Multiplicity of genes encoding secreted aspartic proteinases in Candida species

Secreted Aspartic Proteinases: Key Factors in Candida Infections and Host-Pathogen Interactions

Extracellular proteases are key factors contributing to the virulence of pathogenic fungi from the genus Candida. Their proteolytic activities are crucial for extracting nutrients from the external environment, degrading host defenses, and destabilizing the internal balance of the human organism. Currently, the enzymes most frequently described in this context are secreted aspartic proteases (Saps). This review comprehensively explores the multifaceted roles of Saps, highlighting their importance in biofilm formation, tissue invasion through the degradation of extracellular matrix proteins and components of the coagulation cascade, modulation of host immune responses via impairment of neutrophil and monocyte/macrophage functions, and their contribution to antifungal resistance. Additionally, the diagnostic challenges associated with Candida infections and the potential of Saps as biomarkers were discussed. Furthermore, we examined the prospects of developing vaccines based on Saps and the use of protease inhibitors as adjunctive therapies for candidiasis. Given the complex biology of Saps and their central role in Candida pathogenicity, a multidisciplinary approach may pave the way for innovative diagnostic strategies and open new opportunities for innovative clinical interventions against candidiasis.

Bibliometric analysis and thematic review of Candida pathogenesis: Fundamental omics to applications as potential antifungal drugs and vaccines

Invasive candidiasis caused by the pathogenic Candida yeast species has resulted in elevating global mortality. The pathogenicity of Candida spp. is not only originated from its primary invasive yeast-to-hyphal transition; virulence factors (transcription factors, adhesins, invasins, and enzymes), biofilm, antifungal drug resistance, stress tolerance, and metabolic adaptation have also contributed to a greater clinical burden. However, the current research theme in fungal pathogenicity could hardly be delineated with the increasing research output. Therefore, our study analysed the research trends in Candida pathogenesis over the past 37 years via a bibliometric approach against the Scopus and Web of Science databases. Based on the 3993 unique documents retrieved, significant international collaborations among researchers were observed, especially between Germany (Bernhard Hube) and the UK (Julian Naglik), whose focuses are on Candida proteinases, adhesins, and candidalysin. The prominent researchers (Neils Gow, Alistair Brown, and Frank Odds) at the University of Exeter and the University of Aberdeen (second top performing affiliation) UK contribute significantly to the mechanisms of Candida adaptation, tolerance, and stress response. However, the science mapping of co-citation analysis performed herein could not identify a hub representative of subsequent work since the clusters were semi-redundant. The co-word analysis that was otherwise adopted, revealed three research clusters; the cluster-based thematic analyses indicated the severeness of Candida biofilm and antifungal resistance as well as the elevating trend on molecular mechanism elucidation for drug screening and repurposing. Importantly, the in vivo pathogen adaptation and interactions with hosts are crucial for potential vaccine development.

Toll-like receptor 4 and CD11b expressed on microglia coordinate eradication of Candida albicans cerebral mycosis

The fungal pathogen Candida albicans is linked to chronic brain diseases such as Alzheimer's disease (AD), but the molecular basis of brain anti-Candida immunity remains unknown. We show that C. albicans enters the mouse brain from the blood and induces two neuroimmune sensing mechanisms involving secreted aspartic proteinases (Saps) and candidalysin. Saps disrupt tight junction proteins of the blood-brain barrier (BBB) to permit fungal brain invasion. Saps also hydrolyze amyloid precursor protein (APP) into amyloid β (Aβ)-like peptides that bind to Toll-like receptor 4 (TLR4) and promote fungal killing in vitro while candidalysin engages the integrin CD11b (Mac-1) on microglia. Recognition of Aβ-like peptides and candidalysin promotes fungal clearance from the brain, and disruption of candidalysin recognition through CD11b markedly prolongs C. albicans cerebral mycosis. Thus, C. albicans is cleared from the brain through innate immune mechanisms involving Saps, Aβ, candidalysin, and CD11b.

Metabolic flexibility and extensive adaptability governing multiple drug resistance and enhanced virulence in Candida albicans

Commensal fungus-Candida albicans turn pathogenic during the compromised immunity of the host, causing infections ranging from superficial mucosal to dreadful systemic ones. C. albicans has evolved various adaptive measures which collectively contribute towards its enhanced virulence. Among fitness attributes, metabolic flexibility and vigorous stress response are essential for its pathogenicity and virulence. Metabolic flexibility provides a means for nutrient assimilation and growth in diverse host microenvironments and reduces the vulnerability of the pathogen to various antifungals besides evading host immune response(s). Inside the host micro-environments, C. albicans efficiently utilizes the multiple fermentable and non-fermentable carbon sources to sustain and proliferate in glucose deficit conditions. The utilization of alternative carbon sources further highlights the importance of understanding these pathways as the attractive and potential therapeutic target. A thorough understanding of metabolic flexibility and adaptation to environmental stresses is warranted to decipher in-depth insights into virulence and molecular mechanisms of fungal pathogenicity. In this review, we have attempted to provide a detailed and recent understanding of some key aspects of fungal biology. Particular focus will be placed on processes like nutrient assimilation and utilization, metabolic adaptability, virulence factors, and host immune response in C. albicans leading to its enhanced pathogenicity.

Genetic Manipulation as a Tool to Unravel Candida parapsilosis Species Complex Virulence and Drug Resistance: State of the Art

An increase in the rate of isolation of Candida parapsilosis in the past decade, as well as increased identification of azole-resistant strains are concerning, and require better understanding of virulence-like factors and drug-resistant traits of these species. In this regard, the present review “draws a line” on the information acquired, thus far, on virulence determinants and molecular mechanisms of antifungal resistance in these opportunistic pathogens, mainly derived from genetic manipulation studies. This will provide better focus on where we stand in our understanding of the C. parapsilosis species complex–host interaction, and how far we are from defining potential novel targets or therapeutic strategies—key factors to pave the way for a more tailored management of fungal infections caused by these fungal pathogens.

Viral, bacterial, and fungal infections of the oral mucosa: Types, incidence, predisposing factors, diagnostic algorithms, and management

For millions of years, microbiota residing within us, including those in the oral cavity, coexisted in a harmonious symbiotic fashion that provided a quintessential foundation for human health. It is now clear that disruption of such a healthy relationship leading to microbial dysbiosis causes a wide array of infections, ranging from localized, mild, superficial infections to deep, disseminated life-threatening diseases. With recent advances in research, diagnostics, and improved surveillance we are witnessing an array of emerging and re-emerging oral infections and orofacial manifestations of systemic infections. Orofacial infections may cause significant discomfort to the patients and unnecessary economic burden. Thus, the early recognition of such infections is paramount for holistic patient management, and oral clinicians have a critical role in recognizing, diagnosing, managing, and preventing either new or old orofacial infections. This paper aims to provide an update on current understanding of well-established and emerging viral, bacterial, and fungal infections manifesting in the human oral cavity.

