Differential Recognition of Sporothrix schenckii, Sporothrix brasiliensis, and Sporothrix globosa by Human Monocyte-Derived Macrophages and Dendritic Cells

Sporothrix brasiliensis Gp70 is a cell wall protein required for adhesion, proper interaction with innate immune cells, and virulence

Sporothrix brasiliensis is one of the leading etiological agents of sporotrichosis, a cutaneous and subcutaneous mycosis worldwide distributed. This organism has been recently associated with epidemic outbreaks in Brazil. Despite the medical relevance of this species, little is known about its virulence factors, and most of the information on this subject is extrapolated from Sporothrix schenckii. Here, we generated S. brasiliensis mutants, where GP70 was silenced. In S. schenckii, this gene encodes a glycoprotein with adhesive properties required for virulence. The S. brasiliensis GP70 silencing led to an abnormal cellular phenotype, with smaller, round yeast-like cells that aggregate. Cell aggregation was disrupted with glucanase, suggesting this phenotype is linked to changes in the cell wall. The cell wall characterization confirmed changes in the structural polysaccharide β-1,3-glucan, which increased in quantity and exposure at the cell surface. This was accompanied by a reduction in protein content and N-linked glycans. Mutant strains with high GP70-silencing levels showed minimal levels of 3-carboxy-cis,cis-muconate cyclase activity, this glycoprotein's predicted enzyme function, and decreased ability to bind laminin and fibronectin. These phenotypical changes coincided with abnormal interaction with human peripheral blood mononuclear cells, where production of IL-1β, IL-17, and IL-22 was reduced and the strong dependence on cytokine stimulation via mannose receptor was lost. Phagocytosis by monocyte-derived macrophages was increased and virulence attenuated in a Galleria mellonella larvae. In conclusion, Gp70 is an abundant cell wall glycoprotein in S. brasiliensis that contributes to virulence and proper interaction with innate immnune cells.

Impaired synaptosome phagocytosis in macrophages of individuals with autism spectrum disorder

Dendritic spine abnormalities are believed to be one of the critical etiologies of autism spectrum disorder (ASD). Over the past decade, the importance of microglia in brain development, particularly in synaptic elimination, has become evident. Thus, microglial abnormalities may lead to synaptic dysfunction, which may underlie the pathogenesis of ASD. Several human studies have demonstrated aberrant microglial activation in the brains of individuals with ASD, and studies in animal models of ASD have also shown a relationship between microglial dysfunction and synaptic abnormalities. However, there are very few methods available to directly assess whether phagocytosis by human microglia is abnormal. Microglia are tissue-resident macrophages with phenotypic similarities to monocyte-derived macrophages, both of which consistently exhibit pathological phenotypes in individuals with ASD. Therefore, in this study, we examined the phagocytosis capacity of human macrophages derived from peripheral blood monocytes. These macrophages were polarized into two types: those induced by granulocyte-macrophage colony-stimulating factor (GM-CSF MΦ, traditionally referred to as "M1 MΦ") and those induced by macrophage colony-stimulating factor (M-CSF MΦ, traditionally referred to as "M2 MΦ"). Synaptosomes purified from human induced pluripotent stem cell-derived neuron were used to assess phagocytosis capacity. Our results revealed that M-CSF MΦ exhibited higher phagocytosis capacity compared to GM-CSF MΦ, whereas ASD-M-CSF MΦ showed a marked impairment in phagocytosis. Additionally, we found a positive correlation between phagocytosis capacity and cluster of differentiation 209 expression. This research contributes to a deeper understanding of the pathobiology of ASD and offers new insights into potential therapeutic targets for the disorder.

Milteforan, a promising veterinary commercial product against feline sporotrichosis

Sporotrichosis, the cutaneous mycosis most commonly reported in Latin America, is caused by the Sporothrix clinical clade species, including Sporothrix brasiliensis and Sporothrix schenckii sensu stricto. Due to its zoonotic transmission in Brazil, S. brasiliensis represents a significant health threat to humans and domestic animals. Itraconazole, terbinafine, and amphotericin B are the most used antifungals for treating sporotrichosis. However, many strains of S. brasiliensis and S. schenckii have shown resistance to these agents, highlighting the importance of finding new therapeutic options. Here, we demonstrate that milteforan, a commercial veterinary product against dog leishmaniasis, whose active principle is miltefosine, is a possible therapeutic alternative for the treatment of sporotrichosis, as observed by its fungicidal activity in vitro against different strains of S. brasiliensis and S. schenckii. Fluorescent miltefosine localizes to the Sporothrix cell membrane and mitochondria and causes cell death through increased permeabilization. Milteforan decreases S. brasiliensis fungal burden in A549 pulmonary cells and bone marrow-derived macrophages and also has an immunomodulatory effect by decreasing TNF-α, IL-6, and IL-10 production. Our results suggest milteforan as a possible alternative to treat feline sporotrichosis.

