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Infect. Immun., 07 1996, 2474-2482, Vol 64, No. 7
N Mantis, MC Prevost and P Sansonetti
Shigella flexneri-infected macrophage cells undergo an apoptotic-like death
as early as one hour after infection (A. Zychlinsky, M. C. Prevost, and P.
J. Sansonetti, Nature [London] 358:167-168, 1992). To determine the fate of
infected epithelial cells, we characterized the viability, morphology, and
several metabolic activities of HeLa cells after treatment with M90T, an
invoffve isolate of S. flexneri serotype 5, or BS176, a noninvasive isolate
cured of the 220-kb virulence plasmid. Using standard assays, we found that
for at least 4 h after infection with M90T, HeLa cells remained viable and
did not detach or lyse. The ultrastructural morphology of HeLa cells
heavily infected with M90T was free of hallmarks associated with cells
undergoing apoptosis. Consistent with the idea that intracellular bacterial
growth is metabolically stressful to the host cell, we observed that,
compared with BS176 treated-HeLa cells, M90T-treated HeLa cells showed (i)
a significant decrease in the total pool size of nucleoside triphosphates,
(ii) a reduced ability to incorporate extracellular radiolabeled methionine
into the soluble and insoluble cell fractions, and (iii) a stimulation of
glucose uptake. However, there was no detectable increase in expression of
the stress-inducible hsp70 gene in M90T-infected HeLa cells or activation
of the anaerobic metabolic pathway as determined by measuring total lactate
levels. These results demonstrate clearly that the fate of
S.flexneri-infected cells can vary dramatically between cell types and
agree with the hypothesis that the destruction of epithelial cells observed
in experimental models of shigellosis is due to the host inflammatory
response and probably not bacterial intracellular multiplication per se.
Copyright © 1996, American Society for Microbiology
Analysis of epithelial cell stress response during infection by Shigella flexneri
Unite de Pathogenie Microbienne Moleculaire, INSERM U389, Paris, France.
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