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Infection and Immunity, December 1999, p. 6670-6677, Vol. 67, No. 12
Division of Geographic Medicine and
Infectious Disease1 and Division of
Nephrology,2 New England Medical Center,
Boston, Massachusetts 02111
Received 27 May 1999/Returned for modification 14 July
1999/Accepted 17 September 1999
Shiga toxin-producing Escherichia coli (STEC) is an
important food-borne pathogen that causes hemolytic-uremic syndrome.
Following ingestion, STEC cells colonize the intestine and produce
Shiga toxins (Stx), which appear to translocate across the intestinal epithelium and subsequently reach sensitive endothelial cell beds. STEC
cells produce one or both of two major toxins, Stx1 and Stx2. Stx2-producing STEC is more often associated with disease for reasons
as yet undetermined. In this study, we used polarized intestinal
epithelial cells grown on permeable filters as a model to compare Stx1
and Stx2 movement across the intestinal epithelium. We have previously
shown that biologically active Stx1 is able to translocate across cell
monolayers in an energy-dependent, saturable manner. This study
demonstrates that biologically active Stx2 is also capable of movement
across the epithelium without affecting barrier function, but
significantly less Stx2 crossed monolayers than Stx1. Chilling the
monolayers to 4°C reduced the amount of Stx1 and Stx2 movement by
200-fold and 20-fold respectively. Stx1 movement was clearly
directional, favoring an apical-to-basolateral translocation, whereas
Stx2 movement was not. Colchicine reduced Stx1, but not Stx2,
translocation. Monensin reduced the translocation of both toxins, but
the effect was more pronounced with Stx1. Brefeldin A had no effect on
either toxin. Excess unlabeled Stx1 blocks the movement of
125I-Stx1. Excess Stx2 failed to have any effect on Stx1
movement. Our data suggests that, despite the many common physical and
biochemical properties of the two toxins, they appear to be crossing
the epithelial cell barrier by different pathways.
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Shiga Toxins 1 and 2 Translocate Differently
across Polarized Intestinal Epithelial Cells
and
*
Corresponding author. Mailing address: Division of
Geographic Medicine and Infectious Diseases, New England Medical
Center, Box 041, 750 Washington St., Boston, MA 02111. Phone: (617)
636-7002. Fax: (617) 636-5292. E-mail:
david.acheson{at}es.nemc.org.
Present address: Fogarty International Center, National Institutes
of Health, Bethesda, MD.
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