Publications

Abstract (Expand)

Candida albicans is a common cause of life-threatening fungal bloodstream infections. In the murine model of systemic candidiasis, the kidney is the primary target organ while the fungal load declines over time in liver and spleen. To better understand these organ-specific differences in host-pathogen interaction, we performed gene expression profiling of murine kidney, liver and spleen and determined the fungal transcriptome in liver and kidney. We observed a delayed transcriptional immune response accompanied by late induction of fungal stress response genes in the kidneys. In contrast, early upregulation of the proinflammatory response in the liver was associated with a fungal transcriptome resembling response to phagocytosis, suggesting that phagocytes contribute significantly to fungal control in the liver. Notably, C. albicans hypha-associated genes were upregulated in the absence of visible filamentation in the liver, indicating an uncoupling of gene expression and morphology and a morphology-independent effect by hypha-associated genes in this organ. Consistently, integration of host and pathogen transcriptional data in an inter-species gene regulatory network indicated connections of C. albicans cell wall remodelling and metabolism to the organ-specific immune responses.

Authors: B. Hebecker, S. Vlaic, T. Conrad, Michael Bauer, S. Brunke, M. Kapitan, Jörg Linde, B. Hube, Ilse Jacobsen

Date Published: No date defined

Journal: Sci Rep

Abstract (Expand)

Murine infection models are widely used to study systemic candidiasis caused by C. albicans. Whole-blood models can help to elucidate host-pathogens interactions and have been used for several Candida species in human blood. We adapted the human whole-blood model to murine blood. Unlike human blood, murine blood was unable to reduce fungal burden and more substantial filamentation of C. albicans was observed. This coincided with less fungal association with leukocytes, especially neutrophils. The lower neutrophil number in murine blood only partially explains insufficient infection and filamentation control, as spiking with murine neutrophils had only limited effects on fungal killing. Furthermore, increased fungal survival is not mediated by enhanced filamentation, as a filament-deficient mutant was likewise not eliminated. We also observed host-dependent differences for interaction of platelets with C. albicans, showing enhanced platelet aggregation, adhesion and activation in murine blood. For human blood, opsonization was shown to decrease platelet interaction suggesting that complement factors interfere with fungus-to-platelet binding. Our results reveal substantial differences between murine and human whole-blood models infected with C. albicans and thereby demonstrate limitations in the translatability of this ex vivo model between hosts.

Authors: S. Machata, S. Sreekantapuram, Kerstin Hünniger, Oliver Kurzai, C. Dunker, K. Schubert, Wibke Krüger, B. Schulze-Richter, C. Speth, G. Rambach, Ilse Jacobsen

Date Published: 1st Feb 2021

Journal: Front Immunol

Abstract (Expand)

Burn wounds are highly susceptible sites for colonization and infection by bacteria and fungi. Large wound surface, impaired local immunity, and broad-spectrum antibiotic therapy support growth of opportunistic fungi such as Candida albicans, which may lead to invasive candidiasis. Currently, it remains unknown whether depressed host defenses or fungal virulence drive the progression of burn wound candidiasis. Here we established an ex vivo burn wound model, where wounds were inflicted by applying preheated soldering iron to human skin explants, resulting in highly reproducible deep second-degree burn wounds. Eschar removal by debridement allowed for deeper C. albicans penetration into the burned tissue associated with prominent filamentation. Active migration of resident tissue neutrophils towards the damaged tissue and release of pro-inflammatory cytokine IL-1beta accompanied the burn. The neutrophil recruitment was further increased upon supplementation of the model with fresh immune cells. Wound area and depth decreased over time, indicating healing of the damaged tissue. Importantly, prominent neutrophil presence at the infected site correlated to the limited penetration of C. albicans into the burned tissue. Altogether, we established a reproducible burn wound model of candidiasis using ex vivo human skin explants, where immune responses actively control the progression of infection and promote tissue healing.

Authors: C. von Muller, F. Bulman, L. Wagner, D. Rosenberger, A. Marolda, Oliver Kurzai, P. Eissmann, Ilse Jacobsen, B. Perner, P. Hemmerich, Slavena Vylkova

Date Published: 11th Dec 2020

Journal: Sci Rep

Abstract (Expand)

Candida albicans is a major fungal pathogen of humans. It exists as a commensal in the oral cavity, gut or genital tract of most individuals, constrained by the local microbiota, epithelial barriers and immune defences. Their perturbation can lead to fungal outgrowth and the development of mucosal infections such as oropharyngeal or vulvovaginal candidiasis, and patients with compromised immunity are susceptible to life-threatening systemic infections. The importance of the interplay between fungus, host and microbiota in driving the transition from C. albicans commensalism to pathogenicity is widely appreciated. However, the complexity of these interactions, and the significant impact of fungal, host and microbiota variability upon disease severity and outcome, are less well understood. Therefore, we summarise the features of the fungus that promote infection, and how genetic variation between clinical isolates influences pathogenicity. We discuss antifungal immunity, how this differs between mucosae, and how individual variation influences a person's susceptibility to infection. Also, we describe factors that influence the composition of gut, oral and vaginal microbiotas, and how these affect fungal colonisation and antifungal immunity. We argue that a detailed understanding of these variables, which underlie fungal-host-microbiota interactions, will present opportunities for directed antifungal therapies that benefit vulnerable patients.

