Evaluation of IFN-γ secretion after stimulation with C. neoformans and C. gattii antigens in individuals with frequent exposure to the fungus

In this study we produced antigenic extracts from prototypical strains of C. neoformans (VNI-VNIV) and C. gattii (VGI-VGIV) and tested IFN-γ secretion by Elispot. Antigens from the eight Cryptococcus molecular types (VNI -VNIV and VGI - VGIV) were obtained after capsule reduction. IFN-γ secretion by Elispot method were stimulated with C. neoformans and C. gattii antigens. Peripheral blood mononuclear cells of fourteen healthy control subjects, being: five ecotourists, two mycologists, three poultry keepers, and four individuals without reports of exposure to the fungus. We observed a significant increase in IFN-γ secretion in the group of ecotourists, mycologists and bird keepers in relation to the group of individuals without reports of occupational exposures to these agents. Our results suggest the significant increase in IFN-γ secretion may be related to the continuous exposure of these groups of individuals to the fungus, as well as to the specific antigen memory immune response developed during exposure to Cryptococcus.

Metabolomics and Machine Learning Approaches Combined in Pursuit for More Accurate Paracoccidioidomycosis Diagnoses

Brazil and many other Latin American countries are areas of endemicity for different neglected diseases, and the fungal infection paracoccidioidomycosis (PCM) is one of them. Among the clinical manifestations, pneumopathy associated with skin and mucosal lesions is the most frequent. PCM definitive diagnosis depends on yeast microscopic visualization and immunological tests, but both present ambiguous results and difficulty in differentiating PCM from other fungal infections. This research has employed metabolomics analysis through high-resolution mass spectrometry to identify PCM biomarkers in serum samples in order to improve diagnosis for this debilitating disease. To upgrade the biomarker selection, machine learning approaches, using Random Forest classifiers, were combined with metabolomics data analysis. The proposed combination of these two analytical methods resulted in the identification of a set of 19 PCM biomarkers that show accuracy of 97.1%, specificity of 100%, and sensitivity of 94.1%. The obtained results are promising and present great potential to improve PCM definitive diagnosis and adequate pharmacological treatment, reducing the incidence of PCM sequelae and resulting in a better quality of life.IMPORTANCE Paracoccidioidomycosis (PCM) is a fungal infection typically found in Latin American countries, especially in Brazil. The identification of this disease is based on techniques that may fail sometimes. Intending to improve PCM detection in patient samples, this study used the combination of two of the newest technologies, artificial intelligence and metabolomics. This combination allowed PCM detection, independently of disease form, through identification of a set of molecules present in patients' blood. The great difference in this research was the ability to detect disease with better confidence than the routine methods employed today. Another important point is that among the molecules, it was possible to identify some indicators of contamination and other infection that might worsen patients' condition. Thus, the present work shows a great potential to improve PCM diagnosis and even disease management, considering the possibility to identify concomitant harmful factors.

Case Report: Misleading Serological Diagnosis of Paracoccidioidomycosis in a Young Patient with the Acute Form Disease: Paracoccidioides brasiliensis or Paracoccidioides lutzii?

Negative results in serological routine screening of patients with microbiologically proven Paracoccidioidomycosis (PCM) are occasionally reported. Failure in detecting anti-Paracoccidioides antibodies has been ascribed to factors either related to serological techniques or to the status of the host immune reactivity. Recently, this issue has been renewed by the recognition that the Paracoccidioides genera comprises two species, lutzii and brasiliensis, which have distinct antigenic profiles and, therefore, may elicit different host antibody responses. We describe a patient with the acute form PCM due to Paracoccidioides brasiliensis with negative results on two reference centers' routine screening for P. brasiliensis antibodies, but positive results with Paracoccidioides lutzii antigens. The present case report suggests that antibodies elicited during P. brasiliensis infection recognize antigenic fractions shared by both species, highlighting the difficulties in distinguishing the two infections by means of the currently available routine serological assays.

