RESUMO
The C-type lectin receptor-Syk (spleen tyrosine kinase) adaptor CARD9 facilitates protective antifungal immunity within the central nervous system (CNS), as human deficiency in CARD9 causes susceptibility to fungus-specific, CNS-targeted infection. CARD9 promotes the recruitment of neutrophils to the fungus-infected CNS, which mediates fungal clearance. In the present study we investigated host and pathogen factors that promote protective neutrophil recruitment during invasion of the CNS by Candida albicans. The cytokine IL-1ß served an essential function in CNS antifungal immunity by driving production of the chemokine CXCL1, which recruited neutrophils expressing the chemokine receptor CXCR2. Neutrophil-recruiting production of IL-1ß and CXCL1 was induced in microglia by the fungus-secreted toxin Candidalysin, in a manner dependent on the kinase p38 and the transcription factor c-Fos. Notably, microglia relied on CARD9 for production of IL-1ß, via both transcriptional regulation of Il1b and inflammasome activation, and of CXCL1 in the fungus-infected CNS. Microglia-specific Card9 deletion impaired the production of IL-1ß and CXCL1 and neutrophil recruitment, and increased fungal proliferation in the CNS. Thus, an intricate network of host-pathogen interactions promotes antifungal immunity in the CNS; this is impaired in human deficiency in CARD9, which leads to fungal disease of the CNS.
Assuntos
Proteínas Adaptadoras de Sinalização CARD/imunologia , Candidíase/imunologia , Quimiocina CXCL1/imunologia , Interleucina-1beta/imunologia , Microglia/imunologia , Neutrófilos/imunologia , Animais , Encéfalo/imunologia , Encéfalo/metabolismo , Encéfalo/microbiologia , Proteínas Adaptadoras de Sinalização CARD/genética , Proteínas Adaptadoras de Sinalização CARD/metabolismo , Candida albicans/imunologia , Candida albicans/fisiologia , Candidíase/genética , Candidíase/microbiologia , Quimiocina CXCL1/genética , Quimiocina CXCL1/metabolismo , Citocinas/genética , Citocinas/imunologia , Citocinas/metabolismo , Interações Hospedeiro-Patógeno/imunologia , Inflamassomos/genética , Inflamassomos/imunologia , Inflamassomos/metabolismo , Interleucina-1beta/genética , Interleucina-1beta/metabolismo , Camundongos Knockout , Camundongos Transgênicos , Microglia/metabolismo , Microglia/microbiologia , Infiltração de Neutrófilos/genética , Infiltração de Neutrófilos/imunologia , Neutrófilos/metabolismo , Neutrófilos/microbiologiaRESUMO
Regulation of neutrophil activation is critical for disease control. Neutrophil extracellular traps (NETs), which are web-like structures composed of DNA and neutrophil-derived proteins, are formed following pro-inflammatory signals; however, if this process is uncontrolled, NETs contribute to disease pathogenesis, exacerbating inflammation and host tissue damage1,2. Here we show that myeloid inhibitory C-type lectin-like (MICL), an inhibitory C-type lectin receptor, directly recognizes DNA in NETs; this interaction is vital to regulate neutrophil activation. Loss or inhibition of MICL functionality leads to uncontrolled NET formation through the ROS-PAD4 pathway and the development of an auto-inflammatory feedback loop. We show that in the context of rheumatoid arthritis, such dysregulation leads to exacerbated pathology in both mouse models and in human patients, where autoantibodies to MICL inhibit key functions of this receptor. Of note, we also detect similarly inhibitory anti-MICL autoantibodies in patients with other diseases linked to aberrant NET formation, including lupus and severe COVID-19. By contrast, dysregulation of NET release is protective during systemic infection with the fungal pathogen Aspergillus fumigatus. Together, we show that the recognition of NETs by MICL represents a fundamental autoregulatory pathway that controls neutrophil activity and NET formation.
RESUMO
Immune checkpoint inhibitor (ICI) therapy represents a breakthrough cancer treatment by stimulating dysfunctional T cells in the tumour environment to kill cancer cells. Beyond effects on anticancer immunity, ICI therapy may be associated with increased susceptibility to or more rapid resolution of chronic infections, particularly those caused by human fungal pathogens. In this concise review, we summarise recent observations and findings that implicate immune checkpoint blockade in fungal infection outcomes.
