Natural history of hepatitis B surface antigen mutants in children

Deep sequencing of hepatitis B surface antigen gene in the preserved umbilical cords in immunoprophylaxis failure against mother-to-child HBV transmission

BACKGROUND

Vaccine escape mutants (VEMs) are one of the causes of breakthrough infections in the mother-to-child transmission of hepatitis B virus (HBV). We hypothesized that VEMs existing as minor populations in the maternal blood are associated with breakthrough infections in children. We sought to determine whether VEMs exist as minor populations in the preserved umbilical cords of children with breakthrough infections.

CASE PRESENTATION

Two families (Family 1: three children, Family 2: two children) were enrolled. Despite immunoprophylaxis, a breakthrough infection occurred in two Family 1 children and two Family 2 children. Preserved umbilical cords, serum, and nails were used for the HBV DNA analysis. To detect VEMs, we performed direct and deep sequencing of hepatitis B surface antigen gene. The direct sequencing showed that there were no VEMs in the serum of the children or mother of Family 1 and family 2, but it identified a G145A mutant in the nails of the mother of Family 2. In Family 1, deep sequencing detected a T143S mutant as a minor population (1.7-2.0%) in the umbilical cords and serum of all three children and in the serum of the mother. A T126A mutant was also detected in the umbilical cord (9.2%) and serum (7.0%) of the first-born child of Family 1. In Family 2, the deep sequencing showed no VEMs in the umbilical cords, but it detected D144A (2.5%) and G145A (11.2%) mutants in the serum of the 2nd-born child.

CONCLUSIONS

VEMs were present as minor populations in the preserved umbilical cords of children with breakthrough infections. The VEMs did not become major populations after the breakthrough infections. The evolution of VEMs from a minor form to a major form might not be a prerequisite for breakthrough infections in mother-to-child transmission.

Nearly half of Ultrio plus NAT non-discriminated reactive blood donors were identified as occult HBV infection in South China

Background

Blood donor plasma samples were detected by the Ultrio Plus NAT system for HBV, HCV and HIV-1 in Shenzhen blood center, China. Reactive samples underwent further discriminatory testing of a single virus by the same methodology. A large number of cases of non-discriminated reactive (NDR) donors were found, leaving potential risk of transmitting HBV if not deferrals. This study identified those non-discriminated samples.

Methods

The NDR plasma samples from blood donation screening were detected and classified by additional molecular and serological tests. Molecular characterizations of DNA+ NDR were determined by sequencing analysis.

Results

A number of 259 (0.21%) NDR plasma samples from screening of 123,280 eligible blood donors were detected, which presented a higher rate (91.1%) of anti-HBc reactivity and nearly half (46.7%) of HBV DNA+ that classified as occult HBV infection (OBI). Most OBI strains were wild-type HBV, but some substitutions V168A, S174 N, V177A, Q129R/L/H, G145A/R in S region of genotype B (OBI_B) and T47K/V/A, P49H/L, Q101R/H/K, S174 N, L175S, V177A, T118 M/R/K, G145R/A/K/E, R160K/N in S region of genotype C (OBI_C) strains were identified in high frequency.

Conclusion

Nearly half of NDR blood samples were identified as OBI, in which a number of important mutations were detected. NDR donation might have potential risk for HBV transmission, but need to be further investigated.

Detection of in vivo hepatitis B virus surface antigen mutations-A comparison of four routine screening assays

An important requirement for a state-of-the-art hepatitis B surface antigen (HBsAg) screening assay is reliable detection of mutated HBsAg. Currently, there is a striking shortage of data regarding the detection rates of in vivo HBsAg mutations for these clinically important assays. Therefore, we compared the detection rates of four commercial HBsAg screening assays using a global cohort of 1553 patients from four continents with known HBV genotypes. These samples, which represent the broadest spectrum of known and novel HBsAg major hydrophilic region (MHR) mutations to date, were analyzed for the presence of HBsAg using the Roche Elecsys^® HBsAg II Qualitative, Siemens ADVIA Centaur XP HBsAg II, Abbott Architect HBsAg Qualitative II and DiaSorin Liaison^® HBsAg Qualitative assays, respectively. Of the 1553 samples, 1391 samples could be sequenced; of these, 1013 (72.8%) carried at least one of the 345 currently known amino acid substitutions (distinct HBsAg mutation) in the HBsAg MHR. All 1553 patient samples were positive for HBsAg using the Elecsys^® HBsAg II Qual assay, with a sensitivity (95% confidence interval) of 99.94% (99.64%-100%), followed by the Abbott Architect 99.81% (99.44%-99.96%), Siemens ADVIA 99.81% (99.44%-99.96%) and DiaSorin Liaison^® 99.36% (98.82%-99.69%) assays, respectively. Our results indicate that the Elecsys^® HBsAg II Qual assay exhibits the highest sensitivity among the commercial HBsAg screening assays, and demonstrate that its capacity to detect HBV infection is not compromised by HBsAg MHR mutants.

