Activity of anti-CR3-RP polyclonal antibody against biofilms formed by Candida auris, a multidrug-resistant emerging fungal pathogen

Fungal biofilm has remained a serious medical problem that complicates treatment of mycoses. In particular, once biofilms are formed, they display high levels of resistance against most common antifungals. Candida auris is currently considered as a serious emerging fungal pathogen frequently exhibiting high levels of resistance to antifungals. Recent studies have confirmed that C. auris shares similarity with Candida albicans in regards to virulence-associated proteins involved in adherence and biofilm development. Complement receptor 3-related protein (CR3-RP) is one of the key surface antigens expressed by Candida species during biofilm formation. Here, we have investigated the presence of this cell surface moiety on the surface of C. auris, as well as the potential of anti-CR3-RP polyclonal antibody (Ab) to inhibit biofilm formation by this emerging fungal pathogen. Using indirect immunofluorescence and ELISA, we were able to confirm the presence of CR3-RP in C. auris cells within biofilms. Further, not only anti-CR3-RP Ab was able to inhibit biofilm formation by multiple C. auris strains when added during the adherence phase, but it also demonstrated activity against C. auris 24-h pre-formed biofilms, which compared favorably to levels of inhibition achieved by treatment with current conventional antifungals fluconazole, amphotericin B, and caspofungin. Overall, our data demonstrate the presence of this antigen on the surface of C. auris and points to the potential of anti-CR3-RP Ab in eradication of biofilms formed by this novel fungal pathogen.

Comparative analysis of the binding of antibodies prepared against the insect Spodoptera exigua and against the mycopathogen Nomuraea rileyi

Polyclonal antibodies were produced in mice against Spodoptera exigua (beet armyworm) larval hemolymph and hemocytes and against cell wall surfaces of hyphal bodies and hyphae of the entomopathogenic hyphomycete Nomuraea rileyi. In addition to exhibiting strong activity against their original antigenic substrates, all of the antibodies cross-react extensively with other substrates. The hemolymph antibody binds to hemocytes and vice versa, and both antibodies cross-react to the insect fat body basement membrane (extracellular matrix (ECM) and to N. rileyi and Beauveria bassiana (another entomopathogenic fungus) cell wall surfaces (ECM). Likewise, the anti-fungal antibodies cross-react with S. exigua hemolymph and hemocytes, especially the granules that may contain ECM components, and with fat body basement membrane. These cross-reactivities are specific as indicated by negative controls in the microscopy and Western blotting assays. Parallel labeling experiments using Con A suggest that the reactive epitopes contain mannose; however, none of the antibodies bind to mannose residues of nonentomopathogenic Candida albicans or Saccharomyces cerevisiae yeast cells. Thus, these cross-reactivities suggest that the host mimicry expressed by surface components of entomopathogenic fungi represents an important pathogenic determinant.

A monoclonal antibody to Candida albicans enhances mouse neutrophil candidacidal activity

A monoclonal antibody (MAb) to Candida albicans (MAb B6.1) that protects against candidiasis and the nonprotective MAb B6 were compared for ability to support neutrophil (polymorphonuclear leukocyte [PMN]) candidacidal activity. Both MAbs are immunoglobulin M, and each recognizes distinct C. albicans mannan cell wall determinants. PMN candidacidal activity was assessed by transmission electron microscopy and by an in vitro killing assay. The results indicated that MAb B6.1, but not MAb B6, enhances ingestion and killing of yeast cells by PMN in the presence of serum complement.