The cell biology of the Trichosporon-Host interaction

Fungi of the genus Trichosporon are increasingly recognized as causative agents of superficial and invasive fungal disease in humans. Although most species are considered commensals of the human skin and gastrointestinal tract, these basidiomycetes are an increasing cause of fungal disease among immunocompromised hosts, such as hematological patients and solid organ transplant recipients. The initiation of commensal or pathogenic programs by Trichosporon spp. involves the adaptation to the host microenvironment and its immune system. However, the exact virulence factors activated upon the transition to a pathogenic lifestyle, including the intricate biology of the cell wall, and how these interact with and subvert the host immune responses remain largely unknown. Here, we revisit our current understanding of the virulence attributes of Trichosporon spp., particularly T. asahii, and their interaction with the host immune system, and accommodate this knowledge within novel perspectives on fungal diagnostics and therapeutics.This work was supported by the Northern Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (FEDER) (NORTE-01-0145-FEDER000013), and by Fundação para a Ciência e Tecnologia (FCT) (IF/00735/2014 to AC, and SFRH/BPD/96176/2013 to CC).info:eu-repo/semantics/publishedVersio

Candida parapsilosis secreted lipase as an important virulence factor

The prevalence of Candida parapsilosis, an opportunistic human pathogenic fungal species, is increasing at an alarming rate in the hospital environment. Patients at risk for C. parapsilosis infection include those with immunosuppression, such as individuals with cancer, AIDS, and low birth weight premature neonates as well as patients that had undergone abdominal surgery. Neonatal candidiasis caused by C. parapsilosis has been widely reported across the globe. Various reports have shown that, compared to other Candida species, certain C. parapsilosis clinical isolates were less susceptible to antifungals such as amphotericin B, fluconazole, and caspofungin. In addition, some studies have even reported multi-echinocandin or multi-azole resistant strains of C. parapsilosis. C. parapsilosis has several virulence factors that contribute to its capacity for host invasion and among these factors extracellular lipases have a major role in pathogenesis. In this review we have collected all the recent relevant studies that confirm the involvement of secreted lipases in C. parapsilosis pathogenesis, using both in vitro and in vivo models of infection. Of particular note, an available lipase deficient C. parapsilosis strain has been utilized to demonstrate that the lack of secreted lipases decreased virulence, reduced tissue damage, and was less able to survive within phagocytes or mice compared to the wild type. Since fungal secreted lipases have different characteristics than lipolytic enzymes present in humans, C. parapsilosis extracellular lipases may be potential targets for the development of novel antifungal drugs

Lactobacillus (L.) acidophilus, L. plantarum, L. rhamnosus and L. reuteri Cell-Free-Supernatants inhibit Candida parapsilosis pathogenic potential upon infection of vaginal epithelial cells monolayer and in a transwell co-culture system in vitro.

Vulvovaginal candidiasis (VVC) is a common clinical condition with symptoms and signs of vaginal inflammation in the presence of Candida species. At least one episode of VVC is experienced in up to 75% of women in the reproductive age group during their lifetime, and 5-8% of such women suffer from the chronic form. Most cases of VVC are still caused by C. albicans; however, the incidence of VVC cases by non-albicans (NAC) species, such as C. parapsilosisis, is continuously increasing. Despite the prevalence of VVC from NAC, to date little is known on these species, and almost nothing on the mechanisms that trigger the VVC. Lactobacillus spp. are the most represented microorganisms in the vaginal microbiota of healthy women. Here, cell-free supernatants (CFS) obtained from L. acidophilus, L. plantarum, L. rhamnosus, L. reuteri were assessed for their effect on C. parapsilosis virulence traits. Moreover, we assessed if such effect persists even after removal of the CFS (CFS-preincubation effect). Moreover, a transwell co-culture system was employed, by which the relevant antifungal effect was shown to be attributable to the compounds released by Lactobacilli. Our results suggests that Lactobacilli can work: a) by reducing C. parapsilosis virulence traits, as indicated by the reduced fungal proliferation, viability and metabolic activity and b) by improving epithelial resistance to the fungus. Overall, these data suggest that, in the context of vaginal microbiota, the Lactobacilli may play a role in preventing the onset of mucosal C. parapsilosis infection

Evolution of loss of heterozygosity patterns in hybrid genomes of Candida yeast pathogens

Background Hybrids are chimeric organisms with highly plastic heterozygous genomes that may confer unique traits enabling the adaptation to new environments. However, most evolutionary theory frameworks predict that the high levels of genetic heterozygosity present in hybrids from divergent parents are likely to result in numerous deleterious epistatic interactions. Under this scenario, selection is expected to favor recombination events resulting in loss of heterozygosity (LOH) affecting genes involved in such negative interactions. Nevertheless, it is so far unknown whether this phenomenon actually drives genomic evolution in natural populations of hybrids. To determine the balance between selection and drift in the evolution of LOH patterns in natural yeast hybrids, we analyzed the genomic sequences from fifty-five hybrid strains of the pathogenic yeasts Candida orthopsilosis and Candida metapsilosis, which derived from at least six distinct natural hybridization events. Results We found that, although LOH patterns in independent hybrid clades share some level of convergence that would not be expected from random occurrence, there is an apparent lack of strong functional selection. Moreover, while mitosis is associated with a limited number of inter-homeologous chromosome recombinations in these genomes, induced DNA breaks seem to increase the LOH rate. We also found that LOH does not accumulate linearly with time in these hybrids. Furthermore, some C. orthopsilosis hybrids present LOH patterns compatible with footprints of meiotic recombination. These meiotic-like patterns are at odds with a lack of evidence of sexual recombination and with our inability to experimentally induce sporulation in these hybrids. Conclusions Our results suggest that genetic drift is the prevailing force shaping LOH patterns in these hybrid genomes. Moreover, the observed LOH patterns suggest that these are likely not the result of continuous accumulation of sporadic events—as expected by mitotic repair of rare chromosomal breaks—but rather of acute episodes involving many LOH events in a short period of time.This work was supported by the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. H2020-MSCA-ITN-2014-642095. The TG group also acknowledges the support from the Spanish Ministry of Economy, Industry, and Competitiveness (MEIC) for the EMBL partnership and grants “Centro de Excelencia Severo Ochoa 2013-2017” SEV-2012-0208 and BFU2015-67107 co-founded by the European Regional Development Fund (ERDF); from the CERCA Programme/Generalitat de Catalunya; from the Catalan Research Agency (AGAUR) SGR857 and grants from the European Union’s Horizon 2020 research and innovation program under the grant agreement ERC-2016-724173. TG also receives support from an INB Grant (PT17/0009/0023—ISCIII-SGEFI/ERDF). The authors thank Dr. Powel Golik’s guidance in the identification of PPR proteins, Simone Mozzachiodi and Dr. Gianni Liti for the helpful discussions on the analysis of meiotic patterns, and all Gabaldón lab members for the helpful discussions and comments on this work, especially Marina Marcet-Houben.Peer ReviewedPostprint (author's final draft

Complex and Controversial Roles of Eicosanoids in Fungal Pathogenesis

The prevalence of fungal infections has increased in immunocompromised patients, leading to millions of deaths annually. Arachidonic acid (AA) metabolites, such as eicosanoids, play important roles in regulating innate and adaptative immune function, particularly since they can function as virulence factors enhancing fungal colonization and are produced by mammalian and lower eukaryotes, such as yeasts and other fungi (Candida albicans, Histoplasma capsulatum and Cryptococcus neoformans). C. albicans produces prostaglandins (PG), Leukotrienes (LT) and Resolvins (Rvs), whereas the first two have been well documented in Cryptococcus sp. and H. capsulatum. In this review, we cover the eicosanoids produced by the host and fungi during fungal infections. These fungal-derived PGs have immunomodulatory functions analogous to their mammalian counterparts. Prostaglandin E2 (PGE2) protects C. albicans and C. parapsilosis cells from the phagocytic and killing activity of macrophages. H. capsulatum PGs augment the fungal burden and host mortality rates in histoplasmosis. However, PGD2 potentiates the effects and production of LTB4, which is a very potent neutrophil chemoattractant that enhances host responses. Altogether, these data suggest that eicosanoids, mainly PGE2, may serve as a new potential target to combat diverse fungal infections

Trk1-mediated potassium uptake contributes to cell-surface properties and virulence of Candida glabrata

