Binding of Paracoccidioides brasiliensis to laminin through surface glycoprotein gp43 leads to enhancement of fungal pathogenesis

Detection of circulating gp43 antigen in serum, cerebrospinal fluid, and bronchoalveolar lavage fluid of patients with paracoccidioidomycosis

Paracoccidioidomycosis (PCM) is an important systemic fungal disease, particularly among individuals living and working in rural areas of endemicity in Latin America, who, without antifungal therapy, may develop fatal acute or chronic infection. For such patients, the detection of antibody responses by immunodiffusion is of limited value due to false-negative results. In contrast, the detection of Paracoccidioides brasiliensis gp43 circulating antigen may represent a more practical approach to the rapid diagnosis of the disease. Accordingly, an inhibition enzyme-linked immunosorbent assay (inh-ELISA) was developed for the detection of a 43-kDa P. brasiliensis-specific epitope incorporating a species-specific murine monoclonal antibody. With sera from patients with acute and chronic forms of the disease (n = 81), the overall sensitivity of the test was found to be 95.1%, while specificity was found to be 97.5% compared to that with normal human sera from blood donors (n = 93) and sera from patients with other chronic fungal infections (histoplasmosis [n = 33] and cryptococcosis [n = 20]). The inh-ELISA detected circulating antigen in 100% of patients with the acute form of PCM and in 95.31 and 100% of patients with the chronic multifocal and unifocal forms of PCM according to the patient's clinical presentation. Cerebrospinal fluid from 14 patients with neuroparacoccidioidomycosis and 13 samples of bronchoalveolar lavage fluid from patients with pulmonary unifocal PCM were also tested for gp43 detection, with the test showing 100% sensitivity and specificity. This novel, highly specific inh-ELISA represents a significant addition to the existing tests for the diagnosis of PCM.

Expressed sequence tag analysis of the human pathogen Paracoccidioides brasiliensis yeast phase: identification of putative homologues of Candida albicans virulence and pathogenicity genes

Paracoccidioides brasiliensis, a thermodimorphic fungus, is the causative agent of the prevalent systemic mycosis in Latin America, paracoccidioidomycosis. We present here a survey of expressed genes in the yeast pathogenic phase of P. brasiliensis. We obtained 13,490 expressed sequence tags from both 5' and 3' ends. Clustering analysis yielded the partial sequences of 4,692 expressed genes that were functionally classified by similarity to known genes. We have identified several Candida albicans virulence and pathogenicity homologues in P. brasiliensis. Furthermore, we have analyzed the expression of some of these genes during the dimorphic yeast-mycelium-yeast transition by real-time quantitative reverse transcription-PCR. Clustering analysis of the mycelium-yeast transition revealed three groups: (i) RBT, hydrophobin, and isocitrate lyase; (ii) malate dehydrogenase, contigs Pb1067 and Pb1145, GPI, and alternative oxidase; and (iii) ubiquitin, delta-9-desaturase, HSP70, HSP82, and HSP104. The first two groups displayed high mRNA expression in the mycelial phase, whereas the third group showed higher mRNA expression in the yeast phase. Our results suggest the possible conservation of pathogenicity and virulence mechanisms among fungi, expand considerably gene identification in P. brasiliensis, and provide a broader basis for further progress in understanding its biological peculiarities.

Cleavage of human fibronectin and other basement membrane-associated proteins by a Cryptococcus neoformans serine proteinase

The interaction between the fungal pathogen Cryptococcus neoformans and human fibronectin (HFN) was examined in this study. Polypeptides from cryptococcal whole homogenates and cell wall with molecular masses of 25 and 35 kDa, respectively reacted with HFN. The relevance of the occurrence of these proteins in intact cells was uncertain, since yeast cells from different strains and serotypes of C. neoformans did not significantly adhere to soluble or solid-phased HFN. In contrast, an exocellular proteolytic activity that cleaves HFN was suggested. Degradation of HFN by culture supernatant fluids was demonstrated by Western blotting using a monoclonal anti-HFN antibody. Several fragments of lower molecular weights were observed which reacted with the antibody. Proteolysis was mediated by a serine protease activity, since HFN cleavage was completely inhibited by phenylmethylsulfonyl fluoride (PMSF), aprotinin, and N-tosyl-L-phenylalanyl chloromethylketone (TPCK), but not by inhibitors of metalo, cysteine, or aspartyl proteases. Similar results were obtained when the fluorogenic peptide carbobenzoxy-phenylalanyl-arginyl-7-amido-4-methylcoumarin (CBZ-Phe-Arg-NHmet-C) was used as substrate. The cryptococcal supernatant also cleaved laminin and type IV collagen, as demonstrated by polyacrylamide gel electrophoresis with co-polymerized proteins. The hydrolysis of these proteins was mediated by a single cryptococcal protease with a molecular mass of 75 kDa. The cleavage of key host components of the basement membrane and extracellular matrix by C. neoformans may be a relevant factor in the process of fungal invasion.

Immunity and hypersensitivity to gp43 antigen in susceptible and resistant mice infected withParacoccidioides brasiliensis

Pathogenic mechanisms underlying paracoccidioidomycosis are still poorly understood. A well-established murine model of resistance (mouse lineage A/Sn) and susceptibility (lineage B10.A) to P. brasiliensis pulmonary infection was here employed to compare immune response to gp43, the major antigenic component of the fungus. Mice were infected and their cellular and humoral immunity to gp43 were investigated for up to 16 weeks. In both mouse strains, challenge with gp43 indistinguishably evoked a typical immediate-hypersensitivity response, followed by a 24-h late-phase reaction consistent with the same type of immunological activation. IL-4 was detected in cultures of gp43-stimulated lymph node cells only in susceptible animals 2 weeks post-infection, while IL-5 was found throughout the study in both mouse strains. IL-10 appeared in the supernatants of stimulated cells from resistant and susceptible animals in increasing amounts as infection advanced. Conversely, interferon (IFN)-gamma was produced under gp43 stimulation only by cells from A/Sn animals. The humoral response was characterized by low levels of anti-gp43. Titration of IgG isotypes, however, revealed a predominance of IgG1. IgG2a levels were highest in resistant animals, whereas IgG2b levels were highest in susceptible mice. In conclusion, immunity induced by gp43 exhibits common features in A/Sn and B10.A phenotypes, such as immediate hypersensitivity, late phase reaction and high levels of IL-10, but some differences between the strains are also seen.

