Risk of hepatitis B virus reactivation in cancer patients undergoing treatment with tyrosine kinase-inhibitors

This editorial commented on an article in the World Journal of Gastroenterology titled“Risks of Reactivation of Hepatitis B Virus in Oncological Patients Using Tyrosine Kinase-Inhibitors:Case Report and Literature Analysis”by Colapietro et al.In this editorial,we focused on providing a more comprehensive exploration of hepatitis B virus reactivation(HBVr)associated with the usage of tyrosine kinase inhibitors(TKIs).It includes insights into the mechanisms underlying HBV reactivation,the temporal relationship between TKIs and HBV reactivation,and preventive measures.The aim is to understand the need for nucleos(t)ide analogs(NAT)and serial blood tests for early recognition of reactivation and acute liver injury,along with management strategies.TKIs are considered to be an intermediate(1%-10%)of HBVr.Current guidelines stipulate that patients receiving therapy with high or moderate risks of reactivation or recent cancer diagnosis must have at least tested hepatitis B surface antigen,anti-hepatitis B core antigen(HBc),and anti-hepatitis B surface antibody.Anti-HBc screening in highly endemic areas means people with negative tests should be vaccinated against HBV.Nucleoside or nucleotide analogs(NAs)like entecavir(ETV),tenofovir disoproxil fumarate(TDF),and tenofovir alafenamide(TAF)form the basis of HBV reactivation prophylaxis and treatment during immunosuppression.Conversely,lamivudine,telbivudine,and adefovir are generally discouraged due to their reduced antiviral efficacy and higher risk of fostering drug-resistant viral strains.However,these less effective NAs may still be utilized in cases where ETV,TDF,and TAF are not feasible treatment options.

Effects of two novel nucleoside analogues on different hepatitis B virus promoters

AIM： To explore the effects of the nucleoside analogues β-L-D4A and β-LPA on hepatitis B virus （HBV） promoters. METHODS： Four HBV promoters were amplified by polymerase chain reaction （PCR） and subcloned into the expression vector pEGFP-1. The four recombinants controlled by HBV promoters were confirmed by restriction analysis and sequencing. Human hepatoma HepG2 cells transfected with the recombinant plasmids were treated with various concentrations of β-L-D4A and β-LPA. Then, enhanced green fluorescent protein （EGFP）-positive cells were detected by fluorescence microscopy and using a fluorescence activated cell sorter RESULTS： Four HBV promoters were separately obtained and successfully cloned into pEGFP-1, Expression of EGFP under the control of the surface promoter （Sp） and the X promoter （Xp） was inhibited by β-L-D4A in a dosedependent manner, while expression of EGFP under the control of the core promoter （Cp） and Xp was inhibited by β-LPA in a dose-dependent manner. CONCLUSION： The two novel nucleoside analogues investigated here can inhibit the activities of HBV promoters in a dose-dependent manner. These findings may explain the mechanisms of action by which these two novel compounds inhibit HBV DNA replication.

慢性乙型肝炎患者接受核(苷)酸类似物抗病毒治疗后血清HBV-DNA的表达及临床意义

目的探讨慢性乙型肝炎(CHB)患者接受核(苷)酸类似物(NAs)抗病毒治疗后血清乙型肝炎病毒脱氧核糖核酸(HBV-DNA)的表达及临床意义。方法回顾性分析2021年1月至2022年10月河南省人民医院83例采用NAs抗病毒治疗的CHB患者临床资料,根据血清学应答标准将其分为应答组(46例)和未应答组(37例)。比较两组基线资料、治疗前及治疗3、6、12个月时血清HBV-DNA水平;绘制受试者工作特征(ROC)曲线,以曲线下面积(AUC)检验血清HBV-DNA对CHB患者NAs抗病毒治疗未应答的预测价值。结果治疗前,应答组和未应答组HBV-DNA比较,差异无统计学意义(P>0.05);两组治疗前至治疗12个月的HBV-DNA呈下降趋势,组间、时点、交互效应有统计学意义(P<0.05)。绘制ROC曲线显示,治疗3个月时HBV-DNA对CHB患者NAs抗病毒治疗未应答的预测价值较低(AUC=0.694,P=0.002),治疗6个月时HBV-DNA对CHB患者NAs抗病毒治疗未应答具有一定预测价值(AUC=0.751,P<0.001)。结论血清HBV-DNA表达在CHB患者NAs抗病毒治疗前后变化明显,且治疗6个月时血清HBV-DNA可作为抗病毒治疗未应答的预测指标。

