A chitin-like component on sclerotic cells of Fonsecaea pedrosoi inhibits Dectin-1-mediated murine Th17 development by masking β-glucans

A novel chitinase Chi6 with immunosuppressive activity promotes white spot syndrome virus (WSSV) infection in Penaeus vannamei

Chitinases, a group of glycosylase hydrolases that can hydrolyze chitin, are involved in immune regulation in animals. White spot syndrome virus (WSSV) causes huge losses to crustacean aquaculture every year. We identified a novel chitinase Chi6 from Pacific white shrimp Penaeus vannamei, which contains a catalytic domain but no chitin-binding domain. The Chi6 expression was regulated by multiple immune signaling pathways and increased after immune stimulations. Silencing of Chi6 by RNAi in vivo did not affect Vibrio parahaemolyticus infection, but significantly increased the survival rate of WSSV-infected shrimp. The expression of multiple WSSV immediate early and structural genes was also decreased upon Chi6 silencing. The recombinant Chi6 protein showed no effect on bacterial growth but could attenuate shrimp hemocyte phagocytosis. The mRNA levels of several key elements and downstream genes of the MAPK and Dorsal pathways in Chi6-silenced shrimp were significantly up-regulated, suggesting an inhibitory effect of Chi6 on humoral immune response. Moreover, Chi6 enhanced the regulatory effect of Dorsal on the expression of WSSV ie1 gene. Therefore, Chi6 promotes WSSV infection through immunosuppression and regulation of WSSV gene expression. Targeting Chi6 could be a potential strategy for controlling WSSV disease in shrimp farming.

Curdlan, a Microbial β-Glucan, Has Contrasting Effects on Autoimmune and Viral Models of Multiple Sclerosis

Multiple sclerosis (MS) is an immune-mediated disease characterized by inflammatory demyelination and axonal degeneration in the central nervous system (CNS). Bacterial and fungal infections have been associated with the development of MS; microbial components that are present in several microbes could contribute to MS pathogenesis. Among such components, curdlan is a microbial 1,3-β-glucan that can stimulate dendritic cells, and enhances T helper (Th) 17 responses. We determined whether curdlan administration could affect two animal models for MS: an autoimmune model, experimental autoimmune encephalomyelitis (EAE), and a viral model, Theiler's murine encephalomyelitis virus (TMEV)-induced demyelinating disease (TMEV-IDD). We induced relapsing-remitting EAE by sensitizing SJL/J mice with the myelin proteolipid protein (PLP)139-151 peptide and found that curdlan treatment prior to PLP sensitization converted the clinical course of EAE into hyperacute EAE, in which the mice developed a progressive motor paralysis and died within 2 weeks. Curdlan-treated EAE mice had massive infiltration of T cells and neutrophils in the CNS with higher levels of Th17 and Th1 responses, compared with the control EAE mice. On the other hand, in TMEV-IDD, we found that curdlan treatment reduced the clinical scores and axonal degeneration without changes in inflammation or viral persistence in the CNS. In summary, although curdlan administration exacerbated the autoimmune MS model by enhancing inflammatory demyelination, it suppressed the viral MS model with reduced axonal degeneration. Therefore, microbial infections may play contrasting roles in MS depending on its etiology: autoimmunity versus viral infection.

The Tyrosine Kinase Tec Regulates Effector Th17 Differentiation, Pathogenicity, and Plasticity in T-Cell-Driven Intestinal Inflammation