HBV genotypes and drug resistance mutations in antiretroviral treatment-naive and treatment-experienced HBV-HIV-coinfected patients

BACKGROUND

The presence of HBV resistance mutations upon initiation or during antiretroviral therapy (ART) in HIV-coinfected patients is an important determinant of treatment response. The main objective of the study was to determine the prevalence of HBV resistance mutations in antiretroviral treatment-naive and treatment-experienced HBV-HIV-coinfected Ghanaian patients with detectable HBV viraemia.

METHODS

HBV-HIV-coinfected patients who were ART-naive or had received at least 9 months of lamivudine (3TC)-containing ART were enrolled in a cross-sectional study. Demographic and clinical data were collected and HBV DNA quantified. Partial HBV sequences were amplified by PCR and sequenced bi-directionally to obtain a 2.1-2.2 kb fragment for phylogenetic analysis of HBV genotypes and evaluation of drug resistance mutations.

RESULTS

Of the 100 HBV-HIV-coinfected study patients, 75 were successfully PCR-amplified, and 63 were successfully sequenced. Of these 63 patients, 27 (42.9%) were ART-experienced and 58 (92.1%) had HBV genotype E. No resistance mutations were observed in the 36 ART-naive patients, while 21 (77.8%) of 27 treatment-experienced patients had resistance mutations. All patients with resistance mutations had no tenofovir in their regimens, and 80% of them had HIV RNA <40 copies/ml. The 3TC resistance mutations rtL180M and rtM204V were observed in 10 (47.6%) of the 21 patients, while 5 patients (23.8%) had rtV173L, rtL180M and rtM204V mutations.

CONCLUSIONS

A high proportion of HBV-HIV-coinfected patients with detectable viraemia on 3TC-containing ART had resistance mutations despite good ART adherence as determined by HIV RNA suppression. This study emphasizes the need for dual therapy as part of a fully suppressive ART in all HBV-HIV-coinfected patients in Ghana.

Functional analysis of 'a' determinant mutations associated with occult HBV in HIV-positive South Africans

Occult hepatitis B is defined by the presence of hepatitis B virus (HBV) DNA in the absence of hepatitis B surface antigen (HBsAg). Occult HBV is associated with the development of hepatocellular carcinoma, reactivation during immune suppression, and virus transmission. Viral mutations contribute significantly to the occult HBV phenotype. Mutations in the 'a' determinant of HBsAg are of particular interest, as these mutations are associated with immune escape, vaccine escape and diagnostic failure. We examined the effects of selected occult HBV-associated mutations identified in a population of HIV-positive South Africans on HBsAg production in vitro. Mutations were inserted into two different chronic HBV backbones and transfected into a hepatocyte-derived cell line. HBsAg levels were quantified by enzyme-linked immunosorbent assay (ELISA), while the detectability of mutant HBsAg was determined using an HA-tagged HBsAg expression system. Of the seven mutations analysed, four (S132P, C138Y, N146D and C147Y) resulted in decreased HBsAg expression in one viral background but not in the second viral background. One mutation (N146D) led to a decrease in HBsAg detected as compared to HA-tag, indicating that this mutation compromises the ability of the ELISA to detect HBsAg. The contribution of occult-associated mutations to the HBsAg-negative phenotype of occult HBV cannot be determined adequately by testing the effect of the mutation in a single viral background, and rigorous analysis of these mutations is required.

