Candida Albicans Cell Wall Research Articles

Immunoregulation in experimental murine candidiasis: specific suppression induced by Candida albicans cell wall glycoprotein.

Immune regulation in candidiasis is inferred from studies of both human and animal infection, with a suppressive role suggested for cell wall polysaccharide. To study the immunosuppressive potential of Candida albicans in a murine model, whole blastoconidia or purified cell wall components of C. albicans were tested for their effects on the development of acquired immune responses by superimposing a pretreatment regimen upon an established immunization protocol. CBA/J or BALB/cByJ mice were pretreated twice intravenously with 100 micrograms of mannan (MAN), 100 or 200 micrograms of glycoprotein (GP), or 5 X 10(7) heat-killed C. albicans blastoconidia, followed 1 week later by an immunization protocol of two cutaneous inoculations of viable C. albicans blastoconidia given 2 weeks apart. Delayed hypersensitivity (DTH) to GP or to a membrane-derived antigen, B-HEX, was tested 7 days after the second inoculation, and lymphocyte stimulation was tested with mitogens and Candida antigens after 12 days. To assess protection, mice were challenged intravenously with viable C. albicans blastoconidia 14 days after the second cutaneous inoculation and sacrificed 28 days later for quantitative culture of kidneys and brains. Sera were obtained for enzyme-linked immunosorbent assays at selected intervals. Pretreatment with GP resulted in specific in vivo suppression of DTH to GP but not to B-HEX antigen and specific in vitro suppression of lymphocyte stimulation to GP but not to other Candida antigens or mitogens. MAN and heat-killed C. albicans blastoconidia had no such effects. GP pretreatment also diminished the protective effect of immunization against challenge, demonstrable in the brain, while not altering significantly the production of antibody in response to infection. Contrary to clinical evidence, MAN was not immunosuppressive in this model, and in fact, the immunosuppressive potential of GP, which is composed largely of MAN, was found to be dependent upon the presence of its heat-labile protein moiety.

Isolation and characterization of cell wall and cytoplasmic antigens and peripheral blood leukocyte responses in rabbits immunized with Candida albicans.

The aim of this study is to carry out enzymatic digestion of cell wall polysaccharides using β-(1–3)-glucanase to prepare antigen extracts of cell wall and cytoplasma of Candida albicans. These antigens were used to measure in vitro lymphocyte transformation and in vivo skin test responses in rabbits following inoculation with living C. albicans. The results of this study show that both cell-wall and cytoplasmic antigens of C. albicans in both the yeast and mycelial phases induce high levels of transformation in the infected host. The in vivo skin test, which gave indurated reactions typical of delayed type hypersensitivity, confirmed the in vitro findings. In addition, the in vitro cellular responses were not influenced in any major way by the presence of immune serum. Whole blood and purified leukocyte microculture techniques were established to test cellular reactivity in vitro. Although no report was found in the literature previously on the use of the whole blood leukocyte (WBL) assay system for the measurement of cellular mediated immune (CMI) responses to Candida antigens, the correlation between the WBL and peripheral blood leukocyte assay system indicates that its use is a valid way to measure CMI in vitro. The nature of the cells involved in the in vitro response of immunized rabbits was further characterized. Leukocyte cultures depleted of T-cells, B-cells or monocytes showed that T-cells and monocytes were essential for the production of the transformation response in vitro.

Chemical and antigenic alterations of Candida albicans cell walls related to the action of amphotericin B sub-inhibitory doses.

Sub-inhibitory doses of amphotericin B led to Candida albicans cell wall modifications which involved peptidomannans. The amount of this product was reduced by a third, the decrease being due to mannans whose absolute and relative values fell whereas the amount of amino-acids increased. Concomitantly, the treated cells exhibited a loss in their immunological reactivity.

Effects of aculeacin A and papulacandin B onCandida albicans

Aculeacin A1and papulacandin B2are closely related antimycotic agents that interfere with the synthesis of alkalai-insoluble β 1-3 glucan in the cell wall ofCandida albicans, Saccharomyces cerevisiaeandGeotrichum lactis. The chemical structures of both agents contain a long-chain fatty acid, and both agents are strongly inhibitory toC. albicansand some other fungi while having negligible activity against bacteria or protozoa. Earlier studies involving light microscopy of aculeacin A treated cells revealed rounded, distorted cells aggregated in clumps. The sole TEM micrograph of aculeacin A treated cells showed invaginations and globular bodies associated with plasma membranes.

