Molecular therapeutics of HBV

The hepatitis B virus (HBV) infection is a public health problem worldwide, particularly in East Asia. The current therapy of HBV infection is mostly based on chemical agents and cytokines that have been shown to provide limited efficacy and are also toxic to the human body. Gene therapy is a new therapeutic strategy against HBV infection, involving the transmission of gene drugs into liver cells by specific delivery systems and methods. Although this new anti-HBV infection technique is under active investigation, various promising anti-HBV viral gene drugs have been developed for gene therapy, including antisense RNA and DNA, hammerhead ribozymes, dominant negative HBV core mutants, single chain antibody, co-nuclease fusion protein, and antigen. In order to optimize their antiviral effects and/or enhance anti-HBV immunity, various novel gene delivery systems have also been developed to (specifically) deliver such DNA constructs into liver cells; some of them are viral vectors, such as adenoviral vectors, retroviral vectors and poxviral vectors, and even hepatitis B viral for its hepatocellular specificity. Others are non-viral vectors, in which naked DNA and liposomes are frequently used for DNA vaccine or nucleotide analogs for inhibiting HBV DNA polymerase. This review addresses various aspects of gene therapy for HBV infection, including gene drugs, delivery methods, animal model, and liver transplantation with combination therapy. It also discusses the problems that remain to be solved.