Acute leukaemia in chronic hepatitis B patients with lamivudine therapy

Risk of hepatocellular carcinoma and cancers at other sites among patients diagnosed with chronic hepatitis B virus infection in Sweden

Hepatitis B virus (HBV) infection is one of most common viral infections worldwide. While chronic HBV infection has been shown consistently to be associated with hepatocellular carcinoma, data on associations with cancers at other sites are limited. In this study a total of 10,197 patients were diagnosed with chronic HBV infection in Sweden, and they were retrieved from the nationwide Swedish Hospital Discharge Register and Outpatient Register and linked to Cancer Registry data. Standardized incidence ratios (SIRs) for cancers were calculated for these patients in comparison with the population without HBV infection. Five hundred sixty-seven of whom developed cancer (SIR 1.82 (95% confidence interval (CI) 1.67-1.97)) during the study period. The SIR for hepatocellular carcinoma in patients with HBV infection was 40.58 (95% CI 30.50-50.07). In addition, a total of seven other cancer sites/types showed increased SIRs: cancers of the upper aerodigestive tract, lung, kidney, skin (squamous cell carcinoma), and thyroid gland, and lymphoma and leukemia. The risks of non-Hodgkin lymphoma and acute myeloid leukemia were increased in both Swedish- and foreign-born patients with HBV infection. In summary, chronic HBV infection is a strong risk factor for hepatocellular carcinoma and also increases the risk of seven other cancers. These findings illustrate the need for surveillance for cancers other than hepatocellular carcinoma in patients with HBV infection.

Biological characteristics of the rtA181T/sW172* mutant strain of Hepatitis B virus in animal model

BACKGROUND

The effects of Hepatitis B virus (HBV) rtA181T/sW172* mutation on viral replication and pathogenicity was concerned recently. This study aimed to investigate the biological characteristics of rtA181T/sW172* mutant strain of HBV in animal model.

METHODS

The rtA181T/sW172* mutant plasmid was constructed using the pHBV4.1 (wild type HBV) as a template. The wild and mutant HBV replication mouse models were established utilizing a hydrodynamic technique. The titers of hepatitis B surface antigen (HBsAg), hepatitis B e antigen, and HBV DNA in serum, and the levels of HBsAg, hepatitis B core antigen(HBcAg), HBV DNA replication intermediates (HBV DNA RI) and HBV RNA in liver were measured after 1, 3, 5, 7, 10, 12 and 15 days of plasmid injection.

RESULTS

In wild-type HBV replication mouse model, serum HBsAg was high on day 1, 3, and 5, but became lower since day 7; while in mutant HBV mouse model, serum HBsAg was always at very low level. In liver tissues, HBV DNA RI of wild type HBV was detected on day 1 after transfection. The level subsequently peaked on day 3, gradually declined after day 5, and was almost undetectable on day 10. However, the HBV DNA RI levels of the mutant strain were always higher and lasted longer until day 15. Consistently, the expression levels of HBsAg and HBcAg in liver of the mutant group were significantly increased.

CONCLUSIONS

In the case of the HBV rtA181T/sW172* mutation, the secretion of serum HBsAg was impaired, whereas HBV DNA replication and HBsAg/HBcAg expression were increased in liver. These results suggest that the mutation can impair HBsAg secretion, and may cause the accumulation of viral core particles in liver.

Acute leukemia, a rare but fatal complication after liver transplantation

Little information is available about the risk factors and means to improve the survival rate of acute leukemia in a rare but often fatal complication after liver transplantation (LT). We report the development of AML-M2 in one of the 764 patients who underwent liver transplantation at our center, and review the literature on similar cases. The patient, a 42-year-old man who developed acute leukemia 38 months after liver transplantation, was successfully treated with chemotherapy and has subsequently been in remission. With appropriate adjustment of immunosuppressive agents, he was able to safely benefit from chemotherapy. Only 16 patients with acute leukemia after liver transplantation have been reported, and the mortality rate is extraordinarily high (52.94%, 9/17). More cases of acute leukemia will emerge as the rate of survival after liver transplantation increases. The patient's chromosomal mutation profile, the choice of immunosuppressive agent, and infection by hepatitis virus may be the risk factors for the development of acute leukemia after LT. Our experience suggests that clinicians should adjust the immunosuppressive agents according to the immunosuppressive state of the patient and explore the option of reducing or stopping the medication as long as liver function remains stable. These measures could help reduce the high mortality rate among these patients.

The antiviral drug selected hepatitis B virus rtA181T/sW172* mutant has a dominant negative secretion defect and alters the typical profile of viral rebound

The hepatitis B virus (HBV) mutation that encodes rtA181T is selected in the viral polymerase during antiviral drug therapy and can also encode a stop codon in the overlapping surface gene at amino acid 172 (sW172*) resulting in truncation of the last 55 amino acids of the C-terminal hydrophobic region of the surface proteins. This mutation is usually detected as a mixed population with wild-type HBV. In vitro analysis revealed that the rtA181T/sW172* variant is not only defective in secretion of viral particles causing intracellular retention of surface proteins, it also has a dominant negative effect on virion but not subviral particle secretion when coexpressed with the wild type. This dominant negative effect was attributed to the truncated S protein alone. Furthermore, these truncated surface proteins were less glycosylated, and the truncated L protein was able to support virion secretion. Examination of sequential HBV DNA levels in patients failing lamivudine or adefovir therapy where only the rtA181T change was detected via polymerase chain reaction sequencing revealed that viral load rebound did not occur or was not as large as usually observed with drug-resistant HBV.

CONCLUSION

The rtA181T/sW172* variant has a secretory defect and exerts a dominant negative effect on wild-type HBV virion secretion. The selection of rtA181T/sW172* reduced the typical extent of virological breakthrough, resulting in a missed diagnosis of drug resistance if viral load was used as the only criterion for drug failure, necessitating HBV polymerase chain reaction sequencing or other genotypic methods to diagnose antiviral drug resistance in these cases.

Emergence of a novel lamivudine-resistant hepatitis B virus variant with a substitution outside the YMDD motif

Lamivudine is a major drug approved for treatment of chronic hepatitis B virus (HBV) infection. Emergence of drug-resistant mutants with amino acid substitutions in the YMDD motif is a well-documented problem during long-term lamivudine therapy. Here we report a novel lamivudine-resistant strain of HBV with an intact YMDD motif, which included an amino acid substitution, rtA181T, in the reverse transcriptase (RT) domain of HBV polymerase. The substitution also induced a unique amino acid substitution (W172L) in the overlapping hepatitis B surface (HBs) protein. The YMDD mutant strains were not detected even by using the sensitive peptide nucleic acid-mediated PCR clamping method. The detected nucleotide substitution was accompanied by the emergence of an additional nucleotide substitution that induced amino acid change (S331C) in the spacer domain. The rtA181T mutant strain displayed a threefold decrease in susceptibility to lamivudine in in vitro experiments in comparison with the wild type. In vivo analysis using human hepatocyte-chimeric mice confirmed the resistance of this mutant strain to lamivudine. We developed a method to detect this novel rtA181T mutation and a previously reported rtA181T mutation with the HBs stop codon using restriction fragment length polymorphism PCR and identified one patient with the latter pattern among 40 patients with lamivudine resistance. In conclusion, although the incidence is not high, we have to be careful regarding the emergence of lamivudine-resistant mutant strains with intact YMDD motif.