Fungal infection in a patient with multiple sclerosis

A review on nonviral, nonbacterial infectious agents toxicity involved in neurodegenerative diseases

Neuronal death, decreased activity or dysfunction of neurotransmitters are some of the pathophysiological reasons for neurodegenerative diseases like Alzheimer's, Parkinson's and multiple sclerosis. Also, there is evidence for the role of infections and infectious agents in neurodegenerative diseases and the effect of some metabolites in microorganisms in the pathophysiology of these diseases. In this study, we intend to evaluate the existing studies on the role of infectious agents and their metabolites on the pathophysiology of neurodegenerative diseases. PubMed, Scopus, Google Scholar and Web of Science search engines were searched. Some infectious agents have been observed in neurodegenerative diseases. Also, isolations of some fungi and microalgae have an improving effect on Parkinson's and Alzheimer's.

Systemic Infection by Non-albicans Candida Species Affects the Development of a Murine Model of Multiple Sclerosis

Candidiasis may affect the central nervous system (CNS), and although Candida albicans is predominant, non-albicans Candida species can also be associated with CNS infections. Some studies have suggested that Candida infections could increase the odds of multiple sclerosis (MS) development. In this context, we investigated whether systemic infection by non-albicans Candida species would affect, clinically or immunologically, the severity of experimental autoimmune encephalomyelitis (EAE), which is an animal model used to study MS. For this, a strain of C. glabrata, C. krusei, and C. parapsilosis was selected and characterized using different in vitro and in vivo models. In these analysis, all the strains exhibited the ability to form biofilms, produce proteolytic enzymes, and cause systemic infections in Galleria mellonella, with C. glabrata being the most virulent species. Next, C57BL/6 mice were infected with strains of C. glabrata, C. krusei, or C. parapsilosis, and 3 days later were immunized with myelin oligodendrocyte glycoprotein to develop EAE. Mice from EAE groups previously infected with C. glabrata and C. krusei developed more severe and more prevalent paralysis, while mice from the EAE group infected with C. parapsilosis developed a disease comparable to non-infected EAE mice. Disease aggravation by C. glabrata and C. krusei strains was concomitant to increased IL-17 and IFN-γ production by splenic cells stimulated with fungi-derived antigens and with increased percentage of T lymphocytes and myeloid cells in the CNS. Analysis of interaction with BV-2 microglial cell line also revealed differences among these strains, in which C. krusei was the strongest activator of microglia concerning the expression of MHC II and CD40 and pro-inflammatory cytokine production. Altogether, these results indicated that the three non-albicans Candida strains were similarly able to reach the CNS but distinct in terms of their effect over EAE development. Whereas C. glabrata and C. Krusei aggravated the development of EAE, C. parapsilosis did not affect its severity. Disease worsening was partially associated to virulence factors in C. glabrata and to a strong activation of microglia in C. krusei infection. In conclusion, systemic infections by non-albicans Candida strains exerted influence on the experimental autoimmune encephalomyelitis in both immunological and clinical aspects, emphasizing their possible relevance in MS development.

Curdlan, a Microbial β-Glucan, Has Contrasting Effects on Autoimmune and Viral Models of Multiple Sclerosis

Multiple sclerosis (MS) is an immune-mediated disease characterized by inflammatory demyelination and axonal degeneration in the central nervous system (CNS). Bacterial and fungal infections have been associated with the development of MS; microbial components that are present in several microbes could contribute to MS pathogenesis. Among such components, curdlan is a microbial 1,3-β-glucan that can stimulate dendritic cells, and enhances T helper (Th) 17 responses. We determined whether curdlan administration could affect two animal models for MS: an autoimmune model, experimental autoimmune encephalomyelitis (EAE), and a viral model, Theiler's murine encephalomyelitis virus (TMEV)-induced demyelinating disease (TMEV-IDD). We induced relapsing-remitting EAE by sensitizing SJL/J mice with the myelin proteolipid protein (PLP)139-151 peptide and found that curdlan treatment prior to PLP sensitization converted the clinical course of EAE into hyperacute EAE, in which the mice developed a progressive motor paralysis and died within 2 weeks. Curdlan-treated EAE mice had massive infiltration of T cells and neutrophils in the CNS with higher levels of Th17 and Th1 responses, compared with the control EAE mice. On the other hand, in TMEV-IDD, we found that curdlan treatment reduced the clinical scores and axonal degeneration without changes in inflammation or viral persistence in the CNS. In summary, although curdlan administration exacerbated the autoimmune MS model by enhancing inflammatory demyelination, it suppressed the viral MS model with reduced axonal degeneration. Therefore, microbial infections may play contrasting roles in MS depending on its etiology: autoimmunity versus viral infection.