Expression in bacteria of the gene encoding the gp43 antigen of paracoccidioides brasiliensis: immunological reactivity of the recombinant fusion proteins

gp43 is the major diagnostic antigen of Paracoccidioides brasiliensis, the agent of paracoccidioidomycosis (PCM) in humans. In the present study, cDNA of the gp43 gene (PbGP43) was obtained by reverse transcriptase PCR, inserted into a pGEX vector in frame with the glutathione S-transferase (GST) gene, and expressed in Escherichia coli as inclusion bodies. Immunoblotting showed that all sera from patients with chronic pulmonary and acute lymphatic forms of PCM reacted with the recombinant fusion protein of the mature gp43 (381 amino acids). Reactivity with fusion proteins containing subfragments of the N-terminal, internal, or C-terminal regions occurred eventually, and the C-terminal region was the most antigenic. Lack of reactivity with the subfragments may be due to the conformational nature of the gp43 epitopes. Sera from patients with aspergillosis, candidiasis, and histoplasmosis did not react with the gp43-GST fusion protein. Our results suggest that recombinant gp43 corresponding to the processed antigen can be a useful tool in the diagnosis of PCM.

Paracoccidioides brasiliensis: virulence and an attempt to induce the dimorphic process with fetal calf serum

The virulence of Paracoccidioides brasiliensis strains and the induction of the dimorphic process of the fungus were investigated. The strains were kept under mineral oil for different periods of time, except for one that was successively subcultured on agar slants. Four strains with transitional morphology at room temperature were avirulent to experimental animals. Two strains with typical morphology at 36 degrees C, one of them preserved under mineral oil for 16 years and the other maintained by successive subcultures for 10 years, were virulent to mice. These strains caused macro- and microscopic lesions in various organs, with enlargement of the spleen and heart. An attempt to induce the dimorphic process with fetal calf serum (FCS) in P.brasiliensis strains with transitional morphology failed. FCS was probably unable to stimulate the synthesis of Y cell wall alpha-1,3-glucan. The results demonstrate that keeping strains under mineral oil for a long period of time may have altered the enzymatic activities of the proteinases and other virulence factors that participate in the transition process and in pathogenesis.

Enhanced production of specific IgG4, IgE, IgA and TGF-beta in sera from patients with the juvenile form of paracoccidioidomycosis

Paracoccidioidomycosis (PCM) occurs in two distinct forms, the acute or juvenile form (JF), and the chronic or adult form (AF). To clarify the basis of this dichotomy, specific IgG subclasses, IgA and IgE anti-gp43 were measured by enzyme-linked immunosorbent assay, in patients with different forms of PCM. Serum levels of tumor necrosis factor-alpha, interleukin (IL)-6, IL-8, macrophage inflammatory protein (MIP)-1alpha and transforming growth factor (TGF)-beta were also quantified. We show here that JF patients have significantly higher titers of IgE antibodies against gp43, an immunodominant antigen specific for Paracoccidioides brasiliensis, than do patients with the unifocal adult form (UF-AF, isolated lesions). Patients with the multifocal adult form (MF-AF, lesions in more than one organ) also produced elevated levels of anti-P. brasiliensis IgE. Furthermore, specific IgE levels were correlated with IgG4, IgA and eosinophilia. Patients with JF showed eosinophilia and increased levels of TGF-beta, a switching factor for IgA. These results indicate a T helper (Th)-2 pattern of cytokine expression in both the JF and the MF-AF of PCM. On the other hand, patients with UF-AF had a significantly lower production of specific IgE, IgG4 and IgA than was seen in the other patient groups.

High affinity binding between laminin and laminin binding protein of Leishmania is stimulated by zinc and may involve laminin zinc-finger like sequences

In the course of trying to understand the pathogenesis of leishmaniasis in relation to extracellular matrix (ECM) elements, laminin, a major ECM protein, has been found to bind saturably and with high affinity to a 67-kDa cell surface protein of Leishmania donovani. This interaction involves a single class of binding sites, which are ionic in nature, conformation-dependent and possibly involves sulfhydryls. Binding activity was significantly enhanced by Zn2+, an effect possibly mediated through Cys-rich zinc finger-like sequences on laminin. Inhibition studies with monoclonals against polypeptide chains and specific peptides with adhesive properties revealed that the binding site was localized in one of the nested zinc finger consensus sequences of B1 chain containing the specific pentapeptide sequence, YIGSR. Furthermore, incubation of L. donovani promastigotes with C(YIGSR)3-NH2 peptide amide or antibody directed against the 67-kDa laminin-binding protein (LBP) induced tyrosine phosphorylation of proteins with a molecular mass ranging from 115 to 130 kDa. These studies suggest a role for LBP in the interaction of parasites with ECM elements, which may mediate one or more downstream signalling events necessary for establishment of infection.

The pathobiology of Paracoccidioides brasiliensis

Paracoccidioides brasiliensis causes one of the most prevalent systemic mycoses in Latin America--paracoccidioidomycosis. It is a dimorphic fungus that undergoes a complex transformation in vivo, with mycelia in the environment producing conidia, which probably act as infectious propagules upon inhalation into the lungs, where they transform to the pathogenic yeast form. This transition is readily induced in vitro by temperature changes, resulting in modulation of the composition of the cell wall. Notably, the polymer linkages change from beta-glucan to alpha-glucan, possibly to avoid beta-glucan triggering the inflammatory response. Mammalian oestrogens inhibit this transition, giving rise to a higher incidence of disease in males. Furthermore, the susceptibility of individuals to paracoccidioidomycosis has a genetic basis, which results in a depressed cellular immune response in susceptible patients; resistance is conferred by cytokine-stimulated granuloma formation and nitric oxide production. The latency period and persistence of the disease and the apparent lack of efficacy of humoral immunity are consistent with P. brasiliensis existing as a facultative intracellular pathogen.

Polymorphism in the gene coding for the immunodominant antigen gp43 from the pathogenic fungus Paracoccidioides brasiliensis

The gp43 glycoprotein is an immune-dominant antigen in patients with paracoccidioidomycosis (PCM). It is protective against murine PCM and is a putative virulence factor. The gp43 gene of Paracoccidioides brasiliensis B-339 is located in a 1,329-bp DNA fragment that includes two exons, a 78-bp intron, and a leader peptide-coding region of 105 bp. Polymorphism in gp43 has been suggested by the occurrence, in the same isolate or among different fungal samples, of isoforms with distinct isoelectric points. In the present study we aligned and compared with a consensus sequence the gp43 precursor genes of 17 P. brasiliensis isolates after sequencing two PCR products from each fungal sample. The genotypic types detected showed 1 to 4 or 14 to 15 informative substitution sites, preferentially localized between 578 and 1166 bp. Some nucleotide differences within individual isolates (noninformative sites) resulted in a second isoelectric point for the deduced protein. The most polymorphic sequences were also phylogenetically distant from the others and encoded basic gp43 isoforms. The three isolates in this group were from patients with chronic PCM, and their DNA restriction patterns were distinct in Southern blots. The nucleotides encoding the inner core of the murine T-cell-protective epitope of gp43 were conserved, offering hope for the development of a universal vaccine.

