Immunity to Paracoccidioides brasiliensis infection

Low-level LASER therapy accelerates fungal lesions cicatrization by increasing the production of Th1 and Th2 cytokines

Paracoccidioidomycosis (PCM) is a systemic mycosis with serious clinical consequences in which the use of antifungal drugs requires long-term treatment. Therefore, we studied the effect of low-level LASER therapy (LLLT) to evaluate its prospects as a complementary treatment for PCM and improve the clinical response to the disease.

OBJECTIVES

Our study focused on the resolution of lesions caused by fungal infection using a subcutaneous air pouch model of infection.

METHODS

We evaluated cell profile and cytokines, fungi viability, and the presence of fibroblasts and fibrocytes at the site of infection. Inoculation of P. brasiliensis (Pb) was performed using a subcutaneous air pouch model and the LLLT irradiation was performed on alternate days on the rear paws of mice for 10 days, after which the cells from the air pouch were collected and analyzed.

RESULTS

In animals irradiated with LLLT, the influx of cells to the air pouch was reduced, but they were more activated and produced pro-inflammatory (IL-12, IL-17 and TNF-α) and neutrophil (PMN) activating cytokines (IL-8, GM-CSF and γ-IFN). A better resolution of the infection, evidenced by the reduction in the number of viable fungi with preserved morphology in the air pouch, and an increase in the number of fibrocytes, indicating a healing profile were also observed.

CONCLUSION

LLLT decreased the influx of PMN, but those presents were highly activated, with increased fungicidal activity. LLLT irradiation also resulted in earlier cicatrization at the site of infection, leading to a better outcome of the infection. These data are favorable to the use of LLLT as a complementary therapy in PCM.

Paracoccidioidomycosis: Current Status and Future Trends

Paracoccidioidomycosis (PCM), initially reported in 1908 in the city of São Paulo, Brazil, by Adolpho Lutz, is primarily a systemic and neglected tropical mycosis that may affect individuals with certain risk factors around Latin America, especially Brazil. Paracoccidioides brasiliensis sensu stricto, a classical thermodimorphic fungus associated with PCM, was long considered to represent a monotypic taxon. However, advances in molecular taxonomy revealed several cryptic species, including Paracoccidioides americana, P. restrepiensis, P. venezuelensis, and P. lutzii, that show a preference for skin and mucous membranes, lymph nodes, and respiratory organs but can also affect many other organs. The classical diagnosis of PCM benefits from direct microscopy culture-based, biochemical, and immunological assays in a general microbiology laboratory practice providing a generic identification of the agents. However, molecular assays should be employed to identify Paracoccidioides isolates to the species level, data that would be complemented by epidemiological investigations. From a clinical perspective, all probable and confirmed cases should be treated. The choice of treatment and its duration must be considered, along with the affected organs, process severity, history of previous treatment failure, possibility of administering oral medication, associated diseases, pregnancy, and patient compliance with the proposed treatment regimen. Nevertheless, even after appropriate treatment, there may be relapses, which generally occur 5 years after the apparent cure following treatment, and also, the mycosis may be confused with other diseases. This review provides a comprehensive and critical overview of the immunopathology, laboratory diagnosis, clinical aspects, and current treatment of PCM, highlighting current issues in the identification, treatment, and patient follow-up in light of recent Paracoccidioides species taxonomic developments.

NLRC4 inhibits NLRP3 inflammasome and abrogates effective antifungal CD8+ T cell responses

The recognition of fungi by intracellular NOD-like receptors (NLRs) induces inflammasome assembly and activation. Although the NLRC4 inflammasome has been extensively studied in bacterial infections, its role during fungal infections is unclear. Paracoccidioidomycosis (PCM) is a pathogenic fungal disease caused by Paracoccidioides brasiliensis. Here, we show that NLRC4 confers susceptibility to experimental PCM by regulating NLRP3-dependent cytokine production and thus protective effector mechanisms. Early after infection, NLRC4 suppresses prostaglandin E₂ production, and consequently reduces interleukin (IL)-1β release by macrophages and dendritic cells in the lungs. IL-1β is required to control fungal replication via induction of the nitric oxide synthase 2 (NOS2) pathway. At a later stage of the disease, NLRC4 impacts IL-18 release, dampening robust CD8⁺IFN-γ⁺ T cell responses and enhancing mortality of mice. These findings demonstrate that NLRC4 promotes disease by regulating the production of inflammatory cytokines and cellular responses that depend on the NLRP3 inflammasome activity.

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NLRC4 promotes susceptibility to a highly pathogenic fungus.

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NLRC4 regulates NLRP3 activity.

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NLRC4 inhibits early NLRP3/IL-1β/NOS2/NO axis and promotes fungal replication.

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NLRC4 dampens late IL-18 production, suppressing CD8⁺IFN-γ⁺ T cell responses.

Identification of Potentially Therapeutic Immunogenic Peptides From Paracoccidioides lutzii Species

Paracoccidioidomycosis (PCM) is an endemic mycosis in Latin America caused by the thermodimorphic fungi of the genus Paracoccidioides spp. Paracoccidioides lutzii (PL) is one of the 5 species that constitute the Paracoccidioides genus. PL expresses low amounts of glycoprotein (Gp) 43 (PLGp43) and PLGp43 displays few epitopes in common with the P. brasiliensis (PB) immunodominant antigen PBGp43, which is commonly used for serological diagnosis of PCM. This difference in structure between the glycoproteins markedly reduces the efficiency of serological diagnosis in patients infected with PL. We previously demonstrated that peptide 10 (P10) from the PBGp43 induces protective immune responses in in vitro and in vivo models of PB PCM. Since, P10 has proven to be a promising therapeutic to combat PB, we sought to identify peptides in PL that could similarly be applied for the treatment of PCM. PL yeast cell proteins were isolated from PL: dendritic cell co-cultures and subjected to immunoproteomics. This approach identified 18 PL peptides that demonstrated in silico predictions for immunogenicity. Eight of the most promising peptides were synthesized and applied to lymphocytes obtained from peptide-immunized or PL-infected mice as well as to in vitro cultures with peptides or dendritic cells pulsed the peptides. The peptides LBR5, LBR6 and LBR8 efficiently promoted CD4⁺ and CD8⁺ T cell proliferation and dendritic cells pulsed with LBR1, LBR3, LBR7 or LBR8 stimulated CD4⁺ T cell proliferation. We observed increases of IFN-γ in the supernatants from primed T cells for the conditions with peptides without or with dendritic cells, although IL-2 levels only increased in response to LBR8. These novel immunogenic peptides derived from PL will be employed to develop new peptide vaccine approaches and the proteins from which they are derived can be used to develop new diagnostic assays for PL and possibly other Paracoccidioides spp. These findings identify and characterize new peptides with a promising therapeutic profile for future against this important neglected systemic mycosis.

Paracoccidioidomycosis Protective Immunity

Protective immunity against Paracoccidioides consists of a stepwise activation of numerous effector mechanisms that comprise many cellular and soluble components. At the initial phase of non-specific innate immunity, resistance against Paracoccidioides comes from phagocytic polymorphonuclear neutrophils, natural killer (NK) cells and monocytes, supplemented by soluble factors such as cytokines and complement system components. Invariant receptors (Toll-like receptors (TLRs), Dectins) which are present in cells of the immune system, detect patterns present in Paracoccidioides (but not in the host) informing the hosts cells that there is an infection in progress, and that the acquired immunity must be activated. The role of components involved in the innate immunity of paracoccidioidomycosis is herein presented. Humoral immunity, represented by specific antibodies which control the fungi in the blood and body fluids, and its role in paracoccidioidomycosis (which was previously considered controversial) is also discussed. The protective mechanisms (involving various components) of cellular immunity are also discussed, covering topics such as: lysis by activated macrophages and cytotoxic T lymphocytes, the participation of lytic products, and the role of cytokines secreted by T helper lymphocytes in increasing the efficiency of Paracoccidioides, lysis.

