Rise of a specific and systemic immune response after intragastric inoculation of Shiga toxin-producing Escherichia coli in mice .

RJ FERNANDEZ-BRANDO; G CABRERA; A BASCHKIER; E MILIWEBSKY; MP MEJÍAS; C PANEK; MJ ABREY; MV RAMOS; M RIVAS; M PALERMO

Le Meridien New Delhi, New Delhi

Congreso; Malnutrition, Gut-Microbial interactions and Mucosal Immunity to Vaccines; 2011

Congreso Keystone 2011

Rise of a specific mucosal and systemic immune response after intragastric inoculation of Shiga toxin-producing Escherichia coli in mice. RJ Fernandez-Brando1, G Cabrera1, A Baschkier2, E Miliwebsky2, MP Mejías1, C Panek1, MJ Abrey1, MV Ramos1, M Rivas2, M Palermo1. 1 Departamento de Inmunología, Academia Nacional de Medicina, Buenos Aires, Argentina. 2 Servicio de Fiosiopatogenia, Instituto Nacional de Enfermedades Infecciosas-ANLIS “Carlos G. Malbrán”, Buenos Aires, Argentina (C1425AUM).     Hemolytic Uremic Syndrome (HUS) is a life-threatening complication of Shiga-toxin (Stx) Escherichia coli (STEC) infections and is characterized by acute renal failure, thrombocytopenia and hemolytic anemia. In Argentina HUS constitutes an endemic disease. At present, the STEC-induced immune response is still poorly understood. Since the mucosal associated lymphoid tissue (MALT) constitutes the first immune compartment met by STEC, the aim of this work was to study the local activation of B lymphocytes (BLym) in a mouse model of HUS and to test if a single oral infection has the ability to raise a local and protective immune response against bacterial. We have previously developed a mouse model of HUS after by intragastrical inoculation of an E. coli O157:H7 Stx2+ (125/99) in mice at weaning. Flow cytometry analysis showed an early decrease of BLym absolute number in Peyer’s patches (PP), with a simultaneous increase in mesenteric lymph nodes (MLN) compared to controls: mice inoculated with an E.coli O157:H7 Stx- strain (605/03) or PBS (Ctrl) (mean±SD,n)(PP (x104): Ctrl=4.7±0.6,4; 605/03=5.9±1.2,6; 125/99=3.6±1.0,5; ANOVA p<0.05; NLM (x106): Ctrl=0.6±0.1,4; 605/03=0.5±0.1,8; 125/99=0.9±0.1,8; ANOVA p<0.05 ). Additionally, after 12 h of i.v. injection of allogenic CFSE+Lym only 125/99-inoculated mice showed an increased % of B220+CFSE+ BLym in MLN (Ctrl=12±1,4; 605/03=13±3,2; 125/99=15±2,4; p<0.05). However, we found evidences of BLym activation in 125/99- and 605/03-inoculated mice: at 12 h post-inoculation as an increased CD69+ BLym % in PP (Ctrl=31±2,3; 605/03=43±5,3; 125/99=50±11.3;ANOVA p<0.05). Additionally, 125/99- and 605/03-inoculated mice showed an increased % of IgA+-BLym from PP(Ctrl=10±4,10; 605/03=14±3,15; 125/99=16±3,11; p<0.05), but only 125/99-inoculated mice showed an increased % of IgA+-BLym from NLM(Ctrl=6±2,5; 605/03=7±2,7; 125/99=8±1,11; p<0.05). Finally, only 125/99-inoculated mice that survived the infection showed IgA antibodies against the whole STEC bacteria in fecal extracts and a 30% of them survived the challenge with intravenous Stx2r, thus indicating the presence of Stx2-neutralizing antibodies in plasma.    In conclusion, although both E.coli strains induce a local immune stimulation, only the Stx2-producing strain determines the raise of a specific local and systemic immune response that could provide an effective protection faced with an over-infection.