The pathogenesis of hematogenous disseminated candidiasis appears to involve adhesion events between yeast cells of Candida albicans and specific host tissues. We hypothesize that host antibodies specific for candidal adhesins alter the pathogenesis and may aid host survival. In the PI's laboratory, candidal adhesins have been isolated that cause specific yeast cell adherence to mouse splenic marginal zone macrophages. These adhesins are part of the phosphomannoprotein (PMP) complex on the candidal cell surface. Vaccines made of solubilized adhesins encapsulated in liposomes provoke antibody responses in mice against the adhesins. Vaccinated animals have increased resistance against disseminated candidiasis, their serum neutralizes adhesin activity, prevents yeast cell attachment to the spleen, and appears to transfer protection. Monoclonal antibodies (mAbs) against the PMP-derived adhesins are available in the PI's laboratory. The effects of polyclonal and mAbs on adherence interactions with various tissues will be extensively evaluated by adherence assays.
The specific aims are to: 1. Determine the optimal immunization protocol for protective responses in normal mice. Variables include adhesin composition, dose, effect of adjuvants, routes of administration and booster schedule. 2. Determine the effect of the vaccination in prevention of disseminated candidiasis. Immunization effectiveness will be assessed in normal mice (BALB/c female and male mice and a BALB/c crossed outbread strain). 3. Use passive transfer experiments to determine if antibodies are responsible for immunity. Immune sera from vaccinated animals, mAbs specific for the adhesins of C. albicans, and mAbs against hydrophobic proteins will be tested for their ability to protect naive animals against disseminated candidiasis. Immunologically competent mice, T-cell deficient (nu/nu), T- and B- cell deficient (SCID), and mice with induced neutropenia (mAb RB6-8C5 treated) will be tested. 4. Initiate investigations on mechanisms of protection induced by the vaccine and mAbs. The ex vivo assay, the capillary tube shear-dependent adhesion assay, the endothelial adherence assay, and in vivo intravital microscopic method will be used to determine the effect of immune sera and protective mAbs on adherence characteristics of C. albicans to various host cells, tissues and glycoproteins. The effect of immune sera and mAbs on adherence characteristics of complement opsonized cells and unopsonized cells will be examined. The results may well lead to new preventive and therapeutic strategies for disseminated candidiasis.
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