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.

Efficacy of tenofovir in adefovir-experienced patients compared with treatment-naive patients with chronic hepatitis B

BACKGROUND

Tenofovir (TDF) has similar antiviral efficacy in both treatment-naive and lamivudine-resistant chronic hepatitis B (CHB) patients. Data on TDF use in patients with adefovir (ADV) resistance is inconsistent. The aim of our study was to assess antiviral efficacy of TDF against nucleoside analogue-naive (NN) and ADV-resistant (ADV-R) CHB and suboptimal responders to ADV (ADV-S).

METHODS

A database of 135 CHB patients treated with TDF was analysed. A total of 37 patients with incomplete data were excluded and analysis was performed in 98 (44 NN, 30 ADV-R and 24 ADV-S). Patients with primary ADV-R mutations had either A181T/V or N236T mutations or both. HBV DNA was measured at 3-month intervals until month 24. Primary outcome measures were comparison of the decline of HBV DNA between the three treatment groups.

RESULTS

NN patients had higher baseline HBV DNA compared with ADV-R and ADV-S patients (6.08 log10 IU/ml versus 5.53 and 4.88, respectively; P=0.002). By exponential regression analysis, HBV DNA decline kinetics differed between the three groups. HBV DNA decline was faster in NN patients compared to ADV-R and ADV-S CHB patients (P=0.002 and P=0.004, respectively). Undetectable HBV DNA was achieved in 77.2%, 60% and 75% of NN, ADV-R and ADV-S CHB patients, respectively, at month 12 (P= not significant).

CONCLUSIONS

HBV DNA decline is slower in ADV-experienced patients compared with treatment-naive patients. The clinical significance of this slow response may be important in patients with critical liver reserve and high viral load. Optimal combination treatment (TDF+ entecavir) could be considered in these patients.

Hepatitis B virus DNA in patients with HBsAg in south western Nigeria

There are about 400 million people with chronic hepatitis B virus (HBV) infection worldwide with a potential of adverse sequelae including hepatocellular carcinoma. Recent data have shown that the level of HBV DNA in serum or plasma of an infected person probably reflects more accurately the replicative activity of the virus and therefore may serve as a better maker for management of the infection. This study was designed to determine the rate of detection of HBV DNA in blood samples of patients with HBsAg positive in Nigeria in comparison with the HBe and anti-HBe used widely as serological markers of infectivity. Plasma samples from 105 patients with HBsAg positive were tested for the presence of HBeAg and anti-HBe using a commercial enzyme-linked immunosorbent assay while plasma HBV DNA was quantified using the COBAS Amplicor HBV Monitor assay. Of the 105 HBsAg samples, 17 (16.2%) and 85 (81%) were positive for HBeAg and anti-HBe, respectively, while 8 (7.6%) were negative for both HBeAg and anti-HBe. HBV DNA was detected in 86 (81.9%) of the samples, out of which 15 (18.1%) and 67 (80.7%) were positive for HBeAg and anti-HBe, respectively. HBV DNA was detected in 78.4% of the HBeAg negative samples and in all the eight samples that were negative for both HBeAg and anti-HBe. The implication of these findings in the management of patients with HBV infection is compelling.

An outbreak of hepatitis B with high mortality in India: association with precore, basal core promoter mutants and improperly sterilized syringes

In 2009, an outbreak of hepatitis B with high mortality was observed in Sabarkantha district, Gujarat state, India with 456 cases and 89 deaths. Hospitalized patients with self-limiting disease (152, AVH)) and fulminant hepatic failure (39, FHF including 27 fatal and 12 survivals) were investigated. These were screened for diagnostic markers for hepatitis viruses, hepatitis B virus (HBV) genotyping and mutant analysis. Complete HBV genomes from 22 FHF and 17 AVH cases were sequenced. Serosurveys were carried out in the most and least affected blocks for the prevalence of HBV and identification of mutants. History of injection from a physician was associated with FHF and AVH cases. Co-infection with other hepatitis viruses or higher HBV DNA load was not responsible for mortality. Four blocks contributed to 85.7% (391/456) of the cases and 95.5% (85/89) mortality while two adjacent blocks had negligible mortality. Sequence analysis showed the presence of pre-core and basal core promoter mutants and 4 amino acid substitutions exclusively among FHF cases. None of the self-limiting patients exhibited these dual mutations. Genotype D was predominant, D1 being present in all FHF cases while D2 was most prevalent in AVH cases. Probably due to violation of accepted infection control procedures by the qualified medical practitioners, HBV prevalence was higher in the affected blocks before the outbreak. Gross and continued use of HBV contaminated (mutant and wild viruses) injection devices led to an explosive outbreak with high mortality with a striking association with pre-C/BCP mutants and D1 genotype.

