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Infect. Immun., 09 1997, 3547-3555, Vol 65, No. 9
A Abe, B Kenny, M Stein and BB Finlay
Enteropathogenic Escherichia coli (EPEC) and rabbit EPEC (RDEC-1) cause
unique histopathological features on intestinal mucosa, including
attaching/effacing (A/E) lesions. Due to the human specificity of EPEC,
RDEC-1 has been used as an animal model to study EPEC pathogenesis. At
least two of the previously identified EPEC-secreted proteins, EspA and
EspB, are required for triggering host epithelial signal transduction
pathways, intimate adherence, and A/E lesions. However, the functions of
these secreted proteins and their roles in pathogenesis have not been
characterized. To investigate the function of EspA and EspB in RDEC-1, the
espA and espB genes were cloned and their sequences were compared to that
of EPEC O127. The EspA proteins showed high similarity (88.5% identity),
while EspB was heterogeneous in internal regions (69.8% identity). However,
RDEC-1 EspB was identical to that of enterohemorrhagic E. coli serotype
O26. Mutations in RDEC-1 espA and espB revealed that the corresponding
RDEC-1 gene products are essential for triggering of host signal
transduction pathways and invasion into HeLa cells. Complementation with
plasmids containing EPEC espA or/and espB genes into RDEC-1 mutant strains
demonstrated that they were functionally interchangeable, although the EPEC
proteins mediated higher levels of invasion. Furthermore, maximal
expression of RDEC-1 and EPEC-secreted proteins occurred at their
respective host body temperatures, which may contribute to the lack of EPEC
infectivity in rabbits.
Copyright © 1997, American Society for Microbiology
Characterization of two virulence proteins secreted by rabbit enteropathogenic Escherichia coli, EspA and EspB, whose maximal expression is sensitive to host body temperature
Biotechnology Laboratory, University of British Columbia, Vancouver, Canada.
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