Antiviral therapy delays esophageal variceal bleeding in hepatitis B virus-related cirrhosis

AIM:To investigate the effect of antiviral therapy with nucleoside analogs in hepatitis B virus(HBV)-related cirrhosis and esophageal varices.METHODS:Eligible patients with HBV-related cirrhosis and esophageal varices who consulted two tertiary hospitals in Beijing,China,the Chinese Second Artillery General Hospital and Chinese PLA General Hospital,were enrolled in the study from January 2005 to December 2009. Of 117 patients,79 received treatment with different nucleoside analogs and 38 served as controls. Bleeding rate,change in variceal grade and non-bleeding duration were analyzed. Multivariate Cox proportional hazard regression was used to identify factors related to esophageal variceal bleeding.antiviral group compared to the control group(29.1%vs 65.8%,P < 0.001). Antiviral therapy was an independent factor related to esophageal bleeding in multivariate analysis(HR = 11.3,P < 0.001). The mean increase in variceal grade per year was lower in the antiviral group(1.0 ± 1.3 vs 1.7 ± 1.2,P = 0.003). Nonbleeding duration in the antiviral group was prolonged in the Kaplan-Meier model. Viral load rebound was observed in 3 cases in the lamivudine group and in 1 case in the adefovir group,all of whom experienced bleeding. Entecavir and adefovir resulted in lower bleeding rates(17.2% and 28.6%,respectively) than the control(P < 0.001 and P = 0.006,respectively),whereas lamivudine(53.3%) did not(P = 0.531).CONCLUSION:Antiviral therapy delays the progression of esophageal varices and reduces bleeding risk in HBV-related cirrhosis,however,high-resistance agents tend to be ineffective for long-term treatment.

Survival and prognostic factors in hepatitis B virus-related acute-on-chronic liver failure

AIM:To investigate the survival rates and prognostic factors in patients with hepatitis B virus-related acuteon-chronic liver failure(HBV-ACLF).METHODS:Clinical data in hospitalized patients with HBV-ACLF admitted from 2006 to 2009 were retrospectively analyzed.Their general conditions and survival were analyzed by survival analysis and Cox regression analysis.RESULTS:A total of 190 patients were included in this study.The overall 1-year survival rate was 57.6%.Patients not treated with antiviral drugs had a significantly higher mortality[relative risk(RR)=0.609,P=0.014].The highest risk of death in patients with ACLF was associated with hepatorenal syndrome(HRS)(RR=2.084,P=0.026),while other significant factors were electrolyte disturbances(RR=2.062,P=0.010),and hepatic encephalopathy(HE)(RR=1.879,P<0.001).CONCLUSION:Antiviral therapy has a strong effect on the prognosis of the patients with HBV-ACLF by improving their 1-year survival rate.HRS,electrolyte disturbances,and HE also affect patient survival.

Current therapeutic strategies for recurrent hepatitis B virus infection after liver transplantation

Hepatitis B virus (HBV)-related liver disease is the leading indication for liver transplantation (LT) in Asia,especially in China.With the introduction of hepatitis B immunoglobulin (HBIG) and oral antiviral drugs,the recurrent HBV infection rate after LT has been evidently reduced.However,complete eradication of recurrent HBV infection after LT is almost impossible.Recurrent graft infection may lead to rapid disease progression and is a frequent cause of death within the fi rst year after LT.At present,the availability of new oral medications,especially nucleoside or nucleotide analogues such as adefovir dipivoxil,entecavir and tenofovir disoproxil fumarate,further strengthens our ability to treat recurrent HBV infection after LT.Moreover,since combined treatment with HBIG and antiviral agents after liver re-transplantation may play an important role in improving the prognosis of recurrent HBV infection,irreversible graft dysfunction secondary to recurrent HBV infection in spite of oral medications should no longer be considered an absolute contraindication for liver re-transplantation.Published reviews focusing on the therapeutic strategies for recurrent HBV infection after LT are very limited.In this article,the current therapeutic strategies for recurrent HBV infection after LT and evolving new trends are reviewed to guide clinical doctors to choose an optimal treatment plan in different clinical settings.

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.

