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

Mechanism of Salvia miltiorrhiza Bunge extract to alleviate Chronic Sleep Deprivation-Induced cognitive dysfunction in rats

BACKGROUND

Bidirectional communication between the gut microbiota and the brain may play an essential role in the cognitive dysfunction associated with chronic sleep deprivation(CSD). Salvia miltiorrhiza Bunge (Danshen, DS), a famous Chinese medicine and functional tea, is extensively used to protect learning and memory capacities, although the mechanism of action remains unknown.

PURPOSE

The purpose of this research was to explore the efficacy and the underlying mechanism of DS in cognitive dysfunction caused by CSD.

METHODS

DS chemical composition was analyzed by UPLC-QTOF-MS/MS. Forty rats were randomly assigned to five groups (n = 8): control (CON), model (MOD), low- (1.35 g/kg, DSL), high-dose (2.70 g/kg, DSH) DS group, and Melatonin(100 mg/kg, MT) group. A CSD rat model was established over 21 days. DS's effects and the underlying mechanism were explored using the open-field test(OFT), Morris water-maze(MWM), tissue staining(Hematoxylin and Eosin Staining, Nissl staining, Alcian blue-periodic acid SCHIFF staining, and Immunofluorescence), enzyme-linked immunosorbent assay, Western blot, quantitative real-time polymerase chain reaction(qPCR), and 16S rRNA sequencing.

RESULTS

We demonstrated that CSD caused gut dysbiosis and cognitive dysfunction. Furthermore, 16S rRNA sequencing demonstrated that Firmicutes and Proteobacteria were more in fecal samples from model group rats, whereas Bacteroidota and Spirochaetota were less. DS therapy, on the contrary hand, greatly restored the gut microbial community, consequently alleviating cognitive impairment in rats. Further research revealed that DS administration reduced systemic inflammation via lowering intestinal inflammation and barrier disruption. Following that, DS therapy reduced Blood Brain Barrier(BBB) and neuronal damage, further decreasing neuroinflammation in the hippocampus(HP). Mechanistic studies revealed that DS therapy lowered lipopolysaccharide (LPS) levels in the HP, serum, and colon, consequently blocking the TLR4/MyD88/NF-κB signaling pathway and its downstream pro-inflammatory products(IL-1β, IL-6, TNF-α, iNOS, and COX2) in the HP and colon.

CONCLUSION

DS treatment dramatically improved spatial learning and memory impairments in rats with CSD by regulating the composition of the intestinal flora, preserving gut and brain barrier function, and reducing inflammation mediated by the LPS-TLR4 signaling pathway. Our findings provide novel insight into the mechanisms by which DS treats cognitive dysfunction caused by CSD.

Differential Upregulation of Th1/Th17-Associated Proteins and PD-L1 in Granulomatous Mycosis Fungoides

Granulomatous Mycosis Fungoides (GMF) is a rare form of mycosis fungoides (MF) characterized by a granulomatous infiltrate associated with the neoplastic lymphoid population and is considered to have a worse prognosis compared with regular MF. The upregulation of the T helper (Th) axis, especially Th17, plays an important role in the pathogenesis of several inflammatory/infectious granulomatous cutaneous diseases, but its role in GMF is still not elucidated to date. In this study, we evaluated the immunohistochemical expression of Th1 (Tbet), Th2 (GATA-3), Th17 (RORγT), T regulatory (Foxp3), and immune checkpoint (IC) (PD-1 and PD-L1) markers in a cohort of patients with GMF and MF with large cell transformation (MFLCT). Skin biopsies from 49 patients (28 GMF and 21 MFLCT) were studied. Patients with GMF were associated with early clinical stage (p = 0.036) and lower levels of lactate dehydrogenase (p = 0.042). An increased percentage of cells positive for Tbet (p = 0.017), RORγT (p = 0.001), and PD-L1 (p = 0.011) was also observed among the GMF specimens, while a stronger PD-1 intensity was detected in cases of MFLCT. In this cohort, LCT, RORγT < 10%, Foxp3 < 10%, age, and advanced stage were associated with worse overall survival (OS) in univariate analysis. GMF demonstrated Th1 (cellular response) and Th17 (autoimmunity) phenotype, seen in early MF and granulomatous processes, respectively, which may be related to the histopathological appearance and biological behavior of GMF. Further studies involving larger series of cases and more sensitive techniques are warranted.

Dectin-2 is critical for phagocyte function and resistance to Paracoccidioides brasiliensis in mice

Germline-encoded pattern recognition receptors, particularly C-type lectin receptors (CLRs), are essential for phagocytes to sense invading fungal cells. Among CLRs, Dectin-2 (encoded by Clec4n) plays a critical role in the antifungal immune response as it recognizes high-mannose polysaccharides on the fungal cell wall, triggering phagocyte functional activities and ultimately determining adaptive responses. Here, we assessed the role of Dectin-2 on the course of primary Paracoccidioides brasiliensis systemic infection in mice with Dectin-2-targeted deletion. Paracoccidioides brasiliensis constitutes the principal etiologic agent of paracoccidioidomycosis, the most prominent invasive mycosis in Latin American countries. The deficiency of Dectin-2 resulted in shortened survival rates, high lung fungal burden, and increased lung pathology in mice infected with P. brasiliensis. Consistently, dendritic cells (DCs) from mice lacking Dectin-2 infected ex vivo with P. brasiliensis showed impaired secretion of several proinflammatory and regulatory cytokines, including TNF-α, IL-1β, IL-6, and IL-10. Additionally, when cocultured with splenic lymphocytes, DCs were less efficient in promoting a type 1 cytokine pattern secretion (i.e., IFN-γ). In macrophages, Dectin-2-mediated signaling was required to ensure phagocytosis and fungicidal activity associated with nitric oxide production. Overall, Dectin-2-mediated signaling is critical to promote host protection against P. brasiliensis infection, and its exploitation might lead to the development of new vaccines and immunotherapeutic approaches.

Transcriptional profiling of a fungal granuloma reveals a low metabolic activity of Paracoccidioides brasiliensis yeasts and an actively regulated host immune response

Granulomas are important immunological structures in the host defense against the fungus Paracoccidioides brasiliensis, the main etiologic agent of Paracoccidioidomycosis (PCM), a granulomatous systemic mycosis endemic in Latin America. We have performed transcriptional and proteomic studies of yeasts present in the pulmonary granulomas of PCM aiming to identify relevant genes and proteins that act under stressing conditions. C57BL/6 mice were infected with 1x106 yeasts and after 8- and 12-weeks of infection, granulomatous lesions were obtained for extraction of fungal and murine RNAs and fungal proteins. Dual transcriptional profiling was done comparing lung cells and P. brasiliensis yeasts from granulomas with uninfected lung cells and the original yeast suspension used in the infection, respectively. Mouse transcripts indicated a lung malfunction, with low expression of genes related to muscle contraction and organization. In addition, an increased expression of transcripts related to the activity of neutrophils, eosinophils, macrophages, lymphocytes as well as an elevated expression of IL-1β, TNF-α, IFN-γ, IL-17 transcripts were observed. The increased expression of transcripts for CTLA-4, PD-1 and arginase-1, provided evidence of immune regulatory mechanisms within the granulomatous lesions. Also, our results indicate iron as a key element for the granuloma to function, where a high number of transcripts related to fungal siderophores for iron uptake was observed, a mechanism of fungal virulence not previously described in granulomas. Furthermore, transcriptomics and proteomics analyzes indicated a low fungal activity within the granuloma, as demonstrated by the decreased expression of genes and proteins related to energy metabolism and cell cycle.

