Endobronchial inoculation with Apx toxins of Actinobacillus pleuropneumoniae leads to pleuropneumonia in pigs

To establish the role of the Apx toxins in the pathogenesis of porcine pleuropneumonia, specific-pathogen-free pigs were inoculated deeply endobronchially with either culture filtrates of Actinobacillus pleuropneumoniae serotype 8 or 9, culture filtrates depleted of the Apx toxins by affinity chromatography, depleted culture filtrate supplemented with purified recombinant Apx toxins (rApx), or purified rApx toxins alone. Results of these experiments indicate that ApxI, ApxIII, and, to a lesser extent, ApxII are the bacterial factors that trigger the development of clinical symptoms and lung lesions typical for porcine pleuropneumonia.