New features of invasive candidiasis in humans: amyloid formation by fungi and deposition of serum amyloid P component by the host.
BACKGROUND
Invasive candidiasis occurs in the gastrointestinal tract, especially in neutropenic patients. We were interested in determining whether invasive fungi formed amyloid in humans as they are known to do in vitro. We also sought to characterize the consequence(s) of such amyloid formation.


METHODS
Tissue from 25 autopsy patients with invasive candidiasis of the gastrointestinal tract was stained with amyloidophilic dyes and for the presence of serum amyloid P component (SAP). Confirmation of the interaction of SAP and Candida was demonstrated using Candida albicans and mutants for amyloid formation.


RESULTS
Amyloid was present on the cellular surface of fungi invading gut tissue. Moreover, SAP bound to the fungal cell walls, confirming the presence of amyloid. In vitro observations showed SAP bound avidly to fungi when amyloid formed in fungal cell walls. An unexpected result was the lack of host neutrophils in response to the invading fungi, not only in neutropenic patients but also in patients with normal or increased white blood counts.


CONCLUSIONS
We report the first demonstration of functional fungal amyloid in human tissue and the binding of SAP to invading fungi. It is postulated that fungal amyloid, SAP, or a complex of the proteins may inhibit the neutrophil response.
Department of Pathology, University of Arizona, Tucson, AZ, USA.
Kevin B
KB
Gilchrist
Melissa C
MC
Garcia
Richard
R
Sobonya
Peter N
PN
Lipke
Stephen A
SA
Klotz
D002176:Candida albicans / Q000737:chemistry* / Q000378:metabolism; D058365:Candidiasis, Invasive / Q000382:microbiology / Q000473:pathology*; D005767:Gastrointestinal Diseases / Q000382:microbiology / Q000473:pathology*; D006651:Histocytochemistry; D006801:Humans; D008853:Microscopy; D058225:Plaque, Amyloid / Q000473:pathology*; D000683:Serum Amyloid P-Component / Q000032:analysis*; D013194:Staining and Labeling
D000683:Serum Amyloid P-Component