Hyphae Of Candida Albicans Research Articles

Solubility affects IL-1β-producing activity of the synthetic candidalysin peptide.

Candidalysin, a peptide toxin produced specifically from hyphae of Candida albicans, plays a crucial role in C. albicans pathogenesis in the oral cavity and vagina. Synthetic peptides have been widely used in previous studies to investigate the bioactivity of candidalysin. Although the solubility of the peptide, which is expected to have a hydrophobic property, has not been well characterized, candidalysin solutions are usually prepared in water. In this study, we prepared the synthetic peptide candidalysin in water (CLw) or in dimethyl sulfoxide (CLd) and compared their cytotoxicity and interleukin (IL)-1β-producing activity to determine whether the activity of the peptide would be affected. In addition, we evaluated whether the NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome pathway or other pathways were involved in their activities. Unexpectedly, we found that CLw was not completely solubilized and contained abundant insoluble microparticles. CLw was active at comparably high concentrations (≥ 10 μM). In contrast, CLd is completely solubilized and sufficiently active at low concentrations, that is, 1 μM or less. CLw showed weak cytotoxicity and NLRP3-dependent and cathepsin B-dependent IL-1β-producing activity, whereas CLd showed strong cytotoxicity and cathepsin B-dependent IL-1β-producing activity. Fractionation of CLw revealed that NLRP3-dependent activity was caused by insoluble microparticles. Furthermore, nanoparticle tracking of CLd revealed that the peptide was present as nanoparticles with a size of 96 nm. CLw contained a small amount of such nanoparticles. Thus, the bioactivities of the synthetic peptide candidalysin, especially the IL-1β-producing activity, are affected by the solubility of the peptide depending on the solvent employed. The NLRP3-dependent activity of the synthetic peptide is caused by insoluble microparticles and may not be the intrinsic activity of candidalysin.

Priming with FLO8-deficient Candida albicans induces Th1-biased protective immunity against lethal polymicrobial sepsis

The morphological switch between yeast and hyphae of Candida albicans is essential for its interaction with the host defense system. However, the lack of understanding of host–pathogen interactions during C. albicans infection greatly hampers the development of effective immunotherapies. Here, we found that priming with the C. albicans FLO8-deficient (flo8) mutant, locked in yeast form, protected mice from subsequent lethal C. albicans infection. Deficiency of Dectin-2, a fungus-derived α-mannan recognition receptor, completely blocked flo8 mutant-induced protection. Mechanistically, the flo8 mutant-induced Dectin-2/CARD9-mediated IL-10 production in DCs and macrophages to block thymus atrophy by inhibiting the C. albicans-induced apoptosis of thymic T cells, which facilitated the continuous output of naive T cells from the thymus to the spleen. Continuous recruitment of naive T cells to the spleen enhanced Th1-biased antifungal immune responses. Consequently, depletion of CD4+ T cells or blockade of IL-10 receptor function using specific antibodies in mice completely blocked the protective effects of flo8 mutant priming against C. albicans infection. Moreover, mannans exposed on the surface of the flo8 mutant were responsible for eliciting protective immunity by inhibiting the C. albicans-induced apoptosis of thymic T cells to sustain the number of naive T cells in the spleen. Importantly, priming with the flo8 mutant extensively protected mice from polymicrobial infection caused by cecal ligation and puncture (CLP) by enhancing Th1-biased immune responses. Together, our findings imply that targeting FLO8 in C. albicans elicits protective immune responses against polymicrobial infections and that mannans extracted from the flo8 mutant are potential immunotherapeutic candidate(s) for controlling infectious diseases.

