Paracoccidioides and Paracoccidioidomycosis in the 21st Century

Multiple Tolerization Subtractive Immunization in the Obtention of Specific Monoclonal Antibodies Against Paracoccidioides lutzii

Paracoccidioidomycosis (PCM) is a chronic endemic mycosis in Latin America, predominantly caused by Paracoccidioides brasiliensis (Pb18) and Paracoccidioides lutzii (Pl01). Diagnosing PCM is challenging due to species-specific antigenic differences, therefore new biomarkers for accurate and rapid detection are needed. This study explores multiple tolerization subtractive immunization (MTSI) to generate monoclonal antibodies against rare or weakly expressed epitopes of Pb18 and Pl01, potentially improving PCM diagnosis. These strains were cultured to obtain cell-free antigens (CFA). MTSI involved immunizing BALB/c mice with CFA from Pb18 as a tolerogen and Pl01 as an immunogen, using Freund's adjuvant and cyclophosphamide to induce immune tolerance. The immune response was monitored via Enzyme-linked immunosorbent assay (ELISA) and Western blotting. Hybridomas were generated by fusing splenocytes from immunized mice with myeloma cells, after which clonal selection was conducted based on reactivity to Pl01 antigens. The study explores the presence of various proteins, including gp43 and Hsp60, in the protein profile of CFAs. Additionally, polyclonal antibody reactivity to Pb18 antigens was significantly reduced, suggesting that MTSI effectively promoted immunological tolerance. Followig the screening of hybridomas, clones with good reactivity to Pl01 and less reactive to Pb18 were selected. The monoclonal clones C1 and E6 exhibited potential specificity for Pl01 antigens. The effective generation of P. lutzii-specific antibodies by MTSI demonstrates this technology's promise for the development of accurate PCM diagnostic instruments. These antibodies have the potential to enhance patient outcomes and reduce the incidence of false-negative diagnoses, which could lead to better disease management.

Comparison between PCR-RFLP and sequencing techniques in the analysis of Paracoccidioides spp. biodiversity: limitations and insights into species and variant differentiation

BACKGROUND

The study of Paracoccidioides spp. faces significant challenges due to limitations inherent in the molecular biology techniques employed. Recently, new species were described whose geographical and genetic distributions were investigated. The phylogenetic studies have revealed that genotypes originally thought to be exclusive in specific regions from South American countries are now being found in other areas of the continent. This finding indicates a broader geographic distribution of these genotypes than previously recognized.

OBJECTIVE

To evaluate two molecular biology techniques employed to identify genotypes of Paracoccidioides spp. strains from a Brazilian culture collection previously identified only by mycological methods.

METHODS

DNA samples from 35 Paracoccidioides spp. strains maintained in a Brazilian culture collection were subjected to amplification and enzymatic digestion with PCR-RFLP of tub1 gene, followed by sequencing of gp43 Exon 2 loci. Strains with species identification discrepancies had their tub1 sequences determined to verify possible nucleotide mutations.

RESULTS

The genotypic characterization of Paracoccidioides spp. using PCR-RFLP of the tub1 gene identified 22 isolates as P. brasiliensis sensu stricto, two as P. americana, four as P. restrepiensis, and eight as P. lutzii. Sequencing of the gp43 Exon 2 loci revealed discrepancies in the identification of four P. venezuelensis isolates, previously characterized as P. brasiliensis sensu stricto by PCR-RFLP of tub1. The sequencing of tub1 from P. brasiliensis sensu stricto and P. venezuelensis isolates revealed nucleotide differences in the pyrimidine class (C and T) in their sequences, specifically at the position 176 bp.

CONCLUSION

These molecular tools were able to establish the genetic diversity within the Paracoccidioides genus, crucial for taxonomy and epidemiology studies. The finding of presence of P. venezuelensis in Brazil, previously thought to be exclusive to Venezuela, highlights genetic connections and evolutionary divergences within the genus. While the PCR-RFLP of tub1technique showed limitations in identifying P. venezuelensis, sequencing of the gp43 Exon 2 loci was able to accurately identify this genotype. Thus, our findings contribute to the understanding of the molecular epidemiology of PCM and emphasize the need for precise species characterization in mycological research.

