Localization of antigenic domains on the major subunits of Bordetella pertussis serotype 2 and 3 fimbriae.

Antibody-binding domains on the major subunits of Bordetella pertussis serotype 2 (Fim2) and 3 fimbriae (Fim3) have been identified using synthetic peptides which were screened for recognition by anti-protein monoclonal antibodies (mAbs). The presence of non-contiguous fimbrial epitopes was demonstrated by both anti-Fim2 and anti-Fim3 mAbs, several of which recognized at least two peptides that were discontinuous in the amino acid sequence of the corresponding subunits. The specificity of one mAb, 51/24, directed against Fim2, was investigated by replacement-set analysis of a 10-residue peptide, and revealed that antibody binding to the peptide was dependent on the sequence N94PQ96 which is non-conserved in Fim3. Furthermore, proline at residue 95 was found to be essential for mAb 51/24 binding. The specific anti-Fim3 mAb, AG3A, was found to recognize the 10-residue carboxy-terminal peptide from both Fim3 and, unexpectedly, from Fim2. This result suggests that mAb AG3A serospecificity at the protein level is determined by a conformational constraint which prevents mAb AG3A binding to the Fim2 C-terminal domain. Several free peptides containing amino acid residues which comprise part of the Fim2 and Fim3 epitopic domains were prepared as immunogens. One of these peptides was immunogenic in the mouse, indicating the location of a T-helper cell epitope within the peptide sequence, and induced a strong anti-peptide antibody response. The other peptides each required immunization as a conjugate with a carrier protein for anti-peptide antibody stimulation. All four anti-peptide antibody preparations only weakly recognized fimbriae-coated ELISA plates.(ABSTRACT TRUNCATED AT 250 WORDS)