T helper (Th) 17 cells are not only key in controlling infections mediated by extracellular bacteria and fungi but are also triggering autoimmune responses. Th17 cells comprise heterogeneous subsets, some with pathogenic functions. They can cease to secrete their hallmark cytokine IL-17A and even convert to other T helper lineages, a process known as transdifferentiation relying on plasticity. Both pathogenicity and plasticity are tightly linked to IL-23 signaling. Here, we show that the protein tyrosine kinase Tec is highly induced in Th17 cells. Th17 differentiation was enhanced at low interleukin-6 (IL-6) concentrations in absence of Tec, which correlates with increased STAT3 phosphorylation and higher Il23r expression. Therefore, we uncovered a function for Tec in the IL-6 sensing via STAT3 by CD4+ T cells, defining Tec as a fine-tuning negative regulator of Th17 differentiation. Subsequently, by using the IL-17A fate mapping mouse combined with in vivo adoptive transfer models, we demonstrated that Tec not only restrained effector Th17 differentiation but also pathogenicity and plasticity in a T-cell intrinsic manner. Our data further suggest that Tec regulates inflammatory Th17-driven immune responses directly impacting disease severity in a T-cell-driven colitis model. Notably, consistent with the in vitro findings, elevated levels of the IL-23 receptor (IL-23R) were observed on intestinal pre- and postconversion Th17 cells isolated from diseased Tec-/- mice subjected to adoptive transfer colitis, highlighting a fundamental role of Tec in restraining IL-23R expression, likely via the IL-6-STAT3 signaling axis. Taken together, these findings identify Tec as a negative regulator of Th17 differentiation, pathogenicity, and plasticity, contributing to the mechanisms which help T cells to orchestrate optimal immune protection and to restrain immunopathology.

The Role of IL-17-Producing Cells in Cutaneous Fungal Infections

The skin is the outermost layer of the body and is exposed to many environmental stimuli, which cause various inflammatory immune responses in the skin. Among them, fungi are common microorganisms that colonize the skin and cause cutaneous fungal diseases such as candidiasis and dermatophytosis. The skin exerts inflammatory responses to eliminate these fungi through the cooperation of skin-component immune cells. IL-17 producing cells are representative immune cells that play a vital role in anti-fungal action in the skin by producing antimicrobial peptides and facilitating neutrophil infiltration. However, the actual impact of IL-17-producing cells in cutaneous fungal infections remains unclear. In this review, we focused on the role of IL-17-producing cells in a series of cutaneous fungal infections, the characteristics of skin infectious fungi, and the recognition of cell components that drive cutaneous immune cells.

Immune Sensing and Potential Immunotherapeutic Approaches to Control Chromoblastomycosis

Chromoblastomycosis (CBM) is a neglected, chronic, and progressive subcutaneous mycosis caused by different species of fungi from the Herpotrichiellaceae family. CBM disease is usually associated with agricultural activities, and its infection is characterized by verrucous, erythematous papules, and atrophic lesions on the upper and lower limbs, leading to social stigma and impacts on patients' welfare. The economic aspect of disease treatment is another relevant issue. There is no specific treatment for CBM, and different anti-fungal drug associations are used to treat the patients. However, the long period of the disease and the high cost of the treatment lead to treatment interruption and, consequently, relapse of the disease. In previous years, great progress had been made in the comprehension of the CBM pathophysiology. In this review, we discuss the differences in the cell wall composition of conidia, hyphae, and muriform cells, with a particular focus on the activation of the host immune response. We also highlight the importance of studies about the host skin immunology in CBM. Finally, we explore different immunotherapeutic studies, highlighting the importance of these approaches for future treatment strategies for CBM.

Muriform Cells Can Reproduce by Dividing in an Athymic Murine Model of Chromoblastomycosis due to Fonsecaea pedrosoi

Transformation of Fonsecaea pedrosoi into muriform cells enhances the resistance against phagocytosis and elimination by host immune cells, and links to the chronicity of chromoblastomycosis. Here, we aim to determine whether the muriform cells can reproduce in tissue without reverse transformation into hyphal form by using an experimental nu/nu-BALB/c mouse model of chromoblastomycosis due to F. pedrosoi. During the whole 81-day observation period, most of the hyphal inocula had transformed into muriform cells at 75 days postinoculation and maintained as this parasitic morphology till 81 days postinoculation simultaneously with increased fungal loads in tissue and the worsening of footpad lesion. Scanning and transmitting electronic microscope examinations showed that the muriform cells obtained in tissue or induced in vitro can reproduce daughter cells by dividing, and, meanwhile, the daughter cells had the potential to produce buds and grow into hyphae reversely. Furthermore, exoenzyme examination suggested that the profile of exoenzymes constituted by muriform cells was quite different from that constituted by hyphae although the assay showed both of them had obvious metabolic activity. By contrast, most muriform cells in the footpad gradually transformed into the elongated hyphae without obvious infiltration of inflammatory cells during repeated intraperitoneal administration of cyclophosphamide (50 mg/kg, per every other day) from 50 to 80 days postinoculation. Therefore, we infer that F. pedrosoi can reproduce by dividing as muriform cells in mouse tissue, and the morphological transformation between hyphal form and muriform cells is possibly associated with the host immune status.

