Biology subjects

Drummond, R. A.

Publications and source records attributed to Drummond, R. A..

5 recordsLinked to original sources

bioRxiv2024

Vancomycin impairs macrophage fungal killing by disrupting mitochondrial morphology and function

Vancomycin is a widely prescribed antibiotic used in the treatment of Gram-positive bacterial infections. We recently showed that this antibiotic disrupted protective anti-fungal immune responses via microbiome dysbiosis, enhancing susceptibility to invasive candidiasis. Antibiotics are an independent risk factor for developing this life-threatening fungal infection, but whether microbiota-independent mechanisms also drive this association is not clear. Here, we show that vancomycin directly impairs macrophage responses to Candida albicans, the main causative agent of invasive candidiasis. Vancomycin-treated macrophages were less able to kill C. albicans despite normal phagocytosis rates and were hyper-inflammatory and more likely to die during infection. We found that vancomycin bound to macrophage mitochondria, leading to depolarisation, reduced respiratory capacity and a hyper-fragmented morphology associated with increased ROS production. Taken together, this work demonstrates direct effects of vancomycin on mammalian immune cells, helping us to understand pro-inflammatory effects of this drug and how it promotes susceptibility to life-threatening fungal infection.

immunology↗

bioRxiv2024

Interferonγ and IL-27 positively regulate type 1 regulatory T-cell development during adaptive tolerance

Strong T-cell receptor (TCR) and IL-27 signalling influence type-1 regulatory (Tr1) T-cell development but whether other signals determine their differentiation is unclear. Utilising Tg4 TCR transgenic mice we established a model for rapid Tr1 cell induction. A single high dose of [4Y]-MBP peptide drove the differentiation of Il10+ T-cells with bona fide Tr1 cell protein and mRNA signatures. Kinetic transcriptional analysis revealed that the Tr1 cell module was transient and preceded by a burst of Ifng transcription in CD4+ T-cells. Neutralisation of IFN{gamma} reduced Tr1 cell frequency and strong TCR signalling markers, which was correlated with reduced macrophage activation. Antibody depletion experiments inferred that T-cells - but not NK cells - provided the relevant source of IFN{gamma}. Additionally, we show that blocking IL-27 in combination with IFN{gamma} neutralisation additively reduced Tr1 cell frequency in vivo. These findings reveal that during strong tolerogenic TCR signalling IFN-{gamma} has a non-redundant regulatory role in augmenting the differentiation of Tr1 cells in vivo.

immunology↗

bioRxiv2023

Airway epithelial cells as a novel intracellular host reservoir for Cryptococcus spores

Human fungal pathogens, including Cryptococcus neoformans, cause 1.5 million annual deaths. Cryptococcus causes disease when it disseminates out of the lung and into the brain which can occur years after initial exposure (latency) via mechanisms that remain unknown. Spores of Cryptococcus display distinct surface epitopes, host-interactions, and disease kinetics to the vegetatively growing yeast morphotype, yet they remain understudied likely contributing to our lack of understanding of pathogenesis. One of the first barriers spores encounter are non-professional phagocytic Airway Epithelial Cells (AECs). Here, we demonstrated that Cryptococcus spores preferentially invade AECs both in vitro and in vivo. Once inside spores can germinate, subsequently replicate, persist and/or escape. This ability to enter AECs correlates with a preferential ability of spore to cross AEC barriers. Together our work indicates that AECs can be invaded by Cryptococcus spores and may serve as a previously ignored intracellular host niche, providing alternative hypothesis for both Cryptococcus dissemination and latency.

microbiology↗

bioRxiv2022

CSF1R inhibition by PLX5622 reduces pulmonary fungal infection by depleting MHCIIhi interstitial lung macrophages

PLX5622 is a small molecular inhibitor of the CSF1 receptor (CSF1R) and is widely used to deplete macrophages within the central nervous system (CNS). However, recent reports have indicated that PLX5622 may affect myeloid cells in other organs including the bone marrow and spleen. We investigated the impact of PLX5622 treatment in wild-type C57BL/6 mice and discovered that one-week treatment with PLX5622 was sufficient to deplete interstitial macrophages in the lung and brain-infiltrating Ly6Clow patrolling monocytes, in addition to CNS-resident macrophages. These cell types were previously indicated to act as infection reservoirs for the pathogenic fungus Cryptococcus neoformans. We therefore took advantage of PLX5622-mediated depletion of these myeloid cell subsets to examine their functional role in C. neoformans lung infection and extrapulmonary dissemination. We found that PLX5622-treated mice had significantly reduced fungal lung infection and reduced extrapulmonary dissemination to the CNS but not to the spleen or liver. Fungal lung infection mapped to MHCIIhi interstitial lung macrophages, which underwent significant expansion during infection following monocyte replenishment and not local division. Although PLX5622 depleted CNS infiltrating patrolling monocytes, these cells did not accumulate in the fungal-infected CNS following pulmonary infection. In addition, Nr4a1-deficient mice, which lack patrolling monocytes, had similar control and dissemination of C. neoformans infection to wild-type controls. Our data demonstrate that PLX5622 may have a beneficial effect in the control of intracellular replicating pathogenic fungi that utilise CSF1R-dependent myeloid cells as infection reservoirs.

immunology↗

bioRxiv2022

Microglia protect fungi against copper starvation and promote brain infection

Microglia provide protection against a range of brain infections, but how these glial cells respond to fungi is poorly understood. We investigated the role of microglia in the context of cryptococcal meningitis, the most common cause of fungal brain infections in humans. Using a series of transgenic- and chemical-based microglia depletion methods we found that, contrary to their protective role during other infections, microglia supported cryptococcal fungal brain infection. We show that microglia become hosts for intracellular fungal growth and are a site in which the fungus accesses the restricted micronutrient copper. We developed a reporter fungal strain to track copper starvation responses by the fungus and found that yeast were protected from copper starvation within microglia. Lastly, we show that stimulation of microglia with IFN{gamma} causes restriction of phagosomal copper to intracellular fungi. These data provide a mechanistic explanation for why microglia depletion has a therapeutic effect in the context of this life-threatening fungal infection and is one of the few examples of microglia acting to promote infection. Our data demonstrate how tissue-resident phagocytes can support cryptococcal infections by acting as intracellular reservoirs and sites of microbial nutrient acquisition, and how these mechanisms may be blocked by IFN{gamma} immunotherapy.

immunology↗