title: Mutation in the LPS outer core biosynthesis gene, galU, affects LPS interaction with the RTX toxins ApxI and ApxII and cytolytic activity of Actinobacillus pleuropneumoniae serotype 1.
abstract: Lipopolysaccharides (LPS) 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 surface plasmon resonance 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.
authors: Groupe de recherche sur les maladies infectieuses du porc, Faculté de médecine vétérinaire, Université de Montréal, St-Hyacinthe, QC, Canada J2S 7C6.
authors: Mahendrasingh
authors: M
authors: Ramjeet
authors: Andrew D
authors: AD
authors: Cox
authors: Mark A
authors: MA
authors: Hancock
authors: Michael
authors: M
authors: Mourez
authors: Josée
authors: J
authors: Labrie
authors: Marcelo
authors: M
authors: Gottschalk
authors: Mario
authors: M
authors: Jacques
mesh_terms: D000189:Actinobacillus Infections / Q000382:microbiology / Q000662:veterinary; D016977:Actinobacillus pleuropneumoniae / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity; D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D003001:Cloning, Molecular; D003603:Cytotoxins / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D015870:Gene Expression; D005798:Genes, Bacterial; D006460:Hemolysin Proteins / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000378:metabolism*; D016676:Macrophages, Alveolar / Q000382:microbiology; D009154:Mutation; D054730:Protein Interaction Domains and Motifs; D012329:RNA, Bacterial / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020349:Surface Plasmon Resonance; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology; D014774:Virulence; D037521:Virulence Factors / Q000378:metabolism
chemical_list: C085361:ApxII toxin, bacteria; D001426:Bacterial Proteins; D002352:Carrier Proteins; D003603:Cytotoxins; D006460:Hemolysin Proteins; D008070:Lipopolysaccharides; D012329:RNA, Bacterial; D037521:Virulence Factors; C087744:ApxI toxin, Bacteria