Authors: C. d'Enfert, A. K. Kaune, L. R. Alaban, S. Chakraborty, N. Cole, M. Delavy, D. Kosmala, B. Marsaux, R. Frois-Martins, M. Morelli, D. Rosati, M. Valentine, Z. Xie, Y. Emritloll, P. A. Warn, F. Bequet, M. E. Bougnoux, S. Bornes, Mark Gresnigt, Bernhard Hube, Ilse Jacobsen, M. Legrand, S. Leibundgut-Landmann, C. Manichanh, C. A. Munro, M. G. Netea, K. Queiroz, K. Roget, V. Thomas, C. Thoral, P. Van den Abbeele, A. W. Walker, A. J. P. Brown

Date Published: 24th Nov 2020

Journal: FEMS Microbiol Rev

Abstract (Expand)

Invasive pulmonary aspergillosis (IPA) is a severe infection that is difficult to diagnose due to the ubiquitous presence of fungal spores, the underlying diseases of risk patients, and limitations of currently available markers. In this study, we performed a comprehensive liquid chromatography tandem mass spectrometry (LC-MS/MS)-based identification of host and fungal proteins expressed during IPA in mice and humans. The proteomic analysis of bronchoalveolar lavage samples of individual IPA and control cases allowed the description of common host factors that had significantly increased abundance in both infected animals and IPA patients compared to their controls. Although increased levels of these individual host proteins might not be sufficient to distinguish bacterial from fungal infection, a combination of these markers might be beneficial to improve diagnosis. We also identified 16 fungal proteins that were specifically detected during infection and may be valuable candidates for biomarker evaluation.

Authors: S. Machata, Wolfgang Müller, R. Lehmann, Patricia Sieber, Gianni Panagiotou, A. Carvalho, C. Cunha, K. Lagrou, J. Maertens, Hortense Slevogt, Ilse Jacobsen

Date Published: 12th Oct 2020

Journal: Virulence

Abstract (Expand)

Th cells integrate signals from their microenvironment to acquire distinct specialization programs for efficient clearance of diverse pathogens or for immunotolerance. Ionic signals have recently been demonstrated to affect T cell polarization and function. Sodium chloride (NaCl) was proposed to accumulate in peripheral tissues upon dietary intake and to promote autoimmunity via the Th17 cell axis. Here, we demonstrate that high-NaCl conditions induced a stable, pathogen-specific, antiinflammatory Th17 cell fate in human T cells in vitro. The p38/MAPK pathway, involving NFAT5 and SGK1, regulated FoxP3 and IL-17A expression in high-NaCl conditions. The NaCl-induced acquisition of an antiinflammatory Th17 cell fate was confirmed in vivo in an experimental autoimmune encephalomyelitis (EAE) mouse model, which demonstrated strongly reduced disease symptoms upon transfer of T cells polarized in high-NaCl conditions. However, NaCl was coopted to promote murine and human Th17 cell pathogenicity, if T cell stimulation occurred in a proinflammatory and TGF-beta-low cytokine microenvironment. Taken together, our findings reveal a context-dependent, dichotomous role for NaCl in shaping Th17 cell pathogenicity. NaCl might therefore prove beneficial for the treatment of chronic inflammatory diseases in combination with cytokine-blocking drugs.

Authors: J. Matthias, S. Heink, F. Picard, J. Zeitrag, A. Kolz, Y. Y. Chao, D. Soll, G. P. de Almeida, E. Glasmacher, Ilse Jacobsen, T. Riedel, A. Peters, S. Floess, J. Huehn, D. Baumjohann, M. Huber, T. Korn, C. E. Zielinski

Date Published: 1st Sep 2020

Journal: J Clin Invest

Abstract (Expand)

Typically, established lab strains are widely used to study host-pathogen interactions. However, to better reflect the infection process, the experimental use of clinical isolates has come more into focus. Here, we analyzed the interaction of multiple vaginal isolates of the opportunistic fungal pathogen Candida albicans, the most common cause of vulvovaginal candidiasis in women, with key players of the host immune system: macrophages. We tested several strains isolated from asymptomatic or symptomatic women with acute and recurrent infections. While all clinical strains showed a response similar to the commonly used lab strain SC5314 in various in vitro assays, they displayed remarkable differences during interaction with macrophages. This coincided with significantly reduced beta-glucan exposure on the cell surface, which appeared to be a shared property among the tested vaginal strains for yeast extract/peptone/dextrose-grown cells, which is partly lost when the isolates faced vaginal niche-like nutrient conditions. However, macrophage damage, survival of phagocytosis, and filamentation capacities were highly strain-specific. These results highlight the high heterogeneity of C. albicans strains in host-pathogen interactions, which have to be taken into account to bridge the gap between laboratory-gained data and disease-related outcomes in an actual patient.IMPORTANCE Vulvovaginal candidiasis is one of the most common fungal infections in humans with Candida albicans as the major causative agent. This study is the first to compare clinical vaginal isolates of defined patient groups in their interaction with macrophages, highlighting the vastly different outcomes in comparison to a laboratory strain using commonly applied virulence-determining assays.

