Antibodies specific for the
cytolethal-distending toxin of Haemophilus ducreyi (HdCDT) complex and for the
CdtA, CdtB, and CdtC components were measured by ELISA in the sera of 50 patients with culture and/or PCR proven
chancroid, 42 patients with
periodontitis, 50 blood donors from Tanzania, 50 blood donors from Sweden. In addition, the
biological activity e.g. neutralization capacity of the sera were tested. Our results demonstrate that majority of
chancroid patients and healthy individuals had detectable levels of serum
antibodies to HdCDT complex and to separate toxin components. However, high levels (> or =100 units) of
antibodies to HdCDT complex were significantly more prevalent in the sera of patients with both
chancroid and
periodontitis than in the sera of the corresponding controls (P=0.001 and P=0.04, respectively). In the sera of the 50 patients with
chancroid,
antibodies to
CdtA, CdtB, and CdtC were detected in 50, 35, and 34 individuals, respectively.
Antibodies to CdtC, being less frequently detected than the
antibodies to other components, show a good correlation with the neutralizing capacity of sera. High levels of
neutralizing antibodies (> or =160) were detected in only 22 and 2% of the patients with
chancroid and
periodontitis, respectively. The data suggest that the low levels of anti-HdCDT
antibodies, which include
neutralizing antibodies, may contribute to limited protection in
chancroid and since anti-HdCDT
antibodies, may be detected in healthy individuals and in patients with certain disease conditions (e.g.
periodontitis), they may not be specific markers for
chancroid infection.