Probable presence of beta(1-2)-linked oligomannosides that act as human immunoglobulin G3 epitopes and are distributed over a Candida albicans 14- to 18-kilodalton antigen

Kinetic analysis of candidosis patients' immunoglobulin G3 response has shown that reactivity towards beta(1-2)-linked mannan-derived oligomannosides was associated with the recognition through metaperiodate-sensitive epitopes of a 14- to 18-kDa Candida albicans antigen unreactive with concanavalin A.

Qualitative and quantitative differences in recognition patterns of Candida albicans protein and polysaccharide antigens by human sera

Cytoplasmic and cell wall proteins and glycoproteins extracted from Candida albicans germ tubes were screened by Western blotting for their ability to differentiate between the serological responses of patients with candidosis and healthy individuals. Molecules of 114, 74 and 65 kDa were not recognized by any sera. Qualitative differences were observed for responses to proteins and glycoproteins from 29 to 60 kDa. Conversely, only quantitative differences were found to high molecular mass glycoproteins. Their recognition by control sera was invariably associated with reactivity against a 14-18 kDa antigen. However, despite a high level of antibodies against high molecular mass mannoproteins, some patients sera failed to react with the 14-18 kDa antigen, or lost this reactivity during the course of the disease.

Purification of Pneumocystis carinii trophozoites and identification of their circulating antigens

We have developed a new method to isolate Pneumocystis carinii trophozoites from experimental rat bronchoalveolar lavage specimens by using a Percoll discontinuous gradient and have identified the circulating antigens in experimental rat P. carinii pneumonia. The antigenic components of the trophozoites were compared with those of cysts by immunoblotting. A major immunoreactive band of 90,000 Da and some others of lower molecular mass were found in trophozoites. On the other hand, bands of 110,000, 50,000, and 45,000 Da were observed in cysts. The band of 50,000 Da was not identified when antitrophozoite rabbit serum preabsorbed with P. carinii-infected rat serum was used for immunoblotting. These results suggest that the molecule of 50,000 Da is the major circulating antigen in P. carinii-infected rats.

Characterization of cell wall proteins from yeast and mycelial cells of Candida albicans by labelling with biotin: comparison with other techniques

Candida albicans ATCC 26555 blastoconidia and blastoconidia bearing germ tubes were metabolically labelled by incubating the cells with 14C-labelled protein hydrolysate and were subsequently tagged with biotin. Double-labelled (radioactive and biotinylated) cell wall proteins and glycoproteins were extracted from intact cells of both growth forms by treatment with 2-mercaptoethanol (beta ME) and with beta-glucanases (Zymolyase) after treatment with beta ME. The beta ME- and Zymolyase-extracts were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and western blotted (immunoblotted) to nitrocellulose paper. Polyacrylamide gels were stained with Coomassie blue and processed for fluorography. Western blot analysis was performed either with peroxidase conjugated-concanavalin A (ConA) or Extravidin. Blotted proteins were also reacted with polyclonal antibodies and monoclonal antibodies against mannoprotein components from mycelial cell walls of the ATCC 26555 strain. Labelling with biotin allowed identification of a complex array of cell wall protein and glycoprotein components within a very wide molecular mass range (from 650 to 13 kDa). These appeared to be genuine cell wall components. Biotinylated high-molecular-mass glycoproteins that were not stained with Coomassie blue or that appeared as poorly resolved polydisperse bands by indirect ConA-peroxidase staining of Western blots were detected as sharply defined bands following reaction with the Extravidin-peroxidase conjugate. Biotinylated molecules retained unaltered reactivities against ConA, polyclonal antibodies, and monoclonal antibodies.

Antibodies directed against a yeast carboxyl-terminal peroxisomal targeting signal specifically recognize peroxisomal proteins from various yeasts

