Role of the ApxIB/ApxID exporter in secretion of the ApxII and ApxIII toxins in Actinobacillus pleuropneumoniae

ABSTRACT

Apx toxins are a virulent factor of Actinobacillus pleuropneumoniae (App). At least four genes, apxC, apxA, apxB, and apxD, are involved in the release of Apx toxins from App. apxA encodes Apx toxins, whereas apxB and apxD encode exporters. Some serotypes of App such as serotype 2 retain apxIBD, apxIICA, and ,i>apxIIICABD. Although the specificity of the ApxIB/ApxID exporter to ApxII has been established in those serotypes, that to ApxIII is under-studied. We constructed an apxIB- and apxID-lacking mutant strain of the App serotype 2 to study whether the ApxIB/ApxID exporter is capable of secreting both ApxII and ApxIII toxins.