Biology subjects

Hohl, T. M.

Publications and source records attributed to Hohl, T. M..

13 recordsLinked to original sources

bioRxiv2026

GM-CSF signaling on monocytes and monocyte-derived dendritic cells is required for effective pulmonary immunity to Aspergillus fumigatus

Aspergillus fumigatus is the most common cause of invasive aspergillosis (IA), an opportunistic pulmonary infection of immunocompromised patients that can be fatal, despite treatment with modern antifungal drugs. During infection, myeloid cells, such as neutrophils, monocytes, and monocyte-derived dendritic cells (Mo-DCs) are recruited to the lung and are critical for phagocytosing and killing A. fumigatus spores. Recent evidence has shown that intracellular crosstalk between these professional immune cells and other resident pulmonary cell types is required for an effective immune response to A. fumigatus, and that signaling via the cytokine granulocyte macrophage-colony stimulating factor (GM-CSF) is part of this intracellular communication. In this study, we sought to determine a role for GM-CSF signaling on monocytes and their progeny. We harnessed a mouse model of deletion of GM-CSF receptor {beta} chain (encoded by Csf2rb) in CCR2-expressing cells. Using this model, we found that GM-CSF signaling is required on CCR2+ cells for killing of A. fumigatus and for host survival. This observation expands the importance of GM-CSF in host defense during A. fumigatus pulmonary infection and extends its role in pathways of intracellular crosstalk that mediate effective pulmonary antifungal immunity.

immunology↗

bioRxiv2025

Intracellular acidification by bacteria-derived valeric acid is a mechanism of trans-kingdom ecology against Candida parapsilosis colonization

In hematopoietic cell transplant patients, intestinal Candida parapsilosis expansion and translocation cause life-threatening candidemia, yet how commensal intestinal bacteria prevent Candida expansion remains incompletely defined. Here, we trained a machine learning model on supernatant metabolomic profiles of commensal bacteria to identify bacteria-derived inhibitors of fungal growth, with valeric and butyric acid as top hits. Experimental validation confirmed in silico predictions in three systems. First, in patient fecal samples, valeric and butyric acid levels inversely correlated with C. parapsilosis growth. Second, in vitro, valeric acid potently inhibited C. parapsilosis growth by causing intracellular acidification. Third, administration of glycerol valerate, and free or microencapsulated valeric acid blunted C. parapsilosis growth at murine intestinal sites where valeric acid could be detected. Thus, machine learning could identify a mechanistic driver of trans-kingdom ecology limiting C. parapsilosis intestinal expansion and may inform strategies to reduce patient risk of developing candidiasis during high-risk periods.

microbiology↗

bioRxiv2024

An IFN-STAT1-CYBB Axis Defines Protective Plasmacytoid DC to Neutrophil Crosstalk During Aspergillus fumigatus Infection.

Aspergillus fumigatus is the most common cause of invasive aspergillosis (IA), a devastating infection in immunocompromised patients. Plasmacytoid dendritic cells (pDCs) regulate host defense against IA by enhancing neutrophil antifungal properties in the lung. Here, we define the pDC activation trajectory during A. fumigatus infection and the molecular events that underlie the protective pDC - neutrophil crosstalk. Fungus-induced pDC activation begins after bone marrow egress and results in pDC-dependent regulation of lung type I and type III IFN levels. These pDC-derived products act on type I and type III IFN receptor-expressing neutrophils and control neutrophil fungicidal activity and reactive oxygen species production via STAT1 signaling in a cell-intrinsic manner. Mechanistically, neutrophil STAT1 signaling regulates the transcription and expression of Cybb, which encodes one of five NADPH oxidase subunits. Thus, pDCs regulate neutrophil-dependent immunity against inhaled molds by controlling the local expression of a subunit required for NADPH oxidase assembly and activity in the lung. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=138 SRC="FIGDIR/small/620079v2_ufig1.gif" ALT="Figure 1"> View larger version (50K): org.highwire.dtl.DTLVardef@1394ccforg.highwire.dtl.DTLVardef@e1bb13org.highwire.dtl.DTLVardef@1c0f991org.highwire.dtl.DTLVardef@40d5db_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2024

Perforin-2 is dispensable for host defense against Aspergillus fumigatus and Candida albicans