Paracoccidioides spp.: Escape mechanisms and their implications for the development of this mycosis

Paracoccidioidomycosis (PCM) is a systemic granulomatous mycosis prevalent in individuals who carry out rural activities. Its etiological agent is a thermodimorphic fungus belonging to the genus; Paracoccidioides spp. Seven species of this fungus are known: Paracoccidioides brasiliensis, Paracoccidioides lutzii, Paracoccidioides americana, Paracoccidioides restrepiensis, Paracoccidioides venezuelensis, Paracoccidioides loboi and Paracoccidioides ceti. For a long time, Paracoccidioides brasiliensis was attributed as the only causal agent of this mycosis. What is known about adhesins, virulence, escape mechanisms and fungal involvement with the host's immune system is correlated with the species Paracoccidioides brasiliensis. Interactions between Paracoccidioides spp. and the host are complex and dynamic. The fungus needs nutrients for its needs and must adapt to a hostile environment, evading the host's immune system, thus enabling the development of the infectious process. On the other hand, the host's immune system recognizes Paracoccidioides spp. and employs all protective mechanisms to prevent fungal growth and consequently tissue invasion. Knowing this, understanding how Paracoccidioides spp. escapes the host's immune system, can help to understand the pathogenic mechanisms related to the development of the disease and, therefore, in the design of new specific treatment strategies. In this review we discuss these mechanisms and what are the adhesion molecules of Paracoccidioides spp. uses to escape the hostile environment imposed by the host's defense mechanisms; finally, we suggest how to neutralize them with new antifungal therapies.

Disseminated paracoccidioidomycosis in a captive western black-handed tamarin (Saguinus niger)

Paracoccidioidomycosis (PCM) is an endemic fungal disease that occurs in Latin America and primarily affects humans. The disease has been rarely documented in non-human primates. This report details a disseminated and fatal case of PCM caused by Paracoccidioides brasiliensis in a western black-handed tamarin (Saguinus niger) under human care. Histopathological examination revealed extensive pyogranulomatous inflammation in the lungs, spleen, liver, lymph nodes, kidneys, epididymis, right testicle, heart, adrenal gland and intestines, associated with characteristic yeast forms consistent with Paracoccidioides spp and confirmed by immunohistochemistry. Molecular analysis indicated a high nucleotide similarity with P. brasiliensis sequences for both the 18S rRNA and gp43 genes. This naturally occurring infection highlights the susceptibility of these animals to PCM and their role in ecoepidemiology warrants further investigation.

Diagnosis of Human Endemic Mycoses Caused by Thermally Dimorphic Fungi: From Classical to Molecular Methods

Human endemic mycoses are potentially fatal diseases caused by a diverse group of fungi that can alter their morphology in response to an increase in temperature. These thermally dimorphic fungi affect both healthy and immunocompromised hosts, causing a substantial health and economic burden. Despite this, the diagnosis of endemic mycoses is still a formidable challenge for several reasons, including similar symptomatology, limited utility of classical diagnostic methods, inaccessibility to reliable molecular approaches in most endemic areas, and a lack of clinical suspicion out of these regions. This review summarizes essential knowledge on thermally dimorphic fungi and the life-threatening diseases they cause. The principle, advantages and limitations of the methods traditionally used for their diagnosis are also described, along with the application status and future directions for the development of alternative diagnostic strategies, which could help to reduce the disease burden in endemic areas.

An axillary skin lesion revealing disseminated paracoccidioidomycosis

Paracoccidioidomycosis, uncommon in Europe, primarily affects South America travellers. We report a 58-year-old Colombian man, who has lived in France for 20 years, presented with an axillary skin lesion seven years after his last trip to Colombia. The diagnosis of paracoccidioidomycosis was established using histopathological, mycological and molecular analyses.