Recent Advances in Azole Based Scaffolds as Anticandidal Agents

Aim:

The present review aims to explore the development of novel antifungal agents, such as pharmacology, pharmacokinetics, spectrum of activity, safety, toxicity and other aspects that involve drug-drug interactions of the azole antifungal agents.

Introduction:

Fungal infections in critically ill and immune-compromised patients are increasing at alarming rates, caused mainly by Candida albicans an opportunistic fungus. Despite antifungal annihilators like amphotericin B, azoles and caspofungin, these infections are enormously increasing. The unconventional increase in such patients is a challenging task for the management of antifungal infections especially Candidiasis. Moreover, problem of toxicity associated with antifungal drugs on hosts and rise of drug-resistance in primary and opportunistic fungal pathogens has obstructed the success of antifungal therapy.

Conclusion:

Hence, to conflict these problems new antifungal agents with advanced efficacy, new formulations of drug delivery and novel compounds which can interact with fungal virulence are developed and used to treat antifungal infections.

Zebrafish Egg Infection Model for Studying Candida albicans Adhesion Factors

Disseminated candidiasis is associated with 30-40% mortality in severely immunocompromised patients. Among the causal agents, Candida albicans is the dominant one. Various animal models have been developed for investigating gene functions in C. albicans. Zebrafish injection models have increasingly been applied in elucidating C. albicans pathogenesis because of the conserved immunity, prolific fecundity of the zebrafish and the low costs of care systems. In this study, we established a simple, noninvasive zebrafish egg bath infection model, defined its optimal conditions, and evaluated the model with various C. albicans mutant strains. The deletion of SAP6 did not have significant effect on the virulence. By contrast, the deletion of BCR1, CPH1, EFG1, or TEC1 significantly reduced the virulence under current conditions. Furthermore, all embryos survived when co-incubated with bcr1/bcr1, cph1/cph1 efg1/efg1, efg1/efg1, or tec1/tec1 mutant cells. The results indicated that our novel zebrafish model is time-saving and cost effective.

Test and Evaluation of ff99IDPs Force Field for Intrinsically Disordered Proteins

Over 40% of eukaryotic proteomic sequences have been predicted to be intrinsically disordered proteins (IDPs) or intrinsically disordered regions (IDRs) and confirmed to be associated with many diseases. However, widely used force fields cannot well reproduce the conformers of IDPs. Previously the ff99IDPs force field was released to simulate IDPs with CMAP energy corrections for the eight disorder-promoting residues. In order to further confirm the performance of ff99IDPs, three representative IDP systems (arginine-rich HIV-1 Rev, aspartic proteinase inhibitor IA3, and α-synuclein) were used to test and evaluate the simulation results. The results show that for free disordered proteins, the chemical shifts from the ff99IDPs simulations are in quantitative agreement with those from reported NMR measurements and better than those from ff99SBildn. Thus, ff99IDPs can sample more clusters of disordered conformers than ff99SBildn. For structural proteins, both ff99IDPs and ff99SBildn can well reproduce the conformations. In general, ff99IDPs can successfully be used to simulate the conformations of IDPs and IDRs in both bound and free states. However, relative errors could still be found at the boundaries of ordered residues scattered in long disorder-promoting sequences. Therefore, polarizable force fields might be one of the possible ways to further improve the performance on IDPs.

Transcriptomic analysis of vulvovaginal candidiasis identifies a role for the NLRP3 inflammasome

Treatment of vulvovaginal candidiasis (VVC), caused most frequently by Candida albicans, represents a significant unmet clinical need. C. albicans, as both a commensal and a pathogenic organism, has a complex and poorly understood interaction with the vaginal environment. Understanding the complex nature of this relationship is necessary for the development of desperately needed therapies to treat symptomatic infection. Using transcriptome sequencing (RNA-seq), we characterized the early murine vaginal and fungal transcriptomes of the organism during VVC. Network analysis of host genes that were differentially expressed between infected and naive mice predicted the activation or repression of several signaling pathways that have not been previously associated with VVC, including NLRP3 inflammasome activation. Intravaginal challenge of Nlrp3(-/-) mice with C. albicans demonstrated severely reduced levels of polymorphonuclear leukocytes (PMNs), alarmins, and inflammatory cytokines, including interleukin-1β (IL-1β) (the hallmarks of VVC immunopathogenesis) in vaginal lavage fluid. Intravaginal administration of wild-type (WT) mice with glyburide, a potent inhibitor of the NLRP3 inflammasome, reduced PMN infiltration and IL-1β to levels comparable to those observed in Nlrp3(-/-) mice. Furthermore, RNA-seq analysis of C. albicans genes indicated robust expression of hypha-associated secreted aspartyl proteinases 4, 5, and 6 (SAP4-6), which are known inflammasome activators. Despite colonization similar to that of the WT strain, ΔSAP4-6 triple and ΔSAP5 single mutants induced significantly less PMN influx and IL-1β during intravaginal challenge. Our findings demonstrate a novel role for the inflammasome in the immunopathogenesis of VVC and implicate the hypha-associated SAPs as major C. albicans virulence determinants during vulvovaginal candidiasis.

IMPORTANCE

Vaginitis, most commonly caused by the fungus Candida albicans, results in significant quality-of-life issues for all women of reproductive age. Recent efforts have suggested that vaginitis results from an immunopathological response governed by host innate immunity, although an explanatory mechanism has remained undefined. Using comprehensive genomic, immunological, and pharmacological approaches, we have elucidated the NLRP3 inflammasome as a crucial molecular mechanism contributing to host immunopathology. We have also demonstrated that C. albicans hypha-associated secreted aspartyl proteinases (SAP4-6 and SAP5, more specifically) contribute to disease immunopathology. Ultimately, this study enhances our understanding of the complex interplay between host and fungus at the vaginal mucosa and provides proof-of-principle evidence for therapeutic targeting of inflammasomes for symptomatic vulvovaginal candidiasis.

