Clonal evolution of hepatitis B virus polymerase gene mutations during lamivudine-adefovir combination treatment

AIM:To identify hepatitis B virus polymerase gene mutations during antiviral therapy using lamivudineadefovir sequential monotherapy followed by lamivudine-adefovir combination therapy.METHODS:The patient cohort included four adult chronic hepatitis B patients who had undergone sequential monotherapy,first with lamivudine(LMV) and then,after developing viral breakthrough,with adefovir(ADV) therapy.All of the patients had non-response or viral breakthrough after LMV-ADV sequential monotherapy,which resulted in the switching of their antiviral regimen to LMV-ADV combination therapy.Eleven serum samples from the four patients who showed non-response to rescue LMV-ADV combination therapy were collected sequentially at a time before the antiviral treatment and then during the LMV monotherapy,ADV monotherapy,and LMV-ADV combination therapy.For the genotypic analysis,the whole 1310-bp polymerase gene region was amplified,cloned and sequenced.RESULTS:All patients had been previously treated with 100 mg of LMV once daily for a 15-to 26-mo period.The emergence of resistance mutations to LMV,such as rtM204V/I and/or rtL180M,were found in all patients.Their antiviral regimens were switched to ADV monotherapy as the second line treatment.All patients had viral breakthrough or non-response after the LMV-ADV sequential monotherapy.ADV-resistant mutations were detected after 13 to 19 mo of LMV-ADV sequential monotherapy.The rtA181V/T mutations were predominantly identified during the ADV treatment in the LMV-resistant patients.Twenty-seven of 38 clones were combined with an amino acid change at rt181;three clones had mutations in rt236 and one clone had a combined mutation.The rtA181V/T mutations were not suppressed by the LMV-ADV combination therapy.Thirty-nine of 64 clones showed an rtA181V/T mutation and six clones showed combined mutations in rt181 and rt236.Mutations in rt204 re-emerged during the combination treatment.The rt181 and rt204 mutations did not co-exist in one clone.CONCLUSION:Add-on lamivudine therapy with adefovir for adefovir resistance may not suppress the pre-existing adefovir-resistant mutation that develops during lamivudine-adefovir sequential monotherapy.

Risk of hepatic decompensation from hepatitis B virus reactivation in hematological malignancy treatments

In this editorial,we discussed the apparent discrepancy between the findings described by Colapietro et al,in their case report and data found in the literature.Colapietro et al reported a case of hepatitis B virus(HBV)-related hepatic decompensation in a patient with chronic myeloid leukemia and a previously resolved HBV infection who was receiving Bruton’s tyrosine kinase(BTK)inhibitor therapy.First of all,we recapitulated the main aspects of the immune system involved in the response to HBV infection in order to underline the role of the innate and adaptive response,focusing our attention on the protective role of anti-HBs.We then carefully analyzed literature data on the risk of HBV reactivation(HBVr)in patients with previous HBV infection who were treated with either tyrosine kinase inhibitors or BTK inhibitors for their hematologic malignancies.Based on literature data,we suggested that several factors may contribute to the different risks of HBVr:The type of hematologic malignancy;the type of therapy(BTK inhibitors,especially second-generation,seem to be at a higher risk of HBVr than those with tyrosine kinase inhibitors);previous exposure to an anti-CD20 as first-line therapy;and ethnicity and HBV genotype.Therefore,the warning regarding HBVr in the specific setting of patients with hematologic malignancies requires further investigation.

Visualization of Gene Mutation Complicated Pattern of Hepatitis B Virus Based on Cellular Automata

Hepatitis B virus shows instantaneous and high rate mutations in biological experiments, some sorts of which affect the efficiency of virus replication greatly through enhancing or depressing the viral replication, while others have no influence at all. Taking advantage of prominent features of cellular automata, we simulate the effect of hepatitis B virus gene mutation on its replication efficiency. The computer simulation results demonstrate the feasibility of our novel model by comparing with the results of biological experiments.