Epidemiology, course and disease burden of chronic hepatitis B virus infection. HEPNET study for chronic hepatitis B: a multicentre Greek study

Hepatitis B virus infection (HBV) has been recognized as a major health problem worldwide. Greece belongs to the intermediate endemicity countries with a trend of decreasing prevalence of HBV infection during the last decade. However, the recent massive immigration to our country may have led to alterations of HBV epidemiology. In this study, we evaluated the epidemiological features of HBV infection in a sample of 3480 patients followed up during the years 1997-2006. Immigrants mainly from Albania represented the 18.6% of the total study population and 56.6% of children. The majority of the patients had no family history of HBV infection (67.3%) or of acute hepatitis (95.4%), no known source of infection (64.6%), with intrafamilial spread accounting for 16.9% of the HBV transmission in adults and 33.9% in children. HBeAg(-) hepatitis B was the predominant form of hepatitis (92.1%) among the Greek patients in contrast to the immigrants where 16.6% were HBeAg(+). Liver cirrhosis was diagnosed in 8.8% of the total population and 0.9% had hepatocellular carcinoma. A high proportion of children were HBeAg(+) (62%), 55% from immigrant families, 25.2% were infected in the perinatal period and had no evidence of disease complications. In conclusion our results showed (a) a changing pattern in the epidemiology of HBV infection in Greece due to the significant number of HBeAg(+) patients, especially among children and (b) a considerable number of patients although aware of their infection, present with advanced disease.

Epidemiology of chronic hepatitis B infection in France: risk factors for significant fibrosis--results of a nationwide survey

BACKGROUND

Epidemiological data concerning hepatitis B are scarce in France.

AIM

To describe epidemiological, clinical, virological and histological features of HBsAg-positive patients followed at non-academic hospitals in France.

METHODS

Clinical, biological, virological and histological data of all HBsAg-positive consecutive patients observed from April 1, 2001 to May 31, 2002 in participating centres were recorded prospectively. Multivariate analyses of factors associated with significant fibrosis and cirrhosis were performed.

RESULTS

Nearly 1166 HBsAg-positive patients were seen in the 58 centres: 671 males and 495 females from metropolitan France (32%) and from outside metropolitan France (68%); mean age 41 +/- 15 years. Twenty-nine percent of patients were probable HBsAg inactive carriers, while 50% had chronic hepatitis; 43% of these were HBeAg-positive and 57% HBeAg-negative. Liver biopsy had been performed in 558 (51%) patients; 205 (17.6%) patients had cirrhosis. By multivariate analysis, factors associated with significant fibrosis were: age >40 years (P < 0.05), HBeAg-negative status (P < 0.02) and histological activity (P < 0.0001). Factors associated with cirrhosis: age (P < 0.0001), platelet count <150 000/mm(3) (P < 0.0001) and viral co-infection (P < 0.03).

CONCLUSION

HBV infection represents a significant workload for hepatogastroenterologists at non-academic hospitals in France.

Characteristics of patients with chronic hepatitis B in France: predominant frequency of HBe antigen negative cases

BACKGROUND/AIMS

An increasing prevalence of HBe antigen (HBeAg) negative chronic hepatitis B has been recently reported in many countries. The aim of this study was to analyze the frequency and the characteristics of HBeAg-negative as compared with HBeAg-positive chronic hepatitis B in France.