Polymorphism in the Promoter Region of the IL18 Gene and the Association With Severity on Paracoccidioidomycosis

Paracoccidioidomycosis (PCM) is an important endemic, systemic disease in Latin America caused by Paracoccidioides spp. This mycosis has been associated with high morbidity and sequels, and its clinical manifestations depend on the virulence of the infecting strain, the degree and type of immune response, infected tissues, and intrinsic characteristics of the host. The T helper(Th)1 and Th17/Th22 cells are related to resistance and control of infection, and a Th2/Th9 response is associated with disease susceptibility. In this study, we focused on interleukin(IL)-12p35 (IL12A), IL-18 (IL18), and IFN-γ receptor 1 (IFNGR1) genetic polymorphisms because their respective roles have been described in human PCM. Real-time PCR was employed to analyze IL12A-504 G/T (rs2243115), IL18-607 C/A (rs1946518), and IFNGR1-611 A/G (rs1327474) single nucleotide polymorphisms (SNP). One hundred forty-nine patients with the acute form (AF), multifocal chronic (MC), or unifocal chronic (UC) forms of PCM and 110 non-PCM individuals as a control group were included. In the unconditional logistic regression analysis adjusted by ethnicity and sex, we observed a high risk of the IL18-607 A-allele for both AF [p = 0.015; OR = 3.10 (95% CI: 1.24–7.77)] and MC groups [p = 0.023; OR = 2.61 (95% CI: 1.14–5.96)] when compared with UC. The IL18-607 A-allele associated risk for the AF and MC groups as well as the protective role of the C-allele in UC are possibly linked to higher levels of IL-18 at different periods of the course of the disease. Therefore, a novel role of IL18-607 C/A SNP is shown in the present study, highlighting its importance in the outcome of PCM.

Regulatory T cells in paracoccidioidomycosis

This review addresses the role of regulatory T cells (Tregs), which are essential for maintaining peripheral tolerance and controlling pathogen immunity, in the host response against Paracoccidioides brasiliensis, a primary fungal pathogen. A brief introduction on the general features of Treg cells summarizes their main functions, subpopulations, mechanisms of suppression and plasticity. The main aspects of immunity in the diverse forms of the P. brasiliensis infection are presented, as are the few extant studies on the relevance of Treg cells in the control of severity of the human disease. Finally, the influence of Toll-like receptors, Dectin-1, NOD-like receptor P3 (NLRP3), Myeloid differentiation factor-88 (MyD88), as well as the enzyme indoleamine 2,3 dioxygenase (IDO) on the expansion and function of Treg cells in a murine model of pulmonary paracoccidioidomycosis (PCM) is also discussed. It is demonstrated that some of these components are involved in the negative control of Treg cell expansion, whereas others positively trigger the proliferation and activity of these cells. Finally, the studies here summarized highlight the dual role of Treg cells in PCM, which can be protective by controlling excessive immunity and tissue pathology but also deleterious by inhibiting the anti-fungal immunity necessary to control fungal growth and dissemination.

Effect of ArtinM on Human Blood Cells During Infection With Paracoccidioides brasiliensis

Infections caused by fungi are prominent in our environment and can be potentially fatal. paracoccidioidomycosis (PCM), caused by fungi of the Paracoccidioides genus, is the most frequent systemic mycosis in Brazil and the main cause of death among immunocompetent individuals. The antifungal therapy for PCM is usually effective but side effects and relapses are often reported. The latter could be avoided with alternative or complementary therapies aimed at boosting the immune response to combat this pathogen. Recent reports have pointed at the importance of an effective cellular immune response, with the participation of Th1 cells, in the resistance to and control of Paracoccidioides infection. The ArtinM lectin, extracted from jackfruit (Artocarpus heterophyllus) seeds, exhibits immunomodulatory activity against several intracellular pathogens, including Paracoccidioides brasiliensis, by promoting the development of a Th1 immune response. The aim of this work was to characterize the effect of ArtinM on peripheral blood cells of patients with PCM and on those of control individuals infected with fungal yeasts cells in vitro. Our results demonstrate that ArtinM activates human neutrophils in vitro, leading to an increase in cytokine production and CD54 expression. ArtinM activated P. brasiliensis-infected neutrophils from both healthy individuals and patients with PCM. This activation was not dependent on the dectin-1 receptor, because pre-incubation with laminarin, a dectin-1 receptor blocker, did not reverse the activated state of the cells. ArtinM also stimulated human peripheral blood mononuclear cells to secrete pro-inflammatory Th1-related cytokines, which are protective against Paracoccidioides infection. These data support the immunostimulatory action of ArtinM and encourage new studies using the lectin for the immunotherapy of PCM.

Role of Dectin-1 receptor on cytokine production by human monocytes challenged with Paracoccidioides brasiliensis

Fungal recognition by Dectin-1 receptor triggers a series of cellular mechanisms involved in a protective activation of the immune system. In this study, we aimed to evaluate the participation of Dectin-1 receptor in the induction of IL-8, TNF-α, IL-12, IL-10 and IL-17A secretion by human monocytes activated with different cytokines, and challenged in vitro with Paracoccidioides brasiliensis (P. brasiliensis). Our results show that monocytes challenged with P. brasiliensis (Pb265) are able to produce IL-12, IL-8, IL-17, IL-10 and TNF-α. Dectin-1 receptor blockage decreased the IL-12, IL-17, IL-10 and TNF-α levels indicating the participation of such receptor in the induction of these cytokines. Only IL-8 production was not affected by the blockage. Cells activation with different cytokines showed that GM-CSF was able to induce secretion of all cytokines and the receptor blockage prior to the challenge also decreased the cytokine secretion, except IL-8. Monocytes activated with TNF-α promoted IL-8, IL-10 and TNF-α production, whereas stimulation with IFN-γ promoted mainly IL-12 and TNF-α. Thus, these findings bring new and important knowledge about Dectin-1 participation in cytokines production by monocytes challenged with Pb265.

Recombinant vaccines of a CD4+ T-cell epitope promote efficient control of Paracoccidioides brasiliensis burden by restraining primary organ infection

Paracoccidioidomycosis (PCM) is an infectious disease endemic to South America, caused by the thermally dimorphic fungi Paracoccidioides. Currently, there is no effective human vaccine that can be used in prophylactic or therapeutic regimes. We tested the hypothesis that the immunogenicity of the immunodominant CD4+ T-cell epitope (P10) of Paracoccidioides brasiliensis gp43 antigen might be significantly enhanced by using a hepatitis B virus-derived particle (VLP) as an antigen carrier. This chimera was administered to mice as a (His)6-purified protein (rPbT) or a replication-deficient human type 5 adenoviral vector (rAdPbT) in an immunoprophylaxis assay. The highly virulent Pb18 yeast strain was used to challenge our vaccine candidates. Fungal challenge evoked robust P10-specific memory CD4+ T cells secreting protective Th-1 cytokines in most groups of immunized mice. Furthermore, the highest level of fungal burden control was achieved when rAdPbT was inoculated in a homologous prime-boost regimen, with 10-fold less CFU recovering than in non-vaccinated mice. Systemic Pb18 spreading was only prevented when rAdPbT was previously inoculated. In summary, we present here VLP/P10 formulations as vaccine candidates against PCM, some of which have demonstrated for the first time their ability to prevent progression of this pernicious fungal disease, which represents a significant social burden in developing countries.

Th17-Inducing Cytokines IL-6 and IL-23 Are Crucial for Granuloma Formation during Experimental Paracoccidioidomycosis

Paracoccidioidomycosis (PCM), a chronic granulomatous disease caused by the thermally dimorphic fungus Paracoccidioides brasiliensis and Paracoccidioides lutzii, has the highest mortality rate among systemic mycosis. The T helper 1-mediated immunity is primarily responsible for acquired resistance during P. brasiliensis infection, while susceptibility is associated with Th2 occurrence. Th17 is a population of T CD4⁺ cells that, among several chemokines and cytokines, produces IL-17A and requires the presence of IL-1, IL-6, and TGF-β for differentiation in mice and IL-23 for its maintenance. Th17 has been described as an arm of the immune system that enhances host protection against several bacterial and fungal infections, as Pneumocystis carinii and Candida albicans. In this study, we aimed to evaluate the Th17 immune response and the role of Th17-associated cytokines (IL-6, IL-23, and IL-17A) during experimental PCM. First, we observed that P. brasiliensis infection [virulent yeast strain 18 of P. brasiliensis (Pb18)] increased the IL-17A production in vitro and all the evaluated Th17-associated cytokines in the lung tissue from C57BL/6 wild-type mice. In addition, the deficiency of IL-6, IL-23, or IL-17 receptor A (IL-17RA) impaired the compact granuloma formation and conferred susceptibility during infection, associated with reduced tumor necrosis factor-α, IFN-γ, and inducible nitric oxide synthase enzyme expression. Our data suggest that IL-6 production by bone marrow-derived macrophages (BMDMs) is important to promote the Th17 differentiation during Pb18 infection. In accordance, the adoptive transfer of BMDMs from C57BL/6 to infected IL-6^-/- or IL-17RA^-/- mice reduced the fungal burden in the lungs compared to nontransferred mice and reestablished the pulmonary granuloma formation. Taken together, these results suggest that Th17-associated cytokines are involved in the modulation of immune response and granuloma formation during experimental PCM.