Induction of caspase-11 by aspartyl proteinases of Candida albicans and implication in promoting inflammatory response

We recently demonstrated that the secreted aspartyl proteinases (Saps), Sap2 and Sap6, of Candida albicans have the potential to induce the canonical activation of the NLRP3 inflammasome, leading to the secretion of interleukin-1β (IL-1β) and IL-18 via caspase-1 activation. We also observed that the activation of caspase-1 is partially independent from the NLRP3 activation pathway. In this study, we examined whether Sap2 and Sap6 are also able to activate the noncanonical inflammasome pathway in murine macrophages. Our data show that both Sap2 and Sap6 can activate caspase-11 through type I interferon (IFN) production. Caspase-11 cooperates to activate caspase-1, with a subsequent increase of IL-1β secretion. Endocytosis and internalization of Saps are required for the induction of type I IFN production, which is essential for induction of noncanonical inflammasome activation. Our study indicates a sophisticated interplay between caspase-1 and caspase-11 that connects the canonical and noncanonical pathways of inflammasome activation in response to C. albicans Saps.

Microbial aspartic proteases: current and potential applications in industry

Aspartic proteases are a relatively small group of proteolytic enzymes that are active in acidic environments and are found across all forms of life. Certain microorganisms secrete such proteases as virulence agents and/or in order to break down proteins thereby liberating assimilable sources of nitrogen. Some of the earlier applications of these proteolytic enzymes are found in the manufacturing of cheese where they are used as milk-clotting agents. Over the last decade, they have received tremendous research interest because of their involvement in human diseases. Furthermore, there has also been a growing interest on these enzymes for their applications in several other industries. Recent research suggests in particular that they could be used in the wine industry to prevent the formation of protein haze while preserving the wines' organoleptic properties. In this mini-review, the properties and mechanisms of action of aspartic proteases are summarized. Thereafter, a brief overview of the industrial applications of this specific class of proteases is provided. The use of aspartic proteases as alternatives to clarifying agents in various beverage industries is mentioned, and the potential applications in the wine industry are thoroughly discussed.

Role of Candida albicans-secreted aspartyl proteinases (Saps) in severe early childhood caries

Candida albicans is strongly associated with severe early childhood caries (S-ECC). However, the roles of secreted aspartyl proteinases (Saps), an important virulence factor of C. albicans, in the progress of S-ECC are not clear. In our study, the Saps activities were evaluated by the yeast nitrogen base–bovine serum albumi (YNB–BSA) agar plate method and by the MTT method with bovine serum albumin (BSA) as the substrate. Genotypes of C. albicans and gene expression of Sap1–5 were evaluated. The relationships of Saps activities and genotypes with S-ECC were analyzed. The results showed that enzyme activities of Saps in the S-ECC group were significantly higher than those in the caries free (CF) group (p < 0.05). Genotypes A, B and C were detected in the S-ECC group, and genotypes A and C were detected in the CF group. In the genotype A group, Saps activity in the S-ECC group was significantly different from that in the CF group (p < 0.05). The gene expression level of Sap1 in the S-ECC group was significantly higher than that in the CF group (p = 0.001), while Sap4 expression was significantly lower than that in the CF group (p = 0.029). It can be concluded that Sap1–5 are the predominant proteinase genes expressed in C. albicans from dental biofilm and Sap1 may play an important role in the development of S-ECC.

Impact of glucose levels on expression of hypha-associated secreted aspartyl proteinases in Candida albicans

BACKGROUND

Ten secreted aspartyl proteinase (Sap) genes were identified in Candida albicans. The products of SAP genes are considered to be virulent factors of C. albicans that participated in causing mucocutaneous and systemic candidiasis in humans. Depending on environmental conditions, C. albicans may stay in yeast-form or convert into invasive hypha-form, and these issues may affect the expression of SAP genes. In this study we explored the component(s) of culture media that may affect the expression of hypha-associated SAP genes.

RESULTS

We demonstrate that glucose levels modulate both the hyphae development and the expression strength of hypha-associated SAP genes (SAP4-6). In contrast to high glucose concentration (2%), lower glucose level (0.1%) is more potent to promote hyphae development and to promptly elicit the expression of hypha-associated Sap proteins during yeast-to-hypha transition of C. albicans. Both Cph1-mediated MAP kinase cascade and Efg1-mediated cAMP/PKA pathway, although the latter seemed dominant, participate in convey the glucose signaling to regulate the expression of hypha-associated SAP genes and this glucose level effect may perform at very early stage of yeast-to-hypha transition. In addition, when C. albicans was co-cultured with THP-1 human monocytes, the engulfed C. albicans was developing hypha efficiently within 1 hr and the expression of hypha-associated Sap proteins could be detected on the distal surface of hyphae.

CONCLUSION

We propose that the glucose level of bloodstream (approximately 0.1%) may be facilitated for stimulation of C. albicans to develop invasive hypha-form and to elicit promptly production of high-level hypha-associated Sap proteins.

Sap6, a secreted aspartyl proteinase, participates in maintenance the cell surface integrity of Candida albicans

Background

The polymorphic species Candida albicans is the major cause of candidiasis in humans. The secreted aspartyl proteinases (Saps) of C. albicans, encoded by a family of 10 SAP genes, have been investigated as the virulent factors during candidiasis. However, the biological functions of most Sap proteins are still uncertain. In this study, we applied co-culture system of C. albicans and THP-1 human monocytes to explore the pathogenic roles and biological functions of Sap proteinases.

Results

After 1 hr of co-culture of C. albicans strains and THP-1 human monocytes at 37°C, more than 60% of the THP-1-engulfed wild type and Δsap5 Candida cells were developing long hyphae. However, about 50% of THP-1-engulfed Δsap6 Candida cells were generating short hyphae, and more dead Candida cells were found in Δsap6 strain that was ingested by THP-1 cells (about 15% in Δsap6 strain vs. 2 ~ 2.5% in SC5314 and Δsap5 strains). The immunofluorescence staining demonstrated that the Sap6 is the major hyphal tip located Sap protein under THP-1 phagocytosis. The sap6-deleted strains (Δsap6, Δsap4/6, and Δsap5/6) appeared slower growth on Congo red containing solid medium at 25°C, and the growth defect was exacerbated when cultured at 37°C in Congo red or SDS containing medium. In addition, more proteins were secreted from Δsap6 strain and the β-mercaptoethanol (β-ME) extractable surface proteins from Δsap6 mutant were more abundant than that of extracted from wild type strain, which included the plasma membrane protein (Pma1p), the ER-chaperone protein (Kar2p), the protein transport-related protein (Arf1p), the cytoskeleton protein (Act1), and the mitochondrial outer membrane protein (porin 1). Moreover, the cell surface accessibility was increased in sap6-deleted strains.

