Two msbB genes encoding maximal acylation of lipid A are required for invasive Shigella flexneri to mediate inflammatory rupture and destruction of the intestinal epithelium.
Shigella flexneri is a Gram-negative pathogen that invades and causes inflammatory destruction of the human colonic epithelium, thus leading to bloody diarrhea and dysentery. A type III secretion system that delivers effector proteins into target eukaryotic cells is largely responsible for cell and tissue invasion. However, the respective role of this invasive phenotype and of lipid A, the endotoxin of the Shigella LPS, in eliciting the inflammatory cascade that leads to rupture and destruction of the epithelial barrier, was unknown. We investigated whether genetic detoxification of lipid A would cause significant alteration in pathogenicity. We showed that S. flexneri has two functional msbB genes, one carried by the chromosome (msbB1) and the other by the virulence plasmid (msbB2), the products of which act in complement to produce full acyl-oxy-acylation of the myristate at the 3' position of the lipid A glucosamine disaccharide. A mutant in which both the msbB1 and msbB2 genes have been inactivated was impaired in its capacity to cause TNF-alpha production by human monocytes and to cause rupture and inflammatory destruction of the epithelial barrier in the rabbit ligated intestinal loop model of shigellosis, indicating that lipid A plays a significant role in aggravating inflammation that eventually destroys the intestinal barrier. In addition, neutralization of TNF-alpha during invasion by the wild-type strain strongly impaired its ability to cause rupture and inflammatory destruction of the epithelial lining, thus indicating that TNF-alpha is a major effector of epithelial destruction by Shigella.
D'Hauteville
Hélène
H
Unité de Pathogénie Microbienne Moléculaire and Institut National de la Santé et de la Recherche Médicale, Unité 389, Institut Pasteur, 28 rue du Docteur Roux, 75724 Paris Cedex 15, France.
Khan
Shahid
S
Maskell
Duncan J
DJ
Kussak
Anders
A
Weintraub
Andrej
A
Mathison
John
J
Ulevitch
Richard J
RJ
Wuscher
Nicole
N
Parsot
Claude
C
Sansonetti
Philippe J
PJ
D000215:Acylation; D000217:Acyltransferases / Q000235:genetics*; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D018938:Caco-2 Cells; D004195:Disease Models, Animal; D004405:Dysentery, Bacillary / Q000201:enzymology / Q000378:metabolism / Q000382:microbiology* / Q000473:pathology*; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D006168:Guinea Pigs; D006801:Humans; D007413:Intestinal Mucosa / Q000276:immunology / Q000382:microbiology* / Q000473:pathology*; D008026:Ligation; D008050:Lipid A / Q000378:metabolism*; D009000:Monocytes / Q000382:microbiology / Q000473:pathology; D016296:Mutagenesis; D011817:Rabbits; D012763:Shigella flexneri / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity*; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology; D014774:Virulence
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008050:Lipid A; D014409:Tumor Necrosis Factor-alpha; D000217:Acyltransferases; C097895:MsbB protein, E coli