Bordetella bronchiseptica expresses the fimbrial structural subunit gene fimA

Abstract

The differential host species specificities of Bordetella pertussis, B. parapertussis, and B. bronchiseptica might be explained by polymorphisms in adherence factor genes. We have found that B. parapertussis and B. bronchiseptica, unlike B. pertussis, contain a full-length gene for the fimbrial subunit FimA. B. bronchiseptica expresses fimA in a BvgAS-dependent fashion.The genetic basis for fimbrial expression in Bordetella pertussis has been well characterized. A fimbrial operon located downstream of the filamentous hemagglutinin structural gene fhaB is regulated by the BvgAS two-component system; it contains genes encoding accessory proteins (FimB and FimC) and the fimbrial minor subunit (FimD) (18). The genes for the major fimbrial subunits, Fim2 and Fim3, are expressed elsewhere on the Bordetella chromosome (8, 10). Fimbrial phase variation can be observed in vivo and is controlled by small insertions or deletions in a C-rich region upstream of both fim2 and fim3 (17). The B. pertussis fimbrial operon also contains a pseudogene designated fimA, located at the 5Ј end of the fimbrial gene cluster (Fig. 1) (18). This gene contains a DNA sequence homologous to those of fim2 and fim3 but lacks sequences predicted to encode the N-terminal third of the fimbrial subunit (18).The organization of the Bordetella bronchiseptica and Bordetella parapertussis fimbrial genes and their function are less well characterized than those of the B. pertussis fimbrial genes (5, 6). B. bronchiseptica expresses proteins that are recognized by polyclonal and monoclonal antisera generated against B. pertussis Fim2 and Fim3 (11, 16). Coding sequences for Fim2 and Fim3 are 74 and 94% similar at the nucleotide level, respectively, between B. pertussis and B. bronchiseptica (16).Comparison of 5Ј sequences upstream of fim2 and fim3 in the two species suggests similar mechanisms of transcriptional control. Accessory fimbrial proteins in B. bronchiseptica have not been examined in any detail, although the minor fimbrial subunit in this species, FimD, is predicted to differ from that of B. pertussis by only one amino acid (19). Differences in the host species specificities of these three Bordetella species might reflect polymorphisms at the genetic loci that encode fimbriae and other adherence factors.Structure of B. bronchiseptica and B. parapertussis genomic regions encompassing fimA. Using PCR primers derived from previously published B. pertussis fhaB (positions 10756 to 10781; GenBank no. X52156) and fimA (746 to 729; GenBank no. X64876) sequences (4, 18), we detected a 400-bp amplicon size polymorphism between B. pertussis BP536 (13) and B. bronchiseptica GP1, RB50, 110H, B133, and VPI-FE1 (2, 3) that corresponded to the region just downstream of fhaB. (Sequence analysis at the 3Ј end of GP1 fhaB revealed a substitution, G10781T, at the 3Ј end of the forward priming site.) The 1,105-bp amplicon from B. bronchiseptica guinea pig isolate GP1 (1) was cloned in pBluescript II KS (Stratagene, La Jolla, Calif.), and its sequence was determined...

Role of Bordetella bronchiseptica Fimbriae in Tracheal Colonization and Development of a Humoral Immune Response

“…Bordetella genome sequence data (http://www.sanger.ac.uk) indicate the existence of at least four fimbrial structural genes, and other studies (7,15,28,35) reveal that Bordetella species express fimbriae of at least four serotypes, Fim2, Fim3, FimX, and FimA, which are encoded by the fim2, fim3, fimX, and fimA genes, respectively. These genes are unlinked on the Bordetella chromosome, and their protein products are 57 to 60% identical at the amino acid level (7,15).…”

“…Bordetella genome sequence data (http://www.sanger.ac.uk) indicate the existence of at least four fimbrial structural genes, and other studies (7,15,28,35) reveal that Bordetella species express fimbriae of at least four serotypes, Fim2, Fim3, FimX, and FimA, which are encoded by the fim2, fim3, fimX, and fimA genes, respectively. These genes are unlinked on the Bordetella chromosome, and their protein products are 57 to 60% identical at the amino acid level (7,15). Although results from in vitro and in vivo studies with B. pertussis are consistent with the hypothesis that fimbriae contribute to the adherence of Bordetella to respiratory epithelium (32,33), and Fim2 and Fim3 have been included as components of current acellular pertussis vaccines (21), the precise role of fimbriae in pathogenesis has not been conclusively established.…”

Occurrence of Genes Encoding Virulence Factors in Bordetella Bronchiseptica Strains Isolated from Infected and Healthy Pigs

“…Bbr is motile and encodes full flagellar operon. In the genomes of B. pertussis and B. parapertussis, there is a lack of expression of these factors, which reflects adaptation of the bacteria to specific host niches, and probably enhances the virulence by reducing the number of targets available for recognition by the immune system (1,2,11,21).…”

Investigation of immunogenicity and protective efficiency of Bordetella bronchiseptica fimbriae in mice

“…Fimbriae was initially demonstrated to be constituted of three antigenically related 21, 22 and 24 kDa fimbrial major subunit proteins by Lee et al (1986) and shown to be expressed in variant quantities effecting the host species specificity of B. bronchiseptica strains (4). By different studies, fimbrial subunits of B. bronchiseptica were determined as Fim2, Fim3, FimX (expressed only at very low levels), FimA, FimN and FimD (3,8,13,20,21,26,28). Although being the minor fimbrial subunit, 40 kDa FimD, have important role in adhesion by affecting the expression of the major fimbrial subunits and being necessary in formation of the fimbrial structure (8,31).…”