Despite the existence of safe and efficient vaccines for more than twenty years, hepatitis B remains a public health problem of worldwide importance. It is currently estimated that 370 million people are chronic carriers of hepatitis B virus (HBV), and hepatitis B is held responsible for 1.2 million deaths each year. Furthermore, these chronic carriers represent an important reservoir for viral dissemination. Chronic HBV infection is a major risk factor for the development of cirrhosis and hepatocellular carcinoma, one of the commonest killer tumors in humans.

Ongoing projects include the analysis of genetic alterations in HBV-associated tumors, in collaboration with the Institut Pasteur of Shanghai, and the search for new virus-cell interactions involved in HBV replication and pathogenesis. The Wnt/b-catenin pathway is a key player during development and it is aberrantly reactivated in human liver cancer by somatic mutations of b-catenin. Our major goal is to identify cellular partners and target genes of b-catenin that operate in liver oncogenesis. We have recently found that the FHL2 coactivator interacts with b-catenin and is critically involved in the activation of Wnt-responsive genes such as cyclin D1. Studies in mouse embryo fibroblasts demonstrate that the LIM-only protein FHL2 plays a pivotal role in cell cycle, cell immortalization and transformation. Our recent data in murine models outline FHL2 implication in liver regeneration and fibrosis and in Wnt-related intestinal tumorigenesis.

The aim of our research programm is also to gain a clearer understanding of the immunopathology of chronic liver disease caused by HBV infection and thus to develop therapeutic approaches aimed at controlling viral replication, improving histologic lesions of liver and ultimately to provide a cure for this disease. In the absence of any antiviral therapies that are fully effective in the long term, we are developing new strategies to enable a sustained control of infection in chronic HBV carriers. These are based on active immunotherapy aimed at achieving the control of viral infection by the immune system. It is clear that the immune mechanisms associated with the antiviral response play a major role in disease outcome. Definition of HBV epitopic sequences recognized by T cells during HBV infection and design of vaccine candidates tested in mice transgenic for human MHC molecules allow implementing innovative therapeutic vaccine trials in patients suffering from HBV chronic infection. To this end, we collaborate with physicians from various hospitals to push these projects further. A proof of concept study (phase I trial) of therapeutic DNA-based vaccination for HBV chronic infection was conducted in patients suffering from chronic hepatitis B. Results showed good tolerance to the vaccine and activation of adaptive immunity and of a particular subset of NK cells. A phase II multi-centric trial combining antiviral agents and DNA-based vaccine therapy is ongoing. In this trial we analyze the immune response activated by the DNA vaccine and try to determine whether the response can be linked to control of viral replication after discontinuation of treatment (Dr. H. Fontaine, AP-HP, Hopital Cochin, PI; ANRS is the sponsor of the study).

As an alternative approach to vaccine therapy, we used the HBV genome as a gene therapy vector to deliver foreign antigenic determinants to HBV-infected liver cells and to attract functionally active T cells to liver. We demonstrated that these functional T cells control HBV multiplication and gene expression in liver of HBV-transgenic mice.

Keywords: Hepatitis B, liver, hepatocellular carcinoma, FHL2, T-cells, NK cells, vaccine, immuno-therapy, gene therapy

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