Interactions of an Emerging Fungal Pathogen Scedosporium aurantiacum with Human Lung Epithelial Cells

Transient hypoxia drives soil microbial community dynamics and biogeochemistry during human decomposition

Human decomposition in terrestrial ecosystems is a dynamic process creating localized hot spots of soil microbial activity. Longer-term (beyond a few months) impacts on decomposer microbial communities are poorly characterized and do not typically connect microbial communities to biogeochemistry, limiting our understanding of decomposer communities and their functions. We performed separate year-long human decomposition trials, one starting in spring, another in winter, integrating bacterial and fungal community structure and abundances with soil physicochemistry and biogeochemistry to identify key drivers of microbial community change. In both trials, soil acidification, elevated microbial respiration, and reduced soil oxygen concentrations occurred. Changes in soil oxygen concentrations were the primary driver of microbial succession and nitrogen transformation patterns, while fungal community diversity and abundance was related to soil pH. Relative abundance of facultative anaerobic taxa (Firmicutes and Saccharomycetes) increased during the period of reduced soil oxygen. The magnitude and timing of the decomposition responses were amplified during the spring trial relative to the winter, even when corrected for thermal inputs (accumulated degree days). Further, soil chemical parameters, microbial community structure, and fungal gene abundances remained altered at the end of 1 year, suggesting longer-term impacts on soil ecosystems beyond the initial pulse of decomposition products.

Scedosporiosis and lomentosporiosis: modern perspectives on these difficult-to-treat rare mold infections

SUMMARYAlthough Scedosporium species and Lomentospora prolificans are uncommon causes of invasive fungal diseases (IFDs), these infections are associated with high mortality and are costly to treat with a limited armamentarium of antifungal drugs. In light of recent advances, including in the area of new antifungals, the present review provides a timely and updated overview of these IFDs, with a focus on the taxonomy, clinical epidemiology, pathogenesis and host immune response, disease manifestations, diagnosis, antifungal susceptibility, and treatment. An expansion of hosts at risk for these difficult-to-treat infections has emerged over the last two decades given the increased use of, and broader population treated with, immunomodulatory and targeted molecular agents as well as wider adoption of antifungal prophylaxis. Clinical presentations differ not only between genera but also across the different Scedosporium species. L. prolificans is intrinsically resistant to most currently available antifungal agents, and the prognosis of immunocompromised patients with lomentosporiosis is poor. Development of, and improved access to, diagnostic modalities for early detection of these rare mold infections is paramount for timely targeted antifungal therapy and surgery if indicated. New antifungal agents (e.g., olorofim, fosmanogepix) with novel mechanisms of action and less cross-resistance to existing classes, availability of formulations for oral administration, and fewer drug-drug interactions are now in late-stage clinical trials, and soon, could extend options to treat scedosporiosis/lomentosporiosis. Much work remains to increase our understanding of these infections, especially in the pediatric setting. Knowledge gaps for future research are highlighted in the review.

Extracellular Vesicles from Scedosporium apiospermum Mycelial Cells: Implication for Fungal-Host Interplays

The release of extracellular vesicles (EVs) has been implicated as an alternative transport mechanism for the passage of macromolecules through the fungal cell wall, a phenomenon widely reported in yeasts but poorly explored in mycelial cells. In the present work, we have purified and characterized the EVs released by mycelia of the emerging, opportunistic, widespread and multidrug-resistant filamentous fungus Scedosporium apiospermum. Transmission electron microscopy images and light scattering measurements revealed the fungal EVs, which were observed individually or grouped with heterogeneous morphology, size and electron density. The mean diameter of the EVs, evaluated by the light scattering technique, was 179.7 nm. Overall, the structural stability of S. apiospermum EVs was preserved during incubation under various storage conditions. The lipid, carbohydrate and protein contents were quantified, and the EVs' protein profile was evidenced by SDS-PAGE, revealing proteins with molecular masses ranging from 20 to 118 kDa. Through immunoblotting, ELISA and immunocytochemistry assays, antigenic molecules were evidenced in EVs using a polyclonal serum (called anti-secreted molecules) from a rabbit inoculated with conditioned cell-free supernatant obtained from S. apiospermum mycelial cells. By Western blotting, several antigenic proteins were identified. The ELISA assay confirmed that the anti-secreted molecules exhibited a positive reaction up to a serum dilution of 1:3200. Despite transporting immunogenic molecules, S. apiospermum EVs slightly induced an in vitro cytotoxicity effect after 48 h of contact with either macrophages or lung epithelial cells. Interestingly, the pretreatment of both mammalian cells with purified EVs significantly increased the association index with S. apiospermum conidia. Furthermore, EVs were highly toxic to Galleria mellonella, leading to larval death in a typically dose- and time-dependent manner. Collectively, the results represent the first report of detecting EVs in the S. apiospermum filamentous form, highlighting a possible implication in fungal pathogenesis.

