Mutations within the S gene of hepatitis B virus transmitted from mothers to babies immunized with hepatitis B immune globulin and vaccine

Hepatitis B virus infection after immunization: How serious it is? An updated review

Infection with hepatitis B virus (HBV) is one of the significant challenges worldwide. Despite the availability of antiviral drugs against this virus, the most critical strategy to prevent HBV infection is HB vaccination. Basically, despite widespread conventional HB vaccination, due to various reasons, including waning of hepatitis B surface antibody (HBsAb) titer after vaccination, the emergence of vaccine-escape mutants, failure to respond to the vaccine due to viral and host factors, levels of response in high-risk individuals and non-responders to conventional HB vaccination remains a major, unsolved and severe concern. This review focuses on the underlying reasons for conventional hepatitis B vaccination failures. It also suggests solutions to overcome these failures by highlighting significant advances in vaccination, including hepatitis B third-generation vaccines and adjuvanted hepatitis B vaccines as efficient alternatives to second-generation vaccines. Potentially, these new strategies will compensate for the shortcomings caused by second-generation vaccines. Adherence to these denouements has a significant role in preventing the circulation of HBV among individuals and reducing the global burden of HBV-related diseases.

Rapid quantification assay of hepatitis B virus DNA in human serum and plasma by Fully Automated Genetic Analyzer μTASWako g1

Real-time monitoring of serum hepatitis B virus (HBV) levels is essential for the management of patients with chronic HBV infection in clinical practice, including monitoring the resistance of anti-HBV nucleotide analog or the detection of HBV reactivation. In this context, serum HBV deoxyribonucleic acid (DNA) quantification should be rapidly measured. A rapid HBV DNA quantification assay was established on the Fully Automated Genetic Analyzer, μTASWako g1. The assay performs automated sample preparation and DNA extraction, followed by the amplification and detection of quantitative polymerase chain reaction (PCR) combined with capillary electrophoresis (qPCR-CE) on integrated microfluidic chip. This study aimed to evaluate the analytical and clinical performance of HBV DNA assay on the μTASWako g1 platform in human serum and EDTA-plasma. The HBV DNA assay has a linear quantitative range from 20 to 108 IU/mL of HBV DNA with standard deviation (SD) of ≤0.14 log10 IU/mL. The limits of detection of the assay were 4.18 for the serum and 4.35 for EDTA-plasma. The HBV assay demonstrated the equivalent performance in both human serum and EDTA-plasma matrices. The HBV genotypes A to H were detected with an accuracy of ±0.34 log10 IU/mL. In quantification range, the HBV DNA assay was correlated with Roche cobas AmpliPrep/cobas TaqMan Ver2.0 (CAP/CTM v2) (r = 0.964). The mean difference (μTASWako g1-CAP/CTM v2) of the reported HBV DNA was -0.01 log10 IU/mL. Overall, the sensitivity, accuracy, and precision of the μTASWako g1 HBV assay were comparable to the existing commercial HBV DNA assay, and the assay can be completed within 110 min. This evaluation suggests that the HBV DNA assay on the μTASWako g1 is potentially applied for alternative method of the HBV viral load test, in particular with the advantage of the HBV DNA result availability within 2 h, improving the HBV infection management.

Characterization of Antigen Escape Mutations in Chronic HBV-Infected Patients in Upper Egypt

Background

Mutations within the “a” determinant region (position 124–147) that is present in the major hydrophilic region (MHR, position 99–160) of the hepatitis B surface antigen (HBsAg) are associated with vaccine-escape, lack of diagnosis, and failure to hepatitis B immunoglobulin (HBIG) therapy. Data regarding the amino acid changes of “a” determinant region of HBsAg are limited in Egypt. The prevalence and mutations in this region among chronic HBV (CHB)-infected patients in Upper Egypt are not known.

Material and Methods

Blood samples were collected from HBsAg-positive CHB-infected patients (n=123) admitted to Assiut University Hospitals. Serum samples were screened for HBsAg, HBeAg, anti-HBs and anti-HBe antibodies using commercially available ELISA kits. Viral load was determined by qPCR. In addition, mutational analysis was carried out targeting the HBV surface gene to determine the HBV genotype and vaccine escape mutations.

Results

Sequencing analysis of HBV DNA revealed that genotype D is the major circulating type (81.3%), followed by genotype E (18.7%). Analysis of the HBV genome revealed that 103/123 (83.7%) patients showed wild-type sequences and 20/123 (16.3%) showed mutations in the HBsAg gene. Mutation in seventeen patients (17/20, 85%) showed only one mutation, and three patients showed two mutations (3/20, 15%) in the “a” determinant region. The observed mutations were T115S (3/20, 15%), P120T/S (3/20, 15%), T126S (1/20, 5%), Q129R (2/20, 10%), M133T (2/20, 10%), S143L (5/20, 25%), D144E/A (3/20, 15%), and G145R/A (4/20, 20%). Mutations in the “a” determinant region were detected in genotype D isolates only.

Conclusion

We described for the first time the prevalence and characterization of vaccine escape mutants in CHB patients in Upper Egypt. Mutational analysis of the “a” determinant region revealed the presence of a wide spectrum of mutants in the circulating HBV isolates that could be a potential threat to HBV diagnosis, therapy success, and HBV vaccination program in Upper Egypt.

Antiviral therapy for the sexually transmitted viruses: recent updates on vaccine development

INTRODUCTION

The sexually transmitted infections (STIs) caused by viruses including human T cell leukemia virus type-1 (HTLV-1), human immunodeficiency virus-1 (HIV-1), human simplex virus-2 (HSV-2), hepatitis C virus (HCV), hepatitis B virus (HBV), and human papillomavirus (HPV) are major public health issues. These infections can cause cancer or result in long-term health problems. Due to high prevalence of STIs, a safe and effective vaccine is required to overcome these fatal viruses.

AREAS COVERED

This review includes a comprehensive overview of the literatures relevant to vaccine development against the sexually transmitted viruses (STVs) using PubMed and Sciencedirect electronic search engines. Herein, we discuss the efforts directed toward development of effective vaccines using different laboratory animal models including mice, guinea pig or non-human primates in preclinical trials, and human in clinical trials with different phases.

EXPERT OPINION

There is no effective FDA approved vaccine against the sexually transmitted viruses (STVs) except for HBV and HPV as prophylactic vaccines. Many attempts are underway to develop vaccines against these viruses. There are several approaches for improving prophylactic or therapeutic vaccines such as heterologous prime/boost immunization, delivery system, administration route, adjuvants, etc. In this line, further studies can be helpful for understanding the immunobiology of STVs in human. Moreover, development of more relevant animal models is a worthy goal to induce effective immune responses in humans.

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.

Hepatitis B virus infection: Defective surface antigen expression and pathogenesis

Hepatitis B virus (HBV) infection is a global public health concern. HBV causes chronic infection in patients and can lead to liver cirrhosis, hepatocellular carcinoma, and other severe liver diseases. Thus, understanding HBV-related pathogenesis is of particular importance for prevention and clinical intervention. HBV surface antigens are indispensable for HBV virion formation and are useful viral markers for diagnosis and clinical assessment. During chronic HBV infection, HBV genomes may acquire and accumulate mutations and deletions, leading to the expression of defective HBV surface antigens. These defective HBV surface antigens have been found to play important roles in the progression of HBV-associated liver diseases. In this review, we focus our discussion on the nature of defective HBV surface antigen mutations and their contribution to the pathogenesis of fulminant hepatitis B. The relationship between defective surface antigens and occult HBV infection are also discussed.

