Reactivity of 13 in vitro expressed hepatitis B surface antigen variants in 7 commercial diagnostic assays

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.

Biomarkers of transfusion transmitted occult hepatitis B virus infection: Where are we and what next?

Blood transfusion is a vital procedure, where transfusion-transmitted infection of hepatitis B virus (HBV) remains an important issue, especially from blood donors with occult hepatitis B virus infection (OBI). Occult hepatitis B virus infection is a complex entity to detect using surrogate blood biomarkers for intrahepatic viral transcriptional activity, requiring a continually refined battery of tests utilised for screening. This review aims to critically evaluate the latest advances in the current blood biomarkers to guide the identification of OBI donors and discuss novel HBV markers that could be introduced in future diagnostic practice. Challenges in detecting low HBV surface antigen levels, mutants, and complexes necessitate ultrasensitive multivalent dissociation assays, whilst HBV DNA testing requires improved sensitivity but worsens inaccessibility. Anti-core antibody assays defer almost all potentially infectious donations but have low specificity, and titres of anti-surface antibodies that prevent infectivity are poorly defined with suboptimal sensitivity. The challenges associated with these traditional blood HBV markers create an urgent need for alternative biomarkers that would help us better understand the OBI. Emerging viral biomarkers, such as pre-genomic RNA and HBV core-related antigen, immunological HBV biomarkers of T-cell reactivity and cytokine levels, and host biomarkers of microRNA and human leucocyte antigen molecules, present potential advances to gauge intrahepatic activity more accurately. Further studies on these markers may uncover an optimal diagnostic algorithm for OBI using quantification of various novel and traditional blood HBV markers. Addressing critical knowledge gaps identified in this review would decrease the residual risk of transfusion-transmitted HBV infection without compromising the sustainability of blood supplies.

Cytokines Expression Compared to the Determinants of Cellular Apoptosis Prominently Attributes to the Deleterious Effects of 'A' Determinant Surface Gene Mutations in HBV Transfected Hepatoma Cell Line

BACKGROUND

Previous studies have explored the role of AKT protein in anti-apoptotic/proliferative activities. However, there has been a lack of information regarding the role of Akt in association with cytokines expression in HBV-related (wild type HBV and HBV with mutations of 'a' determinant region) studies either in the case of HBV infection or in transfected hepatoma cells. The present study tries to determine the role of Akt and cytokines expression in the presence of small surface gene mutants in the hepatoma cell line.

METHODS

Mutations of 'a' determinant region, viz. sA128V and sG145R, were created in wild-type pHBV1.3 by site-directed mutagenesis and transfected in hepatoma cell line. Secretory levels of HBsAg in the wild type as well as in both the mutants were analyzed by ELISA. Apoptotic analysis of transfected cells was studied by flow cytometry. Expression analysis of Akt and cytokines (TNF-alpha, IL-6, and IFN-gamma) was done by qPCR.

RESULTS

The presence of significantly more alive cells in sG145R than sA128V transfected cells may be due to the up-regulation of the Akt gene expression. Cytokines expression was nearly similar between sA128V and wild-type pHBV1.3 transfected cells. Presence of sG145R showed dramatically high cytokines expression than sA128V and wild-type pHBV1.3.

CONCLUSION

Cytokines expression predominantly contributes to the detrimental effects associated with the 'a' determinant region mutations particularly sG145R mutant. It may also be inferred that mechanisms associated with cellular apoptosis apparently do not play any major role to assign the 'a' determinant small surface gene mutation(s) for their pathological outcome.

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.

Upconverting nanoparticle reporter-based highly sensitive rapid lateral flow immunoassay for hepatitis B virus surface antigen

Detection of hepatitis B Virus surface antigen (HBsAg) is an established method for diagnosing both acute and chronic hepatitis B virus (HBV) infection. In addition to enzyme immunoassays (EIAs), rapid diagnostic tests (RDTs) are available for the detection of HBsAg in resource-poor settings. However, the available RDTs have inadequate sensitivity and therefore are not suitable for diagnosis of patients with low levels of HBsAg and for blood screening. To provide a high-sensitivity RDT, we developed a lateral flow immunoassay (LFIA) for HBsAg utilizing upconverting nanoparticle (UCNP) reporter. The UCNP-LFIA can use whole blood, serum, or plasma and the results can be read in 30 min using a reader device. When compared with a commercial conventional visually read LFIA, the developed UCNP-LFIA had a Limit of Detection (LoD) of 0.1 IU HBsAg/ml in spiked serum, whereas the LoD of the conventional LFIA was 3.2 IU HBsAg/ml. The developed UCNP-LFIA fulfills the WHO criterion for blood screening (LoD ≤ 0.13 IU HBsAg/ml) in terms of LoD. The UCNP-LFIA and conventional LFIA were evaluated with well-characterized sample panels. The UCNP-LFIA detected 20/24 HBsAg-positive samples within the HBsAg Performance Panel and 8/10 samples within the Mixed Titer Performance Panel, whereas the conventional LFIA detected 8/24 and 4/10 samples in these panels, respectively. The performance of the assays was further evaluated with HBsAg-positive (n = 108) and HBsAg-negative (n = 315) patient samples. In comparison with a central laboratory test, UCNP-LFIA showed 95.4% (95% CI: 89.5–98.5%) sensitivity whereas sensitivity of the conventional LFIA was 87.7% (95%CI: 79.9–93.3%).

A recombinant human immunoglobulin with coherent avidity to hepatitis B virus surface antigens of various viral genotypes and clinical mutants

The hepatitis B virus (HBV) envelope is composed of a lipid bilayer and three glycoproteins, referred to as the large (L), middle (M), and small (S) hepatitis B virus surface antigens (HBsAg). S protein constitutes the major portion of the viral envelope and an even greater proportion of subviral particles (SVP) that circulate in the blood. Recombinant S proteins are currently used as a preventive vaccine, while plasma fractions isolated from vaccinated people, referred to as hepatitis B immune globulin (HBIG), are used for short-term prophylaxis. Here, we characterized a recombinant human IgG1 type anti-S antibody named Lenvervimab regarding its binding property to a variety of cloned S antigens. Immunochemical data showed an overall consistent avidity of the antibody to S antigens of most viral genotypes distributed worldwide. Further, antibody binding was not affected by the mutations in the antigenic ‘a’ determinant found in many clinical variants, including the immune escape mutant G145R. In addition, mutations in the S gene sequence that confer drug resistance to the viral polymerase did not interfere with the antibody binding. These results support for a preventive use of the antibody against HBV infection.

The sK122R mutation of hepatitis B virus (HBV) is associated with occult HBV infection: Analysis of a large cohort of Chinese patients

BACKGROUND

Occult HBV infection (OBI) is of great concern due to their complicated diagnosis and potential for public transmission.

OBJECTIVE

The study aimed to determine the clinical prevalence of OBI and if viral immune escape-associated mutations contribute to the occurrence of OBI.

STUDY DESIGN

A total of 91,037 HBV-infected patients with different related illnesses who were admitted to the Fifth Medical Center of Chinese PLA General Hospital from January 2005 to December 2017 were tested for OBI. Serum samples from 62 patients with OBI manifestations (OBI patients) and 124 matched non-OBI patients were sequenced for possible immune escape-associated mutations within the major hydrophilic region of HBV S protein. HBsAg and HBV DNA levels in representative viral strains were measured.