Authors: F. Gerwien, C. Dunker, Philipp Brandt, E. Garbe, Ilse Jacobsen, Slavena Vylkova

Date Published: 19th Aug 2020

Journal: mSphere

Abstract (Expand)

Extracellular vesicles have an important function in cellular communication. Here, we show that human and mouse monocytes release TGF-beta1-transporting vesicles in response to the pathogenic fungus Candida albicans. Soluble beta-glucan from C. albicans binds to complement receptor 3 (CR3, also known as CD11b/CD18) on monocytes and induces the release of TGF-beta1-transporting vesicles. CR3-dependence is demonstrated using CR3-deficient (CD11b knockout) monocytes generated by CRISPR-CAS9 genome editing and isolated from CR3-deficient (CD11b knockout) mice. These vesicles reduce the pro-inflammatory response in human M1-macrophages as well as in whole blood. Binding of the vesicle-transported TGF-beta1 to the TGF-beta receptor inhibits IL1B transcription via the SMAD7 pathway in whole blood and induces TGFB1 transcription in endothelial cells, which is resolved upon TGF-beta1 inhibition. Notably, human complement-opsonized apoptotic bodies induce production of similar TGF-beta1-transporting vesicles in monocytes, suggesting that the early immune response might be suppressed through this CR3-dependent anti-inflammatory vesicle pathway.

Authors: Luke Donald Halder, E. A. H. Jo, M. Z. Hasan, M. Ferreira-Gomes, Thomas Krüger, M. Westermann, D. I. Palme, G. Rambach, Niklas Beyersdorf, C. Speth, Ilse Jacobsen, Olaf Kniemeyer, Berit Jungnickel, Peter Zipfel, Christine Skerka

Date Published: 11th May 2020

Journal: Nat Commun

Abstract (Expand)

The capacity of Candida albicans to reversibly change its morphology between yeast and filamentous stages is crucial for its virulence. Formation of hyphae correlates with the upregulation of genes ALS3 and ECE1, which are involved in pathogenicity processes such as invasion, iron acquisition, and host cell damage. The global repressor Tup1 and its cofactor Nrg1 are considered to be the main antagonists of hyphal development in C. albicans However, our experiments revealed that Tup1, but not Nrg1, was required for full expression of ALS3 and ECE1 In contrast to NRG1, overexpression of TUP1 was found to inhibit neither filamentous growth nor transcription of ALS3 and ECE1 In addition, we identified the transcription factor Ahr1 as being required for full expression of both genes. A hyperactive version of Ahr1 bound directly to the promoters of ALS3 and ECE1 and induced their transcription even in the absence of environmental stimuli. This regulation worked even in the absence of the crucial hyphal growth regulators Cph1 and Efg1 but was dependent on the presence of Tup1. Overall, our results show that Ahr1 and Tup1 are key contributors in the complex regulation of virulence-associated genes in the different C. albicans morphologies.IMPORTANCE Candida albicans is a major human fungal pathogen and the leading cause of systemic Candida infections. In recent years, Als3 and Ece1 were identified as important factors for fungal virulence. Transcription of both corresponding genes is closely associated with hyphal growth. Here, we describe how Tup1, normally a global repressor of gene expression as well as of filamentation, and the transcription factor Ahr1 contribute to full expression of ALS3 and ECE1 in C. albicans hyphae. Both regulators are required for high mRNA amounts of the two genes to ensure functional relevant protein synthesis and localization. These observations identified a new aspect of regulation in the complex transcriptional control of virulence-associated genes in C. albicans.

Authors: S. Ruben, E. Garbe, Selene Mogavero, Daniela Albrecht-Eckardt, D. Hellwig, A. Hader, Thomas Krüger, K. Gerth, Ilse Jacobsen, O. Elshafee, S. Brunke, Kerstin Hünniger, Olaf Kniemeyer, Axel Brakhage, Joachim Morschhäuser, Bernhard Hube, Slavena Vylkova, Oliver Kurzai, R. Martin

Date Published: 28th Apr 2020

Journal: mBio

Abstract (Expand)

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1, CD66a) is a receptor for Candida albicans. It is crucial for the immune response of intestinal epithelial cells to this opportunistic pathogen. Moreover, CEACAM1 is of importance for the mucosal colonization by different bacterial pathogens. We therefore studied the influence of the human CEACAM1 receptor in human CEACAM1-transgenic mice on the C. albicans colonization and infection utilizing a colonization/dissemination and a systemic infection mouse model. Our results showed no alterations in the host response between the transgenic mice and the wild-type littermates to the C. albicans infections. Both mouse strains showed comparable C. albicans colonization and mycobiota, similar fungal burdens in various organs, and a similar survival in the systemic infection model. Interestingly, some of the mice treated with anti-bacterial antibiotics (to prepare them for C. albicans colonization via oral infection) also showed a strong reduction in endogenous fungi instead of the normally observed increase in fungal numbers. This was independent of the expression of human CEACAM1. In the systemic infection model, the human CEACAM1 expression was differentially regulated in the kidneys and livers of Candida-infected transgenic mice. Notably, in the kidneys, a total loss of the largest human CEACAM1 isoform was observed. However, the overwhelming immune response induced in the systemic infection model likely covered any CEACAM1-specific effects in the transgenic animals. In vitro studies using bone marrow-derived neutrophils from both mouse strains also revealed no differences in their reaction to C. albicans. In conclusion, in contrast to bacterial pathogens interacting with CEACAM1 on different mucosal surfaces, the human CEACAM1-transgenic mice did not reveal a role of human CEACAM1 in the in vivo candidiasis models used here. Further studies and different approaches will be needed to reveal a putative role of CEACAM1 in the host response to C. albicans.