IMPORTANCE

Sporotrichosis is an endemic disease in Latin America caused by different species of Sporothrix. This fungus can infect domestic animals, mainly cats and eventually dogs, as well as humans. Few drugs are available to treat this disease, such as itraconazole, terbinafine, and amphotericin B, but resistance to these agents has risen in the last few years. Alternative new therapeutic options to treat sporotrichosis are essential. Here, we propose milteforan, a commercial veterinary product against dog leishmaniasis, whose active principle is miltefosine, as a possible therapeutic alternative for treating sporotrichosis. Milteforan decreases S. brasiliensis fungal burden in human and mouse cells and has an immunomodulatory effect by decreasing several cytokine production.

Silencing of Sporothrix schenckii GP70 Reveals Its Contribution to Fungal Adhesion, Virulence, and the Host-Fungus Interaction

Sporothrix schenckii is one of the etiological agents of sporotrichosis, a cutaneous and subcutaneous infection distributed worldwide. Like other medically relevant fungi, its cell wall is a molecular scaffold to display virulence factors, such as protective pigments, hydrolytic enzymes, and adhesins. Cell wall proteins with adhesive properties have been previously reported, but only a handful of them have been identified and characterized. One of them is Gp70, an abundant cell wall protein mainly found on the surface of yeast-like cells. Since the protein also has a role in the activity of 3-carboxy-cis,cis-muconate cyclase and its abundance is low in highly virulent strains, its role in the Sporothrix-host interaction remains unclear. Here, a set of GP70-silenced strains was generated, and the molecular and phenotypical characterization was performed. The results showed that mutants with high silencing levels showed a significant reduction in the adhesion to laminin and fibrinogen, enzyme activity, and defects in the cell wall composition, which included reduced mannose, rhamnose, and protein content, accompanied by an increment in β-1,3-glucans levels. The cell wall N-linked glycan content was significantly reduced. These strains induced poor TNFα and IL-6 levels when interacting with human peripheral blood mononuclear cells in a dectin-1-, TLR2-, and TLR4-dependent stimulation. The IL-1β and IL-10 levels were significantly higher and were stimulated via dectin-1. Phagocytosis and stimulation of neutrophil extracellular traps by human granulocytes were increased in highly GP70-silenced strains. Furthermore, these mutants showed virulence attenuation in the invertebrate model Galleria mellonella. Our results demonstrate that Gp70 is a versatile protein with adhesin properties, is responsible for the activity of 3-carboxy-cis,cis-muconate cyclase, and is relevant for the S. schenckii-host interaction.

Milteforan, a promising veterinary commercial product against feline sporotrichosis

Sporotrichosis, the cutaneous mycosis most commonly reported in Latin America, is caused by the Sporothrix clinical clade species, including Sporothrix brasiliensis and Sporothrix schenckii sensu stricto. In Brazil, S. brasiliensis represents a vital health threat to humans and domestic animals due to its zoonotic transmission. Itraconazole, terbinafine, and amphotericin B are the most used antifungals for treating sporotrichosis. However, many strains of S. brasiliensis and S. schenckii have shown resistance to these agents, highlighting the importance of finding new therapeutic options. Here, we demonstrate that milteforan, a commercial veterinary product against dog leishmaniasis whose active principle is miltefosine, is a possible therapeutic alternative for the treatment of sporotrichosis, as observed by its fungicidal activity in vitro against different strains of S. brasiliensis and S. schenckii, and by its antifungal activity when used to treat infected epithelial cells and macrophages. Our results suggest milteforan as a possible alternative to treat feline sporotrichosis.

Differential Recognition of Clinically Relevant Sporothrix Species by Human Granulocytes

Sporotrichosis is a cutaneous mycosis that affects humans and animals and has a worldwide distribution. This infection is mainly caused by Sporothrix schenckii, Sporothrix brasiliensis, and Sporothrix globosa. Current research about anti-Sporothrix immunity has been mainly focused on S. schenckii and S. brasiliensis, using different types of human or animal immune cells. Granulocytes are a group of cells relevant for cytokine production, with the capacity for phagocytosis and the generation of neutrophil extracellular traps (NETs). Considering their importance, this study aimed to compare the capacity of human granulocytes to stimulate cytokines, uptake, and form NETs when interacting with different Sporothrix species. We found that conidia, germlings, and yeast-like cells from S. schenckii, S. brasiliensis, and S. globosa play an important role in the interaction with these immune cells, establishing morphology- and species-specific cytokine profiles. S. brasil-iensis tended to stimulate an anti-inflammatory cytokine profile, whilst the other two species had a proinflammatory one. S. globosa cells were the most phagocytosed cells, which occurred through a dectin-1-dependent mechanism, while the uptake of S. brasiliensis mainly occurred via TLR4 and CR3. Cell wall N-linked and O-linked glycans, along with β-1,3-glucan, played a significant role in the interaction of these Sporothrix species with human granulocytes. Finally, this study indicates that conidia and yeast-like cells are capable of inducing NETs, with the latter being a better stimulant. To the best of our knowledge, this is the first study that reports the cytokine profiles produced by human granulocytes interacting with Sporothrix cells.