The YrbE phospholipid transporter of Salmonella enterica serovar Typhi regulates the expression of flagellin and influences motility, adhesion and induction of epithelial inflammatory responses

Abstract

Salmonella enterica serovar Typhi is the etiologic agent of typhoid fever, a major public health problem in the developing world. Moving toward and adhering to the intestinal epithelium represents key initial steps of infection by S. Typhi. We examined the role of the S. Typhi yrbE gene, which encodes an inner membrane phospholipid transporter, in these interactions with epithelial cells. Disruption of yrbE resulted in elevated expression of flagellin and a hypermotile phenotype. It also significantly reduced the ability of S. Typhi to adhere to the HeLa epithelial cell line and to polarized primary epithelial cells derived from human ileal organoids. Interestingly, the yrbE-deficient strain of S. Typhi induced higher production of interleukin-8 from the primary human ileal epithelial cell monolayers compared to the wild-type bacteria. Deletion of the flagellin gene (fliC) in the yrbE-deficient S. Typhi inhibited motility and attenuated interleukin-8 production, but it did not correct the defect in adhesion. We also disrupted yrbE in S. Typhimurium. In contrast to the results in S. Typhi, the deficiency of yrbE in S. Typhimurium had no significant effect on flagellin expression, motility or adhesion to HeLa cells. Correspondingly, the lack of yrbE also had no effect on association with the intestine or the severity of intestinal inflammation in the mouse model of S. Typhimurium infection. Thus, our results point to an important and serovar-specific role played by yrbE in the early stages of intestinal infection by S. Typhi.

A Versatile Human Intestinal Organoid-Derived Epithelial Monolayer Model for the Study of Enteric Pathogens

“…Organoid-derived epithelial monolayer models like the HIODEM have enabled infection analyses by providing a process by which pathogens can directly interact with the apical side of the epithelium ( 11 , 24 , 33 , 54 – 58 ). While three-dimensional organoid systems are available ( 40 , 59 – 63 ) and “apical-out” organoid systems have been developed ( 64 ), HIODEM and other 2D systems offer easily accessible monolayers for pathogenesis studies in which apical and basolateral cytokine secretion profiles and changes in TEER can be examined in a standard transwell culture setting.…”

A versatile human intestinal organoid-derived epithelial monolayer model for the study of enteric pathogens

“…Organoid-derived epithelial monolayer models like the HIODEM have enabled infection analyses by providing a process by which pathogens can directly interact with the apical side of the epithelium (11,24,33,(54)(55)(56)(57)(58). While three-dimensional organoid systems are available (40,(59)(60)(61)(62)(63) and "apical-out" organoid systems have been developed 64 ileum, cecum, or colon, despite the overall pluripotent state of the stem cells (11,15,71).…”

“…Organoid-derived epithelial monolayer models like the HIODEM have enabled infection analyses by providing a process by which pathogens can directly interact with the apical side of the epithelium (11, 24, 33, 54-58). While three-dimensional organoid systems are available (40, 59-63) and “apical-out” organoid systems have been developed (64), HIODEM and other 2-D systems offer easily accessible monolayers for pathogenesis studies in which apical and basolateral cytokine secretion profiles and changes in TEER can be examined in a standard transwell culture setting.…”

Spheres of Influence: Insights into Salmonella Pathogenesis from Intestinal Organoids

“…The monolayers also maintain the genetic and functional phenotypes of the organoid/enteroids of origin [56] and can be manipulated to express a crypt-like or villus-like phenotype by changing media composition [49]. This system lends itself to many standard functional assays designed for 2D cells as well as to high throughput assays that cannot be easily performed on spherical enteroids/organoids, including but not limited to adhesion/invasion assays, transmigration assays, and inflammatory immune responses [49,51,55,56,59]. These monolayers can be cultured for up to three weeks (Stefania Senger, unpublished observations).…”

“…Organoids/enteroids have been utilized for improving the basic understanding of tissue homeostasis, organogenesis, and physiological functions [4,69]. The systems have also been used to model diseases [49,51], to study host-pathogen interactions [59,65,70,71] and cancer [72], and to test potential vaccines and drugs [73][74][75]. The organoids/enteroids are also used as new tools for personalized medicine, where patient-derived models can serve as platforms for testing treatment options.…”