Hepatitis B virus variants

Elimination of Hepatitis B: Is It a Mission Possible?

Chronic hepatitis B virus (HBV) infection is a global public health issue. Although the disease cannot be cured effectively, disease management has been improved over the past decade. The introduction of potent nucleos(t)ide analogues (NAs) to suppress viral replication represented a giant leap in the control of this disease. It has been shown that tenofovir treatment, a potent NA, complements current immunoprophylaxis to diminish mother-to-infant transmission in pregnant women with a high viral load. For patients with chronic HBV infection, quantitative hepatitis B surface antigen is a useful tool to define inactive carriers and to guide antiviral therapy. Quantification of HBV mutants is also useful in predicting long-term outcomes more precisely than ever. The next challenge is how to achieve an HBV cure; although immunotherapy is a promising strategy, the current results from two clinical trials using therapeutic vaccines to induce HBV-specific immune response in patients with chronic HBV infection are disappointing. In the coming years, we are expecting to see a combination of therapeutic agents with various modes of action to complete the mission of HBV elimination.

The nucleotide changes within HBV core promoter/precore during the first 12weeks of nucleos(t)ide treatment might be associated with a better virological response

OBJECTIVES

We aimed to study the dynamic changes of hepatitis B virus (HBV) core promoter/precore (CP/preC) sequences during antiviral treatment and their associations with virological responses.

MATERIALS AND METHODS

The baseline and 12-week CP/preC sequences (nts 1655-2014) were obtained from 52 chronic hepatitis B patients with positive hepatitis B e antigen (HBeAg), who received a 104-week lamivudine and adefovir dipivoxil combination therapy. The mutations within the CP/preC were analyzed against genotype specific reference sequences. The nucleotide change rates in individuals during therapy were analyzed in a pairwise comparison manner.

RESULTS

There was no significant difference of the mutation rate at each nucleotide site between baseline and week 12 of treatment (P>0.05). The mutation rates of A1762T/G1764A and G1896A were found to decrease from 46.2% (24/52) at baseline to 36.5% (19/52) at week 12 (P=0.426) and from 28.8% (15/52) to 21.2% (11/52) (P=0.497), respectively. The nucleotide change rates varied from 0.0% - 7.8% in individuals [0.0% in Group 1 (N=26); 0.3% - 7.8% in Group 2 (N=26)] during the first 12-week treatment. HBV DNA levels in Group 2 were significantly lower than those in Group 1 throughout therapy (P<0.01) (e.g., 1.5±1.3log₁₀ IU/ml vs. 2.6±1.0log₁₀ IU/ml at week 104, P=0.001). At week 104 the rates of HBV DNA undetectable and HBeAg loss in Group 2 were significantly higher than those in Group 1 (P<0.05). Along with the increased nucleotide change rates, the rate of HBV DNA undetectable at week 104 tended to increase (odds ratio=0.323, 95% confidence interval=0.138-0.758, P<0.001).

CONCLUSION

Our findings suggested that the nucleotide changes within HBV CP/preC region during the first 12-week treatment might be associated with a better virological response.

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.

Small surface antigen variants of HBV associated with responses to telbivudine treatment in chronic hepatitis B patients

BACKGROUND

Nucleoside/nucleotide analogues are widely used to treat chronic HBV infection, but drug resistance is common. The role of HBV surface gene variants in drug resistance to nucleoside/nucleotide analogues is unknown. We are trying to investigate the dynamics of S gene mutations and how they relate to a patient's virological response in this study.

METHODS

Thirty patients with chronic hepatitis B were enrolled and serum samples were collected at multiple time points during treatment with telbivudine (LdT). The coding regions of the small surface antigen (S-HBsAg) were amplified and sequenced using the 454 GS FLX⁺ System.

RESULTS

Sequencing results revealed different dynamics of non-synonymous mutations, such as sL9P, sN40S, sG44E, sW172*, sW182* and sS187F, between patients with a complete virological response and those with a partial virological response. The viral population heterogeneity decreased at week 12 of LdT treatment in patients with a complete virological response, with a concomitant decline in non-synonymous mutations (from an average of 14 to 9.9 per sample) and an increase in the frequencies of major variants (from 14.3% to 40.4%).

CONCLUSIONS

Our findings suggest that the decrease in viral population heterogeneity at an early stage of LdT treatment was associated with the subsequent optimal virological response, and the early appearance of some specific mutations, such as sG44E, sW172* and sW182*, is a potential indicator of a partial virological response in continuing therapy.

Compensatory variances of drug-induced hepatitis B virus YMDD mutations

Although the drug-induced mutations of HBV have been ever documented, the evolutionary mechanism is still obscure. To deeply reveal molecular characters of HBV evolution under the special condition, here we made a comprehensive investigation of the molecular variation of the 3432 wild-type sequences and 439 YMDD variants from HBV genotype A, B, C and D, and evaluated the co-variant patterns and the frequency distribution in the different YMDD mutation types and genotypes, by using the naïve Bayes classification algorithm and the complete induction method based on the comparative sequence analysis. The data showed different compensatory changes followed by the rtM204I/V. Although occurrence of the YMDD mutation itself was not related to the HBV genotypes, the subsequence co-variant patterns were related to the YMDD variant types and HBV genotypes. From the hierarchy view, we clarified that historical mutations, drug-induced mutation and compensatory variances, and displayed an inter-conditioned relationship of amino acid variances during multiple evolutionary processes. This study extends the understanding of the polymorphism and fitness of viral protein.

Hepatitis B virus resistance substitutions: long-term analysis by next-generation sequencing

HBV phylogenetics and resistance-associated mutations (RAMs) were surveyed by next-generation sequencing of 21 longitudinal samples from seven patients entering antiviral therapy. The virus populations were dominated by a few abundant lineages that coexisted with substantial numbers of low-frequency variants. A few low-frequency RAMs were observed before treatment, but new ones emerged, and their frequencies increased during therapy. Together, these results support the idea that chronic HBV infection is dominated by a few virus lineages and that an accompanying plethora of diverse, low-frequency variants may function as a reservoir that potentially contribute to viral genetic plasticity, potentially affecting patient outcome.

Oncogenic circuit constituted by Ser31-HBx and Akt increases risks of chronic hepatitis and hepatocellular carcinoma

The X protein of hepatitis B virus (HBx) has been specifically implicated in the development of hepatocellular carcinoma (HCC). Clinical associations of HBx isoforms with chronic hepatitis and HCC have not been well studied. HBx has two roles in liver cells, namely pro-apoptotic and anti-apoptotic. In this report, we examined the role of Ser31-HBx in HCC and chronic hepatitis. Using the case-control study, we determined risks of chronic hepatitis and HCC conferred by hepatitis B virus (HBV) containing Ser31-HBx that was phosphorylated by Akt. Ser31-HBx isoforms conferred 3.23-fold risk of HCC in male and 3.36-fold risk in female. Ser31 isoforms were associated with 3.12-fold risk of chronic hepatitis and 3.43-fold risk of cirrhosis and also associated with higher HBV viral load and replication efficiency and lower rate of HBe loss. To determine the mechanism, we found that Ser31-HBx constituted an oncogenic circuit with Akt and cooperated with ras to transform NIH3T3 cells in contrast to non-Ser31-HBxs that did not transduce oncogenic signals. Our results give a clue to account for an underlying cause of HBx-mediated hepatocarcinogenesis. It appears that Ser31 phosphorylation of HBx by Akt plays an important role. The current study provides an example of association of HBV genome variations with risks of HCC and chronic hepatitis.

