genotype B may be associated with the development of HCC in young Taiwanese. However, additional large-scale longitudinal studies are needed to confirm the relationship of HBV genotypes to liver disease severity and clinical outcomes.

Genotypic differences in the hepatitis B virus core promoter and precore sequences during seroconversion from HBeAg to anti-HBe

Hepatitis B virus (HBV) strains from anti-HBe positive patients often show specific mutations in the precore gene, the core promoter region, or both. The dynamics of seroconversion in relation to the appearance of these mutations has not been studied and compared between defined HBV genotypes. Samples from patients followed during seroconversion from HBeAg to anti-HBe were amplified by polymerase chain reaction (PCR), sequenced and genotyped. Among 16 sets of samples, 6 belonged to genotype A, 6 to genotype D, 2 to genotype B, 1 to genotype C, and 1 to genotype E. Whereas strains from genotypes B, C and E showed changes in the core promoter, precore codon 28 or both, genotype A and D strains displayed a different pattern. In 4 of 6 anti-HBe positive samples from genotype A, the precore had a wild-type sequence while the core promoter sequence showed a specific TGA mutation. In another genotype A strain a precore stop mutation was preceded by a mutation in codon 15, thus conserving base-pairing at the pregenomic RNA level in this region. In contrast, all genotype D strains showed wild-type sequences in both the core promoter and precore codon 28 in pre- and post-seroconversion samples. Thus, in 8 patients with a mean follow-up time of 17 months, wild-type sequences in both the core promoter and precore codon 28 were found after seroconversion to anti-HBe. This study also confirmed, for genotype D, that HBeAg seroconversion often occurs earlier than genomic conversion.

Subtype-independent immature secretion and subtype-dependent replication deficiency of a highly frequent, naturally occurring mutation of human hepatitis B virus core antigen

The most frequent mutation of the human hepatitis B virus (HBV) core antigen occurs at amino acid 97. Recently, a phenylalanine (F)-to-leucine (L) mutation at this position (mutant F97L) in HBV surface antigen subtype ayw has been shown to result in an immature secretion phenotype, which is characterized by the nonselective export of an excessive amount of virions containing minus-strand, single-stranded HBV DNA. While subtype ayw mutant F97L has been found in Europe, the major reservoir of HBV resides in Asia and Africa. We report here that the immature secretion phenotype indeed can be found in an HBV strain (subtype adr) prevalent in Asia, changing from an isoleucine (I) to a leucine (mutant I97L). Despite its immature secretion phenotype, the adr variant I97L replicates as well as its parental adr wild-type I97I, supporting the conclusion that the extracellular phenotype of immature secretion is not a consequence of the intracellular HBV DNA replication defect. Further studies demonstrated that it is the acquisition of a leucine, rather than the loss of a wild-type amino acid at codon 97, that is important for immature secretion. We conclude that immature secretion is a subtype-independent phenotype and deficiency in intracellular DNA synthesis is a subtype-dependent phenotype. The former is caused by the trans-acting effect of a mutant core protein, while the latter by a cis-acting effect of a mutated nucleotide on the ayw genome. These immature secretion variants provide an important tool for studying the regulation of HBV virion assembly and secretion.

Natural and iatrogenic variation in hepatitis B virus

The existence of HBV as quasispecies is thought to be favoured by the infidelity of HBV RT, which would account for the emergence of the many natural mutants with point substitutions. RT infidelity may also underlie the hypermutation phenomenon. Indeed, the oft-reported point mutation in the preC gene that leads to failure of HBeAg synthesis may be driven by a hypermutation-related mechanism. The presence of mutants with deletions and insertions involving single nucleotides and oligonucleotides at specific positions in the genome, and of mutants with deletions of even longer stretches particularly in the C gene, suggests that other mutagenic mechanisms operate. Candidates include slippage during mispairing between template and progeny DNA strand, the action of cellular topoisomerase I, and gene splicing using alternative donor and acceptor sites. Natural substitutions, deletions or insertions involving the Cp/ENII locus in the X gene can significantly alter the extent of viral replicative activity. Similar mutations occurring at other locations of Cp/ENII, and at B-cell epitope sites of the S gene are associated with failure to detect serological markers of HBV infection. HBV variation can also arise from recombination between coinfecting strains. S gene mutations that become evident following HBIG administration and HBV vaccination are all point substitutions, as are mutations in functional RT domains of the P gene after treatment with viral RT-inhibitory drugs. Widespread and long-term use of prophylactic and therapeutic agents may potentially generate serologically occult HBV variants that might become difficult to eradicate.

