Characterization of gp70 and anti-gp70 monoclonal antibodies in Paracoccidioides brasiliensis pathogenesis

Intercellular adhesion molecule-1 is required for the early formation of granulomas and participates in the resistance of mice to the infection with the fungus Paracoccidioides brasiliensis

The migration of leukocytes to inflammatory sites elicited by Paracoccidioides brasiliensis is supposed to be coordinated by cytokines and chemokines. Here, we investigated the role of intercellular adhesion molecule-1 (ICAM-1) in recruiting inflammatory cells to lungs of mice infected with P. brasiliensis and in determining the outcome of the disease. Expression of ICAM-1 was up-regulated on T lymphocytes after infection with the fungus, and its expression was dependent on interferon-gamma, tumor necrosis factor-alpha, and interleukin-12. Moreover, the absence of ICAM-1 resulted in high susceptibility to the infection and delayed formation of granulomatous lesions. In addition, the absence of ICAM-1 resulted in increased growth and dissemination of fungus, decreased number of CD3+CD4+ and CD3+CD8+ T cells, and increased production of interleukin-4 in the inflammatory site. The organization of a granulomatous reaction in mice deficient of ICAM-1 was delayed, starting only on day 60 after infection, whereas in wild-type mice it was complete on day 30 of infection. These data show that ICAM-1 is effectively involved in cellular migration and in the organization of the granulomatous lesion caused by the fungus P. brasiliensis.

Diagnosis of Paracoccidioidomycosis by detection of antigen and antibody in bronchoalveolar lavage fluids

Paracoccidioidomycosis (PCM) is a systemic infection caused by the fungus Paracoccidioides brasiliensis and is believed to be the leading cause of fungal pulmonary infection. In this study, we used an inhibition enzyme-linked immunosorbent assay to diagnose pulmonary PCM based on the detection of 43-kDa and 70-kDa molecules in bronchoalveolar lavage fluids. The results were compared with results obtained by classical methods for antibody detection.

Defining Virulence Genes in the Dimorphic Fungi

Most dimorphic fungal pathogens cause respiratory disease in mammals and must therefore possess virulence mechanisms to combat and overcome host pulmonary defenses. Over the past decade, advances in genetic tools have made it possible to investigate the basis of dimorphic fungal pathogenesis at the molecular level. Gene disruptions and RNA interference have now formally demonstrated the involvement of six virulence factors: CBP, alpha-(1,3)-glucan, BAD1, SOWgp, Mep1, and urease. Additional candidate virulence-associated genes have been identified on the premise that factors necessary for pathogenicity are associated specifically with the parasitic form. This principle continues to form the foundation for genomics-based analyses to further augment the list. Thus, the stage is set and the tools are in place for the next phase of medical mycology research: defining the virulence-associated factors underlying the success of dimorphic fungal pathogens.

Hybridoma passage in vitro may result in reduced ability of antimannan antibody to protect against disseminated candidiasis

We previously reported the enhanced resistance of monoclonal antibodies B6.1 (an immunoglobulin M [IgM]) and C3.1 (an IgG3) against experimental candidiasis. Both MAbs recognize the same fungal epitope. We have since found that a highly passaged B6.1 hybridoma (hp-B6.1) resulted in antibody that has little protective potential. The potential clinical applicability of the antibody and our interest in understanding antibody protection against candidiasis led us to investigate an explanation for this phenomenon. Antibody genetic structure of hp-B6.1, the original hybridoma clone (ori-B6.1) stored frozen since 1995, a subclone of hp-B6.1 that produces protective antibody, the IgG3-producing hybridoma, and a nonprotective IgG1-producing hybridoma were compared. Variable region gene sequences of heavy (V(H)) and light chains showed genetic instability of V(H) chains with only the hp-B6.1; the V(H) sequences from ori-B6.1 and the subclone were, however, identical. Activation-induced cytidine deaminase levels were greatest in the B6.1 hybridomas, which may explain the instability. The constant region CH3 domain remained unchanged, implying normal N-glycation and complement-fixing potential, and antibody binding affinities appeared unchanged. Complement fixation assays surprisingly showed that ori-B6.1 antibody fixes C3 more rapidly than does hp-B6.1 antibody. The V(H) region primary structure may affect complement activation, which could explain our result. Indeed, antibody from the hp-B6.1 subclone fixed complement like antibody from ori-B6.1. These results show that the greatest protection occurs when antimannan antibodies possess the dual abilities of recognizing the appropriate carbohydrate epitope and rapidly fixing complement; loss of the latter property results in the loss of protective potential by the antibody.

