Project description:To mimic the initial phases of systemic Candida infections with dissemination via the bloodstream, we used an ex vivo whole blood infection model. Dual TP of C. auris in blood gave insights into fungal adaptations and survival mechanisms as well as the host response to the infection.
Project description:Fungal infections claim an estimated 1.5 million lives every year. Mechanisms that protect from fungal infections are still elusive. Recognition of fungal pathogens relies on C-type lectin receptors (CLR) and their downstream signaling kinase SYK. Here we report that the E3-ubiquitin-ligase CBL-B controls proximal C-type lectin receptor signaling in macrophages and dendritic cells. We show that CBL-B associates with SYK and ubiquitinates SYK, Dectin-1, and Dectin-2 upon fungal recognition. Functionally, CBL-B deficiency results in increased inflammasome activation, enhanced reactive oxygen species production, and increased fungal killing. Genetic deletion of Cblb protects mice from morbidity caused by cutaneous infection and markedly improves survival upon a lethal systemic infection with Candida albicans. Based on these findings, we engineered a cell-permeable CBL-B inhibitory peptide that protects mice from lethal C. albicans infections. We thus describe a key role for Cblb in the regulation of innate anti-fungal immunity and establish a novel paradigm for the treatment of fungal sepsis.
Project description:Fungal infections claim an estimated 1.5 million lives every year. Mechanisms that protect from fungal infections are still elusive. Recognition of fungal pathogens relies on C-type lectin receptors (CLR) and their downstream signaling kinase SYK. Here we report that the E3-ubiquitin-ligase CBL-B controls proximal C-type lectin receptor signaling in macrophages and dendritic cells. We show that CBL-B associates with SYK and ubiquitinates SYK, Dectin-1, and Dectin-2 upon fungal recognition. Functionally, CBL-B deficiency results in increased inflammasome activation, enhanced reactive oxygen species production, and increased fungal killing. Genetic deletion of Cblb protects mice from morbidity caused by cutaneous infection and markedly improves survival upon a lethal systemic infection with Candida albicans. Based on these findings, we engineered a cell-permeable CBL-B inhibitory peptide that protects mice from lethal C. albicans infections. We thus describe a key role for Cblb in the regulation of innate anti-fungal immunity and establish a novel paradigm for the treatment of fungal sepsis.
Project description:Candida auris, a multidrug-resistant human fungal pathogen, was first identified in 2009 in Japan. Since then, systemic C. auris infections have now been reported in more than 50 countries, with mortality rates of 30-60%. A major contributing factor to its high inter- and intrahospital clonal transmission is that C. auris, unlike most Candida species, displays unique skin tropism and can stay on human skin for a prolonged period. However, the molecular mechanisms responsible for C. auris skin colonization, intradermal persistence, and systemic virulence are poorly understood. Here, we report that C. auris Hog1 mitogen-activated protein kinase (MAPK) is essential for efficient skin colonization, intradermal persistence, as well as, systemic virulence. RNA-seq analysis of wildtype parental and hog1D mutant strains from YPD-grown cultures revealed marked down-regulation of genes involved in processes such as cell adhesion, cell-wall rearrangement, and pathogenesis in hog1D mutant compared to the wildtype parent. In agreement, we found a prominent role for Hog1 in maintaining cell-wall architecture, as the hog1D mutant demonstrated a significant increase in cell-surface b-glucan exposure and a concomitant reduction in chitin content. Additionally, we observed that Hog1 was required for biofilm formation in vitro and fungal survival when challenged with primary murine macrophages and neutrophils ex vivo. Collectively, these findings have important implications for understanding the C. auris skin adherence mechanisms and penetration of skin epithelial layers preceding bloodstream infections.
Project description:Candida albicans is the most common human fungal pathogen causing mucosal and systemic infections, but human anti-fungal immunity remains poorly defined. Expression profiling of Candida-stimulated human peripheral blood mononuclear cells (PBMCs) provides new insights into Candida-specific host defense mechanisms in humans.
Project description:Within the last decades, invasive fungal infections have gained increasing significance. They are characterized by high mortality rates and are often caused Candida albicans and Aspergillus fumigatus. The increasing number of infections underlines the necessity for additional anti-fungal therapies, which require an extended knowledge of gene regulations during fungal infection. MicroRNAs are regulators of important cellular processes, including immune response. By analyzing their regulation and impact on target genes, novel therapeutic approaches may be developed. Here, we examine the role of microRNAs in human dendritic cells during fungal infections. Dendritic cells represent the bridge between the innate and the adaptive immune systems. Therefore, analysis of gene regulation of dendritic cells is of particular significance. By applying next-generation sequencing of small RNAs, we quantify microRNA expression in monocyte-derived dendritic cells after 6 and 12h of infection with C. albicans and A. fumigatus as well as treatment with LPS. We use two different tools and an online database to determine potential target genes. We identified 29 microRNAs that are differentially regulated after infection by the fungi or LPS. Two and five of them are specific for fungal infections after 6h and 12h, respectively. We further validated interactions of miR-132-5p and miR-212-5p with immunological relevant target genes, such as FKBP1B, KLF4, and SPN, on both RNA and protein level. Our results indicate a fine-tuning function of these microRNAs during fungal infections. Beyond that, we identified previously undiscovered microRNAs. We validated three novel microRNAs via qRT-PCR. A comparison with known microRNAs revealed possible relations with the miR-378 family and miR-1260a/b for two of them, while the third one features a unique sequence with no resemblance to known microRNAs. In summary, this study analyzes the effect of known microRNAs in dendritic cells during fungal infections and proposes novel microRNAs that could be experimentally verified.