Relation between hepatitis B virus genotypes and gene mutation of basic core promoter in Li nationality

Objective：To investigate the relation between hepatitis B virus（HBV） genotypes and the double mutation of A-to-T nucleotide（nt） 1762 and G-to-A nt 1764 in basic core promoter（BCP T1762/A1764） in patients of the Li nationality. Methods：Subjects were 125 HBV DNA positive patients that belong to the Li nationality on Hainan Island. HBV DNA genotype was determined by real time fluorimetry polymerase chain reaction. BCP T1762/A1764 mutation was performed using the direct sequencing method. Results：The prevalence rates of genotype B, genotype C, genotype D, genotype C and D mixed infection（genotype C＋D） and genotype B and D mixed infection （genotype B ＋C） were 31.20%, 53.60%, 12.00%, 2.40% and 0.80% respectively. Mutation frequencies in patients infected with HBV genotype C（58.21%） were significantly higher than in those infected with other genotypes （P 〈 0.01 ）. The serum viral load of the patients with genotype C（5.74_＋ 1.21） was also higher than that of those with genotype B（P 〈0.01）. Conclusion：The major genotypes in the Li nationality were genotype C and genotype B. The infection of genotype D and mixed infection also occurred in the Li nationality. Genotype C HBV has a higher replication rate, and the different degrees of pathogenecity among HBV genotypes may be related to BCP T1762/ A1764 mutation frequency.

Construction of an immune-related prognostic model to predict prognosis and immunotherapy in liver cancer patients with hepatitis B virus-infected

Background:Hepatocellular carcinoma(HCC)appears to be strongly associated with immune-related genes.However,immune-related genes are not well understood as a prognostic marker in HCC caused by the hepatitis B virus(HBV).The purpose of this study was to investigate the prognostic significance of immune-related genes in HBV-infected HCC.Methods:Gene expression data from 114 HBV-infected HCC and 50 normal tissues were integrated into The Cancer Genome Atlas.Differentially expressed immune-associated genes were analyzed to identify immune-associated differential genes associated with overall survival.Least Absolute Shrinkage and Selection Operator and multivariate Cox regressions were used to constructing immunoprognostic models.An independent prognostic factor analysis using multiple Cox regressions was also performed for HBV-infected HCCs.Immunocorrelation analysis markers and immune cell infiltration were also investigated.Results:We found 113 differentially expressed immune-associated genes.Immune-related differential genes were significantly correlated with the overall survival of HCC patients.We constructed an immune-based prognostic model using multivariate Cox regression analysis including seven immune-related genes.According to further analysis,immune-related prognostic factors may serve as independent prognostic indicators in the clinical setting.There is also evidence that the 7-gene prognostic model reflects the tumor immune microenvironment as a result of the risk score model and immune cell infiltration.Conclusions:As a result of our study,we screened immune-related genes for prognosis in HBV-infected HCC and developed a novel immune-based prognostic model.The research not only provides new prognostic biomarkers but also offers insight into the tumor immune microenvironment and lays the theoretical groundwork for immunotherapy.

EFFECTS OF MUTATIONS IN THE POLYMERASE GENE OF HEPATITIS B VIRUS GENOME ON LAMIVUDINETHERAPY

Objective To explore the offects of mutations in tyrosine-methionine-aspartic acid-aspartic acid (YMDD) motif of the polymerase in the hepatitis B virus (HBV) genome on lamivudine antiviral therapy. Methods Partial HBV DNA segment containing the YMDD motif in the P gene wes obtained through amplifi- cation by polymerase chain reaction (PCR )from 19 chronic hepatitis B patients with serum HBV DNA positive at the 48th week treatment with lamivudine and subjected to automatic sequencing. Influences of vartants with YMDD mutations on lamivudine therapy were seen by observing the dynamic changes of serum HBV DNA and ALT levels. Results Serum HBV DNA breakthrough was found in 3 out of 10 individuals with detection of the YMDD mutations at the 48th week and in 5 at the 52th week, 2 of the 5 patients accompanied by serum ALT re-elevation, whereas of 9 subjects without YMDD mutations, 2 experenced an HBV DNA breakthrough at the 48th week and 1 of them had a conversion from HBV DNA positive DNA positive to negative at the 52th week. Patients with detectable HBV DNA level had a fluctuating level of serum ALT all time during the treatment. Conclusion Detection of mutations in the YMDD motif of polymerase gene in HBV genome during the lamivudine therapy will be helpful to monitoring its therapeutic outcomes.

