A glucuronoxylomannan-like glycan produced by Trichosporon mucoides.

Trichosporon asahii shares with Cryptococcus species the ability to produce glucuronoxylomannan (GXM), an immunomodulatory fungal polysaccharide. The ability of other opportunistic species of Trichosporon to produce GXM-like polysaccharides is unknown. In this study, we observed that T. mucoides was less pathogenic than T. asahii in an infection model of Galleria mellonella and asked whether this difference was related to the characteristics of GXM-like molecules. Compositional analysis of samples obtained from both pathogens indicated that the components of GXM (mannose, xylose and glucuronic acid) were, in fact, detected in T. mucoides and T. asahii glycans. The identification of the T. mucoides glycan as a GXM-like molecule was confirmed by its reactivity with a monoclonal antibody raised to cryptococcal GXM and incorporation of the glycan into the cell surface of an acapsular mutant of C. neoformans. T. mucoides and T. asahii glycans differed in molecular dimensions. The antibody to cryptococcal GXM recognized T. mucoides yeast forms less efficiently than T. asahii cells. Experiments with animal cells revealed that the T. mucoides glycan manifested antiphagocytic properties. Comparative phagocytosis assays revealed that T. mucoides and T. asahii were similarly recognized by macrophages. However, fungal association with the phagocytes did not depend on the typical receptors of cryptococcal GXM, as concluded from assays using macrophages obtained from Tlr2-/- and Cd14-/- knockout mice. These results add T. mucoides to the list of fungal pathogens producing GXM-like glycans, but also indicate a high functional diversity of this major fungal immunogen.

A Paracoccidioides brasiliensis glycan shares serologic and functional properties with cryptococcal glucuronoxylomannan.

The cell wall of the yeast form of the dimorphic fungus Paracoccidioides brasiliensis is enriched with α1,3-glucans. In Cryptococcus neoformans, α1,3-glucans interact with glucuronoxylomannan (GXM), a heteropolysaccharide that is essential for fungal virulence. In this study, we investigated the occurrence of P. brasiliensis glycans sharing properties with cryptococcal GXM. Protein database searches in P. brasiliensis revealed the presence of sequences homologous to those coding for enzymes involved in the synthesis of GXM and capsular architecture in C. neoformans. In addition, monoclonal antibodies (mAbs) raised to cryptococcal GXM bound to P. brasiliensis cells. Using protocols that were previously established for extraction and analysis of C. neoformans GXM, we recovered a P. brasiliensis glycan fraction composed of mannose and galactose, in addition to small amounts of glucose, xylose and rhamnose. In comparison with the C. neoformans GXM, the P. brasiliensis glycan fraction components had smaller molecular dimensions. The P. brasiliensis components, nevertheless, reacted with different GXM-binding mAbs. Extracellular vesicle fractions of P. brasiliensis also reacted with a GXM-binding mAb, suggesting that the polysaccharide-like molecule is exported to the extracellular space in secretory vesicles. An acapsular mutant of C. neoformans incorporated molecules from the P. brasiliensis extract onto the cell wall, resulting in the formation of surface networks that resembled the cryptococcal capsule. Coating the C. neoformans acapsular mutant with the P. brasiliensis glycan fraction resulted in protection against phagocytosis by murine macrophages. These results suggest that P. brasiliensis and C. neoformans share metabolic pathways required for the synthesis of similar polysaccharides and that P. brasiliensis yeast cell walls have molecules that mimic certain aspects of C. neoformans GXM. These findings are important because they provide additional evidence for the sharing of antigenically similar components across phylogenetically distant fungal species. Since GXM has been shown to be important for the pathogenesis of C. neoformans and to elicit protective antibodies, the finding of similar molecules in P. brasiliensis raises the possibility that these glycans play similar functions in paracoccidiomycosis.

Advancing drug repurposing research: Trends, collaborative networks, innovation and knowledge leaders.

The advancement of drug repurposing (DR) relies on scientific leadership and innovative institutions with access to knowledge. We performed a bibliometric and social network analysis (covering the period 2011-2020) to map the DR research trends and to identify innovation and knowledge leaders (IKLs). The indexing rate of DR publications has steadily increased. Major research areas included emerging viruses, cancer, methodological approaches, preclinical research, and infectious diseases. Government and academia accounted for nearly 65% of funding. Using a combination of network centrality metrics, 41 IKLs affiliated to central and pericentral institutions in the global research network were identified. These IKLs can facilitate the flow of knowledge and are best positioned to promote interactions within the network, with the potential to contribute significantly to advancing the DR field.

A monoclonal antibody to Histoplasma capsulatum alters the intracellular fate of the fungus in murine macrophages.

Monoclonal antibodies (MAbs) to a cell surface histone on Histoplasma capsulatum modify murine infection and decrease the growth of H. capsulatum within macrophages. Without the MAbs, H. capsulatum survives within macrophages by modifying the intraphagosomal environment. In the present study, we aimed to analyze the affects of a MAb on macrophage phagosomes. Using transmission electron and fluorescence microscopy, we showed that phagosome activation and maturation are significantly greater when H. capsulatum yeast are opsonized with MAb. The MAb reduced the ability of the organism to regulate the phagosomal pH. Additionally, increased antigen processing and reduced negative costimulation occur in macrophages that phagocytose yeast cells opsonized with MAb, resulting in more-efficient T-cell activation. The MAb alters the intracellular fate of H. capsulatum by affecting the ability of the fungus to regulate the milieu of the phagosome.

