The Citrobacter rodentium type III secretion system effector EspO affects mucosal damage repair and antimicrobial responses

Abstract

Infection with Citrobacter rodentium triggers robust tissue damage repair responses, manifested by secretion of IL-22, in the absence of which mice succumbed to the infection. Of the main hallmarks of C. rodentium infection are colonic crypt hyperplasia (CCH) and dysbiosis. In order to colonize the host and compete with the gut microbiota, C. rodentium employs a type III secretion system (T3SS) that injects effectors into colonic intestinal epithelial cells (IECs). Once injected, the effectors subvert processes involved in innate immune responses, cellular metabolism and oxygenation of the mucosa. Importantly, the identity of the effector/s triggering the tissue repair response is/are unknown. Here we report that the effector EspO ,an orthologue of OspE found in Shigella spp, affects proliferation of IECs 8 and 14 days post C. rodentium infection as well as secretion of IL-22 from colonic explants. While we observed no differences in the recruitment of group 3 innate lymphoid cells (ILC3s) and T cells, which are the main sources of IL-22 at the early and late stages of C. rodentium infection respectively, infection with ΔespO was characterized by diminished recruitment of sub-mucosal neutrophils, which coincided with lower abundance of Mmp9 and chemokines (e.g. S100a8/9) in IECs. Moreover, mice infected with ΔespO triggered significantly lesser nutritional immunity (e.g. calprotectin, Lcn2) and expression of antimicrobial peptides (Reg3β, Reg3γ) compared to mice infected with WT C. rodentium. This overlapped with a decrease in STAT3 phosphorylation in IECs. Importantly, while the reduced CCH and abundance of antimicrobial proteins during ΔespO infection did not affect C. rodentium colonization or the composition of commensal Proteobacteria, they had a subtle consequence on Firmicutes subpopulations. EspO is the first bacterial virulence factor that affects neutrophil recruitment and secretion of IL-22, as well as expression of antimicrobial and nutritional immunity proteins in IECs.

An acetate‐yielding diet imprints an immune and anti‐microbial programme against enteric infection

“…Therefore, we examined changes in gene expression levels of C. rodentium virulence genes, Tir and EspB in the colon tissues of infected mice. We found both HAMSA‐ and HAMSB‐fed infected mice exhibited decreased expression of Tir and EspB (Supplementary figure 2g), which are essential for bacterial adhesion to host enterocytes 16‐20 …”

“…Both innate and adaptive arms of the immune response are required to resolve C. rodentium infection. Innate cells and CD4 + T cells can both secrete IL‐22 17,85‐87 . During early infection with C. rodentium , ILC3s are the major producers of IL‐22 88,89 .…”

Intestinal Epithelial Cells and the Microbiome Undergo Swift Reprogramming at the Inception of Colonic Citrobacter rodentium Infection

“…Recently, we reported that C. rodentium subverts IEC metabolism in order to evade innate immune responses and establish a favorable niche in the colon (6, 21). Using multiplex proteomics, we uncovered a significant downregulation of host metabolic pathways, including gluconeogenesis, lipid metabolism, the tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS), with a simultaneous upregulation of cell cycle and DNA replication pathways.…”

MicroRNA-127 Promotes Anti-microbial Host Defense through Restricting A20-Mediated De-ubiquitination of STAT3

“…Accumulating evidences have demonstrated that anti-microbial peptides (AMPs) played a central role in limiting bacterial replication and preventing tissue damage (Madouri et al, 2018;Berger et al, 2018). We therefore assessed the effect of miR-127 on the production of AMPs and initially analyzed the level of IL-22, the presumed inducer of AMPs such as Reg3b and S100A8.…”