The WHO fungal priority pathogens list: a crucial reappraisal to review the prioritisation

In October, 2022, WHO published the first fungal priority pathogen list, which categorised 19 fungal entities into three priority groups (critical, high, and medium), for prioritisation of research efforts. The final ranking was determined via multiple criteria decision analysis, considering both research and development needs and perceived public health importance. In this Personal View, we discuss the positioning of the fungal pathogens, namely, Mucorales, Candida spp, Histoplasma spp, Coccidioides and Paracoccidioides spp, Fusarium spp, eumycetoma causative agents, Talaromyces marneffei, and Pneumocystis jirovecii, while expressing concerns about potential disparities between the WHO fungal priority pathogen list ranking and the actual disease burden associated with these pathogens. Finally, we propose a revised prioritisation list that also considers the regional disparities in the burden of fungal diseases.

Evaluation of commercial immunodiffusion reagents for detecting serum anti-Paracoccidioides antibodies

BACKGROUND

Accurate diagnosis of paracoccidioidomycosis is crucial for improving patient outcomes. Paracoccidioides antibody detection by double immunodiffusion (DID) is a convenient diagnostic tool, but testing performance can vary based on certain factors.

METHODS

We assessed DID performance using a commercially prepared Paracoccidioides reagents (IMMY, USA), involving 40 serum specimens, including 20 from patients with proven paracoccidioidomycosis and 20 from patients without the disease. The DID test demonstrated a sensitivity of 90% (95% CI=68%-99%) and a specificity of 100% (95% CI=83%-100%).

CONCLUSIONS

Our findings suggest that DID using commercial reagents may provide a feasible tool with satisfactory testing performance for anti-Paracoccidioides antibody detection.

Rapid Classification of Serum from Patients with Paracoccidioidomycosis Using Infrared Spectroscopy, Univariate Statistics, and Linear Discriminant Analysis (LDA)

Paracoccidioidomycosis (PCM) is a systemic mycosis that is diagnosed by visualizing the fungus in clinical samples or by other methods, like serological techniques. However, all PCM diagnostic methods have limitations. The aim of this study was to develop a diagnostic tool for PCM based on Fourier transform infrared (FTIR) spectroscopy. A total of 224 serum samples were included: 132 from PCM patients and 92 constituting the control group (50 from healthy blood donors and 42 from patients with other systemic mycoses). Samples were analyzed by attenuated total reflection (ATR) and a t-test was performed to find differences in the spectra of the two groups. The wavenumbers that had p < 0.05 had their diagnostic potential evaluated using receiver operating characteristic (ROC) curves. The spectral region with the lowest p value was used for variable selection through principal component analysis (PCA). The selected variables were used in a linear discriminant analysis (LDA). In univariate analysis, the ROC curves with the best performance were obtained in the region 1551-1095 cm-1. The wavenumber that had the highest AUC value was 1264 cm-1, achieving a sensitivity of 97.73%, specificity of 76.01%, and accuracy of 94.22%. The total separation of groups was obtained in the PCA performed with a spectral range of 1551-1095 cm-1. LDA performed with the eight wavenumbers with the greatest weight from the group discrimination in the PCA obtained 100% accuracy. The methodology proposed here is simple, fast, and highly accurate, proving its potential to be applied in the diagnosis of PCM. The proposed method is more accurate than the currently known diagnostic methods, which is particularly relevant for a neglected tropical mycosis such as paracoccidioidomycosis.

Human Lobomycosis Caused by Paracoccidioides (Lacazia) loboi, Panama, 2022

We report a patient from Panama who had lobomycosis caused by Paracoccidioides (Lacazia) loboi. We used combined clinical-epidemiologic and phylogenetic data, including a new gene sequence dataset on this fungus in Panama, for analysis. Findings contribute useful insights to limited knowledge of this fungal infection in the Mesoamerican Biologic Corridor.

