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.

Stress Conditions Affect the Immunomodulatory Potential of Candida albicans Extracellular Vesicles and Their Impact on Cytokine Release by THP-1 Human Macrophages.

Human immune cells possess the ability to react complexly and effectively after contact with microbial virulence factors, including those transported in cell-derived structures of nanometer sizes termed extracellular vesicles (EVs). EVs are produced by organisms of all kingdoms, including fungi pathogenic to humans. In this work, the immunomodulatory properties of EVs produced under oxidative stress conditions or at host concentrations of CO2 by the fungal pathogen Candida albicans were investigated. The interaction of EVs with human pro-monocytes of the U-937 cell line was established, and the most notable effect was attributed to oxidative stress-related EVs. The immunomodulatory potential of tested EVs against human THP-1 macrophages was verified using cytotoxicity assay, ROS-production assay, and the measurement of cytokine production. All fungal EVs tested did not show a significant cytotoxic effect on THP-1 cells, although a slight pro-oxidative impact was indicated for EVs released by C. albicans cells grown under oxidative stress. Furthermore, for all tested types of EVs, the pro-inflammatory properties related to increased IL-8 and TNF-α production and decreased IL-10 secretion were demonstrated, with the most significant effect observed for EVs released under oxidative stress conditions.

Candida albicans Biofilm-Derived Extracellular Vesicles Are Involved in the Tolerance to Caspofungin, Biofilm Detachment, and Fungal Proteolytic Activity.

It has been repeatedly reported that the cells of organisms in all kingdoms of life produce nanometer-sized lipid membrane-enveloped extracellular vesicles (EVs), transporting and protecting various substances of cellular origin. While the composition of EVs produced by human pathogenic fungi has been studied in recent decades, another important challenge is the analysis of their functionality. Thus far, fungal EVs have been shown to play significant roles in intercellular communication, biofilm production, and modulation of host immune cell responses. In this study, we verified the involvement of biofilm-derived EVs produced by two different strains of Candida albicans-C. albicans SC5314 and 3147 (ATCC 10231)-in various aspects of biofilm function by examining its thickness, stability, metabolic activity, and cell viability in the presence of EVs and the antifungal drug caspofungin. Furthermore, the proteolytic activity against the kininogen-derived antimicrobial peptide NAT26 was confirmed by HPLC analysis for C. albicans EVs that are known to carry, among others, particular members of the secreted aspartic proteinases (Saps) family. In conclusion, EVs derived from C. albicans biofilms were shown to be involved in biofilm tolerance to caspofungin, biofilm detachment, and fungal proteolytic activity.

The Recruitment and Activation of Plasminogen by Bacteria-The Involvement in Chronic Infection Development.

The development of infections caused by pathogenic bacteria is largely related to the specific properties of the bacterial cell surface and extracellular hydrolytic activity. Furthermore, a significant role of hijacking of host proteolytic cascades by pathogens during invasion should not be disregarded during consideration of the mechanisms of bacterial virulence. This is the key factor for the pathogen evasion of the host immune response, tissue damage, and pathogen invasiveness at secondary infection sites after initial penetration through tissue barriers. In this review, the mechanisms of bacterial impact on host plasminogen-the precursor of the important plasma serine proteinase, plasmin-are characterized, principally focusing on cell surface exposition of various proteins, responsible for binding of this host (pro)enzyme and its activators or inhibitors, as well as the fibrinolytic system activation tactics exploited by different bacterial species, not only pathogenic, but also selected harmless residents of the human microbiome. Additionally, the involvement of bacterial factors that modulate the process of plasminogen activation and fibrinolysis during periodontitis is also described, providing a remarkable example of a dual use of this host system in the development of chronic diseases.

Living together: The role of Candida albicans in the formation of polymicrobial biofilms in the oral cavity.

