Candida albicans secreted aspartyl proteinases in virulence and pathogenesis

Aspartyl peptidase May1 induces host inflammatory response by altering cell wall composition in the fungal pathogen Cryptococcus neoformans

Cryptococcus neoformans causes cryptococcal meningoencephalitis, a disease that kills more than 180,000 people annually. Contributing to its success as a fungal pathogen is its cell wall surrounded by a capsule. When the cryptococcal cell wall is compromised, exposed pathogen-associated molecular pattern molecules (PAMPs) could trigger host recognition and initiate attack against this fungus. Thus, cell wall composition and structure are tightly regulated. The cryptococcal cell wall is unusual in that chitosan, the acetylated form of chitin, is predominant over chitin and is essential for virulence. Recently, it was shown that acidic pH weakens the cell wall and increases exposure of PAMPs partly due to decreased chitosan levels. However, the molecular mechanism responsible for the cell wall remodeling in acidic pH is unknown. In this study, by screening for genes involved in cryptococcal tolerance to high levels of CO2, we serendipitously discovered that the aspartyl peptidase May1 contributes to cryptococcal sensitivity to high levels of CO2 due to acidification of unbuffered media. Overexpression of MAY1 increases the cryptococcal cell size and elevates PAMP exposure, causing a hyper-inflammatory response in the host while MAY1 deletion does the opposite. We discovered that May1 weakens the cell wall and reduces the chitosan level, partly due to its involvement in the degradation of Chs3, the sole chitin synthase that supplies chitin to be converted to chitosan. Consistently, overexpression of CHS3 largely rescues the phenotype of MAY1oe in acidic media. Collectively, we demonstrate that May1 remodels the cryptococcal cell wall in acidic pH by reducing chitosan levels through its influence on Chs3.

IMPORTANCE

The fungal cell wall is a dynamic structure, monitoring and responding to internal and external stimuli. It provides a formidable armor to the fungus. However, in a weakened state, the cell wall also triggers host immune attack when PAMPs, including glucan, chitin, and mannoproteins, are exposed. In this work, we found that the aspartyl peptidase May1 impairs the cell wall of Cryptococcus neoformans and increases the exposure of PAMPs in the acidic environment by reducing the chitosan level. Under acidic conditions, May1 is involved in the degradation of the chitin synthase Chs3, which supplies chitin to be deacetylated to chitosan. Consistently, the severe deficiency of chitosan in acidic pH can be rescued by overexpressing CHS3. These findings improve our understanding of cell wall remodeling and reveal a potential target to compromise the cell wall integrity in this important fungal pathogen.

A correlative study of the genomic underpinning of virulence traits and drug tolerance of Candida auris

Candida auris is an opportunistic fungal pathogen with high mortality rates which presents a clear threat to public health. The risk of C. auris infection is high because it can colonize the body, resist antifungal treatment, and evade the immune system. The genetic mechanisms for these traits are not well known. Identifying them could lead to new targets for new treatments. To this end, we present an analysis of the genetics and gene expression patterns of C. auris carbon metabolism, drug resistance, and macrophage interaction. We chose to study two C. auris isolates simultaneously, one drug sensitive (B11220 from Clade II) and one drug resistant (B11221 from Clade III). Comparing the genomes, we confirm the previously reported finding that B11220 was missing a 12.8 kb region on chromosome VI. This region contains a gene cluster encoding proteins related to alternative sugar utilization. We show that B11221, which has the gene cluster, readily assimilates and utilizes D-galactose and L-rhamnose as compared to B11220, which harbors the deletion. B11221 exhibits increased adherence and drug resistance compared to B11220 when grown in these sugars. Transcriptomic analysis of both isolates grown on glucose or galactose showed that the gene cluster was upregulated when grown on D-galactose. These findings reinforce growing evidence of a link between metabolism and drug tolerance. B11221 resists phagocytosis by macrophages and exhibits decreased β-1,3-glucan exposure, a key determinant that allows Candida to evade the host immune system, as compared to B11220. In a transcriptomic analysis of both isolates co-cultured with macrophages, we find upregulation of genes associated with transport and transcription factors in B11221. Our studies show a positive correlation between membrane composition and immune evasion, alternate sugar utilization, and drug tolerance in C. auris.

Differential alteration in Lactiplantibacillus plantarum subsp. plantarum quorum-sensing systems and reduced Candida albicans yeast survival and virulence gene expression in dual-species interaction

Candida albicans (C. albicans) and Lactiplantibacillus plantarum subsp. plantarum (L. plantarum) are frequently identified in various niches, but their dual-species interaction, especially with C. albicans in yeast form, remains unclear. This study aimed to investigate the dual-species interaction of L. plantarum and C. albicans, including proliferation, morphology, and transcriptomes examined by selective agar plate counting, microscopy, and polymicrobial RNA-seq, respectively. Maintaining a stable and unchanged growth rate, L. plantarum inhibited C. albicans yeast cell proliferation but not hyphal growth. Combining optical microscopy and atomic force microscopy, cell-to-cell direct contact and co-aggregation with L. plantarum cells surrounding C. albicans yeast cells were observed during dual-species interaction. Reduced C. albicans yeast cell proliferation in mixed culture was partially due to L. plantarum cell-free culture supernatant but not the acidic environment. Upon polymicrobial transcriptomics analysis, interesting changes were identified in both L. plantarum and C. albicans gene expression. First, two L. plantarum quorum-sensing systems showed contrary changes, with the activation of lamBDCA and repression of luxS. Second, the upregulation of stress response-related genes and downregulation of cell cycle, cell survival, and cell integrity-related pathways were identified in C. albicans, possibly connected to the stress posed by L. plantarum and the reduced yeast cell proliferation. Third, a large scale of pathogenesis and virulence factors were downregulated in C. albicans, indicating the potential interruption of pathogenic activities by L. plantarum. Fourth, partial metabolism and transport pathways were changed in L. plantarum and C. albicans. The information in this study might aid in understanding the behavior of L. plantarum and C. albicans in dual-species interaction.IMPORTANCEThe anti-Candida albicans activity of Lactiplantibacillus plantarum has been explored in the past decades. However, the importance of C. albicans yeast form and the effect of C. albicans on L. plantarum had also been omitted. In this study, the dual-species interaction of L. plantarum and C. albicans was investigated with a focus on the transcriptomes. Cell-to-cell direct contact and co-aggregation with L. plantarum cells surrounding C. albicans yeast cells were observed. Upon polymicrobial transcriptomics analysis, interesting changes were identified, including contrary changes in two L. plantarum quorum-sensing systems and reduced cell survival-related pathways and pathogenesis determinants in C. albicans.

Candida albicans and Candida glabrata: global priority pathogens

SUMMARYA significant increase in the incidence of Candida-mediated infections has been observed in the last decade, mainly due to rising numbers of susceptible individuals. Recently, the World Health Organization published its first fungal pathogen priority list, with Candida species listed in medium, high, and critical priority categories. This review is a synthesis of information and recent advances in our understanding of two of these species-Candida albicans and Candida glabrata. Of these, C. albicans is the most common cause of candidemia around the world and is categorized as a critical priority pathogen. C. glabrata is considered a high-priority pathogen and has become an increasingly important cause of candidemia in recent years. It is now the second most common causative agent of candidemia in many geographical regions. Despite their differences and phylogenetic divergence, they are successful as pathogens and commensals of humans. Both species can cause a broad variety of infections, ranging from superficial to potentially lethal systemic infections. While they share similarities in certain infection strategies, including tissue adhesion and invasion, they differ significantly in key aspects of their biology, interaction with immune cells, host damage strategies, and metabolic adaptations. Here we provide insights on key aspects of their biology, epidemiology, commensal and pathogenic lifestyles, interactions with the immune system, and antifungal resistance.

Candida albicans natural diversity: a resource to dissect fungal commensalism and pathogenesis

Candida albicans is a ubiquitous fungus of humans. It is not only a component of the oral and intestinal microbiota of most healthy adults but also a major cause of mucosal disorders and life-threatening disseminated infections. Until recently, research on the biology and pathogenesis of the fungus was largely based on a single clinical isolate. We review investigations that have started to dissect a diverse set of C. albicans strains. Using different approaches to leverage the species' phenotypic and/or genetic diversity, these studies illuminate the wide range of interactions between fungus and host. While connecting genetic variants to phenotypes of interest remains challenging, research on C. albicans' natural diversity is central to understand fungal commensalism and pathogenesis.