Evaluation of the G145R Mutant of the Hepatitis B Virus as a Minor Strain in Mother-to-Child Transmission

The role of the hepatitis B virus (HBV) mutant G145R, with a single change in amino acid 145 of the surface protein, as a minor population remains unknown in mother-to-child transmission. The minor strain as well as the major strain of the G145R mutant were evaluated in three cohorts using a locked nucleic acid probe-based real-time PCR. The breakthrough cohort consisted of children who were born to HBV carrier mothers and became HBV carriers despite immnoprophylaxis (n = 25). The control cohort consisted of HBV carriers who had no history of receiving the hepatitis B vaccine, hepatitis B immunoglobulin or antiviral treatment (n = 126). The pregnant cohort comprised pregnant women with chronic HBV infection (n = 31). In the breakthrough cohort, 6 showed positive PCR results (major, 2; minor, 4). In the control cohort, 13 showed positive PCR results (major, 0; minor, 13). HBeAg-positive patients were prone to have the G145R mutant as a minor population. Deep sequencing was performed in a total of 32 children (PCR positive, n = 13; negative, n = 19). In the breakthrough cohort, the frequency of the G145R mutant ranged from 0.54% to 6.58%. In the control cohort, the frequency of the G145R mutant ranged from 0.42% to 4.1%. Of the 31 pregnant women, 4 showed positive PCR results (major, n = 0; minor, n = 4). All of the pregnant women were positive for HBeAg and showed a high viral load. Three babies born to 3 pregnant women with the G145R mutant were evaluated. After the completion of immunoprophylaxis, 2 infants became negative for HBsAg. The remaining infant became negative for HBsAg after the first dose of HB vaccine. G145R was detected in one-fourth of the children with immunoprophylaxis failure. However, the pre-existence of the G145R mutant as a minor population in pregnant women does not always cause breakthrough infection in infants.

Hepatitis B virus surface protein mutations clustered mainly in CTL immune epitopes in chronic carriers: results of an Iranian nationwide study

Mutations within the coding region of hepatitis B surface antigen (HBsAg) have been found naturally in chronic carriers. To characterize the mutations of HBsAg from Iranian chronic carriers who were vaccine and/or medication naive. The surface genes from 360 patients were amplified and directly sequenced. The distribution of amino acid substitutions was classified according to different immune epitopes of the surface protein. All isolates belonged to genotype D. 222 (61.6%) of 360 patients contained at least one amino acid substitution. 404 (74.5%) of 542 amino acid changes occurred in different immune epitopes of HBsAg, of which 112 (27.7%) in 32 residues of B-cell epitopes (62 in the 'a' determinant); 111 (27.4%) in 32 residues of T helper; and 197 (48.7%) in 32 residues inside cytotoxic T lymphocyte (CTL) epitopes. One Th (186-197) and two CTL (28-51 and 206-215) epitopes were found to be hotspot motifs for the occurrence of 213 (52.7%) substitutions. 20 stop codons were identified in different epitopes. There was a significant association between amino acid substitutions and anti-HBe seropositivity; however, the correlation between such changes with viral load and ALT levels was not significant. In chronic hepatitis B virus(HBV) carriers, positive selection in particular outside the 'a' determinant appeared to exert influence on the surface proteins. These changes could be immune escape mutations naturally occurring due to the host immune surveillance especially at the T-cell level.

Development of a highly sensitive bioluminescent enzyme immunoassay for hepatitis B virus surface antigen capable of detecting divergent mutants

Hepatitis B virus (HBV) infections are sometimes overlooked when using commercial kits to measure hepatitis B virus surface antigen (HBsAg) due to their low sensitivities and reactivities to mutant strains of various genotypes. We developed an ultrasensitive bioluminescent enzyme immunoassay (BLEIA) for HBsAg using firefly luciferase, which is adaptable to a variety of HBsAg mutants, by combining four monoclonal antibodies with a polyclonal antibody against HBsAg. The measurement of seroconversion panels showed trace amounts of HBsAg during the early infection phase by the BLEIA because of its high sensitivity of 5 mIU/ml. The BLEIA detected HBsAg as early as did PCR in five of seven series and from 2.1 to 9.4 days earlier than commercial immunoassay methods. During the late infection phase, the BLEIA successfully detected HBsAg even 40 days after the disappearance of HBV DNA and the emergence of antibodies against HBsAg. The HBsAg BLEIA successfully detected all 13 recombinant HBsAg and 45 types of HBsAg mutants with various mutations within amino acids 90 to 164 in the S gene product. Some specimens had higher values determined by the BLEIA than those by a commercial chemiluminescent immunoassay; this suggests that such discrepancies were caused by the dissociation of preS1/preS2 peptides from the particle surface. With its highly sensitive detection of low-titer HBsAg, including various mutants, the HBsAg BLEIA is considered to be useful for the early diagnosis and prevention of HBV infection because of the shorter window of infection prior to detection, which facilitates early prediction of recurrence in HBV-infected individuals.

Atypical serological profiles in hepatitis B virus infection

During hepatitis B virus (HBV) infection, at least four antigen-antibody systems are observed: HBsAg and anti-HBs; preS antigen and anti-preS antibody; HBcAg and anti-HBc; and HBeAg and anti-HBe. Through the examination of these antigen-antibody systems, hepatitis B infection is diagnosed and the course of the disorder may be observed. Although the serologic findings that allow both the diagnosis of HBV infection as well as assessing of its clinical course are already well established, the dynamics of viral proteins expression and of the antibodies production may vary during the infection natural course. This causes the HBV infection to be occasionally associated with the presence of uncommon serological profiles, which could lead to doubts in the interpretation of results or suspicion of a serological result being incorrect. This paper is dedicated to the discussion of some of these profiles and their significance.

High prevalence of occult hepatitis B virus infection in children born to HBsAg-positive mothers despite prophylaxis with hepatitis B vaccination and HBIG

BACKGROUND & AIMS

Occult hepatitis B virus (HBV) infection is a well-recognized clinical entity characterized by the detection of HBV DNA in serum and/or liver in the absence of detectable hepatitis B surface antigen (HBsAg). The frequency of the diagnosis depends on the relative sensitivity of both HBsAg and HBV DNA assays. We aimed at determining the prevalence of occult HBV infection in a high risk group of children who developed HBV infection despite immunoprophylaxis.

METHODS

The sera of 75 children born to HBsAg-positive mothers previously immunized by HBIG and prophylaxic vaccine regimen were assayed for HBV DNA by real-time PCR. Subsequently, the samples were tested using a sensitive standard PCR, with an independent set of primers for all HBV genes, and analyzed by direct sequencing.

RESULTS

HBV DNA was detected in 21/75 (28%) children, and ranged between 77 and 9240 copies/ml. All were positive for anti-HBs. Five (24%) children were found to be positive for anti-HBc, while anti-HBc-only positive individuals were not observed. Eight isolates (38%) did not carry any mutation. Thirteen infected children (62%) had at least one mutation in regions known to be involved in functional and/or immune epitope activity. Ten had G145R mutations.

CONCLUSIONS

HBV occult infection seems to be relatively frequent in immunized children born to HBsAg-positive mothers. HBsAg negativity is not sufficient to completely exclude HBV DNA presence. These findings emphasize the importance of considering occult HBV infection in hypo-endemic areas.

