Candida Albicans Yeast Cells Research Articles

Synthesis and Biological Evaluation of a Series of New Hybrid Amide Derivatives of Triazole and Thiazolidine-2,4-dione.

A series of hybrid compounds with triazole and thiazolidine nuclei connected by a linker has been synthesized and extensively studied. Various synthetic methods for the target compounds have been tested. A microbiological assessment of the obtained compounds was carried out on strains of pathogenic fungi C. albicans, C. non-albicans, multidrug-resistant C. auris, Rhizopus arrhizus, Aspergillus spp. and some dermatophytes and other yeasts. The lowest obtained MIC values for target compounds lie between 0.003 µg/mL and 0.5 µg/mL and therefore the compounds are not inferior or several times better than commercial azole drugs. The length of the acylpiperazine linker has a limited effect on antifungal activity. Some bioisosteric analogues were tested in microbiological analysis, but turned out to be weaker than the leader in activity. The highest activity was demonstrated by a compound with para-chlorobenzylidene substituent in the thiazolidine fragment. Molecular modelling was used to predict binding modes of synthesized molecules and rationalize experimentally observed SAR. The leader compound is twice more effective in inhibiting the formation of germ tubes by Candida albicans yeast cells compared to voriconazole. An increased level of Pdr5, an azoles drug efflux pump was observed, but the increase is lower than that caused by azoles. The results can be useful for further development of more powerful and safe antifungal agents.

Instant Candida albicans Detection Using Ultra-Stable Aptamer Conjugated Gold Nanoparticles.

Fungal pathogens such as Candida albicans have significant impacts on women's health and the economy worldwide. Current detection methods often require access to laboratory facilities that are costly, inconvenient, and slow to access. This often leads to self-diagnosis, self-treatment and eventual antifungal resistance. We have created a rapid (within five minutes), cost-effective, and user-friendly method for the early detection of Candida albicans. Our platform utilises aptamer-tagged-gold-core-shell nanoparticles for Candida albicans detection based on the presence of 1,3-β-d glucan molecules. Nanoparticle aggregation occurs in the presence of Candida albicans fungal cells, causing a redshift in the UV-visible absorbance, turning from pink/purple to blue. This colour change is perceptible by the naked eye and provides a "yes"/"no" result. Our platform was also capable of detecting Candida albicans from individual yeast colonies without prior sample processing, dilution or purification. Candida albicans yeast cells were detected with our platform at concentrations as low as 5 × 105 cells within a 50 μL sample volume. We believe that this technology has the potential to revolutionise women's health, enabling women to test for Candida albicans accurately and reliably from home. This approach would be advantageous within remote or developing areas.

Antimicrobial Activity of Milk Whey in Different Mammals.

Antimicrobial activity of milk whey in different mammals against Candida albicans yeast cells was studied by a spectrophotometric method. The activity increased in the order goat→horse→camel→cow→human→mouse. The level of whey activity in mice was higher by 3 and 10 times than in humans and goats, respectively. Similar changes were noted for activity of the whey fraction <100 kDa containing a complex of antimicrobial polypeptides, and there was a direct correlation between these two parameters (r=0.881; p<0.05). The total activity of whey had a high degree of correlation with the content of serum albumin (r=0.992); in mice, the level of serum albumin in the milk whey was close to that in blood serum. Interspecific differences between the activity of whey in mammals may be associated with qualitative and quantitative variability of the antimicrobial polypeptide composition, as well as their synergistic or antagonistic interaction with each other.

The nature of the fungal cargo induces significantly different temporal programmes of macrophage phagocytosis

Phagocytosis is an essential component of our immune defence against fungal pathogens. Differences in the dynamics of phagocyte migration, recognition, uptake and phagolysosome maturation are dependent on the characteristics of the fungal cargo, and in particular to differences in cell wall composition and cellular morphology. However, studies that have focused on phagocyte interactions with individual fungal species have not enabled comparisons in the kinetics of these interactions to be made between these different species. We therefore used live cell video microscopy to examine the temporal dynamics of phagocytosis for a range of fungal cargoes by thioglycollate–elicited peritoneal macrophages from C57BL/6 mice. Uniform populations of macrophages were challenged at the same time with yeast cells of Candida albicans, Candida glabrata, Saccharomyces cerevisiae and Cryptococcus neoformans (wild–type and an acapsular mutant, cap59Δ), and spores of Aspergillus fumigatus and Mucor circinelloides to enable standardized comparative interactions to be quantified from different stages of phagocytosis. Differences in the rate of uptake of fungal cells varied by up to 26–fold, whilst differences in time to induce phagosome acidification varied by as much as 29–fold. Heat-killing or opsonizing the fungal targets markedly affected the kinetics of the interaction in a species–specific manner. Fungal and macrophage killing assays further revealed cargo–specific differences in phagocytosis and diversity in fungal evasion mechanisms. Therefore, simultaneous assessment of the interaction of macrophages with different fungal pathogens highlighted major differences in the kinetics and growth responses during fungus–phagocyte interactions that are likely to impact on pathogenesis and virulence.