PCR for diagnosis of paracoccidioidomycosis

A PCR assay based on oligonucleotide primers derived from the sequence of the gene coding for the 43,000-Da (gp43) antigen was developed to detect Paracoccidioides brasiliensis DNA in sputa. In the standardized conditions, it could detect 10 cells/ml of sputum, providing sufficient accuracy to be useful for diagnosis of paracoccidioidomycosis.

DNA-based vaccination against murine paracoccidioidomycosis using the gp43 gene from paracoccidioides brasiliensis

Gp43, the major 43-kDa antigenic glycoprotein of Paracoccidioides brasiliensis, or its 15-amino acid inner peptide (P10), induces a T-CD4(+), Th1 cellular immune response which protects BALB/c mice from intratracheal infection by virulent yeast forms. We investigated whether DNA vaccination using the gp43 gene could elicit protective immunity against P. brasiliensis. Animals immunised intramuscularly (i.m.) or intradermally (i.d.) with plasmid DNA containing the gp43 gene induced a specific, long lasting humoral and cellular immune response. A mixed Th1/Th2 cellular immune response in DNA-immunized mice was modulated in vivo by IFN-gamma and was protective in BALB/c mice. A significant decrease in the lung colony forming units (CFUs) and reduced, or no dissemination to the spleen and liver of immunised mice were observed.

Adherence and intracellular parasitism of Paracoccidioides brasiliensis in Vero cells

Paracoccidioides brasiliensis is a dimorphic fungus known to produce invasive systemic disease in humans. The 43-kDa glycoprotein of P. brasiliensis is the major diagnostic antigen of paracoccidioidomycosis and may act as a virulence factor, since it is a receptor for laminin.Very little is known about early interactions between this fungus and the host cells, so we developed in vitro a model system employing cultured mammalian cells (Vero cells), in order to investigate the factors and virulence mechanisms of P.brasiliensis related to the adhesion and invasion process. We found that there is a permanent interaction after 30 min of contact between the fungus and the cells. The yeasts multiply in the cells for between 5 and 24 h. Different strains of P. brasiliensis were compared, and strain 18 (high virulence) was the most strongly adherent, followed by strain 113 (virulent), 265 (considered of low virulence) and 113M (mutant obtained by ultraviolet radiation, deficient in gp43). P. brasiliensis adhered to the epithelial cells by a narrow tube, while depressions were noticed in the cell surface, suggesting an active cavitation process. An inhibition assay was performed and it was verified that anti-gp43 serum and a pool of sera from individuals with paracoccidioidomycosis were able to inhibit the adhesion of P. brasiliensis to the Vero cells. Glycoprotein 43 (gp43) antiserum abolished 85% of the binding activity of P. brasiliensis. This fungus can also invade the Vero cells, and intraepithelial parasitism could be an escape mechanism in paracoccidioidomycosis.

Novel mechanism that Trypanosoma cruzi uses to adhere to the extracellular matrix mediated by human galectin-3

Binding of Trypanosoma cruzi trypomastigotes to laminin is enhanced by galectin-3, a beta-galactoside binding lectin. The galectin-3 enhanced binding of trypanosomes to laminin is inhibited by lactose. Co-immunoprecipitations indicate that galectin-3 binds to the 45, 32 and 30 kDa trypanosome surface proteins. Binding of galectin-3 to the 45, 32 and 30 kDa surface proteins is inhibited by lactose. Polyclonal and a monoclonal antibodies to galectin-3 immunoprecipitated a major 64 kDa trypanosome surface protein. T. cruzi monoclonal antibody to mucin recognized the 45 kDa surface protein. The 45, 32 and 30 kDa surface proteins interact with galectin-3 in order to enhance trypanosome adhesion to laminin.

Anti-idiotypic antibodies in patients with different clinical forms of paracoccidioidomycosis

Paracoccidioidomycosis (PCM) is the most prevalent systemic mycosis in Latin America. Patients with PCM show a wide spectrum of clinical and pathological manifestations depending on both host and pathogen factors. Two clinical forms of the disease are recognized: the acute or juvenile form and the chronic or adult form. The major antigenic component of the parasite is a glycoprotein of 43 kDa (gp43). All patient sera present antibodies against gp43 (anti-gp43) and, as demonstrated before by our group, spontaneous anti-idiotypic (anti-Id) antibodies (Ab2) can be detected in patient sera with high titers of anti-gp43. Since it has been postulated that anti-Id antibodies may have a modulating function, we decided to purify and characterize anti-Id antibodies in this system. The possible correlation of Ab2 titers with different clinical forms of disease was also verified. Results showed that purified human anti-Id antibodies (human Ab2) recognized specifically the idiotype of some murine monoclonal anti-gp43 (17c and 3e) but not others (40.d7, 27a, and 8a). Spontaneous anti-Id antibodies were found in all clinical forms of disease. The majority of patients (88%, n = 8) with the acute form of PCM had high titers of Ab2. However, among patients with the multifocal chronic form of the disease, only 29% (n = 14) had high titers of Ab2; 70% (n = 10) of patients with the unifocal chronic form had low titers of Ab2. A correlation between Ab2 titers and anti-gp43 titers was observed before and during antimycotic treatment. Our results suggest that titers of anti-Id antibodies correlate with the severity of PCM in humans.