In Vitro Evaluation of the Virulence Attributes of Oropharyngeal Candida Species Isolated from People Living with Human Immunodeficiency Virus with Oropharyngeal Candidiasis on Antiretroviral Therapy

Background

Oropharyngeal Candida species are part commensal microflora in the the oral cavity of health individuals. Commensal Candida species can become opportunist and transition to pathogenic causes of oropharyngeal candidiasis (OPC) in individuals with impaired immunity through ecological cues and expression of virulence factors. Limited studies have evaluated virulence attributes of oropharyngeal Candida species among people living with human immunodeficiency virus (PLHIV) with OPC on antiretroviral therapy (ART) in Uganda.

Objective

Evaluation of the Virulence Attributes of Oropharyngeal Candida Species Isolated from People Living with Human Immunodeficiency Virus with Oropharyngeal Candidiasis on Antiretroviral Therapy.

Methods

Thirty-five (35) Candida isolates from PLHIV with OPC on ART were retrieved from sample repository and evaluated for phospholipase activity using the egg yolk agar method, proteinase activity using the bovine serum albumin agar method, hemolysin activity using the blood agar plate method, esterase activity using the Tween 80 opacity test medium method, coagulase activity using the classical tube method and biofilm formation using the microtiter plate assay method in vitro.

Results

Phospholipase and proteinase activities were detected in 33/35 (94.3%) and 31/35 (88.6%) of the strains, respectively. Up to 25/35 (71.4%) of the strains exhibited biofilm formation while esterase activity was demonstrated in 23/35 (65.7%) of the strains. Fewer isolates 21/35 (60%) of the strains produced hemolysin and coagulase production was the least virulence activity detected in 18/35 (51.4%).

Conclusion

Phospholipase and proteinase activities were the strongest virulence attributes of oropharyngeal Candida species.

Ascomycetes yeasts: The hidden part of human microbiome

The fungal component of the microbiota, the mycobiota, has been neglected for a long time due to its poor richness compared to bacteria. Limitations in fungal detection and taxonomic identification arise from using metagenomic approaches, often borrowed from bacteriome analyses. However, the relatively recent discoveries of the ability of fungi to modulate the host immune response and their involvement in human diseases have made mycobiota a fundamental component of the microbial communities inhabiting the human host, deserving some consideration in host-microbe interaction studies and in metagenomics. Here, we reviewed recent data on the identification of yeasts of the Ascomycota phylum across human body districts, focusing on the most representative genera, that is, Saccharomyces and Candida. Then, we explored the key factors involved in shaping the human mycobiota across the lifespan, ranging from host genetics to environment, diet, and lifestyle habits. Finally, we discussed the strengths and weaknesses of culture-dependent and independent methods for mycobiota characterization. Overall, there is still room for some improvements, especially regarding fungal-specific methodological approaches and bioinformatics challenges, which are still critical steps in mycobiota analysis, and to advance our knowledge on the role of the gut mycobiota in human health and disease. This article is categorized under: Immune System Diseases > Genetics/Genomics/Epigenetics Immune System Diseases > Environmental Factors Infectious Diseases > Environmental Factors.

Secreted Aspartic Proteinases: Key Factors in Candida Infections and Host-Pathogen Interactions

Extracellular proteases are key factors contributing to the virulence of pathogenic fungi from the genus Candida. Their proteolytic activities are crucial for extracting nutrients from the external environment, degrading host defenses, and destabilizing the internal balance of the human organism. Currently, the enzymes most frequently described in this context are secreted aspartic proteases (Saps). This review comprehensively explores the multifaceted roles of Saps, highlighting their importance in biofilm formation, tissue invasion through the degradation of extracellular matrix proteins and components of the coagulation cascade, modulation of host immune responses via impairment of neutrophil and monocyte/macrophage functions, and their contribution to antifungal resistance. Additionally, the diagnostic challenges associated with Candida infections and the potential of Saps as biomarkers were discussed. Furthermore, we examined the prospects of developing vaccines based on Saps and the use of protease inhibitors as adjunctive therapies for candidiasis. Given the complex biology of Saps and their central role in Candida pathogenicity, a multidisciplinary approach may pave the way for innovative diagnostic strategies and open new opportunities for innovative clinical interventions against candidiasis.

Repositioning of anti-infective compounds against monkeypox virus core cysteine proteinase: a molecular dynamics study

Monkeypox virus (MPXV) core cysteine proteinase (CCP) is one of the major drug targets used to examine the inhibitory action of chemical moieties. In this study, an in silico technique was applied to screen 1395 anti-infective compounds to find out the potential molecules against the MPXV-CCP. The top five hits were selected after screening and processed for exhaustive docking based on the docked score of ≤ -9.5 kcal/mol. Later, the top three hits based on the exhaustive-docking score and interaction profile were selected to perform MD simulations. The overall RMSD suggested that two compounds, SC75741 and ammonium glycyrrhizinate, showed a highly stable complex with a standard deviation of 0.18 and 0.23 nm, respectively. Later, the MM/GBSA binding free energies of complexes showed significant binding strength with ΔGTOTAL from -21.59 to -15 kcal/mol. This report reported the potential inhibitory activity of SC75741 and ammonium glycyrrhizinate against MPXV-CCP by competitively inhibiting the binding of the native substrate.

Unveiling the menace: a thorough review of potential pandemic fungal disease

Fungal diseases have emerged as a significant global health threat, with the potential to cause widespread outbreaks and significant morbidity and mortality. Anticipating future pandemic fungal diseases is essential for effective preparedness and response strategies. This comprehensive literature review aims to provide a comprehensive analysis of the existing research on this topic. Through an extensive examination of scholarly articles, this review identifies potential fungal pathogens that have the potential to become pandemics in the future. It explores the factors contributing to the emergence and spread of these fungal diseases, including climate change, globalization, and antimicrobial resistance. The review also discusses the challenges in diagnosing and treating these diseases, including limited access to diagnostic tools and antifungal therapies. Furthermore, it examines the strategies and interventions that can be employed to mitigate the impact of future pandemic fungal diseases, such as improved surveillance systems, public health education, and research advancements. The findings of this literature review contribute to our understanding of the potential risks posed by fungal diseases and provide valuable insights for public health professionals and policymakers in effectively preparing for and responding to future pandemic outbreaks. Overall, this review emphasizes the importance of proactive measures and collaborative efforts to anticipate and mitigate the impact of future pandemic fungal diseases.

Transcriptomic meta-analysis to identify potential antifungal targets in Candida albicans

BACKGROUND

Candida albicans is a fungal pathogen causing human infections. Here we investigated differential gene expression patterns and functional enrichment in C. albicans strains grown under different conditions.

METHODS

A systematic GEO database search identified 239 "Candida albicans" datasets, of which 14 were selected after rigorous criteria application. Retrieval of raw sequencing data from the ENA database was accompanied by essential metadata extraction from dataset descriptions and original articles. Pre-processing via the tailored nf-core pipeline for C. albicans involved alignment, gene/transcript quantification, and diverse quality control measures. Quality assessment via PCA and DESeq2 identified significant genes (FDR < = 0.05, log2-fold change > = 1 or <= -1), while topGO conducted GO term enrichment analysis. Exclusions were made based on data quality and strain relevance, resulting in the selection of seven datasets from the SC5314 strain background for in-depth investigation.

RESULTS

The meta-analysis of seven selected studies unveiled a substantial number of genes exhibiting significant up-regulation (24,689) and down-regulation (18,074). These differentially expressed genes were further categorized into 2,497 significantly up-regulated and 2,573 significantly down-regulated Gene Ontology (GO) IDs. GO term enrichment analysis clustered these terms into distinct groups, providing insights into the functional implications. Three target gene lists were compiled based on previous studies, focusing on central metabolism, ion homeostasis, and pathogenicity. Frequency analysis revealed genes with higher occurrence within the identified GO clusters, suggesting their potential as antifungal targets. Notably, the genes TPS2, TPS1, RIM21, PRA1, SAP4, and SAP6 exhibited higher frequencies within the clusters. Through frequency analysis within the GO clusters, several key genes emerged as potential targets for antifungal therapies. These include RSP5, GLC7, SOD2, SOD5, SOD1, SOD6, SOD4, SOD3, and RIM101 which exhibited higher occurrence within the identified clusters.

CONCLUSION

This comprehensive study significantly advances our understanding of the dynamic nature of gene expression in C. albicans. The identification of genes with enhanced potential as antifungal drug targets underpins their value for future interventions. The highlighted genes, including TPS2, TPS1, RIM21, PRA1, SAP4, SAP6, RSP5, GLC7, SOD2, SOD5, SOD1, SOD6, SOD4, SOD3, and RIM101, hold promise for the development of targeted antifungal therapies.

