Influence of mutations in hepatitis B virus surface protein on viral antigenicity and phenotype in occult HBV strains from blood donors

Identification and characteristics of mutations promoting occult HBV infection by ultrasensitive HBsAg assay

The significance of occult hepatitis B virus (HBV) infection (OBI) has been increasingly recognized while the underlying mechanisms remain incompletely understood. This study aimed to identify high-frequency OBI-related mutations in HBV surface antigen (HBsAg)-negative samples tested by the ultrasensitive Lumipulse G HBsAg-Quant assay. OBI samples were collected from 32 blood establishments across 14 provinces in China. Lumipulse G HBsAg-Quant assay was performed for the re-testing and reclassification of OBI. Mutations in genotypes B (GTB) and C (GTC) were analyzed to identify high-frequency single and combined mutations. Additionally, the efficacy of commercial reagents commonly employed in clinical diagnostics for detecting mutant HBsAg was evaluated. Western Blot was used for the confirmation of extracellular HBsAg as well as the detection of intracellular HBsAg. Hydrophilicity analysis and transmembrane distribution prediction of HBsAg were utilized for further validation. Single mutations at 17 sites and 9 combined mutations in GTB indicated a significantly elevated mutation frequency. In GTC, there were single mutations at 16 sites and 9 combined mutations. Several commercial reagents commonly demonstrated limited capacity toward mutant HBsAg with T123A/P, K141C, and P142R/I/K/L (GTB) and S114A/P (GTC). The findings indicated that mutations including T123A/C/K/S, S132G/Y, P142L/R/S/T, T143M, D144G, G145A, K160R+V168A, I4T+V168A, M103I+K122R, and M103I+Q181R (GTB), along with Q101H, M103I, R160K+C221Y (GTC), were associated with reduced levels of HBsAg both extracellularly and intracellularly. Additionally, K160R (GTB) and E2G (GTC) were associated with intracellular aggregation. This study elucidates the mutations associated with decreased extracellular HBsAg with ultrasensitive HBsAg assay, providing insight for further investigation into the mechanisms of OBI.

IMPORTANCE

The sensitivity of HBsAg detection reagents directly impacts the identification of occult hepatitis B virus (HBV) infection (OBI). This study aims to identify high-frequency OBI-related mutations in HBV surface antigen (HBsAg)-negative samples evaluated using a Fujirebio-Lumipulse ultrasensitive HBsAg assay and to investigate the implications of these mutations on the antigenicity of HBsAg, the detection capacities of various HBsAg assays, and the effects on intracellular and extracellular levels of HBsAg. Generally, our study offers a new perspective on OBI-related mutations by ultrasensitive HBsAg assay and lays the groundwork for further research on the OBI mechanism and the enhancement of HBsAg detection reagents.

Longstanding, undiagnosed, highly replicative hepatitis B virus reactivation in the presence of high levels of anti-HBs antibodies

INTRODUCTION

Kidney transplant recipients are among the populations at risk for Hepatitis B Virus (HBV) reactivation, and close monitoring is needed for its early detection.

METHODS

We describe a case of HBV reactivation in a patient who underwent kidney transplantation more than 30 years ago, with a known serological profile of past HBV infection.

RESULTS

Reactivation occurred as a highly replicative infection that went undiagnosed for 7 years due to negative results for HB surface antigen (HBsAg) and high levels of anti-HBs antibodies. Viral genome sequencing showed a high number of mutations in the major hydrophilic region of HBsAg that could explain such a profile.

DISCUSSION

This case highlights the usefulness of frequent and systematic HBV viral load testing in patients at risk of reactivation, with anti-hepatitis B core antibodies, regardless of HBsAg detection, aminotransferases, and anti-HBs antibody levels.

Characteristics of hepatitis B virus surface protein and occult hepatitis B infection in infants with immunoprophylaxis failure from Indonesia

Perinatal hepatitis B virus (HBV) infection carries a significant risk of chronicity and complications while making infected people reservoirs for further transmission. Hepatitis B immunization in infants, with or without hepatitis B immune globulin (HBIG), has proven effective in preventing mother-to-child transmission. Nevertheless, some newborns of mothers with high viremia testing positive for hepatitis B e antigen (HBeAg) may not benefit from HBV immunoprophylaxis. Nineteen (10.2 %) of 186 infants born to HBV-infected mothers were HBV DNA-positive. HBV genotypes, serotypes, and hepatitis B surface antigen (HBsAg) sequences were comparable in most mother-cord blood-infant sample pairings, indicating that the infants' HBV strains originated from their mothers. Three (15.3 %) infants had overt HBV infection, whereas 16 (84.2 %) had occult HBV infection (OBI). The HBV isolates from infants exhibited 26 mutations: 38.5 % in the 'a' determinant and 61.5 % in the rest of HBsAg. Mutations were identified in B-cell and T-cell epitopes, impairing humoral and cellular responses to detect or neutralize the virus. This rendered immunoprophylaxis and diagnostics ineffective while inducing tolerance to the infection. HBV strains with these mutations can persist and cause complications, but they can be transmitted undetected by HBsAg tests commonly used in community healthcare. This study reveals the risk of HBV transmission from HBsAg mutant-infected mothers to newborns despite having received the birth dose with HBIG and complete hepatitis B vaccination.

Preliminary analysis of the role of small hepatitis B surface proteins mutations in the pathogenesis of occult hepatitis B infection via the endoplasmic reticulum stress-induced UPR-ERAD pathway

A growing body of evidence has shown that hepatitis B surface antigen (HBsAg) mutations can influence the occurrence of occult hepatitis B infection (OBI), particularly amino acid substitutions in small hepatitis B surface proteins (SHBs). The mechanistic basis for these results, however, remains unclear. This study was designed to explore the potential impact and mechanisms of OBI-related SHBs mutations on serum HBsAg. Huh7 and HepG2 cells were transfected with plasmids encoding wild-type (WT) or OBI-related SHB mutation-containing sequences, after which a chemiluminescence approach was used to detect HBsAg levels in cell culture supernatants. Western blotting was further used to assess HBsAg and endoplasmic reticulum stress (ERS)-related protein levels in lysates prepared from these cells, while the localization of HBsAg within cells was assessed via immunofluorescent staining. Cells transfected with OBI-related SHB mutation-encoding plasmids exhibited lower supernatant HBsAg levels than cells transfected with WT plasmids. Intracellular and extracellular HBsAg levels in these mutant plasmid-transfected cells were lower relative to those for WT plasmid-transfected cells, and HBsAg accumulation within the ER was detected via immunofluorescent staining in cells transfected with OBI-related SHB mutation-encoding plasmids, ERS-related protein content was also significantly increased in mutant plasmid-transfected cells as compared to those in the WT group. These results suggest that proteins harboring OBI-related mutations may tend to accumulate in the ER, thereby triggering an ERS response and impairing the transcription and translation of HBsAg via the activation of the unfolded protein response and ER-associated protein degradation pathway. These effects ultimately reduce the overall assembly of HBV virions in the ER and their associated secretion.

Prevalence and molecular characteristics of occult hepatitis B virus infection among blood donors in Huzhou City, eastern China

Occult hepatitis B virus (HBV) infection (OBI) is a significant challenge for HBV prevention and control. We investigated the prevalence and surface (S) gene mutations of OBI among blood donors in Huzhou City, eastern China. The hepatitis B surface antigen (HBsAg) was routinely screened among 44,256 blood donors. HBV-DNA was detected using the Roche cobas®system. Serum samples that were HBsAg negative and HBV-DNA positive were selected, and the HBV S gene was amplified and sequenced. HBV genotype and S gene mutations were analyzed. The OBI rate in these blood donors was 0.070 % (31/44,256). Among the blood donors with OBI, only two cases (2/31, 6.5 %) were anti-HBc negative. The S gene sequences of 28 samples were successfully obtained, and we found that HBV genotype C (21/28, 70 %) was predominant among blood donors with OBI. Most S gene mutations were associated with OBI, and the high frequency mutations included N40S, G44E, Q51R/P, T113A/S,T118K/M, P120Q/S/T, and Y161F/S. Notably, amino acid substitutions at some sites differed from those reported previously, such as Y72F, G102V, P127L, Q129P, and S143T. Additionally, six novel mutations (S31I/N/R, P46L, S58C, C76Y, Y200F/C, and I208T) that may be associated with OBI were found. OBI was detected in a certain proportion of blood donors in Huzhou City. S gene mutations play an important role in OBI development. Further research is required to explore the functions of novel S gene mutants in OBI pathogenesis. The findings of this study may provide important insights to prevent HBV transmission through blood transfusions.

Incidence of Occult Hepatitis B Infection (OBI) and hepatitis B genotype characterization among blood donors in Cameroon

BACKGROUND

Occult hepatitis B infection (OBI) is characterized by the presence of hepatitis B virus (HBV) DNA at low levels in serum (<200 IU/mL) with a negative hepatitis B surface antigen (HBsAg) test. OBI remains a major challenge to blood safety, particularly in HBV-endemic regions like Cameroon, where HBV detection relies solely on HBsAg testing. This cross-sectional study aimed to investigate the actual incidence and genotype characteristics of OBI in Cameroonian blood donors.