The oral cavity of humans is colonized by diversity of microbial community, although dominated by bacteria, it is also constituted by a low number of fungi, often represented by Candida albicans. Although in the vast minority, this usually commensal fungus under certain conditions of the host (e.g., immunosuppression or antibiotic therapy), can transform into an invasive pathogen that adheres to mucous membranes and also to medical or dental devices, causing mucosal infections. This transformation is correlated with changes in cell morphology from yeast-like cells to hyphae and is supported by numerous virulence factors exposed by C. albicans cells at the site of infection, such as multifunctional adhesins, degradative enzymes, or toxin. All of them affect the surrounding host cells or proteins, leading to their destruction. However, at the site of infection, C. albicans can interact with different bacterial species and in its filamentous form may produce biofilms-the elaborated consortia of microorganisms, that present increased ability to host colonization and resistance to antimicrobial agents. In this review, we highlight the modification of the infectious potential of C. albicans in contact with different bacterial species, and also consider the mutual bacterial-fungal relationships, involving cooperation, competition, or antagonism, that lead to an increase in the propagation of oral infection. The mycofilm of C. albicans is an excellent hiding place for bacteria, especially those that prefer low oxygen availability, where microbial cells during mutual co-existence can avoid host recognition or elimination by antimicrobial action. However, these microbial relationships, identified mainly in in vitro studies, are modified depending on the complexity of host conditions and microbial dominance in vivo.

Isolation and Characteristics of Extracellular Vesicles Produced by Probiotics: Yeast Saccharomyces boulardii CNCM I-745 and Bacterium Streptococcus salivarius K12.

Numerous probiotic microorganisms have repeatedly been shown to produce nanometer-sized structures named extracellular vesicles (EVs). Recently, it has been suggested that similarly to whole microbial cells, EVs produced by probiotics may also demonstrate health benefits to the host, while their application does not involve the risk of infection caused by live microorganisms. In this work, we isolated EVs from two probiotic species originating from different taxonomic domains - yeast Saccharomyces boulardii CNCM I-745 and bacterium Streptococcus salivarius K12. The diameters of S. boulardii EVs were about 142 nm and for S. salivarius EVs about 123 nm. For S. boulardii EVs, 1641 proteins and for S. salivarius EVs, 466 proteins were identified with a liquid chromatography-coupled tandem mass spectrometry and then functionally classified. In both microbial species, metabolic proteins significantly contributed to the cargo of EVs comprising 25% and 26% of all identified vesicular proteins for fungi and bacteria, respectively. Moreover, enzymes associated with cell wall rearrangement, including enzymatically active glucanases, were also identified in EVs. Furthermore, probiotic EVs were shown to influence host cells and stimulate the production of IL-1ß and IL-8 by the human monocytic cell line THP-1, and, at the same time, did not cause any remarkable reduction in the survival rate of Galleria mellonella larvae in this invertebrate model commonly used to evaluate microbial EV toxicity. These observations suggest that the EVs produced by the investigated probiotic microorganisms may be promising structures for future use in pro-health applications.

Candida parapsilosis cell wall proteins-CPAR2_404800 and CPAR2_404780-Are adhesins that bind to human epithelial and endothelial cells and extracellular matrix proteins.

One of the initial steps necessary for the development of Candida infections is the adherence to the host tissues and cells. Recent transcriptomic studies suggest that, in Candida parapsilosis-a fungal infectious agent that causes systemic candidiasis in immunosuppressed individuals-the adhesion is mediated by pathogen cell-exposed proteins belonging to the agglutinin-like sequence (Als) family. However, to date, the actual interactions of individual members of this family with human cells and extracellular matrix (ECM) have not been characterized in detail. In the current study, we focused attention on two of these C. parapsilosis Als proteins-CPAR2_404800 and CPAR2_404780-that were proteomically identified in the fungal cell wall of yeasts grown in the media suitable for culturing human epithelial and endothelial cells. Both proteins were extracted from the cell wall and purified, and using a microplate binding assay and a fluorescence microscopic analysis were shown to adhere to human cells of A431 (epithelial) and HMEC-1 (endothelial) lines. The human extracellular matrix components that are also plasma proteins-fibronectin and vitronectin-enhanced these interactions, and also could directly bind to CPAR2_404800 and CPAR2_404780 proteins, with a high affinity (KD in a range of 10-7 to 10-8 M) as determined by surface plasmon resonance measurements. Our findings highlight the role of proteins CPAR2_404800 and CPAR2_404780 in adhesion to host cells and proteins, contributing to the knowledge of the mechanisms of host-pathogen interactions during C. parapsilosis-caused infections.

More than Just Protein Degradation: The Regulatory Roles and Moonlighting Functions of Extracellular Proteases Produced by Fungi Pathogenic for Humans.

