Submitted to: Vaccine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 6, 2004
Publication Date: November 15, 2004
Citation: Register, K.B. 2004. Comparative sequence analysis of bordetella bronchiseptica pertactin gene (prn) repeat region variants in swine vaccines and field isolates. Vaccine. 23:48-57.
Interpretive Summary: Bordetella bronchiseptica is a significant swine respiratory disease pathogen. It causes or is involved in atrophic rhinitis, pneumonia, and porcine respiratory disease complex. Although vaccines against B. bronchiseptica are widely used in the swine industry worldwide, vaccine efficacy is reported as being low. One of the proteins produced by B. bronchiseptica, called pertactin, is known to elicit a protective immune response in swine. Recently, it was discovered that different forms of pertactin are produced by some isolates. It is not presently known which pertactin types are most frequently found in strains causing disease in swine. In this study, the pertactin types made by 83 recent United States B. bronchiseptica swine isolates were compared with the types found in 5 different vaccine strains. Only two vaccines are derived from strains with pertactin types identical to those found in the majority of swine isolates. Two other vaccines have pertactin types almost never found in swine isolates. Vaccine strains that contain the same pertactin type as strains that are currently causing disease in swine herds are more likely to provide the best protection. The results of this study may assist vaccine manufacturers in improving the efficacy of their products.
The product of the B. bronchiseptica pertactin gene, prn, has been implicated as an adhesin and a protective immunogen in swine. Recent studies demonstrate prn sequence heterogeneity in swine isolates and vaccine strains within and surrounding the region 1 amino acid repeat GGXXPn and the region 2 amino acid repeat PQPn. However, only a few isolates have been evaluated. Allelic variation between vaccine strains and field isolates may affect vaccine efficacy, since region 2 is known to encode an immunodominant protective epitope. In the present study, the DNA and predicted amino acid sequences of the pertactin repeat regions from a collection of 83 recent swine field isolates and 5 vaccine strains from the United States were determined. Two region 1 variants and four region 2 variants, one of which has not been previously reported, were identified, comprising 4 pertactin types. Four vaccines are derived from strains with a region 1 variant identical to that found in the majority of field isolates. However, only two vaccines possess the most commonly identified sequence in region 2, while two others contain a variant that has not been found in any swine isolate. Vaccines containing the novel region 2 variant were found by ribotype analysis to be less closely related to the majority of swine isolates than other vaccine strains analyzed. No relationship was observed between pertactin type and ribotype.