Comparison of diagnostic methods to detect Histoplasma capsulatum in serum and blood samples from AIDS patients

BACKGROUND

Although early and rapid detection of histoplasmosis is essential to prevent morbidity and mortality, few diagnostic tools are available in resource-limited areas, especially where it is endemic and HIV/AIDS is also epidemic. Thus, we compared conventional and molecular methods to detect Histoplasma capsulatum in sera and blood from HIV/AIDS patients.

METHODOLOGY

We collected a total of 40 samples from control volunteers and patients suspected of histoplasmosis, some of whom were also infected with other pathogens. Samples were then analyzed by mycological, serological, and molecular methods, and stratified as histoplasmostic with (group I) or without AIDS (group II), uninfected (group III), and infected with HIV and other pathogens only (group IV). All patients were receiving treatment for histoplasmosis and other infections at the time of sample collection.

RESULTS

Comparison of conventional methods with nested PCR using primers against H. capsulatum 18S rRNA (HC18S), 5.8S rRNA ITS (HC5.8S-ITS), and a 100 kDa protein (HC100) revealed that sensitivity against sera was highest for PCR with HC5.8S-ITS, followed by immunoblotting, double immunodiffusion, PCR with HC18S, and PCR with HC100. Specificity was equally high for double immunodiffusion, immunoblotting and PCR with HC100, followed for PCR with HC18S and HC5.8-ITS. Against blood, sensitivity was highest for PCR with HC5.8S-ITS, followed by PCR with HC18S, Giemsa staining, and PCR with HC100. Specificity was highest for Giemsa staining and PCR with HC100, followed by PCR with HC18S and HC5.8S-ITS. PCR was less efficient in patients with immunodeficiency due to HIV/AIDS and/or related diseases.

CONCLUSION

Molecular techniques may detect histoplasmosis even in cases with negative serology and mycology, potentially enabling early diagnosis.

Fast protocol for the production of Histoplasma capsulatum antigens for antibody detection in the immunodiagnosis of histoplasmosis

BACKGROUND

Current methods for the production of Histoplasma capsulatum antigens are problematic in terms of standardization, specificity, stability, repeatability and reproducibility.

AIMS

In this study, we sought to optimize the methodology for producing H. capsulatum antigens, and to evaluate its applicability.

METHODS

Antigenic preparations obtained from 12 H. capsulatum isolates were evaluated by double immunodiffusion and immunoblotting assays against homologous and heterologous sera.

RESULTS

The evaluated and optimized protocol allowed a more stable production, as well as repeatable, reproducible, with shorter culture time and less costly. By double immunodiffusion and immunoblotting assays, the best pattern of reactivity was observed for antigens obtained with 33 days of culture from the isolates 200 and 406 against the M antigen and for the isolate 200 with 15 days against H antigen. The SDS-PAGE presented antigenic components of molecular masses between 17 and 119kDa. The immunoblotting sensitivity was 95.5% and 100% with histoplasmosis sera from ill patients and sera from H. capsulatum infected but otherwise healthy patients, respectively, to the antigen derived from isolates 200 and 406.

CONCLUSIONS

We suggest the employment of the antigen from isolate 200, with 15 or 30 days of culture, in the double immunodiffusion and immunoblotting assays due to its good ability to discriminate both sera from patients with histoplasmosis illness and histoplasmosis infection, in addition to its high specificity against heterologous sera.

Standardization and validation of Dot-ELISA assay for Paracoccidioides brasiliensis antibody detection

Background

Paracoccidioidomycosis (PCM) is a neglected systemic mycosis caused by a dimorphic fungus of the Paracoccidioides genus. The standard diagnosis is based on isolation of the fungi in culture, and by microscopic visualization of characteristic multiple budding yeast cells in biological samples. However, in some situations, access to the site of injury prevents the collection of biological material. A variety of immuno-serological techniques has proven useful for allowing inferring diagnosis with a certain degree of certainty, thus optimizing time. The aim of this study was to standardize and validate the Dot-ELISA (DE) assay, comparing it with the serological standard, double immunodiffusion (DI).