Candida tropicalis Systemic Infection Redirects Leukocyte Infiltration to the Kidneys Attenuating Encephalomyelitis

Environmental factors, including infections, are strongly associated with the pathogenesis of multiple sclerosis (MS), which is an autoimmune and demyelinating disease of the central nervous system (CNS). Although classically associated with bacterial and viral agents, fungal species have also been suspected to affect the course of the disease. Candida tropicalis is an opportunistic fungus that affects immunocompromised individuals and is also able to spread to vital organs. As C. tropicalis has been increasingly isolated from systemic infections, we aimed to evaluate the effect of this fungus on experimental autoimmune encephalomyelitis (EAE), a murine model to study MS. For this, EAE was induced in female C57BL/6 mice 3 days after infection with 10⁶ viable C. tropicalis yeasts. The infection decreased EAE prevalence and severity, confirmed by the less inflammatory infiltrate and less demyelization in the lumbar spinal cord. Despite this, C. tropicalis infection associated with EAE results in the death of some animals and increased urea and creatinine serum levels. The kidneys of EAE-infected mice showed higher fungal load associated with increased leukocyte infiltration (CD45⁺ cells) and higher expression of T-box transcription factor (Tbx21) and forkhead box P3 (Foxp3). Altogether, our results demonstrate that although C. tropicalis infection reduces the prevalence and severity of EAE, partially due to the sequestration of leukocytes by the inflamed renal tissue, this effect is associated with a poor disease outcome.

Hidradenitis suppurativa - The role of interleukin-17, the aryl hydrocarbon receptor and the link to a possible fungal aetiology

Hidradenitis Suppurativa (HS) is a chronic, recurrent, debilitating skin disease of the hair follicle that usually presents after puberty with painful, deep-seated, inflamed lesions in the apocrine gland bearing areas of the body, most commonly the axillae, inguinal and anogenital regions. The pathophysiology of the disease remains elusive, with newer therapies targeting various aspects of the dysregulated immune system. This presents a useful opportunity to look at the cytokine profile in HS and other inflammatory conditions that share similar patterns with the aim of teasing out less considered explanations for HS pathogenesis. It has been observed that IL-17 appears to be the most common denominator linking HS with other immune mediated diseases like Crohn, ulcerative colitis, multiple sclerosis and psoriasis. Given that IL-17 plays an important role in antifungal immunity, evidenced by the cytokine pattern in fungal disease and the bulk of data citing their potential involvement in Crohn, ulcerative colitis, multiple sclerosis and psoriasis; it is fair to suggest the need to explore the role that fungi play in the setting of HS going forward. The aryl hydrocarbon receptor (ahr) is a ubiquitous and largely conserved entity that is gaining interest in inflammatory conditions such as psoriasis and atopic dermatitis. It is well known to modulate autoimmune states. Its activation by both exogenous and endogenous agents result in secretion of IL-17 by Th17 cells. One of such agents is the tryptophan metabolite 6-formylindolo [3,2-b] carbazole (FICZ)-which can be produced by microorganisms such as fungi. It will be interesting to explore its usefulness in HS pathogenesis.

Candida Pathogenicity and Interplay with the Immune System

Candida species are opportunistic fungal pathogens that are part of the normal skin and mucosal microflora. Overgrowth of Candida can cause infections such as thrush or life-threatening invasive candidiasis in immunocompromised patients. Though Candida albicans is highly prevalent, several non-albicans species are also isolated from nosocomial infections. Candida sp. are over presented in the gut of people with Crohn's disease and certain types of neurological disorders, with hyphal form and biofilms being the most virulent states. In addition, Candida uses several secreted and cell surface molecules such as pH related antigen 1, High affinity glucose transporter, Phosphoglycerate mutase 1 and lipases to establish pathogenicity. A strong innate immune response is elicited against Candida via dendritic cells, neutrophils and macrophages. All three complement pathways are also activated. Production of proinflammatory cytokines IL-10 and IL-12 signal differentiation of CD4⁺ cells into Th1 and Th2 cells, whereas IL-6, IL-17 and IL-23 induce Th17 cells. Importance of T-lymphocytes is reflected in depleted T-cell count patients being more prone to Candidiasis. Anti- Candida antibodies also play a role against candidiasis using various mechanisms such as targeting virulent enzymes and exhibiting direct candidacidal activity. However, the significance of antibody response during infection remains controversial. Furthermore, some of the Candida strains have evolved molecular strategies to evade the sophisticated host attack by proteolysis of components of immune system and interfering with immune signalling pathways. Emergence of several non-albicans species that are resistant to current antifungal agents makes treatment more difficult. Therefore, deeper insight into interactions between Candida and the host immune system is required for discovery of novel therapeutic options.