Genetic variation of hepatitis B virus and its significance for pathogenesis

Hepatitis B virus (HBV) has a worldwide distribution and is endemic in many populations. Due to its unique life cycle which requires an error-prone reverse transcriptase for replication, it constantly evolves, resulting in tremendous genetic variation in the form of genotypes, sub-genotypes, and mutations. In recent years, there has been considerable research on the relationship between HBV genetic variation and HBV-related pathogenesis, which has profound implications in the natural history of HBV infection, viral detection, immune prevention, drug treatment and prognosis. In this review, we attempted to provide a brief account of the influence of HBV genotype on the pathogenesis of HBV infection and summarize our current knowledge on the effects of HBV mutations in different regions on HBV-associated pathogenesis, with an emphasis on mutations in the preS/S proteins in immune evasion, occult HBV infection and hepatocellular carcinoma (HCC), mutations in polymerase in relation to drug resistance, mutations in HBV core and e antigen in immune evasion, chronicalization of infection and hepatitis B-related acute-on-chronic liver failure, and finally mutations in HBV x proteins in HCC.

Effects of interaction between genetic variants in human leukocyte antigen DQ and granulysin genes in Chinese Han subjects infected with hepatitis B virus

Single nucleotide polymorphisms (SNPs) of HLA-DQ and granulysin (GNLY) are reportedly associated with HBV infection. The aim of this study was to investigate the effects of interactions between SNPs in HLA-DQ and GNLY on the outcome of hepatitis B virus (HBV) infection in Chinese Han subjects. HLA-DQ (rs9275572) and GNLY (rs1866139 and rs11127) were genotyped in 310 subjects with HBV-related chronic liver disease, 295 in whom spontaneous clearance of HBV had occurred and 316 who had not been exposed to HBV. HLA-DQ rs9275572 was significantly correlated with HBV clearance (dominant genetic model: OR, 1.84; 95% CI, 1.30-2.61; adjusted P = 0.001). There was no statistical association of GNLY rs1866139 and rs11127with HBV infection outcomes. However, significant sex-specific associations with HBV susceptibility were observed in men who carried rs1866139 CG or rs11127 TC and in women who carried rs1866139 GG or rs11127 CC. The findings were the same in the validation cohort, which was composed of 829 subjects. Based on a multifactor dimensionality reduction test with permutation correction, a three-way interaction between SNPs in HLA-DQ and GNLY was identified in terms of HBV clearance. In conclusion, additional evidence for an association of HLA-DQ and GNLY SNPs with HBV infection outcomes has been identified and a SNP-SNP interaction between HLA-DQ and GNLY on HBV clearance observed.

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.

Deep sequencing of hepatitis B virus basal core promoter and precore mutants in HBeAg-positive chronic hepatitis B patients

Mutants in the basal core promoter (BCP) and precore (PC) regions of hepatitis B virus (HBV) genome are associated with the progression of chronic hepatitis B (CHB) infection. However, quasispecies characteristics of naturally occurring mutants in those regions in HBeAg-positive CHB patients has not been well described, partly limited by quantitative assay. This study aimed to develop an Ion Torrent deep sequencing assay to determine BCP and PC mutant percentages in HBeAg-positive CHB patients who were treatment naïve and correlate them with different viral and host factors. Our results showed that Ion Torrent deep sequencing could achieve high accuracy (R²>0.99) within a dynamic range between 1% and 100%. Twelve hotspots with prevalence of greater than 20% were observed in EnhII/BCP/PC regions. G1719T, T1753V, A1762T and G1764A were genotype C related. BCP A1762T/G1764A double mutants were generally accompanied with PC 1896 wild type or lower PC G1896A mutant percentage. Lower serum HBeAg and HBsAg levels were associated with higher BCP A1762T/G1764A mutant percentages (≥50%). ALT levels were higher in patients with PC G1896A mutant percentage greater than 10%. In conclusion, deep sequencing such as Ion Torrent sequencing could accurately quantify HBV mutants for providing clinical relevant information during HBV infection.

Evaluation of the dynamic pattern of viral evolution in patients with virological breakthrough during treatment with nucleoside/nucleotide analogs by ultra‑deep pyrosequencing

Virological breakthrough is a clinical manifestation in patients infected with chronic hepatitis B (CHB), who undergo treatment with nucleoside/nucleotide analogs (NUCs). The current understanding of the underlying mechanism of virological breakthrough is limited. Ultra‑deep pyrosequencing (UDPS) is a novel and powerful tool used to investigate minor viral variants and viral evolution. The present study used UDPS to investigate the viral evolution pattern during virological breakthrough in patients with CHB treated with NUCs. A total of 12 patients who experienced virological breakthrough were recruited in the present study. During the treatment with lamivudine, adefovir was added as a rescue therapy when virological breakthrough emerged, and the therapy was continued until week 96. Serum samples from each patient were collected at different time points for UDPS analysis. Treatment with lamivudine resulted in an increased rate of the viral mutations, rtM204V/I, rtL180M and rtL80I. Virological breakthrough was accompanied by significant rtM204I/V substitutions in eight of the patients. A total of three types of rt204 mutation, associated with virological breakthrough, were observed, including YIDD variant‑dominated, YVDD variant‑dominated and YMDD wild‑type‑dominated virological breakthrough. YVDD variants reverted to the wild‑type following the adefovir add‑on rescue therapy, although the YIDD variants remained dominant following the combination therapy. The mechanism underlying virological breakthrough was revealed to be complex and associated with the rapid replication of mutated variants. UDPS analysis, therefore, provided a useful tool to investigate the dynamic evolution pattern of hepatitis B virus.

Virus evolution during chronic hepatitis B virus infection as revealed by ultradeep sequencing data

Despite chronic hepatitis B virus (HBV) infection (CHB) being a leading cause of liver cirrhosis and cancer, HBV evolution during CHB is not fully understood. Recent studies have indicated that virus diversity progressively increases along the course of CHB and that some virus mutations correlate with severe liver conditions such as chronic hepatitis, cirrhosis and hepatocellular carcinoma. Using ultradeep sequencing (UDS) data from an intrafamilial case, we detected such mutations at low frequencies among three immunotolerant patients and at high frequencies in an inactive carrier. Furthermore, our analyses indicated that the HBV population from the seroconverter patient underwent many genetic changes in response to virus clearance. Together, these data indicate a potential use of UDS for developing non-invasive biomarkers for monitoring disease changes over time or in response to specific therapies. In addition, our analyses revealed that virus clearance seemed not to require the virus effective population size to decline. A detailed genetic analysis of the viral lineages arising during and after the clearance suggested that mutations at or close to critical elements of the core promoter (enhancer II, epsilon encapsidation signal, TA2, TA3 and direct repeat 1-hormone response element) might be responsible for a sustained replication. This hypothesis requires the decline in virus load to be explained by constant clearance of virus-producing hepatocytes, consistent with the sustained progress towards serious liver conditions experienced by many CHB patients.

