PROFILE OF IMMUNE STIMULATION INDUCED LOCALLY AFTER ESCHERICHIA COLI O157:H7 INTRAGASTRICAL INOCULATION IN MICE AT WEANING

FERNÁNDEZ BRANDO, ROMINA J; MEJIAS MP; RAMOS, M. VICTORIA; ABREY-RECALDE MARIA JIMENA; IBARRA, C; PALERMO, MARINA S

Boston

Congreso; 9th International Symposium On Shiga Toxin (Verocytotoxin) Producing Escherichia coli Infections.; 2015

VTEC

Introduction: During the acute stage of gastrointestinal infection, the interaction between local antigen-presenting cells and STEC strains leads to the activation of mucosal CD4+ T lymphocytes with the consecutive release of pro-inflammatory cytokines that contributes toan effective immune response but also to a possibly deleterious inflammation. Theaim was to assess the involvement of dendritic cells (DCs) in the local immune response as well as the cytokine profile induced in a mouse model of HUS by intragastrically administered STEC strains. Methods: We evaluated DC subsets (CD11b+, CD8alfa+, CD11b-/CD8alfa-) by flow cytometry, and in vitro proliferation and cytokine production (IL10, IL17, IL6, IL4) by lymphocytes from mesenteric lymph nodes (MLN) by MTT assay and ELISA respectively, at 10 h after infection. Tounderstand the role of Stx in the local immune activation, we administered the isogenicStx-negative strain (ΔStx) in a group of mice. Data were compared by ANOVAfollowed by comparison between treatments by SNK test, p < 0.05.Results and Discussion: We observed a significantlyincreased percentage of CD11b+ DCs in MLN from STEC- and DStx-inoculatedanimals compared to control (PBS-inoculated) [mean %±SEM,n]: Ctrol=26.11±3.03,3; DStx=38.70±2.54, 5; STEC=38.96±2.86, 5. Simultaneously, there was asignificant increased number of pre-activated lymphocytes as well as increased levels of IL10, IL17 and IL6 in both bacterial-inoculated mice when stimulated with CD3/CD28 in vitro. Proliferation  OD570±SEM,n]: Ctrol=0.28±0.04, 6;DStx=0.53±0.02, 7; STEC=0.48±0.04, 14. IL17 [mean pg/ml ±SEM,n]: Ctrol=22.2±6.2,9; DStx=203.0±62.8, 7; STEC=127.6±50.3, 10. On the other hand, IL4 wassignificantly increased only in DStx-inoculated animals: Ctrol=158±24, 10;DStx=295±37, 7; STEC=143±25, 14. Although both bacterial strains induced asimilar local immune activation and cytokine profile, DStx strain determined higher levels in cytokine release.Implications: Stx production could limit local inflammation and this would benefit STEC persistence in host intestine, thus favoring HUS outcome.