Clinical implications of hepatitis B virus mutations: Recent advances

Hepatitis B virus (HBV) infection is a major cause of acute and chronic hepatitis, and of its long-term complications. It is the most variable among DNA viruses, mostly because of its unique life cycle which includes the activity of error-prone enzyme, reverse transcriptase, and the very high virion production per day. In last two decades, numerous research studies have shown that the speed of disease progression, reliability of diagnostic methods and the success of antiviral therapy and immunization are all influenced by genetic variability of this virus. It was shown that mutations in specific regions of HBV genome could be responsible for unwanted clinical outcomes or evasion of detection by diagnostic tools, thus making the monitoring for these mutations a necessity in proper evaluation of patients. The success of the vaccination programs has now been challenged by the discovery of mutant viruses showing amino acid substitutions in hepatitis B surface antigen (HBsAg), which may lead to evasion of vaccine-induced immunity. However, the emergence of these mutations has not yet raised concern since it was shown that they develop slowly. Investigations of HBV genetic variability and clinical implications of specific mutations have resulted in significant advances over the past decade, particularly in regard to management of resistance to antiviral drugs. In the era of drugs with high genetic barrier for resistance, on-going monitoring for possible resistance is still essential since prolonged therapy is often necessary. Understanding the frequencies and clinical implications of viral mutations may contribute to improvement of diagnostic procedures, more proper planning of immunization programs and creating the most efficient therapeutic protocols.

HBsAg variants: diagnostic-escape and diagnostic dilemma

A wide variety of commercial assays is available for the detection of hepatitis B surface antigen (HBsAg). Clearly, the sensitivity of an assay to detect a variant is dependent on the anti-HBs usage. Thus, it is not surprising that there are examples of variants that cannot be detected by all assays. Data from Europe, Asia and Africa about HBsAg variants which are not recognized by either monoclonal or polyclonal antibodies specific for wild-type group 'a' determinant, but positive by DNA polymerase chain reaction (PCR) in chronic patients and from vaccinated children are increasing. This would impose a challenge for public health issues of hepatitis B virus. In this review we tried to summarize the discrepancies between results of HBsAg assays and to explain some rationales for these inconsistencies.

[Microbiological diagnosis of viral hepatitis]

Hepatitis of viral aetiology caused by hepatotropic virus (A, E, B, D and C) represents an important work load for the clinical virology laboratory. Most of the diagnostic is based upon detection in serum and plasma samples of different serological and virological markers, which correlates with different infection stages. In chronic infection by HBV and HCV is necessary to perform diagnostic by molecular methods as well as antigen detection in sequential samples along the course of the disease taking into account that a reliable storage must be provided for stability of structural components of the virus. Recent knowledge about mutations variants in some of the virus may alter the validity of particular markers.

Frequency of hepatitis B virus 'a' determinant variants in unselected Spanish chronic carriers

The prevalence in the population of hepatitis B virus (HBV) surface antigen (HBsAg) variants that may impair diagnosis, or allow the virus to escape vaccine-induced immunity or passive immunoglobulin therapy is unknown. A genome fragment encoding HBsAg amino acids 112-212 was amplified and sequenced from the sera of 272 unselected DNA-positive, HBV-chronic carriers from Spain. The genotype and the HBsAg subtype were predicted from the sequences. Analysis of amino-acid positions 112-157 revealed single or multiple substitutions in 39% of the carriers studied. Mutations were not detected for residues 121, 135, 137, 139, 140, 141, 142, 146, 147, 148, 149, 151, 152, 153, 155, 156, and 157. Substitutions reported previously to be in association with failures of diagnostic tests or with vaccine or immunoglobulin therapy escape were found in 12.5%, 6.6%, and 9.2% of carriers, respectively. Met133Thr (2.2%); Gln129His, Met133Ile, Phe/Tyr134Asn (1.8%); Phe/Tyr134Leu, Gly145Ala (1.5%), and Pro120Thr (1.1%) were the most frequent. Other substitutions, including Gly145Arg (0.4%), were found at a frequency of less than 1%. Samples containing HBV mutants were tested with three commercial assays for HBsAg screening. Almost all the mutants reacted to the upper cut-off values of the assays, but six samples with weak reactivity with one or more of the methods were also found. Thus, HBV mutants with a potential impact on clinical and public health issues are moderately frequent among chronic carriers from Spain, although their influence on the performance of diagnostic tests seems to be slight.