Arterial wall fibrosis in Takayasu arteritis and its potential for therapeutic modulation

Arterial wall damage in Takayasu arteritis (TAK) can progress despite immunosuppressive therapy. Vascular fibrosis is more prominent in TAK than in giant cell arteritis (GCA). The inflamed arterial wall in TAK is infiltrated by M1 macrophages [which secrete interleukin-6 (IL-6)], which transition to M2 macrophages once the inflammation settles. M2 macrophages secrete transforming growth factor beta (TGF-β) and glycoprotein non-metastatic melanoma protein B (GPNMB), both of which can activate fibroblasts in the arterial wall adventitia. Mast cells in the arterial wall of TAK also activate resting adventitial fibroblasts. Th17 lymphocytes play a role in both TAK and GCA. Sub-populations of Th17 lymphocytes, Th17.1 lymphocytes [which secrete interferon gamma (IFN-γ) in addition to interleukin-17 (IL-17)] and programmed cell death 1 (PD1)-expressing Th17 (which secrete TGF-β), have been described in TAK but not in GCA. IL-6 and IL-17 also drive fibroblast activation in the arterial wall. The Th17 and Th1 lymphocytes in TAK demonstrate an activation of mammalian target organ of rapamycin 1 (mTORC1) driven by Notch-1 upregulation. A recent study reported that the enhanced liver fibrosis score (derived from serum hyaluronic acid, tissue inhibitor of metalloproteinase 1, and pro-collagen III amino-terminal pro-peptide) had a moderate-to-strong correlation with clinically assessed and angiographically assessed vascular damage. In vitro experiments suggest the potential to target arterial wall fibrosis in TAK with leflunomide, tofacitinib, baricitinib, or mTORC1 inhibitors. Since arterial wall inflammation is followed by fibrosis, a strategy of combining immunosuppressive agents with drugs that have an antifibrotic effect merits exploration in future clinical trials of TAK.

Genome-Wide Association Study Reveals CLEC7A and PROM1 as Potential Regulators of Paracoccidioides brasiliensis-Induction of Cytokine Production in Peripheral Blood Mononuclear Cells

Paracoccidioidomycosis (PCM) is a systemic mycosis caused by fungi of the genus Paracoccidioides and the different clinical forms of the disease are associated with the host immune responses. Quantitative trait loci mapping analysis was performed to assess genetic variants associated with mononuclear-cells-derived cytokines induced by P. brasiliensis on 158 individuals. We identified the rs11053595 SNP, which is present in the CLEC7A gene (encodes the Dectin-1 receptor) and the rs62290169 SNP located in the PROM1 gene (encodes CD133) associated with the production of IL-1β and IL-22, respectively. Functionally, the blockade of the dectin-1 receptor abolished the IL-1β production in P. brasiliensis-stimulated PBMCs. Moreover, the rs62290169-GG genotype was associated with higher frequency of CD38+ Th1 cells in PBMCs cultured with P. brasiliensis yeasts. Therefore, our research indicates that the CLEC7A and PROM1 genes are important for the cytokine response induced by P. brasiliensis and may influence the Paracoccidioidomycosis disease outcome.

Itraconazole and neutrophil interactions in the immune-inflammatory response of paracoccidioidomycosis using a murine air pouch infection model

Paracoccidioidomycosis (PCM) caused by Paracoccidioides brasiliensis (Pb), is a severe mycosis, prevalent in tropical countries. The presence of polymorphonuclear neutrophils (PMN) in lesions is conspicuous, indicating their central role in innate immunity through the direct killing of Pb and the production of cytokines that activate acquired immunity in the presence of itraconazole (Itra). The toxicity and direct antifungal activity of Itra on Pb in splenocyte co-cultures were evaluated in vitro. Itra showed no toxic effect but marked antifungal activity against Pb. Purified PMN were obtained by the subcutaneous (SC) injection of Pb into mice. Results showed the effect of Itra on the size of the air pouch produced, the cellular population that migrated to the infection site, protein, and mitochondrial metabolism patterns, production of ROS an NO, and the number of cytokines synthesized. Lower doses (3 and 10 mg/kg) of Itra did not affect the cellular profile but led to a lower influx of viable more active PMN, and increased production of ROS and proteins. At a dose of 50 mg/kg the PMN profile remained unchanged along with all other parameters analyzed remained unaltered. Decreases in most cytokine levels were inversely proportional to the Itra concentration. Lower Itra concentrations may elicit activation of the immune response because the combined effects of therapy and immune response are needed, while the higher dose does not require it. Itra also promotes the activation of the cytokines which elicit PMN activation and consequently the resolution of Pb18 infection in the air pouch.

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.

IL-17RA receptor signaling contributes to lung inflammation and parasite burden during Toxocara canis infection in mice

IL-17 is a cytokine produced by innate and acquired immunity cells that have an action against fungi and bacteria. However, its action in helminth infections is unclear, including in Toxocara canis infection. Toxocariasis is a neglected zoonosis representing a significant public health problem with an estimated seroprevalence of 19% worldwide. In the present study, we describe the immunopathological action of IL-17RA in acute T. canis infection. C57BL/6j (WT) and IL-17RA receptor knockout (IL-17RA-/-) mice were infected with 1000 T. canis eggs. Mice were evaluated 3 days post-infection for parasite load and white blood cell count. Lung tissue was harvested for histopathology and cytokine expression. In addition, we performed multiparametric flow cytometry in the BAL and peripheral blood, evaluating phenotypic and functional changes in myeloid and lymphoid populations. We showed that IL-17RA is essential to control larvae load in the lung; however, IL-17RA contributed to pulmonary inflammation, inducing inflammatory nodular aggregates formation and presented higher pulmonary IL-6 levels. The absence of IL-17RA was associated with a higher frequency of neutrophils as a source of IL-4 in BAL, while in the presence of IL-17RA, mice display a higher frequency of alveolar macrophages expressing the same cytokine. Taken together, this study indicates that neutrophils may be an important source of IL-4 in the lungs during T. canis infection. Furthermore, IL-17/IL-17RA axis is important to control parasite load, however, its presence triggers lung inflammation that can lead to tissue damage.

