title: Elucidating pathways of Toxoplasma gondii invasion in the gastrointestinal tract: involvement of the tight junction protein occludin.
abstract: Toxoplasma gondii is an obligate intracellular parasite infecting one third of the world's population. The small intestine is the parasite's primary route of infection, although the pathway of epithelium transmigration remains unclear. Using an in vitro invasion assay and live imaging we showed that T. gondii (RH) tachyzoites infect and transmigrate between adjacent intestinal epithelial cells in polarized monolayers without altering barrier integrity, despite eliciting the production of specific inflammatory mediators and chemokines. During invasion, T. gondii co-localized with occludin. Reducing the levels of endogenous cellular occludin with specific small interfering RNAs significantly reduced the ability of T. gondii to penetrate between and infect epithelial cells. Furthermore, an in vitro invasion and binding assays using recombinant occludin fragments established the capacity of the parasite to bind occludin and in particular to the extracellular loops of the protein. These findings provide evidence for occludin playing a role in the invasion of T. gondii in small intestinal epithelial cells.
authors.affiliation: Gut Health and Food Safety Institute Strategic Programme, Norwich Research Park, Norwich, NR4 7UA, UK; Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich, NR4 7UA, UK.
authors.forename: Caroline M
authors.initials: CM
authors.lastname: Weight
authors.affiliation: Gut Health and Food Safety Institute Strategic Programme, Norwich Research Park, Norwich, NR4 7UA, UK; Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich, NR4 7UA, UK.
authors.forename: Emily J
authors.initials: EJ
authors.lastname: Jones
authors.affiliation: Gut Health and Food Safety Institute Strategic Programme, Norwich Research Park, Norwich, NR4 7UA, UK.
authors.forename: Nikki
authors.initials: N
authors.lastname: Horn
authors.affiliation: Analytical Sciences Unit, Institute of Food Research, Norwich Research Park, Norwich, NR4 7UA, UK.
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Wellner
authors.affiliation: Gut Health and Food Safety Institute Strategic Programme, Norwich Research Park, Norwich, NR4 7UA, UK; Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich, NR4 7UA, UK. Electronic address: Simon.Carding@IFR.ac.uk.
authors.forename: Simon R
authors.initials: SR
authors.lastname: Carding
mesh_terms: D000818:Animals; D002460:Cell Line; D004847:Epithelial Cells / Q000469:parasitology*; D054884:Host-Pathogen Interactions; D051379:Mice; D008954:Models, Biological; D062793:Occludin / Q000378:metabolism*; D014122:Toxoplasma / Q000502:physiology*; D014124:Toxoplasmosis, Animal / Q000469:parasitology; D057705:Transendothelial and Transepithelial Migration
chemical_list: D062793:Occludin
keywords: Intestinal epithelial cells; Invasion; Occludin; Toxoplasma gondii