Protective efficacy, immunotherapeutic potential, and safety of hepatitis B vaccines

Hepatitis B vaccines are highly effective and safe and have been incorporated into national immunization programs in over 150 countries. The major humoral immune response is to the common a determinant of the surface antigen protein of the virus. Approximately 5-10% of healthy immunocompetent subjects do not mount an antibody response (anti-HBs). Non-response is associated with different HLA-DR alleles and impaired Th cell response, among other factors such as route of injection, age, gender, body mass, and other factors. Important hepatitis B surface antigen variants have also been identified, which may have a potential impact on immunization and routine screening of blood, blood products and tissues, and organs for transplantation. Strategies for hepatitis B immunization are reviewed. Over 1,000 million doses of hepatitis B vaccine have been used with an outstanding record of safety. There is no evidence of an association between hepatitis B vaccines and the sudden infant death syndrome, chronic fatigue syndrome, and multiple sclerosis (MS). Several studies are in progress on treatment of chronic hepatitis B infection by immunization with multiple antigenic components, combination of vaccine with antiviral drugs and cytokines, T cell vaccines, DNA vaccines alone or with DNA encoded immunomodulatory cytokines, and direct genetic manipulation of antigen presenting cells.

Coexistence of hepatitis B surface antigen (HBs Ag) and anti-HBs antibodies in chronic hepatitis B virus carriers: influence of "a" determinant variants

In chronic hepatitis B (CHB), the persistence of hepatitis B surface antigen (HBs Ag) is sometimes associated with antibodies (Ab) to HBs (anti-HBs). To assess the hypothesis of the selection of HBs Ag immune escape variants in CHB patients, the variability of the HBV S gene was determined for patients persistently carrying both HBs Ag and anti-HBs antibodies and patients solely positive for HBs Ag. We selected 14 patients who presented both markers (group I) in several consecutive samples and 12 patients positive for HBs Ag only (group II). The HBs Ag-encoding gene was amplified and cloned, and at least 15 clones per patient were sequenced and analyzed. The number of residue changes within the S protein was 2.7 times more frequent for group I than for group II patients and occurred mostly in the "a" determinant of the major hydrophilic region (MHR), with 9.52 versus 2.43 changes per 100 residues (P = 0.009), respectively. Ten patients (71%) from group I, but only three (25%) from group II, presented at least two residue changes in the MHR. The most frequent changes in group I patients were located at positions s145, s129, s126, s144, and s123, as described for immune escape variants. In CHB patients, the coexistence of HBs Ag and anti-HBs Ab is associated with an increase of "a" determinant variability, suggesting a selection of HBV immune escape mutants during chronic carriage. The consequences of this selection process with regard to vaccine efficacy, diagnosis, and clinical evolution remain partially unknown.

Hepatitis B virus genetic diversity

Hepatitis B virus (HBV) is a human DNA virus, which replicates through an RNA intermediate because of the reverse-transcriptase (RT) activity of its DNA polymerase. As a result, the mutation rate for HBV is higher than the rate observed for most DNA viruses. HBVs are classified into genotypes based on genomic sequencing, and antigenic subtypes based on the antigenic properties of its major surface glycoprotein, the HBV surface antigen (HBsAg). Subgenotypes have been identified within most of the HBV genotypes. The HBV groups defined by the different genotype-HBsAg subtype associations found over the world display characteristic geographical distributions, reflecting the movements of human populations and other epidemiologically significant events. Such HBV groups constitute genetically stable viral populations sharing a common evolutionary history, but additional stable changes, originating from mutation and mutant selection, are observed within all of them. These viral sub-populations are known as the HBV variants, and some of which have medical and public health relevance. Pre-core (pre-C) defective variants have been shown to make HBV infection much less susceptible to interferon treatment, and treatment failures with other antiviral drugs have been associated with selection of resistant variants that display specific mutations in the genome region encoding the viral RT activity. Since the RT region of the genome overlaps the sequence encoding the HBsAg molecule, selection of drug resistant variants involves, in some cases, the indirect selection of HBsAg variants. Viral variants displaying changes in HBsAg seem to be very common among chronic HBV carriers; and some of these variants may emerge under the pressure of the neutralizing antibody response, leading to vaccine resistance and resistance to immunotherapy. Mutations conferring resistance to immunotherapy are noted often among liver transplant recipients and among babies born to HBV-carrier mothers. In addition, some of these HBsAg variants have been associated with lack of detection by HBsAg tests used for the diagnosis of HBV infection, for the identification of chronic carriers, for screening of blood donations for transfusion, and in the manufacture of therapeutic blood products.

