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World J Gastroenterol. Sep 28, 2007; 13(36): 4839-4847
Published online Sep 28, 2007. doi: 10.3748/wjg.v13.i36.4839
Host and viral factors contributing to CD8+ T cell failure in hepatitis C virus infection
Christoph Neumann-Haefelin, Hans Christian Spangenberg, Hubert E Blum, Robert Thimme
Christoph Neumann-Haefelin, Hans Christian Spangenberg, Hubert E Blum, Robert Thimme, Department of Medicine II, University Hospital Freiburg, Germany
Author contributions: All authors contributed equally to the work.
Supported by the Deutsche Forschungsgemeinschaft (Emmy Noether Programm, SFB 610), the Wilhelm Sander Stiftung, and the Bundesministerium fuer Wissenschaft und Forschung (Start-up fonds Kompetenznetz Hepatitis)
Correspondence to: Christoph Neumann-Haefelin, Depa-rtment of Medicine II, University Hospital Freiburg, Hugstetter Strasse 55, Freiburg D-79106, Germany. christoph.neumann-haefelin@uniklinik-freiburg.de
Telephone: +49-761-2703401 Fax: +49-761-2703725
Received: June 26, 2007
Revised: July 2, 2007
Accepted: July 9, 2007
Published online: September 28, 2007
Abstract

Virus-specific CD8+ T cells are thought to be the major anti-viral effector cells in hepatitis C virus (HCV) infection. Indeed, viral clearance is associated with vigorous CD8+ T cell responses targeting multiple epitopes. In the chronic phase of infection, HCV-specific CD8+ T cell responses are usually weak, narrowly focused and display often functional defects regarding cytotoxicity, cytokine production, and proliferative capacity. In the last few years, different mechanisms which might contribute to the failure of HCV-specific CD8+ T cells in chronic infection have been identified, including insufficient CD4+ help, deficient CD8+ T cell differentiation, viral escape mutations, suppression by viral factors, inhibitory cytokines, inhibitory ligands, and regulatory T cells. In addition, host genetic factors such as the host’s human leukocyte antigen (HLA) background may play an important role in the efficiency of the HCV-specific CD8+ T cell response and thus outcome of infection. The growing understanding of the mechanisms contributing to T cell failure and persistence of HCV infection will contribute to the development of successful immunotherapeutical and -prophylactical strategies.

Keywords: Hepatitis C virus; CD8+ T cells; T cell failure; Viral escape; Programmed death 1; Regulatory T cells; T cell maturation; Human leukocyte antigen