Induction of protective immunity by aerosol or oral application of candidate vaccines in a dose-controlled pig aerosol infection model

In order to outline basic concepts for the design of a bacterial aerosol infection model, the development of a pig model with Actinobacillus pleuropneumoniae is described. First, reproducibility of aerosol parameters should be maintained by optimizing generating and sampling conditions. Survival rates of the chosen strain must be predictable. Secondly, inhalation conditions for the recipients have to be standardized to enable the determination of deposition sites and the dose administered. Subsequently, dose-response relationship should be evaluated to find a suitable challenge dose. Furthermore, it seems necessary to establish methods to obtain local specimens for determination of the local immune responses. The present study demonstrates that after aerosol challenge pigs were completely protected after inhalation and partially protected after oral application of A. pleuropneumoniae vaccines and describes techniques to administer bacteria in a dose-dependent, viable way. Using the infection model several stages of the disease from acute pleuropneumonia to chronic infection can be induced for research purposes.