A novel method for the analysis of drug-resistant phenotypes of hepatitis B virus

Substitutions of rtL228 and/or L229 are involved in the regulation of replication and HBsAg secretion in hepatitis B virus, and do not affect susceptibility to nucleos(t)ide analogs

Nucleos(t)ide analogs (NAs) are widely used in the treatment of hepatitis B virus (HBV) and human immunodeficiency virus (HIV). The mutation L210W of HIV‑1 reverse transcriptase (RT) is one of the six principal mutations which confer in vivo resistance to zidovudine. Due to the similar 3D‑structure and high conservation between HIV‑RT and HBV‑RT, the present study aimed to clarify whether corresponding mutations in HBV may decrease its susceptibility to relevant NAs. Mutations including rtL228C/W, rtL229W and rtL228W/L229W were introduced into a HBV replication competent plasmid by fusion polymerase chain reaction. Replication capacity, HBs/e antigen (Ag) levels and susceptibility to NAs were subsequently analyzed in vitro. Single or combination mutations of rtL228 and rtL229 impaired HBV replication. Decreased HBsAg secretion in the supernatant and production in the cell lysate wasobserved with single rtL229W or in combination with rtL228W, while there was no significant difference between wild‑type and mutant HBV with regard to the level of HBeAg in the supernatant and susceptibility to commonly‑used NAs. Substitution mutations of rtL228 and/or L229 in HBV did not alter the susceptibility of the virus to NAs, although replication and HBsAg secretion were affected.

A modified murine model based on hydrodynamic injection for the analysis of chronic human hepatitis B virus infection

Hepatitis B virus (HBV) is a persistent pathogen that causes acute and chronic necroinflammatory liver disease and is attributable to ~1 million deaths per year. In the present study, a conventional murine model was introduced based on the hydrodynamic injection of engineered replication‑competent HBV DNA into the tail veins of C57BL/6 mice. In a previous study, nine in‑frame ATG (start) codons in the S open reading frame (S1‑S9) were analyzed. The highly conserved ATG S5 was mutated to ACG by T378C, which led to the substitution sM75T and inhibition of the production and secretion of the hepatitis B surface antigen (HBsAg), and subsequent inhibition of HBV replication. In the present study, T378C was introduced into the pAAV‑HBV1.3 plasmid and was confirmed to affect HBsAg production and secretion, and HBV replication in vivo, which was in agreement with the previous in vitro results. Furthermore, the murine model was improved by co‑injection of the replication‑competent HBV plasmid DNA with Lipofectamine 2000 (LP). In this model, LP not only significantly enhanced HBV replication in mice, but also upregulated the expression of HBsAg and the hepatitis B core antigen. The current modified murine model was superior to the conventional murine HBV model based on HBV challenge by hydrodynamic injection.

Substitution rtq267h of hepatitis B virus increases the weight of replication and Lamivudine resistance

BACKGROUND

Nucleus(t)ide analogs (NAs), containing Lamivudine (LMV), adefovir dipivoxil (ADV), endeavor (ETV), telbivudine (LdT), and tenofovir (TDF) are widely used for the treatment of chronic hepatitis B (CHB), but long term anti-Hepatitis B virus (HBV) therapy with NAs may give rise to the emergence of drug-resistant viral mutants.

OBJECTIVES

This study aimed to find and identify some new resistance mutations of HBV from the patients accepted anti-HBV therapy.

PATIENTS AND METHODS

The reverse transcriptase (RT) coding region of HBV was PCR-amplified using HBV DNA extracted from patients' blood samples and sequenced.

RESULTS

Nineteen substitution mutations were detected. Among them, rtQ267H was often observed in patients receiving LMV administration. This LMV therapy-related mutation was introduced into HBV replication-competent plasmids. The in vitro susceptibility of both wild-type (WT) and mutant-type (MT) HBV to NAs was analyzed by Southern blot, and/or quantitative real-time PCR (qRT-PCR). The rtQ267H substitution enhanced HBV replication not merely in single-site mutation, but also in multisite mutations. The in vitro susceptibility analysis showed that the existence of rtQ267H in WT and LMV-resistant (LMVr) HBV were responsible for the reduced susceptibility to LMV to varying degrees, and enhanced HBV replication capacity. However, HBV harbored this substitution retained normal susceptibility to ADV, LdT, ETV, and TDF.

CONCLUSIONS

The result suggested that rtQ267H is a potential adaptive mutation of HBV to LMV.