Gutierrez-Perez, C. | bioRxiv Science

bioRxiv2025

Insights into Aspergillus fumigatus morphogenesis and pathogenesis through the putative lipid transporter ArvA

Aspergillus fumigatus poses a significant threat to human well-being, in part due to the increasing emergence of strains resistant to frontline antifungal therapy. In this study, we observe that the gene, arvA, is required for A. fumigatus morphogenesis, antifungal drug susceptibility, and cell wall homeostasis. Intriguingly, our study reveals novel morphological and growth aberrations in the absence of arvA. Loss of arvA results in hyper-swollen conidia that give rise to stunted, polarity-deficient hyphae in numerous environmental conditions, indicating a pivotal role for arvA in A. fumigatus morphogenesis. Surprisingly, despite these severe in vitro morphological and cell wall defects, arvA was not required for morbidity and mortality in immunologically distinct murine models of invasive pulmonary aspergillosis (IPA). However, growth in natural calf lung surfactant was able to normalize{Delta} arvA growth with the wild-type strain suggesting lung surfactant may partially complement the severe in vitro morphological defects of arvA loss in vivo. Taken together our observations reveal arvA as a mediator of A. fumigatus antifungal drug susceptibility and highlight the complex and ill-defined pulmonary nutrient environments role in mediating A. fumigatus pathogenesis and disease progression. IMPORTANCEAspergillus fumigatus is a challenging fungal pathogen in the clinic in part due to increasing azole drug resistance. In this study, we observe that loss of the A. fumigatus gene arvA results in increased azole susceptibility and significant in vitro morphological changes highlighted by hyper-swollen conidia that yield stunted and polarity deficient hyphae. Importantly, despite these severe in vitro morphological and growth abnormalities,{Delta} arvA surprisingly retains full pathogenicity and virulence in two immunologically distinct murine models of invasive pulmonary aspergillosis. These results challenge our understanding of the in-host environment and how it mediates fungal morphogenesis and pathogenesis. These results, consequently, not only enhances our understanding of the role of arvA in A. fumigatus morphogenesis and drug susceptibility, but further emphasizes the importance of in vivo animal models in fully evaluating potential antifungal drug targets.

microbiology↗

bioRxiv2022

Post-Influenza Environment Reduces Aspergillus fumigatus Conidia Clearance and Facilitates Invasive Aspergillosis In Vivo

Aspergillus fumigatus is a human fungal pathogen that is most often avirulent in immune competent individuals because the innate immune system is efficient at eliminating fungal conidia. However, recent clinical observations have shown that severe Influenza A virus (IAV) infection can lead to secondary A. fumigatus infections with high mortality. Little is currently known about how IAV infection alters the innate antifungal immune response. Here, we established a murine model of IAV-induced A. fumigatus (IAV-Af) superinfection by inoculating mice with IAV followed 6 days later by A. fumigatus conidia challenge. We observed increased mortality in the IAV-Af superinfected mice compared to mice challenged with either IAV or A. fumigatus alone. A. fumigatus conidia were able to germinate and establish a biofilm in the lungs of the IAV-Af superinfection group, which was not seen following fungal challenge alone. While we did not observe any differences in inflammatory cell recruitment in the IAV-Af superinfection group compared to single infection controls, we observed defects in Aspergillus conidial uptake and killing by both neutrophils and monocytes after IAV infection. pHrodo-Zymosan and CM-H2DCFDA staining, indicators of phagolysosome maturation and ROS production, respectively, revealed that the fungal killing defect was due in part to reduced phagolysosome maturation. Collectively, our data demonstrate that the ability of neutrophils and monocytes to kill and clear Aspergillus conidia is strongly reduced in the pulmonary environment of an IAV-infected lung, which leads to Invasive Pulmonary Aspergillosis and increased overall mortality in our mouse model recapitulating what is observed clinically in humans. IMPORTANCEInfluenza A virus (IAV) is a common respiratory virus that causes seasonal illness in humans, but can cause pandemics and severe infection in certain patients. Since the emergence of the 2009 H1N1 pandemic strains, there has be an increase in clinical reports of IAV infected patients in the intensive care unit (ICU) developing secondary pulmonary aspergillosis. These cases of flu-Aspergillus superinfections are associated with worse clinical outcomes than secondary bacterial infections in the setting of IAV. To date, we have a limited understanding of the cause(s) of secondary fungal infections in immune competent hosts. IAV-induced modulation of cytokine production and innate immune cellular function generates a unique immune environment in the lung, which could make the host vulnerable to a secondary fungal infection. Our work shows that defects in phagolysosome maturation in neutrophils and monocytes after IAV infection impairs the ability of these cells to kill A. fumigatus thus leading to increased fungal germination and growth and subsequent invasive aspergillosis. Our work lays a foundation for future mechanistic studies examining the exact immune modulatory events occurring in the respiratory tract after viral infection leading to secondary fungal infections.

immunology↗