Severe Paracoccidioidomycosis in a 14-Year-Old Boy

Paracoccidioidomycosis (PCM) is the most important systemic mycoses in Latin America. We describe a severe case of paracoccidioidomycosis in a 14-year-old boy, with a rapid disease progression. The fungal strain was isolated and inoculated into a T and/or B cell immunocompromised mice, which revealed a highly virulent strain. The case report presented herein emphasizes the importance of considering PCM in the differential diagnosis of patients with other infectious diseases in endemic areas and highlights a novel isolate.

Paracoccidioides brasiliensis infection promotes thymic disarrangement and premature egress of mature lymphocytes expressing prohibitive TCRs

BACKGROUND

Paracoccidioidomycosis, a chronic granulomatous fungal disease caused by Paracoccidioides brasiliensis yeast cells affects mainly rural workers, albeit recently cases in immunosuppressed individuals has been reported. Protective immune response against P. brasiliensis is dependent on the activity of helper T cells especially IFN-γ-producing Th1 cells. It has been proposed that Paracoccidioides brasiliensis is able to modulate the immune response towards a permissive state and that the thymus plays a major role in it.

METHODS

In this paper, we show that acute infection of BALB/c mice with P. brasiliensis virulent isolate (Pb18) might cause alterations in the thymic environment as well as the prohibitive TCR-expressing T cells in the spleens.

RESULTS

After seven days of infection, we found yeast cells on the thymic stroma, the thymic epithelial cells (TEC) were altered regarding their spatial-orientation and inflammatory mediators gene expression was increased. Likewise, thymocytes (differentiating T cells) presented higher migratory ability in ex vivo experiments. Notwithstanding, P. brasiliensis-infected mice showed an increased frequency of prohibitive TCR-expressing T cells in the spleens, suggesting that the selection processes that occur in the thymus may be compromised during the acute infection.

CONCLUSION

In this paper, for the first time, we show that acute infection with Paracoccidioides brasiliensis yeast cells promotes thymic alterations leading to a defective repertoire of peripheral T cells. The data presented here may represent new mechanisms by which P. brasiliensis subverts the immune response towards the chronic infection observed in humans.

Paracoccidioides-host Interaction: An Overview on Recent Advances in the Paracoccidioidomycosis

Paracoccidioides brasiliensis and P. lutzii are etiologic agents of paracoccidioidomycosis (PCM), an important endemic mycosis in Latin America. During its evolution, these fungi have developed characteristics and mechanisms that allow their growth in adverse conditions within their host through which they efficiently cause disease. This process is multi-factorial and involves host-pathogen interactions (adaptation, adhesion, and invasion), as well as fungal virulence and host immune response. In this review, we demonstrated the glycoproteins and polysaccharides network, which composes the cell wall of Paracoccidioides spp. These are important for the change of conidia or mycelial (26°C) to parasitic yeast (37°C). The morphological switch, a mechanism for the pathogen to adapt and thrive inside the host, is obligatory for the establishment of the infection and seems to be related to pathogenicity. For these fungi, one of the most important steps during the interaction with the host is the adhesion. Cell surface proteins called adhesins, responsible for the first contact with host cells, contribute to host colonization and invasion by mediating this process. These fungi also present the capacity to form biofilm and through which they may evade the host's immune system. During infection, Paracoccidioides spp. can interact with different host cell types and has the ability to modulate the host's adaptive and/or innate immune response. In addition, it participates and interferes in the coagulation system and phenomena like cytoskeletal rearrangement and apoptosis. In recent years, Paracoccidioides spp. have had their endemic areas expanding in correlation with the expansion of agriculture. In response, several studies were developed to understand the infection using in vitro and in vivo systems, including alternative non-mammal models. Moreover, new advances were made in treating these infections using both well-established and new antifungal agents. These included natural and/or derivate synthetic substances as well as vaccines, peptides, and anti-adhesins sera. Because of all the advances in the PCM study, this review has the objective to summarize all of the recent discoveries on Paracoccidioides-host interaction, with particular emphasis on fungi surface proteins (molecules that play a fundamental role in the adhesion and/or dissemination of the fungi to host-cells), as well as advances in the treatment of PCM with new and well-established antifungal agents and approaches.

The Effects of Paracoccidioides brasiliensis Infection on GM-CSF- and M-CSF-Induced Mouse Bone Marrow-Derived Macrophage from Resistant and Susceptible Mice Strains

Considering the importance of macrophages as the first line of defense against fungal infection and the different roles played by the two M1- and M2-like polarized macrophages, we decided to evaluate the effects of Paracoccidioides brasiliensis infection on GM-CSF- and M-CSF-induced bone marrow-derived macrophages (BMM) from the A/J and B10.A mouse strains, an established model of resistance/susceptibility to PCM, respectively. Upon differentiation, the generated GM- or M-BMMs were characterized by morphological analyses, gene expression profiles, and cytokines production. Our main results demonstrate that GM-BMMs derived from A/J and B.10 produced high levels of pro- and anti-inflammatory cytokines that may contribute to generate an unbalanced early immune response. In accordance with the literature, the B10.A susceptible mice lineage has an innate tendency to polarize into M1-like phenotype, whereas the opposite phenotype occurs in A/J resistance mice. In this context, our data support that susceptibility and resistance are strongly correlated with M1 and M2 polarization, respectively.

Expression of dectin-1 and enhanced activation of NALP3 inflammasome are associated with resistance to paracoccidioidomycosis

Dectin-1 is a pattern recognition receptor (PRR) that recognizes β-glucans and plays a major role in the immunity against fungal pathogens. Paracoccidioides brasiliensis, the causative agent of paracoccidioidomycosis, has a sugar-rich cell wall mainly composed of mannans and glucans. To investigate the role of dectin-1 in the innate immunity of resistant (A/J) and susceptible (B10.A) mice to P. brasiliensis infection, we evaluated the role of curdlan (a dectin-1 agonist) and laminarin (a dectin-1 antagonist) in the activation of macrophages from both mouse strains. We verified that curdlan has a negligible role in the activation of B10.A macrophages but enhances the phagocytic and fungicidal abilities of A/J macrophages. Curdlan up-regulated the expression of costimulatory molecules and PRRs in A/J macrophages that express elevated levels of dectin-1, but not in B10.A cells. In addition, curdlan treatment inhibited arginase-1 and enhanced NO-synthase mRNA expression in infected A/J macrophages but had not effect in B10.A cells. In contrast, laminarin reinforced the respective M2/M1 profiles of infected A/J and B10.A macrophages. Following curdlan treatment, A/J macrophages showed significantly higher Syk kinase phosphorylation and expression of intracellular pro-IL-1β than B10.A cells. These findings led us to investigate if the NRLP3 inflammasome was differently activated in A/J and B10.A cells. Indeed, compared with B10.A cells A/J macrophages showed an increased expression of NALP3, ASC, and IL-1β mRNA. They also showed elevated caspase-1 activity and secreted high levels of mature IL-β and IL-18 after curdlan treatment and P. brasiliensis infection. Our data demonstrate that soluble and particulate β-glucans exert opposed modulatory activities on macrophages of diverse genetic patterns. Moreover, the synergistic action of dectin-1 and NALP3 inflammasome were for the first time associated with the innate response of resistant hosts to P. brasiliensis infection.

rPbPga1 from Paracoccidioides brasiliensis Activates Mast Cells and Macrophages via NFkB

Background

The fungus Paracoccidioides brasiliensis is the leading etiological agent of paracoccidioidomycosis (PCM), a systemic granulomatous disease that typically affects the lungs. Cell wall components of P. brasiliensis interact with host cells and influence the pathogenesis of PCM. In yeast, many glycosylphosphatidylinositol (GPI)-anchored proteins are important in the initial contact with the host, mediating host-yeast interactions that culminate with the disease. PbPga1 is a GPI anchored protein located on the surface of the yeast P. brasiliensis that is recognized by sera from PCM patients.

