Biology subjects

Cseresnyes, Z.

Publications and source records attributed to Cseresnyes, Z..

9 recordsLinked to original sources

bioRxiv2026

The murine lung microbiome is dynamic and transient

BackgroundWhether the lung microbiome represents a stable microbial colonization or a transient ecosystem shaped by continuous microbial turnover and controlled by host immunity remains unresolved. The murine lung microbiome largely consists of species from the former Lactobacillus genus with Ligilactobacillus murinus as a dominant species, bacterial genera such as Streptococcus, Staphylococcus, Mammaliicoccus, Enterococcus and other less frequently detected bacteria. Here, we directly addressed the question of persistence and host interaction of a dominant murine lung commensal in vivo and focused on the host immune response towards lung commensal bacteria. ResultsWe developed a transformation strategy for stable genomic integration of a green fluorescent protein (GFP)-encoding gene to track the fate of a lung bacterium. Following intranasal administration of GFP-labeled L. murinus in mice, bacteria were readily detected in the lungs at early time points but declined rapidly and became undetectable after 72 hours, as determined by quantification of viable bacteria and qPCR. Flow cytometry and fluorescence imaging revealed efficient uptake of GFP-labeled bacteria by lung phagocytes. These findings indicate that even dominant members of the murine pulmonary microbiota normally detected at low abundances are transiently present in the lungs without causing infection. We further analyzed the effects of moderate and high bacterial concentrations. While moderate bacterial loads were efficiently controlled without clinical effects, high concentrations induced severe lethargy, indicating a threshold-dependent host response. Finally, we demonstrated that pulmonary commensals such as L. murinus, Staphylococcus xylosus, and Mammaliicoccus sciuri, as well as conidia of the opportunistic lung pathogen Aspergillus fumigatus, are phagocytosed at comparable rates in macrophage assays. ConclusionsOur data demonstrate that even lung-adapted bacterial species fail to establish stable colonization and are instead subject to rapid immune-mediated elimination contributing to the maintenance of a low microbial burden in the lungs. While this homeostatic balance supports health, elevated bacterial loads trigger immune activation and, at high levels, lead to health deterioration. Together, these results support a model of a highly dynamic and transient lung microbiome, maintained by continual microbial immigration rather than long-term colonization. Accounting for the lung microbiome dynamics is essential for understanding host-microbiota interactions and respiratory health.

microbiology↗

bioRxiv2025

Convergent evolution of a fungal effector enabling phagosome membrane penetration

The ability of pathogens to evade phagosomal killing is critical for their pathogenicity. Previously, we had identified the HscA effector protein in the clinically important fungal pathogen Aspergillus fumigatus, which redirects conidia-containing phagosomes from the degradative to the non-degradative pathway. Here, we discovered a pathogenic form of this surface protein, determined by a single tyrosine residue (Y) at position 596, which is lacking in most fungi analyzed, that have a leucine (L) instead. Y596 enables HscA to penetrate the phagosomal membrane. In line, the introduction of a single L- to-Y exchange in the orthologous Ssb protein of Saccharomyces cerevisiae enabled the protein to penetrate phagosomal membranes that was reduced by deletion of one of the two Y-encoding SSB genes in the pathogenic fungus Candida glabrata. These data suggest a convergent evolution of HscA/Ssb proteins among human-pathogenic fungi and that a single amino acid exchange determines a virulence factor. HighlightsO_LIHscA with Y596 penetrates host cell membranes and causes phagosomal damage C_LIO_LIMost fungi (96%) have a leucine at the respective position C_LIO_LIAn L-to-Y mutation in Ssb enables S. cerevisiae to damage phagosomes C_LIO_LIRecruitment of ESCRT complex to the phagosomal membrane requires human p11 protein C_LI

microbiology↗

bioRxiv2022

Re-direction of phagosomes to the recycling expulsion pathway by a fungal pathogen

The analysis of host-pathogen interactions bears the potential to discover novel pathogenicity mechanisms and to obtain novel insights into basic mechanisms of cell biology. Here, we obtained unprecedented insight into both. We discovered that the HscA protein on the conidial surface of the clinically important human-pathogenic fungus Aspergillus fumigatus acts as an effector protein. It inhibits phagosome maturation and reprograms phagosomes for expulsion of conidia. HscA anchors the human p11 protein to phagosomes. p11 is a decisive factor for targeting phagosomes either to the degradative or secretory pathway. The relevance of our findings is indicated by the identification of an SNP in the non-coding region of the human p11 gene that affects its translation and is associated with heightened susceptibility to invasive pulmonary aspergillosis.