A low rate of hepatitis B virus vaccine breakthrough infections in Mongolia

A nation-wide hepatitis B virus (HBV) immunization program of all newborn babies was launched in Mongolia in 1991. However, the continuation of clinical icteric viral hepatitis infections in children led to the investigation to determine whether HBV breakthrough infections were occurring and if any were due to hepatitis B surface antigen (HBsAg) mutants. Hepatitis A virus (HAV) infections accounted for most of these cases with 3% of the jaundiced children shown to have acute hepatitis B. Hepatitis B vaccine protection was 93% against HBV infection and 97% against HBV carriage. A G145A "escape mutant" was found in one HBV carrier child only. Anti-HBs levels, however, were low with 85% having titers less than 100 IU/L, 46% of whom had levels less than 10 IU/L. The results from this study demonstrate that the HBV immunization program in Mongolia provides an effective level of protection. However, continued surveillance of breakthrough infections and close monitoring of "vaccine escape" mutants is required.

Hepatitis B virus genotypes and precore and core mutants in Brazilian patients

A method for genotyping hepatitis B virus by partial HBsAg gene sequencing with primers common to all known genotypes was developed. Mutations related to anti-HBs resistance are also detected with this method. Samples from 103 Brazilian patients were analyzed. Precore and core region of these viruses were also sequenced in 101 patients. Genotypes A, B, C, D, and F were found with frequencies of 49.5, 2.9, 13.6, 24.3, and 9.7%, respectively. Genotypes B and C were found only in Asian patients, whereas genotypes A, D, and F were more common in patients without an Asian background. Precore mutants were found in 32 (31.7%) of 101 patients, with a higher frequency in those infected with genotype D (22 of 25 [88.0%]). Analysis of nucleotide 1858 showed presence of thymine in all patients with genotypes B, C, and D and in a few patients with genotypes A (10.0%) and F (30.0%), who showed more frequently the presence of cytosine. This nucleotide was closely related to the presence of precore mutants. Mutations in the basal core promoter were found in 64 of 101 (63.4%) samples. These mutations were more frequent in patients infected with genotype F (90.0%) and less frequent in patients infected with genotype B (33.3%). Deletions in this region were found in two genotype C-infected patients.

Wild-type and 'a' epitope variants in chronic hepatitis B virus carriers positive for hepatitis B surface antigen and antibody

AIMS

This study aims to examine the genomic variants of the 'a' epitope in chronic hepatitis B virus (HBV) carriers positive for both hepatitis B surface antigen (HBsAg) and antibody to HBsAg (anti-HBs).

METHODS

Eighteen HBV carriers were studied. Hepatitis B virus (HBV) DNA was extracted and the 'a' epitope region was amplified and sequenced.

RESULTS

Eighteen Chinese asymptomatic HBV carriers were studied. There were 13 patients who were positive for both HBsAg and anti-HBs. Of these, one patient had only wild-type HBV, three had a viral mixture, and five had only 'a' epitope variant HBV. Of the three patients with a viral mixture, all had variants in the less conserved region (123-137). Of the five patients with pure HBsAg mutants, three had variants in the less conserved region while two had variants in the highly conserved region. In this study with a limited number of patients, the serum alanine aminotransferase (ALT) levels were higher in patients with wild-type HBV, compared with those with either 'a' epitope variants or a viral mixture consisting of wild type and variants.

CONCLUSION

Eight of the nine (89%) patients positive for both HBsAg and anti-HBs harbored an 'a' epitope variant. The lower ALT levels seen in patients who had either pure 'a' epitope variant or a mixture of wild type and mutants suggest that a closer monitoring of these 'a' epitope variants should be required, as patients carrying these infectious viral strains may remain asymptomatic.