Extracellular proteases belong to the main virulence factors of pathogenic fungi. Their proteolytic activities plays a crucial role in the acquisition of nutrients from the external environment, destroying host barriers and defenses, and disrupting homeostasis in the human body, e.g., by affecting the functions of plasma proteolytic cascades, and playing sophisticated regulatory roles in various processes. Interestingly, some proteases belong to the group of moonlighting proteins, i.e., they have additional functions that contribute to successful host colonization and infection development, but they are not directly related to proteolysis. In this review, we describe examples of such multitasking of extracellular proteases that have been reported for medically important pathogenic fungi of the Candida, Aspergillus, Penicillium, Cryptococcus, Rhizopus, and Pneumocystis genera, as well as dermatophytes and selected endemic species. Additional functions of proteinases include supporting binding to host proteins, and adhesion to host cells. They also mediate self-aggregation and biofilm formation. In addition, fungal proteases affect the host immune cells and allergenicity, understood as the ability to stimulate a non-standard immune response. Finally, they play a role in the proper maintenance of cellular homeostasis. Knowledge about the multifunctionality of proteases, in addition to their canonical roles, greatly contributes to an understanding of the mechanisms of fungal pathogenicity.

Insight Into the Properties and Immunoregulatory Effect of Extracellular Vesicles Produced by Candida glabrata, Candida parapsilosis, and Candida tropicalis Biofilms.

Currently, non-albicans Candida species, including C. tropicalis, C. glabrata, and C. parapsilosis, are becoming an increasing epidemiological threat, predominantly due to the distinct collection of virulence mechanisms, as well as emerging resistance to antifungal drugs typically used in the treatment of candidiasis. They can produce biofilms that release extracellular vesicles (EVs), which are nanometric spherical structures surrounded by a lipid bilayer, transporting diversified biologically active cargo, that may be involved in intercellular communication, biofilm matrix production, and interaction with the host. In this work, we characterize the size and protein composition of these structures for three species of non-albicans Candida fungi forming biofilm, indicating considerable heterogeneity of the investigated population of fungal EVs. Examination of the influence of EVs on cytokine production by the human monocytic cell line THP-1 differentiated into macrophage-like cells revealed that the tested vesicles have a stimulating effect on the secretion of tumor necrosis factor α and interleukin 8, while they reduce the production of interleukin 10. This may indicate the proinflammatory nature of the effect of EVs produced by these species on the host immune cells. Moreover, it has been indicated that vesicles may be involved in C. tropicalis biofilm resistance to fluconazole and caspofungin. This reveals the important role of EVs not only in the physiology of C. tropicalis, C. glabrata, and C. parapsilosis fungi but also in the pathogenesis of infections associated with the production of fungal biofilm.

Fungi-A Component of the Oral Microbiome Involved in Periodontal Diseases.

The human oral cavity is a diverse ecological niche favorable for colonization by hundreds of different species of microorganisms. They include not only bacteria but also numerous species of fungi, many of which are able to cause opportunistic infections when the host's immunity is impaired, predominantly by systemic and chronic diseases like diabetes, pulmonary diseases, renal disorders, or acquired immunodeficiency syndrome. Within the dental biofilm and subgingival sites, fungi of the genus Candida are often found, also in individuals affected with periodontitis. Moreover, fungal species of other genera, including Malassezia, Aspergillus, Penicillium, and Rhodotorula were identified in the oral cavity as well. The wide range of various virulence factors and mechanisms displayed by fungal pathogens allows them effectively invading host tissues during periodontal infections. These pathogenicity-related mechanisms include firstly the fungal ability to adhere successfully to the host tissues closely related to the formation of hyphae, the increase in the surface hydrophobicity, and the surface display of a wide variety of adhesins. Further mechanisms include biofilm formation and secretion of an armory of hydrolytic enzymes and toxins enabling the attack on host cells, modulation of the local inflammatory state, and evading the host immune system. In the pathogenesis of periodontitis, the significant role of fungal co-existence with key bacterial periodontopathogens has been demonstrated, and such interactions were primarily confirmed for Candida albicans and Porphyromonas gingivalis, where the presence of fungi ensured the survival of strictly anaerobic bacteria under unfavorable aerobic conditions. However, several other mechanisms, including those related to the production of quorum sensing molecules, might also be indicated as particularly important for synergistic or antagonistic interactions with a variety of bacterial species within mixed biofilms. These interactions constitute an extraordinary challenge for applying effective methods of combating biofilm-related infections in the periodontium without the risk of the development of drug resistance, the recurrence of disease symptoms, and the progress of life-threating systemic complications.

