Mechanisms of skin adherence, penetration and tissue necrosis production by Haemophilus ducreyi, the causative agent of chancroid.
Haemophilus ducreyi (H. ducreyi) strains, representing both reference strains and low-passage isolates, were investigated in terms of surface structures and enzymatic equipment. The interaction of these factors with host tissue was analysed using new in vitro- and in vivo-models. By electron microscopy studies there was no evidence of an extracellular capsule or surface appendages such as pili or flagella. Interaction of all isolates tested with the lectin Phaseolus vulgaris suggests N-acetyl-D-glucosamine units as common structural features of H. ducreyi cell envelope polysaccharide. In attachment to epithelial cells more than one hemagglutinin might be implicated as different haemagglutination patterns could be observed whereby the activity was not heat-labile, but was abolished by formaldehyde. Hydrophobic interactions might be of importance as well as strains showed a wide range of reactions from hydrophobic to hydrophilic, low hydrophobicity being more marked with the older strains. No elaboration of degradative enzymes based on the measurement of enzymatic activity using insoluble dye-protein complexes could be detected in case of H. ducreyi, using Azocoll and Remazol Brilliantblue hide powder for detection of proteolytic activity and elastinorcein for detection of elastase activity. In vitro studies using human keratinocytes and Vero cells did not show any morphological changes when incubated with H. ducreyi culture filtrates. In vivo studies with a new mouse model for H. ducreyi infection could confirm the results of the in vitro studies. Mere contact to undamaged skin both of whole cell organisms, live or heat-killed, and of culture filtrates did not lead to any reaction or even damage of mouse skin. However, when the outer epidermal layer was overcome by intradermal injection of shaved mice ulcers developed. Tissue necrosis production was not bound to live organisms as dead ones showed the same effect. There is great evidence that this tissue necrosis is associated with H. ducreyi lipopolysaccharide (LPS) because intradermal injection of purified H. ducreyi LPS lead to the same reaction pattern. For the first time a cell mediated immune response could be demonstrated in case of H. ducreyi infection as different antigen preparations of H. ducreyi isolates induced proliferation of lymphocytes isolated from healthy unexposed individuals and from a chancroid-sensitized male. In the latter case measured cell responses were much stronger. The dose-dependent phenomenon was associated with interleukin-2 production. In summary, H. ducreyi isolates do not exhibit cytotoxic effects on the epithelial cells of the skin.(ABSTRACT TRUNCATED AT 400 WORDS)
Abeck
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Department of Dermatology, Ludwig-Maximilians-Universität, Munich.
Korting
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D000818:Animals; D002455:Cell Division; D002602:Chancroid / Q000382:microbiology* / Q000473:pathology / Q000503:physiopathology; D004195:Disease Models, Animal; D006191:Haemophilus ducreyi / Q000502:physiology*; D006801:Humans; D007111:Immunity, Cellular / Q000276:immunology; D037102:Lectins / Q000502:physiology; D008297:Male; D051379:Mice; D008854:Microscopy, Electron; D009336:Necrosis; D012867:Skin / Q000382:microbiology* / Q000473:pathology / Q000503:physiopathology
D037102:Lectins