Authors: Esther Klaile, M. M. Muller, C. Zubiria-Barrera, S. Brehme, Tilman Klassert, M. Stock, A. Durotin, T. D. Nguyen, S. Feer, B. B. Singer, Peter Zipfel, Sven Rudolphi, Ilse Jacobsen, Hortense Slevogt

Date Published: 19th Dec 2019

Journal: Front Microbiol

Abstract (Expand)

Alterations of the microbial composition in the gut and the concomitant dysregulation of the mucosal immune response are associated with the pathogenesis of opportunistic infections, chronic inflammation, and inflammatory bowel disease. To create a platform for the investigation of the underlying mechanisms, we established a three-dimensional microphysiological model of the human intestine. This model resembles organotypic microanatomical structures and includes tissue resident innate immune cells exhibiting features of mucosal macrophages and dendritic cells. The model displays the physiological immune tolerance of the intestinal lumen to microbial-associated molecular patterns and can, therefore, be colonised with living microorganisms. Functional studies on microbial interaction between probiotic Lactobacillus rhamnosus and the opportunistic pathogen Candida albicans show that pre-colonization of the intestinal lumen of the model by L. rhamnosus reduces C. albicans-induced tissue damage, lowers its translocation, and limits fungal burden. We demonstrate that microbial interactions can be efficiently investigated using the in vitro model creating a more physiological and immunocompetent microenvironment. The intestinal model allows a detailed characterisation of the immune response, microbial pathogenicity mechanisms, and quantification of cellular dysfunction attributed to alterations in the microbial composition.

Authors: M. Maurer, M. S. Gresnigt, A. Last, T. Wollny, F. Berlinghof, R. Pospich, Z. Cseresnyes, A. Medyukhina, K. Graf, M. Groger, M. Raasch, F. Siwczak, S. Nietzsche, Ilse Jacobsen, Marc Thilo Figge, Bernhard Hube, O. Huber, A. S. Mosig

Date Published: 10th Aug 2019

Journal: Biomaterials

Abstract (Expand)

BACKGROUND: Omics data provide deep insights into overall biological processes of organisms. However, integration of data from different molecular levels such as transcriptomics and proteomics, still remains challenging. Analyzing lists of differentially abundant molecules from diverse molecular levels often results in a small overlap mainly due to different regulatory mechanisms, temporal scales, and/or inherent properties of measurement methods. Module-detecting algorithms identifying sets of closely related proteins from protein-protein interaction networks (PPINs) are promising approaches for a better data integration. RESULTS: Here, we made use of transcriptome, proteome and secretome data from the human pathogenic fungus Aspergillus fumigatus challenged with the antifungal drug caspofungin. Caspofungin targets the fungal cell wall which leads to a compensatory stress response. We analyzed the omics data using two different approaches: First, we applied a simple, classical approach by comparing lists of differentially expressed genes (DEGs), differentially synthesized proteins (DSyPs) and differentially secreted proteins (DSePs); second, we used a recently published module-detecting approach, ModuleDiscoverer, to identify regulatory modules from PPINs in conjunction with the experimental data. Our results demonstrate that regulatory modules show a notably higher overlap between the different molecular levels and time points than the classical approach. The additional structural information provided by regulatory modules allows for topological analyses. As a result, we detected a significant association of omics data with distinct biological processes such as regulation of kinase activity, transport mechanisms or amino acid metabolism. We also found a previously unreported increased production of the secondary metabolite fumagillin by A. fumigatus upon exposure to caspofungin. Furthermore, a topology-based analysis of potential key factors contributing to drug-caused side effects identified the highly conserved protein polyubiquitin as a central regulator. Interestingly, polyubiquitin UbiD neither belonged to the groups of DEGs, DSyPs nor DSePs but most likely strongly influenced their levels. CONCLUSION: Module-detecting approaches support the effective integration of multilevel omics data and provide a deep insight into complex biological relationships connecting these levels. They facilitate the identification of potential key players in the organism's stress response which cannot be detected by commonly used approaches comparing lists of differentially abundant molecules.

Authors: Theresia Conrad, Olaf Kniemeyer, S. G. Henkel, T. Kruger, D. J. Mattern, V. Valiante, Reinhard Guthke, Ilse Jacobsen, Axel Brakhage, S. Vlaic, Jörg Linde

Date Published: 20th Oct 2018

Journal: BMC Syst Biol

Abstract (Expand)

Rationale: The liver is a central organ not only for metabolism but also immune function. Life-threatening infections of both bacterial and fungal origin can affect liver function but it is yet unknown whether molecular changes differ depending on the pathogen. We aimed to determine whether the hepatic host response to bacterial and fungal infections differs in terms of hepatic metabolism and liver function. Methods: We compared murine models of infection, including bacterial peritoneal contamination and infection (PCI), intraperitoneal and systemic C. albicans infection, at 6 and 24 h post-infection, to sham controls. The molecular hepatic host response was investigated by the detection of regulatory modules based on large-scale protein-protein interaction networks and expression data. Topological analysis of these regulatory modules was used to reveal infection-specific biological processes and molecular mechanisms. Intravital microscopy and immunofluorescence microscopy were used to further analyze specific aspects of pathophysiology such as cholestasis. Results: Down-regulation of lipid catabolism and bile acid synthesis was observed after 6 h in all infection groups. Alterations in lipid catabolism were characterized by accumulation of long chain acylcarnitines and defective beta-oxidation, which affected metabolism by 6 h. While PCI led to an accumulation of unconjugated bile acids (BA), C. albicans infection caused accumulation of conjugated BA independent of the route of infection. Hepatic dye clearance and transporter expression revealed reduced hepatic uptake in fungal infections vs. defects in secretion following polybacterial infection. Conclusion: Molecular phenotypes of lipid accumulation and cholestasis allow differentiation between pathogens as well as routes of infection at early stages in mice. Targeted metabolomics could be a useful tool for the profiling of infected/septic patients and the type of pathogen, with subsequent customization and targeting of therapy.