Removing N-terminal sequences in pre-S1 domain enhanced antibody and B-cell responses by an HBV large surface antigen DNA vaccine

Although the use of recombinant hepatitis B virus surface (HBsAg) protein vaccine has successfully reduced global hepatitis B infection, there are still a number of vaccine recipients who do not develop detectable antibody responses. Various novel vaccination approaches, including DNA vaccines, have been used to further improve the coverage of vaccine protection. Our previous studies demonstrated that HBsAg-based DNA vaccines could induce both humoral and CMI responses in experimental animal models. However, one form of the the HBsAg antigen, the large S antigen (HBs-L), expressed by DNA vaccine, was not sufficiently immunogenic in eliciting antibody responses. In the current study, we produced a modified large S antigen DNA vaccine, HBs-L(T), which has a truncated N-terminal sequence in the pre-S1 region. Compared to the original HBs-L DNA vaccine, the HBs-L(T) DNA vaccine improved secretion in cultured mammalian cells and generated significantly enhanced HBsAg-specific antibody and B cell responses. Furthermore, this improved HBsL DNA vaccine, along with other HBsAg-expressing DNA vaccines, was able to maintain predominantly Th1 type antibody responses while recombinant HBsAg protein vaccines produced in either yeast or CHO cells elicited mostly Th2 type antibody responses. Our data indicate that HBsAg DNA vaccines with improved immunogenicity offer a useful alternative choice to recombinant protein-based HBV vaccines, particularly for therapeutic purposes against chronic hepatitis infection where immune tolerance led to poor antibody responses to S antigens.

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.

Amino acid substitutions at positions 122 and 145 of hepatitis B virus surface antigen (HBsAg) determine the antigenicity and immunogenicity of HBsAg and influence in vivo HBsAg clearance

A variety of amino acid substitutions, such as K122I and G145R, have been identified around or within the a determinant of hepatitis B surface antigen (HBsAg), impair HBsAg secretion and antibody binding, and may be responsible for immune escape in patients. In this study, we examined how different substitutions at amino acid positions 122 and 145 of HBsAg influence HBsAg expression, secretion, and recognition by anti-HBs antibodies. The results showed that the hydrophobicity, the presence of the phenyl group, and the charges in the side chain of the amino acid residues at position 145 reduced HBsAg secretion and impaired reactivity with anti-HBs antibodies. Only the substitution K122I at position 122 affected HBsAg secretion and recognition by anti-HBs antibodies. Genetic immunization in mice demonstrated that the priming of anti-HBs antibody response was strongly impaired by the substitutions K122I, G145R, and others, like G145I, G145W, and G145E. Mice preimmunized with wild-type HBsAg (wtHBsAg) or variant HBsAg (vtHBsAg) were challenged by hydrodynamic injection (HI) with a replication-competent hepatitis B virus (HBV) clone. HBsAg persisted in peripheral blood for at least 3 days after HI in mice preimmunized with vtHBsAg but was undetectable in mice preimmunized with wtHBsAg, indicating that vtHBsAgs fail to induce proper immune responses for efficient HBsAg clearance. In conclusion, the biochemical properties of amino acid residues at positions 122 and 145 of HBsAg have a major effect on antigenicity and immunogenicity. In addition, the presence of proper anti-HBs antibodies is indispensable for the neutralization and clearance of HBsAg during HBV infection.

Hepatitis B surface gene 145 mutant as a minor population in hepatitis B virus carriers

BACKGROUND

Hepatitis B virus (HBV) can have mutations that include the a determinant, which causes breakthrough infection. In particular, a single mutation at amino acid 145 of the surface protein (G145) is frequently reported in the failure of prophylactic treatment. The aim of this study was to evaluate the frequency of the a determinant mutants, especially the G145 variant, in Japan, where universal vaccination has not been adopted.

METHODS

The present study was a retrospective study. The study cohorts were defined as follows: group 1, children with failure to prevent mother-to-child transmission despite immunoprophylaxis (n = 18, male/female = 8/10, age 1-14 years; median 6 years); group 2, HBV carriers who had not received vaccination or hepatitis B immunoglobulin (n = 107, male/female = 107, age 1-52 years; median 16 years). To detect the G145R and G145A mutants in patients, we designed 3 probes for real-time PCR. We also performed direct sequencing and cloning of PCR products.

RESULTS

By mutant-specific real-time PCR, one subject (5.6%) was positive for the G145R mutant in group 1, while the G145 mutant was undetectable in group 2. The a determinant mutants were detected in one (5.6%) of the group 1 subjects and 10 (9.3%) of the group 2 subjects using direct sequencing, but direct sequencing did not reveal the G145 mutant as a predominant strain in the two groups. However, the subject who was positive according to the mutant-specific real-time PCR in group 1 had overlapped peaks at nt 587 in the electropherogram. In group 2, 11 patients had overlapped peaks at nt 587 in the electropherogram. Cloning of PCR products allowed detection of the G145R mutant as a minor strain in 7 (group 1: 1 subject, group 2: 6 subjects) of 12 subjects who had overlapped peaks at nt 587 in the electropherogram.

CONCLUSIONS

The frequency of the a determinant mutants was not high in Japan. However, the G145R mutant was often present as a minor population in children and adults. HBV carriers might have the a determinant mutants as a minor form.

N-terminal myristoylation-dependent masking of neutralizing epitopes in the preS1 attachment site of hepatitis B virus

BACKGROUNDS & AIMS

The N-terminally myristoylated preS1 domain of the large hepatitis B surface protein (LHBs) mediates specific attachment of hepatitis B virus (HBV) to hepatocytes. Its B-cell epitopes leading to neutralization of infectivity are not yet characterized.

METHODS

We inserted C- and N-terminal preS1 peptides into the most immunogenic region of HBV core particles, therewith immunized Balb/c mice and determined binding properties and neutralization potential of resulting antibodies in vitro.

RESULTS

The particles with preS1 inserts were highly immunogenic and the corresponding anti-preS antibodies strongly bound to HBV particles from chronic carriers infected with different HBV genotypes A-F. However, antibodies binding to the C-terminal part of preS1 did not neutralize HBV infectivity for susceptible hepatocyte cultures. In contrast, antibodies elicited by the complete N-terminal attachment site of preS1(2-48) strongly neutralized with an IC50<3μg/ml of total immunoglobulin. Interestingly, antibodies against the very N-terminal part of preS1(1-21) could not neutralize infectivity although this sequence contains the most conserved and essential part of the attachment site. These antibodies reacted well with non-myristoylated preS1 peptides but only weakly with myristoylated preS1 peptides, natural HBsAg or HBV.

CONCLUSIONS

N-terminal myristic acid obviously favors a topology of LHBs that makes the most essential part of the preS1 attachment site inaccessible for neutralizing antibodies, whereas antibodies to neighbouring sequences neutralized very well. Thus, addition of the preS1(2-48) peptide in a highly immunogenic form to the current hepatitis B vaccine may improve protective immunity and reduce selection of escape mutations.

[One example of false negative hepatitis B surface antigen (EIA) result due to variant S area strain and reagment reactiveness related to hepatitis B surface antigen]

The presence in serum of the Hepatitis B surface antigen (HBsAg), the outer envelope of the hepatitis B virus (HBV), indicates viral infection, used in laboratory tests to confirm this. We report a case of discrepancy among HBsAg test results detected between measurements in a subject with HB infection. Gene analysis demonstrated several S region gene mutations, not detected previously. We tested 12 measurements e.g., EIA, CLIA, CLEIA, F-EIA, MAT, and IC for whether they could detect our subject's HBsAg and found that it was not recognized by a method using only a single monoclonal antibody to detect HBsAg in two detection processes, in contrast to the 11 other measurements, which used two different antibodies. This case shows that amino acid substitution may cause a false negative result for HBsAg. Gene mutations known to occur in HBV, should thus trigger an awareness of the need to keep in mind that false negative results can happen in case such as ours.

The underlying mechanisms for the "simultaneous HBsAg and anti-HBs serological profile"

The course of HBV infection is determined by the interplay between viral replication via HBV protein production and the host's immune response. Therefore, the diagnosis of infection in clinical practice is established by the serological detection of HBV protein products as well as antibodies produced by the host. Although the serological findings for assessing the clinical course of infection are already well established, the expression of viral proteins and the dynamics of antibody production may vary during the natural course of infection. This causes the HBV infection to be occasionally associated with the presence of unusual serologic profiles, which can lead to doubts in the interpretation of results and mistaken serological diagnosis. The simultaneous detection of HBsAg and anti-HBs in the blood stream comprises an atypical serological profile, somewhat incoherent, whose significance can be complicated to establish. Outlined in this article are some immunological and molecular mechanisms which could justify the existence of this profile in which there is a great laboratorial and clinical interest.