Importance of complement 3 and mannose receptors in phagocytosis ofParacoccidioides brasiliensisconidia byNramp1congenic macrophages lines

Genetic factors influence susceptibility to Paracoccidioidomycosis, a Latin American endemic mycosis. The pattern of susceptibility of congenic mouse strains infected with Paracoccidioides brasiliensis resembles the pattern of the Nramp1 gene. Thus, congenic murine bone-marrow-derived macrophage lines B10R (Nramp1rGly169) and B10S (null Nramp1 protein expression, Nramp1sAsp169) were infected with P. brasiliensis conidia and compared, under opsonic and nonopsonic conditions. Opsonization increased the percentage of phagocytosis by both cell lines. B10R macrophages exhibited a higher percentage of cells with associated conidia and higher number of conidia per macrophage than B10S. Heat-inactivation and EDTA treatment of serum used for opsonization, and treatment of macrophages with anti-complement receptor 3 (CR3) decreased phagocytosis by both cell lines. alpha-methyl-d-mannoside reduced phagocytosis by B10R macrophages, suggesting that the mannose receptor participates in phagocytosis by these cells. The CR3 expression was similar on both cell lines and B10R expressed more mannose receptors, but neither cell line expressed CR1. IFNgamma decreased the conversion of conidia to the yeast form of P. brasiliensis in B10R, but not in B10S macrophages.

Paracoccin, a GlcNAc-binding lectin from Paracoccidioides brasiliensis, binds to laminin and induces TNF-α production by macrophages

Paracoccidioides brasiliensis components interact with host cells and can influence the pathogenesis of paracoccidioidomycosis (PCM). Among the components released by P. brasiliensis, gp 43 and a heavily glycosylated antigen with MM>160 kDa are the most recognized by serum antibodies from patients with PCM. In order to isolate the high MM glycoconjugate, we carried out affinity chromatography of a crude exoantigen preparation on immobilized jacalin. The bound fraction (JBE, jacalin binding exoantigen) consisted of a major antigen of high MM and frequently of an additional 70-kDa minor protein. This protein, designated paracoccin, exhibited selective binding to immobilized GlcNAc, a property that was used for its purification. The structural data of paracoccin obtained by mass spectrometry of tryptic peptides did not match any known protein. Anti-paracoccin serum localized the lectin on the surface of P. brasiliensis yeasts, especially in the budding regions. Paracoccin was able to interact with laminin in a dose-dependent manner. This interaction was inhibited by GlcNAc, followed by D-glucose and D-mannose, but not by D-galactose, N-acetyl-galactosamine or L-fucose. Interestingly, paracoccin induced both resident and elicited mouse peritoneal cavity macrophages to release high and persistent levels of TNF-alpha in vitro, a fact that was associated with high nitric oxide production in elicited cells. Because binding to laminin can favor yeast adhesion and invasion of host tissues, and overproduction of NO has been associated with suppression of cell immunity, paracoccin is suggested to play an important role in PCM pathogenesis.

Granuloma formation in vitro requires B-1 cells and is modulated by Paracoccidioides brasiliensis gp43 antigen

The mechanisms that determine granuloma formation and the significance of this type of inflammatory response in the pathogenesis of fungal diseases such as paracoccidioidomycosis are far from fully understood. We developed a granuloma model in vitro using beads to evaluate the role of isolated mouse peritoneal macrophages and B-1 cells. We also investigated granuloma formation in the presence of gp43, the main antigenic component of Paracoccidioides brasiliensis, which is secreted exocellularly. To determine whether B-1 cells, macrophages, or both, participate in granuloma formation, peritoneal cells from Xid mice, which lack B-1 cells, were used. Granuloma-like structures were not formed with Xid peritoneal cells or with cells from wild type mice that had their peritoneal and pleural cavities irradiated before the cultures were established. Granulomas were observed either when total adherent peritoneal cells or when isolated B-1 cells were added to macrophage cultures. The data strongly suggest that an interaction of B-1 cells and macrophages plays an important role in granuloma-like formation in this experimental model and that the presence of gp43 strongly stimulates this response.

B1 cells contribution to susceptibility in experimental paracoccidioidomycosis: immunoglobulin isotypes and repertoire determination

Paracoccidioidomycosis (PCM) is the most prevalent systemic mycosis in Latin America. The experimental murine model has been used to approach the disease, with susceptible and resistant mice strains that reproduce most of the main human immunological features. Since the hypergammaglobulinemia observed in susceptible mice and humans might have an influence on B1 cells, we investigated its role during the experimental infection with Paracoccidiodes brasiliensis. CBA/Nxid mice, deficient in B1 cells, and CBA/Nxid reconstituted with B1 cells isolated from the non-mutant CBA/J strain were infected with 106 yeast forms of P. brasiliensis. At the 8th and 22nd week post infection the DTH response of CBA/Nxid mice was significantly higher after 24 h of P. brasiliensis antigens inoculation and the specific humoral response was reduced, in comparison to CBA/J or recCBA/Nxid. Production of NAbs is a hallmark of the B1 subset. Higher Ig productions to auto antigens such as DNA, MBP and RBC were observed in CBA/J infected mice or recCBA/Nxid. Anti P. brasiliensis IgG2a was produced by CBA/Nxid mice early in infection, while CBA/J or recCBA/Nxid presented increased levels of this isotype only after the 8th week of infection. Furthermore, western blotting analysis showed that CBA/Nxid mice expanded less clones against P. brasiliensis antigens, with weakly detectable anti-gp43 antibodies while CBA/J mice produce IgM anti-gp43 at the 2nd week of infection and IgG anti-gp43 at the 2nd and 8th week. On the other hand, recognition of gp70, a fungal antigen that, as gp43, inhibits macrophage activation was not compromised in B1 deficient mice. These results suggest that B1 cells might have influence in the kinetic of production of protective isotypes of immunoglobulins and their repertoire that could contribute to an early drive towards a Th2 response, affecting the cellular response in susceptible mice during experimental paracoccidiodomycosis.