Crosstalk between the calcineurin and cell wall integrity pathways prevents chitin overexpression in Candida albicans.

ABSTRACTEchinocandins such as caspofungin are frontline antifungal drugs that compromise β-1,3 glucan synthesis in the cell wall. Recent reports have shown that fungal cells can resist killing by caspofungin by upregulation of chitin synthesis, thereby sustaining cell wall integrity (CWI). When echinocandins are removed, the chitin content of cells quickly returns to basal levels, suggesting that there is a fitness cost associated with having elevated levels of chitin in the cell wall. We show here that simultaneous activation of the calcineurin and CWI pathways generates a subpopulation of Candida albicans yeast cells that have supra-normal chitin levels interspersed throughout the inner and outer cell wall, and that these cells are non-viable, perhaps due to loss of wall elasticity required for cell expansion and growth. Mutations in the Ca2+-calcineurin pathway prevented the formation of these non-viable supra-high chitin cells by negatively regulating chitin synthesis driven by the CWI pathway. The Ca2+-calcineurin pathway may therefore act as an attenuator that prevents the overproduction of chitin by coordinating both chitin upregulation and negative regulation of the CWI signaling pathway. This article has an associated First Person interview with the first author of the paper.

Preparation and In Vitro Evaluation of Alginate Microparticles Containing Amphotericin B for the Treatment of Candida Infections.

Invasive candidiasis (IC) remains as a major cause of morbidity and mortality in critically ill patients. Amphotericin B (AmB) is one of the most effective antifungal agents commonly used to treat this infection. However, it induces severe side effects such as nephrotoxicity, cardiac alterations, nausea, fever, and liver damage. The utilization of drug delivery systems has been explored to overcome these limitations. Several AmB lipid formulations have been developed and are currently available in the market. Although they have the ability to reduce the main side effects of free AmB, their high cost, necessity of repeated intravenous injections for successful treatment, and incidence of pulmonary toxicity have limited their use. In the last decades, alginate has gained significant interest in drug delivery applications as a cost-effective strategy to improve the safety and therapeutic effect of toxic drugs. In this work, the clinically relevant drug AmB was encapsulated into alginate microparticles using the emulsification/external gelation method. We hypothesize that this synthesis strategy may positively impact the antifungal efficacy of AmB-loaded MCPs toward Candida albicans cells while reducing the toxicity in human lung cells. To prove this hypothesis, the ability of the microplatform to disrupt the cellular membrane potential was tested and its antifungal effectiveness toward Candida albicans cells was evaluated using the cell counting and plate count methods. Moreover, the toxicity of the microplatform in human lung cells was evaluated using CellTiter 96® AQueous cell viability assay and qualitative diffusion analysis of acridine orange. Our results demonstrated that the platform developed in this work was able to induce antifungal toxicity against Candida albicans yeast cells at the same level of free AmB with minimal toxicity to lung cells, which is one of the main side effects induced by commercial drug delivery systems containing AmB. Overall, our data provides convincing evidence about the effectiveness of the alginate-based microplatform toward Candida albicans cells. In addition, this vehicle may not require several infusions for a successful treatment while reducing the pulmonary toxic effect induced by commercial lipid formulations.

