Keywords: Actinobacillus pleuropneumoniae, Ap, oral vaccine, immune tolerance, local immunity, mucosa, mouse model, porcine contagious pleuropneumonia, pigs, serum antibodies
Immunity development following oral vaccination against Actinobacillus pleuropneumoniae in a mouse model
Porcine contagious pleuropneumonia caused by Actinobacillus pleuropneumoniae (Ap) is a deadly disease in pigs. In this work, we attempt to determine immunogenic properties of an oral Ap vaccine in a mouse model. Formalin-inactivated, whole-cell Ap suspension is included in two vaccine formulations: the classic injectable form with aluminium adjuvant and the oral form encapsulated into enteric-coated polymer microspheres. Two groups of mice, each vaccinated with one of the vaccines, are subjected to immunomorphology investigations in comparison with the non-vaccinated control group. Experimental results reveal pronounced systemic immunity and serum antibodies in the group vaccinated by injection. The orally vaccinated group demonstrated more expressed local immunity and mucous antibodies than control group. However, in this group, some tolerance induction occurred in the lungs during the first two vaccinations. We thus developed the means of overcoming primary tolerance, which might become a highly promising approach in improving the potency of oral vaccines.