A representative of arylcyanomethylenequinone oximes effectively inhibits growth and formation of hyphae in Candida albicans and influences the activity of protein kinases in vitro

In this study, we applied various assays to reveal new activities of phenylcyanomethylenequinone oxime-4-(hydroxyimino) cyclohexa-2,5-dien-1-ylidene](phenyl)ethanenitrile (4-AN) for potential anti-microbial applications. These assays demonstrated (a) the antimicrobial effect on bacterial and fungal cultures, (b) the effect on the in vitro activity of the kinase CK2, (c) toxicity towards human erythrocytes, the Caco-2 cancer cell line, and embryonic development of Zebrafish. We demonstrated the activity of 4-AN against selected bacteria and Candida spp. The MIC ranging from 4 µg/ml to 125 µg/ml proved effective in inhibition of formation of hyphae and cell aggregation in Candida, which was demonstrated at the cytological level. Noteworthy, 4-AN was found to inhibit the CK2 kinase with moderate potency. Moreover, at low concentrations, it did not exert any evident toxic effects on human erythrocytes, Caco-2 cells, or Zebrafish embryos. 4-AN can be a potential candidate as a novel drug against Candida infections.

Biofilm development by blastospores and hyphae of Candida albicans on abraded denture acrylic resin surfaces

Candida albicans is a known etiologic agent of denture stomatitis. Candida hyphae exhibit the ability to respond directionally to environmental stimuli. This characteristic is thought to be important in the penetration of substrata such as resilient denture liners and host epithelium. It has been suggested that hyphal production also enhances adhesion and survival of Candida on host and denture surfaces. Surface roughness, in addition, can enhance adhesion where stronger interactions occur between cells and surface features of similar dimensions. The purpose of this study was to assess the development of hyphal and blastospore biofilms on abraded denture acrylic resin specimens and measure the ease of removal of these biofilms. Biofilms were grown for 48 hours on abraded 1-cm² denture acrylic resin specimens from adhered hyphal phase C albicans or from adhered blastospores. Subsequently, all specimens were stained with Calcofluor White and examined with confocal scanning laser microscopy. Biofilms were removed by vortex mixing in sterile phosphate buffered saline solution. Removed cells were filtered (0.2-μm pore size). Filters were dried at 37°C for 24 hours for dry weight measurements. Any cells that remained on the acrylic resin specimens were stained with 0.03% acridine orange and examined with epifluorescence microscopy. Biofilms grown from both cell types contained all morphologic forms of C albicans. Although the underlying surface topography did not affect the amount of biofilm produced, biofilms grown from hyphal phase Candida were visibly thicker and had greater biomass (P<.05). These biofilms were less easily removed from the denture acrylic resin, especially in the case of rougher surfaces, evidenced by the higher numbers of retained cells (P≤.05). The presence of hyphae in early Candida biofilms increased biofilm mass and resistance to removal. Increased surface roughness enhances retention of hyphae and yeast cells, and, therefore, will facilitate plaque regrowth. Therefore, minimization of denture abrasion during cleaning is desirable.

Dectin-1 plays a prominent role in the immune response against the dermatophyte "Trichophyton rubrum" in murine model