Expression of hepatitis B virus genes in early embryonic cells originated from hamster ova and human spermatozoa transfected with the complete viral genome

Aim： To detect the expression of hepatitis B virus （HBV） genes （HB S and C genes） in early embryonic cells after introducing motile human sperm carrying HBV DNA into zona-free hamster oocytes via the in vitro fertilization （IVF） technique. Methods： Human sperm-mediated HBV genes were delivered into zona-free hamster oocytes by the IVF method. Polymerase chain reaction （PCR） was used to detect HB S and pre-Core/Core （pre-C/C） coding genes both in one- and two-cell embryos. Reverse transcription-PCR （RT-PCR） analysis was used to study the expression of the two genes. Fluorescence in situ hybridization （FISH） analysis using the full-length HBV DNA as the hybridization probe was performed to confirm the integration of viral DNA in the host embryonic genome. Results： Both HB S and pre-C/C coding genes are present and transcribed in one- and two-cell embryos originated from hamster ova IVF with human spermatozoa carrying HBV DNA sequences. Conclusion： Sperm-mediated HBV genes are able to replicate and express themselves in early embryonic cells. These results provide direct evidence that HBV DNA could transmit vertically to the next generation via the male germ line.

Overview of hepatitis B virus mutations and theirimplications in the management of infection

Hepatitis B virus(HBV)affects approximately two billion people worldwide and more than 240 million people in the world are currently chronic carrier that could develop serious complications in the future,like liver cirrhosis and hepatocellular carcinoma.Although an extended HBV immunization program is being carried out since the early‘80s,representing effective preventive measure,leading to a dramatic reduction of HBV hepatitis incidence,globally HBV infection still represents a major public health problem.The HBV virus is a DNA virus belongs to the Hepadnaviridae family.The HBV-DNA is a circular,partial double strand genome.All coding information is on the minus DNA strand and it is organized into four open reading frames.Despite hepatitis B virus is a DNA virus,it has a high mutation rate due to its replicative strategy,that leads to the production of many nonidentical variants at each cycle of replication.In fact,it contains a polymerase without the proofreading activity,and uses an RNA intermediate(pg RNA)during its replication,so error frequencies are comparable to those seen in retroviruses and other RNA viruses rather than in more stable DNA viruses.Due to the low fidelity of the polymerase,the high replication rate and the overlapping reading frames,mutations occur throughout the genome and they have been identified both in the structural and not structural gene.The arise of mutations being to develop of a whole of viral variants called"quasi-species"and the prevalent population,which favors virus replication,was selected by viral fitness,host’s immune pressure and external pressure,i.e.,vaccination or antiviral therapy.Naturally occurring mutations were found both in acute and chronic subjects.In the present review we examine and discuss the most recent available data about HBV genetic variability and its significance.

Gene heterogeneity of hepatitis B virus isolates from patients with severe hepatitis B

BACKGROUND: The pathogenesis of severe hepatitis B remains unknown. Reports have indicated that hepatitis B virus (HBV) mutations are important factors in the pathogenesis of this disease. This study was to investigate the genetic heterogeneity of HBV strains from serum samples of patients with fulminant hepatitis B. METHODS: Full-length HBV genomes from 4 patients with severe hepatitis B were cloned and sequenced to observe mutations in every open reading-frame ( ORF). Serum samples of another 25 patients with severe hepatitis B, 30 patients with chronic hepatitis B, and 25 HBV carriers were collected for sequencing and comparison of mutations in preS2, preC and core promoter regions. RESULTS: Of 4 HBV full-length genome sequences, 3 had a G to A mutation at nucleotide A1896 in the preC region and 1 had double mutations of T1762-A1764 in the core promoter region. The 4 sequences showed mutations in the known B or T cell epitopes of the preS2 and C regions. For the other 3 groups, more mutations were seen in the preS2 region in the HBV isolates from the patients with severe hepatitis B than those from the patients with chronic hepatitis B and HBV carriers (P <0.01). There was a significant difference of mutations in the T cell epitope region of preS2 between the patients with severe hepatitis B and those with chronic hepatitis B or HBV carriers (P <0.01). In the preC and core promoter regions, the mutation frequencies of T1653 and C1753 were 48.0% and 24.0% respectively in the patients with severe hepatitis B, but none of these mutations were observed in the patients with chronic hepatitis B group or HBV carriers (P <0.01). The mutation frequency of T1762-A1764 was 76.0% in the patients with severe hepatitis B, 40.0% in the patients with chronic hepatitis B (P <0. 01) , and 16. 0% in the HBV carriers ( P < 0. 01). There was a significant difference in A1896 mutation between the patients with severe hepatitis B and the patients with chronic hepatitis B (P < 0. 05 ) or the HBV carriers (P<0.05). CONCLUSION: Our observations suggest that the accumulation and persistence of high frequency mutations or complex mutations may be associated with the development and deterioration of HBV infection.

