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

The clinical implications of hepatitis B virus genotypes and HBeAg in pediatrics

Although a successful vaccine against HBV has been implemented in 184 countries, eradication of hepatitis B virus (HBV) is still not on the horizon. There are over 240 million chronic carriers of HBV globally. The risk of developing chronic hepatitis ranges from >90% in newborns of hepatitis Be antigen (HBeAg)‐positive mothers, 25%–35% in children under 5 years of age and <5% in adults. HBeAg, a non‐particulate viral protein, is a marker of HBV replication. This is the only HBV antigen to cross the placenta, leading to specific unresponsiveness of helper T cells to the capsid protein and HBeAg in newborns. HBeAg is tolerated in utero and acts as a tolerogen after birth. Perinatal transmission is frequent when mothers are HBeAg‐positive, whereas it occurs less frequently when mothers are HBeAg‐negative. Sequence heterogeneity is a feature of HBV. Based on an intergroup divergence >7.5% across the complete genome, HBV is classified phylogenetically into at least nine genotypes. With between ~4% and 8% intergroup nucleotide divergence, genotypes A–D, F, H and I are classified further into subgenotypes. HBV genotypes/subgenotypes may have distinct geographical distribution and can develop different mutations in the regions of the HBV genome that code for HBeAg. These differences can be related to the role of HBV genotypes to the natural history of infection and mode of transmission. Thus genotypes/subgenotypes of HBV can be responsible for the different natural history of infection and modes of transmission in children, found in various regions of the world, where different genotypes/subgenotypes prevail. Copyright © 2016 John Wiley & Sons, Ltd.

[Prophylaxis of mother-to-infant transmission of hepatitis B virus]

Hepatitis B virus (HBV) infection is a worldwide health problem and mother-to-infant (or vertical) transmission is the main source of chronic infection in Asian countries. Administration of HBV vaccine to the infant at birth, with or without concurrent specific immunoglobulin, efficiently prevents such transmission (efficacy>90%). In France, testing Ag HBs is mandatory during pregnancy in all pregnant women. Infants born to Ag HBs-positive mothers should receive the first injection of vaccine and one injection of specific immunoglobulins at birth. Vaccination should thereafter be completed according to a three-injection protocol (at 1 and 6 months) or a four-injection protocol in case of prematurity. Failure of immunoprophylaxis can be observed when the viral load is very high in the mother during pregnancy (HBV-DNA levels>200,000 IU/mL). In such women, antiviral therapy with analogs (lamivudine, telbivudine, or tenofovir) during the third trimester of pregnancy and 1 month post-partum, in association with accurate immunoprophylaxis, may prevent vertical transmission. The optimal cut-off value of maternal viral load for antiviral therapy in late pregnancy and post-partum to prevent vertical transmission is still under debate.

Effects of maternal screening and universal immunization to prevent mother-to-infant transmission of HBV

BACKGROUND & AIMS

Mother-to-infant transmission is the major cause of hepatitis B virus (HBV) infection among immunized children. There has been much debate about screening pregnant women and administering hepatitis B immunoglobulin (HBIG) to newborns. We analyzed the rate of HBV infection among children born to hepatitis B surface antigen (HBsAg)-positive mothers and whether HBIG administration reduces transmission.

METHODS

We analyzed data from 2356 children born to HBsAg-positive mothers, identified through prenatal maternal screens. In addition to HBV vaccines, HBIG was given to all 583 children with hepatitis B e antigen (HBeAg)-positive mothers and to 723 of 1773 children with HBeAg-negative mothers. Serology tests for HBV were performed from 2007 to 2009, when children were 0.5-10 years old.

RESULTS

A significantly greater percentage of children with HBeAg-positive mothers tested positive for antibodies against the hepatitis B core protein (16.76%) and HBsAg (9.26%) than children with HBeAg-negative mothers (1.58% and 0.29%, respectively; P < .0001 and <.001). Among the HBV-infected children, the rate of chronicity also was higher among children with HBeAg-positive mothers than children with HBeAg-negative mothers (54% vs 17%; P = .002). Similar rates of antibodies against the hepatitis B core protein (0.99% and 1.88%; P = .19) and HBsAg (0.14% and 0.29%; P = .65) were noted in children born to HBeAg-negative mothers who were or were not given HBIG. Infantile fulminant hepatitis developed in 1 of 1050 children who did not receive HBIG (.095%).