Conclusion

From these results, we speculated that the cell surface constitution of C. albicans Δsap6 strain was defect. This may cause the more accessible of β-ME to disulfide-bridged cell surface components and may weaken the resistance of Δsap6 strain encountering phagocytosis of THP-1 cells. Sap6 protein displays a significant function involving in maintenance the cell surface integrity.

Genetic determinants of virulence - Candida parapsilosis

The global epidemiology of fungal infections is changing. While overall, Candida albicans remains the most common pathogen; several institutions in Europe, Asia and South America have reported the rapid emergence to predominance of Candida parapsilosis. This mini-review examines the impact of gene deletions achieved in C. parapsilosis that have been published to date. The molecular approaches to gene disruption in C. parapsilosis and the molecularly characterized genes to date are reviewed. Similar to C. albicans, factors influencing virulence in C. parapsilosis include adherence, biofilm formation, lipid metabolism, and secretion of hydrolytic enzymes such as lipases, phospholipases and secreted aspartyl proteinases. Development of a targeted gene deletion method has enabled the identification of several unique aspects of C. parapsilosis genes that play a role in host-pathogen interactions - CpLIP1, CpLIP2, SAPP1a, SAPP1b, BCR1, RBT1, CpFAS2, OLE1, FIT-2. This manuscript is part of the series of works presented at the "V International Workshop: Molecular genetic approaches to the study of human pathogenic fungi" (Oaxaca, Mexico, 2012).

Aspartic proteinases of Candida spp.: role in pathogenicity and antifungal resistance

Fungal infections represent a serious health risk as they are particularly prevalent in immunocompromised individuals. Candida spp. pathogenicity depends on several factors and secreted aspartic proteinases (Sap) are considered one of the most critical factors as they are associated with adhesion, invasion and tissue damage. The production of proteinases is encoded by a family of 10 genes known as SAP, which are distributed differently among the species. The expression of these genes may be influenced by environmental conditions, which generally result in a higher fungal invasive potential. Non-pathogenic Candida spp. usually have fewer SAP genes, which are not necessarily expressed in the genome. Exposure to subinhibitory concentrations of antifungal agents promotes the development of resistant strains with an increased expression of SAP genes. In general, Candida spp. isolates that are resistant to antifungals show a higher secretion of Sap than the susceptible isolates. The relationship between Sap secretion and the susceptibility profile of the isolates is of great interest, although the role of SAPs in the development of resistance to antifungal agents remains still unclear. This review is the first one to address these issues.

Secreted aspartic protease cleavage of Candida albicans Msb2 activates Cek1 MAPK signaling affecting biofilm formation and oropharyngeal candidiasis

Perception of external stimuli and generation of an appropriate response are crucial for host colonization by pathogens. In pathogenic fungi, mitogen activated protein kinase (MAPK) pathways regulate dimorphism, biofilm/mat formation, and virulence. Signaling mucins, characterized by a heavily glycosylated extracellular domain, a transmembrane domain, and a small cytoplasmic domain, are known to regulate various signaling pathways. In Candida albicans, the mucin Msb2 regulates the Cek1 MAPK pathway. We show here that Msb2 is localized to the yeast cell wall and is further enriched on hyphal surfaces. A msb2Δ/Δ strain formed normal hyphae but had biofilm defects. Cek1 (but not Mkc1) phosphorylation was absent in the msb2Δ/Δ mutant. The extracellular domain of Msb2 was shed in cells exposed to elevated temperature and carbon source limitation, concomitant with germination and Cek1 phosphorylation. Msb2 shedding occurred differentially in cells grown planktonically or on solid surfaces in the presence of cell wall and osmotic stressors. We further show that Msb2 shedding and Cek1 phosphorylation were inhibited by addition of Pepstatin A (PA), a selective inhibitor of aspartic proteases (Saps). Analysis of combinations of Sap protease mutants identified a sap8Δ/Δ mutant with reduced MAPK signaling along with defects in biofilm formation, thereby suggesting that Sap8 potentially serves as a major regulator of Msb2 processing. We further show that loss of either Msb2 (msb2Δ/Δ) or Sap8 (sap8Δ/Δ) resulted in higher C. albicans surface β-glucan exposure and msb2Δ/Δ showed attenuated virulence in a murine model of oral candidiasis. Thus, Sap-mediated proteolytic cleavage of Msb2 is required for activation of the Cek1 MAPK pathway in response to environmental cues including those that induce germination. Inhibition of Msb2 processing at the level of Saps may provide a means of attenuating MAPK signaling and reducing C. albicans virulence.

Physicochemical characterization of an aspin (rBm-33) from a filarial parasite Brugia malayi against the important human aspartic proteases

The aspartic protease inhibitory efficiency of rBm-33, an aspin from a filarial parasite Brugia malayi was investigated. rBm-33 was found to be thermostable up to 90°C and it forms a stable 'enzyme-product' complex with human pepsin. Aspartic protease inhibitory activity was investigated using UV spectroscopy and isothermal titration calorimetry. Our results suggest that rBm-33 inhibits the activity of important human aspartic proteases that were examined with binding constants (Kb) values between 10.23 × 10(3) and 6.52 × 10(3) M(-1). The binding reactions were enthalpy driven with ΔHb values between -50.99 and -46.07 kJ mol(-1). From kinetic studies, pepsin inhibition by rBm-33 was found to be linear competitive with an inhibition constant (Ki) of 2.5 (±0.8) nM. Because of the inhibitory efficacy of Bm-33 against important human aspartic proteases which play a vital role in immune-regulation along with other functions, Bm-33 can be projected as a drug target for the filariasis.

The identification of gene duplication and the role of secreted aspartyl proteinase 1 in Candida parapsilosis virulence

In this study, we analyzed the role of Candida parapsilosis-secreted aspartyl proteinase isoenzyme 1 (SAPP1) in virulence. The in silico analysis of SAPP1 sequence revealed a 2871 base pair-duplicated region (SAPP1a and SAPP1b) in the genome of C. parapsilosis. We generated homozygous ΔΔsapp1a, ΔΔsapp1b, and ΔΔsapp1a-ΔΔsapp1b mutants. Notably, Sapp1 production in an inducer medium was reduced by approximately 50% in the ΔΔsapp1a and ΔΔsapp1b mutants, but the other validated SAPP gene (SAPP2) was not affected. In contrast, Sapp2 production was increased in the ΔΔsapp1a-ΔΔsapp1b mutant relative to wild-type (WT) yeast. The ΔΔsapp1a-ΔΔsapp1b strain was hypersusceptible to human serum and was attenuated in its capacity to damage host-effector cells. The phagocytosis and killing of ΔΔsapp1a-ΔΔsapp1b yeasts by human peripheral blood mononuclear cells (PBMCs) and PBMC-derived macrophages (PBMC-DM) was significantly enhanced relative to WT. Phagolysosomal fusion in PBMC-DMs occurred more than twice as frequently with ingested ΔΔsapp1a-ΔΔsapp1b yeast cells compared with WT.