Myeloid phagocytes are essential for antifungal immunity against pulmonary Aspergillus fumigatus and systemic Candida albicans infections. However, the molecular mechanisms underlying fungal clearance by phagocytes remain incompletely understood. In this study, we investigated the role of perforin-2 (Mpeg1) in antifungal immunity. We found that Mpeg1-/- mice generated on a mixed C57BL/6J-DBA/2 background exhibited enhanced survival, reduced lung fungal burden, and greater neutrophil fungal killing activity compared to wild-type C57BL/6J (B6) mice, suggesting that perforin-2 may impair antifungal immune responses. However, when we compared Mpeg1-/- mice with co-housed Mpeg+/+ littermate controls, these differences were no longer observed, indicating that initial findings were likely influenced by differences in the murine genetic background or the microbiota composition. Furthermore, perforin-2 was dispensable for antifungal immunity during C. albicans bloodstream infection. These results suggest that perforin-2 is not essential for host defense against fungal infections in otherwise immune competent mice and highlight the importance of generating co-housed littermate controls to minimize murine genetic and microbiota-related factors in studies of host defense mechanisms. IMPORTANCEAspergillus fumigatus is the leading cause of invasive aspergillosis (IA), which is associated with significant mortality, particularly in immunocompromised patients such as those with acute leukemia or undergoing hematopoietic stem cell transplants, where death rates reach 40-50% despite standard care. Treatments for IA remain limited and resistance to antifungals is emerging, leading the World Health Organization to recently classify A. fumigatus as a critical priority fungal pathogen. A greater understanding of how the immune system clears A. fumigatus could lead to host-directed therapies that could complement our current armamentarium of antifungal drugs and improve patient outcomes. Our findings reveal that perforin-2 is not essential for antifungal immunity against A. fumigatus in otherwise immune-competent mice and underscore the necessity of using co-housed littermate controls to avoid confounding factors in immunological studies.

immunology↗

bioRxiv2024

GM-CSF-mediated epithelial-immune cell crosstalk orchestrates pulmonary immunity to Aspergillus fumigatus

Aspergillus fumigatus causes life-threatening mold pneumonia in immune compromised patients, particularly in those with quantitative or qualitative defects in neutrophils. While innate immune cell crosstalk licenses neutrophil antifungal activity in the lung, the role of epithelial cells in this process is unknown. Here, we find that that surfactant protein C (SPC)-expressing lung epithelial cells integrate infection-induced IL-1 and type III interferon signaling to produce granulocyte-macrophage colony-stimulating factor (GM-CSF) preferentially at local sites of fungal infection and neutrophil influx. Using in vivo models that distinguish the role of GM-CSF during acute infection from its homeostatic function in alveolar macrophage survival and surfactant catabolism, we demonstrate that epithelial-derived GM-CSF increases the accumulation and fungicidal activity of GM-CSF-responsive neutrophils, with the latter being essential for host survival. Our findings establish SPC+ epithelial cells as a central player in regulating the quality and strength of neutrophil-dependent immunity against inhaled mold pathogens. HIGHLIGHTSO_LIGM-CSF is essential for host defense against A. fumigatus in the lung C_LIO_LIIL-1 and IFN-{lambda} promote GM-CSF production by lung epithelial cells in parallel C_LIO_LIEpithelial cell-derived GM-CSF increases neutrophil accumulation and fungal killing capacity C_LIO_LIEpithelial cells preferentially upregulate GM-CSF in local sites of inflammation C_LI GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=128 SRC="FIGDIR/small/574062v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@708497org.highwire.dtl.DTLVardef@11106f7org.highwire.dtl.DTLVardef@e08140org.highwire.dtl.DTLVardef@1459e89_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2023

Dectin-1/CARD9-induction of the TFEB and TFE3 gene network is dispensable for phagocyte anti-Aspergillus activity in the lung

Myeloid phagocytes of the respiratory immune system, such as neutrophils, monocytes, and alveolar macrophages, are essential for immunity to Aspergillus fumigatus, the most common etiologic agent of mold pneumonia worldwide. Following engulfment of A. fumigatus conidia, fusion of the phagosome with the lysosome, is a critical process for killing conidia. TFEB and TFE3 are transcription factors that regulate lysosomal biogenesis under stress and are activated by inflammatory stimuli in macrophages, but it is unknown whether TFEB and TFE3 contribute to anti-Aspergillus immunity during infection. We found that lung neutrophils express TFEB and TFE3, and their target genes were upregulated during A. fumigatus lung infection. Additionally, A. fumigatus infection induced nuclear accumulation of TFEB and TFE3 in macrophages in a process regulated by Dectin-1 and CARD9 signaling. Genetic deletion of Tfeb and Tfe3 impaired macrophage killing of A. fumigatus conidia. However, in a murine immune competent Aspergillus infection model with genetic deficiency of Tfeb and Tfe3 in hematopoietic cells, we surprisingly found that lung myeloid phagocytes had no defects in conidial phagocytosis or killing. Loss of TFEB and TFE3 did not impact murine survival or clearance of A. fumigatus from the lungs. Our findings indicate that myeloid phagocytes activate TFEB and TFE3 in response to A. fumigatus, and while this pathway promotes macrophage fungicidal activity in vitro, genetic loss can be functionally compensated at the portal of infection in the lung, resulting in no measurable defect in fungal control and host survival.