Event Abstract Back to Event Dectin-1 plays a prominent role in the immune response against the dermatophyte "Trichophyton rubrum" in murine model Fábio S. Yoshikawa1* and Sandro R. De Almeida1 1 Universidade de São Paulo, Department of Clinical and Toxicological Analyses - Faculty of Pharmaceutical Sciences, Brazil Introduction: "Trichophyton rubrum" is the main agent of dermatophytosis in humans. However, little is known about the immunological mechanisms underlying these mycoses. Dectin-1 is an immune receptor involved in responses to fungi. It can induce production of cytokines and shape the immune response, like IL-1β, a key cytokine for the induction of TH17 responses. The aim of this study was to elucidate the role of Dectin-1 in the immune response against "T.rubrum". Materials and Methods: Bone-marrow derived macrophages (BMMs) from C57BL/6 mice (wild-type and dectin-1-/-) were primed with LPS and incubated with "T.rubrum" conidia for 4, 6, 8 and 10 hours. The interaction was evaluated by optical microscopy and IL-1β levels were measured by ELISA. Groups of 3 C57BL/6 mice (wild-type and dectin-1-/-) were infected with "T.rubrum" conidia intraperitoneally. Animals were maintained for 7 and 14 days before being euthanized. Liver and spleen were collected for determination of fungal burden and cytokine measurements (IL-1β, IFN-γ, IL-4). Results: Wild-type BMMs phagocytosed conidia and secreted IL-1β in response to the pathogen, but were destroyed by the fungal growth. Dectin-1-/- counterparts, however, showed reduced phagocytose and cytokine production, but conidia were unable to become hyphae. Dectin-1-/- mice could not control the fungal burden and showed higher production of IFN-γ and IL-4, but lower levels of IL-1β, than their wild-type correlates. Conclusions: Results showed that Dectin-1 is important for phagocytose of "T.rubrum" conidia and production of IL-1β. "In vivo" results suggest that dectin-1 is necessary for infection control by induction of IL-1β. Acknowledgements Financial Support: FAPESP References BROWN, G.D. Dectin-1: a signaling non-TLR pattern-recognition receptor. Nat. Rev. Immunol., 6(1), p. 33-43, 2006. BROWN, G.D. Innate antifungal immunity: the key role of phagocytes. Annu.Rev.Immunol., 29, p.1-21, 2011. CAMPOS, M.R.M.; RUSSO, M.; GOMES, E.; ALMEIDA, S.R. Stimulation, inhibition and death of macrophages infected with Trichophyton rubrum. Microbes Infect., 8(2), p.372-79, 2006. CHENG, S.C.; VAN DE VEERDONK, F.L.; LENARDON, M.; STOFFELS, M.; PLANTINGA, T.; SMEEKENS, S.; RIZZETTO, L.; MUKAREMERA, L.; PREECHASUTH, K.; CAVALIERI, D.; KANNEGANTI, T.D.; VAN DE MEER, J.W.; KULLBERG, B.J.; JOOSTEN, L.A.; GOW, N.A.; NETEA, M.G. The dectin-1/inflammasome pathway is responsible for the induction of the protective T-helper 17 responses that discriminate between yeasts and hyphae of Candida albicans. J.Leukoc.Biol., 90(2), p. 357-66, 2011. Keywords: dectin-1, Trichophyton rubrum, IL-1beta, Macrophages, dermatophyte Conference: 15th International Congress of Immunology (ICI), Milan, Italy, 22 Aug - 27 Aug, 2013. Presentation Type: Abstract Topic: Host-pathogen interactions Citation: Yoshikawa FS and De Almeida SR (2013). Dectin-1 plays a prominent role in the immune response against the dermatophyte "Trichophyton rubrum" in murine model. Front. Immunol. Conference Abstract: 15th International Congress of Immunology (ICI). doi: 10.3389/conf.fimmu.2013.02.00059 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 08 Mar 2013; Published Online: 22 Aug 2013. * Correspondence: Mr. Fábio S Yoshikawa, Universidade de São Paulo, Department of Clinical and Toxicological Analyses - Faculty of Pharmaceutical Sciences, São Paulo, São Paulo, 05508-000, Brazil, faseiti@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. 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Ferric reductase genes involved in high‐affinity iron uptake are differentially regulated in yeast and hyphae of Candida albicans

The pathogenic yeast Candida albicans possesses a reductive iron uptake system which is active in iron-restricted conditions. The sequestration of iron by this mechanism initially requires the reduction of free iron to the soluble ferrous form, which is catalysed by ferric reductase proteins. Reduced iron is then taken up into the cell by a complex of a multicopper oxidase protein and an iron transport protein. Multicopper oxidase proteins require copper to function and so reductive iron and copper uptake are inextricably linked. It has previously been established that Fre10 is the major cell surface ferric reductase in C. albicans and that transcription of FRE10 is regulated in response to iron levels. We demonstrate here that Fre10 is also a cupric reductase and that Fre7 also makes a significant contribution to cell surface ferric and cupric reductase activity. It is also shown, for the first time, that transcription of FRE10 and FRE7 is lower in hyphae compared to yeast and that this leads to a corresponding decrease in cell surface ferric, but not cupric, reductase activity. This demonstrates that the regulation of two virulence determinants, the reductive iron uptake system and the morphological form of C. albicans, are linked.

The dectin-1/inflammasome pathway is responsible for the induction of protective T-helper 17 responses that discriminate between yeasts and hyphae of Candida albicans.

