Date of Award

2007

Degree Type

Thesis

Degree Name

Master of Science

Program

Microbiology and Immunology

Supervisor

Dr. John McCormick

Abstract

Streptococcus pyogenes is a Gram-positive bacterial pathogen associated with an extraordinary range of human infections. Streptococcal pyrogenic exotoxins are key secreted virulence factors secreted by S. pyogenes that function as superantigens to cause massive T cell activation by cross linking T cell receptors on T cells, and MHC class II molecules on antigen presenting cells. Superantigens can engage MHC class II in two radically divergent ways. One interface is of relative high-affinity, requires zinc, and is present on most streptococcal superantigens. A second interface present on many staphylococcal superantigens is of relative low-affinity, does not require zinc, but the presence of this interface on streptococcal superantigens is controversial. Herein, mutagenesis analysis of multiple streptococcal superantigens, demonstrates the low-affinity MHC class Il binding interface is likely present on all streptococcal superantigens. A complete functional map of this interface on the streptococcal superantigen SpeC provides a molecular basis for MHC class II discrimination by streptococcal superantigens.

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