Depression of the lymphocyte transformation response to microbial antigens and to phytohemagglutinin during pregnancy.

Lymphocyte transformation (LT) responses to Chlamydia trachomatis, to four other microbial antigens, and to phytohemagglutinin (PHA) were studied in 201 women during pregnancy and/or 3-18 wk postpartum. The LT responses to all stimulants tested were significantly depressed during pregnancy when compared with postpartum LT responses. This difference occurred whether LT assays were performed in autologous or pooled heterologous plasma collected from nonpregnant donors. Among women studied in the third trimester and again postpartum, the autologous LT stimulation index (LTSI) rose from 1.7 to 3.4 (P less than 0.001) with C. trachomatis elementary body antigen, from 3.7 to 7.9 (P less than 0.001) with Candida albicans cell wall extract, from 4.5 to 7.8 (P = 0.008) with streptokinase-streptodornase, from 1.7 to 3.0 (P = 0.007) with fluid tetanus toxoid, from 1.7 to 2.8 (P = 0.046) with mumps virus skin test antigen, from 35.5 to 87.0 (P less than 0.001) with PHA (2 micrograms/ml), and from 107.2 to 181.9 (P = 0.007) with PHA (10 micrograms/ml). LT responses to C. trachomatis were compared in 52 pregnant women and 58 nonpregnant women; all the women had C. trachomatis isolated at the time of LT assay. Using either plasma supplement, the mean LTSI with C. trachomatis antigen was significantly higher in nonpregnant women than in pregnant women, regardless of trimester (P less than 0.001). Among 12 women who were serially tested and remained culture positive for C. trachomatis throughout pregnancy and the postpartum period, the mean autologous LTSI rose from 1.9 in the third trimester to 7.8 postpartum (P = 0.0004). These data are the first to show that the immune response to an ongoing bacterial infection is depressed during pregnancy and to definitively document the depressed LT responses during human pregnancy.

Cytochemical and ultrastructural studies of Candida albicans: II. Evidence for a cell wall coat using concanavalin A

Cytochemical localization of carbohydrates in the surface layers the cell wall of Candida albicans was investigated using an indirect concanavalin A—peroxidase or ferritin technique on cryostat sections of cellular pellets. Continuous labeling of the cell wall surface was observed and the plasma membrane was also stained. In particular, the results obtained with the concanavalin A—peroxidase method clearly showed the presence of a surface coat surrounding the cells. It is thought that this coat may represent an external capsular or slime layer. This surface layer could not be visualized by cytochemical techniques performed on ultrathin sections which detected only inner carbohydrate components in the cell wall. A comparison of the results obtained by these different techniques as well as by enzyme extraction suggested that the cell wall coat contained a large amount of glycoproteins. The validity of the cytochemical procedure and hypothesis concerning the role and the nature of the cell wall coat are discussed.

Chemical and enzymatic changes in the cell walls of Candida albicans and Saccharomyces cerevisiae by scanning electron microscopy.

Candida albicans and Saccharomyces cerevisiae cells were examined by scanning scanning electron microscopy before and after extraction of the mannans of the cell wall. The surfaces of control cells were smooth; after mannan extraction they were rough and showed erosions which were particularly striking within the area of the scars. Helicase digested irregular holes through the cell wall within 20 min; these increased in size during an additional 40 min of digestion. These holes were not localized in or on the bud scars, which remained intact even after the long digestion period. The results were used to construct a model for yeast cell wall structure.

The porosity of the cell wall of Candida albicans.

Polyethylene glycols of different molecular sizes have been used to study the penetrability of the cell wall of Candida albicans harvested at the end of the growth phase and after prolonged incubation in the stationary phase. No differences were found which could account for the greater resistance of cells from stationary phase cultures of C. albicans to the antimycotic agents amphotericin B methyl ester and miconazole.