In the mucosa, the immune pathways discriminating between colonizing and invasive Candida, thus inducing tolerance or inflammation, are poorly understood. Th17 responses induced by Candida albicans hyphae are central for the activation of mucosal antifungal immunity. An essential step for the discrimination between yeasts and hyphae and induction of Th17 responses is the activation of the inflammasome by C. albicans hyphae and the subsequent release of active IL-1β in macrophages. Inflammasome activation in macrophages results from differences in cell-wall architecture between yeasts and hyphae and is partly mediated by the dectin-1/Syk pathway. These results define the dectin-1/inflammasome pathway as the mechanism that enables the host immune system to mount a protective Th17 response and distinguish between colonization and tissue invasion by C. albicans.

Mechanical and spatial determinants of cytoskeletal geodesic dome formation in cardiac fibroblasts

This study tests the hypothesis that the cell cytoskeletal (CSK) network can rearrange from geodesic dome type structures to stress fibers in response to microenvironmental cues. The CSK geodesic domes are highly organized actin microarchitectures within the cell, consisting of ordered polygonal elements. We studied primary neonatal rat cardiac fibroblasts. The cues used to trigger the interconversion between the two CSK architectures (geodesic domes and stress fibers) included factors affecting spatial order and the degree of CSK tension in the cells. Microfabricated three-dimensional substrates with micrometre sized grooves and peaks were used to alter the spatial order of cell growth in culture. CSK tension was modified by 2,3-butanedione 2-monoxime (BDM), cytochalasin D and the hyphae of Candida albicans. CSK geodesic domes occurred spontaneously in about 20% of the neonatal rat cardiac fibroblasts used in this study. Microfabricated structured surfaces produced anisotropy in the cell CSK and effectively converted geodesic domes into stress fibers in a dose-dependent manner (dependence on the period of the features). Affectors of actin structure, inhibitors of CSK tension and cell motility, e.g. BDM, cytochalasin D and the hyphae of C. albicans, suppressed or eliminated the geodesic domes. Our data suggest that the geodesic domes, similar to actin stress fibers, require maintenance of CSK integrity and tension. However, microenvironments that promote structural anisotropy in tensed cells cause the transformation of the geodesic domes into stress fibers, consistent with topographic cell guidance and some previous CSK model predictions.

An unusual case of deep candidosis presenting as an infiltrating tumour of the chest wall

A 45-year-old man presented with an unclear rapidly growing, infiltrating tumour of the anterior chest wall. Biopsies were non-specific, serologies remained unremarkable. Shortly after admission the patient developed blurred vision. Ophthalmoscopical findings were typical of candida endophthalmitis. Meanwhile, the tumour continued to grow. When it was resected, hyphae of Candida albicans were yielded from the tissue revealing it as a manifestation of deep candidosis. The infection had probably been acquired endogenously during abdominal surgery for early stage rectal carcinoma which the patient had undergone several weeks ago and which was followed by an unexplained fever. Interestingly, deep candidosis presenting as an infiltrating tumour of the anterior chest wall often combined with candidal endophthalmitis has been described almost exclusively in intravenous drug users after the injection of contaminated heroin [Collignon PJ, Sorrell TC. Disseminated candidiasis: evidence of a distinctive syndrome in heroin abusers. Br Med J (Clin Res Ed) 1983;287(6396):861-2; Dupont B, Drouhet E. Cutaneous, ocular, and osteoarticular candidiasis in heroin addicts: new clinical and therapeutic aspects in 38 patients. J Infect Dis 1985;152(3):577-91; Bisbe J, Miro JM, Latorre X, Moreno A, Mallolas J, Gatell JM, et al. Disseminated candidiasis in addicts who use brown heroin: report of 83 cases and review. Clin Infect Dis 1992;15(6):910-23.]. Why the tumours only develop on the anterior thoracic wall is unknown. To our knowledge this is the first case described in literature in which endogenously acquired deep candidosis manifested as an infiltrating tumour in a patient who was neither immunosuppressed nor had a history of intravenous drug use.