Methodology/Principal Findings

Endogenous PbPga1 was localized to the surface of P. brasiliensis yeast cells in the lungs of infected mice using a polyclonal anti-rPbPga1 antibody. Furthermore, macrophages stained with anti-CD38 were associated with P. brasiliensis containing granulomas. Additionally, rPbPga1 activated the transcription factor NFkB in the macrophage cell line Raw 264.7 Luc cells, containing the luciferase gene downstream of the NFkB promoter. After 24 h of incubation with rPbPga1, alveolar macrophages from BALB/c mice were stimulated to release TNF-α, IL-4 and NO. Mast cells, identified by toluidine blue staining, were also associated with P. brasiliensis containing granulomas. Co-culture of P. Brasiliensis yeast cells with RBL-2H3 mast cells induced morphological changes on the surface of the mast cells. Furthermore, RBL-2H3 mast cells were degranulated by P. brasiliensis yeast cells, but not by rPbPga1, as determined by the release of beta-hexosaminidase. However, RBL-2H3 cells activated by rPbPga1 released the inflammatory interleukin IL-6 and also activated the transcription factor NFkB in GFP-reporter mast cells. The transcription factor NFAT was not activated when the mast cells were incubated with rPbPga1.

Conclusions/Significance

The results indicate that PbPga1 may act as a modulator protein in PCM pathogenesis and serve as a useful target for additional studies on the pathogenesis of P. brasiliensis.

Paracoccidioidomycosis (PCM), one of the most prevalent mycoses in Latin America, is caused by the thermodimorphic fungus Paracoccidioides brasiliensis. P. brasiliensis is thought to infect the host through the respiratory tract. Cell wall components of P. brasiliensis interact with host cells producing granulomas, thus influencing the pathogenesis of PCM. PbPga1 is an O-glycosylated, GPI-anchored protein that is localized on the yeast cell surface and is up-regulated in the pathogenic yeast form. GPI anchored proteins are involved in cell-cell and cell-tissue adhesion and have a key role in the interaction between fungal and host cells. In the present study, the authors show that both macrophages and mast cells are associated with the P.brasiliensis granulomas. Furthermore, recombinant PbPga1 was able to activate both alveolar macrophages and mast cells via the transcription factor NFkB to release inflammatory mediators. The results of this study indicate that the surface antigen, PbPga1, may play an important role in PCM pathogenesis by activating macrophages and mast cells. Additionally, PbPga1 may be a target for new strategies for detecting and treating PCM.

Importance of adhesins in virulence of Paracoccidioides spp

Members of the Paracoccidioides genus are the etiologic agents of paracoccidioidomycosis (PCM). This genus is composed of two species: Paracoccidioides brasiliensis and Paracoccidioides lutzii. The correct molecular taxonomic classification of these fungi has created new opportunities for studying and understanding their relationships with their hosts. Paracoccidioides spp. have features that permit their growth under adverse conditions, enable them to adhere to and invade host tissues and may contribute to disease development. Cell wall proteins called adhesins facilitate adhesion and are capable of mediating fungi-host interactions during infection. This study aimed to evaluate the adhesion profile of two species of the genus Paracoccidioides, to analyze the expression of adhesin-encoding genes by real-time PCR and to relate these results to the virulence of the species, as assessed using a survival curve in mice and in Galleria mellonella after blocking the adhesins. A high level of heterogeneity was observed in adhesion and adhesin expression, showing that the 14-3-3 and enolase molecules are the most highly expressed adhesins during pathogen-host interaction. Additionally, a survival curve revealed a correlation between the adhesion rate and survival, with P. brasiliensis showing higher adhesion and adhesin expression levels and greater virulence when compared with P. lutzii. After blocking 14-3-3 and enolase adhesins, we observed modifications in the virulence of these two species, revealing the importance of these molecules during the pathogenesis of members of the Paracoccidioides genus. These results revealed new insights into the host-pathogen interaction of this genus and may enhance our understanding of different isolates that could be useful for the treatment of this mycosis.

Therapeutic administration of recombinant Paracoccin confers protection against paracoccidioides brasiliensis infection: involvement of TLRs

BACKGROUND

Paracoccin (PCN) is an N-acetylglucosamine-binding lectin from the human pathogenic fungus Paracoccidioides brasiliensis. Recombinant PCN (rPCN) induces a T helper (Th) 1 immune response when prophylactically administered to BALB/c mice, protecting them against subsequent challenge with P. brasiliensis. In this study, we investigated the therapeutic effect of rPCN in experimental paracoccidioidomycosis (PCM) and the mechanism accounting for its beneficial action.

METHODOLOGY/PRINCIPAL FINDINGS

Four distinct regimens of rPCN administration were assayed to identify which was the most protective, relative to vehicle administration. In all rPCN-treated mice, pulmonary granulomas were less numerous and more compact. Moreover, fewer colony-forming units were recovered from the lungs of rPCN-treated mice. Although all therapeutic regimens of rPCN were protective, maximal efficacy was obtained with two subcutaneous injections of 0.5 µg rPCN at 3 and 10 days after infection. The rPCN treatment was also associated with higher pulmonary levels of IL-12, IFN-γ, TNF-α, nitric oxide (NO), and IL-10, without IL-4 augmentation. Encouraged by the pulmonary cytokine profile of treated mice and by the fact that in vitro rPCN-stimulated macrophages released high levels of IL-12, we investigated the interaction of rPCN with Toll-like receptors (TLRs). Using a reporter assay in transfected HEK293T cells, we verified that rPCN activated TLR2 and TLR4. The activation occurred independently of TLR2 heterodimerization with TLR1 or TLR6 and did not require the presence of the CD14 or CD36 co-receptors. The interaction between rPCN and TLR2 depended on carbohydrate recognition because it was affected by mutation of the receptor's N-glycosylation sites. The fourth TLR2 N-glycan was especially critical for the rPCN-TLR2 interaction.

CONCLUSIONS/SIGNIFICANCE

Based on our results, we propose that PCN acts as a TLR agonist. PCN binds to N-glycans on TLRs, triggers regulated Th1 immunity, and exerts a therapeutic effect against P. brasiliensis infection.

Plasmacytoid dendritic cells in cutaneous lesions of patients with chromoblastomycosis, lacaziosis, and paracoccidioidomycosis: a comparative analysis

Plasmacytoid dendritic cells (pDCs) are characterized by expression of CD123 and BDCA-2 (Blood Dendritic Cell Antigen 2) (CD303) molecules, which are important in innate and adaptive immunity. Chromoblastomycosis (CBM), lacaziosis or Jorge Lobo's disease (JLD), and paracoccidioidomycosis (PCM), are noteworthy in Latin America due to the large number of reported cases. The severity of lesions is mainly determined by the host's immune status and in situ responses. The dendritic cells studied in these fungal diseases are of myeloid origin, such as Langerhans cells and dermal dendrocytes; to our knowledge, there are no data for pDCs. Forty-three biopsies from patients with CBM, 42 from those with JLD and 46 diagnosed with PCM, were evaluated by immunohistochemistry. Plasmacytoid cells immunostained with anti-CD123 and anti-CD303 were detected in 16 cases of CBM; in those stained with anti-CD123, 24 specimens were obtained from PCM. We did not detect the presence of pDCs in any specimen using either antibody in JLD. We believe that, albeit a secondary immune response in PCM and CBM, pDCs could act as a secondary source of important cytokines. The BDCA-2 (CD303) is a c-type lectin receptor involved in cell adhesion, capture, and processing of antigens. Through the expression of the c-lectin receptor, there could be an interaction with fungi, similar to other receptors of this type, namely, CD207 in PCM and CD205 and CD209 in other fungal infections. In JLD, the absence of expression of CD123 and CD303 seems to indicate that pDCs are not involved in the immune response.

