Biology subjects

Marshall, M. E.

Publications and source records attributed to Marshall, M. E..

5 recordsLinked to original sources

bioRxiv2026

Spatial transcriptomics identifies the Pseudomonas aeruginosa major outer membrane protein OprF as a critical factor in blinding corneal infections

Pseudomonas aeruginosa is a globally recognized pathogen causing pulmonary, skin, and severe corneal infections (keratitis), with the potential to induce irreversible blindness if untreated. Spatial transcriptomic analysis of P. aeruginosa infected corneas identified elevated expression of the outer membrane proteins OprF and OprL and PA1414, which encodes the small RNA SicX in the corneal stroma compared with corneal epithelium. Comparative spatial transcriptomics analysis of corneas infected with an oprF transposon (TN) mutant showed reduced expression of the type III effector protein ExoT, which was absent in an oprF deficient mutant ({Delta}oprF) and in contrast to PA14, did not inhibit reactive oxygen species (ROS) production by neutrophils. Corneal infection with the {Delta}oprF mutant resulted in reduced corneal virulence and lower CFU compared to the parental PA14 strain. Collectively, our findings demonstrate a coordinated virulence program connecting OprF functionality with the release of ExoT and its ability to block ROS production and survive in infected corneas.

microbiology↗

bioRxiv2026

Phagocytic Clearance of SARS-CoV-2 Nucleocapsid- and RNA-Containing Immune Complexes Drives Inflammatory Cytokine Production and Endothelial Dysfunction

The aberrant inflammation that characterizes severe COVID-19 is incompletely understood. Given the persistence of SARS-Cov-2 RNA and nucleocapsid protein (N) and the presence of anti-N antibody during the course of severe infection, we investigated the role of RNA-containing immune complexes (ICs) in driving inflammation. We found that ICs consisting of SARS-CoV-2 RNA, N, and anti-N IgG1 are internalized by primary human monocytes and stimulate inflammatory cytokines and chemokines in a manner dependent on Fc{gamma} receptors and partially dependent on toll-like receptor-8. In addition, the inflammatory response induced in monocytes by RNA-containing ICs caused endothelial dysfunction in vascularized micro-organs. Using nasopharyngeal samples from SARS-CoV-2-infected individuals, SARS-CoV-2 RNA and N were captured by anti-N monoclonal antibody in the absence of lysing reagents, indicating that SARS-CoV-2 RNA and N complexes are present outside of virions and cells. Finally, we found that during an early wave of COVID-19, higher anti-N IgG:IgM ratios were associated with more severe clinical outcomes, consistent with a role for inflammatory, IgG-mediated phagocytic clearance of nucleic acid-containing ICs in SARS-CoV-2 pathogenesis, perhaps mitigated by non-inflammatory, IgM-mediated clearance. We conclude that RNA-containing ICs may play a role in the pathogenesis of severe COVID-19. Since all pathogenic viruses encode nucleic acid-binding proteins, such as N, and these proteins often elicit an antibody response, inflammatory clearance of nucleic acid-containing ICs may also contribute to disease severity in other viral infections.

immunology↗

bioRxiv2025

Alpha hemolysin polymorphisms in methicillin-resistant Staphylococcus aureus clinical isolates regulate ADAM10-dependent neutrophil IL-1 beta secretion

Staphylococcus aureus -hemolysin (Hla) is a major virulence factor that utilizes cell surface ADAM10 to oligomerize and form a functional heptameric pore. We show here that Hla from strain USA300 is required to induce IL-1{beta} secretion by neutrophils and to cause severe corneal disease in mice. We also demonstrate that in contrast to USA300 and other clonal complex 8 (CC8) methicillin resistant S. aureus (MRSA) isolated from the skin, CC5 Hla from corneas of infected patients have single nucleotide polymorphisms (SNP) that result in two amino acid substitutions, D208E (Asp-Glu) and I275T (Ile-Thr). Structural modeling predicts CC5 Hla self-assembly and altered binding to ADAM10 that is distinct from CC8 Hla. The ADAM10 inhibitor GI254023X blocked neutrophil IL-1{beta} secretion induced by Hla-expressing CC8, but not by CC5 conditioned media, indicating that these Hla polymorphisms play an important role in Hla receptor binding and neutrophil IL-1{beta} secretion, and affect corneal disease severity.