Authors: Barbara Schaarschmidt, S. Vlaic, A. Medyukhina, S. Neugebauer, S. Nietzsche, F. A. Gonnert, J. Rodel, M. Singer, M. Kiehntopf, Marc Thilo Figge, Ilse Jacobsen, Michael Bauer, A. T. Press

Date Published: 8th Aug 2018

Journal: Theranostics

Abstract (Expand)

Life-threatening systemic infections often occur due to the translocation of pathogens across the gut barrier and into the bloodstream. While the microbial and host mechanisms permitting bacterial gut translocation are well characterized, these mechanisms are still unclear for fungal pathogens such as Candida albicans, a leading cause of nosocomial fungal bloodstream infections. In this study, we dissected the cellular mechanisms of translocation of C. albicans across intestinal epithelia in vitro and identified fungal genes associated with this process. We show that fungal translocation is a dynamic process initiated by invasion and followed by cellular damage and loss of epithelial integrity. A screen of >2,000 C. albicans deletion mutants identified genes required for cellular damage of and translocation across enterocytes. Correlation analysis suggests that hypha formation, barrier damage above a minimum threshold level, and a decreased epithelial integrity are required for efficient fungal translocation. Translocation occurs predominantly via a transcellular route, which is associated with fungus-induced necrotic epithelial damage, but not apoptotic cell death. The cytolytic peptide toxin of C. albicans, candidalysin, was found to be essential for damage of enterocytes and was a key factor in subsequent fungal translocation, suggesting that transcellular translocation of C. albicans through intestinal layers is mediated by candidalysin. However, fungal invasion and low-level translocation can also occur via non-transcellular routes in a candidalysin-independent manner. This is the first study showing translocation of a human-pathogenic fungus across the intestinal barrier being mediated by a peptide toxin.IMPORTANCECandida albicans, usually a harmless fungus colonizing human mucosae, can cause lethal bloodstream infections when it manages to translocate across the intestinal epithelium. This can result from antibiotic treatment, immune dysfunction, or intestinal damage (e.g., during surgery). However, fungal processes may also contribute. In this study, we investigated the translocation process of C. albicans using in vitro cell culture models. Translocation occurs as a stepwise process starting with invasion, followed by epithelial damage and loss of epithelial integrity. The ability to secrete candidalysin, a peptide toxin deriving from the hyphal protein Ece1, is key: C. albicans hyphae, secreting candidalysin, take advantage of a necrotic weakened epithelium to translocate through the intestinal layer.

Authors: Stefanie Allert, Toni Förster, Carl-Magnus Svensson, J. P. Richardson, T. Pawlik, B. Hebecker, Sven Rudolphi, M. Juraschitz, M. Schaller, M. Blagojevic, Joachim Morschhäuser, Marc Thilo Figge, Ilse Jacobsen, J. R. Naglik, Lydia Kasper, Selene Mogavero, Bernhard Hube

Date Published: 5th Jun 2018

Journal: mBio

Abstract (Expand)

The human plasma contact system is an immune surveillance system activated by the negatively charged surfaces of bacteria and fungi and includes the kallikrein-kinin, the coagulation, and the fibrinolytic systems. Previous work shows that the contact system also activates complement, and that plasma enzymes like kallikrein, plasmin, thrombin, and FXII are involved in the activation process. Here, we show for the first time that kallikrein cleaves the central complement component C3 directly to yield active components C3b and C3a. The cleavage site within C3 is identical to that recognized by the C3 convertase. Also, kallikrein-generated C3b forms C3 convertases, which trigger the C3 amplification loop. Since kallikrein also cleaves factor B to yield Bb and Ba, kallikrein alone can trigger complement activation. Kallikrein-generated C3 convertases are inhibited by factor H; thus, the kallikrein activation pathway merges with the amplification loop of the alternative pathway. Taken together, these data suggest that activation of the contact system locally enhances complement activation on cell surfaces. The human pathogenic microbe Candida albicans activates the contact system in normal human serum. However, C. albicans immediately recruits factor H to the surface, thereby evading the alternative and likely kallikrein-mediated complement pathways.

Authors: Sarah Irmscher, N. Doring, Luke Donald Halder, E. A. H. Jo, I. Kopka, C. Dunker, Ilse Jacobsen, S. Luo, Hortense Slevogt, S. Lorkowski, Niklas Beyersdorf, Peter Zipfel, Christine Skerka

Date Published: 14th Dec 2017

Journal: J Innate Immun

Abstract (Expand)

Upon systemic infection with human pathogenic yeast Candida albicans (C. albicans), human monocytes and polymorph nuclear neutrophilic granulocytes are the first immune cells to respond and come into contact with C. albicans. Monocytes exert immediate candidacidal activity and inhibit germination, mediate phagocytosis, and kill fungal cells. Here, we show that human monocytes spontaneously respond to C. albicans cells via phagocytosis, decondensation of nuclear DNA, and release of this decondensed DNA in the form of extracellular traps (called monocytic extracellular traps: MoETs). Both subtypes of monocytes (CD14(++)CD16(-)/CD14(+)CD16(+)) formed MoETs within the first hours upon contact with C. albicans. MoETs were characterized by the presence of citrullinated histone, myeloperoxidase, lactoferrin, and elastase. MoETs were also formed in response to Staphylococcus aureus and Escherichia coli, indicating a general reaction of monocytes to infectious microbes. MoET induction differs from extracellular trap formation in macrophages as MoETs are not triggered by simvastatin, an inhibitor of cholesterol synthesis and inducer of extracellular traps in macrophages. Extracellular traps from both monocytes and neutrophils activate complement and C3b is deposited. However, factor H (FH) binds via C3b to the extracellular DNA, mediates cofactor activity, and inhibits the induction of the inflammatory cytokine interleukin-1 beta in monocytes. Altogether, the results show that human monocytes release extracellular DNA traps in response to C. albicans and that these traps finally bind FH via C3b to presumably support clearance without further inflammation.

