All ETDs from UAB

Advisory Committee Chair

Suzanne M Michalek

Advisory Committee Members

Jannet Katz

Louis Justement

Susan Bellis

Daniel Balkovetz

Document Type

Dissertation

Date of Award

2010

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

Francisella tularensis, a facultative intracellular, gram-negative coccobacillus, is the causative agent of tularemia and has been classified as a category A biological agent. Since there currently is no licensed vaccine available, in this study, we assessed the potential of a bivalent subunit vaccine comprising of DnaK and Tul4 to protect against respiratory tularemia. Intranasal immunization of C57BL/6 mice with DnaK, Tul4, and the adjuvant GPI-0100 resulted in mucosal and systemic antibody responses to DnaK and Tul4. In addition to antibody responses, this immunization regimen also induced both Th1 and Th2 cell-mediated immune responses specific for DnaK and Tul4. Finally, more than 80% of the mice immunized with DnaK, Tul4 and GPI-0100 were completely protected against a lethal respiratory challenge with F. tularensis live vaccine strain. These results provide strong evidence for the use of the DnaK and Tul4 as potential subunit vaccine antigens. For the development of a safe and effective vaccine, it is important to understand the molecular interactions of the vaccine components with the immune system. In this regard, dendritic cells (DC) and B cells express Toll-like receptors (TLR) and TLR signaling in these cells shape innate as well as adaptive immune responses. Therefore, we determined the precise requirement of TLR signaling in DC and B cells for innate immune responses to DnaK and Tul4. Tul4 activated both DC and B cells to produce cytokines and upregulate costimulatory molecules in an entirely TLR2 dependent manner. On the other hand, activation of DC by DnaK was dependent on TLR4 signaling, and both MyD88 and TRIF signaling pathways were essential for an optimal DnaK induced cytokine response. Interestingly, CD40 and BCR signaling synergized with DnaK and Tul4 mediated activation of B cells to induce a distinct set of cytokines and chemokines, highlighting the crosstalk between these receptors. This is the first report demonstrating the effectiveness of a bivalent, mucosal tularemia vaccine and provides evidence on possible cellular mechanisms involved in the ability of this vaccine to induce protective immunity against F. tularensis infection.

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