Tumor necrosis factor prevents Candida albicans biofilm formation

The Characterization of the Th1/Th2 Ratio in Multiple Sclerosis Patients and its Response to a Dietary Supplement Regimen

INTRODUCTION

Multiple sclerosis (MS) is a debilitating neurodegenerative disease affecting the central nervous system, causing disability and life-threatening complications. The interplay between immune cells and signaling pathways is a topic for investigating novel therapies. Past research has shown how the Th1/Th2 ratio plays a key role in the pathogenesis of MS lesions. Modulating the Th1/Th2 ratios with an efficacious dietary supplement may improve some of the consequences of MS.

METHODS

Participants (n = 15) diagnosed with MS for an average of 12.4 years (standard deviation = 7.4; range = 2, 25) were enrolled in a clinical trial in which they consumed a dietary supplement regimen daily for 12 months. Venous blood was drawn at baseline and 12-month follow-up and peripheral blood mononuclear cells, cytokines, and growth factors were quantified. Infections, physical functioning, and quality of life were also assessed at baseline and 12 months.

RESULTS

The IL-2/IL-10 and IFN-γ/IL-10 ratios were significantly higher than those of the healthy adults, and while only IFN-γ/IL-10 increased significantly at 12 months, all ratios other than IFN-γ/TNF-α increased over the course of the intervention. The decrease in yeast infections was inversely correlated with IL-2/TNF-α and IFN-γ/TNF-α. Significant improvements in physical functioning and quality of life correlated with changes in the Th1/Th2 ratios in response to the dietary supplement regimen.

CONCLUSIONS

The results show that dietary supplementation somewhat impacted the Th1/Th2 ratios over the course of the intervention (toward more Th1 dominance), and those changes were related to various clinical improvements of the participants' symptoms in cognitive, motor, and psychosocial dimensions.

Possible Molecular Targeting of Biofilm-Associated Genes by Nano-Ag in Candida albicans

The treatment of candidiasis infections is hindered by the presence of biofilms. Here, we report the biofilm-associated genes as potential molecular targets by silver nanoparticles (nano-Ag) in Candida albicans. Nano-Ag was biosynthesized using Bacillus licheniformis, Bacillus cereus, and Fusarium oxysporum. The physicochemical properties of the microbial-synthesized of nano-Ag are widely characterized by visual observation, ultraviolet-visible spectroscopy, scanning electron microscopy, X-ray diffraction spectroscopy, and Fourier transform infrared spectroscopy. Characterization results revealed the formation of nano-Ag. Antiplanktonic cells and antibiofilm activities of nano-Ag were also demonstrated by minimum inhibition concentrations (MIC), minimum fungicidal concentration (MFC), MFC/MIC ratio, crystal violet staining, 2,3-bis (2-methoxy-4-nitro-5 sulfophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide (XTT), and microscopic image analysis. We have analyzed the expressions of biofilm-associated genes in C. albicans treated with different concentrations of nano-Ag based on MIC. The expression profile of BCR1, ALS1, ALS3, HWP1, and ECE1 showed downregulated genes involved in these pathways by the treatment with nanoparticles. Negative regulators, TUP1, NRG1, and TOR1, were upregulated by the treatment of nano-Ag. Our study suggests that nano-Ag affects gene expression and may subsequently decrease the pathogenesis of C. albicans by inhibiting biofilm formation. Molecular targeting of biofilm-associated genes involved in biofilm formation by nano-Ag may be an effective treatment strategy for candidiasis infections.

Evaluation of some immunological markers in co-infection of COVID-19 with thrush candidiasis

OBJECTIVE

COVID-19 infection poses significant risks, including life-threatening consequences and fungus synchronization, making it a significant concern. This study seeks to assess the effect of concurrent infection of COVID-19 with Thrush Candida albicans on the patient's health state by measuring the proportion of immune cells and certain interleukins such as IL-8, -10, -17, and -33.

METHODS

The study involved 70 patients (30 patients with COVID-19, 17 patients with thrush candidiasis, and 23 patients with Thrush Candida albicans) and 50 healthy individuals as a control group. COVID-19 was identified using RT-PCR, while C. albicans were identified through culture media, biochemical testing, and oral swabs. Ruby equipment and ELISA kits were used for blood counts and interleukin detection.