Functional genome of the human pathogenic fungus Paracoccidioides brasiliensis

Paracoccidioides brasiliensis is a dimorphic and thermo-regulated fungus which is the causative agent of paracoccidioidomycosis, an endemic disease widespread in Latin America. Pathogenicity is assumed to be a consequence of the cellular differentiation process that this fungus undergoes from mycelium to yeast cells during human infection. In an effort to elucidate the molecular mechanisms involved in this process a network of Brazilian laboratories carried out a transcriptome project for both cell types. This review focuses on the data analysis yielding a comprehensive view of the fungal metabolism and the molecular adaptations during dimorphism in P. brasiliensis from analysis of 6022 groups, related to expressed genes, which were generated from both mycelium and yeast phases.

Diagnosis of neuroparacoccidioidomycosis by detection of circulating antigen and antibody in cerebrospinal fluid

Neuroparacoccidioidomycosis (neuroPCM) is the central nervous system infection by the fungus Paracoccidioides brasiliensis. Its diagnosis is a difficult task that depends on neuroimaging techniques such as computed tomography and magnetic resonance imaging. However, the detection of circulating P. brasiliensis antigens in body fluids by inhibition enzyme-linked immunosorbent assay (inh-ELISA) has provided encouraging results. In this study, 14 cerebrospinal fluid (CSF) and 11 serum samples of patients with neuroPCM were analyzed by inh-ELISA for detection of circulating glycoprotein antigens of 43 kDa (gp43) and 70 kDa (gp70). Circulating gp43 and gp70 antigens were detected in all CSF samples from patients with neuroPCM at mean concentrations of 19.3 and 6.8 mug/ml, respectively. In addition, both gp43 and gp70 antigens were detected in 10 of 11 serum samples analyzed at mean concentrations of 4.6 and 4.0 mug/ml, respectively. By immunodiffusion test, CSF samples were determined to be negative in 13 of 14 samples. The detection of anti-gp43 and anti-gp70 antibodies by conventional ELISA showed positive results for all CSF samples, with titers ranging from 1:50 to 1:51,200. Therefore, the high sensitivity of the inh-ELISA technique in detecting gp43 and gp70 antigens in the CSF of neuroPCM patients strongly indicates that this assay can be considered as a powerful diagnostic tool. In addition, the finding of anti-gp43 and anti-gp70 antibodies in CSF samples by conventional ELISA also seems to be a promising diagnostic method for this special modality of PCM.

Atypical serological response marked by a lack of detectable anti-gp43 antibodies in a patient with disseminated paracoccidioidomycosis

Serological tests are frequently used to diagnosis paracoccidioidomycosis. A glycoprotein of 43 kDa is considered to be the main diagnostic antigen, being recognized by virtually all patients' sera. A case of atypical serological response, consisting of a lack of detectable anti-gp43 antibodies, in a patient with disseminated paracoccidioidomycosis is presented.

Detection of Paracoccidioides brasiliensis gp70 circulating antigen and follow-up of patients undergoing antimycotic therapy

Paracoccidioidomycosis (PCM), one of the most important systemic mycoses in Central and South America, is caused by the dimorphic fungus Paracoccidioides brasiliensis and has a high prevalence in Brazil. Glycoproteins of 43 and 70 kDa are the main antigenic compounds of P. brasiliensis and are recognized by Western blotting by 100 and 96% of PCM patient sera, respectively. In the present study, an inhibition enzyme-linked immunosorbent assay (ELISA) was used to detect gp70 in different biological samples from patients with PCM. gp70 was detected in 98.76% of 81 serum samples, with an average concentration of 8.19 microg/ml. The test was positive for 100% of the patients with the acute and chronic unifocal forms of PCM and 98.43% of the patients with the multifocal chronic form, with average concentrations of 11.86, 4.83, and 7.87 microg/ml, respectively. Bronchoalveolar lavage fluid from 23 patients with pulmonary unifocal PCM and 14 samples of cerebrospinal fluid from patients with neurological PCM were also tested for gp70 detection, with the test showing 100% sensitivity and 100% specificity, with mean gp70 concentrations of 7.5 and 6.78 microg/ml, respectively. To investigate the potential of gp70 detection by inhibition ELISA for the follow-up of PCM patients during antimycotic therapy with itraconazole (ITZ), the sera of 23 patients presenting with the chronic multifocal form of PCM were monitored at regular intervals of 1 month for 12 months. The results showed a decrease in circulating gp70 levels during treatment which paralleled the reduction in anti-P. brasiliensis antibody levels. The detection of P. brasiliensis gp70 from the biological fluids of patients suspected of having PCM proved to be a promising method for diagnosing infection and evaluating the efficacy of ITZ treatment.