A major cell surface antigen of Coccidioides immitis which elicits both humoral and cellular immune responses

Multinucleate parasitic cells (spherules) of Coccidioides immitis isolates produce a membranous outer wall component (SOW) in vitro which has been reported to be reactive with antibody from patients with coccidioidal infection, elicits a potent proliferative response of murine immune T cells, and has immunoprotective capacity in a murine model of coccidioidomycosis. To identify the antigenic components of SOW, the crude wall material was first subjected to Triton X-114 extraction, and a water-soluble fraction derived from this treatment was examined for protein composition and reactivity in humoral and cellular immunoassays. Protein electrophoresis revealed that the aqueous fraction of three different isolates of C. immitis each contained one or two major glycoproteins (SOWgps), distinguished by their molecular sizes, which ranged from 58 to 82 kDa. The SOWgps, however, showed identical N-terminal amino acid sequences, and each was recognized by sera from patients with C. immitis infection. Antibody raised against the purified 58-kDa glycoprotein (SOWgp58) of the Silveira isolate was used for Western blot and immunolocalization analyses. Expression of SOWgp was shown to be parasitic phase specific, and the antigen was localized to the membranous SOW. The water-soluble fraction of SOW and the purified SOWgp58 were tested for the ability to stimulate proliferation of human peripheral monocytic cells (PBMC). The latter were obtained from healthy volunteers with positive skin test reaction to spherulin, a parasitic-phase antigen of C. immitis, and from volunteers who showed no skin test reaction to the same antigen. The SOW preparations stimulated proliferation of PBMC from skin test-positive but not skin test-negative donors, and the activated cells secreted gamma interferon, which is indicative of a T helper 1 pathway of immune response. Results of this study suggest that SOWgp is a major parasitic cell surface-expressed antigen that elicits both humoral and cellular immune responses in patients with coccidioidal infection.

Subcutaneous infection of mice with Paracoccidiodes brasiliensis induces a peculiar pattern of inflammatory and immune responses

It is well established that resistance or susceptibility to Paracoccidioidis brasiliensis infection in mice is under strict host's genetic control. Mice from A/Sn strain inoculated by the ip route are resistant to fungal infection while infection induced in mice from B10.A strain results in a fatal disease. The early cellular events of infection in both strains are characterized by a marked neutrophilic infiltration that is more prominent in B10.A mice. A peculiar characteristic of the Paracoccidioides brasiliensis-mouse model is that the subcutaneous (sc) inoculations of the fungus either in resistant (A/Sn) or susceptible (B10.A) mice is self-curing and tums mice from the B10.A strain able to express typical DTH reaction to fungal antigens, as observed in A/Sn mice. Here we report the investigation on the early events of the inflammatory response induced by the inoculation of live fungus into the hind footpad of A/Sn (resistant) and B10.A (susceptible) mice. The influence of neutrophils on the inflammatory response and antibody titers or DTH response to gp43, the major fungal antigen, was also evaluated. Results showed a different course of the inflammatory response induced by fungal inoculation in A/Sn and B10.A mice. Neutrophil depletion before infection differently influenced the kinetics of the inflammatory process in both mice strains but did not modify the fungal load in the lesions. In neutrophil depleted mice from both strains, a decrease in DTH response and an increase in total antibody titers to gp43 were observed. The significant increase in the fungal load in lesions seen in nude mice indicates that the self-limited infection evoked by fungal inoculation into the subcutaneous tissue is a T-cell dependent phenomenon. The implications of these observations in the pathogenesis of paracoccidioidomycosis are discussed.

Adhesion of the human pathogen Sporothrix schenckii to several extracellular matrix proteins

The pathogenic fungus Sporothrix schenckii is the causative agent of sporotrichosis. This subcutaneous mycosis may disseminate in immunocompromised individuals and also affect several internal organs and tissues, most commonly the bone, joints and lung. Since adhesion is the first step involved with the dissemination of pathogens in the host, we have studied the interaction between S. schenckii and several extracellular matrix (ECM) proteins. The binding of two morphological phases of S. schenckii, yeast cells and conidia, to immobilized type II collagen, laminin, fibronectin, fibrinogen and thrombospondin was investigated. Poly (2-hydroxyethyl methacrylate) (poly-HEMA) was used as the negative control. Cell adhesion was assessed by ELISA with a rabbit anti-S. schenckii antiserum. The results indicate that both morphological phases of this fungus can bind significantly to type II collagen, fibronectin and laminin in comparison to the binding observed with BSA (used as blocking agent). The adhesion rate observed with the ECM proteins (type II collagen, fibronectin and laminin) was statistically significant (P < 0.05) when compared to the adhesion obtained with BSA. No significant binding of conidia was observed to either fibrinogen or thrombospondin, but yeast cells did bind to the fibrinogen. Our results indicate that S. schenckii can bind to fibronectin, laminin and type II collagen and also show differences in binding capacity according to the morphological form of the fungus.

Detection of the basement membrane-degrading proteolytic activity of Paracoccidioides brasiliensis after SDS-PAGE using agarose overlays containing Abz-MKALTLQ-EDDnp

We have characterized, in the Paracoccidioides brasiliensis yeast phase, an exocellular SH-dependent serine proteinase activity against Abz-MKRLTL-EDDnp and analogous fluorescent-quenched peptides, and showed that it is also active against constituents of the basement membrane in vitro. In the present study, we separated the components of P. brasiliensis culture filtrates by electrophoresis and demonstrated that the serine-thiol exocellular proteinase has a diffuse and heterogeneous migration by SDS-PAGE, localizing in a region between 69 and 43 kDa. The hydrolytic activity was demonstrable after SDS-PAGE using buffered agarose overlays of Abz-MKALTLQ-EDDnp, following incubation at 37 degrees C, and detection of fluorescent bands with a UV transilluminator. Hydrolysis was more intense when incubation was carried out at basic pH, and was completely inhibited with 2.5 mM PMSF and partially with sodium 7-hydroxymercuribenzoate (2.5 mM p-HMB), suggesting its serine-thiol nature. A proteolytic band with similar characteristics was observed in conventional gelatin zymograms, but could not be correlated with a silver-stained component. Detection of the serine-thiol proteinase in substrate gels after SDS-PAGE provides a useful way of monitoring purification of the basement membrane degrading enzyme.

Isolation of a laminin-binding protein from the protozoan parasite Leishmania donovani that may mediate cell adhesion

Extracellular matrix (ECM)-binding proteins on the surface of Leishmania are thought to play a crucial role in the onset of leishmaniasis, as these parasites invade mononuclear phagocytes in various organs after migrating through the ECM. In a previous report, we presented several lines of evidence suggesting that Leishmania has a specific receptor for laminin, a major ECM protein, with a Kd in the nanomolar range. Here we describe the identification, purification and biochemical characterization of the Leishmania laminin receptor. When the outer membrane proteins of L. donovani were blotted on to nitrocellulose paper and probed with laminin, a prominent laminin-binding protein of 67 kDa was identified. The purified protein was isolated by a three-step process involving DEAE-cellulose, Con A (concanavalin A)-Sepharose and laminin-Sepharose affinity chromatography and was used to raise a monospecific antibody. The same protein was obtained when parasite membrane extracts were adsorbed to antibody affinity matrix and eluted with glycine. The affinity-purified protein bound to laminin in a detergent-solubilized form as well as after integration into artificial bilayers, and was subsequently characterized as an integral membrane protein. Metaperiodate oxidation and metabolic inhibition of glycosylation studies indicate the binding protein to be glycoprotein in nature and that N-linked oligosaccharides play a part in the interaction of laminin with the binding protein. Surface-labelled parasites attached to microtitre wells coated with laminin and the 67 kDa protein blocked the adhesion to laminin substrate. We propose that the 67 kDa protein is an adhesin involved in the attachment of Leishmania to host tissues.