RESULTS

COVID-19, thrush candidiasis, and Thrush Candida albicans infections occur in a wide range of age groups (4-80 years), with no significant differences between sexes (p>0.05). Immunologically, our study found that Thrush Candida albicans patients had the highest rate of neutrophils (89.6%) and basophils (2.01%), while corona patients had the highest percentage of lymphocytes (70.12%) and eosinophils (7.11%), and patients with thrush candidiasis had the highest percentage of monocytes. Thrush Candida albicans patients showed increased IL-8 (56.7 pg/mL) and IL-17 (101.1 pg/mL) concentrations, with the greatest concentration of IL-33 (200.5 pg/mL) in COVID-19, and a decrease in the level of IL-10 in patient groups compared with controls.

CONCLUSION

Patient groups showed increased neutrophils, lymphocytes, monocytes, and IL-8 levels, with a significant linear association between proinflammatory interleukins and these cells.

Biofilm-associated genes as potential molecular targets of nano-Fe3O4 in Candida albicans

BACKGROUND

There are few effective treatments for Candida biofilm-associated infections. The present study demonstrated changes in the expression of biofilm-associated genes in Candida albicans treated with magnetic iron oxide nanoparticles (denoted as nano-Fe₃O₄).

METHODS

Nano-Fe₃O₄ was biologically synthesized using Bacillus licheniformis, Bacillus cereus, and Fusarium oxysporum. Additionally, the biologically synthesized nano-Fe₃O₄ was characterized by visual observation; ultraviolet-visible spectroscopy, scanning electron microscopy, X-ray diffraction spectroscopy, and Fourier transform infrared spectroscopy. The biologically synthesized nano-Fe₃O₄ was tested for growth and biofilm formation in C. albicans. Furthermore, quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR) was used to study the inhibition of biofilm-associated genes in C. albicans treated with nano-Fe₃O₄.

RESULTS

The production of biologically synthesized nano-Fe₃O₄ was confirmed using extensive characterization methods. The nano-Fe₃O₄ inhibited growth and biofilm formation. Nano-Fe₃O₄ exhibited growth inhibition with minimum inhibition concentrations (MICs) of 50 to 200 μg mL^-1. The anti-biofilm effects of nano-Fe₃O₄ were shown by 2,3-bis (2-methoxy-4-nitro-5 sulfophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide (XTT) reduction assay, crystal violet staining, and light field microscopy. The gene expression results showed that the downregulation of BCR1, ALS1, ALS3, HWP1, and ECE1 genes inhibited the biofilm formation in C. albicans. ALS1 reduction was greater than others, with downregulation of 1375.83-, 1178.71-, and 768.47-fold at 2 × MIC, 1 × MIC, and ½ × MIC of nano-Fe₃O₄, respectively.

CONCLUSION

Biofilm-associated genes as potential molecular targets of nano-Fe₃O₄ in C. albicans may be an effective novel treatment strategy for biofilm-associated infections.

Battle royale: Immune response on biofilms – host-pathogen interactions

The research interest of the scientific community in biofilm-forming microorganisms is growing due to the problems caused by their infections affecting humans and animals, mainly because of the difficulty of the host immune system in eradicating these microbial complex communities and the increasing antimicrobial resistance rates worldwide. This review describes the virulence factors and their interaction with the microbial communities of four well-known and highly biofilm-forming pathogens, more exactly, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus spp., and Candida spp. The innate and adaptive immune responses caused by the infection with these microorganisms and their evasion to the host immune system by biofilm formation are discussed in the present work. The relevance of the differences in the expression of certain virulence factors and the immune response in biofilm-associated infections when compared to planktonic infections is usually described as the biofilm architecture protects the pathogen and alters the host immune responses, here we extensively discussed these mechanisms.