Cecropin D-derived synthetic peptides in the fight against Candida albicans cell filamentation and biofilm formation.

The recent progressive increase in the incidence of invasive fungal infections, especially in immunocompromised patients, makes the search for new therapies crucial in the face of the growing drug resistance of prevalent nosocomial yeast strains. The latest research focuses on the active compounds of natural origin, inhibiting fungal growth, and preventing the formation of fungal biofilms. Antimicrobial peptides are currently the subject of numerous studies concerning effective antifungal therapy. In the present study, the antifungal properties of two synthetic peptides (ΔM3, ΔM4) derived from an insect antimicrobial peptide - cecropin D - were investigated. The fungicidal activity of both compounds was demonstrated against the yeast forms of Candida albicans, Candida tropicalis, and Candida parapsilosis, reaching a MFC99.9 in the micromolar range, while Candida glabrata showed greater resistance to these peptides. The scanning electron microscopy revealed a destabilization of the yeast cell walls upon treatment with both peptides; however, their effectiveness was strongly modified by the presence of salt or plasma in the yeast environment. The transition of C. albicans cells from yeast to filamentous form, as well as the formation of biofilms, was effectively reduced by ΔM4. Mature biofilm viability was inhibited by a higher concentration of this peptide and was accompanied by increased ROS production, activation of the GPX3 and SOD5 genes, and finally, increased membrane permeability. Furthermore, both peptides showed a synergistic effect with caspofungin in inhibiting the metabolic activity of C. albicans cells, and an additive effect was also observed for the mixtures of peptides with amphotericin B. The results indicate the possible potential of the tested peptides in the prevention and treatment of candidiasis.

Proteinous Components of Neutrophil Extracellular Traps Are Arrested by the Cell Wall Proteins of Candida albicans during Fungal Infection, and Can Be Used in the Host Invasion.

One of defense mechanisms of the human immune system to counteract infection by the opportunistic fungal pathogen Candida albicans is the recruitment of neutrophils to the site of invasion, and the subsequent production of neutrophil extracellular traps (NETs) that efficiently capture and kill the invader cells. In the current study, we demonstrate that within these structures composed of chromatin and proteins, the latter play a pivotal role in the entrapment of the fungal pathogen. The proteinous components of NETs, such as the granular enzymes elastase, myeloperoxidase and lactotransferrin, as well as histones and cathelicidin-derived peptide LL-37, are involved in contact with the surface of C. albicans cells. The fungal partners in these interactions are a typical adhesin of the agglutinin-like sequence protein family Als3, and several atypical surface-exposed proteins of cytoplasmic origin, including enolase, triosephosphate isomerase and phosphoglycerate mutase. Importantly, the adhesion of both the elastase itself and the mixture of proteins originating from NETs on the C. albicans cell surface considerably increased the pathogen potency of human epithelial cell destruction compared with fungal cells without human proteins attached. Such an implementation of adsorbed NET-derived proteins by invading C. albicans cells might alter the effectiveness of the fungal pathogen entrapment and affect the further host colonization.

The Role of Candida albicans Virulence Factors in the Formation of Multispecies Biofilms With Bacterial Periodontal Pathogens.

