Mucosal immune stimulation after intragastrical inoculation of Shiga toxin-producing Escherichia coli (STEC) in mice immediately after weaning.

FERNÁNDEZ BRAMDO R; MILIWEBSKY E; MEJÍAS MP; PANEK CA; BENTANCOR LV; RAMOS MV; RIVAS, M;; PALERMO MS

Viña del Mar, Chile

Congreso; 9th Lat in American Congress of Immunology (ALAI),; 2009

Asociación Latinoamericana de Inmunología (ALAI)

Hemolytic Uremic Syndrome (HUS) is a life-threatening complication of STEC infection. Because the mucosal associated lymphoid tissue (MALT) constitutes the first immune compartment encountered by STEC, we studied immune stimulation in Peyer’s Patches (PP) and mesenteric lymphoid nodes (MLN) by flow cytometry, after intragastrical inoculation of two E.coli O157:H7 strains, one Stx+(125/99) and another Stx-(605/03) or PBS(Ctrl). A decreased B-cell percentage in PP was found in 125/99-inoculated mice, since 24h post-inoculation (mean+SD,ANOVA)(Ctrl=77±4,n=17,605/03=72±6,n=11,125/99=68±9,n=26,p<0.0005). A transient increase in MLN B-cell percentage was observed in 125/99-inoculated mice, followed by a decrease up to 7d(7d:Ctrl=25±5,605/03=24±5,125/99=19±6,p<0.0001). It might suggest B-cell traffic from PP to MLN and effector sites. Only 605/03 inoculated-mice showed a decreased B-cell CD62L MIF in MLN 24h post-inoculation (Ctrl=1566±223,605/03=574±153,125/99=1214±122,p<0.005). Nevertheless, both experimental groups showed a dropped T-cell CD62L-MIF (Ctrl=2790±225,605/03=1186±206,125/99=1863±324,p<0.005). To evaluate Stx-effect on leukocytes, recombinant Stx2 was injected in the rear-footpad and the draining node was studied. We observed an increased CD69+ B-cell percentage(48hs:Ctrl=15±3,Stx2r=84±4,t-test p<0.0001) and CD11c+ dendritic cells(DC) percentage(48hs:Ctrl=0.4±03,Stx2r=2.4±1.1,t-test p<0.01) since 24h. B-cell percentage didn’t drop, ruling out a Stx-direct toxic effect. Although both E.coli strains induced MALT activation, discrepancies were observed. B-cell activation and DC recruitment induced by recombinant-Stx2, might explain partially MALT differences observed between both E.coli strains.