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

High mutation prevalence of precore and basal core promoter in pregnant women who underwent spontaneous HBeAg seroconversion within one year postpartum

BACKGROUND

Seroconversion of hepatitis B e antigen (HBeAg) is a critical event in the natural course of hepatitis B virus (HBV) infection.

AIM

We herein characterize the virological factors associated with postpartum spontaneous HBeAg seroconversion.

METHODS

A total of 214 pregnant women positive for both hepatitis B surface antigen (HBsAg) and HBeAg were followed up at 7-12 months postpartum.

RESULTS

Of the subjects, 26 (12.1%) achieved spontaneous HBeAg seroconversion. Receiver operating curve analysis indicated that HBV DNA level <1.0 × 10⁷ IU/mL, HBsAg <1.0 × 10⁴ IU/mL and HBeAg <7.36 × 10² S/CO each independently predicted HBeAg seroconversion within 12 months postpartum. At delivery, 73.1% (19/26) women with postpartum HBeAg seroconversion had precore (PC) and/or basal core promoter (BCP) mutations, higher than that (5/36, 13.9%) in the women without postpartum seroconversion. Binary logistic regression analysis indicated that the presence of mutations in PC, BCP, and both PC and BCP at delivery was associated with an increased likelihood (OR = 13.286, 16. 238, and 22.143 respectively, all P < 0.05) to undergo postpartum spontaneous HBeAg seroconversion.

CONCLUSION

These results suggest that quantitative determination of virological markers and sequencing PC and BCP can predict spontaneous HBeAg seroconversion, which could be valuable in deciding antiviral therapy against HBV.

High Frequency of Either Altered Pre-Core StartCodon or Weakened Kozak Sequence in the CorePromoter Region in Hepatitis B Virus A1 Strainsfrom Rwanda

Hepatitis B virus (HBV) is endemic in Rwanda and is a major etiologic agent for chronic liver disease in the country. In a previous analysis of HBV strains from Rwanda, the S genes of most strains segregated into one single clade of subgenotype, A1. More than half (55%) of the anti-HBe positive individuals were viremic. In this study, 23 complete HBV genomes and the core promoter region (CP) from 18 additional strains were sequenced. Phylogenetic analysis of complete genomes confirmed that most Rwandan strain formed a single unique clade, within subgenotype A1. Strains from 17 of 22 (77%) anti-HBe positive HBV carriers had either mutated the precore start codon (9 strains with either CUG, ACG, UUG, or AAG) or mutations in the Kozak sequence preceding the pre-core start codon (8 strains). These mutually exclusive mutations were also identified in subgenotypes A1 (70/266; 26%), A2 (12/255; 5%), and A3 (26/49; 53%) sequences from the GenBank. The results showed that previous, rarely described HBV variants, expressing little or no HBeAg, are selected in anti-HBe positive subgenotype Al carriers from Rwanda and that mutations reducing HBeAg synthesis might be unique for a particular HBV clade, not just for a specific genotype or subgenotype.

Expression of wild-type or G1862T mutant HBe antigen of subgenotype A1 of hepatitis B virus and the unfolded protein response in Huh7 cells

The G1862T mutation, which occurs most frequently in subgenotype A1 of the hepatitis B virus (HBV), results in a valine to phenylalanine substitution at the -3 position of the signal peptide cleavage site at the amino end of the precore/core (preC/C) precursor protein. The objective of this study was to functionally characterize the G1862T mutation relative to its wild-type counterpart in subgenotype A1. Huh7 cells were transfected with subgenotype A1 replication-competent plasmids, with and without G1862T. Secretion of HBsAg and HBeAg, preC/C/HBeAg expression in the secretory pathway, activation of the unfolded protein response (UPR) and subsequent activation of apoptosis were monitored. The introduction of G1862T did not affect HBsAg expression. Cells transfected with the G1862T subgenotype A1 plasmid showed decreased expression of intracellular HBcAg and of nuclear preC/C/HBeAg and extracellular HBeAg, when compared to cells transfected with its wild-type counterpart as a result of the accumulation of the mutant protein in the endoplasmic reticulum (ER) and ER-Golgi intermediate compartment (ERGIC) . This accumulation of preC/C/HBeAg protein in the ER led to the earlier activation of the three UPR pathways, but not to an increase in apoptosis. Therefore, it is evident that the presence of G1862T in subgenotype A1 does not completely abolish HBeAg expression, but affects the rate of HBeAg maturation, its passage through the secretory pathway and activation of the UPR. Increase in ER stress can result in liver damage, which has been shown to be a contributing factor to hepatocarcinogenesis and may explain why G1862T is frequently found in subgenotype A1 from liver disease patients.

