Protzer Lab

HBV replication is strictly non-cytopathic and is hardly recognized by the infected cell. Thus, hepatitis B viruses avoid harming their hosts. Since they are optimized to persist life long, these viruses established a well-controlled replication strategy and an intimate cross talk with their host cells. To study this, we established preparation and culture of primary hepatocytes from animal and human liver tissue as well as the infectable cell line HepaRG and the novel cell line HepG2-H1.3, which allow us to study the effect of antivirals and interferons on the persistence form of HBV, the nuclear covalently closed circular (ccc) DNA.

HBV only infects humans and chimpanzees. Systemic studies on the immune control of infection using HBV in a convenient, well characterized animal model are therefore limited. To overcome the species barrier, we have established adenoviral vectors that transfer replication competent HBV genomes (AdHBV) into a broad range of cultured cells and in vivo into animals. This system allows for the first time to follow onset and clearance of HBV infection and will help to dissect cellular and molecular mechanisms essential for HBV clearance.

To break tolerance in chronic HBV infection, CD4+ as well as CD8+ effector T cells need to be induced. Additionally neutralizing anti-HBs antibody responses are desired to block virus spread and tolerizing effects of HBsAg. We aim at establishing vaccination schemes able to achieve both. Using HBV transgenic mice, we showed that DC based vaccines as well a as properly formulated, particulate HBV vaccine (collaboration Rheinbiothech/Dynavax Europe) can induce anti-HBs seroconversion as well as a CD8+ effector T cell response.

To be able to study anti-HBV therapies, we use HBV replicating cell lines after transient or stable transfection of replication competent HBV genomes, the cell line HepaRG, which can be infected with HBV and supports the complete replication cycle, and HBV transgenic mouse models for in vivo testing. We established medium-throughput, infection- and transfection-based HBV assays that allow phenotypic testing of HBV variants isolated from patient material as well as antiviral screening. In addition, we have designed bifunctional siRNAs, which besides gene silencing trigger the cytosolic pattern recognition receptor Rig I and control HBV very efficiently and long-lasting.

An efficient T cell response is essential to control and finally clear HBV infection. We therefore exploit T cell therapy strategies to eliminate HBV. On the other hand, we cloned graft T cell receptors (TCR) from patients with resolved HBV infection and use them to graft T cells to retarget them against HBV infected cells. Alternatively, we use chimeric antigen receptors (CAR), which are composed of intracellular TCR signaling domains and „single chain” antibody fragments (scFv) directed against HBV envelope proteins recognizing these HBV proteins on infected cells independent of peptide presentation on MHC.