Methods

In order to standardize the DE assay, 143 serum samples were used. Out of those, 23 were from apparently healthy patients, 77 were from patients with confirmed PCM and 43 were from patients with other lung infections (tuberculosis, aspergillosis and histoplasmosis). To validate the DE technique, 300 serum samples from patients with PCM clinical suspicion (probable and possible cases) were employed, and these results were compared with those of DI.

Results

The DE assay showed sensitivity of 91%, specificity of 95.4%, positive predictive value of 96%, negative predictive value of 98.2%, accuracy of 93%, and great precision (k = 0.93). In addition, the nitrocellulose membranes have proved to be viable for using at least 90 days after P. brasiliensis B-339 antigen sensitization.

Conclusion

Dot-ELISA method was found to be an extremely promising tool as serologic screening technique, because of its high sensitivity. Furthermore, Dot-ELISA shows the prospect of being transferred to laboratories of mycoserology including those with fewer resources or even to be used directly in the field. It has an excellent shelf life – membranes coated with antigen can be used for testing without changes in the pattern of reactivity among laboratories – and presents reliable values of sensitivity, specificity, predictive values, accuracy and a high correlation with the serological standard methodology. Based on the present findings, it possible to state that this technique constitutes a remarkable option to be used in routine diagnosis for public health centers.

Immunological assays employed for the elucidation of an histoplasmosis outbreak in São Paulo, SP

Several reports showed outbreaks of histoplasmosis acquired while bat-inhabited caves were visited by tourists, miners or researchers. We evaluated the performance of double immunodifusion (DI) and immunoblotting (IB) assays, employed for the histoplasmosis outbreak elucidation occurred in Vale do Paraíba, São Paulo. The existence of epidemiologic link, four patients with clinical signs suggestive of histoplasmosis and mycological confirmation has made that all 35 individuals involved to the cave visit were subjected to serological evaluation. By DI, we observed reactivity against H. capsulatum antigen in a single serum examined nearly 20 days after exposure to fungal propagules. On the other hand, IB showed reactivity against H and M fractions in 50% of samples evaluated. The analysis of the second sample batch, collected two months after the exposure showed that 96.7% were reactive by DI with antibodies titers ranging from 1 to 16 and 100% of reactivity against H and M fractions, by IB, suggesting an acute infection. The analysis of the overall agreement between the methods showed to be reasonable (κ = 0.37). This study confirms the importance and efficacy of more sensitive methodologies, such as IB assay, to early elucidation of disease, especially in cases of patients without mycological information.

Importance of the association of molecular and immunological diagnosis in immunocompetent patient with Histoplasma capsulatum and Cryptoccocus neoformans infection: a case report

This case reports an immunocompetent 29-year-old woman with suspected pneumonia, suggestive of fungal infection. Immunoblotting analysis reactivity against Histoplasma capsulatum and Paracoccidioides brasiliensis were observed. Nested-PCR in blood employing species-specific primers was positive for H. capsulatum and Cryptococcus neoformans. The evaluation of paucisymptomatic patients with positive results for H. capsulatum and C. neoformans could be relevant for the prevention as well as the possible evaluation of the reactivated quiescent foci. In conclusion, the associated methodology may have contributed to the monitoring endogenous reactivation of these diseases.

Prevalence and serological diagnosis of relapse in paracoccidioidomycosis patients