CONCLUSIONS

Children born to HBeAg-positive mothers are at greatest risk for chronic HBV infection (9.26%), despite immunization. Administration of HBIG to infants born to HBeAg-negative mothers did not appear to reduce the rate of chronic HBV infection, but might prevent infantile fulminant hepatitis. Screening pregnant women for HBsAg and HBeAg might control mother-to-infant transmission of HBV.

Prevalence of the precore G1896A mutation in Chinese patients with e antigen negative hepatitis B virus infection and its relationship to pre-S1 antigen

This study investigated the prevalence of the precore G1896A mutation in Chinese patients with hepatitis B e antigen (HBeAg) negative HBV infection and its relation to serum HBV pre-S1 antigen. The overall prevalence of the precore G1896A mutation was 72.6% in HBeAg-negative Chinese patients with detectable serum HBV DNA. The prevalence of the precore G1896A is significantly higher in Chinese HBeAg-negative patients with chronic hepatitis B than that in inactive HBV carriers with detectable serum HBV DNA. Serum pre-S1 and the precore G1896A mutation were simultaneously detected in most of Chinese HBeAg-negative patients.

Application of a novel, rapid, and sensitive oligonucleotide ligation assay for detection of cancer-predicting mutations in the precore and basal core promoter of hepatitis B virus

Hepatocellular carcinoma (HCC) and cirrhosis are important causes of mortality worldwide. Persistent hepatitis B virus (HBV) infection is a major cause of these diseases. Double mutations in the basal core promoter (BCP) (A1762T and G1764A) and precore (pre-C) (G1896A) regions of the virus are associated with progression to HCC. The current study is aimed at developing a simple method for screening and detecting BCP and pre-C mutations in HBV carriers. We have developed and validated an oligonucleotide ligation assay (OLA) to detect point mutations in the HBV core gene. We have applied OLA methods to samples from HBV-infected carriers recruited from the Gambia Liver Cancer Study (GLCS) comprising asymptomatic HBsAg carriers, patients with cirrhosis, and patients with HCC. We observed an 89.3% and 95.8% concordance between the OLA and DNA sequencing for BCP and pre-C mutations, respectively. OLA detected the mutations in single-strain infections and in infections with mixtures of wild-type and mutant viruses under conditions where sequencing detected only the single dominant strains. BCP mutations were detected in 75.7% of patients with advanced liver disease (cirrhosis/HCC) compared to 47.6% of asymptomatic carriers, while pre-C mutations were detected in 34.5% of advanced liver disease patients and in 47.6% of asymptomatic HBsAg carriers. There was a significant association between the presence of BCP mutations and advanced liver disease. In conclusion, OLA is a simple, economical, and reliable assay for detection of pre-C and BCP mutations. Its application can lead to improvement in diagnosis and clinical care in regions where HBV is endemic.

Distinct geographic distributions of hepatitis B virus genotypes in patients with acute infection in Japan