Recombinant paracoccin reproduces the biological properties of the native protein and induces protective Th1 immunity against Paracoccidioides brasiliensis infection

BACKGROUND

Paracoccin is a dual-function protein of the yeast Paracoccidioides brasiliensis that has lectin properties and N-acetylglucosaminidase activities. Proteomic analysis of a paracoccin preparation from P. brasiliensis revealed that the sequence matched that of the hypothetical protein encoded by PADG-3347 of isolate Pb-18, with a polypeptide sequence similar to the family 18 endochitinases. These endochitinases are multi-functional proteins, with distinct lectin and enzymatic domains.

METHODOLOGY/PRINCIPAL FINDINGS

The multi-exon assembly and the largest exon of the predicted ORF (PADG-3347), was cloned and expressed in Escherichia coli cells, and the features of the recombinant proteins were compared to those of the native paracoccin. The multi-exon protein was also used for protection assays in a mouse model of paracoccidioidomycosis.

CONCLUSIONS/SIGNIFICANCE

Our results showed that the recombinant protein reproduced the biological properties described for the native protein-including binding to laminin in a manner that is dependent on carbohydrate recognition-showed N-acetylglucosaminidase activity, and stimulated murine peritoneal macrophages to produce high levels of TNF-α and nitric oxide. Considering the immunomodulatory potential of glycan-binding proteins, we also investigated whether prophylactic administration of recombinant paracoccin affected the course of experimental paracoccidioidomycosis in mice. In comparison to animals injected with vehicle (controls), mice treated with recombinant paracoccin displayed lower pulmonary fungal burdens and reduced pulmonary granulomas. These protective effects were associated with augmented pulmonary levels of IL-12 and IFN-γ. We also observed that injection of paracoccin three days before challenge was the most efficient administration protocol, as the induced Th1 immunity was balanced by high levels of pulmonary IL-10, which may prevent the tissue damage caused by exacerbated inflammation. The results indicated that paracoccin is the protein encoded by PADG-3347, and we propose that this gene and homologous proteins in other P. brasiliensis strains be called paracoccin. We also concluded that recombinant paracoccin confers resistance to murine P. brasiliensis infection by exerting immunomodulatory effects.

Characterization of the immune response in human paracoccidioidomycosis

OBJECTIVES

Paracoccidioidomycosis (PCM) is a systemic mycosis caused by the dimorphic fungus Paracoccidioides brasiliensis that presents two main clinical forms: the adult form (AF) and the juvenile form (JF); and an asymptomatic form denominated PCM-infection (PI). These forms of PCM are related to the immune response developed after infection, which has been associated with Th1 and Th2 responses. However, some PCM characteristics cannot be explained by this balance. In this study we aimed to complement the characterization of the immune response in PCM, including the newly described T cells subpopulations (Th17, Th9 and Th22).

METHODS

We analyzed the expression of cytokines and transcription factors characteristics of these different subpopulations of CD4(+) T cells in PBMCs from PCM patients and a PI group.

RESULTS

The results showed that the PI group presented a predominant Th1 response; that JF patients were characterized by a mixed Th2/Th9 response; and AF patients were characterized by a predominant Th17/Th22 response, as well as substantial participation of Th1 cells.

CONCLUSIONS

These results contribute to the existing knowledge on the immune responses associated with resistance or susceptibility to the P. brasiliensis infection, and thus could lead to the development of new strategies for patient management.

The lung in paracoccidioidomycosis: new insights into old problems

OBJECTIVES

Chronic paracoccidioidomycosis can diffusely affect the lungs. Even after antifungal therapy, patients may present with residual respiratory abnormalities due to fungus-induced lung fibrosis.

METHODS

A cross-sectional analysis of 50 consecutive inactive, chronic paracoccidioidomycosis patients was performed using high resolution computed tomography, pulmonary function tests, ergospirometry, the six-minute walk test and health-related quality of life questionnaires.

RESULTS

Radiological abnormalities were present in 98% of cases, the most frequent of which were architectural distortion (90%), reticulate and septal thickening (88%), centrilobular and paraseptal emphysema (84%) and parenchymal bands (74%). Patients typically presented with a mild obstructive disorder and a mild reduction in diffusion capacity with preserved exercise capacity, including VO2max and six-minute walking distance. Patient evaluation with the Saint-George Respiratory Questionnaire showed low impairment in the health-related quality of life, and the Medical Research Council questionnaire indicated a low dyspnea index. There were, however, patients with significant oxygen desaturation upon exercise that was associated with respiratory distress compared with the non-desaturated patients. The initial counterimmunoelectrophoresis of these patients was higher and lung emphysema was more prominent; however, there were no differences in the interstitial fibrotic tomographic abnormalities, tobacco exposure, functional responses, exercise capacity or quality of life.

CONCLUSIONS

Inactive, chronic paracoccidioidomycosis patients show persistent and disseminated radiological abnormalities by high resolution computed tomography, short impairments in pulmonary function and low impacts on aerobic capacity and quality of life. However, there was a subset of individuals whose functional impairment was more severe. These patients present with higher initial serology and more severe emphysema, stressing the importance of adequate treatment associated with tobacco exposure cessation.

Lipidomic analysis of extracellular vesicles from the pathogenic phase of Paracoccidioides brasiliensis

BACKGROUND

Fungal extracellular vesicles are able to cross the cell wall and transport molecules that help in nutrient acquisition, cell defense, and modulation of the host defense machinery.

METHODOLOGY/PRINCIPAL FINDINGS

Here we present a detailed lipidomic analysis of extracellular vesicles released by Paracoccidioides brasiliensis at the yeast pathogenic phase. We compared data of two representative isolates, Pb3 and Pb18, which have distinct virulence profiles and phylogenetic background. Vesicle lipids were fractionated into different classes and analyzed by either electrospray ionization- or gas chromatography-mass spectrometry. We found two species of monohexosylceramide and 33 phospholipid species, including phosphatidylcholine, phosphatidylethanolamine, phosphatidic acid, phosphatidylserine, phosphatidylinositol, and phosphatidylglycerol. Among the phospholipid-bound fatty acids in extracellular vesicles, C181 predominated in Pb3, whereas C18:2 prevailed in Pb18. The prevalent sterol in Pb3 and Pb18 vesicles was brassicasterol, followed by ergosterol and lanosterol. Inter-isolate differences in sterol composition were observed, and also between extracellular vesicles and whole cells.

CONCLUSIONS/SIGNIFICANCE

The extensive lipidomic analysis of extracellular vesicles from two P. brasiliensis isolates will help to understand the composition of these fungal components/organelles and will hopefully be useful to study their biogenesis and role in host-pathogen interactions.

Protective effect of rPb40 as an adjuvant for chemotherapy in experimental paracoccidioidomycosis

The conventional treatment for the most prevalent mycosis in Latin America, paracoccidioidomycosis (PCM), involves long periods of therapy that results in side effects and a high frequency of relapses. The search for a new, alternative treatment is necessary. Pb40 is an antigenic protein from P. brasiliensis fraction F0. This fraction has already been shown to have significant protective activity when used as a PCM vaccine in experimental models. The complete cDNA sequence corresponding to Pb40 was cloned into a pET-21a plasmid, expressed in E. coli with a his-tag and purified by affinity chromatography. The predicted protein sequence exhibited nearly 100% homology to a fragment of the hypothetical EF-hand domain containing protein of P. brasiliensis. Immunization with this recombinant protein was used together with chemotherapy in an attempt to improve PCM treatment. The combined drug/rPb40 treatment exhibited long-lasting control of PCM in the liver and spleen and largely preserved the tissue structures of these organs. Despite the lack of a reduction in CFUs in the group that received the combined treatment, there was a significant reduction in the size of the lesions in the lungs after 70 days of infection. At the same time, the IL-10 levels were higher in the treated mice than in the infected-only mice. Moreover, significant levels of rPb40-specific IgG antibodies were detected in the sera of immunized mice. Thus, the treatment protocol consisting of rPb40 immunization in addition to fluconazole chemotherapy showed an additive protective effect after intratracheal challenge, preventing fungal dissemination to other sites of infection and preventing relapses. These results provide new prospects for PCM immunotherapy.