METHODS

Eight hundred and sixty-five patients with histologically proven chronic hepatitis B seen in 26 University centers were included. The proportion with HBeAg-negative chronic hepatitis B was 72% and higher in patients born in Africa, Middle East, Eastern, and Southern Europe than in those of French or Asian origin. HBeAg-negative patients were significantly older (p<0.001) and had lower ALT levels and HBV DNA serum levels (p<0.01) than HBeAg-positive patients. An unknown source of infection was more prevalent in HBeAg-negative patients (p<0.05). Fibrosis score (p<0.05) and proportion of cirrhosis (p<0.01) were significantly higher in HBeAg-negative patients. Age older than 50 years, male gender and viral load lower than 5 logs10 copies/mL were independently associated with cirrhosis.

RESULTS

HBeAg-negative chronic hepatitis B is predominant in France. This observation is important for an optimized clinical management and future therapeutic trials in chronic hepatitis B.

Hepatitis B virus (HBV) DNA levels and the management of HBV-infected health care workers

Different guidelines exist for the management of hepatitis B virus (HBV)-infected health care workers (HCWs). Various HBV DNA levels are used as a cutoff level to determine whether an HBV-infected HCW is allowed to perform exposure-prone procedures (EPPs) or not. In this paper we discuss the factors that determine HBV DNA levels and the implications of different HBV DNA cutoff levels for EPP performing HCWs. If the level of HBV DNA in the serum of HCWs is used to determine acceptability for the conduct of EPPs, it is necessary to take into account the variability in time of HBV DNA levels in HBV carriers and the reliability and reproducibility of the molecular diagnostic test involved. The issue of standardization has to be addressed, before a universal, maximum level of viraemia for EPP performing HCWs can be introduced.

Community-based epidemiology of hepatitis B virus infection in West Bengal, India: prevalence of hepatitis B e antigen-negative infection and associated viral variants

BACKGROUND AND AIMS

There is a paucity of population-based epidemiological information regarding hepatitis B virus (HBV) infection in India. The present study was planned to outline the magnitude and pattern of HBV infection, hepatitis B e antigen (HBeAg)-negative infection and the associated viral mutants in India.

METHODS

A community-based epidemiological study of HBV infection was carried out in West Bengal, India. Serological markers of infection and potential risk factors for HBV transmission were determined. Among the infected individuals, HBV-DNA, genotypes and mutations in the precore (PC) stop codon and basal core promoter (BCP) regions were determined by DNA sequencing and polymerase chain reaction (PCR) restriction fragment length polymorphism methods.

RESULTS

Of the 7653 people included in the study, 227 (2.97%) tested positive for hepatitis B surface antigen (HBsAg), of whom 204 (90%) were HBeAg-negative and hepatitis B e antibody (anti-HBe)-positive, and 78% had normal alanine aminotransferase (ALT) levels. HBV-DNA could be detected by PCR in only 32% of people. G1896A PC stop codon mutants were present in 12% of people, BCP mutants in 18% and the remainder (70%) of the HBeAg-negative infections were associated with wild type sequences in these regions.

CONCLUSIONS

This first general population-based epidemiological study of HBV infection from India suggests that HBV acquisition starts in early childhood and peaks in adulthood. Most infections in the community are e-negative and inactive. The point prevalence of PC stop codon and BCP mutants is low in this primarily inactive and asymptomatic HBV-infected population sample in eastern India.

The precore mutation is associated with severity of liver damage in Brazilian patients with chronic hepatitis B

BACKGROUND

The clinical relevance of the G1896A precore mutation in chronic hepatitis B is still poorly understood.

OBJECTIVES

To assess the frequency of G1896A precore mutation in Brazilian patients with chronic hepatitis B, as well as its relation to the viral genotype, serum HBV-DNA levels and liver damage.

STUDY DESIGN

Fifty chronic hepatitis B patients (29 HBeAg-negative and 21 HBeAg-positive) were studied. HBV-DNA was quantified by the Amplicor HBV Monitor test and precore region and S gene were amplified and submitted to automatic sequencing. The histological activity index (HAI), degrees of hepatic fibrosis and distribution of core antigen (HBcAg) in hepatocytes were determined.