Genotypes of hepatitis B virus (HBV) were determined in 145 patients with acute hepatitis B from various districts in Japan to establish their geographic distribution and evaluating the influence on the clinical illness and outcome. Genotypes were A in 27 (19%) patients, B in 8 (5%), C in 109 (75%) and mixed with B and C in the remaining one (1%). Genotype A was more frequent in metropolitan than the other areas (21/69 (30%) vs. 6/76 (8%), P < 0.001). On phylogenetic analysis, seven of the nine (78%) HBV/A isolates selected at random clustered with those from Europe and the United States, while the remaining two with those of subgroup A' prevalent in Asia and Africa. Maximum ALT levels were lower (2069 +/- 1075 vs. 2889 +/- 1867 IU/L, P = 0.03) and baseline HBV DNA titers were higher (5.90 +/- 1.45 vs. 5.13 +/- 1.36 log genome equivalents (LGE)/ml, P = 0.002) in patients infected with genotype A than C. Hepatitis B surface antigen persisted longer in patients infected with genotype A than C (1.95 +/- 1.09 vs. 1.28 +/- 1.42 months, P = 0.02). HBV infection became chronic in one (4%) patient with genotype A and one (1%) with genotype C infection. Fulminant hepatic failure developed in none of the patients with genotype A, one (13%) with genotype B and five (5%) with genotype C. The point mutation in the precore region (A1896) or the double mutations in the basic core promoter (BCP) region (T1762/A1764) were detected in none of the patients with genotype A, two (25%) with genotype B and 27 (26%) with genotype C. In conclusion, genotype A is frequent in patients with acute hepatitis B in metropolitan areas of Japan, probably reflecting particular transmission routes, and associated with longer and milder clinical course than genotype C.

High frequency of the 1896 precore mutation in patients and blood donors with hepatitis B virus infection from the Indian subcontinent

AIM

Hepatitis B virus (HBV) e antigen (HBeAg)-negative variants are reported to harbor 1896 precore mutants, and predict a worse clinical outcome. The aim of this study was to estimate the incidence of a precore mutation (1896) in both patients with chronic hepatitis B (CH-B) infection and blood donors in a tertiary care hospital in south India.

METHODS

One hundred and twenty-two consecutive HBV DNA-positive CH-B patients (group I) and 102 HBsAg-positive 'healthy' blood donors (group II) were recruited. Samples found to be positive for HBV DNA were further studied. A nested PCR was used for the detection of HBV DNA. The 1896 precore mutation was detected using PCR-restriction fragment length polymorphism (RFLP). Nucleotide sequencing was performed on representative samples to confirm PCR-RFLP findings. The study population was stratified comprising: group IA: 17 HBeAg-positive CH-B patients; group IB: 105 HBeAg-negative CH-B patients; group IIA: 12 HBeAg-positive blood donors; and group IIB: 55 HBeAg-negative blood donors.

RESULTS

There was no significant difference in the HBeAg-positive status between groups I and II. Significantly higher levels of alanine transaminase (ALT) were seen in groups IA and IB than in groups IIA and IIB, respectively (p = 0.033; p = 0.004). A significantly higher proportion of CH-B patients (32.7%) were positive for anti-HBc IgM compared with the blood donor groups (10.4%; p = 0.0006). Among the HBeAg-negative subjects, 69% of the CH-B patients and 65% of the blood donors showed evidence of 1896 precore mutant. This infection included the 1896 mutant exclusively or mixed infection involving the 1896 mutant and 1896 wild-type.

DISCUSSION

The absence of detectable HBeAg in most of the viremic blood donors and patients emphasizes the need for HBV DNA testing irrespective of HBeAg status. Mixed infection was detected in a higher proportion (42.6%) of CH-B patients than in blood donors (26.8%; p = 0.031). Among those with mixed infection, a significant proportion (44.2%) of CH-B patients, had ALT levels greater than the upper limit of normal (ULN), as compared with the blood donor groups (16.6%; p = 0.036).

CONCLUSIONS

The majority of CH-B patients and blood donors were negative for HBeAg despite their positive HIV DNA status. About two-thirds of the HBsAg-positive blood donors were viremic. Mixed infection was detected more frequently in CH-B patients and appears to be associated with more pronounced liver damage, as indicated by increased ALT levels.

Evaluation of a line probe assay for identification of hepatitis B virus precore variants in serum from chronic hepatitis B carriers