Immunolocalization of IFN-gamma in the lesions of resistant and susceptible mice to Paracoccidioides brasiliensis infection

The important role of interferon-gamma (IFN-γ) in protective immunity in mycosis is well established, except for its participation in fungal granulomas. Herein, we employ immunohistochemical reactions to describe the in situ localization of IFN-γ in granulomas of susceptible (B10.A) and resistant (A/J) mice to infection with Paracoccidioides brasiliensis (Pb). After infection with the highly virulent Pb18, IFN-γ-positive lymphomononuclear cells were localized mainly at the periphery of granulomas in both mouse strains. The numbers of positive cells found in compact granulomas of A/J mice increased significantly from 15 to 120 days postinfection. At this time, significantly more positive cells were detected in the compact granulomas of resistant mice than in the loose, multifocal lesions of the susceptible ones. In infection with the slightly virulent Pb265, the same pattern of IFN-γ localization was found as in Pb18 infection, but there was decreased staining at 120 days due to the presence of only residual lesions in both mouse strains. The marked IFN-γ staining observed in the granulomas of resistant mice at the later stage of Pb infection confirms its importance in fungal dissemination control, and suggests a contribution to the development of paracoccidioidal granuloma.

Vesicle and vesicle-free extracellular proteome of Paracoccidioides brasiliensis: comparative analysis with other pathogenic fungi

Microorganisms release effector molecules that modulate the host machinery enabling survival, replication, and dissemination of a pathogen. Here we characterized the extracellular proteome of Paracoccidioides brasiliensis at its pathogenic yeast phase. Cell-free culture supernatants from the Pb18 isolate, cultivated in defined medium, were separated into vesicle and vesicle-free fractions, digested with trypsin, and analyzed by liquid chromatography-tandem mass spectrometry. In vesicle and vesicle-free preparations we identified, respectively, 205 and 260 proteins with two or more peptides, including 120 overlapping identifications. Almost 70% of the sequences were predicted as secretory, mostly using nonconventional secretory pathways, and many have previously been localized to fungal cell walls. A total of 72 proteins were considered as commonly transported by extracellular vesicles, considering that orthologues have been reported in at least two other fungal species. These sequences were mostly related to translation, carbohydrate and protein metabolism, oxidation/reduction, transport, response to stress, and signaling. This unique proteomic analysis of extracellular vesicles and vesicle-free released proteins in a pathogenic fungus provides full comparison with other fungal extracellular vesicle proteomes and broadens the current view on fungal secretomes.

Paracoccidioides brasiliensis GP43-derived peptides are potent modulators of local and systemic inflammatory response

Paracoccidioidomycosis is a systemic granulomatous disease caused by the dimorphic fungus Paracoccidioides brasiliensis. Its major antigen is a 43 kDa glycoprotein whose peptides embody different functions: P10 peptide, a T-cell epitope, induces protective response while P4 and P23 peptides inhibit both, macrophage functions and inflammatory reaction, thus facilitating infection. Here we investigated the modulating mechanisms of the immune response exerted by P4 and P23 involved in the latter inhibitory effect on macrophages. Moreover we analyzed the peptides effects in different models in vivo. While evaluating whether P4 and P23 present systemic anti-inflammatory effects in vivo, we showed that their intraperitonial administration decreased footpad swelling in mice infected with either P. brasiliensis or Mycobacterium bovis. Both, qPCR and ELISA assays suggested that this anti-inflammatory effect depended on alterations in the kinetics of production of innate immunity modulators such as TNF-α, IL6, IL10 and TLR2. IL10 seems to be early produced than TNF-α and IL6, produced later in presence of peptides. Higher doses or intravenously given P4 and P23 resulted in earlier and more prolonged anti-inflammatory effects. Moreover, continuous treatment with P4 and P23 sustained the anti-inflammatory activity throughout.

Effects of pretreating serum samples on the performance of a latex agglutination test for serodiagnosis of paracoccidioidomycosis

Paracoccidioidomycosis (PCM) is a fungal disease caused by Paracoccidioides brasiliensis, and Brazil is one of the principal countries where it is endemic. Diagnosis is based on the observation of budding P. brasiliensis yeast in clinical specimens from patients; however, the sensitivity of the visualization of fungi is low, indicating that serological tests are used for early diagnosis. The double-immunodiffusion test (ID) is the "gold standard" test for serology in PCM, although the execution of this test requires the availability of laboratorial infrastructure. We report the improved performance of a latex agglutination test (LAT) by pretreating 30 serum samples from PCM patients and 71 controls (histoplasmosis and aspergillosis patients, patients with bacterial infections, and normal human sera) with a dilution buffer incubated at 37°C for 30 min. The sensitivity and specificity of the LAT test in the nonpretreated samples were 73% and 79%, respectively. However, when samples were pretreated, the sensitivity and specificity of the test increased to 90%. In this study, we did not observe cross-reactivity with histoplasmosis patient sera, but some reactions to sera from patients with aspergillosis and bacterial infections were noted. Normal human sera were not reactive in our tests. These results indicate the need for the elimination of heterologous reactions so that we can adequately use this method for screening cases of PCM.

Structural and topographic dynamics of pulmonary histopathology and local cytokine profiles in Paracoccidioides brasiliensis conidia-infected mice

BACKGROUND

Paracoccidioidomycosis (PCM), an endemic systemic mycosis caused by the fungus Paracoccidioides brasiliensis (Pb), usually results in severe lung damage in patients.

METHODS AND FINDINGS

Considering the difficulties to sequentially study the infection in humans, this work was done in mice inoculated intranasally with infective Pb-conidia. Lungs of control and Pb-infected mice were studied after 2-hours, 4, 8, 12 and 16-weeks post-infection (p.i) in order to define histopathologic patterns of pulmonary lesions, multiplex-cytokine profiles and their dynamics during the course of this mycosis. Besides the nodular/granulomatous lesions previously informed, results revealed additional non-formerly described lung abnormalities, such as periarterial sheath inflammation and pseudotumoral masses. The following chronologic stages occurring during the course of the experimental infection were defined: Stage one (2-hours p.i): mild septal infiltration composed by neutrophils and macrophages accompanied by an intense "cytokine burst" represented by significant increases in IL-1α, IL-1β, IL-4, IL-5, IL-6, IL-10, IL12p70, IL-13, IL-17, Eotaxin, G-CSF, MCP1, MIP1α, GM-CSF, IFN-γ, MIP1β and TNFα levels. Stage two (4-weeks p.i): presence of nodules, evidence of incipient periarterial- and intense but disperse parenchymal- inflammation, abnormalities that continued to be accompanied by hyper-secretion of those cytokines and chemokines mentioned in the first stage of infection. Stages three and four (8 and 12-weeks p.i.): fungal proliferation, inflammation and collagenesis reached their highest intensity with particular involvement of the periarterial space. Paradoxically, lung cytokines and chemokines were down-regulated with significant decreases in IL-2,IL-3,IL-5,IL-9,IL-13,IL-15,GM-CSF,IFN-γ,MIP1β and TNFα. Stage five (16-weeks p.i.): inflammation decreased becoming limited to the pseudotumoral masses and was accompanied by a "silent" cytokine response, except for PDGF, MIG, RANTES and IL12p40 which remained up-regulated for the duration of the experiment.

CONCLUSIONS

Results of this study identified both classic and novel patterns corresponding to histopathologic and immunologic responses occurring during the course of experimental PCM.