Authors: Luke Donald Halder, M. A. Abdelfatah, E. A. Jo, Ilse Jacobsen, M. Westermann, Niklas Beyersdorf, S. Lorkowski, Peter Zipfel, Christine Skerka

Date Published: 31st Jan 2017

Journal: Front Immunol

Abstract (Expand)

Aspergillus fumigatus is the predominant airborne pathogenic fungus causing invasive aspergillosis in immunocompromised patients. During infection A. fumigatus has to adapt to oxygen-limiting conditions in inflammatory or necrotic tissue. Previously, we identified a mitochondrial protein to be highly up-regulated during hypoxic adaptation. Here, this protein was found to represent the novel oxidoreductase HorA. In Saccharomyces cerevisiae a homologue was shown to play a role in biosynthesis of coenzyme Q. Consistently, reduced coenzyme Q content in the generated DeltahorA mutant indicated a respective function in A. fumigatus. Since coenzyme Q is involved in cellular respiration and maintaining cellular redox homeostasis, the strain DeltahorA displayed an impaired response to both oxidative and reductive stress, a delay in germination and an accumulation of NADH. Moreover, an increased resistance against antifungal drugs was observed. All phenotypes were completely reversed by the addition of the synthetic electron carrier menadione. The deletion strain DeltahorA showed significantly attenuated virulence in two murine infection models of invasive pulmonary aspergillosis. Therefore, the biosynthesis of coenzyme Q and, particularly, the fungal-specific protein HorA play a crucial role in virulence of A. fumigatus. Due to its absence in mammals, HorA might represent a novel therapeutic target against fungal infections. This article is protected by copyright. All rights reserved.

Authors: K. Kroll, E. Shekhova, D. J. Mattern, A. Thywissen, Ilse Jacobsen, M. Strassburger, T. Heinekamp, Ekaterina Shelest, Axel Brakhage, Olaf Kniemeyer

Date Published: 19th Mar 2016

Journal: Mol Microbiol

Abstract (Expand)

Candida albicans and Candida glabrata account for the majority of candidiasis cases worldwide. Although both species are in the same genus, they differ in key virulence attributes. Within this work, live cell imaging was used to examine the dynamics of neutrophil activation after confrontation with either C. albicans or C. glabrata. Analyses revealed higher phagocytosis rates of C. albicans than C. glabrata that resulted in stronger PMN (polymorphonuclear cells) activation by C. albicans. Furthermore, we observed differences in the secretion of chemokines, indicating chemotactic differences in PMN signalling towards recruitment of further immune cells upon confrontation with Candida spp. Supernatants from co-incubations of neutrophils with C. glabrata primarily attracted monocytes and increased the phagocytosis of C. glabrata by monocytes. In contrast, PMN activation by C. albicans resulted in recruitment of more neutrophils. Two complex infection models confirmed distinct targeting of immune cell populations by the two Candida spp.: In a human whole blood infection model, C. glabrata was more effectively taken up by monocytes than C. albicans and histopathological analyses of murine model infections confirmed primarily monocytic infiltrates in C. glabrata kidney infection in contrast to PMN-dominated infiltrates in C. albicans infection. Taken together, our data demonstrate that the human opportunistic fungi C. albicans and C. glabrata are differentially recognized by neutrophils and one outcome of this differential recognition is the preferential uptake of C. glabrata by monocytes.

Authors: S. Duggan, F. Essig, Kerstin Hünniger, Z. Mokhtari, Michael Bauer, T. Lehnert, S. Brandes, A. Hader, Ilse Jacobsen, R. Martin, Marc Thilo Figge, Oliver Kurzai

Date Published: 5th May 2015

Journal: Cell Microbiol

Abstract (Expand)

Only few Candida species, e.g., Candida albicans, Candida glabrata, Candida dubliniensis, and Candida parapsilosis, are successful colonizers of a human host. Under certain circumstances these species can cause infections ranging from superficial to life-threatening disseminated candidiasis. The success of C. albicans, the most prevalent and best studied Candida species, as both commensal and human pathogen depends on its genetic, biochemical, and morphological flexibility which facilitates adaptation to a wide range of host niches. In addition, formation of biofilms provides additional protection from adverse environmental conditions. Furthermore, in many host niches Candida cells coexist with members of the human microbiome. The resulting fungal-bacterial interactions have a major influence on the success of C. albicans as commensal and also influence disease development and outcome. In this chapter, we review the current knowledge of important survival strategies of Candida spp., focusing on fundamental fitness and virulence traits of C. albicans.

