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Molecular characterization of a common 48-kilodalton outer membrane protein of Actinobacillus pleuropneumoniae.

ABSTRACT: Previous studies have shown that a vaccine prepared from outer membranes of Actinobacillus pleuropneumoniae serotype 5 can elicit protective immunity in swine against challenge with either serotype 5 or serotype 1. These results suggest the presence of common subcapsular surface antigens, such as outer membrane proteins, that contribute to cross-protective immunity. We have identified a 48-kDa outer membrane protein that is common to all 12 capsular serotypes of A. pleuropneumoniae but is not present in the outer membranes of related species of gram-negative swine pathogens. This protein is immunogenic in swine infected with either A. pleuropneumoniae serotype 5 or 1A, as well as in swine vaccinated with A. pleuropneumoniae serotype 5 outer membranes. This 48-kDa protein is readily detected in outer membranes produced by sucrose density gradient centrifugation, but it is sarcosyl soluble and therefore not found in outer membranes prepared by detergent treatment. The gene encoding the 48-kDa outer membrane protein has been cloned from A. pleuropneumoniae serotype 5 and and has been designated aopA, for Actinobacillus outer membrane protein A. The gene is 1,347 bp in length and encodes a protein, designated AopA, of 449 amino acids with a predicted molecular weight of 48,603. Southern blot analysis under high-stringency conditions showed that strains of all 12 serotypes of A. pleuropneumoniae contain DNA homologous to this gene, as do strains of two closely related species, Actinobacillus suis and Pasteurella multocida. Whether antibodies against the AopA antigen contribute to cross-protective immunity against A. pleuropneumoniae infection remains to be determined.

SUBMITTER: Cruz WT

PROVIDER: S-EPMC173731 | biostudies-other | 1996 Jan

REPOSITORIES: biostudies-other

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Molecular characterization of a common 48-kilodalton outer membrane protein of Actinobacillus pleuropneumoniae.

Cruz W T WT Nedialkov Y A YA Thacker B J BJ Mulks M H MH

Infection and immunity 19960101 1

Previous studies have shown that a vaccine prepared from outer membranes of Actinobacillus pleuropneumoniae serotype 5 can elicit protective immunity in swine against challenge with either serotype 5 or serotype 1. These results suggest the presence of common subcapsular surface antigens, such as outer membrane proteins, that contribute to cross-protective immunity. We have identified a 48-kDa outer membrane protein that is common to all 12 capsular serotypes of A. pleuropneumoniae but is not pr ...[more]

PMID: 8557378

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Project description:Outer membrane vesicles (OMVs) are spontaneously released by Gram-negative bacteria, including Actinobacillus pleuropneumoniae, which causes contagious pleuropneumonia in pigs and leads to considerable economic losses in the swine industry worldwide. A. pleuropneumoniae OMVs have previously been demonstrated to contain Apx toxins and proteases, as well as antigenic proteins. Nevertheless, comprehensive characterizations of their contents and interactions with host immune cells have not been made. Understanding the protein compositions and immunomodulating ability of A. pleuropneumoniae OMVs could help illuminate their biological functions and facilitate the development of OMV-based applications. In the current investigation, we comprehensively characterized the proteome of native A. pleuropneumoniae OMVs. Moreover, we qualitatively and quantitatively compared the OMV proteomes of a wild-type strain and three mutant strains, in which relevant genes were disrupted to increase OMV production and/or produce OMVs devoid of superantigen PalA. Furthermore, the interaction between A. pleuropneumoniae OMVs and porcine alveolar macrophages was also characterized. Our results indicate that native OMVs spontaneously released by A. pleuropneumoniae MIDG2331 appeared to dampen the innate immune responses by porcine alveolar macrophages stimulated by either inactivated or live parent cells. The findings suggest that OMVs may play a role in manipulating the porcine defense during the initial phases of the A. pleuropneumoniae infection. IMPORTANCE Owing to their built-in adjuvanticity and antigenicity, bacterial outer membrane vesicles (OMVs) are gaining increasing attention as potential vaccines for both human and animal use. OMVs released by Actinobacillus pleuropneumoniae, an important respiratory pathogen in pigs, have also been investigated for vaccine development. Our previous studies have shown that A. pleuropneumoniae secretes OMVs containing multiple immunogenic proteins. However, immunization of pigs with these vesicles was not able to relieve the pig lung lesions induced by the challenge with A. pleuropneumoniae, implying the elusive roles that A. pleuropneumoniae OMVs play in host-pathogen interaction. Here, we showed that A. pleuropneumoniae secretes OMVs whose yield and protein content can be altered by the deletion of the nlpI and palA genes. Furthermore, we demonstrate that A. pleuropneumoniae OMVs dampen the immune responses in porcine alveolar macrophages stimulated by A. pleuropneumoniae cells, suggesting a novel mechanism that A. pleuropneumoniae might use to evade host defense.

Dataset Information

Molecular characterization of a common 48-kilodalton outer membrane protein of Actinobacillus pleuropneumoniae.

Publications

Molecular characterization of a common 48-kilodalton outer membrane protein of Actinobacillus pleuropneumoniae.

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