Geniposide ameliorates acute kidney injury via enhancing the phagocytic ability of macrophages towards neutrophil extracellular traps

Acute kidney injury (AKI) is a clinically serious disorder associated with high mortality rates and an increased risk of progression to end-stage renal disease. As an essential supportive treatment for patients with respiratory failure, mechanical ventilation not only save many critically ill patients, but also affect glomerular filtration function by changing renal hemodynamics, neurohumoral and positive end-expiratory pressure, eventually leading to AKI. AMP-activated protein kinase (AMPK), a crucial energy homeostasis regulator, could enhance macrophage phagocytic ability and inhibit inflammation, but whether it can engulf neutrophil extracellular traps (NETs) and alleviate mechanical ventilation-associated AKI is still unclear. In this study, we found that geniposide significantly ameliorated histopathological damage, reduced serum Cre and BUN levels. Besides, geniposide can also induce AMPK activation and enhance macrophage phagocytic ability toward NETs. Moreover, geniposide can markedly reduce the levels of high mobility group box 1 (HMGB1), and these effects were dependent on AMPK-PI3K/Akt signaling. Altogether, these results indicated that geniposide promoted macrophage efferocytosis by inducing AMPK-PI3K/Akt signaling activation, clearing NETs and ameliorating AKI.

Scedosporium boydii finding in an immunocompromised patient and review of the literature

BACKGROUND

Scedosporiasis is an emerging mycosis that has gained importance in recent years due to its worldwide prevalence. It is caused by species of the Scedosporium apiospermum complex. These species can cause opportunistic infections in immunocompromised patients and, occasionally, in immunocompetent patients as well. The high intrinsic antifungal resistance make these infections difficult to manage.

AIMS

The objective of this study was to interpret the mycological findings in a transplant patient, together with the images obtained in the radiological studies, in order to provide an early and effective antifungal therapy.

METHODS

The mycological analysis of samples taken from a heart transplant patient with radiological images suggesting a fungal infection was performed. Computed tomography scan of the head and thorax showed space-occupying lesions in both the frontal lobe and cerebellum, and multiple pulmonary nodules. The nodules were punctured and the samples obtained were analyzed according to the procedures for mycological analysis. The identity of the isolates was confirmed by nucleotide sequencing. Eventually, the antifungal susceptibility was studied.

RESULTS

The fungal isolates obtained, whose identity was confirmed by sequencing, belonged to the species Scedosporium boydii. Injured tissues were surgically removed and a treatment with amphotericin B and voriconazole-minimum inhibitory concentration (MIC) 0.5μg/mL and ≥0.5μg/mL respectively - was administered.

CONCLUSIONS

Although the patient died due to complications of a Klebsiella pneumoniae sepsis refractory to treatment, the progression of the fungal disease, although slow, was favourable in the early phases of the treatment due to a correct diagnosis and the antifungal susceptibility test carried out. Clinical cases of this nature highlight the need to increase the epidemiological study of these microorganisms, as well as the proper treatment of the diseases caused, in order to achieve early diagnoses that reduce the morbidity and mortality of patients.

