Bovine Colostrum Contains Immunoglobulin G Antibodies against Intimin, EspA, and EspB and Inhibits Hemolytic Activity Mediated by the Type Three Secretion System of Attaching and Effacing Escherichia coli

Abstract

Enterohemorrhagic Escherichia coli (EHEC) is the main cause of hemolytic-uremic syndrome, an endemic disease in Argentina which had an incidence in 2005 of 13.9 cases per 100,000 children younger than 5 years old. Cattle appear to be a major reservoir of EHEC, and a serological response to EHEC antigens has been demonstrated in natural and experimental infections. In the current study, antibodies against proteins implicated in EHEC's ability to form attaching and effacing lesions, some of which are exported to the host cell via a type three secretion system (TTSS), were identified in bovine colostrum by Western blot analysis. Twenty-seven (77.0%) of the 35 samples examined contained immunoglobulin G (IgG) antibodies against the three proteins assayed in this study: EspA, EspB, and the carboxy-terminal 280 amino acids of ␥-intimin, an intimin subtype associated mainly with O157:H7 and O145:H-serotypes. Every colostrum sample was able to inhibit, in a range between 45.9 and 96.7%, the TTSS-mediated hemolytic activity of attaching and effacing E. coli. The inhibitory effect was partially mediated by IgG and lactoferrin. In conclusion, we found that early colostrum from cows contains antibodies, lactoferrin, and other unidentified substances that impair TTSS function in attaching and effacing E. coli strains. Bovine colostrum might act by reducing EHEC colonization in newborn calves and could be used as a prophylactic measure to protect non-breast-fed children against EHEC infection in an area of endemicity.

Strain-Dependent Cellular Immune Responses in Cattle following Escherichia coli O157:H7 Colonization

“…In support of this hypothesis, vaccination of sows with intimin has been shown to reduce the level of EHEC O157:H7 colonization of suckling piglets (24), presumably through antibody-mediated blocking of bacterial binding. In addition, bovine colostrum has been shown to reduce T3SS-mediated hemolysis in vitro (25), and passive transfer of EspB, intimin, and neutralizing antibodies against Stx2 to calves has been demonstrated following maternal vaccination (26). H7 flagellin has also been demonstrated to act as an adhesion factor, and anti-H7 antibodies reduce the level of binding of bacteria to primary cell cultures (27).…”

“…Despite high antibody titers following vaccination with these antigens, vaccination is only partially protective (13,14,(28)(29)(30)(31), while antibody titers are inconsistently correlated with bacterial shedding (32)(33)(34). The serological response of cattle to colonization has also been studied extensively, and antibodies against O157 lipopolysaccharide (LPS), H7, Tir, intimin, EspA, EspB, EspD, EspM2, NleA, TccP, Stx1, and Stx2 have been demonstrated (25,(33)(34)(35)(36). Despite this, prior exposure to EHEC O157:H7 results in only partial and transient protection against reinfection (33,34,37).…”

Enterohemorrhagic Escherichia coli Adhesins

“…Similar results were seen using intimin-α and EPEC (94). Intimin-based vaccines have also been shown to be effective in rabbits (95) and adult cattle (96), and infant calves were protected by anti-intimin antibodies obtained from colostrum (97). Second, there have also been a number of different vector systems used to produce intimin, such as developing a plant-derived edible version of intimin (98), or using attenuated Salmonella as the delivery vehicle (99,100).…”

Lactoferrin inhibits E. coli O157:H7 growth and attachment to intestinal epithelial cells

“…In addition, LEE encodes proteins of the type III secretion system (TTSS), which is made up of an EspA multifilament needle complex, used for insertion of the bacterial effector proteins EspB, EspD and Tir into the host cell. Injection of bacterial virulence factors via the TTSS and binding of intimin to Tir leads to a strong interaction between bacteria and host cells (Cookson and Woodward, 2003;Vilte et al, 2008). Virulence arises also from Shiga toxin production, encoded by Shiga toxin genes (stx1 and stx2), which are the primary factors responsible for the hemorrhagic aspect of diarrhoea and systemic complications (HUS).…”