immunology↗

bioRxiv2023

Aspergillus fumigatus cytochrome c impacts conidial survival during sterilizing immunity

Invasive pulmonary aspergillosis (IPA) is a life-threatening infection caused by species in the ubiquitous fungal genus Aspergillus. While leukocyte-generated reactive oxygen species (ROS) are critical for the clearance of fungal conidia from the lung and resistance to IPA, the processes that govern ROS-dependent fungal cell death remain poorly defined. Using a flow cytometric approach that monitors two independent cell death markers, an endogenous histone H2A:mRFP nuclear integrity reporter and Sytox Blue cell impermeable (live/dead) stain, we observed that loss of A. fumigatus cytochrome c (cycA) results in reduced susceptibility to cell death from hydrogen peroxide (H2O2) treatment. Consistent with these observations in vitro, loss of cycA confers resistance to both NADPH-oxidase -dependent and -independent killing by host leukocytes. Fungal ROS resistance is partly mediated in part by Bir1, a homolog to survivin in humans, as Bir1 overexpression results in decreased ROS-induced conidial cell death and reduced killing by innate immune cells in vivo. We further report that overexpression of the Bir1 N-terminal BIR domain in A. fumigatus conidia results in altered expression of metabolic genes that functionally converge on mitochondrial function and cytochrome c (cycA) activity. Together, these studies demonstrate that cycA in A. fumigatus contributes to cell death responses that are induced by exogenous H2O2 and by host leukocytes. ImportanceAspergillus fumigatus can cause a life-threatening infection known as invasive pulmonary aspergillosis (IPA), which is marked by fungus-attributable mortality rates of 20%-30%. Individuals at risk of IPA harbor genetic mutations or incur pharmacologic defects that impair myeloid cell numbers and/or function, exemplified by bone marrow transplant recipients, patients that receive corticosteroid therapy, or patients with Chronic Granulomatous Disease (CGD). However, treatments for Aspergillus infections remains limited, and resistance to the few existing drug classes is emerging. Recently, the World Health Organization (WHO) classified A. fumigatus as a critical priority fungal pathogen. Our research identifies an important aspect of fungal biology that impacts susceptibility to leukocyte killing. Furthering our understanding of mechanisms that mediate the outcome of fungal-leukocyte interactions will increase our understanding of both the underlying fungal biology governing cell death and innate immune evasion strategies utilized during mammalian infection pathogenesis. Consequently, our studies are a critical step toward leveraging these mechanisms for novel therapeutic advances.

microbiology↗

bioRxiv2022

Inflammatory ER Stress Responses Dictate the Immunopathogenic Progression of Systemic Candidiasis

Recognition of pathogen-associated molecular patterns can trigger the IRE1 arm of the endoplasmic reticulum (ER) stress response in immune cells. IRE1 activation has been shown to maintain ER homeostasis while simultaneously coordinating diverse immunomodulatory programs in the setting of bacterial and viral infections. However, the role of IRE1 signaling in innate immune responses to fungal pathogens is unknown. Here we report that systemic infection with the fungus Candida albicans causes severe renal immunopathology by triggering inflammatory IRE1 hyperactivation in host myeloid cells. Mechanistically, sensing of fungal {beta}-glucans by the C-type lectin receptor Dectin-1 induced Src-Syk-NOX-dependent accumulation of intracellular reactive oxygen species and the ensuing generation of lipid peroxidation byproducts that sustained IRE1 activation. Selective deletion of IRE1 in leukocytes, or treatment with an IRE1 pharmacological inhibitor, reduced detrimental inflammatory responses in the kidney and extended survival in mice systemically infected with C. albicans. Hence, controlling IRE1 overactivation may be useful to impede the fatal immunopathogenic progression of disseminated candidiasis. One sentence summaryInnate IRE1 signaling in disseminated candidiasis

immunology↗

bioRxiv2022

Relative enrichment of oral bacteria in feces indicates loss of intestinal commensals with implications for host health