SYNTHESIS AND PROPERTIES OF NEW N-ACYL DERIVATIVES OF ANTHRANILIC ACID

A series of N-acyl derivatives of anthranil (or o -aminobenzoic acid) was first synthesized, namely 2-(4-octylbenzamido)benzoic acid, 2-(4-(heptyloxy)- benzamido)benzoic acid, 2-(4-(heptylsulfanyl)benz-amido)benzoic acid. 2-(4-octylbenzamido)benzoic acid was synthesized in five stages of octylbenzene, by acylating chloride acid using a Friedie-Crafts reaction. 2-(4-(heptyloxy)benzamido)benzoic acid was prepared from the methyl ester of p-hydroxybenzoic acid which, at the first stage, was activated with 1-bromoheptane in acetonitrile with potassium carbonate and catalytic amount of sodium iodide at heating. After that, hydrolysis of the ester group by hydroxide in the methanol–water system was performed. Synthesis of 2-(4-(heptylsulfanyl)benzamido)benzoic acid was carried out from p-sulfanylbenzoic acid, which was activated with 1-bromoheptane, in a system of ethanol–water with sodium hydroxide. Chlorinated hydrides of acids were obtained by reaction of acids with chlorinated thionyl in benzene. Acylation of the tret-butyl ester of anthranilic acid with formed chlorohydrides was carried out in pyridine upon heating and in dichloromethane with triethylamine (as the base), and dimethylaminopyridine (catalyst).At the last stage of the synthesis of all derivatives, the hydrolysis of tret-butyl esters with trifluoroacetic acid in dichloromethane to the formation of terminal compounds took place.The composition and structure of the synthesized compounds were determined using NMR 1H, infrared spectroscopy. The shape and position of the bands in the IR absorption spectra of the synthesized anthranilic acid derivatives are shifted and splited in comparison with the parent acid due to the presence of a secondary amino group, an additional aromatic moiety, and a different nature of the substitutes in the para-position to the amino group. For all synthesized derivatives, the sensitivity of various morphological forms Candida albicans was determined. The influence of the test substances on the cells of the yeast fungus was determined for 24–48 hours using Saburo and Spider nutrient media with the addition of mannitol. Compared with the already known influence of anthranilic acid on Candida albicans cells grown in Saburo nutrient medium for 24 hours, the compounds studied were more effective at all stages of cultivation. It has been shown that the synthetic derivatives studied are more active with respect to the cells in the biofilm composition, which consists of the yeast-like form of Candida albicans, than those cells that form a hyphal type biofilm. The yeast-like form of the Candida albicans cell is susceptible to synthetic derivatives. It is shown that the level of sensitivity of compounds 1-3 is higher in 4-6 times compared with anthranilic acid. Glyphs have been found to be more susceptible to the effects of the compounds studied than Е yeast cells of Candida albicans

Serum Amyloid P Component Bound to Fungal Functional Amyloid Is Anti-Phagocytic and Anti-inflammatory

Abstract Invasive fungal disease is often characterized by a sparse cellular inflammatory response, and we have proposed that deposition of serum amyloid P component (SAP, also called PTX2) on fungal surfaces dampens the innate immune response. Binding of SAP to fungi was dependent upon fungal expression of cell surface functional amyloid, with 92% of Candida albicans yeast cells binding SAP, whereas only 18% of yeasts of an amyloid-depleted strain of Saccharomyces cerevisiae bound SAP. Furthermore, SAP bound to 40% of S. cerevisiae cells expressing the amyloidogenic C. albicans adhesin Als5pWT, but only 19% of cells expressing a non-amyloidogenic single site mutant, Als5pV326N. Macrophages phagocytosed fungi in proportion to expression of surface amyloid: C. albicans &amp;gt; S. cerevisiae expressing Als5pWT &amp;gt;&amp;gt;&amp;gt;S. cerevisiae expressing Als5pV326N or S. cerevisiae. Macrophages incubated with C. albicans yeasts secreted significantly increased amounts of IFNγ, IL-6, TNFα and IL-10. Pre-treatment of macrophages with SAP or yeasts with SAP reduced C. albicans phagocytosis by more than 80% within 30 minutes, and led to reductions of IFNγ, IL-6, TNFα, but to an increase in the secretion of the anti-inflammatory cytokine IL-10. The structurally similar pentraxin, C-reactive protein, demonstrated negligible binding to Candida (7% on flow cytometry) and slightly increased macrophage phagocytosis of yeasts. Thus SAP, whether added exogenously to macrophages or coating fungi, rapidly dampened the host cellular immune response. These findings support the hypothesis that amyloid-dependent SAP binding diminishes cellular innate immunity in invasive candidiasis in humans.