Preliminary study on the production of transgenic mice harboring hepatitis B virus X gene

AIM To establish transgenic mice lineage xharboring hepatitis B virus X gene and to provide an efficient animal model for studying the exact role of the HBx gene in the process of hepatocarcinogenesis. METHODS The HBx transgenic mice were produced by microinjecting the construct with X gene of HBV (subtype adr) DNA fragment into fertilized eggs derived from inbred C57 BL/6 strain; transgenic mice were identified by using Nested PCR; expression and phenotype of HBx gene were analyzed in liver from transgenic mice at the age of 8 weeks by RT PCR, pathologic examination and periodic acid schiff staining (PAS), respectively. RESULTS Five hundred and fourteen fertilized eggs of C57 BL/6 mice were microinjected with recombinant retroviral DNA fragment, and 368 survival eggs injected were transferred to the oviducts of 18 pseudopregnant recipient mice, 8 of them became pregnant and gave birth to 20 F1 offspring. Of 20 offsprings, four males and two females carried the hybrid gene (HBx gene). Four male mice were determined as founder, named X1, X5, X9 and X15. These founders were back crossed to set up F1 generations with other inbred C57BL/6 mice or transgenic littermates, respectively. Transmission of HBx gene in F1 offspring of X1, X5 and X9 except in X15 followed Mendelian rules. The expression of HBx mRNA was detected in liver of F1 offspring from the founder mice (X1 and X9), which showed vacuolation lesion and glycogen positive foci. CONCLUSION Transgenic mice harboring HBx gene were preliminarily established.

Detection of hyper-conserved regions in hepatitis B virus X gene potentially useful for gene therapy

AIM To detect hyper-conserved regions in the hepatitis B virus(HBV) X gene(HBX) 5' region that could be candidates for gene therapy.METHODS The study included 27 chronic hepatitis B treatmentnaive patients in various clinical stages(from chronic infection to cirrhosis and hepatocellular carcinoma, both HBeA g-negative and HBeA g-positive), and infected with HBV genotypes A-F and H. In a serum sample from each patient with viremia > 3.5 log IU/m L, the HBX 5' end region [nucleotide(nt) 1255-1611] was PCRamplified and submitted to next-generation sequencing(NGS). We assessed genotype variants by phylogenetic analysis, and evaluated conservation of this region by calculating the information content of each nucleotide position in a multiple alignment of all unique sequences(haplotypes) obtained by NGS. Conservation at the HBx protein amino acid(aa) level was also analyzed.RESULTS NGS yielded 1333069 sequences from the 27 samples, with a median of 4578 sequences/sample(2487-9279, IQR 2817). In 14/27 patients(51.8%), phylogenetic analysis of viral nucleotide haplotypes showed a complex mixture of genotypic variants. Analysis of the information content in the haplotype multiple alignments detected 2 hyper-conserved nucleotide regions, one in the HBX upstream non-coding region(nt 1255-1286) and the other in the 5' end coding region(nt 1519-1603). This last region coded for a conserved amino acid region(aa 63-76) that partially overlaps a Kunitz-like domain.CONCLUSION Two hyper-conserved regions detected in the HBX 5' end may be of value for targeted gene therapy, regardless of the patients' clinical stage or HBV genotype.

Key role of hepatitis B virus mutation in chronic hepatitis B development to hepatocellular carcinoma

Chronic hepatitis B virus(HBV) infection is a major risk factor for hepatocellular carcinoma(HCC). The HBV mutations, which include point mutation, deletion,insertion and truncation mutation of HBV gene in 4 open reading frames(S, C, P, X), are closely associated with HCC pathogenesis. Some mutations accumulated during chronic HBV infection could be regarded as a biomarker to predict the occurrence of HCC. The detection of the mutations in clinical practice could be helpful for defining better preventive and therapeutic strategies and, moreover, predicting the progression of liver disease.