The increased relative abundance of oral bacteria detected in fecal samples has been associated with intestinal diseases and digestive disorders. This observation raises two competing hypotheses: either oral bacteria invade the gut bacterial population and expand in the intestine (the Expansion hypothesis), or oral bacteria transit through and their relative increase in feces marks a depletion of the gut bacterial population (the Marker hypothesis). To address this, we conducted a comprehensive analysis of quantitative microbiome data from mouse experiments and diverse patient cohorts. Our findings consistently support the Marker hypothesis as the primary explanation. We further establish a robust inverse correlation between the total fraction of oral bacteria and decreased total bacterial abundance in feces. This correlation underlies the associations between the oral bacterial fraction and multiple patient outcomes consistent with a depleted gut microbiota. By distinguishing between the two hypotheses, our study guides the interpretation of microbiome compositional data and their links with human health.

microbiology↗

bioRxiv2021

Resistance to miltefosine results from amplification of the RTA3 floppase or inactivation of flippases in Candida parapsilosis

Flippases and floppases are two classes of proteins that have opposing functions in the maintenance of lipid asymmetry of the plasma membrane. Flippases translocate lipids from the exoplasmic leaflet to the cytosolic leaflet, and floppases act in the opposite direction. Phosphatidylcholine (PC) is a major component of the eukaryotic plasma membrane and is asymmetrically distributed, being more abundant in the exoplasmic leaflet. Here we show that gene amplification of a putative PC floppase or double disruption of two PC flippases in the pathogenic yeast Candida parapsilosis results in resistance to miltefosine, an alkylphosphocholine drug that affects PC metabolism that has recently been granted orphan drug designation approval by the US FDA for treatment of invasive candidiasis. We analysed the genomes of 170 C. parapsilosis isolates and found that 107 of them have copy number variations (CNVs) at the RTA3 gene. RTA3 encodes a putative PC floppase whose deletion is known to increase the inward translocation of PC in Candida albicans. RTA3 copy number ranges from 2 to >40 across the C. parapsilosis isolates. Interestingly, 16 distinct CNVs with unique endpoints were identified, and phylogenetic analysis shows that almost all of them have originated only once. We found that increased copy number of RTA3 correlates with miltefosine resistance. Additionally, we conducted an adaptive laboratory evolution experiment in which two C. parapsilosis isolates were cultured in increasing concentrations of miltefosine over 26 days. Two genes, CPAR2_303950 and CPAR2_102700, gained homozygous protein-disrupting mutations in the evolved strains and code for putative PC flippases homologous to S. cerevisiae DNF1. Our results indicate that alteration of lipid asymmetry across the plasma membrane is a key mechanism of miltefosine resistance. We also find that C. parapsilosis is likely to gain resistance to miltefosine rapidly, because many isolates carry loss-of-function alleles in one of the flippase genes. Author summaryMiltefosine was developed as an anticancer drug but is commonly used to treat infections with the protozoan parasites Leishmania and Trypanosoma cruzi. More recently, it has been used to treat fungal infections, and in 2021 it was designated as an orphan drug by the US Food and Drug Administration for treatment of invasive candidiasis. Miltefosine is a derivative of phosphatidylcholine (PC), a major constituent of the cell membrane. PC and other phospholipids are asymmetrically distributed across the cell membrane. The mechanism of action of miltefosine is unknown. Here, we show that either increasing the activity of a putative floppase, which controls outward "flop" movement of phospholipids, or decreasing the activity of flippases, which control inward "flip" movement, results in increased resistance of the fungal pathogen Candida parapsilosis to miltefosine. This result suggests that miltefosine acts by controlling the localisation of PC or other phospholipids in the membrane. Importantly, we find that many C. parapsilosis isolates carry mutations in one flippase gene, which renders them partially resistant to miltefosine, and prone to easily acquiring increased resistance.

genomics↗

bioRxiv2021

Identification of a novel Candida metapsilosis isolate suggests ongoing hybridization.