Monitoring Organelle‐Specific Responses to Amphotericin B in Mammalian Cells and Candida albicans Biofilms

The use of indwelling medical devices such as catheters or dentures in combination with immunosuppressive therapies increase the body's susceptibility to fungal infections as a pathway to life threatening systemic infections. In particular, Candida albicans, an opportunistic pathogen existing in the normal microbial flora can produce serious systemic infections. This species is unique in its ability to exist in two phases: a yeast form and hyphal biofilm. Once it advances into its biofilm formation, Candida albicans is resistant towards drug treatment, making it immensely difficult to treat in clinical settings. Confocal laser microscopy using organelle‐specific fluorescent probes provides an internal view of Candida albicans along the stages of development and drug response. We have developed and deployed a series of our own naphthalimide‐based fluorescent probes targeted to mitochondria, lysosomes, and the Golgi apparatus to monitor organelle vitality in real time. The brightness, chemical and photo‐stability of our organelle probes allows us to image live cells in their appropriate culture media to observe cellular responses to drug treatments. The resistance to photobleaching makes them useful for longer periods of laser exposure as well as 3D imaging. We have investigated the various liposomal as well as micellar formulations of Amphotericin B including Fungizone, Abelcet, and Ambisome. All formulations of Amphotericin B display some level of toxicity, but lipid formulations such as Abelcet and Ambisome have shown a great reduction in human toxicity without significantly sacrificing their antifungal activity. Using our organelle probes in vitro, we are able to monitor the changes in specific organelles in both model human cells and Candida albicans yeast and hyphal cells to pinpoint the intracellular responses to Amphotericin B in both the target and host. Thus far we have found that Amphotericin B, especially Fungizone, leads to depolarization of mitochondria in some human cell lines while having little acute effect on mitochondria in Candida albicans biofilms. Comparable Amphotericin B doses in the forms of Abelcet and Ambisome, on the other hand, seem to allow for the maintenance of mitochondrial membrane potential in human cells as seen by persistent polarization following multiple hours of incubation. We are currently investigating the time‐dependent relationship between organelle vitality and the differing Amphotericin B formulations with all our probes and cell lines to provide insight as to how Amphotericin B affects mammalian, yeast and biofilm cells differently. Gaining this intracellular perspective of cell health will open doors for the optimization of antifungal drugs through pinpointing their effective mechanisms against fungi while minimizing cellular casualties resulting from organelle decline.Support or Funding InformationOffice of Research and Sponsored Programs‐UW‐Eau Claire

Direct electric current modifies important cellular aspects and ultrastructure features of Candida albicans yeasts: Influence of doses and polarities.

Available treatments against human fungal pathogens present high levels of resistance, motivating the development of new antifungal therapies. In this context, the present work aimed to analyze direct electric current (DC) antifungal action, using an in vitro apparatus equipped with platinum electrodes. Candida albicans yeast cells were submitted to three distinct conditions of DC treatment (anodic flow-AF; electroionic flow-EIF; and cathodic flow-CF), as well as different charges, ranging from 0.03 to 2.40 C. Our results indicated C. albicans presented distinct sensibility depending on the DC intensity and polarity applied. Both the colony-forming unit assay and the cytometry flow with propidium iodide indicated a drastic reduction on cellular viability after AF treatment with 0.15 C, while CF- and EIF-treated cells stayed alive when DC doses were increased up to 2.40 C. Additionally, transmission electron microscopy revealed important ultrastructural alterations in AF-treated yeasts, including cell structure disorganization, ruptures in plasmatic membrane, and cytoplasmic rarefaction. This work emphasizes the importance of physical parameters (polarity and doses) in cellular damage, and brings new evidence for using electrotherapy to treat C. albicans pathology process. Bioelectromagnetics. 38:95-108, 2017. © 2016 Wiley Periodicals, Inc.

Autophagy and Reactive Oxygen Species Are Involved in Neutrophil Extracellular Traps Release Induced by C. albicans Morphotypes.

Neutrophil extracellular traps (NETs) are a combination of DNA fibers and granular enzymes, such as elastase and myeloperoxidase. In this study, we demonstrate that Candida albicans hyphal (CAH) cells and yeast (CAY) cells induce differential amounts, kinetics and mechanisms of NET release. CAH cells induced larger quantities of NET compared to CAY cells and can stimulate rapid NET formation up to 4 h of incubation. CAY cells are, also, able to induce rapid NET formation, but this ability was lost at 4 h. Both reactive oxygen species (ROS) and autophagy are implicated in NET induced by CAH and CAY cells, but with a time-different participation of these two mechanisms. In particular, in the early phase (15 min) CAH cells stimulate NET via autophagy, but not via ROS, while CAY cells induce NET via both autophagy and ROS. At 4 h, only CAH cells stimulate NET formation using autophagy as well as ROS. Finally, we demonstrate that NET release, in response to CAH cells, involves NF-κB activation and is strongly implicated in hyphal destruction.

