AG Lohmann

Our interest focuses on the understanding of hepatitis C virus RNA replication. This includes the analysis of structure and composition of the HCV replication complex, the identification of cellular factors involved in HCV RNA replication and studies on the initiation of RNA synthesis by HCV polymerase.

Research Team Members

Research Projects

I. Purification and characterization of the HCV replication complex

Hepatitis C virus (HCV) replication takes place at distinct vesicular membrane structures but beyond this little is known about the architecture of these viral replication complexes. We have quantitatively analysed viral RNA and proteins involved in HCV replication and found that each active complex is composed of only a few viral RNAs but multiple copies of the nonstructural proteins, indicating that one or more of them serve a structural role in replication complex formation (Quinkert et al., 2005). Based on this analysis we have developed a purification strategy for HCV replication complexes and try to identify and evaluate cellular proteins that are involved in HCV replication.

II. Cellular factors determining the permissiveness of host cells for HCV replication

After development of a cell culture system for HCV RNA replication based on subgenomic replicons in the human hepatoma cell line Huh-7 (Lohmann et al., 1999), we found that adaptive mutations in the viral genome and the permissiveness of the host cell play a critical role for efficient HCV replication (Lohmann et al., 2001; Krieger et al., 2001; Lohmann et al., 2003).
We currently try to identify and evaluate cellular candidate genes that correlate with permissiveness by genomic and proteomic analyses to find cellular proteins that are involved in HCV replication. Since viral persistence has been implicated with HCV modulating the innate antiviral response by NS3/4A protease dependent interference with the IRF-3 pathway, we also try to elucidate the extend to which the innate antiviral response of the host cell is capable of controlling permissiveness to HCV.

III. Initiation and regulation of HCV RNA synthesis

RNA synthesis by the viral polymerase/replication complex is a crucial step in the HCV life cycle. As for all positive strand RNA viruses RNA replication results in a five- to tenfold excess of positive versus negative strand progeny RNA. We are interested in the mechanisms regulating the initiation of RNA synthesis and want to elucidate the viral determinants that are involved in this process. This includes the analysis of recombinant RNA dependent RNA polymerase of different isolates (Lohmann et al., 1997, 1999) as well as studies on subgenomic replicons (Lohmann et al.,1999, 2003).