The absence of high-affinity potassium uptake in Candida glabrata, the consequence of the deletion of the TRK1 gene encoding the sole potassium-specific transporter, has a pleiotropic effect. Here, we show that in addition to changes in basic physiological parameters (e.g., membrane potential and intracellular pH) and decreased tolerance to various cell stresses, the loss of high affinity potassium uptake also alters cell-surface properties, such as an increased hydrophobicity and adherence capacity. The loss of an efficient potassium uptake system results in diminished virulence as assessed by two insect host models, Drosophila melanogaster and Galleria mellonella, and experiments with macrophages. Macrophages kill trk1Δ cells more effectively than wild type cells. Consistently, macrophages accrue less damage when co-cultured with trk1Δ mutant cells compared to wild-type cells. We further show that low levels of potassium in the environment increase the adherence of C. glabrata cells to polystyrene and the propensity of C. glabrata cells to form biofilms

A Novel Cold-Active Lipase from Candida albicans: Cloning, Expression and Characterization of the Recombinant Enzyme

A novel lipase gene lip5 from the yeast Candida albicans was cloned and sequenced. Alignment of amino acid sequences revealed that 86–34% identity exists with lipases from other Candida species. The lipase and its mutants were expressed in the yeast Pichia pastoris, where alternative codon usage caused the mistranslation of 154-Ser and 293-Ser as leucine. 154-Ser to leucine resulted in loss of expression of Lip5, and 293-Ser to leucine caused a marked reduction in the lipase activity. Lip5-DM, which has double mutations that revert 154 and 293 to serine residues, showed good lipase activity, and was overexpressed and purified by (NH4)2SO4 precipitation and ion-exchange chromatography. The pure Lip5-DM was stable at low temperatures ranging from 15–35 °C and pH 5–9, with the optimal conditions being 15–25 °C and pH 5–6. The activation energy of recombinant lipase was 8.5 Kcal/mol between 5 and 25 °C, suggesting that Lip5-DM was a cold–active lipase. Its activity was found to increase in the presence of Zn2+, but it was strongly inhibited by Fe2+, Fe3+, Hg2+ and some surfactants. In addition, the Lip5-DM could not tolerate water-miscible organic solvents. Lip5-DM exhibited a preference for the short-and medium-chain length p-nitrophenyl (C4 and C8 acyl group) esters rather than the long chain length p-nitrophenyl esters (C12, C16 and C18 acyl group) with highest activity observed with the C8 derivatives. The recombinant enzyme displayed activity toward triacylglycerols, such as olive oil and safflower oil

Variability of biofilm formation and macro morphology among Candida Parapsilosis clinical isolates

The human pathogenic yeast Candida parapsilosis has gained significant importance over the past decades as one of the principal causes of fungal bloodstreaminfections. Its capacity to adhere to host cells and clinically used abiotic surfaces (e.g. prostheses or catheters) is crucial during colonization processes and theestablishment of infections. Isolates of C. parapsilosis are known to be able to switch between several different colony morphologies in vitro, which are correlated with different cell shapes and altered cell surface properties.Prompted by a set of clinical specimen from a single patient that yielded stable smooth­ as well as crepe­morphology lineages, we investigated the differences between these 5 linages and characterized the phenotypic spectrum as well as underlying mechanisms in >300 different­morphology clinical isolates.In contrast to the initial assumption that the 5 different patient isolates were switched forms of an otherwise clonal strain, we found by genome sequencing that the patient was colonized by at least three distinct linages of C. parapsilosis. Detailed statistical analysis placed the linages distantly across the population of C. parapsilosis. Interestingly the Candidemia­associated blood culture isolate was of smooth morphology and matched with an isolate from the patient’s nose of similar morphology; however the BC­isolate had undergone significant genomic rearrangements.Next we analyzed biofilm formation capacity and differences in morphotypes among several hundred clinical isolates which showed a multitude of phenotypiccombinations, but no correlation with site of isolation was evident. Differences in colony morphology correlated with biofilm formation capacity and agar invasion, but not necessarily with virulence in a galleria infection model. Drug susceptibility profiles were altered between groups of biofilm­forming vs. non­forming isolates.In addition to a core cell wall proteome consisting of carbohydrate­active enzymes a set of adhesins were detected in the cell walls of selected hyperbiofilm­formingisolates by mass spectrometry. Downstream analyses showed distinct correlations of phenotypes such as altered virulence or morphology with adhesinincorporation. Incorporation of specific adhesin proteins into the cell wall of C. parapsilosis is associated with colony morphology which governs clinical parameterssuch as biofilm formation capacity and alters drug susceptibility