Precore/core region mutations of hepatitis B virus related to clinical severity

Despite the availability of an effective vaccine, hepatitis B virus (HBV) infection remains a major health problem, with more than 350 million chronically infected people worldwide and over 1 million annual deaths due to cirrhosis and liver cancer. HBV mutations are primarily generated due both to a lack of proofreading capacity by HBV polymerase and to host immune pressure, which is a very important factor for predicting disease progression and therapeutic outcomes. Several types of HBV precore/core (preC/C) mutations have been described to date. The host immune response against T cells drives mutation in the preC/C region. Specifically, preC/C mutations in the MHC class II restricted region are more common than in other regions and are significantly related to hepatocellular carcinoma. Certain mutations, including preC G1896A, are also significantly related to HBeAg-negative chronic infection. This review article mainly focuses on the HBV preC/C mutations that are related to disease severity and on the HBeAg serostatus of chronically infected patients.

New perspective on the natural course of chronic HBV infection

Chronic hepatitis B virus (HBV) infection is a significant threat to public health and an enormous burden on society. Mechanisms responsible for chronic HBV infection remain poorly understood. A better understanding of the natural course of chronic HBV infection may shed new light on the mechanisms underlying this disease and help in designing new antiviral strategies. Natural course of chronic HBV infection is conventionally viewed as an uninterrupted process that is usually marked by HBV e antigen (HBeAg) seroconversion or characterized by different phases associated with assumed host responses to HBV infection. However, none of these descriptions captures or highlights the core events that determine the natural course of chronic HBV infection. In this review, we briefly present the current knowledge on this subject and explain the significance and implication of events that occur during infection. A pre-core mutant becomes predominant in the viral population following elimination of the wild-type virus in duck hepatitis B virus-chronically infected animals. The coupled events in which first there is viral clearance that clears wild-type virus and then there is the reinfection of wild-type virus cleared livers with mutant virus are highly relevant to understanding of the natural course of chronic HBV infection under both treated and untreated conditions. In our new perspective, a general natural course of chronic HBV infection comprises cycles of viral clearance and reinfection, and such cycles prolong the chronic HBV infection course. Reviewing published data on the natural course of chronic HBV infection can reduce the possibility of missing important points in the initial data interpretation.

Characterization of the basal core promoter and precore regions in anti-HBe-positive inactive carriers of hepatitis B virus

BACKGROUND

The study of hepatitis B virus (HBV) genomic heterogeneity has become a major issue in investigations aimed at understanding the relationship between HBV mutants and the wide spectrum of clinical and pathological conditions associated with HBV infection. Although most chronically infected HBV patients are inactive carriers, several virological aspects of this state remain unclear.

METHODS

In order to determine the prevalence and clinical significance of mutations in the basal core promoter (BCP) and precore (pC) regions among inactive carriers, the nucleotide sequences from 41 inactive carriers were analyzed and compared with those from 29 individuals with chronic active hepatitis.

RESULTS

Genotypes A (24.3%), D (37.1%), F1b (12.9%), and F4 (18.6%) were the most prevalent. Mutations in the BCP/pC regions were observed in most of the inactive carriers (92.7%) and in most of the patients with chronic active hepatitis (93.1%). The prevalence of mutation 1764(A) was significantly higher in patients with chronic active hepatitis (65.5%) than in inactive carriers (36.6%) (p=0.038), whereas the prevalences of mutations at the other positions analyzed were not significantly different. Older patients (>50 years) showed BCP/pC patterns with a higher number of substitutions. Mutations were found to be biased by genotype: the 1896(A) mutation was highly prevalent in genotypes D and F4, while alternative substitutions in the pC region were more prevalent in genotypes A and F1b.

CONCLUSIONS

Mutations in the BCP/pC regions are the hallmark of chronic anti-HBe-positive individuals; nevertheless, the even distribution of mutations in active and inactive carriers suggests that BCP/pC mutations may occur during HBV infection not strictly related to the HBV infection activity.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Novel mutation in Hepatitis B virus preventing HBeAg production and resembling primate strains

Chronic carriers of hepatitis B infection often harbour virus strains with mutations in the precore region. These mutations are temporally associated with the development of HBeAg loss and seroconversion to anti-HBe. The most common precore mutation is a stop codon at position 1896, but other mutations leading to abolished HBeAg secretion have been described. Here, a novel precore mutation introducing a lysine in the precore position 28, a sequence shared by non-human primates but not by other human isolates, is described. However, the insertion causes a frame-shift preventing the expression of HBeAg by introducing a stop codon 5 aa downstream of the mutation. Analysis of the predicted RNA secondary structure indicates that the insertion could occur without fatally affecting the stability of the stem–loop encapsidation signal.

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

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

Four years of treatment with lamivudine: clinical and virological evaluations in HBe antigen-negative chronic hepatitis B

AIM

To evaluate the clinical and virological impact of the prolonged use of lamivudine in 94 patients with HBe antigen-negative chronic hepatitis B.

METHODS

Initial virological and biochemical responses were obtained in 84 (89%) and in 83 (88%) patients respectively.

RESULTS

The virological response peaked within the first 12 months, but diminished to 39% at 48 months because of drug resistance. Overall a virological breakthrough developed in 44 patients (52.4%). After virological breakthrough, the actuarial probability of maintaining biochemical remission diminished to 15% at 24 months and 0% at 29 months. There was no response in 10.6%. Polymerase gene mutations were observed in 82.5% of virological breakthroughs but also in 75% of the non-responders. Overall 7.4% of patients developed a hepatocellular carcinoma.