Aspartyl protease in the secretome of honey bee trypanosomatid parasite contributes to infection of bees

BACKGROUND

The exoproteome, which consists of both secreted proteins and those originating from cell surfaces and lysed cells, is a critical component of trypanosomatid parasites, facilitating interactions with host cells and gut microbiota. However, its specific roles in the insect hosts of these parasites remain poorly understood.

METHODS

We conducted a comprehensive characterization of the exoproteome in Lotmaria passim, a trypanosomatid parasite infecting honey bees, under culture conditions. We further investigated the functions of two conventionally secreted proteins, aspartyl protease (LpAsp) and chitinase (LpCht), as representative models to elucidate the role of the secretome in L. passim infection of honey bees.

RESULTS

Approximately 48% of L. passim exoproteome proteins were found to share homologs with those found in seven Leishmania spp., suggesting the existence of a core exoproteome with conserved functions in the Leishmaniinae lineage. Bioinformatics analyses suggested that the L. passim exoproteome may play a pivotal role in interactions with both the host and its microbiota. Notably, the deletion of genes encoding two secretome proteins revealed the important role of LpAsp, but not LpCht, in L. passim development under culture conditions and its efficiency in infecting the honey bee gut.

CONCLUSIONS

Our results highlight the exoproteome as a valuable resource for unraveling the mechanisms employed by trypanosomatid parasites to infect insect hosts by interacting with the gut environment.

Promising immunotherapeutic targets for treating candidiasis

In the last twenty years, there has been a significant increase in invasive fungal infections, which has corresponded with the expanding population of individuals with compromised immune systems. As a result, the mortality rate linked to these infections remains unacceptably high. The currently available antifungal drugs, such as azoles, polyenes, and echinocandins, face limitations in terms of their diversity, the escalating resistance of fungi and the occurrence of significant adverse effects. Consequently, there is an urgent need to develop new antifungal medications. Vaccines and antibodies present a promising avenue for addressing fungal infections due to their targeted antifungal properties and ability to modulate the immune response. This review investigates the structure and function of cell wall proteins, secreted proteins, and functional proteins within C. albicans. Furthermore, it seeks to analyze the current advancements and challenges in macromolecular drugs to identify new targets for the effective management of candidiasis.

Macrophage pyroptosis induced by Candida albicans

Candida albicans (C. albicans) is a prevalent opportunistic pathogen that causes mucocutaneous and systemic infections, particularly in immunocompromised individuals. Macrophages play a crucial role in eliminating C. albicans in local and bloodstream contexts, while also regulating antifungal immune responses. However, C. albicans can induce macrophage lysis through pyroptosis, a type of regulated cell death. This process can enable C. albicans to escape from immune cells and trigger the release of IL-1β and IL-18, which can impact both the host and the pathogen. Nevertheless, the mechanisms by which C. albicans triggers pyroptosis in macrophages and the key factors involved in this process remain unclear. In this review, we will explore various factors that may influence or trigger pyroptosis in macrophages induced by C. albicans, such as hypha, ergosterol, cell wall remodeling, and other virulence factors. We will also examine the possible immune response following macrophage pyroptosis.

A comprehensive guide to assess gut mycobiome and its role in pathogenesis and treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD) is an immune mediated chronic inflammatory disorder of gastrointestinal tract, which has underlying multifactorial pathogenic determinants such as environmental factors, susceptibility genes, gut microbial dysbiosis and a dysregulated immune response. Human gut is a frequent inhabitant of complex microbial ecosystem encompassing bacteria, viruses, parasites, fungi and other microorganisms that have an undisputable role in maintaining balanced homeostasis. All of these microbes interact with immune system and affect human gut physiology either directly or indirectly with interaction of each other. Intestinal fungi represent a smaller but crucial component of the human gut microbiome. Besides interaction with bacteriome and virome, it helps in balancing homoeostasis between pathophysiological and physiological processes, which is often dysregulated in patients with IBD. Understanding of gut mycobiome and its clinical implications are still in in its infancy as opposed to bacterial component of gut microbiome, which is more often focused. Modulation of gut mycobiome represents a novel and promising strategy in the management of patients with IBD. Emerging mycobiome-based therapies such as diet interventions, fecal microbiota transplantation (FMT), probiotics (both fungal and bacterial strains) and antifungals exhibit substantial effects in calibrating the gut mycobiome and restoring dysbalanced immune homeostasis by restoring the core gut mycobiome. In this review, we summarized compositional and functional diversity of the gut mycobiome in healthy individuals and patients with IBD, gut mycobiome dysbiosis in patients with IBD, host immune-fungal interactions and therapeutic role of modulation of intestinal fungi in patients with IBD.

Bibliometric analysis and thematic review of Candida pathogenesis: Fundamental omics to applications as potential antifungal drugs and vaccines

Invasive candidiasis caused by the pathogenic Candida yeast species has resulted in elevating global mortality. The pathogenicity of Candida spp. is not only originated from its primary invasive yeast-to-hyphal transition; virulence factors (transcription factors, adhesins, invasins, and enzymes), biofilm, antifungal drug resistance, stress tolerance, and metabolic adaptation have also contributed to a greater clinical burden. However, the current research theme in fungal pathogenicity could hardly be delineated with the increasing research output. Therefore, our study analysed the research trends in Candida pathogenesis over the past 37 years via a bibliometric approach against the Scopus and Web of Science databases. Based on the 3993 unique documents retrieved, significant international collaborations among researchers were observed, especially between Germany (Bernhard Hube) and the UK (Julian Naglik), whose focuses are on Candida proteinases, adhesins, and candidalysin. The prominent researchers (Neils Gow, Alistair Brown, and Frank Odds) at the University of Exeter and the University of Aberdeen (second top performing affiliation) UK contribute significantly to the mechanisms of Candida adaptation, tolerance, and stress response. However, the science mapping of co-citation analysis performed herein could not identify a hub representative of subsequent work since the clusters were semi-redundant. The co-word analysis that was otherwise adopted, revealed three research clusters; the cluster-based thematic analyses indicated the severeness of Candida biofilm and antifungal resistance as well as the elevating trend on molecular mechanism elucidation for drug screening and repurposing. Importantly, the in vivo pathogen adaptation and interactions with hosts are crucial for potential vaccine development.

A Malassezia pseudoprotease dominates the secreted hydrolase landscape and is a potential allergen on skin

Malassezia globosa is abundant and prevalent on sebaceous areas of the human skin. Genome annotation reveals that M. globosa possesses a repertoire of secreted hydrolytic enzymes relevant for lipid and protein metabolism. However, the functional significance of these enzymes is uncertain and presence of these genes in the genome does not always translate to expression at the cutaneous surface. In this study we utilized targeted RNA sequencing from samples isolated directly from the skin to quantify gene expression of M. globosa secreted proteases, lipases, phospholipases and sphingomyelinases. Our findings indicate that the expression of these enzymes is dynamically regulated by the environment in which the fungus resides, as different growth phases of the planktonic culture of M. globosa show distinct expression levels. Furthermore, we observed significant differences in the expression of these enzymes in culture compared to healthy sebaceous skin sites. By examining the in situ gene expression of M. globosa's secreted hydrolases, we identified a predicted aspartyl protease, MGL_3331, which is highly expressed on both healthy and disease-affected dermatological sites. However, molecular modeling and biochemical studies revealed that this protein has a non-canonical active site motif and lacks measurable proteolytic activity. This pseudoprotease MGL_3331 elicits a heightened IgE-reactivity in blood plasma isolated from patients with atopic dermatitis compared to healthy individuals and invokes a pro-inflammatory response in peripheral blood mononuclear cells. Overall, our study highlights the importance of studying fungal proteins expressed in physiologically relevant environments and underscores the notion that secreted inactive enzymes may have important functions in influencing host immunity.

Revealing anti-fungal potential of plant-derived bioactive therapeutics in targeting secreted aspartyl proteinase (SAP) of Candida albicans: a molecular dynamics approach

Candida species have established themselves as a major source of nosocomial infections. Increased expression of secreted aspartyl proteinases (SAP5) plays a crucial role in the pathogenesis of Candida species. Phytotherapeutics continue to serve as a viable resource for discovering novel antifungal agents. Hence the main aim of the present investigation is to explore the possible inhibitory role of the selected bioactive molecules against the SAP5 enzyme of C. albicans using in silico approach. Molecular docking and dynamic simulations were utilized to predict the binding affinity of the lead molecules using the AutoDock and Gromacs in-silico screening tools. Results of preliminary docking simulations show that the compounds hesperidin, vitexin, berberine, adhatodine, piperine, and chlorogenic acid exhibit significant interactions with the core catalytic residues of the target protein. The best binding ligands (hesperidin, vitexin, fluconazole) were subjected to molecular dynamics (MD) and essential dynamics of the trajectories. Results of the MD simulation confirm that the ligand-protein complexes became more stable from 20 ns until 100 ns. The calculated residue-level contributions to the interaction energy along a steady simulation trajectory of all three hits (hesperidin (-132.720 kJ/mol), vitexin (-83.963 kJ/mol) and fluconazole (-98.864 kJ/mol)) ensure greater stability of the leads near the catalytic region. Essential dynamics of PCA and DCCM analysis signifies that the binding of hesperidin and vitexin created a more structurally stable environment in the protein target. The overall outcomes of this study clearly emphasize that the bioactive therapeutics found in medicinal herbs may have remarkable scope in managing Candida infection.