Potent anti-inflammatory activity of the lectin-like domain of TNF in joints

In view of the crucial role of tumor necrosis factor (TNF) in joint destruction, TNF inhibitors, including neutralizing anti-TNF antibodies and soluble TNF receptor constructs, are commonly used therapeutics for the treatment of arthropathies like rheumatoid arthritis (RA). However, not all patients achieve remission; moreover, there is a risk of increased susceptibility to infection with these agents. Spatially distinct from its receptor binding sites, TNF harbors a lectin-like domain, which exerts unique functions that can be mimicked by the 17 residue solnatide peptide. This domain binds to specific oligosaccharides such as N'N'-diacetylchitobiose and directly target the α subunit of the epithelial sodium channel. Solnatide was shown to have anti-inflammatory actions in acute lung injury and glomerulonephritis models. In this study, we evaluated whether the lectin-like domain of TNF can mitigate the development of immune-mediated arthritis in mice. In an antigen-induced arthritis model, solnatide reduced cell influx and release of pro-inflammatory mediators into the joints, associated with reduction in edema and tissue damage, as compared to controls indicating that TNF has anti-inflammatory effects in an acute model of joint inflammation via its lectin-like domain.

T cell responses to control fungal infection in an immunological memory lens

In recent years, fungal vaccine research emanated significant findings in the field of antifungal T-cell immunity. The generation of effector T cells is essential to combat many mucosal and systemic fungal infections. The development of antifungal memory T cells is integral for controlling or preventing fungal infections, and understanding the factors, regulators, and modifiers that dictate the generation of such T cells is necessary. Despite the deficiency in the clear understanding of antifungal memory T-cell longevity and attributes, in this review, we will compile some of the existing literature on antifungal T-cell immunity in the context of memory T-cell development against fungal infections.

In vitro and in vivo Characterization of Host–Pathogen Interactions of the L3881 Candida albicans Clinical Isolate

Candida albicans is a human commensal fungus and the etiologic agent of nosocomial infections in immunocompromised individuals. Candida spp. is the most studied human fungal pathogen, and the mechanisms by which this fungus can evade the immune system affecting immunosuppressed individuals have been extensively studied. Most of these studies focus on different species of Candida, and there is much to be understood in virulence variability among lineages, specifically different C. albicans clinical isolates. To better understand the main mechanisms of its virulence variability modulated in C. albicans clinical isolates, we characterized L3881 lineage, which has been previously classified as hypovirulent, and SC5314 lineage, a virulent wild-type control, by using both in vitro and in vivo assays. Our findings demonstrated that L3881 presented higher capacity to avoid macrophage phagocytosis and higher resistance to oxidative stress than the wild type. These characteristics prevented higher mortality rates for L3881 in the animal model of candidiasis. Conversely, L3881 has been able to induce an upregulation of pro-inflammatory mediators both in vitro and in vivo. These results indicated that in vitro and in vivo functional characterizations are necessary for determination of virulence in different clinical isolates due to its modulation in the host–pathogen interactions.

COVID-19-Associated Candidiasis: Possible Patho-Mechanism, Predisposing Factors, and Prevention Strategies

The coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is threatening public health. A large number of affected people need to be hospitalized. Immunocompromised patients and ICU-admitted patients are predisposed to further bacterial and fungal infections, making patient outcomes more critical. Among them, COVID-19-associated candidiasis is becoming more widely recognized as a part of severe COVID-19 sequelae. While the molecular pathophysiology is not fully understood, some factors, including a compromised immune system, iron and zinc deficiencies, and nosocomial and iatrogenic transmissions, predispose COVID-19 patients to candidiasis. In this review, we discuss the existing knowledge of the virulence characteristics of Candida spp. and summarize the key concepts in the possible molecular pathogenesis. We analyze the predisposing factors that make COVID-19 patients more susceptible to candidiasis and the preventive measures which will provide valuable insights to guide the effective prevention of candidiasis in COVID-19 patients.

Intestinal Infection of Candida albicans: Preventing the Formation of Biofilm by C. albicans and Protecting the Intestinal Epithelial Barrier