Combinatorial RNA Interference Therapy Prevents Selection of Pre-existing HBV Variants in Human Liver Chimeric Mice

Selection of escape mutants with mutations within the target sequence could abolish the antiviral RNA interference activity. Here, we investigated the impact of a pre-existing shRNA-resistant HBV variant on the efficacy of shRNA therapy. We previously identified a highly potent shRNA, S1, which, when delivered by an adeno-associated viral vector, effectively inhibits HBV replication in HBV transgenic mice. We applied the “PICKY” software to systemically screen the HBV genome, then used hydrodynamic transfection and HBV transgenic mice to identify additional six highly potent shRNAs. Human liver chimeric mice were infected with a mixture of wild-type and T472C HBV, a S1-resistant HBV variant, and then treated with a single or combined shRNAs. The presence of T472C mutant compromised the therapeutic efficacy of S1 and resulted in replacement of serum wild-type HBV by T472C HBV. In contrast, combinatorial therapy using S1 and P28, one of six potent shRNAs, markedly reduced titers for both wild-type and T472C HBV. Interestingly, treatment with P28 alone led to the emergence of escape mutants with mutations in the P28 target region. Our results demonstrate that combinatorial RNAi therapy can minimize the escape of resistant viral mutants in chronic HBV patients.

Quantitative evaluation of hepatitis B virus mutations and hepatocellular carcinoma risk: a meta-analysis of prospective studies

BACKGROUND

The temporal relationship between hepatitis B virus (HBV) mutations and hepatocellular carcinoma (HCC) remains unclear.

METHODS

We conducted a meta-analysis including cohort and nested case-control studies to prospectively examine the HCC risk associated with common variants of HBV in the PreS, Enhancer II, basal core promoter (BCP) and precore regions. Pertinent studies were identified by searching PubMed, Web of Science and the Chinese Biological Medicine databases through to November 2014. Study-specific risk estimates were combined using fixed or random effects models depending on whether significant heterogeneity was detected.

RESULTS

Twenty prospective studies were identified, which included 8 cohort and 12 nested case-control studies. There was an increased risk of HCC associated with any PreS mutations with a pooled relative risk (RR) of 3.82 [95% confidence interval (CI): 2.59-5.61]. The pooled-RR for PreS deletion was 3.98 (95% CI: 2.28-6.95), which was higher than that of PreS2 start codon mutation (pooled-RR=2.63, 95% CI: 1.30-5.34). C1653T in Enhancer II was significantly associated with HCC risk (pooled-RR=1.83; 95% CI: 1.21-2.76). For mutations in BCP, statistically significant pooled-RRs of HCC were obtained for T1753V (pooled-RR=2.09; 95% CI: 1.49-2.94) and A1762T/G1764A double mutations (pooled-RR=3.11; 95% CI: 2.08-4.64). No statistically significant association with HCC risk was observed for G1896A in the precore region (pooled-RR=0.77; 95% CI: 0.47-1.26).

CONCLUSIONS

This study demonstrated that PreS mutations, C1653T, T1753V, and A1762T/G1764A, were associated with an increased risk of HCC. Clinical practices concerning the HCC risk prediction and diagnosis may wish to focus on patients with these mutations.

Prediction of virological response by pretreatment hepatitis B virus reverse transcriptase quasispecies heterogeneity: the advantage of using next-generation sequencing

Prediction of antiviral efficacy prior to treatment remains largely unavailable. We have previously demonstrated the clinical value of on-treatment hepatitis B virus (HBV) reverse transcriptase (RT) quasispecies (QS) evolution patterns. In this study, we aimed to elucidate the relevance for prediction of pretreatment HBV RT QS characteristics by comparing the performance of next-generation sequencing (NGS) and clone-based Sanger sequencing (CBS). Thirty-six lamivudine-treated patients were retrospectively studied, including 18 responders and 18 non-responders. CBS and NGS data of pretreatment serum HBV were used to generate RT QS genetic complexity and diversity scores, according to our previous studies. The ability of both methods to predict responsiveness was evaluated with receiver operating characteristic (ROC) curves. A cut-off value was generated on the basis of prediction ability. Responders had significantly higher pretreatment RT QS genetic complexity and diversity (in the first two parts, which overlapped with the S gene, at both the nucleotide and amino acid levels) than non-responders by NGS-based testing. NGS-based algorithms predicted response better than CBS in the ROC curve analysis. The mean distance of the second contig had the highest area under the curve (AUC) value. When the cut-off value was set to 0.007186, the difference between survival curves was significant (p 0.0090). Pretreatment HBV RT QS heterogeneity in the overlapping region of the RT and S genes could be a predictor of antiviral efficacy. NGS improves the predictions of virological outcomes relative to CBS algorithms. This may have important implications for the clinical management of subjects chronically infected with HBV.

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.

Genomic Diversity of Hepatitis B Virus Infection Associated With Fulminant Hepatitis B Development

CONTEXT

After five decades of Hepatitis B Virus (HBV) vaccine discovery, HBV is still a major public health problem. Due to the high genetic diversity of HBV and selective pressure of the host immune system, intra-host evolution of this virus in different clinical manifestations is a hot topic of research. HBV infection causes a range of clinical manifestations from acute to chronic infection, cirrhosis and hepatocellular carcinoma. Among all forms of HBV infection manifestations, fulminant hepatitis B infection possesses the highest fatality rate. Almost 1% of the acutely infected patients develop fulminant hepatitis B, in which the mortality rate is around 70%.

EVIDENCE ACQUISITION

All published papers deposited in Genbank, on the topic of fulminant hepatitis were reviewed and their virological aspects were investigated. In this review, we highlight the genomic diversity of HBV reported from patients with fulminant HBV infection.

RESULTS

The most commonly detected diversities affect regulatory motifs of HBV in the core and S region, indicating that these alterations may convert the virus to an aggressive strain. Moreover, mutations at T-cell and B-cell epitopes located in pre-S1 and pre-S2 proteins may lead to an immune evasion of the virus, likely favoring a more severe clinical course of infection. Furthermore, point and frame shift mutations in the core region increase the viral replication of HBV and help virus to evade from immune system and guarantee its persistence.

CONCLUSIONS

Fulminant hepatitis B is associated with distinct mutational patterns of HBV, underlining that genomic diversity of the virus is an important factor determining its pathogenicity.