Three cases of severe subfulminant hepatitis in heart-transplanted patients after nosocomial transmission of a mutant hepatitis B virus

Fulminant and severe viral hepatitis are frequently associated with mutant hepatitis B virus (HBV) strains. In this study, the genetic background of a viral strain causing severe subfulminant outcome in heart-transplanted patients was studied and compared with viral hepatitis B strains that were not linked to severe liver disease in the same setting. A total of 46 patients infected nosocomially with HBV genotype A were studied. Five different viral strains were detected, infecting 3, 9, 5, 24, and 5 patients, respectively. Only one viral strain was found to be associated with the subfulminant outcome and 3 patient deaths as a consequence of severe liver disease. The remaining 43 patients with posttransplantation HBV infection did not show this fatal outcome. Instead, symptoms of hepatitis were generally mild or clinically undiagnosed. Comparison of this virus genome with the four other strains showed an accumulation of mutations in the basic core promoter, a region that influences viral replication, but also in hepatitis B X protein (HBX) (7 mutant motifs), core (10 mutant motifs), the preS1 region (5 mutant motifs), and the HBpolymerase open reading frame (17 motifs). Some of these variations, such as those in the core region, were located on the tip of the protruding spike of the viral capsid (codons 60 to 90), also known in part as an important HLA class II-restricted epitope region. These mutations might therefore influence the immune-mediated response. The viral strain causing subfulminant hepatitis was, in addition, the only strain with a preCore stop codon mutation and, thus, hepatitis B e antigen (HBeAg) expression was never observed. The combination of these specific viral factors is thought to be responsible for the fatal outcome in these immune-suppressed heart-transplant recipients.

Mutations in the basic core promotor and the precore region of hepatitis B virus and their selection in children with fulminant and chronic hepatitis B

The involvement of precore stop codon 1896-A and base exchanges in the AT-rich region at positions 1762 and 1764 of the hepatitis B core promotor has been controversely discussed in adults with fulminant hepatitis B. Because no data are currently available on children, we analyzed the basic core promotor (BCP) and precore region in children with chronic and fulminant hepatitis B. The BCP and precore region were sequenced directly and after cloning from mothers and infants. Thirteen children suffered from chronic liver disease, 6 of whom were treated with interferon alfa (IFN-alpha). All 13 patients seroconverted from hepatitis B e antigen (HBeAg) to hepatitis B e antigen antibodies (anti-HBe), and sera were analyzed before and after seroconversion. Nine vertically infected infants developed a fulminant course of hepatitis B. The occurrence of BCP (1762-T/1764-A, 7.7%) and precore (1896-A, 7.7%; 1899-A, 15%) mutations in chronic hepatitis B was rare. A genotype shift from D to A was observed in 3 patients after development of anti-HBe. A high number of base exchanges was detected in those infants with fulminant hepatitis B. Eight of nine showed a G-A exchange at positions 1896/97 (89%), 1899 (56%), and/or mutations at nucleotide (nt) positions 1762 (56%) and 1764 (78%). All virus strains belonged to genotype D, whereas in the only surviving infant, a D-to-A shift was detected. Hepatitis B virus (HBV) DNA clones were examined from 3 babies and 5 mothers. Our results showed a heterogeneous virus population in 4 of 5 mothers. In contrast, a homogeneous virus population emerged in the infants. According to our data, the analysis in children with fulminant and chronic hepatitis B revealed a striking presence of BCP and precore mutants in infants with fulminant hepatitis (FH) when compared with clinically inapparent anti-HBe-positive children (P <.002), which could be one factor in the pathogenesis of fulminant hepatitis B in children.

Different hepatitis B virus genotypes are associated with different mutations in the core promoter and precore regions during hepatitis B e antigen seroconversion

Mutations in the core promoter and precore regions are frequently found in hepatitis B e antigen (HBeAg)-negative patients, but precore stop codon mutation is restricted to hepatitis B virus (HBV) genotypes that have T at nucleotide 1858. The aims of this study were to determine the role of core promoter and/or precore mutations in HBeAg seroconversion and their impact on the subsequent course of liver disease, and to determine if core promoter mutations are more frequently selected in patients with HBV genotypes that preclude the development of precore stop codon mutation. Serial sera from 45 patients with chronic HBV infection were polymerase chain reaction (PCR)-amplified, and the HBV core promoter and precore regions were sequenced. Ninety-two percent of patients had core promoter or precore mutations after HBeAg seroconversion: 42% had core promoter changes only, 38% had precore stop codon mutations only, and 12% had changes in both regions. Seventy-three percent of the patients had persistently normal aminotransferases, and only 8% had multiple flares in aminotransferases after HBeAg seroconversion. Core promoter changes were significantly more common in patients infected with HBV who have C at nucleotide 1858 (91% vs. 27%; P <.01), while precore stop codon changes were exclusively found in patients infected with HBV who have T at nucleotide 1858 (87% vs. 0; P <.01). The vast majority of our patients had core promoter and/or precore mutations after HBeAg seroconversion. Nevertheless, most patients had sustained remission of liver disease. Our data suggest that core promoter changes are preferentially selected in patients infected with HBV genotypes that preclude the development of precore stop codon mutation.