Assuntos
Neoplasias , Humanos , Neoplasias/patologia , Imunoterapia , Antígeno CTLA-4RESUMO
Resistance to infection is critically dependent on the ability of pattern recognition receptors to recognize microbial invasion and induce protective immune responses. One such family of receptors are the C-type lectins, which are central to antifungal immunity. These receptors activate key effector mechanisms upon recognition of conserved fungal cell-wall carbohydrates. However, several other immunologically active fungal ligands have been described; these include melanin, for which the mechanism of recognition is hitherto undefined. Here we identify a C-type lectin receptor, melanin-sensing C-type lectin receptor (MelLec), that has an essential role in antifungal immunity through recognition of the naphthalene-diol unit of 1,8-dihydroxynaphthalene (DHN)-melanin. MelLec recognizes melanin in conidial spores of Aspergillus fumigatus as well as in other DHN-melanized fungi. MelLec is ubiquitously expressed by CD31+ endothelial cells in mice, and is also expressed by a sub-population of these cells that co-express epithelial cell adhesion molecule and are detected only in the lung and the liver. In mouse models, MelLec was required for protection against disseminated infection with A. fumigatus. In humans, MelLec is also expressed by myeloid cells, and we identified a single nucleotide polymorphism of this receptor that negatively affected myeloid inflammatory responses and significantly increased the susceptibility of stem-cell transplant recipients to disseminated Aspergillus infections. MelLec therefore recognizes an immunologically active component commonly found on fungi and has an essential role in protective antifungal immunity in both mice and humans.
Assuntos
Aspergillus fumigatus/imunologia , Lectinas Tipo C/imunologia , Melaninas/imunologia , Naftóis/imunologia , Animais , Aspergilose/imunologia , Aspergilose/microbiologia , Aspergilose/prevenção & controle , Aspergillus fumigatus/química , Aspergillus fumigatus/patogenicidade , Parede Celular/química , Parede Celular/imunologia , Feminino , Humanos , Macrófagos/imunologia , Melaninas/química , Camundongos , Camundongos Endogâmicos C57BL , Naftóis/química , Ratos , Ratos Sprague-Dawley , Esporos Fúngicos/química , Esporos Fúngicos/imunologia , Especificidade por SubstratoRESUMO
BACKGROUND: Our previous proteomics data obtained from Candida albicans recovered after serial passage in a murine model of systemic infection revealed that Orf19.36.1 expression correlates with the virulence of the fungus. Therefore, the impact of ORF19.36.1 upon virulence was tested in this study. MATERIALS & METHODS: CRISPR-Cas9 technology was used to construct homozygous C. albicans orf19.36.1 null mutants and the phenotypes of these mutants examined in vitro (filamentation, invasion, adhesion, biofilm formation, hydrolase activities) and in vivo assays. RESULTS: The deletion of ORF19.36.1 did not significantly impact the phenotypes examined or the virulence of C. albicans in two infection models. CONCLUSION: These results suggest that, although Orf19.36.1 expression correlates with virulence, this protein is not essential for C. albicans pathobiology.
Assuntos
Candida albicans , Candidíase , Proteínas Fúngicas , Animais , Camundongos , Candidíase/microbiologia , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Virulência/genéticaRESUMO
Fungi can cause disease in humans, from mucocutaneous to life-threatening systemic infections. Initiation of antifungal immunity involves fungal recognition by pattern recognition receptors such as C-type lectin receptors (CLRs). These germline-encoded receptors trigger a multitude of innate responses including phagocytosis, fungal killing, and antigen presentation which can also shape the development of adaptive immunity. Recently, studies have shed light on how CLRs directly or indirectly modulate lymphocyte function. Moreover, CLR-mediated recognition of commensal fungi maintains homeostasis and prevents invasion from opportunistic commensals. We present an overview of current knowledge of antifungal T cell immune responses, with emphasis on the role of C-type lectins, and discuss how these receptors modulate these responses at different levels.
