Characterization of a highly immunogenic lipoprotein Mhp366 identified by peptide spot array
Résumé
Enzootic Pneumonia (EP) in pigs caused by is a highly prevalent, chronic respiratory disease, which causes considerable economic losses in the swine industry. Most herds are vaccinated, but classical bacterin vaccines do not prevent colonization and it is not possible to detect flourishing infections in vaccinated herds since commonly used commercial ELISAs can not differentiate infected from vaccinated animals. To solve this problem, new immunogenic proteins, up-regulated or solely expressed during infection, need to be identified. For this purpose a peptide spot array was constructed which presents 105 potential linear B-cell epitopes identified by analysis in 35 putative lipoproteins encoded on the genome of type strain 232. Subjecting this array to immunoblotting using porcine convalescent serum revealed a single strongly immunoreactive epitope on the Mhp366 protein which did not react with serum from bacterin-immunized pigs. In addition, it was not possible to detect Mhp366 in total cell lysates of grown strains, using a polyclonal rabbit serum raised against a recombinant GST-Mhp366 fusion protein. To investigate the possibility of using an Mhp366-based ELISA in the field for differentiating vaccinated herds with and without a flourishing infection it was shown that i) homologues of the corresponding gene were present in all 17 strains and porcine lung samples tested from different geographic origins and ii) an ELISA based on epitope-specific synthetic peptides as solid phase antigen allowed a classification of field samples. Therefore, Mhp366 might be the first antigen identified which facilitates the detection of flourishing infections even in vaccinated herds.
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