METHODS

Between March and June 2023, samples were collected from 288 HBsAg-negative blood donors aged 18 to 55 years and analysed for antibodies against the HBV core (anti-HBc) and surface antigens (anti-HBs). Following DNA extraction from the serum samples, qualitative nested PCR and quantitative real-time PCR were used to detect HBV viral DNA and viral load respectively. For positive samples, sequencing of a fragment of the S gene was performed to identify the circulating HBV genotypes.

RESULTS

The findings revealed that 58% (n = 167/288) of blood donors tested positive for anti-HBc, 29% (n = 83/288) tested positive for anti-HBs, and 26% (n = 75/288) being positive for both anti-HBc and anti-HBs. Occult hepatitis was confirmed in 4.5% of the blood donors, all of whom belonged to either HBV genotypes A or E, which are predominant in Cameroon. The amino acid substitution sA184V associated with HBsAg detection failure in genotype E was observed in 70% of OBI sequences, and the HBsAg immune escape variants (sT131N and sS143L) implicated in OBI were also observed. The mutation rtN139K in the reverse transcriptase (RT) domain of the overlapping HBV polymerase (P) gene was present in 17% of OBI-positive sequences of genotype E, likely contributing to masking HBsAg secretion.

CONCLUSION

The results suggest a considerable risk of transfusion-transmitted HBV in this region. Therefore, to ensure blood safety, nucleic acid testing (NAT) is recommended, as relying solely on HBsAg assays is insufficient to eliminate this risk.

Evolution and diversity of the hepatitis B virus genome: Clinical implications

Hepatitis B virus (HBV) infection remains a significant global health burden. The genetic variation of HBV is complex. HBV can be divided into nine genotypes, which show significant differences in geographical distribution, clinical manifestations, transmission routes and treatment response. In recent years, substantial progress has been made through various research methods in understanding the development, pathogenesis, and antiviral treatment response of clinical disease associated with HBV genetic variants. This progress provides important theoretical support for a deeper understanding of the natural history of HBV infection, virus detection, drug treatment, vaccine development, mother-to-child transmission, and surveillance management. This review summarizes the mechanisms of HBV diversity, discusses methods used to detect viral diversity in current studies, and the impact of viral genome variation during infection on the development of clinical disease.

An overview of occult hepatitis B infection (OBI) with emphasis on HBV vaccination

Background

The prevalence of chronic hepatitis B virus (HBV) poses a significant threat to the lives of 257 million individuals globally, potentially resulting in severe outcomes such as liver cirrhosis or hepatocellular carcinoma. Among the existing preventive measures, yeast-derived vaccines have proven to be the most efficacious approach in combatting hepatitis B. Nonetheless, as scientific inquiries focus more on occult HBV infection (OBI) in vaccinated persons and the lingering risk of vertical transmission affecting 10-30 % of babies born to HBsAg-positive mothers, there is a growing apprehension regarding the inability of HBV vaccines to ensure complete immunity. This study aims to offer a more comprehensive understanding of the implications of widespread HBV vaccination initiatives on OBI while tackling the primary limitations associated with current vaccine formulations.

Methods

The exploration was conducted on PubMed, Scopus, and Web of Science databases to pinpoint research on OBI within vaccinated cohorts. A sum of 76 suitable studies was recognized.

Discussion

Multiple studies have documented the occurrence of OBI in fully vaccinated individuals, including both the general population and high-risk groups, such as newborns born to HBsAg-positive mothers. Factors contributing to vaccine failures include low-level anti-HBs antibodies, high maternal viral loads in mother-to-child transmission cases, as well as the presence of vaccine escape mutants and heterologous HBV genotypes. However, further research is needed to precisely understand the impact of active immunization on the emergence of OBI in vaccinated populations. Nonetheless, it is apparent that the advancement of more effective HBV vaccines could potentially lead to the extinction of HBV.

Inherent symmetry and flexibility in hepatitis B virus subviral particles

Chronic hepatitis B virus (HBV) infection poses a major global health challenge with massive morbidity and mortality. Despite a preventive vaccine, current treatments provide limited virus clearance, necessitating lifelong commitment. The HBV surface antigen (HBsAg) is crucial for diagnosis and prognosis, yet its high-resolution structure and assembly on the virus envelope remain elusive. Utilizing extensive datasets and advanced cryo-electron microscopy analysis, we present structural insights into HBsAg at a near-atomic resolution of 3.7 angstroms. HBsAg homodimers assemble into subviral particles with D2- and D4-like quasisymmetry, elucidating the dense-packing rules and structural adaptability of HBsAg. These findings provide insights into how HBsAg assembles into higher-order filaments and interacts with the capsid to form virions.

Molecular Characterization of Hepatitis B Virus in People Living with HIV in Rural and Peri-Urban Communities in Botswana

(1) Background: Hepatitis B virus (HBV) sequencing data are important for monitoring HBV evolution. We aimed to molecularly characterize HBV sequences from participants with HBV surface antigen-positive (HBsAg+) serology and occult hepatitis B infection (OBI+). (2) Methods: We utilized archived plasma samples from people living with human immunodeficiency virus (PLWH) in Botswana. HBV DNA was sequenced, genotyped and analyzed for mutations. We compared mutations from study sequences to those from previously generated HBV sequences in Botswana. The impact of OBI-associated mutations on protein function was assessed using the Protein Variation Effect Analyzer. (3) Results: Sequencing success was higher in HBsAg+ than in OBI+ samples [86/128 (67.2%) vs. 21/71 (29.2%)]. Overall, 93.5% (100/107) of sequences were genotype A1, 2.8% (3/107) were D3 and 3.7% (4/107) were E. We identified 13 escape mutations in 18/90 (20%) sequences with HBsAg coverage, with K122R having the highest frequency. The mutational profile of current sequences differed from previous Botswana HBV sequences, suggesting possible mutational changes over time. Mutations deemed to have an impact on protein function were tpQ6H, surfaceV194A and preCW28L. (4) Conclusions: We characterized HBV sequences from PLWH in Botswana. Escape mutations were prevalent and were not associated with OBI. Longitudinal HBV studies are needed to investigate HBV natural evolution.

HBsAg and TLR7/8 dual-targeting antibody-drug conjugates induce sustained anti-HBV activity in AAV/HBV mice: a preliminary study

Hepatitis B virus (HBV) infection is a significant global health concern due to elevated immunosuppressive viral antigen levels, the host immune system's inability to manage HBV, and the liver's immunosuppressive conditions. While immunotherapies utilizing broadly reactive HBV neutralizing antibodies present potential due to their antiviral capabilities and Fc-dependent vaccinal effects, they necessitate prolonged and frequent dosing to achieve optimal therapeutic outcomes. Toll-like receptor 7/8 (TLR7/8) agonists have been demonstrated promise for the cure of chronic hepatitis B, but their systemic use often leads to intense side effects. In this study, we introduced immune-stimulating antibody conjugates which consist of TLR7/8 agonists 1-[[4-(aminomethyl)phenyl]methyl]-2-butyl-imidazo[4,5-c]quinolin-4-amine (IMDQ) linked to an anti-hepatitis B surface antigen (HBsAg) antibody 129G1, and designated as 129G1-IMDQ. Our preliminary study highlights that 129G1-IMDQ can prompt robust and sustained anti-HBsAg specific reactions with short-term administration. This underscores the conjugate's potential as an effective strategy for HBsAg clearance and seroconversion, offering a fresh perspective for a practical therapeutic approach in the functional cure of CHB.

HIGHLIGHTS

HBV-neutralizing antibody 129G1 was linked with a TLR7/8 agonist small molecule compound IMDQ.Treatment with 129G1-IMDQ has shown significant promise in lowering HBsAg levels in AAV/HBV mice.129G1-IMDQ were eliciting a strong and lasting anti-HBsAg immune response after short-term treatment in AAV/HBV mice.

M133S mutation possibly involve in the ER stress and mitophagy pathway in maintenance hemodialysis patients with occult hepatitis B infection

Occult hepatitis B virus infection (OBI) is characterized by the presence of HBV DNA in the absence of detectable HBsAg. OBI is an important risk factor for cirrhosis and hepatocellular carcinoma, but its pathogenesis has not been fully elucidated. Mutations in the HBV preS/S genes can lead to impaired secretion of either HBsAg or S-protein resulting in the accumulation of defective viruses or S protein in cells. In our previous work, the M133S mutation was present in the HBV S gene of maintenance hemodialysis (MHD) patients with OBI. In this study, we investigated the potential role of amino acid substitutions in S proteins in S protein production and secretion through the construction of mutant S gene plasmids, structural prediction, transcriptome sequencing analysis, and in vitro functional studies. Protein structure prediction showed that the S protein M133S mutant exhibited hydrophilic modifications, with greater aggregation and accumulation of the entire structure within the membrane phospholipid bilayer. Differential gene enrichment analysis of transcriptome sequencing data showed that differentially expressed genes were mainly concentrated in protein processing in the endoplasmic reticulum (ER). The expression of heat shock family proteins and ER chaperone molecules was significantly increased in the wild-type and mutant groups, whereas the expression of mitochondria-associated proteins was decreased. Immunofluorescence staining and protein blotting showed that the endoplasmic reticulum-associated protein PDI, the autophagy marker LC3, and the lysosome-associated protein LAMP2 co-localized with the S proteins in the wild-type and mutant strains, and their expression was increased. The mitochondria-associated TOMM20 protein was also co-expressed with the S protein, but expression was significantly reduced in the mutant. The M133S mutation in the S gene is expressed as a defective and misfolded protein that accumulates in the endoplasmic reticulum causing secretion-impaired endoplasmic reticulum stress, which in turn triggers mitochondrial autophagy and recruits lysosomes to fuse with the autophagosome, leading to mitochondrial clearance. This study preliminarily demonstrated that the mutation of M133S in the S gene can cause OBI and is associated with disease progression, providing a theoretical basis for the diagnosis and treatment of OBI.

