Treatment recommendations for non-HIV associated cryptococcal meningoencephalitis including management of post-infectious inflammatory response syndrome

Pathway-instructed therapeutic selection of ruxolitinib reduces neuroinflammation in fungal postinfectious inflammatory syndrome

Therapies to reduce neuroinflammation following resolution of acute central nervous system (CNS) infections are urgently needed, particularly for patients with non-HIV-associated cryptococcal meningoencephalitis complicated by a postinfectious inflammatory response syndrome (cPIIRS). To identify druggable targets in cPIIRS, patient cerebral spinal fluid samples underwent transcriptional analysis, revealing a Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway dominance in neuroinflammatory gene signatures. MurinecPIIRS models recapitulated this pathway predominance and treatment with the JAK inhibitor ruxolitinib, confirmed a mechanistic requirement for this pathway in disease pathology. Ruxolitinib treatment improved markers of neuronal damage, reduced activated T cell and myeloid cells, and improved weight. On the basis of these findings, we conducted a first-in-human ruxolitinib treatment of patients with cPIIRS (NCT00001352). Ruxolitinib treatment of six patients led to demonstrated tolerability, reductions in inflammatory biomarkers and activated immune cells, and improved brain imaging. These results advocate for pathway-instructed therapeutics in neuroinflammatory diseases and endorse JAK inhibitors in further clinical studies of cPIIRS.

Case report: A diabetic patient with cryptococcal meningoencephalitis complicated by post-infectious inflammatory response syndrome

We report on a previously non-HIV-diagnosed, 47-year-old male diagnosed with diabetes mellitus (DM) and cryptococcal meningoencephalitis, who was referred to our institution for antifungal treatment. During the course of treatment, due to the development of refractory intracranial hypertension, Ommaya reservoirs were employed for cranial pressure reduction. The patient gradually recovered during subsequent antifungal therapy; however, symptoms worsened in the third month of treatment, leading to consideration of post-infectious inflammatory response syndrome (PIIRS) on examination. Once diagnosed, the symptoms improved significantly after approximately 130 days of treatment with additional corticosteroids.

The pathobiology of human fungal infections

Human fungal infections are a historically neglected area of disease research, yet they cause more than 1.5 million deaths every year. Our understanding of the pathophysiology of these infections has increased considerably over the past decade, through major insights into both the host and pathogen factors that contribute to the phenotype and severity of these diseases. Recent studies are revealing multiple mechanisms by which fungi modify and manipulate the host, escape immune surveillance and generate complex comorbidities. Although the emergence of fungal strains that are less susceptible to antifungal drugs or that rapidly evolve drug resistance is posing new threats, greater understanding of immune mechanisms and host susceptibility factors is beginning to offer novel immunotherapeutic options for the future. In this Review, we provide a broad and comprehensive overview of the pathobiology of human fungal infections, focusing specifically on pathogens that can cause invasive life-threatening infections, highlighting recent discoveries from the pathogen, host and clinical perspectives. We conclude by discussing key future challenges including antifungal drug resistance, the emergence of new pathogens and new developments in modern medicine that are promoting susceptibility to infection.

Global trends in Cryptococcus and its interactions with the host immune system: a bibliometric analysis

Objectives

This manuscript undertakes a systematic examination of the research landscape concerning global Cryptococcus species and their dynamism with the host immune system spanning the past decade. It furnishes a detailed survey of leading knowledge institutions and critical focal points in this area, utilizing bibliometric analysis.

Methods

VOSviewer and CiteSpace software platforms were employed to systematically analyze and graphically depict the relevant literature indexed in the WoSCC database over the preceding ten years.

Results

In the interval between October 1, 2013, and October 1, 2023, a corpus of 795 publications was amassed. The primary research institutions involved in this study include Duke University, the University of Minnesota, and the University of Sydney. The leading trio of nations, in terms of publication volume, comprises the United States, China, and Brazil. Among the most prolific authors are Casadevall, Arturo; Wormley, Floyd L., Jr.; and Olszewski, Michal A., with the most highly cited author being Perfect, Jr. The most esteemed journal is Mbio, while Infection and Immunity commands the highest citation frequency, and the Journal of Clinical Microbiology boasts the most significant impact factor. Present research foci encompass the intricate interactions between Cryptococcus pathogenesis and host immunity, alongside immune mechanisms, complications, and immunotherapies.

Conclusion

This represents the first exhaustive scholarly review and bibliometric scrutiny of the evolving landscapes in Cryptococcus research and its interactions with the host immune system. The analyses delineated herein provide insights into prevailing research foci and trajectories, thus furnishing critical directions for subsequent inquiries in this domain.

