Inhibition of hepatitis B virus replication by APOBEC3G in vitro and in vivo

AIM： To investigate the effect of APOBEC3G mediated antiviral activity against hepatitis B virus （HBV） in cell cultures and replication competent HBV vector-based mouse model. METHODS： The mammalian hepatoma cells Huh7 and HepG2 were cotransfected with various amounts of CMV-driven expression vector encoding APOBEC3G and replication competent 1.3 fold over-length HBV. Levels of HBsAg and HBeAg in the media of the transfected cells were determined by ELISA. The expression of HBcAg in transfected cells was detected by western blot. HBV DNA and RNA from intracellular core particles were examined by Northern and Southern blot analyses. To assess activity of the APOBEC3G in vivo, an HBV vector-based model was used in which APOBEC3G and the HBV vector were co-delivered via high-volume tail vein injection. Levels of HBsAg and HBV DNA in the sera of mice as well as HBV core-associated RNA in the liver of mice were determined by ELISA and quantitative PCR analysis respectively. RESULTS： There was a dose dependent decrease in the levels of intracellular core-associated HBV DNA and extracellular production of HBsAg and HBeAg. The levels of intracellular core-associated viral RNA also decreased, but the expression of HBcAg in transfected cells showed almost no change. Consistent with in vitro results, levels of HBsAg in the sera of mice were dramatically decreased. More than 1.5 log10 decrease in levels of serum HBV DNA and liver HBV RNA were observed in the APOBEC3G-treated groups compared with the control groups.CONCLUSION： These findings indicate that APOBEC3G could suppress HBV replication and antigen expression both in vivo and in vitro, promising an advance in treatment of HBV infection.

Management of chronic hepatitis B in pregnancy

Pregnancy associated with chronic hepatitis B (CHB) is a common and important problem with unique challenges. Pregnant women infected with CHB are different from the general population, and their special problems need to be considered: such as the effect of hepatitis B virus (HBV) infection on the mother and fetus, the effect of pregnancy on replication of the HBV, whether mothers should take HBV antiviral therapy during pregnancy, the effect of these treatments on the mother and fetus, how to carry out immunization of neonates, whether it can induce hepatitis activity after delivery and other serious issues. At present, there are about 350 million individuals with HBV infection worldwide, of which 50% were infected during the perinatal or neonatal period, especially in HBV-endemic countries. Currently, the rate of HBV infection in thechild-bearing age group is still at a high level, and the infection rate is as high as 8.16%. Effective prevention of mother-to-child transmission is an important means of reducing the global burden of chronic HBV infection. Even after adopting the combined immunization measures, there are still 5%-10% of babies born with HBV infection in hepatitis B e antigen positive pregnant women. As HBV perinatal transmission is the main cause of chronic HBV infection, we must consider how to prevent this transmission to reduce the burden of HBV infection. In this population of chronic HBV infected women of childbearing age, specific detection, intervention and follow-up measures are particularly worthy of attention and discussion.

Current trends in management of hepatitis B virus reactivation in the biologic therapy era

Hepatitis B virus (HBV) reactivation represents an emerging cause of liver disease in patients undergoing treatment with biologic agents. In particular, the risk ofHBV reactivation is heightened by the use monoclonalantibodies, such as rituximab (anti-CD20) and alemtuzumab (anti-CD52) that cause profound and longlasting immunosuppression. Emerging data indicatethat HBV reactivation could also develop following theuse of other biologic agents, such as tumor necrosis factor (TNF)-α inhibitors. When HBV reactivation is di-agnosed, it is mandatory to suspend biologic treatmentand start antiviral agents immediately. However, preemptive antiviral therapy prior to monoclonal antibodyadministration is crucial in preventing HBV reactivationand its clinical consequences. Several lines of evidencehave shown that risk of HBV reactivation is greatlyreduced by the identifi cation of high-risk patients andthe use of prophylactic antiviral therapy. In this article, we discuss current trends in the management of HBV reactivation in immunosuppressed patients receiving biologic therapy, such as rituximab, alemtuzumab and TNF-α antagonists.

Targeting host factors:A novel rationale for the management of hepatitis C virus

Hepatitis C is recognized as a major threat to global public health. The current treatment of patients with chronic hepatitis C is the addition of ribavirin to interferon-based therapy which has limited efficacy, poor tolerability, and significant expense. New treatment options that are more potent and less toxic are much needed. Moreover, more effective treatment is an urgent priority for those who relapse or do not respond to current regimens. A major obstacle in combating hepatitis C virus （HCV） infection is that the fidelity of the viral replication machinery is notoriously low, thus enabling the virus to quickly develop mutations that resist compounds targeting viral enzymes. Therefore, an approach targeting the host cofactors, which are indispensable for the propagation of viruses, may be an ideal target for the development of antiviral agents because they have a lower rate of mutation than that of the viral genome, as long as they have no side effects to patients. Drugs targeting, for example, receptors of viral entry, host metabolism or nuclear receptors, which are factors required to complete the HCV life cycle, may be more effective in combating the viral infection. Targeting host cofactors of the HCV life cycle is an attractive concept because it imposes a higher genetic barrier for resistance than direct antiviral compounds. However the principle drawback of this strategy is the greater potential for cellular toxicity.