Role of extracellular phospholipase B of Candida albicans as a virulent factor in experimental keratomycosis.
OBJECTIVE
To determine the virulence of extracellular phospholipase B (PLB) of Candida albicans in keratomycosis.


METHODS
A model of keratomycosis was established in 48 New Zealand albino rabbits covered with contact lenses. Effects of PLB-deficient mutant strain of C. albicans and its isogenic parental strain on the keratomycosis were compared. In vitro, these two strains were incubated with corneal stromal cells respectively (37 degrees C, 5% CO(2)). The influence of the strains on monolayer keratocytes was detected by scanning electron microscopy, enzyme-linked immunosorbent assay, and flow cytometry with Annexin-V/propidium iodide.


RESULTS
Fungal hyphae grew perpendicularly to the corneal stromal lamellae. The difference of the two strains in hyphal invasion was significant at two days after inoculation (p = 0.002) but not significant at the other timepoints. Severity of inflammation in rabbits with the parental strain was the same as that with the PLB null strain (p > 0.05). The morphogenesis and number of adherent germ tubes of the two strains were similar (p > 0.05), but the number of germ tubes penetrating cell monolayer was significantly different (p = 0.009). More prostaglandin E(2) was detected in the culture supernatants of the parental strain group than the null strain group. The percentages of cells with damaged cellular membrane were 3.02%, 2.04%, and 0.12% in the parental group, the PLB null group, and the control group, respectively. Apoptosis cells accounted for 33.17%, 27.56%, and 1.46%, and living cells accounted for 63.81%, 70.40%, and 98.41% in the three groups, respectively.


CONCLUSIONS
PLB can play a role as a virulent factor in triggering fungal invasion in corneas immediately after fungal adherence by decomposing membrane phospholipids and leading to cell lysis. However, its virulent effect does not appear to be as critical as in the hematogenous model of disseminated candidiasis.
The State Key Lab Cultivation Base, Shandong Provincial Key Lab of Ophthalmology, Shandong Eye Institute, Qingdao, China.
Lin
L
Ma
Lixin
L
Xie
Xiaoguang
X
Dong
Weiyun
W
Shi
D000818:Animals; D002176:Candida albicans / Q000201:enzymology* / Q000472:pathogenicity*; D002177:Candidiasis / Q000382:microbiology* / Q000473:pathology; D002478:Cells, Cultured; D003316:Corneal Diseases / Q000382:microbiology* / Q000473:pathology; D003319:Corneal Stroma / Q000382:microbiology / Q000648:ultrastructure; D004271:DNA, Fungal / Q000032:analysis; D015232:Dinoprostone / Q000378:metabolism; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D015821:Eye Infections, Fungal / Q000382:microbiology* / Q000473:pathology; D005434:Flow Cytometry; D025301:Hyphae / Q000502:physiology / Q000648:ultrastructure; D008245:Lysophospholipase / Q000502:physiology*; D008855:Microscopy, Electron, Scanning; D016133:Polymerase Chain Reaction; D011817:Rabbits; D014774:Virulence
D004271:DNA, Fungal; D008245:Lysophospholipase; D015232:Dinoprostone