RESULTS

Of the 91,037 tested patients, 487 (0.53 %) were negative for HBsAg but positive for HBV DNA and were defined as OBI patients. The prevalence in different illness categories varied. Immune escape-associated mutations were more frequently detected in OBI patients than in non-OBI patients (59.68 % vs. 35.48 %, P < 0.01), as did the coexistence of multiple mutations (43.55 % vs. 22.58 %, P < 0.01). Specifically, the prevalence rates of sT118 K, sK122R, and sV168A were increased in OBI patients. Strains with sK122R mutants (sK122R, sK122R + D144E, sK122R + C121R + D144E, and sK122R + F134L + D144E) from a follow-up OBI patient all showed significantly lower levels of HBsAg production than a wild-type strain.

CONCLUSIONS

The study clarified the clinical prevalence of OBI, verified the influence of immune escape-associated mutations, and identified the role of the sK122R mutation in multiple OBI patients.

A Hyper-Glycosylation of HBV Surface Antigen Correlates with HBsAg-Negativity at Immunosuppression-Driven HBV Reactivation in Vivo and Hinders HBsAg Recognition in Vitro

Immune-suppression driven Hepatitis B Virus (HBV)-reactivation poses serious concerns since it occurs in several clinical settings and can result in severe forms of hepatitis. Previous studies showed that HBV strains, circulating in patients with HBV-reactivation, are characterized by an enrichment of immune-escape mutations in HBV surface antigen (HBsAg). Here, we focused on specific immune-escape mutations associated with the acquisition of N-linked glycosylation sites in HBsAg (NLGSs). In particular, we investigated profiles of NLGSs in 47 patients with immunosuppression-driven HBV-reactivation and we evaluated their impact on HBsAg-antigenicity and HBV-replication in vitro. At HBV-reactivation, despite a median serum HBV-DNA of 6.7 [5.3–8.0] logIU/mL, 23.4% of patients remained HBsAg-negative. HBsAg-negativity at HBV-reactivation correlated with the presence of >1 additional NLGSs (p < 0.001). These NLGSs are located in the major hydrophilic region of HBsAg (known to be the target of antibodies) and resulted from the single mutation T115N, T117N, T123N, N114ins, and from the triple mutant S113N+T131N+M133T. In vitro, NLGSs strongly alter HBsAg antigenic properties and recognition by antibodies used in assays for HBsAg-quantification without affecting HBsAg-secretion and other parameters of HBV-replication. In conclusion, additional NLGSs correlate with HBsAg-negativity despite HBV-reactivation, and hamper HBsAg-antigenicity in vitro, supporting the role of NGSs in immune-escape and the importance of HBV-DNA for a proper diagnosis of HBV-reactivation.

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

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

Occult Hepatitis B Virus Infection: An Old Entity With Novel Clinical Involvements

Background

Occult hepatitis B infection (OBI) is recognized as a risk factor for cirrhosis and hepato-cellular carcinoma. However, OBI brings together a large spectrum of patients who might harbor different characteristics and prognosis.

Methods

We analyzed the databases of a university hospital in Paris to identify OBI among patients (n = 3966) concomitantly tested for hepatitis B virus (HBV) DNA and serology during a 7-year period. OBI patients were gathered into clinical entities according to their clinical records.

Results

Forty-seven OBIs were identified (1.2%). All patients had detectable anti-HBc, isolated (n = 26) or associated with anti-HBs (n = 21). The proportion of OBIs was 3.4% for patients with isolated anti-HBc and 4.2% for patients with both anti-HBc and anti-HBs. Four clinical categories of OBI patients were identified: patients with a passed HBV infection with HBs Ag clearance (group A, 23.4%); HBV-exposed patients receiving immunosuppressive therapy (group B, 29.8%); HIV/HBV-coinfected patients with therapy discontinuation (group C, 17%); HBV-exposed patients with severe liver conditions (group D, 29.8%). Significant follow-up was available for 32 patients, showing a more deleterious prognosis in group D patients, associated more with their underlying condition than the OBI status.

Conclusions

OBI is a heterogeneous condition with various clinical implications.

Molecular Characterization of Near Full-Length Genomes of Hepatitis B Virus Isolated from Predominantly HIV Infected Individuals in Botswana

The World Health Organization plans to eliminate hepatitis B and C Infections by 2030. Therefore, there is a need to study and understand hepatitis B virus (HBV) epidemiology and viral evolution further, including evaluating occult (HBsAg-negative) HBV infection (OBI), given that such infections are frequently undiagnosed and rarely treated. We aimed to molecularly characterize HBV genomes from 108 individuals co-infected with human immunodeficiency virus (HIV) and chronic hepatitis B (CHB) or OBI identified from previous HIV studies conducted in Botswana from 2009 to 2012. Full-length (3.2 kb) and nearly full-length (~3 kb) genomes were amplified by nested polymerase chain reaction (PCR). Sequences from OBI participants were compared to sequences from CHB participants and GenBank references to identify OBI-unique mutations. HBV genomes from 50 (25 CHB and 25 OBI) individuals were successfully genotyped. Among OBI participants, subgenotype A1 was identified in 12 (48%), D3 in 12 (48%), and E in 1 (4%). A similar genotype distribution was observed in CHB participants. Whole HBV genome sequences from Botswana, representing OBI and CHB, were compared for the first time. There were 43 OBI-unique mutations, of which 26 were novel. Future studies using larger sample sizes and functional analysis of OBI-unique mutations are warranted.

Genetic variation of hepatitis B surface antigen among acute and chronic hepatitis B virus infections in The Netherlands

Genetic variation within hepatitis B surface antigen (HBsAg), in particular within the major hydrophobic region (MHR), is related to immune/vaccine and test failures and can have a significant impact on the vaccination and diagnosis of acute infection. This study shows, for the first time, variation among acute cases and compares the amino acid variation within the HBsAg between acute and chronic infections. We analyzed the virus isolated from 1231 acute and 585 chronic cases reported to an anonymized public health surveillance database between 2004 and 2014 in The Netherlands. HBsAg analysis revealed the circulation of 6 genotypes (Gt); GtA was the dominant genotype followed by GtD among both acute (68.2% and 17.4%, respectively) and chronic (34.9% and 34.2%, respectively) cases. Variation was the highest among chronic strains compared to that among acute strains. Both acute and chronic GtD showed the highest variation compared to that of other genotypes (P < .01). Substitutions within the MHR were found in 8.5% of the acute strains and 18.6% of the chronic strains. Specific MHR substitutions described to have an impact on vaccine/immune escape and/or HBsAg test failure were found among 4.1% of the acute strains and 7.0% of the chronic strains. In conclusion, we show a high variation of HBsAg among acute and chronic hepatitis B virus–infected cases in The Netherlands, in particular among those infected with GtD, and compare, for the first time, variation in frequencies between acute and chronic cases. Additional studies on the impact of these variations on vaccination and test failure need to be conducted, as well as whether HBsAg false–negative variants have been missed.

Occult Hepatitis B Virus Infection and Associated Genotypes among HBsAg-negative Subjects in Burkina Faso

Background

The presence of HBV DNA in the liver (with detectable or undetectable HBV DNA in the serum) of individuals tested HBsAg negative by currently available assays is defined occult B Infection (OBI). It remains a potential transmission threat and risk to HBV chronic infection. The purpose of this study was to determine the OBI prevalence among HBsAg negative subjects and to characterize associated genotypes.