cell biology↗

bioRxiv2022

The lipid raft-associated protein stomatin is required for accumulation of dectin-1 in the phagosomal membrane and for full activity of macrophages against Aspergillus fumigatus

Alveolar macrophages are among the first cells to come into contact with inhaled fungal conidia of the human pathogenic fungus Aspergillus fumigatus. In lung alveoli, they contribute to phagocytosis and elimination of conidia. As a counter defense, conidia contain a grey-green pigment allowing them to survive in phagosomes of macrophages for some time. Previously, we showed that this conidial pigment interferes with the formation of flotillin-dependent lipid-rafts in the phagosomal membrane thereby preventing the formation of functional phagolysosomes. In this study, the role of the lipid raft-associated protein stomatin in macrophages during antifungal defense was investigated. To determine the function of this integral membrane protein, a stomatin-deficient macrophage cell line was generated by CRISPR/Cas9 gene editing. Immunofluorescence and flow cytometry revealed that stomatin contributes to the phagocytosis of conidia and is important for recruitment of both the {beta}-glucan receptor dectin-1 and the vATPase to the membrane of phagosomes. In the stomatin knockout cell line, fusion of phagosomes and lysosomes was reduced when infected with pigmentless pksP conidia. Thus, our data suggest that stomatin is involved in maturation of phagosomes via fostering fusion of phagosomes with lysosomes.

microbiology↗

bioRxiv2022

Toxin-producing endosymbionts shield pathogenic fungus against micropredators

The phytopathogenic fungus Rhizopus microsporus harbours a bacterial endosymbiont (Mycetohabitans rhizoxinica) for the production of the toxin rhizoxin, the causative agent of rice seedling blight. This toxinogenic bacterial-fungal alliance is, however, not restricted to the plant disease, but has been detected in numerous environmental isolates from geographically distinct sites covering all five continents. Yet, the ecological role of rhizoxin beyond rice seedling blight has been unknown. Here we show that rhizoxin serves the fungal host in fending off protozoan and metazoan predators. Fluorescence microscopy and co-culture experiments with the fungivorous amoeba Protostelium aurantium revealed that ingestion of R. microsporus spores is toxic to P. aurantium. This amoebicidal effect is caused by the bacterial rhizoxin congener rhizoxin S2, which is also lethal towards the model nematode Caenorhabditis elegans. By combining stereomicroscopy, automated image analyses, and quantification of nematode movement we show that the fungivorous nematode Aphelenchus avenae actively feeds on R. microsporus that is lacking endosymbionts, while worms co-incubated with symbiotic R. microsporus are significantly less lively. This work uncovers an unexpected ecological role of rhizoxin as shield against micropredators. This finding suggests that predators may function an evolutionary driving force to maintain toxin-producing endosymbionts in non-pathogenic fungi.

microbiology↗

bioRxiv2021

Human macrophage polarization determines bacterial persistence of Staphylococcus aureus in a liver-on-chip-based infection model

Infections with Staphylococcus aureus (S. aureus) have been reported from various organs ranging from asymptomatic colonization to severe infections and sepsis associated with multiple organ dysfunction. Although considered an extracellular pathogen, S. aureus can invade and persist in professional phagocytes such as monocytes and macrophages. Its capability to persist and manipulate phagocytes is considered a critical step to evade host antimicrobial reactions. For the first time we leveraged a human liver-on-chip model and tailored image analysis algorithms to demonstrate that S. aureus (USA300) specifically targets macrophages in the liver models as essential niche facilitating bacterial persistence and phenotype switching to small colony variants (SCVs). In vitro M2 polarization was found to favor SCV-formation and was associated with increased intracellular bacterial loads in macrophages, increased cell death, and impaired recruitment of circulating monocytes to sites of infection. These findings expand the knowledge about the role of liver macrophages in the course of systemic infection. Further, the results might be relevant for understanding infection mechanisms in patients with chronic liver disease such as fibrosis that display increased frequencies of M2 polarized liver macrophages and have a higher risk for developing chronic infections and relapsing bacteremia.

microbiology↗

bioRxiv2021

Targeted delivery of a phosphoinositide 3-kinase γ inhibitor to restore organ function in sepsis through dye-functionalized lipid nanocarriers