The story of Paracoccidiodes gp43

This review is about Dr. Luiz Rodolpho Raja Gabaglia Travassos' scientific contributions to paracoccidioidomycosis as told by myself, Rosana Puccia, but co-written with Dr. Carlos P. Taborda, my younger scientific brother, collaborator, and dear friend. Dr. Travassos' pioneer papers and scientific insights covering biochemistry, immunology, cell biology, and molecular biology in the paracoccidiodomycosis area are key contributions that we acknowledge here, with focus on the Paracoccidioides antigen gp43. Importantly, we tell some personal stories behind the scene. Dr. Travassos' contribution to science is available in a number of quality publications, while his influence to hundreds of people who gravitated around him will be kept alive inside each one of us forever.

The Response of Paracoccidioides lutzii to the Interaction with Human Neutrophils

The fungal pathogen Paracoccidioides lutzii causes systemic mycosis Paracoccidioidomycosis (PCM), which presents a broad distribution in Latin America. Upon infection, the fungus undergoes a morphological transition to yeast cells and provokes an inflammatory granulomatous reaction with a high number of neutrophils in the lungs. In this work, we employed proteomic analysis to investigate the in vitro response of the fungus to the interaction with human neutrophils. Proteomic profiling of P. lutzii yeast cells harvested at 2 and 4 h post interaction with human polymorphonuclear cells allowed the identification of 505 proteins differentially accumulated. The data indicated that P. lutzii yeast cells underwent a shift in metabolism from glycolysis to Beta oxidation, increasing enzymes of the glyoxylate cycle and upregulating enzymes related to the detoxification of oxidative and heat shock stress. To our knowledge, this is the first study employing proteomic analysis in the investigation of the response of a member of the Paracoccidioides genus to the interaction with neutrophils.

Mycological diagnosis of paracoccidioidomycosis in a hospital from a nonendemic area: classical and molecular methods

Introduction

Paracoccidioidomycosis is a systemic mycosis endemic in Latin America. Climate change and host migration emphasize the need to optimize this infection diagnosis.

Objective

To evaluate the implementation of Paracoccidioides spp. DNA detection in the mycological diagnosis of patients with suspected paracoccidioidomycosis.

Materials and methods

It is a retrospective study with laboratory data from patients with clinical suspicion of paracoccidioidomycosis, who consulted a university hospital from a non-endemic area.

Results

We analyzed the laboratory results of samples from 19 patients with suspected paracoccidioidomycosis. Seventeen out of 19 patients were born in or had visited an endemic area in Latin America. Fourteen adult male patients were confirmed to have paracoccidioidomycosis by conventional diagnosis: the direct examination was positive in 12 samples while fungal growth was found only in 4. Anti-Paracoccidioides spp. antibodies were detected in 10 patients, 8 of them with proven paracoccidioidomycosis. Nested PCR for Paracoccidioides spp. detection was performed on clinical samples from 14 patients, and positive results were obtained for 9 out of 10 patients with the conventional diagnosis of paracoccidioidomycosis.

Conclusions

The incorporation of molecular techniques to detect Paracoccidioides spp. DNA complements the conventional diagnosis of paracoccidioidomycosis. This tool allows the prescription of antifungal treatment in those cases where the fungus is not observed in the clinical samples.

Of Mycelium and Men: Inherent Human Susceptibility to Fungal Diseases

In medical mycology, the main context of disease is iatrogenic-based disease. However, historically, and occasionally, even today, fungal diseases affect humans with no obvious risk factors, sometimes in a spectacular fashion. The field of “inborn errors of immunity” (IEI) has deduced at least some of these previously enigmatic cases; accordingly, the discovery of single-gene disorders with penetrant clinical effects and their immunologic dissection have provided a framework with which to understand some of the key pathways mediating human susceptibility to mycoses. By extension, they have also enabled the identification of naturally occurring auto-antibodies to cytokines that phenocopy such susceptibility. This review provides a comprehensive update of IEI and autoantibodies that inherently predispose humans to various fungal diseases.