Methods

Blood samples of 219 HBsAg-negative subjects tested by ELISA were collected. HBV DNA was investigated in all samples. Viral loads were determined using quantitative real-time PCR. All samples were screened for HBV markers (anti-HBc, anti-HBe, HBsAg). The Pre-S/S region of the HBV genome was sequenced. The database was analyzed using the SPSS and Epi info software. Phylogenetic analysis was performed using the BioEdit and MEGA software.

Results

Of the 219 samples, 20.1% were anti-HBc positive, 1.8% HBeAg and 22.8% were anti-HBe positive. Fifty-six (56) (25.6%) of the samples had a detectable HBV DNA and viral loads ranging from 4 IU/mL to 13.6 10⁶ IU/mL. Sixteen of them (16/56) had a viral load < 200 IU/mL, resulting in an OBI prevalence of 7.3% (16/219) in our study. The remaining 40 subjects had viral loads > 200 IU/mL, resulting in a “false OBI” prevalence of 18.3% (40/219). HBV genotype E was predominant followed by the quasi-sub-genotype A3. A single “false OBI” strain had the characteristic mutation G145R. Other mutations were observed and all located in the major hydrophilic region (MHR) of the S gene.

Conclusion

The study reported a prevalence of 7.3% of occult hepatitis B infection. It confirms the predominance of genotype E and the existence of a subgroup of quasi-sub-genotype A3 of HBV in Burkina Faso. It further provides information on the presence of “false OBI.” This study has found mutations in the major hydrophilic region (MHR) of the pre-S/S gene of HBV.

Synergistic impact of mutations in Hepatitis B Virus genome contribute to its occult phenotype in chronic Hepatitis C Virus carriers

We characterized occult HBV (OHBV) from hepatitis B surface antigen (HBsAg)-negative chronic HCV carriers of Eastern India to explore the impact of genomic variability of HBV in causing undetectability of HBsAg and low viremia that define the occult phenomenon. Screening of sera samples revealed the presence of OHBV in 17.8% of HCV-infected patients. Determination of full-length OHBV sequences and comparison with that from HBsAg-positive carriers led to the detection of distinct substitutions/mutations in PreS2, S, P and X ORFs and in X-promoter and Enhancer-II of OHBV. These mutations were introduced in wild-type HBV and their effects were evaluated by transfection in Huh7 cells. In vitro assays demonstrated that S-substitutions resulted in antigenically modified HBsAg that escaped detection by immunoassays whereas those in ORF-P caused significant decline in viral replication. Impairment in Enhancer-II and X-promoter activities were noted due to occult-associated mutations that generated reduced pregenomic RNA and intracellular HBV-DNA. Additionally, Enhancer-II mutations altered the small to large surface protein ratio and diminished extracellular HBV-DNA and HBsAg secretion. Further, mutations in PreS2, X and enhancer-II increased Grp78-promoter activity, suggesting that OHBV could trigger endoplasmic reticulum stress. Thus viral mutations contribute synergistically towards the genesis of occult phenotype and disease progression.

Molecular characterization of occult hepatitis B virus infection in patients with end-stage liver disease in Colombia

Background

Hepatitis B virus (HBV) occult infection (OBI) is a risk factor to be taken into account in transfusion, hemodialysis and organ transplantation. The aim of this study was to identify and characterize at the molecular level OBI cases in patients with end-stage liver disease.

Methods

Sixty-six liver samples were obtained from patients with diagnosis of end-stage liver disease submitted to liver transplantation in Medellin (North West, Colombia). Samples obtained from patients who were negative for the surface antigen of HBV (n = 50) were tested for viral DNA detection by nested PCR for ORFs S, C, and X and confirmed by Southern-Blot. OBI cases were analyzed by sequencing the viral genome to determine the genotype and mutations; additionally, viral genome integration events were examined by the Alu-PCR technique.

Results

In five cases out of 50 patients (10%) the criteria for OBI was confirmed. HBV genotype F (subgenotypes F1 and F3), genotype A and genotype D were characterized in liver samples. Three integration events in chromosomes 5q14.1, 16p13 and 20q12 affecting Receptor-type tyrosine-protein phosphatase T, Ras Protein Specific Guanine Nucleotide Releasing Factor 2, and the zinc finger 263 genes were identified in two OBI cases. Sequence analysis of the viral genome of the 5 OBI cases showed several punctual missense and nonsense mutations affecting ORFs S, P, Core and X.

Conclusions

This is the first characterization of OBI in patients with end-stage liver disease in Colombia. The OBI cases were identified in patients with HCV infection or cryptogenic cirrhosis. The integration events (5q14.1, 16p13 and 20q12) described in this study have not been previously reported. Further studies are required to validate the role of mutations and integration events in OBI pathogenesis.

Impact of deletions and mutations in Hepatitis B virus envelope proteins on serological profile and clinical evolution

The Hepatitis B virus (HBV) envelope glycoproteins are essential for viral entry into the hepatocyte and are also targets for host immune response. The study of these proteins could allow us to highlight molecular hot points influencing HBV fitness, which would subsequently modify the clinical evolution of the disease, both under anti-viral therapy or without treatment. The present short communication underlines the importance of the high variability in HBV envelope proteins, in regard with the literature and in our hands, for HBV-infected patients either on anti-HBV treatment or not. We report mutations in antigenic areas of S protein, i.e. CD8⁺/CD4⁺ T-cell epitopes and B-cell epitopes in the major hydrophilic region (MHR), such as sI126N and sG145R possibly involved in the rare coexisting Hepatitis B surface Antigen (HBsAg)/anti-HBs serological pattern. We mostly report serial mutations in preS region including preS1 deletion (aa 1-6, 31-71, 38-73, 72-104) and preS2 deletion (aa132-141) in patients with various clinical evolutions. Some of these viral envelope mutations, due to immune selection pressure, may result in a worsening of the hepatic disease.

Investigation of a Novel Hepatitis B Virus Surface Antigen (HBsAg) Escape Mutant Affecting Immunogenicity

Mutation in the hepatitis B virus surface antigen (HBsAg) may affect the efficiency of diagnostic immunoassays or success of vaccinations using HBsAg. Thus, antigenicity and immunogenicity analyses of the mutated HBsAg are necessary to develop novel diagnostic tools and efficient vaccinations. Here, the in vitro antigenicity of three wild-type HBsAg open reading frames (ORFs) (adr4, W1S [subtype adr] and W3S [subtype adr]) isolated from clinically infected patients and nineteen synthesized single/double/multiple amino acid-substituted mutants were tested with commercial ELISA kits. Immunofluorescence staining of transfected cells and Western blot analysis confirmed that these ORFs were expressed at comparable levels in HEK-293 cells. W1S and adr4 were clearly detected, whereas W3S could not be detected. Using the same commercial immunoassay kit, we found that the single mutants, K120P and D123T, were marginally reactive, whereas W3S-aW1S and the double mutant, K120P/D123T, exhibited antigenicity roughly equivalent to the wild-type wako1S. On the other hand, the single mutants of W1S, P120K and T123D, significantly impaired the reactivity, while W1S-aW3S and the double mutant of W1S, P120K/T123D, resulted in a complete loss of antigenicity. In addition, ELISA revealed reduced HBs antigenicity of two mutants, W1S N146G and W1S Q129R/G145R. These commercial ELISA-based antigenic reactivities of HBsAg were also strongly correlated with the predicted Ai alterations of affected amino acids due to the specific mutation. In conclusion, this study showed for the first time that lysine (K120) and aspartate (D123) simultaneously affected HBsAg antigenicity, leading to diagnostic failure. These findings will improve diagnostic assays and vaccine development.