ZnSe:Mn aqueous colloidal quantum dots for optical and biomedical applications

AbstractIn this study, we present the optimization of the optical properties of Mn2+ doped ZnSe QDs (also referred to as d‐dots) coated with thioglycolic acid in aqueous medium. The nanoparticles were characterized by ionic coupled plasma, electron paramagnetic resonance, transmission electron microscopy and X‐ray diffractometry. By applying a controlled dose of UV irradiation, we obtained efficient orange emitting d‐dots (4T1→ 6A1 transition centered at 580 nm). The results point out to a doping fraction in the nanoparticles smaller than 1% (0.89%), and that the Mn2+ ions are preferentially located close to the particle's surface. The UV photoactivation procedure has a definite influence on the emission intensity and on the colloidal stability of the particles. Photoactivated Mn2+ d‐dots were conjugated to Concanavalin A and labeled specifically Candida albicans yeast cells, by targeting carbohydrate residues depicting the successful use of these QDs as fluorescent probes. (© 2016 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Sustained Nitric Oxide-Releasing Nanoparticles Induce Cell Death in Candida albicans Yeast and Hyphal Cells, Preventing Biofilm Formation In Vitro and in a Rodent Central Venous Catheter Model.

Candida albicansis a leading nosocomial pathogen. Today, candidal biofilms are a significant cause of catheter infections, and such infections are becoming increasingly responsible for the failure of medical-implanted devices.C. albicansforms biofilms in which fungal cells are encased in an autoproduced extracellular polysaccharide matrix. Consequently, the enclosed fungi are protected from antimicrobial agents and host cells, providing a unique niche conducive to robust microbial growth and a harbor for recurring infections. Here we demonstrate that a recently developed platform comprised of nanoparticles that release therapeutic levels of nitric oxide (NO-np) inhibits candidal biofilm formation, destroys the extracellular polysaccharide matrices of mature fungal biofilms, and hinders biofilm development on surface biomaterials such as the lumen of catheters. We found NO-np to decrease both the metabolic activity of biofilms and the cell viability ofC. albicansin vitroandin vivo Furthermore, flow cytometric analysis found NO-np to induce apoptosis in biofilm yeast cellsin vitro Moreover, NO-np behave synergistically when used in combination with established antifungal drug therapies. Here we propose NO-np as a novel treatment modality, especially in combination with standard antifungals, for the prevention and/or remediation of fungal biofilms on central venous catheters and other medical devices.

Unnatural amino acid-mediated synthesis of silver nanoparticles and their antifungal activity against Candida species

In this study, the biocompatible unnatural amino acid, 3,4-dihydroxy-l-phenylalanine (l-dopa), which is used in protein engineering, was employed in the facile synthesis of silver nanoparticles (AgNPs). The surface plasmon resonance (SPR) band of the UV–Vis spectrum at 406 nm demonstrates the possibility of formation of smaller nanoparticles; the symmetrical shape of the band demonstrates a narrow size distribution of AgNPs, the formation of AgNPs, and the face-centered cubic (fcc) crystalline structure of nanoparticles was confirmed by X-ray diffraction (XRD). Additionally, transmission electron microscopic (TEM) images revealed that these particles were spherical in shape with diameters of 2.7–12.2 nm (average = 8.7 nm). These nanoparticles exhibited antifungal activity against both planktonic and biofilm yeast cells of Candida albicans and C. dubliniensis. The minimum inhibitory concentrations (MICs) and minimum fungicidal concentrations (MFCs) were determined by microdilution assays. C. albicans were shown to be less susceptible than C. dubliniensis to AgNPs based on the MIC (ranging from 7.8 to 15.6 µg ml−1) and MFC (ranging from 31.2 to 62.5 µg ml−1). With regard to biomass quantification, AgNPs did not induce a significant reduction of the biomass of Candida species; however, treatment of biofilm with 500 µg/ml of AgNPs induced a 2.99−log10 (P < 0.001) and 3.53−log10 (P < 0.001) significant reduction in the number of culturable cells of CFUs when compared to control samples of C. albicans and C. dubliniensis, respectively. Thus, AgNPs-based antifungal agents would be an effective alternative to conventional drugs to overcome drug resistance in Candida-associated infections.

