The broad objective of this project is to elucidate the immune mechanisms responsible for killing of virally infected hepatocytes. Studies conducted as part of this project have found that hepatocytes are resistant to perforin and granzyme dependent mechanisms of cytotoxic T lymphocyte (CTL) killing and that clearance of virally infected hepatocytes from the liver is mediated predominately by alternative CTL effector mechanisms that utilize Fas/FasL, TNF/TNFR1 and/or other death receptor mediated pathways. These results lead us to hypothesize that hepatocyte resistance to the cytotoxic effects of the perforin and granzyme mediated CTL effector pathway is important in limiting the degree of liver injury during intrahepatic immune responses. To address this hypothesis and to explore the mechanisms responsible for the unique repertoire of CTL effector mechanisms employed during anti-viral immunity in the liver;we propose to explore mechanisms responsible for resistance of virally infected hepatocytes to the granule exocytosis pathway of CTL effector function. Preliminary findings indicate that cytokines produced during antiviral immune responses induce expression of the granzyme B specific inhibitors proteinase inhibitor 9 (PI-9) and serine proteinase inhibitor 6 (SPI-6) in human and mouse hepatocytes respectively. In proposed studies, we will determine the repertoire of serine proteinase inhibitors (serpins) expressed in normal and virally infected murine hepatocytes and determine the role of cytokines in regulating such serpin expression in vitro and in vivo. We will then explore the role that serpins and/or cathepsin B play in mediating hepatocyte resistance to granzymes and perforin, respectively. Finally, we will determine whether silencing of serpin and/or cathepsin B genes in vivo renders virally infected hepatocytes susceptible to perforin and granzyme dependent cytotoxicity and thereby accelerates immune clearance of virally infected hepatocytes and exacerbates viral hepatitis.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
3R01DK053933-09S1
Application #
8101392
Study Section
Hepatobiliary Pathophysiology Study Section (HBPP)
Program Officer
Doo, Edward
Project Start
1999-07-01
Project End
2011-03-31
Budget Start
2010-09-01
Budget End
2011-03-31
Support Year
9
Fiscal Year
2010
Total Cost
$46,751
Indirect Cost
Name
University of Texas Sw Medical Center Dallas
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
800771545
City
Dallas
State
TX
Country
United States
Zip Code
75390
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Getachew, Yonas; Stout-Delgado, Heather; Miller, Bonnie C et al. (2008) Granzyme C supports efficient CTL-mediated killing late in primary alloimmune responses. J Immunol 181:7810-7
Stout-Delgado, Heather W; Getachew, Yonas; Miller, Bonnie C et al. (2007) Intrahepatic lymphocyte expression of dipeptidyl peptidase I-processed granzyme B and perforin induces hepatocyte expression of serine proteinase inhibitor 6 (Serpinb9/SPI-6). J Immunol 179:6561-7
Stout-Delgado, Heather W; Getachew, Yonas; Rogers, Thomas E et al. (2007) The role of serpinb9/serine protease inhibitor 6 in preventing granzyme B-dependent hepatotoxicity. Hepatology 46:1530-40
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Barrie, Mahmoud B; Stout, Heather W; Abougergi, Marwan S et al. (2004) Antiviral cytokines induce hepatic expression of the granzyme B inhibitors, proteinase inhibitor 9 and serine proteinase inhibitor 6. J Immunol 172:6453-9
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