Project description:Candida albicans is the most common human fungal pathogen causing mucosal and systemic infections, but human anti-fungal immunity remains poorly defined. Expression profiling of Candida-stimulated human peripheral blood mononuclear cells (PBMCs) provides new insights into Candida-specific host defense mechanisms in humans. Total RNA was extracted from PBMCs from healthy human volunteers. PBMCs were stimulated with heat-killed Candida albicans (10^6/ml), non-fungal inflammatory stimuli or RPMI control for 4 or 24 hours. A large number of biological replicates (>20) were included per stimulation condition and duration.
Project description:Sepsis is a clinical syndrome that can be caused by bacteria or fungi. Early knowledge on the nature of the causative agent is a prerequisite for targeted anti-microbial therapy. Besides currently used detection methods like blood culture and PCR-based assays, the analysis of the transcriptional response of the host to infecting organisms holds great promise. In this study, we aim to examine the transcriptional footprint of infections caused by the bacterial pathogens Staphylococcus aureus and Escherichia coli and the fungal pathogens Candida albicans and Aspergillus fumigatus in a human whole-blood model. Moreover, we use the expression information to build a random forest classifier to determine if the pathogen is bacterial, fungal or neither of the two. After normalizing the transcription intensities using stably expressed reference genes, we filtered the gene set for biomarkers of bacterial or fungal blood infections. This selection is based on differential expression and an additional gene relevance measure. In this way, we identified 38 biomarker genes, including IL6, SOCS3, and IRG1 which were already associated to sepsis by other studies. Using these genes, we trained the classifier and assessed its performance. It yielded a 96% accuracy (sensitivities >93%, specificities >97%) for a 10-fold stratified cross-validation and a 92% accuracy (sensitivities and specificities >83%) for an additional dataset comprising Cryptococcus neoformans infections. Furthermore, the noise-robustness of the classifier suggests high rates of correct class predictions on datasets of new species. In conclusion, this genome-wide approach demonstrates an effective feature selection process in combination with the construction of a well-performing classification model. Further analyses of genes with pathogen-dependent expression patterns can provide insights into the systemic host responses, which may lead to new anti-microbial therapeutic advances. Analysis of innate immune activation on the basis of gene expression of whole blood cells during ex vivo whole blood infection with bacterial (Staphylococcus aureus, Escherichia coli) and fungal pathogens (Candida albicans, Aspergillus fumigatus) in comparison to mock-treated blood.
Project description:The mammalian gastrointestinal tract and the bloodstream are highly disparate biological niches, and yet certain commensal-pathogenic microorganisms are able to thrive in both environments. Here, we report the evolution of a unique transcription circuit in the yeast, Candida albicans, which determines its fitness in both host niches. Our comprehensive analysis of the DNA-binding proteins that regulate iron uptake by this organism suggests the evolutionary intercalation of a transcriptional activator called Sef1 between two broadly conserved transcriptional repressors, Sfu1 and Hap43. The Sef1 activator of iron uptake genes promotes virulence in a mouse model of bloodstream infection, whereas the Sfu1 repressor is dispensable for virulence but promotes gastrointestinal commensalism. We propose that the ability to alternate between genetic programs conferring resistance to iron depletion in the bloodstream versus iron toxicity in the gut may be a fundamental attribute of gastrointestinal commensal-pathogens.
Project description:Gene modified autologous hematopoietic stem cells (HSC) can provide significant clinical benefits to patients suffering from X-linked chronic granulomatous disease (X-CGD), a rare inherited immunodeficiency characterized by recurrent, often life threatening bacterial and fungal infections. Here we report on the molecular and cellular events observed in two patients treated by gene therapy in 2004. After the initial resolution of bacterial and fungal infections, both patients exhibited silencing of transgene expression due to methylation of the viral promoter, and myelodysplasia with monosomy 7 as a result of insertional activation of EVI1. One patient died from overwhelming sepsis 27 months after gene therapy, whereas a second patient underwent an allogeneic HSC transplantation. Our data shows that forced overexpression of MDS1/EVI1 or EVI1 in human cells disrupts normal centrosome duplication, linking MDS1/EVI1 activation to the development of genomic instability, monosomy 7 and clonal progression towards myelodysplasia.