Chronic hepatitis B: Virology, natural history, current management and a glimpse at future opportunities

The host immune system plays an important role in chronic hepatitis B (CHB), both in viral clearance and hepatocellular damage. Advances in our understanding of the natural history of the disease have led to redefining the major phases of infection, with the "high replicative, low inflammatory" phase now replacing what was formerly termed the "immune tolerant" phase, and the "nonreplicative phase" replacing what was formerly termed the "inactive carrier" phase. As opposed to the earlier view that HBV establishes chronic infection by exploiting the immaturity of the neonate's immune system, new findings on trained immunity show that the host is already somewhat "matured" following birth, and is actually very capable of responding immunologically, potentially altering future hepatitis B treatment strategies. While existing therapies are effective in reducing viral load and necroinflammation, often restoring the patient to near-normal health, they do not lead to a cure except in very rare cases and, in many patients, viremia rebounds after cessation of treatment. Researchers are now challenged to devise therapies that will eliminate infection, with a particular focus on eliminating the persistence of viral cccDNA in the nuclei of hepatocytes. In the context of chronic hepatitis B, new definitions of 'cure' are emerging, such as 'functional' and 'virological' cure, defined by stable off-therapy suppression of viremia and antigenemia, and the normalization of serum ALT and other liver-related laboratory tests. Continued advances in the understanding of the complex biology of chronic hepatitis B have resulted in the development of new, experimental therapies targeting viral and host factors and pathways previously not accessible to therapy, approaches which may lead to virological cures in the near term and functional cures upon long term follow-up. This article forms part of a symposium in Antiviral Research on "An unfinished story: from the discovery of the Australia antigen to the development of new curative therapies for hepatitis B."

CpG islands of hepatitis B virus genome isolated from Chinese patients

There are differences in the distribution and length of HBV CpG islands and the viral mutations contribute greatly to the development of HBV-related diseases. However, little is known regarding the effects of such difference and mutations in HBV genotypes B and C sequences on the regulation of HBV gene expression and their clinical outcomes. To study the distribution, length and genetic trait of CpG islands in normal and mutant sequences of HBV genotypes B and C, 320 HBV isolates from Chinese patients were retrieved from GenBank. Programs CLUSTALX 1.83 and MethPrimer were employed to perform multiple sequence alignments and to predict CpG islands, respectively. 72.0% genotype B isolates contained three conventional CpG islands, and 76.1% genotype C only contained CpG islands II and III. 14.6% genotype B and 7.5% genotype C contained three novel CpG islands. In genotype B, lengths of conventional CpG islands between normal and mutant isolates exhibited substantial variations, but in genotype C, those were relatively stable. CpG island II could be "truncated" or "split". "Truncated" region mutations were associated with structural and functional abnormalities of HBV genes. Rate of "split" CpG island II in genotype B was much higher than that in genotype C. In the majority of isolates from HCC and HBV-ACLF, genotype C lacked CpG island I and novel islands. Distribution, length and genetic trait of CpG islands in HBV genotypes B and C might affect their methylation status, and further affect regulation of HBV gene expression, leading to different clinical outcomes.

Hepatitis B virus genotypes and variants

At least 10 hepatitis B virus (HBV) genotypes (A to J) with distinct geographic distributions and several HBV mutants, including precore/core promoter mutations and pre-S/S deletion mutations, have been recognized to be not only predictive of liver disease progression but also associated with response to antiviral therapy. HBV genotype-specific pathogenesis may contribute to heterogeneous clinical outcomes in chronic hepatitis B patients across the world. For example, patients with HBV genotypes C and D infection have a lower rate of spontaneous HBeAg seroconversion. In addition, HBV genotypes C and D have a higher frequency of core promoter and pre-S mutations than genotypes A and B. Genotypes C and D also carry a higher lifetime risk of cirrhosis and HCC development than genotypes A and B. Core promoter and pre-S mutations also correlate with an increased risk of hepatocellular carcinoma (HCC). Therapeutically, genotypes A and B patients have a better response to interferon-based therapy than genotypes C and D patients, but the response to nucleos(t)ide analogs is comparable across different HBV genotypes. In conclusion, HBV genotypes and variants may serve as viral genetic markers to predict disease progression as well as help practicing physicians optimize individualized antiviral therapy in clinical practice.

Genotypes and viral variants in chronic hepatitis B: A review of epidemiology and clinical relevance

The Hepatitis B Virus (HBV) has a worldwide distribution and is endemic in many populations. It is constantly evolving and 10 genotypic strains have been identified with varying prevalences in different geographic regions. Numerous stable mutations in the core gene and in the surface gene of the HBV have also been identified in untreated HBV populations. The genotypes and viral variants have been associated with certain clinical features of HBV related liver disease and Hepatocellular carcinoma. For example Genotype C is associated with later hepatitis B e antigen (HBeAg) seroconversion, and more advanced liver disease. Genotype A is associated with a greater risk of progression to chronicity in adult acquired HBV infections. Genotype D is particularly associated with the precore mutation and HBeAg negative chronic hepatitis B (CHB). The genotypes prevalent in parts of West Africa, Central and South America, E, F and H respectively, are less well studied. Viral variants especially the Basal Core Promotor mutation is associated with increased risk of fibrosis and cancer of the liver. Although not currently part of routine clinical care, evaluation of genotype and viral variants may provide useful adjunctive information in predicting risk about liver related morbidity in patients with CHB.

MICA SNPs and the NKG2D system in virus-induced HCC

Hepatocellular carcinoma (HCC) is one of the most frequent causes of cancer-related death globally. Above well-known risk factors for HCC development ranging from various toxins to diseases such as diabetes mellitus, chronic infection with hepatitis B virus and hepatitis C virus (HCV) poses the most serious threat, constituting the cause in more than 80 % of cases. In addition to the viral genes intensively investigated, the pathophysiological importance of host genetic factors has also been greatly and increasingly appreciated. Genome-wide association studies (GWAS) comprehensively search the host genome at the single-nucleotide level, and have successfully identified the genomic region associated with a whole variety of diseases. With respect to HCC, there have been reports from several groups on single nucleotide polymorphisms (SNPs) associated with hepatocarcinogenesis, among which was our GWAS discovering MHC class I polypeptide-related sequence A (MICA) as a susceptibility gene for HCV-induced HCC. MICA is a natural killer (NK) group 2D (NKG2D) ligand, whose interaction with NKG2D triggers NK cell-mediated cytotoxicity toward the target cells, and is a key molecule in tumor immune surveillance as its expression is induced on stressed cells such as transformed tumor cells for the detection by NK cells. In this review, the latest understanding of the MICA-NKG2D system in viral HCC, particularly focused on its antitumor properties and the involvement of MICA SNPs, is summarized, followed by a discussion of targets for state-of-the-art cancer immunotherapy with personalized medicine in view.

Mutations and CpG islands among hepatitis B virus genotypes in Europe

BACKGROUND

Hepatitis B virus (HBV) genotypes have a distinct geographical distribution and influence disease progression and treatment outcomes. The purpose of this study was to investigate the distribution of HBV genotypes in Europe, the impact of mutation of different genotypes on HBV gene abnormalities, the features of CpG islands in each genotype and their potential role in epigenetic regulation.

RESULTS

Of 383 HBV isolates from European patients, HBV genotypes A-G were identified, with the most frequent being genotype D (51.96%) in 12 countries, followed by A (39.16%) in 7 countries, and then E (3.66%), G (2.87%), B (1.57%), F (0.52%) and C (0.26%). A higher rate of mutant isolates were identified in those with genotype D (46.7%) followed by G (45.5%), and mutations were associated with structural and functional abnormalities of HBV genes. Conventional CpG island I was observed in genotypes A, B, C, D and E. Conventional islands II and III were detected in all A-G genotypes. A novel CpG island IV was found in genotypes A, D and E, and island V was only observed in genotype F. The A-G genotypes lacked the novel CpG island VI. "Split" CpG island I in genotypes D and E and "split" island II in genotypes A, D, E, F and G were observed. Two mutant isolates from genotype D and one from E were found to lack both CpG islands I and III.