The carboxyl-terminal tripeptide Ala-Lys-Ile is essential for targeting Candida tropicalis trifunctional enzyme (hydratase-dehydrogenase-epimerase) to peroxisomes of both Candida albicans and Saccharomyces cerevisiae (Aitchison,J.D., Murray, W.W. and Rachubinski, R. A. (1991).J. Biol. Chem. 266, 23197-23203). We investigated the possibility that this tripeptide may act as a general peroxisomal targeting signal (PTS) for other proteins in the yeasts C. tropicalis, C. albicans, Yarrowia lipolytica and S. cerevisiae, and in rat liver. Anti-AKI antibodies raised against the carboxyl-terminal 12 amino acids of trifunctional enzyme were used to search for this PTS in proteins of these yeasts and of rat liver. The anti-AKI antibodies reacted exclusively with multiple peroxisomal proteins from the yeasts C. tropicalis, C. albicans and Y. lipolytica. There was a weak reaction of the antibodies with one peroxisomal protein from S. cerevisiae and no reaction with peroxisomal proteins from rat liver. Antibodies directed against a synthetic peptide containing a carboxyl-terminal Ser-Lys-Leu PTS (Gould, S. J., Krisans, S., Keller, G.-A. and Subramani, S. (1990). J. Cell Biol. 110,27-34) reacted with multiple peroxisomal proteins of rat liver and with peroxisomal proteins of yeast distinct from those identified with anti-AKI antibodies. These results provide evidence that several peroxisomal proteins of different yeasts contain a PTS antigenically similar to that of C. tropicalis trifunctional enzyme and that this signal is absent from peroxisomal proteins from at least one mammalian system, rat liver.

A murine model of allergic bronchopulmonary aspergillosis with elevated eosinophils and IgE

A model of allergic bronchopulmonary aspergillosis was developed by exposing BALB/c mice to Aspergillus fumigatus (AF) Ag. Animals immunized intranasally (i.n.) with soluble AF Ag produced low levels of serum IgE compared to animals given alum precipitated AF Ag i.p. The latter treatment also produced higher levels of serum IgG1 and AF-specific IgG1 than soluble AF given i.p. or i.n.. Blood and lung eosinophilia was detected in mice repeatedly exposed to AF by i.n. but not in the groups injected i.p. Particulate AF Ag-induced striking blood and lung eosinophilia and elevated levels of serum IgE in mice preexposed to AF Ag. The results indicate that route of inoculation and physical nature of Ag determine the immune response and can be manipulated to obtain enhanced IgE, eosinophils, or both in the animal model.

Concanavalin A-nonbinding Aspergillus fumigatus antigen: a major immunogen in allergic bronchopulmonary aspergillosis

Humoral immune responses in allergic bronchopulmonary aspergillosis (ABPA) have been well studied. However, reports of cell-mediated immune responses in ABPA are conflicting and not well documented, perhaps because well-characterized antigens are not available. In the present study, we assessed the role of peripheral blood mononuclear cells (PBMCs) from patients with ABPA in their ability to respond to both crude and semipurified Aspergillus fumigatus antigens by in vitro proliferation and immunoglobulin E synthesis. Eight patients with ABPA, eight patients with immediate wheal and flare skin reactivity to A. fumigatus, and ten healthy control subjects with nonreactive skin tests were included in this study. Four A. fumigatus antigens were tested in vitro. Antigens included culture filtrate, mycelial extract, concanavalin A-nonbinding, and concanavalin A-binding antigens. There was a wide range of response to each antigen by each group of subjects. However, PBMCs from patients with ABPA showed greater response to the antigens than did those from the healthy control subjects when evaluated by lymphoproliferation (tritiated thymidine uptake) and immunoglobulin E synthesis (isotype-specific enzyme-linked immunosorbent assay). The concanavalin A-nonbinding antigen fraction had the ability to specifically stimulate proliferation of PBMCs from seven of eight patients with ABPA and from four of eight skin-reactive subjects; none of the healthy control subjects responded. Significantly high levels of immunoglobulin E were detected in unstimulated PBMC cultures from five patients with ABPA when compared with those from healthy control subjects. These results indicate that concanavalin A-nonbinding A. fumigatus antigens may be significant in the cellular immune response of ABPA; such results are similar to those from previous humoral studies of the disease.

Characterization of a monoclonal antibody (P40) against the 68 kD major allergen of Penicillium notatum

