Isolation and characterization of cell surface mutants of Candida albicans

Abstract

Mutant strains of Candida albicans were obtained by selecting for cells that escaped agglutination by a polyclonal antiserum raised against standard C. albicans serotype A isolate B311. Mutants were obtained from strains B311 and B792 and from four strains isolated from patients with acquired immunodeficiency syndrome. All 15 tested mutants retained characteristic sugar assimilation patterns. All but one of the mutants retained the ability to form germ tubes and chlamydospores. Two mutants from an acquired immunodeficiency syndrome-derived isolate were deficient in binding complement ligands iC3b and C3d, whereas another mutant was deficient in binding ligand iC3b but not C3d. The hyphae of these three mutants lacked antigens when examined by Western immunoblotting with monoclonal antibody Ca-A, which detects several glycoproteins, including C3d-binding proteins. One of the complement-binding-deficient mutants was tested for its ability to colonize the gastrointestinal tract of rabbits but did not differ from the wild-type parent in site or degree of colonization. The proton magnetic resonance spectra of bulk mannan carbohydrate extracted from tested mutants showed the loss of a signal characteristic of the mannosyl a-PO4 linkage; each mutant also had a distinct pattern of other changes.

Isolation of avirulent clones of Candida albicans with reduced ability to recognize the CR2 ligand C3d

“…Quantitative changes in the 60and 50-kDa proteins were also seen, as described above for other antibodies. The reduced activity with the 60-kDa protein is similar to that reported with other cell surface mutants (39).…”

“…Several approaches have been used to isolate cell surface mutants of C. albicans (4,39). Calderone et al (4) isolated cerulenin-resistant, spontaneous mutants of C. albicans, one of which (m-10) was impaired in its ability to adhere to a variety of host cells in vitro, was avirulent in endocarditis and vaginitis models (4,24), and had significantly reduced levels of iC3b binding (31).…”

“…On the basis of this rather limited analysis of strains with impaired iC3b binding, one might suggest that this protein is essential for virulence. More recently, Whelan et al (39) isolated several cell surface mutants of C. albicans by nonagglutination with a hyperimmune rabbit antiserum against wild-type cells. Each of four mutants tested caused reduced levels of rosetting of either EAiC3b or EAC3d (39).…”

“…More recently, Whelan et al (39) isolated several cell surface mutants of C. albicans by nonagglutination with a hyperimmune rabbit antiserum against wild-type cells. Each of four mutants tested caused reduced levels of rosetting of either EAiC3b or EAC3d (39). Correlations with CR activity and virulence were not possible because virulence studies were not completed, although one of the mutants was as virulent as the parent in a rabbit model of systemic disease (39).…”

“…Each of four mutants tested caused reduced levels of rosetting of either EAiC3b or EAC3d (39). Correlations with CR activity and virulence were not possible because virulence studies were not completed, although one of the mutants was as virulent as the parent in a rabbit model of systemic disease (39).…”