Comparative Proteomic Analysis of Candida albicans and Candida glabrata

Introduction

Candida albicans and Candida glabrata are the two most common opportunistic pathogens which are part of the normal flora in humans. Clinical diagnosis of infection by these organisms is still largely based on culturing of these organisms. In order to identify species-specific protein expression patterns, we carried out a comparative proteomic analysis of C. albicans and C. glabrata.

Methods

We used “isobaric tag for relative and absolute quantitation” (iTRAQ) labeling of cell homogenates of C. albicans and C. glabrata followed by LC-MS/MS analysis using a quadrupole time-of-flight mass spectrometer. The MS/MS data was searched against a protein database comprised of known and predicted proteins reported from these two organisms. Subsequently, we carried out a bioinformatics analysis to group orthologous proteins across C. albicans and C. glabrata and calculated protein abundance changes between the two species.

Results and Conclusions

We identified 500 proteins from these organisms, the large majority of which corresponded to predicted transcripts. A number of proteins were observed to be significantly differentially expressed between the two species including enolase (Eno1), fructose-bisphosphate aldolase (Fba1), CCT ring complex subunit (Cct2), pyruvate kinase (Cdc19), and pyruvate carboxylase (Pyc2). This study illustrates a strategy for investigating protein expression patterns across closely related organisms by combining orthology information with quantitative proteomics.

Secretion of an endogenous subtilisin by Pichia pastoris strains GS115 and KM71

The methylotrophic yeast Pichia pastoris is widely used for the expression of heterologous enzymes. While the purity of the desired expression product is of major importance for many applications, we found that recombinant enzymes produced in methanol medium were contaminated by a 37-kDa endogenous yeast protease. This enzyme was completely inhibited by phenylmethanesulfonyl fluoride (PMSF) but not by 1,10-phenanthroline, EDTA, and pepstatin A, suggesting the nature of a serine protease. Its secretion was abolished in P. pastoris strains GS115 and KM71 by specific mutagenesis of a subtilisin gene (SUB2) but not by inactivation of the gene encoding vacuolar proteinase B (PRB). Bioinformatic comparisons of Sub2 protein with subtilisins from other fungal genomes and phylogenetic analyses indicated that this enzyme is not an orthologue of the vacuolar protease cerevisin generally present in yeasts but is more closely related to another putative subtilisin found in a small number of yeast genomes. During growth of P. pastoris, Sub2 was produced as a secreted enzyme at a concentration of 10 microg/ml of culture supernatant after overexpression of the full-length SUB2 gene. During fermentative production of recombinant enzymes in methanol medium, 1 ml of P. pastoris culture supernatant was found to contain approximately 3 ng of Sub2, while the enzyme was not detected during growth in a medium containing glycerol as a carbon source. The mutant strain GS115-sub2 was subsequently used as a host for the production of recombinant proteases without endogenous subtilisin contamination.

Characterization of Candida parapsilosis infection of an in vitro reconstituted human oral epithelium

Oral candidosis is a common problem in immunocompromised patients, and whilst Candida albicans is regarded as the principal cause of infection, other non-Candida albicans Candida (NCAC) species are increasingly being recognized as human pathogens. Relatively little is known about the virulence factors associated with NCAC species, and the aim of this study was to use a reconstituted human oral epithelium (RHOE) to examine epithelial infection withCandida parapsilosis. Strains originating from the oral and vaginal mucosa and from the urinary tract were all shown to colonize RHOE in a strain-dependent manner. Strain differences were found in the colonizing morphology and in the extent of invasion of the RHOE. Low invasion of RHOE was detected for strains after 12 h, whereas extensive tissue damage was evident after 24 h when assessed using histological examination and lactate dehydrogenase activity determination. Tissue damage was reduced in the presence of pepstatin A, although C. parapsilosis invasion of the tissue was not inhibited. Real-time polymerase chain reaction of secreted aspartyl proteinase (SAP) genes (SAPP1-3) showed that expression was strain dependent, with an increased expression generally occurring for Candida infecting RHOE compared with planktonic equivalents. In summary, C. parapsilosis was not highly invasive of RHOE but did induce significant tissue damage, which could relate to specific SAPgene expression.

HIV aspartyl protease inhibitors as promising compounds against Candida albicans André Luis Souza dos Santos

Cells of Candida albicans (C. albicans) can invade humans and may lead to mucosal and skin infections or to deep-seated mycoses of almost all inner organs, especially in immunocompromised patients. In this context, both the host immune status and the ability of C. albicans to modulate the expression of its virulence factors are relevant aspects that drive the candidal susceptibility or resistance; in this last case, culminating in the establishment of successful infection known as candidiasis. C. albicans possesses a potent armamentarium consisting of several virulence molecules that help the fungal cells to escape of the host immune responses. There is no doubt that the secretion of aspartyl-type proteases, designated as Saps, are one of the major virulence attributes produced by C. albicans cells, since these hydrolytic enzymes participate in a wide range of fungal physiological processes as well as in different facets of the fungal-host interactions. For these reasons, Saps clearly hold promise as new potential drug targets. Corroborating this hypothesis, the introduction of new anti-human immunodeficiency virus drugs of the aspartyl protease inhibitor-type (HIV PIs) have emerged as new agents for the inhibition of Saps. The introduction of HIV PIs has revolutionized the treatment of HIV disease, reducing opportunistic infections, especially candidiasis. The attenuation of candidal infections in HIV-infected individuals might not solely have resulted from improved immunological status, but also as a result of direct inhibition of C. albicans Saps. In this article, we review updates on the beneficial effects of HIV PIs against the human fungal pathogen C. albicans, focusing on the effects of these compounds on Sap activity, growth behavior, morphological architecture, cellular differentiation, fungal adhesion to animal cells and abiotic materials, modulation of virulence factors, experimental candidiasis infection, and their synergistic actions with classical antifungal agents.