Candida metapsilosis is a member of the C. parapsilosis species complex, a group of opportunistic human pathogens. Of all the members of this complex, C. metapsilosis is the least virulent, and accounts for a small proportion of invasive Candida infections. Previous studies established that all C. metapsilosis isolates are hybrids, originating from a single hybridization event between two lineages, parent A and parent B. Here, we use MinION and Illumina sequencing to characterize a C. metapsilosis isolate that originated from a separate hybridization. One of the parents of the new isolate is very closely related to parent A. However, the other parent (parent C) is not the same as parent B. Unlike C. metapsilosis AB isolates, the C. metapsilosis AC isolate has not undergone introgression at the Mating Type-like Locus. In addition, the A and C haplotypes are not fully collinear. The C. metapsilosis AC isolate has undergone Loss of Heterozygosity (LOH) with a preference for haplotype A, indicating that this isolate is in the early stages of genome stabilization.

genomics↗

bioRxiv2020

Strain specific persistence in the murine lung of Aspergillus fumigatus conidia causes an Allergic Broncho-Pulmonary Aspergillosis-like disease phenotype

Aspergillus fumigatus is a filamentous fungus which can cause multiple diseases in humans. Allergic Broncho-pulmonary Aspergillosis (ABPA) is a disease diagnosed primarily in Cystic Fibrosis patients caused by a severe allergic response often to long-term A. fumigatus colonization in the lungs. Mice develop an allergic response to repeated inhalation of A. fumigatus spores; however, no strains have been identified that can survive long-term in the mouse lung and cause ABPA-like disease. We characterized A. fumigatus strain W72310 by whole genome sequencing and in vitro and in vivo viability assays in comparison to a common reference strain, CEA10. W72310 was resistant to leukocyte-mediated killing and persisted in the mouse lung longer than CEA10, a phenotype that correlated with greater resistance to oxidative stressors, hydrogen peroxide and menadione, in vitro. In animals both sensitized and challenged with W72310, conidia, but not hyphae, were viable in the lungs for up to 21 days in association with eosinophilic airway inflammation, airway leakage, serum IgE, and mucus production. W72310-sensitized mice that were recall-challenged with conidia had increased inflammation, Th1 and Th2 cytokines, and airway leakage compared to controls. Collectively, our studies demonstrate that a unique strain of A. fumigatus resistant to leukocyte killing can persist in the mouse lung in conidial form and elicit features of ABPA-like disease. IMPORTANCEAllergic Broncho-pulmonary Aspergillosis (ABPA) patients often present with long-term colonization of Aspergillus fumigatus. Current understanding of ABPA pathogenesis has been complicated by a lack of long-term in vivo fungal persistence models. We have identified a clinical isolate of A. fumigatus, W72310, which persists in the murine lung and causes an ABPA-like disease phenotype. Surprisingly, while viable, W72310 showed little to no growth beyond the conidial stage in the lung. This indicates that it is possible that A. fumigatus can cause allergic disease in the lung without any significant hyphal growth. The identification of this strain of A. fumigatus can not only be used to better understand disease pathogenesis of ABPA and potential anti-fungal treatments, but also to identify features of fungal strains that drive long-term fungal persistence in the lung. Consequently, these observations are a step toward helping resolve the long-standing question when to utilize antifungal therapies in patients with ABPA and fungal allergic type diseases.

microbiology↗

bioRxiv2019

The gut microbiota influences circulatory immune cell dynamics in humans

The gut microbiota influences development and homeostasis of the mammalian immune system1-3, can alter immune cell compositions in mice4-7, and is associated with responses to immunotherapy that rely on the activity of peripheral immune cells8-12. Still, our understanding of how the microbiota modulates immune cells dynamics remains limited, particularly in humans where a lack of deliberate manipulations makes inference challenging. Here we study hundreds of hospitalized--and closely monitored--patients receiving hematopoietic cell transplantation as they recover from chemotherapy and stem cell engraftment. This aggressive treatment causes large shifts in both circulatory immune cell and microbiota populations, allowing the relationships between the two to be studied simultaneously. We analyzed daily changes in white blood cells from 2,235 patients, and 10,680 longitudinal microbiota samples to identify bacteria associated with those changes. Bayesian inference and validation across patient cohorts revealed consistent associations between gut bacteria and white blood cell dynamics in the context of immunomodulatory medications, clinical metadata and homeostatic feedbacks. We contrasted the potency of fermentatively active, obligate anaerobic bacteria with that of medications with known immunomodulatory mechanism to estimate the potential of the microbiota to influence peripheral immune cell dynamics. Our analysis establishes and quantifies the link between the gut microbiota and the human immune system, with implications for microbiota-driven modulation of immunity.

microbiology↗