Detection and characterization of plasminogen receptors on clinical isolates of Trichosporon asahii

Trichosporon asahii: emerging challenges in pathogenesis and drug resistance

Trichosporon asahii (T. asahii) is an opportunistic pathogenic fungus that often causes severe infections in immunosuppressed patients. Among Trichosporon species, T. asahii is the most pathogenic and lethal species. Current research faces challenges related to unknown pathogenic mechanisms, complex resistance mechanisms, insufficiently rapid and accurate diagnostic methods, and insufficient research on susceptibility to infection. These issues need to be explored in depth. This review summarizes research progress on the origin and classification of T. asahii, its virulence factors and pathogenic mechanisms, epidemiological characteristics, infection modes, diagnostic methods, drug treatment options, and drug resistance mechanisms. Traditional culture combined with molecular biology techniques, such as polymerase chain reaction and gene sequencing, has improved the accuracy and speed of detection. Treatment relies mainly on azole antifungal drugs and amphotericin B; however, patients are facing the problem of drug resistance. New techniques, such as gene knockout and gene sequencing, have identified resistance mechanisms, thus supporting the development of novel antifungal drugs. In summary, an in-depth study of T. asahii will aid in developing more effective diagnostic and therapeutic methods and improve patient prognosis.

Identification of heparin-binding proteins expressed on Trichosporon asahii cell surface

Trichosporon asahii is a pathogenic yeast that cause trichosporonosis. T. asahii exhibits several colony morphologies, such as white (W)- or off-white (O)-type, which may affect virulence. In this study, we compared the expression pattern of heparin-binding proteins in various colony morphologies and identified heparin-binding protein in T. asahii. Surface plasmon resonance analysis revealed that cell surface molecules attached more strongly to heparin in W- than O-type cells. We purified and identified a heparin-binding protein strongly expressed in W-type cells using heparin-Sepharose beads, named it heparin-binding protein 1 (HepBP1), and expressed Flag-tagged HepBP1 in mammalian cells. The heparin-binding ability of Flag-tagged HepBP1 was confirmed by pulldown assay using heparin-Sepharose beads. Thus, HepBP1 is a heparin-binding protein on T. asahii cell surface. These results suggest that several T. asahii cell surface proteins interact with glycosaminoglycans; therefore, they could contribute to infection.

Hemagglutination ability and hemolytic activity of Trichosporon asahii

Trichosporon asahii is a human fungal pathogen that causes deep-seated infections in immunocompromised patients. While the pathogenic mechanisms of T. asahii remain unknown, our previous studies indicate that adherent colony morphologies were generated from parent strains, which may contribute to their pathogenicity. In the present study, we analyzed the hemolytic and hemagglutination activities of T. asahii. We report that T. asahii cells demonstrate hemagglutination and hemolytic activities, and that cell surface molecules play a role in the hemagglutination activity of adherent strains. These observations suggest that hemagglutination and hemolysis may be one of the pathogenic mechanisms of T. asahii.

[Identification of Heparin-binding Proteins on the Cell Surface of Cryptococcus neoformans]

Interactions between virulence factors of pathogens and host responses play an important role in the establishment of infection by microbes. We focused on interactions between Cryptococcus neoformans proteins and heparin, which is abundant on host epithelial cells. Surface proteins were extracted and analyzed. Fractions from anion-exchange column chromatography interacted with heparin in surface plasmon resonance analyses. Heparin-binding proteins were purified and then separated by gel electrophoresis; and were identified as transaldolase, glutathione-disulfide reductase, and glyoxal oxidase. These results imply that multifunctional molecules on C. neoformans cells, such as those involved in heparin binding, may play roles in adhesion that trigger responses in the host.

Plasminogen-binding proteins as an evasion mechanism of the host's innate immunity in infectious diseases

Pathogens have developed particular strategies to infect and invade their hosts. Amongst these strategies’ figures the modulation of several components of the innate immune system participating in early host defenses, such as the coagulation and complement cascades, as well as the fibrinolytic system. The components of the coagulation cascade and the fibrinolytic system have been proposed to be interfered during host invasion and tissue migration of bacteria, fungi, protozoa, and more recently, helminths. One of the components that has been proposed to facilitate pathogen migration is plasminogen (Plg), a protein found in the host’s plasma, which is activated into plasmin (Plm), a serine protease that degrades fibrin networks and promotes degradation of extracellular matrix (ECM), aiding maintenance of homeostasis. However, pathogens possess Plg-binding proteins that can activate it, therefore taking advantage of the fibrin degradation to facilitate establishment in their hosts. Emergence of Plg-binding proteins appears to have occurred in diverse infectious agents along evolutionary history of host–pathogen relationships. The goal of the present review is to list, summarize, and analyze different examples of Plg-binding proteins used by infectious agents to invade and establish in their hosts. Emphasis was placed on mechanisms used by helminth parasites, particularly taeniid cestodes, where enolase has been identified as a major Plg-binding and activating protein. A new picture is starting to arise about how this glycolytic enzyme could acquire an entirely new role as modulator of the innate immune system in the context of the host–parasite relationship.

Sequence-based identification, genotyping and virulence factors of Trichosporon asahii strains isolated from urine samples of hospitalized patients (2011-2016)

INTRODUCTION

Trichosporon asahii is the most common species that causes trichosporonosis.

MATERIALS AND METHODS

In the present study, a collection of 68T. asahii strains recovered from hospitalized patients urine samples between 2011 and 2016 was examined. T. asahii strains were identified by sequencing the intergenic spacer 1 region (IGS1) and genotyped. In addition, proteinase, phospholipase, esterase, haemolytic activity, and biofilm formation of a total of T. asahii strains were investigated.

RESULTS

The predominant genotype was 1 (79.3%) and followed by 5 (8%), 3 (6.9%), 6 (3.4%), 4 (1.1%), 9 (1.1%). In none of the 68 strains, proteinase and phospholipase activities could be detected, while all were found to be esterase positive. Biofilm production and hemolytic activity were detected in 23.5 and 97% respectively.

DISCUSSION

Our results indicated that six genotypes were (1, 5, 3, 6, 4, 9) present among T. asahii strains and no property was found to associate with a genotype, in terms of virulence factors.