A monoclonal antibody (MoAb P40) against the 68 kD major allergen of Penicillium notatum (P. notatum) was obtained by immunizing the mouse with a crude extract of P. notatum. Analysed by two-dimensional gel electrophoresis and immunoblotting, P40 reacted with two different isoforms of the 68 kD component of P. notatum with pIs of 5.4 and 5.5. In addition to P. notatum, P40 showed positive ELISA activity to Aspergillus fumigatus (A. fumigatus) but not to components of six other fungi including Alternaria porri, Cladosporium cladosporoides, Aureobasidium pullulans, Fusarium solani, Rhizopus arrhizus and Candida albicans. Analysed by ELISA, MoAb P40 also showed positive activity to two (P. frequentans and P. roseopurpureum) of the 10 other Penicillium species and two (A. terreus and A. flavus) of the four other Aspergillus species tested. SDS-PAGE and immunoblotting studies demonstrated P40 positive reactivity to components with MW of about 67 kD in all these Penicillium and Aspergillus species with positive ELISA activity to P40. Furthermore, immunoblotting activity of MoAb P40 to the 67 kD component of A. niger was also observed. The epitope of the 68 kD allergen of P. notatum recognized by MoAb P40 was resistant to treatment of periodate oxidation with concentration of NaIO4 up to 20 mM. This MoAb may thus be useful in the characterization and purification of the 68 kD allergen from crude extracts, and in the molecular cloning of allergen genes.

Coccidioides immitis fractions which are antigenic for immune T lymphocytes

The principal mechanism of resistance to coccidioidomycosis in experimental animals has been reported to be T-cell-mediated immunity. We have generated a Coccidioides immitis antigen-specific murine T-cell line to identify specific macromolecules capable of eliciting an immune mouse T-cell proliferative response. The murine T cells were stimulated in vitro with a soluble conidial wall fraction (SCWF), which has been previously characterized by humoral and cellular immunoassays. The SCWF was separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electrotransferred to a nitrocellulose membrane, and the stained blot was cut into seven pieces based on the molecular size of the SCWF components. The nitrocellulose membrane strips were converted into antigen-bearing particles and tested in a T-cell proliferation assay. Antigenic components of the SCWF in the molecular size range of 43 to 66 kDa were identified as the most immunoreactive. In a parallel study, we used a cDNA expression library derived from mRNA of the mycelial phase of C. immitis, which was constructed in lambda gt11 to identify clones that encoded T-cell-reactive fusion proteins (FPs). The cDNA library was screened by using anti-SCWF rabbit serum, and the FPs expressed in Escherichia coli were isolated and tested for T-cell response in the same manner as the SCWF components. The nucleotide sequence of a 0.2-kb cDNA insert encoding a protein which elicited vigorous T-cell response was determined. The isolated cDNA insert hybridized to a single 1.9-kb mRNA band in a Northern blot of the total RNA fraction of the mycelial phase of C. immitis. Antibody with affinity for the T-cell-reactive FP was isolated from anti-SCWF rabbit serum by solid-phase immunoadsorption. The FP-specific antibody reacted with a 47-kDa polypeptide in Western blots (immunoblots) of the SCWF. The same antibody preparation was used for immunoelectron microscopy to show that the FP was localized in the walls of arthroconidia and spherules of C. immitis. Attempts to clone and sequence the entire gene which encodes the T-cell-reactive protein are under way. The results of this study should lead to the determination of the complete structure of an important T-cell-stimulating antigen of C. immitis.

HSP 90, yeasts and Corynebacterium jeikeium

Recovery from disseminated candidosis is associated with seroconversion to a 47 kDa breakdown product of the Heat Shock Protein (HSP) 90 of Candida albicans. Cloning, sequencing and epitope mapping has allowed the delineation of the immunodominant epitopes LKVIRKNIVKKMIE and STDEPAGESA. Monoclonal and polyclonal antibodies specific to these epitopes are used to show that all strains of C. albicans tested produce HSP 90 in both the yeast and mycelial phases. Homologous proteins are demonstrated in Saccharomyces cerevisiae, Candida parapsilosis and Corynebacterium jeikeium but not in Torulopsis glabrata. Evidence is presented for the existence of two distinct HSP 90s in C. albicans. The first of these is expressed constitutively whilst the second is produced on heat shocking the yeast from 23 to 37 degrees C.

Heat shock protein 88 and Aspergillus infection

Immunoblotting was used to dissect the antibody responses in the sera of 50 patients with proven invasive aspergillosis, 28 patients with suspected invasive aspergillosis, 35 patients with allergic bronchopulmonary aspergillosis, and 10 patients with an aspergilloma. This demonstrated the immunodominance of antigenic bands at 88, 84, 51, and 40 kDa. Monoclonal antibodies against the heat shock protein 90 complexes of Candida albicans and the water mold Achlya ambisexualis identified these four antigenic bands as homologous proteins. Similar antigens have been described in humans, mice, Saccharomyces cerevisiae, chickens, and Drosophila species. The antibody against A. ambisexualis has previously been shown to cross-react with antigens belonging to the human heat shock protein 90 complex. Aspergillus heat shock protein 90 was extracted from the sera of patients with invasive aspergillosis by affinity chromatography. This was done with both a rabbit hyperimmune antiserum raised against an extract of Aspergillus fumigatus NCPF 2109 and a monoclonal antibody against the heat shock protein 90 of C. albicans. In vivo expression of the antigen was demonstrated in an aspergilloma surgically removed from a patient. The role of the antigen as an allergen in allergic bronchopulmonary aspergillosis is also discussed.