The effect of chitin size, shape, source and purification method on immune recognition.

The animal immune response to chitin is not well understood and needs to be investigated further. However, this is a challenging topic to study because of the technical difficulties in purifying chitin, and because this material usually comes associated with contaminating components that can activate the immune system. In this study, improvements to previously described purification protocols were investigated for chitin obtained from different sources, including commercial shellfish, Candida albicans yeast and hyphal cell walls, as well as cell walls of the filamentous fungi Aspergillus fumigatus and Mucor circinelloides. The immune response to these different chitin preparations was tested using human peripheral blood mononuclear cells. In agreement with previous literature, small chitin particles of an average size of 0.2 µm were not immunogenic. On the other hand, bigger chitin particles induced in some cases a pro-inflammatory response. The results of this work suggest that not only the purity and size of the chitin particles, but also their shape can influence immune recognition.

A family of secreted pathogenesis‐related proteins in Candida albicans

Analysing culture supernatants of yeast and hyphal cells of Candida albicans, we found two close homologues of pathogenesis-related (PR-) 1 proteins, Rbe1p and Rbt4p, in the secretome. Due to sequence homology, three additional, yet not characterized open reading frames, ORF19.6200, ORF19.2787 and ORF19.2336, together with RBE1 and RBT4 were assigned to a novel family of CaPRY proteins. In a Δrbe1/Δrbt4 deletion strain, genome-wide transcriptional analysis revealed differential transcription of only a limited set of genes implicated in virulence and oxidative stress response. Single deletion of RBE1 or RBT4 in a clinical C. albicans isolate resulted in a moderate but significant attenuation in virulence in a mouse model for disseminated candidiasis. However, a synergistic effect was observed in a Δrbe1/Δrbt4 double deletion strain, where virulence was strongly affected. Remarkably, transcription of RBT4 and RBE1 was each upregulated in blastospores of Δrbe1 or hyphae of Δrbt4 deletion strains respectively, indicating functional complementation thereby compensating a potential virulence defect in the single deletion strains. Furthermore, the double deletion strain showed increased sensitivity to attack by polymorphonuclear leucocytes. Therefore, the crucial contribution of both C. albicans pathogenesis-related proteins to virulence might be vested in protection against phagocyte attack.

Curcumin antifungal and antioxidant activities are increased in the presence of ascorbic acid

The objective of this study was to evaluate the antifungal and antioxidant activities of curcumin, ascorbic acid and the mixture of these two compounds. For the antifungal assay, the minimum inhibitory concentrations (MIC) were determined using Candida strains (ATCC and clinical isolates). Curcumin alone inhibited growth of Candida albicans yeast cells, whereas ascorbic acid did not present effects. However, when the mixture of ascorbic acid and curcumin was assayed to determine the association of the two compounds, the curcumin MIC decreased 5- to 10-fold. In the antioxidant assays, the sum of the alone activities of curcumin and ascorbic acid were lower than the activity of the two-compound mixture. This study highlights the importance of the association between two common antioxidants in foods, to improve the antifungal and antioxidant activities of curcumin (in vitro), and can be applied to Candida spp. infection and diseases associated with oxidative stress.

Candida albicans Infection of Caenorhabditis elegans Induces Antifungal Immune Defenses

Candida albicans yeast cells are found in the intestine of most humans, yet this opportunist can invade host tissues and cause life-threatening infections in susceptible individuals. To better understand the host factors that underlie susceptibility to candidiasis, we developed a new model to study antifungal innate immunity. We demonstrate that the yeast form of C. albicans establishes an intestinal infection in Caenorhabditis elegans, whereas heat-killed yeast are avirulent. Genome-wide, transcription-profiling analysis of C. elegans infected with C. albicans yeast showed that exposure to C. albicans stimulated a rapid host response involving 313 genes (124 upregulated and 189 downregulated, ∼1.6% of the genome) many of which encode antimicrobial, secreted or detoxification proteins. Interestingly, the host genes affected by C. albicans exposure overlapped only to a small extent with the distinct transcriptional responses to the pathogenic bacteria Pseudomonas aeruginosa or Staphylococcus aureus, indicating that there is a high degree of immune specificity toward different bacterial species and C. albicans. Furthermore, genes induced by P. aeruginosa and S. aureus were strongly over-represented among the genes downregulated during C. albicans infection, suggesting that in response to fungal pathogens, nematodes selectively repress the transcription of antibacterial immune effectors. A similar phenomenon is well known in the plant immune response, but has not been described previously in metazoans. Finally, 56% of the genes induced by live C. albicans were also upregulated by heat-killed yeast. These data suggest that a large part of the transcriptional response to C. albicans is mediated through “pattern recognition,” an ancient immune surveillance mechanism able to detect conserved microbial molecules (so-called pathogen-associated molecular patterns or PAMPs). This study provides new information on the evolution and regulation of the innate immune response to divergent pathogens and demonstrates that nematodes selectively mount specific antifungal defenses at the expense of antibacterial responses.