Jaundice, the clinical hallmark of infection-associated liver dysfunction, reflects altered membrane organization of the canalicular pole of hepatocytes and portends poor outcomes. Mice lacking phosphoinositide 3-kinase-{gamma} (PI3K{gamma}) are protected against membrane disintegration and hepatic excretory dysfunction. However, they exhibit a severe immune defect that hinders neutrophil recruitment to sites of infection. To exploit the therapeutic potential of PI3K{gamma} inhibition in sepsis, a targeted approach to deliver drugs to hepatic parenchymal cells without compromising other cells, in particular immune cells, seems warranted. Here we demonstrate that nanocarriers functionalized through DY-635, a fluorescent polymethine dye and a ligand of organic anion transporters can selectively deliver therapeutics to hepatic parenchymal cells. Applying this strategy to a murine model of sepsis, we observed PI3K{gamma}-dependent restoration of biliary canalicular architecture, maintained excretory liver function, and improved survival without impairing host defense mechanisms. This strategy carries the potential to expand targeted nanomedicines to disease entities with systemic inflammation and concomitantly impaired barrier functionality. One-Sentence SummaryDye-functionalized liposomes allow delivery of a PI3K{gamma} inhibitor to hepatocytes to resolve sepsis-related liver failure without off-target effects on immunity. Graphical AbstractTargeting PI3K{gamma} in hepatocytes by dye-functionalized liposomes to resolve sepsis-related liver failure without off-target effects on immunity. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=178 SRC="FIGDIR/small/427305v1_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@d52fdeorg.highwire.dtl.DTLVardef@39bf3aorg.highwire.dtl.DTLVardef@13999c7org.highwire.dtl.DTLVardef@9edfa0_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2019

Human neutrophils produce antifungal extracellular vesicles against Aspergillus fumigatus

Polymorphonuclear granulocytes (PMNs) are indispensable for controlling life-threatening fungal infections. In addition to various effector mechanisms, PMNs also produce extracellular vesicles (EVs). Their contribution to antifungal defense has remained unexplored. We reveal that the clinically important human pathogenic fungus Aspergillus fumigatus triggers PMNs to release a distinct set of antifungal EVs (afEVs). Proteome analyses indicated that afEVs are enriched in antimicrobial proteins. The cargo and release kinetics of EVs are modulated by the fungal strain confronted. Tracking of afEVs indicated that they associated with fungal cells and even entered fungal hyphae, resulting in alterations in the morphology of the fungal cell wall and dose-dependent antifungal effects. Two human proteins enriched in afEVs, cathepsin G and azurocidin, were heterologously expressed in fungal hyphae, which led to reduced fungal growth relative to a control retinol binding protein 7 producing strain. In conclusion, the production of afEVs by PMNs offers an intriguing, previously overlooked mechanism of antifungal defense against A. fumigatus. ImportanceInvasive fungal infections caused by the mold Aspergillus fumigatus are a growing concern in the clinic due to the increasing use of immunosuppressive therapies and increasing antifungal drug resistance. These infections result in high mortality as treatment and diagnostic options remain limited. In healthy individuals, neutrophilic granulocytes are critical for elimination of A. fumigatus from the host; however, the exact extracellular mechanism of neutrophil-mediated antifungal activity remains unresolved. Here, we present a mode of antifungal defense employed by human neutrophils against A. fumigatus not previously described. We find that extracellular vesicles produced by neutrophils in response to A. fumigatus infection are able to associate with the fungus, limit growth, and elicit cell damage by delivering antifungal cargo. In the end, antifungal extracellular vesicle biology provides a significant step forward in our understanding of A. fumigatus host pathogenesis and opens up novel diagnostic and therapeutic possibilities.

microbiology↗

bioRxiv2019

Flotillin-dependent lipid-raft microdomains are required for functional phagolysosomes against fungal infections

Lipid rafts form signaling platforms on biological membranes with incompletely characterized role in immune response to infection. Here we report that lipid raft microdomains are essential components of the phagolysosomal membrane of macrophages. Genetic deletion of the lipidraft chaperons flotillin-1 and flotillin-2 demonstrate that the assembly of both major defense complexes vATPase and NADPH oxidase on the phagolysosomal membrane requires lipid rafts. Furthermore, we discovered a new virulence mechanism leading to the dysregulation of lipid-raft formation by melanized wild-type conidia of the important human-pathogenic fungus Aspergillus fumigatus. This results in reduced phagolysosomal acidification. Phagolysosomes with ingested melanized conidia contain a reduced amount of free Ca2+ ions as compared to phagolysosomes with melanin-free conidia. In agreement with a role of Ca2+ for generation of functional lipid rafts, we show that Ca2+-dependent calmodulin activity is required for lipid-raft formation on the phagolysosome. We identified a single nucleotide polymorphism in the human FLOT1 gene that results in heightened susceptibility for invasive aspergillosis in hematopoietic stem-cell transplant recipients. Collectively, flotillin-dependent lipid rafts on the phagolysosomal membrane play an essential role in protective antifungal immunity in humans.

microbiology↗