title: CD8(+) T cell control of hepatitis B virus replication: direct comparison between cytolytic and noncytolytic functions.
abstract: Resolution of hepatitis B virus (HBV) infection was believed to be attributed to the cytotoxic T cell-mediated killing of infected hepatocytes. However, studies in HBV transgenic mice and HBV-infected chimpanzees revealed that T cell control of HBV replication also involves cytokine-mediated noncytolytic mechanisms. The relative role of cytolytic and noncytolytic functions of virus-specific CD8(+) T cells during interaction with HBV-producing hepatocytes is not well understood. By using HLA-A2 matched effector cells (CD8(+) T cell line or clone) and target cells supporting full HBV replication, we demonstrate that virus-specific CD8(+) T cells can inhibit HBV replication in HBV-producing hepatocytes with minimal cell lysis. Although CD8(+) T cells kill a fraction of infected cells, this effect is minimal, and most of the viral inhibition is mediated by noncytolytic mechanisms. CD8(+) T cells produce an array of cytokines, among which IFN-gamma and TNF-alpha are responsible for HBV inactivation in the target cells. Blockade of IFN-gamma and TNF-alpha abrogated the noncytolytic inhibition of HBV, indicating that these two cytokines mediate the control of HBV by noncytolytic mechanisms. Furthermore, treatment of the HBV-producing hepatocytes with rIFN-gamma and rTNF-alpha resulted in an efficient suppression of viral replication without cytotoxicity. In contrast, coculture of the same target cells with activated HLA-mismatched mitogen-activated lymphomononuclear cells caused a marked cytolytic effect and was less effective in HBV control. These results provide direct evidence that virus-specific CD8(+) T cells efficiently control HBV replication by noncytolytic mechanisms, and this effect is mediated by IFN-gamma and TNF-alpha.
authors: Institute of Hepatology, University College London, London, U.K. s.phillips@ucl.ac.uk
authors: Sandra
authors: S
authors: Phillips
authors: Shilpa
authors: S
authors: Chokshi
authors: Antonio
authors: A
authors: Riva
authors: Alexander
authors: A
authors: Evans
authors: Roger
authors: R
authors: Williams
authors: Nikolai V
authors: NV
authors: Naoumov
mesh_terms: D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D045744:Cell Line, Tumor; D018920:Coculture Techniques; D003602:Cytotoxicity, Immunologic; D005434:Flow Cytometry; D006509:Hepatitis B / Q000276:immunology*; D006515:Hepatitis B virus / Q000502:physiology; D006801:Humans; D007371:Interferon-gamma / Q000096:biosynthesis / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000276:immunology; D014779:Virus Replication / Q000276:immunology
chemical_list: D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma