Biology subjects

Silva-Pereira, I.

Publications and source records attributed to Silva-Pereira, I..

4 recordsLinked to original sources

bioRxiv2025

Mapping Histoplasma in Bats and Cave Ecosystems: Evidence from Midwestern Brazil

Caves serve as natural reservoirs for diverse microbial species due to their unique biotic and abiotic conditions. Histoplasma spp. is frequently associated with guano-enriched soil, low luminosity, and high humidity, particularly in Latin America, a region highly endemic for histoplasmosis. Despite the continents diverse biomes, local environmental and host distributions of Histoplasma remain poorly understood. To address this knowledge gap, we conducted a Histoplasma-specific quantitative PCR (qPCR) assay targeting the hc100 gene on guano samples from seven bat-inhabited caves and tissue samples from 74 bats of nine species in the Federal District of Brazil and surround-ing regions. We detected Histoplasma DNA in 16 of 80 soil samples (20%) and in 33 bats representing seven species. Among 222 tissue samples (74 lung, 74 spleen, 74 brain), 39 tested positive: 22 lung, 10 spleen, and 7 brain samples. Four bats had Histoplasma DNA in both lung and brain, and two in both lung and spleen. By mapping the presence of Histoplasma across sampled caves, we identified environmental hotspots of fungal prevalence, emphasizing the need for targeted surveillance. ImportanceOur study provides critical insights into the environmental and host distribution of Histoplasma spp. in Brazil, identifying caves with high fungal prevalence and demonstrating its presence in multiple bat species. These findings underscore the necessity of public health interventions to mitigate the risk of histoplasmosis among cave visitors in the region. Additionally, we highlight the utility of qPCR for detecting Histoplasma in environmental and biological samples, supporting future epidemiological research in Latin America.

microbiology↗

bioRxiv2020

Molecular mechanisms of LC3-associated phagocytosis in the macrophage response to Paracoccidioides spp.

Paracoccidiomycosis is a systemic fungal infection that is endemic in Latin America. The etiologic agents are thermodimorphic fungi from the Paracoccidiodes genus, which are facultative intracellular parasites of macrophages. LC3-associated phagocytosis (LAP), a noncanonical form of autophagy, is important in the immune response to similar pathogens, so we sought to determine the role LAP plays in the macrophage response to Paracoccidioides spp. By immunofluorescence, we found that LC3 was recruited to phagosomes containing Paracoccidioides spp. in both RAW264.7 and J774.16 cell lines and in bone marrow-derived macrophages. Interference with autophagy using RNAi against ATG5 reduced the antifungal activity of J774.16 cells, showing that LC3 recrutiment is important for proper control of the fungus by macrophages. Finally, we used pharmacological Syk kinase and NAPH oxidase inhibitors, which inhibit signalling pathways necessary for macrophage LAP against Aspergillus fumigatus and Candida albicans, to dissect part of the signaling pathways that trigger LAP agains Paracoccidioides spp. Interestingly, these inhibitors did not decrease LAP against P. brasiliensis, possibly due to differences in the fungal cell surface compositions. These observations suggest a potential role for autophagy as target for host-directed paracoccidioidomycosis therapies.

immunology↗

bioRxiv2020

Faster Cryptococcus melanization increases virulence in experimental and human cryptococcosis

Cryptococcus spp. are important human pathogens responsible for about 180,000 deaths per year. Studying their virulence attributes can lead to better cryptococcosis prevention and treatment. In this work, we systematically investigated virulence attributes of Cryptococcus spp. clinical isolates and correlated them with patient data. We collected 66 C. neoformans and 19 C. gattii isolates from Brazilian patients and analyzed multiple phenotypes related with their capsule, production of laccase, melanin and extracellular vesicles. We also tested their virulence in Galleria mellonella and ability to evade macrophage LC3-associated phagocytosis (LAP). All phenotypes analyzed varied widely among the isolates, but C. neoformans isolates tended to melanize faster and more intensely and produce thinner capsules in comparison with C. gattii. We also observed correlations that match previous studies, such as that between secreted laccase - but not total melanin production - and disease outcome in patients. The most striking results, though, came from our measurements of Cryptococcus colony melanization kinetics, which followed a sigmoidal curve for most isolates. Faster melanization correlated positively with LAP evasion, virulence in G. mellonella and worse prognosis in humans. These results suggest that the speed of melanization, more than the total amount of melanin Cryptococcus spp. produces, is crucial for virulence. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=162 SRC="FIGDIR/small/222794v2_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@41c48borg.highwire.dtl.DTLVardef@1ce8e1eorg.highwire.dtl.DTLVardef@1d4568corg.highwire.dtl.DTLVardef@17e2003_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2019

A hidden battle in the dirt: soil amoebae interactions with Paracoccidioides spp

Paracoccidioides spp. are thermodimorphic pathogenic fungi endemic to Latin America. Predation is believed to drive the evolution of virulence for soil saprophytes. We evaluated the presence of environmental amoeboid predators in soil from armadillo burrows where Paracoccidioides had been previously detected and tested if interaction of Paracoccidioides with amoebae increased fungal virulence. Nematodes, ciliates and amoebae - all potential predators of fungi - grew in cultures from soil samples. Microscopical observation and ITS sequencing identified the amoebae as Acanthamoeba spp, Allovahlkampfia spelaea and Vermamoeba vermiformis. These three amoebae efficiently ingested, killed and digested Paracoccidioides spp. yeast cells, as did laboratory-adapted axenic Acanthamoeba castellanii. Sequential co-cultivation of Paracoccidioides with A. castellanii selected for phenotypical traits related to survival of the fungus within a natural predator as well as in murine macrophages and in vivo (Galleria mellonella and mice). This increase in virulence is linked to the accumulation of cell wall alpha-glucans, polysaccharides that masks recognition of fungal molecular patterns by host pattern recognition receptors. Altogether, our results indicate that Paracoccidioides inhabits a complex environment with multiple amoeboid predators that can exert selective pressure to guide the evolution of virulence traits.

microbiology↗