Oral Colonization by Candida Species in Patients with Multiple Sclerosis

INTRODUCTION

Multiple sclerosis (MS) is a chronic inflammatory demyelinating autoimmune disease that affects the central nervous system. Since immune system plays a key role in this disease, patients with MS can present higher risk of infections.

PURPOSE

This study aimed to investigate the prevalence of Candida spp. in the oral cavity of MS patients in relation to a control group METHODS: In total, 100 individuals were selected: 55 diagnosed with MS and 45 healthy individuals (control group). Saliva samples were collected and seeded in culture media selecting for Candida. Following an incubation period of 48 h, colony-forming units (CFU mL^-1) were counted and colonies were isolated for Candida species identification by multiplex PCR. The results were analysed by chi-squared and Mann-Whitney U statistical tests considering a significance level of 5%.

RESULTS

Candida spp. were confirmed in the oral cavity of 50.09% patients in the MS group and 35.55% individuals in the control group. In individuals positive for the growth of Candida spp., the median values of Candida colonies were 220 CFU mL^-1 for the MS group and 120 CFU mL^-1 for the control group. However, no statistically significant differences were observed between groups for both prevalence and CFU mL^-1 count. Of the Candida species identified, 73.91% were C. albicans, 21.73% C. glabrata, 2.17% C. tropicalis, and 2.17% C. krusei.

CONCLUSIONS

The colonization of Candida spp. in the oral cavity of individuals with multiple sclerosis was higher than in the control group; however these findings were not proven to be statistically significant.

The Beneficial and Debilitating Effects of Environmental and Microbial Toxins, Drugs, Organic Solvents and Heavy Metals on the Onset and Progression of Multiple Sclerosis

Multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system is common amongst young adults, leading to major personal and socioeconomic burdens. However, it is still considered complex and challenging to understand and treat, in spite of the efforts made to explain its etiopathology. Despite the discovery of many genetic and environmental factors that might be related to its etiology, no clear answer was found about the causes of the illness and neither about the detailed mechanism of these environmental triggers that make individuals susceptible to MS. In this review, we will attempt to explore the major contributors to MS autoimmunity including genetic, epigenetic and ecological factors with a particular focus on toxins, chemicals or drugs that may trigger, modify or prevent MS disease.

Differential Behavior of Non-albicans Candida Species in the Central Nervous System of Immunocompetent and Immunosuppressed Mice

The genus Candida includes commensal fungi that can cause local and systemic infections, frequently involving vital organs as the central nervous system (CNS). Candida spp. occupy the fourth place among infections that affect the CNS. Although the incidence of Candida albicans is decreasing among patients under immunosuppressive therapies, the incidence of non-albicans Candida is increasing. In this context, the objective of this work was to evaluate the ability of non-albicans Candida species to spread to the CNS of immunocompetent and immunosuppressed mice. Adult female C57BL/6 mice were treated with prednisolone, intravenously infected with Candida glabrata, Candida krusei and Candida parapsilosis yeasts and then evaluated at the 3rd and 14th days after infection. All Candida species disseminated to the brain from immunocompetent animals and induced local inflammation at the third day post-infection. The immunosuppression resulted in body weight loss, leukopenia and reduced IL-2 production by spleen cell cultures. Higher fungal loads were recovered from the CNS of immunosuppressed mice. Inflammatory infiltration associated to a Th1 subset profile was higher in brain samples from C. krusei immunosuppressed mice compared with immunocompetent ones. Additionally, C. krusei was able to transform into pseudohypha inside microglia in vitro infected cells and also to induce elevated nitric oxide production. Altogether, these results indicate that C. glabrata, C. krusei and C. parapsilosis are able to disseminate to the CNS and promote local inflammation in both immunocompetent and immunosuppressed mice. C. krusei displayed a distinct behavior at the CNS triggering a local Th1 profile. The possible contribution of these non-albicans Candida species to other CNS pathologies as multiple sclerosis, Parkinson’s and Alzheimer’s diseases deserves further attention.