RNA-Seq-Based Transcriptomics and GC-MS Quantitative Analysis Reveal Antifungal Mechanisms of Essential Oil of Clausena lansium (Lour.) Skeels Seeds against Candida albicans

Infections caused by Candida albicans (C. albicans) and increasing resistance to commonly used drugs lead to a variety of mucosal diseases and systemic infectious diseases. We previously confirmed that the essential oil of Clausena lansium (Lour.) Skeels seeds (CSEO) had antifungal activity against C. albicans, but the detailed mechanism between the chemical components and antifungal activity is unclear. In this study, a quantitative analysis of five volatile components of CSEO, including sabinene, α-phellandrene, β-phellandrene, 4-terpineol, and β-caryophyllene, was carried out using the gas chromatography-mass spectrometry (GC-MS) method. Both the broth dilution and kinetic growth methods proved that the antifungal activity of CSEO against fluconazole-resistant C. albicans was better than that of its main components (sabinene and 4-terpineol). To further investigate the inhibitory mechanism, the transcriptional responses of C. albicans to CSEO, sabinene, and 4-terpineol treatment were determined based on RNA-seq. The Venn diagram and clustering analysis pattern of differential expression genes showed the mechanism of CSEO and 4-terpineol's anti-C. albicans activity might be similar from the perspective of the genes. Functional enrichment analysis suggested that CSEO regulated adherence-, hyphae-, and biofilm-formation-related genes, which may be CSEO's active mechanism of inhibiting the growth of fluconazole-resistant C. albicans. Overall, we preliminarily revealed the molecular mechanism between the chemical components and the antifungal activity of CSEO against C. albicans. This study provides new insights to overcome the azole resistance of C. albicans and promote the development and application of C. lansium (Lour.) Skeels seeds.

Enhancement of antifungal activity and transdermal delivery of 5-flucytosine via tailored spanlastic nanovesicles: statistical optimization, in-vitro characterization, and in-vivo biodistribution study

Aim and background: This current study aimed to load 5-flucytosine (5-FCY) into spanlastic nanovesicles (SPLNs) to make the drug more efficient as an antifungal and also to load the 5-FCY into a hydrogel that would allow for enhanced transdermal permeation and improved patient compliance. Methods: The preparation of 5-FCY-SPLNs was optimized by using a central composite design that considered Span 60 (X1) and the edge activator Tween 80 (X2) as process variables in achieving the desired particle size and entrapment efficiency. A formulation containing 295.79 mg of Span 60 and 120.00 mg of Tween 80 was found to meet the prerequisites of the desirability method. The optimized 5-FCY-SPLN formulation was further formulated into a spanlastics gel (SPG) so that the 5-FCY-SPLNs could be delivered topically and characterized in terms of various parameters. Results: As required, the SPG had the desired elasticity, which can be credited to the physical characteristics of SPLNs. An ex-vivo permeation study showed that the greatest amount of 5-FCY penetrated per unit area (Q) (mg/cm2) over time and the average flux (J) (mg/cm2/h) was at the end of 24 h. Drug release studies showed that the drug continued to be released until the end of 24 h and that the pattern was correlated with an ex-vivo permeation and distribution study. The biodistribution study showed that the 99mTc-labeled SFG that permeated the skin had a steadier release pattern, a longer duration of circulation with pulsatile behavior in the blood, and higher levels in the bloodstream than the oral 99mTc-SPNLs. Therefore, a 5-FCY transdermal hydrogel could possibly be a long-acting formula for maintenance treatment that could be given in smaller doses and less often than the oral formula.

Unveiling the mechanism of action of acylated temporin L analogues against multidrug-resistant Candida albicans

The increasing resistance of fungi to conventional antifungal drugs has prompted worldwide the search for new compounds. In this work, we investigated the antifungal properties of acylated Temporin L derivatives, Pent-1B and Dec-1B, against Candida albicans, including the multidrug-resistant strains. Acylated peptides resulted to be active both on reference and clinical strains with MIC values ranging from 6.5 to 26 µM, and they did not show cytotoxicity on human keratinocytes. In addition, we also observed a synergistic or additive effect with voriconazole for peptides Dec-1B and Pent-1B through the checkerboard assay on voriconazole-resistant Candida strains. Moreover, fluorescence-based assays, NMR spectroscopy, and confocal microscopy elucidated a potential membrane-active mechanism, consisting of an initial electrostatic interaction of acylated peptides with fungal membrane, followed by aggregation and insertion into the lipid bilayer and causing membrane perturbation probably through a carpeting effect.

Dual Antifungal and Antiproliferative Activities of a Novel Protein Fraction from a Medicinally Important Herb Trillium govanianum Wall. ex. D. Don

Antimicrobial resistance of microorganisms and the unwanted side effects of chemoradiation therapy in cancer are major issues in healthcare. In recent times, protein-based drugs have emerged as promising candidates due to their high specificity, less side effects, etc. In this context, the rhizome of Trillium govanianum was first explored for biologically active proteins/peptides. For this, three protein fractions namely Aqueous protein fraction (APF), Hexane-Methanol-treated aqueous protein fraction (HMAPF), and Methanol-treated aqueous protein fraction (MAPF) were prepared and evaluated for antimicrobial and antiproliferative activities. In antifungal activity, HMAPF showed the lowest MIC90 values of 1.56 µg/ml against Candida parapsilosis and Candida glabrata and 3.12 µg/ml against Candida albicans and Candida auris. The antifungal activity was further confirmed by a chitinase assay, a growth kinetics and a proteinase inhibitory assay. Surprisingly, none of the three protein fractions exhibited antibacterial activity against Escherichia coli and Staphylococcus aureus. Moreover, APF exhibited potent antiproliferative and antioxidant activities with IC50 values of 18 µg/ml and 227 µg /ml, respectively. For HMAPF, an IC50 value of 70 µg/ml against the MDA-MB-231 cell line was observed. The present results demonstrate that the protein fractions, particularly HMAPF and APF, might serve as potential sources of a dual antifungal and antiproliferative protein-based drug.

Development and Validation of a Model for Postpancreatectomy Hemorrhage Risk

Importance

Postpancreatectomy hemorrhage (PPH) due to postoperative pancreatic fistula (POPF) is a life-threatening complication after pancreatoduodenectomy. However, there is no prediction tool for early identification of patients at high risk of late PPH.

Objective

To develop and validate a prediction model for PPH.

Design, Setting, and Participants

This retrospective prognostic study included consecutive patients with clinically relevant POPF who underwent pancreatoduodenectomy from January 1, 2009, to May 20, 2023, at the University Hospital Mannheim (derivation cohort), and from January 1, 2012, to May 31, 2022, at the University Hospital Dresden (validation cohort). Data analysis was performed from May 30 to July 29, 2023.

Exposure

Clinical and radiologic features of PPH.

Main Outcomes and Measures

Accuracy of a predictive risk score of PPH. A multivariate prediction model-the hemorrhage risk score (HRS)-was established in the derivation cohort (n = 139) and validated in the validation cohort (n = 154).

Results

A total of 293 patients (187 [64%] men; median age, 69 [IQR, 60-76] years) were included. The HRS comprised 4 variables with associations: sentinel bleeding (odds ratio [OR], 35.10; 95% CI, 5.58-221.00; P < .001), drain fluid culture positive for Candida species (OR, 14.40; 95% CI, 2.24-92.20; P < .001), and radiologic proof of rim enhancement of (OR, 12.00; 95% CI, 2.08-69.50; P = .006) or gas within (OR, 12.10; 95% CI, 2.22-65.50; P = .004) a peripancreatic fluid collection. Two risk categories were identified with patients at low risk (0-1 points) and high risk (≥2 points) to develop PPH. Patients with PPH were predicted accurately in the derivation cohort (C index, 0.97) and validation cohort (C index 0.83). The need for more invasive PPH management (74% vs 34%; P < .001) and severe complications (49% vs 23%; P < .001) were more frequent in high-risk patients compared with low-risk patients.

