E. coli O157:H7 is an emerging pathogen of major importance. Disease caused by E. coli O157:H7 is characterized by diarrhea, hemorrhagic colitis, and the potentially fatal complication, hemolytic uremic syndrome (HUS). Shiga toxin (Stx) is a major virulence factor of E. coli O157:H7. Two major antigenic variants of Shiga toxin, Stx1 and Stx2, share 55% amino acid homology, however Stx2 production has been associated with progression to severe disease, including HUS. We propose to examine two aspects of Shiga toxin in the pathogenesis of disease caused by E. coli O157:H7 - regulation of Shiga toxin production in the intestine and the molecular basis for the difference in potency between Stx1 and Stx2. The genes for Shiga toxin are encoded on bacterial viruses. Regulation of toxin production is strongly linked to factors that affect the virus life cycle, specifically factors that induce the viral lytic cycle, for example antibiotics such as ciprofloxicin.
In Specific Aim 1 we will characterize factors that influence Stx2 expression in vitro and in vivo. In addition to amount of toxin production, the type of Shiga toxin produced during infection can influence the severity of disease, with Stx2 being by far the more potent toxin. While it is clear that Stx2 can induce cellular death, it is not clear that cellular death is required for development of HUS, and toxicity may occur at the organismal level.
In Specific Aim 2 we will characterize hybrid Stx2/Stx1 mutants to determine why Stx2 is more potent than Stx1 using in vitro cell culture models.
In Specific Aim 3 we will determine the potency of the hybrid mutants in vivo using a mouse model of disease. Understanding the viral, bacterial and host factors that influence Shiga toxin production and potency could lead to treatments that reduce the incidence of fatal disease.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
Project #
Application #
Study Section
Bacterial Pathogenesis Study Section (BACP)
Program Officer
Baqar, Shahida
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Cincinnati
Schools of Medicine
United States
Zip Code
Karve, Sayali S; Pradhan, Suman; Ward, Doyle V et al. (2017) Intestinal organoids model human responses to infection by commensal and Shiga toxin producing Escherichia coli. PLoS One 12:e0178966
Pellino, Christine A; Karve, Sayali S; Pradhan, Suman et al. (2016) AB5 Preassembly Is Not Required for Shiga Toxin Activity. J Bacteriol 198:1621-30
Karve, Sayali S; Weiss, Alison A (2014) Glycolipid binding preferences of Shiga toxin variants. PLoS One 9:e101173
Gaston, Marsha A; Pellino, Christine A; Weiss, Alison A (2013) Failure of manganese to protect from Shiga toxin. PLoS One 8:e69823
Gallegos, Karen M; Conrady, Deborah G; Karve, Sayali S et al. (2012) Shiga toxin binding to glycolipids and glycans. PLoS One 7:e30368
Fuller, Cynthia A; Pellino, Christine A; Flagler, Michael J et al. (2011) Shiga toxin subtypes display dramatic differences in potency. Infect Immun 79:1329-37
Conrady, Deborah G; Flagler, Michael J; Friedmann, David R et al. (2010) Molecular basis of differential B-pentamer stability of Shiga toxins 1 and 2. PLoS One 5:e15153
McGannon, Colleen Marie; Fuller, Cynthia Ann; Weiss, Alison Ann (2010) Different classes of antibiotics differentially influence shiga toxin production. Antimicrob Agents Chemother 54:3790-8
Flagler, Michael J; Mahajan, Sujit S; Kulkarni, Ashish A et al. (2010) Comparison of binding platforms yields insights into receptor binding differences between shiga toxins 1 and 2. Biochemistry 49:1649-57
Kulkarni, Ashish A; Fuller, Cynthia; Korman, Henry et al. (2010) Glycan encapsulated gold nanoparticles selectively inhibit shiga toxins 1 and 2. Bioconjug Chem 21:1486-93

Showing the most recent 10 out of 12 publications