Frequency of HBsAg variants in occult hepatitis B virus infected patients and detection by ARCHITECT HBsAg quantitative

Objective

To analyze the amino acid substitution caused by mutations in the major hydrophilic region (MHR) of the S-region genes in the serum samples of occult hepatitis B virus infection (OBI), and to explore the reasons for the missed detection of HBsAg.

Method

The full-length gene of the S-region in hepatitis B virus(HBV) in the chronic hepatitis B virus(CHB)(10 samples) and OBI groups(42 samples) was amplified using a lab-developed, two-round PCR amplification technology. The PCR amplification products were sequenced/clone sequenced, and the nucleotide sequences of the S-region gene in HBV were compared to the respective genotype consensus sequence.

Results

Only 20 of the 42 samples in the OBI group had the S-region genes successfully amplified, with the lowest HBV DNA load of 20.1IU/ml. As S-region genes in HBV, 68 cloned strains were sequenced. In the OBI and CHB groups MHR region, with a mutation rate of 3.21% (155/4828) and 0.70% (5/710). The genetic mutation rate was significantly higher in the OBI group than in the CHB group (P<0.05). The common mutation types in the MHR region were: I126T, L162R, K122E, C124R, and C147Y.Mutations at s122, s126, and s162 were associated with subgenotypes, most of which being C genotypes. The high-frequency mutation sites L162R and K122E found in this study have not been reported in previous literature.

Conclusion

The results of this study confirmed that MHR mutations can cause the missed detection of HBsAg, giving rise to OBI.

Effect of S-region mutations on HBsAg in HBsAg-negative HBV-infected patients

BACKGROUND

Occult HBV infection (OBI) is a special form of hepatitis B virus (HBV) infection that may cause Liver cirrhosis and hepatocellular carcinoma, causing significant harm to patients. Given the insidious nature of OBI, it is usually not easy to be detected. Most of the samples currently studied are concentrated on blood donors, however, patients in this special state have not been fully studied. This project aimed to study the effect of HBV S region mutations on HBsAg in patients with clinical OBI.

METHODS

Collect 107 HBsAg-/HBV DNA + blood samples from Beijing Youan Hospital, Capital Medical University from August 2022 to April 2023. Next, the successfully extracted and amplified HBV DNA S regions were sequenced. Construct mutant plasmids to verify the cell function of the high-frequency mutation sites and explore the possible molecular mechanism.

RESULTS

Sixty-eight HBsAg-negative samples were sequenced, revealing high-frequency amino acid substitution sites in the HBV S protein, including immune escape mutations (i.e., sY100C、sK122R、sI126T、sT131P、and sS114T) and TMD (Transmembrane domain) region substitutions (i.e., sT5A、sG10D、sF20S、and sS3N). We constructed a portion of the mutant plasmids and found that sT5A, sF20S, sG10D, sS3N, sI68T, and sI126T single point mutations or combined mutations may decrease HBsAg expression or change the antigenicity of HBsAg leading to detection failure.

CONCLUSIONS

HBsAg-negative patients may show various mutations and amino acid replacement sites at high frequency in the HBV S-region, and these mutations may lead to undetectable Hepatitis B surface antigen (HBsAg), HBsAg antigenic changes or secretion inhibition.

Prevalence of transfusion-transmitted infections in hospitalized patients before transfusion and volunteer blood donors in Zhejiang Province, China

OBJECTIVES

To assess the need for screening of transfusion-transmitted infections (TTIs) in blood products, we assessed TTI seroprevalence in blood donors and hospitalized patients.

METHODS

We collected 2760 serum samples from three regions of Hangzhou, Ningbo and Huzhou from April 2021 to March 2022, and they tested by enzyme-linked immunosorbent assay (ELISA) for Hepatitis B surface antigen (HBsAg), Hepatitis C (HCV), Treponema pallidum (TP), Cytomegalovirus (CMV), Epstein-Barr virus (EBV), Hepatitis E virus (HEV) and Human T-cell lymphotropic virus type 1/2 (HTLV-1/2) antibody levels.

RESULTS

Screening test results showed that the positive rates for HBsAg, anti-HCV and anti-TP were 3.01 %, 0.39 % and 0.18 %, respectively. The positive rates for CMV IgM and CMV IgG were 0.76 % and 96.96 %, while the positive rates for EB VCA-IgM and EB EA-IgG were 1.88 % and 10.47 %; those for HEV IgM and HEV IgG were 1.16 % and 26.05 %, while the HTLV-1/2 antibody positive rate was 0.04 %. The positive rates for CMV IgG, EB EA-IgG and HEV IgG in hospitalized patients before transfusion were higher than in volunteer blood donors, and the difference was statistically significant (P < 0.05). The overall co-infection rate was 0.29 %. The positive rates for EB VCA-IgM in the males were significantly higher than in females, and EB VCA-IgM and HEV IgG prevalence varied significantly by age.

CONCLUSION

Our data demonstrate the risk of TTI exposure and TTI transmission in the Zhejiang population, which poses a threat to blood safety. It is hoped that expansion of pathogen categories (CMV, EBV, HEV and HTLV-1/2) and blood screening programs will contribute to the future adoption of scientific blood transfusion methods.

Hepatitis B Surface Antigen Isoforms: Their Clinical Implications, Utilisation in Diagnosis, Prevention and New Antiviral Strategies

The hepatitis B surface antigen (HBsAg) is a multifunctional glycoprotein composed of large (LHB), middle (MHB), and small (SHB) subunits. HBsAg isoforms have numerous biological functions during HBV infection-from initial and specific viral attachment to the hepatocytes to initiating chronic infection with their immunomodulatory properties. The genetic variability of HBsAg isoforms may play a role in several HBV-related liver phases and clinical manifestations, from occult hepatitis and viral reactivation upon immunosuppression to fulminant hepatitis and hepatocellular carcinoma (HCC). Their immunogenic properties make them a major target for developing HBV vaccines, and in recent years they have been recognised as valuable targets for new therapeutic approaches. Initial research has already shown promising results in utilising HBsAg isoforms instead of quantitative HBsAg for correctly evaluating chronic infection phases and predicting functional cures. The ratio between surface components was shown to indicate specific outcomes of HBV and HDV infections. Thus, besides traditional HBsAg detection and quantitation, HBsAg isoform quantitation can become a useful non-invasive biomarker for assessing chronically infected patients. This review summarises the current knowledge of HBsAg isoforms, their potential usefulness and aspects deserving further research.

Global prevalence of occult HBV infection in children and adolescents: A systematic review and meta-analysis

INTRODUCTION AND OBJECTIVES

Occult HBV infection (OBI) is a specific form of hepatitis B virus (HBV) infection and has the possibility of developing into hepatocellular carcinoma (HCC) in adults. This study aimed to estimate the global prevalence of occult HBV infection in children and adolescents.

MATERIALS AND METHODS

We systematically searched PubMed, Embase, Web of Science, and Cochrane databases for relevant studies on the prevalence of OBI in children and adolescents. Meta-analysis was performed using STATA 16 software.

RESULTS

Fifty studies were included. The overall prevalence of OBI in children and adolescents was 7.5% (95% CI: 0.050-0.103). In different risk populations, OBI prevalence was remarkably high in the HIV-infected population (24.2%, 95% CI: 0.000-0.788). The OBI prevalence was 0.8% (95% CI:0.000-0.029) in the healthy population, 3.8% (95% CI:0.012-0.074) in the general population, and 6.4% (95% CI: 0.021-0.124) in children born to HBsAg-positive mothers. Based on different serological profiles, the prevalence of OBI in HBsAg-negative and anti-HBc-positive patients was 6.6% (95% CI: 0.016-0.136), 3.0% (95% CI: 0.009-0.059) in HBsAg-negative and anti-HBc-negative patients, 4.6% (95% CI: 0.015-0.088) in HBsAg-negative and anti-HBs-positive patients, and 3.7% (95% CI: 0.001-0.102) in HBsAg-negative and anti-HBs-negative patients.

CONCLUSIONS

Despite HBV vaccination and hepatitis B immunoglobulin (HBIG), OBI is common in children and adolescents in high-risk groups.