Assuntos
Imunidade Inata , Lectinas Tipo C , Micoses , Linfócitos T , Fungos/imunologia , Humanos , Imunidade Inata/imunologia , Lectinas Tipo C/imunologia , Micoses/imunologia , Linfócitos T/imunologiaRESUMO
Fungal cells change shape in response to environmental stimuli, and these morphogenic transitions drive pathogenesis and niche adaptation. For example, dimorphic fungi switch between yeast and hyphae in response to changing temperature. The basidiomycete Cryptococcus neoformans undergoes an unusual morphogenetic transition in the host lung from haploid yeast to large, highly polyploid cells termed Titan cells. Titan cells influence fungal interaction with host cells, including through increased drug resistance, altered cell size, and altered Pathogen Associated Molecular Pattern exposure. Despite the important role these cells play in pathogenesis, understanding the environmental stimuli that drive the morphological transition, and the molecular mechanisms underlying their unique biology, has been hampered by the lack of a reproducible in vitro induction system. Here we demonstrate reproducible in vitro Titan cell induction in response to environmental stimuli consistent with the host lung. In vitro Titan cells exhibit all the properties of in vivo generated Titan cells, the current gold standard, including altered capsule, cell wall, size, high mother cell ploidy, and aneuploid progeny. We identify the bacterial peptidoglycan subunit Muramyl Dipeptide as a serum compound associated with shift in cell size and ploidy, and demonstrate the capacity of bronchial lavage fluid and bacterial co-culture to induce Titanisation. Additionally, we demonstrate the capacity of our assay to identify established (cAMP/PKA) and previously undescribed (USV101) regulators of Titanisation in vitro. Finally, we investigate the Titanisation capacity of clinical isolates and their impact on disease outcome. Together, these findings provide new insight into the environmental stimuli and molecular mechanisms underlying the yeast-to-Titan transition and establish an essential in vitro model for the future characterization of this important morphotype.
Assuntos
Cryptococcus neoformans/citologia , Cryptococcus neoformans/patogenicidade , Animais , Criptococose/microbiologia , Cryptococcus neoformans/genética , AMP Cíclico/metabolismo , Modelos Animais de Doenças , Feminino , Proteínas Fúngicas/metabolismo , Interações Hospedeiro-Patógeno , Humanos , Hifas/citologia , Hifas/crescimento & desenvolvimento , Hifas/patogenicidade , Pulmão/microbiologia , Pneumopatias Fúngicas/microbiologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Microscopia Eletrônica de Transmissão , Modelos Biológicos , Morfogênese , Poliploidia , Fatores de Transcrição/metabolismo , VirulênciaRESUMO
Neurotrophic factors can promote the survival of degenerating retinal cells through the activation of STAT3 pathway. Thus, augmenting STAT3 activation in the retina has been proposed as potential therapy for retinal dystrophies. On the other hand, aberrant activation of STAT3 pathway is oncogenic and implicated in diverse human diseases. Furthermore, the STAT3/SOCS3 axis has been shown to induce the degradation of rhodopsin during retinal inflammation. In this study, we generated and used mice with constitutive activation of STAT3 pathway in the retina to evaluate the safety and consequences of enhancing STAT3 activities in the retina as a potential treatment for retinal degenerative diseases. We show that long-term activation of the STAT3 pathway can induce retinal degenerative changes and also exacerbate uveitis and other intraocular inflammatory diseases. Mechanisms underlying the development of vision impairment in the STAT3c-Tg mice derived in part from STAT3-mediated inhibition of rhodopsin and overexpression of SOCS3 in the retina. These results suggest that much caution should be exercised in the use of STAT3 augmentation therapy for retinal dystrophies.
Assuntos
Envelhecimento , Retina/patologia , Degeneração Retiniana/patologia , Fator de Transcrição STAT3/metabolismo , Animais , Camundongos , Camundongos Endogâmicos C57BL , Proteína 3 Supressora da Sinalização de Citocinas/metabolismo , Proteínas Supressoras da Sinalização de Citocina , Uveíte/patologiaRESUMO
The fungal pathogen Cryptococcus neoformans (C. neoformans) forms yeast cells of different sizes and morphological characteristics during infection. These features are usually not seen in standard laboratory in vitro conditions. Here, we describe in vivo cell morphologies when C. neoformans is grown in human plasma-like medium at 37°C, 5% CO2. We observed mixed-size populations of cells less than 1 µm up to 16.8 µm in cell diameter, increased capsule size, high chitin, and DNA content in larger cells. Our findings show that serum is not required for human plasma-like medium (HPLM)-induced C. neoformans cellular heterogeneity. Thus, this new method offers an opportunity to investigate factors of C. neoformans that mediate pathogenesis or host-pathogen interactions in a physiologically relevant setting.IMPORTANCEWe provide a description of new in vitro culture condition using the human plasma-like medium that supports the formation of the full range of in vivo cell morphologies of C. neoformans.
