Knockout mutants of Actinobacillus pleuropneumoniae serotype 1 that are devoid of RTX toxins do not activate or kill porcine neutrophils

• Published in: Infection and Immunity Vol. 63; no. 1; pp. 27 - 37
• Main Authors: Jansen, R. (ID-DLO, Lelystad, The Netherlands.), Briaire, J, Smith, H.E, Dom, P, Haesebrouck, F, Kamp, E.M, Gielkens, L.J, Smits, M.A
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for Microbiology 01.01.1995
• Subjects: ACTINOBACILLUS PLEUROPNEUMONIAE; Actinobacillus pleuropneumoniae - genetics; Actinobacillus pleuropneumoniae - immunology; Actinobacillus pleuropneumoniae - pathogenicity; Animal bacterial diseases; Animals; Bacterial diseases; Bacterial Proteins - biosynthesis; Bacterial Proteins - genetics; Bacterial Proteins - toxicity; Bacterial Toxins - biosynthesis; Bacterial Toxins - genetics; Bacterial Toxins - toxicity; Base Sequence; Biological and medical sciences; Cell Death; CERDO; Drug Resistance, Microbial - genetics; Electroporation; GENE; GENES; Genotype; GRANULOCITOS; GRANULOCYTE; Hemolysin Proteins; ID Lelystad, Institute for Animal Science and Health; ID-Lelystad, Instituut voor Dierhouderij en Diergezondheid; Infectious diseases; Medical sciences; Molecular Sequence Data; MUTACION; Mutagenesis, Insertional; MUTANT; MUTANTES; MUTATION; Neutrophil Activation; OXIDACION; OXYDATION; PATHOGENESE; PATOGENESIS; Phenotype; PORCIN; PROTEINAS; PROTEINE; RECOMBINACION; RECOMBINAISON; Recombination, Genetic; Respiratory Burst; SECRECION; SECRETION; Swine; TOXICIDAD; TOXICITE; TOXINAS; TOXINE; Transformation, Genetic; Virulence - genetics; Lung disease; Pneumonia; Respiratory disease; Pathogenesis; Host agent relation; Pig; Infection; Pasteurellaceae; Toxin; Vertebrata; Mammalia; Bacteriosis; Bacteria; Artiodactyla; Mutation; Neutrophil; Actinobacillus pleuropneumoniae; Ungulata
• ISSN: 0019-9567; 1098-5522
• DOI: 10.1128/iai.63.1.27-37.1995

The Actinobacillus pleuropneumoniae RTX-toxins ApxI, ApxII, and ApxIII are important virulence factors of this swine pathogen. It is hypothesized that the Apx toxins are deleterious to defense cells of the host, enabling the bacterium to infect the host. To confirm this, we studied the effect on porcine polymorphonuclear neutrophils of mutant strains of A. pleuropneumoniae that were devoid of Apx toxins. For this purpose, we developed a system for targeted mutagenesis of A. pleuropneumoniae based on the conditionally replicating plasmid pVE6063 and insertional mutagenesis by homologous recombination. Employing this system on the reference strain of serotype 1, a strain that secretes ApxI and ApxII, we generated mutant strains that were devoid of ApxI and/or ApxII. We compared the ability of the parent strain and the mutant strains to provoke an oxidative burst in porcine neutrophils and to kill these cells. The parent strain and mutants that secreted either ApxI or ApxII provoked an oxidative burst and killed the neutrophils, whereas mutant strains that were devoid of ApxI and ApxII did not. These experiments indicate the importance of ApxI and ApxII to these profound effects on neutrophils and emphasize the importance of ApxI and ApxII in pathogenesis