Periodontal disease depends on the presence of different microorganisms in the oral cavity that during the colonization of periodontal tissues form a multispecies biofilm community, thus allowing them to survive under adverse conditions or facilitate further colonization of host tissues. Not only numerous bacterial species participate in the development of biofilm complex structure but also fungi, especially Candida albicans, that often commensally inhabits the oral cavity. C. albicans employs an extensive armory of various virulence factors supporting its coexistence with bacteria resulting in successful host colonization and propagation of infection. In this article, we highlight various aspects of individual fungal virulence factors that may facilitate the collaboration with the associated bacterial representatives of the early colonizers of the oral cavity, the bridging species, and the late colonizers directly involved in the development of periodontitis, including the "red complex" species. In particular, we discuss the involvement of candidal cell surface proteins-typical fungal adhesins as well as originally cytosolic "moonlighting" proteins that perform a new function on the cell surface and are also present within the biofilm structures. Another group of virulence factors considered includes secreted aspartic proteases (Sap) and other secreted hydrolytic enzymes. The specific structure of the candidal cell wall, dynamically changing during morphological transitions of the fungus that favor the biofilm formation, is equally important and discussed. The non-protein biofilm-composing factors also show dynamic variability upon the contact with bacteria, and their biosynthesis processes could be involved in the stability of mixed biofilms. Biofilm-associated changes in the microbe communication system using different quorum sensing molecules of both fungal and bacterial cells are also emphasized in this review. All discussed virulence factors involved in the formation of mixed biofilm pose new challenges and influence the successful design of new diagnostic methods and the application of appropriate therapies in periodontal diseases.

Als3-mediated attachment of enolase on the surface of Candida albicans cells regulates their interactions with host proteins.

The multifunctional protein enolase has repeatedly been identified on the surface of numerous cell types, including a variety of pathogenic microorganisms. In Candida albicans-one of the most common fungal pathogens in humans-a surface-exposed enolase form has been previously demonstrated to play an important role in candidal pathogenicity. In our current study, the presence of enolase at the fungal cell surface under different growth conditions was examined, and a higher abundance of enolase at the surface of C. albicans hyphal forms compared to yeast-like cells was found. Affinity chromatography and chemical cross-linking indicated a member of the agglutinin-like sequence protein family-Als3-as an important potential partner required for the surface display of enolase. Analysis of Saccharomyces cerevisiae cells overexpressing Als3 with site-specific deletions showed that the Ig-like N-terminal region of Als3 (aa 166-225; aa 218-285; aa 270-305; aa 277-286) and the central repeat domain (aa 434-830) are essential for the interaction of this adhesin with enolase. In addition, binding between enolase and Als3 influenced subsequent docking of host plasma proteins-high molecular mass kininogen and plasminogen-on the candidal cell surface, thus supporting the hypothesis that C. albicans can modulate plasma proteolytic cascades to affect homeostasis within the host and propagate inflammation during infection.

Structural Insights into the Interactions of Candidal Enolase with Human Vitronectin, Fibronectin and Plasminogen.

Significant amounts of enolase-a cytosolic enzyme involved in the glycolysis pathway-are exposed on the cell surface of Candida yeast. It has been hypothesized that this exposed enolase form contributes to infection-related phenomena such as fungal adhesion to human tissues, and the activation of fibrinolysis and extracellular matrix degradation. The aim of the present study was to characterize, in structural terms, the protein-protein interactions underlying these moonlighting functions of enolase. The tight binding of human vitronectin, fibronectin and plasminogen by purified C. albicans and C. tropicalis enolases was quantitatively analyzed by surface plasmon resonance measurements, and the dissociation constants of the formed complexes were determined to be in the 10-7-10-8 M range. In contrast, the binding of human proteins by the S.cerevisiae enzyme was much weaker. The chemical cross-linking method was used to map the sites on enolase molecules that come into direct contact with human proteins. An internal motif 235DKAGYKGKVGIAMDVASSEFYKDGK259 in C. albicans enolase was suggested to contribute to the binding of all three human proteins tested. Models for these interactions were developed and revealed the sites on the enolase molecule that bind human proteins, extensively overlap for these ligands, and are well-separated from the catalytic activity center.

Plant-Derived Substances in the Fight Against Infections Caused by Candida Species.

Yeast-like fungi from the Candida genus are predominantly harmless commensals that colonize human skin and mucosal surfaces, but under conditions of impaired host immune system change into dangerous pathogens. The pathogenicity of these fungi is typically accompanied by increased adhesion and formation of complex biofilms, making candidal infections challenging to treat. Although a variety of antifungal drugs have been developed that preferably attack the fungal cell wall and plasma membrane, these pathogens have acquired novel defense mechanisms that make them resistant to standard treatment. This causes an increase in the incidence of candidiasis and enforces the urgent need for an intensified search for new specifics that could be helpful, alone or synergistically with traditional drugs, for controlling Candida pathogenicity. Currently, numerous reports have indicated the effectiveness of plant metabolites as potent antifungal agents. These substances have been shown to inhibit growth and to alter the virulence of different Candida species in both the planktonic and hyphal form and during the biofilm formation. This review focuses on the most recent findings that provide evidence of decreasing candidal pathogenicity by different substances of plant origin, with a special emphasis on the mechanisms of their action. This is a particularly important issue in the light of the currently increasing frequency of emerging Candida strains and species resistant to standard antifungal treatment.

