Functional studies of intimin in vivo and ex vivo: implications for host specificity and tissue tropism.
Intimin is an outer-membrane adhesin that is essential for colonization of the host gastrointestinal tract by attaching and effacing pathogens including enteropathogenic Escherichia coli (EPEC), enterohaemorrhagic E. coli (EHEC) and Citrobacter rodentium (CR). The N-terminus of intimin from the different strains is highly conserved while the C-terminus, which harnesses the active receptor-binding site, shows sequence and antigenic polymorphism. This diversity was used to define a number of distinct intimin types, the most common of which are alpha, beta and gamma. Intimin binds the type III secretion system effector protein Tir. However, a large body of evidence suggests that intimin also binds a host-cell-encoded receptor(s) (Hir), and interaction of different intimin types with Hir contributes to tissue and host specificity. The aims of this study were to compare the activity of the major intimin types (alpha, beta and gamma) in vivo and ex vivo, using the CR mouse model and in vitro organ culture (IVOC), and to determine their exchangeability. The results confirm that intimin gamma is not functional in the CR mouse model. In the pig, intimin beta can substitute for EPEC intimin alpha but when placed in an EHEC O157 : H7 background it does not produce an intimin alpha-like tropism, although some adhesion to the small and large intestine was observed. In contrast, in human IVOC, intimin beta in an EHEC background produces small intestinal colonization in a similar manner to intimin alpha.
Mundy
Rosanna
R
Division of Cell and Molecular Biology, Imperial College London, London, UK.
Schüller
Stephanie
S
Centre for Paediatric Gastroenterology, Royal Free and University College Medical School, London, UK.
Girard
Francis
F
Groupe de Recherche sur les Maladies Infectieuses du Porc (GREMIP), Faculté de Medicine Vétérinaire, Université de Montréal, St-Hyacinthe, Canada.|Division of Cell and Molecular Biology, Imperial College London, London, UK.
Fairbrother
John M
JM
Groupe de Recherche sur les Maladies Infectieuses du Porc (GREMIP), Faculté de Medicine Vétérinaire, Université de Montréal, St-Hyacinthe, Canada.
Phillips
Alan D
AD
Centre for Paediatric Gastroenterology, Royal Free and University College Medical School, London, UK.
Frankel
Gad
G
Division of Cell and Molecular Biology, Imperial College London, London, UK.
D018829:Adhesins, Bacterial / Q000378:metabolism; D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism*; D044082:Citrobacter rodentium / Q000737:chemistry / Q000378:metabolism / Q000472:pathogenicity*; D004756:Enterobacteriaceae Infections / Q000382:microbiology*; D004927:Escherichia coli Infections / Q000382:microbiology; D019453:Escherichia coli O157 / Q000737:chemistry / Q000378:metabolism / Q000472:pathogenicity*; D029968:Escherichia coli Proteins / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000382:microbiology; D007421:Intestine, Small / Q000382:microbiology; D051379:Mice; D008809:Mice, Inbred C3H; D009924:Organ Culture Techniques; D013552:Swine; D014774:Virulence
D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C073819:eaeA protein, E coli