Occult hepatitis B in blood donors in Indonesia: altered antigenicity of the hepatitis B virus surface protein

BACKGROUND AND AIMS

Occult hepatitis B virus infection (OBI) poses a challenge to the safety of blood donation. The prevalence of OBI is not well documented in Indonesia, although this information in such an endemic country is needed. This study was aimed to evaluate the prevalence of occult hepatitis B in blood donors from two cities of Indonesia, and to study the genetic variation and its effect on the predicted antigenicity of HBsAg.

METHODS

Serum samples of 309 regular blood donors negative for HBsAg were tested for anti-HBs and anti-HBc. Hepatitis B virus (HBV) DNA isolated from anti-HBc-positive samples were analyzed by polymerase chain reaction, cloned and sequenced. Antigenic properties of identified HBsAg mutants were predicted by calculation of the antigenic index.

RESULTS

Of the 309 HBsAg-negative samples, anti-HBc was positive in 134 (43.4%) and HBV DNA was detected in 25 (8.1%). Seven of the viremic samples had nucleotide substitutions (A521G, A551T, C582T, and A562G) in the S gene, causing amino acid mutations (T123A, M133L, and T143M) in the 'a' determinant of HBsAg that resulted in changes in the predicted antigenicity.

CONCLUSIONS

OBI was detected in blood donors' samples in Indonesia. Anti-HBc was shown to be a better screening parameter than HBsAg, however, it might result in the loss of donors particularly in endemic countries. HBsAg detection failure in this study might be due to mutations altering the protein antigenicity and/or the low-level carriage of HBV.

A novel nucleotide insertion in S gene of hepatitis B virus in a chronic carrier

Hepatitis B virus DNA was extracted from serum of a chronic carrier and polymerase chain reaction was performed on S gene. Direct sequencing showed a variant HBsAg with additional 4-amino acid insertion, and clone sequencing confirmed the mixture of variant HBsAg and wildtype HBsAg. Of 16 clones with 12-nucleotide insertion, 15 clones had identical AGAACAACACAA insertion between nucleotide 494 and nucleotide 495, and one clone had GGAACAACTCAA insertion in the same position plus 3-nucleotide deletion from nucleotide 491 to nucleotide 493. S114T, C121Y, T126S/A, Q129K, G130R, T131N, M133T, G145R, N146D substitution and premature stop codon were also found in those clones. However, the origin of HBV with 4-amino acid insertion in HBsAg was unclear.

Characterization of a Hepatitis B virus strain in southwestern Paraná, Brazil, presenting mutations previously associated with anti-HBs Resistance

The present study investigated if hepatitis B virus (HBV) mutants circulate in the southwestern region of the State of Paraná, Brazil, by analyzing samples from children who received immunoprophylaxis but were born to HBV carrier mothers. Samples from 25 children were screened for HBV serum markers and for HBV DNA by PCR. Only one sample was positive for HBsAg, anti-HBs and HBV DNA, although the child had been vaccinated. Analysis of the S gene sequence of this sample showed the presence of a proline at position 105, a serine at position 114, three threonines at positions 115, 116 and 140, and a glutamine at position 129. The presence of these amino acids, except for serine at position 114, has been related to monoclonal or polyclonal therapy with anti-HBs after liver transplantation, whereas the presence of threonine at position 116 has been described in immunized children from Singapore. This finding demonstrates the possible circulation of HBV strains resistant to hepatitis B immunoprophylaxis in southwestern Paraná, Brazil. The genotype of the sample was identified as genotype D, which is frequently found in the region studied. Since 36% of the children had received incomplete or no immunoprophylaxis, more extensive follow-up of children born to HBsAg-positive mothers is needed.

Hepatitis B viral surface mutations in patients with adefovir resistant chronic hepatitis B with A181T/V polymerase mutations

The hepatitis B virus (HBV) polymerase gene has overlapping reading frames with surface genes, which allows to alter the amino acid codon of the surface genes. In adefovir (ADV) treated chronic hepatitis B patients carrying rtA181T/rtA181V mutations, overlap with surface gene mutations such as sW172stop/sL173F has been reported. However, the clinical consequences of such surface mutations have not been determined. The aim of this study was to determine the surface gene sequence in ADV-resistant patients carrying the A181T/V mutation and to describe the clinical significance. Of the 22 patients included in this study, 13 were ADV-resistant with rtA181T/V mutations (polymerase mutation group, Group P) and nine were antiviral treatment-naïve (control group, Group C). The Pre-S1 gene mutation, V60A, was detected in 11 patients (Group P=8, Group C=3). A start codon mutation in the Pre-S2 gene was found in five patients (Group P=3, Group C=2). An S gene mutation, sA184V, was found in nine patients, all of whom were in group P. Although sW172stop and sL173F mutations were detected, reduced HBsAg titer was not observed. Further study of these mutations and their clinical implications are needed.

An investigation of perinatal hepatitis B virus infections among a high risk population: the delivery hospital as a safety net

BACKGROUND

There was an increase in perinatal hepatitis B virus (HBV) infections in one Arkansas county that disproportionately affected Marshallese infants.

METHODS

An estimated 6000 to 10,000 Marshallese, from the Pacific island nation of the Marshall Islands where HBV is highly endemic, live in one Arkansas county. We conducted a retrospective review of hospital and health department records from 2003 to 2005 in that county. We compared maternal screening for hepatitis B surface antigen (HBsAg) between Marshallese and non-Marshallese. We also reviewed birth and immunization records for infants born to HBsAg-positive mothers to evaluate postexposure prophylaxis (PEP).

RESULTS

Ten percent (n = 41) of Marshallese births and 0.1% (n = 15) of non-Marshallese births were to HBsAg-positive women. Among those born to HBsAg-positive women, Marshallese and non-Marshallese infants were equally likely to receive PEP with hepatitis B vaccine (98% vs. 100%; P[r] = 0.98) and hepatitis B immune globulin (HBIG) <or=12 hours after birth (88% vs. 87%; P = 0.91). Approximately 57% (n = 32) of all infants born to HBsAg-positive women were tested for perinatal HBV infection. The proportion of Marshallese (17%) and non-Marshallese (13%) infants who tested positive for HBsAg at ages 9 to 25 months was similar (P = 0.78). Receiving HBIG >12 hours after birth was the only factor significantly associated with infection.

CONCLUSIONS

Although HBV infection was more prevalent among Marshallese compared with non-Marshallese women, there were no differences in infant receipt of PEP and perinatal HBV infection. Delivery hospitals in this county had standing orders to administer hepatitis B vaccine to all newborns, which likely provided a safety net to prevent perinatal HBV transmission in this high-risk population.

Hepatitis B caused by a hepatitis B surface antigen escape mutant

Amino acid substitutions within the S gene involving the major antigenic a determinant of the hepatitis B virus (HBV) surface antigen (HBsAg) have been detected in cases of failure of immunization against the virus. Our report showed development of clinical hepatitis in presence of antibody to HBsAg in a healthy individual. A single amino acid substitution (G145R) within the a determinant of the HBsAg was determined by sequencing of the isolated HBV strain. Lamivudine treatment efficiently cleared the peripheral HBV DNA, HBsAg, and hepatitis B e antigen. In conclusion, the immune escape mutant in the S gene can cause hepatitis despite pre-existing naturally acquired immunity.

