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Infect. Immun., Jul 1996, 2657-2665, Vol 64, No. 7
CA Geuijen, RJ Willems and FR Mooi
Bordetella pertussis fimbriae are composed of major and minor subunits, and
recently it was shown that the minor fimbrial subunit binds to Vla- 5, a
receptor located on monocytes (W. Hazenbos, C. Geuijen, B. van den Berg, F.
Mooi, and R. van Furth, J. Infect. Dis. 171:924-929, 1995). Here we present
evidence that the major subunits bind to sulfated sugars, which are
ubiquitous in the respiratory tract. Binding was observed to chondroitin
sulfate, heparan sulfate, and dextran sulfate but not to dextran. Removal
of the minor subunit from fimbriae did not significantly affect binding to
sulfated sugars, indicating that the major subunit alone is sufficient for
this binding. Fimbriae were also able to bind HEp-2 cells, which are known
to display glycoconjugates on their surface. This binding was not dependent
on the presence of the minor subunit. However, binding was dependent on the
sulfation state of the glycoconjugates, since inhibition of the sulfation
resulted in a significant reduction of fimbria binding. The specificity of
fimbria binding was further characterized by using heparan sulfate-derived
disaccharides in inhibition assays. Two disaccharides were highly effective
inhibitors, and it was observed that both the degree of sulfation and the
arrangement of the sulfate groups on the disaccharides were important for
binding to fimbriae. B. pertussis bacteria also bound to sulfated sugars
and HEp-2 cells, and analysis of B. pertussis mutants indicated that both
filamentous hemagglutinin and fimbriae were required for this binding. A
host protein present in the extracellular matrix, fibronectin, has binding
activities similar to those of B. pertussis fimbriae, binding to both Vla-5
and sulfated sugars. Two regions in the major fimbrial subunit were
identified which showed similarity with fibronectin peptides which bind to
sulfated sugars. Thus, B. pertussis fimbriae exemplify molecular mimicry
and may co-opt host processes by mimicking natural ligand-receptor
interactions.
Copyright © 1996, American Society for Microbiology
The major fimbrial subunit of Bordetella pertussis binds to sulfated sugars
Molecular Microbiology Unit, National Institute of Health and Environmental Protection, The Netherlands.
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