The large mortality and morbidity rate of C. albicans infections is a crucial problem in medical mycology. Because the generation of biofilms and drug resistance are growing concerns, the growth of novel antifungal agents and the looking for newer objectives are necessary. In this review, inhibitors of C. albicans biofilm generation and molecular mechanisms of intestinal epithelial barrier protection are elucidated. Recent studies on various transcription elements; quorum-sensing molecules; host responses to adherence; and changes in efflux pumps, enzymes, bud to hyphal transition, and lipid profiles have increased the knowledge of the intricate mechanisms underlying biofilm resistance. In addition, the growth of novel biomaterials with anti-adhesive nature, natural products, drugs, bioactive compounds, proteins, lipids, and carbohydrates are being researched. Recently, more and more attention has been given to various metal nanoparticles that have also appeared as antibiofilm agents in C. albicans. The intestinal epithelial obstacle exerts an crucial effect on keeping intestinal homeostasis and is increasingly associated with various disorders associated with the intestine such as inflammatory bowel disease (IBD), irritable bowel syndrome, metabolic syndrome, allergies, hepatic inflammation, septic shock, etc. However, whether their involvement in the prevention of other intestinal disorders like IBD are useful in C. albicans remains unknown. Further studies must be carried out in order to validate their inhibition functions in intestinal C. albicans. This provides innovates ideas for intestinal C. albicans treatment.

Responses of Mast Cells to Pathogens: Beneficial and Detrimental Roles

Mast cells (MCs) are strategically located in tissues close to the external environment, being one of the first immune cells to interact with invading pathogens. They are long living effector cells equipped with different receptors that allow microbial recognition. Once activated, MCs release numerous biologically active mediators in the site of pathogen contact, which induce vascular endothelium modification, inflammation development and extracellular matrix remodeling. Efficient and direct antimicrobial mechanisms of MCs involve phagocytosis with oxidative and non-oxidative microbial destruction, extracellular trap formation, and the release of antimicrobial substances. MCs also contribute to host defense through the attraction and activation of phagocytic and inflammatory cells, shaping the innate and adaptive immune responses. However, as part of their response to pathogens and under an impaired, sustained, or systemic activation, MCs may contribute to tissue damage. This review will focus on the current knowledge about direct and indirect contribution of MCs to pathogen clearance. Antimicrobial mechanisms of MCs are addressed with special attention to signaling pathways involved and molecular weapons implicated. The role of MCs in a dysregulated host response that can increase morbidity and mortality is also reviewed and discussed, highlighting the complexity of MCs biology in the context of host-pathogen interactions.

The impact of the Fungus-Host-Microbiota interplay upon Candida albicans infections: current knowledge and new perspectives

Candida albicans is a major fungal pathogen of humans. It exists as a commensal in the oral cavity, gut or genital tract of most individuals, constrained by the local microbiota, epithelial barriers and immune defences. Their perturbation can lead to fungal outgrowth and the development of mucosal infections such as oropharyngeal or vulvovaginal candidiasis, and patients with compromised immunity are susceptible to life-threatening systemic infections. The importance of the interplay between fungus, host and microbiota in driving the transition from C. albicans commensalism to pathogenicity is widely appreciated. However, the complexity of these interactions, and the significant impact of fungal, host and microbiota variability upon disease severity and outcome, are less well understood. Therefore, we summarise the features of the fungus that promote infection, and how genetic variation between clinical isolates influences pathogenicity. We discuss antifungal immunity, how this differs between mucosae, and how individual variation influences a person's susceptibility to infection. Also, we describe factors that influence the composition of gut, oral and vaginal microbiotas, and how these affect fungal colonisation and antifungal immunity. We argue that a detailed understanding of these variables, which underlie fungal-host-microbiota interactions, will present opportunities for directed antifungal therapies that benefit vulnerable patients.

Coadministration of liposomal methylglyoxal increases the activity of amphotericin B against Candida albicans in leukopoenic mice

In this study, we investigated the therapeutic efficacy of a combination of liposomal amphotericin B (Lip-Amp B) and Methylglyoxal (Lip-MG) against Candida albicans in the leukopoenic mice. The antifungal efficacy of Lip-Amp B or Lip-MG or a combination of Lip-Amp B and Lip-MG was evaluated by the analysis of the survival rate and the fungal load in the treated mice. The immune-stimulatory effect of Lip-MG on macrophages was evaluated by analysing the secretion of proinflammatory cytokines. C. albicans infected mice treated at the doses of 1 and 2 mg/kg of Lip-Amp B showed 20% and 50% survival rates, respectively. Whereas the mice treated with free Amp B at the same doses died within 40 days of treatment. Interestingly, C. albicans infected mice treated with a combination of Lip-Amp B and Lip-MG had 70% survival rate on day 40 postinfection. Moreover, treatment of macrophages with Lip-MG increased their fungicidal activity and the secretion of proinflammatory cytokines, including TNF-α and IL-1β. These findings suggested that co-treatment with Lip-Amp B and Lip-MG had a synergistic effect and could be effective against C. albicans in immunocompromised subjects.