Hepatitis B vaccines

Immunization is the most effective way to prevent transmission of HBV and, hence, the development of acute or chronic hepatitis B. The national strategy to eliminate transmission of the virus in the United States includes vaccination of all newborn infants, children, adolescents, and high-risk adults. Postexposure prophylaxis is also advocated, depending on the vaccination and anti-HBs status of the exposed person. Seroprotection after vaccination, defined as anti-HBs > or = 10 mIU/mL, is achieved in over 95% of all vaccinees. The hepatitis B vaccines are very well tolerated with usually minimal adverse effects. Predictors of non-response include increasing age, male gender, obesity, tobacco smoking, and immunocompromising chronic dis-ease. For those who remain nonresponders after the second series of vaccination, adjuvants such as GM-CSF may be considered, but their results are variable.

Prevalence of hepatitis B, C, and delta virus infections among children in Mongolia: progress in childhood immunization

Mongolia is highly endemic for hepatitis B virus (HBV), hepatitis C virus (HCV), and hepatitis delta virus (HDV) infections among apparently healthy adults. However, the age-specific prevalence of ongoing HBV, HCV, and HDV infections among children in Mongolia remains unknown. Therefore, samples obtained from a total of 655 apparently healthy children of 0.3-15 years of age (307 boys and 348 girls; age, mean +/- standard deviation [SD], 8.4 +/- 4.2 years) living in Mongolia, between October 2005 and January 2006, were tested for serological and molecular markers of HBV, HCV, and HDV infections. Although 88.7% of the 655 children studied were immunized against hepatitis B, 64 (9.8%) tested positive for hepatitis B surface antigen (HBsAg) and/or HBV DNA and 13 (2.0%) for HDV RNA. Twenty-seven children (4.1%) had detectable HCV RNA. Collectively, 82 (12.5%) were viremic for one or more of these viruses, including eight children with dual viremia of HBV/HCV and one child with triple HBV/HCV/HDV viremia. When children without anti-HBc, anti-HCV and anti-HDV IgG (n = 510) served as a control, a history of hospitalization was significantly associated with HBV viremia (P < 0.0001), anti-HBc positivity (P < 0.0001), and HCV viremia (P = 0.0001). HBsAg mutation was found in 18 (31.6%) of the 57 children with viremia, including those at amino acid position 126, 127, 129, 131, 134, 143 or 144. There were no significant differences in the frequency of HBsAg mutation in relation to age, sex, and hepatitis B vaccination status of the children, suggesting that HBsAg mutation plays a limited role in failure of vaccination in Mongolia.

Early upsurge in anti-HBs titer possibly caused by the immunomodulative, not by the mutagenetic effect of interferon and ribavirin

A patient with chronic hepatitis B and C undergoing treatment with interferon and ribavirin showed an upsurge in hepatitis B virus surface antibody (anti-HBs) titer, accompanied by a decrease in hepatitis B virus surface antigen (HBsAg) during the early treatment phase. Simultaneously, elevation of alanine aminotransferase (ALT) was observed. Subsequently, the hepatitis B virus (HBV) DNA titer decreased and HBV e antigen (HBeAg) to anti-HBe seroconversion occurred. The anti-HBs titer gradually returned to the pretreatment level after cessation of ribavirin treatment and HBV-DNA became undetectable. We found no nucleotide mutations in HBV-DNA that could explain the sudden elevation in anti-HBs titer. The appearance of anti-HBs was considered to be a break in immune tolerance against some epitopes in HBsAg, possibly the r epitope, stimulated by interferon/ribavirin treatment. The immunomodulatory effect of ribavirin might have caused this unexpected early immune response to HBsAg that preceded seroconversion to anti-HBe.

Immune-mediated hepatitis-associated aplastic anemia caused by the emergence of a mutant hepatitis B virus undetectable by standard assays

Hepatitis-associated aplastic anemia (HAA) is characterized by marrow failure developing after acute seronegative hepatitis. A patient with agammaglobulinemia developed HAA in association with HBsAg-negative, hepatitis B virus (HBV) DNA-positive acute hepatitis. Sequence analysis showed several substitutions in the major antigenic determinant of HBsAg, potentially affecting the detection by diagnostic immunoassays. Viral mutants may therefore be implicated as etiologic agents of HBsAg-negative HAA. HBV DNA determination may be necessary to exclude mutant HBV as a cause of HAA, particularly in categories at high risk of mutant selection such as agammaglobulinemic and transplanted patients.

Hepatitis B virus genetic variability and evolution

Hepatitis B virus has been evolving gradually over a long period of time, resulting in a large amount of genetic diversity, despite the constraints imposed by the complex genetic organization of the viral genome. This diversity is partly due to virus/host interactions and partly due to parallel evolution in geographically distinct areas. Recombination also appears to be an important element in HBV evolution. Also, human intervention in the form of mass vaccination and antiviral treatment will reduce the burden of HBV-related liver disease but may also be accelerating evolution of the virus.

Oral immunogenicity of potato-derived HBsAg middle protein in BALB/c mice

The antibodies to preS2 synthetic peptides have been probed to neutralize hepatitis B virus (HBV), and also the addition of preS2 sequence could enhance the antibody response compared with a conventional vaccine in the non- and low responders. Previously, we generated transgenic potatoes expressing middle protein, which contains additional 55 amino acid preS2 region at the N-terminus of the S protein, of HBV to determine the feasibility of developing a plant-delivered HBV vaccine. In this study, we monitored the immune response after induction of immunoglobulin by boosting and assessed the efficacy of the mucosal immune response with regard to generate IgA antibodies. The HBsAg middle protein expressed in our transgenic potatoes was well immunized at low antigenic quantities in mice and the induced anti-S or anti-preS2 antibodies were sustained for the whole period without decrease. Orally delivery of plant-derived HBsAg middle protein to mice resulted in fecal anti-S or anti-preS2 as well as serum IgG. In addition, we used antibodies induced from the immunized mice with the potato-derived rHBsAg in competition assay as competitors to confirm the binding ability of preS2 antibodies to surface antigen of hepatitis virus. Anti-preS2 antibodies induced from immunized mice with transgenic potatoes effectively competed with anti-preS2 murine antibody H8 as expected. From these results, the inclusion of preS2 antigen to HBV plant vaccine may provide additional protective immunity in the HBV prevention.

Prevalence of naturally occurring surface antigen variants of hepatitis B virus in Korean patients infected chronically

Although Korea is one of the endemic areas of hepatitis B virus (HBV) infection, the prevalence of naturally occurring variants in the major hydrophilic region (MHR) of the surface (S) gene of HBV has not been determined. In the present study, the prevalence of these variants was examined in terms of the clinical state, and HBeAg serostatus in a large series of Korean patients with chronic HBV infection by direct sequencing analysis of part of the S gene containing the MHR of HBV isolated from 101 chronic HBV patients (51 HBeAg-positive and 50 HBeAg-negative): 37 were asymptomatic carriers, 21 had chronic hepatitis, 20 had liver cirrhosis, and 23 had hepatocellular carcinoma (HCC). Forty-seven MHR variants (46.5%) of the 101 patients were detected, involving a total of 59 amino acid substitutions at 12 positions inside and 14 position outside the 'a' determinant, and 33 'a' determinant variants (32.7%). A total of 17 novel variants and 14 novel mutation patterns were detected. The prevalence of MHR variants in HBeAg-negative patients tended to be higher than in HBeAg-positive patients (54.0% vs.39.2%) and the prevalence of MHR variants in HCC and liver cirrhosis tended to be higher than in asymptomatic carriers (65.2% vs. 40.5% and 50.0% vs. 40.5%, respectively). In conclusion, three important findings were found in the present study. First, an unexpectedly high prevalence of naturally occurring MHR variants was found in Korean chronic patients. Second, several novel variants associated with mutations outside the 'a' determinant were detected. Finally, a higher prevalence of MHR variants was associated with HBeAg-negative serostatus and severe liver disease, particularly HCC.