Authors: M. Polke, Bernhard Hube, Ilse Jacobsen

Date Published: 24th Feb 2015

Journal: Adv Appl Microbiol

Abstract (Expand)

Following antifungal treatment, Candida albicans, and other human pathogenic fungi can undergo microevolution, which leads to the emergence of drug resistance. However, the capacity for microevolutionary adaptation of fungi goes beyond the development of resistance against antifungals. Here we used an experimental microevolution approach to show that one of the central pathogenicity mechanisms of C. albicans, the yeast-to-hyphae transition, can be subject to experimental evolution. The C. albicans cph1Delta/efg1Delta mutant is nonfilamentous, as central signaling pathways linking environmental cues to hyphal formation are disrupted. We subjected this mutant to constant selection pressure in the hostile environment of the macrophage phagosome. In a comparatively short time-frame, the mutant evolved the ability to escape macrophages by filamentation. In addition, the evolved mutant exhibited hyper-virulence in a murine infection model and an altered cell wall composition compared to the cph1Delta/efg1Delta strain. Moreover, the transcriptional regulation of hyphae-associated, and other pathogenicity-related genes became re-responsive to environmental cues in the evolved strain. We went on to identify the causative missense mutation via whole genome- and transcriptome-sequencing: a single nucleotide exchange took place within SSN3 that encodes a component of the Cdk8 module of the Mediator complex, which links transcription factors with the general transcription machinery. This mutation was responsible for the reconnection of the hyphal growth program with environmental signals in the evolved strain and was sufficient to bypass Efg1/Cph1-dependent filamentation. These data demonstrate that even central transcriptional networks can be remodeled very quickly under appropriate selection pressure.

Authors: A. Wartenberg, Jörg Linde, R. Martin, M. Schreiner, F. Horn, Ilse Jacobsen, S. Jenull, Thomas Wolf, K. Kuchler, Reinhard Guthke, Oliver Kurzai, A. Forche, C. d'Enfert, S. Brunke, Bernhard Hube

Date Published: 4th Dec 2014

Journal: PLoS Genet

Abstract (Expand)

OBJECTIVES: Candida albicans is an important fungal pathogen that can cause life-threatening disseminated infections. To determine the efficacy of therapy in murine models, a determination of renal fungal burden as cfu is commonly used. However, this approach provides only a snapshot of the current situation in an individual animal and cryptic sites of infection may easily be missed. Thus, we aimed to develop real-time non-invasive imaging to monitor infection in vivo. METHODS: Bioluminescent C. albicans reporter strains were developed based on a bioinformatical approach for codon optimization. The reporter strains were analysed in vitro and in vivo in the murine model of systemic candidiasis. RESULTS: Reporter strains allowed the in vivo monitoring of infection and a determination of fungal burden, with a high correlation between bioluminescence and cfu count. We confirmed the kidney as the main target organ but additionally observed the translocation of C. albicans to the urinary bladder. The treatment of infected mice with caspofungin and fluconazole significantly improved the clinical outcome and clearance of C. albicans from the kidneys; however, unexpectedly, viable fungal cells persisted in the gall bladder. Fungi were secreted with bile and detected in the faeces, implicating the gall bladder as a reservoir for colonization by C. albicans after antifungal therapy. Bile extracts significantly decreased the susceptibility of C. albicans to various antifungals in vitro, thereby probably contributing to its persistence. CONCLUSIONS: Using in vivo imaging, we identified cryptic sites of infection and persistence of C. albicans in the gall bladder during otherwise effective antifungal treatment. Bile appears to directly interfere with antifungal activity.

Authors: Ilse Jacobsen, A. Luttich, Oliver Kurzai, Bernhard Hube, Matthias Brock

Date Published: 20th Jun 2014

Journal: J Antimicrob Chemother

Abstract (Expand)

Little is known regarding the role of NK cells during primary and secondary disseminated Candida albicans infection. We assessed the role of NK cells for host defense against candidiasis in immunocompetent, as well as immunodeficient, hosts. Surprisingly, depletion of NK cells in immunocompetent WT mice did not increase susceptibility to systemic candidiasis, suggesting that NK cells are redundant for antifungal defense in otherwise immunocompetent hosts. NK-cell-depleted mice were found to be protected as a consequence of attenuation of systemic inflammation. In contrast, the absence of NK cells in T/B/NK-cell-deficient NSG (NOD SCID gamma) mice led to an increased susceptibility to both primary and secondary systemic C. albicans infections compared with T/B-cell-deficient SCID mice. In conclusion, this study demonstrates that NK cells are an essential and nonredundant component of anti-C. albicans host defense in immunosuppressed hosts with defective T/B-lymphocyte immunity, while contributing to hyperinflammation in immunocompetent hosts. The discovery of the importance of NK cells in hosts with severe defects of adaptive immunity might have important consequences for the design of adjunctive immunotherapeutic approaches in systemic C. albicans infections targeting NK-cell function.

Authors: J. Quintin, J. Voigt, R. van der Voort, Ilse Jacobsen, I. Verschueren, Bernhard Hube, E. J. Giamarellos-Bourboulis, J. W. van der Meer, L. A. Joosten, Oliver Kurzai, M. G. Netea

Date Published: 27th May 2014

Journal: Eur J Immunol

Abstract (Expand)

Oral candidiasis remains one of the most common forms of Candida infections and occurs if the balance between host, Candida and microbiota is disturbed, e.g., by broad spectrum antibiotics or immunosuppression. In recent years, identification of fungal factors contributing to host cell damage and new insights into host defense mechanisms have significantly extended our understanding of the pathogenesis of oral candidiasis. In this review, we will provide an overview of the pathogenicity mechanisms during oral Candida infections and discuss some approaches by which this knowledge could be transferred into therapeutic approaches.

