Current pharmacotherapy for the treatment of chronic hepatitis B

Correlation between hepatitis B virus genotypes and clinical outcomes

Hepatitis B virus (HBV) has been classified into 10 genotypes (A-J) according to genome sequence divergence. HBV genotypes have a distinct geographical distribution. As chronic HBV infection is endemic in the Asian region, genotypes B and C prevail there, and genotypes A and D are mainly found in the western world and Europe. Genotypes A, B, C, and D have been studied most extensively. In Europe and Asia, most patients with genotypes A and B have acute hepatitis B; however, some mutants may tend to cause fulminant hepatitis B. Many studies have indicated that the severity and outcomes of chronic hepatitis B infections are more serious in patients with genotypes C and D than in those with genotypes A and B. Cirrhosis and hepatocellular carcinoma (HCC) are more frequently diagnosed in carriers of genotypes C and D than in those of genotypes A and B. Accumulating evidence indicated that higher plasma HBV DNA levels, infection with HBV genotype C, as well as mutations at 1653T, 1753V, and A1762T/G1764A are independently associated with the risk of HCC in Asian men. However, the therapeutic responses differ with regard to the different HBV genotypes. For example, the response to interferon-α treatment in patients with genotypes A and B was better than that in patients with genotypes C, D, and mixed genotypes. Some studies have shown seroconversion after treatment, i.e., genotypes A and C may switch to genotypes D and B, respectively. Some reports indicated a correlation between the emergence of the hepatitis B e antigen-negative variant in patients with genotypes C and D and worsening of liver injury without sustained response. In order to provide better treatment options for these poorly responding patients, further studies, e.g, novel immunomodulatory therapies, are required. Many studies have shown that HBV genotypes have remarkable clinical and epidemical differences; however, HBV sub-genotypes, mixed genotype infections, and the effect of different genotypes on the treatment of HBV infections require further studies.

A novel model for evaluating the risk of hepatitis B recurrence after liver transplantation

BACKGROUND

Hepatitis B virus (HBV) recurrence is a major risk factor affecting the long-term survival of recipients for liver transplantation (LTx). Therefore, a model that can assess this risk before transplantation is highly desirable.

METHODS

One hundred and eighty-five consecutive liver transplant recipients because of HBV-related end-stage liver diseases were selected. Their perioperative laboratory examination results, treatment protocol and the status of HBV recurrence were the primary parameters used to assess their risk of post-transplant HBV recurrence. A model that may be generally used to evaluate the risk of post-transplant HBV recurrence was thus established. A cohort for further validation and a cross-validation were designed.

RESULTS

After a follow-up time of 26.0 ± 10.8 months, the overall HBV recurrence rate was 8.6%. The 1-, 2- and 3-year cumulative survival rates were 98.5, 89.2 and 83.4% respectively. By correlation with the pretransplant presence of hepatocelluar carcinoma (HCC), serum HBV DNA level and status of antiviral treatment (AVT), the risk assessment model can be summarized using the following equation: RISK=-4.378 + 1.493 × HCC + 1.286 × DNA - 2.426 × AVT. The HBV recurrence rate and survival were found to be significantly different between the recipients with risk scores ≤-2.8 and >-2.8. The model was well validated in this work.

CONCLUSIONS

Pretransplant HBV DNA level, presence of HCC, AVT status and post-transplant viral mutation were identified as the major risk factors associated with HBV recurrence after LTx. A novel model incorporating these factors could effectively evaluate the risk of post-transplant HBV recurrence before transplantation.

Lamivudine and interferon versus lamivudine monotherapy for HBeAg-positive hepatitis B treatment: a meta-analysis of randomized, controlled trials

The suboptimal outcomes of current chronic hepatitis B treatments have prompted the notion of combination therapy as a means of augmenting the therapeutic response. In this study, investigators compared lamivudine monotherapy versus its combination with conventional or pegylated interferon-alpha, pooling data from all pertinent randomized controlled studies into the meta-analysis. The studies were evaluated for methodologic quality and heterogeneity. Rates of sustained virologic and biochemical responses and of hepatitis B e antigen clearance and seroconversion were used as primary efficacy measures. Quantitative metaanalyses were conducted to assess differences between groups for conventional and pegylated interferon, and overall. Analysis yielded greater sustained virologic, biochemical, and seroconversion rates with the addition of conventional (odds ratio [OR]=4.5, 95% confidence interval [CI]=2.2-9.4, P<.001; OR=2.1, 95% CI=1.3-3.2, P=.002; and OR=2.6, 95% CI=1.4-4.8, P=.001, respectively) and pegylated (OR=2.0, 95% CI=1.1-3.6, P=.02; OR=1.8, 95% CI=1.3-2.6, P<.001; and OR=1.6, 95% CI=1.1-2.3, P=.03, respectively) interferon-alpha to lamivudine, with the former also yielding greater hepatitis B e antigen clearance rates (OR=2.6, 95% CI=1.3-5.2, P=.008). As previous studies suggested that pegylated interferon monotherapy and its combination with lamivudine were comparable, the use of this combination is not justified. In contrast, when conventional interferon-a is used, its combination with lamivudine should be considered.

