Candida albicans C3d receptor, isolated by using a monoclonal antibody

Abstract

Pseudohyphae of Candida albicans possess a receptor for C3d, a fragment of the complement component C3. This receptor was partially purified by using a monoclonal antibody (CA-A) that previously had been shown to inhibit the binding of C3d to C. albicans pseudohyphae. Purffied immunoglobulin G from ascites fluid (CA-A) was coupled to a cyanogen bromide-activated Sepharose column, and an affinity-purified fraction (A2) from C. albicans pseudohyphae was obtained. This fraction inhibited rosetting of the EAC3d receptor by pseudohyphae and appeared to contain glycoprotein, since receptor activity could be removed when A2 was incubated with lectins specific for mannose and glucose. A2 was analyzed by sodium dodecyl sulfatepolyacrylamide gel electrophoresis, and two polypeptides of approximately 60 and 70 kilodaltons (kDa) were consistently identified in reducing gels. The 60-kDa protein was identified as a glycoprotein by concanavalin A binding. A2 was further analyzed by high-pressure liquid chromatography (HPLC). Of three fractions obtained by HPLC, one containing the 60-kDa protein was found to have receptor activity. When analyzed by HPLC, this protein was found to contain mannose and glucose in approximately equal amounts. Both immunofluorescence and electron microscopy of pseudohyphae treated with CA-A identified A2 as a surface moiety. Thus, the C3d receptor of C. albicans, isolated with CA-A, is a glycoprotein of approximately 60 kDa.

Cell extracts of Candida albicans block adherence of the organisms to endothelial cells

“…Extraction was carried out in the presence of 1 mM phenylmethylsulfonyl fluoride (Sigma Chemical Co., St. Louis, Mo.) to inhibit proteolysis (20). Each lyophilized extract was subjected to ConA-Sepharose R-4B (Pharmacia, Uppsala, Sweden) affinity chromatography as described below.…”

“…SDS-PAGE and Western blotting (immunoblotting). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting were performed by standard procedures (20,22). Electrophoresis was carried out in a minigel system (Bio-Rad Laboratories, Richmond, Calif.).…”

“…The primary antibody was diluted 1:400 for immunoblotting of extracts. Binding of the primary antibody to C. albicans antigens was detected with alkaline phosphatase-labeled protein A as described previously (20,22).…”

The influence of subinhibitory concentrations of conventional and experimental antifungal drugs on the expression of the iC3b binding protein in Candida albicans strains during filamentation

“…This ¢nding was con¢rmed by Lopez-Ribot et al who isolated a C. albicans gene encoding part of the 58-kDa ¢brinogen binding mannoprotein [10]. Other mannoproteins include the analogues of human L2 integrins, which are able to recognize the complement C3 conversion products iC3b and C3d [11,12]. L2 integrin analogues/iC3b binding proteins of C albicans have been studied in detail.…”

Host‐Parasite Relationships in Candidosis

“…The protein from C. albicans is only found on hyphal/pseudohyphal forms of the organism and is apparently absent from the yeast-phase cells. A summary of the characteristics of the CR,-like protein from C. albicans is shown in Table 5 (from Linehan et al 1988).…”