Naturally Occurring Surface Antigen Variants of Hepatitis B Virus in Tunisian Patients

In Tunisia, the prevalence of naturally occurring surface (S) gene variants of hepatitis B virus (HBV) has not been determined. In the present study, the prevalence of these variants was examined in terms of the clinical and viral state in a series of 99 Tunisian patients with HBV infection. The S genes were amplified and directly sequenced. Genotype D was predominant (98%), 40.4% isolates belonged to subgenotypes D7 and 1 to subgenotype D2. The most common subtype was ayw2 (95.9%). In total, 60.6% of the studied strains harbored S mutations. Several novel mutation patterns were detected. Interestingly, the presence of S mutations was significantly correlated with the D7 subgenotype, low HBV DNA and advancing age (≥35 years), and tended to be higher in liver cirrhosis than in chronic infection. The global prevalence of the major hydrophilic region variants was 12.1%, with substitution S143L/T as the most frequent (4%). Only 33.9% of S substitutions produced amino acid changes in the polymerase gene. In conclusion, a high prevalence of naturally occurring HBsAg variants was observed among Tunisian HBV carriers. Natural viral variability in a geographical region and duration of infection are among the major factors associated with the occurrence of S mutations.

Impacts of the G145R Mutation on the Structure and Immunogenic Activity of the Hepatitis B Surface Antigen: A Computational Analysis

BACKGROUND

Vaccine-escaped hepatitis B virus (HBV) mutations occur within the "a" determinant area, which is located in the major hydrophilic region (MHR) of the hepatitis B surface antigen (HBsAg) protein. It is now well established that the common G145R mutation is highly capable of escaping from HBsAg immune recognition. However, the impacts of this mutation on the structure and immunogenic activity of HBsAg have been poorly investigated.

OBJECTIVES

The present study analyzed the effects of the G145R mutation on the structure and immunogenic activity of the HBsAg.

MATERIALS AND METHODS

Three-dimensional (3D) structure of HBsAg for both the wild-type and G145R mutant were predicted and refined using several web tools. After quantitative evaluations, the effects of the G145R mutation on the secondary and 3D structures of the HBsAg were investigated. In parallel, the immunogenic activity of the wild-type and mutant HBsAg was also analyzed using a ClusPro docking server as well as the IEDB web tool. Further analyses were performed via molecular dynamics (MD) simulations using the GROMACS v5.0.2 simulation package.

RESULTS

The G145R mutation causes a considerable reduction in the immunogenic activity of the HBsAg through a conformational change in the HBsAg antigenic loops. This mutation inserts a new β-strand in the "a" determinant region of the HBsAg, leading to a reduced binding affinity to its monoclonal antibody, MAb12. The G145R mutation also increased the compactness and stability of the HBsAg by enhancing the rigidity of the "a" determinant.

CONCLUSIONS

These data will be beneficial for designing more advanced antibodies for the recognition of the HBsAg in diagnostics. In addition, the results of this study may assist in the design or development of more effective hepatitis B vaccines.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Genetic variation of occult hepatitis B virus infection

Occult hepatitis B virus infection (OBI), characterized as the persistence of hepatitis B virus (HBV) surface antigen (HBsAg) seronegativity and low viral load in blood or liver, is a special form of HBV infection. OBI may be related mainly to mutations in the HBV genome, although the underlying mechanism of it remains to be clarified. Mutations especially within the immunodominant “α” determinant of S protein are “hot spots” that could contribute to the occurrence of OBI via affecting antigenicity and immunogenicity of HBsAg or replication and secretion of virion. Clinical reports account for a large proportion of previous studies on OBI, while functional analyses, especially those based on full-length HBV genome, are rare.

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

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

Stable Human Hepatoma Cell Lines for Efficient Regulated Expression of Nucleoside/Nucleotide Analog Resistant and Vaccine Escape Hepatitis B Virus Variants and Woolly Monkey Hepatitis B Virus

Hepatitis B virus (HBV) causes acute and chronic hepatitis B (CHB). Due to its error-prone replication via reverse transcription, HBV can rapidly evolve variants that escape vaccination and/or become resistant to CHB treatment with nucleoside/nucleotide analogs (NAs). This is particularly problematic for the first generation NAs lamivudine and adefovir. Though now superseded by more potent NAs, both are still widely used. Furthermore, resistance against the older NAs can contribute to cross-resistance against more advanced NAs. For lack of feasible HBV infection systems, the biology of such variants is not well understood. From the recent discovery of Na⁺-taurocholate cotransporting polypeptide (NTCP) as an HBV receptor new in vitro infection systems are emerging, yet access to the required large amounts of virions, in particular variants, remains a limiting factor. Stably HBV producing cell lines address both issues by allowing to study intracellular viral replication and as a permanent source of defined virions. Accordingly, we generated a panel of new tetracycline regulated TetOFF HepG2 hepatoma cell lines which produce six lamivudine and adefovir resistance-associated and two vaccine escape variants of HBV as well as the model virus woolly monkey HBV (WMHBV). The cell line-borne viruses reproduced the expected NA resistance profiles and all were equally sensitive against a non-NA drug. The new cell lines should be valuable to investigate under standardized conditions HBV resistance and cross-resistance. With titers of secreted virions reaching >3x10⁷ viral genome equivalents per ml they should also facilitate exploitation of the new in vitro infection systems.

A new vaccine escape mutant of hepatitis B virus causes occult infection

There is growing public concern regarding assay sensitivity to HBsAg mutants in clinical diagnosis and vaccine escape. The aim of this study is to introduce a new HBsAg mutant strain. The serum samples were those of patient X at the age of 3 months and 3 years respectively, and of her mother immediately before parturition, which were used to amplify the HBsAg-coding DNA fragments by PCR. The HBsAg DNA sequences were translated into their corresponding amino acid sequences and then aligned in pubmed with nucleotide blast. The sequencing data of S coding regions shows that patient X has been infected by a new HBV variant with an A to C substitution at nt431, resulting in an Asp(GAC)to Ala(GCC) substitution at aa144 of major protein; CC to AA substitution at nt359 and nt360, resulting in an Pro(CCC) to Gln(CAA) substitution at aa120 of pre "a" epitope; A to G substitution at nt491, resulting in an Glu(GAG) to Gly(GGG) substitution at aa164 of post "a" epitope. Three new mutations (S171F, S174N and Q181R) at the antigenic epitopes of HBV presented by HLA class I molecules are found. The HBV mutant strain causes vaccine escape and occult infection.

