Evidence of antibodies against Enterohemorrhagic Escherichia coli virulence associated proteins in bovine colostrum.

VILTE DA; LARZÁBAL MARIANO; ELIZONDO AM; CATALDI AA; MERCADO EC

Montevideo

Simposio; 7º; Seminario de la OIE en Biotecnología, 12º; Simposio Internacional de la Asociación Mundial de Laboratorios de Diagnóstico Veterinario.; 2005

   Enterohemorrhagic Escherichia coli (EHEC), a subset of Shiga toxin-producing Escherichia coli (STEC), are cause of severe disease in man, whose clinical spectrum includes diarrhea, hemorrhagic colitis and hemolytic uremic syndrome (HUS), the leading cause of renal failure in children. Health cattle are recognized as the main source of human EHEC infections, although a limited number of serogroups have been associated with diarrhea in young calves. Similar to classical enteropathogenic E.coli (EPEC), most EHEC colonize intestinal mucosa with a characteristic lesion, defined as “attaching and effacing” (A/E), which results from the activation of the genes clustered in the chromosomal island called the locus of enterocyte effacement (LEE). Intimin (Int), Esp (EPEC-secreted protein) A and EspB, are LEE-encoded proteins that elicit an antibody response in serum during human EHEC infections. Antibodies reacting with these proteins were also detected in human colostra. In this work we examined 35 samples of bovine colostra for the presence of IgG antibodies to Int gamma, EspA and EspB by immunoblot analysis using recombinant His6-tagged fusion proteins from EHEC strains isolated from diarrheic calves. Most of the samples (77.1%) were positive for both Int-gamma and EspB proteins at a dilution 1:10. No anti-EspA IgG antibodies were detected in any of the samples. Colostrum antibodies to Int-gamma and EspB proteins might indicate previous infections with highly virulent human EHEC serogroups (O157, O111 or O145). It was reported that EHEC faecal shedding in calves increases after weaning; this observation strongly suggests that antibodies against LEE-encoded proteins present in bovine colostra protect calves from early EHEC infection. Vaccines based in these bacterial proteins could be used to reduce the carriage of EHEC in older calves and thus reduce the risk of EHEC infections in humans.