Th17.1 lymphocytes: emerging players in the orchestra of immune-mediated inflammatory diseases

It is now well established that Th17 lymphocytes associate with myriad immune-mediated inflammatory diseases. Over the past one and a half decades, a subset of Th17 lymphocytes viz. Th17.1 lymphocytes has been identified in pre-clinical and clinical models of inflammatory rheumatic diseases. These lymphocytes secrete IL-17A (signature cytokine of Th17 lymphocytes) as well as IFN-γ (the signature cytokine of Th1 lymphocytes). They express the chemokine markers for Th1 (CXCR3) as well as Th17 (CCR6) lymphocytes. Th17.1 lymphocytes also express the drug efflux protein p-glycoprotein, which associates with resistance to corticosteroids and other immunosuppressive drugs. This narrative review overviews the evidence regarding Th17.1 lymphocytes in different inflammatory rheumatic diseases. It is now recognized that Th17.1 lymphocytes are increased in the synovial fluid of affected joints in rheumatoid arthritis (RA) and associate with poor treatment response to abatacept. Th17.1 lymphocytes from synovial fluid of RA are less responsive to immunosuppression than those from the peripheral blood. In sarcoidosis, Th17.1 lymphocytes are concentrated in mediastinal lymph nodes and alveolar lining. Such Th17.1 lymphocytes in sarcoidosis are the predominant source of IFN-γ in the sarcoid lung. Th17.1 lymphocytes are elevated in lupus and Takayasu arteritis and associate with disease activity. Future studies should evaluate isolated Th17.1 lymphocytes from peripheral blood or sites of pathology such as synovial fluid and assess their modulation with immunosuppressive therapy in vitro. The analysis of gene expression signature of isolated Th17.1 lymphocytes might enable the identification of newer therapeutic strategies specifically targeting these cell populations in inflammatory rheumatic diseases. Key Points • Th17.1 lymphocytes are a subset of Th17 lymphocytes secreting both IFN-γ and IL-17 • Th17.1 lymphocytes drive neutrophilic inflammation, granuloma formation, and corticosteroid resistance • Th17.1 lymphocytes are elevated in rheumatoid arthritis and sarcoidosis at sites of inflammation • Increased circulating Th17.1 lymphocytes have been identified in lupus and Takayasu arteritis and associate with active disease.

Cellular Mechanisms of Inflammaging and Periodontal Disease

Increased age is associated with an increased prevalence of chronic inflammatory diseases and conditions. The term inflammaging has been used to describe the age-related changes to the immune response that results in a chronic and elevated inflammatory state that contributes, in part, to the increased prevalence of disease in older adults. Periodontal disease is a chronic inflammatory condition that affects the periodontium and increases in prevalence with age. To better understand the mechanisms that drive inflammaging, a broad body of research has focused on the pathological age-related changes to key cellular regulators of the immune response. This review will focus on our current understanding of how certain immune cells (neutrophils, macrophages, T cells) change with age and how such changes contribute to inflammaging and more specifically to periodontal disease.

Assessment of Experimental Techniques That Facilitate Human Granuloma Formation in an In Vitro System: A Systematic Review

The process of granuloma formation is complex, and due to species differences, the validity of animal studies is somewhat questioned. Moreover, the large number of animals needed to observe the different stages of development also raises ethical questions. Therefore, researchers have explored the use of human peripheral blood mononuclear cells (PBMCs), a heterogeneous population of immune cells, in an in vitro model. This review included in vitro studies that focused on exposing PBMCs—from healthy, sensitized, or diseased individuals—to antigens derived from infectious agents—such as mycobacteria or Schistosoma spp.—or inorganic antigens—such as beryllium. The reviewed studies mainly explored how human in vitro granuloma models can contribute towards understanding the pathogenesis of granulomatous diseases, especially during the early stages of granuloma formation. The feasibility of granuloma modelling was thus largely assessed via experimental techniques including (1) granuloma scoring indices (GI), (2) cell surface markers and (3) cytokine secretion profiling. While granuloma scoring showed some similarities between studies, a large variability of culture conditions and endpoints measured have been identified. The lack of any standardization currently impedes the success of a human in vitro granuloma model.

Novel Th17 Lymphocyte Populations, Th17.1 and PD1+Th17, are Increased in Takayasu Arteritis, and Both Th17 and Th17.1 Sub-Populations Associate with Active Disease

Purpose

We evaluated T helper lymphocyte profile, including novel Th17 subsets Th17.1 (secrete IFN-γ, associate with corticosteroid resistance) and PD1+Th17 (secrete TGF-β1, implicated in fibrosis), and related cytokines in peripheral blood of Takayasu arteritis (TAK).

Materials and Methods

We evaluated circulating Th1, Th2, Th17, Th17.1, PD1+CD4+ T lymphocytes, PD1+Th17, and Treg lymphocytes, inflammatory (IFN-γ, IL-4, IL-6, IL-17A, IL-23, IL-1β, TNF-α) and regulatory (IL-10, TGF-β1) cytokines in peripheral blood of TAK (n = 57; median age 35 (interquartile range 26–45) years; 40 females) in a cross-sectional design. We studied inflammatory and regulatory cytokines in culture supernatant of peripheral blood mononuclear cells (PBMCs) from TAK following stimulation with anti-CD3/anti-CD28 and their modulation by tacrolimus (immunosuppressive) with/without tadalafil (anti-fibrotic). Furthermore, we followed up immunosuppressive-naïve active TAK (n = 16) and compared T helper lymphocyte populations and cytokines before and after immunosuppressive therapy. Healthy controls (HC, n = 21) and sarcoidosis (disease control, n = 11) were compared against TAK.

Results

TAK had higher Th17, Th17.1 and PD1+Th17 lymphocytes than HC (p < 0.001), and higher PD1+CD4+ T lymphocytes than sarcoidosis (p < 0.001). Th17 lymphocytes associated with active TAK after multivariable-adjusted logistic regression (p = 0.008). TAK had greater cytokine secretion from PBMCs (IFN-γ, IL-17A, IL-10 versus HC; IL-6, TNF-α, IL-1β versus HC or sarcoidosis) (p < 0.05). In-vitro, PBMCs from TAK showed reduced secretion of all inflammatory cytokines with tacrolimus, with synergistic reduction in IL-17A, IL-6, IL-1β and IL-10 following addition of tadalafil to tacrolimus. Serial follow-up of immunosuppressive-naïve TAK (n = 16) showed reduction in serum IL-6 and TGF-β1 (p < 0.05) and IL-6 in culture supernatant (p < 0.05) following immunosuppressive therapy.

Conclusion

Novel Th17 sub-populations (Th17.1 and PD1+Th17) are elevated in TAK. Th17 lymphocytes associate with active TAK. In-vitro experiments on cultured PBMCs suggest promise for further evaluation of a combination of immunosuppressive tacrolimus with anti-fibrotic tadalafil (or other anti-fibrotic therapies) in clinical trials of TAK.

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Tissue eosinophilia correlates with mice susceptibility, granuloma formation, and damage during Toxocara canis infection

An increase in peripheral blood eosinophils in helminth infections is expected, and these cells are known to promote immunity against these parasites. However, studies have suggested that in some specific helminths, eosinophils may promote the needs and longevity of these parasites, and their role in these infections remains undefined, including in Toxocara canis infection. Thus, this study aimed to investigate the role of eosinophils in the context of larval migration of T. canis and the immunopathological aspects of infection. For this, we used wild-type mice and mice genetically deficient for the transcription factor GATA-binding factor 1 (GATA1−/−), infected with 1000 eggs of T. canis. At 0, 3, 14 and 63 days post-infection, parasite load, tissue cytokine production, leucocyte profile, bronchoalveolar lavage cells and histopathological analyses were carried out. Collectively, our results demonstrate that the presence of eosinophils mediates susceptibility to T. canis, inducing leucocytosis and the formation of granulomas, increasing the pulmonary and cerebral parasite load, and reducing the number of neutrophils, which may be necessary to control the infection.