Characterization of thiol‐specific antioxidant 1 (TSA1) of Candida albicans

We previously identified several proteins that are differentially expressed in pathogenic hyphae by comparing protein profiles of yeast and hyphae of Candida albicans. One of these, thiol-specific antioxidant 1 (TSA1), attracted our attention because it may play some roles in surviving an unfavourable oxidative environment created by host cells. Two alleles of the C. albicans TSA1 (CaTSA1) gene are located in opposite orientation on the same chromosome. Using PCR-directed disruption cassettes and URA-Blaster, a series of deletion mutants that lack one to four copies were constructed to examine the functions of CaTSA1. Northern and Western analyses showed that both the transcript and protein products of CaTSA1 decreased proportionally to the disrupted copy number and were completely absent in the null mutant, indicating that all four TSA1 copies are equally functional at the transcriptional level. Intracellular H2O2 increased by an order of magnitude in deletion mutants lacking three to four copies, suggesting that CaTsa1p is not a redundant H2O2 scavenger. CaTsa1p was indispensable for yeast-to-hyphal transition when C. albicans was cultured under oxidative stress. The level of its oxidized form increased approximately five-fold in hyphal cells, whereas that of the reduced form increased two-fold compared to yeast cells. The ratio of oxidized to reduced form was increased three-fold in hyphal cells. This overall increase was found to be controlled at the post-transcriptional level. Interestingly, CaTsa1p is translocated to the nucleus of hyphal cells. These findings may be of biological significance for differentiation and pathogenicity.

Micafungin enhances neutrophil fungicidal functions against Candida pseudohyphae.

We evaluated the effect of the combination of micafungin and polymorphonuclear leukocytes (PMN) against hyphae of Candida albicans and Candida dubliniensis. Micafungin enhanced the PMN oxidative burst dose dependently. The combination was synergistic (C. albicans) or additive (C. dubliniensis); when PMN were pretreated with granulocyte-macrophage colony-stimulating factor, the combination was more effective.

Identification of genes differentially expressed in hyphae of Candida albicans

The ability to switch from yeast to hyphal forms is essential for Candida albicans virulence. This morphological switch involves the expression of hyphal-specific genes under the control of transcriptional factors. To contribute to the discovery of hyphal-specific genes, we used a differential screening method where clones of a genomic DNA library were hybridized with yeast and hyphal cDNA probes. Two clones with increased expression in hyphae were selected for study. Sequencing these clones, we found that they encoded two important metabolic genes, CaHXT7 (high-affinity hexose transporter) and CaYLL34 (member of the AAA ATPase family). CaHXT7 and CaYLL34 ORFs were completely determined. Analyses of the putative proteins show that: (1) CaHxt7p has one hexose transporter domain and (2) CaYll34p has two AAA ATPase domains. These results show, for the first time, increased expression of metabolic genes in C. albicans hyphae. Also, because the proteins encoded by CaHXT7 and CaYLL34 may be necessary for the switching to hyphae, they could be new targets for antifungal drugs.

The adhesin Hwp1 and the first daughter cell localize to the a/a portion of the conjugation bridge during Candida albicans mating.

The cell wall protein Hwp1 was originally demonstrated to be expressed exclusively in hyphae of Candida albicans and cross-linked to human epithelium by mammalian transglutaminase. Hwp1 is expressed on the walls of hyphae formed by a/alpha, a/a, and alpha/alpha cells. Hence, it is expressed on hyphae independently of mating type. However, Hwp1 is selectively expressed on the wall of conjugation tubes formed by a/a cells, but not alpha/alpha cells, in the mating process. This was demonstrated in all possible crosses between four unrelated natural a/a strains and four unrelated alpha/alpha strains. In zygotes, Hwp1 is restricted to that portion of the wall of the conjugation bridge contributed by the a/a parent cell. Hwp1 staining further revealed that the first daughter bud that emerges from the conjugation bridge does so from the a/a-contributed portion. Hwp1 expression and localization during the mating process is, therefore, mating type specific, opaque phase specific, and alpha-pheromone induced. These results indicate that the mating type-specific contributions to the conjugation bridge during the mating process in C. albicans are qualitatively and functionally distinct and that the a/a portion of the bridge, which selectively contains Hwp1, bears the first daughter cell in the mating process.

