Cardiotoxicity of Streptococcal Pyrogenic Exotoxins

Schlievert, Patrick

Abstract

The long term goals of this project are two fold: a) to evaluate the role of pyrogenic toxin superantigens, notably streptococcal pyrogenic exotoxins (SPEs, scarlet fever toxins, in causing both acute toxic shock syndrome and vascular illnesses and chronic autoimmune and allergic diseases, and b) to analyze the structure:function relationships among the SPEs and between the SPEs and the staphylococcal enterotoxins and toxic shock syndrome toxin-1, with the intent of clarifying the molecular mechanisms of action of the toxins, developing toxoid vaccines, and developing useful adjuvants of the toxins.
Specific aims of the present application include: a) Biochemical and immunobiological characterization of SPEs J and L, and determining the three dimensional structure of both toxins (complex structures of the SPEs with the variable part of the beta chain of the T cell receptor and major histocompatibility complex II molecules will be determined if such structures are likely to generate new data). Our role in this aim will be to characterize the new SPEs, provide toxins for structural studies, consult on the best conditions for use in crystallization, and preparation and testing mutant toxins for confirmation that important contact residues on the SPEs are required for activity; b) Characterization of SPE C's, and possibly SPE J's ability to cross mucosal surfaces. Studies will include establishment of vaginal epithelial monolayers and stratified epithelium in Transwells and evaluation of the mechanism by which the toxin(s) traverse the layers. We will also evaluate the ability of biologically inactive toxins to permeabilize the epithelium, both in vitro and in rabbits, to other agents, and thus, determine whether the toxoids may be useful as delivery agents (and possibly adjuvants) for transmucosal immunization; and c) Characterization of the mechanism of streptococcal toxic shock syndrome with necrotizing fasciitis in rabbits. We hypothesize that SPEs cause both hypotension and delayed phagocytosis through exaggerated cytokine release, which in turn allows continued growth of the invasive organism with production of necrotizing fasciitis through hemolysins and protease.