Assuntos
Criptococose , Cryptococcus neoformans , Meios de Cultura , Cryptococcus neoformans/citologia , Humanos , Meios de Cultura/química , Criptococose/microbiologia , Animais , Camundongos , Plasma/microbiologia , Interações Hospedeiro-PatógenoRESUMO
Host recognition of the pathogen-associated molecular pattern (PAMP), ß-1,3-glucan, plays a major role in antifungal immunity. ß-1,3-glucan is an essential component of the inner cell wall of the opportunistic pathogen Candida albicans. Most ß-1,3-glucan is shielded by the outer cell wall layer of mannan fibrils, but some can become exposed at the cell surface. In response to host signals such as lactate, C. albicans shaves the exposed ß-1,3-glucan from its cell surface, thereby reducing the ability of innate immune cells to recognise and kill the fungus. We have used sets of barcoded xog1 and eng1 mutants to compare the impacts of the secreted ß-glucanases Xog1 and Eng1 upon C. albicans in vitro and in vivo. Flow cytometry of Fc-dectin-1-stained strains revealed that Eng1 plays the greater role in lactate-induced ß-1,3-glucan masking. Transmission electron microscopy and stress assays showed that neither Eng1 nor Xog1 are essential for cell wall maintenance, but the inactivation of either enzyme compromised fungal adhesion to gut and vaginal epithelial cells. Competitive barcode sequencing suggested that neither Eng1 nor Xog1 strongly influence C. albicans fitness during systemic infection or vaginal colonisation in mice. However, the deletion of XOG1 enhanced C. albicans fitness during gut colonisation. We conclude that both Eng1 and Xog1 exert subtle effects on the C. albicans cell surface that influence fungal adhesion to host cells and that affect fungal colonisation in certain host niches.
RESUMO
An important feature of the adaptive immune response is its remarkable capacity to regulate the duration of inflammatory responses, and effector T cells have been shown to limit excessive immune responses by producing anti-inflammatory cytokines such as IL-10 and IL-27. However, how anti-inflammatory cytokines mediate their suppressive activities is not well understood. In this study, we show that STAT3 contributes to mechanisms that control the duration of T cell proliferation by regulating the subcellular location of FoxO1 and FoxO3a, two Class O Forkhead transcription factors that mediate lymphocyte quiescence and inhibit T cell activation. We show that active FoxO1 and FoxO3a reside exclusively in the nucleus of naïve T cells whereas inactive pFoxO1 and pFoxO3a were most abundant in activated T cells and sequestered in their cytoplasm in association with unphosphorylated STAT3 (U-STAT3) and 14-3-3. We further show that FoxO1/FoxO3a rapidly relocalized into the nucleus in response to pSTAT3 activation by IL-6 or IL-10, and the accumulation of FoxO1/FoxO3a in their nuclei coincided with increased expression of p27(Kip1) and p21(WAF1). STAT3 inhibitors completely abrogated cytokine-induced translocation of FoxO1/FoxO3a into the nucleus. In naïve or resting STAT3-deficient T cells, expression of pFoxO1/pFoxO3a was predominantly in the cytoplasm and correlated with defects in p27(Kip1) and p21(WAF1) expression, suggesting requirement of STAT3 for importation or retention of FoxO in the nucleus and attenuation of lymphocyte proliferation. Taken together, these results suggest that U-STAT3 collaborates with 14-3-3 to sequester pFoxO1/pFoxO3a in cytoplasm and thus prolong T cell activation, whereas pSTAT3 activation by anti-inflammatory cytokines would curtail the duration of TCR activation and re-establish lymphocyte quiescence by inducing nuclear localization of FoxO1/FoxO3a and FoxO-mediated expression of growth-inhibitory proteins.
