TOWARD DESIGNING A MORE EFFECTIVE VACCINE: MECHANISMS OF PRIMING T CELLS IN VIVO
Open Access
- Author:
- Donohue, Keri B
- Graduate Program:
- Integrative Biosciences
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- August 27, 2009
- Committee Members:
- Christopher Charles Norbury, Dissertation Advisor/Co-Advisor
Christopher Charles Norbury, Committee Chair/Co-Chair
Leslie Joan Parent, Committee Member
Todd Schell, Committee Member
John Warren Wills, Committee Member
Charles H Lang, Committee Member - Keywords:
- antigen presentation
T cell activation
cross-priming
antigen processing
vaccine vector - Abstract:
- The infectious diseases that currently pose the greatest threat to humans, AIDS, tuberculosis and malaria, are likely to require a vaccine strategy designed to elicit T cell-mediated immunity. Rational vaccine design requires a mechanistic understanding of how T cells are activated in vivo. Thus, we sought to examine the requirements of the direct and cross-priming pathways of CD8+ T cell activation as well as examine the antigen processing and presentation pathways available to a model antigen when expressed by viral vaccine vectors. Investigation of the requirements for direct and cross-priming revealed that the two pathways utilize different pools of antigen. Direct presentation requires newly synthesized, rapidly degraded antigen while cross-priming requires long-lived stable antigen. Additionally, antigen donor cells had no requirement for proteasomal processing, protein synthesis or vesicular transport of the antigen or other cellular factors in order to donate antigen to the cross-priming pathway in vivo. Investigation of the antigen processing and presentation pathways available to a model antigen, OVA, when expressed from viral vectors produced unexpected results. We found that recombinant Vaccinia Virus (rVV) expressed OVA was permitted to access the TAP-independent cross-priming pathway- a pathway which OVA is normally unable to access. Although rVV expression permitted the model antigen to access an additional antigen processing and presentation pathway, recombinant Vesicular Stomatitis Virus (rVSV) expression stimulated 5- fold more model antigen-specific CD8+ T cells. Initially, rVSV-expressed OVA also appeared to require TAP for MHC class II presentation. However, subsequent experiments revealed that the lack of presentation in TAP knockout mice was not due to TAP-dependent MHC class II presentation of rVSV-expressed OVA but instead due to a lack of antigen presenting cell subsets in the gamma-irradiated TAP knockout mice. Together these findings have broad implications for the rational design of vaccines aimed at the generation of protective T cell responses.