Embryonic stem cell-derived exosomes inhibit doxorubicin-induced TLR4-NLRP3-mediated cell death-pyroptosis

Doxorubicin (Dox)-induced cardiac side effects are regulated through increased oxidative stress and apoptosis. However, it remains unknown whether Dox induces the specific inflammatory-mediated form of cell death called pyroptosis. The current study is undertaken to determine whether Dox induces pyroptosis in an in vitro model and to test the potential of exosomes derived from embryonic stem cells (ES-Exos) in inhibiting pyroptosis. H9c2 cells were exposed to Dox to generate pyroptosis and then subsequently treated with exosomes to investigate the protective effects of ES-Exos. Mouse embryonic fibroblast-exosomes (MEF-Exos) were used as a cell line control. We confirmed pyroptosis by analyzing the presence of Toll-like receptor 4 (TLR4)-pyrin domain containing-3 (NLRP3) inflammasome that initiates pyroptosis, which was further confirmed with pyroptotic markers caspase-1, IL-1β, caspase-11, and gasdermin-D. The presence of inflammation was confirmed for proinflammatory cytokines, TNF-α, and IL-6. Our data show that Dox exposure significantly (P < 0.05) increases expression of TLR4, NLRP3, pyroptotic markers (caspase-1, IL-1β, caspase-11, and gasdermin-D), and proinflammatory cytokines (TNF-α and IL-6) in H9c2 cells. The increased expression of inflammasome, pyroptosis, and inflammation was significantly (P < 0.05) inhibited by ES-Exos. Interestingly, our cell line control, MEF-Exos, did not show any protective effects. Furthermore, our cytokine array data suggest increased anti-inflammatory (IL-4, IL-9, and IL-13) and decreased proinflammatory cytokines (Fas ligand, IL-12, and TNF-α) in ES-Exos, suggesting that anti-inflammatory cytokines might be mediating the protective effects of ES-Exos. In conclusion, our data show that Dox induces pyroptotic cell death in the H9c2 cell culture model and is attenuated via treatment with ES-Exos.NEW & NOTEWORTHY Doxorubicin (Dox)-induced cardiotoxicity is mediated through increased oxidative stress, apoptosis, and necrosis. We report for the first time as per the best of our knowledge that Dox initiates Toll-like receptor 4 and pyrin domain containing-3 inflammasome formation and induces caspase-1-mediated inflammatory pyroptotic cell death in H9c2 cells. Moreover, we establish that inflammation and pyroptosis is inhibited by embryonic stem cell-derived exosomes that could be used as a future therapeutic option to treat Dox-induced cardiotoxicity.

[Long-pulsed 1064 nm Nd: YAG laser combined with terbinafine against chromoblastomycosis caused by Fonsecaea nubica and the effect of laser therapy in a Wistar rat model]