Hepatitis B: the pathway to recovery through treatment

Hepatitis B is a major public health problem in the world today. Since 1985, the number of reported cases has declined as a direct result of universal immunization of neonates, vaccination of at-risk populations, lifestyle or behavioral changes in high-risk groups, refinements in the screening of blood donors, and the use of virally inactivated or genetically engineered products in patients with bleeding disorders. New and potent antiviral agents being developed and evaluated provide hope and optimism for those who are chronically infected with hepatitis B virus. Prevention remains the most effective strategy in the global management of hepatitis B virus. Universal immunization programs prevent hepatitis B virus transmission and circumvent acute and chronic infection.

Genotypic resistance to lamivudine among hepatitis B virus isolates in Mexico

BACKGROUND

Drug resistance of hepatitis B virus (HBV) is an increasing clinical problem. Resistance to lamivudine in HBV isolates in Mexico has been poorly explored.

OBJECTIVES

To characterize the mutation patterns associated with genotypic resistance to lamivudine and their prevalence among HBV isolates in Mexico.

MATERIAL AND METHODS

Thirty-nine Mexican HBV isolates were analysed by PCR and line probe assay for detection of genetic variants in the polymerase open reading frame domains B and C (INNO-LiPA HBV DR; INNOGENETICS N. V., Ghent, Belgium). This assay detects wild-type and mutations at codons 180, 204 and 207 of the HBV polymerase gene, and at codon positions 171, 172, 195, 196, 198 and 199 of the HBV surface antigen (HBsAg). HBV isolates were obtained from HBsAg-positive serum samples of 15 chronic hepatitis patients, two haemodialysis patients with chronic HBV carriage, 20 men found positive for HBsAg when seeking HIV testing and two AIDS patients with chronic HBV infection. None of the participants had received antiviral therapy.

RESULTS

Overall, HBV wild-type was found in 37 (94.9%) out of the 39 isolates studied. Two (5.1%) out of the 39 isolates showed mixed wild-type and mutant populations. These mutations occurred in isolates from one hepatitis patient and one haemodialysis patient. The isolate from the hepatitis patient showed a double mutation at codon positions 180 (L180M) and 204 (M204V), thus a 2.6% prevalence of genotypic resistance to lamivudine was found. The isolate from the haemodialysis patient showed a single mutation at codon position 180 (L180M). The two HBV mutant isolates were further analysed for genotype and both isolates were genotype H.

CONCLUSIONS

HBV genotypic resistance to lamivudine exists in Mexican isolates. The results highlight the importance of testing for HBV resistance before treatment and have implications for a more rational use of drugs.

Cloning and characterization of a novel hepatitis B virus core binding protein C12

AIM: To elucidate the biological function of HBV core antigen (HBcAg) on pathogenesis of hepatitis B, a novel gene C12 coding for protein with unknown function interacting with HBcAg in hepatocytes was identified and characterized.

METHODS: HBcAg bait plasmid pGBKT7-HBcAg was constructed and transformed into yeast AH109, then the transformed yeast was mated with yeast Y187 containing liver complementary DNA (cDNA) library plasmid in 2×YPDA medium. Diploid yeast was plated on synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) and synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) containing X-α -gal for screening twice. After extracting and sequencing of plasmid from blue colonies, we isolated a cDNA clone encoding a novel protein designated as C12 that directly interacted with HBcAg. The interaction between HBcAg and C12 was verified again by re-mating. pEGFP-N1-C12 fluorescent protein fusion gene was transfected in 293 and L02 cell, and observed by fluorescent microscope. MTT reduction assay was used to study the action of C12 protein effect on metabolism of mammal cell. Yeast two-hybrid and cDNA microarray were performed to search binding protein and differential expression genes regulated by C12 protein.

RESULTS: C12 gene was screened and identified by yeast two-hybrid system 3. The interaction between HBcAg and the novel protein coded by the new gene C12 was further confirmed by re-mating. After 48 h, fluorescence of fusion protein could be observed steadily in the 293 and L02 cell plasma. Under MTT assay, we found that the expression of C12 did not influence the growth of liver cells. Seventeen differential expression genes in HepG2 cells transfected with C12 protein expression plasmid by cDNA microarray, of which 16 genes were upregulated and 1 gene was downregulated by C12 protein. Twenty-one colonies containing 16 different genes coding for C12 protein binding proteins were isolated by yeast two-hybrid, there were 2 new genes with unknown function.

CONCLUSION: The novel protein C12 is located in cell plasma, and its overexpression has no significant effect on the metabolism of liver cell. It interacts with many proteins in hepatocytes and may be involved in many processes of gene expression.