Recent developments in less known and multi-resistant fungal opportunists

Fungal infections have increased in recent years due to host factors, such as oncohaematological and transplant-related disorders, immunosuppressive therapy, and AIDS. Additionally, molecular and proteomic facilities have become available to identify previously unrecognizable opportunists. For these reasons, reports on less-known and recalcitrant mycoses, such as those caused by black fungi, hyaline filamentous fungi, coelomycetes, Mucorales, and non-Candida yeasts have emerged. In this review, novel taxonomy in these groups, which often are multi-resistant to one or several classes of antifungals, is discussed. Clinical presentations, diagnosis and current treatment of some major groups are summarised.

Scedosporium spp. from Clinical Setting in Argentina, with the Proposal of the New Pathogenic Species Scedosporium americanum

Species of the genus Scedosporium (family Microascaceae, phylum Ascomycota) are responsible for a wide range of opportunistic human infections, and have a low susceptibility to most antifungal drugs. It is well known that the pattern of Scedosporium species distribution varies according to geographic region. To assess the diversity of Scedosporium species in Argentina involved in human infections, we carried out a retrospective study reviewing 49 strains from clinical samples sent for diagnosis to the National Clinical Mycology Reference Laboratory between 1985 and 2019. Then, a phenotypic characterization, a phylogenetic study and and in vitro susceptibility test to antifungals were carried out. An analysis of combined nucleotide sequences dataset of the internal transcribed spacer of the ribosomal DNA (ITS) and of a fragment of the β-tubulin gene (BT2) demonstrated that 92% of the strains belonged to the species S. boydii, S. apiospermum and S. angustum, all them pertaining to S. apiospermum species complex. However, two strains (4%) were identified as S. aurantiacum, a species never reported in clinical settings in the Americas’. Surprisingly, one of them displayed a polycytella-like conidiogenesis, up to date only reported for S. apiospermum. In addition, the strain DMic 165285 was phylogenetically located far away from the rest of the species, so is proposed as the novel species Scedosporium americanum. On the other hand, from all seven antifungals tested, voriconazole and posaconazole were the most active drugs against Scedosporium spp.

The Host Immune Response to Scedosporium/Lomentospora

Infections caused by the opportunistic pathogens Scedosporium/Lomentospora are on the rise. This causes problems in the clinic due to the difficulty in diagnosing and treating them. This review collates information published on immune response against these fungi, since an understanding of the mechanisms involved is of great interest in developing more effective strategies against them. Scedosporium/Lomentospora cell wall components, including peptidorhamnomannans (PRMs), α-glucans and glucosylceramides, are important immune response activators following their recognition by TLR2, TLR4 and Dectin-1 and through receptors that are yet unknown. After recognition, cytokine synthesis and antifungal activity of different phagocytes and epithelial cells is species-specific, highlighting the poor response by microglial cells against L. prolificans. Moreover, a great number of Scedosporium/Lomentospora antigens have been identified, most notably catalase, PRM and Hsp70 for their potential medical applicability. Against host immune response, these fungi contain evasion mechanisms, inducing host non-protective response, masking fungal molecular patterns, destructing host defense proteins and decreasing oxidative killing. In conclusion, although many advances have been made, many aspects remain to be elucidated and more research is necessary to shed light on the immune response to Scedosporium/Lomentospora.

Fun(gi)omics: Advanced and Diverse Technologies to Explore Emerging Fungal Pathogens and Define Mechanisms of Antifungal Resistance

The landscape of infectious fungal agents includes previously unidentified or rare pathogens with the potential to cause unprecedented casualties in biodiversity, food security, and human health. The influences of human activity, including the crisis of climate change, along with globalized transport, are underlying factors shaping fungal adaptation to increased temperature and expanded geographical regions. Furthermore, the emergence of novel antifungal-resistant strains linked to excessive use of antifungals (in the clinic) and fungicides (in the field) offers an additional challenge to protect major crop staples and control dangerous fungal outbreaks.

