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Infect. Immun., 11 1997, 4539-4547, Vol 65, No. 11
JE Raulston
Iron is a well-established mediator of virulence in several bacterial
pathogens, yet little is known about the role of iron in infectious disease
processes caused by obligate intracellular bacterial pathogens. In this
study, the effect of iron limitation was examined for the sexually
transmitted infectious agent Chlamydia trachomatis in an in vitro model of
human genital infection using the intracellular iron- chelating reagent
deferoxamine mesylate (Desferal). Iron restriction caused a significant
reduction in infectivity of C. trachomatis elementary bodies (EB) harvested
from Desferal-exposed polarized epithelial cells when compared to that of
EB harvested from iron- sufficient control cell cultures. Replacement of
the Desferal exposure medium with medium containing iron-saturated
transferrin restored chlamydial infectivity, whereas replacement with
growth medium alone had no effect. The following three prominent
morphological features were observed by electron microscopic examination of
chlamydia-infected cells exposed to Desferal: (i) inclusions containing
chlamydiae greatly delayed in maturation, (ii) substantial blebbing within
chlamydial inclusions, and (iii) electron-dense material surrounding
inclusions. Protein analyses of highly purified EB by two-dimensional
polyacrylamide gel electrophoresis revealed that there were at least 19
candidate iron-repressible proteins in C. trachomatis and at least one
protein which was iron inducible. One putative iron-repressible protein was
confirmed by Western blot (immunoblot) analysis to be the chlamydial heat
shock protein 60 (hsp60). The enhanced production of this antigen by
chlamydiae as a result of iron limitation is of particular importance since
there is a well-documented association between chlamydial hsp60 and
destructive immunopathological sequelae in infected patients.
Copyright © 1997, American Society for Microbiology
Response of Chlamydia trachomatis serovar E to iron restriction in vitro and evidence for iron-regulated chlamydial proteins
Department of Microbiology and Immunology, University of North Carolina School of Medicine, Chapel Hill 27599-7290, USA. raulston@med.unc.edu
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