Assuntos
Linfócitos T CD4-Positivos/metabolismo , Núcleo Celular/metabolismo , Citoplasma/metabolismo , Fatores de Transcrição Forkhead/metabolismo , Fator de Transcrição STAT3/metabolismo , Proteínas 14-3-3/genética , Proteínas 14-3-3/imunologia , Proteínas 14-3-3/metabolismo , Transporte Ativo do Núcleo Celular/imunologia , Animais , Linfócitos T CD4-Positivos/citologia , Linfócitos T CD4-Positivos/imunologia , Núcleo Celular/genética , Núcleo Celular/imunologia , Inibidor de Quinase Dependente de Ciclina p21/genética , Inibidor de Quinase Dependente de Ciclina p21/imunologia , Inibidor de Quinase Dependente de Ciclina p21/metabolismo , Inibidor de Quinase Dependente de Ciclina p27/genética , Inibidor de Quinase Dependente de Ciclina p27/imunologia , Inibidor de Quinase Dependente de Ciclina p27/metabolismo , Citocinas/genética , Citocinas/imunologia , Citocinas/metabolismo , Citoplasma/genética , Citoplasma/imunologia , Proteína Forkhead Box O1 , Proteína Forkhead Box O3 , Fatores de Transcrição Forkhead/genética , Fatores de Transcrição Forkhead/imunologia , Regulação da Expressão Gênica/imunologia , Humanos , Células Jurkat , Ativação Linfocitária/fisiologia , Camundongos , Camundongos Knockout , Receptores de Antígenos de Linfócitos T/genética , Receptores de Antígenos de Linfócitos T/imunologia , Receptores de Antígenos de Linfócitos T/metabolismo , Fator de Transcrição STAT3/genética , Fator de Transcrição STAT3/imunologiaRESUMO
STAT3 regulates CD4+ T cell survival and differentiation. However, its effects on CD8+ T cells are not well understood. Here, we show that in comparison to WT CD8+ T cells, STAT3-deficient CD8+ T cells exhibit a preactivated memory-like phenotype, produce more IL-2, proliferate faster, and are more sensitive to activation-induced cell death (AICD). The enhanced proliferation and sensitivity to AICD correlated with downregulation of class-O forkhead transcription factors (FoxO1, FoxO3A), p21(waf1), p27(KIP1), Bcl-2, OX-40, and upregulation of FasL, Bax, and Bad. We examined whether STAT3-deficient CD8+ T cells can mount effective response during herpes simplex virus (HSV-1) infection and experimental autoimmune uveitis (EAU). Compared to WT mice, HSV-1-infected STAT3-deficient mice (STAT3KO) produced less IFN-γ and virus-specific KLRG-1+ CD8+ T cells. STAT3KO mice are also resistant to EAU and produced less IL-17-producing Tc17 cells. Resistance of STAT3KO to EAU correlated with marked expansion of IL-10-producing regulatory CD8+ T cells (CD8-Treg) implicated in recovery from autoimmune encephalomyelitis. Thus, increases of IL-6-induced STAT3 activation observed during inflammation may inhibit expansion of CD8-Tregs, thereby impeding recovery from uveitis. These results suggest that STAT3 is a potential therapeutic target for upregulating CD8+ T cell-mediated responses to viruses and suggest the successful therapeutic targeting of STAT3 as treatment for uveitis, derived, in part, from promoting CD8-Treg expansion.
Assuntos
Linfócitos T CD8-Positivos/citologia , Herpes Simples/metabolismo , Interleucina-10/metabolismo , Fator de Transcrição STAT3/genética , Uveíte/imunologia , Animais , Apoptose , Doenças Autoimunes/imunologia , Proliferação de Células , Separação Celular , Citometria de Fluxo , Regulação da Expressão Gênica , Herpes Simples/virologia , Herpesvirus Humano 1 , Inflamação , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fenótipo , Fator de Transcrição STAT3/metabolismo , Regulação para Cima , Uveíte/virologiaRESUMO
Introduction: Invasive aspergillosis (IA) is the most prevalent infectious complication in patients with chronic granulomatous disease (CGD). Yet, understanding of fungal pathogenesis in the CGD host remains limited, particularly with regards to A. nidulans infection. Methods: We have used a murine model of X-linked CGD to investigate how the pathogenesis of IA varies between A. fumigatus and A. nidulans, comparing infection in both X-linked CGD (gp91-/-) mice and their parent C57BL/6 (WT) mice. A 14-colour flow cytometry panel was used to assess the cell dynamics over the course of infection, with parallel assessment of pulmonary cytokine production and lung histology. Results: We observed a lack of association between pulmonary pathology and infection outcome in gp91-/- mice, with no significant mortality in A. nidulans infected mice. An overwhelming and persistent neutrophil recruitment and IL-1 release in gp91-/- mice following both A. fumigatus and A. nidulans infection was observed, with divergent macrophage, dendritic cell and eosinophil responses and distinct cytokine profiles between the two infections. Conclusion: We have provided an in-depth characterisation of the immune response to pulmonary aspergillosis in an X-linked CGD murine model. This provides the first description of distinct pulmonary inflammatory environments in A. fumigatus and A. nidulans infection in X-linked CGD and identifies several new avenues for further research.