CONCLUSION

Almost 90% of patients responded initially to lamivudine but the emergence of drug resistance progressively reduced the rate of virological remission to 39% at the fourth year of therapy. YMDD mutants explained the 75% of lamivudine resistances and were also selected very early in non-responders. Although the biochemical response is invariably lost within 29 months of the YMDD mutant's duration, the clinical outcome was benign despite severe postvirological breakthrough hepatitic flares in about 12% of cases.

Epidemiological and sequence differences between two subtypes (Ae and Aa) of hepatitis B virus genotype A

Complete nucleotide sequences of 19 hepatitis B virus (HBV) isolates of genotype A (HBV/A) were determined and analysed along with those of 20 previously reported HBV/A isolates. Of the 19 HBV/A isolates, six including three from Japan and three from the USA clustered with the 14 HBV/A isolates from Western countries. The remaining 13 isolates including four from The Philippines, two from India, three from Nepal and four from Bangladesh clustered with the six HBV/A isolates reported from The Philippines, South Africa and Malawi. Due to distinct epidemiological distributions, genotype A in the 20 HBV isolates was classified into subtype Ae (e for Europe), and that in the other 19 into subtype Aa (a for Asia and Africa) provisionally. The 19 HBV/Aa isolates had a sequence variation significantly greater than that of the 20 HBV/Ae isolates (2.5+/-0.3 % vs 1.1+/-0.6 %, P<0.0001); they differed by 5.0+/-0.4 % (4.1-6.4 %). The double mutation (T1762/A1764) in the core promoter was significantly more frequent in HBV/Aa isolates than in HBV/Ae isolates (11/19 or 58 % vs 5/20 or 25 %, P<0.01). In the pregenome encapsidation (epsilon) signal, a point mutation from G to A or T at nt 1862 was detected in 16 of the 19 (84 %) HBV/Aa isolates but not in any of the 20 HBV/Ae isolates, which may affect virus replication and translation of hepatitis B e antigen. Subtypes Aa and Ae of genotype A deserve evaluation for any clinical differences between them, with a special reference to hepatocellular carcinoma prevalent in Africa.

Prevalência de genótipos e de mutantes pré-core A-1896 do vírus da hepatite B e suas implicações na hepatite crônica, em uma população da Amazônia oriental

A infecção pelo virus da hepatite B apresenta amplo espectro de manifestações clínicas. Objetivando conhecer os genótipos do HBV mais prevalentes e determinar a ocorrência da mutação pré-core A-1896, em uma população da Amazônia oriental, correlacionando com o diagnóstico clínico, foram selecionados 51 pacientes portadores crônicos de HBsAg e HBV-DNA positivos e divididos em três grupos: grupo A (n=14, pacientes assintomáticos); grupo B (n=20, sintomáticos HBeAg positivos) e grupo C (n=17, sintomáticos HBeAg negativos), sendo usado o sequenciador automático ABI modelo 377 para identificação de genótipos e mutantes pré-core. Os resultados evidenciaram o genótipo A como o mais prevalente, 81,8%, 89,5% e 93,7%, nos grupos A, B e C, respectivamente. A mutação pré-core A-1896 foi encontrada em 11,5% (3/26), sendo todos assintomáticos. Concluiu-se que na população estudada o genótipo A foi o mais prevalente e houve baixa ocorrência do mutante pré-core A-1896, ambos não se constituindo fatores agravantes da doença hepática.

N/A

N/A

Analysis of clinical, biochemical and viral factors associated with early relapse after lamivudine treatment for hepatitis B e antigen-negative chronic hepatitis B patients in Taiwan

The efficacy of lamivudine for HBeAg-negative chronic hepatitis B (CHB) Chinese patients has not been fully investigated. The role of the Hepatitis B virus (HBV) genotype on the treatment effect of lamivudine is controversial. Thirty-two consecutive patients with HBeAg-negative CHB were enrolled. All patients were treated with lamivudine 100 mg once daily of 7-12 months duration. The mean total period of follow-up since entry for all patients was 24 +/- 3.5 months. HBV genotypes were classified by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and verified by sequencing. Precore (G1896A) and basic core promoter (BCP, A1762T & G1764A) mutations were determined by PCR and direct sequencing. Twenty-one (65.6%) patients were infected by genotype B and, 11 (34.4%) by genotype C. G1896A was predominant in genotype B infected patients (95.2%vs 63.6%, P = 0.037). At the end of treatment, 31 (96.8%) and 14 (43.8%) patients achieved biochemical and virological responses, respectively. The biochemical and virological response rates were 40.6 and 0% at 12 months after treatment. Eighteen (56.3%) patients had biochemical relapse within 12 months after withdrawal of lamivudine. By multivariate analysis, the pretreatment serum level of HBV DNA >/=12 Meq/mL was the only factor associated with early biochemical relapse (Odds ratio = 9.333, 95% CI = 1.497 approximately 58.197, P = 0.017). In conclusion, the virological effect of lamivudine for HBeAg-negative CHB is transient. Most patients had biochemical relapse within 12 months after lamivudine treatment regardless of HBV genotype. A high pretreatment viral load is the determinant for early biochemical relapse.

