Biology subjects

Wells, B. L.

Publications and source records attributed to Wells, B. L..

3 recordsLinked to original sources

bioRxiv2026

A cornea-specific role for the Aspergillus fumigatus carbon catabolite repressor, CreA, in tissue penetration and infection establishment

PurposeElucidate the influence of glucose metabolic pathways on A. fumigatus lung and corneal infection. MethodsThe A. fumigatus acuF and creA genes were deleted in an mcherry-expressing strain. The mutants were tested for alterations in radial growth, cell wall composition by fluorescence staining assays, and antifungal sensitivity through broth microdilution assays. Hyphal penetration of the strains through explanted porcine corneas was tracked by confocal microscopy using the mCherry signal. Virulence was evaluated in established models of invasive pulmonary aspergillosis (IPA) and fungal keratitis (FK) using C57BL/6J mice. ResultsDeletion of the A. fumigatus phosphoenolpyruvate carboxykinase (acuF) resulted in a dependency on exogenous glucose to support growth in vitro, but did not impact virulence in either the IPA or FK models. Loss of the carbon catabolite repressor CreA resulted in a broad dysregulation of carbon metabolic pathways and altered cell wall homeostasis. Surprisingly, whereas the{Delta} creA remained fully virulent in the lung, the mutant was unable to establish infection in the FK model. This in vivo phenotype corresponded to an inability of{Delta} creA to physically invade porcine corneal explants, which we attributed to a marked reduction in cell wall chitin content. ConclusionsGluconeogenesis is dispensable for A. fumigatus lung and corneal infection, suggesting tissue-derived glucose supports fungal growth in both environments. Loss of CreA disrupts glucose assimilation, its synthesis into chitin and, consequently, cell rigidity and hyphal invasion into the dense corneal stroma. Thus, CreA and other cell wall regulatory proteins may serve as targets for novel FK antifungals.

microbiology↗

bioRxiv2023

Aspergillus fumigatus hypoxia adaptation is critical for the establishment of fungal keratitis.

Purpose: The poor visual outcomes associated with fungal keratitis (FK) underscore a need to identify fungal pathways that can serve as novel antifungal targets. In this report, we investigated whether hypoxia develops in the FK cornea and, by extension, if fungal hypoxia adaptation is essential for virulence in this setting. Methods: C57BL/6j mice were inoculated with Aspergillus fumigatus and Fusarium solani var petroliphilum via topical overlay or instrastromal injection. At various time points post-inoculation (p.i.), animals we were injected with pimonidazole for the detection of tissue hypoxia through immunofluorescence imaging. The A. fumigatus srbA gene was deleted through Cas9-mediated homologous recombination and its virulence was assessed in the topical infection model using slit-lamp microscopy and optical coherence tomography (OCT). Results: Topical inoculation with A. fumigatus resulted in diffuse pimonidazole staining across the epithelial and endothelial layers within 6 h. Stromal hypoxia was evident by 48 h p.i., which corresponded to leukocytic infiltration. Instrastromal inoculation with either A. fumigatus or F. solani similarly led to diffuse staining patterns across all corneal cell layers. The A. fumigatus srbA deletion mutant was unable to grow at oxygen levels below 3% in vitro, and corneas inoculated with the mutant failed to develop signs of corneal opacification, inflammation or fungal burden. Conclusions: These results suggest that fungal antigen rapidly drives the development of corneal hypoxia, thus rendering fungal SrbA or related pathways essential for the establishment of infection. Such pathways may therefore serve as targets for novel antifungal intervention.

pathology↗

bioRxiv2023

Basal UPR activity in Aspergillus fumigatus regulates adaptation to nutrient stress and is critical for the establishment of corneal infection

The Aspergillus fumigatus unfolded protein response (UPR) is a two-component relay consisting of the ER-bound IreA protein, which splices and activates the mRNA of the transcription factor HacA. Spliced hacA accumulates under conditions of acute ER stress in vitro, and UPR null mutants are hypovirulent in a murine model of invasive pulmonary infection. In this report, we demonstrate that a hacA deletion mutant is completely unable to establish infection in a model of fungal keratitis, a corneal infection and an important cause of ocular morbidity and unilateral blindness worldwide. Contrary to our initial prediction, however, we demonstrate that hacA splicing is not increased above baseline conditions in the cornea, nor is the expression of genes classically associated with UPR activation, such as protein chaperones. We employed transcriptomics on wild-type and{Delta} hacA strains in gelatin media, as a proxy for the corneal environment, and found that hacA supports the expression of numerous primary and secondary metabolic processes that likely promote adaptation to nutrient limitation. Taken together, our results support a model in which the cornea, similar to growth on protein in vitro, is a source of sub-acute ER stress for A. fumigatus, but one nevertheless that requires the UPR pathway for proper adaptation. The data also suggest that this pathway could be a target for novel antifungals that improve visual outcomes for fungal keratitis patients. AUTHOR SUMMARYFungal keratitis has emerged as a leading cause of ocular morbidity and unilateral blindness worldwide. Relative to other infectious contexts, however, little is known about the fungal genes or pathways that regulate invasive growth and virulence in the corneal environment. In this report, we demonstrate that genetic disruption of the Aspergillus fumigatus unfolded protein response (UPR) abolishes the ability of the mold to establish infection in a mouse model of FK. Despite this critical role for virulence, however, we did not detect a concerted activation of the pathway beyond levels observed on standard medium, suggesting that the host environment is not an acute source of endoplasmic reticulum stress. Transcriptomic profiling of the wild-type and UPR-deficient strains under host-relevant nutrient conditions revealed a critical role for the pathway in regulating primary and secondary metabolism, cell wall biology, and mitochondrial function, all of which likely modulate fungal growth within and interactions with the host. These results expand our understanding of UPR regulation and function in this important mold pathogen and suggest the pathway could serve as a target for novel antifungals that improve visual outcomes in the setting of fungal keratitis.

microbiology↗