Spontaneous and protein-induced secretion of proteinases from Saccharomyces cerevisiae

Many fungi are capable of secreting the wide spectrum of hydrolytic enzymes. We characterized an inducible proteinase secretion in yeasts, Saccharomyces cerevisiae. The proteinase secretion by S. cerevisiae was induced in the presence of yeast extract, or of purified proteins, such as bovine serum albumin, casein, or ovalbumin, and some proteolytic activity was present also without protein inducer. We found that properties of proteinases induced under cultivation conditions were different in various aspects (temperature- and pH-dependencies, substrate specificities, sensitivities to proteinase inhibitors). Proteinase activities were also characterized by gelatin zymography. Multiple proteinase bands with wide-molecular weights (ranging from 45 to 240 kDa) were detected and patterns of proteinase bands were different. S. cerevisiae cells were able to retain the information about previous contacts with protein inducer resulting in faster and more intensive proteinase secretion response after repeated induction.

Stimulation of cell motility and expression of late markers of differentiation in human oral keratinocytes by Candida albicans

A hallmark of the mucosa of immunocompromized hosts in oral candidiasis is a hyperkeratinized region heavily colonized with fungi at the surface of the terminally differentiated epithelium. To gain insight into the processes important for promoting mucosal invasion by fungi, we characterized the response of keratinocytes to the presence of Candida albicans. Indirect immunofluorescence and kymographic analyses revealed a multifaceted keratinocyte response of OKF6/TERT-2 cells to C. albicans that consisted of: cytoskeletal reorganization within 3 h, motility and cell expansion with formation of E-cadherin-mediated cell-cell adhesions within 6 h, increased expression of late differentiation markers and decreased expression of calprotectin. The initial expansive phase was followed by dissolution of cell-cell adhesions and a decrease in cell size accompanied by loss of E-cadherin. The keratinocyte response depended on soluble factors associated with hyphal growth as demonstrated using the efg1Delta/efg1Delta, cap1Delta/cap1Delta, als3Delta/als3Delta, hwp1Delta/hwp1Deltaand sap4-6Delta/sap4-6Delta mutants and was not observed in the presence of the non-pathogenic yeast, Saccharomyces cerevisiae. These studies show the potential for C. albicans to manipulate the stratified epithelial cells to a state of differentiation that is more permissive of fungal colonization of oral tissue, which is likely to play an important role in the pathogenesis of candidiasis.

Cloning and expression of carp acetylcholinesterase gene in Pichia pastoris and characterization of the recombinant enzyme

The gene encoding acetylcholinesterase (AChE) was cloned from common carp muscle tissue. The full-length cDNA was 2368 bp that contains a coding region of 1902 bp, corresponding to a protein of 634 amino acids. The deduced amino acid sequence showed a significant homology with those of ichthyic AChEs and several common features among them, including T peptide encoded by exon T in the C-terminus. Three yeast expression vectors were constructed and introduced into the yeast Pichia pastoris. The transformant harboring carp AChE gene lacking exon T most effectively produced AChE activity extracellularly. The replacement of the native signal sequence with the yeast alpha-factor prepro signal sequence rather decreased the production. A decrease in cultivation temperature from 30 to 15 degrees C increased the activity production 32.8-fold. The purified recombinant AChE lacking T peptide, eluted as a single peak with a molecular mass of about 230 kDa on the gel filtration chromatography, exhibited the specific activity of 4970 U/mg. On the SDS-PAGE, three proteins with molecular masses of 73, 54, and 22 kDa were observed. These proteins were N-glycosylated, and their N-terminal sequence showed that the latter two were produced from the former probably by proteolytic cleavage at the C-terminal region. Thus, the recombinant AChE is homotrimer of three identical subunits with 73 kDa. The optimal temperature and pH of the recombinant were comparable to those of the native enzyme purified previously, but the values of kinetic parameters and the sensitivities to substrate inhibition and inhibitors were considerably different between them.

Candida albicans cell wall proteins

The Candida albicans cell wall maintains the structural integrity of the organism in addition to providing a physical contact interface with the environment. The major components of the cell wall are fibrillar polysaccharides and proteins. The proteins of the cell wall are the focus of this review. Three classes of proteins are present in the candidal cell wall. One group of proteins attach to the cell wall via a glycophosphatidylinositol remnant or by an alkali-labile linkage. A second group of proteins with N-terminal signal sequences but no covalent attachment sequences are secreted by the classical secretory pathway. These proteins may end up in the cell wall or in the extracellular space. The third group of proteins lack a secretory signal, and the pathway(s) by which they become associated with the surface is unknown. Potential constituents of the first two classes have been predicted from analysis of genome sequences. Experimental analyses have identified members of all three classes. Some members of each class selected for consideration of confirmed or proposed function, phenotypic analysis of a mutant, and regulation by growth conditions and transcription factors are discussed in more detail.

Niche-specific gene expression during C. albicans infection

Infection by the opportunistic pathogen Candida albicans may occur in virtually any organ of the human host. Studies of C. albicans gene expression during experimental infection reveal that different stress responses are mounted during different types of infection, presumably because different environments present different challenges. In addition, at least two mechanisms allow expression of common genes or activities in multiple sites within the host: differential expression of isozymes in a multigene family and regulation of a common set of genes by multiple transcription factors. Thus, analysis of C. albicans gene expression illuminates details of host-pathogen interactions and the differences between sites within the host.

Differential expression of Candida albicans secreted aspartyl proteinase in human vulvovaginal candidiasis

The opportunistic pathogen Candida albicans secretes aspartic proteinases (Saps), which raises a particular interest because of their role as virulence factors. Candida albicans possesses at least 10 members of a SAP gene family, all of which have been sequenced. Although the expression of the SAP genes has been extensively characterised under laboratory growth conditions and Saps contribute to the virulence of C. albicans in animal models of infection, few studies have analysed the difference of the in vivo expression of these proteinases in recurrent vulvovaginal candidiasis (RVVC), vulvovaginal candidiasis (VVC) and asymptomatic Candida carriers. The RT-PCR protocol was used to determine which of the SAP 1 to SAP 7 genes are expressed by C. albicans during asymptomatic Candida carriage, VVC and RVVC infection in this study. We found SAP 2, the SAP 4-6 and SAP 7 were the predominant proteinase genes expressed in the sample of both Candida carriers and patients with VVC and RVVC. SAP 2 and SAP 4-6 mRNA were detected in all subjects. SAP 1 and SAP 3 transcripts were observed only in patients with VVC and RVVC. SAP 7 mRNA expressions were detected in several of the patients and carriers samples. All seven SAP genes were simultaneously expressed in some patients with VVC and RVVC. This study demonstrates the differential expression of the secreted aspartic proteinases (Saps) genes during colonisation and VVC and RVVC infection in humans and correlates the expression of specific Candida species virulence genes with active disease and anatomical location.

