Bacterial ghosts as vaccine candidates for veterinary applications.

The application of new strategies to develop effective vaccines is essential in modern veterinary medicine. The bacterial ghost system is a novel vaccine delivery system endowed with intrinsic adjuvant properties. Bacterial ghosts are nonliving Gram-negative bacterial cell envelopes devoid of cytoplasmic contents while maintaining their cellular morphology and native surface antigenic structures including bioadhesive properties. They are produced by PhiX174 protein E-mediated lysis of Gram-negative bacteria. The intrinsic adjuvant properties of bacterial ghost preparations enhance immune responses against envelope bound antigens, including T-cell activation and mucosal immunity. Since native and foreign antigens can be expressed in the envelope complex of ghosts before E-mediated lysis, multiple antigens of various origins can be presented to the immune system simultaneously. The advantages of bacterial ghosts include the simplicity of the production method, safety, independence from the cold chain, and versatility as a combination vaccine.