JAK/STAT Signaling Predominates in Human and Murine Fungal Post-infectious Inflammatory Response Syndrome

Post-infection inflammatory syndromes have been increasingly recognized as a cause of host damage in a variety of infectious diseases including tuberculosis, bacterial meningitis, and COVID-19. Recently, a post-infectious inflammatory response syndrome (PIIRS) was described in non-HIV-infected cryptococcal fungal meningoencephalitis (CM) as a major cause of mortality. Inflammatory syndromes are particularly severe in neurological infections due to the skull's rigid structure which limits unchecked tissue expansion from inflammatory-induced edema. In the present studies, neurologic transcriptional pathway analysis utilizing a murine PIIRS model demonstrated a predominance of Janus kinase/signal transducer and activator of transcription (JAK/STAT) activation. JAK/STAT inhibitor treatment resulted in improvements in CNS damage markers, reductions in intrathecal CD44hiCD62lo CD4+ effector CD4+ T-cells and MHC II+ inflammatory myeloid cells, and weight gains in mice, the latter after treatment with antifungals. Based on these data, pathway-driven steroid-sparing human treatment for steroid-refractory PIIRS was initiated using short courses of the JAK/STAT inhibitor ruxolitinib. These were well tolerated and reduced activated HLA-DR+ CD4+ and CD8+ cells and inflammatory monocytes as well as improved brain imaging. Together, these findings support the role of JAK/STAT in PIIRS as well as further study of JAK/STAT inhibitors as potential adjunctive therapy for PIRS and other neural inflammatory syndromes.

Cryptococcal meningitis

Cryptococcus neoformans and Cryptococcus gattii species complexes cause meningoencephalitis with high fatality rates and considerable morbidity, particularly in persons with deficient T cell-mediated immunity, most commonly affecting people living with HIV. Whereas the global incidence of HIV-associated cryptococcal meningitis (HIV-CM) has decreased over the past decade, cryptococcosis still accounts for one in five AIDS-related deaths globally due to the persistent burden of advanced HIV disease. Moreover, mortality remains high (~50%) in low-resource settings. The armamentarium to decrease cryptococcosis-associated mortality is expanding: cryptococcal antigen screening in the serum and pre-emptive azole therapy for cryptococcal antigenaemia are well established, whereas enhanced pre-emptive combination treatment regimens to improve survival of persons with cryptococcal antigenaemia are in clinical trials. Short courses (≤7 days) of amphotericin-based therapy combined with flucytosine are currently the preferred options for induction therapy of cryptococcal meningitis. Whether short-course induction regimens improve long-term morbidity such as depression, reduced neurocognitive performance and physical disability among survivors is the subject of further study. Here, we discuss underlying immunology, changing epidemiology, and updates on the management of cryptococcal meningitis with emphasis on HIV-associated disease.

Tocilizumab as a Potential Adjunctive Therapy to Corticosteroids in Cryptococcal Post-infectious Inflammatory Response Syndrome (PIIRS): a Report of Two Cases

PURPOSE

Non-HIV cryptococcal meningoencephalitis (CM) in previously healthy individuals is often complicated by a post-infectious inflammatory response syndrome (c-PIIRS) characterized by neurologic deterioration after appropriate antifungal therapy with sterilization of CSF fungal cultures. c-PIIRS results from an excessive inflammatory response to fungal antigens released during fungal lysis, mediated by IFN-γ, IL-6, and activated T-helper cells, leading to immune-mediated host damage that responds to pulse-corticosteroid taper therapy (PCT). Typically, oral steroids may take up to a year to taper, and occasionally, patients will be refractory to steroid therapy or may demonstrate high-risk lesions such as those involving intracranial arteries. Also, patients can have problematic side effects from prolonged corticosteroids. Hence, appropriate adjunctive agents are needed to reduce corticosteroid doses in the treatment of c-PIIRS. Due to a possible role of IL-6 in pathogenesis, IL-6 receptor blockade by tocilizumab may be useful in the treatment of c-PIIRS.

METHODS

Two previously healthy patients with non-HIV cPIIRS were seen at the NIH. Due to concerns for intracranial vascular rupture in an area of inflammation (Patient 1) and intractable symptoms on high-dose oral corticosteroids (Patient 2) with evidence of persistent CSF inflammation, patients were treated with 4-8 mg/kg tocilizumab every 2 weeks while maintained on a constant dose of prednisone.

RESULTS

Two patients exhibited rapid immunological improvement following treatment with tocilizumab. Patient 1 remained vascularly stable, and Patient 2 had near resolution of headaches with improvement in mental status as evidenced by improved MOCA score. The two had improved CSF inflammatory parameters and no significant side effects. Both CSF cultures remained negative throughout treatment.

CONCLUSIONS

Tocilizumab may be a safe adjunctive treatment for CM-related PIIRS suggesting further study.

Inbred SJL mice recapitulate human resistance to Cryptococcus infection due to differential immune activation

IMPORTANCE

Cryptococcosis studies often utilize the common C57BL/6J mouse model. Unfortunately, infection in these mice fails to replicate the basic course of human disease, particularly hampering immunological studies. This work demonstrates that SJL/J mice can recapitulate human infection better than other mouse strains. The immunological response to Cryptococcus infection in SJL/J mice was markedly different from C57BL/6J and much more productive in combating this infection. Characterization of infected mice demonstrated strain-specific genetic linkage and differential regulation of multiple important immune-relevant genes in response to Cryptococcus infection. While our results validate many of the previously identified immunological features of cryptococcosis, we also demonstrate limitations from previous mouse models as they may be less translatable to human disease. We concluded that SJL/J mice more faithfully recapitulate human cryptococcosis serving as an exciting new animal model for immunological and genetic studies.