Efficacy of lamivudine in patients with hepatitis B e antigen-negative/hepatitis B virus DNA-positive (precore mutant) chronic hepatitis B. Lamivudine Precore Mutant Study Group

This placebo controlled, double-blind study evaluated the efficacy and safety of lamivudine in patients with hepatitis B e antigen (HBeAg)-negative/hepatitis B virus (HBV) DNA-positive chronic hepatitis B. Patients were randomized to receive 100 mg lamivudine orally once daily for 52 weeks (n = 60) or placebo for 26 weeks (n = 65). Patients who were HBV DNA positive at week 24 were withdrawn at week 26. The primary efficacy endpoint was loss of serum HBV DNA plus normalization of alanine transaminase (ALT) at week 24. A significantly higher proportion of patients receiving lamivudine (63%) had a complete response at week 24 compared with patients receiving placebo (6%) (P <.001). Secondary efficacy parameters included histological response from baseline to week 52 in the lamivudine-treated patients. At week 52, 60% of lamivudine-treated patients with liver biopsy specimens available showed histological improvement (>/=2-point reduction in Knodell necro-inflammatory score), 29% showed no change, and 12% worsened. In a ranked assessment of pretreatment and post-treatment biopsy pairs 11% improved, 86% showed no change, and 2% worsened in fibrosis. At week 52, 27% of patients receiving lamivudine had YMDD (tyrosine-methionine-aspartate-aspartate amino acid motif of HBV polymerase) variant HBV. The incidence of adverse events and laboratory abnormalities was similar in both groups. In conclusion, lamivudine treatment results in a significant virological and biochemical improvement compared with placebo, induces an improvement or no change in histology in most patients, and is well tolerated. The response to lamivudine therapy in HBeAg-negative patients is similar to the response reported in previous studies of patients with HBeAg-positive chronic hepatitis B.

Prevalence of mutations in core promoter/precore region in Japanese patients with chronic hepatitis B virus infection

We examined the frequency and significance of mutations in the core promoter and precore region in 103 Japanese patients with chronic hepatitis B virus (HBV) infection. HBV DNAs from the patients' sera were amplified by polymerase chain reaction and were directly sequenced. A double mutation (T1762 A1764) in the core promoter was frequently observed in the patients regardless of HBeAg status except for asymptomatic carriers with HBeAg. Furthermore, a mutation at nucleotide 1753 from T to C or G was frequently found in anti-HBe positive patients and was often accompanied by the double mutation. The A1896 mutation was found in only about one fourth of the patients with anti-HBe. These data suggest that the patients with chronic liver diseases frequently had a double mutation regardless of HBeAg status and a mutation at nucleotide 1753 might be associated with HBeAg-negative chronic hepatitis B virus infection.

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

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

The hepatitis B virus seroconversion to anti-HBe is frequently associated with HBV genotype changes and selection of preS2-defective particles in chronically infected children

In order to investigate the generation and selection of hepatitis B virus mutants and the influence of interferon on their evolution, a longitudinal study including 22 patients was performed. The complete preS1/S2 open reading frame was analyzed by direct sequencing from serum samples obtained before and after seroconversion to anti-HBe in 11 children without alpha-interferon treatment. Furthermore, in 11 cases with therapy additional samples obtained during interferon therapy were investigated. The comparison of each patient's preS sequences analyzed before and during therapy did not show any nucleotide change, while in both groups numerous silent and missense mutations were found immediately after seroconversion. Surprisingly, in 7 cases the hepatitis B virus changed genotype from A to D (subtype adw to ayw) after seroconversion. Additional rearrangements were observed in 4 patients. In 3 cases the selection of preS2 start codon mutants was detected after seroconversion and in 1 individual a 183-nucleotide deletion was found during and after HBeAg positivity. In conclusion, the emergence of preS rearrangements and numerous base exchanges provide evidence for a strong selection process focused against the preS region. Moreover, the appearance of genotype changes after anti-HBe seroconversion reveales a thus far unrecognized event during the natural course of HBV infection in childhood.

Functional characterization of naturally occurring variants of human hepatitis B virus containing the core internal deletion mutation

Naturally occurring variants of human hepatitis B virus (HBV) containing the core internal deletion (CID) mutation have been found frequently in HBV carriers worldwide. Despite numerous sequence analysis reports of CID variants in patients, in the past decade, CID variants have not been characterized functionally, and thus their biological significance to HBV infection remains unclear. We report here two different CID variants identified from two patients that are replication defective, most likely due to the absence of detectable core protein. In addition, we were unable to detect the presence of the precore protein and e antigen from CID variants. However, the production of polymerase appeared to be normal. The replication defect of the CID variants can be rescued in trans by complementation with wild-type core protein. The rescued CID variant particles, which utilize the wild-type core protein, presumably are enveloped properly since they can be secreted into the medium and band at a position similar to that of mature wild-type Dane particles, as determined by gradient centrifugation analysis. Our results also provide an explanation for the association of CID variants with helper or wild-type HBV in nature. The significance of CID variants in HBV infection and pathogenesis is discussed.

