Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: February 21, 2003
Publication Date: April 20, 2003
Citation: REGISTER, K.B. SEQUENCE HETEROGENEITY IN THE FILAMENTOUS HEMAGGLUTININ GENE (FHAB) REPEAT REGIONS OF BORDETELLA BRONCHISEPTICA. 103rd GENERAL MEETING OF THE AMERICAN SOCIETY FOR MICROBIOLOGY. 2003. Abstract p. 89, #B-311.
Background: The Bordetella virulence factor filamentous hemagglutinin, encoded by fhaB, functions as an adhesin and immunogen. The fhaB gene of Bordetella bronchiseptica isolate GP1 contains two 19-residue pseudo-repeats, designated R1 and R2, similar to those described in Bordetella pertussis. In GP1, 40 copies of the R1 repeat and 13 copies of the R2 repeat are present. Since sequence polymorphisms frequently occur in amino acid repeat regions, and are known to exist in repeat regions of one other Bordetella adhesin, the sequence of the R1 and R2 repeats of several B. bronchiseptica strains was examined. Methods: Strains were derived from a variety of host species, including pigs, dogs, humans, seals and turkeys. PCR amplicons encompassing R1 and R2 fhaB repeats were purified and subjected to fluorescence-based cycle sequencing. Sequences were analyzed using Vector NTI Suite software. Results: Relative to the sequence of GP1, all strains examined possess multiple nonconservative base substitutions throughout R1. Some are shared among multiple strains while others are associated with only a single strain. The most significant alteration found is a predicted 152 amino acid insertion, located between repeats 8 and 9 of the GP1 sequence and comprising 8 additional repeats, present in strains acquired from a turkey, pig, and human. Only a few R1 repeats are conserved among all strains analyzed. Numerous nonconservative base substitutions were also found in the R2 repeats of all strains examined, although the overall rate of substitution is lower than for R1. Interestingly, many R1 and R2 substitutions shared by strains containing the large R1 insertion are identical to sequence previously reported for B. pertussis. Conclusion: This is the first report of DNA sequence polymorphisms in the fhaB gene of a Bordetella species. At least some predicted alterations in protein sequence are likely to affect the structure of mature Fha and may have consequences for immunogenicity, host cell tropism, and other characteristics and functions of this protein.