RESULTS

Precore mutation occurred in 1/21 (4.8%) HBeAg-positive patients and in 17/29 (58.6%) HBeAg-negative (p < 0.0001). Genotype D was identified in 56.5%, genotype A in 41.3%, and genotype F in 2.2%. The frequency of genotypes D and A, as well as serum levels of ALT and HBV-DNA were similar in patients infected with wild type and with precore mutant. Patients infected with precore mutant presented a higher frequency of moderate/severe HAI (p: 0.03) and moderate/severe fibrosis and cirrhosis (p: 0.03) than those infected with wild type. There was no association between G1896A mutation and cytoplasmic expression of HBcAg.

CONCLUSIONS

Precore mutation was frequent among Brazilian subjects with chronic hepatitis B and its presence was associated with greater severity of liver disease.

Reactivation of resolved hepatitis B virus infection after allogeneic haematopoietic stem cell transplantation

Hepatitis B virus (HBV) reactivation after allogeneic haematopoietic stem cell transplantation (allo-HSCT) is well known in HBsAg-positive carriers but has only occasionally been reported in patients with resolved HBV infection. We investigated six allo-HSCT recipients with pretransplant anti-HBs and anti-HBc antibodies for serologic markers of HBV infection and for the presence of HBV-DNA in serum. Reverse seroconversion, that is, reappearance of HBsAg after a gradual loss of anti-HBs, but no severe liver damage was observed in three patients at 14, 22 and 12 months after HSCT, respectively. There was an increase in HBV-DNA concentration prior to reverse seroconversion. One patient was repeatedly HBV-DNA positive (10(2)-10(3) copies/ml) without reverse seroconversion. Sequencing of the HBsAg and precore region derived from the four HBV-DNA-positive patients showed no relevant mutations. In conclusion, this study demonstrated a high risk (50%) of reverse seroconversion in allo-HSCT recipients with resolved HBV infection. A highly sensitive HBV-DNA assay (TaqMan-PCR) allowed early identification of the individual patients at risk.

Precision and stability of hepatitis B virus DNA levels in chronic surface antigen carriers

Quantitative determination of hepatitis B virus (HBV) DNA concentration is the most important measure for an estimation of the infectivity of an HBV positive health care worker and the basis for the decision whether he or she is allowed to perform exposure prone procedures. Thus questions are raised on how reliable quantitative HBV DNA assays are, and how stable is the HBV DNA concentration is in a healthy chronic HBV carrier. Therefore, in the present study two commercially available quantitative HBV DNA assays, the Amplicor HBV Monitor and the HBV Test Hybrid Capture II, and an "in house" quantitative HBV TaqMan PCR, analysing 101 sera of HBsAg positive patients for HBV DNA were compared. In addition, HBV DNA concentrations were followed in 14 healthy chronic carriers for up to 6 years. Despite a good overall correlation between the three tests considerable differences were found for the results of individual sera. Fifty-one percent of sera showed differences within one order of magnitude, 45% differed by a factor above 10 and 4% even by a factor of 100 and higher. The follow-up of the HBV DNA concentrations in 14 carriers showed in 7 carriers a rather stable course with variations within one order of magnitude, whereas in the other half the DNA concentrations fluctuated by factors between 10(2) and 10(6) over the observation period. Thus, viral load determinations in health care workers have to be interpreted with some caution, especially when they are the basis of far-reaching decisions.

Sequential combination therapy of HBe antigen-negative/virus-DNA-positive chronic hepatitis B with famciclovir or lamivudine and interferon-alpha-2a

BACKGROUND/AIMS

Hepatitis B e antigen-negative/hepatitis B virus (HBV) DNA-positive chronic hepatitis B (CHBe-) exhibits a high relapse rate on monotherapy with lamivudine or interferon-alpha (IFN-alpha). We investigated, whether sequential therapy with famciclovir or lamivudine followed by combination with IFN-alpha-2a improves durable virologic response in CHBe- characterized by mutation analysis of the HBV precore genome region.