Hepatitis B virus S mutants in liver transplant recipients who were reinfected despite hepatitis B immune globulin prophylaxis

Long-term hepatitis B immune globulin (HBIG) has been shown to reduce hepatitis B virus (HBV) reinfection in patients transplanted for hepatitis B. The aim of this study was to determine the prevalence of HBV S gene mutations in liver transplant recipients who developed recurrent hepatitis B despite HBIG prophylaxis, and to determine if these mutations can revert after withdrawal of HBIG. The entire S gene sequences in pre- and posttransplant sera from 20 patients who developed recurrent hepatitis B despite HBIG prophylaxis were compared. Ten (50%) patients had 18 amino acid substitutions involving the 'a' determinant in the posttransplant samples. These mutations were absent in 93% of the pretransplantation clones analyzed. There was a significant correlation between the development of mutations in the 'a' determinant region and the duration of HBIG therapy. Most of the mutations result in changes in predicted antigenicity of the S protein. During follow-up, mutations in 14 (78%) of 18 affected codons in the 'a' determinant region reverted back to the pretransplantation sequences; only 1 codon had a de novo change after the withdrawal of HBIG. Two control patients who did not receive HBIG had no change in the 'a' determinant in their posttransplantation samples. These data support the hypothesis that mutations in the S gene were induced or selected by immune pressure exerted by HBIG. HBV S mutants may play a role in HBV reinfection in liver transplant recipients who received HBIG prophylaxis.

Hepatitis B virus precore mutants in serum and liver of Southern African Blacks with hepatocellular carcinoma

BACKGROUND/AIM

The aim of this study was to sequence the precore region of HBV isolated from serum and tumorous and non-tumorous liver tissue from patients with hepatocellular carcinoma to identify mutations that might play a role in malignant transformation.

METHODS

HBV DNA was extracted from 62 sera, 14 tumorous and 12 non-tumorous liver tissue samples of patients with hepatocellular carcinoma, amplified by the polymerase chain reaction and sequenced directly.

RESULTS

Thirty-nine patients were HBeAg-negative and 23 HBeAg-positive. Missense mutations were present predominantly in HBeAg-negative sera. The most common missense mutation, a guanine to thymine transversion, occurred at nucleotide 1862 in the bulge of the encapsidation signal; it was more prevalent in HBeAg-negative (10/39) than in HBeAg-positive patients (1/23) (p = 0.03). Mutations known to prevent HBeAg synthesis were detected in seven sera; five with an 1896 stop-codon mutation, one with an 1817 nonsense mutation, and one with a frameshift mutation caused by an insertion between 1838 and 1839. Missense mutations and deletions were present more often in tumorous tissue derived from HBsAg-negative patients. In the tumours missense mutations occurred at position 1862 and 1899, and the deletions affected direct repeat 1 and/or the encapsidation signal and included the x gene stop-codon.

CONCLUSIONS

The 1862 mutation, and other missense mutations and deletions detected in the precore gene, may disrupt HBV DNA replication and/or signal peptide cleavage leading to HBeAg-negativity. Disruption of viral replication may promote integration of unencapsidated replicative intermediates and hence contribute to hepatocarcinogenesis.

Analysis of hepatitis B virus genotypes and pre-core region variability during interferon treatment of HBe antigen negative chronic hepatitis B

The clinical importance of hepatitis B virus (HBV) genome variability has been reported recently. One example is the occurrence of hepatitis B virus pre-core mutants, which arise during spontaneous or interferon-induced seroconversion from HBeAg to anti-HBe and are thought to be selected by immune pressure. A survey of HBV pre-core mutants and viral genotypes in 35 HBeAg negative patients during interferon therapy was carried out to understand viral pathogenesis in this form of chronic hepatitis B. Seventeen patients responded to interferon therapy as assessed by the sustained normalization of serum ALT levels and the significant decrease of viremia levels. The response rate to interferon was independent of both initial serum viral DNA level and interferon doses. During interferon therapy, a significant decrease of M0 (wild-type pre-core sequence at pos. 1887-1908), M1 (TGG to TAG at pos. 1896) or M2 (TGG to TAG at pos. 1896, and GGC to GAC at pos. 1899) positive viral genomes was found in 48%, 42%, and 33% of patients, respectively. A higher response rate to interferon therapy was observed in patients infected with HBV genotype A (70%) or M0 positive strains (75%) as compared to patients infected with genotype D/E (40%) or M1/M2 positive strains (44%). The data support the hypothesis that pre-core defective HBV represent viral mutants with an increased capacity to resist exogenous alpha interferon. These findings emphasize that characterization of HBV genome variability prior to interferon therapy may help to predict antiviral response in HBeAg negative patients.