The pathogenic fungus Paracoccidioides brasiliensis exports extracellular vesicles containing highly immunogenic α-Galactosyl epitopes

Exosome-like vesicles containing virulence factors, enzymes, and antigens have recently been characterized in fungal pathogens, such as Cryptococcus neoformans and Histoplasma capsulatum. Here, we describe extracellular vesicles carrying highly immunogenic α-linked galactopyranosyl (α-Gal) epitopes in Paracoccidioides brasiliensis. P. brasiliensis is a dimorphic fungus that causes human paracoccidioidomycosis (PCM). For vesicle preparations, cell-free supernatant fluids from yeast cells cultivated in Ham's defined medium-glucose were concentrated in an Amicon ultrafiltration system and ultracentrifuged at 100,000 × g. P. brasiliensis antigens were present in preparations from phylogenetically distinct isolates Pb18 and Pb3, as observed in immunoblots revealed with sera from PCM patients. In an enzyme-linked immunosorbent assay (ELISA), vesicle components containing α-Gal epitopes reacted strongly with anti-α-Gal antibodies isolated from both Chagas' disease and PCM patients, with Marasmius oreades agglutinin (MOA) (a lectin that recognizes terminal α-Gal), but only faintly with natural anti-α-Gal. Reactivity was inhibited after treatment with α-galactosidase. Vesicle preparations analyzed by electron microscopy showed vesicular structures of 20 to 200 nm that were labeled both on the surface and in the lumen with MOA. In P. brasiliensis cells, components carrying α-Gal epitopes were found distributed on the cell wall, following a punctuated confocal pattern, and inside large intracellular vacuoles. Lipid-free vesicle fractions reacted with anti-α-Gal in ELISA only when not digested with α-galactosidase, while reactivity with glycoproteins was reduced after β-elimination, which is indicative of partial O-linked chain localization. Our findings open new areas to explore in terms of host-parasite relationships in PCM and the role played in vivo by vesicle components and α-galactosyl epitopes.

Involvement of regulatory T cells in the immunosuppression characteristic of patients with paracoccidioidomycosis

Patients with paracoccidioidomycosis (PCM) exhibit a suppression of the cellular immune response characterized by negative delayed-type hypersensitivity (DTH) to Paracoccidioides brasiliensis antigens, the apoptosis of lymphocytes, and high levels of expression of cytotoxic-T-lymphocyte-associated antigen 4 (CTLA-4), interleukin-10 (IL-10), and transforming growth factor β (TGF-β). The aim of this study was to investigate whether and how regulatory T cells (Treg cells) are involved in this immunosuppression by analyzing the number, phenotype, and activity of these cells in patients with active disease (AD group) and patients who had received treatment (TD group). Our results showed that the AD patients had more Treg cells than the TD patients or controls (C group) and also had elevated levels of expression of regulatory markers (glucocorticoid-induced tumor necrosis factor [TNF] receptor-related protein [GITR], CTLA-4, CD95L, LAP-1, and CD38). An analysis of regulatory activity showed that Treg cells from the AD group had greater activity than did cells from the other groups and that cell-cell contact is mandatory for this activity in the C group but was only partially involved in the regulatory activity of cells from AD patients. The addition of anti-IL-10 and anti-TGF-β neutralizing antibodies to the cultures showed that the production of cytokines may be another mechanism used by Treg cells. In conclusion, the elevated numbers of these cells with an increased regulatory phenotype and strong suppressive activity suggest a potential role for them in the immunosuppression characteristic of paracoccidioidomycosis. In addition, our results indicate that while Treg cells act by cell-cell contact, cytokine production also plays an important role.

Immunological basis for the gender differences in murine Paracoccidioides brasiliensis infection

This study aimed to investigate the immunological mechanisms involved in the gender distinct incidence of paracoccidioidomycosis (pcm), an endemic systemic mycosis in Latin America, which is at least 10 times more frequent in men than in women. Then, we compared the immune response of male and female mice to Paracoccidioides brasiliensis infection, as well as the influence in the gender differences exerted by paracoccin, a P. brasiliensis component with carbohydrate recognition property. High production of Th1 cytokines and T-bet expression have been detected in the paracoccin stimulated cultures of spleen cells from infected female mice. In contrast, in similar experimental conditions, cells from infected males produced higher levels of the Th2 cytokines and expressed GATA-3. Macrophages from male and female mice when stimulated with paracoccin displayed similar phagocytic capability, while fungicidal activity was two times more efficiently performed by macrophages from female mice, a fact that was associated with 50% higher levels of nitric oxide production. In order to evaluate the role of sexual hormones in the observed gender distinction, we have utilized mice that have been submitted to gonadectomy followed by inverse hormonal reconstitution. Spleen cells derived from castrated males reconstituted with estradiol have produced higher levels of IFN-γ (1291±15 pg/mL) and lower levels of IL-10 (494±38 pg/mL), than normal male in response to paracoccin stimulus. In contrast, spleen cells from castrated female mice that had been treated with testosterone produced more IL-10 (1284±36 pg/mL) and less IFN-γ (587±14 pg/mL) than cells from normal female. In conclusion, our results reveal that the sexual hormones had a profound effect on the biology of immune cells, and estradiol favours protective responses to P. brasiliensis infection. In addition, fungal components, such as paracoccin, may provide additional support to the gender dimorphic immunity that marks P. brasiliensis infection.

Osteopontin involvement in granuloma formation and in the severity of Paracoccidioides brasiliensis infection

The participation of osteopontin (OPN) in Paracoccidioides brasiliensis infected mice, its association to granulomatogenesis, severity of infection, pattern of lesions, nitric oxide (NO) levels and fungal load were evaluated in this investigation. Immunohistochemistry analysis showed marked OPN staining in extracellular matrix and in macrophages and multinucleated giant cells at the center of lesions, suggesting a possible role of OPN in the distribution of these cells within the granulomas. At 15 days post-infection with a virulent P. brasiliensis isolate, OPN+ cells were more numerous and intensely immunostained in the loose granulomas of susceptible mice than in those of resistant mice. In addition, high fungal loads and low NO levels were observed in susceptible mice. At 120 days after infection, resistant mice had increased total OPN levels (ELISA) and OPN positivity in compact granulomas, higher NO levels and lower fungal loads than susceptible mice. Residual lesions associated with low OPN levels, high NO and control of fungal dissemination were observed in both mouse strains at 120 days post-infection with the slightly virulent fungal isolate. Therefore, OPN could be associated with higher severity of the disease in an early phase of infection and with a degree of control of the progressive infection.

Medicinal importance of fungal beta-(1-->3), (1-->6)-glucans

Non-cellulosic beta-glucans are now recognized as potent immunological activators, and some are used clinically in China and Japan. These beta-glucans consist of a backbone of glucose residues linked by beta-(1-->3)-glycosidic bonds, often with attached side-chain glucose residues joined by beta-(1-->6) linkages. The frequency of branching varies. The literature suggests beta-glucans are effective in treating diseases like cancer, a range of microbial infections, hypercholesterolaemia, and diabetes. Their mechanisms of action involve them being recognized as non-self molecules, so the immune system is stimulated by their presence. Several receptors have been identified, which include: dectin-1, located on macrophages, which mediates beta-glucan activation of phagocytosis and production of cytokines, a response co-ordinated by the toll-like receptor-2. Activated complement receptors on natural killer cells, neutrophils, and lymphocytes, may also be associated with tumour cytotoxicity. Two other receptors, scavenger and lactosylceramide, bind beta-glucans and mediate a series of signal pathways leading to immunological activation. Structurally different beta-glucans appear to have different affinities toward these receptors and thus generate markedly different host responses. However, the published data are not always easy to interpret as many of the earlier studies used crude beta-glucan preparations with, for the most part, unknown chemical structures. Careful choice of beta-glucan products is essential if their benefits are to be optimized, and a better understanding of how beta-glucans bind to receptors should enable more efficient use of their biological activities.

Histological and serological evidence of experimental paracoccidioidomycosis in Calomys callosus (Rodentia: Cricetidae)

The responses of animal experimental models related to the infectivity, virulence and pathogenicity of Paracoccidioides brasiliensis is constantly used to develop new perspectives of investigation. The rodent Calomys callosus, Rengger 1830 (Rodentia: Cricetidae) is an indigenous inhabitant of the savannah environment found in the central regions of Brazil. The aim of the present work was to evaluate the histopathological and serological features of C. callosus after inoculation with the Pb18 strain of P. brasiliensis. Furthermore, A/Sn and B10.A mice strains were also tested to compare the results obtained in C. callosus to these well-established experimental models of resistance and susceptibility respectively. In every instance, survival analysis was performed, and histopathological study of the lungs, liver and spleen was employed to investigate tissue involvement, degree of inflammation and fungal presence. Levels of antibodies to P. brasiliensis were measured by using an enzyme-linked immunosorbent assay after 4 weeks and at the advanced stage of infection. The mortality rate was proportional to inoculation dose in all groups, but overall it was much superior in C. callosus than in the B10.A-susceptible mice. Macroscopical and microscopical pathological alterations were also more extensive and remarkable for C. callosus, once again proportional to inoculation dose, but more noticeable differences among the studied groups were found with 0.6x10(5) inoculum. In addition, the serological profile of C. callosus was similar to that found for B10.A-susceptible mice. Infection of C. callosus with 0.6x10(8) Pb18 inoculum resulted in more serious illness, and it decreased in severity in proportion to the inoculum dose. This difference was more pronounced in C. callosus, and the clinical, serological and pathological findings in this animal were more intense and precocious compared with the B10.A-susceptible mice. The present results suggest that C. callosus is a potentially alternative experimental animal model for paracoccidioidomycosis infection.