Involvement of the major glycoprotein (gp43) of Paracoccidioides brasiliensis in attachment to macrophages

The yeast form of Paracoccidioides brasiliensis, the causative agent of a deep mycosis in humans, is known to be phagocytized by, and to multiply inside, macrophages. In this work we describe the involvement of gp43, a major antigenic protein of P. brasiliensis, in the initial steps of attachment of the fungus to macrophages. Anti-gp43 F(ab) polyclonal fragments were capable of inhibiting phagocytosis in a concentration-dependent manner. Sheep red blood cells sensitized with purified gp43 were more endocytized than SRBC alone, and this process was also inhibited by anti-gp43 F(ab) fragments. Inhibition tests indicated the involvement of fucose and mannose residues in the phagocytosis of the fungus and of SRBC-gp43 by macrophages. Taken together, these results suggest that gp43 may be involved in the adherence and uptake of the fungus by murine peritoneal macrophages, and that this binding may be dependent on monosaccharide residues that are part of the gp43 glycoprotein.

Pattern of immune response to GP43 from Paracoccidioides brasiliensis in susceptible and resistant mice is influenced by antigen-presenting cells

Paracoccidioidomycosis (PCM), endemic in Latin America, is a progressive systemic mycosis caused by Paracoccidioides brasiliensis. The infection can evolve to different clinical forms that are associated with various degrees of suppressed cell-mediated immunity. In the murine model, A/Sn and B10.A isogenic strains of mice are known to be resistant and susceptible, respectively, to this fungal infection. Assuming that the effector immune response is a consequence of the preferential activation of either Th1 or Th2 subsets, in the present work we evaluated the importance of two antigen-presenting cells (APCs), macrophages and B cells, in the development of the immune response to P. brasiliensis. In resistant mice, purified gp43, the main antigenic component of P. brasiliensis, seems to have been preferentially presented by macrophages and stimulated Th1 lymphokine production. On the other hand, in susceptible animals gp43 was distinguishably presented by B cells, which led to stronger activation of Th2 subsets. Moreover, T cells from resistant mice responded as those from susceptible animals when stimulated by gp43 presented by APCs from susceptible mice and vice versa, indicating that there are no significant differences in the T cell repertoires from A/Sn and B10.A mice. When T cells from F1 (A/Sn x B10.A) mice were stimulated by gp43 presented by APCs from A/Sn or B10.A, impaired behavior of B10.A macrophages in activating Th1 cells and a B10.A B cell tendency to stimulate T cells that secrete higher levels of IL-10 were observed. Taken together, our results suggest that APCs may be implicated in the outcome of P. brasiliensis infection.

Evidence of idiotypic modulation in the immune response to gp43, the major antigenic component of Paracoccidioides brasiliensis in both mice and humans

Paracoccidioidomycosis (PCM) is a systemic mycosis endemic in Latin America, with a high prevalence in Brazil, Argentina, Colombia and Venezuela. The aetiologic agent of disease is a thermal dimorphic fungus, Paracoccidioides brasiliensis. A glycoprotein of 43,000 D (gp43) is the major antigen of P. brasiliensis. Antibodies directed to this antigen are detected in the sera of all patients with PCM. Gp43 binds to laminin, thus participating in adhesion, invasion and pathogenesis of the fungus. As the role of antibodies in PCM is not fully understood, we decided to investigate the outcome of mice immunization with three distinct anti-gp43 MoAbs (17c, 8a and 24a) coupled with keyhole limpet haemocyanin (KLH). Results show not only the expected presence of anti-Id (AB2) antibodies in the sera of these animals but also a spontaneous and increasing amount of anti-anti-Id (AB3) antibodies after the third course of immunization. Hybridomas producing both AB2 and AB3 MoAbs were obtained using spleen cells from mice immunized with MoAb 17c. AB3 MoAbs were also obtained with spleen cells of mice immunized with MoAbs 8a and 24a. It was also shown that human PCM patients' sera with high titres of anti-gp43 antibodies generate anti-Id antibodies. These data suggest that the immune response to P. brasiliensis can be spontaneously modulated by the idiotypic network.

Virulence factors in fungi of systemic mycoses

Pathogenic fungi that cause systemic mycoses retain several factors which allow their growth in adverse conditions provided by the host, leading to the establishment of the parasitic relationship and contributing to disease development. These factors are known as virulence factors which favor the infection process and the pathogenesis of the mycoses. The present study evaluates the virulence factors of pathogenic fungi such as Blastomyces dermatitidis, Coccidioides immitis, Cryptococcus neoformans, Histoplasma capsulatum and Paracoccidioides brasiliensis in terms of thermotolerance, dimorphism, capsule or cell wall components as well as enzyme production. Virulence factors favor fungal adhesion, colonization, dissemination and the ability to survive in hostile environments and elude the immune response mechanisms of the host. Both the virulence factors presented by different fungi and the defense mechanisms provided by the host require action and interaction of complex processes whose knowledge allows a better understanding of the pathogenesis of systemic mycoses.

Electrophoretic karyotypes and genome sizing of the pathogenic fungus Paracoccidioides brasiliensis

Here we present the karyotype analysis and genome sizing of Paracoccidioides brasiliensis, a pathogen refractory to conventional genetic analysis. We have established pulsed-field gel electrophoresis (PFGE) conditions to resolve the high-molecular-weight chromosomal bands of two clinical isolates of P. brasiliensis. Both isolates showed four megabase-sized bands, ranging from 2.0 to 10.0 Mbp. Significant differences in chromosome sizes and in the chromosomal location of genes for the gp43 antigen and chitin synthase were found. Different technical approaches were employed to estimate the DNA content and to define the ploidy of P. brasiliensis. An estimated genome size in the range of 45.7 to 60.9 Mbp was provided by the analysis of data generated by measuring the amplitude of fluorescence intensity of DAPI (4',6-diamidino-2-phenylindole)-stained nuclei (by confocal microscopy). The nuclear genome size estimated by confocal microscopy is twice that estimated by the average sum of the molecular weight of chromosome-sized DNA molecules by PFGE, suggesting that each separated P. brasiliensis chromosomal band is diploid.

