The design and application of a bacterial ghost vaccine to evaluate immune response and defense against avian pathogenic Escherichia coli O2:K1 serotype.

An Escherichia coli (E. coli) O2:K1 bacterial ghost was produced by controlled expression of bacteriophage PhiX 174 lysis gene E. Temperature controlled expression of this gene caused tunnels and holes in the cell wall of E. coli O2:K1 bacterium， leading to loss of cytoplasmic contents. Formation of E. coli O2:K1 ghost was confirmed by scanning electron microscopy and determination of colony forming units. To evaluate the efficiency of this bacterial ghost vaccine to elicit cellular and humoral immune responses， 85 one day old chickens from Ross 308 breed were divided into the following 5 groups; group 1 (non-immunized control)， group 2 (vaccine administered by injection of E. coli O2:K1 killed vaccine)， group 3 (vaccine administered by injection of E. coli O2:K1 ghost)， group 4 (vaccine administered by inhalation of E. coli O2:K1 ghost)， and group 5 (neither immunized， nor challenged as negative control). The groups of 2， 3， and 4 were received vaccines at days 7， 14， and 22. Groups 1 to 4 were challenged with the wild type at day 33. Evaluation of post-mortem lesions and immune responses in all groups showed that chicken injected with the killed vaccine and the bacterial ghost had the best protection. These findings suggest that this bacterial ghost has the potential to be used as a poultry colibacillosis vaccine.