Vaccine escape challenges virus prevention: The example of two vaccine-preventable oncogenic viruses

Over the years, the pace of developing vaccines for HBV and HPV has never stopped. After more than 30 years of application, the HBV vaccine has reduced 80% of hepatocellular carcinoma (HCC). However, vaccine escape variants occur under selective pressure induced by widespread vaccination and antiviral therapy, which results in fulminant infection and horizontal transmission. Several mechanisms have been studied to explain HBV vaccine escape, including vaccine escape mutations (VEMs) in the major hydrophilic region, which leads to a decrease in the binding ability to neutralize antibodies and is the primary escape mechanism, protein conformational and N-linked glycosylation sites changes caused by VEMs, differences in genotype distribution, gene recombination, and some temporarily unknown reasons. However, effective solutions are still being explored. The HPV vaccine has also been proven to prevent 70%-90% of cervical cancer worldwide. Cases of HPV infection after being vaccinated have been observed in clinical practice. However, few researchers have paid attention to the mechanism of HPV vaccine escape. Thus, we reviewed the literature on vaccine escape of both HBV and HPV to discuss the mechanism of the virus escaping from vaccine protection and possible solutions to this problem. We analyzed the gap between studies of HPV and HBV and made prospects for further research in HPV vaccine escape.

Detection of Immune Escape and Basal Core Promoter/Precore Gene Mutations in Hepatitis B Virus Isolated from Asymptomatic Hospital Attendees in Two Southwestern States in Nigeria

Several mutations in the surface (S), basal core promoter (BCP), and precore (PC) genes of the hepatitis B virus have been linked to inaccurate diagnosis and the development of immune escape mutants (IEMs) of the infection, which can lead to chronic infection. Understanding the prevalence and spread of these mutations is critical in the global effort to eliminate HBV. Blood samples were collected from 410 people in Osun and Ekiti states, southwest Nigeria, between 2019 and 2021. Participants were drawn from a group of asymptomatic people who were either blood donors, outpatients, or antenatal patients with no record of HBV infection at the medical outpatients' unit of the hospital. DNA was extracted from plasma using a Qiagen DNEasy kit, followed by nested PCR targeting HBV S and BCP/PC genes. The Sanger sequencing method was used to sequence the positive PCR amplicons, which were further analyzed for IEMs, BCP, and PC mutations. HBV-DNA was detected in 12.4% (51/410) of individuals. After DNA amplification and purification, 47.1% (24) of the S gene and 76.5% (39) of the BCP/PC gene amplicons were successfully sequenced. Phylogenetic analysis showed that all the HBV sequences obtained in this study were classified as HBV genotype E. Mutational analysis of the major hydrophilic region (MHR) and a-determinant domain of S gene sequences revealed the presence of three immune escape mutations: two samples harbored a T116N substitution, six samples had heterogenous D144A/N/S/H substitution, and one sample had a G145E substitution, respectively. The BCP/PC region analysis revealed a preponderance of major BCP mutants, with the prevalence of BCP double substitutions ranging from 38.5% (A1762T) to 43.6% (G1764A). Previously reported classical PC mutant variants were observed in high proportion, including G1896A (33.3%) and G1899A (12.8%) mutations. This study confirms the strong presence of HBV genotype E in Nigeria, the ongoing circulation of HBV IEMs, and a high prevalence of BCP/PC mutants in the cohorts. This has implications for diagnosis and vaccine efficacy for efficient management and control of HBV in the country.

Hepatitis B Virus Genotype D: An Overview of Molecular Epidemiology, Evolutionary History, and Clinical Characteristics

The hepatitis B virus (HBV) genotype D (HBV/D) is the most extensively distributed genotype worldwide with distinct molecular and epidemiological features. This report provides an up-to-date review on the history of HBV/D subgenotyping and misclassifications, along with large-scale analysis of over 1000 HBV/D complete genome sequences, with the aim of gaining a thorough understanding of the global prevalence and geographic distribution of HBV/D subgenotypes. We have additionally explored recent paleogenomic findings, which facilitated the detection of HBV/D genomes dating back to the late Iron Age and provided new perspectives on the origins of modern HBV/D strains. Finally, reports on distinct disease outcomes and responses to antiviral therapy among HBV/D subgenotypes are discussed, further highlighting the complexity of this genotype and the importance of HBV subgenotyping in the management and treatment of hepatitis B.

A Novel Insertion in the Hepatitis B Virus Surface Protein Leading to Hyperglycosylation Causes Diagnostic and Immune Escape

Chronic hepatitis B virus (HBV) infection is a global health threat. Mutations in the surface antigen of HBV (HBsAg) may alter its antigenicity, infectivity, and transmissibility. A patient positive for HBV DNA and detectable but low-level HBsAg in parallel with anti-HBs suggested the presence of immune and/or diagnostic escape variants. To support this hypothesis, serum-derived HBs gene sequences were amplified and cloned for sequencing, which revealed infection with exclusively non-wildtype HBV subgenotype (sgt) D3. Three distinct mutations in the antigenic loop of HBsAg that caused additional N-glycosylation were found in the variant sequences, including a previously undescribed six-nucleotide insertion. Cellular and secreted HBsAg was analyzed for N-glycosylation in Western blot after expression in human hepatoma cells. Secreted HBsAg was also subjected to four widely used, state-of-the-art diagnostic assays, which all failed to detect the hyperglycosylated insertion variant. Additionally, the recognition of mutant HBsAg by vaccine- and natural infection-induced anti-HBs antibodies was severely impaired. Taken together, these data suggest that the novel six-nucleotide insertion as well as two other previously described mutations causing hyperglycosylation in combination with immune escape mutations have a critical impact on in vitro diagnostics and likely increase the risk of breakthrough infection by evasion of vaccine-induced immunity.

Characterization of Hepatitis B Virus in Tenofovir-Treated and Untreated Chronically Infected Mothers and Their Immunoprophylaxis Failure Infants

BACKGROUND

Maternal tenofovir disoproxil fumarate (TDF) therapy during late pregnancy can reduce mother-to-infant transmission of hepatitis B virus (HBV). We investigated HBV mutations associated with maternal TDF therapy and their role in infant immunonophylaxis failure (IPF).

METHODS

Serum samples from untreated (n = 89) and TDF-treated (n = 68), highly viremic, chronically infected mothers and their infants were analyzed for HBV DNA by nested polymerase chain reaction (PCR) and direct sequencing.

RESULTS

At delivery, compared with untreated mothers, TDF-treated mothers had a lower HBV DNA titer and a higher frequency of basal core promoter (BCP) gene mutations, but they had similar frequencies in pre-S/S and pre-core/core mutations. The 14 mothers harboring surface "a" determinant mutants did not transmit the mutants to their immunized infants. Such mutants were found in 3 of 13 IPF infants; the 13 mothers had wild-type hepatitis B surface antigen (HBsAg). In univariable analysis, maternal HBV DNA titer (odds ratio [OR]: 1.54; 95% confidence intervals [CI]: 1.02-2.33; P = .039), genotype C (OR: 4.18; 95% CI: 1.28-13.62; P = .018) and pre-S1 wild-type sequence (OR: 6.33; 95% CI: 1.85-21.68; P = .003) at delivery were associated with infant IPF. Multivariable analyses showed that maternal genotype C (OR: 3.71; 95% CI: 1.11-12.36; P = .033) and pre-S1 wild-type (OR: 6.34; 95% CI: 1.79-22.44; P = .004) were associated with infant IPF independently of maternal viremia.

CONCLUSIONS

Along with high maternal HBV DNA titer at delivery, maternal genotype C and pre-S1 wild-type sequence were potential risk factors for infant IPF, although BCP mutations were not. The offspring of pregnant women harboring "a" determinant mutants as major strains seemed to be protected by immunoprophylaxis.

CLINICAL TRIALS REGISTRATION

NCT01312012.

Comparative analysis of hepatitis B virus infections in blood donors born before and after the implementation of universal HBV vaccination in southern China

BACKGROUND

In China, the vaccinated blood donors have rapidly increased by recent years, which may impact blood safety. The true prevalence of HBV between vaccinated blood donors and non-vaccinated blood donors should be explored.

STUDY DESIGN AND METHODS

The samples of blood donors were collected and detected for serologic markers of HBV in the Shenzhen Blood Centre (SZBC). The discrepant results were tested with commercial electrochemiluminescence immunoassay (ELCI) for HBsAg, anti-HBs, HBeAg, Anti-HBe and Anti-HBc, alternative MPX ID NAT, nested PCR, and a quantitative real-time polymerase chain reaction (qPCR) assay for HBV DNA. The serological and molecular characteristics of HBV infected blood donors were analysed, and the effects on blood safety for donors born before and after the implementation of universal HBV vaccination were compared.

RESULTS

Out of 242 presumed HBV infected donors from 26 318 donations, 131 (0.49%, [95% CI, 0.43-0.59]) chronic HBV infections (CHB, HBsAg detected with or without DNA), 58 (0.22%, [95% CI, 0.17-0.28]) occult hepatitis B infections (OBI, HBsAg not detected, assume anti-HBc positive and/or anti-HBs with HBV DNA) and 3 (0.011%, [95% CI, 0.0023-0.033]) window period (WP) infections were confirmed respectively. There were 28 CHBs (0.44%), 7 OBIs (0.11%) and 1 WP (0.016%) from vaccinated blood donor and 103 CHBs (0.52%), 51 OBIs (0.26%) and 2 WPs (0.01%) from non-vaccinated blood donor. The HBV+ (CHBs, OBIs and WPs) rate (0.56%) in vaccinated donors was lower than in non-vaccinated donors (0.78%, p < 0.05). The HBsAg titers of vaccinated infected blood donors (Median: 128.8 IU/ml) were much higher than non-vaccinated infected blood donors (58.4 IU/ml). The OBI yield rates in the vaccinated blood donors was significantly lower than the non-vaccinated blood donors (p < 0.05). There 102/124 (82.3%) samples were genotype B, 22/124 (17.7%) were genotype C respectively. There was no significant difference in the distribution of genotype between non-vaccinated blood donors (B/C, 86/17) and vaccinated blood donors (B/C, 23/6; p > 0.05). High frequency of vaccine escape mutations M133L (32.4%) and E164G in S region of genotype B strains and substitution L175S (40.9%) related to vaccine escape in S region of genotype C strains were identified.