Characteristics of Extracellular Vesicles Released by the Pathogenic Yeast-Like Fungi Candida glabrata, Candida parapsilosis and Candida tropicalis.

Candida spp. yeast-like fungi are opportunistic pathogens in humans and have been recently found to release extracellular vesicles (EVs) that are involved in many vital biological processes in fungal cells. These include communication between microorganisms and host-pathogen interactions during infection. The production of EVs and their content have been significantly characterized in the most common candidal species Candida albicans, including the identification of numerous virulence factors and cytoplasmic proteins in the EV cargo. We have here conducted the isolation and proteomic characterization of EVs produced by the clinically important non-albicans Candida species C. glabrata, C. tropicalis and C. parapsilosis. With the use of ultracentrifugation of the cell-free culture supernatant, the candidal EVs were collected and found to be a heterogeneous population of particles for each species with sizes ranging from 60-280 nm. The proteinaceous contents of these vesicles were analyzed using LC-MS/MS, with particular attention paid to surface-expressed proteins that would come into immediate and direct contact with host cells. We thereby identified 42 extracellular and surface-connected proteins from C. glabrata, 33 from C. parapsilosis, and 34 from C. tropicalis, including membrane-associated transporters, glycoproteins and enzymes involved in the organization of the fungal cell wall, as well as several cytoplasmic proteins, including alcohol dehydrogenase, enolase, glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate kinase and pyruvate kinase, for which the vesicular transport is a possible mechanism underlying their non-classical secretion.

Moonlighting Proteins at the Candidal Cell Surface.

The cell wall in Candida albicans is not only a tight protective envelope but also a point of contact with the human host that provides a dynamic response to the constantly changing environment in infection niches. Particularly important roles are attributed to proteins exposed at the fungal cell surface. These include proteins that are stably and covalently bound to the cell wall or cell membrane and those that are more loosely attached. Interestingly in this regard, numerous loosely attached proteins belong to the class of "moonlighting proteins" that are originally intracellular and that perform essentially different functions in addition to their primary housekeeping roles. These proteins also demonstrate unpredicted interactions with non-canonical partners at an a priori unexpected extracellular location, achieved via non-classical secretion routes. Acting both individually and collectively, the moonlighting proteins contribute to candidal virulence and pathogenicity through their involvement in mechanisms critical for successful host colonization and infection, such as the adhesion to host cells, interactions with plasma homeostatic proteolytic cascades, responses to stress conditions and molecular mimicry. The documented knowledge of the roles of these proteins in C. albicans pathogenicity has utility for assisting the design of new therapeutic, diagnostic and preventive strategies against candidiasis.

Peptidylarginine Deiminase of Porphyromonas gingivalis Modulates the Interactions between Candida albicans Biofilm and Human Plasminogen and High-Molecular-Mass Kininogen.

Microorganisms that create mixed-species biofilms in the human oral cavity include, among others, the opportunistic fungus Candida albicans and the key bacterial pathogen in periodontitis, Porphyromonas gingivalis. Both species use arsenals of virulence factors to invade the host organism and evade its immune system including peptidylarginine deiminase that citrullinates microbial and host proteins, altering their function. We assessed the effects of this modification on the interactions between the C. albicans cell surface and human plasminogen and kininogen, key components of plasma proteolytic cascades related to the maintenance of hemostasis and innate immunity. Mass spectrometry was used to identify protein citrullination, and microplate tests to quantify the binding of modified plasminogen and kininogen to C. albicans cells. Competitive radioreceptor assays tested the affinity of citrullinated kinins to their specific cellular receptors. The citrullination of surface-exposed fungal proteins reduced the level of unmodified plasminogen binding but did not affect unmodified kininogen binding. However, the modification of human proteins did not disrupt their adsorption to the unmodified fungal cells. In contrast, the citrullination of kinins exerted a significant impact on their interactions with cellular receptors reducing their affinity and thus affecting the role of kinin peptides in the development of inflammation.