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Journal of Virology, October 1998, p. 8301-8308, Vol. 72, No. 10
Third Department of Internal Medicine, Kagawa
Medical University, Kagawa, Japan
Received 18 August 1997/Accepted 2 July 1998
The induction of an efficient CD4+ T-cell response
against hepatitis C virus (HCV) is critical for control of the
chronicity of HCV infection. The ability of HCV structural protein
endogenously expressed in an antigen-presenting cell (APC) to be
presented by class II major histocompatibility complex molecules to
CD4+ T cells was investigated by in vitro culture analyses
using HCV core-specific T-cell lines and autologous Epstein-Barr
virus-transformed B-lymphoblastoid cell lines (B-LCLs) expressing
structural HCV antigens. The T- and B-cell lines were generated
from peripheral blood mononuclear cells derived from HCV-infected
patients. Expression and intracellular localization of core
protein in transfected cells were determined by immunoblotting and
immunofluorescence. By stimulation with autologous B-LCLs expressing
viral antigens, strong T-cell proliferative responses were induced
in two of three patients, while no substantial stimulatory effects
were produced by B-LCLs expressing a control protein
(chloramphenicol acetyltransferase) or by B-LCLs alone. The results
showed that transfected B cells presented mainly endogenously
synthesized core peptides. Presentation of secreted antigens from
adjacent antigen-expressing cells was not enough to stimulate a
core-specific T-cell response. Only weak T-cell proliferative
responses were generated by stimulation with B-LCLs that had been
pulsed beforehand with at least a 10-fold-higher amount of transfected
COS cells in the form of cell lysate, suggesting that presentation of
antigens released from dead cells in the B-LCL cultures had a minimal
role. Titrating numbers of APCs, we showed that as few as
104 transfected B-LCL APCs were sufficient to stimulate T
cells. This presentation pathway was found to be leupeptin
sensitive, and it can be blocked by antibody to HLA class II
(DR). In addition, expression of a costimulatory signal by B7/BB1 on B
cells was essential for T-cell activation.
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Efficient Class II Major Histocompatibility Complex Presentation
of Endogenously Synthesized Hepatitis C Virus Core Protein by
Epstein-Barr Virus-Transformed B-Lymphoblastoid Cell Lines to
CD4+ T Cells

and
*
Corresponding author. Present address: Department of
Microbiology, University of Texas Southwestern Medical Center at
Dallas, NA2.116 Harry Hines Blvd., Dallas, TX 75235-9048. Phone: (214) 648-5945. Fax: (214) 648-5905. E-mail:
m.chen{at}mci2000.com.
Present address: Department of Microbiology, Yamaguchi University
School of Medicine, Ube City, Yamaguchi 755, Japan.
Present address: Department of Microbiology and Immunology, Nippon
Medical School, Bunkyoku, Tokyo, Japan.
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