CONCLUSION

The universal HBV vaccination program markedly reduces the risk of HBV infection in blood donors, and provides a significant guarantee for the safety of blood transfusion. Several important mutations detected related vaccine escape and notable mutations needed further investigated.

Combination therapy of therapeutic antibody and vaccine or entecavir in HBV carrier mice

Chronic infection with the hepatitis B virus (HBV) is a leading causes of liver cirrhosis and hepatocellular carcinoma. However, managing HBV treatments is challenging due to the lack of effective monotherapy. Here, we present two combination approaches, both of which aim to target and enhance the clearance of HBsAg and HBV-DNA. The first approach involves the use of antibodies to continuously suppress HBsAg, followed by the administration of a therapeutic vaccine in a sequential manner. This approach results in better therapeutic outcomes compared to the use of these treatments individually. The second approach involves combining antibodies with ETV, which effectively overcomes the limitations of ETV in suppressing HBsAg. Thus, the combination of therapeutic antibodies, therapeutic vaccines, and other existing drugs is a promising strategy for the development of novel strategies to treat hepatitis B.

Circulating immune complexes and mutations of HBsAg are associated with the undetectable HBsAg in anti-HBs and HBeAg positive occult hepatitis B virus infection

Introduction

Occult hepatitis B virus infection (OBI) is an HBsAg negative state in HBV infection with usually inactive HBV replication. However, there were a minority of individuals with positive HBeAg and anti-HBs among OBI blood donors and few studies have focused on this unusual serological pattern.

Methods

2022 plasma of blood donors that preliminary screened reactive for HBV DNA and non-reactive for HBsAg were collected from 16 provinces in China from 2015 to 2018. HBV DNA and HBsAg in these samples were retested using the Cobas TaqScreen MPX test and ARCHITECT HBsAg Quantitative II assay. Lumipulse HBsAg-HQ assay and polyethylene glycol (PEG)-double precipitation following HCl and trypsin digestion were performed to detect HBsAg from HBsAg-anti-HBs circulating immune complexes (CICs).

Results

1487 of 2022 samples were positive for Cobas HBV DNA test and non-reactive for ARCHITECT HBsAg assay, while 404 of them were positive using Lumipulse HBsAg-HQ assay. 10 HBsAg-/anti-HBs+/HBeAg+ OBI blood donor samples were further dissociated and HBsAg-CICs were detected in 7 samples. Sequencing analysis showed that D44N, N98T, G73S, Del 56-116, and I161T occurred in the pre-S region, and immune escape mutations such as P127T, F134L, G145R, V168A, and I126T/S in the S region were found.

Discussion

In conclusion, there were a minority of HBsAg-/anti-HBs+/HBeAg+ individuals in OBI blood donors. The undetectable HBsAg in these individuals was mainly due to HBsAg-CICs. Immune escape-associated mutations also happened under the host’s selective pressure. HBsAg dissociation methods or Lumipulse HBsAg-HQ assay is recommended to distinguish these individuals.

Hepatitis B Virus Research in South Africa

Despite being vaccine-preventable, hepatitis B virus (HBV) infection remains the seventh leading cause of mortality in the world. In South Africa (SA), over 1.9 million people are chronically infected with HBV, and 70% of all Black chronic carriers are infected with HBV subgenotype A1. The virus remains a significant burden on public health in SA despite the introduction of an infant immunization program implemented in 1995 and the availability of effective treatment for chronic HBV infection. In addition, the high prevalence of HIV infection amplifies HBV replication, predisposes patients to chronicity, and complicates management of the infection. HBV research has made significant progress leading to better understanding of HBV epidemiology and management challenges in the SA context. This has led to recent revision of the national HBV infection management guidelines. Research on developing new vaccines and therapies is underway and progress has been made with designing potentially curative gene therapies against HBV. This review summarizes research carried out in SA on HBV molecular biology, epidemiology, treatment, and vaccination strategies.

The Investigation of HBV Pre-S/S Gene Mutations in Occult HBV Infected Blood Donors with anti-HBs Positive

Introduction

The coexistence of hepatitis B virus (HBV) and hepatitis B surface antibodies (anti-HBs) in occult hepatitis B virus infection (OBI) is a contradictory phenomenon, and the underlying mechanism is not fully understood. The characteristics of pre-S/S mutations in OBI genotypes B and C (OBI_B and OBI_C) in the presence or absence of anti-HBs were analyzed extensively in this study. Methodology. The amino acid substitutions of envelope proteins of 21 OBI strains, including 4 HBs (+) OBI_B, 6 HBs (−) OBI_B, 6 HBs (+) OBIc, and 5 HBs (−) OBI_C samples, were analyzed and fully compared among groups of HBV genotypes and the presence of anti-HBs.

Results

The mutation rates in pre-S1, pre-S2, and S proteins of OBI_C were significantly higher than wild-type HBV (wt-HBV) genotype C strains, but only the mutation rate of S protein in OBI_B was significantly higher compared to wild-type HBV genotype B. The mutation rates in S protein of anti-HBs (−) OBI were higher than anti-HBs(+) OBI samples (4.40% vs. 2.43% in genotype B, P > 0.05; 6.81% vs. 3.47% in genotype C, P < 0.05). For these high-frequency substitutions in the pre-S/S region, the mutations sN40S and sK122R were found in 27.3% and 45.5% of anti-HBs (−) OBI strains, respectively. 7 substitutions were uniquely found in OBI_C strains and 9 substitutions were commonly detected in OBI_B and OBI_C strains.

Conclusions

These results suggested that the mutations might occur randomly and were not selected by antibody pressure.

Occult Hepatitis B Virus Infection: An Update

Occult hepatitis B virus (HBV) infection (OBI) refers to a condition in which replication-competent viral DNA is present in the liver (with detectable or undetectable HBV DNA in the serum) of individuals testing negative for the HBV surface antigen (HBsAg). In this peculiar phase of HBV infection, the covalently closed circular DNA (cccDNA) is in a low state of replication. Many advances have been made in clarifying the mechanisms involved in such a suppression of viral activity, which seems to be mainly related to the host's immune control and epigenetic factors. OBI is diffused worldwide, but its prevalence is highly variable among patient populations. This depends on different geographic areas, risk factors for parenteral infections, and assays used for HBsAg and HBV DNA detection. OBI has an impact in several clinical contexts: (a) it can be transmitted, causing a classic form of hepatitis B, through blood transfusion or liver transplantation; (b) it may reactivate in the case of immunosuppression, leading to the possible development of even fulminant hepatitis; (c) it may accelerate the progression of chronic liver disease due to different causes toward cirrhosis; (d) it maintains the pro-oncogenic properties of the "overt" infection, favoring the development of hepatocellular carcinoma.

Mapping the conformational epitope of a therapeutic monoclonal antibody against HBsAg by in vivo selection of HBV escape variants

BACKGROUND AND AIMS

Hepatitis B immunoglobulin (HBIG) has been routinely applied in the liver transplantation setting to block HBV reinfection of grafts. However, new monoclonal anti-HBV surface antibodies have been developed to replace HBIG. The epitopes of such monoclonal antibodies may affect the emergence of escape variants and deserve study.

APPROACH AND RESULTS

The conformational epitope of sLenvervimab, a surrogate form of Lenvervimab, which is a monoclonal anti-HBsAg antibody currently under phase 3 trial, was investigated by selecting escape mutants from a human liver chimeric mouse. HBV-infected chimeric mice treated with sLenvervimab monotherapy showed an initial decline in circulating HBsAg levels, followed by a quick rebound in 1 month. Sequencing of circulating or liver HBV DNA revealed emerging variants, with replacement of amino acid E164 or T140, two residues widely separated in HBsAg. E164 HBV variants strongly resisted sLenvervimab neutralization in cell culture infection, and the T140 variant moderately resisted sLenvervimab neutralization. Natural HBV variants with amino-acid replacements adjacent to E164 were constructed and examined for sLenvervimab neutralization effects. Variants with K160 replacement also resisted neutralization. These data revealed the conformational epitope of sLenvervimab.

CONCLUSIONS

Selection of antibody-escape HBV variants in human chimeric mice works efficiently. Analysis of such emerging variants helps to identify anchor amino-acid residues of the conformational epitope that are difficult to discover by conventional approaches.

Molecular characteristics of the full-length genome of occult hepatitis B virus from blood donors in China

The characteristics of a large sample size of the full-length genome of occult hepatitis B virus (HBV) infection (OBI) have not been extensively explored in China. Voluntary blood donors who were HBsAg-negative/HBV NAT-positive (HBsAg−/HBV NAT+) were identified by blood screening and recruited. Blood samples were tested for HBV serologic markers, viral loads, and PCR to identify OBI. HBV full-length genomes were obtained by amplifying two fragments using nested PCR. The characterization of OBI strains was based on sequence analyses compared with HBsAg+ strains obtained from the same donor population. Of the 50 full-length genomes of 172 identified OBI strains, 33 were classified as genotype B (OBI_B) and 17 strains as genotype C (OBI_C). Significantly higher nucleotide variabilities were observed in the Pre-S2/S promoter region (SP2) and core upstream regulatory sequence (CURS) in OBI_B than in their HBsAg+ controls (P < 0.05). Both OBI_B and OBI_C showed higher amino acid (aa) variabilities in Pol and Pre-S/S regions than their controls (P < 0.05). In addition, 19 novel OBI-related mutations were found spanning the four open reading frames (ORFs) of the HBV genome. Four novel deletions and one novel insertion were also found in OBI_C strains. Several novel OBI-related mutations spanning the four ORFs of the virus were identified by characterizing a large sample size of the full-length OBI genome, which may affect the production of HBsAg and contribute to the occult infection of HBV.

Research Progress on the Mechanism of Persistent Low-Level HBsAg Expression in the Serum of Patients with Chronic HBV Infection

Among HBV-infected persons, there is a group of people with hepatitis B surface antigen (HBsAg) showing persistently low levels of expression. The production of low-level HBsAg does not mean a good outcome of chronic HBV infection. Patients still have virus replication and sustained liver damage, and they have the potential to transmit the infection. This risk poses a challenge to clinical diagnosis and blood transfusion safety and is a major concern of experts. However, the mechanism behind persistent low-level HBsAg expression in serum is not completely clear, and complete virus clearance by the host is vital. In this review, we summarize the research progress on the mechanism behind low-level expression of HBsAg in patients with chronic HBV infection in recent years.

A potent neutralizing and protective antibody against a conserved continuous epitope on HSV glycoprotein D

Infections caused by herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) remain a serious global health issue, and the medical countermeasures available thus far are limited. Virus-neutralizing monoclonal antibodies (NAbs) are crucial tools for studying host-virus interactions and designing effective vaccines, and the discovery and development of these NAbs could be one approach to treat or prevent HSV infection. Here, we report the isolation of five HSV NAbs from mice immunized with both HSV-1 and HSV-2. Among these were two antibodies that potently cross-neutralized both HSV-1 and HSV-2 with the 50% virus-inhibitory concentrations (IC₅₀) below 200 ng/ml, one of which (4A3) exhibited high potency against HSV-2, with an IC₅₀ of 59.88 ng/ml. 4A3 neutralized HSV at the prebinding stage and prevented HSV infection and cell-to-cell spread. Significantly, administration of 4A3 completely prevented weight loss and improved survival of mice challenged with a lethal dose of HSV-2. Using structure-guided molecular modeling combined with alanine-scanning mutagenesis, we observed that 4A3 bound to a highly conserved continuous epitope (residues 216 to 220) within the receptor-binding domain of glycoprotein D (gD) that is essential for viral infection and the triggering of membrane fusion. Our results provide guidance for developing NAb drugs and vaccines against HSV.

Anti-rheumatic drug-induced hepatitis B virus reactivation and preventive strategies for hepatocellular carcinoma

To date, an estimated 3 million people worldwide have been infected with chronic hepatitis B virus (HBV). Although anti-HBV therapies have improved the long-term survival profile of chronic carriers, viral reactivation still poses a significant challenge for preventing HBV-related hepatitis, hepatocellular carcinoma (HCC), and death. Immuno-modulating drugs, which are widely applied in managing rheumatic conditions, are commonly associated with HBV reactivation (HBVr) as a result of drug-induced immune suppression. However, there are few reports on the risk of HBVr and the medication management plan for HBV carriers, especially rheumatic patients. In this review, we summarize immuno-modulating drug-induced HBVr during rheumatoid therapy and its preventive strategies for HBVr-induced liver diseases, especially cirrhosis and HCC. These findings will assist with developing treatments for rheumatic patients, and prevent HBV-related cirrhosis and HCC.

A broad-spectrum nanobody targeting the C-terminus of the hepatitis B surface antigen for chronic hepatitis B infection therapy

Sustainable viral suppression with hepatitis B surface antigen (HBsAg) loss is the new treatment goal for chronic hepatitis B (CHB). The role of antibodies in therapies for persistent hepatitis B virus (HBV) infection has received constant attention. While immunotherapy holds great promise, challenges for the antibody-based prevention and control of HBV in CHB include broad HBV antigenic diversity and the need for long-term viral suppression. In this study, we identified a new anti-HBsAg nanobody (Nb), 125s, isolated from HBsAg-immunized alpaca and confirmed its excellent potency in HBsAg clearance and broad-spectrum therapeutic activity against three HBV subtypes in vivo. In addition, we characterized a novel epitope at the C-terminus of the HBsAg surface motif from amino acids 157 to 174. A 125s-based long-term passive immunization program was efficacious at HBsAg clearance and inducing cellular immune responses, offering a promising outlook for CHB immunotherapy.

Advances in human monoclonal antibody therapy for HBV infection

HBV neutralizing antibodies target the viral envelope antigens (HBsAg) and confer long-term immune protection in vaccinees and infected humans who seroconvert. They recognize various HBsAg epitopes, and can be armed with Fc-dependent effector functions essential for eliminating infected cells and stimulating adaptive immunity. Hundreds of HBsAg-specific monoclonal antibodies (mAbs) were produced from the early 80's, but it is only recently that bona fide human anti-HBV mAbs were generated from vaccinees and seroconverters. Neutralizing HBV mAbs have in vivo prophylactic and therapeutic efficacy in animal models, and the capacity to decrease antigenemia and viremia in infected humans. Thus, polyfunctional, potent and broad human HBV neutralizing mAbs offer novel opportunities to develop effective interventions to prevent and treat HBV infection. Here, we summarize recent findings on the humoral immune response to HBV, and explore the potential of human HBV neutralizing mAbs as immunotherapeutics to help achieving a functional cure for HBV.

Hepatitis B Virus Reactivation Associated With Therapeutic Interventions

Hepatitis B virus (HBV) reactivation associated with various therapeutic interventions is an important cause of morbidity and mortality in patients with current or resolved HBV infection. Because no curative treatment for HBV infection is yet available, there are many individuals at risk for HBV reactivation in the general population. Populations at risk for HBV reactivation include patients who are currently infected with HBV or who have been exposed to HBV in the past. HBV reactivation and its potential consequences is a concern when these populations are exposed to anti-cancer chemotherapy, immunosuppressive or immunomodulatory therapies for the management of various malignancies, rheumatologic diseases, inflammatory bowel disease, or solid-organ or hematologic stem cell transplantation. Accordingly, it has become important to understand the basics of HBV reactivation and the mechanisms by which certain therapies are more susceptible to HBV reactivation. This review aims to raise the awareness of HBV reactivation and to understand the mechanisms and the risks of HBV reactivation in various clinical settings.

E2 Site Mutations in S Protein Strongly Affect Hepatitis B Surface Antigen Detection in the Occult Hepatitis B Virus

The mechanism of occult hepatitis B infection (OBI) has not yet been fully clarified. Our previous research found that novel OBI-related mutation within S protein, E2G, could cause the hepatitis B surface antigen (HBsAg) secretion impairment, which resulted in intracellular accumulation in OBI of genotype B. Here, to further explore the role of E2 site mutations in the occurrence of OBI, we analyzed these site mutations among 119 OBI strains identified from blood donors. Meanwhile, 109 wild-type HBV strains (HBsAg positive/HBV DNA positive) were used as control group. Furthermore, to verify the E2 site mutations, two conservative 1.3-fold full-gene expression vectors of HBV genotype B and C (pHBV1.3B and pHBV1.3C) were constructed. Then, the E2 mutant plasmids on the basis of pHBV1.3B or pHBV1.3C were constructed and transfected into HepG2 cells, respectively. The extracellular and intracellular HBsAg were analyzed by electrochemical luminescence and cellular immunohistochemistry. The structural characteristics of S proteins with or without E2 mutations were analyzed using relevant bioinformatics software. E2 mutations (E2G/A/V/D) existed in 21.8% (26/119) of OBIs, while no E2 mutations were found in the control group. E2G/A/V/D mutations could strongly affect extracellular and intracellular level of HBsAg (p < 0.05). Notably, unlike E2G in genotype B that could cause HBsAg intracellular accumulation and secretion decrease (p < 0.05), E2G in genotype C could lead to a very significant HBsAg decrease both extracellularly (0.46% vs. pHBV1.3C) and intracellularly (11.2% vs. pHBV1.3C) (p < 0.05). Meanwhile, for E2G/A mutations, the relative intracellular HBsAg (110.7-338.3% vs. extracellular) and its fluorescence intensity (1.5-2.4-fold vs. with genotype-matched pHBV1.3B/C) were significantly higher (p < 0.05). Furthermore, N-terminal signal peptides, with a typical cleavage site for peptidase at positions 27 and 28, were exclusively detected in S proteins with secretion-defective mutants (E2G/A). Our findings suggest that: (1) E2G/A/V/D mutations were confirmed to significantly influence the detection of HBsAg, (2) the underlying mechanism of OBI caused by E2G mutation is quite different between genotype B and genotype C, and (3) E2G/A could produce a N-terminal truncated S protein, which might attribute to the HBsAg secretion impairment in the OBIs.