Ultrastructural Changes in the Cell Wall of Candida albicans Following Cessation of Growth and their Possible Relationship to the Development of Polyene Resistance

The ultrastructure of the wall of Candida albicans strain 6406 was examined in polyeneresistant organisms obtained by continued incubation after the cessation of growth. The walls of organisms harvested either during the exponential phase of growth or after 24 h starvation, when examined in situ, showed the typical layered appearance. After 72 h starvation, when the resistance to amphotericin B methyl ester (AME) was 60 times greater than that of exponentially growing organisms, both the periplasmic material and the distinct electron-dense layers were absent from the wall. At this stage there was no increase in the thickness of the wall. After 144 h starvation the thickness of the wall had increased from 143 +/-22 nm (exponential phase organisms) to 211+/-58 nm. If after 144 h starvation the organisms were incubated for 1 h in fresh nutrient medium they regained their sensitivity to AME and the wall regained the periplasmic material and its characteristic multilayered appearance. During the first 24 h starvation there was a considerable fall in the soluble glucan fraction, but on continued incubation there was little change in the relative proportions of the major carbohydrate constituents of the cell. Thin sections of purified walls isolated from organisms harvested either during exponential growth or after 144 h starvation were identical in appearance and characterized by the absence of the electrondense layers observed in sections of intact cells and by a reduction in thickness to 100+/-20nm.

Hemodynamic effects of the glycoprotein isolated from cell wall of Candida albicans

Hemodynamic effects of the glycoprotein isolated from cell wall of Candida albicans

The effect of glycoprotein from Candida albicans on functions of rat platelets

The glycoprotein from the cell wall of Candida albicans released serotonin from isolated platelets and/or platelet-rich plasma. The release was dose-dependent and was higher in isolated platelets than in plasma. The glycoprotein significantly decreased the spontaneous sedimentation-aggregation rate of isolated platelets induced by ADP. No aggregation of stirred isolated platelets or platelet-rich plasma was induced and glycoprotein did not inhibit the short-time aggregation induced by ADP of either isolated platelets or platelet-rich plasma.

The use of ferritin-conjugated antibodies in the study of cell wall components of Candida albicans.

Studies on the antigenic sites of the cell wall of Candida albicans were performed with ferritin-conjugated antisera of rabbits immunized with heat-killed cells in the yeast phase. Whole cells, from yeast and mycelial forms, and preparations of walls from disrupted cells were labeled with ferritin-conjugated antibodies. Ferritin-labeled anti-yeast phase IgG antibodies reacted equally well with the yeast and mycelial forms. The label was uniformly distributed over both the internal and external surfaces of the cell wall. This study demonstrates the continuity of antigenic determinants in the cell wall of both forms of C. albicans.

Visulization of new ultrastructural components in the cell wall of Candida albicans with fixatives containing TAPO.

Visulization of new ultrastructural components in the cell wall of Candida albicans with fixatives containing TAPO.

The lipid content of cell walls obtained from juvenile, yeast-like and filamentous cells of Candida albicans.

Purified cell walls ofCandida albicans obtained from juvenile cells, mature yeast-like cells and filamentous cells were analyzed for their lipid components. Chloroform: methanol (2:1 v v) extraction of the acetone-treated dried cell walls indicated the total lipid content to be 2.1% of the dry weight of the juvenile cell walls, 1.8% of the mature yeast-like cell walls and 4.5% of the filamentous cell walls. Separation of the chloroform: methanol extractable fraction through a silicie acid column and quantitative determination of the fractions showed significant amounts of sterol esters, triglycerides, sterols, free fatty acids, and phospholipids in these extracts. Following acetone extraction sterols were shown to constitute a greater percentage of the cell wall of juvenile cells than mature cells. Thin-layer chromatography separated the acetone-extractable lipids into at least four components. Diethyl ether extracts of the cell walls indicated the presence of small amounts of glycerol phospholipids in the cell walls of juvenile and mature yeast cells. Boiling 95% ethanol also removed a small lipid fraction from the cell walls of both juvenile and mature yeast which could include sphingosine phosphatides or glycosides.

Some immunochemical observations on the cell walls of yeasts.

Cell wall preparations of 17 species of yeasts were examined for the presence of amino acids and sugars. There were no distinct patterns of amino acids in the yeasts investigated, although 2 patterns of sugar components were found. Cell wall agglutination tests with an antiserum prepared against cell walls of Candida albicans reacted against 14 cell wall preparations; the sugar components of all of these were glucose and mannose.