Enzyme immunoassays for invasive Candida infections: reactivity of somatic antigens of Candida albicans

The main problem encountered with serodiagnostic tests for Candida infections is their failure to differentiate between invasive and superficial candidosis. Recent immunoblotting studies suggested that the use of selective somatic proteins of Candida albicans as antigens might be a promising approach toward developing a new generation of serodiagnostic assays. In this study major cytoplasmic protein antigens with molecular weights of 47,000 (47K), 46,000 (46K), 45,000 (45K), and 29,000 (29K) were identified as potential marker antigens for antibody detection in invasive candidosis. Continuous-flow isoelectric focusing was employed to enrich the proteins in two fractions, one of them containing the 47K and 29K proteins and the other one containing predominantly the 47K and 45K major proteins. These antigens and a whole somatic antigen extract were used to establish enzyme immunoassays (EIAs) for antibody detection. Whereas all tests were able to discriminate between patients with invasive candidosis (n = 27) and normal healthy volunteers (n = 167), as proved by graphic marker analysis, the selective antigen EIAs were highly superior to the whole somatic antigen EIA and two serological standard assays (indirect immunofluorescence assay and indirect hemagglutination assay) when a panel of sera from patients with superficial candidosis (n = 34) was used as a negative control group. The use of the 47K-29K antigen fraction allowed the best differentiation between invasive and noninvasive candidosis. The corresponding immunoglobulin G class-specific EIA had a sensitivity of 81.5% and a specificity of 97% for both negative control groups as well.

Further structural studies of the carbohydrate moiety of the allergen Ag-54 (Cla h II) from the mould Cladosporium herbarum

The carbohydrate moiety of the glycoprotein allergen Ag-54, isolated from the mould Cladosporium herbarum, has been characterised partly, using acetolysis, methylation analysis, and n.m.r. spectroscopy. Ag-54 contained a highly branched galactoglucomannan and two branched mannogluco-oligosaccharide chains. The oligosaccharides contained terminal, (1----4)-, and (1----4,6)-linked alpha-Glc residues and terminal, (1----2)-, and some (1----3)-linked alpha-Man residues. The n.m.r. data indicated the galactoglucomannan to have a main chain made up of (1----6)-linked alpha-Man and (1----4)-linked alpha-Glc residues, with the latter attached to position 6 of alpha-Man residues. Oligosaccharides with (1----6)-linked beta-Galf and (1----2)-linked alpha-Man were attached to the main chain. Acetolysis of the galactoglucomannan yielded linear and branched oligosaccharides. The presence of (1----2,3)-linked alpha-Man residues indicated either that other than (1----6) linkages were present in the main chain or that there was 2,3-branching in the side chains.

Antigen complex of Coccidioides immitis which elicits a precipitin antibody response in patients