A review of 400 clinical records of paracoccidioidomycosis (PCM) patients, 93 with the acute/subacute (AF) and 307 with the chronic form (CF), attended from 1977 to 2011, selected as to the schedule of release for study by the Office of Medical Records at the University Hospital of the Faculdade de Medicina de Botucatu-São Paulo State University--UNESP, was performed to detect cases in relapse. The control of cure was performed by clinical and serological evaluation using the double agar gel immunodiffusion test (DID). In the diagnosis of relapse, DID, enzyme-linked immunosorbent assay (ELISA) and immunoblotting assay (IBgp70 and IBgp43) were evaluated. Out of 400 patients, 21 (5.2%) went through relapse, 18 of them were male and 3 were female, 6∶1 male/female ratio. Out of the 21 patients in relapse, 15 (4.8%) showed the CF, and 6 (6.4%) the AF (p>0.05). The sensitivity of DID and ELISA before treatment was the same (76.1%). DID presented higher sensitivity in pre-treatment (80%) than at relapse (45%; p = 0.017), while ELISA showed the same sensitivity (80% vs 65%; p = 0.125). The serological methods for identifying PCM patients in relapse showed low rates of sensitivity, from 12.5% in IBgp70 to 65.0% in IBgp43 identification and 68.8% in ELISA. The sensitivity of ELISA in diagnosing PCM relapse showed a strong tendency to be higher than DID (p = 0.06) and is equal to IBgp43 (p = 0.11). In sum, prevalence of relapse was not high in PCM patients whose treatment duration was based on immunological parameters. However, the used methods for serological diagnosis present low sensitivity. While more accurate serological methods are not available, we pay special attention to the mycological and histopathological diagnosis of PCM relapse. Hence, direct mycological, cytopathological, and histopathological examinations and isolation in culture for P. brasiliensis must be appropriately and routinely performed when the hypothesis of relapse is considered.

Chronic paracoccidioidomycosis of the intestine as single organ involvement points to an alternative pathogenesis of the mycosis

Current knowledge on the natural history of paracoccidioidomycosis states that the chronic form of the disease results from reactivation of quiescent foci established years or decades before during the primary lung infection. Once reactivated, the fungi can disseminate to virtually any organ or system. We present herein two chronic paracoccidioidomycosis patients with a single organ involvement that points to an alternative pathogenesis of the mycosis. These patients suggest that the chronic form may also arise from reactivation of foci not confined to the lungs, due to the early dissemination of yeast cells during the primary infection.

Cryptic species of Paracoccidioides brasiliensis: impact on paracoccidioidomycosis immunodiagnosis

We aimed to evaluate whether the occurrence of cryptic species of Paracoccidioides brasiliensis, S1, PS2, PS3 and Paracoccidioides lutzii, has implications in the immunodiagnosis of paracoccidioidomycosis (PCM). Small quantities of the antigen gp43 were found in culture filtrates of P. lutzii strains and this molecule appeared to be more variable within P. lutzii because the synonymous-nonsynonymous mutation rate was lower, indicating an evolutionary process different from that of the remaining genotypes. The production of gp43 also varied between isolates belonging to the same species, indicating that speciation events are important, but not sufficient to fully explain the diversity in the production of this antigen. The culture filtrate antigen AgEpm83, which was obtained from a PS3 isolate, showed large quantities of gp43 and reactivity by immunodiffusion assays, similar to the standard antigen (AgB-339) from an S1 isolate. Furthermore, AgEpm83 was capable of serologically differentiating five serum samples from patients from the Botucatu and Jundiaí regions. These patients had confirmed PCM but, were non-reactive to the standard antigen, thus demonstrating an alternative for serological diagnosis in regions in which S1 and PS2 occur. We also emphasise that it is not advisable to use a single antigen preparation to diagnose PCM, a disease that is caused by highly diverse pathogens.

Reactivity of antibodies from patients with acute and chronic paracoccidioidomycosis to a high molecular mass antigen from Paracoccidioides brasiliensis

Yeast forms of Paracoccidioides brasiliensis produce polydispersed high molecular mass (h-MM) antigens. We investigated the antibodies to an h-MM antigen from P. brasiliensis by immunoblotting and ELISA in sera from paracoccidioidomycosis (PCM) patients. IgG from the sera of chronic PCM patients was able to recognize the h-MM antigen at a higher frequency in the cell-free antigen (CFA) (8/13) than in the somatic antigen (SA) (2/13), as assessed by immunoblotting. The CFA was fractionated by Sephadex G-200 chromatography, and fraction 17 (F17) with the h-MM antigen of approximately 366 kDa was used in ELISA to analyze specific levels of IgG and IgE. Patients with the chronic form showed significantly higher levels of IgG (P<0.05) but not IgE (P>0.05) to F17 by ELISA, compared to patients with the acute form or to healthy donors. In conclusion, CFA is better than SA as a source of the P. brasiliensis h-MM antigen. This study reveals a new characteristic to differentiate between the acute and chronic forms of PCM, by demonstrating a higher level of seric IgG to h-MM antigen in chronic compared to acute PCM patients.

