Lass-Floerl, C. | Search bioRxiv

bioRxiv2025

Arp2/3 complex contributes to the actin-dependent uptake of Aspergillus terreus conidia by alveolar epithelial cells

Aspergillus terreus is an opportunistic fungal pathogen associated with high mortality rates and intrinsic resistance to amphotericin B. Its ability to persist within host tissues without inducing strong immune responses was suggested to contribute to poor clinical outcomes. The cellular mechanisms underlying A. terreus interactions with host cells remain largely unexplored. In this study, we have used a micropattern-based infection model to investigate the early interactions between A. terreus conidia and alveolar epithelial cells, focusing on the role of Arp2/3-dependent actin remodeling. This system allows quantitative analysis of conidia-cell interactions under defined spatial conditions. We show that A. terreus conidia rapidly bind to micropatterned A549 cell islands, with conidial numbers increasing over time. Conidia were found in actin- and Lamp1-positive vesicles already after one hour of infection. Inhibition of the Arp2/3 complex significantly impaired conidial binding and disrupted the formation of actin-positive vesicles, confirming the essential role of Arp2/3-mediated actin remodeling in early stages of conidial uptake. A subset of internalized conidia was localized to Lamp1-positive phagolysosomes and accumulated over time. Interestingly, we have identified a small but consistent population of phagolysosomes decorated with actin patches, potentially resembling actin flashes. These structures were entirely abolished upon Arp2/3 inhibition, indicating active cytoskeletal remodeling at the phagolysosomal interface. Our findings provide the first mechanistic insights into A. terreus internalization by alveolar epithelial cells and establish Arp2/3-mediated actin dynamics as a key process in early host-pathogen interactions. This cellular pathway may contribute to intracellular persistence and help understand the delayed onset of A. terreus infections.

microbiology↗

bioRxiv2022

COVID-19 Associated Pulmonary Aspergillosis isolates are genomically diverse but similar to each other in their responses to infection-relevant stresses

Secondary infections caused by the pulmonary fungal pathogen Aspergillus fumigatus are a significant cause of mortality in patients with severe Coronavirus Disease 19 (COVID-19). Even though epithelial cell damage and aberrant cytokine responses have been linked with susceptibility to COVID-19 associated pulmonary aspergillosis (CAPA), little is known about the mechanisms underpinning co-pathogenicity. Here, we analysed the genomes of 11 A. fumigatus isolates from patients with CAPA in three centres from different European countries. CAPA isolates did not cluster based on geographic origin in a genome-scale phylogeny of representative A. fumigatus isolates. Phenotypically, CAPA isolates were more similar to the A. fumigatus A1160 reference strain than to the Af293 strain when grown in infection-relevant stresses; except for interactions with human immune cells wherein macrophage responses were similar to those induced by the Af293 reference strain. Collectively, our data indicates that CAPA isolates are genomically diverse but are more similar to each other in their responses to infection-relevant stresses. A larger number of isolates from CAPA patients should be studied to identify genetic drivers of co-pathogenicity in patients with COVID-19. ImportanceCoronavirus disease 2019 (COVID-19)-associated pulmonary aspergillosis (CAPA) has been globally reported as a life-threatening complication in some patients with severe COVID-19. Most of these infections are caused by the environmental mould Aspergillus fumigatus which ranks third in the fungal pathogen priority list of the WHO. However, little is known about the molecular epidemiology of Aspergillus fumigatus CAPA strains. Here, we analysed the genomes of 11 A. fumigatus isolates from patients with CAPA in three centres from different European countries and, carried out phenotypic analyses with a view to understand the pathophysiology of the disease. Our data indicates that A. fumigatus CAPA isolates are genomically diverse but are more similar to each other in their responses to infection-relevant stresses.

cell biology↗