Heptitis C virus (HCV) is the most common cause of chronic viral hepatitis in the United States. In the infected host, both CD4 and CD8 T cell responses directed at HCV are thought to be important in both the host's control of viral replication and the liver pathology that results from the ongoing T cell attack against virus persisting in the liver. Despite the central role of T cells in the immune pathogenesis of chronic hepatitis, technical limitations have so far prevented the acquisition of definitive data on the most basic features of the anti-HCV T cell response in infected individuals, the frequency of the specific T cells in vivo, their fine specificity (the actual peptide-determinants they recognize), and their effector class (defined by their cytokine expression patterns and cytolytic activity). Without the ability to define clearly these basic parameters of T cell-mediated immunity, our understanding of protective vs. pathogenic T cell response types in HCV infection remains incomplete, and this precludes studies aimed at altering the antiviral immune response and preventing or treating HCV-related disease. It is hypothesized that the complete clonal size (the magnitude) and fine specificity of the HCV-core-antigen-specific T cell response can be assessed, irrespective of the patient's HLA haplotype, by ex vivo ELISPOT assays that test an overlapping 10-mer peptide series that walks the core protein sequence in steps of single amino acids. (The core protein was selected to demonstrate the feasibility of this approach).
In Aims 1 and 2, therefore, it is proposed to perform systematic ELISPOT determinant mapping with an overlapping HCV-core peptide series. It is further hypothesized that measurements of cytokine coexpression patterns in two-color ELISPOT assays are suitable for characterizing the quality of the core-antigen-specific CD4 and CD8 T cell response and that cytokine coexpression in the specific cells studied at single-cell resolution proves to be more highly regulated than predicted by the Th1/Th2, Tcl/Tc2 model. To test this hypothesis, in Aim 3, it is proposed to measure the coexpression of cytokine and granzyme B in individual, freshly isolated HCV-peptide-reactive memory cells. Finally, by defining repeatedly, over the 5 years of this project, in individual HCV-infected patients the magnitude, the fine specificity and the cytokine quality of the HCV-core-protein-specific T cell response.
In Aim 4, the stability of the T cell response will be tested, thus addressing the hypothesis that the T cell repertoire directed at this HCV antigen can be dynamic, shifting the determinants targeted.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI047839-04
Application #
6632305
Study Section
Immunological Sciences Study Section (IMS)
Program Officer
Taylor, Katherine A
Project Start
2000-05-15
Project End
2005-04-30
Budget Start
2003-05-01
Budget End
2004-04-30
Support Year
4
Fiscal Year
2003
Total Cost
$306,000
Indirect Cost
Name
Case Western Reserve University
Department
Pathology
Type
Schools of Medicine
DUNS #
077758407
City
Cleveland
State
OH
Country
United States
Zip Code
44106
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