Innate and mild Th17 cutaneous immune responses elicited by subcutaneous infection of immunocompetent mice with Cladosporium cladosporioides

Cladosporium cladosporioides is a dematiaceous hyphomycete that is pathogenic in the superficial and deep tissues of both immunodeficient and immunocompetent humans and animals. Our aim was to evaluate the antifungal immune responses elicited by C. cladosporioides in immunocompetent mice. Hence, we subcutaneously injected suspensions of C. cladosporioides spores into immunocompetent mice to investigate the anti-fungal immune responses in the skin. We collected skin tissue samples for histopathological examination, immunofluorescence staining, and quantitative real-time polymerase chain reaction analysis. We observed subcutaneous abscesses in mice after subcutaneous injection of C. cladosporioides. A large number of inflammatory cells, including dendritic cells, macrophages, and neutrophils, infiltrated the focal abscess, with comparatively few infiltrating inflammatory cells in the epidermal and dermal layers of the skin. We detected the expression of CD54 in the abscesses and the skin. Gene expression of the pattern recognition receptors Dectin-1 and TLR-2 was higher in infected mice than in controls. Gene expression of the cytokines IL-6, IL-1β, and IL-17A also increased after infection, suggesting that the Th17 signaling pathway may be involved in the anti-fungal response. Although the pathogenicity of C. cladosporioides in healthy mice was weak after subcutaneous infection, resulting in few serious pathological phenomena, it appears that innate and Th17 immune responses play important roles in the cutaneous host response to C. cladosporioides. These findings lay a foundation for further study of the pathogenic mechanism and treatment of C. cladosporioides infection.

The Role of Dimorphism Regulating Histidine Kinase (Drk1) in the Pathogenic Fungus Paracoccidioides brasiliensis Cell Wall

Dimorphic fungi of the Paracoccidioides genus are the causative agents of paracoccidioidomycosis (PCM), an endemic disease in Latin America with a high incidence in Brazil. This pathogen presents as infective mycelium at 25 °C in the soil, reverting to its pathogenic form when inhaled by the mammalian host (37 °C). Among these dimorphic fungal species, dimorphism regulating histidine kinase (Drk1) plays an essential role in the morphological transition. These kinases are present in bacteria and fungi but absent in mammalian cells and are important virulence and cellular survival regulators. Hence, the purpose of this study was to investigate the role of PbDrk1 in the cell wall modulation of P. brasiliensis. We observed that PbDrk1 participates in fungal resistance to different cell wall-disturbing agents by reducing viability after treatment with iDrk1. To verify the role of PbDRK1 in cell wall morphogenesis, qPCR results showed that samples previously exposed to iDrk1 presented higher expression levels of several genes related to cell wall modulation. One of them was FKS1, a β-glucan synthase that showed a 3.6-fold increase. Furthermore, confocal microscopy analysis and flow cytometry showed higher β-glucan exposure on the cell surface of P. brasiliensis after incubation with iDrk1. Accordingly, through phagocytosis assays, a significantly higher phagocytic index was observed in yeasts treated with iDrk1 than the control group, demonstrating the role of PbDrk1 in cell wall modulation, which then becomes a relevant target to be investigated. In parallel, the immune response profile showed increased levels of proinflammatory cytokines. Finally, our data strongly suggest that PbDrk1 modulates cell wall component expression, among which we can identify β-glucan. Understanding this signalling pathway may be of great value for identifying targets of antifungal molecular activity since HKs are not present in mammals.

FABP4 facilitates inflammasome activation to induce the Treg/Th17 imbalance in preeclampsia via forming a positive feedback with IL-17A

Preeclampsia (PE) is one of the leading causes of maternal death worldwide. Elevated fatty acid binding protein 4 (FABP4) levels have been observed in patients with PE, however, the mechanism by which FABP4 contributes to the pathogenesis of PE remains unclear. In this study, we compared the levels of FABP4 and cytokines between 20 PE patients and 10 healthy pregnant women by using ELISA, immunohistochemistry (IHC) analysis, and flow cytometry (fluorescence-activated cell sorting, FACS). Elevated FABP4 was accompanied by regulatory T (Treg)/T helper type 17 (Th17) imbalance in PE. Knockdown of FABP4 attenuated lipopolysaccharide (LPS)-induced NLR family pyrin domain containing 3 (NLRP3) inflammasome activation and interleukin-17A (IL-17A) production in primary macrophages. In addition, silencing of FABP4 also suppressed Th17 differentiation via paracrine signaling. Overexpression of FABP4 promoted Th17 differentiation via increasing IL-17A/IL-23 release. Reciprocally, IL-17A upregulated FABP4 and activated the NLRP3 inflammasome in vitro and in vivo. The in vivo studies revealed that FABP4 inhibitor BMS309403 ameliorated PE clinical phenotypes, the Treg/Th17 imbalance, and NLRP3 inflammasome activation in PE mice model. In conclusion, FABP4 facilitates inflammasome activation to induce the imbalance of Treg/Th17 in PE via forming a positive feedback with IL-17A.

Contribution of Gut Microbiota to Immunological Changes in Alzheimer's Disease

Emerging evidence suggests that both central and peripheral immunological processes play an important role in the pathogenesis of Alzheimer's disease (AD), but regulatory mechanisms remain unknown. The gut microbiota and its key metabolites are known to affect neuroinflammation by modulating the activity of peripheral and brain-resident immune cells, yet an overview on how the gut microbiota contribute to immunological alterations in AD is lacking. In this review, we discuss current literature on microbiota composition in AD patients and relevant animal models. Next, we highlight how microbiota and their metabolites may contribute to peripheral and central immunological changes in AD. Finally, we offer a future perspective on the translation of these findings into clinical practice by targeting gut microbiota to modulate inflammation in AD. Since we find that gut microbiota alterations in AD can induce peripheral and central immunological changes via the release of microbial metabolites, we propose that modulating their composition may alter ongoing inflammation and could therefore be a promising future strategy to fight progression of AD.

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.

Native and IgE-primed rat peritoneal mast cells exert pro-inflammatory activity and migrate in response to yeast zymosan upon Dectin-1 engagement

Mast cells (MCs) play an essential role in host defense, primarily because of their location, their ability to pathogen destruction via several mechanisms, and the pattern recognition receptors they express. Even though most data is available regarding MC activation by various bacteria- or virus-derived molecules, those cells' activity in response to constituents associated with fungi is not recognized enough. Our research aimed to address whether Saccharomyces cerevisiae-derived zymosan, i.e., β-(1,3)-glucan containing mannan particles, impacts MC activity aspects. Overall, the obtained results indicate that zymosan has the potential to elicit a pro-inflammatory response of rat peritoneal MCs. For the first time ever, we provided evidence that zymosan induces fully mature MC migration, even in the absence of extracellular matrix (ECM) proteins. Moreover, the zymosan-induced migratory response of MCs is almost entirely a result of directional migration, i.e., chemotaxis. We found that zymosan stimulates MCs to degranulate and generate lipid mediators (cysLTs), cytokines (IFN-α, IFN-β, IFN-γ, GM-CSF, TNF), and chemokine (CCL2). Zymosan also upregulated mRNA transcripts for several cytokines/chemokines with pro-inflammatory/immunoregulatory activity. Moreover, we documented that zymosan activates MCs to produce reactive oxygen species (ROS). Lastly, we established that the zymosan-induced MC response is mediated through activation of the Dectin-1 receptor. In general, our results strongly support the notion that MCs contribute to innate antifungal immunity and bring us closer to elucidate their role in host-pathogenic fungi interactions. Besides, provided findings on IgE-sensitized MCs appear to indicate that exposure to fungal zymosan could affect the severity of IgE-dependent disorders, including allergic ones.

