Pre-Exposure With Extracellular Vesicles From Aspergillus fumigatus Attenuates Inflammatory Response and Enhances Fungal Clearance in a Murine Model Pulmonary Aspergillosis

Extracellular vesicles and endothelial dysfunction in infectious diseases

Cardiovascular diseases (CVDs) remain the leading cause of mortality and morbidity globally. Studies have shown that infections especially bacteraemia and sepsis are associated with increased risks for endothelial dysfunction and related CVDs including atherosclerosis. Extracellular vesicles (EVs) are small, sealed membrane-derived structures that are released into body fluids and blood from cells and/or microbes and are critically involved in a variety of important cell functions and disease development, including intercellular communications, immune responses and inflammation. It is known that EVs-mediated mechanism(s) is important in the development of endothelial dysfunction in infections with a diverse spectrum of microorganisms including Escherichia coli, Candida albicans, SARS-CoV-2 (the virus for COVID-19) and Helicobacter pylori. H. pylori infection is one of the most common infections globally. During H. pylori infection, EVs can carry H. pylori components, such as lipopolysaccharide, cytotoxin-associated gene A, or vacuolating cytotoxin A, and transfer these substances into endothelial cells, triggering inflammatory responses and endothelial dysfunction. This review is to illustrate the important role of EVs in the pathogenesis of infectious diseases, and the development of endothelial dysfunction in infectious diseases especially H. pylori infection, and to discuss the potential mechanisms and clinical implications.

Extracellular vesicles from Candida albicans modulate immune cells function and play a protective role in fungal keratitis

Fungal keratitis (FK) is a highly blinding infectious corneal disease caused by pathogenic fungi. Candida albicans (C. albicans) is one of the main pathogens of fungal keratitis. Extracellular vesicles (EVs), lipid bilayer compartments released by almost all living cells, including fungi, have garnered attention for their role in pathogenic microbial infection and host immune responses in recent years. Studies have reported that pretreating the host with fungal EVs can reduce the inflammatory response of the host when attacked by fungi and reduce the lethality of fungal infection. However, there are no studies that have evaluated whether C. albicans EVs can modulate the inflammatory response associated with C. albicans keratitis. Our study revealed that C. albicans EVs could activate the polymorphonuclear cells (PMNs) and promote their secretion of proinflammatory cytokines and nitric oxide (NO), enhance their phagocytic and fungicidal abilities against C. albicans. C. albicans EVs also induced a proinflammatory response in RAW264.7 cells, which was characterized by increased production of inflammatory cytokines and elevated expression of the chemokine CCL2. Similarly, stimulation of C. albicans EVs to RAW264.7 cells also enhanced the phagocytosis and killing ability of cells against C. albicans. Besides, in our in vivo experiments, after receiving subconjunctival injection of C. albicans EVs, C57BL/6 mice were infected with C. albicans. The results demonstrated that pre-exposure to C. albicans EVs could effectively diminish the severity of keratitis, reduce fungal load and improve prognosis. Overall, we conclude that C. albicans EVs can modulate the function of immune cells and play a protective role in C. albicans keratitis.

Aspergillus fumigatus-Derived Extracellular Vesicles Mitigate Fungal Keratitis by Modulating the Immune Cell Function

Fungal keratitis (FK) is a refractory global disease characterized by a high incidence of blindness and a lack of effective therapeutic options, and Aspergillus fumigatus (A. fumigatus, AF) is one of the most common causative fungi. This study aimed to investigate the role of extracellular vesicles (EVs) from A. fumigatus in the immune cell function and their protective role in A. fumigatus keratitis in order to explore their therapeutic potential. First, we isolated and characterized the EVs (AF-derived EVs). In vitro, we stimulated RAW264.7 cells and polymorphonuclear cells with AF-derived EVs. The expression levels of inflammatory factors increased in both immune cells along with an M1 polarization variation of RAW264.7 cells. After being incubated with AF-derived EVs, both immune cells exhibited an increased conidia-phagocytic index and a decreased conidia survival rate. In vivo, we injected EVs subconjunctivally on mice resulting in a heightened production of secretory immunoglobulin A (sIgA) in tear fluid. By the injection of EVs on mice in advance, a significant reduction in severity of A. fumigatus FK was witnessed by lower clinical scores, inflammatory appearances, and mitigated fungal load. Collectively, these results positioned AF-derived EVs as a promising and innovative immune therapy for combating FK, while also providing a platform for further investigation into developing an optimal formulation for modulating inflammation in the context of FK.