Conclusions and Relevance

In this retrospective prognostic study, a robust prediction model for PPH was developed and validated. This tool may facilitate early identification of patients at high risk for PPH.

Activatable prodrug for controlled release of an antimicrobial peptide via the proteases overexpressed in Candida albicans and Porphyromonas gingivalis

We report the controlled release of an antimicrobial peptide using enzyme-activatable prodrugs to treat and detect Candida albicans and Porphyromonas gingivalis . Our motivation lies in the prevalence of these microorganisms in the subgingival area where the frequency of fungal colonization increases with periodontal disease. This work is based on an antimicrobial peptide that is both therapeutic and induces a color change in a nanoparticle reporter. This antimicrobial peptide was then built into a zwitterionic prodrug that quenches its activity until activation by a protease inherent to these pathogens of interest: SAP9 or RgpB for C. albicans and P. gingivalis , respectively. We first confirmed that the intact zwitterionic prodrug has negligible toxicity to fungal, bacterial, and mammalian cells absent a protease trigger. Next, the therapeutic impact was assessed via disk diffusion and viability assays and showed a minimum inhibitory concentration of 3.1 - 16 µg/mL, which is comparable to the antimicrobial peptide alone (absent integration into prodrug). Finally, the zwitterionic design was exploited for colorimetric detection of C. albicans and P. gingivalis proteases. When the prodrugs were cleaved, the plasmonic nanoparticles aggregated causing a color change with a limit of detection of 10 nM with gold nanoparticles and 3 nM with silver nanoparticles. This approach has value as a convenient and selective protease sensing and protease-induced treatment mechanism based on bioinspired antimicrobial peptides.

Abstract Figure

Toll-like receptor 4 and CD11b expressed on microglia coordinate eradication of Candida albicans cerebral mycosis

The fungal pathogen Candida albicans is linked to chronic brain diseases such as Alzheimer's disease (AD), but the molecular basis of brain anti-Candida immunity remains unknown. We show that C. albicans enters the mouse brain from the blood and induces two neuroimmune sensing mechanisms involving secreted aspartic proteinases (Saps) and candidalysin. Saps disrupt tight junction proteins of the blood-brain barrier (BBB) to permit fungal brain invasion. Saps also hydrolyze amyloid precursor protein (APP) into amyloid β (Aβ)-like peptides that bind to Toll-like receptor 4 (TLR4) and promote fungal killing in vitro while candidalysin engages the integrin CD11b (Mac-1) on microglia. Recognition of Aβ-like peptides and candidalysin promotes fungal clearance from the brain, and disruption of candidalysin recognition through CD11b markedly prolongs C. albicans cerebral mycosis. Thus, C. albicans is cleared from the brain through innate immune mechanisms involving Saps, Aβ, candidalysin, and CD11b.

The Yeast and Hypha Phases of Candida krusei Induce the Apoptosis of Bovine Mammary Epithelial Cells via Distinct Signaling Pathways

Infection with Candida spp. is a significant cause of bovine mastitis globally. We previously found that C. krusei was the main pathogen causing mycotic mastitis in dairy cows in Yinchuan, Ningxia, China. However, whether the infection of this pathogen could induce apoptosis in BMECs remained unclear. In this report, we explored the apoptosis and underlying mechanism of BMECs induced by C. krusei yeast and hypha phases using a pathogen/host cell co-culture model. Our results revealed that both the yeast and hypha phases of C. krusei could induce BMEC apoptosis; however, the yeast phase induced more cell apoptosis than the hypha phase, as assessed via electronic microscopy and flow cytometry assays. This finding was further corroborated via the measurement of the mitochondrial membrane potential (MMP) and the TUNEL test. Infection by both the yeast and hypha phases of C. krusei greatly induced the expression of proteins associated with cell death pathways and important components of toll-like receptor (TLR) signaling, including TLR2 and TLR4 receptors, as determined via a Western blotting assay. BMECs mainly underwent apoptosis after infection by the C. krusei yeast phase through a mitochondrial pathway. Meanwhile, BMEC apoptosis induced by the C. krusei hypha phase was regulated by a death ligand/receptor pathway. In addition, C. krusei-induced BMEC apoptosis was regulated by both the TLR2/ERK and JNK/ERK signaling pathways. These data suggest that the yeast phase and hypha phase of C. krusei induce BMEC apoptosis through distinct cell signaling pathways. This study represents a unique perspective on the molecular processes underlying BMEC apoptosis in response to C. krusei infection.

Molecular association of Candida albicans and vulvovaginal candidiasis: focusing on a solution

Candida albicans-mediated vulvovaginal candidiasis (VVC) is a significant challenge in clinical settings, owing to the inefficacy of current antifungals in modulating virulence, development of resistance, and poor penetration into the biofilm matrix. Various predisposition factors are molecular drivers that lead to the dysbiosis of normal microflora of the vagina, upregulation of central metabolic pathways, morphogenesis, hyphal extension, adhesion, invasion, and biofilm formation leading to chronic infection and recurrence. Hence, it is crucial to understand the molecular mechanism behind the virulence pathways driven by those drivers to decode the drug targets. Finding innovative solutions targeting fungal virulence/biofilm may potentiate the antifungals at low concentrations without affecting the recurrence of resistance. With this background, the present review details the critical molecular drivers and associated network of virulence pathways, possible drug targets, target-specific inhibitors, and probable mode of drug delivery to cross the preclinical phase by appropriate in vivo models.

Secreted aspartyl protease 3 regulated by the Ras/cAMP/PKA pathway promotes the virulence of Candida auris

The surge of multidrug-resistant fungal pathogens, especially Candida auris, poses significant threats to global public health. Candida auris exhibits resistance to multiple antifungal drugs, leading to major outbreaks and a high mortality rate. With an urgent call for innovative therapeutic strategies, this study focused on the regulation and pathobiological significance of secreted aspartyl proteinases (SAPs) in C. auris, as these enzymes play pivotal roles in the virulence of some fungal species. We delved into the Ras/cAMP/PKA signaling pathway's influence on SAP activity in C. auris. Our findings underscored that the Ras/cAMP/PKA pathway significantly modulates SAP activity, with PKA catalytic subunits, Tpk1 and Tpk2, playing a key role. We identified a divergence in the SAPs of C. auris compared to Candida albicans, emphasizing the variation between Candida species. Among seven identified secreted aspartyl proteases in C. auris (Sapa1 to Sapa7), Sapa3 emerged as the primary SAP in the pathogen. Deletion of Sapa3 led to a significant decline in SAP activity. Furthermore, we have established the involvement of Sapa3 in the biofilm formation of C. auris. Notably, Sapa3 was primarily regulated by Tpk1 and Tpk2. Deletion of SAPA3 significantly reduced C. auris virulence, underscoring its pivotal role in C. auris pathogenicity. The outcomes of this study provide valuable insights into potential therapeutic targets, laying the groundwork for future interventions against C. auris infection.

Antifungal Efficacy of Antimicrobial Peptide Octominin II against Candida albicans

Most clinically isolated Candida albicans strains are drug-resistant, emphasizing the urgent need to discover alternative therapies. In this study, the previously characterized Octominin was modified into a shorter peptide with an 18 amino acid sequence (1GWLIRGAIHAGKAIHGLI18) and named Octominin II. The secondary structure of Octominin II is a random coil with a helical turn and a positive charge (+2.46) with a hydrophobic ratio of 0.46. Octominin II inhibited C. albicans, C. auris, and C. glabrata with minimum inhibitory and fungicidal concentrations against C. albicans of 80 and 120 µg/mL, respectively. Field emission scanning electron microscopy confirmed that Octominin II treatment caused ultra-structural changes in C. albicans cells. Furthermore, membrane permeability results for the fluorescent indicator propidium iodide revealed modifications in cell wall integrity in Octominin II-treated C. albicans. Octominin II treatment increases the production of reactive oxygen species (ROS) in C. albicans. Gene expression studies revealed that Octominin II suppresses virulence genes of C. albicans such as CDR1, TUP1, AGE3, GSC1, SAP2, and SAP9. In addition, a nucleic acid binding assay revealed that Octominin II degraded genomic DNA and total RNA in a concentration-dependent manner. Additionally, Octominin II inhibited and eradicated C. albicans biofilm formation. Octominin II showed relatively less cytotoxicity on raw 264.7 cells (0-200 µg/mL) and hemolysis activity on murine erythrocytes (6.25-100 µg/mL). In vivo studies confirmed that Octominin II reduced the pathogenicity of C. albicans. Overall, the data suggests that Octominin II inhibits C. albicans by employing different modes of action and can be a promising candidate for controlling multidrug-resistant Candida infections.