Cryptococcal Meningoencephalitis in Phenotypically Normal Patients

Cryptococcosis is an invasive fungal infection found worldwide that causes significant morbidity and mortality among a broad range of hosts. There are approximately 223,000 new cases of cryptococcosis annually throughout the world, and at least 180,000 deaths are attributed to this infection each year. Most of these are due to complications of cryptococcal meningoencephalitis among HIV-infected patients in resource-limited environments. The majority of individuals diagnosed with cryptococcosis have underlying conditions associated with immune dysfunction such as HIV, solid organ transplant, hematologic malignancy, organ failure syndromes, and/or the use of immunosuppressive agents such as glucocorticosteroids and biologic agents. In most clinical series, there is a small proportion of patients with cryptococcosis who are phenotypically normal; that is, they have no clinically obvious predisposition to disease. Cryptococcal meningoencephalitis (CME) presentation and management differ substantially between these normal individuals and their immunocompromised counterparts. In this review, we will focus on CME in the phenotypically normal host and underscore differences in the clinical presentation, management, outcome, and potential risk factors for these patients compared to immunocompromised persons who develop this potential devastating invasive fungal infection.

Chronic cryptococcal meningitis with a cryptococcoma presenting as normal pressure hydrocephalus: a case report

Chronic meningitis may present with clinical features related to hydrocephalus. We report a 76-year-old female who presented to an outpatient clinic with cognitive decline and gait disturbance with recurrent falls. The initial diagnosis of normal pressure hydrocephalus (NPH) was based on the clinical symptoms and magnetic resonance imaging (MRI) of the brain, which showed ventriculomegaly without an obstructive lesion. During follow-up, however, there was remarkable cognitive decline, and she was unable to walk without assistance. Lumbar puncture and brain MRI showed respective lymphocyte-dominant pleocytosis that was positive for cryptococcal antigen and a new encapsulated abscess-like lesion in a left caudate head. Treatment for cryptococcal meningitis was initiated, and the patient was cured after a long treatment with an antifungal agent. As chronic meningitis could be misdiagnosed as NPH, differential diagnoses of etiologies that can cause hydrocephalus should be addressed.

Severe meningoencephalitis: epidemiology and outcomes

PURPOSE OF REVIEW

This article aims to provide an updated review on the epidemiology and outcomes of severe meningoencephalitis.

RECENT FINDINGS

Meningoencephalitis is a critical medical condition characterized by inflammation in both the meninges and brain parenchyma. Bacterial, viral, or fungal infections are common causes, although noninfectious factors, such as autoimmune causes, can also contribute. In patients requiring intensive care, meningoencephalitis is associated with a severe prognosis, including mortality rates ranging from 11 to 25% and functional disability in 15-25% of survivors. Recent multicenter studies have identified several parameters linked to poor outcomes, including older age, immunocompromised status, focal neurologic signs, abnormal brain imaging, and delayed administration of antimicrobials. The use of new multiplex PCR techniques for diagnosis has generated debate based on recent data. Investigation is still needed to determine the effectiveness of adjunctive therapies, including seizure prophylaxis, and adjunctive steroids for nonbacterial causes.

SUMMARY

Recent multicenter studies have enhanced our understanding of the current epidemiology and outcomes of severe meningoencephalitis in adult patients.

Cryptococcal Meningitis in Young, Immunocompetent Patients: A Single-Center Retrospective Case Series and Review of the Literature

Background

Cryptococcal meningitis is an uncommon but serious infection with high mortality and morbidity. Classically described in immunocompromised patients, including those with solid organ transplants or HIV/AIDS, cryptococcosis has also been reported in young and otherwise healthy patients, albeit rarely.

Methods

We retrospectively searched for all cases of cryptococcal meningitis in young (≤50 years) and previously healthy patients with no known immunocompromising conditions from January 2015 to January 2022 at Indiana University Health (IU Health). Additionally, a PubMed literature review was performed with the keywords "cryptococcal meningitis" and "immunocompetent" from January 1988 to January 2022. Clinical courses, including outcomes and treatment regimens, were evaluated.

Results

We identified 4 local cases of cryptococcal meningitis in otherwise healthy patients age ≤50 years. Three cases were due to Cryptococcus neoformans, with 1 experiencing a postinfectious inflammatory response syndrome (PIIRS). The PubMed search identified 51 additional cases, with 32 (63%) being caused by Cryptococcus neoformans and 8 (17%) by Cryptococcus gattii. Of the 51 cases, only 2 resulted in death directly due to cryptococcosis. Fifteen (29%) had PIIRS, with steroid treatment documented in 11 of 15. Antifungal induction regimens and duration were varied but predominately consisted of amphotericin and flucytosine, with a mean induction duration of 5.0 weeks.

Conclusions

Cryptococcal meningitis in young, previously healthy patients is likely under-recognized. PIIRS (akin to immune reconstitution inflammatory syndrome observed in HIV/AIDS) with prolonged recovery should be of concern. Determining risk factors for cryptococcosis in these patients remains elusive.