Antibodies produced against a fragment of filamentous haemagglutinin (FHA) of Bordetella pertussis are able to inhibit hemagglutination induced by the whole adhesin.

Filamentous hemagglutinin adhesin (FHA) is important for the adherence of Bordetella pertussis to the host ciliary epithelial cells of the respiratory tract. Several binding domains have been characterized in the FHA molecule. For example, an putative heparin-binding domain of FHA was previously located in the FHA(442-863) region. In this work, the HEP fragment, corresponding to FHA(430-873) was amplified by PCR and subcloned in an Escherichia coli expression plasmid. Purified recombinant HEP was used to produce polyclonal antibodies in mice that were able to recognize HEP and FHA in ELISA and in Western-blot assays. Although recombinant HEP displayed low ability to bind heparin and no hemagglutination activity, the anti-HEP antibodies were able to inhibit FHA mediated hemagglutination activity in goose erythrocytes. These results indicate that other amino acid residues that are not present in the FHA(430-873) fragment may be necessary for heparin binding. Further studies to address the immunogenic response against HEP are also required.

Vir90, a virulence-activated gene coding for a Bordetella pertussis iron-regulated outer membrane protein.

Bordetella pertussis undergoes phenotypic changes modulated by the bvgAS locus, which regulates the expression of many genes related to virulence and immunogenicity. We previously reported the N-terminal sequence of a 90 kDa bvg-regulated outer membrane protein (OMP) of B. pertussis (SWISS-PROT accession No. p81549), a novel potential virulence factor that we named Vir90. The open reading frames (ORFs) which potentially code for Vir90 in B. pertussis, B. parapertussis and B. bronchiseptica were identified by computer analysis of the genomic sequences available for the three Bordetella species. Nucleotide sequence analysis of the vir90 upstream region revealed the presence of a putative promoter, a BvgA binding site and a putative Fur binding site. The B. pertussis Vir90 protein showed significant homology with ferrisiderophore receptors from Gram-negative bacteria. An antiserum raised against Vir90His recombinant protein recognized the 90-kDa protein in immunoblots of OMPs from these three virulent Bordetella species. The accumulation of the Vir90 protein increased 4-fold under low iron growth conditions. Therefore, the vir90 gene is expressed in the tested species and its expression is regulated positively by the BvgAS system and negatively under high iron concentration, likely by Fur.