We report a case of chromoblastomycosis caused by Fonsecaea nubica, which was successfully treated by long-pulsed 1064 nm Nd: YAG laser combined with terbinafine. A 60-year-old man was admitted for the presence of a 30 mm×40 mm erythematous plaque on the dorsum of his right hand for about 10 months without any subjective symptoms. Both microscopic examination and tissue biopsy of the lesion showed characteristic sclerotic bodies of chromoblastomycosis. Lesion tissue culture on SDA at 26 ℃ for 2 weeks resulted in a black colony, and slide culture identified the isolate as Fonsecaea species. ITS sequence analysis of the isolate showed a 99% homology with F. nubica strain KX078407. The in vitro susceptibility of the isolate to 9 antifungal agents was determined using the microdilution method according to the guidelines of CLSI M38-A2 protocol, and terbinafine showed the lowest MIC (0.125 μg/ml). We subsequently established a Wistar rat model of chromoblastomycosis using the clinical isolate F. nubica and treated the rats with long-pulsed 1064 nm Nd: YAG laser (pulse width of 3.0 ms, fluence of 24 J/cm², spot size of 3 mm, frequency of 4 Hz, repeated 3 times at an interval of 30 s) twice a week for a total of 8 sessions. Although the laser treatment alone was not able to eliminate the fungi, histopathological examination showed the aggregation of numerous lymphocytes in the local affected tissue, indicating an immune response that consequently facilitate the regression of the lesion. The patient was successfully treated by long-pulsed 1064 nm Nd: YAG laser once a week combined with terbinafine (0.25 /bid) for 8 weeks, and follow-up for 20 months did not reveal any signs of recurrence.

Immune Responses of Mammals and Plants to Chitin-Containing Pathogens

Chitin-containing organisms, such as fungi and arthropods, use chitin as a structural component to protect themselves from harsh environmental conditions. Hosts such as mammals and plants, however, sense chitin to initiate innate and adaptive immunity and exclude chitin-containing organisms. A number of protein factors are then expressed, and several signaling pathways are triggered. In this chapter, we focus on the responses and signal transduction pathways that are activated in mammals and plants upon invasion by chitin-containing organisms. As host chitinases play important roles in the glycolytic processing of chitin, which is then recognized by pattern-recognition receptors, we also pay special attention to the chitinases that are involved in immune recognition.

Chitin and Its Effects on Inflammatory and Immune Responses

Chitin, a potential allergy-promoting pathogen-associated molecular pattern (PAMP), is a linear polymer composed of N-acetylglucosamine residues which are linked by β-(1,4)-glycosidic bonds. Mammalians are potential hosts for chitin-containing protozoa, fungi, arthropods, and nematodes; however, mammalians themselves do not synthetize chitin and thus it is considered as a potential target for recognition by mammalian immune system. Chitin is sensed primarily in the lungs or gut where it activates a variety of innate (eosinophils, macrophages) and adaptive immune cells (IL-4/IL-13 expressing T helper type-2 lymphocytes). Chitin induces cytokine production, leukocyte recruitment, and alternative macrophage activation. Intranasal or intraperitoneal administration of chitin (varying in size, degree of acetylation and purity) to mice has been applied as a routine approach to investigate chitin's priming effects on innate and adaptive immunity. Structural chitin present in microorganisms is actively degraded by host true chitinases, including acidic mammalian chitinases and chitotriosidase into smaller fragments that can be sensed by mammalian receptors such as FIBCD1, NKR-P1, and RegIIIc. Immune recognition of chitin also involves pattern recognition receptors, mainly via TLR-2 and Dectin-1, to activate immune cells to induce cytokine production and creation of an immune network that results in inflammatory and allergic responses. In this review, we will focus on various immunological aspects of the interaction between chitin and host immune system such as sensing, interactions with immune cells, chitinases as chitin degrading enzymes, and immunologic applications of chitin.

Fonsecaea pedrosoi Sclerotic Cells: Secretion of Aspartic-Type Peptidase and Susceptibility to Peptidase Inhibitors

Fonsecaea pedrosoi is a dematiaceous fungus and the main causative agent of chromoblastomycosis that is a chronic disease usually affecting the human skin and subcutaneous tissues, which causes deformations and incapacities, being frequently refractory to available therapies. A typical globe-shaped, multiseptated and pigmented cells, known as sclerotic cells, are found in the lesions of infected individuals. In the present work, we have investigated the production of aspartic-type peptidase in F. pedrosoi sclerotic cells as well as the effect of peptidase inhibitors (PIs) on its enzymatic activity and viability. Our data showed that sclerotic cells are able to secrete pepstatin A-sensible aspartic peptidase when grown under chemically defined conditions. In addition, aspartic PIs (ritonavir, nelfinavir, indinavir, and saquinavir), which are clinically used in the HIV chemotherapy, significantly decreased the fungal peptidase activity, varying from 55 to 99%. Moreover, sclerotic cell-derived aspartic peptidase hydrolyzed human albumin, an important serum protein, as well as laminin, an extracellular matrix component, but not immunoglobulin G and fibronectin. It is well-known that aspartic peptidases play important physiological roles in fungal cells. With this task in mind, the effect of pepstatin A, a classical aspartic peptidase inhibitor, on the F. pedrosoi proliferation was evaluated. Pepstatin A inhibited the fungal viability in both cellular density- and drug-concentration manners. Moreover, HIV-PIs at 10 μM powerfully inhibited the viability (>65%) of F. pedrosoi sclerotic cells. The detection of aspartic peptidase produced by sclerotic cells, the parasitic form of F. pedrosoi, may contribute to reveal new virulence markers and potential targets for chromoblastomycosis therapy.