The multiple frontiers in the study of extracellular vesicles produced by fungi

The production of extracellular vesicles (EVs) by fungi has been recognized for about a decade. Here we discuss the roles played by fungal EVs in biofilm formation, antifungal resistance, and release of immunogens with vaccine potential. We also explore their significance in promoting international collaboration and understanding of fungal biology.

Fungal extracellular vesicle-mediated regulation: from virulence factor to clinical application

Invasive fungal disease (IFD) poses a significant threat to immunocompromised patients and remains a global challenge due to limited treatment options, high mortality and morbidity rates, and the emergence of drug-resistant strains. Despite advancements in antifungal agents and diagnostic techniques, the lack of effective vaccines, standardized diagnostic tools, and efficient antifungal drugs contributes to the ongoing impact of invasive fungal infections (IFI). Recent studies have highlighted the presence of extracellular vesicles (EVs) released by fungi carrying various components such as enzymes, lipids, nucleic acids, and virulence proteins, which play roles in both physiological and pathological processes. These fungal EVs have been shown to interact with the host immune system during the development of fungal infections whereas their functional role and potential application in patients are not yet fully understood. This review summarizes the current understanding of the biologically relevant findings regarding EV in host-pathogen interaction, and aim to describe our knowledge of the roles of EV as diagnostic tools and vaccine vehicles, offering promising prospects for the treatment of IFI patients.

The emerging role of extracellular vesicles in fungi: a double-edged sword

Fungi are eukaryotic microorganisms found in nature, which can invade the human body and cause tissue damage, inflammatory reactions, organ dysfunctions, and diseases. These diseases can severely damage the patient's body systems and functions, leading to a range of clinical symptoms that can be life-threatening. As the incidence of invasive fungal infections has progressively increased in the recent years, a wealth of evidence has confirmed the "double-edged sword" role of fungal extracellular vesicles (EVs) in intercellular communication and pathogen-host interactions. Fungal EVs act as mediators of cellular communication, affecting fungal-host cell interactions, delivering virulence factors, and promoting infection. Fungal EVs can also have an induced protective effect, affecting fungal growth and stimulating adaptive immune responses. By integrating recent studies, we discuss the role of EVs in fungi, providing strong theoretical support for the early prevention and treatment of invasive fungal infections. Finally, we highlight the feasibility of using fungal EVs as drug carriers and in vaccine development.

Aspergillus fumigatus Extracellular Vesicles Display Increased Galleria mellonella Survival but Partial Pro-Inflammatory Response by Macrophages

Fungal extracellular vesicles (EVs) mediate intra- and interspecies communication and are critical in host-fungus interaction, modulating inflammation and immune responses. In this study, we evaluated the in vitro pro- and anti-inflammatory properties of Aspergillus fumigatus EVs over innate leukocytes. A. fumigatus EVs induced a partial proinflammatory response by macrophages, characterized by increased tumor necrosis factor-alpha production, and increased gene expression of induced nitric oxide synthase and adhesion molecules. EVs induce neither NETosis in human neutrophils nor cytokine secretion by peripheral mononuclear cells. However, prior inoculation of A. fumigatus EVs in Galleria mellonella larvae resulted in increased survival after the fungal challenge. Taken together, these findings show that A. fumigatus EVs play a role in protection against fungal infection, although they induce a partial pro-inflammatory response.

Gut-derived fungemia due to Kodamaea ohmeri combined with invasive pulmonary aspergillosis: a case report

BACKGROUND

Kodamaea ohmeri is a rare pathogen with high mortality and is found among blood samples in a considerable proportion; however, gastrointestinal infection of K. ohmeri is extremely rare. Invasive pulmonary aspergillosis is also an uncommon fungal; these two fungal infections reported concomitantly are unprecedented.

CASE PRESENTATION

We described a case of a 37-year-old male who got infected with K. ohmeri and invasive pulmonary aspergillosis. We used the mass spectrometry and histopathology to identify these two fungal infections separately. For the treatment of K. ohmeri, we chose caspofungin. As for invasive pulmonary aspergillosis, we used voriconazole, amphotericin B, and then surgery. The patient was treated successfully through the collaboration of multiple disciplines.

CONCLUSIONS

We speculate that the destruction of the intestinal mucosa barrier can make the intestine one of the ways for certain fungi to infect the human body.