Inhibition of hepatitis B virus by oxymatrine in vivo

AIM To investigate the anti-HBV effect ofoxymatrine (oxy) in vivo.METHODS HBV transgenic mice were producedby micro-injection of a 4.2kb fragmentcontaining the complete HBV genomes.Expression level of HBsAg and HBcAg in thetransgenic mice liver was determined byimmunohistochemical assay.RESULTS Four groups (6 mice in each group)were injected intraperitoneally with oxy at thedosage of 100,200, and 300 mg/kg or with salineonce a day for 30 days. Both HBsAg and HBcAgwere positive in livers of all the six mice in thecontrol group (injected with saline), and werepositive in livers of two mice in 100 mg/kg groupand 300mg/kg group. In 200mg/kg group,HBsAg and HBcAg were negative in livers of allthe six mice. Based on the results, 200 mg/kg isthe ideal dosage to explore the effect of oxy atdifferent time points. According to the oxytreatment time, mice were divided into fourgroups: 10 d, 20 d, 30 d and 60 d (4 mice in eachgroup). Each mouse underwent liver biopsy twoweeks before the treatment of oxy. Down-regulation of HBsAg and HBcAg appeared aftertreatment of oxymatrine for 10 d and 20 d, Dane-like particles disappeared after the treatment ofoxy for 20d under electron microscopy,however, the expression level of HBsAg andHBcAg returned to normal 60 d later after oxytreatment.CONCLUSION oxymatrine can reduce thecontents of HBsAg and HBcAg in transgenic miceliver, longer treatment time and larger dosagedo not yield better effects.

Hepatitis B virus reactivation with a rituximab-containing regimen

Rituximab is currently used not only in the treatment of B-cell lymphoma but also for various other diseases, including autoimmune diseases, post-transplant graft vs host disease, and rejection following kidney transplants. Due to rituximab's widespread use, great progress has been made regarding research into complications that arise from its use, one of the most serious being the reactivation of hepatitis B virus(HBV), and efforts continue to establish guidelines for preventive treatment against this occurrence. This report discusses preventive measures against rituximab-induced HBV reactivation and future objectives.

Novel approaches towards conquering hepatitis B virus infection

Currently approved treatments for hepatitis B virus （HBV） infection include the immunomodulatory agent, IFN-α, and nucleos（t）ide analogues. Their efficacy is limited by their side effects, as well as the induction of viral mutations that render them less potent. It is thus necessary to develop drugs that target additional viral antigens. Chemicals and biomaterials by unique methods of preventing HBV replication are currently being developed, including novel nucleosides and newly synthesized compounds such as capsid assembling and mRNA transcription inhibitors. Molecular therapies that target different stages of the HBV life cycle will aid current methods to manage chronic hepatitis B （CriB） infection. The use of immunomodulators and gene therapy are also under consideration. This report summarizes the most recent treatment possibilities for CHB infection. Emerging therapies and their potential mechanisms, efficacy, and pitfalls are discussed.

Clinical relevance of hepatitis B virus variants

The hepatitis B virus(HBV) is a global public health problem with more than 240 million people chronically infected worldwide, who are at risk for end-stage liver disease and hepatocellular carcinoma. There are an estimated 600000 deaths annually from complications of HBV-related liver disease. Antiviral therapy with nucleos/tide analogs(NA) targeting the HBV polymerase(P) can inhibit disease progression by long-term suppression of HBV replication. However, treatment may fail with first generation NA therapy due to the emergence of drugresistant mutants, as well as incomplete medication adherence. The HBV replicates via an error-prone reverse transcriptase leading to quasispecies. Due to overlapping open reading frames mutations within the HBV P can cause concomitant changes in the HBV surface gene(S) and vice versa. HBV quasispecies diversity is associated with response to antiviral therapy, disease severity and long-term clinical outcomes. Specific mutants have been associated with antiviral drug resistance, immune escape, liver fibrosis development and tumorgenesis. An understanding of HBV variants and their clinical relevance may be important for monitoring chronic hepatitis B disease progression and treatment response. In this review, we will discuss HBV molecular virology, mechanism of variant development, and their potential clinical impact.

