Servicio de Información Comunitario sobre Investigación y Desarrollo - CORDIS

Analysis of the protection due to live oral vaccines in rabbits

EPEC, a major cause of severe disease with diarrhoea in infants, is also involved in weaned rabbit colibacillosis. EPEC O103 is frequent in rabbit-fattening units of Western Europe. It causes high mortality and growth retardation, leading to substantial economic losses.

WP10 had two objectives:
- To analyse immune responses associated with protection in the rabbit AEEC model. Very few data are available on the responses in this type of infection, whichever the species involved;

- To find a vaccination train that may be used against AEEC infections in rabbit breeding units. This WP benefited of the work proposed in WP08 (new attenuated strains that could be used as live vaccine), WP09 (physiopathology) and WP19 (stability of LEE). Work in the rabbit model may be representative to develop vaccines against AEEC in other animals.

Major finding during the project:
Vaccine candidate strain. We constructed (by allelic exchange of an EPEC O103 strain mutated in espB and tir) two essential virulence genes. Upon live oral administration to weaned rabbits, the E22DTirEspB mutant strain efficiently colonized the intestinal tract without any adverse consequences. The rabbits were challenged with the highly pathogenic parental strain E22. The mutant provided complete protection to rabbits and total resistance to intestinal colonization by E22.

In addition, E22DTirEspB strain induced a specific humoral response against the bacterial adhesion AF/R2. The Abs prevents bacterial attachment to epithelial cells in vitro. These results open the way for the development of an efficient vaccine strategy against rabbit EPEC infections.

Immune response of the rabbits. Using ELISA and Western-blot, we have been able to show the production of specific antibodies against Eae/Intimin, Afr2G, and EspA. However, it was very difficult to estimate by ELISPOT the frequency of specific antibody producing cell due to heavy non-specific responses.

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INRA-ENVT Microbiologie
23 chemin des Capelles
31000 Toulouse
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