SYSTEMIC IMMUNIZATION OF COWS WITH EspA, EspB, GAMMA-INTIMIN and Stx2 PROTEINS FROM Escherichia coli O157:H7 INDUCES SPECIFIC COLOSTRAL ANTIBODIES THAT ARE EFFICIENTLY TRANSFERRED TO NEWBORN CALVES.

RABINOVITZ BC; TIRONI FARINATI C; ABDALA A; GALARZA R; LARZÁBAL MARIANO; VILTE DA; CATALDI A; IBARRA C; MERCADO EC

Buenos Aires

Simposio; 7th International Symposium on Shiga Toxin (verocytotoxin)- producing Escherichi coli infections; 2009

Enterohaemorrhagic Escherichia coli (EHEC) are responsible for producing intestinal disease and hemolytic uremic syndrome (HUS), a serious systemic complication which particularly affects children. Cattle infected by EHEC are the main source of infection for humans. Vaccination of pregnant cows with EHEC virulence factors could induce specific antibodies –enriched colostrum, a biological tool to confer protection against intestinal colonization of calves and non- breastfed children In this study we evaluated the ability of recombinant gamma-Intimin, EspA and EspB and inactivated Shiga toxin 2 (Stx2) to induce specific antibodies in colostrum and sera of calves after colostrum administration. Recombinants proteins EspA, EspB, the C-terminal fragment of 280 aa of gamma-intimin (gamma-Int1-280) and Stx2 were used as immunogens in combination with an water/oil/water adjuvant (ISA206, SEPPIC, France). We selected 25 Fresian pregnant cows confirmed to be negative for EHEC O157:H7 infection. Animals were immunized by the intramuscular route at 60, 40 and 20 days pre-partum. Separated groups of five cows received 100 ìg/dose of the each protein formulated in 1ml of adjuvant. A control vaccine group received PBS in adjuvant alone. Colostrum was collected from cows at parturition. Blood samples were taken from cows at the beginning of the vaccination and at parturition. Calves were bled 48 h after the first colostrum administration. Milk samples were collected the day 40 post-partum. Specific IgG titres against recombinant proteins in colostrum, milk and sera were determined by an enzyme-linked immunosorbent assay (ELISA) and confirmed by western blot. Anti-Stx2 titers were determined by neutralization in Vero cell cultures. The possible inhibitory effect of colostrum on the hemolytic activity exhibited by type three secretion system (TTSS)-encoding E. coli strains was evaluated. All vaccinated cows mounted a significant serum and colostrum IgG response against gamma-Int1-280, EspA and EspB. Levels of anti-gamma-Int1-280 were significantly higher than those in EspA- and EspB –vaccinated cows. Colostrum fed calves also exhibited elevated serum IgG titers against EspA, EspB and gamma-Int1-280, although antibody titers to gamma-Int1-280 were higher than to other proteins. Western blotting assays confirmed the specificity of the responses measured by ELISA. Colostrum from EspB-vaccinated cows showed a significant inhibitory effect on the hemolytic activity of exhibited by the TTSS-encoding E. coli strain. Colostrum and sera from colostrum fed calves from vaccinated cows also exhibited high titers anti-Stx2 compared with the control groups. In conclusion, bovine colostrum with elevated levels of antibodies against EHEC O157:H7 were obtained by systemic immunization of cows, and specific antibodies were efficiently transferred to newborn calves by feeding colostrum. It may be an alternative to protect calves from early colonization by E. coli O157: H7 and a key source of antibodies which could to block colonization and toxic activity of that bacterium in the human intestine.