Mapping of the T-cell epitope in the major 43-kilodalton glycoprotein of Paracoccidioides brasiliensis which induces a Th-1 response protective against fungal infection in BALB/c mice

The 43-kDa glycoprotein of Paracoccidioides brasiliensis is the major diagnostic antigen of paracoccidioidomycosis, the prevalent systemic mycosis of Latin America. Apart from eliciting high antibody titers, gp43 is also immunodominant in delayed-type hypersensitivity reactions in infected animals and humans. The cellular immune response in mice to gp43 administered in complete Freund's adjuvant involves CD4+ Th-1 lymphocytes, secreting gamma interferon (IFN-gamma) and interleukin 2 (IL-2) but not IL-4 and IL-10. The T-cell epitope of this antigen was mapped to a 15-amino-acid peptide (P10) based on lymphoproliferations with primed cells from three different haplotypes and on a computer-assisted protein analysis. The structural requirements of the T-cell epitope were determined by assaying a series of P10 analogous and truncated peptides. Only 12-mer or longer sequences were active, confirming presentation by major histocompatibility complex II. The HTLAIR inner core of P10 is the essential domain of the epitope, with various flanking regions possible. Immunization of mice with both gp43 and P10 led to vigorous protection against intratracheal challenge by virulent P. brasiliensis, with a >200-fold decrease in lung CFU and halting of dissemination to the spleen and liver. The protective effect of P10 is mainly attributed to an IFN-gamma-mediated cellular immune response. Unlike gp43, which induces an antibody response compatible with both Th-1 and Th-2 activation in infected BALB/c mice, P10 does not induce a humoral response. Protection by gp43 and P10 was characterized by a few well-demarcated lung granulomas with numerous nonviable yeast forms or resolved lesions with no detectable fungal cells.

Prospects for the development of fungal vaccines

In an era that emphasizes the term "cost-effective," vaccines are the ideal solution to preventing disease at a relatively low cost to society. Much of the previous emphasis has been on childhood scourges such as measles, mumps, rubella, poliomyelitis, and Haemophilus influenzae type b. The concept of vaccines for fungal diseases has had less impact because of the perceived limited problem. However, fungal diseases have become increasingly appreciated as serious medical problems that require recognition and aggressive management. The escalation in the incidence and prevalence of infection has prompted a renewed interest in vaccine development. Herein, I discuss the most recent developments in the search for vaccines to combat fungal infections. Investigators have discovered several inert substances from various fungi that can mediate protection in animal models. The next challenge will be to find the suitable mode of delivery for these immunogens.

Expression of glycoprotein gp43 in stage-specific forms and during dimorphic differentiation of Paracoccidioides brasiliensis

Expression of the 43 kDa glycoprotein (gp43) was analysed in several Paracoccidioides brasiliensis isolates. Using one- and two-dimensional analysis of crude cellular extracts, it was shown that protein expression in yeast and mycelium was dependent on the isolate analysed. In two strains, in both yeast and mycelium cells. gp43 was present, whereas expression was restricted to the yeast phase of two other strains. The clinical implications of this phase-specific gp43 expression are uncertain.

A Trypanosoma cruzi-secreted 80 kDa proteinase with specificity for human collagen types I and IV

Specific interactions between parasites and extracellular matrix components are an important mechanism in the dissemination of Chagas' disease. Binding of the extracellular matrix proteins to Trypanosoma cruzi receptors has been described as a significant step in this phenomenon. In this study, a specific proteinase activity was identified in cell-free extracts of amastigote, trypomastigote and epimastigote forms of T. cruzi using the collagenase fluorogenic substrate N-Suc-Gly-Pro-Leu-Gly-Pro-7-amido-4-methylcoumarin. Isolation of this activity was achieved by a four-step FPLC procedure. Optimal enzyme activity was found to occur at pH 8.0 and was associated with a single T. cruzi 80 kDa protein (Tc 80 proteinase) on SDS/PAGE under reducing conditions. An internal peptide sequence of Tc 80 proteinase was obtained (AGDNYTPPE), and no similarity was found to previously described proteinases of T. cruzi. This enzyme activity is strongly inhibited by HgCl2, tosyl-lysylchloromethane ('TLCK') p-chloromercuribenzoate and benzyloxycarbonyl-Phe-Ala-diazomethane. The purified enzyme was able to hydrolyse purified human [14C]collagen types I and IV at neutral pH, but not 14C-labelled BSA, rat laminin, rabbit IgG or small proteins such as insulin or cytochrome c. In addition, Tc 80 proteinase activity was found to be secreted by T. cruzi forms infective to mammalian cells. Furthermore we demonstrated that purified Tc 80 proteinase mediates native collagen type I hydrolysis in rat mesentery. This feature is compared with that of Clostridium histolyticum collagenase. These findings suggest that Tc 80 proteinase may facilitate T. cruzi host-cell infection by degrading the collagens of the extracellular matrix and could represent a good target for Chagas' disease chemotherapy.

Sialic acid-dependent recognition of laminin and fibrinogen by Aspergillus fumigatus conidia

In an attempt to define the molecular basis of the adherence of Aspergillus fumigatus conidia to the host tissues, a step which might be mediated by the recognition of basement membrane laminin or fibrinogen, we analyzed the binding of these glycoproteins by flow cytometry and a microtiter plate adherence assay. Flow cytometry revealed that the binding of fluorescein isothiocyanate-labeled laminin to conidia was saturable and specific. Moreover, the ability of conidia to bind laminin increased with their maturation. Competition experiments showed a cross-reactivity between laminin and fibrinogen binding and a lack of interactions with glycosaminoglycans. In addition, the binding of laminin was not inhibited by the different adhesive synthetic peptides tested. Furthermore, the microtiter plate assay of adherence to chymotrypsin degradation products of laminin or fibrinogen purified by gel filtration suggested a unique binding site common to sequential degradation fragments or the presence of multiple binding sites on the two ligands. Therefore, the role of carbohydrates in the recognition process was investigated. Among the carbohydrates tested, constitutive of the conidial wall or of the oligosaccharide side chains of laminin and fibrinogen, only N-acetylneuraminic acid and sialyllactose inhibited the binding of these glycoproteins to conidia. In conclusion, these results strengthen the idea that the laminin and fibrinogen receptors in A. fumigatus are identical and suggest an interaction mediated by a sialic acid-specific lectin of the conidial wall.