Plasma activated Ezhangfeng Cuji as innovative antifungal agent and its inactivation mechanism

Candida albicans is a highly drug-resistant fungus for which new treatments are urgently needed due to the lack of clinically effective options. In this study, we evaluated the antifungal activity and mechanism of plasma-activated Ezhangfeng Cuji (PAEC) against Candida albicans and compared it with physiological saline (PS), plasma-activated physiological saline (PAPS) and Ezhangfeng Cuji (EC). After dielectric barrier discharge (DBD) plasma treatment with EC for 20 min followed by a 10 min immersion of Candida albicans, the fungus was reduced by approximately 3 orders of magnitude. High performance liquid chromatography (HPLC) results showed an increase of 41.18% and 129.88% in the concentration of oxymatrine and rhein, respectively, after plasma-treated EC. The concentrations of reactive species (RS), such as H₂O₂, [Formula: see text], and O₃, were found to be higher and the pH value was getting lower in PS after plasma treatment. Detailed analysis of intracellular material leakage, reactive oxygen species (ROS), apoptosis for Candida albicans and observation by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) demonstrated that PAPS, EC and PAEC disrupt the morphological structure of Candida albicans to varying degrees.Additionally, specific analyses on Candida albicans virulence factors, such as adhesion to tissue surfaces, cell surface hydrophobicity (CSH), the transition of yeast-phase cells to mycelium-phase cells, and the secretion of hydrolytic enzymes for Candida albicans were conducted and found to be inhibited after PAPS/EC/PAEC treatment. In our investigation, the inhibitory effects on Candida albicans were ranked from strong to weak as follows: PAEC, EC, PAPS, and PS.

Phenotypic and genetic features of a novel clinically isolated rough morphotype Candida auris

Introduction

Candida auris is a newly emerging pathogenic fungus of global concern and has been defined by the World Health Organization (WHO) as a member of the critical group of the most health-threatening fungi.

Methods

This study reveals and reports for the first time that a rough morphotype C. auris strain causes urinary tract infections in non-intensive care unit (ICU) inpatients. Furthermore, the morphology, the scanning electronmicroscopy (SEM), Whole-genome resequencing and RNA sequencing of C. auris possessing rough morphotype colonies compared to their smooth morphotype counterparts.

Results

The newly identified phenotypic variation of C. auris appears round, convex, dry, and burr-like with a rough texture. SEM shows that rough type C. auris has a rough and uneven colony surface with radial wrinkles and irregular spore arrangement. Cells of the rough morphotype C. auris naturally aggregate into clusters with tight connections in the liquid, and it seems that the cell division is incomplete. A genome-wide analysis of the rough type C. auris confirmed its genetic association with the smooth type of C. auris prevalent in China (Shenyang) two years ago; however, single nucleotide polymorphism (SNP) mutations of five genes (ACE2, IFF6, RER2, UTP20, and CaO19.5847) were identified more recently. RNA-seq revealed IFF2/HYR3, DAL5, PSA31, and SIT1 were notably up-regulated, while multiple cell wall-associated genes (ALS1, MNN1, PUL1, DSE1, SCW11, PGA38, RBE1, FGR41, BGLI, GIT3, CEP3, and SAP2) were consistently down-regulated in rough morphotype C. auris.

Discussion

The rough phenotypic variation of C. auris is likely to be related to the structural and functional changes in cell wall proteins. This novel rough morphotype C. auris will provide a basis for further studies concerning the evolutionary characteristics of C. auris.

Vitamin D3: A promising antifungal and antibiofilm agent against Candida species

Background and Purpose

Candida species are opportunistic fungal pathogens that cause mild to life-threatening infections in both immunocompetent and immunocompromised populations. The increasing prevalence of drug-resistant Candida species has posed a significant challenge to the management of infections in clinical settings. Therefore, this study aimed to investigate the direct antifungal and antibiofilm effect of vitamin D3 against Candida species.

Materials and Methods

The antifungal activity of vitamin D3 was evaluated by broth microdilution method based on the Clinical and Laboratory Standard Institute. Prevention of biofilm formation by Candida albicans was measured using the XTT assay following exposure to different concentrations of vitamin D3. Moreover, expression of Agglutinin-like sequence gene 1 (ALS1), hyphal wall protein gene (HWP1), secreted aspartyl proteinase 6 gene (SAP6), and morphogenesis pathway regulatory gene (EFG1) were analyzed by real-time polymerase chain reaction using the comparative Ct method (ΔΔ Ct) after exposure to vitamin D3.

Results

Vitamin D3 showed antifungal activity against Candida species ranging from 1-128 μg/mL. Furthermore, vitamin D3 inhibited biofilm formation in a dose-dependent manner, with IC50 of 7.5 μg/mL. Treatment with vitamin D3 resulted in significant upregulation of the EFG1, ALS1, and SAP6 genes under hypha-inducing conditions to overcome environmental challenges.

Conclusion

Results of the current study demonstrated that vitamin D3 has a significant inhibitory effect on Candida growth and biofilm formation. Considering its demonstrated antifungal and antibiofilm properties, vitamin D3 holds promise as a potential agent for medical applications.

Association of polymicrobial interactions with dental caries development and prevention

Dental caries is a common oral disease. In many cases, disruption of the ecological balance of the oral cavity can result in the occurrence of dental caries. There are many cariogenic microbiota and factors, and their identification allows us to take corresponding prevention and control measures. With the development of microbiology, the caries-causing bacteria have evolved from the traditional single Streptococcus mutans to the discovery of oral symbiotic bacteria. Thus it is necessary to systematically organized the association of polymicrobial interactions with dental caries development. In terms of ecology, caries occurs due to an ecological imbalance of the microbiota, caused by the growth and reproduction of cariogenic microbiota due to external factors or the disruption of homeostasis by one's own factors. To reduce the occurrence of dental caries effectively, and considering the latest scientific viewpoints, caries may be viewed from the perspective of ecology, and preventive measures can be taken; hence, this article systematically summarizes the prevention and treatment of dental caries from the aspects of ecological perspectives, in particular the ecological biofilm formation, bacterial quorum sensing, the main cariogenic microbiota, and preventive measures.

Integrated post-genomic cell wall analysis reveals floating biofilm formation associated with high expression of flocculins in the pathogen Pichia kudriavzevii

The pathogenic yeast Pichia kudriavzevii, previously known as Candida krusei, is more distantly related to Candida albicans than clinically relevant CTG-clade Candida species. Its cell wall, a dynamic organelle that is the first point of interaction between pathogen and host, is relatively understudied, and its wall proteome remains unidentified to date. Here, we present an integrated study of the cell wall in P. kudriavzevii. Our comparative genomic studies and experimental data indicate that the general structure of the cell wall in P. kudriavzevii is similar to Saccharomyces cerevisiae and C. albicans and is comprised of β-1,3-glucan, β-1,6-glucan, chitin, and mannoproteins. However, some pronounced differences with C. albicans walls were observed, for instance, higher mannan and protein levels and altered protein mannosylation patterns. Further, despite absence of proteins with high sequence similarity to Candida adhesins, protein structure modeling identified eleven proteins related to flocculins/adhesins in S. cerevisiae or C. albicans. To obtain a proteomic comparison of biofilm and planktonic cells, P. kudriavzevii cells were grown to exponential phase and in static 24-h cultures. Interestingly, the 24-h static cultures of P. kudriavzevii yielded formation of floating biofilm (flor) rather than adherence to polystyrene at the bottom. The proteomic analysis of both conditions identified a total of 33 cell wall proteins. In line with a possible role in flor formation, increased abundance of flocculins, in particular Flo110, was observed in the floating biofilm compared to exponential cells. This study is the first to provide a detailed description of the cell wall in P. kudriavzevii including its cell wall proteome, and paves the way for further investigations on the importance of flor formation and flocculins in the pathogenesis of P. kudriavzevii.

Modulation of innate immunity in airway epithelium for host-directed therapy

Innate immunity of the mucosal surfaces provides the first-line defense from invading pathogens and pollutants conferring protection from the external environment. Innate immune system of the airway epithelium consists of several components including the mucus layer, mucociliary clearance of beating cilia, production of host defense peptides, epithelial barrier integrity provided by tight and adherens junctions, pathogen recognition receptors, receptors for chemokines and cytokines, production of reactive oxygen species, and autophagy. Therefore, multiple components interplay with each other for efficient protection from pathogens that still can subvert host innate immune defenses. Hence, the modulation of innate immune responses with different inducers to boost host endogenous front-line defenses in the lung epithelium to fend off pathogens and to enhance epithelial innate immune responses in the immunocompromised individuals is of interest for host-directed therapy. Herein, we reviewed possibilities of modulation innate immune responses in the airway epithelium for host-directed therapy presenting an alternative approach to standard antibiotics.

