title: Potential use an Actinobacillus pleuropneumoniae double mutant strain DeltaapxIICDeltaapxIVA as live vaccine that allows serological differentiation between vaccinated and infected animals.
abstract: Actinobacillus pleuropneumoniae is the causative agent of porcine pleuropneumonia, a highly contagious and often fatal disease. We have previously reported the construction and characterization of a single gene apxIIC deletion mutant HB04C(-) based on A. pleuropneumoniae serovar 7 which produces ApxII toxin and ApxIV. A precisely defined DeltaapxIICDeltaapxIVA double-deletion mutant of A. pleuropneumoniae was constructed based on HB04C(-) by transconjugation and counterselection, and the levels of virulence of the DeltaapxIIC single mutant and DeltaapxIICDeltaapxIVA double mutant were compared in an experimental infection in mice and pigs. The results demonstrated that the DeltaapxIICDeltaapxIVA double mutant strain was less virulent than HB04C(-). Despite attenuation of virulence, the DeltaapxIICDeltaapxIVA double mutant remains immunogenic and conferred a similar level of protective immunity to pigs against challenge with a lethal dose of a heterologous fully virulent standard serovar 1 strain of A. pleuropneumoniae. The results of the virulence study suggest that ApxIV is a critical virulence factor of A. pleuropneumoniae serovar 7 and is able to induce clinical disease, but it not required for efficient vaccination of pigs against A. pleuropneumoniae infection. Two weeks after the booster immunization, animals vaccinated with HB04C(-) were positive in the ApxIVAM-ELISA based on a recombinant GST-fusion protein GST-ApxIVAM as the solid-phase antigen while animals vaccinated with the DeltaapxIICDeltaapxIVA double mutant were negative. These data demonstrate that the double mutant DeltaapxIICDeltaapxIVA can be used as an effective live marker vaccine allowing serological differentiation between vaccinated and infected animals.
authors.affiliation: Laboratory of Animal Infectious Diseases, College of Animal Science & Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei 430070, China.
authors.forename: Jinlin
authors.initials: J
authors.lastname: Liu
authors.forename: Xia
authors.initials: X
authors.lastname: Chen
authors.forename: Liwen
authors.initials: L
authors.lastname: Lin
authors.forename: Chen
authors.initials: C
authors.lastname: Tan
authors.forename: Yan
authors.initials: Y
authors.lastname: Chen
authors.forename: Yi
authors.initials: Y
authors.lastname: Guo
authors.forename: Meilin
authors.initials: M
authors.lastname: Jin
authors.forename: Aizhen
authors.initials: A
authors.lastname: Guo
authors.forename: Weicheng
authors.initials: W
authors.lastname: Bei
authors.forename: Huanchun
authors.initials: H
authors.lastname: Chen
mesh_terms: D016977:Actinobacillus pleuropneumoniae / Q000235:genetics / Q000276:immunology*; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D001426:Bacterial Proteins / Q000235:genetics*; D001428:Bacterial Vaccines / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006460:Hemolysin Proteins / Q000235:genetics*; D007074:Immunoglobulin G / Q000097:blood; D051379:Mice; D008807:Mice, Inbred BALB C; D009154:Mutation; D013552:Swine; D014611:Vaccination; D014613:Vaccines, Attenuated / Q000276:immunology; D014614:Vaccines, Synthetic / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; C085361:ApxII toxin, bacteria; C122177:ApxIVA protein, Actinobacillus pleuropneumoniae; D001426:Bacterial Proteins; D001428:Bacterial Vaccines; D006460:Hemolysin Proteins; D007074:Immunoglobulin G; D014613:Vaccines, Attenuated; D014614:Vaccines, Synthetic