Paucity of initial cerebrospinal fluid inflammation in cryptococcal meningitis is associated with subsequent immune reconstitution inflammatory syndrome

Molecular Diagnostics of Cryptococcus spp. and Immunomics of Cryptococcosis-Associated Immune Reconstitution Inflammatory Syndrome

Cryptococcal infection poses a significant global public health challenge, particularly in regions near the equator. In this review, we offer a succinct exploration of the Cryptococcus spp. genome and various molecular typing methods to assess the burden and genetic diversity of cryptococcal pathogens in the environment and clinical isolates. We delve into a detailed discussion on the molecular pathogenesis and diagnosis of immune reconstitution inflammatory syndrome (IRIS) associated with cryptococcosis, with a specific emphasis on cryptococcal meningitis IRIS (CM-IRIS). Our examination includes the recent literature on CM-IRIS, covering host cellulomics, proteomics, transcriptomics, and genomics.

Complex Decisions in HIV-Related Cryptococcosis: Addressing Second Episodes of Cryptococcal Meningitis

PURPOSE OF REVIEW

This review highlights the difficulties in diagnosing and treating persons with a prior history of cryptococcal meningitis who improve but suffer from a recurrence of symptoms. This scenario is well known to those who frequently care for patients with cryptococcal meningitis but is not well understood. We highlight major gaps in knowledge.

RECENT FINDINGS

We recently summarized our experience with 28 persons with paradoxical immune reconstitution inflammatory syndrome (IRIS) and 81 persons with microbiological relapse. CD4 count and cerebrospinal fluid white blood cell count were higher in IRIS than relapse but neither was reliable enough to routinely differentiate these conditions. Second-episode cryptococcal meningitis remains a difficult clinical scenario as cryptococcal antigen, while excellent for initial diagnosis has no value in differentiating relapse of infection from other causes of recurrent symptoms. Updated research definitions are proposed and rapid, accurate diagnostic tests are urgently needed.

Divergent neuroimmune signatures in the cerebrospinal fluid predict differential gender-specific survival among patients with HIV-associated cryptococcal meningitis

Introduction

Survival among people with HIV-associated cryptococcal meningitis (CM) remains low, particularly among women, despite the currently optimal use of antifungal drugs. Cryptococcus dissemination into the central nervous system [brain, spinal cord, and cerebrospinal fluid (CSF)] elicits the local production of cytokines, chemokines, and other biomarkers. However, no consistent diagnostic or prognostic neuroimmune signature is reported to underpin the risk of death or to identify mechanisms to improve treatment and survival. We hypothesized that distinct neuroimmune signatures in the CSF would distinguish survivors from people who died on antifungal treatment and who may benefit from tailored therapy.

Methods

We considered baseline clinical features, CSF cryptococcal fungal burden, and CSF neuroimmune signatures with survival at 18 weeks among 419 consenting adults by "gender" (168 women and 251 men by biological sex defined at birth).

Results

Survival at 18 weeks was significantly lower among women than among men {47% vs. 59%, respectively; hazard ratio (HR) = 1.4 [95% confidence interval (CI), 1.0 to 1.9; p = 0.023]}. Unsupervised principal component analysis (PCA) demonstrated divergent neuroimmune signatures by gender, survival, and intragender-specific survival. Overall, women had lower levels of programmed death ligand 1, Interleukin (IL) (IL-11RA/IL-1F30, and IL-15 (IL-15) than men (all p < 0.028). Female survivors compared with those who died expressed significant elevations in levels of CCL11 and CXCL10 chemokines (both p = 0.001), as well as increased T helper 1, regulatory, and T helper 17 cytokines (all p < 0.041). In contrast, male survivors expressed lower levels of IL-15 and IL-8 compared with men who died (p < 0.044).

Conclusions

Survivors of both genders demonstrated a significant increase in the levels of immune regulatory IL-10. In conclusion, the lower survival among women with CM was accompanied by distinct differential gender-specific neuroimmune signatures. These female and male intragender-specific survival-associated neuroimmune signatures provide potential targets for interventions to advance therapy to improve the low survival among people with HIV-associated CM.

