ABSTRACTGastrointestinal (GI) colonization of 2-day-old (P2) rat pups withEscherichia coliK1 results in translocation of the colonizing bacteria across the small intestine, bacteremia, and invasion of the meninges, with animals frequently succumbing to lethal infection. Infection, but not colonization, is strongly age dependent; pups become progressively less susceptible to infection over the P2-to-P9 period. Colonization leads to strong downregulation of the gene encoding trefoil factor 2 (Tff2), preventing maturation of the protective mucus barrier in the small intestine. Trefoil factors promote mucosal homeostasis. We investigated the contribution of Tff2 to protection of the neonatal rat fromE. coliK1 bacteremia and tissue invasion. Deletion oftff2, using clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9, sensitized P9 pups toE. coliK1 bacteremia. There were no differences betweentff2−/−homozygotes and the wild type with regard to the dynamics of GI colonization. Loss of the capacity to elaborate Tff2 did not impact GI tract integrity or the thickness of the small-intestinal mucus layer but, in contrast to P9 wild-type pups, enabledE. coliK1 bacteria to gain access to epithelial surfaces in the distal region of the small intestine and exploit an intracellular route across the epithelial monolayer to enter the blood circulation via the mesenteric lymphatic system. Although primarily associated with the mammalian gastric mucosa, we conclude that loss of Tff2 in the developing neonatal small intestine enables the opportunistic neonatal pathogenE. coliK1 to enter the compromised mucus layer in the distal small intestine prior to systemic invasion and infection.
Promoter hypermethylation and downregulation of trefoil factor 2 in human gastric cancer