Increased apoptosis during the early phase of experimental paracoccidioidomycosis as a phenotypic marker of resistance

Paracoccidiodomycosis (PCM) is a systemic mycosis that presents a wide spectrum of clinical manifestations caused by Paracoccidiodes brasiliensis. The experimental murine model has been used to approach the disease with susceptible and resistant mouse strains that reproduce most of the main human immunological features. We investigated whether the pattern of apoptosis of peritoneal cells from two polar strains of mice after infection with P. brasiliensis could be associated with the susceptibility or resistance to this pathogen. Apoptosis of A/J mouse cells (resistant), cultured in the presence or absence of LPS as stimuli, was observed as early as on the first day of infection. Cells from the infected susceptible strain BALB/c did not exhibit apoptosis in absence of LPS and persistently at a lesser degree than that observed in resistant mice. The apoptosis induced by the infection in resistant mice was not due to nitric oxide, since its blockage either in vitro or in vivo did not revert it. Analysis of additional strains of polar susceptibilities to PCM assured the dissociation of NO production and apoptosis. Interestingly, IL-6 and IL-10 were secreted in high amounts, by BALB/c cells and might be involved in shielding cells from apoptosis induced by P. brasiliensis. Furthermore, IFNgamma(-/-) mice did not show apoptosis of peritoneal cells while the Wt controls presented levels similar to those of A/J strain that secreted high amounts of IFNgamma and IL-1beta. The expression of Fas was increased in both strains and in Wt mice, whereas FasL was decreased in the susceptible strain and not significantly modulated in TNFRI and IFNgamma KO mice. These results suggest that apoptosis might be a mechanism of control of engagement of cells that could otherwise contribute to the susceptible phenotype observed in some strains of mice.

Tropical dermatology: fungal tropical diseases

Fungal infections are common in tropical countries and can have an important impact on public health. Lobomycosis is a common fungal infection in the tropical rain forest of South America, and paracoccidioidomycosis (South American blastomycosis) is a widespread and sometimes severe illness. Penicilliosis marneffei is an opportunistic infection of AIDS patients in southeast Asia. Chromoblastomycosis and mycetomas are causes of morbidity around the world. Sporotrichosis is a worldwide subcutaneous mycosis with a high incidence in tropical countries and is an important illness in immunocompromised patients. Rhinosporidiosis was classed as a fungal infection but is now considered a protistan parasite that belongs to the class Mesomycetozoea. It is included in this review because of its historical classification. In the past, most of these mycoses were restricted to specific geographic areas and natural reservoirs. There are, however, situations in which people from other regions come in contact with the pathogen. A common situation involves an accidental contamination of a traveler or worker who has contact with a tropical mycosis. Even minor trauma to the skin surface or inhalation of the fungal conidia can infect the patient. Thus recognition of the clinical symptoms and the dermatologic findings of the diseases, as well as the geographic distribution of the pathogens, can be critical in diagnosis of the tropical mycoses. This review discusses some of the more common tropical subcutaneous and systemic mycoses, as well as their signs, symptoms, methods of diagnosis, and therapies.

LEARNING OBJECTIVE

At the completion of this learning activity, participants should be able to recognize the clinical and histologic presentations of tropical fungal diseases with cutaneous manifestations and be familiar with the appropriate therapies.

A new Paracoccidioides brasiliensis 70-kDa heat shock protein reacts with sera from paracoccidioidomycosis patients

A cDNA coding for a new member of the 70-kDa heat shock proteins (HSP70) family from the dimorphic and pathogenic fungus, Paracoccidioides brasiliensis, was cloned and characterized. The cDNA-deduced sequence coded for 655 amino acid residues and showed 95% identity to a previously described P. brasiliensis hsp70 gene. Cytoplasmic and typical nuclear localization signals, which indicate induction upon stress, were identified in the deduced peptide. The complete hsp70 cDNA coding region was cloned into a pGEX 4T-3 plasmid and expressed in Escherichia coli as a glutathione-S-transferase-tagged fusion protein. The recombinant protein reacted with a rabbit polyclonal antibody against HSP70. Western immunoblot experiments demonstrated that sera from paracoccidioidomycosis patients recognized the purified recombinant protein, suggesting an immunological role for this protein in the infectious process. The antigenicity analysis of rHSP70 detected three internal peptides that could act as activators of T-cell proliferation.

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.

Identification of immunogenic proteins from Paracoccidioides brasiliensis antigenic fractions F0, FII and FIII

Paracoccidioides brasiliensis causes a chronic granulomatous mycosis prevalent in South America, and cell-mediated immunity is the principal mode of protection against this fungal infection. In this context, one of the strategies to discover proteins that are target of an effective immune response against P. brasiliensis is the partial sequencing of cDNA from an expression library previously screened with immunoglobulins (Ig) to generate antigen sequence tags (AST). In the present work, a P. brasiliensis yeast cDNA expression library was screened with affinity chromatography-purified IgG from rabbit sera immunized with P. brasiliensis antigenic fractions (F0, FII or FIII) or from paracoccidioidomycosis (PCM) patient sera by indirect ELISA. From 119 clones selected by the immunoscreening procedure, 40% were recognized by IgG from PCM patients, 25% were recognized by anti-F0, 8% were selected by anti-FII and 11% recognized by FIII specific antibodies. The remaining clones presented cross-reaction to all anti-sera tested. The AST homologies with previously reported sequences in the nonredundant GenBank at NCBI revealed high significant homology to fungal proteins of known function. One of them matched calcineurin B of Neurospora crassa with 35% identity and 55% similarity in amino acid sequence. We also identified an AST homologous to a Kinesin like protein from Ustilagus maydis and other fungi with 86% identity and 91% similarity. On the other hand, the vast majority of selected cDNA clones are new genes and represent 60% of the total. Prediction of transmembrane regions with the prediction transmembrane protein topology with a hidden markov model (TMHMM) revealed consensus sequences representing structural membrane segments in 28 encoded proteins.

Binding of laminin to Paracoccidioides brasiliensis induces a less severe pulmonary paracoccidioidomycosis caused by virulent and low-virulence isolates

The pathogenic fungus Paracoccidioides brasiliensis is the causative agent of paracoccidioidomycosis (PCM). This pulmonary mycosis, acquired by inhalation of airborne propagules, may disseminate to several internal organs and tissues, leading to severe disease. Adhesion to host cell components is the first step involved in dissemination of pathogens. Previous studies showed that laminin, the most abundant glycoprotein of the basement membrane, binds to P. brasiliensis yeast cells, enhancing their pathogenicity in the hamster testicle model. As PCM is primarily a pulmonary infection, we studied the influence of previous treatment of yeast cells with laminin on the course of the intratracheal infection of resistant and susceptible mice using high-virulence (Pb18) and low-virulence (Pb265) P. brasiliensis isolates. Laminin treatment did not alter fungal loads, delayed-type hypersensitivity reactions, levels of pulmonary cytokines and production of specific antibodies in any group of Pb18-infected mice. However, early in the infection, a less intense inflammatory reaction was detected in the lungs of the laminin-treated groups. In addition, laminin treatment of Pb265 resulted in a less severe infection as revealed by the lower fungal loads recovered from lungs. Antibody and cytokine levels, however, did not change after laminin treatment. Altogether, our results demonstrate that laminin binding to yeast cells diminishes P. brasiliensis pathogenicity. The lower inflammatory response observed with the virulent isolate and the decreased pulmonary fungal burden with the low-virulence isolate indicate an inhibitory effect of laminin treatment on P. brasiliensis infectivity and interaction with pulmonary host cells or extracellular matrix proteins.