Galleria mellonella as a model invertebrate host for the study of muriform cells of dematiaceous fungi

AIM

To study the pathogenesis of chromoblastomycosis using the alternative model host Galleria mellonella.

METHODOLOGY

We analyzed the virulence of different dematiaceous fungal strains and the host immune responses (hemocytes density and morphological changes) to Fonsecaea monophora by the alternative infection model. Then detected the development of the pathogenic muriform cells within larvae under microscope.

RESULTS

Increasing inocula resulted in greater larval mortality and Cladophialophora carrionii was the most virulent. Low inocula activated the humoral immune response significantly. Moreover, the conidia underwent morphological transition to muriform cells within larvae.

CONCLUSION

We developed an invertebrate host model that can be used to evaluate the virulence of dematiaceous fungi, which may provide further insights into overcoming current limitations in studying chromoblastomycosis in vivo.

Dynamic Fungal Cell Wall Architecture in Stress Adaptation and Immune Evasion

Deadly infections from opportunistic fungi have risen in frequency, largely because of the at-risk immunocompromised population created by advances in modern medicine and the HIV/AIDS pandemic. This review focuses on dynamics of the fungal polysaccharide cell wall, which plays an outsized role in fungal pathogenesis and therapy because it acts as both an environmental barrier and as the major interface with the host immune system. Human fungal pathogens use architectural strategies to mask epitopes from the host and prevent immune surveillance, and recent work elucidates how biotic and abiotic stresses present during infection can either block or enhance masking. The signaling components implicated in regulating fungal immune recognition can teach us how cell wall dynamics are controlled, and represent potential targets for interventions designed to boost or dampen immunity.

Transformation of Fonsecaea pedrosoi into sclerotic cells links to the refractoriness of experimental chromoblastomycosis in BALB/c mice via a mechanism involving a chitin-induced impairment of IFN-γ production

Fonsecaea pedrosoi (F. pedrosoi) is the most common agent of chromoblastomycosis. Transformation of this fungus from its saprophytic phase into pathogenic sclerotic cells in tissue is an essential link to the refractoriness of this infection. Experimental studies in murine models have shown that the absence of CD4+ T cells impairs host defense against F. pedrosoi infection. Clinical research has also suggested that a relatively low level of the Th1 cytokine INF-γ and inefficient T cell proliferation are simultaneously present in patients with severe chromoblastomycosis upon in vitro stimulation with ChromoAg, an antigen prepared from F. pedrosoi. In the present study, we show that in mice intraperitoneally infected with F. pedrosoi-spores, -hyphae or in vitro-induced sclerotic cells respectively, the transformation of this causative agent into sclerotic cells contributes to a compromised Th1 cytokine production in the earlier stage of infection with impaired generation of neutrophil reactive oxygen species (ROS) and pan-inhibition of Th1/Th2/Th17 cytokine production with disseminated infection in the later stage by using a CBA murine Th1/Th2/Th17 cytokine kit. In addition, we have further demonstrated that intraperitoneal administration of recombinant mouse IFN-γ (rmIFN-γ) effectively reduces the fungal load in the infected mouse spleen, and dampens the peritoneal dissemination of F. pedrosoi-sclerotic cells. Meanwhile, exogeneous rmIFN-γ contributes to the formation and maintenance of micro-abscess and restores the decrease in neutrophil ROS generation in the mouse spleen infected with F. pedrosoi-sclerotic cells. Of note, we have once again demonstrated that it is a chitin-like component, but not β-glucans or mannose moiety, that exclusively accumulates on the outer cell wall of F. pedrosoi-sclerotic cells which were induced in vitro or isolated from the spleens of intraperitoneally infected BALB/c mice. In addition, our results indicate that decreased accumulation of chitin on the surface of live F. pedrosoi-sclerotic cells after chitinase treatment can be self-compensated in a time-dependent manner. Importantly, we have for the first time demonstrated that exclusive accumulation of chitin on the transformed sclerotic cells of F. pedrosoi is involved in an impaired murine Th1 cytokine profile, therefore promoting the refractoriness of experimental murine chromoblastomycosis.