The interaction of fungi with dendritic cells: implications for Th immunity and vaccination.

Human beings are continuously exposed to fungi, yet they rarely get fungal diseases. The delicate balance between the host and these otherwise harmless pathogens may turn into a parasitic relationship, resulting in the development of severe infections. The ability to reversibly switch between unicellular and filamentous forms, all of which can be found in infected tissues, is thought to be important for virulence. Efficient responses to the different forms of fungi require different mechanisms of immunity. Dendritic cells (DC) are uniquely able at decoding the fungus-associated information and translating it in qualitatively different T helper (Th) immune responses, in vitro and in vivo. Myeloid DC phagocytosed yeasts and hyphae of Candida albicans and conidia and hyphae of Aspergillus fumigatus, both in vitro and in vivo. Phagocytosis occurred through distinct phagocytic morphologies, involving the engagement and cooperativity of distinct recognition receptors. However, receptor engagement and cooperativity were greatly modified by opsonization. The engagement of distinct receptors translated into disparate downstream signaling events, ultimately affecting cytokine production and costimulation. In vivo studies confirmed that the choice of receptor and mode of entry of fungi into DC was responsible for Th polarization and patterns of susceptibility or resistance to infection. Adoptive transfer of different types of DC activated protective, nonprotective and regulatory T cells, ultimately affecting the outcome of infection. The conclusions are that the selective exploitation of receptors and mode of entry into DC may determine the full range of host's immune relationships with fungi and have important implications in the design of vaccine-based strategies.

In vitro survival and germination of Candida albicans in the presence of nitrogen compounds.

The in vitro effect of nitric oxide (NO) and nitrite on blastoconidia and hyphae of Candida albicans was studied. Sodium nitroprusside (SNP) and S-nitroso-N-acetylpenicillamine (SNAP) were used as NO donors. Both minimal and complex media at two pH values, 7.0 and 4.5, were used for the assays. Blastoconidia were more susceptible than hyphae to NO. The NO effect on blastoconidia was greater at acidic pH. Nitrite affected the viability of blastoconidia in complex medium. The percentage germination and the relative rate of elongation of hyphae were both enhanced when NO was present in acidic conditions.

Coiling phagocytosis of trypanosomatids and fungal cells.

Coiling phagocytosis has previously been studied only with the bacteria Legionella pneumophila and Borrelia burgdorferi, and the results were inconsistent. To learn more about this unconventional phagocytic mechanism, the uptake of various eukaryotic microorganisms by human monocytes, murine macrophages, and murine dendritic cells was investigated in vitro by video and electron microscopy. Unconventional phagocytosis of Leishmania spp. promastigotes, Trypanosoma cruzi trypomastigotes, Candida albicans hyphae, and zymosan particles from Saccharomyces cerevisiae differed in (i) morphology (rotating unilateral pseudopods with the trypanosomatids, overlapping bilateral pseudopods with the fungi), (ii) frequency (high with Leishmania; occasional with the fungi; rare with T. cruzi), (iii) duration (rapid with zymosan; moderate with the trypanosomatids; slow with C. albicans), (iv) localization along the promastigotes (flagellum of Leishmania major and L. aethiopica; flagellum or posterior pole of L. donovani), and (v) dependence on complement (strong with L. major and L. donovani; moderate with the fungi; none with L. aethiopica). All of these various types of unconventional phagocytosis gave rise to similar pseudopod stacks which eventually transformed to a regular phagosome. Further video microscopic studies with L. major provided evidence for a cytosolic localization, synchronized replication, and exocytic release of the parasites, extending traditional concepts about leishmanial infection of host cells. It is concluded that coiling phagocytosis comprises phenotypically similar consequences of various disturbances in conventional phagocytosis rather than representing a single separate mechanism.

Dynamic expression of cell-surface antigens probed with Candida albicans-specific monoclonal antibodies.