Clinical utility of complex mutations in the core promoter and proximal precore regions of the hepatitis B virus genome

The core promoter and proximal precore regions are the most complex portions of the hepatitis B virus(HBV) genome. These regions cooperatively regulate viral replication and differentially regulate the synthesis of the viral proteins E,core,and X. Multiple mutations in these regions are associated with the persistency of viral infection and the development of cirrhosis and hepatocellular carcinoma(HCC). In South Korea,nearlyall HBVs are classified as HBV genotype C2; the majority of these viruses have the basal core promoter double mutation,a precore stop mutation,or both. These mutations may play a role in the alteration of viral and clinical features,and abundant and complex mutations are particularly prevalent in the core promoter and proximal precore regions. We previously demonstrated that the accumulation of ≥ 6 mutations at eight key nucleotides located in these regions(G1613A,C1653 T,T1753 V,A1762 T,G1764 A,A1846 T,G1896 A,and G1899A) is a useful marker to predict the development of HCC regardless of advanced liver disease. In addition,certain mutation combinations were predominant in cases with ≥ 4 mutations. In cases with ≤ 5 mutations,a low Hepatitis B e antigen titer(< 35 signal to noise ratio) was indicative of HCC risk. Viral mutation data of the single HBV genotype C2 suggest that the combined effect of the number and pattern of mutations in the core promoter and proximal precore regions is helpful in predicting HCC risk.

Characterization of hepatitis B virus X gene quasispecies complexity in mono-infection and hepatitis delta virus superinfection

Hepatitis delta virus(HDV) seems to strongly suppress hepatitis B virus(HBV)replication, although little is known about the mechanism of this interaction. Both these viruses show a dynamic distribution of mutants, resulting in viral quasispecies. Next-generation sequencing is a viable approach for analyzing the composition of these mutant spectra. As the regulatory hepatitis B X protein(HBx) is essential for HBV replication, determination of HBV X gene(HBX)quasispecies complexity in HBV/HDV infection compared to HBV monoinfection may provide information on the interactions between these two viruses.AIM To compare HBV quasispecies complexity in the HBX 5' region between chronic hepatitis delta(CHD) and chronic HBV mono-infected patients.METHODS Twenty-four untreated patients were included: 7/24(29.2%) with HBeAgnegative chronic HBV infection(CI, previously termed inactive carriers), 8/24(33.3%) with HBeAg-negative chronic hepatitis B(CHB) and 9/24(37.5%) with CHD. A serum sample from each patient was first tested for HBV DNA levels.The HBX 5' region [nucleotides(nt) 1255-1611] was then PCR-amplified for subsequent next-generation sequencing(MiSeq, Illumina, United States). HBV quasispecies complexity in the region analyzed was evaluated using incidencebased indices(number of haplotypes and number of mutations), abundancebased indices(Hill numbers of order 1 and 2), and functional indices(mutation frequency and nucleotide diversity). We also evaluated the pattern of nucleotide changes to investigate which of them could be the cause of the quasispecies complexity.RESULTS CHB patients showed higher median HBV-DNA levels [5.4 logIU/mL,interquartile range(IQR) 3.5-7.9] than CHD(3.4 logIU/mL, IQR 3-7.6)(P = n.s.)or CI(3.2 logIU/mL, IQR 2.3-3.5)(P < 0.01) patients. The incidence and abundance indices indicated that HBV quasispecies complexity was significantly greater in CI than CHB. A similar trend was observed in CHD patients, although only Hill numbers of order 2 showed statistically significant differences(CHB2.81, IQR 1.11-4.57 vs CHD 8.87, 6.56-11.18, P = 0.038). There were no significant differences in the functional indices, but CI and CHD patients also showed a trend towards greater complexity than CHB. No differences were found for any HBV quasispecies complexity indices between CHD and CI patients. G-to-A and C-to-T nucleotide changes, characteristic of APOBEC3 G, were higher in CHD and CI than in CHB in genotype A haplotypes, but not in genotype D. The proportion of nt G-to-A vs A-to-G changes and C-to-T vs T-to-C changes in genotype A and D haplotypes in CHD patients showed no significant differences. In CHB and CI the results of these comparisons were dependent on HBV genotype.CONCLUSION The lower-replication CHD and CI groups show a trend to higher quasispecies complexity than the higher-replication CHB group. The mechanisms associated with this greater complexity require elucidation.

