Submitted to: Infection and Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 24, 2000
Publication Date: N/A
Interpretive Summary: Bordetella bronchiseptica is a causative agent of atrophic rhinitis and pneumonia in swine. Pertactin, a protein that is made by B. bronchiseptica, is believed to be involved in attachment of the bacterium to host cells in the respiratory tract. Previous studies have shown that antibodies to pertactin can protect swine from pneumonia and atrophic rhinitis. In a prior study, based on the analysis of a limited number of swine isolates, we found that some strains of B. bronchiseptica produced different versions of pertactin. Three unique types were detected. Since these different types differ in regions of the protein that provoke antibody responses, different versions of pertactin may not elicit cross- protective antibodies. In the present study, a larger number of B. bronchiseptica strains were evaluated representing isolates from many sources, including pigs, dogs, rabbits, turkeys, and others. Eight different versions of pertactin were detected from these isolates. Additional data suggests that even more variants are yet to be identified. Vaccines that contain one version of pertactin may not protect against strains that possess a different version. Improved vaccine efficacy may be achieved by including strains that produce the pertactin types found circulating in the field.
The outer membrane protein pertactin, encoded by the prn gene, is produced by several species of Bordetella. It has been demonstrated to act as an adhesin for Bordetella pertussis and is believed to function similarly in Bordetella bronchiseptica. The importance of B. bronchiseptica pertactin as a protective immunogen has been clearly demonstrated in both mice and pigs. Previous sequence analysis of prn from a canine isolate of B. bronchiseptica, CN7531, identified 2 regions predicted to encode amino acid repeat motifs. Region 1, approximately 800 bp from the 5' end of prn, encodes the repeat GGxxPn. Region 2, roughly 900 bp 3' of region 1, encodes a reiterated PQPn. Recent studies have documented DNA sequence heterogeneity in both regions 1 and 2 among animal and human isolates of B. bronchiseptica. The present study describes 4 additional region 1 prn variants as well as 4 additional region 2 variants. Based on the combined predicted amino acid sequences encoded by the prn repeat regions, 8 pertactin types could be distinguished among the strains examined, 6 of which have not been previously identified. Immunoblotting demonstrated strain heterogeneity in pertactin consistent with the predicted combined sizes of the repeat regions, suggesting that all or most pertactin heterogeneity is likely to arise from variations in regions 1 and/or 2. A revised system for classifying B. bronchiseptica pertactin variants is proposed.