IgG hybridomas were produced with preferentially reacted with cell-surface antigens of either yeast cells or hyphae of Candida albicans. Four mAbs were used in an immunostaining procedure to follow the expression dynamics of these antigens in media supplemented with glucose or galactose. Yeast cell growth was analysed during the lag phase, the early- and late-exponential phases and the stationary phase, and mycelium formation was analysed between 0.5 and 24 h induction at 37 degrees C. It appears that yeast cell-surface antigens 5C11 and 2E11 are expressed throughout all phases of yeast cell growth as well as on young hyphae after up to 1 h induction. Longer hyphae only faintly react with these two mAbs as they switch to hyphal cell-surface antigens 2G8 and 4E1 after 3 h induction. The reactivity to mAbs 2G8 and 4E1 was induced after a 3 h temperature shift and was confined to the terminal third of growing mycelia. Growth and hyphae induction in galactose prolonged the reactivity of young hyphae with the two anti-yeast-cell mAbs, whereas the expression of surface antigens 2G8 and 2E11 appeared delayed and desynchronized on hyphae. Whereas a similar reactivity was found with ten ATCC strains of C. albicans, four clinical isolates had a unique pattern of reactivity. Immunoblot analyses of DTT extracts of cell-surface constituents indicated that the antigens were proteinaceous in nature and showed that yeast-cell antigens 5C11 and 2E11 are detected in four bands between 68 and 104 kDa, whereas mycelial antigens 4E1 and 2G8 are detected in 117 kDa and 104 kDa bands found in mycelial but not in yeast-cell extracts. Present data support the concept of a dynamic balance in the expression of phase-specific antigens in C. albicans.

Helical growth of hyphae of Candida albicans.

When grown on a range of surfaces in conditions favouring hyphal growth, hyphae of Candida albicans grew in a right-handed helical fashion. This phenomenon was observed with eight strains and with two nutrient media. It is suggested that this is a result of rotation of the hyphal apex as it extends, which on some surfaces results in a helical hyphal wall, but which in a liquid results in a straight hypha. The consequence is that on a surface, a helically growing hypha will be exposed to a more diverse environment than a straight hypha. This phenomenon may have significance in the colonization of tissue by C. albicans.

Oral hairy leukoplakia: ultrastructural features.

Ten instances of a white plaque of the lateral tongue unique to homosexual males and referred to as oral hairy leukoplakia were analysed ultrastructurally. The surface epithelial layer exhibited extracellular, intracellular and intranuclear penetration by hyphae of Candida albicans, sometimes accompanied by coccobacilli in the extracellular space. The subcorneal epithelial layer included koilocytoid ballooned cells which had a paucity of cytoplasmic organelles and displayed condensation and emargination of the chromatin. Cells that exhibited these nuclear changes were found to be infected by a herpes-type virus which was visualized by electron microscopy in all ten cases. Clusters of nucleocapsids (86-110 nm in diameter) occurred in the nuclei and enveloped virions (111-175 nm in diameter) occurred in the cytoplasm and extracellular spaces. Virions showed budding from the nuclear envelope. Bundles of tubular structures (20 nm diameter) arranged in parallel occurred in the cytoplasm of some koilocytoid cells. There was no evidence by electron microscopy of the presence of papilloma virus within koilocytotic nuclei.

Ultrastructure of chitin in hyphae ofCandida albicans and other dimorphic and mycelial fungi

Chitin microfibrils exposed by chemical extraction of hyphal walls ofCandida albicans, Histoplasma capsulatum, Blastomyces dermatitidis, Paracoccidiodes brasiliensis, Coprinus cinereus andMucor mucedo were of variable morphology but gave identical infrared spectra and behaved as pure chitin in chromatographic analyses. The microfibrils of the four dimorphic fungi studied were shorter than those in the mouldsC. cinereus andM. mucedo but were similar to those reported for the yeastSaccharomyces cerevisiae. InC. albicans the microfibrils in the septal plates of hyphae were predominantly tangentially orientated and were longer than those in the lateral walls. Microfibrils produced by chitin synthasein vitro were very much longer than any observed from hyphal preparations.