microbiology↗

bioRxiv2024

A biofilm-tropic Pseudomonas aeruginosa bacteriophage uses the exopolysaccharide Psl as receptor

Bacteria in nature can exist in multicellular communities called biofilms. Biofilms also form in the course of many infections. Pseudomonas aeruginosa infections frequently involve biofilms, which contribute materially to the difficulty to treat these infections with antibiotic therapy. Many biofilm-related characteristics are controlled by the second messenger, cyclic-di-GMP, which is upregulated on surface contact. Among these factors is the exopolysaccharide Psl, which is a critically important component of the biofilm matrix. Here we describe the discovery of a P. aeruginosa bacteriophage, which we have called Clew-1, that directly binds to and uses Psl as a receptor. While this phage does not efficiently infect planktonically growing bacteria, it can disrupt P. aeruginosa biofilms and replicate in biofilm bacteria. We further demonstrate that the Clew-1 can reduce the bacterial burden in a mouse model of P. aeruginosa keratitis, which is characterized by the formation of a biofilm on the cornea. Due to its reliance on Psl for infection, Clew-1 does not actually form plaques on wild-type bacteria under standard in vitro conditions. This argues that our standard isolation procedures likely exclude bacteriophage that are adapted to using biofilm markers for infection. Importantly, the manner in which we isolated Clew-1 can be easily extended to other strains of P. aeruginosa and indeed other bacterial species, which will fuel the discovery of other biofilm-tropic bacteriophage and expand their therapeutic use.

microbiology↗

bioRxiv2024

The differential virulence of Fusarium oxysporum strains causing corneal infections and plant diseases is associated with accessory chromosome composition

Fusarium oxysporum is a cross-kingdom pathogen. While some strains cause disseminated fusariosis and blinding corneal infections in humans, others are responsible for devastating vascular wilt diseases in plants. To better understand the distinct adaptations of F. oxysporum to animal or plant hosts, we conducted a comparative phenotypic and genetic analysis of two strains: MRL8996 (isolated from a keratitis patient) and Fol4287 (isolated from a wilted tomato [Solanum lycopersicum]). Infection of mouse corneas and tomato plants revealed that, while both strains cause symptoms in both hosts, MRL8996 caused more severe corneal disease in mice, whereas Fol4287 induced more pronounced wilting symptoms in tomato plants. In vitro assays using abiotic stress treatments revealed that the human pathogen MRL8996 was better adapted to elevated temperatures, whereas the plant pathogen Fol4287 was more tolerant to osmotic and cell wall stresses. Both strains displayed broad resistance to antifungal treatment, with MRL8996 exhibiting the paradoxical effect of increased tolerance to higher concentrations of the antifungal caspofungin. We identified a set of accessory chromosomes (ACs) that encode genes with different functions and have distinct transposon profiles between MRL8996 and Fol4287. Interestingly, ACs from both genomes also encode proteins with shared functions, such as chromatin remodeling and post-translational protein modifications. Our phenotypic assays and comparative genomics analyses lay the foundation for future studies correlating genotype with phenotype and for developing targeted antifungals for agricultural and clinical uses. ImportanceFusarium oxysporum is a cross-kingdom fungal pathogen that infects both plants and animals. In addition to causing many devastating wilt diseases, this group of organisms was recently recognized by the World Health Organization as a high-priority threat to human health. Climate change has increased the risk of Fusarium infections, as Fusarium strains are highly adaptable to changing environments. Deciphering fungal adaptation mechanisms is crucial to developing appropriate control strategies. We performed a comparative analysis of Fusarium strains using an animal (mouse) and plant (tomato) host and in vitro conditions that mimic abiotic stress. We also performed comparative genomics analyses to highlight the genetic differences between human and plant pathogens and correlate their phenotypic and genotypic variations. We uncovered important functional hubs shared by plant and human pathogens, such as chromatin modification, transcriptional regulation, and signal transduction, which could be used to identify novel antifungal targets.

microbiology↗