Detection and significance of a G1862T variant of hepatitis B virus in Chinese patients with fulminant hepatitis

The prevalence of a G1862T variant of hepatitis B virus (HBV) has been investigated in patients with fulminant hepatitis and chronic liver disease, using primer mismatch amplification, followed by restriction fragment length polymorphism analysis. This variant was five times more common in patients with fulminant hepatitis (13.7%, 7 of 52) than in chronic carriers (2.5%, 2 of 81). The G-->T substitution at position 1862 leads to an amino acid change in codon 17 of the precore protein of the virus, which is part of a signal peptidase recognition motif. Variants with this mutation were only seen in patients infected with genotype B. In vitro translation experiments showed that this variant has greatly reduced capacity to produce hepatitis B e antigen (HBeAg) from its precore protein precursor. Furthermore, 88.5% of patients with fulminant hepatitis had mutations that are known to be associated with abrogated or reduced production of HBeAg. This suggests that, following HBV infection, the absence or reduced amounts of HBeAg may be a contributing factor in fulminant disease.

Efficacy of lamivudine in HBeAg-negative chronic hepatitis B

Hepatitis B e antigen (HBeAg)-negative chronic hepatitis B results from infection with hepatitis B virus mutants unable to produce HBeAg. It accounts for 7-30% of patients with chronic hepatitis B virus (HBV) worldwide, with the highest rates reported for Mediterranean Europe and Asia. Interferon (IFN) is currently the only approved therapy for these patients, but it has an unfavorable tolerance profile and limited efficacy. Studies show that responses to IFN are lower in HBeAg-negative than in HBeAg-positive patients; joint HBV DNA loss/ALT normalization is obtained in 38-59% of HBeAg-negative patients treated for 4-24 months with a high rate of virological relapse (54-87%), at 6-24 months posttreatment. Lamivudine is a nucleoside analogue with potent antiviral properties against HBV. Studies show that response rates in HBeAg-negative and HBeAg-positive patients are equivalent. After 12 months of treatment, 65-96% of HBeAg-negative patients have joint HBV DNA loss/ALT normalization, although 48-74% of patients relapse within 1 year posttreatment. 60% of patients have histological improvement after 12 months of treatment. Lamivudine is well tolerated with a safety profile equivalent to that of placebo. The incidence of YMDD variants increases with extended lamivudine treatment, present in up to 57-64% of patients after 2 years. Their clinical impact is unclear; some studies show breakthrough infection associated with their emergence, whereas other studies show maintained response to lamivudine. Lamivudine has benefits over IFN in its safety and efficacy profile in this patient group. Extended lamivudine treatment beyond 2 years is an option, but further investigation is required to define stopping criteria and the impact of YMDD variants.

In vivo suppression of precore mRNA synthesis is associated with mutations in the hepatitis B virus core promoter

We have examined the in vivo effect of hepatitis B virus (HBV) core promoter mutations on the expression of precore mRNA and pregenomic RNA transcripts in the liver of 24 patients with chronic HBV infection, applying a novel transcript-specific RT-PCR assay. The double A1762T/G1764A mutation in the basic core promoter was detected in 11 cases. This mutation was in all cases associated with absence or low levels of precore mRNA transcripts without significantly affecting the levels of total core promoter-directed transcription in the liver of infected patients. Precore mRNA synthesis was suppressed by the A1762T/G1764A mutation regardless of the presence of the precore stop codon mutation G1896A, suggesting that in addition to downregulating an immunomodulatory protein this double basic core promoter mutation may also confer a replication advantage to the virus. Additional mutations detected in the core promoter may also contribute to the observed changes in precore mRNA levels. Our in vivo study shows therefore that the double A1762T/G1764A mutation is associated with the specific suppression of precore mRNA synthesis directed by the HBV core promoter.

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.

Long-term follow-up of patients with anti-HBe/HBV DNA-positive chronic hepatitis B treated for 12 months with lamivudine

BACKGROUND/AIMS

Interferon alpha provides benefit in only a limited number of patients with chronic anti-HBe-positive hepatitis B. The aim of this study was to verify the long-term efficacy of lamivudine treatment of these patients and the incidence of lamivudine-resistant hepatitis B virus mutants.

METHODS

Fifteen consecutive patients with chronic anti-HBe-positive hepatitis B were treated with lamivudine 100 mg once daily for 52 weeks. Levels of alanine aminotransferase, HBV DNA, hepatitis B surface antigen, and IgM antibodies to hepatitis B core antigen were monitored during therapy and 12-month follow up. The polymerase gene was amplified by polymerase chain reaction and the region coding for YMDD amino acid motif was directly sequenced.