Monocyte-Derived Dendritic Cells Can Revert In Vitro Antigen-Specific Cellular Anergy in Active Human Paracoccidioidomycosis

We investigated the in vitro effects of two Paracoccidioides brasiliensis antigens on monocyte-derived dendritic cells (moDCs) from patients with paracoccidioidomycosis (PCM). MoDCs from patients with active or treated PCM and non-PCM subjects were generated, stimulated with TNF-α, and P. brasiliensis antigens, 43 kDa glycoprotein (gp43) and cell-free antigen (CFA), and analyzed by flow cytometry and enzyme-linked immunosorbent assays (ELISA). Our data revealed that patients with PCM had a high frequency of HLA-DR⁺ cells, but the treated group had more CD86⁺ cells with increased IL-12p40. Patients with active PCM had more CD80⁺ moDCs, and as a novel finding, large amounts of chemokine (C-C motif) ligand 18 (CCL18) in the supernatants from their in vitro moDC cultures. Both gp43- and CFA-stimulated moDCs from the patients with PCM successfully reverted the in vitro antigen-specific anergy, inducing a proliferative response. However, CFA-stimulated moDCs led to higher lymphoproliferation, with increased IFN-γ and TNF-α in the cells from the patients with active PCM compared with gp43. These original results combined with constant IL-10 and increased IL-12p40 levels suggest that a more complex antigen, such as CFA, may be a better inducer of the protective Th1 immune response than purified gp43 is, and a suitable target for future studies on anti-P. brasiliensis dendritic cell (DC)-based vaccines.

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.

Zymosan enhances in vitro phagocyte function and the immune response of mice infected with Paracoccidioides brasiliensis

Paracoccidioides brasiliensis is the major etiologic agent of Paracoccidioidomycosis (PCM), the most frequent human deep mycosis in Latin America. It is proposed that masking of β-glucan in P. brasiliensis cell wall is a critical virulence factor that contributes to the development of a chronic disease characterized by a long period of treatment, which is usually toxic. In this context, the search for immunomodulatory agents for therapeutic purposes is highly desirable. One strategy is to use pattern recognition receptors (PRRs) ligands to stimulate the immune response mediated by phagocytes. Here, we sought to evaluate if Zymosan, a β-glucan-containing ligand of the PRRs Dectin-1/TLR-2, would enhance phagocyte function and the immune response of mice challenged with P. brasiliensis. Dendritic cells (DCs) infected with P. brasiliensis and treated with Zymosan showed improved secretion of several proinflammatory cytokines and expression of maturation markers. In addition, when cocultured with splenic lymphocytes, these cells induced the production of a potential protective type 1 and 17 cytokine patterns. In macrophages, Zymosan ensued a significant fungicidal activity associated with nitric oxide production and phagolysosome acidification. Importantly, we observed a protective effect of Zymosan-primed DCs delivered intranasally in experimental pulmonary PCM. Overall, our findings support the potential use of β-glucan-containing compounds such as Zymosan as an alternative or complementary antifungal therapy.

LAY SUMMARY

We report for the first time that Paracoccidioides brasiliensis-infected phagocytes treated with Zymosan (cell wall extract from bakers' yeast) show enhanced cytokine production, maturation, and fungal killing. Also, Zymosan-primed phagocytes induce a protective immune response in infected mice.

The Role of the Interleukin-17 Axis and Neutrophils in the Pathogenesis of Endemic and Systemic Mycoses

Systemic and endemic mycoses are considered life-threatening respiratory diseases which are caused by a group of dimorphic fungal pathogens belonging to the genera Histoplasma, Coccidioides, Blastomyces, Paracoccidioides, Talaromyces, and the newly described pathogen Emergomyces. T-cell mediated immunity, mainly T helper (Th)1 and Th17 responses, are essential for protection against these dimorphic fungi; thus, IL-17 production is associated with neutrophil and macrophage recruitment at the site of infection accompanied by chemokines and proinflammatory cytokines production, a mechanism that is mediated by some pattern recognition receptors (PRRs), including Dectin-1, Dectine-2, TLRs, Mannose receptor (MR), Galectin-3 and NLPR3, and the adaptor molecules caspase adaptor recruitment domain family member 9 (Card9), and myeloid differentiation factor 88 (MyD88). However, these PRRs play distinctly different roles for each pathogen. Furthermore, neutrophils have been confirmed as a source of IL-17, and different neutrophil subsets and neutrophil extracellular traps (NETs) have also been described as participating in the inflammatory process in these fungal infections. However, both the Th17/IL-17 axis and neutrophils appear to play different roles, being beneficial mediating fungal controls or detrimental promoting disease pathologies depending on the fungal agent. This review will focus on highlighting the role of the IL-17 axis and neutrophils in the main endemic and systemic mycoses: histoplasmosis, coccidioidomycosis, blastomycosis, and paracoccidioidomycosis.

Therapeutic Vaccination with Cationic Liposomes Formulated with Dioctadecyldimethylammonium and Trehalose Dibehenate (CAF01) and Peptide P10 Is Protective in Mice Infected with Paracoccidioides brasiliensis

The peptide P10 is a vaccine candidate for Paracoccidioidomycosis, a systemic mycosis caused by fungal species of the genus Paracoccidioides spp. We have previously shown that peptide P10 vaccination, in the presence of several different adjuvants, induced a protective cellular immune response mediated by CD4⁺ Th₁ lymphocytes that was associated with the increased production of IFN-γ in mice challenged with a virulent isolate of Paracoccidoides brasiliensis. Cationic liposomes formulated with dioctadecyldimethylammonium and trehalose dibehenate (DDA/TDB, termed also CAF01–cationic adjuvant formulation) have been developed for safe administration in humans and CAF01 liposomes are utilized as an adjuvant for modulating a robust Th₁/Th₁₇ cellular response. We evaluated the efficacy of the adsorption of peptide P10 to CAF01 cationic liposomes and used the generated liposomes to vaccinate C57Bl/6 mice infected with P. brasiliensis. Our results showed that P10 was efficiently adsorbed onto CAF01 liposomes. The vaccination of infected mice with cationic liposomes formulated with DDA/TDB 250/50 µg/mL and 20 µg of P10 induced an effective cellular immune response with increased levels of Th₁₇ cytokines, which correlated with significant decreases in the fungal burdens in lungs and protective granulomatous tissue responses. Hence, cationic liposomes of DDA/TDB 250/50 µg/mL with 20 µg of P10 are a promising therapeutic for safely and effectively improving the treatment of paracoccidioidomycosis.

