The Rabbit Model of Cryptococcal Meningitis.

Cryptococcal meningitis (CM) is a fungal disease caused by the invasion of Cryptococcus yeast cells into the central nervous system. The organism is thought to enter the body through the lungs and then escape due to dysregulation of the immune response. Multiple animal species have been used to model the infection and characterize CM including mice, rats, dogs, guinea pigs, and rabbits. The rabbit model has over 40 years of data and has been used to study host-pathogen interactions and the efficacy of antifungal therapeutics. The model begins with immune suppression to eliminate the lymphocytic cell population followed by direct infection of the central nervous system via an injection of a suspension of yeast cells into the cisterna magna. The organism remains in the CNS during the course of infection, and cerebrospinal fluid can be repeatedly sampled to quantify the burden of organism, measure drug levels in the CSF, profile the immune response in the CSF, and/or characterize the yeast cells. The rabbit model of infection is a robust experimental model for better understanding CM and Cryptococcus cellular behavior.

Mouse Organotypic Brain Slice Cultures: A Novel Model for Studying Neuroimmune Responses to Cryptococcal Brain Infections.

Cryptococcal meningitis affects millions of people worldwide and is especially prevalent in regions with a high burden of HIV/AIDS. The study of the pathophysiology of this often fatal disease has been significantly hindered by the lack of reliable experimental models, especially at the level of the brain, which is the main organ of injury. Here we outline our novel protocol for the use of hippocampal organotypic brain slice cultures (HOCs) to study the host-fungal interactions during cryptococcal infections of the brain. HOCs are a powerful platform for investigating neuroimmune interactions as they allow for the preservation of all innate neuroglial cells including microglia, astrocytes, and neurons, all of which maintain their three-dimensional architecture and functional connectivity. We made HOCs from neonatal mice and infected these with a fluorescent strain of Cryptococcus neoformans for 24 h. Using immunofluorescent staining, we confirmed the presence and morphology of microglia, astrocytes, and neurons in HOCs prior to infection. Using fluorescent and light microscopy, we also confirmed that Cryptococcus neoformans encapsulates and buds in vitro, as it would in a host. Finally, we demonstrate that infection of HOCs with Cryptococcus neoformans results in close association of the fungal cells with host microglial cells. Our results demonstrate the utility of HOCs as a model to study the pathophysiology and host neuroimmune responses in neurocryptococcosis, which may assist in improving our collective understanding of the pathogenesis of this disease.

Zebrafish Larvae as an Experimental Model of Cryptococcal Meningitis.

This chapter provides guidance for introducing Cryptococcus neoformans into the zebrafish larvae model system to establish a CNS infection phenotype that mimics cryptococcal meningitis as seen in humans. The method outlines techniques for visualizing different stages of pathology development, from initial to severe infection profiles. The chapter provides tips for real time visualization of the interactions between the pathogen and different aspects of the CNS anatomy and immune system.

Is Ferroptosis a Future Direction in Exploring Cryptococcal Meningitis?

Cryptococcal meningitis (CM) is the leading cause of mortality among patients infected with human immunodeficiency virus (HIV). Although treatment strategies for CM are continually being developed, the mortality rate is still high. Therefore, we need to explore more therapeutic strategies that are aimed at hindering its pathogenic mechanism. In the field of CM, several studies have observed rapid iron accumulation and lipid peroxidation within the brain, all of which are hallmarks of ferroptosis, which is a type of programmed cell death that is characterized by iron dependence and lipid peroxidation. In recent years, many studies have confirmed the involvement of ferroptosis in many diseases, including infectious diseases such as Mycobacterium tuberculosis infection and coronavirus disease-2019 (COVID-19). Furthermore, ferroptosis is considered as immunogenic and pro-inflammatory as the ferroptotic cells release damage-associated molecular pattern molecules (DAMPs) and alarmin, both of which regulate immunity and pro-inflammatory activity. Hence, we hypothesize that there might be a relationship between this unique cell death modality and CM. Herein, we review the evidence of ferroptosis in CM and consider the hypothesis that ferroptotic cell death may be involved in the cell death of CM.

Disseminated cryptococcosis and anti-granulocyte-macrophage colony-stimulating factor autoantibodies: An underappreciated association.

