The incidence and clinical outcome of YMDD mutants in hepatitis B surface antigen-positive renal allograft recipients after prolonged lamivudine therapy

Safety and efficacy of adefovir therapy for lamivudine-resistant hepatitis B virus infection in renal transplant recipients

BACKGROUND/PURPOSE

The emergence of lamivudine (LAM)-resistant mutants after prolonged LAM therapy may reduce its therapeutic effects against hepatitis B virus (HBV). Adefovir dipivoxil (ADV) is an effective treatment of LAM-resistant HBV infections. However, only limited data are available regarding the safety and efficacy of ADV for treating HBsAg-positive renal transplant recipients.

METHODS

Fourteen HBsAg-positive patients who underwent renal transplantation and developed the YMDD mutation after prolonged LAM therapy were retrospectively analyzed. Five patients were administered ADV monotherapy, while nine patients received ADV plus LAM combination therapy. Data on age, gender, duration of previous LAM treatment, pre-LAM HBV DNA and liver enzyme levels, duration of LAM treatment prior to the emergence of mutations, duration of ADV rescue therapy, and the clinical outcomes of treatment (i.e., normalization of alanine transaminase (ALT) and undetectable HBV DNA levels) were analyzed.

RESULTS

The mean age of the patients was 46.8 ± 11.5 years. Males were predominantly studied. The mean follow-up duration of rescue therapy was 38.2 ± 18.3 months. At the beginning of rescue therapy, the mean serum ALT level was 142.2 ± 99.8 IU/mL, while the median serum level of HBV DNA was 7.85 log(10) copies/mL. Patients who received combination therapy tended to demonstrate undetectable serum HBV DNA levels, but no significant differences in terms of clinical outcomes were observed between patients who received ADV monotherapy and patients who received combination therapy. After 12 months of treatment, 13 patients (92.8%) developed normalized ALT levels. Five (35.7%) and six (42.8%) patients achieved undetectable serum HBV DNA levels after 12 months and 24 months of treatment, respectively. No virological breakthroughs were observed. Twenty-nine percent of the patients developed moderate to severe renal insufficiency.

CONCLUSION

Although no statistical difference was noted, ADV plus LAM combination therapy tended to demonstrate a higher therapeutic efficacy than ADV monotherapy for treating LAM-resistant HBV infection in renal transplant recipients. Renal function should be closely monitored in order to ameliorate nephrotoxicity.

The therapeutic response of antiviral therapy in HBsAg-positive renal transplant recipients and a long-term follow-up

BACKGROUND

Early prediction of lamivudine (LAM) response by individualized monitoring of serum HBV DNA like roadmap concept, and investigation of the outcome after LAM discontinuation in renal transplant recipients (RTRs) with chronic hepatitis B (CHB).

METHODS

We conducted a study on 19 RTRs with HBV infection receiving LAM treatment for 2 years from 2004 to 2007. HBV DNA level was assessed at baseline, 12, 24, 52, and 104 weeks after treatment. Risk factors of tyrosine-methionine-aspartate-aspartate (YMDD) mutation on treatment and relapse rate of HBV after LAM discontinuation were analyzed.

RESULTS

HBV DNA levels became undetectable in 32, 37, 63, and 53% of patients after 12, 24, 52, and 104 weeks of LAM treatment, respectively. Overall, three (16%) and five (33%) patients were detected with YMDD mutations at week 52 and 104, respectively. In the concept of roadmap, of the seven patients with inadequate virologic response (IAVR) at week 24, five had YMDD mutations. There was no significant association of YMDD mutations with age, gender, genotype, cirrhosis, HBeAg status, baseline HBV DNA, precore/core promoter mutations, and primary response, except IAVR at week 24 (P = 0.001). The relapse rate of HBV after LAM discontinuation was high (75%) during a median follow-up of 65 weeks.

CONCLUSIONS

The rate of LAM resistance in RTRs is similar to immunocompetent CHB patients in a 2-year therapy. By roadmap concept, RTRs with IAVR require a change in therapy to prevent viral resistance. Relapse after LAM withdrawal is frequent. Long-term antiviral therapy is crucial for immunosuppressed patients.