A prototype line probe assay (LiPA) for identifying hepatitis B virus (HBV) precore variants (INNO-LiPA HBV precore) was evaluated using a panel of 50 sera from 46 patients with HBV infection. The assay detected sequence variations detected commonly in the precore promoter region and in amino acid codons 28 and 29 of the precore gene. There was strong agreement between INNO-LiPA HBV precore results and those of a codon 28 point mutation assay (PMA), with identical results obtained in 40 of 43 sera (93%) typeable by both assays (kappa coefficient (kappa)=0.90). In addition, the precore codon 29 sequence identified by the INNO-LiPA HBV precore was confirmed by nucleotide sequencing in all seven samples analysed. However, the INNO-LiPA HBV precore identified precore promoter sequences much less efficiently. The prototype assay could identify codon 28/29 sequences from as little as 10 HBV genome equivalents in 10 microl serum, and in experiments using artificially prepared mixtures of variants could identify a minor component constituting 2.5% of the total viral DNA population. The INNO-LiPA HBV precore was also straightforward technically and rapid, and is therefore likely to be useful for epidemiological investigations into the prevalence, distribution and clinical significance of HBV precore variants.

HBV DNA levels and transmission of hepatitis B by health care workers

BACKGROUND

Laboratory-based study funded by the Research and Development Division of the Department of Health to inform the decision making on guidelines for the conduct of exposure prone procedures (EPPs) by health care workers who are hepatitis B carriers.

OBJECTIVES

Define the quantity and nature of hepatitis B virus (HBV) DNA in hepatitis carriers whose serum does not contain hepatitis B e antigen (HBeAg) and in surgeons previously cleared to conduct EPPs who have transmitted HBV to their patients.

STUDY DESIGN

Cross-sectional survey using HBV DNA quantification, genotyping and sequencing comparing transmitting surgeons and asymptomatic carriers.

RESULTS

HBV DNA could be detected and quantified in 64.5% (136 of 211) of carriers whose serum did not contain HBeAg with a median level 3.6 log(10) copies/ml (range of 5.7 log(10) copies). Pre-core mutation appeared not to affect the HBV DNA level, however, all surgeons carried codon 28 variants and transmitted these variants to their patients. The lowest HBV DNA level in a transmitting surgeon was 4 x 10(4) copies/ml.

CONCLUSIONS

Pre-core mutations are common in carriers whose serum does not contain HBeAg and do not specifically identify carriers whose HBV DNA levels are high. It was possible to define a level of virus above which transmission of hepatitis B during conduct of EPPs could not be excluded.

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.

Quantity of mutant K-ras gene in pancreatic secretions for diagnosis of pancreatic carcinoma with different assays: analysis of 100 patients

BACKGROUND

Two types of quantitative assay kits for K-ras mutations, PCR-preferential homoduplex formation assay (PHFA) and enriched PCR and enzyme-linked mini-sequence assay (ELMA), were recently developed. The K-ras mutations were analyzed using these assays.

MATERIALS AND METHODS

DNA was extracted from the pancreatic juice which was obtained by endoscopy from 38 patients with pancreatic neoplasms (23 adenocarcinomas and 15 intraductal papillary neoplasms) and from 62 without it.

RESULTS

The results of the two methods were mutually correlative. K-ras mutation was detected at high levels (mutant ras genes occupied >2% of all K-ras genes) in 25 of the 38 cases (66%) with pancreatic neoplasm. It was also detected at high levels in 9 of the 14 cases (64%) with pancreatic cyst. In contrast, the mutant gene was detected at a lower level (<2%) in other cases.

CONCLUSIONS

Quantitative analysis of the mutant ras gene provided a useful tool for diagnosing the pancreatic carcinoma when the percentage of the mutant is high, especially when the types of mutation were either GAT or GTT.

Quantitative analysis of K-ras gene mutation in pancreatic tissue obtained by endoscopic ultrasonography-guided fine needle aspiration: clinical utility for diagnosis of pancreatic tumor

OBJECTIVES

Endoscopic ultrasonography-guided fine needle aspiration (EUS-FNA) has become established in the diagnosis of pancreatic cancer. The combination of pathological diagnosis and analysis for mutant K-ras gene was investigated to improve the accuracy of diagnosis.

METHODS

EUS-FNA was performed in 34 patients with pancreatic masses (26 adenocarcinomas and eight chronic pancreatitis). Mutant ras gene was analyzed semiquantitatively in the specimens obtained by EUS-FNA as well as in pancreatic juice obtained by ERCP.