Living Within the Macrophage: Dimorphic Fungal Pathogen Intracellular Metabolism

Histoplasma and Paracoccidioides are related thermally dimorphic fungal pathogens that cause deadly mycoses (i.e., histoplasmosis and paracoccidioidomycosis, respectively) primarily in North, Central, and South America. Mammalian infection results from inhalation of conidia and their subsequent conversion into pathogenic yeasts. Macrophages in the lung are the first line of defense, but are generally unable to clear these fungi. Instead, Histoplasma and Paracoccidioides yeasts survive and proliferate within the phagosomal compartment of host macrophages. Growth within macrophages requires strategies for acquisition of sufficient nutrients (e.g., carbon, nitrogen, and essential trace elements and co-factors) from the nutrient-depleted phagosomal environment. We review the transcriptomic and recent functional genetic studies that are defining how these intracellular fungal pathogens tune their metabolism to the resources available in the macrophage phagosome. In addition, recent studies have shown that the nutritional state of the macrophage phagosome is not static, but changes upon activation of adaptive immune responses. Understanding the metabolic requirements of these dimorphic pathogens as they thrive within host cells can provide novel targets for therapeutic intervention.

Paracoccidioides brasiliensis infection increases regulatory T cell counts in female C57BL/6 mice infected via two distinct routes

Studies that show an overview of the peripheral immune response in a model of Paracoccidioides brasiliensis (Pb) infection in females are scarce in the literature. We sought to characterize the innate and adaptive immune responses in female C57BL/6 mice infected with Pb through two distinct routes of administration, intranasal and intravenous. In addition to the lung, P. brasiliensis yeast cells were observed in liver and brain tissues of females infected intravenously. To our knowledge, our study is the first to prove the presence of this pathogenic fungus in the cerebral cortex of female mice. During the initial stages of infection, augmented expression of both MHCII and CD86 was observed on the surface of CD11c⁺ pulmonary antigen-presenting cells (APCs) in intranasally and intravenously infected females. However, CD40 expression was downregulated in these cells. Concomitantly with increasing serum IL-10 levels, we noted that splenic dendritic cells (DCs) from both intravenously- and intranasally-infected female mice had acquired an immature phenotype. Further, increased T regulatory cell counts were observed in female mice infected via both routes, along with an increase in the infiltration of IL-10-producing CD8⁺ T cells into the lungs. Moreover, we noted that P. brasiliensis infection resulted in enhanced IL-10 production - by CD11c⁺ APCs in the lung tissue - and induction of Th17 polarization. Taken together, our results suggest that P. brasiliensis could modulates the immune response in female mice by influencing the balance between regulatory T cells (Tregs) and Th17 polarization.

Rhizopus-host interplay of disseminated mucormycosis in immunocompetent mice

Aim: To investigate the immune response of disseminated Ryzopus oryzae infection in immunocompetent mice. Methods: C57Bl/6, BALB/c and Swiss wild-type mice were intravenously infected with R. oryzae; the parameters of infection and immune response were determined. Transcriptional signature of Th17 immune response and infection in Il17ra^-/- mice were also evaluated. Results: All mouse strains showed an initial spread of R. oryzae in the target tissues; however, after 30 days, C57Bl/6 and BALB/c mice showed an effective fungal clearance associated with specific production of IL-17 and IL-2. We also observed that 60% of Il17ra^-/- mice succumbed to infection within 16 days. Conclusion: This study has established an immunocompetent model for disseminated mucormycosis and highlighted the role of IL-17 signaling in immunity against R. oryzae.

Th17 lymphocytes in atypical cutaneous leishmaniasis caused by Leishmania (L.) infantum chagasi in Central America

Skin lesions in nonulcerated cutaneous leishmaniasis (NUCL) caused by Leishmania (L.) infantum chagasi are characterized by a mononuclear inflammatory infiltrate in the dermis, which is composed mainly of lymphocytes, followed by macrophages, few plasma cells and epithelioid granulomas with mild tissue parasitism. Previous studies have shown that the main population of lymphocytes present in the dermal infiltrate is CD8⁺ T cells, followed by CD4⁺ T cells, which are correlated with IFN-γ⁺ cells. To improve the knowledge of cellular immune responses in NUCL, skin biopsies were submitted to immunohistochemistry using anti-ROR-γt, anti-IL-17, anti-IL-6, anti-TGF-β, and anti-IL-23 antibodies to characterize the involvement of Th17 cells in the skin lesions of patients affected by NUCL. ROR-γt⁺ , IL-17⁺ , IL-6⁺ , TGF-β⁺ and IL-23⁺ cells were observed in the dermal inflammatory infiltrate of NUCL skin lesions. A positive correlation between CD4⁺ T-lymphocytes and ROR-γt⁺ and IL-17⁺ cells suggests that some of the CD4⁺ T-lymphocytes in NUCL could be Th17 lymphocytes. Moreover, a positive correlation between ROR-γt⁺ cells and TGF-β⁺ , IL-6⁺ , IL-17⁺ and IL-23⁺ cells could indicate the role of these cytokines in the differentiation and maintenance of Th17 lymphocytes. Our findings improve knowledge of the pathogenesis of this rare and atypical clinical form of leishmaniasis.

IL-22 Promotes IFN-γ-Mediated Immunity against Histoplasma capsulatum Infection

Histoplasma capsulatum is the agent of histoplasmosis, one of the most frequent mycoses in the world. The infection initiates with fungal spore inhalation, transformation into yeasts in the lungs and establishment of a granulomatous disease, which is characterized by a Th1 response. The production of Th1 signature cytokines, such as IFN-γ, is crucial for yeast clearance from the lungs, and to prevent dissemination. Recently, it was demonstrated that IL-17, a Th17 signature cytokine, is also important for fungal control, particularly in the absence of Th1 response. IL-22 is another cytokine with multiple functions on host response and disease progression. However, little is known about the role of IL-22 during histoplasmosis. In this study, we demonstrated that absence of IL-22 affected the clearance of yeasts from the lungs and increased the spreading to the spleen. In addition, IL-22 deficient mice (Il22-/-) succumbed to infection, which correlated with reductions in the numbers of CD4+ IFN-γ+ T cells, reduced IFN-γ levels, and diminished nitric oxide synthase type 2 (NOS2) expression in the lungs. Importantly, treatment with rIFN-γ mitigated the susceptibility of Il22-/- mice to H. capsulatum infection. These data indicate that IL-22 is crucial for IFN-γ/NO production and resistance to experimental histoplasmosis.

Sarcoidosis and the mTOR, Rac1, and Autophagy Triad

Sarcoidosis is an enigmatic multisystem disease characterized by the development and accumulation of granulomas: a compact collection of macrophages that have differentiated into epithelioid cells and which are associated with T helper (Th)1 and Th17 cells. Although no single causative factor has been shown to underlie sarcoidosis in humans, its etiology has been related to microbial, environmental, and genetic factors. We examine how these factors play a role in sarcoidosis pathogenesis. Specifically, we propose that dysfunction of mTOR, Rac1, and autophagy-related pathways not only hampers pathogen or nonorganic particle clearance but also participates in T cell and macrophage dysfunction, driving granuloma formation. This concept opens new avenues for potentially treating sarcoidosis and may serve as a blueprint for other granulomatous disorders.