Naturally derived anti-hepatitis B virus agents and their mechanism of action

Despite that some approved drugs and genetically engineered vaccines against hepatitis B virus(HBV)are available for HBV patients,HBV infection is still a severe public health problem in the world.All the approved therapeutic drugs(including interferonalpha and nucleoside analogues)have their limitations.No drugs or therapeutic methods can cure hepatitis B so far.Therefore,it is urgently needed to discover and develop new anti-HBV drugs,especially nonnucleoside agents.Naturally originated compounds with enormous molecular complexity and diversity offer a great opportunity to find novel anti-HBV lead compounds with specific antiviral mechanisms.In this review,the natural products against HBV are discussed according to their chemical classes such as terpenes,lignans,phenolic acids,polyphenols,lactones,alkaloids and flavonoids.Furthermore,novel mode of action or new targets of some representative anti-HBV natural products are also discussed.The aim of this review is to report new discoveries and updates pertaining to anti-HBV natural products in the last 20years,especially novel skeletons and mode of action.Although many natural products with various skeletons have been reported to exhibit potent anti-HBV effects to date,scarcely any of them are found in the list of conventional anti-HBV drugs worldwide.Additionly,in anti-HBV mechanism of action,only a few references reported new targets or novel mode of action of antiHBV natural products.

Management of psoriasis patients with hepatitis B or hepatitis C virus infection

The systemic therapies available for the management of Psoriasis (PsO) patients who cannot be treated with more conservative options, such as topical agents and/or phototherapy, with the exception of acitretin, can worsen or reactivate a chronic infection. Therefore, before administering immunosuppressive therapies with either conventional disease-modifying drugs (cDMARDs) or biological ones (bDMARDs) it is mandatory to screen patients for some infections, including hepatitis B virus (HBV) and hepatitis C virus (HCV). In particular, the patients eligible to receive an immunosuppressive drug must be screened for the following markers: antibody to hepatitis B core, antibody to hepatitis B surface antigen (anti-HBsAg), HBsAg, and antibody to HCV (anti-HCV). In case HBV or HCV infection is diagnosed, a close collaboration with a consultant hepatologist is needed before and during an immunosuppressive therapy. Concerning therapy with immunosuppressive drugs in PsO patients with HBV or HCV infection, data exist mainly for cyclosporine a (CyA) or bDMARDs (etanercept, adalimumab, infliximab, ustekinumab). The natural history of HBV and HCV infection differs significantly as well as the effect of immunosuppression on the aforementioned infectious diseases. As a rule, in the case of active HBV infection, systemic immunosuppressive antipsoriatic therapies must be deferred until the infection is controlled with an adequate antiviral treatment. Inactive carriers need to receive antiviral prophylaxis 2-4 wk before starting immunosuppressive therapy, to be continued after 6-12 mo from its suspension. Due to the risk of HBV reactivation, these patients should be monitored monthly for the first 3 mo and then every 3 mo for HBV DNA load together with transaminases levels. Concerning the patients who are occult HBV carriers, the risk of HBV reactivation is very low. Therefore, these patients generally do not need antiviral prophylaxis and the sera HBsAg and transaminases dosing can be monitored every 3 mo. Concerning PsO patients with chronic HCV infection their management with immunosuppressive drugs is less problematic as compared to those infected by HBV. In fact, HCV reactivation is an extremely rare event after administration of drugs such as CyA or tumor necrosis factor-&#x003b1; inhibitors. As a rule, these patients can be monitored measuring HCV RNA load, and ALT, aspartate transaminase, gamma-glutamyl-transferase, bilirubin, alkaline phosphatase, albumin and platelet every 3-6 mo. The present article provides an updated overview based on more recently reported data on monitoring and managing PsO patients who need systemic antipsoriatic treatment and have HBV or HCV infection as comorbidity.

Differing profiles of people diagnosed with acute and chronic hepatitis B virus infection in British Columbia,Canada