Hepatitis B virus and renal transplantation

Hepatitis B virus (HBV) infection remains an important cause of liver disease in the renal transplant (RT) population, potentially diminishing survival. Consequences of HBV infection after RT include progression to decompensated cirrhosis and an increased risk of hepatocellular carcinoma. Although precautions initially recommended by the Centers for Diseases Control and Prevention 30 years ago have substantially reduced HBV transmission within hemodialysis units, acute HBV outbreaks continue to be reported in patients with chronic kidney disease on maintenance hemodialysis. In addition, immigration from areas of high HBV prevalence implies that HBV-infected organs with chronic kidney disease will continue to enter the RT pool. Fortunately, the advent of oral therapy for HBV infection now reduces the risk of HBV progression post-RT.

Chronic viral hepatitis in kidney transplantation

Chronic hepatitis B virus (HBV) or hepatitis C virus (HCV) infection in potential kidney transplant candidates-once considered absolute contraindications to kidney transplantation-no longer creates overt barriers to transplantation. Advances in the medical management of HBV and HCV infection have created opportunities for a substantial number of patients to be effectively treated with antiviral therapy before transplantation. For HBV infection, a number of new drugs enable clearance of the virus with minimal adverse effects and drug resistance. Pretransplantation antiviral therapy is advisable for patients with HCV infection, but adverse effects are common and viral eradication remains challenging. Regardless of viral clearance, pretransplant patients without bridging fibrosis (as confirmed by liver biopsy) or clinical stigmata of cirrhosis should be considered for kidney transplantation as survival is superior when compared to treatment with dialysis, and progression of liver disease is unlikely. For patients with advanced liver disease, simultaneous liver-kidney transplantation is an important consideration. These treatment advances further increase the burden of organ donor shortage; however, organs from deceased donors with chronic HBV or HCV infection could be efficiently allocated to certain individuals with a viral infection of the same type to increase the pool of available transplant organs.

Mutation pattern of lamivudine resistance in relation to hepatitis B genotypes: hepatitis B genotypes differ in their lamivudine resistance associated mutation pattern

Little is known about differences between individual hepatitis B genotypes and mutation patterns associated with lamivudine resistance. This study analyses the lamivudine-associated mutation pattern in relation to the four major HBV genotypes A-D. The PubMed database was screened for keywords "HBV OR Hepatitis B," "YMDD," "genotype," and "lamivudine"; all identified publications published till June 2009 were analyzed for differences in mutation pattern. To confirm the literature-based findings the databases of two reference laboratories in Tübingen (Germany), and Melbourne (Australia) were analyzed. Twenty-nine studies were identified reporting 827 patients with known hepatitis B genotype who underwent lamivudine treatment and developed resistance mutations. The literature data revealed that genotype A favors the rtM204V mutation unlike the other major genotypes (P<0.001), which corresponds to a significant difference in the mutation pattern of genotypes endemic in Asian countries and those found in the rest of the world. These significant findings of the literature-review could be reproduced in the analysis of the databases from Tübingen and Melbourne. Furthermore, the rtL180M mutation is significantly connected to the rtM204V mutation in genotypes A, B, and C, respectively. It is concluded that there is proof that HBV genotypes differ in their mutation pattern of lamivudine resistance. Future studies will need to evaluate whether this will translate into genotype-specific differences in resistance emergence on either entecavir or telbivudine as these antivirals differ in their mutation profile, rtM204V for entecavir and rtM204I for telbivudine.

In vitro effects of a novel nucleoside analog beta-LPA against hepatitis B virus

AIM: To explore the in vitro effects of a novel nucleoside analog (β-LPA) against hepatitis B virus (HBV).

METHODS: HepG2.2.2.15 cells were cultured and treated with various concentrations of β-LPA. Serum HBsAg and HBeAg were determined by enzyme-linked immunosorbent assay (ELISA). Intracelluar DNA was extracted and subjected to Southern blotting, hybridized with ³²P-labeled HBV probe and autoradiographed. The intensity of the autoradiographic bands was quantified by densitometric scans of computer and ED₅₀ value was calculated. Cytotoxicity with different concentrations of drugs was examined by methyl thiazolyl tetrazolium (MTT) method and ID₅₀ value was calculated.

RESULTS: Autoradiographic bands showed that β-LPA inhibited the replication of HBV DNA in a dose-dependent manner. ED₅₀ value was 0.01 μmol/L. Cytotoxicity experiment showed that the ID₅₀ value of β-LPA was 50 μmol/L. The contents of HBsAg and HBeAg were decreased in a concentration-dependent manner. β-LPA at a low concentration had no marked effect on HBsAg and HBeAg in supernate.

CONCLUSION: β-LPA possesses potent inhibitory effect on the replication of HBV in vitro with little cytotoxicity.