The Interplay between Candida albicans, Vaginal Mucosa, Host Immunity and Resident Microbiota in Health and Disease: An Overview and Future Perspectives

Vulvovaginal candidiasis (VVC), which is primarily caused by Candida albicans, is an infection that affects up to 75% of all reproductive-age women worldwide. Recurrent VVC (RVVC) is defined as >3 episodes per year and affects nearly 8% of women globally. At mucosal sites of the vagina, a delicate and complex balance exists between Candida spp., host immunity and local microbial communities. In fact, both immune response and microbiota composition play a central role in counteracting overgrowth of the fungus and maintaining homeostasis in the host. If this balance is perturbed, the conditions may favor C. albicans overgrowth and the yeast-to-hyphal transition, predisposing the host to VVC. To date, the factors that affect the equilibrium between Candida spp. and the host and drive the transition from C. albicans commensalism to pathogenicity are not yet fully understood. Understanding the host- and fungus-related factors that drive VVC pathogenesis is of paramount importance for the development of adequate therapeutic interventions to combat this common genital infection. This review focuses on the latest advances in the pathogenic mechanisms implicated in the onset of VVC and also discusses novel potential strategies, with a special focus on the use of probiotics and vaginal microbiota transplantation in the treatment and/or prevention of recurrent VVC.

Secreted aspartyl proteases family: a perspective review on the regulation of fungal pathogenesis

Secreted aspartyl proteases (SAPs) are important enzymes for fungal pathogenicity, playing a significant role in infection and survival. This article provides insight into how SAPs facilitate the transformation of yeast cells into hyphae and engage in biofilm formation, invasion and degradation of host cells and proteins. SAPs and their isoenzymes are prevalent during fungal infections, making them a potential target for antifungal and antibiofilm therapies. By targeting SAPs, critical stages of fungal pathogenesis such as adhesion, hyphal development, biofilm formation, host invasion and immune evasion can potentially be disrupted. Developing therapies that target SAPs could provide an effective treatment option for a wide range of fungal infections.

Morphogenic plasticity: the pathogenic attribute of Candida albicans

Candida albicans is a commensal organism of the human gastrointestinal tract and a prevalent opportunistic pathogen. It exhibits different morphogenic forms to survive in different host niches with distinct environmental conditions (pH, temperature, oxidative stress, nutrients, serum, chemicals, radiation, etc.) and genetic factors (transcription factors and genes). The different morphogenic forms of C. albicans are yeast, hyphal, pseudohyphal, white, opaque, and transient gray cells, planktonic and biofilm forms of cells. These forms differ in the parameters like cellular phenotype, colony morphology, adhesion to solid surfaces, gene expression profile, and the virulent traits. Each form is functionally distinct and responds discretely to the host immune system and antifungal drugs. Hence, morphogenic plasticity is the key to virulence. In this review, we address the characteristics, the pathogenic potential of the different morphogenic forms and the conditions required for morphogenic transitions.

Characterization of Aspartic Proteases from Paracoccidioides brasiliensis and Their Role in Fungal Thermo-Dimorphism

Paracoccidioidomycosis (PCM) is the most prevalent systemic mycosis in Latin America and is caused by fungi from the Paracoccidioides genus. The infection begins after inhalation of the fungal propagules and their thermo-dimorphic shift to yeast form. Proteases play an important role in the host invasion process and immune modulation in many pathogenic microorganisms. Aspartyl proteases are virulence factors in many human fungal pathogens that play an important role in the host invasion process morphogenesis, cellular function, immunity, and nutrition. In the present study, we characterized the modulation of acid proteases from Paracoccidioides brasiliensis. We detected four aspartyl proteases in P. brasiliensis with high homology to aspartic protease from Saccharomyces cerevisiae Pep4. Furthermore, we demonstrated that Pepstatin A can inhibit dimorphic switching (mycelium→yeast) in P. brasiliensis. In addition, these genes were modulated during thermo-dimorphism (M→Y transition) in the presence or absence of carbon and nitrogen sources and during growth at pH 4 during 24 and 48 h. We also observed that P. brasiliensis increase the secretion of aspartic proteases when cultivated at pH 4, and these acid proteases cleave BSA, collagen, and hemoglobin. These data suggest that aspartyl proteases are modulated by environmental conditions and during fungal thermo-dimorphism. Thus, this work brings new possibilities for studying the role of aspartyl proteases in the host-pathogen relationship and P. brasiliensis biology.

Characterization of Virulence Factors in Candida Species Causing Candidemia in a Tertiary Care Hospital in Bangkok, Thailand

Candidemia is often associated with high mortality, and Candida albicans, Candida tropicalis, Candida glabrata, and Candida parapsilosis are common causes of this disease. The pathogenicity characteristics of specific Candida spp. that cause candidemia in Thailand are poorly understood. This study aimed to characterize the virulence factors of Candida spp. Thirty-eight isolates of different Candida species from blood cultures were evaluated for their virulence properties, including exoenzyme and biofilm production, cell surface hydrophobicity, tissue invasion, epithelial cell damage, morphogenesis, and phagocytosis resistance; the identity and frequency of mutations in ERG11 contributing to azole-resistance were also determined. C. albicans had the highest epithelial cell invasion rate and phospholipase activity, with true hyphae formation, whereas C. tropicalis produced the most biofilm, hydrophobicity, protease activity, and host cell damage and true hyphae formation. ERG11 mutations Y132F and S154F were observed in all azole-resistant C. tropicalis. C. glabrata had the most hemolytic activity while cell invasion was low with no morphologic transition. C. glabrata was more easily phagocytosed than other species. C. parapsilosis generated pseudohyphae but not hyphae and did not exhibit any trends in exoenzyme production. This knowledge will be crucial for understanding the pathogenicity of Candida spp. and will help to explore antivirulence-based treatment.

Is Candida albicans a contributor to cancer? A critical review based on the current evidence

The association between Candida albicans (C. albicans) and cancer has been noticed for decades. Whether C. albicans infection is a complication of cancer status or as a contributor to cancer development remains to be discussed. This review systematically summarized the up-to-date knowledge about associations between C. albicans and various types of cancer, and discussed the role of C. albicans in cancer development. Most of the current clinical and animal evidence support the relationship between C. albicans and oral cancer development. However, there is insufficient evidence to demonstrate the role of C. albicans in other types of cancer. Moreover, this review explored the underlying mechanisms for C. albicans promoting cancer. It was hypothesized that C. albicans may promote cancer progression by producing carcinogenic metabolites, inducing chronic inflammation, remodeling immune microenvironment, activating pro-cancer signals, and synergizing with bacteria.

Anti-Fungal Potential of Structurally Diverse FDA-Approved Therapeutics Targeting Secreted Aspartyl Proteinase (SAP) of Candida albicans: an In Silico Drug Repurposing Approach

In recent years, candidiasis attains major clinical importance due to its unique pathogenic strategy, which distinguishes it from other nosocomial infections. Secreted aspartyl proteinases (SAPs) is a hydrolytic enzyme secreted by Candida species that mediate versatile biological activity including hyphal formation, adherence, biofilm formation, phenotypic adaptation, etc. Emerging clinical evidence strongly suggested that conventional anti-fungal agent's are often prone to high level of resistance upon repeated exposure. Drug repurposing is an ideal strategy that shall impose the additional clinical benefits of the already approved molecules. Hence, through this realistic pathway, the potential of the suitable lead candidates will be explored in order to prolong the life span of existing molecules thereby need for newer therapeutics shall be avoided. The main aim of the present investigation is to determine the enzyme inhibitory potential of certain FDA-approved antibiotics and to validate its efficacy against the virulent enzyme secreted aspartyl proteinase (SAP) of Candida albicans via the AutoDock simulation program. The outcome of in silico dynamic simulations depicts that the drugs such as gentamicin, clindamycin, meropenem, metronidazole, and aztreonam emphasize superior binding affinity in terms of demonstrating considerable interaction with the core catalytic residues (Asp 32, Asp86, Asp 218, Gly220, Thr 221, and Thr 222). Data further indicates that the drug gentamicin exhibited best binding affinity of - 14.16 kcal/mol followed by meropenem (- 9.20 kcal/mol), clindamycin (- 9.00 kcal/mol), ciprofloxacin (- 8.95 kcal/mol), and imipenem (- 8.00 kcal/mol). In conclusion, repurposed antibiotics like gentamicin, clindamycin, meropenem, metronidazole, and aztreonam shall be considered an alternate drug of choice for the clinical management of drug resistant candida infections in the near future.

