Accession Number : AD1012856


Title :   Comparisons of Native and Chimeric Shiga Toxins Indicate that the Binding Subunit Dictates Degree of Toxicity


Descriptive Note : Technical Report


Corporate Author : Uniformed Services University Of The Health Sciences Bethesda United States


Personal Author(s) : Russo,Lisa M


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/1012856.pdf


Report Date : 17 Mar 2014


Pagination or Media Count : 183


Abstract : Shiga toxin (Stx) producing Escherichia coli (STEC), particularly serotype0157:H7, are important food bome human pathogens that cause outbreaks of hemorrhagic colitis and a severe sequela, the hemolytic uremic syndrome. Stx, the primary virulence factor for this group of organisms, is responsible for the histopathological kidney lesions that result after infection with STEC. An 0157:H7 strain may produce Stxla, Stx2a, or both Stxs. The Stxs are biologically similar, though antigenically distinct, ABS toxins with an identical mode of action that inhibits host cell protein synthesis and leads to cell death. The A subunit is comprised of two parts, the A1 subunit that is responsible for the N-glycosidase activity of the molecule and the A2 peptide that is threaded through the center of the homopentameric B subunit and non-covalently links the A and B subunits globotriaosylceramide (Gb3).Although the Stxs have an identical mode of action, Stxla is associated with increased cytotoxicity for Vero cells in vitro compared to Stx2a, while Stx2a is associated with increased in vivo toxicity compared to Stxla. The primary goal of this dissertation was to investigate that paradox. First, we determined the oral toxicity of the Stxs in a mouse model. We assessed the oral LD50 for Stx2a, defined the resultant kidney histopathology, and, finally, protected and rescued mice with a monoclonal antibody against Stx2a. However, we did not observe any morbidity or mortality after intoxication with Stx 1 a. Second, we used chimeric toxins to analyze the contribution of the individual Stx subunits to in vitro cytotoxicity and in vivo morbidity and mortality. Our chimeras were unique in that the A1 and B subunit were generated from one native Stx, while theA1 subunit that contained the catalytic domain was derived from the heterologous Stx. We found that the A1 peptide increased stability of the chimeric holotoxin. Our chimeric were the first such molecules reported to exhibit activity


Descriptors :   Toxins and antitoxins , Pathogenesis


Distribution Statement : APPROVED FOR PUBLIC RELEASE