RESULTS

Mutant gene was detected at high amounts (more than 2% of total ras genes) in 20 of 26 (77%) specimens of EUS-FNA and in 12 of 19 (63%) of pancreatic juice in cases with pancreatic carcinoma. Cytological diagnosis of malignancy by EUS-FNA was found in 16 of 26 (62%) patients with pancreatic cancer. Accurate diagnosis of the carcinoma was 21 of 26 (81%) by combined cytology and molecular method of EUS-FNA, and increased to 23 of 26 (88%) by adding molecular analysis of pancreatic juice. In contrast, mutant gene was absent or low level despite suspicious cytology in patients with benign pancreatic lesion.

CONCLUSION

Quantitative analysis of mutant ras gene supplemented conventional cytology of EUS-FNA and ERCP. Detection of mutation at high amounts may represent pancreatic cancer, whereas its absence increased the possibility of benign lesion.

Novel immunoassay for the detection of hepatitis B surface 'escape' mutants and its application in liver transplant recipients

Hepatitis B virus (HBV) strains with mutations in the surface gene are responsible for the failure of prophylaxis with hepatitis B immunoglobulin (HBIG) in a proportion of patients transplanted for HBsAg positive cirrhosis. So far, the emergence and evolution of these 'surface antibody escape' mutants have been studied by DNA sequencing. In this study the use of an immunoassay is described for diagnosis and characterisation of HBV recurrence after liver transplantation (OLT), based on a monoclonal antibody able to recognise both wild-type and mutant HBsAg. Pre- and post-transplant samples from 22 patients transplanted for HBsAg positive cirrhosis were studied: Group A: 12 patients who reinfected the graft despite receiving HBIG; Group B: 6 patients with no HBV recurrence with continuous HBIG; Group C: 4 patients with HBV recurrence without prophylaxis. By running the new assay in parallel with an immunoassay that is susceptible to HBsAg mutants, 4 of 12 cases were identified in Group A with HBV recurrence due to surface antibody escape mutants, whereas in 8 patients this was due to the wild-type HBV. The results from the immunoassays were confirmed in all cases by HBV DNA sequencing. The surface gene mutations in the 4 patients affected codons 144 and 145 and in one of these 4 patients HBV strains with mutations in both codons were detected before and after transplantation. The epitope recognised by the new monoclonal antibody that reacts with both wild-type and mutant HBsAg seems to remain stable in the HBIG-induced HBV mutants. This serological approach allows rapid and cost-effective screening for HBsAg escape mutants in the liver transplant setting and may be helpful in the selection of appropriate prophylaxis.

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.

A novel primer-extension assay for the detection of a G to A mutation in the distal precore region of hepatitis B virus DNA

The roles of genetic heterogeneity of the hepatitis B virus (HBV) precore gene in the pathogenesis of HBV infection are unclear. Various methods have been used to detect nucleotide (nt) 1896 precore mutants. We established a new primer-extension assay to facilitate the detection of these mutants. This assay is based upon the fact that there is no adenine in the distal precore region of wild-type HBV. Polymerase chain reaction (PCR)-amplified template DNA was denatured and annealed to the [gamma-32P]-labelled primer. During primer extension in the presence of DNA polymerase and dCTP, dGTP, dTTP and ddATP, the reaction terminates if there is a nucleotide A. When mixtures of different ratios of wild-type and nt 1896 precore mutants were analysed in the primer-extension assay, correlation between the percentage known amounts and the percentage measured amounts of nt 1896 precore mutants was excellent (r2=0. 9669). When the primer-extension assay and direct sequencing were compared in hepatitis B e antigen (HBeAg)-positive and -negative chronic active hepatitis B patients, the primer-extension assay detected a greater number of nt 1896 precore mutants than direct sequencing and thus most HBV infections were found to be mixed infections. In conclusion, the primer-extension assay is a reliable and sensitive method for the detection of nt 1896 precore mutants.