"Under Pressure" - How fungi evade, exploit, and modulate cells of the innate immune system

The human immune system uses an arsenal of effector mechanisms to prevent and counteract infections. Yet, some fungal species are extremely successful as human pathogens, which can be attributed to a wide variety of strategies by which these fungi evade, exploit, and modulate the immune system. These fungal pathogens normally are either harmless commensals or environmental fungi. In this review we discuss how commensalism, but also life in an environmental niche without human contact, can drive the evolution of diverse and specialized immune evasion mechanisms. Correspondingly, we discuss the mechanisms contributing to the ability of these fungi to cause superficial to life-threatening infections.

Secreted Aspartyl Proteinases Targeted Multi-Epitope Vaccine Design for Candida dubliniensis Using Immunoinformatics

Candida dubliniensis is an opportunistic pathogen associated with oral and invasive fungal infections in immune-compromised individuals. Furthermore, the emergence of C. dubliniensis antifungal drug resistance could exacerbate its treatment. Hence, in this study a multi-epitope vaccine candidate has been designed using an immunoinformatics approach by targeting C. dubliniensis secreted aspartyl proteinases (SAP) proteins. In silico tools have been utilized to predict epitopes and determine their allergic potential, antigenic potential, toxicity, and potential to elicit interleukin-2 (IL2), interleukin-4 (IL4), and IFN-γ. Using the computational tools, eight epitopes have been predicted that were then linked with adjuvants for final vaccine candidate development. Computational immune simulation has depicted that the immunogen designed emerges as a strong immunogenic candidate for a vaccine. Further, molecular docking and molecular dynamics simulation analyses revealed stable interactions between the vaccine candidate and the human toll-like receptor 5 (TLR5). Finally, immune simulations corroborated the promising candidature of the designed vaccine, thus calling for further in vivo investigation.

Membrane component ergosterol builds a platform for promoting effector secretion and virulence in Magnaporthe oryzae

The plasma membrane (PM) functions as a physical border between the extracellular and cytoplasmic environments that contribute to the interaction between host plants and pathogenic fungi. As a specific sterol constituent in the cell membrane, ergosterol plays a significant role in fungal development. However, the role of ergosterol in the infection of the rice blast fungus Magnaporthe oryzae remains unclear. In this study, we found that a sterol reductase, MoErg4, is involved in ergosterol biosynthesis and the regulation of plasma membrane integrity in M. oryzae. We found that defects in ergosterol biosynthesis disrupt lipid raft formation in the PM and cause an abnormal distribution of the t-soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein MoSso1, inhibiting its interaction with the v-SNARE protein MoSnc1. In addition, we found that MoSso1-MoSnc1 interaction is important for biotrophic interface complex development and cytoplasmic effector protein secretion. Our findings suggested that ergosterol-enriched lipid rafts constitute a platform for interactions among various SNARE proteins that are required for the development and pathogenicity of M. oryzae.

Synthesis, In Silico Study, Antibacterial and Antifungal Activities of N-phenylbenzamides

Antibiotic and antifungal resistance problems have been prevalent in recent decades. One of the efforts to solve the problems is to develop new medicines with more potent antibacterial and antifungal activity. N-phenylbenzamides have the potential to be developed as antibacterial and antifungal medicine. This study aimed to synthesize N-phenylbenzamides and evaluate their in silico and in vitro antibacterial and antifungal activities. The in silico studies conducted absorption, distribution, metabolism, excretion and toxicity (ADMET) predictions along with molecular docking studies. ADMET predictions used pkCSM software online, while the docking studies used MVD software (Molegro ^® Virtual Docker version 5.5) on Aminoglycosid-2 ″-phosphotransferase-IIa (APH2 ″-IIa) enzyme with protein data bank (PDB) ID code 3HAV as antibacterial and aspartic proteinases enzyme (Saps) with PDB ID code 2QZX as an antifungal. In vitro, antibacterial and antifungal tests were carried out using the zone of inhibition (ZOI) method. The five N-phenylbenzamides (3a-e) were successfully synthesized with a high yield. Based on in silico and in vitro studies, compounds 3a-e have antibacterial and antifungal activities, where they can inhibit the growth of Gram-positive bacteria (Staphylococcus aureus), Gram-negative (Escherichia coli), and Candida albicans. Therefore, compounds 3a-e can be developed as a topical antibacterial and antifungal agent.

Ger1 is a secreted aspartic acid protease essential for spore germination in Ustilago maydis

Ustilago maydis expresses a number of proteases during its pathogenic lifecycle. Some of the proteases including both intracellular and extracellular ones have previously been shown to influence the virulence of the pathogen. However, any role of secreted proteases in the sporulation process of U. maydis have not been explored earlier. In this study we have investigated the biological function of one such secreted protease, Ger1 belonging to aspartic protease A1 family. An assessment of the real time expression of ger1 revealed an infection specific expression of the protein especially during late phases of infection. We also evaluated any contribution of the protein in the pathogenicity of the fungus. Our data revealed an involvement of Ger1 in the sporulation and spore germination processes of U. maydis. Ger1 also showed positive influence on the pathogenicity of the fungus and accordingly the ger1 deletion mutant exhibited reduced pathogenicity. The study also demonstrated the protease activity associated with Ger1 to be essential for its biological function. Fluorescence microscopy of maize plants infected with U. maydis cells expressing Ger1-mcherry-HA also revealed that Ger1 is efficiently secreted within maize apoplast.

Expanding the therapeutic options for Candida infections using novel inhibitors of secreted aspartyl proteases

For widening the therapeutic options for Candida management, the druggability of Candida proteome was systematically investigated using an innovative pipeline of high-throughput data mining algorithms, followed by in vitro validation of the observations. Through this exercise, HIV-1 protease was found to share structural similarity with secreted aspartyl protease-3 (SAP3), a virulence protein of Candida. Using the molecular fingerprint of HIV-1 protease inhibitor GRL-09510, we performed virtual screening of peptidomimetic library followed by high-precision docking and MD simulations for discovery of SAP inhibitors. Wet-lab validation of the four shortlisted peptidomimetics revealed that two molecules, when used in combination with fluconazole, could significantly reduce the dosage of fluconazole required for 50% inhibition of Candida albicans. The SAP inhibitory activity of these peptidomimetics was confirmed through SAP assays and found to be on par with pepstatin A, a known peptidomimetic inhibitor of aspartyl proteases.

Fungal resilience and host-pathogen interactions: Future perspectives and opportunities

We are constantly exposed to the threat of fungal infection. The outcome-clearance, commensalism or infection-depends largely on the ability of our innate immune defences to clear infecting fungal cells versus the success of the fungus in mounting compensatory adaptive responses. As each seeks to gain advantage during these skirmishes, the interactions between host and fungal pathogen are complex and dynamic. Nevertheless, simply compromising the physiological robustness of fungal pathogens reduces their ability to evade antifungal immunity, their virulence, and their tolerance against antifungal therapy. In this article I argue that this physiological robustness is based on a 'Resilience Network' which mechanistically links and controls fungal growth, metabolism, stress resistance and drug tolerance. The elasticity of this network probably underlies the phenotypic variability of fungal isolates and the heterogeneity of individual cells within clonal populations. Consequently, I suggest that the definition of the fungal Resilience Network represents an important goal for the future which offers the clear potential to reveal drug targets that compromise drug tolerance and synergise with current antifungal therapies.

The secreted FolAsp aspartic protease facilitates the virulence of Fusarium oxysporum f. sp. lycopersici

Pathogens utilize secretory effectors to manipulate plant defense. Fusarium oxysporum f. sp. lycopersici (Fol) is the causal agent of Fusarium wilt disease in tomatoes. We previously identified 32 secreted effector candidates by LC-MS analysis. In this study, we functionally identified one of the secreted proteins, FolAsp, which belongs to the aspartic proteases (Asp) family. The FolAsp was upregulated with host root specifically induction. Its N-terminal 1-19 amino acids performed the secretion activity in the yeast system, which supported its secretion in Fol. Phenotypically, the growth and conidia production of the FolAsp deletion mutants were not changed; however, the mutants displayed significantly reduced virulence to the host tomato. Further study revealed the FolAsp was localized at the apoplast and inhibited INF1-induced cell death in planta. Meanwhile, FolAsp could inhibit flg22-mediated ROS burst. Furthermore, FolAsp displayed protease activity on host protein, and overexpression of FolAsp in Fol enhanced pathogen virulence. These results considerably extend our understanding of pathogens utilizing secreted protease to inhibit plant defense and promote its virulence, which provides potential applications for tomato improvement against disease as the new drug target.