CONCLUSIONS

HBV genotypes A-G were identified in European patients. Structural and functional abnormalities of HBV genes were caused by mutations leading to the association of genotypes D and G with increased severity of liver disease. The distribution, length and genetic traits of CpG islands were different between genotypes and their biological and clinical significances warrant further study, which will help us better understand the potential role of CpG islands in epigenetic regulation of the HBV genome.

Treating Immune-tolerant Hepatitis B

Hepatitis B virus (HBV) infection is a major cause of cirrhosis and hepatocellular carcinoma worldwide. On the basis of virus-host interactions, the natural history of HBV carriers can be divided into four chronological phases. In the first immune tolerance phase, HBV carriers are positive for hepatitis B e antigen (HBeAg) and have high HBV replication activity, normal ALT levels as well as minimal liver disease. Ample evidence has shown that patients in the immune tolerance phase have very low viral evolution and minimal risk of fibrosis progression. However, recent immunological studies argued that HBV-specific immune responses already exist in a proportion of immune-tolerant patients and the immune activities are comparable to those in the immune clearance phase. Regarding antiviral therapy, whether these immune-tolerant patients are indicated for treatment remains debated. Previous studies showed that HBeAg-positive patients with normal or near-normal ALT levels, who are assumed to be in the immune tolerance phase, have a lower HBeAg seroconversion rate receiving either pegylated interferon or nucleos(t)ide analogue treatment. The latest clinical trial focusing on-treatment response of immune-tolerant patients with tenofovir disoproxil fumarate-based therapy also confirmed the results. The HBeAg seroconversion rates are <5% at 4 years of treatment. Considering the minimal risk of disease progression and low treatment response rates in immune-tolerant patients, current antiviral therapy should not be recommended unless the patients have advanced liver fibrosis. In addition, novel agents targeting the HBV template known as covalently closed circular DNA and aiming to reduce or eliminate it are urgently required.

High rate of core promoter and precore mutations in patients with chronic hepatitis B

Background

The prevalence of precore (PC) and core promoter (CP) mutations in patients with chronic hepatitis B virus (HBV) infection (CHB) and their impact on liver disease is incompletely defined in the United States.

Methods

A retrospective chart review using a cross-sectional approach of 1,186 CHB patients was conducted.

Results

Of 926 patients tested for HBV e antigen (HBeAg), 37 % were HBeAg+. Of 194 patients tested for mutations, 80 % had PC or CP mutations or both; 89 % of HBeAg-negative and 56 % of HBeAg+ patients had PC or CP mutations or both (p < 0.001). The mean log₁₀ ALT was significantly lower in patients with both mutations compared to patients without mutations. The mean log₁₀ HBV DNA was significantly lower in patients with only PC mutations (4.82) compared to patients without mutations (5.71, p = 0.019). With the study population divided into four subgroups based on ALT level at time of diagnosis, cirrhosis incidence was significantly higher in patients with ALT 1–2 × ULN and ALT > 2 × ULN compared to patients with ALT ≤ 0.5 × ULN.

Conclusions

Our finding that PC and CP mutations may be associated with milder liver disease in some patients could serve as the basis for longitudinal studies to help delineate treatment need and duration in patients with these mutations. If confirmed, the finding of an association between ALT 1–2 × ULN and increased incidence of cirrhosis could call into question guidelines which only recommend treatment with ALT > 2 × ULN.

Establishment of drug-resistant HBV small-animal models by hydrodynamic injection

In antiviral therapy of hepatitis B virus (HBV) infection, drug resistance remains a huge obstacle to the long-term effectiveness of nucleoside/tide analogs (NAs). Primary resistance mutation (rtM204V) contributes to lamivudine (LAM)-resistance, and compensatory mutations (rtL180M and rtV173L) restore viral fitness and increase replication efficiency. The evaluation of new anti-viral agents against drug-resistant HBV is limited by the lack of available small-animal models. We established LAM-resistance HBV replication mice models based on clinical LAM-resistant HBV mutants. Double (rtM204V+rtL180M) or triple (rtM204V+rtL180M+rtV173L) lamivudine-resistant mutations were introduced into HBV expression vector, followed by hydrodynamic injection into tail vein of NOD/SCID mice. Viremia was detected on days 5, 9, 13 and 17 and liver HBV DNA was detected on day 17 after injection. The serum and liver HBV DNA levels in LAM-resistant model carrying triple mutations are the highest among the models. Two NAs, LAM and entecavir (ETV), were used to test the availability of the models. LAM and ETV inhibited viral replication on wild-type model. LAM was no longer effective on LAM-resistant models, but ETV retains a strong activity. Therefore, these models can be used to evaluate anti-viral agents against lamivudine-resistance, affording new opportunities to establish other drug-resistant HBV small-animal models.

Peginterferon α in the treatment of chronic hepatitis B

INTRODUCTION

Hepatitis B virus (HBV) infection is a global health problem. Peginterferon α (PEG-IFN), which includes PEG-IFN α-2a (Pegasys) and PEG-IFN α-2b (Peg-Intron), can be used to treat patients with chronic hepatitis B (CHB) infection. A finite duration of PEG-IFN therapy may lead to long-term viral suppression. Clinically, it is important to identify super-responders and null-responders to PEG-IFN due to its substantial side effects.

AREAS COVERED

From the literature review, it is known that PEG-IFN is more effective for hepatitis B e antigen (HBeAg)-positive patients who have high pre-treatment alanine aminotransferase level, lower HBV DNA level and genotype A (vs genotype D), as well as those with more favourable viral predictors, such as precore stop codon or basal core promoter mutants infections in Asian patients and wild-type virus in Caucasian patients. For HBeAg-positive patients and HBeAg-negative patients with genotype D infection, PEG-IFN therapy could be terminated early at week 12 or 24 in primary non-responders defined by the Hepatitis B surface antigen stopping rules. With regard to host factors, single nucleotide polymorphisms of IL28B do not seem to affect the treatment outcomes in Asian patients, but its role in Caucasian patients remains disputed.

EXPERT OPINION

Most of the known predictors need validation by large prospective trials. In addition, we need to identify more baseline predictors for super-responders in order to achieve personalised PEG-IFN treatment for CHB.

A description of the hepatitis B virus genomic background in a high-prevalence area in China

Background

Hepatitis B (HB) is an important disease worldwide. Almost 350 million people are positive for Hepatitis B virus surface antigen (HBsAg), and one-third of them live in China. According to a nation-wide serosurvey in China in 2006, the prevalence of HBsAg was higher in Northwest China than in other areas. However, the epidemic HBV strains in this area are poorly studied.