Pathogenesis of chronic liver disease in patients with chronic hepatitis B virus infection without serum HBeAg

Chronic hepatitis B in patients lacking hepatitis B e antigen has been attributed to a hepatitis B virus variant (G-to-A mutation at nucleotide 1896 in the precore region of the genome). We therefore assessed the frequency and significance of this variant among 43 United States patients (10 with chronic hepatitis B seropositive for e antigen, 19 seronegative for e antigen, and 14 healthy carriers). Sera were tested for HBV DNA by polymerase chain reaction and branched DNA assay. The A1896 variant was detected by direct sequencing and ligase chain reaction. Serum HBV DNA was more frequently found among patients with e antigen-positive than e antigen-negative chronic hepatitis B. Viral titers were generally higher in those with e antigen. None of the e antigen-positive and only 24% of e antigen-negative patients harbored the A1896 variant. Patients infected with the variant were more often Asian, had had hepatitis B for longer and had higher levels of viral DNA than HBeAg-negative patients with the wild-type virus. The A1896 variant was found exclusively in patients infected with HBV genotypes C and D. Thus, the A1896 variant is uncommon in the United States. The activity of liver disease appears to be more closely related to the level of HBV replication than the presence of mutations at nucleotide 1896 in the genome.

A revised secondary structure model for the 3'-end of hepatitis B virus pregenomic RNA

The polymerase encoded by human hepatitis B virus, which has reverse transcriptase and RNase H activity, binds to its pregenomic RNA template in a two-step process involving a terminal redundancy. Both first strand and second strand DNA synthesis involve primer translocation and second strand synthesis involves a template jump. Three parts of the genome, including the so-called core promoter, are known to show deletions in strains usually arising after long-standing HBV infection, but also in some patients treated with interferon. A computer-based study of RNA template folding in the core promoter region, accommodating well-known point mutations, has generated a model for the 3' DR1 primer binding site as being part of a superstructure encompassing an already well-established stem-loop. Depending on the identity of nucleotides 1762 and 1764, the DR1 region may assume two alternative secondary structures which stabilize it as a primer binding site to different extents. Remarkably, one of these structures includes a pronounced loop which coincides with at least 12 related deletions seen in HBV DNA from different patients. Thus according to the model, the 5'- and 3'-ends of pregenomic RNA, which share primary sequences but have separate functions, are not structural equivalents. An RNA superstructure near the 3'-end of all HBV transcripts could have far-reaching implications for the modulation of both genome replication and post-transcriptional processing.

Distribution of the predominant hepatitis B virus precore variants in hepatitis B e antigen-positive children and their effect on treatment response

Little is known about the distribution of precore hepatitis B virus mutants and their influence on the outcome of interferon therapy in children with chronic hepatitis B. In this study, serum samples were analyzed from 60 children with chronic hepatitis B e antigen+ (HBeAg+) hepatitis. Fifty-two of these children underwent different interferon trials, and a second serum sample was taken from 25 of them at the end of therapy. Fifty-six of the original 60 children were simultaneously infected by wild-type and precore mutant hepatitis B virus variants. The remaining four children were infected by the wild type alone. In 50/56 of children with a mixed viral population, the wild-type variant comprised more than 50% of the total viremia. With respect to the influence of precore variants on the outcome of interferon treatment, the prevalence of mixed viral population was similar in responders and nonresponders (96 versus 88%, respectively). However, precore mutant variants were prevalent (> 50% of the viral population) in 21% of the nonresponders, but in none of the responder children (p < 0.05). Viremia levels were significantly higher in nonresponder than in responder children (p < 0.05). No substantial changes in the prevalence of mutants were observed throughout the interferon therapy. In conclusion, mixed viral infection is found in a high percentage of children with chronic B HBeAg+ hepatitis. Response to interferon therapy does not seem to be related to the presence of hepatitis B virus precore mutants, but rather to the levels of viremia.

Heterogeneity of hepatitis B virus (HBV) core gene in a patient with HBV-associated cirrhosis and serum negativity for anti-HBc

AIMS

We describe here the case of a patient suffering from severe chronic hepatitis B associated with an unusual hepatitis B virus serology: HBsAg and HBeAg were both positive while anti-HBc was negative by radioimmunoassay.

METHODS

A very sensitive anti-HBc ELISA (IMx CORE) was performed and was able to detect anti-HBc sporadically throughout the clinical course. Molecular characterization of hepatitis B virus strains in this patient enabled us to explain this particular serological and clinical pattern of hepatitis B virus infection.

