title: Influences of ORF1 on the virulence and immunogenicity of Actinobacillus pleuropneumoniae.
abstract: Actinobacillus pleuropneumoniae is a Gram-negative pathogen that causes porcine pleuropneumonia. The pathogenicity of A. pleuropneumoniae is strongly correlated with the production of active repeat-in-toxin (RTX) proteins such as ApxIVA. We evaluated the contribution of a potential ApxIVA activator, ORF1, to the virulence and immunogenicity of A. pleuropneumoniae in pigs. The orf1 gene in A. pleuropneumoniae SLW03 (serovar 1, ΔapxICΔapxIIC) was deleted, producing strain SLW05 (ΔapxICΔapxIICΔorf1). The virulence of strains SLW03 and SLW05 was compared in pigs. Clinical signs and pulmonary lesions induced by strain SLW05 were slighter than that of strain SLW03 (P < 0.05). The immunogenicity and protective efficacy of strains SLW03 and SLW05 were similar. All pigs immunized with strain SLW03 or SLW05 developed high antibody titers against ApxIA, ApxIIA, and ApxIVA before challenge. Two weeks after a second immunization, pigs were challenged intratracheally with either a fully virulent A. pleuropneumoniae serovar 1 or serovar 3 strain. Vaccination with strains SLW03 or SLW05 provided significantly greater protection compared to the negative control (P < 0.01). Immunized pigs displayed significantly fewer clinical signs and lower lung lesion scores than non-immunized pigs. These results suggested that ORF1 plays an important role in the development of ApxIVA toxicity. Furthermore, strain SLW05 is a highly attenuated strain able to induce protective immunity against A. pleuropneumoniae infection.
authors.affiliation: Division of Animal Infectious Diseases, State Key Laboratory of Agricultural Microbiology, College of Animal Science & Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, Hubei, China.
authors.forename: Fangyan
authors.initials: F
authors.lastname: Yuan
authors.forename: Jinlin
authors.initials: J
authors.lastname: Liu
authors.forename: Yi
authors.initials: Y
authors.lastname: Guo
authors.forename: Chen
authors.initials: C
authors.lastname: Tan
authors.forename: Shulin
authors.initials: S
authors.lastname: Fu
authors.forename: Jin
authors.initials: J
authors.lastname: Zhao
authors.forename: Huanchun
authors.initials: H
authors.lastname: Chen
authors.forename: Weicheng
authors.initials: W
authors.lastname: Bei
mesh_terms: D000189:Actinobacillus Infections / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D016977:Actinobacillus pleuropneumoniae / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology*; D004269:DNA, Bacterial / Q000235:genetics; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D006651:Histocytochemistry / Q000662:veterinary; D011897:Random Allocation; D017384:Sequence Deletion / Q000276:immunology; D013552:Swine; D013553:Swine Diseases / Q000276:immunology / Q000382:microbiology*; D014611:Vaccination / Q000662:veterinary; D014774:Virulence / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; C122177:ApxIVA protein, Actinobacillus pleuropneumoniae; D001426:Bacterial Proteins; D004269:DNA, Bacterial