Protection of rabbits against enteropathogenic Escherichia coli (EPEC) using an intimin null mutant.
BACKGROUND
Diarrhea and mortality resulting from infections with enteropathogenic Escherichia coli (EPEC) are of major economic importance in the rabbit meat industry. There is a growing need for an effective vaccine to cope with these problems and to reduce the use of antibiotics. EPEC are characterized by an attaching and effacing virulence mechanism. This is partly mediated by the intimate binding between an adhesin, called intimin, and a translocated receptor (Tir) of prokaryote origin. We constructed an intimin deletion mutant of the rabbit EPEC (REPEC) wild-type strain 97/241.6 (bio-/serogroup 3-/O15) and examined its protective capacity.


RESULTS
After verifying its complete loss of virulence, we used the attenuated strain in vaccination-challenge experiments in which complete protection against a homologous, but virulent, strain was observed. The attenuated strain was able to persist in the intestinal lumen, where it elicited an immune response against EPEC-related virulence proteins, as was shown using an EspB-specific ELISA. Despite the priming of an immune response and the generation of specific antibodies, the intimin mutant was not able to fully protect rabbits against challenges with REPEC strains of other bio-/serogroups.


CONCLUSIONS
These data indicate that protection against REPEC infections is at least partly bio-/serogroup dependent and a multivalent vaccine may be needed for protection against the full range of REPEC types. Such a combination vaccine may be developed using intimin null mutants, as the latter were clearly shown to be safe and effective against homologous infections.
Stakenborg
Tim
T
Department of Bacteriology & Immunology, Veterinary and Agrochemical Research Centre, Groeselenberg 99, 1180 Brussels, Belgium. tista@var.fgov.be
Vandekerchove
Dominique
D
Mariën
Jonas
J
Laevens
Hans
H
Imberechts
Hein
H
Peeters
Johan
J
D018829:Adhesins, Bacterial / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D000818:Animals; D001428:Bacterial Vaccines / Q000276:immunology*; D003967:Diarrhea / Q000382:microbiology / Q000517:prevention & control / Q000662:veterinary; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D004927:Escherichia coli Infections / Q000517:prevention & control / Q000662:veterinary*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D017353:Gene Deletion; D009154:Mutation; D011817:Rabbits / Q000276:immunology* / Q000382:microbiology
D018829:Adhesins, Bacterial; D001428:Bacterial Vaccines; D029968:Escherichia coli Proteins; C073819:eaeA protein, E coli