AIM To describe the characteristics of people diagnosed with acute and chronic hepatitis B virus(HBV) infection in British Columbia(BC).METHODS We used data from the BC Hepatitis Testers Cohort(BCHTC),which includes all individuals tested for hepatitis C virus(HCV) or human immunodeficiency virus(HIV) or those diagnosed with HBV or active tuberculosis in BC since 1990.These data were integrated with prescription drug,medical visit,hospitalization and mortality data.HBV cases were classified as acute or chronic according to provincial guidelines.We compared characteristics of individuals by HBV infection group(acute,chronic and negative).Factors associated with acute or chronic HBV infection were assessed with multinomial logistic regression models in comparison to the HBV negative group.RESULTS46498 of the 1058056 eligible BC-HTC participants were diagnosed with HBV infection.4.3% of HBV positive individuals were diagnosed with acute HBV infections while 95.7% had chronic infections.Problematic alcohol use,injection drug use,and HIV or HCV co-infection were more common among individuals diagnosed with acute HBV compared to those with chronic infections and HBV negative individuals.In multivariable multinomial logistic regression models,we observed significant associations between acute or chronic HBV diagnosis and being male,age at HBV diagnosis or birth cohort,South and East Asian ethnicity,HCV or HIV infection,and injection drug use.The odds of acute HBV decreased with increasing age among people who inject drugs,while the opposite was true for chronic HBV.Persons with acute HBV were predominantly White(78%) while those with chronic HBV were mostly East Asian(60%).Relative to Whites,East Asians had 12 times greater odds of being diagnosed with chronic HBV infection.These odds increased with increasing socioeconomic deprivation.CONCLUSION Differences in the profiles of people diagnosed with acute and chronic HBV infection necessitate differentiated screening,prevention,care and treatment programs.

Treatment of hepatitis B virus-associated glomerulonephritis:A meta-analysis

AIM:To evaluate the efficacy of antiviral or corticosteroid treatment on hepatitis B virus-associated glomerulonephritis(HBV-GN) . METHODS:Six and five trials were used respectively to evaluate the efficacy of either antiviral or corticosteroid treatment on HBV-GN.Pediatric patients were pooled separately to assess their response to the above treatment modalities.The primary and secondary outcomes were remission of proteinuria and clearance of Hepatitis B e-antigen(HBeAg) ,respectively.A fixed or random effect model was established to collect the data. RESULTS:The remission rate of proteinuria(RR=1.69,95%CI:1.08-2.65) and the clearance rate of HBeAg(RR =6.44,95%CI:3.11-13.35) were significantly higher in antiviral treatment group than in control group.The proteinuria remission was significantly associated with HBeAg clearance(P=0.002) .However,the difference in proteinuria remission rate was not statistically significant between corticosteroid treatment group and controlgroup(RR=1.45,95%CI:0.68-3.11) .Antiviral therapy could significantly promote the HBeAg clearance in pediatric patients,but neither antiviral nor corticosteroid therapy could significantly decrease proteinuria in pediatric patients compared to controls. CONCLUSION:Antiviral but not corticosteroid treatment can decrease proteinuria and promote HBeAg clearance in HBV-GN patients.

Application of hepatitis B virus replication mouse model

AIM:To evaluate the value of the hepatitis B virus(HBV) replication mouse model with regard to several aspects of the study of HBV biology.METHODS:To evaluate the HBV replication mouse model in detecting the efficacy of anti-HBV agents,the interferon inducer polyinosinic-polytidylin acid(polyIC) and nucleotide analogues adefovir and entecavir were administered to mice injected with wild type pHBV4.1,and the inhibiting effect of these agents on HBV DNA replication was evaluated.To identify the model's value in a replication ability study of HBV drug-resistant mutants and a HBx-minus mutant,telbivudine resistance mutants(rtM204I,ayw subtype),adefovir resistance mutants(rtA181V + rtN236T,ayw subtype) and HBxminus mutants were injected respectively,and their corresponding HBV DNA replication intermediates in mouse liver were assessed.RESULTS:Compared with the wild type HBV replication mouse model without antiviral agent treatment,the HBV DNA replication intermediates of the polyICtreated group were decreased 1-fold;while in the entecavir-and adefovir-treated groups,the levels of HBV DNA replication intermediates were inhibited 13.6-fold and 1.4-fold,respectively.For the mouse models injected with telbivudine resistance mutant,adefovir resistance mutant and HBx-minus mutant,HBV DNA replication intermediates could still be detected,but the levels of HBV DNA replication intermediates of these mutants decreased 4.5-fold,5.6-fold and 2.9-fold respectively,compared with the mouse model with wild type HBV plasmid.CONCLUSION:The HBV replication mouse model we established was a useful and convenient tool to detect the efficacy of antiviral agents and to study the replication ability of HBV mutants in vivo.

Resistant mutants induced by adefovir dipivoxil in hepatitis B virus isolates

AIM: To investigate the loci of adefovir dipivoxil (ADV)-induced resistance in hepatitis B virus (HBV) isolates and optimize the management of ADV-treated patients.

