[Candida albicans cerebral granuloma in an immunocompetent patient. A case report]

Advancements in Cerebrospinal Fluid Biosensors: Bridging the Gap from Early Diagnosis to the Detection of Rare Diseases

Cerebrospinal fluid (CSF) is a body fluid that can be used for the diagnosis of various diseases. However, CSF collection requires an invasive and painful procedure called a lumbar puncture (LP). This procedure is applied to any patient with a known risk of central nervous system (CNS) damage or neurodegenerative disease, regardless of their age range. Hence, this can be a very painful procedure, especially in infants and elderly patients. On the other hand, the detection of disease biomarkers in CSF makes diagnoses as accurate as possible. This review aims to explore novel electrochemical biosensing platforms that have impacted biomedical science. Biosensors have emerged as techniques to accelerate the detection of known biomarkers in body fluids such as CSF. Biosensors can be designed and modified in various ways and shapes according to their ultimate applications to detect and quantify biomarkers of interest. This process can also significantly influence the detection and diagnosis of CSF. Hence, it is important to understand the role of this technology in the rapidly progressing field of biomedical science.

From Mendel to mycoses: Immuno-genomic warfare at the human-fungus interface

Fungi are opportunists: They particularly require a defect of immunity to cause severe or disseminated disease. While often secondary to an apparent iatrogenic cause, fungal diseases do occur in the absence of one, albeit infrequently. These rare cases may be due to an underlying genetic immunodeficiency that can present variably in age of onset, severity, or other infections, and in the absence of a family history of disease. They may also be due to anti-cytokine autoantibodies. This review provides a background on how human genetics or autoantibodies underlie cases of susceptibility to severe or disseminated fungal disease. Subsequently, the lessons learned from these inborn errors of immunity marked by fungal disease (IEI-FD) provide a framework to begin to mechanistically decipher fungal syndromes, potentially paving the way for precision therapy of the mycoses.

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.

Of Mycelium and Men: Inherent Human Susceptibility to Fungal Diseases

In medical mycology, the main context of disease is iatrogenic-based disease. However, historically, and occasionally, even today, fungal diseases affect humans with no obvious risk factors, sometimes in a spectacular fashion. The field of “inborn errors of immunity” (IEI) has deduced at least some of these previously enigmatic cases; accordingly, the discovery of single-gene disorders with penetrant clinical effects and their immunologic dissection have provided a framework with which to understand some of the key pathways mediating human susceptibility to mycoses. By extension, they have also enabled the identification of naturally occurring auto-antibodies to cytokines that phenocopy such susceptibility. This review provides a comprehensive update of IEI and autoantibodies that inherently predispose humans to various fungal diseases.

The molecular immunology of human susceptibility to fungal diseases: lessons from single gene defects of immunity

INTRODUCTION

Fungal diseases are a threat to human health. Therapies targeting the fungus continue to lead to disappointing results. Strategies targeting the host response represent unexplored opportunities for innovative treatments. To do so rationally requires the identification and neat delineation of critical mechanistic pathways that underpin human antifungal immunity. The study of humans with single-gene defects of the immune system, i.e. inborn errors of immunity (IEIs), provides a foundation for these paradigms. Areas covered: A systematic literature search in PubMed, Scopus, and abstracts of international congresses was performed to review the history of genetic resistance/susceptibility to fungi and identify IEIs associated with fungal diseases. Immunologic mechanisms from relevant IEIs were integrated with current definitions and understandings of mycoses to establish a framework to map out critical immunobiological pathways of human antifungal immunity. Expert opinion: Specific immune responses non-redundantly govern susceptibility to their corresponding mycoses. Defining these molecular pathways will guide the development of host-directed immunotherapies that precisely target distinct fungal diseases. These findings will pave the way for novel strategies in the treatment of these devastating infections.