The development of disseminated cryptococcosis has historically occurred in patients living with advanced human immunodeficiency virus or other immunosuppressive conditions affecting T-cell function. Recently, patients with anti-cytokine neutralising autoantibodies have been recognised to be at risk for disseminated infections by opportunistic intracellular pathogens, including Cryptococcus species. Herein, we present a previously healthy 26-year-old man who was evaluated with disseminated cryptococcosis involving the bone, lung, mediastinum and brain. The patient's serum cryptococcal antigen titres were >1:1,100,000, and evaluation for an underlying immunodeficiency revealed high titres for anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) autoantibodies. We also review the literature of all published cases of disseminated cryptococcosis associated with the presence of anti-GM-CSF autoantibodies. Clinicians should have a heightened awareness of anti-cytokine autoantibodies in patients without a known immunodeficiency and development disseminated infections by opportunistic intracellular pathogens.

Trehalose as quantitative biomarker for in vivo diagnosis and treatment follow-up in cryptococcomas.

Brain lesions caused by Cryptococcus neoformans or C. gattii (cryptococcomas) are typically difficult to diagnose correctly and treat effectively, but rapid differential diagnosis and treatment initiation are crucial for good outcomes. In previous studies, cultured cryptococcal isolates and ex vivo lesion material contained high concentrations of the virulence factor and fungal metabolite trehalose. Here, we studied the in vivo metabolic profile of cryptococcomas in the brain using magnetic resonance spectroscopy (MRS) and assessed the relationship between trehalose concentration, fungal burden, and treatment response in order to validate its suitability as marker for early and noninvasive diagnosis and its potential to monitor treatment in vivo. We investigated the metabolites present in early and late stage cryptococcomas using in vivo 1H MRS in a murine model and evaluated changes in trehalose concentrations induced by disease progression and antifungal treatment. Animal data were compared to 1H and 13C MR spectra of Cryptococcus cultures and in vivo data from 2 patients with cryptococcomas in the brain. In vivo MRS allowed the noninvasive detection of high concentrations of trehalose in cryptococcomas and showed a comparable metabolic profile of cryptococcomas in the murine model and human cases. Trehalose concentrations correlated strongly with the fungal burden. Treatment studies in cultures and animal models showed that trehalose concentrations decrease following exposure to effective antifungal therapy. Although further cases need to be studied for clinical validation, this translational study indicates that the noninvasive MRS-based detection of trehalose is a promising marker for diagnosis and therapeutic follow-up of cryptococcomas.

Cryptococcal infection in haematologic malignancies and haematopoietic stem cell transplantation.

This review summarises both the recent and relevant studies about cryptococcal infections in haematologic malignancies and haematopoietic stem cell transplantation. Although uncommon in this patient population, this infection carries a high mortality, especially if left untreated. Given the limited data, we draw some conclusions with respect to management from the solid organ transplantation and HIV-infected literature. Herein, we discuss cryptococcosis with a particular attention to its background, epidemiology, risk factors, clinical presentation, diagnosis, treatment and prevention in this group.

Cryptococcus Meningitis Can Co-occur with Anti-NMDA Receptor Encephalitis.

We herein report a 50-year-old man with alcoholic cirrhosis who developed loss of consciousness and tremor of the upper limbs. Magnetic resonance imaging findings were suggestive of limbic encephalitis with bilateral hippocampal damage, and a cerebrospinal fluid (CSF) examination confirmed anti-N-methyl-D-aspartate (NMDA) and anti-glutamate receptor antibodies. Despite initial corticosteroid therapy, meningeal irritation symptoms appeared, owing to the development of cryptococcal meningitis (CM), diagnosed by the detection of cryptococcal capsular polysaccharide antigen in the follow-up CSF analysis. Cerebral infarction with reversible stenosis of major cerebral arteries during the clinical course was also observed. Following administration of antifungals and corticosteroids, the number of cells in the CSF gradually declined, and NMDA receptor antibodies disappeared. Our study demonstrates the unique coexistence of CM with anti-NMDA receptor encephalitis in adults.

Recurring Multicentric Granulomatous Cryptococcomas in the Contralateral Cerebral Hemisphere in an Adult Immunocompetent Patient with Known Previous Disease.