Tinospora cordifolia Aqueous Extract Alleviates Cyclophosphamide- Induced Immune Suppression, Toxicity and Systemic Candidiasis in Immunosuppressed Mice: In vivo Study in Comparison to Antifungal Drug Fluconazole

OBJECTIVE

The present study was aimed to evaluate the effect of the aqueous extract of Tinospora cordifolia (AETC) against cyclophosphamide-induced immunosuppression and systemic Candida albicans infection in a murine model.

METHODS

The protective effect of AETC against cyclophosphamide-induced leukopenia was evaluated by quantitative and qualitative analysis of the leukocytes. The immune-stimulating potential of AETC on macrophages was assessed by determining the levels of secreted cytokines. To determine the direct antifungal activity, AETC or fluconazole was administered to C. albicans infected mice. The efficacy of treatment was assessed by determining the survival rate, kidney fungal burden, the organ index and liver inflammation parameters.

RESULTS

Cyclophosphamide administration resulted in substantial depletion of leukocytes, whereas AETC treatment induced the recovery of leukocytes in cyclophosphamide-injected mice. Moreover, AETC treatment of macrophages resulted in enhanced secretion of IFN-γ, TNF-α and IL-1β. C. albicans infected mice treated with AETC at the doses of 50 and 100 mg/kg exhibited 40% and 60% survival rate, whereas the mice treated with fluconazole at a dose of 50 mg/kg showed 20% survival rate. Like survival data, the fungal load was found to be the lowest in the kidney tissues of mice treated with AETC at a dose of 100 mg/kg. Interestingly, mice infected with C. albicans demonstrated improvement in the organ indices and liver functioning after AETC treatment.

CONCLUSION

These results suggest that AETC may potentially be used to rejuvenate the weakened immune system and eliminate systemic candidiasis in mice.

Unraveling How Candida albicans Forms Sexual Biofilms

Biofilms, structured and densely packed communities of microbial cells attached to surfaces, are considered to be the natural growth state for a vast majority of microorganisms. The ability to form biofilms is an important virulence factor for most pathogens, including the opportunistic human fungal pathogen Candida albicans. C. albicans is one of the most prevalent fungal species of the human microbiota that asymptomatically colonizes healthy individuals. However, C. albicans can also cause severe and life-threatening infections when host conditions permit (e.g., through alterations in the host immune system, pH, and resident microbiota). Like many other pathogens, this ability to cause infections depends, in part, on the ability to form biofilms. Once formed, C. albicans biofilms are often resistant to antifungal agents and the host immune response, and can act as reservoirs to maintain persistent infections as well as to seed new infections in a host. The majority of C. albicans clinical isolates are heterozygous (a/α) at the mating type-like (MTL) locus, which defines Candida mating types, and are capable of forming robust biofilms when cultured in vitro. These “conventional” biofilms, formed by MTL-heterozygous (a/α) cells, have been the primary focus of C. albicans biofilm research to date. Recent work in the field, however, has uncovered novel mechanisms through which biofilms are generated by C. albicans cells that are homozygous or hemizygous (a/a, a/Δ, α/α, or α/Δ) at the MTL locus. In these studies, the addition of pheromones of the opposite mating type can induce the formation of specialized “sexual” biofilms, either through the addition of synthetic peptide pheromones to the culture, or in response to co-culturing of cells of the opposite mating types. Although sexual biofilms are generally less robust than conventional biofilms, they could serve as a protective niche to support genetic exchange between mating-competent cells, and thus may represent an adaptive mechanism to increase population diversity in dynamic environments. Although conventional and sexual biofilms appear functionally distinct, both types of biofilms are structurally similar, containing yeast, pseudohyphal, and hyphal cells surrounded by an extracellular matrix. Despite their structural similarities, conventional and sexual biofilms appear to be governed by distinct transcriptional networks and signaling pathways, suggesting that they may be adapted for, and responsive to, distinct environmental conditions. Here we review sexual biofilms and compare and contrast them to conventional biofilms of C. albicans.