Assuntos
Aspergilose , Aspergillus nidulans , Doença Granulomatosa Crônica , Infecções Fúngicas Invasivas , Animais , Camundongos , Camundongos Endogâmicos C57BL , Aspergillus fumigatus/genética , Aspergillus nidulans/genética , Doença Granulomatosa Crônica/complicações , Modelos Animais de Doenças , CitocinasRESUMO
The immunogenicity of Candida albicans cells is influenced by changes in the exposure of microbe-associated molecular patterns (MAMPs) on the fungal cell surface. Previously, the degree of exposure on the C. albicans cell surface of the immunoinflammatory MAMP ß-(1,3)-glucan was shown to correlate inversely with colonisation levels in the gastrointestinal (GI) tract. This is important because life-threatening systemic candidiasis in critically ill patients often arises from translocation of C. albicans strains present in the patient's GI tract. Therefore, using a murine model, we have examined the impact of gut-related factors upon ß-glucan exposure and colonisation levels in the GI tract. The degree of ß-glucan exposure was examined by imaging flow cytometry of C. albicans cells taken directly from GI compartments, and compared with colonisation levels. Fungal ß-glucan exposure was lower in the cecum than the small intestine, and fungal burdens were correspondingly higher in the cecum. This inverse correlation did not hold for the large intestine. The gut fermentation acid, lactate, triggers ß-glucan masking in vitro, leading to attenuated anti-Candida immune responses. Additional fermentation acids are present in the GI tract, including acetate, propionate, and butyrate. We show that these acids also influence ß-glucan exposure on C. albicans cells in vitro and, like lactate, they influence ß-glucan exposure via Gpr1/Gpa2-mediated signalling. Significantly, C. albicans gpr1Δ gpa2Δ cells displayed elevated ß-glucan exposure in the large intestine and a corresponding decrease in fungal burden, consistent with the idea that Gpr1/Gpa2-mediated ß-glucan masking influences colonisation of this GI compartment. Finally, extracts from the murine gut and culture supernatants from the mannan grazing gut anaerobe Bacteroides thetaiotaomicron promote ß-glucan exposure at the C. albicans cell surface. Therefore, the local microbiota influences ß-glucan exposure levels directly (via mannan grazing) and indirectly (via fermentation acids), whilst ß-glucan masking appears to promote C. albicans colonisation of the murine large intestine.
RESUMO
Environmental factors, particularly fungi, influence the pathogenesis of allergic airway inflammation, but the mechanisms underlying these effects are still unclear. Melanin is one fungal component which is thought to modulate pulmonary inflammation. We recently identified a novel C-type lectin receptor, MelLec (Clec1a), which recognizes fungal 1,8-dihydroxynaphthalene (DHN)-melanin and is able to regulate inflammatory responses. Here we show that MelLec promotes pulmonary allergic inflammation and drives the development of Th17 T-cells in response to spores of Aspergillus fumigatus. Unexpectedly, we found that MelLec deficiency was protective, with MelLec-/- animals showing normal weight gain and significantly reduced pulmonary inflammation in our allergic model. The lungs of treated MelLec-/- mice displayed significantly reduced inflammatory foci and reduced bronchial wall thickening, which correlated with a reduced cellular influx (particularly neutrophils and inflammatory monocytes) and levels of inflammatory cytokines and chemokines. Notably, fungal burdens were increased in MelLec-/- animals, without apparent adverse effects, and there were no alterations in the survival of these mice. Characterization of the pulmonary T-cell populations, revealed a significant reduction in Th17 cells, and no alterations in Th2, Th1 or Treg cells. Thus, our data reveal that while MelLec is required to control pulmonary fungal burden, the inflammatory responses mediated by this receptor negatively impact the animal welfare in this allergic model.
