We have initiated studies to characterize the role of CD8 + T cells in immunity to the intracellular bacterium, Shigellaflexneri. During infection, S. flexneri enters cells and escapes into the host cell cytosol. We expected that proteins excreted from Shigella would be proteolytically degraded into peptides by the MHC-I processing pathway, and that the resulting cell-surface peptide:MHC-I complexes would stimulate CD8 + T-cells. During infection with Listeria monocytogenes, another cytosolic bacterial pathogen, Listeria- derived peptides, in complex with host MHC-I, are recognized by CD8 ? T cells and contribute to the generation of protective immunity. However, we have found that CD8 + T cells do not appear to play a role in protective immunity to S. flexneri. Even when the Shigella have been engineered to constitutively secrete heterologous epitopes known to stimulate potent CD8 + T cell responses, those responses were not dectected. We also found that when cultured cells were infected with these epitope-tagged S. flexneri strains, the cells were not recognized by established T-cell clones specific for the epitope tag. These findings have suggested to us that a step (or steps) in the normal MHC-I processing pathway is inhibited in cells infected with S. flexneri. The experiments in this proposal seek to identify and characterize the defect in MHC-I processing and/or presentation that occurs during S. flexneri infection. Specifically: 1) using biochemical assays, we will analyze the MHC-I pathway during Shigella infection to determine if there is inhibition of specific activities; and 2) we will use two parallel genetic screens to identify S. flexneri gene product(s) responsible for the inhibition. Through these experiments, we expect to identify and describe the activity of a bacterial inhibitor of MHC-I processing and presentation. Such an inhibitor might represent a novel class of virulence determinants specifically able to inhibit pathogen recognition by the adaptive immune system of the host. Understanding how this inhibition affects bacterial virulence and acquired immunity will further our understanding of the complex interaction of this bacterial pathogen and its mammalian host.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI055962-05
Application #
7151186
Study Section
Special Emphasis Panel (ZRG1-BM-1 (01))
Program Officer
Van de Verg, Lillian L
Project Start
2003-06-15
Project End
2008-03-31
Budget Start
2006-12-01
Budget End
2008-03-31
Support Year
5
Fiscal Year
2007
Total Cost
$401,791
Indirect Cost
Name
Harvard University
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
047006379
City
Boston
State
MA
Country
United States
Zip Code
02115
Zhang, Xuqing; Starnbach, Michael N (2015) An Excess of the Proinflammatory Cytokines IFN-? and IL-12 Impairs the Development of the Memory CD8+ T Cell Response to Chlamydia trachomatis. J Immunol 195:1665-75
Nogueira, Catarina V; Zhang, Xuqing; Giovannone, Nicholas et al. (2015) Protective immunity against Chlamydia trachomatis can engage both CD4+ and CD8+ T cells and bridge the respiratory and genital mucosae. J Immunol 194:2319-29
Fankhauser, Sarah C; Starnbach, Michael N (2014) PD-L1 limits the mucosal CD8+ T cell response to Chlamydia trachomatis. J Immunol 192:1079-90
Jehl, Stephanie P; Nogueira, Catarina V; Zhang, Xuqing et al. (2012) IFN? inhibits the cytosolic replication of Shigella flexneri via the cytoplasmic RNA sensor RIG-I. PLoS Pathog 8:e1002809
Jehl, Stephanie P; Doling, Amy M; Giddings, Kara S et al. (2011) Antigen-specific CD8(+) T cells fail to respond to Shigella flexneri. Infect Immun 79:2021-30
van der Velden, Adrianus W M; Dougherty, Jeffrey T; Starnbach, Michael N (2008) Down-modulation of TCR expression by Salmonella enterica serovar Typhimurium. J Immunol 180:5569-74
Shaw, Christine A; Starnbach, Michael N (2008) Both CD4+ and CD8+ T cells respond to antigens fused to anthrax lethal toxin. Infect Immun 76:2603-11
Shaw, Christine A; Starnbach, Michael N (2008) Antigen delivered by anthrax lethal toxin induces the development of memory CD8+ T cells that can be rapidly boosted and display effector functions. Infect Immun 76:1214-22
D'Orazio, Sarah E F; Shaw, Christine A; Starnbach, Michael N (2006) H2-M3-restricted CD8+ T cells are not required for MHC class Ib-restricted immunity against Listeria monocytogenes. J Exp Med 203:383-91
Hang, Howard C; Loureiro, Joana; Spooner, Eric et al. (2006) Mechanism-based probe for the analysis of cathepsin cysteine proteases in living cells. ACS Chem Biol 1:713-23

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