Transmission of G145R mutant of HBV to an unrelated contact

Household contacts of HBV-related chronic liver disease patients constitute a high-risk group for acquisition of HBV infection. Some of the HBsAg mutants are associated with liver disease and some are reported to be transmitted vertically. There is limited information on the horizontal transmission of Gly 145 Arg (G145R) mutant to related contacts. Its possible transmission to an unrelated third degree contact is reported in the present study. An HBV related chronic liver disease patient; the index patient, and his 11 household contacts were studied. This included four 1 degrees, three 2 degrees, one 3 degrees, and a sexual contact. Surface gene sequencing including the "a" determinant region was carried out in HBV DNA+ve subjects. The sequences were aligned and compared for the homology. HBV DNA was found to be positive in one 1 degrees, three 2 degrees, and one 3 degrees contact, besides the index patient. Histopathological studies revealed evidence of chronic hepatitis in all these contacts. Mutation T118V was present in all the six subjects. Mutant G145R along with T118V and T143M was identified in three subjects who included one 1 degrees, one 2 degrees, and one 3 degrees contact. Presence of T118V and T143M mutations along with G145R mutation in these subjects provides an indirect evidence for the possible horizontal transmission of G145R HBV variant to a 3 degrees unrelated contact. Of these three contacts with G145R mutation, only one 1 degrees contact was found to be HBsAg-ve. The data also reaffirms the earlier finding of HBsAg positivity in presence of G145R mutation of the S-gene. HBV exists as quasi-species and mixed population in subjects with chronic HBV infection.

Contributions of the viral genetic background and a single amino acid substitution in an immunodominant CD8+ T-cell epitope to murine coronavirus neurovirulence

The immunodominant CD8+ T-cell epitope of a highly neurovirulent strain of mouse hepatitis virus (MHV), JHM, is thought to be essential for protection against virus persistence within the central nervous system. To test whether abrogation of this H-2Db-restricted epitope, located within the spike glycoprotein at residues S510 to 518 (S510), resulted in delayed virus clearance and/or virus persistence we selected isogenic recombinants which express either the wild-type JHM spike protein (RJHM) or spike containing the N514S mutation (RJHM(N514S)), which abrogates the response to S510. In contrast to observations in suckling mice in which viruses encoding inactivating mutations within the S510 epitope (epitope escape mutants) were associated with persistent virus and increased neurovirulence (Pewe et al., J Virol. 72:5912-5918, 1998), RJHM(N514S) was not more virulent than the parental, RJHM, in 4-week-old C57BL/6 (H-2b) mice after intracranial injection. Recombinant viruses expressing the JHM spike, wild type or encoding the N514S substitution, were also selected in which background genes were derived from the neuroattenuated A59 strain of MHV. Whereas recombinants expressing the wild-type JHM spike (SJHM/RA59) were highly neurovirulent, A59 recombinants containing the N514S mutation (SJHM(N514S)/RA59) were attenuated, replicated less efficiently, and exhibited reduced virus spread in the brain at 5 days postinfection (peak of infectious virus titers in the central nervous system) compared to parental virus encoding wild-type spike. Virulence assays in BALB/c mice (H-2d), which do not recognize the S510 epitope, revealed that attenuation of the epitope escape mutants was not due to the loss of a pathogenic immune response directed against the S510 epitope. Thus, an intact immunodominant S510 epitope is not essential for virus clearance from the CNS, the S510 inactivating mutation results in decreased virulence in weanling mice but not in suckling mice, suggesting that specific host conditions are required for epitope escape mutants to display increased virulence, and the N514S mutation causes increased attenuation in the context of A59 background genes, demonstrating that genes other than that for the spike are also important in determining neurovirulence.

Overlapping gene mutations of hepatitis B virus in a chronic hepatitis B patient with hepatitis B surface antigen loss during lamivudine therapy

Disappearance of hepatitis B surface antigens (HBsAg) in chronic hepatitis B usually indicates clearance of hepatitis B virus (HBV) infection. However, false HBsAg negativity with mutations in pre-S2 and 'a' determinant has been reported. It is also known that YMDD mutations decrease the production of HBV and escape detection of serum HBsAg. Here, we report overlapping gene mutations in a patient with HBsAg loss during the lamivudine therapy. After 36 months of lamivudine therapy in a 44-yrold Korean chronic hepatitis B patient, serum HBsAg turned negative while HBV DNA remained positive by a DNA probe method. Nucleotide sequence of serum HBV DNA was compared with the HBV genotype C subtype adr registered in NCBI AF 286594. Deletion of nucleotides 23 to 55 (amino acids 12 to 22) was identified in the pre-S2 region. Sequencing of the 'a' determinant revealed amino acid substitutions as I126S, T131N, M133T, and S136Y. Methionine of rtM204 in the P gene was substituted for isoleucine indicating YIDD mutation (rtM204I). We identified a HBV mutant composed of pre-S2 deletions and 'a' determinant substitutions with YMDD mutation. Our result suggests that false HBsAg negativity can be induced by combination of overlapping gene mutations during the lamivudine therapy.

Genotyping of hepatitis B virus in Malaysia based on the nucleotide sequence of preS and S genes

Hepatitis B virus (HBV) has been classified into eight genotypes, designated A-H. These genotypes are known to have distinct geographic distributions. The clinical importance of genotype-related differences in the pathogenicity of HBV has been revealed recently. In Malaysia, the current distribution of HBV remains unclear. The aim of this study was to determine the genotypes and subtypes of HBV by using PCR, followed by DNA sequencing, as well as to analyse the mutations in the immunodominant region of preS and S proteins. The S gene sequence was determined from HBV DNA of four apparently healthy blood donors' sera and three sera from asymptomatic chronic hepatitis B carriers. Of this batch of sera, the preS gene sequence was obtained from HBV DNA from three out of the four blood donors and two out of the three chronic carriers. Due to insufficient sera, we had to resort to using sera from another blood donor to make up for the sixth DNA sequence of the preS gene. Based on the comparative analysis of the preS sequences with the reported sequences in the GenBank database, HBV DNA from two normal carriers was classified as genotype C. Genotype B was assigned to HBV from one blood donor and two hepatitis B chronic carriers, whereas HBV of one chronic carrier was of genotype D. Based on the S gene sequences, HBV from three blood donors was of genotype C, that of one blood donor and one chronic carrier was of genotype B, and the remaining, of genotype D. In the five cases where both preS and S gene sequences were determined, the genotypes assigned based on either the preS or S gene sequences were in concordance. The nature of the deduced amino acid (aa) sequences at positions 125, 127, 134, 143, 159, 161 and 168 of the S gene enabled the classification of these sequences into subtypes, namely, adrq+, adw2 and ayw2. The clustering of our DNA sequences into genotype groups corresponded to their respective subtype, that is, adw2 in genotype B, adrq in genotype C and ayw in genotype D. Analysis of the point mutations revealed that five of the sequences contained aa substitutions at immunodominant epitopes involved in B or/and T cell recognition. In conclusion, despite the low numbers of samples studied, due to budget constraints, these data are still worthwhile reporting, as it is important for the control of HBV infections. In addition, the genotype and mutational data obtained in this study may be useful for designing new treatment regimes for HBV patients.

Hepatitis B NAT virus-positive blood donors in the early and late stages of HBV infection: analyses of the window period and kinetics of HBV DNA

BACKGROUND AND OBJECTIVES

The Japanese Red Cross (JRC) carries out nucleic acid amplification testing (NAT) for hepatitis B virus (HBV), hepatitis C virus (HCV) and human immunodeficiency virus-1 (HIV-1) by using a multiplex (MPX) reagent. Screening is undertaken on serologically negative units. In this study we characterized HBV NAT-positive donations individually and analysed the window period and kinetics of HBV DNA, during acute infection, in follow-up studies.

