HEADDr MEURS Eliane / emeurs@pasteur.fr
  MEMBERSMalek AHMADI POUR / Dr Agata BUDKOWSKA /Michela BURLONE/ Stéphanie DABO / Dr Patrick MAILLARD /Sylvie PAULOUS/ Myriam VILASCO / Dr Damien VITOUR / Marine WALIC

  Annual Report

We investigate the mechanisms of cell infection with hepatitis C virus (HCV) and of its interaction with the host immune response, to develop new approaches targeting virus replication and propagation. We analyse mechanisms of HCV cell entry and egress and its interaction with the Interferon (IFN) inducing pathway.

Mechanisms of HCV cellular entry and egress: role of lipoproteins, lipoprotein receptors and microtubule network (A.Budkowska).

HCV is remarkably efficient in establishing chronic infection and evading from the host immune response. We showed that HCV core protein and viral nucleocapsids bind IgG, via an Fcγ-receptor-like site which has biochemical characteristics of the human « neonatal » Fcγ receptor (FcRn). Thus, HCV may escape immunological defence mechanisms by interfering with the function of the Fcγ region of anti-core antibodies or mimicking FcRn . We showed that human “scavenger receptor” SR-BI/Cla1 mediates HCV cellular uptake and that HCV/receptor interaction is not mediated by viral envelope but by the virus-associated VLDL. Therefore Apo-B containing lipoproteins promote virus entry and assure protection against neutralising antibodies . We provided first evidence that HCV can use lipoprotein lipase (LPL)-dependent alternative pathway for cell entry, through the formation of a bridge between virus-associated triglyceride-rich lipoproteins and cell surface heparan sulfate. LPL has a potent inhibitory effect on HCV infection, probably leading the virus to an abortive infection, and as such can have anti-viral activity in vivo . These findings demonstrate an essential role for lipoproteins in HCV life cycle thereby providing new targets for treatment of HCV infection. We showed that the microtubule network is required for HCV cell entry and release of the virus from infected cells. The direct interaction of HCV core with α/β tubulin enhances tubulin polymerization in vitro. These findings suggest that HCV can exploit microtubule polymerization mechanisms to promote virus transport and assembly. Microtubules could thus represent a potential target for a new therapeutic intervention against HCV infection

The role of the Interferon (IFN) inducing pathway in the control of HCV infection (E.Meurs)

Pegylated recombinant IFN (in combination with ribavirin) is the current treatment against HCV infection. Natural IFN is also produced by the HCV-infected cells during the innate immune response but its efficacy is limited, in part due to defense mechanisms developed by the virus to inhibit both its induction and antiviral effects. IFN induction occurs after recognition of the 5’ppp end and dsRNAs structures of the HCV genome by the cytosolic pathogen-recognition receptor RNA helicase RIG-I, and its subsequent association with the mitochondria-bound adapter MAVS/Cardif. This triggers downstream signaling pathways, involving the NF-κB-activating IKKα/IKKβ kinases and the IRF3-phosphorylating TBK1/IKKε kinases, concurring to IFN induction. We showed that the RIG-I-mediated IFN induction pathway is inhibited by the HCV NS3/4A protease in an HCV replicon system but can be restored by overexpression of RIG-I, TBK1 or IKKε (J Virol, 2005). Analysis of liver biopsies revealed a down regulation of the RNAs expression levels of IKKε and of the RNA helicases RIG-I, Mda5 and LGP2 in HCV-infected patients non responders to IFN treatment, thus indicating that HCV may preferentially replicate in cells in which the IFN-inducing pathway is impaired (Hepatology, 2006). IKKε, and not TBK1, associates preferentially with Cardif at the mitochondria. Through a yeast two-hybrid search, we identified a cell cycle-related kinase as a partner for both Cardif and IKKε and we demonstrated that it behaves as a new cellular regulator of the IFN inducing pathway (submitted). By screening peptide libraries, we are generating inhibitors of the association of this new partner with Cardif in view of facilitating functional studies on the consequences of this interaction on cell growth and on HCV infection.

Keywords: HCV, lipoproteins, microtubules, Interferon, RIG-I pathway, Cardif, TBK1/IKK kinases



Maillard P;, J-P. Lavergne JP. , S. Siberil S. , Faure G., Roohvand F., . Petres S. , J-L. Teillaud JL. and A. Budkowska A.  Fcγ receptor-like activity of Hepatitis C virus core protein . Journal of Biological Chemistry. 2004 279, 2340-2347 (PMID: 14610077)

Breiman, A., N. Grandvaux, R. Lin, C. Ottone, S. Akira, M. Yoneyama, T. Fujita, J. Hiscott, and E. F. Meurs. 2005. Inhibition of RIG-I-dependent signaling to the interferon pathway during hepatitis C virus expression and restoration of signaling by IKKepsilon. J Virol 79:3969-7 (PMID: 15767399)

Maillard, P., T. Huby, U. Andreo, M. Moreau, J. Chapman, and A. Budkowska. 2006. The interaction of natural hepatitis C virus with human scavenger receptor SR-BI/Cla1 is mediated by ApoB-containing lipoproteins. Faseb J 20:735-7. (PMID: 16476701)

Vilasco, M., E. Larrea, D. Vitour, S. Dabo, A. Breiman, B. Regnault, J. I. Riezu, P. Eid, J. Prieto, and E. F. Meurs. 2006. The protein kinase IKKepsilon can inhibit HCV expression independently of IFN and its own expression is downregulated in HCV-infected livers. Hepatology 44:1635-47. (PMID: 17133498)

Andreo, U., Maillard, P., Kalinina, O., Walic, M., Meurs, E., Martinot, M., Marcellin, P., and Budkowska, A. 2007. Lipoprotein lipase mediates hepatitis C virus (HCV) cell entry and inhibits HCV infection.Cellular Microbiology 9, 2445-2456. (PMID: 17517063)

Activity Reports 2007 - Institut Pasteur
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