Neutralisation of virulence activity of enterohemorrhagic Escherichia coli O157 : H7 in vitro through hyperimmune bovine colostrum

Abstract

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 infection in humans may cause bloody diarrhea, hemorrhagic colitis and hemolytic uremic syndrome (HUS). Cattle are the main reservoir of EHEC and a source of infection for humans. It has been previously demonstrated that hyperimmune bovine colostrum (HC) against virulence factors of EHEC was efficiently transferred to newborn calves through lactation. Also, it is well described that human consumption of HC can provide therapeutic effects on several gastrointestinal infections.AIM(s): The objective of the present work was to produce HC using two recombinant virulence factors of EHEC as immunogen: C-terminal fragment of Intimin (C280-Int) and Shiga toxin type 2 (Stx2). Then, to evaluate specific IgG levels and correlate them with the ability of HC to neutralize the cytotoxic activity of Stx2 and EHEC O157:H7 adhesion.METHODS: For this, 12 pregnant Aberdeen Angus breed cows were immunized with two doses of C280-Int and Stx2 at 40 and 20 days before calving. Colostrum was obtained within 24 h after delivery, and specific IgG against Stx2 and Intimin were evaluated by ELISA. Stx2 neutralization capacity of HC was evaluated on Vero cells. EHEC O157:H7 adherence inhibition was evaluated on human intestinal epithelial cells (HCT-8).MAJOR FINDINGS: Stx2 neutralization capacity was observed in nine of the HC samples obtained, and ten colostrum samples could inhibit adherence of EHEC O157:H7 to HCT-8 cells. A correlation was observed between Stx2 neutralization and adherence inhibition of EHEC with specific IgG levels, indicating that specific IgG levels may predict the neutralization capacity of colostrum.SCIENTIFIC or INDUSTRIAL IMPLICATIONS: HC against EHEC virulence factors is effective in neutralizing the virulence activity of EHEC O157:H7. This opens a perspective on the utilization of HC for controlling EHEC colonization in calves and preventing the development of HUS in humans.