Assuntos
Aspergillus fumigatus/patogenicidade , Asma/etiologia , Lectinas Tipo C/fisiologia , Animais , Asma/imunologia , Brônquios/patologia , Citocinas/biossíntese , Melaninas/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Células Th17/imunologiaRESUMO
Macrophages provide a first line of defense against microorganisms, and while some mechanisms to kill pathogens such as the oxidative burst are well described, others are still undefined or unknown. Here, we report that the Rab32 guanosine triphosphatase and its guanine nucleotide exchange factor BLOC-3 (biogenesis of lysosome-related organelles complex-3) are central components of a trafficking pathway that controls both bacterial and fungal intracellular pathogens. This host-defense mechanism is active in both human and murine macrophages and is independent of well-known antimicrobial mechanisms such as the NADPH (reduced form of nicotinamide adenine dinucleotide phosphate)-dependent oxidative burst, production of nitric oxide, and antimicrobial peptides. To survive in human macrophages, Salmonella Typhi actively counteracts the Rab32/BLOC-3 pathway through its Salmonella pathogenicity island-1-encoded type III secretion system. These findings demonstrate that the Rab32/BLOC-3 pathway is a novel and universal host-defense pathway and protects mammalian species from various pathogens.
Assuntos
Salmonella typhi , Proteínas rab de Ligação ao GTP , Animais , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Humanos , Lisossomos/metabolismo , Macrófagos/metabolismo , Mamíferos/metabolismo , Camundongos , Proteínas rab de Ligação ao GTP/metabolismoRESUMO
The discovery of liquid water at several locations in the solar system raises the possibility that microbial life may have evolved outside Earth and as such could be accidently introduced into the Earth's ecosystem. Unusual sugars or amino acids, like non-proteinogenic isovaline and α-aminoisobutyric acid that are vanishingly rare or absent from life forms on Earth, have been found in high abundance on non-terrestrial carbonaceous meteorites. It is therefore conceivable that exo-microorganisms might contain proteins that include these rare amino acids. We therefore asked whether the mammalian immune system would be able to recognize and induce appropriate immune responses to putative proteinaceous antigens that include these rare amino acids. To address this, we synthesised peptide antigens based on a backbone of ovalbumin and introduced isovaline and α-aminoisobutyric acid residues and demonstrated that these peptides can promote naïve OT-I cell activation and proliferation, but did so less efficiently than the canonical peptides. This is relevant to the biosecurity of missions that may retrieve samples from exoplanets and moons that have conditions that may be permissive for life, suggesting that accidental contamination and exposure to exo-microorganisms with such distinct proteomes might pose an immunological challenge.
RESUMO
Phagocytosis is a receptor-mediated process critical to innate immune clearance of pathogens. It proceeds in a regulated sequence of stages: (a) migration of phagocytes towards pathogens, (b) recognition of PAMPs and binding through PRRs, (c) engulfment and internalisation into phagosomes, (d) phagosome maturation, and (e) killing of pathogen or host cells. However, little is known about the role that individual receptors play in these discrete stages in the recognition of fungal cells. In a previous study, we found that dectin-2 deficiency impacted some but not all stages of macrophage-mediated phagocytosis of Candida glabrata. Because the C-type lectin receptor dectin-2 critically requires coupling to the FcRγ chain for signalling, we hypothesised that this coupling may be important for regulating phagocytosis of fungal cargo. We therefore examined how deficiency in FcRγ itself or two receptors to which it couples (dectin-2 and mincle) impacts phagocytosis of six fungal organisms representing three different fungal taxa. Our data show that deficiency in these proteins impairs murine bone marrow-derived macrophage migration, engulfment, and phagosome maturation, but not macrophage survival. Therefore, FcRγ engagement with selective C-type lectin receptors (CLRs) critically affects the spatio-temporal dynamics of fungal phagocytosis.