Metabolic Programming of Macrophages: Implications in the Pathogenesis of Granulomatous Disease

Metabolic reprogramming is rapidly gaining appreciation in the etiology of immune cell dysfunction in a variety of diseases. Tuberculosis, schistosomiasis, and sarcoidosis represent an important class of diseases characterized by the formation of granulomas, where macrophages are causatively implicated in disease pathogenesis. Recent studies support the incidence of macrophage metabolic reprogramming in granulomas of both infectious and non-infectious origin. These publications identify the mechanistic target of rapamycin (mTOR), as well as the major regulators of lipid metabolism and cellular energy balance, peroxisome proliferator receptor gamma (PPAR-γ) and adenosine monophosphate-activated protein kinase (AMPK), respectively, as key players in the pathological progression of granulomas. In this review, we present a comprehensive breakdown of emerging research on the link between macrophage cell metabolism and granulomas of different etiology, and how parallels can be drawn between different forms of granulomatous disease. In particular, we discuss the role of PPAR-γ signaling and lipid metabolism, which are currently the best-represented metabolic pathways in this context, and we highlight dysregulated lipid metabolism as a common denominator in granulomatous disease progression. This review therefore aims to highlight metabolic mechanisms of granuloma immune cell fate and open up research questions for the identification of potential therapeutic targets in the future.

Caspase-11-dependent IL-1α release boosts Th17 immunity against Paracoccidioides brasiliensis

The granulomatous lesion resulting from infection with the fungus Paracoccidioides brasiliensis is characterized by a compact aggregate of mature cells, surrounded by a fibroblast- and collagen-rich content. Granuloma formation requires signaling elicited by inflammatory molecules such as members of the interleukin-1 family. Two members of this family have been thoroughly studied, namely IL-1α and IL-1β. In this study, we addressed the mechanisms underlying IL-1α secretion and its functional role on the host resistance to fungal infection. We found that, the expression of caspase-11 triggered by P. brasiliensis infection of macrophages depends on IFN-β production, because its inhibition reduced procaspase-11 levels. Curiously, caspase-11 deficiency did not impair IL-1β production, however caspase-11 was required for a rapid pore-mediated cell lysis. The plasma membrane rupture facilitated the release of IL-1α, which was necessary to induce NO production and restrict fungal replication. Furthermore, P. brasiliensis-infected macrophages required IL-1α to produce optimal levels of IL-6, a major component of Th17 lymphocyte differentiation. Indeed, IL-1α deficiency accounted for a significant reduction of Th17 lymphocytes in lungs of infected mice, correlating with diminished neutrophil infiltration in the lungs. Strikingly, we identified that IL-1α directly reprograms the transcriptional profile of Th17-committed lymphocytes, increasing cellular proliferation, as for boosting IL-17 production by these cells. Beyond neutrophil chemotaxis in vivo, IL-17 also amplified IL-1α production by infected macrophages in vitro, endorsing a critical amplification loop of the inflammatory response. Therefore, our data suggest that the IFN-β/caspase-11/IL-1α pathway shapes a protective antifungal Th17 immunity, revealing a molecular mechanism underlying the cross-talk between innate and adaptive immunity.

Therapeutic effect of DNA vaccine encoding the 60-kDa-heat shock protein from Paracoccidoides brasiliensis on experimental paracoccidioidomycosis in mice

Paracoccidioidomycosis (PCM) is a systemic mycosis autochthonous to Latin America and endemic to Brazil, which has the majority of the PCM cases. PCM is acquired through the inhalation of propagules of fungi from genus Paracoccidioides spp. and mainly affects the lungs. We have previously shown that P. brasiliensis-infected mice treated with single-dose of recombinant 60-kDa-heat shock protein from P. brasiliensis (rPbHsp60) had a worsening infection in comparison to animals only infected. In this study, we investigate whether the treatment of infected mice with PB_HSP60 gene cloned into a plasmid (pVAX1-PB_HSP60) would result in efficient immune response and better control of the disease. The harmful impact of single-dose therapy with protein was not seen with plasmid preparations. Most importantly, three doses of pVAX1-PB_HSP60 and protein induced a beneficial effect in experimental PCM with a reduction in fungal load and lung injury when compared with infected mice treated with pVAX1 or PBS. The increase of the cytokines IFN-γ, TNF, and IL-17 and the decrease of IL-10 observed after treatment with three doses of pVAX1-PB_HSP60 appears to be responsible for the control of infection. These results open perspectives of the therapeutic use of Hsp60 in PCM.

Interleukin-17 and matrix metalloprotease-9 expression in the mycetoma granuloma

Mycetoma is a persistent, progressive granulomatous inflammatory disease caused either by fungi or by bacteria. Characteristic of this disease is that the causative agents organise themselves in macroscopic structures called grains. These grains are surrounded by a massive inflammatory reaction. The processes leading to this host tissue reaction and the immunophenotypic characteristics of the mycetoma granuloma are not known. Due to the massive immune reaction and the tissue remodeling involved, we hypothesised that the expression levels of interleukin-17 (IL-17) and matrix metalloprotease-9 (MMP-9) in the mycetoma granuloma formation were correlated to the severity of the disease and that this correlation was independent of the causative agent responsible for the granuloma reaction. To determine the expression of IL-17 and MMP-9 in mycetoma lesions, the present study was conducted at the Mycetoma Research Centre, Sudan. Surgical biopsies from 100 patients with confirmed mycetoma were obtained, and IL-17 and MMP-9 expression in the mycetoma granuloma were evaluated immunohistochemically. IL-17 was mainly expressed in Zones I and II, and far less in Zone III. MMP-9 was detected mainly in Zones II and III, and the least expression was in Zone I. MMP-9 was more highly expressed in Actinomadura pelletierii and Streptomyces somaliensis biopsies compared to Madurella mycetomatis biopsies. MMP-9 levels were directly proportional to the levels of IL-17 (p = 0.001). The only significant association between MMP9 and the patients' characteristics was the disease duration (p<0.001). There was an insignificant correlation between the IL-17 levels and the patients' demographic characteristics.

Dichotomous response of Malassezia-infected macrophages to Malassezia pachydermatis and Malassezia furfur

Malassezia pachydermatis and Malassezia furfur are lipophilic yeasts of the cutaneous microbiome, although these organisms are occasionally responsible for serious invasive infections in neonates. Since phagocytosis is an important mechanism mediating the adaptive immune response, here we evaluated the phagocytosis capacity and production of nitric oxide and cytokine by macrophages after challenged with M. furfur CBS-1878 and M. pachydermatis CBS-1696. The phagocytic indexes was determined using RAW 264.7 cultivated or not with M. furfur or M. pachydermatis in the concentrations of 5:1 or 2:1 (yeasts:macrophages ratio) for 6 h, 24 h, and 48 h following the challenges. Evaluation of nitric oxide and pro- and anti-inflammatory cytokines (interleukin [IL]-2, IL-4, IL-6, IL-10, IL-17A, interferon (IFN)-γ and tumor necrosis factor [TNF]-α) by Griess method and flow cytometry, respectively, were performed in the different intervals by collecting the cell culture supernatant. Results showed a higher phagocytic index in the 5:1 ratio in 24 h for both species. Malassezia pachydermatis-infected macrophages had superior phagocytic indexes than M. furfur-infected macrophages. Phagocytosis evaluation at 48 h showed significant microorganisms proliferation and macrophages death, particularly in macrophages infected with M. pachydermatis, suggesting yeast evasion mechanism. Significant variations in the nitric oxide production were observed in macrophages infected with both species. Levels of TNF-α and IL-4 cytokines have increased in M. furfur and M. pachydermatis macrophage-infected cultures, respectively. The low microbicidal activity and the presence of pro- and anti-inflammatory cytokines reinforce the dichotomous character of the relation of these yeasts with the host, acting as a commensal in the cutaneous microbiome or causing infection.