Fatal exacerbation of peripheral neuropathy during lamivudine therapy: evidence for iatrogenic mitochondrial damage

A 57-year-old man with mild neuropathy who was positive for hepatitis B and C viruses was treated with lamivudine 300 mg.day(-1). After 3 months he presented with dysphonia and progressive muscle weakness. Subsequently, he developed tetraparesis followed by acute respiratory failure requiring mechanical ventilation, which was complicated by sudden cardiac arrest. After lamivudine was stopped, the neuropathy improved and respiratory capacity improved. Unfortunately, the patient died suddenly in spite of haemodynamic, ventilatory and metabolic support. Electrophysiological studies showed evidence of a sensory-motor axonal neuropathy. Nerve biopsy, muscle biopsy, biochemistry and mitochondrial DNA molecular genetics suggested possible widespread iatrogenic mitochondrial damage. Mitochondrial DNA dysfunction could be a potential cause of the sudden cardiac arrest. Stopping lamivudine treatment sooner after the onset of peripheral neuropathy or its exacerbation is important as continued therapy could lead to acute respiratory failure requiring mechanical ventilation and intensive care unit admission.

Chronic Hepatitis B and Viral Genotype: The Clinical Significance of Determining HBV Genotypes

The global health challenge posed by the hepatitis B virus (HBV) centres around the widespread distribution and the serious complications as a result of persistent infection with the virus. As with other chronic diseases mediated by pathogens such as human immunodeficiency virus (HIV) and hepatitis C virus (HCV), clinicians are searching for epidemiological, pathological and viral characteristics of HBV infection that may lead to more effective management of patients with chronic infection. Unlike HCV, the role of HBV genotype in disease progression, severity, response to therapy and drug resistance is still under investigation and just beginning to be clarified. This review examines the potential role of HBV genotype determination in the clinic with emphasis on how this genetic information may used to provide effective management for the treatment of patients with chronic hepatitis B.

YMDD variants of HBV DNA polymerase gene: Rapid detection and clinicopathological analysis with long-term lamivudine therapy after liver transplantation

AIM: To look for a rapid low-cost technique for the detection of HBV variants.

METHODS: Two patients who underwent orthotopic liver transplantation (OLT) for HBV infection were treated with lamivudine (100 mg daily) and HBV infection recurred in the grafted livers. The patients were monitored intensively for liver enzymes, hepatitis B surface antigen (HBsAg) and HBV DNA in serum. Liver biopsy was performed regularly. HBV DNA in a conserved polymerase domain (the YMDD locus) was amplified from serum of each patient by PCR and sequenced. HBV genotypes were analyzed by restriction fragment length polymorphism (RFLP) of the PCR products generated from a fragment of the polymerase gene.

RESULTS: YMDD wild-type HBV was detected in one patient by PCR-RFLP and DNA sequencing 19 mo after OLT, and YIDD mutant-type HBV in the other patient, 16 mo after OLT.

CONCLUSION: PCR-RFLP assay is an accurate and simple method for genotyping lamivudine-resistant HBV variants.

Global epidemiology of hepatitis B virus

The burden of hepatitis B virus (HBV) disease and efforts to control infection will determine the future size of the population requiring treatment of HBV infection. To quantify the current prevalence of HBV infection and to reexamine the epidemiology of HBV infection, a structured review was conducted that focused on available primary literature for over 30 countries worldwide. The prevalence of chronic HBV infection continues to be highly variable, ranging over 10% in some Asian and Western Pacific countries to under 0.5% in the United States and northern European countries. The current global estimate of the number of HBV infected individuals is 350 million. Routes of transmission include vertical (mother to child or generation to generation through close contact and sanitary habits), early life horizontal transmission (through bites, lesions, and sanitary habits), and adult horizontal transmission (through sexual contact, intravenous drug use, and medical procedure exposure) and are evident to varying degrees in every country. Younger age at acquisition of infection continues to be the most important predictor of chronic carriage. However, the choice of serologic markers, temporal influences, and representativeness of the study population limit comparability of HBV seroprevalence results. HBV vaccination programs will decrease the future global burden of HBV infection and evidence of reduced burden is mounting in country-specific populations, but vaccination programs have still not been implemented in all countries, thereby maintaining reservoirs of infection and continued HBV transmission. Regardless of vaccination, large numbers of persons are infected with HBV or will become infected. Preventing the most severe HBV disease consequences in infected individuals, such as cirrhosis and hepatocellular carcinoma, will require appropriate therapeutic agents.

Antiviral therapy for treatment-naïve hepatitis B virus patients

Hepatitis B virus infection is a major public health problem worldwide,responsible for considerable morbidity and mortality from chronic liver disease. It is estimated that there are 350 million hepatitis B virus carriers globally. The prevalence of chronic hepatitis B infection varies greatly in different regions of the world. In the United States, approximately 1.5 million people are infected and 50,000 to 100,000 new cases are reported annually despite the availability of effective vaccines. This article reviews various antiviral therapies for treatment naïve hepatitis B virus patients.

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