MATERIALS AND METHODS

Two hundred and seventy-seven HBV DNA-positive donations have been identified in Japan since the introduction of NAT screening of 50-donation minipools. The viral loads and genotypes of these HBV DNA-positive donations were characterized. The doubling time and half-life of HBV was estimated from the data of 123 follow-up donors. The sensitivity of the NAT system (based on 50-donation minipools) was compared with the sensitivities of the enzyme immunoassay (EIA) and the chemiluminescence immunoassay (CLIA). Samples that were CLIA negative, but with > 10(4) copies/ml of HBV DNA, were analysed by sequencing the hepatitis B surface antigen (HBsAg) region.

RESULTS

Out of 277 HBV NAT-positive samples, 125 (45%) were found to have an increasing viral load and 45 (16%) a decreasing viral load. Forty per cent of HBV NAT-positive samples with an increasing viral load, and 33% of those with a decreasing viral load, were negative when tested by using the CLIA. No mutations related to escape mutants were found in the samples that were CLIA negative but with HBV DNA loads of > 10(4) copies/ml. The median HBV doubling time was 2.6 days (n = 93, 1.3-15.2 days) and the half-life was 1.6 days (n = 55, 0.9-6.3 days). Some kinetic difference was observed between genotypes A and B.

CONCLUSIONS

HBV NAT screening detected HBV DNA in both early (the so-called serological window period) and late stages of acute HBV infection.

Occult hepatitis B virus infection: implications in transfusion

Hepatitis B virus (HBV) presents a higher residual risk of transmission by transfusion than hepatitis C virus (HCV) or human immunodeficiency virus (HIV). While most infectious blood units are removed by screening for hepatitis B surface antigen (HBsAg), there is clear evidence that transmission by HBsAg-negative components occurs, in part, during the serologically negative window period, but more so during the late stages of infection. Donations negative for HBsAg, but positive for HBV DNA, with or without the presence of HBV antibodies, correspond to 'occult' HBV infection (OBI). The frequency of OBI depends on the relative sensitivity of both HBsAg and HBV DNA assays. It also depends on the prevalence of HBV infection in the population. OBI may follow recovery from infection, displaying antibody to hepatitis B surface antigen (anti-HBs) and persistent low-level viraemia, escape mutants undetected by the HBsAg assays, or healthy carriage with antibodies to hepatitis B e antigen (anti-HBe) and to hepatitis B core antigen (anti-HBc). Over time, in the latter situation, anti-HBe and, later, anti-HBc may become undetectable. The critical question is whether or not OBI is infectious by transfusion. All forms have been shown to be infectious in immunocompromised individuals, such as organ- or bone marrow-transplant recipients. In immunocompetent recipients, there is no evidence that anti-HBs-containing components (even at low titre) are infectious. Anti-HBc only, with HBV DNA, can be associated with infectivity, as can rare cases of HBV DNA without any serological HBV marker. If HBV nucleic acid amplification technology (NAT) is considered, the OBI viral load would usually be < 500 IU/ml, making testing of plasma pools unsuitable unless the sensitivity of NAT significantly increases by genome enrichment or test improvement.

Mutation of the "a" determinant of HBsAg with discordant HBsAg diagnostic kits

Sera from 1003 in- and out-patients were investigated for hepatitis B surface antigen (HBsAg) mutation at Siriraj Hospital, Bangkok, Thailand. Individual samples were screened using two commercial HBsAg kits on automatic machine-based assays set up in parallel. The first kit was a sandwich ELISA kit that used monoclonal capture/monoclonal conjugate and color detection whereas the second was a sandwich MEIA, using monoclonal capture/polyclonal indicator and fluorochrome determination. Six specimens were found discordant by negative EIA and positive MEIA; two specimens of which were detectable of HBV DNA. Three out of four discordant results were confirmed by an anti-HBs neutralization assay. Based on direct sequencing, one HBsAg/anti-HBs sample with multiple mutations in the S gene was found. The mutation included the common glycine to arginine escape mutation at amino acid position 145 of the "a" determinant. The observation should alert the blood bank to the necessity of using screening kits capable of detecting HBV mutant carriers as well as providing verification for the phenomenon of vaccine-escape mutation in Thailand.

Prevalence of HBsAg mutants and impact of hepatitis B infant immunisation in four Pacific Island countries

The prevalence rate of hepatitis B virus (HBV) infection in Pacific Island countries is amongst the highest in the world. Hepatitis B immunisation has been incorporated into national programmes at various times, often with erratic supply and coverage, until a regionally co-ordinated programme, which commenced in 1995 ensured adequate supply. The effectiveness of these programmes was recently evaluated in four countries, Vanuatu and Fiji in Melanesia, Tonga in Polynesia and Kiribati in Micronesia. That evaluation established that the programmes had a substantial beneficial impact in preventing chronic hepatitis B infection [Vaccine 18 (2000) 3059]. Several studies of hepatitis B vaccination programmes in endemic countries have identified the potential significance of surface gene mutants as a cause for failure of immunisation. In the study outlined in this paper, we screened infected children and their mothers for the emergence and prevalence of these variants in specimens collected from the four country evaluation. Although the opportunity for the emergence of HBV vaccine escape mutants in these populations was high due to the presence of a considerable amount of the virus in the population and the selection pressure from vaccine use, there were no "a" determinant vaccine escape mutants found. This suggests that vaccine escape variants are not an important cause for failure to prevent HBV transmission in this setting. Other HBsAg variants were detected, but their functional significance remains to be determined. The failure to provide satisfactory protection during such immunisation programmes reflects the need for achieving and sustaining high vaccine coverage, improving the timeliness of doses as well as improving 'cold-chain' support, rather than the selection of vaccine-escape mutants of HBV.

Hepatitis B virus infection after renal transplantation in the presence of antibody to hepatitis B surface antigen immunity

BACKGROUND AND AIM

Hepatitis B virus (HBV) infection has been known to be hampered by immunity against hepatitis B surface antigen (HBsAg). However, HBV with mutations within the common antigenic epitope of HBsAg, the "a" determinant region, can escape from humoral immunity. Moreover, HBV infection by "a" determinant mutants in chronic HBV patients has been reported after renal transplantation. In the present study, the authors investigated HBV infection after renal transplantation despite passive immunization or resolved HBV infection.

METHODS

A total of 1682 patients who underwent a renal transplant between 1979 and 1998 at the Severance Hospital, Yonsei University College of Medicine, Korea, were enrolled. The sequence of the HBV genome was analyzed from two patients with antibody to HBsAg (anti-HBs) immunity.

RESULTS

Of 1682 patients who were HBsAg negative before transplantation, 21 patients were found to be HBsAg positive, with elevated aspartate aminotransferase and alanine aminotransferase levels after transplantation. Interestingly, six of 21 (28.6%) patients were anti-HBs positive before the transplantation. Sequence analysis of the cloned HBV from two of six patients with anti-HBs immunity showed no evidence of significant mutations within the "a" determinant region, suggesting a wild-type of HBV. Their donors were not exposed to HBV before transplantation (all HBV markers were negative). Seven deaths of 21 patients were ascribed to HBV-related complications.

CONCLUSIONS

Regardless of anti-HBs immunity, HBV infection occurred in immunosuppressed patients in a high endemic area. The molecular mechanism and clinical impact of HBV infection after renal transplantation in patients with anti-HBs immunity should be further reappraised.

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.

Hepatitis B vaccines

Immunization is the most effective way to prevent transmission of HBV and, hence, the development of acute or chronic hepatitis B. The national strategy to eliminate transmission of the virus in the United States includes vaccination of all newborn infants, children, adolescents, and high-risk adults. Postexposure prophylaxis is also advocated, depending on the vaccination and anti-HBs status of the exposed person. Seroprotection after vaccination, defined as anti-HBs > or = 10 mIU/mL, is achieved in over 95% of all vaccinees. The hepatitis B vaccines are very well tolerated with usually minimal adverse effects. Predictors of non-response include increasing age, male gender, obesity, tobacco smoking, and immunocompromising chronic disease. For those who remain nonresponders after the second series of vaccination, adjuvants such as GM-CSF may be considered, but their results are variable.