RESULTS

Hepatitis B virus genotype determined by size polymorphism of the core gene and the pre-S region was found to be D/E and consistent with the results of serological subtyping (HBV ayw2-4). DNA sequence analysis of the pre-C/C region showed the presence of significant nucleotide changes. In association with a wild type hepatitis B virus strain, we could detect at least four hepatitis B virus variants with nucleotide deletions leading to a frameshift in the core gene. According to the position of the mutations, these hepatitis B virus core variants are expected to be defective for B-cell epitopes and TH-cell epitopes.

CONCLUSIONS

These mutations explain the low level production of anti-HBc antibody. It is noteworthy that the absence of detectable anti-HBc in serum was associated with severe liver damage, suggesting that the deficient humoral response to HBcAg was not accompanied by a cellular immune tolerance to HBc/eAg, the supposed target for cytotoxic T-cell lysis.

Anti-HBe titre in patients infected with wild-type and e-minus variant of hepatitis B virus

Serum samples from 77 HBsAg- and anti-HBe-positive chronic hepatitis B patients were studied for a G to A point mutation at the 1896 nucleotide of the precore region by polymerase chain reaction and oligonucleotide hybridization. Patients were grouped as: A, infected only by the wild-type virus; B, infected only by e-minus variant; C, coinfected by the wild-type and e-minus variant; and D, no precore/core gene of hepatitis B virus detected. All samples were assayed for the titre of anti-HBe by ELISA and compared as grouped. A significantly higher titre was found in the coinfected group C compared to groups A (p < 0.01) and D (p < 0.05). Results indicate that a high titre of anti-HBe is required as immune selective pressure for E-minus variant to overtake the wild-type virus.

Analysis of hepatitis B virus genotypes and pre-core region variability during interferon treatment of HBe antigen negative chronic hepatitis B

The clinical importance of hepatitis B virus (HBV) genome variability has been reported recently. One example is the occurrence of hepatitis B virus pre-core mutants, which arise during spontaneous or interferon-induced seroconversion from HBeAg to anti-HBe and are thought to be selected by immune pressure. A survey of HBV pre-core mutants and viral genotypes in 35 HBeAg negative patients during interferon therapy was carried out to understand viral pathogenesis in this form of chronic hepatitis B. Seventeen patients responded to interferon therapy as assessed by the sustained normalization of serum ALT levels and the significant decrease of viremia levels. The response rate to interferon was independent of both initial serum viral DNA level and interferon doses. During interferon therapy, a significant decrease of M0 (wild-type pre-core sequence at pos. 1887-1908), M1 (TGG to TAG at pos. 1896) or M2 (TGG to TAG at pos. 1896, and GGC to GAC at pos. 1899) positive viral genomes was found in 48%, 42%, and 33% of patients, respectively. A higher response rate to interferon therapy was observed in patients infected with HBV genotype A (70%) or M0 positive strains (75%) as compared to patients infected with genotype D/E (40%) or M1/M2 positive strains (44%). The data support the hypothesis that pre-core defective HBV represent viral mutants with an increased capacity to resist exogenous alpha interferon. These findings emphasize that characterization of HBV genome variability prior to interferon therapy may help to predict antiviral response in HBeAg negative patients.

Hepatitis B virus infection: precore mutants and its relation to viral genotypes and core mutations

The precore-core gene of hepatitis B virus (HBV) was directly sequenced from serum samples of 42 patients with chronic B hepatitis (19 hepatitis B e antigen [HBeAg]+ and 23 anti-HBE+). Viral genotypes were determined by comparison with 11 reference sequences and by restriction analysis. Genotype A was identified in 16 cases, genotype D in 24 cases, and other genotypes in 2 cases. Precore mutations, mainly M1 (stop at codon 28), were differently distributed among the viral genotypes: 3 cases (18.8%) with genotype A and 18 cases (75%) with genotype D. In sequences with precore mutants, the encapsidation signal was more stable (negative stabilization energy) than in sequences without precore mutants. In genotype A, the M1 mutation coexisted with a second mutation (C-->T at position 1858 in codon 15), and both mutations were paired in the secondary structure of the RNA encapsidation signal, which justified the rare presence of precore mutants in this genotype. The analysis showed different distribution of mutations depending on the viral genotype; patients with genotype D were more likely to have persistent HBV infection by selection of precore mutants. Multiple amino acid substitutions were detected in the core region, mainly in two subsequences that have been previously described as epitopes (flanked by codons 11 to 27 and 74 to 83); the presence of these mutations was significantly related to the presence of precore variants which abolished the expression of HBeAg.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical relevance of mutations in the precore genome of the hepatitis B virus