Clinical significance of hepatitis B surface antigen mutants

Hepatitis B virus (HBV) infection is a major public health problem in many countries, with nearly 300 million people worldwide carrying HBV chronic infection and over 1 million deaths per year due to cirrhosis and liver cancer. Several hepatitis B surface antigen (HBsAg) mutations have been described, most frequently due to a single amino acid substitution and seldom to a nucleotide deletion. The majority of mutations are located in the S region, but they have also been found in the pre-S1 and pre-S2 regions. Single amino acid substitutions in the major hydrophilic region of HBsAg, called the “a” determinant, have been associated with immune escape and the consequent failure of HBV vaccination and HBsAg detection, whereas deletions in the pre-S1 or pre-S2 regions have been associated with the development of hepatocellular carcinoma. This review article will focus on the HBsAg mutants and their biological and clinical implications.

Virological Characteristics of Acute Hepatitis B in Eastern India: Critical Differences with Chronic Infection

Hepatitis B Virus (HBV) manifests high genetic variability and is classifiable into ten genotypes (A-J). HBV infection can lead to variable clinical outcomes, ranging from self-limiting acute hepatitis to active chronic hepatitis, cirrhosis and hepatocellular carcinoma. The present study characterizes HBV strains circulating among patients with acute (AHB) and chronic HBV infection (CHB). Among a total of 653 HBsAg positive cases, 40 manifested acute infection. After sequencing the surface(S), basal core promoter/pre-core(BCP/PC) and the X gene regions, phylogenetic tree was constructed using MEGA4 by neighbor-joining method. Statistical robustness was established with bootstrap analysis. Nucleotide diversity was determined by Shannon entropy per site using the Entropy program of the Los Alamos National Laboratories. Analyses of acute patients revealed that HBV/D2 is the major circulating sub-genotype and commonly associated with sexual promiscuity and the age group between15-30 years. Comparison of AHB and CHB patients revealed that HBeAg positivity, ALT levels and genotype D were significantly high in AHB, whereas CHB patients were predominantly male, had a high viral load, and were commonly associated with genotype C. The frequencies of mutations in the S, BCP/PC, and X gene were low in AHB as compared to CHB. Drug resistant mutations were not detectable in the polymerase gene of AHB. Average nucleotide diversity in AHB was considerably low as compared to CHB. Further, the highest average ΔH (average difference in entropy between chronic and acute infection) was observed in the BCP/PC region implying that this region was most vulnerable to mutations upon HBV persistence, especially in case of genotype C. Additionally, among all substitutions, the A1762T and G1764A BCP mutations were the strongest indicators of chronicity. In conclusion, the study exhibits a general portrait of HBV strains circulating among acute hepatitis B patients in Eastern India and their intricate differences with chronic patients which should be useful from the clinical point of view.

Occult HBV Infection May Be Transmitted through Close Contact and Manifest as an Overt Infection

The importance of transmission of occult HBV infection (OBI) via transfusion, organ transplantation and hemodialysis has been widely recognized. However, data regarding the transmission of OBI through close contact remain limited. In this study, serum samples were obtained from a child and his parents. The child had received the standard vaccination regimen at birth and produced protective antibody. Sera were tested for HBV serological markers. Nested PCR assays were used to detect HBV DNA and the amplicons were cloned and their sequences subjected to phylogenetic analysis. The results showed that both parents had occult infections while the child had an overt infection. Twelve, eleven and nine clones, from the father, mother and son, respectively, were sequenced. Serotypes adrq+, ayw1, ayw and ayr were found in the father and ayw1, adw2 and adwq+ in the mother; adrq+ was the only serotype in son. Genotype B, subgenotype C2 and a recombinant were identified in the father and genotype B, subgenotype C5 and three recombinants were found in the mother. Subgenotype C2 was the only genotype identified in the child. A phylogenetic tree showed that all of the child’s sequences and most of the father’s sequences clustered together. However, none of mother’s sequences clustered with those of the child. The surface gene from the child and his father had the same amino acid substitution pattern (T118K, T123N and G145A). We concluded that the father was the source of the son’s HBV infection, suggesting that occult HBV infection may be transmitted through close contact and manifest as an overt infection.

Ultradeep Sequencing for Detection of Quasispecies Variants in the Major Hydrophilic Region of Hepatitis B Virus in Indonesian Patients

Quasispecies of hepatitis B virus (HBV) with variations in the major hydrophilic region (MHR) of the HBV surface antigen (HBsAg) can evolve during infection, allowing HBV to evade neutralizing antibodies. These escape variants may contribute to chronic infections. In this study, we looked for MHR variants in HBV quasispecies using ultradeep sequencing and evaluated the relationship between these variants and clinical manifestations in infected patients. We enrolled 30 Indonesian patients with hepatitis B infection (11 with chronic hepatitis and 19 with advanced liver disease). The most common subgenotype/subtype of HBV was B3/adw (97%). The HBsAg titer was lower in patients with advanced liver disease than that in patients with chronic hepatitis. The MHR variants were grouped based on the percentage of the viral population affected: major, ≥20% of the total population; intermediate, 5% to <20%; and minor, 1% to <5%. The rates of MHR variation that were present in the major and intermediate viral population were significantly greater in patients with advanced liver disease than those in chronic patients. The most frequent MHR variants related to immune evasion in the major and intermediate populations were P120Q/T, T123A, P127T, Q129H/R, M133L/T, and G145R. The major population of MHR variants causing impaired of HBsAg secretion (e.g., G119R, Q129R, T140I, and G145R) was detected only in advanced liver disease patients. This is the first study to use ultradeep sequencing for the detection of MHR variants of HBV quasispecies in Indonesian patients. We found that a greater number of MHR variations was related to disease severity and reduced likelihood of HBsAg titer.

The prevalence of mutations in the major hydrophilic region of the surface antigen of hepatitis B virus varies with subgenotype

Mutations in the major hydrophilic region (MHR) of the surface antigen of hepatitis B virus (HBV) may result in vaccine escape, failure of immunotherapy and antiviral resistance. These mutants may be transmitted and constitute a public health threat. We aimed to determine the prevalence of MHR mutations of HBV in areas of high endemicity in Guangxi, China. HBV surface gene was analysed from 278 HBsAg-positive asymptomatic individuals recruited from Guangxi using cluster sampling. Three genotypes, B, C and I, were identified. The overall prevalence of MHR mutations is 17·6%. The prevalence of MHR mutations in genotype B (15·1%) is not significantly different from that in genotype C (16·4%). However, the prevalence in subgenotype C5 (31·1%) is significantly higher than in subgenotype C2 (13·0%) (χ2= 6·997,P< 0·05). The prevalence of escape mutations and overlapping polymerase substitutions in subgenotype C5 is significantly higher than in subgenotypes B2 and C2. In total, 7·9% of MHR mutants are escape mutations and 72·1% of MHR mutations produced amino-acid changes in the overlapping polymerase, including resistance mutations to entecavir. Our results suggest that the prevalence of MHR mutations varies with subgenotype. The prevalence of escape mutations and polymerase mutations may be associated with subgenotype.

Clinical implications of hepatitis B virus mutations: Recent advances

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

Prevalence and molecular analysis of occult hepatitis B virus infection isolated in a sample of cryptogenic cirrhosis patients in iran

OBJECTIVES

The aims of this study are to investigate the prevalence of occult hepatitis B virus infection among patients with cryptogenic cirrhosis and to analyze the relationship between surface protein variability and occult hepatitis B virus infection, which may be related to the pathogenesis of occult hepatitis B virus infection in cryptogenic cirrhosis. Occult hepatitis B virus infection is a well-recognized clinical entity characterized by the detection of hepatitis B virus DNA in serum and/or liver in the absence of detectable hepatitis B virus surface antigen, with or without any serological markers of a past infection.