The occurrence in patients of elevated levels of immunoglobulin M (IgM) precipitin antibody to Coccidioides immitis antigens, which are commonly detected by the immunodiffusion-tube precipitin (TP) assay, is suggestive of primary nondisseminating coccidioidomycosis. We previously demonstrated that the concanavalin A-bound mycelial culture filtrate plus lysate preparation is a source of at least two TP antibody-reactive antigens (TP-Ags), which were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis as 120- and 110-kDa fractions. Evidence is presented here that the crude filtrate plus lysate preparation contains additional lectin-bound, TP antibody-reactive fractions as well as a component which elicits a complement fixation antibody response in patients. The 120- and 110-kDa fractions were isolated from the antigen complex and further characterized in this paper. Both TP-Ags are glycoproteins and have been shown by immunoelectron microscopy to be colocalized within cytoplasmic vesicles and the wall of spherules. Deglycosylation of these TP-Ags by sodium periodate treatment resulted in a loss in patients of 82 to 95% of IgM adsorption to the antigens as detected by the enzyme-linked immunosorbent assay (ELISA). Comparison of their carbohydrate compositions revealed that mannose and glucose are the predominant monosaccharides of both TP-Ags but only the 120-kDa fraction contained 3-O-methylmannose, a sugar which appears to be unique to C. immitis among the systemic fungal pathogens. We previously showed that 3-O-methylmannose is at least partly responsible for the reactivity of IgM antibody with the 120-kDa TP-Ag. Good correlation was shown between results of immunodiffusion-TP assays and ELISAs of IgM response to both the 120- and 110-kDa fractions by using 70 serum samples from patients with proved coccidioidomycosis. However, only 2.8% (3 of 109) of the serum samples from patients with other mycoses and nonmycotic infections showed IgM adsorption to the 120-kDa TP-Ag as detected by the ELISA, while 21.1% (23 of 109) showed IgM adsorption to the 110-kDa TP-Ag. The 120-kDa TP-Ag is a potentially valuable serodiagnostic reagent for detection of specific IgM by ELISA in patients with primary coccidioidomycosis.

An immunoreactive apoglycoprotein purified from Coccidioides immitis

Deglycosylation of glycoproteins in a lysate of spherules of Coccidioides immitis has permitted purification and partial characterization of a proline-rich pronase-sensitive antigen. Moreover, soluble antigen specifically stimulated lymphocytes from persons with dermal delayed-type hypersensitivity to coccidioidal antigens. When related to reference coccidioidin by tandem two-dimensional immunoelectrophoresis, the antigen fused in the anodal region with a specific reference antigen (antigen 2). It did not show identity with coccidioidal antigens used in conventional serologic assays. Although immunoblots of the purified protein with monospecific rabbit antiserum showed a single antigen at 33 kDa, the parent spherule lysate bound the same antibody in a broad band between 70 and greater than 200 kDa, which could be explained by microheterogeneity of glycosylation. Immunoelectron microscopy using affinity-purified human antibodies localized the antigen to the cell wall and internal septa of spherules. These findings suggest that the apoglycoprotein may be important in human immune responses to coccidioidal infection.

Identification and characterization of a thermolabile antigen (TLAb, glyceraldehyde-3-phosphate dehydrogenase) in Saccharomyces cerevisiae

Five thermolabile antigens (TLAa, TLAb, TLAc, TLAd, and TLAe) have been purified from Saccharomyces cerevisiae. Recently, we reported that TLAa was identical with yeast enolase (EC 4.2.1.11). In this paper, TLAb was identified as yeast glyceraldehyde-3-phosphate dehydrogenase (GAPDH, EC 1.2.1.12) on the following bases: (1) Mr, N-terminal amino acid sequence, and isomer number of TLAb were the same as those of GAPDH; (2) anti-TLAb serum was reactive to GAPDH in the Ouchterlony test and in sodium dodecyl sulfate-polyacrylamide gel electrophoresis immunoblotting; and (3) TLAb possessed GAPDH enzyme activity which was inhibited by anti-TLAb serum. The effect of various growth conditions on the proportion of three TLAb isoproteins (TLAb-1, TLAb-2, and TLAb-3) was examined. The proportion of two TLAb isoproteins (TLAb-1 and TLAb-2) changed depending on the cell growth phase the carbon sources, and sodium chloride shock. It is concluded that environmental stress has a differential effect on the biosynthesis of TLAb isoproteins.

Differences in Cryptococcus neoformans capsular polysaccharide structure influence assembly of alternative complement pathway C3 convertase on fungal surfaces

Binding of complement component C3 and Factor B to Cryptococcus neoformans serotypes A through D via the alternative complement pathway was measured in a system containing fresh nonimmune human serum. Serotypes B and C (C. neoformans var. gattii) bound approximately half as many molecules of both complement components as serotypes A and D (C. neoformans var. neoformans). In contrast, removal of xylosyl and glucuronyl side chains from the mannan main chain of capsular polysaccharide by the Smith degradation procedure resulted in binding of similar quantities of C3 to each of the four serotypes. We conclude that the relatively high degree of side chain substitution of capsular polysaccharide from C. neoformans variety gattii contributes to inefficient surface assembly of the alternative pathway C3 convertase. Inefficient binding of alternative pathway complement components to serotypes B and C may contribute to the relative difficulty in successfully treating infections caused by these organisms.