A stop codon in the precore genome of the hepatitis B virus (HBV) in anti-HBe positive HBV carriers may be associated with a more progressive form of HBV infection. Earlier studies, however, were mainly performed in patients from the Mediterranean area who had severe infection. The aim of this study was to evaluate the prevalence of precore mutants in an unselected population living in northern Europe. Twenty of 42 of these patients are infected predominantly with a virus strain, which has the typical stop codon in the precore genome, characterised by a mutation at base 83. In six patients there was an additional G to A mutation at base 86 of the precore genome. Statistical analysis showed no difference between the patients with or without a stop codon in the precore genome. When patients with a double mutation at base 83 and 86 of the precore genome were compared with the other anti-HBe positive HBV carriers, however, the corresponding clinical data were worse. Therefore we suggest, that it is not the stop codon in the precore gene itself, but the occurrence of a double mutation at bases 83 and 86, which is associated with a more severe course of disease in anti-HBe positive HBV carriers.

Hepatitis B virus precore mutants in HBeAg carriers with chronic hepatitis treated with interferon

Precore mutants of hepatitis B virus (HBV) were looked for in 18 hepatitis B e antigen (HBeAg) carriers who were treated with recombinant interferon-alpha (rIFN) and the results were compared with those obtained in 12 untreated carriers who underwent spontaneous HBeAb seroconversion. Molecular analysis of the HBV precore region was carried out by polymerase chain reaction (PCR) amplification and direct sequencing. Precore mutants with a stop codon at codon 28 were detectable at baseline in 19/30 carriers. However, wild-type strains predominated in the baseline sera of both treated (n = 16) and untreated (n = 10) patients. Sera from the remaining four patients contained predominantly or exclusively mutant virions. Following IFN treatment, there was a shift from the wild-type pattern to the mutant pattern in all patients, with the precore pattern prevailing in long-term responders (six out of nine) compared with the non-responders (none of nine). The wild-type pattern predominated among the non-responders (eight vs three), suggesting that the long-term response to IFN was associated with take-over of precore mutants. There were no relationships between any pretreatment precore molecular pattern and disease severity or outcome of treatment. Precore mutants also took over in 10 of the 12 untreated patients (83%), who underwent spontaneous HBeAb seroconversion. Thus, a shift from wild-type to precore mutant pattern occurs in most Italian patients undergoing IFN-induced or spontaneous HBeAb seroconversion.

Precore and core mutations in HBV from individuals in India with chronic infection

Ten hepatitis B surface antigen seropositive carriers (5 asymptomatic and 5 with chronic liver disease) were tested for HBeAg/anti-HBe and for HBV-DNA using the polymerase chain reaction. Five were DNA-positive, 2 with HBeAg and 3 with anti-HBe. Nucleotide sequences were determined for these 5 cases. Hepatitis B virus DNA from one cirrhotic carrier with anti-HBe had a mutation in the precore region (nucleotide position 1862) which may affect signal peptide cleavage and HBeAg synthesis. In the other 2 anti-HBe- and DNA-positive cases, a cirrhotic carrier and an asymptomatic case, there was a mutation at nucleotide position 1896 leading to a termination codon in the precore region. In all 5 patients, except for one or two missense mutations, there was no significant variation in the core region.

Single-step nested polymerase chain reaction for detection of different genotypes of hepatitis C virus

Hepatitis C virus (HCV) exhibits considerable sequence variability and circulates in the blood at extremely low levels. Current methods for detecting HCV RNA are based mostly on nested polymerase chain reaction (PCR), in which part of the first amplification product is reamplified in the second tube by an internal primer pair. A novel nested PCR method was developed in which the two successive amplification processes are carried out in the same tube with a single step of physical manipulation. Careful selection of highly conserved sequences of the 5' noncoding region as primers enabled successful detection of all three major genotypes circulating in France, including the one with variation in this region. Retaining high sensitivity of the conventional nested PCR, the novel method reduced greatly the risk of carry-over contaminations. It was also cost- and time-saving. The one-step nested PCR method is especially suitable for routine diagnosis of HCV infection in clinical laboratories.