METHODS

Sera from patients with cryptogenic chronic liver disease were tested for hepatitis B virus DNA using both real-time and nested PCR. In the detected hepatitis B virus DNA samples, the surface gene was analyzed for mutations.

RESULTS

Hepatitis B virus DNA was detected in 38% of patients, all of whom had a viral load below 10,000 copies/mL. All hepatitis B virus belonged to genotype D. There were no significant associations between occult hepatitis B virus infection status and age, gender, ALT/AST levels, viral load or serologic markers of previous hepatitis B virus infection. There were 14 mutations found in 5 patients; 6 were in the major hydrophilic region, of which 4 were Y134F assigning for the "a" determinant region. All patients who acquired Y134F contained S207R (within HLA-A2-restricted CTL epitope) as a combination.

CONCLUSION

Hepatitis B virus surface antigen variants may arise as a result of natural selection to evade the immune surveillance of the infected host, and subsequently may go undetected by conventional hepatitis B virus surface antigen screening tests. Etiological diagnosis of cryptogenic cirrhosis is significantly underestimated with current serology testing methods alone.

HBV transmission from an occult carrier with five mutations in the major hydrophilic region of HBsAg to an immunosuppressed plasma recipient

We describe the case of transmission of an HBsAg-negative hepatitis B infection to an immunosuppressed patient by plasma donation from an HBsAg-negative subject, but with very low serum HBV DNA (about 50 IU/ml) and five mutations in the major hydrophilic region of HBsAg.

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.

Analyzing titers of antibodies against bacterial and viral antigens, and bacterial toxoids in the intravenous immunoglobulins utilized in Taiwan

Intravenous immunoglobulin (IVIG) manufactured from human plasma contains IgG as the primary ingredient, and is used for indications such as immunodeficiency syndrome. Available IVIGs in Taiwan are either manufactured from Taiwanese or North American plasma. The effectiveness of the national immunization program of Taiwan can be evaluated by analyzing and comparing IVIG antibody titers that are induced through the corresponding vaccines (tetanus, diphtheria, and pertussis, measles, rubella, hepatitis A, hepatitis B and varicella). Both enzyme-linked immunosorbent assay (ELISA) and the in vitro neutralization test demonstrated that all IVIGs provide adequate clinical protection against diphtheria and tetanus toxins. ELISA results further revealed that plasma of Taiwanese subjects contains higher levels of pertussis toxin and filamentous hemagglutinin antibodies, when compared to foreign IVIGs. This may be related to the later adoption of acellular pertussis vaccine in Taiwan. Antibodies titers against measles, rubella, hepatitis A, and varicella-zoster virus were otherwise low. Low titers of hepatitis B surface antigen antibodies are present in Taiwanese plasma IVIG, indicating immune memory decline or loss. In conclusion, our results show that Taiwanese IVIG contains varying titers of vaccine-induced antibodies, and serves as a guide for future amendments to Taiwan's immunization program.

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.

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.

Comprehensive analysis of the prevalence of hepatitis B virus escape mutations in the major hydrophilic region of surface antigen

Escape mutations in the major hydrophilic region (MHR) of hepatitis B surface antigen (HBsAg) are reported widely worldwide; these mutations lead to diagnostic problems, emergence of vaccine-escape mutants, and hepatitis B immunoglobulin (HBIG) therapy failure. However, the prevalence of these mutations in different genotypes remains to be studied systematically. In the current study, 11,221 non-redundant hepatitis B virus (HBV) sequences of 8 genotypes (from A to H), obtained from the National Center for Biotechnology Information (NCBI), were analyzed to determine the prevalence of HBsAg escape mutations that were previously described. Eight important mutations associated with diagnostic failure, P120T, T126S, Q129H, G130N, S143L, D144A, and G145A/R, were prevalent in one or more genotypes, with the frequency of no less than 1%. With regard to escape variants that evade vaccine or immunoglobulin therapy, mutations were located mainly at positions 120, 126, 129, 130, 133, 134, 137, 140, 143, 144, and 145. The majority of such mutations showed genotypic heterogeneity, indicating the different distribution of the escape mutations. Most of the escape mutations clustered in the "a" determinant, indicating that this region was more likely to be affected by immune selection or antiviral therapy than other regions. Understanding the prevalence and heterogeneity of escape mutations could provide useful guidance for the improvement of diagnostic assays, design of new vaccines, and prevention of failure of HBIG therapy.

Molecular mechanisms underlying occult hepatitis B virus infection

Chronic hepatitis B virus (HBV) infection is a complex clinical entity frequently associated with cirrhosis and hepatocellular carcinoma (HCC). The persistence of HBV genomes in the absence of detectable surface antigenemia is termed occult HBV infection. Mutations in the surface gene rendering HBsAg undetectable by commercial assays and inhibition of HBV by suppression of viral replication and viral proteins represent two fundamentally different mechanisms that lead to occult HBV infections. The molecular mechanisms underlying occult HBV infections, including recently identified mechanisms associated with the suppression of HBV replication and inhibition of HBV proteins, are reviewed in detail. The availability of highly sensitive molecular methods has led to increased detection of occult HBV infections in various clinical settings. The clinical relevance of occult HBV infection and the utility of appropriate diagnostic methods to detect occult HBV infection are discussed. The need for specific guidelines on the diagnosis and management of occult HBV infection is being increasingly recognized; the aspects of mechanistic studies that warrant further investigation are discussed in the final section.

Molecular mechanisms underlying occult hepatitis B virus infection

Chronic hepatitis B virus (HBV) infection is a complex clinical entity frequently associated with cirrhosis and hepatocellular carcinoma (HCC). The persistence of HBV genomes in the absence of detectable surface antigenemia is termed occult HBV infection. Mutations in the surface gene rendering HBsAg undetectable by commercial assays and inhibition of HBV by suppression of viral replication and viral proteins represent two fundamentally different mechanisms that lead to occult HBV infections. The molecular mechanisms underlying occult HBV infections, including recently identified mechanisms associated with the suppression of HBV replication and inhibition of HBV proteins, are reviewed in detail. The availability of highly sensitive molecular methods has led to increased detection of occult HBV infections in various clinical settings. The clinical relevance of occult HBV infection and the utility of appropriate diagnostic methods to detect occult HBV infection are discussed. The need for specific guidelines on the diagnosis and management of occult HBV infection is being increasingly recognized; the aspects of mechanistic studies that warrant further investigation are discussed in the final section.

T cell responses and viral variability in blood donation candidates with occult hepatitis B infection

BACKGROUND & AIMS

Occult HBV infection (OBI) is defined by the presence of HBV DNA in the liver and/or serum and negative HBsAg testing. Since the implementation of highly sensitive HBV DNA screening, OBI is also detected in healthy blood donors. The aims of this study were to investigate HBV-specific immune responses and genetic variability in donors with OBI, established by HBV DNA in serum.