The Major Chromoblastomycosis Etiologic Agent Fonsecaea pedrosoi Activates the NLRP3 Inflammasome

Fonsecaea pedrosoi is the main etiologic agent of chromoblastomycosis (CBM), one of the most prevalent subcutaneous mycosis in tropical and subtropical countries. CBM is a poorly characterized chronic infection that commonly starts after transcutaneous inoculation of conidia and saprophytic hyphae of F. pedrosoi. Recently, we have shown that unlike conidia, hyphae and muriform cells (the parasitic morphotype) of F. pedrosoi promotes an intense inflammatory response pattern in vivo, which comprises the production of an inflammasome-derived cytokine, IL-1β. Nonetheless, the mechanisms underlying IL-1β production and maturation upon F. pedrosoi infection and its functional output in the course of CBM remains unknown. We show here that F. pedrosoi hyphae, differently from conidia, induce IL-1β secretion in both bone marrow-derived dendritic cells and macrophages. Using inhibitors and knockout cells, we demonstrated that the mechanisms underlying IL-1β production by hyphae-infected macrophages were dependent on dectin-1, -2, and -3 receptors and the Syk-NF-kB signaling pathway. Furthermore, F. pedrosoi promoted a NLRP3-dependent inflammasome activation, which required potassium efflux, reactive oxygen species production, phagolysosomal acidification, and cathepsin B release as triggers. IL-1β processing and release was mediated primarily by caspase-1 and, to a lesser extent, by caspase-8-dependent cleavage. Finally, we showed using a murine CBM model that F. pedrosoi elicits a NLRP3-regulated IL-1β and interleukin-18 release in vivo, but without NLRP3 inflammasome activation interfering in the course of the experimental infection.

The Interaction of Pneumocystis with the C-Type Lectin Receptor Mincle Exerts a Significant Role in Host Defense against Infection

Pneumocystis pneumonia (PCP) remains a major cause of morbidity and mortality within immunocompromised patients. In this study, we examined the potential role of macrophage-inducible C-type lectin (Mincle) for host defense against Pneumocystis Binding assays implementing soluble Mincle carbohydrate recognition domain fusion proteins demonstrated binding to intact Pneumocystis carinii as well as to organism homogenates, and they purified major surface glycoprotein/glycoprotein A derived from the organism. Additional experiments showed that rats with PCP expressed increased Mincle mRNA levels. Mouse macrophages overexpressing Mincle displayed increased binding to P. carinii life forms and enhanced protein tyrosine phosphorylation. The binding of P. carinii to Mincle resulted in activation of FcRγ-mediated cell signaling. RNA silencing of Mincle in mouse macrophages resulted in decreased activation of Syk kinase after P. carinii challenge, critical in downstream inflammatory signaling. Mincle-deficient CD4-depleted (Mincle^-/-) mice showed a significant defect in organism clearance from the lungs with higher organism burdens and altered lung cytokine responses during Pneumocystis murina pneumonia. Interestingly, Mincle^-/- mice did not demonstrate worsened survival during PCP compared with wild-type mice, despite the markedly increased organism burdens. This may be related to increased expression of anti-inflammatory factors such as IL-1Ra during infection in the Mincle^-/- mice. Of note, the P. murina-infected Mincle^-/- mice demonstrated increased expression of known C-type lectin receptors Dectin-1, Dectin-2, and MCL compared with infected wild-type mice. Taken together, these data support a significant role for Mincle in Pneumocystis modulating host defense during infection.