CSF in acute and chronic infectious diseases

Infections of the nervous system are an important and challenging aspect of clinical neurology. Immediate correct diagnosis enables to introduce effective therapy, in conditions that without diagnosis may leave the patient with severe neurological incapacitation and sometimes even death. The cerebrospinal fluid (CSF) is a mirror that reflects nervous system pathology and can promote early diagnosis and therapy. The present chapter focuses on the CSF findings in neuro-infections, mainly viral and bacterial. Opening pressure, protein and glucose levels, presence of cells and type of the cellular reaction should be monitored. Other tests can also shed light on the causative agent: serology, culture, staining, molecular techniques such as polymerase chain reaction. Specific examination such as panbacterial and panfungal examinations should be examined when relevant. Our chapter is a guide-text that combines clinical presentation and course with CSF findings as a usuaful tool in diagnosis of neuroinfections.

Fungal Infection in the Brain: What We Learned from Intravital Imaging

Approximately 1.2 billion people suffer from fungal diseases worldwide. Arguably, the most serious manifestation occurs when pathogenic fungi infect the brain, often causing fatal meningoencephalitis. For most fungi, infection occurs via the vascular route. The organism must first be arrested in the brain microvasculature and transmigrate into the brain parenchyma across the blood–brain barrier. As a result, host immune cells are recruited into the brain to contain the fungi. However, it remains poorly understood how fungi traffic to, and migrate into the brain and how immune cells interact with invading fungi in the brain. A new era of intravital fluorescence microscopy has begun to provide insights. We are able to employ this powerful approach to study dynamic interactions of disseminating fungi with brain endothelial cells as well as resident and recruited immune cells during the brain infection. In this review, with a focus on Cryptococcus neoformans, we will provide an overview of the application of intravital imaging in fungal infections in the brain, discuss recent findings and speculate on possible future research directions.

Imaging Candida Infections in the Host

Disseminated fungal infections caused by Candida species are associated with homing of the pathogen to specific organs in human and murine hosts. Kidneys are a primary target organ of Candida albicans, and invasion into the kidney medulla can lead to loss of renal function and death. Therefore, development of noninvasive methods to assess kidney infections could aid in the management of disseminated candidemia. We describe a magnetic resonance imaging method utilizing iron oxide-based contrast agents to noninvasively assess recruitment of phagocytes and kidney inflammation. C. albicans also colonizes the brain and can cause meningoencephalitis. We describe additional imaging methods to assess loss of the blood-brain barrier function that initiates brain infections.

Impaired RASGRF1/ERK-mediated GM-CSF response characterizes CARD9 deficiency in French-Canadians

BACKGROUND

Caspase recruitment domain-containing protein 9 (CARD9) deficiency is an autosomal recessive primary immunodeficiency conferring human susceptibility to invasive fungal disease, including spontaneous central nervous system candidiasis (sCNSc). However, clinical characterization of sCNSc is variable, hindering its recognition. Furthermore, an in-depth understanding of the bases for this susceptibility has remained elusive.

OBJECTIVES

We sought to comprehensively characterize sCNSc and to dissect the mechanisms by which a hypomorphic CARD9 mutation causes susceptibility to Candida species.

METHODS

We describe the clinical and radiologic findings of sCNSc caused by CARD9 deficiency in a French-Canadian cohort. We performed genetic, cellular, and molecular analyses to further decipher its pathophysiology.

RESULTS

In our French-Canadian series (n = 4) sCNSc had onset in adulthood (median, 38 years) and was often misinterpreted radiologically as brain malignancies; 1 patient had additional novel features (eg, endophthalmitis and osteomyelitis). CARD9 deficiency resulted from a hypomorphic p.Y91H mutation and allelic imbalance established in this population through founder effects. We demonstrate a consistent cellular phenotype of impaired GM-CSF responses. The ability of CARD9 to complex with B-cell CLL/lymphoma 10 (BCL10) and mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) is intact in our series, arguing against its involvement in susceptibility to fungi. Instead, we show that the p.Y91H mutation impairs the ability of CARD9 to complex with Ras protein-specific guanine nucleotide-releasing factor 1 (RASGRF1), leading to impaired activation of nuclear factor κB and extracellular signal-regulated kinase (ERK) in monocytes and subsequent GM-CSF responses. Successful treatment of a second patient with adjunctive GM-CSF bolsters the clinical relevance of these findings.

