Me. Konkel et al., Bacterial secreted proteins are required for the internalization of Campylobacter jejuni into cultured mammalian cells, MOL MICROB, 32(4), 1999, pp. 691-701
Presented here is the first evidence that Campylobacter jejuni secrete prot
eins upon co-cultivation with host cells and in INT 407 cell-conditioned me
dium. A C. jejuni gene designated ciaB for Campylobacter Invasion antigen B
was identified, using a differential screening technique, which is require
d for this secretion process and the efficient entry of this bacterium into
a host cell. The C. jejuni ciaB gene encodes a protein of 610 amino acids
with a calculated molecular mass of 73 154 Da. The deduced amino acid seque
nce of the CiaB protein shares similarity with type III secreted proteins a
ssociated with the invasion of host cells from other more extensively chara
cterized bacterial pathogens. In vitro binding and internalization assays r
evealed that the binding of C. jejuni ciaB null mutants was indistinguishab
le from that of the parental isolate, whereas a significant reduction was n
oted in internalization. Confocal microscopic examination of C. jejuni-infe
cted cells revealed that CiaB was translocated into the cytoplasm of the ho
st cells. Culturing C. jejuni with INT 407 cells or in INT 407-conditioned
medium resulted in the secretion of at least eight proteins, ranging in siz
e from 12.8 to 108 kDa, into the culture medium. C. jejuni ciaB null mutant
s were deficient in the secretion of all eight proteins, indicating that Ci
aB is required for the secretion process. The identification of the C. jeju
ni ciaB gene represents a significant advance in understanding the molecula
r mechanism of C, jejuni internalization and the pathogenesis of C. jejuni-
mediated enteritis.