RESULTS

Only 2/15 patients (13%) had a sustained virological and biochemical response and improved histologically. Eleven out of 15 (74%) showed inhibition of viral replication and normalization of alanine aminotransferase levels during lamivudine treatment but relapsed 1-12 months after terminating therapy. In the two remaining patients (13%), HBV DNA initially became negative but reappeared in the serum after 24 weeks, and in both patients the emergence of YMDD mutants was demonstrated.

CONCLUSIONS

Our data confirm the antiviral efficacy of lamivudine in anti-HBe-positive patients, but response to a 1-year course was only transient as the majority of patients relapsed after therapy withdrawal. The lack of a sustained effect and the emergence of lamivudine-resistant mutants suggest that therapy for chronic hepatitis B should be based on a combination of several therapeutic agents.

Differential antigen-processing pathways of the hepatitis B virus e and core proteins

BACKGROUND & AIMS

Hepatitis B e antigen (HBeAg) and hepatitis B core antigen (HBcAg) seem to play different roles in the induction and regulation of the antiviral immune response, although the two antigens share all major CD4(+) T-cell epitopes, and these epitopes can be processed from both antigens via the exogenous antigen-presenting pathway. The aim of this study was to test the ability of antigen-presenting cells to present epitopes from endogenously synthesized HBcAg/HBeAg on HLA class II molecules.

METHODS

Lymphoblastoid cell lines infected with recombinant vaccinia viruses containing various HBcAg or HBeAg constructs and stable transfectants were tested for their ability to stimulate HBcAg/HBeAg-specific CD4(+) T-cell clones.

RESULTS

Only antigen-presenting cells infected with HBeAg constructs but not those infected with HBcAg constructs were able to stimulate HBcAg/HBeAg-specific CD4(+) T-cell clones. T-cell activation by HBeAg constructs was completely inhibited by brefeldin A but not affected by chloroquin. In contrast, T-cell activation by exogenous, recombinant HBcAg was inhibited by chloroquin but not by brefeldin A.

CONCLUSIONS

The findings indicate that processing and HLA class II-associated presentation of endogenously synthesized HBeAg in virus-infected cells, including hepatocytes, may occur. This mechanism may be involved in the regulation of the CD4(+) T-cell response to HBcAg/HBeAg.

Structure and function of the encapsidation signal of hepadnaviridae

The hepatitis B virus (HBV) and other members of the hepadnaviridae replicate by reverse transcription of an RNA intermediate, pregenomic RNA (pgRNA). pgRNA is also translated into core protein and polymerase (reverse transcriptase) protein. Before being reverse transcribed, pgRNA is sequestrated from the cytoplasm by being packaged, together with polymerase, into subviral particles composed of core protein. For pgRNA to be encapsidated, its 5' end is folded into a stem-loop structure, known as the encapsidation signal or epsilon (epsilon). This stable bipartite stem-loop structure contains a bulge and an apical loop. Besides encapsidation, epsilon is involved in the activation of polymerase, in template restriction and in the initiation of DNA synthesis by reverse transcription. HBV DNA encoding epsilon forms part of the template that is translated into the precore/core fusion protein that is in turn post-translationally modified to produce hepatitis B e antigen (HBeAg). The DNA encoding epsilon may be recombinogenic. Mutations within epsilon can affect its function and sequence conservation within epsilon in natural isolates is therefore high. epsilon could provide a practical target for antiviral therapy.

Incidence and clinical significance of hepatitis B virus precore gene translation initiation mutations in e antigen-negative patients

Hepatitis Be antigen (HBeAg)-negative chronic hepatitis B (CHB) is associated with hepatitis B virus (HBV) variants harbouring changes in the precore region. Most commonly, a G to A point mutation at nucleotide 1896 (m1896) creates a novel translation stop codon that prevents HBeAg production. In the Mediterranean region the m1896 mutation prevails in greater than 98% of HBeAg-negative CHB patients. In this study the prevalence of additional mutations in the precore region was investigated among patients with chronic HBV infection. Precore sequences were determined by sequencing serum HBV DNA amplified by polymerase chain reaction (PCR) with primers flanking the precore/core region. Thirty-one HBeAg-negative and five HBeAg-positive individuals were studied. All HBeAg-negative patients (100%) harboured the m1896 mutation and 20 (64.5%) also had a G to A mutation at nucleotide 1899 (m1899). Additional mutations affecting the translation initiation of the precore gene were found in seven (22.5%) patients, all with active liver disease, five of whom had episodes of HBV reactivation. HBeAg-positive patients had no mutations in these positions and neither did any of the five BHeAg-negative patients with normal levels of liver enzymes, representing the healthy carrier state of HBV infection. Serial sample analysis from one patient revealed that the initiation codon mutation developed following HBeAg seroconversion and the appearance of m1896. During periods of high HBV replication, the ratio of mutant to wild-type ATG was found to increase in parallel with HBV DNA levels. These data show that a significant proportion of HBeAg-negative patients who already harbour the 1896 stop codon mutation may subsequently develop precore translation initiation mutations, which appear to be associated with enhanced HBV replication and severe liver disease.