The landscape of infectious fungal agents includes previously unidentified or rare pathogens with the potential to cause unprecedented casualties in biodiversity, food security, and human health. The influences of human activity, including the crisis of climate change, along with globalized transport, are underlying factors shaping fungal adaptation to increased temperature and expanded geographical regions. Furthermore, the emergence of novel antifungal-resistant strains linked to excessive use of antifungals (in the clinic) and fungicides (in the field) offers an additional challenge to protect major crop staples and control dangerous fungal outbreaks. Hence, the alarming frequency of fungal infections in medical and agricultural settings requires effective research to understand the virulent nature of fungal pathogens and improve the outcome of infection in susceptible hosts. Mycology-driven research has benefited from a contemporary and unified approach of omics technology, deepening the biological, biochemical, and biophysical understanding of these emerging fungal pathogens. Here, we review the current state-of-the-art multi-omics technologies, explore the power of data integration strategies, and highlight discovery-based revelations of globally important and taxonomically diverse fungal pathogens. This information provides new insight for emerging pathogens through an in-depth understanding of well-characterized fungi and provides alternative therapeutic strategies defined through novel findings of virulence, adaptation, and resistance.

Comprehensive host-pathogen protein-protein interaction network analysis

BACKGROUND

Infectious diseases are a cruel assassin with millions of victims around the world each year. Understanding infectious mechanism of viruses is indispensable for their inhibition. One of the best ways of unveiling this mechanism is to investigate the host-pathogen protein-protein interaction network. In this paper we try to disclose many properties of this network. We focus on human as host and integrate experimentally 32,859 interaction between human proteins and virus proteins from several databases. We investigate different properties of human proteins targeted by virus proteins and find that most of them have a considerable high centrality scores in human intra protein-protein interaction network. Investigating human proteins network properties which are targeted by different virus proteins can help us to design multipurpose drugs.

RESULTS

As host-pathogen protein-protein interaction network is a bipartite network and centrality measures for this type of networks are scarce, we proposed seven new centrality measures for analyzing bipartite networks. Applying them to different virus strains reveals unrandomness of attack strategies of virus proteins which could help us in drug design hence elevating the quality of life. They could also be used in detecting host essential proteins. Essential proteins are those whose functions are critical for survival of its host. One of the proposed centralities named diversity of predators, outperforms the other existing centralities in terms of detecting essential proteins and could be used as an optimal essential proteins' marker.

CONCLUSIONS

Different centralities were applied to analyze human protein-protein interaction network and to detect characteristics of human proteins targeted by virus proteins. Moreover, seven new centralities were proposed to analyze host-pathogen protein-protein interaction network and to detect pathogens' favorite host protein victims. Comparing different centralities in detecting essential proteins reveals that diversity of predator (one of the proposed centralities) is the best essential protein marker.

Insights into the interaction of Scedosporium apiospermum, Scedosporium aurantiacum, Scedosporium minutisporum, and Lomentospora prolificans with lung epithelial cells

Scedosporium spp. and Lomentospora prolificans are filamentous fungi that emerged as human pathogens; however, their mechanisms of virulence/pathogenesis are still largely unknown. In the present work, we have evaluated the interaction of S. apiospermum, S. minutisporum, S. aurantiacum, and L. prolificans with lung epithelial cells (A549 line). The results showed that conidia were able to interact with A549 cells, displaying association indexes of 73.20, 117.98, 188.01, and 241.63 regarding S. apiospermum, L. prolificans, S. minutisporum, and S. aurantiacum, respectively. Light microscopy images evidenced morphological changes in epithelial cells, including rounding and detachment, especially during the interaction with L. prolificans. Plasma membrane injuries were detected in A549 cells after 1 h of co-culturing with S. aurantiacum and S. minutisporum and after 4 h with S. apiospermum and L. prolificans, as judged by the passive incorporation of propidium iodide. After 24 h of fungi-epithelial cells interaction, only mycelia were observed covering the A549 monolayer. Interestingly, the mycelial trap induced severe damage in the A549 cells, culminating in epithelial cell death. Our results demonstrate some relevant events that occur during the contact between lung epithelial cells and Scedosporium/Lomentospora species, including conidial adhesion and hyphal growth with consequent irreversible injury on A549 cells, adding light to the infection process caused by these opportunistic and multidrug-resistant fungi.