Regulation of pentraxin-3 by antioxidants

BackgroundPentraxin-3 (PTX3) may be a useful biomarker in sepsis, but its regulatory mechanisms are still unclear. Oxidative stress is well defined in patients with sepsis and has a role in regulation of inflammatory pathways which may include PTX3. We undertook an in vitro study of the effect of antioxidants on regulation of PTX3 in endothelial cells combined with a prospective observational pilot study of PTX3 in relation to markers of antioxidant capacity and oxidative stress in patients with sepsis.MethodsHuman endothelial cells were cultured with lipopolysaccharide 2 µg ml−1, peptidoglycan G 20 µg ml−1, tumour necrosis factor (TNF) α 10 ng ml−1, interleukin-1 (IL-1) β 20 ng ml−1, or killed Candida albicans yeast cells plus either N-acetylcysteine (NAC) 25 mM, trolox 100 mM, or idebenone 1 µM. Plasma samples were obtained from 15 patients with sepsis and 11 healthy volunteers.ResultsPTX3 levels in plasma were higher in patients with sepsis than in healthy people [26 (1–202) ng ml−1 compared with 6 (1–12) ng ml−1, P=0.01]. Antioxidant capacity was lower in patients with sepsis than healthy controls [0.99 (0.1–1.7) mM compared with 2.2 (1.3–3.3) mM, P=0.01]. In patients with sepsis, lipid hydroperoxide levels were 3.32 (0.3–10.6) nM and undetectable in controls. We found no relationship between PTX3 and antioxidant capacity or lipid hydroperoxides. Cell expression of PTX3 increased with all inflammatory stimulants but was highest in cells treated with TNFα plus IL-1β. PTX3 concentrations were lower in cells co-treated with antioxidants (all P<0.05), associated with lower nuclear factor κB expression for NAC and trolox (P<0.05).ConclusionsPTX3 expression is down-regulated in vitro by antioxidants. Plasma levels of PTX3 are elevated in sepsis but seem to be unrelated to markers of oxidant stress or antioxidant capacity.

Identification and cloning of GCA1, a gene that encodes a cell surface glucoamylase from Candida albicans

Adherence of yeast cells of Candida albicans to human oesophageal cells is greater when cells are grown in 500 m m D-galactose in comparison to d-glucose at the same concentration. Moreover, a 190 kDa mannoprotein (MP190) from a yeast cell wall preparation is highly expressed when cells are grown in the presence of galactose but less so in glucose. We now report on the identification of the MP190 and the isolation of its encoding gene. MP190 was purified, and three internal peptides were isolated and sequenced. Each of the three peptides showed significant homology (65–85%) with a glucoamylase (GAM1) from the yeast, Schwanniomyces occidentalis. In order to isolate the C. albicans homologue of GAM1 (GCA1), we probed a genomic library with a 0·9-kb internal fragment of the S. occidentalis GAM1 and isolated a 2·3-kb clone that corresponded to the 5′ region of the gene. Polymerase chain reaction (PCR) amplification was used to isolate the remainder of the open reading frame. GCA1 encodes a 946 amino acid protein containing three putative hydrophobic, membrane-spanning domains and 15 potential N-glycosylation sites. Both Gca1p and GAM1 are novel to the family of glycosyl hydrolases. Northern analysis indicated that GCA1 is transcribed to a greater extent in galactose than in sucrose or glucose. Also, using reverse transcriptase (RT)-PCR, we observed expression of GCA1 in a rat model of oral candidiasis, indicating that Gca1p is expressed during disease development.