Precore wild-type DNA and immune complexes persist in chronic hepatitis B after seroconversion: no association between genome conversion and seroconversion

Precore hepatitis B virus (HBV) mutants may gradually prevail during or after seroconversion (SC) from hepatitis B e antigen (HBeAg) to hepatitis B e antigen antibody (anti-HBe) status in many chronic hepatitis B (CH-B) patients. However, patients with CH-B still produce anti-HBe more than several years after SC, and the relationship between SC and genome conversion in the precore region has not been clarified. Therefore, in patients with CH-B who had a sustained loss of HBeAg and complete remission of hepatitis after SC, the precore region was sequenced in paired serum samples from 1 year before SC to 3 years after SC. Mutant precore defective HBV DNA was found in only 6 (19%) of 31 CH-B patients who had a complete remission of hepatitis after SC. Mixed-type HBV DNA (precore wild-type and mutant-type) was found in 4 (13%) patients. Wild-type HBV DNA was found in 21 (68%) CH-B patients after SC. Longer-term follow-up of 11 CH-B patients indicated that 3 of 11 patients experienced precore genome conversion 2 to 3 years after SC. E-plus DNA or e-minus DNA was semiquantitated by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) assays before and after SC. E-plus DNA levels decreased from 10(5.56+/-1.58) to 10(2.45+/-1.61). Similarly, e-minus DNA levels declined from 10(4.25+/-1.56) to 10(1.86+/-1.37). By dot-blot assay, serum HBV DNA became negative soon after SC, as did serum HBeAg. In contrast, HBeAg-containing immune complexes were still detected after SC. Anti-HBe antibody was produced throughout SC and thereafter, as determined by a sensitive experimental assay. Therefore, we conclude that genome-conversion in the precore region is a separate event from HBeAg/anti-HBe seroconversion.

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.

Variability of the Hepatitis B Surface Protein in HBV-Infected Liver Transplant Recipients

Variations in the major surface proteins (HBsAg) of hepatitis B virus (HBV) have been implicated in the high rate of reinfection in HBV-infected recipients of orthotopic liver transplantations (OLT). Sera from 6 OLT patients positive for HBsAg and from 3 recipients negative for it prior to transplantation were analyzed over several years, and 39 HBsAg sequences were compared. Despite anti-HBs immunoprophylaxis resulting in the disappearance of HBsAg, HBV DNA was detectable by a sensitive nested PCR in almost all sera. In 1 patient, a significant temporary shift in HBV subtypes was observed, indicating a mixed infection or the presence of multiple HBV populations in this patient; this was also true for other patients. Amino acid substitutions compared to wild-type HBV subtypes in 7 patients and variations within patients in 5 patients were detectable over time; the 'escape mutation' at amino acid position 145 was detected in 2 patients. Our data suggest that the high rate of reinfection in OLT recipients seems not to be associated with specific sequence variations in the major HBs gene, but shows a remarkable inter- and intraindividual variability. Obviously, no correlation between heterogeneity in this gene and clinical outcome was present. Copyright 1997 S. Karger AG, Basel

Precore codon 28 stop mutation in hepatitis B virus from patients with hepatocellular carcinoma

OBJECTIVES

Hepatitis B virus (HBV) with a stop mutation at precore codon 28 (TGG-->TAG, tryptophan-->stop) was investigated to clarify if such a mutant virus might play a role in hepatocarcinogenesis.

METHODS

A total of 73 patients with HBV-related hepatocellular carcinoma were included in this study. Polymerase chain reaction (PCR) was performed in DNA samples extracted from 73 sera to amplify a HBV-DNA segment involving the precore and proximal core regions, and sequences of PCR products were analyzed to see the presence of the mutations at precore codon 28 by a direct sequencing method.

RESULTS

HBV-DNA was detectable in 64 (88%) patients by PCR. The stop mutation at precore codon 28 was identified in 50 of 58 PCR products (86%), in which direct sequencing was performed. Among patients with this mutant HBV, 21/50 (42%) patients were co-infected with wild-type HBV. The mutant virus was found in 23/28 (82%) patients with hepatitis B e antigen (HBeAg) and 27/30 (90%) patients without HBeAg. The mutant HBV alone was found in 10/28 (36%) patients with HBeAg and 19/30 (63%) without HBeAg. Among those patients on whom laparoscopy was performed, 22/24 (92%) with the precore codon 28 stop mutant alone had cirrhosis, compared to 12/19 (63%) co-infected by both the mutant and the wild-type (p < 0.05). The association of this mutant virus with both the presence and absence of HBeAg, and its association with cirrhosis when there is no co-infection with wild-type HBV, suggests an evolving pattern of liver pathology.

CONCLUSION

The high prevalence of a stop mutation at precore codon 28 in these patients with hepatocellular carcinoma suggests that HBV with this mutation may contribute to the development of hepatocellular carcinoma.

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.

