Jr. Forney et al., A role for host phosphoinositide 3-kinase and cytoskeletal remodeling during Cryptosporidium parvum infection, INFEC IMMUN, 67(2), 1999, pp. 844-852
Cryptosporidium parvum preferentially infects epithelial cells lining the i
ntestinal mucosa of mammalian hosts. Parasite development and propagation o
ccurs within a unique intracellular but extracytoplasmic parasitophorous va
cuole at the apical surface of infected cells. Parasite-induced host cell s
ignaling events and subsequent cytoskeletal remodeling were investigated by
using cultured bovine fallopian tube epithelial (BFTE) cells inoculated wi
th C. parvum sporozoites. Indirect-immunofluorescence microscopy detected h
ost tyrosine phosphorylation within 30 s of inoculation. At >30 min postino
culation, actin aggregates were detected at the site of parasite attachment
by fluorescein isothiocyanate-conjugated phalloidin staining as well as by
indirect immunolabeling with monoclonal anti-actin. The actin-binding prot
ein villin was also detected in focal aggregates at the site of attachment.
Host cytoskeletal rearrangement persisted for the duration of the parasito
phorous vacuole and contributed to the formation of long, branched microvil
li clustered around the cryptosporidial vacuole. The phosphoinositide 3-kin
ase inhibitor wortmannin significantly inhibited (P < 0.05) C parvum infect
ion when BFTE cells were pretreated for 60 min at 37 degrees C prior to ino
culation. Similarly, treatment of BFTE cells with the protein kinase inhibi
tors genistein and staurosporine and the cytoskeletally acting compounds 1-
(5-iodonaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazapine, cytochalasin D,
and 2,3-butanedione monoxime significantly inhibited (P < 0.05) in vitro in
fection at 24 h postinoculation. These findings demonstrate a prominent rol
e for phosphoinositide 3-kinase activity during the early C. parvum infecti
on process and suggest that manipulation of host signaling pathways results
in actin rearrangement at the site of sporozoite attachment.