In silico analysis of mutations associated with occult hepatitis B virus (HBV) infection in South Africa

Occult hepatitis B virus (OBI) infection is defined by the presence of viral DNA in the liver and/or serum in absence of hepatitis B surface antigen (HBsAg). While multiple studies have identified mutations that are associated with OBI, only a small portion of these mutations have been functionally characterized in vitro. Using complementary in silico approaches, the effects of OBI-associated amino acid mutations on HBV protein function in HBV/HIV-positive ART-naïve South Africans were evaluated. Two OBI-associated mutations in the PreS1 region, one in the PreS2 region, and seven in the surface region of subgenotype A1 sequences were identified as deleterious. In subgenotype A2 sequences, 11 OBI-associated mutations in the PreS1 region, seven in the PreS2 region, and 31 in the surface region were identified as deleterious. In the polymerase region, 14 OBI-associated mutations in subgenotype A1 and 71 OBI-associated mutations in subgenotype A2 were identified as deleterious. This study utilized in silico approaches to characterize the likely impact of OBI-associated mutations on viral function, thereby identifying and prioritizing candidates and reducing the significant cost associated with functional studies that are essential for mechanistic studies of the OBI phenotype.

Molecular and Serological Characterization of Hepatitis B Virus (HBV)-Positive Samples with Very Low or Undetectable Levels of HBV Surface Antigen

BACKGROUND

Gaps remain in the detection of nucleic acid test (NAT) yield and occult hepatitis B virus (HBV) infection (OBI) by current HBV surface antigen (HBsAg) assays. The lack of detection may be due to HBsAg levels below current assay detection limits, mutations affecting HBsAg assays or HBsAg levels, or the masking of HBsAg by antibody to HBsAg (anti-HBs). In this study, we evaluate the incremental detection of NAT yield and OBI from five diverse geographic areas by an improved sensitivity HBsAg assay and characterize the samples relative to the viral load, anti-HBs status, and PreS1-S2-S mutations. Included is a comparison population with HBV DNA levels comparable to OBI, but with readily detectable HBsAg (High Surface-Low DNA, HSLD).

METHODS

A total of 347 samples collected from the USA, South Africa, Spain, Cameroon, Vietnam, and Cote D'Ivoire representing NAT yield (HBsAg(-), antibody to HBV core antigen (anti-HBc)(-), HBV DNA(+), N = 131), OBI (HBsAg(-), anti-HBc(+), HBV DNA(+), N = 188), and HSLD (HBsAg(+), anti-HBc(+), HBV DNA(+), N = 28) were tested with ARCHITECT HBsAg NEXT (HBsAgNx) (sensitivity 0.005 IU/mL). The sequencing of the PreS1-S2-S genes from a subset of 177 samples was performed to determine the genotype and assess amino acid variability, particularly in anti-HBs(+) samples.

RESULTS

HBsAgNx detected 44/131 (33.6%) NAT yield and 42/188 (22.3%) OBI samples. Mean HBV DNA levels for NAT yield and OBI samples were lower in HBsAgNx(-) (50.3 and 25.9 IU/mL) than in HBsAgNx(+) samples (384.1 and 139.5 IU/mL). Anti-HBs ≥ 10 mIU/mL was present in 28.6% HBsAgNx(+) and 45.2% HBsAgNx(-) OBI, and in 3.6% HSLD samples. The genotypes were A1, A2, B, C, D, E, F, and H. There was no significant difference between HBsAgNx(-) and HBsAgNx(+) in the proportion of samples harboring substitutions or in the mean number of substitutions per sample in PreS1, PreS2, or S for the NAT yield or OBI (p range: 0.1231 to >0.9999). A total of 21/27 (77.8%) of HBsAgNx(+) OBI carried S escape mutations, insertions, or stop codons. HSLD had more PreS1 and fewer S substitutions compared to both HBsAgNx(-) and HBsAgNx(+) OBI. Mutations/deletions associated with impaired HBsAg secretion were observed in the OBI group.

CONCLUSIONS

HBsAgNx provides the improved detection of NAT yield and OBI samples. Samples that remain undetected by HBsAgNx have exceptionally low HBsAg levels below the assay detection limit, likely due to low viremia or the suppression of HBsAg expression by host and viral factors.

Identification of mutations in the S gene of hepatitis B virus in HIV positive Mexican patients with occult hepatitis B virus infection

INTRODUCTION AND AIM

Occult hepatitis B virus infection (OBI) is characterized by the presence of replication-competent hepatitis B virus (HBV) DNA in the liver and/or serum of patients with undetectable levels of the HBV surface antigen (HBsAg). Due to the shared infection routes HIV positive patients are at higher risk of developing OBI, thus, the aim of this study was to determine the frequency of OBI in Mexican HIV-infected patients and to identify mutations in the HBV S gene that could be associated to the development of OBI.

MATERIALS AND METHODS

Plasma samples from 50 HIV-infected patients with undetectable levels of the HBsAg were obtained and analyzed. The Core, PreS and S genes were amplified by nested PCR and sequenced by the Sanger method. To analyze HBV diversity in the OBI-positive patients, ten sequences of 762bp from the HBV S gene were selected, cloned, and subsequently sequenced for mutational analyses.

RESULTS

OBI infection was found with a frequency of 36% (18/50). All the HBV sequences corresponded to the H genotype. The most common mutations were: C19Y, Q129H, E164D, and I195M, with a frequency of 44%, 36%, 39% and 48% respectively.

CONCLUSIONS

In this study, we report the presence of OBI in a cohort of Mexican HIV-infected patients with an overall prevalence of 36%. Mutational analyses revealed that four non-silent mutations were frequent in different regions of the HBsAg gene, suggesting that they might be associated to the development of OBI in this population, nevertheless, further studies are required to determine their role in the pathogenesis of OBI.

Specific determination of hepatitis B e antigen by antibodies targeting precore unique epitope facilitates clinical diagnosis and drug evaluation against hepatitis B virus infection

Hepatitis B e antigen (HBeAg) is a widely used marker both for chronic hepatitis B (CHB) clinical management and HBV-related basic research. However, due to its high amino acid sequence homology to hepatitis B core antigen (HBcAg), most of available anti-HBe antibodies are cross-reactive with HBcAg resulting in high interference against accurate measurement of the status and level of HBeAg. In the study, we generated several monoclonal antibodies (mAbs) targeting various epitopes on HBeAg and HBcAg. Among these mAbs, a novel mAb 16D9, which recognizes the SKLCLG (aa -10 to -5) motif on the N-terminal residues of HBeAg that is absent on HBcAg, exhibited excellent detection sensitivity and specificity in pairing with another 14A7 mAb targeting the HBeAg C-terminus (STLPETTVVRRRGR, aa141 to 154). Based on these two mAbs, we developed a novel chemiluminescent HBeAg immunoassay (NTR-HBeAg) which could detect HBeAg derived from various HBV genotypes. In contrast to widely used commercial assays, the NTR-HBeAg completely eliminated the cross-reactivity with secreted HBcAg from precore mutant (G1896A) virus in either cell culture or patient sera. The improved specificity of the NTR-HBeAg assay enables its applicability in cccDNA-targeting drug screening in cell culture systems and also provides an accurate tool for clinical HBeAg detection.

Role of quantitative hepatitis B surface antibodies in preventing hepatitis B virus-related hepatitis in patients treated with rituximab

Hepatitis B virus (HBV) reactivation is a well-known complication after rituximab-based chemotherapy in patients with B cell lymphoma (BCL) who have resolved HBV infection. This retrospective cohort study used electronic medical records from the Kaohsiung Chang Gung Memorial Hospital. There were 128 patients with BCL and resolved HBV infection treated with 1st-line rituximab-containing therapy from 2008 to 2013. No patient received antiviral prophylaxis. Patients with high pretreatment hepatitis B surface antibody (anti-HBs titer ≥100 mIU/mL), had significantly less HBV reactivation (2.0%, 1/49) than patients with low (10-100 mIU/mL, 10.8%, 4/37) or negative anti-HBs (<10 mIU/mL, 23.8%, 10/42) (p = 0.001). No patient in the high group vs. 1 (2.7%) low group vs. 6 (14.3%) negative group developed HBV-related hepatitis (p = 0.002). Patients with high pretreatment anti-HBs have a low risk of HBV-related complications and may not require antiviral prophylaxis. We propose an algorithm for the management of HBV reactivation risk in BCL.

High Frequency Occult Hepatitis B Virus Infection Detected in Non-Resolved Donations Suggests the Requirement of Anti-HBc Test in Blood Donors in Southern China

Background

Most Chinese Blood Centers adopted mini pool (MP) nucleic acid testing (NAT) for HBV screening due to high cost of Individual donation (ID) NAT, and different proportions of MP-reactive but ID-non-reactive donations (MP+/ID-, defined as non-resolved donations) have been observed during daily donor screening process. Some of these non-resolved donations are occult HBV infections (OBIs), which pose potential risk of HBV transmission if they are not deferred. This study is aimed to further analyze these non-resolved donations.