Laminin-binding epitope on gp43 from Paracoccidioides brasiliensis is recognized by a monoclonal antibody raised against Staphylococcus aureus laminin receptor

Adhesion is regarded as an important step in the pathogenesis of several microorganisms. Thus, the ability to recognize extracellular matrix proteins, such as laminin or fibronectin, has been correlated with invasiveness. Studying the already characterized laminin-binding protein of Paracoccidioides brasiliensis, the 43 kDa glycoprotein (gp43), we evaluated whether MAb 1.H12, raised against the laminin-binding protein from Staphylococcus aureus, cross-reacts with that fungal protein. By immunoblot analysis we show that MAb 1.H12 recognizes gp43. This interaction is able to inhibit the laminin-mediated adhesion to epithelial cells as well as the P. brasiliensis infection in vivo. Moreover, through immunoenzymatic assays, we show that MAb 1.H12 recognizes gp43 in solid phase and that this interaction is partially inhibited by the addition of anti-gp43 MAbs. These results show that MAb 1.H12 recognizes the gp43, suggesting the presence of an epitope similar to those found in the other laminin-binding proteins from phylogenetically very distant cells. These findings reinforce the possibility of evolutionary conservation of such epitopes.

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.

Monoclonal antibody capture enzyme immunoassay for detection of Paracoccidioides brasiliensis antibodies in paracoccidioidomycosis

Four murine monoclonal antibodies (MAbs 17C, 21A, 21F, and 32B) raised against the 43-kDa glycoprotein of Paracoccidioides brasiliensis were tested in a capture enzyme immunoassay (EIA) for the detection of specific human anti-gp43 immunoglobulin G in patients with paracoccidioidomycosis (PCM). All MAbs reacted similarly in the assay. These MAbs, which detected anti-gp43 at levels of as low as 500 pg/ml, were demonstrated to specifically recognize at least two different epitopes in gp43 binding assays. Specific antibodies in the sera of patients with active PCM were detected at dilutions of as high as 1:819,200, and the reactivities of patient sera, as measured by optical densities, were found to be significantly higher than those of control sera. The comparison between classical ELISA and our capture enzyme immunoassay showed that both sensitivity and specificity were greatly improved by the latter. These MAbs represent the first specific reagents to P. brasiliensis described for use in serological tests for PCM.

Characterization of glycoprotein gp43, the major laminin-binding protein of Paracoccidioides brasiliensis

We have demonstrated that laminin mediates the adhesion of P. brasiliensis to monolayers of epithelial cells through specific binding to the surface glycoprotein gp43. This binding seems to be related to the fungal pathogenesis. We now report the confirmation of these findings by scanning electron microscopy and show that some isolates that do not secrete gp43 do express the protein as seen by studying whole cell extracts. These results confirm the ability of these strains to produce paracoccidioidomycosis but should not be used for serological purposes since the absence of gp43 in exoantigens may lead to false negative results.

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

Extracellular matrix protein laminin binds specifically to yeast forms of Paracoccidioides brasiliensis and enhances adhesion of the fungus to the surface of epithelial Madin-Darby canine kidney cells in vitro. Immunoblotting of fungal extracts showed that the gp43 glycoprotein is responsible for adhesion. This was confirmed by binding assays using purified gp43, with a Kd of 3.7 nM. The coating of P. brasiliensis yeast forms with laminin before injection into hamster testicles enhanced the fungus virulence, resulting in a faster and more severe granulomatous disease. These results indicate that interaction of fungi with extracellular matrix elements may constitute a basis for the evolution of fungal infection toward regional spreading and dissemination.