Lipopolysaccharides and Apx toxins are major virulence factors of Actinobacillus pleuropneumoniae, a pathogen of the respiratory tract of pigs. Here, we evaluated the effect of LPS core truncation in haemolytic and cytotoxic activities of this microorganism. We previously generated a highly attenuated galU mutant of A. pleuropneumoniae serotype 1 that has an LPS molecule lacking the GalNAc-Gal II-Gal I outer core residues. Our results demonstrate that this mutant exhibits wild type haemolytic activity but is significantly less cytotoxic to porcine alveolar macrophages. However, no differences were found in gene expression and secretion of the haemolytic and cytotoxic toxins ApxI and ApxII, both secreted by A. pleuropneumoniae serotype 1. This suggests that the outer core truncation mediated by the galU mutation affects the toxins in their cytotoxic activities. Using both ELISA and SPR binding assays, we demonstrate a novel interaction between LPS and the ApxI and ApxII toxins via the core oligosaccharide. Our results indicate that the GalNAc-Gal II-Gal I trisaccharide of the outer core is fundamental to mediating LPS/Apx interactions. The present study suggests that a lack of binding between LPS and ApxI/II affects the cytotoxicity and virulence of A. pleuropneumoniae
lipopolysaccharides, Actinobacillus pleuropneumoniae, toxins, virulence factors
NCBI PubMed ID: 18713318Journal NLM ID: 8712028Publisher: Blackwell Publishing
Correspondence: mariojacques@umontreal.ca
Institutions: Groupe de recherche sur les maladies infectieuses du porc (GREMIP), Faculte de medecine veterinaire, Universite de Montreal, St-Hyacinthe, QC, Canada J2S 7C6
Methods: ELISA, serological methods, genetic methods, UV, CD, statistical analysis
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