BACKGROUND: Fungal mass lesions in the central nervous system rarely reach a size large enough to directly cause neurologic deterioration. In terms of the etiologic incidence of fungal mass lesions in the central nervous system, whereas cryptococcomas may be the most common, they rarely reach any appreciable size. One form of this specific fungal infection, namely the granulomatous form of cryptococcomatosis, challenges this paradigm, and these lesions can reach an alarming size. CASE DESCRIPTION: We previously reported a case of multicentric granulomatous cryptococcomas occurring in an adult immunocompetent male patient published in WORLD NEUROSURGERY in mid-2018. We now report that despite confirmed gross total resection and subsequent neurologic improvement having been achieved at that time, the patient was not compliant with his prescribed adjuvant antifungal medical therapy, and for 6 months was lost to follow-up. We now report that the same patient again presented to our unit in early-2019 with recurrent granulomatous cryptococcomas, of an alarming even larger size, in the contralateral hemisphere. Fortunately, were again were able to successfully manage him surgically and have now adapted our surveillance plan to include booked follow-up magnetic resonance imaging. CONCLUSIONS: According to our review of the English literature, to our knowledge, this is the first report of recurrent granulomatous cryptococcomas occurring in the contralateral hemisphere within 6 months of surgery. The case illustrates the importance of the adjuvant antifungal medial therapy if recurrence is to be avoided.

Landmark clinical observations and immunopathogenesis pathways linked to HIV and Cryptococcus fatal central nervous system co-infection.

Cryptococcal meningitis remains one of the leading causes of death among HIV-infected adults in the fourth decade of HIV era in sub-Saharan Africa, contributing to 10%-20% of global HIV-related deaths. Despite widespread use and early induction of ART among HIV-infected adults, incidence of cryptococcosis remains significant in those with advanced HIV disease. Cryptococcus species that causes fatal infection follows systemic spread from initial environmental acquired infection in lungs to antigenaemia and fungaemia in circulation prior to establishment of often fatal disease, cryptococcal meningitis in the CNS. Cryptococcus person-to-person transmission is uncommon, and deaths related to blood infection without CNS involvement are rare. Keen to the persistent high mortality associated with HIV-cryptococcal meningitis, seizures are common among a third of the patients, altered mental status is frequent, anaemia is prevalent with ensuing brain hypoxia and at autopsy, brain fibrosis and infarction are evident. In addition, fungal burden is 3-to-4-fold higher in those with seizures. And high immune activation together with exacerbated inflammation and elevated PD-1/PD-L immune checkpoint expression is immunomodulated phenotypes elevated in CSF relative to blood. Lastly, though multiple Cryptococcus species cause disease in this setting, observations are mostly generalised to cryptococcal infection/meningitis or regional dominant species (C neoformans or gattii complex) that may limit our understanding of interspecies differences in infection, progression, treatment or recovery outcome. Together, these factors and underlying mechanisms are hypotheses generating for research to find targets to prevent infection or adequate therapy to prevent persistent high mortality with current optimal therapy.

Fungal kinases and transcription factors regulating brain infection in Cryptococcus neoformans.

Cryptococcus neoformans causes fatal fungal meningoencephalitis. Here, we study the roles played by fungal kinases and transcription factors (TFs) in blood-brain barrier (BBB) crossing and brain infection in mice. We use a brain infectivity assay to screen signature-tagged mutagenesis (STM)-based libraries of mutants defective in kinases and TFs, generated in the C. neoformans H99 strain. We also monitor in vivo transcription profiles of kinases and TFs during host infection using NanoString technology. These analyses identify signalling components involved in BBB adhesion and crossing, or survival in the brain parenchyma. The TFs Pdr802, Hob1, and Sre1 are required for infection under all the conditions tested here. Hob1 controls the expression of several factors involved in brain infection, including inositol transporters, a metalloprotease, PDR802, and SRE1. However, Hob1 is dispensable for most cellular functions in Cryptococcus deuterogattii R265, a strain that does not target the brain during infection. Our results indicate that Hob1 is a master regulator of brain infectivity in C. neoformans.

Assessing the virulence of Cryptococcus neoformans causing meningitis in HIV infected and uninfected patients in Vietnam.

