Background: Bacterial ghosts, genetically inactivated Gram-negative bacterial pathogens, possess significant advantages over commonly used vaccination technologies. The autolysis of the bacteria, by the expression of a cloned viral gene, results in empty bacterial envelopes through the expulsion of cytoplasmic content. Immunostimulatory properties are generally presented through the targeting of professional antigen-presenting cells (APCs), such as macrophages and dendritic cells (DCs).Material/Methods: This study investigated the interactions between porcine antigen-presenting cells and bacterial ghosts derived from the bacterial pathogen Actinobacillus pleuropneumoniae. The maturation process of DCs and their generation of immune responses to bacterial ghosts was shown by the expression of activation markers on their surface, as well as in the functional tests.Results: A population of porcine APCs was generated from PBS by incubation with rpo-GMCSF and rh-IL-4. The cells expressed SWC3, MIL-2, CD80/86 molecules, as well as a high level of MSA3 molecules. The internalization of bacterial ghosts by the cells resulted in increased expression of MSA3 molecules. The capacity of T cells to proliferate when induced by bacterial ghosts was 4 times higher in the cultures including APCs than in cultures stimulated with bacterial ghosts only.Conclusions: We found that antigen-presenting cells have the capacity to stimulate specific T cells after the internalization and processing of Actinobacillus ghosts, as demonstrated by a strong specific T-cell response generated against the ghost antigens.

Keywords: Actinobacillus pleuropneumoniae - cytology, Actinobacillus pleuropneumoniae - immunology, Histocompatibility Antigens - immunology, Actinobacillus pleuropneumoniae - immunology, Antigen-Presenting Cells - immunology, Coculture Techniques, Histocompatibility Antigens - immunology, Phenotype, Swine, T-Lymphocytes - metabolism, Vaccination