Alzheimer's disease might depend on enabling pathogens which do not necessarily cross the blood-brain barrier

The development of Alzheimer's Disease (AD) might reflect, in its acquired aspects, a cooperative pathogenesis whereby infectious enablers which do not necessarily cross the blood-brain barrier augment the invasive properties of a less virulent organism, thus enabling it to infect the brain. An example interaction is described which involves Chlamydia species, Human papillomavirus (HPV), microbiota, and yeast, where yeast is a pathogen of low virulence which crosses the blood-brain barrier. The cooperative pathogenesis begins at the mucosal epithelium. Infection by Chlamydia, HPV, or dysbiosis of commensal bacteria disrupts the integrity of the mucosal epithelium, thereby allowing colonizing yeast to penetrate the epithelial barrier and enter into the bloodstream. Chlamydia and enabling commensals promote insulin resistance, which provides yeast with glucose and also sets the stage for accumulation of amyloid beta protein (ABP). Meanwhile, HPV-induced and hyperglycemia-induced immunological changes enable the spread of newly invasive yeast to the brain, where the release of inflammatory cytokines in response to yeast promotes production of ABP. Chlamydia also cross reacts with Candida species, which may stimulate further brain inflammation in response to Candida and may augment production of ABP thereby The yeast's less virulent origins, coupled with immune modulation by enablers, might explain why AD as a model of infectious encephalitis is always slow and insidious rather than occasionally febrile, accompanied by seizures, or marked by signs of meningeal inflammation.

Mannich base limits Candida albicans virulence by inactivating Ras-cAMP-PKA pathway

Mannich bases and its derivatives are regarded as supreme pharmacophores in therapeutics. The study investigates the antimycotic potential of Mannich bases, 1-((1H-benzimidazol-1-yl) methyl) urea (C1) and 1-((3-hydroxynapthalen-2-yl) methyl) thiourea (C2), against Candida albicans. Biofilm and hyphal inhibitory activities of the Mannich bases were tested by crystal violet quantification, fluorescence imaging cAMP rescue, qRT PCR, and by molecular docking analysis. The compounds inhibited the biofilms of C. albicans and restrained the filamentation abilities of the pathogen. Structure-activity relationship studies revealed that the presence of urea or thiourea moiety in the tail section is essential for interacting with adenylate cyclase (AC). The Mannich bases seemed to block Ras-cAMP-PKA pathway by inhibiting second messenger activity required for hyphal induction and biofilm formation. In conclusion, the study warrants point-of-care testing of C1/C2 and provides a starting point for deriving several structurally modified Mannich bases which might plausibly replace the prevailing antimycotic drugs in future.

Listeriolysin O Causes ENaC Dysfunction in Human Airway Epithelial Cells

Pulmonary permeability edema is characterized by reduced alveolar Na⁺ uptake capacity and capillary barrier dysfunction and is a potentially lethal complication of listeriosis. Apical Na⁺ uptake is mainly mediated by the epithelial sodium channel (ENaC) and initiates alveolar liquid clearance. Here we examine how listeriolysin O (LLO), the pore-forming toxin of Listeria monocytogenes, impairs the expression and activity of ENaC. To that purpose, we studied how sub-lytic concentrations of LLO affect negative and positive regulators of ENaC expression in the H441 airway epithelial cell line. LLO reduced expression of the crucial ENaC-α subunit in H441 cells within 2 h and this was preceded by activation of PKC-α, a negative regulator of the channel's expression. At later time points, LLO caused a significant reduction in the phosphorylation of Sgk-1 at residue T256 and of Akt-1 at residue S473, both of which are required for full activation of ENaC. The TNF-derived TIP peptide prevented LLO-mediated PKC-α activation and restored phospho-Sgk-1-T256. The TIP peptide also counteracted the observed LLO-induced decrease in amiloride-sensitive Na⁺ current and ENaC-α expression in H441 cells. Intratracheally instilled LLO caused profound pulmonary edema formation in mice, an effect that was prevented by the TIP peptide; thus indicating the therapeutic potential of the peptide for the treatment of pore-forming toxin-associated permeability edema.