Results

In this study, 242 complete hepatitis B virus (HBV) genome sequences were obtained from HBV asymptomatic carriers in major cities of Northwest China. The 242 HBV sequences clustered into genotypes B, C and D. Through comparison of the genotype consensus sequences, 158 genotype-dependent positions were observed in P, S and X ORFs. Clinically relevant mutation screening in this study revealed that no HBV antiviral drug resistance mutations were observed and the vaccination failure mutations were heavily underrepresented.

Conclusions

The role of genotype D strains in HBV prevalence should not be ignored in Northwest China. Due to low prevalence of vaccination failure mutations, it can be inferred that the genotype B, C and D strains in Northwest China may have less likelihood of vaccine escape.

Potential mutations associated with occult hepatitis B virus status

CONTEXT

Occult hepatitis B virus (HBV) status (OHBS) is simply defined as the presence of HBV DNA in the liver (with or without detectable HBV DNA in the serum), in the absence of serum HBV surface antigen (HBsAg). Importance of OHBS is mostly clinical, related to its possible role in spreading through blood transfusion and liver transplantation; causing classic forms of HBV. Mechanisms underlying this entity are poorly defined. Several possibilities have been suggested, with major classification into two groups: defective host immune response and viral replication activity through mutations of HBV DNA sequence. Mutations are extensively investigated in all four overlapping open reading frames (ORFs) of HBV genome, to define their possible role in the pathogenesis of OHBS. Some of these mutations like S-escape mutants could not be detected by the routine available assays, making them difficult to diagnosis. Therefore, trying to detect this covert condition could be more helpful for defining better preventive and therapeutic strategies.

EVIDENCE ACQUISITION

In the present study we provided an in-depth review of the most important new data available on different mutations in HBV genome of patients with OHBS, which may play a role in the pathogenesis of OHBS. The data were collected through reviewing the full-text articles, identified by the PubMed search, using the following keywords and their different combinations: occult hepatitis B, HBV genome, "a" determinant, HBV open reading frames, S mutations, X mutations, P mutations and C mutations.

RESULTS

Variants within the major hydrophilic region (MHR) of the HBsAg, deletions in the pre-S1region, codon stop in the S open reading frames (ORF), sporadic non common mutations, some mutations affecting the posttranslational production of HBV proteins in the S ORF like deletion mutations, mutations in start codon and nucleotide changes in the X ORF, deletion and point mutations in P ORF and sometimes, nucleotide substitution in the C ORF are among the assumed mutations detected to have a role in OHBS appearance.

CONCLUSIONS

Studies mostly lacked a control group and the whole-length HBV sequencing was scant with conflicting results, suggesting that OHBS is often a result of multiple mechanisms. Additional studies on full-length HBV genomes from occult and non-occult HBV cases may shed more light on the interplay between different mechanisms involved in the pathogenesis of OHBS.

Hepatitis B virus genetic variation and TP53 R249S mutation in patients with hepatocellular carcinoma in Thailand

Chronic hepatitis B virus (HBV) infection and dietary exposure to aflatoxin B1 (AFB1) are major risk factors for hepatocellular carcinoma (HCC). The aim of this study was to evaluate the role of HBV genetic variation and the R249S mutation of the p53 gene, a marker of AFB1-induced HCC, in Thai patients chronically infected with HBV. Sixty-five patients with and 89 patients without HCC were included. Viral mutations and R249S mutation were characterized by direct sequencing and restriction fragment length polymorphism (RFLP) in serum samples, respectively. The prevalences of T1753C/A/G and A1762T/G1764A mutations in the basal core promotor (BCP) region were significantly higher in the HCC group compared to the non-HCC group. R249S mutation was detected in 6.2% and 3.4% of the HCC and non-HCC groups, respectively, which was not significantly different. By multiple logistic regression analysis, the presence of A1762T/G1764A mutations was independently associated with the risk of HCC in Thai patients.

Amino acid similarities and divergences in the small surface proteins of genotype C hepatitis B viruses between nucleos(t)ide analogue-naïve and lamivudine-treated patients with chronic hepatitis B

Entire C-genotype small hepatitis B surface (SHBs) sequences were isolated from 139 nucleos(t)ide analogues (NA)-naïve and 74 lamivudine (LMV)-treated chronic hepatitis B (CHB) patients. The conservation and variability of total 226 amino acids (AAs) within the sequences were determined individually, revealing significant higher mutant isolate rate and mutation frequency in LMV-treated cohort than those in the NA-naïve one (P=0.009 and 0.0001, respectively). Three absolutely conserved fragments (s16-s19, s176-s181 and s185-s188) and seven moderately conserved regions (a few AA sites acquiring increased variability after LMV-treatment) were identified. The significant mutation rate increase after LMV-treatment occurred primarily in major hydrophilic region (except 'a' determinant) and transmembrane domain 3/4, but not in other upstream functional regions of SHBs. With little influence on immune escape-associated mutation frequencies within 'a' determinant, LMV-monotherapy significantly induced classical LMVr-associated mirror changes sE164D/rtV173L, sI195M/rtM204V and sW196L/S/rtM204I, as well as non-classical ones sG44E/rtS53N, sT47K/A/rtH55R/Q and sW182stop/rtV191I outside 'a' determinant. Interestingly, another newly-identified truncation mutation sC69stop/rtS78T decreased from 7.91% (11/139) in NA-naïve cohort to 2.70% (2/74) in LMV-treated one. Altogether, the altered AA conservation and diversity in SHBs sequences after LMV-treatment in genotype-C HBV infection might shed new insights into how LMV-therapy affects the SHBs variant evolution and its antigenicity.

Suppression of interferon-mediated antiviral immunity by hepatitis B virus: an overview of research progress

Interferon (IFN)-α is an indispensable drug for hepatitis B treatment in clinical settings. However, hepatitis B virus (HBV) can attenuate IFN-mediated antiviral responses to avoid being inhibited or cleared. Much progress has been made in exploring how the IFN-induced anti-HBV effect is inhibited. This review examines and summarizes new advances regarding the molecular mechanism underlying the HBV-induced suppression of type I IFN-mediated antiviral immunity.

Hepatitis B virus depicts a high degree of conservation during the immune-tolerant phase in familiarly transmitted chronic hepatitis B infection: deep-sequencing and phylogenetic analysis

When intrafamilial transmission of hepatitis B virus (HBV) occurs, a virus with the same characteristics interacts with diverse hosts' immune systems and may thus result in different mutations to escape immune pressure. In this study, the HBV genomic characterization was assessed longitudinally after intrafamilial transmission using nucleotide sequence data of phylogenetic and mutational analyses, including those obtained by deep-sequencing for the first time. Furthermore, HBeAg-anti-HBe profile and variability of HBV core-derived epitopes were also evaluated. Strong evidence was obtained from intrafamilial transmission of HBV genotype D1 by phylogenetic inferences. HBV isolates exhibited high degree (~99%) of genomic conservation for almost 20 years, when patients were persistently HBeAg positive with normal amino transferase levels. This identity remained high among immune-tolerant siblings. In contrast, it diminished significantly (P = 0.02) when the mother cleared HBeAg (immune clearance phase). By deep-sequencing, the quantitative analysis of the dynamics of basal core promoter (BCP) (A1762T, G1764A; A1766C; T1773C; 8-bp deletion; and other) and precore (G1896A) variants among HBV isolates from family members exhibited differences during the follow-up. However, only those from the mother showed amino acid variations at core protein that would impair their MHC-II binding. Hence, when intrafamilial transmission occurs, HBV was highly conserved under the immune-tolerant phase, but it exhibited mutations more frequently during the immune clearance phase. The analysis of the HBV BCP and precore mutants after intrafamilial HBV transmission contributes to a better understanding of how they evolve over time.

