Attachment of Haemophilus ducreyi to human foreskin fibroblasts involves LOS and fibronectin

Haemophilus ducreyi is the causative agent of the genital ulcer disease Chancroid. Chancroid has been shown to increase the risk of heterosexual transmission of HIV. Little is known regarding the attachment or localization of this organism to human cells in either the dermal or epidermal layer. In this study the attachment of H. ducreyi to human foreskin fibroblast (HFF) cells was further characterized. Attachment was mediated by more than one mechanism. Proteinase K treatment but not trypsinization of H. ducreyi significantly reduced attachment suggesting protein involvement. In addition, purified lipooligosaccharide (LOS) was able to inhibit attachment in a dose dependent manner. It appeared that the organism binds to fibronectin in the extracellular matrix of HFF cells, since competition studies using fibronectin showed that it was able to significantly reduce attachment in a dose dependent manner whereas collagen did not. We hypothesize that the attachment of H. ducreyi involves both a protein mediator of attachment (likely pili) as well as LOS and that one or both of these bacterial components interacts with fibronectin in the extracellular matrix to mediate attachment to HFF cells.