We previously observed a substantial burden of cryptococcal meningitis in Vietnam atypically arising in individuals who are uninfected with human immunodeficiency virus (HIV). This disease was associated with a single genotype of Cryptococcus neoformans (sequence type [ST]5), which was significantly less common in HIV-infected individuals. Aiming to compare the phenotypic characteristics of ST5 and non-ST5 C. neoformans, we selected 30 representative Vietnamese isolates and compared their in vitro pathogenic potential and in vivo virulence. ST5 and non-ST5 organisms exhibited comparable characteristics with respect to in vitro virulence markers including melanin production, replication at 37°C, and growth in cerebrospinal fluid. However, the ST5 isolates had significantly increased variability in cellular and capsular sizing compared with non-ST5 organisms (P < .001). Counterintuitively, mice infected with ST5 isolates had significantly longer survival with lower fungal burdens at day 7 than non-ST5 isolates. Notably, ST5 isolates induced significantly greater initial inflammatory responses than non-ST5 strains, measured by TNF-α concentrations (P < .001). Despite being generally less virulent in the mouse model, we hypothesize that the significant within strain variation seen in ST5 isolates in the tested phenotypes may represent an evolutionary advantage enabling adaptation to novel niches including apparently immunocompetent human hosts.

Usefulness and safety from stereotactic biopsy in posterior fossa lesions in adult patients.

BACKGROUND: Stereotactic biopsy has been reported as a useful and safety procedure in pediatric patients. In adult patients exist more controversy because a greater number of diagnostic options. OBJECTIVE: To demonstrate its usefulness and safety in adult patients with posterior fossa pathology. METHOD: From 2006-2014, 23 patients were operated from posterior fossa. Variables: age, gender, state, pre- and postoperative diagnosis, stereotactic device, location and complications. RESULTS: 52.2% females and 47.8% males. The location was ponto-mesencephalic 43.5%, cerebellum 39.1%, bulbar 13% and pineal region 4.3%. The preoperative diagnosis was brainstem glioma 78.2%, lymphoma 8.7%, and meningioma, metastasis and abscess 4.3% each one. In 73.9% Zamorano-Dujovni device was used and in 26.1% the CRW. The definitive diagnosis was pilocytic astrocytoma 17.4%, diffuse astrocytoma 13%, inflammatory response 13%, anaplastic astrocytoma 8.7%, gliosis 8.7%, glioblastoma, neuroectodermic primitive tumor, germinoma, pineocytoma and cryptococcosis 4.3% each one. In 17.4% there was no diagnosis. The preoperative diagnosis was concordant in 43.5%. One transient deficit and one pin displacement 4.3% were present. 91.4% without complications. CONCLUSIONS: It is a useful, necessary and safety procedure in adult patients.

ANTECEDENTES: La biopsia por estereotaxia ha sido reportada como segura y útil en pediatría. En adultos es más controvertida debido a la mayor diversidad de opciones diagnósticas. OBJETIVO: Demostrar su utilidad y seguridad en pacientes adultos con patología de fosa posterior. MÉTODO: En 2006-2014 se operaron 23 pacientes de fosa posterior. Variables: edad, sexo, diagnóstico preoperatorio y posoperatorio, estereotáctico, localización y complicaciones. RESULTADOS: 52.2% mujeres y 47.8% hombres. La localización fue la región pontomesencefálica en el 43.5%, el cerebelo en el 39.1%, bulbar en el 13% y pineal en el 4.3%. El diagnóstico preoperatorio fue glioma de tallo en el 78.2%, linfoma en el 8.7% y meningioma, metástasis y absceso en el 4.3% cada uno. En el 73.9% se utilizó el sistema Zamorano-Dujovni y en el 26.1% el CRW. El diagnóstico definitivo fue astrocitoma pilocítico en el 17.4%, astrocitoma difuso en el 13%, respuesta inflamatoria en el 13%, astrocitoma anaplásico en el 8.7%, gliosis en el 8.7%, y glioblastoma, tumor neuroectodérmico primitivo, germinoma, pineoctioma y criptococosis en el 4.3% cada uno. En el 17.4% no hubo diagnóstico. El diagnóstico preoperatorio fue concordante en el 43.5%. Hubo un déficit transitorio y un desplazamiento de uno de los pinchos en el 4.3% de los casos. En el 91.4% no hubo complicaciones. CONCLUSIONES: Es un procedimiento útil, necesario y seguro en pacientes adultos.

Intrathecal IgG Synthesis and Persistent Inflammation Are Associated with White Matter Lesions in HIV-negative Patients with Cryptococcal Meningoencephalitis.