Association of mutations in the core promoter and precore region of hepatitis virus with fulminant and severe acute hepatitis in Japan

It was recently reported that mutations in the precore and core promoter region of hepatitis B virus (HBV) are associated with fulminant hepatitis. The aim of this study was to investigate the association of mutations in the precore and core promoter region of HBV with fulminant and severe acute hepatitis. We studied Japanese patients with acute HBV infection, including seven patients with fulminant hepatitis, 12 with severe acute hepatitis and 41 with acute self-limited hepatitis. The presence of HBV mutants was examined by using a point mutation assay to detect a G to A transition at position 1896 in the precore region and an A to T transition at position 1762 and a G to A transition at position 1764 in the core promoter region. Significant differences in the proportion of mutations in the precore or core promoter region were present between patients with fulminant hepatitis and self-limited acute hepatitis (7/7 (100%) vs 4/41 (9.8%), P<0.01) and between severe acute hepatitis and self-limited acute hepatitis (6/12 (50.0%) vs 4/41 (9.8%), P<0.01). The frequency of mutation increased proportionately with the severity of disease in patients with acute HBV infection. Fulminant hepatitis B in Japan is closely associated with mutations in the core promoter and precore gene of HBV. Point mutation assays for HBV precore and core promoter analysis may be useful to predict the outcome of liver disease in patients with acute HBV infection.

Perinatal hepatitis B: update & recommendations

The hepatitis B virus (HBV) is the most prevalent chronic infectious disease in the world, and should be better understood by nurses caring for families. Perinatal acquisition is the major cause of infection in infants and children. Without vaccine during infancy, 90% of infants born to women positive for the virus will go on to become lifelong carriers. There are significant sequelae associated with HBV infection, ranging from fulminant HBV to chronic liver disease to an increased risk for carcinoma. A comprehensive prevention and treatment strategy has been developed by the Centers for Disease Control and Prevention, which includes screening of all pregnant women for the presence of HBV, the administration of hepatitis B immunoglobulin (HBIG) at birth, and the administration of hepatitis B vaccine at birth, at 1 month of age, and at 6 months of age. Nurses working in the perinatal and pediatric specialties must understand the implications of HBV to help prevent transmission and to assist in the coordination of care and advocacy for affected populations. The community health implications for the care of women and children with HBV are clear, giving nurses the opportunity to develop a closer linkage between hospital- and community-based nursing practice.

Colourimetric point mutation assay: for detection of precore mutants of hepatitis B

A colourimetric assay for the analysis of point mutations in PCR amplified DNA fragments from hepatitis B virus (HBV) is described. The method was applied for analysis of the single point mutation in codon 28 of the precore gene of HBV, which inhibits expression of HBe antigen. The assay, which uses a microtitre plate formate, incorporates fluorescein-labelled dideoxynucleotides as opposed to radioactively-labelled deoxynucleotides used in methods described previously. Synthetic control wild type and mutant oligonucleotides were tested to optimise the reaction conditions. The assay was thus shown to yield both qualitative and quantitative data on the relative proportions of wild type and mutant sequences within a given sample. Amplicons from clinical specimens of known sequence were analysed to validate the assay. Sixteen chronic carriers of HBV were tested using the codon 28 point mutation assay, and the results were confirmed by direct sequencing. The method described is suitable for applications where point mutations are of interest.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Semiquantitative assessment of pre-core stop-codon mutant and wildtype hepatitis B virus during the course of chronic hepatitis B using a new PCR-based assay