Structure-based specificity mapping of secreted aspartic proteases of Candida parapsilosis, Candida albicans, and Candida tropicalis using peptidomimetic inhibitors and homology modeling

Secreted aspartic proteases (Saps) of pathogenic Candida spp. represent a specific target for antifungal drug development. We synthesized a series of peptidomimetic inhibitors with different isosteric groups and modifications at individual positions and tested them with purified Saps from C. albicans (Sap2p), C. tropicalis (Sapt1p), and C. parapsilosis (Sapp1p). The kinetic parameters indicated that all three proteases prefer binding of inhibitors containing bulky hydrophobic residues between positions P3 and P3'. The most divergent specificity was found for Sapp1p. The sequence alignment of Sap2p, Sapt1p, and Sapp1p, and homology modeling of Sapp1p with the crystal structure of Sapt1p and the complex of Sap2p with a peptidomimetic inhibitor showed that the overall folds of Sap2p, Sapt1p, and Sapp1p are similar. However, the N- and C-terminal loops formed by disulfide bonds between residues 47-53 and 258-292 are significantly shorter in Sapp1p, and a unique insertion following Tyr 129 in Sapp1p results in the formation of a loop that can interact with inhibitor residues. These Sapp1p structural differences might lead to its altered susceptibility to inhibition.

Tetracycline-inducible expression of individual secreted aspartic proteases in Candida albicans allows isoenzyme-specific inhibitor screening

The yeast Candida albicans possesses a gene family that encodes secreted aspartic proteases (Saps), which are important for the virulence of this human fungal pathogen. Inhibitors of the Saps could therefore be used as novel antimycotic agents for the treatment of C. albicans infections. In the present study, we established a bioassay which allows testing of the activity of potential protease inhibitors against specific Sap isoenzymes by their ability to inhibit protease-dependent growth of C. albicans. In a medium containing bovine serum albumin (BSA) as the sole source of nitrogen, C. albicans specifically expresses the Sap2p isoenzyme, which degrades the BSA and thereby enables the fungus to grow. As the other SAP genes are not significantly expressed under these conditions, mutants lacking SAP2 are unable to utilize BSA as a nitrogen source and cannot grow in such a medium. To investigate whether forced expression of SAP genes other than SAP2 would also allow growth on BSA, we constructed a set of strains expressing each of the 10 SAP genes from a tetracycline-inducible promoter in a sap2Delta mutant background. Expression of Sap1p, Sap2p, Sap3p, Sap4p, Sap5p, Sap6p, Sap8p, and a C-terminally truncated, secreted Sap9p restored the growth of the sap2Delta mutant with different efficiencies. This set of strains was then used to test the activities of various aspartic protease inhibitors against specific Sap isoenzymes by monitoring growth on BSA in the presence of the inhibitors. While pepstatin blocked the activity of all of the Saps tested, the human immunodeficiency virus protease inhibitors ritonavir and saquinavir inhibited growth of the strains expressing Sap1p to Sap3p and Sap1p, respectively, but not that of strains expressing other Saps. Therefore, the strain set can be used to test the activity of new protease inhibitors against individual C. albicans Sap isoenzymes by their ability to block the growth of the pathogen.

Sulphite efflux pumps in Aspergillus fumigatus and dermatophytes

Dermatophytes and other filamentous fungi excrete sulphite as a reducing agent during keratin degradation. In the presence of sulphite, cystine in keratin is directly cleaved to cysteine and S-sulphocysteine, and thereby, reduced proteins become accessible to hydrolysis by a variety of secreted endo- and exoproteases. A gene encoding a sulphite transporter in Aspergillus fumigatus (AfuSSU1), and orthologues in the dermatophytes Trichophyton rubrum and Arthroderma benhamiae (TruSSU1 and AbeSSU1, respectively), were identified by functional expression in Saccharomyces cerevisiae. Like the S. cerevisiae sulphite efflux pump Ssu1p, AfuSsu1p, TruSsu1p and AbeSsu1p belong to the tellurite-resistance/dicarboxylate transporter (TDT) family which includes the Escherichia coli tellurite transporter TehAp and the Schizosaccharomyces pombe malate transporter Mae1p. Seven genes in the A. fumigatus genome encode transporters of the TDT family. However, gene disruption of AfuSSU1 and of the two more closely related paralogues revealed that only AfuSSU1 encodes a sulphite efflux pump. TruSsulp and AbeSsulp are believed to be the first members of the TDT family identified in dermatophytes. The relatively high expression of TruSSU1 and AbeSSU1 in dermatophytes compared to that of AfuSSU1 in A. fumigatus likely reflects a property of dermatophytes which renders these fungi pathogenic. Sulphite transporters could be a new target for antifungal drugs in dermatology, since proteolytic digestion of hard keratin would not be possible without prior reduction of disulphide bridges.

Characterization of Candida albicans infection of an in vitro oral epithelial model using confocal laser scanning microscopy

INTRODUCTION

Oral candidosis presents as several distinct forms and one of these, chronic hyperplastic candidosis, is distinguished by penetration of the epithelium by Candida. The aim of this study was to use confocal laser scanning microscopy to examine invasion of the oral epithelium by Candida albicans from different oral conditions and to determine whether inherent strain differences exist that could relate to infection type. Reverse transcription-polymerase chain reaction was also used to detect products from virulence gene families.

METHODS

C. albicans (n = 19) was used to infect reconstituted human oral epithelium, which was incubated for 12 h. One half of the reconstituted human oral epithelium was then fixed and stained with concanavalin A-Alexa 594, pan-cytokeratin antibody-Alexa 488 and Hoechst nucleic acid dye. RNA was extracted from the remaining tissue for reverse transcription-polymerase chain reaction targeting secreted aspartyl proteinase, phospholipase and agglutinin-like sequence genes of C. albicans.

RESULTS

Confocal laser scanning microscopy revealed strain-dependent tissue invasion, with differences evident in surface colonization, C. albicans morphology and the extent and pattern of tissue penetration. Hyphae were seen to directly penetrate epithelial cells and migrate between keratinocytes with yeast budding also evident in the reconstituted human oral epithelium. A relationship between 'high tissue invasion' and expression of secreted aspartyl proteinase genes 4-6 was noted. Interestingly, four of the five 'high invaders' originated from chronic hyperplastic candidosis.

CONCLUSIONS

Confocal laser scanning microscopy permitted high resolution analysis of reconstituted human oral epithelium invasion by C. albicans and identified strain differences in the invasion process. Association between extensive hyphal morphology, direct epithelial penetration and high surface colonization were made with the 'highly invasive' strains.