METHODS

HBV-specific T-cell responses to HBV antigens were tested in 34 OBI donors by IFN-γ ELISpot, cytometric bead array, and intracellular cytokine staining. As comparison populations, 36 inactive HBV carriers, 22 donors with spontaneously resolved HBV infection, 24 vaccinated donors, and 25 seronegative donors were also included. Surface, pre-S, and pre-c/core genes from 44 genotype D isolates (24 OBI and 20 HBsAg-positive) were sequenced.

RESULTS

The immune response of OBI donors to the 3 HBV antigens was 29-41%, similar to the response in subjects with resolved HBV infection and higher than that in HBsAg-positive subjects. On sequence analysis, OBI donors presented a higher HBsAg mutation rate than HBsAg-positive subjects. Mutations were clustered in the major hydrophilic region of HBsAg, and no stop codons or relevant mutations that could affect antigen formation or detection were observed.

CONCLUSIONS

Our results suggest that immune response can suppress viral replication to low levels and HBsAg expression to undetectable levels in OBI blood donors. Relevant mutations were not found in the genomic HBsAg coding region. Hence, the fact that HBsAg was not detected in OBI is likely due to low HBsAg production, rather than to a failure of laboratory reagents.

Reducing the risk of hepatitis B virus transfusion-transmitted infection

Before 1970, approximately 6% of multi-transfused recipients acquired a transfusion-transmitted Hepatitis B virus (HBV) infection. The safety improvements since then have been tremendous. From a level of a few infections per 1000 donations, the risk today, depending on the screening algorithm and additional measurements performed, has decreased to around 1:500,000 to 1:1,000,000, an improvement greater than 1000-fold compared to 50 years ago. This enormous gain in safety has been achieved through many factors, including development of increasingly more sensitive Hepatitis B antigen (HBsAg) assays; the adoption in some countries of hepatitis B core antibody (anti-HBc) screening; an improved donor selection procedure; HBV vaccination programs; and finally the introduction of HBV nucleic acid testing (NAT). Because there is a tendency in transfusion medicine to add one safety measure on top of another to approach the ultimate goal of zero risks, costs become increasingly a matter of debate. It is obvious that any new measure in addition to existing methods or measures will have very poor cost effectiveness. Therefore each country needs to perform its own calculation based on the country’s own epidemiology, resources, political and public awareness of the risks, in order to choose the correct and most cost-efficient measures. Ideally, each country would make decisions regarding implementation of additional blood safety measures in the context of both the perceived benefit and the allocation of overall health care resources.

Expression of Hepatitis B Virus Surface Antigen Containing Y100C Variant Frequently Detected in Occult HBV Infection

Small hepatitis B virus surface protein (S-HBsAg) variant Y100C has been associated with HBsAg-negative phenotype. To determine whether Y100C substitution yields impaired HBsAg or small amounts of HBsAg that may reduce HBsAg detection by commercial anti-HBsAg antibodies, two eukaryotic expression plasmids, one containing a wild-type S and the other an S gene from a Y100C variant, were constructed and their levels of HBsAg compared by ELISA after transfection of HuH7 cells. Unexpectedly, the extracellular HBsAg levels detected with Y100C plasmid were higher than those observed with the wild-type plasmid, but without statistical significance. We concluded that the Y100C substitution alone did not play a role in reducing HBsAg amounts or HBsAg affinity by commercial ELISA assay. Further studies on in vitro replication fitness with the complete genome of HBV isolates displaying or not Y100C substitution may elucidate whether this mutation affects HBV replication and consequently HBsAg production.

Prediction of conformational changes by single mutation in the hepatitis B virus surface antigen (HBsAg) identified in HBsAg-negative blood donors

BACKGROUND

Selection of hepatitis B virus (HBV) by host immunity has been suggested to give rise to variants with amino acid substitutions at or around the 'a' determinant of the surface antigen (HBsAg), the main target of antibody neutralization and diagnostic assays. However, there have never been successful attempts to provide evidence for this hypothesis, partly because the 3 D structure of HBsAg molecules has not been determined. Tertiary structure prediction of HBsAg solely from its primary amino acid sequence may reveal the molecular energetic of the mutated proteins. We carried out this preliminary study to analyze the predicted HBsAg conformation changes of HBV variants isolated from Indonesian blood donors undetectable by HBsAg assays and its significance, compared to other previously-reported variants that were associated with diagnostic failure.

RESULTS

Three HBV variants (T123A, M133L and T143M) and a wild type sequence were analyzed together with frequently emerged variants T123N, M133I, M133T, M133V, and T143L. Based on the Jameson-Wolf algorithm for calculating antigenic index, the first two amino acid substitutions resulted in slight changes in the antigenicity of the 'a' determinant, while all four of the comparative variants showed relatively more significant changes. In the pattern T143M, changes in antigenic index were more significant, both in its coverage and magnitude, even when compared to variant T143L. These data were also partially supported by the tertiary structure prediction, in which the pattern T143M showed larger shift in the HBsAg second loop structure compared to the others.

CONCLUSIONS

Single amino acid substitutions within or near the 'a' determinant of HBsAg may alter antigenicity properties of variant HBsAg, which can be shown by both its antigenic index and predicted 3 D conformation. Findings in this study emphasize the significance of variant T143M, the prevalent isolate with highest degree of antigenicity changes found in Indonesian blood donors. This highlights the importance of evaluating the effects of protein structure alterations on the sensitivity of screening methods being used in detection of ongoing HBV infection, as well as the use of vaccines and immunoglobulin therapy in contributing to the selection of HBV variants.

Impact of hepatitis B virus surface protein mutations on the diagnosis of occult hepatitis B virus infection

Genotype D occult hepatitis B virus (HBV) infections (OBIs) have a high frequency of amino acid substitutions in the major hydrophilic region of the small surface protein (S protein). This possibly reflects an escape mutation mechanism to evade detection by the host immune system. Mutations may also impact the detection of hepatitis B surface antigen (HBsAg) by commercial assays. To test these hypotheses, 20 recombinant HBV genotype D surface proteins from OBI carriers with or without antibody to hepatitis B surface antigen (anti-HBs) were expressed in yeast. Recombinant surface protein (rS protein) variants were nonreactive with autologous anti-HBs but reacted weakly with vaccine-induced anti-HBs supporting an immune escape mechanism. rS protein variants tested with a wide range of HBs antibodies, and HBsAg commercial assays showed significantly lower antigenic reactivity in anti-HBs carriers than in donors with antibody to hepatitis B core antigen (anti-HBc) only. Eight out of 10 recombinant variants from anti-HBs carriers reacted weakly or were nonreactive with antibodies to HBs as well as with qualitative and quantitative commercial HBsAg assays, whereas eight out of 10 anti-HBc-only plasmas were fully reactive. rS proteins with substitutions of wild-type cysteine at positions 121, 124, and 137 were nonreactive or showed poor reactivity. However, mutation of cysteine 147 did not alter reactivity compared with controls. Restoration of cysteines 124 and 137 by site-directed mutagenesis improved antigenic reactivity.

CONCLUSION

Escape mutation is a mechanism associated with OBI, which also leads to decreased reactivity in HBsAg detection assays. Performance of commercial assays would be improved by the incorporation of OBI mutants in reagent development.