Expression and identification of a laminin-binding protein in Aspergillus fumigatus conidia

Adhesion of Aspergillus fumigatus, the causative agent of human aspergillosis, to the extracellular matrix protein laminin has been previously demonstrated. This study investigated the expression of laminin receptors during swelling of conidia, a step leading to germination and subsequent colonization of tissues. Scanning electron microscopy showed that the laminin binding sites were distributed over the external rodlet layer of resting conidia. During swelling, the characteristic rodlet layer progressively disintegrated and conidia surrounded by a smooth cell wall layer appeared. Flow cytometry using fluorescein isothiocyanate-conjugated laminin demonstrated that expression of laminin receptors at the surface of conidia was swelling dependent. Resting conidia expressed high levels of laminin receptors on their surface. A gradual decrease of laminin binding was then observed as swelling occurred, reaching a minimum for 4-h-swollen conidia. This correlated with a loss of adherence of swollen conidia to laminin immobilized on microtiter plates. Trypsin pretreatment of conidia reduced laminin binding. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and ligand blotting with laminin identified in a cell wall extract a major 72-kDa cell wall glycoprotein which binds laminin. Thus, one of the initial events in the host colonization may be the recognition of basement membrane laminin by this 72-kDa cell wall surface component.

Differences in reactivity of paracoccidioidomycosis sera with gp43 isoforms

The glycoprotein gp43 from Paracoccidioides brasiliensis is the main antigenic component in paracoccidioidomycosis (PCM) because it is recognized by 100% of PCM patients. It has also been shown that different fungal strains produce gp43 with at least four isoform profiles. In this study, different isoform profiles from gp43, with pIs ranging from 5.8 to 8.5, were affinity purified from various P. brasiliensis (B-339, S.S., 1925 and I9) exoantigens. Because of the isoform heterogeneity, we questioned whether those isoform profiles could be similarly recognized by acute or chronic PCM patients. By using a specific and sensitive method for detection of human IgG anti-gp43 antibodies, the monoclonal antibody capture immunoassay, we report that not all gp43 isoform profiles are equally recognized in PCM sera when anti-gp43 MAb 17c was employed as capturing antibody. Our results showed that recognition of pI8.5 gp43 isoform was significantly lower for both acute (56%) and chronic patients (71%), compared with gp43 isoforms from the standard strain B-339. On the other hand, when anti-gp43 MAb 8a, which recognizes a different antigenic epitope was used to capture the different gp43 isoform profiles, all patient's sera reacted similarly. The results described suggest that not all the antigenic epitopes expressed by gp43 are equally present in all P. brasiliensis strains.

Monoclonal antibodies against the 43,000 Da glycoprotein from Paracoccidioides brasiliensis modulate laminin-mediated fungal adhesion to epithelial cells and pathogenesis

The surface glycoprotein gp43, a highly immunogenic component of Paracoccidioides brasiliensis, is used in the serodiagnosis of paracoccidioidomycosis (PCM) and has recently been shown to specifically bind the extracellular matrix protein laminin. Binding to laminin induces the increased adhesion of the fungus to epithelial cells; a hamster testicle infection model has shown that the gp43-dependent binding of fungal cells to laminin enhances their pathogenicity in vivo. We report on the production and characterization of 12 monoclonal antibodies against the gp43 that recognize peptide sequences in the molecule detecting at least three different epitopes as well as different isoforms of this antigen. MAbs interfered in the fungal pathogenicity in vivo either by inhibiting or enhancing granuloma formation and tissue destruction. Results suggest that P. brasiliensis propagules may start infection in man by strongly adhering to human lung cells. Thus, laminin-mediated fungal adhesion to human lung carcinoma (A549) cells was much more intense than to Madin-Darby canine kidney cells (MDCK), indicating differences in binding affinity. Subsequent growth of fungi bound to the lung cells could induce the granulomatous inflammatory reaction characteristic of PCM. Both steps are greatly stimulated by laminin binding in infective cells expressing gp43.

Virulence factors of medically important fungi

Human fungal pathogens have become an increasingly important medical problem with the explosion in the number of immunocompromised patients as a result of cancer, steroid therapy, chemotherapy, and AIDS. Additionally, the globalization of travel and expansion of humankind into previously undisturbed habitats have led to the reemergence of old fungi and new exposure to previously undescribed fungi. Until recently, relatively little was known about virulence factors for the medically important fungi. With the advent of molecular genetics, rapid progress has now been made in understanding the basis of pathogenicity for organisms such as Aspergillus species and Cryptococcus neoformans. The twin technologies of genetic transformation and "knockout" deletion construction allowed for genetic tests of virulence factors in these organisms. Such knowledge will prove invaluable for the rational design of antifungal therapies. Putative virulence factors and attributes are reviewed for Aspergillus species, C. neoformans, the dimorphic fungal pathogens, and others, with a focus upon a molecular genetic approach. Candida species are excluded from coverage, having been the subject of numerous recent reviews. This growing body of knowledge about fungal pathogens and their virulence factors will significantly aid efforts to treat the serious diseases they cause.

Immunochemical and subcellular localization of the 43 kDa glycoprotein antigen of Paracoccidioides brasiliensis with monoclonal antibodies

Two monoclonal antibodies ST-7 (IgG1) and ST-8 (IgG2b), directed against a 43 kDa glycoprotein (gp43) of Paracoccidioides brasiliensis were produced. It was possible to detect the gp43 by ELISA in amounts as low as 100 ng per well, and by Western blot about 300 ng were detected. Mild treatment of the gp43 with sodium metaperiodate did not alter its reactivity with ST-7 and ST-8, which suggests that these MAbs recognize peptide epitopes. Confirming the periodate oxidation data, the 38 kDa protein resulting from deglycosylation of the gp43 with trifluoromethanesulphonic acid (TMFS), was reactive with ST-7 and ST-8. Immunoelectron microscopy showed that the gp43 is stored inside large dense core vesicles, which flowed into the plasma membrane and extruded from cell membrane into the cell wall. Finally the antigen was secreted into the extracellular space as dense membrane-free material. Secretion of the gp43 occurred at scattered sites interspersed along the cell surface.

