Oral ingestion of egg yolk immunoglobulin from hens immunized with an enterotoxigenic Escherichia coli strain prevents diarrhea in rabbits challenged with the same strain.

White Leghorn hens were immunized with enterotoxigenic Escherichia coli B16-4 with heat-labile enterotoxin and colonization factor antigen I in Freund's adjuvant. Specific antibodies were detected by an enzyme-linked immunosorbent assay in the serum after 8 days and in eggs after 10 days, with levels reaching peaks at 15 and 20 days after the first immunization, respectively. The protective effects of the egg yolk antibodies were tested in the rabbit reversible ileal tie model of diarrhea. Five control rabbits developed severe diarrhea within 72 h after inoculation with enterotoxigenic E. coli B16-4. Oral ingestion of egg yolks from immunized hens for 4 days prior to inoculation protected five rabbits from diarrhea after challenge with the same strain of E. coli. The rabbits showed no adverse effects from the ingestion of the egg yolks. Four rabbits fed control eggs were also afforded some protection in that three rabbits developed mild diarrhea and one rabbit remained entirely well. In vitro experiments showed that immunoglobulin from egg yolks interfered with the binding of E. coli to purified small bowel mucins; immunoglobulin from immunized hens reduced binding more than immunoglobulin from nonimmunized hens. These findings indicate that eggs from hens immunized with appropriate antigens have potential as a useful source of passive immunity.