Authors: B. Hebecker, J. R. Naglik, Bernhard Hube, Ilse Jacobsen

Date Published: 7th May 2014

Journal: Expert Rev Anti Infect Ther

Abstract (Expand)

Human fungal pathogens are distributed throughout their kingdom, suggesting that pathogenic potential evolved independently. Candida albicans is the most virulent member of the CUG clade of yeasts and a common cause of both superficial and invasive infections. We therefore hypothesized that C. albicans possesses distinct pathogenicity mechanisms. In silico genome subtraction and comparative transcriptional analysis identified a total of 65 C. albicans-specific genes (ASGs) expressed during infection. Phenotypic characterization of six ASG-null mutants demonstrated that these genes are dispensable for in vitro growth but play defined roles in host-pathogen interactions. Based on these analyses, we investigated two ASGs in greater detail. An orf19.6688Delta mutant was found to be fully virulent in a mouse model of disseminated candidiasis and to induce higher levels of the proinflammatory cytokine interleukin-1beta (IL-1beta) following incubation with murine macrophages. A pga16Delta mutant, on the other hand, exhibited attenuated virulence. Moreover, we provide evidence that secondary filamentation events (multiple hyphae emerging from a mother cell and hyphal branching) contribute to pathogenicity: PGA16 deletion did not influence primary hypha formation or extension following contact with epithelial cells; however, multiple hyphae and hyphal branching were strongly reduced. Significantly, these hyphae failed to damage host cells as effectively as the multiple hypha structures formed by wild-type C. albicans cells. Together, our data show that species-specific genes of a eukaryotic pathogen can play important roles in pathogenicity.

Authors: D. Wilson, F. L. Mayer, P. Miramon, F. Citiulo, S. Slesiona, Ilse Jacobsen, Bernhard Hube

Date Published: 7th Mar 2014

Journal: Eukaryot Cell

Abstract (Expand)

BACKGROUND: Natural killer (NK) cells are innate lymphocytes with potent cytotoxic activity. Whereas activity of NK cells has been demonstrated against the fungal pathogens Aspergillus fumigatus and Cryptococcus neoformans, little was known about their interaction with Candida albicans. METHODS: Primary human NK cells were isolated from buffy coats, primed with a cytokine cocktail and used for confrontation assays with C. albicans. Interaction was monitored and quantified using live cell imaging, confocal microscopy, flow cytometry, and enzyme-linked immunosorbent assay. RESULTS: Human NK cells actively recognized C. albicans, resulting in degranulation and secretion of granulocyte-macrophage colony-stimulating factor, interferon gamma, and tumor necrosis factor alpha . Uniquely, activation of NK cells was triggered by actin-dependent phagocytosis. Antifungal activity of NK cells against C. albicans could be detected and mainly attributed to secreted perforin. However, NK cells were unable to inhibit filamentation of C. albicans. Human polymorphonuclear neutrophils (PMNs) counteracted the proinflammatory reaction of NK cells by preventing direct contact between NK cells and the fungal pathogen. Activation of PMNs was enhanced in the presence of NK cells, resulting in increased fungicidal activity. CONCLUSIONS: Our results show a unique pattern of NK cell interaction with C. albicans, which involves direct proinflammatory activation and modulation of PMN activity. For the first time, phagocytosis of a pathogen is shown to contribute to NK cell activation.

Authors: J. Voigt, Kerstin Hünniger, M. Bouzani, Ilse Jacobsen, D. Barz, Bernhard Hube, Jürgen Löffler, Oliver Kurzai

Date Published: 25th Oct 2013

Journal: J Infect Dis

Abstract

Not specified

Authors: G. P. Otto, K. Ludewig, Ilse Jacobsen, Barbara Schaarschmidt, Bernhard Hube, Michael Bauer

Date Published: 12th Jun 2013

Journal: Crit Care

Abstract (Expand)

The amino acid cysteine has long been known to be toxic at elevated levels for bacteria, fungi, and humans. However, mechanisms of cysteine tolerance in microbes remain largely obscure. Here we show that the human pathogenic yeast Candida albicans excretes sulfite when confronted with increasing cysteine concentrations. Mutant construction and phenotypic analysis revealed that sulfite formation from cysteine in C. albicans relies on cysteine dioxygenase Cdg1, an enzyme with similar functions in humans. Environmental cysteine induced not only the expression of the CDG1 gene in C. albicans, but also the expression of SSU1, encoding a putative sulfite efflux pump. Accordingly, the deletion of SSU1 resulted in enhanced sensitivity of the fungal cells to both cysteine and sulfite. To study the regulation of sulfite/cysteine tolerance in more detail, we screened a C. albicans library of transcription factor mutants in the presence of sulfite. This approach and subsequent independent mutant analysis identified the zinc cluster transcription factor Zcf2 to govern sulfite/cysteine tolerance, as well as cysteine-inducible SSU1 and CDG1 gene expression. cdg1Delta and ssu1Delta mutants displayed reduced hypha formation in the presence of cysteine, indicating a possible role of the newly proposed mechanisms of cysteine tolerance and sulfite secretion in the pathogenicity of C. albicans. Moreover, cdg1Delta mutants induced delayed mortality in a mouse model of disseminated infection. Since sulfite is toxic and a potent reducing agent, its production by C. albicans suggests diverse roles during host adaptation and pathogenicity.

Authors: F. Hennicke, M. Grumbt, U. Lermann, N. Ueberschaar, K. Palige, B. Bottcher, Ilse Jacobsen, C. Staib, J. Morschhauser, M. Monod, Bernhard Hube, C. Hertweck, P. Staib

Date Published: 15th Feb 2013

Journal: Eukaryot Cell

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