Functional characterization of the putative hepatitis B virus core protein late domain using retrovirus chimeras

The hepatitis B virus (HBV) Core protein encodes a late (L)-domain like motif (₁₂₉PPAYRPPNAP¹³⁸) that has been purported to serve as a docking site for recruitment of host factors such as Nedd4 that can mediate viral particle release from infected cells. However, mutation of this region of Core typically disrupts nucleocapsid formation in the cytoplasm, making it difficult to ascertain if the Core PPAY motif constitutes a functional L-domain that mediates HBV release in the context of replicating virus. Since many viral L-domains are functionally interchangeable between different virus families, and such swapping experiments have been used as a tool to identify other viral sequences with L-domain activity, we generated chimeric constructs between murine leukemia virus (MLV) Gag and HBV Core to determine if the potential HBV L-domain motif is sufficient to stimulate virus release. We found that the HBV Core PPAY motif, but not the PNAP motif, demonstrates L-domain activity in the context of MLV replication to direct virus release and infectious virion production. Additionally, we found that overexpression of the cellular Nedd4 or WWP1 ubiquitin ligases stimulates release of a partially defective PPAY domain mutant, providing further evidence supporting a role for the Nedd4 ubiquitin ligase in promoting HBV release. These studies lend further insight into the mechanisms used by HBV to mediate its release from infected cells.

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.

Anti-HBV treatment induces novel reverse transcriptase mutations with reflective effect on HBV S antigen

INTRODUCTION

The identification of novel reverse-transcriptase (RT) drug-resistance mutations is critical in predicting the probability of success to anti-HBV treatment. Furthermore, due to HBV-RT/HBsAg gene-overlap, they can have an impact on HBsAg-detection and quantification.

METHODS

356 full-length HBV-RT sequences from 197 drug-naive patients and 159 patients experiencing virological-breakthrough to nucleoside/nucleotide-analogs (NUCs) were analyzed. Mutants and wild-type HBs-antigens were expressed in HuH7-hepatocytes and quantified in cell-supernatants and cell-lysates by Architect HBsAg-assay.

RESULTS

Ten novel RT-mutations (rtN53T-rtS78T-rtS85F-rtS135T-rtA181I-rtA200V-rtK212Q-rtL229V/F-rtM309K) correlated with specific NUC-treatments and classical drug-resistance mutations on divergent evolutionary pathways. Some of them reduced RT-binding affinity for anti-HBV drugs and altered S-antigen structure. Indeed, rtS78T (prevalence: 1.1% in drug-naïve and 12.2% in adefovir-failing patients) decreased the RT-affinity for adefovir more than the classical adefovir-resistance mutations rtA181 T/V (WT:-9.63 kcal/mol, rtA181T:-9.30 kcal/mol, rtA181V:-7.96 kcal/mol, rtS78T:-7.37 kcal/mol). Moreover, rtS78T introduced a stop-codon at HBsAg-position 69, and completely abrogated HBsAg-quantification in both supernatants and cell-lysates, indicating an impaired HBsAg-secretion/production. Furthermore, the HBsAg-mutation sP217L, silent in RT, significantly correlated with M204V/I-related virological-breakthrough and increased HBsAg-quantification in cell-lysate.

CONCLUSIONS

Mutations beyond those classically known can affect drug-binding affinity of mutated HBV-RT, and may have potential effects on HBsAg. Their cumulative effect on resistance and HBV-pathogenicity indicates the importance of preventing therapeutic failures.

Precore and core promoter mutants are associated with higher HBeAg seroconversion but low disease remission rates in HBV patients treated with nucleos(t)ide analogues

HBeAg seroconversion in HBV patients is considered an important event. We determined precore (PC) and base core promoter (BCP) mutations in 137 HBeAg-positive nucleos(t)ide analogues (NA) treated patients by INNO-LiPA HBV PreCore assay (Innogenetics). The majority of patients with nongenotype A had PC/BCP mutants present at baseline (P = 0.02). During 29 months of therapy, 45 patients achieved HBeAg seroconversion. Probability of HBeAg seroconversion was higher in patients with PC and/or BCP mutants (P = 0.01). After HBeAg seroconversion, patients with BCP mutants had more HBeAg relapse (P = 0.07), and PC mutants less often achieved HBV DNA < 2000 IU/mL (P = 0.07).

Clinical use of anti-TNF therapy and increased risk of infections

Biologics such as antitumor necrosis factor (anti-TNF) drugs have emerged as important agents in the treatment of many chronic inflammatory diseases, especially in cases refractory to conventional treatment modalities. However, opportunistic infections have become a major safety concern in patients on anti-TNF therapy, and physicians who utilize these agents must understand the increased risks of infection. A literature review of the published data on the risk of bacterial, viral, fungal, and parasitic infections associated with anti-TNF therapy was performed and the clinical presentation, diagnostic tests, management, and prevention of opportunistic infections in patients receiving anti-TNF therapy were reviewed. Awareness of the therapeutic potential and associated adverse events is necessary for maximizing therapeutic benefits while minimizing adverse effects from anti-TNF treatments. Patients should be adequately vaccinated when possible and closely monitored for early signs of infection. When serious infections occur, withdrawal of anti-TNF therapy may be necessary until the infection has been identified and properly treated.

Distinct evolution and predictive value of hepatitis B virus precore and basal core promoter mutations in interferon-induced hepatitis B e antigen seroconversion

Precore (PC) (G1896A) and basal core promoter (BCP) (A1762T/G1764A) mutations of the hepatitis B virus (HBV) genome often emerge in chronic hepatitis B (CHB) patients. Their roles in hepatitis B e antigen (HBeAg) seroconversion induced by interferon (IFN) therapy remain controversial, partly because quantitative analysis for these mutants is lacking. This study aimed to develop a new assay to accurately quantify the PC and BCP mutant percentages and correlate their dynamic changes with IFN-induced HBeAg seroconversion in HBeAg-positive CHB patients. The PC and BCP mutant percentages were analyzed by polymerase chain reaction (PCR)-pyrosequencing. Our results showed that this quantitative assay for PC and BCP mutants achieved high accuracy (R(2) > 0.99) within a range between 10% and 90% mutants. We examined dynamic changes of the PC and BCP mutant percentages following IFN treatment in 203 HBeAg-positive CHB patients. By multiple logistic regression analysis, we found that the chance of HBeAg seroconversion increased by 2.2% (odds ratio [OR] = 1.022, 95% confidence interval [CI]: 1.009-1.034, P = 0.001) and 2.3% (OR = 1.023, 95% CI: 1.010-1.037, P = 0.001) per 1% increase of the pretreatment PC and BCP mutant percentages, respectively, after adjustment for other predictors. However, only the pretreatment PC mutation percentage was significantly associated with HBeAg seroconversion with HBV DNA < 2,000 IU/mL (OR = 1.030, 95% CI: 1.014-1.047, P < 0.001). Furthermore, the mutant percentage of PC, but not BCP, in patients achieving HBeAg seroclearance with HBV DNA < 20,000 IU/mL increased significantly during IFN treatment (P = 0.039). Interestingly, patients with HBeAg seroconversion who had a high PC mutant percentage at the end of IFN treatment tended to exhibit high viremia after seroconversion.