Acute self-limiting hepatitis B after immunoprophylaxis failure in an infant

The occurrence of acute hepatitis after failure of immunoprophylaxis in cases of mother-to-infant transmission of hepatitis B virus (HBV) is uncommon. Because immunoprophylaxis failure is caused by the emergence of an "a" determinant escape mutant, the infants usually become HBV carriers. To evaluate whether mutations in the S gene coding for the surface protein that contains the "a" determinant are associated with acute hepatitis after immunoprophylaxis failure, HBV DNA of an infant in with acute hepatitis developed with seroconversion to anti-HBs antibodies at 12 months of age despite administration of anti-hepatitis B immunoglobulin and hepatitis B vaccine was analyzed. The S gene from HBV DNA isolated from the serum of the infant at 12, 19, and 27 months of age was cloned and sequenced. Mutations affecting amino acid residues in the first loop within the "a" determinant (codons 124-147) were found at 12 months of age. Moreover, a novel deletion mutant, with a 1-bp deletion at nucleotide 449 of the S gene, was found at 19 and 27 months of age. This deletion resulted in a frame shift and it introduced a stop codon (TAG) at codon 176. Because the open reading frame of the S gene is completely overlapped by the polymerase gene, mutations in the S gene may affect the polymerase gene. Based on this case, this study suggests that the observed frame-shift mutation in the S gene might affect the polymerase protein and induce prompt suppression of viral replication.

48-mer synthetic peptide analogue of the hepatitis B virus "a" determinant induces an anti-HBs antibody response after a single injection

An extended (48 amino acid) synthetic peptide analogue of the hepatitus B virus (HBV) S protein (HBsAg) 'a' determinant has been produced by using 9-fluorenylmethoxycarbonyl (fmoc) chemistry and a low substitution polystyrene resin as the solid phase support. This peptide (S121/48) elicited a sustained anti-peptide antibody response in BALB/c (H-2(d)) mice when immunised with Freund's complete adjuvant (FCA). Cross-reactive, anti-HBs antibodies were induced, directed against a significant proportion of the conformationally restrained epitope repertoire on the native HBsAg particles. Similar responses were obtained by injection of guinea pigs, a species known both to be exquisitely sensitive to HBsAg and to produce a wide range of B cell responses to HBsAg antigens. Taken together, these data show for the first time, that a synthetic peptide mimicking conformational epitopes can be produced by chemical synthesis and can be used to induce significant titres of anti-HBs antibodies after a single injection. This immunogen has considerable potential for incorporation into novel delivery systems, e.g., microspheres, thus offering the potential of a controlled release, single dose hepatitis B vaccine.

Current topics in hepatitis B

Over two billion people around the world have been infected with hepatitis B virus, of whom over 350 million are chronic carriers. Some 25% of carriers develop progressive liver disease. The annual mortality from hepatitis B infection and its sequelae is 1-2 million people worldwide.The following current topics are reviewed: immunization strategies against hepatitis B and the kinetics and antibody response; the controversy on screening blood donors for anti-core antibodies; mutations of hepatitis B surface antigen, including evidence that not all such mutants are detectable by current laboratory tests and, finally, the introduction of second generation nucleoside analogues for treatment of chronic hepatitis B infection, including treatment of patients with decompensated liver disease and liver transplantation.

Unusual hepatitis B surface antigen variation in a child immunised against hepatitis B

Perinatal transmission of and infection with hepatitis B (HBV) in early childhood are observed in a small proportion of the offspring of hepatitis B surface antigen (HBsAg)-positive mothers who are vaccinated against HBV immediately after giving birth. The children may be infected by wild-type HBV or by variants with amino acid substitutions in the "a" determinant of HBsAg, particularly at position 145 and, rarely, at positions 120, 126, 129, 131, 141, and 144. Four hundred and forty-six newborn infants of HBsAg-positive mothers in the northeastern part of the Czech Republic received combined active and passive immunisation against HBV. Only one child became an HBsAg carrier. This followed a mild, acute HBV illness in the beginning of the second year of his life. HBV DNA encoding the "a" determinant and surrounding region of HBsAg was sequenced after amplification from the plasma of the child and his mother. The child was infected with variants of HBsAg with substitutions at residues 137 and 139. The virus of the mother had changes at residues 120 and 121. HBV from both child and mother had an unusual substitution at residue 118 and seemed to be of the ayw subdeterminant.

Genetic alterations in the S gene of hepatitis B virus in patients with acute hepatitis B, chronic hepatitis B and hepatitis B liver cirrhosis before and after liver transplantation

BACKGROUND

Several studies have shown that hepatitis B immunoglobulin (HBIG) imposes a selection pressure on the hepatitis B virus (HBV) S gene, and that the emergence of mutations in this region would make reinfection after orthotopic liver transplantation (OLT) possible.

