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

Abstract

Background, Context or Rationale Enterohemorrhagic Escherichia coli (EHEC) O157:H7 infection in humans may cause bloody diarrhoea, haemorrhagic colitis and haemolytic 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 objectives of the present work were 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), and then to evaluate specific IgG levels and correlate them with the ability of HC to neutralise the cytotoxic activity of Stx2 and EHEC O157:H7 adhesion.

Methods For this, 12 pregnant Aberdeen Angus breed cows were immunised 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 was evaluated by ELISA. Stx2 neutralisation 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 neutraliation capacity was observed in nine of the HC obtained, and 10 colostrum could inhibit adherence of EHEC O157:H7 to HCT-8 cells. A correlation was observed between Stx2 neutralisation and adherence inhibition of EHEC with specific IgG levels thus indicating that specific IgG levels may predict the neutralisation capacity of colostrum.

Scientific or Industrial Implications HC against EHEC virulence factors is effective in neutralising the virulence activity of EHEC O157:H7. This opens a perspective on the utilisation of HC for controlling EHEC colonisation in calves and to prevent the development HUS in humans.