METHODS

Fourteen patients were treated with famciclovir (n=3) or lamivudine for 4 weeks to reduce the viral load, and subsequently with the combination of the nucleoside analogue and IFN-alpha-2a until 16 weeks beyond the loss of serum HBV-DNA.

RESULTS

Median duration of therapy was 29.0 weeks (range 20.6-48.3 weeks). Serum HBV-DNA was undetectable and alanine aminotransferase had normalized in all patients at the end of treatment. Seven (50%) patients maintained a sustained response 12 months after end of treatment. Only two of them had been infected by HBV with the G1896A mutation. Most patients (5/7) with the G1896A mutation relapsed within 4 months after therapy.

CONCLUSION

Sequential combination therapy can induce sustained virologic response in a subgroup of CHBe-, but most with the G1896A precore mutant HBV relapse. Trials of CHBe- should be based on characterization of HBV mutants.

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

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

Evidence for a dynamic host-parasite relationship in e-negative hepatitis B carriers

Anti-hepatitis Be (HBe) carriers are perceived as having low infectivity, with hepatitis B virus (HBV) DNA levels far below those seen in the HBeAg carrier. However, the temporal stability of HBV DNA in anti-HBe carriers remains poorly characterised. UK Department of Health guidelines use HBV DNA levels to define whether HBV-infected health care workers may perform exposure-prone procedures. Two samples separated by 1-23 years available from 147 carriers were analysed for precore variants and HBV DNA levels. Among 15 HBeAg carriers, HBV DNA was maintained at high levels. There was a 5 log(10) fold reduction in DNA in 11 individuals who developed anti-HBe during follow-up evaluation. Proportional changes in HBV DNA levels in anti-HBe carriers were similar to those in HBeAg carriers, although there was a trend for changes in viral DNA to be more marked in anti-HBe carriers followed up for longer periods. Closer sampling in 20 anti-HBe carriers demonstrated large fluctuations of DNA levels over short periods. Serum transaminases and precore mutant status at the outset failed to predict those in whom HBV DNA levels fluctuated. HBV DNA was below the detection threshold (<400 copies/ml) in 36 anti-HBe carriers at first sampling and remained so in all but 5 of these carriers. Twelve individuals who were previously viraemic lost detectable HBV DNA during follow-up evaluation. While HBV DNA levels are found to fluctuate in carriers, our results indicate that once below the threshold of detectability, levels are unlikely to rise. This is an important factor when assessing health care workers for exposure-prone procedures.

Viral genotype and hepatitis B virus DNA levels are correlated with histological liver damage in HBeAg-negative chronic hepatitis B virus infection

OBJECTIVES

We aimed to study the relationship between the hepatitis B virus (HBV) genotypes, core promoter/precore stop codon mutations, and histological liver damage among hepatitis B e antigen (HBeAg)-negative patients.

METHODS

Liver biopsy specimens of 55 HBeAg-negative chronic HBV-infected patients were studied. A histological activity index was scored for degree of necroinflammation (HAI-NI) and fibrosis (HAI-F) as described by Knodell et al. HBV DNA was determined by a cross-linking assay and polymerase chain reaction (PCR) at the core promoter/precore region and the S region. PCR-positive samples were directly sequenced for core promoter and precore mutations and examined by restriction fragment length polymorphism for genotyping.

RESULTS

Forty-one males and 14 females at a median age of 43 were studied. HBV DNA was detectable in 32 (58%) and 37 (67%) patients by the cross-linking assay and PCR, respectively, at the time of liver biopsy. The median (range) HAI-NI and HAI-F scores were 5 (1-10) and 2 (0-4), respectively. HBV DNA detectable by either the cross-linking assay or PCR was associated with a higher HAI-NI score. Eleven and 31 patients had genotypes B and C HBV, respectively. Genotype C HBV was associated with higher HAI-NI than genotype B HBV. Core promoter mutations and precore stop codon mutation were detected in 74% and 40% patients, respectively, but they were not associated with higher HAI-NI or HAI-F scores.