Investigation of immune escape-associated mutations of hepatitis B virus in patients harboring hepatitis B virus drug-resistance mutations

It is unclear whether immune escape-associated mutations in the major hydrophilic region of hepatitis B virus surface antigen(HBsAg)are associated with nucleoside/nucleotide analog resistance.AIM To evaluate the association between immune escape-associated mutations and nucleoside/nucleotide analog resistance mutations.METHODS In total,19440 patients with chronic hepatitis B virus infection,who underwent resistance testing at the Fifth Medical Center of Chinese PLA General Hospital between July 2007 and December 2017,were enrolled.As determined by sequence analysis,6982 patients harbored a virus with resistance mutations and 12458 harbored a virus lacking resistance mutations.Phenotypic analyses were performed to evaluate HBsAg production,replication capacity,and drug-induced viral inhibition of patient-derived drug-resistant mutants with or without the coexistence of sA159V.RESULTS The rate of immune escape-associated mutation was significantly higher in 9 of the 39 analyzed mutation sites in patients with resistance mutations than in patients without resistance mutations.In particular,these mutations were sQ101H/K/R,sS114A/L/T,sT118A/K/M/R/S/V,sP120A/L/Q/S/T,sT/I126A/N/P/S,sM133I/L/T,sC137W/Y,sG145A/R,and sA159G/V.Among these,sA159V was detected in 1.95%(136/6982)of patients with resistance mutations and 1.08%(134/12,458)of patients lacking resistance mutations(P<0.05).The coexistence of sA159V with lamivudine(LAM)and entecavir(ETV)-resistance mutations in the same viral genome was identified during follow-up in some patients with drug resistance.HBsAg production was significantly lower and the replication capacity was significantly higher,without a significant difference in LAM/ETV susceptibility,in sA159V-containing LAM/ETV-resistant mutants than in their sA159V-lacking counterparts.CONCLUSION In summary,we observed a close link between the increase in certain immune escape-associated mutations and the development of resistance mutations.sA159V might increase the fitness of LAM/ETV-resistant mutants under environmental pressure in some cases.

Hepatitis B virus recurrence after liver transplantation: An old tale or a clear and present danger?

Hepatitis B virus(HBV) recurrence after liver transplantation(LT) has been described more than 50 years ago. Similarly, to other clinical conditions, in which impairment of host immune defense favors viral replication, early reports described in details recurrence and reactivation of HBV in liver transplant recipients. The evidence of a possible, severe, clinical evolution of HBV reappearance in a significant percentage of these patients, allowed to consider,for some years, HBV positivity a contraindication for LT. Moving from the old to the new millennium this picture has changed dramatically. Several studies contributed to establish efficient prophylactic protocols for HBV recurrence and with the advent of more potent anti-viral drugs an increased control of infection was achieved in transplanted patients as well as in the general immunecompetent HBV population. Success obtained in the last decade led some authors to the conclusion that HBV is now to consider just as a "mere nuisance".However, with regard to HBV and LT, outstanding issues are still on the table:(1)A standard HBV prophylaxis protocol after transplant has not yet been clearly defined;(2) The evidence of HBV resistant strains to the most potent antiviral agents is claiming for a new generation of drugs;and(3) The possibility of prophylaxis withdrawal in some patients has been demonstrated, but reliable methods for their selection are still lacking. The evolution of LT for HBV is examined in detail in this review together with the description of the strategies adopted to prevent HBV recurrence and their pros and cons.

Molecular diagnosis and treatment of drug-resistant hepatitis B virus

Oral antiviral agents have been developed in the last two decades for the treatment of chronic hepatitis B(CHB).However,antiviral resistance remains an important challenge for long-term CHB therapy.All of the clinically available oral antiviral agents are nucleoside or nucleotide analogues that target the activity of viral reverse transcriptase(RT),and all are reported to have resistant mutations.Since the hepatitis B virus(HBV)RT,like other viral polymerases,lacks proofreading activity,the emergence of drug-resistance occurs readily under selective pressure from the administration of antiviral agents.The molecular diagnosis of drug-resistant HBV is based on sequence variations,and current diagnostic methods include sequencing,restriction fragment polymorphism analysis,and hybridization.Here,we will discuss the currently available molecular diagnosis tools,in vitro phenotypic assays for validation of drug-resistant HBV,and treatment options for drug-resistant HBV.