Immunization of mouse dams with a Stx2B-based immunogen is able to fully protect pups from a lethal challenge with E.coli O157:H7.

MEJIAS MP; CABRERA GABRIEL; BASCHKIER, A; FERNÁNDEZ BRANDO, ROMINA J; MILIWEBSKY, E; ZYLBERMAN, VANESA; GOLDBAUM, FERNANDO; RIVAS, M; PALERMO, MARINA S

Ottawa, Ontario, Canada

Simposio; Immunological Mechanisms of Vaccination (S3); 2012

Keystone Symposia

Post-diarrhea Hemolytic Uremic Syndrome (HUS) is a life-threatening complication of Shiga toxin (Stx)-producing E. coli (STEC) infections, characterized by acute renal failure, thrombocytopenia and hemolytic anemia. We generated a fusion protein between the B subunit (binding unit, non-toxic) of Stx type 2 (Stx2, most associated with HUS) and a highly immunogenic protein (the protein was named Chimera,Ch) that was able to elicit a strong humoral response in mice and fully protect them against lethal challenge with Stx2. Since HUS mainly occurs in children below 5 years old, we tested if immunized dams were able to transfer immunity to their pups. Female BALB/c mice were immunized with 3 doses of Ch or PBS (Ct) in Aluminum hydroxide s.c. and were mated 10 days after the last dose. Ch pups showed anti-Stx2B IgG in serum (Mean OD492nm±SEM)(Ct: 0,3±0,004 n=13; Ch: 1,53±0,06 n=14; p<0.005) and feces (Mean OD492nm/gFeces±SEM)(Ct: 1,57±0,36; Ch: 5,84±0,16; p<0.005) at weaning. Pups were challenged by i.g. inoculation of 4x109 CFU/mouse of E. coli O157:H7 Stx2+. Only Ct pups showed increased urea levels at 72h post-inoculation (p.i.), (Mean mg%±SEM)(72h: Ct: 290,5±81,8; Ch: 49,9±0,9). At this time point, 69% of Ct pups shed bacteria in stool samples but only 7% of Ch pups did (p<0.005), indicating that colonization was limited in Ch pups. Finally, 0% of Ct pups and 100% of Ch pups survived the challenge (p<0.0001). Surviving Ch pups developed IgA antibodies against whole STEC in feces, that were not observed in non-challenged Ch pups (ncCh), 1,5 months p.i. (Mean OD492nm/gFeces±SEM)(Ch:16,5±5,9; ncCh:1,1±0,7; p<0.05). In conclusion, immunized dams were able to fully protect their pups against lethal challenge with STEC and surviving mice developed antibodies against STEC that could provide protection in a re-infection.