Objective Cryptococcal meningoencephalitis (CM) causes significant morbidity and mortality in human immunodeficiency virus (HIV)-negative and HIV-positive populations. White matter lesions (WMLs) have been reported in both populations of CM patients; however, the mechanisms underlying WML formation remain unknown. We herein report the relationship between the intrathecal immune response and the development of WMLs in HIV-negative patients with CM. Methods Eleven consecutive HIV-negative patients with CM who presented at one of three emergency hospitals in Japan from April 2001 to March 2018 were enrolled. For all patients, we retrospectively assessed the relationships between clinical and laboratory information and the presence of WMLs. Results At presentation, 6 patients had WMLs on magnetic resonance imaging (MRI). The cerebrospinal fluid immunoglobulin G (CSF IgG) index was significantly higher in the patients with WMLs than in those without WMLs (mean, 1.34 vs. 0.70, p=0.017). The time from the symptom onset to initial neuroimaging was also significantly longer in the patients with WMLs than in those without WMLs (median, 31.5 vs. 7.0 days; p=0.008). The clinical outcome was comparable among the patients with and without WMLs. Conclusion In HIV-negative patients with CM, a persistent, aberrant immune response to Cryptococcus, such as intrathecal IgG synthesis, may induce WML formation.

The clinical characteristics of adult cryptococcal meningitis patients who died within one year of treatment with a focus on those with early mortality.

Cryptococcal meningitis (CM) is a serious infectious disease of the central nervous system, and associated brain injuries can be found in the very early stage of disease. In this study, 92 adult CM patients (59 men, 33 women; median age 54.66 years, range 20-86 years) were enrolled, and their clinical, laboratory, neuroimaging features and therapeutic outcomes were analyzed. Two main clinical comparative analyses of the clinical characteristics and laboratory and neuroimaging features were made in this study. The first compared clinical differences between the survivors and non-survivors of all enrolled patients, and the second compared differences between the following three groups: Group I, the patients who died within 14 days of initiating treatment; Group II, the patients who died within 15 days to 1 year of initiating treatment, and Group III, the patients who survived for more than 1 year after initiating treatment. Prognostic factors including initial altered consciousness, increased cerebrospinal fluid (CSF) lactate level and the presence of cryptococcemia were significantly different between the different groups. The patients with early mortality had a higher CSF lactate level and higher rate of cryptococcemia. The presence of cryptococcemia was an important prognostic factor, and the patients with cryptococcemia had a higher incidence of positive CSF India ink stain. Further large-scale studies are needed to delineate the clinical and laboratory features of CM patients with early mortality.

Toward a clinical antifungal peptoid: Investigations into the therapeutic potential of AEC5.

Cryptococcus neoformans is a fungal pathogen that causes cryptococcal meningitis in immunocompromised individuals. Existing antifungal treatment plans have high mammalian toxicity and increasing drug resistance, demonstrating the dire need for new, nontoxic therapeutics. Antimicrobial peptoids are one alternative to combat this issue. Our lab has recently identified a tripeptoid, AEC5, with promising efficacy and selectivity against C. neoformans. Here, we report studies into the broad-spectrum efficacy, killing kinetics, mechanism of action, in vivo half-life, and subchronic toxicity of this compound. Most notably, these studies have demonstrated that AEC5 rapidly reduces fungal burden, killing all viable fungi within 3 hours. Additionally, AEC5 has an in vivo half-life of 20+ hours and no observable in vivo toxicity following 28 days of daily injections. This research represents an important step in the characterization of AEC5 as a practical treatment option against C. neoformans infections.

Idiopathic CD4 lymphopenia in a case of disseminated cryptococcosis with brain, vertebral spine and reproductive organ involvement.

Cryptococcosis is an opportunistic fungal infection commonly seen in HIV cases. We present a case of disseminated cryptococcosis with multiple non-continuous infective foci in a non-HIV, non-transplant case.

A case report of disseminated histoplasmosis and concurrent cryptococcal meningitis in a patient treated with ruxolitinib.

BACKGROUND: Ruxolitinib is a highly potent janus kinase inhibitor that places its users at risk for various bacterial infections and viral reactivation. However new reports are also emerging that suggest greater immunosuppression and risk for fungal disease. CASE PRESENTATION: We report the case of a 51 year-old veteran from Guam, treated with ruxolitinib for polycythemia vera, who developed disseminated histoplasmosis and concurrent cryptococcal meningitis. CONCLUSION: This case draws attention to the degree of immunosuppression that may be seen with this drug and the need for heightened vigilance for opportunistic infections in those treated with inhibitors of janus kinase/signal transducers and activators of transcription (JAK/STAT) such as ruxolitinib.