IDENTIFICATION OF HIGHLY CONSERVED AND SPECIES-SPECIFIC POLYPEPTIDES OF HAEMOPHILUS-DUCREYI

Chancroid is a sexually transmitted diseased caused by Haemophilus ducreyi. The pathological manifestations of chancroid are unique among Haemophilus species and the virulence factors of H. ducreyi that account for these features have not been identified. Some of these virulence factors may be unique components of H. ducreyi that, but attempts to identify H. ducreyi-specific components have been unsuccessful. Four polypeptides-A, B, C and D of 83, 77, 56 and 28 kDa, respectively-were identified with a panel of nine H. ducrey-specific monoclonal antibodies (MAbs). Polypeptide C was one of the five major proteins in H. ducreyi and demonstrated micro-heterogeneity in SDS-PAGE. Polypeptides A, B and D were present in only small amounts in whole-cell lysates of H. ducreyi. The relative amounts of A and B varied, suggesting that they may be precursor molecules. The unique polypeptides C and D were not exposed on the surface. Polypeptide C was highly soluble and did not appear to be membrane-bound, whereas polypeptide D appeared to partition with the cytoplasmic membrane and was soluble in Sarkosyl. All four polypeptides appeared to be unique to H. ducreyi since MAbs directed against them did not cross-react with H. influenzae, H. parainfluenzae or Neisseria gonorrhoeae. The mol. wts of all of these polypeptides were conserved throughout 35 clinical isolates collected from 15 cities in eight countries and one reference strain of H. ducreyi that were tested. Based on the immune cross-reactivities, it was concluded that the four polypeptides belonged to a family of proteins with partial sequence homology that may have been derived from the same precursor polypeptide or the same transcription unit. A sequence relationship model for the polypeptides was proposed based on their cross-reactivities with the MAbs.