CONCLUSION

Quantitative analysis of PC and BCP mutants can predict IFN-induced HBeAg seroconversion and demonstrate their distinct evolution patterns during HBeAg seroconversion. (HEPATOLOGY 2013).

Comparative analysis of CpG islands among HBV genotypes

DNA methylation is being increasingly recognized to play a role in regulation of hepatitis B virus (HBV) gene expression. The aim of this study was to compare the CpG island distribution among different HBV genotypes. We analyzed 176 full-length HBV genomic sequences obtained from the GenBank database, belonging to genotypes A through J, to identify the CpG islands in the HBV genomes. Our results showed that while 79 out of 176 sequences contained three conventional CpG islands (I–III) as previously described, 83 HBV sequences harbored only two of the three known islands. Novel CpG islands were identified in the remaining 14 HBV isolates and named as CpG island IV, V, and VI. Among the eight known HBV genotypes and two putative genotypes, while HBV genomes containing three CpG islands were predominant in genotypes A, B, D, E, and I; genotypes C, F, G, and H tended to contain only two CpG islands (II and III). In conclusion, the CpG islands, which are potential targets for DNA methylation mediated by the host functions, differ among HBV genotypes, and these genotype-specific differences in CpG island distribution could provide new insights into the understanding of epigenetic regulation of HBV gene expression and hepatitis B disease outcome.

Genetic diversity of hepatitis B virus genotypes B6, D and F among circumpolar indigenous individuals

Hepatitis B virus (HBV) infection is highly prevalent in circumpolar indigenous peoples. However, the clinical outcome is extremely variable, such that while hepatocellular carcinoma (HCC) is uncommon in Canadian Inuit, the incidence of HCC is slightly higher in Greenlanders than in Danes, and it is especially high in Alaskan Native people infected with HBV genotypes F (HBV/F) and C (HBV/C). These differences may be associated with the genomic variability of the predominant HBV genotype in each group. The purpose of this study was to determine the rate, nature and regional susceptibility of HBV genomic mutations among circumpolar indigenous individuals. Paired serum samples, separated by 5-6 years, were analysed from Canadian and Greenlandic Inuit infected with HBV genotype B6 (HBV/B6) and HBV/D, respectively, and from Alaskan Native people infected with HBV/F, each having subsequently developed HCC. Phylogenetic and mutational analyses were performed on full-genome sequences, and the dynamic evolution within the quasispecies population of each patient group was determined by clonal analysis of the non-overlapping core coding region. Mutations associated with severe outcomes predominated in HBV/F, mostly within the precore/core and PreS1 region. HBV/B6 genomes exhibited higher diversity compared to HBV/D and HBV/F, particularly within the core coding region. Thus, differing mutational profiles and genetic variability were observed among different HBV genotypes predominating in circumpolar indigenous patients. The unusual observation of persistently high genetic variability with HBV/B6 despite clinical inactivity could be due to the evolution of a host-pathogen balance, but other possible factors also need to be explored.

Precore and basal core promoter mutations in Asian American patients with hepatitis B e antigen-positive chronic hepatitis B

BACKGROUND

Prior studies have shown that precore mutations abolish and basal core promoter (BCP) mutations down-regulate hepatitis B e antigen (HBeAg) production. Thus, the presence of precore and BCP mutations in HBeAg-positive patients indicates an infection with a mixed viral population of wild-type and precore and/or BCP mutant hepatitis B virus (HBV). To date, there has been limited study of the prevalence and clinical significance of precore and BCP mutations in patients with HBeAg-positive chronic hepatitis B.

AIM

To determine the prevalence, predictors and clinical characteristics of mixed wild-type and precore/BCP HBV infection, through a cross-sectional study, in a US cohort of patients with chronic hepatitis B.

METHODS

We conducted a retrospective study of 828 chronic hepatitis B patients with HBV genotype and mutation panel testing seen at three US gastroenterology and liver clinics from June 2005 to September 2009.

RESULTS

A majority of our patients (92.3%) were either Vietnamese or Chinese American. In the HBeAg-positive cohort, 17% of patients had precore mutations only, 28% had BCP mutations only and 5% had both BCP and precore mutations. On multivariate analyses, HBV genotype C, increasing age, lower HBV DNA level and an ALT quotient >2 were independent predictors for the presence of precore and/or BCP mutations.

CONCLUSIONS

The current distinction and management recommendations for HBeAg-positive vs. HBeAg-negative patients with chronic hepatitis B should be reassessed. Additional biomarkers and treatment endpoints should be studied for their usefulness in predicting continued viral suppression after treatment discontinuation.

Antiviral treatment to prevent chronic hepatitis B or C-related hepatocellular carcinoma

Antiviral treatment is the only option to prevent or defer the occurrence of hepatocellular carcinoma (HCC) in patients chronically infected with hepatitis B virus (HBV) or hepatitis C virus (HCV). The approved medication for the treatment of chronic HBV infection is interferon-α (IFNα) and nucleos(t)ide analogues (NAs), including lamivudine, adefovir dipivoxil, telbivudine, entecavir and tenofovir disoproxil fumarate. IFNα is the most suitable for young patients with less advanced liver diseases and those infected with HBV genotype A. IFNα treatment significantly decreases the overall incidence of HBV-related HCC in sustained responders. However, side effects may limit its long-term clinical application. Orally administered NAs are typically implemented for patients with more advanced liver diseases. NA treatment significantly reduces disease progression of cirrhosis and therefore HCC incidence, especially in HBV e antigen-positive patients. NA-resistance due to the mutations in HBV polymerase is a major limiting factor. Of the NA resistance-associated mutants, A181T mutant significantly increases the risk of HCC development during the subsequent course of NA therapy. It is important to initiate treatment with NAs that have a high genetic barrier to resistance, to counsel patients on medication adherence and to monitor virological breakthroughs. The recommended treatment for patients with chronic HCV infection is peg-IFN plus ribavirin that can decrease the occurrence of HCC in those who achieve a sustained virological response and have not yet progressed to cirrhosis. IFN-based treatment is reserved for patients with decompensated cirrhosis who are under evaluation of liver transplantation to reduce post-transplant recurrence of HCV. More effective therapeutic options such as direct acting antiviral agents will hopefully increase the response rate in difficult-to-treat patients with HCV genotype 1. However, the risk of HCC remains in cirrhotic patients (both chronic HBV and HCV infection) if treatment is initiated after cirrhosis is established. Future research should focus on investigating new agents, especially for those patients with hepatic decompensation or post-transplantation.