Mapping the Brazilian microscopy landscape: A bibliometric and network analysis.

Understanding how a technology is introduced and shared in a society has a strategic value for the planning of technological development and assessing new market opportunities. Among other technologies, microscopy has had a significant role in advancing different fields of science. In Brazil, its use spans from biomedical to engineering areas. Here, we used social network analysis (SNA) to map and quantify the flow of interaction between Brazilian researchers involved in microscopy techniques. The analysis examines co-occurrence of thematic networks and scientific co-authorship in articles published in a ten years window, as retrieved from Scopus database. The results showed an increasing volume of publications using microscopy in Brazil. The two major areas of interest are material and life sciences, which present significant intra-regional interaction. USA, Spain, Germany, Portugal and the United Kingdom are the main partner countries for international scientific collaborations. The share of Brazilian publications applying microscopy follows the global trends, with a slight predominance in health and life sciences. Our results provide a context of the strengths and gaps of the field in Brazil and may help to inform researchers and policy makers for further advancing the field.

Analysis of multiple components involved in the interaction between Cryptococcus neoformans and Acanthamoeba castellanii.

Cryptococcus neoformans is an environmental fungus that can cause lethal meningoencephalitis in immunocompromised individuals. The mechanisms by which environmental microbes become pathogenic to mammals are still obscure, but different studies suggest that fungal virulence evolved from selection imposed by environmental predators. The soil-living Acanthamoeba castellanii is a well-known predator of C. neoformans. In this work, we evaluated the participation of C. neoformans virulence-associated structures in the interaction of fungal cells with A. castellanii. Fungal extracellular vesicles (EVs) and the polysaccharide glucuronoxylomannan (GXM) were internalized by A. castellanii with no impact on the viability of amoebal cells. EVs, but not free GXM, modulated antifungal properties of A. castellanii by inducing enhanced yeast survival. Phagocytosis of C. neoformans by amoebal cells and the pathogenic potential in a Galleria mellonella model were not affected by EVs, but previous interactions with A. castellanii rendered fungal cells more efficient in killing this invertebrate host. This observation was apparently associated with marked amoeba-induced changes in surface architecture and increased resistance to both oxygen- and nitrogen-derived molecular species. Our results indicate that multiple components with the potential to impact pathogenesis are involved in C. neoformans environmental interactions.

Phosphorus-rich structures and capsular architecture in Cryptococcus neoformans.

AIM: In this study, we aimed to analyze the relationship of phosphorus-rich structures with surface architecture in Cryptococcus neoformans. METHODS: Phosphorus-rich structures in C. neoformans were analyzed by combining fluorescence microscopy, biochemical extraction, scanning electron microscopy, electron probe x-ray microanalysis and 3D reconstruction of high pressure frozen and freeze substituted cells by focused ion beam-scanning electron microscopy (FIB-SEM). RESULTS & CONCLUSION: Intracellular and surface phosphorus-enriched structures were identified. These molecules were required for capsule assembly, as demonstrated in experiments using polysaccharide incorporation by capsule-deficient cells and mutants with defects in polyphosphate synthesis. The demonstration of intracellular and cell wall-associated polyphosphates in C. neoformans may lead to future studies involving their participation in both physiologic and pathogenic events.

Cryptococcus neoformans glucuronoxylomannan fractions of different molecular masses are functionally distinct.

AIMS: Glucuronoxylomannan (GXM) is the major polysaccharide component of Cryptococcus neoformans. We evaluated in this study whether GXM fractions of different molecular masses were functionally distinct. MATERIALS & METHODS: GXM samples isolated from C. neoformans cultures were fractionated to generate polysaccharide preparations differing in molecular mass. These fractions were used in experiments focused on the association of GXM with cell wall components of C. neoformans, as well as on the interaction of the polysaccharide with host cells. RESULTS & CONCLUSION: GXM fractions of variable molecular masses bound to the surface of a C. neoformans acapsular mutant in a punctate pattern that is in contrast to the usual annular pattern of surface coating observed when GXM samples containing the full molecular mass range were used. The polysaccharide samples were also significantly different in their ability to stimulate cytokine production by host cells. Our findings indicate that GXM fractions are functionally distinct depending on their mass.

Research trends on pathogenic Cryptococcus species in the last 20 years: a global analysis with focus on Brazil.

AIMS: Recent data demonstrates that cryptococcosis caused by Cryptococcus neoformans or Cryptococcus gattii kills approximately 600,000 people per year in the world. In Brazil, cryptococcosis has recently been identified as the most fatal mycosis in AIDS patients. In this study, we aimed to map research into C. neoformans and C. gattii in the world, with a focus on the Brazilian contribution to this area. METHODS: The parameters used for this analysis were based on publication records, including number of articles published, citation indices, journal impact factor and distribution of authorship in the last two decades. RESULTS: Our global analysis of publications demonstrated that, in the last 20 years, the USA was the country that produced the highest number of scientific articles in the Cryptococcus field, while Brazil occupied the third position. Brazilian productivity, however, showed a steady tendency to increase, in contrast to the USA and other countries. The average impact factor of journals at which articles authored by Brazilians were published was 2.58, which represented approximately half the value found for papers of American authorship. Studies authored by Brazilian scientists showed relatively low averages of citations per article, in comparison to papers published by researchers from the USA, France, Australia, The Netherlands and Germany, among others. CONCLUSION: This study demonstrates that the contribution of Brazilian scientists to the Cryptococcus field is continually growing, although papers produced in Brazil apparently have poor repercussion in comparison to those generated in developed countries.