Quantitative molecular methods in virology

During the past few years, significant technical effort was made to develop molecular methods for the absolute quantitation of nucleic acids in biological samples. In virology, semi-quantitative and quantitative techniques of different principle, complexity, and reliability were designed, optimized, and applied in basic and clinical researches. The principal data obtained in successful pilot applications in vivo are reported in this paper and show the real usefulness of these methods to understand more details of the natural history of viral diseases and to monitor specific anti-viral treatments in real time. Theoretical considerations and practical applications indicate that the competitive polymerase chain reaction (cPCR) and competitive reverse-transcription PCR (cRT-PCR) assay systems share several advantages over other quantitative molecular methodologies, thus suggesting that these techniques are the methods of choice for the absolute quantitation of viral nucleic acids present in low amounts in biological samples. Although minor obstacles to a wide use of these quantitative methods in clinical virology still remain, further technical evolution is possible, thus making the quantitative procedures easier and apt to routine applications.

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.

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.

Association of the core clustering mutations (codon 21-34) and the severity of chronic hepatitis B in Korean patients

OBJECTIVES

There are regions in the core gene of hepatitis B virus (HBV) where missense mutations are clustered, and mutations in that region are related to severe liver disease. However, there were some differences of the major regions for mutation clustering among ethnic groups. To explore the phenomenon of clustering mutations in Korean patients with chronic HBV infection and to elucidate the correlation between clustering mutation region of the core gene and the severity of liver damage, we analyzed the precore/core gene sequence of HBV in the sera from fifteen chronic hepatitis B (CH-B) patients.

METHODS

We analysed the HBV precore and core sequences in the sera obtained from fifteen patients (14 males and 1 female, mean age 30.0 years) with biopsy-proven CH-B. The patients were divided into two groups according to the pathological severity of CH-B; namely, group I consisted of 8 patients with chronic persistent hepatitis (CPH), and group II included 7 patients with chronic active hepatitis (CAH). After extraction of HBV DNA from each serum by proteinase K and phenol-chloroform solution, the entire precore and core region of HBV was amplified by PCR, and then the PCR products were subjected to direct sequencing using thermostable DNA polymerase. Fisher's exact test and Mann-Whitney U test were used for statistical analysis.

RESULTS

A total of 181 nucleotide substitutions were found in the HBV core gene from the 15 CH-B patients, of which 23 were missense and 158 were silent. The nucleotide and amino acid substitution rates were not significantly different between the two groups (p > 0.05). Two mutational hot spots (MHS), codons 21-34 (MHS1) and codons 85-100 (MHS2), were found in the deduced amino acid alignment of the core gene. The alteration rate of amino acid residue in these regions were 2.857 x 10(-2) and 5.000 x 10(-2), respectively. Of 8 CPH patients, 5 showed missense mutations only in MHS2. In comparison, of 7 CAH patients, 3 showed them both in MHS1 and MHS2, 1 only in MHS1, and 1 only in MHS2; thus, missense mutation in MHS1 was exclusively found in patient with CAH.

CONCLUSIONS

There were two mutation clusterings in the core region of adr subtype of HBV from Korean CH-B patients. Mutations in MHS1 (codon 21-34), but not in MHS2 (codon 85-100), are more likely to be related to the severity of CH-B. A longitudinal study using sequential samples is warranted to further clarify the role of MHS1 in the pathogenesis of more severe CH-B.

Hepatitis B virus precore mutations and HBeAg negative reactivation of chronic hepatitis B after interferon therapy

The objective of this study was to look for HBV precore mutations in three patients with chronic active hepatitis B who developed HBV-DNA-positive/HBeAg-negative reactivation after HBe seroconversion induced by interferon therapy. Direct sequencing of polymerase chain reaction products was performed on serum collected before and after HBe seroconversion. In two patients precore sequence showed only wild-type HBV before and after interferon therapy. In one patient, precore sequence showed only wild-type HBV before interferon therapy and a mixed infection by wild-type HBV and precore mutant viruses (1858 and 1896 nucleotide mutations) after treatment. The presence of HBeAg/anti-HBe immune complexes was found after HBe seroconversion in all cases. Our results suggest that: 1) precore mutations are not always found in patients with chronic hepatitis B who develop HBV DNA-positive/HBeAg-negative reactivation; and 2) HBeAg negativity, despite the presence of wild-type HBV, might be due to HBeAg/anti-HBe immune complexes. We speculate that the production of these immune complexes may be favored by interferon therapy.

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.

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.

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.

Different prevalence of precore mutants in five members of a hepatitis-B-virus-infected family: evidence for a precore variant type in an asymptomatic anti-HBs patient

Chronic active hepatitis B (CAH-B), anti-HBe (+) has been associated with a hepatitis B virus variant carrying a stop codon at the distal pre-C region that prevents HBeAg synthesis. We analyzed the HBV DNA pre-C region in five members of a Turkish family. The mother presented an anti-HBe (+) CAH-B and the four children different hepatitis B virus serological and clinical profiles. The pre-C region was analyzed by cloning after DNA amplification in sera and peripheral blood mononuclear cells. A method for rapid screening of a large number of cloned polymerase chain reaction products was developed for the presence of the most frequent pre-C mutations (G to A substitution at nucleotide position 1896 and 1899). At least 60 independent clones were tested for each patient by selective oligonucleotide hybridization using non-mutated (M0), one (M1) and two (M2) point-mutated probes. Results were confirmed by sequencing. The mutation 1896 was present in 91% of DNA clones from the mother. The same mutation was also found in 85% of the clones in the youngest child (D), but in less than 10% of the clones from children A and C. Only the pre-C wild-type strain was observed in child B. X gene deletions (3 to 20 nt) were also present in some clones from the mother and children A, B and C. No significant difference between serum and peripheral blood mononuclear cells concerning the viral population was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of hepatitis B precore region in serum and liver of chronic hepatitis B virus carriers