Hepatitis B virus transfusion risk in China: proficiency testing for the detection of hepatitis B surface antigen

Because of the high prevalence of Hepatitis B virus (HBV), HBsAg tests play an extremely significant role in donor screening in China. In our multicentre study, the HBsAg assays used in blood screening were evaluated for their analytical sensitivity and the ability to detect mutants. A panel of eight samples was sent to 85 blood banks. The panel included four HBsAg-positive serum samples at concentrations of 0·16, 0·46, 0·9 and 1·73 IU mL(-1) ; three recombinant HBsAg mutants (G145R, T131I and K141E) with defined concentrations and one negative sample. All laboratories were required to detect the samples with their routine procedures.All the 85 blood banks reported their results before the closing date, and 170 data sets were submitted. The wild-type samples at concentrations of 1·73 and 0·9 IU mL(-1) were correctly identified as positive in all data sets, whereas the other two samples (at concentrations 0·16 and 0·46 IU mL(-1) ) were not consistently detected as positive. Regarding the mutants, significantly different results were reported among all the assays involved. All users of Hepanostika HBsAg Ultra and most users (16/17) of Abbott Murex HBsAg Version 3 detected all mutant samples, whereas some of the commercial assays failed to detect any of the three mutant samples. Some HBsAg assays with unsatisfactory sensitivities and capabilities of mutant detection were used by a large percentage of blood banks, which might lead to a high transfusion risk in China. A list of assays of high sensitivity and good ability of mutant detection should be recommended for use in blood screening.

Prevalence of hepatitis B virus MHR mutations and their correlation with genotypes and antiviral therapy in chronically infected patients in Serbia

Understanding the prevalence and diversity of HBsAg variants in a population is fundamental to assay design and planning vaccination programs. It has been shown that mutations within the S gene, caused by selection or natural variation, can lead to false-negative results in assays for HBsAg, or have clinical implications, such as evading anti-HBV immunoglobulin therapy or vaccine-induced immunity. The region of HBsAg where most of these mutations occur is known as the major hydrophilic region (MHR). The aim of this study was to determine the prevalence and mutational patterns of MHR mutations in patients with chronic hepatitis B, and their correlation with patient characteristics, viral factors and antiviral therapy. The study comprised 164 plasma samples from patients with chronic hepatitis B, of which, 34.8% were on long-term lamivudine monotherapy. Direct sequencing of part of the S/pol gene was used for identification of HBsAg mutations, HBV genotypes, subgenotypes and HBsAg subtypes. The overall frequency of MHR mutations was 22.6%, but it varied significantly between untreated and treated patients (16.8% vs. 33.3%). The most frequent substitution was at position 120 (9.1%) whereas the most common vaccine-escape position, 145, was affected in 1.8% of isolates. The presence of MHR mutations was correlated with genotype D, subgenotype D3, and ayw2/ayw3 HBsAg subtypes and to older age (>40 years). It is concluded that natural viral variability present in a geographical region, duration of infection, and antiviral therapy are among the major factors associated with the occurrence of MHR mutations.

Detection of highly prevalent hepatitis B virus coinfection among HIV-seropositive persons in Ghana

Simple hepatitis B surface antigen (HBsAg) tests may facilitate ascertainment of hepatitis B virus (HBV) infection in settings with high endemicity but limited infrastructure. We evaluated two rapid HBsAg tests and characterized HBV coinfection in a Ghanaian HIV-positive cohort. Samples from 838 patients were tested by the rapid assays Determine and Vikia and the reference assays Architect, Murex version 3, and Liaison Ultra. The assays were also evaluated using the 2nd International Standard, a seroconversion panel, and two mutant panels. HBsAg-positive samples underwent HBV DNA quantification by real-time PCR and surface and polymerase gene population sequencing. Overall, 140/838 patients (16.7%; 95% confidence interval, 14.2 to 19.2%) were HBsAg positive, and of these, 103/140 (73.6%) were e-antigen negative and 118/140 (84.3%) showed an HBV DNA level of >14 IU/ml (median, 8,279 IU/ml). Assay sensitivities and specificities were as follows: Architect, 97.9 and 99.6%; Liaison, 97.1 and 99.4%; Murex, 98.6 and 99.3%; Determine, 69.3 and 100%; and Vikia, 70.7 and 100%. With Determine, the limit of detection was >1.5 to 3.4 HBsAg IU/ml, and the median HBV DNA loads were 598 and 10,905 IU/ml in Determine-negative and -positive samples, respectively (P = 0.0005). Results were similar with the Vikia assay. HBV DNA sequencing indicated infection with genotype E in 82/86 (95.3%) patients. HBsAg mutations affected assay performance, including a T123A mutant that escaped detection by Architect. Major drug resistance mutations were observed in 4/86 patients (4.6%). The prevalence of HBV coinfection was high in this HIV-positive Ghanaian cohort. The two rapid assays identified HBsAg-positive patients at risk for liver disease with high specificity, albeit with only moderate sensitivity.

Long-term outcome of patients with lamivudine after early cessation of hepatitis B immunoglobulin for prevention of recurrent hepatitis B following liver transplantation

BACKGROUND

The aim of this study is to examine the efficacy of long-term prophylaxis with lamivudine (LAM) after a course of post-operative hepatitis B immunoglobulin (HBIG) in patients who underwent liver transplantation (LT) for hepatitis B virus (HBV)-related disease.

RESULT

The medical records of HBV-infected patients who underwent a LT in our institution between July 2001 and May 2005 were reviewed. There were 15 liver transplant recipients who were administered HBIG for <18 months and used LAM as a maintenance prophylaxis regime enrolled in this study. At enrollment, all patients were hepatitis B surface antigen (HBsAg) positive and three patients were HBeAg positive. There were 13 patients who were HBV DNA positive with a mean viral load of 5.4 log copies/mL, and among them, 12 recipients were on antiviral therapy with LAM (100 mg/d orally) for 12-168 d, resulting in HBV DNA negative levels in nine patients prior to their transplant. HBV recurrence post-LT was noted in two patients who had very high-HBV DNA levels pre-LT. Both of these patients showed LAM-resistant mutation at the time of recurrence. The 11 patients who were HBV DNA negative before LT (low-risk patients) had no HBV recurrence during a follow-up at a median of 58 months post-LT. This included five patients who had intermittent low-level HBV DNA post-LT (HBsAg negative), of whom two had YMDD mutation and these two were given adefovir in addition to LAM.

CONCLUSION

Our retrospective study demonstrated excellent long-term outcomes in the low-risk patients treated with LAM after a short course of HBIG.

Surface gene mutations of hepatitis B virus among high-risk patients with occult hepatitis B virus infection

Surface gene mutants of hepatitis B virus (HBV) have been reported in a variety of patient groups. Because of limited data regarding these mutations in patients with occult HBV infections; we aimed to determine these mutations among high-risk patients with occult HBV infection. The presence of HBV-DNA was determined in patients with isolated anti-HBc by real-time polymerase chain reaction (PCR). Then, surface gene region was amplified by nested PCR and mutations were analyzed after sequencing. The mutations that resulted in nonfunctional hepatitis B surface antigen (HBsAg) were insertion of single nucleotide in 2 cases, which causes frameshift and single-nucleotide replacement, and premature stop codons at Leu15 and Gly10 in the other 2 cases. Amino acid substitution at amino acid position 207(S207N) was found in the other isolates. Our study suggested that "a" region mutations did not play a major role in HBsAg detection, and other genetic and nongenetic factors may be responsible for failure to detect HBsAg by routine laboratory tests.