Development of a recombinant attenuated Salmonella typhimurium against Hemolytic Uremic Syndrome (HUS)

L. V. BENTANCOR; C. BRAGA; M. E. SBROGIO-ALMEIDA; R. J. FERNÁNDEZ BRANDO; G. C. FERNANDEZ; M. V. RAMOS; P. D. GHIRINGHELLI; L. C. FERREIRA; M. S. PALERMO

Rio de Janeiro, Brasil

Congreso; 13th International Congress of Immunology; 2007

Infection with Shiga toxin (Stx)-producing E. coli could lead to a complication known as HUS. Experimental vaccines have not been effective because the B subunit has low immunoprophylactic potential and the A subunit is toxic. We developed a DNA vaccine expressing the Stx2 without its active site but conserving the last 31 aas of the A subunit and the B subunit.  Sera from mice immunized with this construction showed neutralizing activity (100% to 15d.p.v.) and they survived to challenge (50%). To improve the immune response and to evaluate the mucosal immunity, we obtained three recombinant attenuated Salmonella as vaccine vector (Salmonella typhimurium SL3261 and Salmonella Dublin ICB5, both expressing flagellin, and Salmonella Dublin SL5928, without flagellin).  Mice immunized (four oral doses of 1010 CFU per mouse at 0, 7, 14 and 21 days) with the strains expressing flagellin developed a major IgA response (13d.p.v.; 30d.p.v. ICB5Stx2DAB=1399; 2610, SL3261Stx2DAB=3065; 10000, SL5928Stx2DAB=165; 2565, each value corresponding to a pool of 5 mice, controls were <300).  Systemic response was negative. Since Salmonella colonization was detected only up to 16 hs, the in vitro study of Stx2DAB-kinetic expression suggested that the it was toxic for this strain, giving into account the absence of systemic response (OD600nm of SL3261Stx2DAB to 8hs induced vs not induced; 1.87 +/- 0.04 vs 8.48 +/- 0.03).  These results encourage us to assay immunization trials using a priming-boost regimen (DNA vaccine and SL3261Stx2DAB), which could protect mice against a natural infection by the presence of systemic and local response.