Profile of immune stimulation induced locally after Escherichia coli O157:H7 intragastrical inoculation in mice at weaning

FERNANDEZ BRANDO, ROMINA J; MEJIAS, MARIA PILAR; RAMOS, MARIA VICTORIA; ABREY-RECALDE, MARIA JIMENA; IBARRA, C; PALERMO, MARINA SANDRA

Boston

Congreso; 9th International Symposium on Shiga Toxin (Verocytotin)-Producing Escherichia coli Infections . VTEC2015; 2015

Profile of immune stimulation induced locally after Escherichia coli O157:H7 intragastrical inoculation in mice at weaningRomina Fernández-Brando1, M. Pilar Mejías1, M. Victoria Ramos1, M. Jimena Abrey-Recalde1, Cristina Ibarra2, Marina S. Palermo1.1Laboratorio de Patogenia e Inmunología de Procesos Infecciosos, Instituto de Medicina Experimental (IMEX)- CONICET-ANM, Buenos Aires, Argentina.2Laboratorio de Fisiopatogenia, Facultad de Medicina, UBA, Buenos Aires, Argentina. 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 to an effective immune response but also to a possibly deleterious inflammation. The aim 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+, CD8α+, CD11b-/CD8α-) 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. To understand the role of Stx in the local immune activation, we administered the isogenic Stx-negative strain (ΔStx) in a group of mice. Data were compared by ANOVA followed by comparison between treatments by SNK test, p < 0.05.Results and Discussion: We observed a significantly increased percentage of CD11b+ DCs in MLN from STEC- and ΔStx-inoculated animals compared to control (PBS-inoculated) [mean %±SEM,n]: Ctrol=26.11±3.03, 3; ΔStx=38.70±2.54, 5; STEC=38.96±2.86, 5. Simultaneously, there was a significant 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 [mean OD570±SEM,n]: Ctrol=0.28±0.04, 6; ΔStx=0.53±0.02, 7; STEC=0.48±0.04, 14. IL17 [mean pg/ml ±SEM,n]: Ctrol=22.2±6.2, 9; ΔStx=203.0±62.8, 7; STEC=127.6±50.3, 10. On the other hand, IL4 was significantly increased only in ΔStx-inoculated animals: Ctrol=158±24, 10; ΔStx=295±37, 7; STEC=143±25, 14. Although both bacterial strains induced a similar local immune activation and cytokine profile, ΔStx 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.