Methods

The non-resolved plasma samples were further analyzed by serological tests and various HBV DNA amplification assays including quantitative PCR (qPCR) and nested PCR amplifying the basic core and pre-core promoter regions (BCP/PC; 295 base pairs) and HBsAg (S) region (496 base pairs). Molecular characterizations of HBV DNA+ non-resolved samples were determined by sequencing analysis.

Results

Of 17,226 MPs from 103,356 seronegative blood donations, 98 MPs were detected reactive for HBV. Fifty-six out of these 98 (57.1%) reactive MPs were resolved as HBV DNA+, but the remaining 42 pools (42.9%, 252 donations) were left non-resolved with a high rate (53.2%) of anti-HBc+. Surprisingly, among 42 non-resolved MPs, 17 contained one donation identified as OBIs by alternative NAT assays. Sequence analysis on HBV DNAs extracted from these OBI donations showed some key mutations in the S region that may lead to failure in HBsAg detection and vaccine escape.

Conclusion

A total of 53.2% of the non-resolved donations were anti-HBc+, and OBIs were identified in 40.5% of these non-resolved pools. Therefore, non-resolved donations with anti-HBc+ might pose potential risk for HBV transmission. Our present analysis indicates that anti-HBc testing in non-resolved donations should be used to identify OBIs in order to further increase blood safety in China.

Role of core protein mutations in the development of occult HBV infection

BACKGROUND & AIMS

Occult HBV infection (OBI) is associated with transfusion-transmitted HBV infection and hepatocellular carcinoma. Studies on OBI genesis have concentrated on mutations in the S region and the regulatory elements. Herein, we aimed to determine the role of mutations in the core region on OBIs.

METHODS

An OBI strain (SZA) carrying 9 amino acid (aa) substitutions in the core protein/capsid (Cp) was selected by sequence alignment and Western blot analysis from 26 genotype B OBI samples to extensively explore the impact of Cp mutations on viral antigen production in vitro and in vivo.

RESULTS

A large panel of 30 Cp replicons were generated by a replication-competent pHBV1.3 carrying SZA or wild-type (WT) Cp in a 1.3-fold over-length of HBV genome, in which the various Cp mutants were individually introduced by repairing site mutations of SZA-Cp or creating site mutations of WT-Cp by site-directed mutagenesis. The expression of HBcAg, HBeAg, and HBsAg and viral RNA was quantified from individual SZA and WT Cp mutant replicons in transfected Huh7 cells or infected mice, respectively. An analysis of the effect of Cp mutants on intracellular or extracellular viral protein production indicated that the W62R mutation in Cp had a critical impact on the reduction of HBcAg and HBeAg production during HBV replication, whereas P50H and/or S74G mutations played a limited role in influencing viral protein production invivo.

CONCLUSIONS

W62R and its combination mutations in HBV Cp might massively affect HBcAg and HBeAg production during viral replication, which, in turn, might contribute to the occurrence of OBI.

LAY SUMMARY

Occult hepatitis B virus infections (OBIs) have been found to be associated with amino acid mutations in the S region of the HBV, but the role of mutations in the core protein (Cp) remains unclear. In this study, an OBI strain (SZA) carrying 9 amino acid substitutions in Cp has been examined comprehensively in vitro and in vivo. The W62R mutation in Cp majorly reduces HBcAg and HBeAg production during HBV replication, potentially contributing to the occurrence of OBI.

HBV S antigen evolution in the backdrop of HDV infection affects epitope processing and presentation

INTRODUCTION

HBV can evolve under selection pressure exerted by drugs and/or host immunity, resulting in accumulation of escape mutations that can affect the drug or the immune activity. Hepatitis delta virus (HDV) coinfection is also known to exert selection pressure on HBV, which leads to selective amplification of certain mutations, especially in genes that are required for HDV pathogenesis, such as HBsAg. However, little is known about the function of these mutations on HBV or HDV life cycle. The purpose of this study is to determine mutations selectively amplified in the backdrop of HDV, and how these mutations affect processing of CD4- and CD8-T cell epitopes.

METHODS

HBsAg was successfully amplified from 49/50 HBV mono- and 36/50 coinfected samples. The sequences were used to identify mutations specific to each study group, followed by an in silico analysis to determine the effect of these mutations on (1) proteasomal degradation, (2) MHC-I and MHC-II biding, and (3) processing of T-cell epitopes.

RESULTS

HBV-HDV coinfected sequences exhibited certain unique mutations in HBsAg genes. Some of these mutations affected the generation of proteasomal sites, binding of HBsAg epitopes to MHC-I and -II ligands, and subsequent generation of T- cell epitopes.

CONCLUSION

These observations suggest that HBV selectively amplifies certain mutations in the backdrop of HDV coinfection. Selective amplification of these mutations at certain strategic locations might not only enable HBV to counteract the inhibitory effects of HDV on HBV replication but also facilitate its survival by escaping the immune response.

In situ analysis of biomolecular interactions on nano/microparticles in formulations

Nano/microparticle-based formulations are attracting more and more attention in the drug and vaccine formulation field. Analytical methodologies are needed for analyzing the function of the protein molecules before and after their adsorption onto particles. Here, we report a fluorescence imaging-based high content analysis (HCA) for analyzing bimolecular interactions on the particle surface. Subtle conformational alteration of antigen epitope overlapping were shown to be feasible using this microplate-based HCA method. This HCA is highly amenable for automation, making it a method of choice for early formulation development as well as for stability test of products in late stage development.

Neonatal hepatitis B vaccination protects mature adults from occult virus infection

BACKGROUND

Among elder children/young adults who received hepatitis B virus (HBV) vaccination during infancy, the serological status of HBsAg-negative and anti-HBc-positive [HBsAg(-)/anti-HBc(+)] was frequently reported, indicating potential occult HBV infection (OBI). It is required to define the long-term protection of neonatal vaccination against OBI in their mature adulthood.

METHODS

Building upon the 1983-1990 established Qidong Hepatitis B Intervention Study, we sampled 10% of the 28-35-year-old participants, who remained in the cohort by 2012. Each participant was tested for serological markers of HBsAg, anti-HBs, HBeAg, anti-HBe and anti-HBc. HBV-DNA and relaxed circular DNA (rcDNA) were determined in some HBsAg(-)/anti-HBc(+) individuals.

RESULTS

Totally, 3615 individuals from the neonatal vaccination group and 3100 individuals from the control group donated blood samples, respectively. In the vaccination group, the prevalence of HBsAg was 1.58% (57/3615), HBsAg(-)/anti-HBc(+) was 4.70% (170/3615), significantly lower than in the control group, which was 7.45% (231/3100) and 19.48% (640/3100) respectively (all p < 0.001). With aging, HBsAg(-)/anti-HBc(+) prevalence increased in the sampled participants from the control group (pfor trend < 0.001), but uncertain from the vaccination group. Of HBsAg(-)/anti-HBc(+), HBV-DNA was detected in 13.08% (17/130) from the vaccination group, and in 4.18% (12/287) from the control group. HBV rcDNA was detected in most sera that were tested positive for HBV-DNA.

CONCLUSIONS

OBI occurred in some vaccinated adults. However, neonatal HBV vaccination kept the effective protection against OBI in mature adults.

Profiles of mutations in hepatitis B virus surface and polymerase genes isolated from treatment-naïve Nigerians infected with genotype E

Introduction. Hepatitis B virus (HBV) infection is the leading cause of hepatitis, liver cirrhosis, and hepatocellular carcinoma (HCC). HBV genotype E (HBV/E) is the predominant genotype in West Africa and has been linked epidemiologically with chronic and occult HBV infections as well as development of HCC. Mutations in the surface and polymerase genes of HBV have been associated with occult infection, drug resistance, vaccine escape, as well as HCC.Hypothesis/Gap Statement. There is limited data on the occurrence and patterns of mutations associated with occult infection, drug resistance, vaccine escape and HCC for HBV/E.Aim. This study characterized amino acid (aa) substitutions in the major hydrophilic (MHR) and reverse transcriptase (RT) regions of the surface and polymerase genes respectively of HBV sequences from a group of Nigerians with genotype E infection. The CpG islands of the PreC/C and PreS/S regions of these sequences were also described.Methodology. HBV surface and polymerase genes were detected using PCR techniques. Occurrence of new and previously described mutations in these genes were analysed using phylogenetic techniques.Results. Overall 13 HBV isolates were each sequenced for polymerase and surface genes mutations. Thirteen and nine PreS/S and PreC/C HBV genes respectively were analysed for CpG islands. Mutations in the MHR and a-determinants region of the S protein were discovered in eleven and nine of the 13 tested isolates respectively. These mutations were concomitant with aa changes in the RT functional domains of the isolates. Mutations associated with vaccine escape, occult infection and poor HCC prognosis were identified in HBV/E isolated in this study. Furthermore, all the isolates had at least one putative nucleotide analogue resistance mutations. Drug resistance mutations had the highest association with CpG islands.Conclusion. The results of this study contribute to further understanding of HBV variability in Nigeria and the West African region. This will aid the planning of adequate HBV immunization and treatment programmes for the countries in the region.