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.
|Yonkers, Nicole L; Rodriguez, Benigno; Post, Anthony B et al. (2006) HIV coinfection impairs CD28-mediated costimulation of hepatitis C virus-specific CD8 cells. J Infect Dis 194:391-400|
|Kuekrek, Haydar; Schlingmann, Tobias; Valdez, Hernan et al. (2005) Differential effect of interleukin-2 treatment on primary and secondary immunizations in HIV infected individuals. AIDS 19:1967-74|
|Berner, Beate R; Tary-Lehmann, Magdalena; Yonkers, Nicole L et al. (2005) Phenotypic and functional analysis of EBV-specific memory CD8 cells in SLE. Cell Immunol 235:29-38|
|Quast, Stefan; Zhang, Wenji; Shive, Carey et al. (2005) IL-2 absorption affects IFN-gamma and IL-5, but not IL-4 producing memory T cells in double color cytokine ELISPOT assays. Cell Immunol 237:28-36|
|Ott, Patrick A; Berner, Beate R; Herzog, Bernhard A et al. (2004) CD28 costimulation enhances the sensitivity of the ELISPOT assay for detection of antigen-specific memory effector CD4 and CD8 cell populations in human diseases. J Immunol Methods 285:223-35|
|Anthony, Donald D; Yonkers, Nicole L; Post, Anthony B et al. (2004) Selective impairments in dendritic cell-associated function distinguish hepatitis C virus and HIV infection. J Immunol 172:4907-16|
|Anthony, Donald D; Valdez, Hernan; Post, Anthony B et al. (2002) Comprehensive determinant mapping of the hepatitis C-specific CD8 cell repertoire reveals unpredicted immune hierarchy. Clin Immunol 103:264-76|
|Valdez, Hernan; Carlson, Nicole L; Post, Anthony B et al. (2002) HIV long-term non-progressors maintain brisk CD8 T cell responses to other viral antigens. AIDS 16:1113-8|