Gaining Insights from Candida Biofilm Heterogeneity: One Size Does Not Fit All

Despite their clinical significance and substantial human health burden, fungal infections remain relatively under-appreciated. The widespread overuse of antibiotics and the increasing requirement for indwelling medical devices provides an opportunistic potential for the overgrowth and colonization of pathogenic Candida species on both biological and inert substrates. Indeed, it is now widely recognized that biofilms are a highly important part of their virulence repertoire. Candida albicans is regarded as the primary fungal biofilm forming species, yet there is also increasing interest and growing body of evidence for non-Candida albicans species (NCAS) biofilms, and interkingdom biofilm interactions. C. albicans biofilms are heterogeneous structures by definition, existing as three-dimensional populations of yeast, pseudo-hyphae, and hyphae, embedded within a self-produced extracellular matrix. Classical molecular approaches, driven by extensive studies of laboratory strains and mutants, have enhanced our knowledge and understanding of how these complex communities develop, thrive, and cause host-mediated damage. Yet our clinical observations tell a different story, with differential patient responses potentially due to inherent biological heterogeneity from specific clinical isolates associated with their infections. This review explores some of the recent advances made in an attempt to explore the importance of working with clinical isolates, and what this has taught us.

The Interface between Fungal Biofilms and Innate Immunity

Fungal biofilms are communities of adherent cells surrounded by an extracellular matrix. These biofilms are commonly found during infection caused by a variety of fungal pathogens. Clinically, biofilm infections can be extremely difficult to eradicate due to their resistance to antifungals and host defenses. Biofilm formation can protect fungal pathogens from many aspects of the innate immune system, including killing by neutrophils and monocytes. Altered immune recognition during this phase of growth is also evident by changes in the cytokine profiles of monocytes and macrophages exposed to biofilm. In this manuscript, we review the host response to fungal biofilms, focusing on how these structures are recognized by the innate immune system. Biofilms formed by Candida, Aspergillus, and Cryptococcus have received the most attention and are highlighted. We describe common themes involved in the resilience of fungal biofilms to host immunity and give examples of biofilm defenses that are pathogen-specific.

Recognition of Candida albicans by gingival fibroblasts: The role of TLR2, TLR4/CD14, and MyD88

Recent evidence indicates that nonprofessional immune cells such as epithelial cells, endothelial cells, and fibroblasts also contribute to innate immunity via secretion of cytokines. Fibroblasts are the principal type of cell found in the periodontal connective tissues and they are involved in the immune response during periodontal disease. The role of fibroblasts in the recognition of pathogens via Toll-like receptors (TLRs) has been established; however, few studies have been conducted concerning the involvement of innate immune receptors in the recognition of Candida albicans by gingival fibroblast. In the current study, we investigate the functional activity of TLR2, cluster of differentiation 14 (CD14), and myeloid differentiation primary response gene 88 (MyD88) molecules in the recognition of C. albicans by gingival fibroblast. First, we identified that gingival fibroblasts expressed TLR2, TLR3, and TLR4. Our results showed that TLR agonists had no effect on these receptors' expression by TLR2, MyD88, and CD14-deficient cells. Notably, C. albicans and a synthetic triacylated lipoprotein (Pam3CSK4) induced a remarkable increase of TLR3 expression on MyD88-deficient gingival fibroblasts. TLR4 expression levels were lower than TLR2 and TLR3 levels and remained unchanged after TLR agonist stimulation. Gingival fibroblasts presented morphological similarities; however, TLR2 deficiency on these cells leads to a lower proliferative response, whereas the deficiency on CD14 expression resulted in lower levels of type I collagen by these cells. In addition, the recognition of C. albicans by gingival fibroblasts had an effect on the secretion of cytokines and it was dependent on a specific recognition molecule. Specifically, tumor necrosis factor-α (TNF-α) production after the recognition of C. albicans was dependent on MyD88, CD14, and TLR2 molecules, whereas the production of interleukin-1β (IL-1β) and IL-13 was dependent on TLR2. These findings are the first to describe a role of gingival fibroblast in the recognition of C. albicans and the pathways involved in this process. An understanding of these pathways may lead to alternative treatments for patients with periodontal disease.