The Role of Phagocytes and NETs in Dermatophytosis

Innate immunity is the host first line of defense against pathogens. However, only in recent years, we are beginning to better understand the ways it operates. A key player is this branch of the immune response that are the phagocytes, as macrophages, dendritic cells and neutrophils. These cells act as sentinels, employing specialized receptors in the sensing of invaders and host injury, and readily responding to them by production of inflammatory mediators. They afford protection not only by ingesting and destroying pathogens, but also by providing a suitable biochemical environment that shapes the adaptive response. In this review, we aim to present a broad perspective about the role of phagocytes in dermatophytosis, focusing on the mechanisms possibly involved in protective and non-protective responses. A full understanding of how phagocytes fit in the pathogenesis of these infections may open the venue for the development of new and more effective therapeutic approaches.

Immune response in human chromoblastomycosis and eumycetoma - focusing on human interleukin-17A, interferon-gamma, tumour necrosis factor-alpha, interleukin-1 beta and human beta-defensin-2

Knowledge regarding host immune response to chromoblastomycosis and eumycetoma is limited, particularly concerning cytokines and antimicrobial peptides production. This was a retrospective study of 12 paraffin-embedded tissue samples from patients diagnosed with chromoblastomycosis or eumycetoma from histological findings and tissue culture. DNA extraction and polymerase chain reaction (PCR) from tissues were done to evaluate human interleukin-17A (IL-17A), interferon-gamma (IFN-γ), tumour necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β) and human beta-defensin-2 (HBD-2) expressions. Human beta-actin primer was used for confirming DNA detection, and DNA extracted from psoriasis lesional skin samples was used as positive controls. The twelve paraffin-embedded sections used in this study consisted of five chromoblastomycosis and seven eumycetoma tissues. All PCR reactions showed beta-actin band at 51 bp in all clinical specimens, confirming adequate DNA levels in each reaction. As positive control, the psoriasis skin samples revealed bands for IL-17A at 174 bp, IFN-γ at 273 bp, TNF-α at 360 bp, IL-1β at 276 bp and HBD-2 at 255 bp. For the chromoblastomycosis and eumycetoma tissues, PCR analyses showed IL-17A band at 174 bp in two eumycetoma tissues and HBD-2 band at 255 bp in a chromoblastomycosis tissue. This study demonstrated IL-17A expression in human eumycetoma and HBD-2 expression in human chromoblastomycosis for the first time. However, their role in immune response remains to be elucidated.

Dectin-1 and Dectin-2 promote control of the fungal pathogen Trichophyton rubrum independently of IL-17 and adaptive immunity in experimental deep dermatophytosis

Dermatophytoses are chronic fungal infections, the main causative agent of which is Trichophyton rubrum (T. rubrum). Despite their high occurrence worldwide, the immunological mechanisms underlying these diseases remain largely unknown. Here, we uncovered the C-type lectin receptors, Dectin-1 and Dectin-2, as key elements in the immune response to T. rubrum infection in a model of deep dermatophytosis . In vitro, we observed that deficiency in Dectin-1 and Dectin-2 severely compromised cytokine production by dendritic cells. In vivo, mice lacking Dectin-1 and/or Dectin-2 showed an inadequate pro-inflammatory cytokine production in response to T. rubrum infection, impairing its resolution. Strikingly, neither adaptive immunity nor IL-17 response were required for fungal clearance, highlighting innate immunity as the main checkpoint in the pathogenesis of T. rubrum infection.

The Ligands of C-Type Lectins

In this chapter, a comprehensive overview of the known ligands for the C-type lectins (CTLs) is provided. Emphasis has been placed on the chemical structure of the glycans that bind to the different CTLs and the amount of structural variation (or overlap) that each CTL can tolerate. In this way, both the synthetic carbohydrate chemist and the immunologist can more readily gain insight into the existing structure-activity space for the CTL ligands and, ideally, see areas of synergy that will help identify and refine the ligands for these receptors.