In most patients with chronic hepatitis B positive for antibodies (anti-HBe) to HBe antigen (HBeAg), a pre-core mutant hepatitis B virus (HBV) with a point-mutation at nt. 1896 can be isolated. Clinical significance of the mutant virus in chronic hepatitis B is not proven yet, and screening of large numbers of sera during different clinical courses of numerous patients is necessary. We therefore aimed to develop a fast and reliable assay, that allows to discriminate wildtype from nt. 1896 G-->A mutant HBV and to determine the ratio of mutant and wildtype HBV in patients' sera. A mutation specific polymerase chain reaction (ms PCR) with new primers served to distinguish nt. 1896 G-->A mutant from wildtype HBV. This msPCR proved to be more sensitive and specific than similar assays described previously. When compared to a dilution series of a cloned HBV-DNA standard, the amount of wildtype and nt. 1896 G-->A mutant HBV could be determined semiquantitatively. 10(2) to 10(7) copies of each HBV-DNA (equivalent to 10(5) to 10(10) copies of HBV-DNA/ml patients' serum) could be amplified with steadily increasing signals. MsPCR proved to be specific as 10(7) copies did not give an amplification signal if they did not match the respective primer pair used. In a mixed population of mutant and wildtype virus, msPCR allows to detect even a low amount of the minor HBV strain (0.1-0.01%, of the viral population) and to determine the ratio of wildtype and mutant HBV. MsPCR is as fast and convenient to perform as an unmodified PCR. It requires careful performance to avoid contamination but no specific equipment. Clinical usefulness of msPCR was demonstrated when the ratio of wildtype to mutant HBV was determined in 86 sera collected during 3 to 7.5 years follow up of 9 patients suffering from anti-HBe positive chronic hepatitis B. We conclude that this assay conveniently allows to study patients with chronic hepatitis B in order to detect and follow-up the emergence of pre-core stop-codon mutant HBV in correlation to the clinical course.

Hepatitis B nucleotide sequence analysis: linking an outbreak of acute hepatitis B to contamination of a cryopreservation tank

An epidemiological investigation indicated that six patients treated in a haematology unit who developed acute hepatitis B may have been infected as a result of contamination of a liquid nitrogen bone marrow storage tank. The clinical details are described elsewhere (Tedder et al., 1995); we describe the virological methods used to support the findings. HBV DNA was amplified from sera using a nested PCR with primers for the surface gene, and a region encompassing precore, the 3' end of X, and the 5' end of core. HBV DNA was also extracted from the frozen detritus in the liquid nitrogen storage tank. After equilibration, the aqueous material was filtered, co-precipitated with albumin and polyethylene glycol and the HBV DNA extracted by phenol-chloroform and ethanol precipitation. Direct nucleotide sequence analysis indicated that four patients were infected with HBsAg subtype adw viruses which carried novel amino acid substitutions at codons 145 and 146 of the X gene. HBV DNA extracted from the storage tank detritus contained identical sequences. The samples from two other patients, subtype ayw, did not contain the novel sequence changes in X and had other sequence differences. These findings linked conclusively the four patients as a cluster and the rescue of HBV-DNA sequences from the contaminated storage tank by the method described confirmed this as the common source of infection. Two other HBsAg-positive patients were excluded from the cluster by sequence analysis. Demonstration of infection by this route has implications for the safe storage of bone marrow and other related biological materials.

Hepatitis B virus surface mutations associated with infection after liver transplantation

BACKGROUND/AIMS

Liver transplantation for chronic liver disease due to hepatitis B virus infection is associated with a high risk of graft infection, graft failure and death. Many centres restrict this procedure to those seronegative for HBV-DNA (by hybridisation assay) and use prophylactic polyclonal human hepatitis B specific immunoglobulin to prevent infection of the graft, despite the very high cost.

METHODS

We describe three patients who underwent liver transplantation for chronic HBV-related disease in whom death was due to fibrosing cholestatic hepatitis following graft infection with hepatitis B virus, despite receiving hepatitis B specific immunoglobulin. Variation within the immunodominant a epitope of HBsAg was sought by analysis of hepatitis B virus sequences and the use of a point mutation assay, following amplification from serum by the polymerase chain reaction.

RESULTS

Prior to transplantation, Cases 1 and 2 had mutations at nucleotide 1902 (codon 145), resulting in G-C substitutions, which persisted at a low level after transplantation. In Case 2 a second mutant type with a G-A substitution at nucleotide 1902, became the predominant viral type post transplant. Case 3 had exclusively wild type virus before and after transplantation. The emergence of mutant type virus in Case 2 may have occurred because of immune pressure exerted by high titre anti-HBs detectable for more than 7 months. Cases 1 and 3 received only brief courses of anti-HBs therapy. The mutant viral surface antigen was not detected by a monoclonal antibody-based assay, and therefore the choice of HBsAg assay for post-transplant monitoring of patients who receive liver grafts for hepatitis B virus disease is important.

