Adherence of Platelets toCandidaSpecies In Vivo

Abstract

The in vivo interactions of platelets with Candida species yeast cells were investigated in a murine model. Mice were injected intravenously via the lateral caudal vein, and blood drawn by periorbital puncture was collected in phosphate-buffered saline-formaldehyde to avoid in vitro platelet activation. The study of the clearance of blastoconidia of Candida albicans and Candida glabrata showed that these cells disappeared quickly from the bloodstream. Microscopic observation of blood samples, stained by Calcofluor white or May Grunwald Giemsa, demonstrated the rapid attachment of platelets to fungal elements of all the Candida spp. tested. The attachment of murine platelets to C. albicans cells, observed by scanning electron microscopy, revealed morphological changes. The platelets lost their discoid shape, generated pseudopodia, and flattened against the yeast cells. The reversibility of platelet binding to C. albicans by chelating agents suggests a cationdependent link. In contrast, the fixation of C. glabrata and Candida tropicalis was not modified by chelating agents. The mechanisms involved in the in vivo adherence of platelets to Candida cells may therefore differ according to the species of Candida.

Susceptibilities ofCryptococcus neoformansStrains to Platelet Binding In Vivo and to the Fungicidal Activity of Thrombin-Induced Platelet Microbicidal Proteins In Vitro

“…Most studies of interactions between platelets and pathogenic fungi have been carried out in vitro (33), and interactions between C. neoformans and platelets have been only partially studied (35). In a recent study, it was demonstrated that platelets adhere to several Candida species in vivo, using different mechanisms according to the species of Candida (30). In the present study, we describe for the first time an in vivo procedure for the study of adherence of mouse platelets to C. neoformans cells.…”

“…For a negative control, 20 l of blood from an uninfected mouse was mixed with the above buffer supplemented with 5 ϫ 10 5 yeast cells. The blood samples were examined by photonic fluorescence microscopy following yeast labeling with Calcofluor white as described previously (30). When blood from mice inoculated with yeast cells of C. neoformans 111C, 222A, NIH B-3501, CAP59, or CAP67 was observed in the presence of Calcofluor white with a UV microscope, it was very easy to locate yeast cells (Fig.…”

“…After 5 min the erythrocytes were lysed and yeast cells were labeled with fluorescent brightener (Calcofluor white; Sigma, St. Louis, Mo.) as previously described (30). The enumeration of yeast cells was realized by a direct hemacytometer count under fluorescence microscopy using a Nikon incident light fluorescence microscope with an excitation filter with peak transmission at 365 nm and a barrier filter that transmitted light at wavelengths of Ͼ420 nm.…”

Short fungal fractions of β-1,3 glucans affect platelet activation

“…Platelets also interact with the yeast form and hyphae of C. albicans (50). In a mouse model of invasive candidiasis, platelets adhered to C. albicans, lost their discoid shape, and generated pseudopodia against yeast cells (37).…”

Effect of pathogenic yeasts on human platelet aggregation

“…The aggregation of platelets releases microbicidal or microbistatic substances that are active against Candida spp. [24,25]. Therefore, the ability of C. albicans to inhibit the aggregation of platelets could contribute to its survival in the blood during vascular infections.…”