Cloning, characterization, and epitope expression of the major diagnostic antigen of Paracoccidioides brasiliensis

The 43,000-Da glycoprotein (gp43) of Paracoccidioides brasiliensis is an immunodominant antigen for antibody-dependent and immune cellular responses in patients with paracoccidioidomycosis. In order to identify the peptide epitopes involved in the immunological reactivities of the gp43 and to obtain highly specific recombinant molecules for diagnosis of the infection, genomic and cDNA clones representing the entire coding region of the antigen were sequenced. The gp43 open reading frame was found in a 1,329-base pair fragment with 2 exons interrupted by an intron of 78 nucleotides. The gene is present in very few copies per genome, as indicated by Southern blotting and chromosomal megarestriction analysis. A single transcript of 1.5 kilobase pairs was verified in the yeast phase. The gene encodes a polypeptide of 416 amino acids (Mr 45,947) with a leader peptide of 35 residues; the mature protein has a single N-glycosylation site. The deduced amino acid sequence showed similarities of 56-58% with exo-1,3- beta-D-glucanases from Saccharomyces cerevisiae and Candida albicans. However, the gp43 is devoid of hydrolase activity and does not cross-react immunologically with the fungal glucanases. Internal and COOH-terminal gene fragments of the gp43 were expressed as recombinant fusion proteins, which reacted with antibodies elicited against the native antigen.

Interaction of laminin with Entamoeba histolytica cysteine proteinases and its effect on amebic pathogenesis

The Entamoeba histolytica 27-kDa cysteine proteinases exhibit striking binding specificities for immobilized laminin over other components of the extracellular matrix, such as collagen and fibronectin. Inactivation of the proteinase with the active-site inhibitor L-trans-epoxysuccinyl-leucylamido(4-guanidino)butane abolishes laminin binding by the enzyme, and conversely, laminin inhibits cleavage of a fluorogenic dipeptide substrate of the amebic cysteine proteinase, suggesting that the substrate binding pocket of the enzyme is involved in the binding of laminin. The addition of laminin but not fibronectin or collagen to E. histolytica trophozoites significantly reduces amebic liver abscess formation in severe combined immunodeficient mice, further supporting the hypothesis that E. histolytica cysteine proteinases play an important role in amebic pathogenesis. The specific interaction of amebic proteinases with laminin may be exploited in designing new inhibitors of these enzymes.

Murine laminin binds to Histoplasma capsulatum. A possible mechanism of dissemination

Histoplasmosis, an increasingly important opportunistic infection in immunosuppressed subjects, is characterized by hematogenous dissemination of the yeast from the lung. The mechanism of this dissemination is not fully understood. Laminin, the major glycoprotein of the extracellular matrix, is known to mediate the attachment of various invasive pathogens to host tissues. In the current study, laminin is demonstrated to bind to Histoplasma capsulatum in a rapid, specific, and saturable manner. Scatchard analysis with 125I-labeled laminin revealed an estimated 3.0 x 10(4) binding sites per yeast with an apparent Kd for laminin binding of 1.6 x 10(-9) M. Laminin binding to H. capsulatum was decreased from 62 +/- 1 to 17 +/- 1 ng (P < 0.001) in the presence of 3,000 nM of Ile-Lys-Val-Ala-Val, a pentapeptide within one major cell attachment site of laminin. A 50-kD H. capsulatum laminin-binding protein was demonstrated using an 125I-Ln blot of H. capsulatum cell wall proteins. The 50-kD protein is also recognized by antibodies directed at the 67-kD laminin receptor, suggesting they are related. This study proposes a possible mechanism for H. capsulatum attachment to laminin, an important first step required for the yeast to recognize and traverse the basement membrane.

Characterization of an exocellular serine-thiol proteinase activity in Paracoccidioides brasiliensis

An exocellular proteinase activity has been characterized in Paracoccidioides brasiliensis culture filtrates. Chromatographic analysis showed that the activity was eluted from an anion-exchange Resource Q column at 0.08-0.1 M NaCl, and by gel filtration near ovalbumin elution, in a single peak. Purification of the proteinase, however, was hampered by the low protein yield, in contrast to the high peptidase activity. Numerous chromogenic peptidyl p-nitroanilide derivatives and internally quenched fluorescent peptides, flanked by Abz (O-aminobenzoyl) and EDDnp (ethylenediaminedinitrophenyl), were tested as substrates. Cleavage was observed with Abz-MKRLTL-EDDnp, Abz-FRLVR-EDDnp, and Abz-PLGLLGR-EDDnp at Leu-Thr, Leu-Val and Leu-Leu/Leu-Gly bonds respectively as determined by isolation of the corresponding fragments by HPLC. Leucine at P1 seemed to be restrictive for the activity of the exocellular enzyme, but threonine (P'1) and leucine (P'2) in Abz-MKRLTL-EDDnp apparently were not essential. Also, a pair of alanines could substitute for lysine (P3) and arginine (P2) in this substrate, with a decrease in the Km values. The exocellular peptidase activity of P. brasiliensis had an optimum pH of > 9.0 and was irreversibly inhibited by PMSF, mercuric acetate and p-hydroxymercuribenzoate. Inhibition of the mercuriate compounds could be partially reversed by Cys/EDTA. E-64 [trans-epoxysuccinyl-L-leucylamido-(4-guanido)butene] was a weak and reversible inhibitor, whereas EDTA and pepstatin were not inhibitory. These results suggest that P. brasiliensis exocellular enzyme belongs to the subfamily of SH-containing serine proteinases.

Expression and isoforms of gp43 in different strains of Paracoccidioides brasiliensis

Individual exoantigens from 13 Paracoccidioides brasiliensis isolates were obtained and tested against a panel of 50 sera from patients with paracoccidioidomycosis by immunodiffusion test. The index of positivity varied from 20 to 100% according to the isolate. When these exoantigens were analysed by SDS-PAGE, eight presented high amounts of the glycoprotein gp43, two presented small amounts and in three there was no detectable gp43. The eight isolates presenting high amounts of gp43 were submitted to isoelectric focusing, blotted to nitrocellulose membranes, and revealed by monoclonal and polyclonal anti-gp43 antibodies. Four gp43 isoform profiles were obtained: profile A presenting pIs of 6.0, 6.2, 6.6 and 7.0, profile B presenting pIs of 6.4, 6.8 and 7.2, profile C presenting pI > 8.5 and profile D, presenting pIs of 5.8, 6.2 and 6.6. In each pattern observed, a major band with a distinct pI was detected. Despite this variation, our results strongly suggest an epitopic conservation among all isoforms analysed, since all of them were recognized by anti-gp43 monoclonal antibodies.