Using an oligonucleotide hybridization assay we studied the prevalence of wild-type and the predominant pre-core mutant hepatitis B virus in serum and liver of 49 antibody to hepatitis B e antigen carriers and three hepatitis B e antigen positive patients. Of the 45 serum samples from the anti-HBe carriers analyzed (no serum sample was available in four patients), 36 (80%) had hepatitis B virus DNA. In 26 of these 36 patients (72%) a mixed population was detected, wild-type genome alone was found in six patients (16%), the single mutant (nucleotide position 1896), in three cases (8%) and in one patient (2%) the viral DNA had the two nucleotide mutation (1896 and 1899). Of the liver biopsies from the 36 anti-HBe patients studied (no liver biopsy was available in 13 patients), 33 (92%) had hepatitis B virus DNA. A mixed viral population was detected in 23 patients (69%), only wild-type virus or a single mutation was found in eight (34%) and two patients (8%), respectively. In all cases, wild-type was the predominant genome. In serum and liver samples from the same patient, we found a concordance of the presence of wild-type HBV and the pre-core mutants studied in 23/26 (88%) of the patients. Alanine aminotransferase levels were higher (p < 0.01) and the duration of hepatitis B surface antigen carrier lower (p < 0.02) in patients with a predominance of precore mutant in comparison to wild-type.(ABSTRACT TRUNCATED AT 250 WORDS)

Nucleotide sequence analysis of the precore region in patients with spontaneous reactivation of chronic hepatitis B

The role of HBV precore mutations in the spontaneous reactivation of chronic hepatitis B (CHB) is currently unknown. We studied 10 patients with CHB; five were HBeAg+ (group I) and five were anti-HBe+ (group II). All 10 had spontaneous reactivation of CHB as defined by the appearance of clinical symptoms along with an increase of serum ALT activity at least 5X above baseline values, in the absence of any other known causes of liver disease or CHB reactivation. The precore (87 nt) and proximal core (81 nt) regions were sequenced after PCR amplification. From each patient three serum samples studied: one 3-12 months before, one during, and one six months after reactivation. Prior to reactivation, none of the group I patients harbored an HBV strain having a mutation that prevented HBeAg synthesis; however, 2/5 developed such a mutation during reactivation (G to A transition at nt 1896). Among the group II patients, three harbored an HBeAg defective mutant both before and during reactivation; after six months, two of these three patients were HBV DNA negative in serum by PCR. Several other sequence polymorphisms, some of which changed the predicted amino acid sequence, were either present initially or developed during reactivation. In conclusion, in this small group of CHB patients who were HBeAg+ spontaneous reactivation was accompanied in some cases by a shift to an HBeAg defective mutant, while in patients who were anti-HBe+, such mutations were frequently present prior to reactivation. In patients already harboring precore defective mutants, spontaneous reactivation may precede an attenuation of viral replication.

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.

Naturally occurring hepatitis B virus mutants with deletions in the core promoter region

A novel class of hepatitis B virus mutants in patients with chronic hepatitis B is described. The predicted effect of the mutations is to disrupt the X open reading frame. The location of the genetic alterations within the putative precore promoter also suggests that they may ameliorate precore transcription, which would provide an alternate mechanism for HBeAg(-) escape variation. Definitive conclusions regarding the effects of these mutations must await additional in vitro and in vivo studies.

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)

Competitive polymerase chain reaction and analysis of viral activity at the molecular level

Due to the high sensitivity level (which can be pushed to the limit of one molecule) and its extraordinary flexibility, the polymerase chain reaction (PCR) is the method of choice for the detection of nucleic acids present in very low concentration in biological samples. Since the qualitative features of PCR amplification have limited its use, several PCR-based approaches for the quantitation of low-abundance nucleic acid species have been planned and proposed in the last few years. Recently, different lines of evidence have indicated that competitive PCR and competitive reverse-transcription-PCR share several advantages over other quantitative approaches. This evidence opens up unexpected possibilities in many biological fields, including virology; in fact, availability of reliable techniques for the absolute quantitation of DNA and RNA species may be the key to a better understanding of the pathogenic steps of most viral diseases and for a more precise monitoring of patients treated with specific antiviral compounds. In this review article, we summarize the procedures adopted for this quantitative molecular approach; additionally, several important technical aspects to plan novel competitive PCR-based applications are analyzed, and early results obtained using cPCR for the direct evaluation of viral activity in vivo are discussed.

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.