The Protective Role of 1,8-Dihydroxynaphthalene-Melanin on Conidia of the Opportunistic Human Pathogen Aspergillus fumigatus Revisited: No Role in Protection against Hydrogen Peroxide and Superoxides

New developments in Aspergillus fumigatus and host reactive oxygen species responses

Aspergillus fumigatus is a filamentous fungus abundant in the environment and the most common causative agent of a spectrum of human diseases collectively termed aspergillosis. Invasive pulmonary aspergillosis is caused by deficiencies in innate immune function that result in the inability of the host to clear inhaled Aspergillus conidia that then germinate and form invasive hyphae. Myeloid cells, and their ability to generate reactive oxygen species (ROS), are essential for conidia clearance from the host. To combat ROS, A. fumigatus employs an expansive antioxidant system, though how these canonical antioxidant mechanisms contribute to infection initiation and disease progression remain to be fully defined. Recent research has identified noncanonical pathways in the A. fumigatus ROS response and new host populations with ROS deficiencies that are at-risk for invasive aspergillosis. Here, we highlight recent developments in the understanding of ROS at the interface of the dynamic A. fumigatus-host interaction.

"We've got to get out"-Strategies of human pathogenic fungi to escape from phagocytes

Human fungal pathogens are a deadly and underappreciated risk to global health that most severely affect immunocompromised individuals. A virulence attribute shared by some of the most clinically relevant fungal species is their ability to survive inside macrophages and escape from these immune cells. In this review, we discuss the mechanisms behind intracellular survival and elaborate how escape is mediated by lytic and non-lytic pathways as well as strategies to induce programmed host cell death. We also discuss persistence as an alternative to rapid host cell exit. In the end, we address the consequences of fungal escape for the host immune response and provide future perspectives for research and development of targeted therapies.

Fungi's Swiss Army Knife: Pleiotropic Effect of Melanin in Fungal Pathogenesis during Cattle Mycosis

Fungal threats to public health, food security, and biodiversity have escalated, with a significant rise in mycosis cases globally. Around 300 million people suffer from severe fungal diseases annually, while one-third of food crops are decimated by fungi. Vertebrate, including livestock, are also affected. Our limited understanding of fungal virulence mechanisms hampers our ability to prevent and treat cattle mycoses. Here we aim to bridge knowledge gaps in fungal virulence factors and the role of melanin in evading bovine immune responses. We investigate mycosis in bovines employing a PRISMA-based methodology, bioinformatics, and data mining techniques. Our analysis identified 107 fungal species causing mycoses, primarily within the Ascomycota division. Candida, Aspergillus, Malassezia, and Trichophyton were the most prevalent genera. Of these pathogens, 25% produce melanin. Further research is required to explore the involvement of melanin and develop intervention strategies. While the literature on melanin-mediated fungal evasion mechanisms in cattle is lacking, we successfully evaluated the transferability of immunological mechanisms from other model mammals through homology. Bioinformatics enables knowledge transfer and enhances our understanding of mycosis in cattle. This synthesis fills critical information gaps and paves the way for proposing biotechnological strategies to mitigate the impact of mycoses in cattle.

Light-induced antifungal activity of nanoparticles with an encapsulated porphyrin photosensitizer

The strong antifungal effect of sulfonated polystyrene nanoparticles (NPs) with an encapsulated tetraphenylporphyrin (TPP) photosensitizer is reported here. TPP is activated by visible light, resulting in the generation of singlet oxygen. Its antifungal action is potentiated in the presence of potassium iodide, yielding I₂/I₃⁻, another antifungal species. The NPs exhibit no dark toxicity, but a broad spectrum of antifungal photodynamic effects. The efficiency of this rapid killing (on the order of minutes) depends on the concentration of TPP NPs, potassium iodide, yeast species and temperature. A strong antifungal activity of TPP NPs is demonstrated on eleven pathogenic and opportunistic pathogenic yeast species (six Candida species and other yeast species, including melanized Hortaea werneckii). The composition and architecture of yeast cell envelope structures clearly influence the efficacy of photodynamic therapy. Candida krusei is the most sensitive to photodynamic therapy. Despite expectations, melanin does not provide Hortaea cells with marked resistance compared to white yeast species. The kinetics of the interaction of NPs with yeast cells is also described. This study may inspire and promote the fabrication of a new type of antiseptic for various skin injuries in clinical medicine.