AIMS

This study was undertaken to analyze the presence of HBV S-gene mutations in the different stages of HBV infection and the relationship between HBIG therapy and the emergence of mutations in liver transplant recipients.

METHODS

The frequency and location of mutations in the coding region of the HBV S gene were studied by PCR and direct sequencing in 30 patients (7 with acute self-limited hepatitis B, 16 with chronic hepatitis B and 7 recipients of (OLT) for HBV-related end stage liver disease who became reinfected).

RESULTS

The average number of amino acid changes was higher in patients with a more advanced stage of disease, 0.57 mutations/100 positions in acute hepatitis B and 1.57 in chronic hepatitis B (1.28 in HBeAg-positive and 1.8 in anti-HBe-positive patients). The average number of substitutions in the transplanted patients was 2.7 before OLT and 3 after OLT. No amino acid substitutions were detected in the "a" determinant of HBsAg in acute hepatitis B, however, 8 substitutions were observed in 6 chronic patients. In 3 OLT patients, 4 substitutions were observed in samples before and after OLT. One of these patients, who had protective levels of anti-HBs, showed 3 additional new amino acid substitutions after OLT, suggesting escape mutant selection by the effect of HBIG therapy. No changes were observed between the consensus sequences obtained several years before and after transplantation, indicating consensus sequence stability.

CONCLUSION

These results show that there is an accumulation of HBV S-gene mutations in HBV-related end-stage liver disease. Prophylaxis with HBIG mainly obtained from acute self-limited hepatitis patients who have a highly homogeneous viral population, may be one factor underlying the reinfection after liver transplantation.

At least three epitopes are recognized by the human repertoire in the hepatitis B virus group a antigen inducing protection; possible consequences for seroprevention and serodiagnosis

Many recent investigations have shown that both HBV and anti-HBs antibodies coexist in the same patient, and HBV can be found in individuals with anti-HBc antibodies in the absence of immunologically detectable HBsAg. In most cases, mutant forms of HBV affecting the region of the envelope gene coding for the group a determinant recognized by human antibodies have been found. The nature of the group a determinant was revisited with an ELISA involving dissociated, but not alkylated, envelope subunits. No antibody recognizing a continuous epitope of the major S envelope protein could be found in humans; the full activity of human anti-HBs antibodies appeared to be focused on the discontinuous group a determinant. The immunological human repertoire against the HBsAg group a determinant was analysed by competitive inhibition of three mouse monoclonal antibodies (mAbs) selected as recognizing three distinct specificities on the group a determinant. Antibodies to specificities #1 and 3 were found in 52/70 anti-HBs human sera and generally predominated over specificity #2, which was lacking in some sera. The heterogeneity of the group a determinant suggested by these data argue for the use of more than one type of anti-HBs mAb for seroprevention of recurrence after liver transplantation and HBs serodiagnosis. Provided all three types of mAbs characterized here recognize HBV variants with mutations in the a determinant and are virus-neutralizing, it may be helpful, after association of such mAbs, to use them for diagnosis and to devise new immunotherapeutic strategies to prevent emergence of HBsAg escape mutants.

Efficacy of immunization of high-risk infants against hepatitis B virus evaluated by polymerase chain reaction

The polymerase chain reaction (PCR) is a rapid and very sensitive method to detect viral genomes. In the present study, the efficacy of immunization against hepatitis B virus (HBV) of high-risk infants was evaluated by PCR. Twenty-nine infants born to 24 HBeAg-positive carrier mothers were given hepatitis B immune globulin (HBIG) at birth and thereafter received repeated inoculations of plasma-derived vaccine or HBIG, or both, within 1 year. Serum samples at 1 year following immunization were stored at -40 degrees C for later analysis using PCR to detect HBV-DNA. When HBV genomes were detected in infants, the DNA sequences in the S gene of HBV were determined. Of 29 infants, 2 were positive for HBV-DNA at the 1 year following immunization; one had the HBV containing only the wild-type sequence in the S gene and became negative for HBV-DNA during the follow-up period. In contrast, another had the HBV, which contained nucleotide substitutions that altered the expression of the common group-specific determinant "a" of the S gene and resulted in clinical hepatitis with viral persistence. PCR analysis suggests that immunization against HBV prevents effectively high-risk infants from mother-to-child transmission. Even then, however, it is possible that amino acid substitutions in the "a" determinant of the S gene are associated with failure of conventional immunization against HBV.