Host cellular micro RNA involvement in the control of hepatitis B virus gene expression and replication

A large number of studies have demonstrated that the synergistic collaboration of a number of micro RNAs(mi RNAs), their growth factors and their downstream agents is required for the initiation and completion of pathogenesis in the liver. mi RNAs are thought to exert a profound effect on almost every aspect of liver biology and pathology. Accumulating evidence indicates that several mi RNAs are involved in the hepatitis B virus(HBV) life cycle and infectivity, in addition to HBVassociated liver diseases including fibrosis, cirrhosis and hepatocellular carcinoma(HCC). In turn, HBV can modulate the expression of several cellular mi RNAs, thus promoting a favorable environment for its replication and survival. In this review, we focused on the involvement of host cellular mi RNAs that are directly and indirectly associated with HBV RNA or HBV associated transcription factors. Exploring different facets of the interactions among mi RNA, HBV and HCV infections, and the carcinogenesis and progress of HCC, could facilitate the development of novel and effective treatment approaches for liver disease.

Precore/core region mutations of hepatitis B virus related to clinical severity

Despite the availability of an effective vaccine, hepatitis B virus (HBV) infection remains a major health problem, with more than 350 million chronically infected people worldwide and over 1 million annual deaths due to cirrhosis and liver cancer. HBV mutations are primarily generated due both to a lack of proofreading capacity by HBV polymerase and to host immune pressure, which is a very important factor for predicting disease progression and therapeutic outcomes. Several types of HBV precore/core (preC/C) mutations have been described to date. The host immune response against T cells drives mutation in the preC/C region. Specifically, preC/C mutations in the MHC class II restricted region are more common than in other regions and are significantly related to hepatocellular carcinoma. Certain mutations, including preC G1896A, are also significantly related to HBeAg-negative chronic infection. This review article mainly focuses on the HBV preC/C mutations that are related to disease severity and on the HBeAg serostatus of chronically infected patients.

Upreguiation of human telomerase reverse transcriptase mRNA expression by in vitro transfection of hepatitis B virus X gene into human hepatocarcinoma and cholangiocarcinoma cells

AIM： To study the changes of human telomerase reverse transcriptase （hTERT） mRNA expression in human hepatocarcinoma cell lines （HepG2） and cholangiocarcinoma cell lines （QBC939） after HBx gene transfection and to illustrate the significance of transcriptional regulation of hTERT gene by HBx gene in the carcinogenesis. METHODS： HepG2 and QBC939 cell lines were cultured and co-transfected with eukaryotic expression vector containing the HBx coding region and cloning vector containing enhanced green fluorescent protein （EGFP） coding sequence using lipid-mediated gene transduction technique. Thirty-six hours after transfection, EGFP expression in cells was used as the indicator of successful transfection. Flow cytometry was performed to determine the transfection efficiency. Cells were harvested and total RNA was extracted using TRIzol reagent. The expression of hTERT mRNA in HepG2 and QBC939 cell lines was assayed by reverse transcriptionpolymerase chain reaction. The expression of HBx protein in both cell lines was detected by immunocytochemical staining and Western blotting. RESULTS： Flow cytometry showed that the transfection efficiency was 46.4% in HepG2 cells and 29.6% in QBC939 cells for both HBx gene expression vector and blank vector. The expression of hTERT mRNA was meaningfully increased in HepG2 and QBC939 cell lines when transfected with HBx gene expression vector compared to those transfected with OPTI-MEM medium and blank vector. Immunocytochemical staining and Western blotting revealed HBx protein expression in HepG2 and QBC939 cells only when transfected with HBx gene. CONCLUSION： HBx gene transfection can upregulate the transcriptional expression of hTERT mRNA. The transactivation of hTERT gene by HBx gene is a newfound mechanism for pathogenesis of hepatocarcinomas and cholangiocarcinomas after HBV infection. 2005 The WJG Press and Elsevier Inc. All rights reserved

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.

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=l.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 AI762T/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.

X region mutations of hepatitis B virus related to clinical severity

Chronic hepatitis B virus (HBV) infection remains a major health problem, with more than 240 million people chronically infected worldwide and potentially 650000 deaths per year due to advanced liver diseases including liver cirrhosis and hepatocellular carcinoma (HCC). HBV-X protein (HBx) contributes to the biology and pathogenesis of HBV via stimulating virus replication or altering host gene expression related to HCC. The HBV X region contains only 465 bp encoding the 16.5 kDa HBx protein, which also contains several critical cis-elements such as enhancer II, the core promoter and the microRNA-binding region. Thus, mutations in this region may affect not only the HBx open reading frame but also the overlapped cis-elements. Recently, several types of HBx mutations significantly associated with clinical severity have been described, although the functional mechanism in most of these cases remains unsolved. This review article will mainly focus on the HBx mutations proven to be significantly related to clinical severity via epidemiological studies.