Insulin Modulates Paracoccidioides brasiliensis-Induced Inflammation by Restoring the Populations of NK Cells, Dendritic Cells, and B Lymphocytes in Lungs

Paracoccidioidomycosis, a key issue for Brazilian health service, can be aggravated in patients with impaired immunological responses, such as diabetic patients. We evaluated the role of insulin in inflammatory parameters in diabetic and nondiabetic mice using a systemic mycosis Paracoccidioides brasiliensis (Pb) model. Diabetic C57BL-6 mice and controls were infected with Pb18 and treated with insulin for 12 days prior to experiments. After 55 days, infected diabetic mice exhibited fewer leukocytes in both peritoneal lavage fluid (PeLF) and bronchoalveolar lavage fluid and reduced secretion of interleukin- (IL-) 6 in lungs. In addition, diabetic mice presented a reduced influx of TCD4+ cells, TCD8+ cells, B lymphocytes, NK cells, and dendritic cells compared to control infected groups. Insulin treatment restored the leukocyte number in PeLF and restored the presence of B lymphocytes, dendritic cells, and NK cells in lungs of diabetic animals. The data suggest that diabetic mice present impaired immunological response to Pb18 infection and insulin modulates inflammation by reducing IL-6 levels in lung and CINC-1 levels in spleen and liver homogenates, restoring leukocyte concentrations in PeLF and also restoring populations of dendritic cells and B lymphocytes in lungs of diabetic mice, permitting the host to better control the infection.

Pulsatilla decoction inhibits Candida albicans proliferation and adhesion in a mouse model of vulvovaginal candidiasis via the Dectin-1 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Pulsatilla decoction (PD) is a classical prescription in Traditional Chinese Medicine (TCM) and has been reported to have inhibitory effects on Candida albicans proliferation.

STUDY AIM

To investigate the therapeutic effects of PD in the treatment of Vulvovaginal candidiasis (VVC) and elucidate the potential mechanism.

MATERIALS AND METHODS

Female BALB/c mice (N = 90) were randomized to six treatment groups, including the Control group, Model group, three PD groups and Fluconazole group which served as a positive control (20 mg/kg weekly). The three PD groups (low dose group, medium dose group and high dose group) were given a daily intragastric gavage of PD at doses of 5, 10 and 20 g/kg, respectively. Five animals from each group were euthanized on Day 4, Day 7 and Day 14 after treatment. Colony forming unit (CFU) was measured by the serial dilution method. The degree of infection was assessed by Gram staining, Periodic acid schiff (PAS) staining, Hematoxylin and eosin (H&E) staining and Scanning electron microscopy (SEM). The serum inflammation levels were determined by a Luminex assay. Gene and protein expression levels of components of the Dectin-1 signaling pathway were determined by Real-time PCR, Western-blot and immunohistochemistry, respectively.

RESULTS

The administration of PD significantly decreased the fungal load from Day 7 post-infection onwards and decreased the number of visible microorganisms based on findings from Gram staining, PAS staining and SEM. H&E staining indicated that the impaired histological profiles were improved in all three PD groups. PD led to a significantly lower level of IL-23 in the serum; the levels of IL-10 and TNF-α were also decreased, although the differences were not significant. Furthermore, a substantial downregulation of Dectin-1, CARD9 and NF-κB mRNA levels and Dectin-1, Syk, CARD9 and NF-κB protein levels was observed after the administration of PD.

CONCLUSION

This study suggests that PD exerts inhibitory effects on C. albicans proliferation, adhesion and inflammation and simultaneously downregulates the expression levels of important genes and proteins associated with the Dectin-1 pathway, highlighting the potential application of PD to improve the clinical management of VVC.

CD18 Regulates Monocyte Hematopoiesis and Promotes Resistance to Experimental Schistosomiasis

Infection with Schistosoma mansoni causes a chronic parasitic disease that progress to severe liver and gastrointestinal damage, and eventually death. During its development into mammalian hosts, immature schistosomula transit through the lung vasculature before they reach the liver to mature into adult worms. A low grade inflammatory reaction is induced during this process. However, molecules that are required for efficient leukocyte accumulation in the lungs of S. mansoni-infected subjects are unknown. In addition, specific leukocyte subsets that mediate pulmonary response during S. mansoni migration through the lung remain to be elucidated. β₂ integrins are fundamental regulators of leukocyte trans-endothelial migration and function. Therefore, we investigated their role during experimental schistosomiasis. Mice that express low levels of CD18 (the common β₂ integrin subunit) and wild type C57BL/6 mice were subcutaneously infected with S. mansoni cercariae. Cellular profiles of lungs and livers were evaluated in different time points after infection by flow cytometry. Low levels of CD18 affected the accumulation of patrolling Ly6C^low, intermediate Ly6C^inter monocytes, monocyte-derived macrophages and monocyte-derived dendritic cells in the lungs 7 days after infection. This correlated with increased TNF-α levels. Strikingly, low CD18 expression resulted in monocytopenia both in the peripheral blood and bone marrow during acute infection. After 48 days, S. mansoni worm burdens were higher in the hepatic portal system of CD18^low mice, which also displayed reduced hepatic accumulation of patrolling Ly6C^low and intermediate Ly6C^inter, but not inflammatory Ly6C^high monocytes. Higher parasite burden resulted in increased granulomatous lesions in the liver, increased egg deposition and enhanced mortality. Overall, our data point for a fundamental role of CD18 for monocyte hematopoiesis during infection, which promotes an efficient host response against experimental schistosomiasis.

A Dectin-1-Caspase-8 Pathway Licenses Canonical Caspase-1 Inflammasome Activation and Interleukin-1β Release in Response to a Pathogenic Fungus

Background

Paracoccidioides brasiliensis is equipped with an arsenal of virulence factors that are crucial for causing infection. Our group previously defined the NLRP3 inflammasome as a mediator of P brasiliensis-induced cell damage recognition and induction of effective Th1 immune responses. However, deficiency of caspase-1 only partially reduced interleukin (IL)-1β levels.

Methods

In this study, using chemical inhibitors as well as genetically modified mice, we identify an additional pathway for IL-1β production in response to P brasiliensis infection.

Results

Paracoccidioides brasiliensis initiated caspase-8-mediated IL-1β production, an event that was necessary for transcriptional priming and posttranslational processing of pro-IL-1β. Caspase-8 synergizes with the canonical NLRP3 inflammasome pathway to control caspase-1 processing and IL-1β maturation, providing a regulatory role for caspase-8 in host resistance to in vivo P brasiliensis infection.

Conclusions

Taken together, these findings revealed an important role for caspase-8 in the innate immune response of host cells to P brasiliensis infection, demonstrating a connected network between noncanonical and canonical inflammasomes to coordinate IL-1β production during fungal challenge.