CONCLUSIONS

Hypomorphic CARD9 deficiency caused by p.Y91H results in adult-onset disease with variable penetrance and expressivity. Our findings establish the CARD9/RASGRF1/ERK/GM-CSF axis as critical to the pathophysiology of sCNSc.

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.

Inherited CARD9 deficiency in otherwise healthy children and adults with Candida species-induced meningoencephalitis, colitis, or both

BACKGROUND

Invasive infections of the central nervous system (CNS) or digestive tract caused by commensal fungi of the genus Candida are rare and life-threatening. The known risk factors include acquired and inherited immunodeficiencies, with patients often displaying a history of multiple infections. Cases of meningoencephalitis, colitis, or both caused by Candida species remain unexplained.

OBJECTIVE

We studied 5 previously healthy children and adults with unexplained invasive disease of the CNS, digestive tract, or both caused by Candida species. The patients were aged 39, 7, 17, 37, and 26 years at the time of infection and were unrelated, but each was born to consanguineous parents of Turkish (2 patients), Iranian, Moroccan, or Pakistani origin. Meningoencephalitis was reported in 3 patients, meningoencephalitis associated with colitis was reported in a fourth patient, and the fifth patient had colitis only.

METHODS

Inherited caspase recruitment domain family, member 9 (CARD9) deficiency was recently reported in otherwise healthy patients with other forms of severe disease caused by Candida, Trichophyton, Phialophora, and Exophiala species, including meningoencephalitis but not colitis caused by Candida and Exophiala species. Therefore we sequenced CARD9 in the 5 patients.

RESULTS

All patients were found to be homozygous for rare and deleterious mutant CARD9 alleles: R70W and Q289* for the 3 patients with Candida albicans-induced meningoencephalitis, R35Q for the patient with meningoencephalitis and colitis caused by Candida glabrata, and Q295* for the patient with Candida albicans-induced colitis. Regardless of their levels of mutant CARD9 protein, the patients' monocyte-derived dendritic cells responded poorly to CARD9-dependent fungal agonists (curdlan, heat-killed C albicans, Saccharomyces cerevisiae, and Exophiala dermatitidis).

CONCLUSION

Invasive infections of the CNS or digestive tract caused by Candida species in previously healthy children and even adults might be caused by inherited CARD9 deficiency.

Fungal infections of the central nervous system

The epidemiology of invasive fungal infections in immunocompromised patients is rapidly changing. Several of the fungi have worldwide distribution. However, some have specific geographical distribution. Sinocranial aspergillosis, mostly described from countries with temperate climates, occurs mostly in otherwise immunocompetent individuals Most of the systemic fungal pathogens have been associated with central nervous system (CNS) involvement. The major advances in CNS fungal infections are in the pathobiology, new diagnostic tools, and new therapies. In spite of these developments, there is still considerable delay in the diagnosis of CNS fungal infection. CNS fungal infections are associated with considerable morbidity and mortality. To achieve good outcomes early diagnosis and early institution of appropriate therapies are the key issues.

MRI confirms loss of blood-brain barrier integrity in a mouse model of disseminated candidiasis

Disseminated candidiasis primarily targets the kidneys and brain in mice and humans. Damage to these critical organs leads to the high mortality associated with such infections, and invasion across the blood-brain barrier can result in fungal meningoencephalitis. Candida albicans can penetrate a brain endothelial cell barrier in vitro through transcellular migration, but this mechanism has not been confirmed in vivo. MRI using the extracellular vascular contrast agent gadolinium diethylenetriaminepentaacetic acid demonstrated that integrity of the blood-brain barrier is lost during C. albicans invasion. Intravital two-photon laser scanning microscopy was used to provide the first real-time demonstration of C. albicans colonizing the living brain, where both yeast and filamentous forms of the pathogen were found. Furthermore, we adapted a previously described method utilizing MRI to monitor inflammatory cell recruitment into infected tissues in mice. Macrophages and other phagocytes were visualized in kidney and brain by the administration of ultrasmall iron oxide particles. In addition to obtaining new insights into the passage of C. albicans across the brain microvasculature, these imaging methods provide useful tools to study further the pathogenesis of C. albicans infections, to define the roles of Candida virulence genes in kidney versus brain infection and to assess new therapeutic measures for drug development.