Nucleotide sequence analysis of precore and proximal core regions in patients with chronic hepatitis B treated with interferon

The aim of the study was to estimate the prevalence of HBeAg defective mutants among patients with chronic hepatitis B (CHB) in the United States and to study the effect of interferon-alpha (IFN-alpha) on determining the occurrence of mutations in the HBV precore and proximal core regions. Twenty CHB patients who were treated with IFN-alpha were studied. Initially, all were HBV DNA positive by dot-blot hybridization; 17/20 were HBeAg positive, and 3/20 were anti-HBe positive. The precore (87 nt) and proximal core (81 nt) regions were sequenced after PCR amplification by the dideoxy chain termination method. In pretreatment sera, 15/20 patients harbored wild-type HBV only, while in 5/20 at least one nucleotide substitution was found. Mutations that prevent HBeAg synthesis were found in three patients, all of whom had G-to-A substitution at nt 1896 and two of them were anti-HBe positive. Follow-up sera were available in 18 patients. With respect to pretreatment specimen, 15/18 patients had no changes in the sequenced regions after therapy. Sequence changes were observed in the remaining three patients: In one an HBeAg defective strain was replaced by a wild-type strain; in the second a wild-type strain was replaced by an HBeAg defective strain; and in the third two mutations changing the deduced amino acid sequence of the core protein developed in the wild-type strain. In conclusion, most of our patients (85%) were initially infected by HBV strains having no mutations that prevented HBeAg synthesis. IFN-alpha therapy infrequently resulted in the appearance of mutations in the precore and proximal core regions.

Hepatitis B virus with mutations in the core promoter for an e antigen-negative phenotype in carriers with antibody to e antigen

Hepatitis B virus (HBV) DNA clones were propagated from 57 carriers with antibody to hepatitis B e antigen (HBeAg) and sequenced within nucleotides (nt) 1685 to 1926 including the core promoter (nt 1742 to 1849) and the pre-C region (nt 1814 to 1900). Mutations in the core promoter or those in the pre-C region, or both, were detected in 328 (97.9%) of 335 clones from them. Five carriers were infected with HBV mutants with mutations in the core promoter alone, while 20 carriers were infected only with those in the pre-C region to abort the translation of HBeAg precursor; the remaining 32 carriers were infected with HBV mutants with mutations in both the core promoter and pre-C region. Some carriers infected with HBV with mutations in the core promoter exclusively had high HBV DNA titers, comparable with those in carriers infected with wild-type HBV, thereby indicating that such mutations would not affect the transcription of the HBV pregenome extensively. Two point mutations in the core promoter, from A to T at nt 1762 and from G to A at nt 1764, were most prevalent. The other mutations included a point mutation at either of the two nucleotides and their deletion. All of these mutations involved the TTAAA sequence (nt 1758 to 1762) at 28 bp upstream of the initiation site for shorter pre-C mRNAs (nt 1790 +/- 1). The ATAAATT sequence (nt 1789 to 1795) at 23 bp upstream of the initiation site for the pregenome RNA (nt 1818), however, remained intact in all 335 HBV DNA clones. HBV mutants with mutations in the core promoter, unaccompanied by pre-C mutations, prevailed and replaced wild-type HBV in two carriers as they seroconverted from HBeAg to the corresponding antibody. These results indicate that HBV mutants with an HBeAg- phenotype would be generated by mutations in the core promoter which might abort the transcription of pre-C mRNA but do not seriously affect that of pregenome RNA.

Cytotoxic T lymphocyte response to a wild type hepatitis B virus epitope in patients chronically infected by variant viruses carrying substitutions within the epitope

Mutations that abrogate recognition of a viral epitope by class I-restricted cytotoxic T lymphocyte (CTL) can lead to viral escape if the CTL response against that epitope is crucial for viral clearance. The likelihood of this type of event is low when the CTL response is simultaneously directed against multiple viral epitopes, as has been recently reported for patients with acute self-limited hepatitis B virus (HBV) infection. The CTL response to HBV is usually quite weak, however, during chronic HBV infection, and it is generally acknowledged that this is a major determinant of viral persistence in this disease. If such individuals were to produce a mono- or oligospecific CTL response, however, negative selection of the corresponding mutant viruses might occur. We have recently studied two HLA-A2-positive patients with chronic hepatitis B who, atypically, developed a strong HLA-A2-restricted CTL response against an epitope (FLPSDFFPSV) that contains an HLA-A2-binding motif located between residues 18-27 of the viral nucleocapsid protein, hepatitis B core antigen (HBcAg). These patients failed, however, to respond to any of other HLA-A2-restricted HBV-derived peptides that are generally immunogenic in acutely infected patients who successfully clear the virus. Interestingly, DNA sequence analysis of HBV isolates from these two patients demonstrated alternative residues at position 27 (V --> A and V --> I) and position 21 (S --> N, S --> A, and S --> V) that reduced the HLA and T cell receptor-binding capacities of the variant sequences, respectively. Synthetic peptides containing these alternative sequences were poorly immunogenic compared to the prototype HBc18-27 sequence, and they could not be recognized by CTL clones specific for the prototype peptide. While we do not know if the two patients were originally infected by these variant viruses or if the variants emerged subsequent to infection because of immune selection, the results are most consistent with the latter hypothesis. If this is correct, the data suggest that negative selection of mutant viral genomes might contribute to viral persistence in a subset of patients with chronic HBV infection who express a narrow repertoire of anti-HBV CTL responses.

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.

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.