Multiple sclerosis and mixed microbial infections. Direct identification of fungi and bacteria in nervous tissue

Multiple sclerosis (MS) is the prototypical inflammatory disease of the central nervous system (CNS), leading to multifocal demyelination and neurodegeneration. The etiology of this incurable disease is unknown and remains a matter of intensive research. The possibility that microbial infections, such as viruses or bacteria, can trigger an autoimmune reaction in CNS tissue has been suggested. However, the recent demonstration that bacteria are present in CNS tissue points to a direct involvement of microbial infections in the etiology of MS. In the present study, we provide the first evidence of fungal infection in CNS tissue of MS patients, and demonstrate that fungal DNA from different species can be detected in the CNS. We used, nested PCR assays together with next-generation sequencing to identify the fungal species in the nervous tissue of 10 patients with MS. Strikingly, Trichosporon mucoides was found in the majority of MS patients, and particularly high levels of this fungus were found in two patients. Importantly, T. mucoides was not detected in the CNS of control subjects. We were also able to visualize fungal structures in CNS tissue sections by immunohistochemistry using specific antifungal antibodies, which also revealed the accumulation of a number of microbial cells in microfoci. Again, microbial structures were not observed in CNS sections from controls. In addition to fungi, neural tissue from MS patients was also positive for bacteria. In conclusion, our present observations point to the novel concept that MS could be caused by polymicrobial infections. Thus, mycosis of the CNS may be accompanied by opportunistic bacterial infection, promoting neuroinflammation and directly causing focal lesions, followed by demyelination and axonal injury.

Infectious agents and amyotrophic lateral sclerosis: another piece of the puzzle of motor neuron degeneration

Amyotrophic lateral sclerosis (ALS) is the most common neurodegenerative disease affecting motor neurons (MN). This fatal disease is characterized by progressive muscle wasting and lacks an effective treatment. ALS pathogenesis has not been elucidated yet. In a small proportion of ALS patients, the disease has a familial origin, related to mutations in specific genes, which directly result in MN degeneration. By contrast, the vast majority of cases are though to be sporadic, in which genes and environment interact leading to disease in genetically predisposed individuals. Lately, the role of the environment has gained relevance in this field and an extensive list of environmental conditions have been postulated to be involved in ALS. Among them, infectious agents, particularly viruses, have been suggested to play an important role in the pathogenesis of the disease. These agents could act by interacting with some crucial pathways in MN degeneration, such as gene processing, oxidative stress or neuroinflammation. In this article, we will review the main studies about the involvement of microorganisms in ALS, subsequently discussing their potential pathogenic effect and integrating them as another piece in the puzzle of ALS pathogenesis.

The role of Candida albicans in the severity of multiple sclerosis

The purpose of this study was to compare the specific activity of proteinase A in Candida albicans (C. albicans) between multiple sclerosis (MS) patients and controls. A total of 135 and 100 C. albicans strains were isolated from superficial surfaces of MS patients and healthy controls. Analytical models (regression and neural network) were applied to predict the severity of MS considering specific enzyme activity (SEA) and other factors which affect the expanded disability status scale (EDSS). The SEA of C. albicans in MS patients (3466.95 ± 277.25 μmol min^-1 mg^-1 ) was significantly more than that of healthy controls (1108.98 ± 294.51 μmol min^-1 mg^-1 ) that was confirmed by regression model (P < 0.001). The SEA had a positive correlation with the severity of MS (P < 0.001, r = 0.65). Analytical models showed that SEA played the most important role (among all included factors that affect on EDSS) in the severity of MS. The SEA of C. albicans in MS patients was significantly more than the healthy controls. The results suggest that the level of SEA of proteinase A and probably the capacity of C. albicans isolates to invade the host tissue is associated with the severity of MS.

Evaluation of APR1 Gene Expression in Candida albicans Strains Isolated From Patients With Multiple Sclerosis

BACKGROUND

Intracellular aspartic proteinase A enzyme is expressed by the APR1 gene and is one of the important factors in the development of systemic candidiasis caused by Candida albicans.

OBJECTIVES

The aim of this study was to evaluate the expression of the APR1 gene in C. albicans isolates obtained from patients with multiple sclerosis (MS) and from controls.

PATIENTS AND METHODS

The samples were obtained from 135 MS patients with candidiasis and 100 matched controls of healthy individuals during 2010 - 2011. The clinical and control isolates of C. albicans obtained from individuals were cultured onto sabouraud dextrose agar (SDA). The evaluation of APR1 gene expression was performed using the reverse transcriptase-polymerase chain reaction (RT-PCR) method.

RESULTS

There was a statistically significant difference in APR1 gene expression of C. albicans strains between MS patients (mean ± SD: 0.5208 ± 0.11518) and the control group (mean ± SD: 0.7603 ± 0.11405) (P = 0.000). Significant correlations were found between the APR1 gene expression of C. albicans strains from MS patients with regard to age and the expanded disability status scale (EDSS) (P = 0.000). The mean values of EDSS were 1.6074 ± 0.1081 after antifungal treatment and 2.2519 ± 0.1323 before antifungal treatment (P = 0.000). No significant correlation was observed between the APR1 gene expression with regard to sex and MS subtypes.