CONCLUSIONS

Detectable HBV DNA and genotype C HBV, but not core promoter or precore stop codon mutations, are associated with more severe liver damage in HBeAg-negative patients.

World-wide epidemiology of HBeAg-negative chronic hepatitis B and associated precore and core promoter variants

Hepatitis B is a serious disease that is endemic in many parts of the world. A significant proportion of patients with chronic hepatitis B (CHB) are infected with a variant form of the hepatitis B virus (HBV) which decreases or abolishes the production of hepatitis B e-antigen (HBeAg). The purpose of this literature review is to describe the epidemiology of HBeAg-negative CHB (e-CHB) worldwide. A literature search was conducted to identify studies pertaining to e-CHB and underlying variants (precore and core promoter). Fifty studies were included in our analysis. The median prevalence of e-CHB among patients with chronic HBV infection was 33% in the Mediterranean, 15% in Asia Pacific, and 14% in the USA and Northern Europe. The pre core stop codon variant was detected in a median of 60% (range 0-100%) of HBeAg-negative patients overall, 92% in the Mediterranean, 50% in Asia Pacific and 24% in the USA and Northern Europe. There were very few data on the prevalence of core promoter variants outside Asia where the median prevalence among HBeAg-negative patients was 77%. This literature review revealed that e-CHB is more common than previously suspected and that it is present worldwide with marked variations in the prevalence of associated HBV variants across different geographical regions. Additional research using population based samples of adequate size based on a consensus definition of e-CHB and using standardized HBV DNA assays is needed to better estimate the true prevalence of e-CHB and its associated HBV variants.

Immunopathogenesis of hepatitis B e antigen negative chronic hepatitis B infection

Hepatitis B e antigen (HBeAg) negative chronic hepatitis B represents currently the predominant form of chronic hepatitis due to the hepatitis B virus (HBV) in several parts of the world. In this review, recent data regarding the process of HBeAg negative HBV strain selection during the course of chronic HBV infection are presented and the potential virus and/or host-mediated mechanisms that lead to chronic liver necroinflammation, i.e. chronic hepatitis are outlined.

Epidemiology of precore mutants of hepatitis B in the United Kingdom

A point mutation assay was used to study the codon 28 and codon 1 precore mutant status of 310 chronic hepatitis B carriers (82 HBeAg positive and 228 HBeAg negative). Fourteen of 228 (6%) of HBeAg negative carriers had high levels of serum HBV DNA. Nine of these were explained by precore variants, three by core promoter variants, and two were not explained by recognised precore changes. Nested PCR detected serum HBV DNA in 36% (82/228) of HBeAg negative carriers and 63% (52/82) of these had precore variants. Four of 82 (4%) of the HBeAg positive carriers had precore variants, all as mixed mutant/wild type populations and evidence indicated that these carriers were seroconverting. Overall 23% (52/228) of HBeAg negative carriers had both serum HBV DNA and codon 1 or 28 precore mutations. A sexual transmission event from an HBeAg negative carrier with a relatively low serum HBV DNA level (10(4)-10(6) genome copies/ml) and only core promoter mutations was observed. Despite high rates of variant carriage in the antenatal sub-group perinatal transmission was not observed. The results of direct sequencing on 45 carriers validated the point mutation assay and also showed that codon 28 mutations were only seen in carriers with the genotype CCT at codon 15. For the Caucasian population a higher prevalence of codon 28 mutations (13/25 or 52%) than expected was seen. Liver biopsy data indicated that there was no link between the presence or absence of precore mutants and the severity of liver disease.

Genetic variations of hepatitis B virus

The emergence of hepatitis B virus genetic variants occurs under the influence of host immunity, immunization, the use of immune globulin or antiviral chemotherapy. Most of these are probably the result of the 'immune escape' phenomenon. Some variants, in particular those in the precore and core promoter regions, have been associated with disease severity and progression. Surface antigen variants have implications for the accuracy of laboratory diagnosis and may reduce the effectiveness of vaccination. Polymerase variants are selected as a result of the use of antiviral chemotherapeutic agents. It is important to monitor the occurrence of these variants.