Cleavage of E-cadherin: a mechanism for disruption of the intestinal epithelial barrier by Candida albicans

To investigate how intestinal epithelial cells respond to contact with Candida albicans, an organism able to invade the bloodstream via the gastrointestinal tract, we focused on the junction proteins occludin, E-cadherin, and desmoglein-2. The levels of these 3 junction proteins were reduced in lysates of human intestinal epithelial monolayers (Caco-2) after a 24-h inoculation with C. albicans, compared with lysates from Saccharomyces cerevisiae-inoculated monolayers. Treatment with pepstatin A did not change the effect of C. albicans on full-length occludin, desmoglein-2, and E-cadherin; however, pepstatin A enhanced the accumulation of a 35-kDa fragment derived from the intracellular portion of E-cadherin. This 35-kDa fragment also accumulated in the presence of gamma-secretase inhibitors. These observations suggest that enhancement of E-cadherin cleavage by C. albicans generates an intracellular E-cadherin fragment that can serve as a substrate for gamma-secretase. An 89-kDa extracellular fragment of E-cadherin was detected in supernatants of C. albicans-inoculated monolayers; this cleavage event was insensitive to both pepstatin A and gamma-secretase inhibitors. Transepithelial electrical resistance, a measure of monolayer integrity, decreased significantly and synchronously with increased generation of the 89-kDa extracellular E-cadherin fragment. Cleavage of E-cadherin may destabilize the homotypic interactions between adjacent epithelial cells and could contribute to loss of monolayer integrity. These experiments identify 2 E-cadherin cleavage events that are enhanced by contact with C. albicans: an intracellular cleavage event that generates a substrate for gamma-secretase and an extracellular cleavage event that is temporally associated with an increase in monolayer permeability.

Candida glabrata: an emerging oral opportunistic pathogen

Following the widespread use of immunosuppressive therapy and broad-spectrum antimycotic prophylaxis, C. glabrata has emerged as an important opportunistic pathogen in the oral mucosa. In the past, studies on the virulence factors and host-pathogen interactions of this organism were scarce, but continued to rise in recent years. Denture-wearing, immunosuppression, antibiotic therapy, and aging are risk factors for oral colonization or infection with C. glabrata. Compared with C. albicans, C. glabrata exhibits lower oral keratinocyte-adherence capacity, but higher denture-surface-adherence ability. The role of extracellular hydrolase production in the virulence of this organism does not appear to be as important as it is in C. albicans pathogenesis. Although traditionally thought of as a non-transforming yeast organism, both phenotypic switching and pseudohyphal formation have recently been identified in C. glabrata, but their role in pathogenesis is not known. With the exception of granulocyte monocyte colony-stimulating factor, C. glabrata triggers a lower proinflammatory cytokine response in oral epithelial cells than does C. albicans, in a strain-dependent manner. C. glabrata is less susceptible to killing by human beta-defensins than is C. albicans and exhibits various degrees of resistance to the antifungal activity of salivary histatins and mucins. In addition, C. glabrata possesses both innate and acquired resistance against antifungal drugs, due to its ability to modify ergosterol biosynthesis, mitochondrial function, or antifungal efflux. This resistance allows for its relative overgrowth over other susceptible species and may contribute to the recent emergence of C. glabrata infections in chronically immunocompromised populations. Further investigations on the virulence and host-pathogen interactions of C. glabrata are needed to better define the pathogenesis of oral C. glabrata infection in susceptible hosts.

Candida species adhesion to oral epithelium: factors involved and experimental methodology used

Due to the increasing prevalence and emergence of Non-Candida albicans Candida (NCAC) species, especially in immunosupressed patients, it is becoming urgent to deepen the current knowledge about virulence factors of these species. Adhesion of cells to epithelium is considered one of the major virulence factors of Candida species. However, relatively little is known concerning the adhesion mechanisms of NCAC species to epithelium, as well as about the factors affecting the adhesion process. This review focuses both the mechanisms that regulate the adhesion interactions and the factors involved and the description of the experimental methodology that has been used to perform the adhesion assays.

Cloning and characterization of Sapp2p, the second aspartic proteinase isoenzyme from Candida parapsilosis

The human fungal pathogen Candida parapsilosis possesses at least three genes encoding secreted aspartic proteinases. Whereas the Sapp1p isoenzyme has already been biochemically characterized, the SAPP2 and SAPP3 gene products have not. The Sapp2p precursor, pro-Sapp2p, was therefore expressed in Escherichia coli and purified. Autoactivation of pro-Sapp2p in acidic conditions was inefficient and resulted in a protein extended by eight amino acids at the N-terminus (Sapp2p(+8)). The correct promature junction KR/SSPSS was cleaved by trypsin or by a membrane-bound Kex2-like proteinase from Candida parapsilosis. The mature Sapp2p obtained by the assisted activation was proteolytically active. Its activity was more than twofold higher than that of the self-processed protein species Sapp2p(+8), as measured by the hemoglobin cleavage test. The substrate specificity of Sapp2p differs from that of Sapp1p. Peptides containing aromatic residues in the P1 and P1' positions are cleaved poorly by Sapp2p. A fluorogenic substrate was synthesized to facilitate further studies.

In vitro evaluation of virulence attributes of Candida spp. isolated from patients affected by diabetes mellitus

BACKGROUND

Diabetes mellitus is a common disease found worldwide and it has been previously suggested that oral candidal infections may be more frequent or severe in patients with this disease. Systemic and local factors may influence the balance between the host and yeasts, and favour the transformation of Candida isolates from commensal to pathogenic microorganisms. Candida species have developed specific virulence mechanisms that confer the ability to colonise host surfaces, to invade deeper host tissue, or to evade host defences. Few studies have investigated the expression of the virulence attributes of oral Candida isolates in patients with diabetes mellitus.

MATERIAL AND METHODS

The in vitro extracellular proteinase production and the in vitro ability to adhere to fibronectin of 229 Candida isolates of two geographic different groups of patients with diabetes mellitus and of healthy subjects were assessed.

RESULTS

Candida isolates of patients with diabetes mellitus expressed a higher ability to adhere than those of healthy subjects. Higher levels of adhesion were also recorded in patients with a lower oral Candida colonisation. No differences were observed in the in vitro expression of extracellular proteinase of Candida isolates of patients with diabetes mellitus and those of non-diabetic subjects. Isolates of patients with type 2 diabetes mellitus expressed greater levels of proteinase than isolates of type 1 diabetes mellitus.

CONCLUSIONS

Diabetes mellitus could be considered as an additional variable that may influence not only oral Candida carriage but also the ability of isolates to enhance the expression of virulence attributes.