Molecular epidemiology of hepatitis B and C virus infections in Asia

The present paper provides a review of the current literature regarding the molecular-based epidemiology of hepatitis B virus (HBV) and hepatitis C virus (HCV), which are very important viruses underlying the etiology of blood-borne infectious diseases worldwide. Particularly, both HBV and HCV are widespread on the Asian continent and are associated with acute and chronic liver diseases, including hepatocellular carcinoma. HBV has been classified into genotypes A through G and shown to have a distinct geographic distribution. In Asia, genotypes B and C of HBV prevail, and genotype C has been shown to cause more serious liver disease than genotype B. High prevalence of HBV mutants with various forms, such as the pre-S mutant, basal core promoter mutant, YMDD motif mutant and vaccine escape mutant, were seen in Asia and these were found to be related to the severity of liver disease and sensitivity to therapy. HCV has also been classified into multiple genotypes and associated with geographic distribution. HCV genotype 1 is less sensitive to interferon therapy and may be associated with the presence of more serious liver disease than the other genotypes. Data on the relation among the HBV/HCV genotypes, their pathogenicity in chronic liver diseases including hepatocellular carcinoma and their effect on therapy are awaited with great interest, especially in Asia, which is an endemic region of blood-borne hepatitis viruses.

Occult hepatitis B virus infection

The detection of HBV DNA without HBsAg with or without the presence of HBV antibodies outside the acute phase window period defines occult HBV infection. This condition has been described in hepatocellular carcinoma (HCC), chronic hepatitis B, healthy HBV carriage and recovered infection, chronic hepatitis C and individuals without serological markers of HBV. The frequency of the diagnosis depends on the relative sensitivity of both HBsAg and HBV DNA assays. It also depends on the prevalence of HBV infection in the population. Occult HBV in blood donors has a wide range of potential origins within the natural history of the infection. It may originate from recovered infections with anti-HBs and persistent, low-level, viral replication, escape mutants undetected by the HBsAg assays or healthy chronic carriage. The last situation is mostly found with anti-HBc only. Over time, antibody markers may become undetectable leaving HBV DNA as the only marker of the infection. In all cases, the viral load is low, mostly below 10(4) IU/ml, often below 100 IU/ml. At these levels, nucleic acid testing (NAT) in pools is likely to be largely ineffective. Is occult HBV transmissible by transfusion? Carriers of anti-HBs or anti-HBc only were shown infectious in immunosuppressed organ or bone marrow transplant recipients. In immunocompetent recipients, there is no evidence that anti-HBs-containing components are infectious, even in low titre. Donations carrying anti-HBc only and HBV DNA can be infectious and this is a threat where anti-HBc is not screened. Anti-HBc screening identifies most occult HBV infection but not all. HBV NAT needs either extreme sensitivity or to be performed on individual donations to eliminate HBV DNA-containing units.

Quantitative analysis of HBV DNA level and HBeAg titer in hepatitis B surface antigen positive mothers and their babies: HBeAg passage through the placenta and the rate of decay in babies

It is well documented that perinatal transmission is the major cause of chronic HBV infection in China. However, the mechanisms of HBV perinatal transmission are not defined clearly. It is not known whether hepatitis B e antigen can cross the human placenta, and the rate of HBeAg decay in babies with and without HBV breakthrough has not been studied. In this study, HBV serological markers were investigated in 95 hepatitis B surface antigen positive pregnant women. These markers were also studied in the babies at birth and at the age of 6 months and 12 months. The data show that 7.4% (7/95) children were infected with HBV during the first year after birth despite receiving passive-active immunoprophylaxis with hepatitis B immune globulin and hepatitis B vaccine. The surface gene fragment of HBV DNA was cloned and sequenced following PCR amplification in 7 cases of HBsAg positive babies and their mothers. All babies had the same sequences as their mothers, although two babies also had sequences that would produce an amino acid substitution within the "a" determinant. Furthermore, we measured HBeAg titers and HBV DNA levels by using Abbott AxSYM system and LightCycler-based real-time fluorescence quantitative PCR in 54 mother-infant pairs. Thirty-three mothers were HBeAg positive, and 21 mothers were HBeAg negative. Seventy percent (23/33) of neonates from HBeAg-positive mothers were HBeAg positive at birth compared with 0% (0/21) of neonates from HBeAg negative mothers. HBeAg was present at higher titer in the birth sera of the babies with HBV breakthrough than in babies without breakthrough. HBeAg was cleared from the serum in all 19 babies without breakthrough. In 17 of these 19 babies, the HBeAg was cleared within 6 months, and in two babies clearance took 12 months. The mean serum HBV DNA level in the mothers of the 4 infants with HBV breakthrough was significantly higher than in the mothers of babies who did not become infected. In conclusion, this data suggests that HBeAg can cross the human placenta, and disappears from serum within 6 months in most babies. HBV DNA levels in hepatitis B carrier mothers are associated with the failure of HBIG and vaccine immunization, and the additional influence of transmitted HBeAg cannot be excluded.

High frequency of hepatitis B virus infection in patients with beta-thalassemia receiving multiple transfusions

BACKGROUND AND OBJECTIVES

Hepatitis B virus (HBV) may occasionally be transmitted through transfusion of blood units that are hepatitis B surface antigen (HBsAg) negative but HBV DNA positive. Children with beta-thalassemia are particularly susceptible to HBV because they receive multiple blood transfusions. These children have high infection rates despite vaccination against HBV. Post-vaccination infections may be a result of viruses harbouring surface (S)-gene mutations (e.g. G587A) in a region critical for reactivity to antibody to hepatitis B surface antigen (anti-HBs). The true prevalence of HBV in individuals with beta-thalassemia has not been studied previously.

PATIENTS AND METHODS

Seventy patients with beta-thalassemia (median age 6 years; range 8 months to 22 years; 49 male), who had received seven to 623 (median 61) units of blood each and three doses (10/20 micro g) of HBV vaccine (Engerix B) before presentation to us, were included in the study; 50 of the 70 patients had received transfusions prior to vaccination. Enzyme-linked immunoassay for serological markers [HBsAg, antibody to hepatitis B core antigen (anti-HBc) and quantitative anti-HBs] and polymerase chain reaction (PCR) followed by Southern hybridization for molecular detection of hepatitis B, was performed on all samples. The PCR-amplified product was cloned, sequenced and the nucleotide and deduced amino acid sequences for the HBV S and polymerase (P) genes were analysed for mutations.

RESULTS

Four of 70 (5.7%) individuals with beta-thalassemia were HBsAg positive and 14 (20%) were anti-HBc positive. The prevalence of serological markers increased with number of transfusions (P < 0.01). Of 70 patients, 53 (75.7%) had an anti-HBs titre of > 10 IU/l following vaccination and 17 (24.3%) were non-responders (< 10 IU/l); 22 (31.4%) of the 70 were DNA positive. The frequency of HBV infection in beta-thalassemia was similar in vaccine responders and non-responders. The virus was of subtype ayw (genotype D) in the five DNA-positive samples in which a 388-nucleotide region of the S gene was sequenced. Mutations occurred at 13 positions in the S gene and at 10 positions in the P gene. Hydrophobicity plots revealed differences in amino acid regions 117-165 and 195-211. Some of these amino acid substitutions coincided with the putative cytotoxic T-lymphocyte epitopes of both S and P proteins.

CONCLUSIONS

A high frequency of HBV infection was seen using molecular methods in thalassemic patients. The frequency of infection was similar in vaccine responders and non-responders. A number of mutations were observed in the S gene, which could have implications for viral replication as well as virus-host cell interaction.