Submitted to: Pig Veterinary Society International Congress Proceedings
Publication Type: Proceedings
Publication Acceptance Date: June 7, 2000
Publication Date: September 15, 2000
Technical Abstract: The product of the B. bronchiseptica pertactin gene (prn) has been implicated as an adhesin and protective immunogen. Previous analysis of prn revealed 2 regions that encode amino acid repeat motifs. Region 1, approximately 800 bp from the 5' end of prn, contains the repeat GGXXPn. Region 2, roughly 900 bp 3' of region 1, encodes a reiterated PQPn. Variation in Region 1 of prn from Bordetella pertussis has been postulated to account for recently observed decreases in vaccine efficacy in humans. Variation in B. bronchiseptica prn has not been evaluated. The goal of this study was to determine whether heterogeneity exists in Regions 1 and 2 of prn genes from vaccine and field strains of B. bronchiseptica. PCR products derived from Region 1 or Region 2 were digested with restriction enzymes and their mobilities were compared on agarose gels. When Region 1 PCR products were digested with Sau 3A, 1 of the 3 predicted fragments was found to vary in size between strains. Similarly, a variable fragment was apparent in Region 2 PCR products digested with BstX I. Sequencing of PCR products revealed 2 GGXXP variants, containing either 3 or 4 repeats, and 3 PQP variants, containing 6, 7, or 8 repeats. The prn gene from each strain evaluated was assigned a variant designation, depending on the combination of GGXXP and PQP repeats present. The pertactin variants associated with field isolates are unique from those of vaccine strains. These results imply that vaccine strains may not be antigenically identical to disease- causing field strains. The existence of antigenic variants has profound implications for vaccine design.