CONCLUSIONS

A search for mutations affecting the a determinant prior to liver transplantation for HBV-related liver disease may help to identify those at risk of failure of prophylaxis. Monoclonal antibodies specific to the codon 145-mutant surface antigen might prevent graft infection, but other mutations might then emerge.

Variability in hepatitis B virus DNA: phylogenetic, epidemiological and clinical implications

Hepatitis B virus has the smallest of all known human DNA virus genomes (3.2 kb) and a unique replication strategy with an intermediate reverse transcription step. The naturally occurring genetic variability between different HBV strains provides the basis for phylogenetic analysis. Four main genotypes of HBV have been found, with the possible existence of 1 or 2 more. The different genotypes largely follow a distinctive geographical distribution. Point mutations and nucleotide deletions in the genes (pre-S and S) encoding different forms of the surface protein have been shown to arise both spontaneously and after interferon treatment or vaccination. An immune escape mechanism is believed to be the reason for these mutations. The clinical implications of variations in the HBV X gene have not been widely studied, but these variations may be of importance in the development of hepatocellular carcinoma. Seroconversion from HBeAg to anti-HBe can be correlated with specific changes in the core promoter, and/or with a translational stop in precore codon 28. In both cases the production of HBeAg protein would be shut off. Mutations in the precore region may have a larger impact at another level, by inhibiting or enhancing viral replication through changes in folding of the transcript.

Selection of a precore mutant after vertical transmission of different hepatitis B virus variants is correlated with fulminant hepatitis in infants

The incidence of perinatal transmission of hepatitis B virus (HBV) depends on the HBeAg/anti-HBe status of the mother. While children of HBeAg-positive mothers have a 90% probability of acquiring a chronic hepatitis B virus carrier state, babies of anti-HBe-positive mothers are more likely to develop fulminant hepatitis within the first 3 to 4 months of life. There is evidence that precore (pre-C) mutations of the HBV can be associated with fulminant hepatitis. The pre-C region was therefore examined in sera from nine infants with fulminant hepatitis after vertical transmission, one HBeAg-positive and seven anti-HBe-positive mothers by polymerase chain reaction (PCR) and direct sequence analysis. In five mother/infant pairs the virus populations were characterized in addition by analysing clones of the amplified products. All mothers were infected with two or four variants of HBV with mutations at different positions of the preC genome including position 1896, which results in a stop codon. While the precore stop codon was detected in a portion of the virus populations of the HBeAg-positive and of four anti-HBe-positive mothers the dominating viral strain was represented by the wild type virus in three. In contrast, the virus populations of all babies showed the 1896 precore variant as the prevalent virus strain during the phase of active disease. In the surviving baby only wild type sequences were detected after recovery. Subtype ayw was found in all mothers and infants and adw2 was present in three mothers and in the surviving child. The findings suggest that all mothers carried a wild type HBV population with a certain number of different HBV variants. After transmission of the mixed virus population a selection process was started in the baby. The association of subtype ayw with the precore mutations and with the fatal outcome of the hepatitis B might be the result of a directed selection of this variant with a particular advantage in the viral life cycle.

Hepatitis B transmission from contaminated cryopreservation tank

Over a 25-month period, six multiply transfused patients undergoing cytotoxic treatment for haematological or other malignant disorders developed icteric acute hepatitis B virus (HBV) infection. Bone marrow or peripheral-blood stem cells had been harvested from all six patients and stored in the same cryopreservation tank for possible future transplantation. Human DNA, HBsAg, and HBV DNA with sequences identical to those from four patients with related infections were subsequently found in the liquid nitrogen. Leakage of the cryopreservation bags used to store bone marrow harvested from the first patient when acutely infected with HBV led to contamination of the tank and its contents with HBV and subsequent transmission to patients after transplantation. This incident emphasises the continuing need to screen donors of tissue to be cryopreserved for bloodborne virus infections. It also reinforces the requirement for primary containers used to cryopreserve human tissue to be sealed in a way which prevents exchange of material between the specimen and the liquid nitrogen.