CONCLUSIONS

The results suggested that APR1 gene expression in C. albicans strains isolated from MS patients may be an important factor for invasive C. albicans strains in the progression of MS disease.

Experimental autoimmune encephalomyelitis development is aggravated by Candida albicans infection

Multiple sclerosis (MS) is an inflammatory/autoimmune disease of the central nervous system (CNS) mainly mediated by myelin specific T cells. It is widely believed that environmental factors, including fungal infections, contribute to disease induction or evolution. Even though Candida infection among MS patients has been described, the participation of this fungus in this pathology is not clear. The purpose of this work was to evaluate the effect of a Candida albicans infection on experimental autoimmune encephalomyelitis (EAE) that is a widely accepted model to study MS. Female C57BL/6 mice were infected with C. albicans and 3 days later, animals were submitted to EAE induction by immunization with myelin oligodendrocyte glycoprotein. Previous infection increased the clinical score and also the body weight loss. EAE aggravation was associated with expansion of peripheral CD4⁺ T cells and production of high levels of TNF-α, IFN-γ IL-6, and IL-17 by spleen and CNS cells. In addition to yeast and hyphae, fungus specific T cells were found in the CNS. These findings suggest that C. albicans infection before EAE induction aggravates EAE, and possibly MS, mainly by CNS dissemination and local induction of encephalitogenic cytokines. Peripheral production of encephalitogenic cytokines could also contribute to disease aggravation.

Evidence for fungal infection in cerebrospinal fluid and brain tissue from patients with amyotrophic lateral sclerosis

Among neurogenerative diseases, amyotrophic lateral sclerosis (ALS) is a fatal illness characterized by a progressive motor neuron dysfunction in the motor cortex, brainstem and spinal cord. ALS is the most common form of motor neuron disease; yet, to date, the exact etiology of ALS remains unknown. In the present work, we have explored the possibility of fungal infection in cerebrospinal fluid (CSF) and in brain tissue from ALS patients. Fungal antigens, as well as DNA from several fungi, were detected in CSF from ALS patients. Additionally, examination of brain sections from the frontal cortex of ALS patients revealed the existence of immunopositive fungal antigens comprising punctate bodies in the cytoplasm of some neurons. Fungal DNA was also detected in brain tissue using PCR analysis, uncovering the presence of several fungal species. Finally, proteomic analyses of brain tissue demonstrated the occurrence of several fungal peptides. Collectively, our observations provide compelling evidence of fungal infection in the ALS patients analyzed, suggesting that this infection may play a part in the etiology of the disease or may constitute a risk factor for these patients.

Alzheimer's disease and disseminated mycoses

Alzheimer's disease (AD) is characterized by the presence in the brain of amyloid plaques and neurofibrillary tangles that provoke neuronal cell death, vascular dysfunction and inflammatory processes. In the present work, we have analyzed the existence of fungal infection in AD patients. A number of tests have been carried out in blood serum, including the detection of antibodies against several yeast species and fungal proteins, and also the presence of fungal (1,3)-β-glucan. Results from this analysis indicate that there is disseminated fungal infection in the majority of AD patients tested. Of interest, several AD patients contain high levels of fungal polysaccharides in peripheral blood, reflecting that disseminated fungal infection occurs in these patients. Together, these results suggest the presence of disseminated mycoses in blood serum from AD patients. To our knowledge these findings represent the first evidence that fungal infection is detectable in blood samples in AD patients. The possibility that this may represent a risk factor or may contribute to the etiological cause of AD is discussed.

Fungal infection in cerebrospinal fluid from some patients with multiple sclerosis

Multiple sclerosis (MS) is the prototypical inflammatory disease of the central nervous system and spinal cord, leading to axonal demyelination of neurons. Recently, we have found a correlation between fungal infection and MS in peripheral blood of patients. The present work provides evidence of fungal infection in the cerebrospinal fluid (CSF) of some MS patients. Thus, fungal antigens can be demonstrated in CSF, as well as antibodies reacting against several Candida species. Comparison was made between CSF and blood serum for the presence of fungal antigens (proteins) and antibodies against different Candida spp. Analyses of both CSF and serum are complementary and serve to better evaluate for the presence of disseminated fungal infection. In addition, PCR analyses indicate the presence of DNA from different fungal species in CSF, depending on the patient analyzed. Overall, these findings support the notion that fungal infection can be demonstrated in CSF from some MS patients. This may constitute a risk factor in this disease and could also help in understanding the pathogenesis of MS.