Recurrent Cryptococcal Meningitis in a Late Presenter of HIV: A Rare Case Report and Review of Literature

BACKGROUND The highly active antiretroviral treatment (HAART) and the primary prophylaxis in newly diagnosed people living with HIV (PLHIV) have reduced the incidence of opportunistic infections such as cryptococcal meningitis (CM). Relapse of CM is associated with increased morbidity and mortality. The aim of the present case presentation is to report the clinical progress relapse of CM in a man who was a late presenter PLHIV, 1 year after ART initiation with increased CD4 cell count, undetectable viral load, and excellent compliance after disruption of secondary antifungal prophylaxis. CASE REPORT One year after initial diagnosis of HIV and CM, the patient had no neurological or other symptoms, and viral suppression and increased CD4 cell count were achieved. After the completion of 12 months of secondary prophylaxis with fluconazole, an episode of partial seizure with secondary generalization occurred, followed by a short-term memory loss. Magnetic resonance imaging (MRI) indicated a focal lesion in right frontal-parietal brain region. Lumbar puncture was conducted and Cryptococcus neoformans non-resistant to fluconazole was isolated. He received antiepileptic treatment, induction antifungal treatment with liposomal amphotericin and fluconazole, consolidation treatment with fluconazole, and secondary prophylaxis with fluconazole, as in the first episode of CM. One year after the relapse, antiepileptic treatment and secondary prophylaxis with fluconazole continues and no new episode has been reported. The diagnosis of immune reconstitution inflammatory syndrome (IRIS)-related relapse of CM cannot be excluded. CONCLUSIONS Further studies are needed for the evaluation of parameters such as duration of secondary prophylaxis and treatment options for induction and consolidation therapy to reduce the relapse rate of CM.

Utility of Cerebrospinal Fluid Protein Levels as a Potential Predictive Biomarker of Disease Severity in HIV-Associated Cryptococcal Meningitis

Background

Cerebrospinal fluid (CSF) protein levels exhibit high variability in HIV-associated cryptococcal meningitis from being normal to markedly elevated. However, the clinical implications of CSF protein levels in cryptococcal meningitis remain unclear.

Methods

We analysed data from 890 adults with HIV-associated cryptococcal meningitis randomized into two clinical trials in Uganda between 2015 and 2021. CSF protein was grouped into ≥100 mg/dL (n=249) and <100 mg/dL (n=641). We described baseline clinical variables and mortality by CSF protein levels.

Results

Approximately one-third of individuals had a baseline CSF protein ≥100 mg/dL. Those with CSF protein ≥100 mg/dL were more likely to present with Glasgow coma scale scores <15 (P<0.01), self-reported seizures at baseline (P=0.02), higher CD4 T-cells (p<0.001), and higher CSF white cells (p<0.001). Moreover, those with a baseline CSF protein ≥100 mg/dL also had a lower baseline CSF fungal burden (p<0.001) and a higher percentage of sterile CSF cultures at day 14 (p=0.02). Individuals with CSF protein ≥100 mg/dL demonstrated a more pronounced immune response consisting of upregulation of immune effector molecules pro-inflammatory cytokines, type-1 T-helper cell cytokines, type-3 chemokines, and immune-exhaustion marker (p<0.05). 18-week mortality risk in individuals with a CSF protein <100 mg/dL was 34% higher, (unadjusted Hazard Ratio 1.34; 95% CI, 1.05 to 1.70; p=0.02) than those with ≥100 mg/dL.

Conclusion

In cryptococcal meningitis, individuals with CSF protein ≥100 mg/dL more frequently presented with seizures, altered mental status, immune activation, and favourable fungal outcomes. Baseline CSF protein levels may serve as a surrogate marker of immune activation and prognosis.

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.

Divergent Neuroimmune Signatures in the Cerebrospinal Fluid Predict Differential Gender-Specific Survival Among Patients With HIV-Associated Cryptococcal Meningitis

Survival among people with HIV-associated cryptococcal meningitis (CM) remains low, exceptionally among women with the increased threat of death on current optimal use of antifungal drugs. Cryptococcus dissemination into the central nervous system (CNS) prompts a neuroimmune reaction to activate pathogen concomitant factors. However, no consistent diagnostic or prognostic immune-mediated signature is reported to underpin the risk of death or mechanism to improve treatment or survival. We theorized that the distinct neuroimmune cytokine or chemokine signatures in the cerebrospinal fluid (CSF), distinguish survivors from people who died on antifungal treatment, who may benefit from tailored therapy. We considered the baseline clinical disease features, cryptococcal microbiologic factors, and CSF neuroimmune modulated signatures among 419 consenting adults by gender (biological sex assigned at birth) (168 females and 251 males) by 18 weeks of survival on antifungal management. Survival at 18 weeks was inferior among females than males (47% vs. 59%; hazard ratio HR=1.4, 95% CI: 1.0 to 1.9, and p=0.023). Unsupervised principal component analysis (PCA) demonstrated the divergent neuroimmune signatures by gender, survival, and intragender-specific survival. Overall, females displayed lower levels of PD-L1, IL-1RA, and IL-15 than males (all p≤0.028). Female survivors compared with those who died, expressed significant fold elevations in levels of CSF (CCL11 - myeloid and CXCL10 - lymphoid chemokine (in both p=0.001), and CSF Th1, Th2, and Th17 cytokines. In contrast, male survivors expressed distinctly lower levels of CSF IL-15 and IL-8 compared with those who died. Survivors of either gender demonstrated a significant increase in the levels of immune regulatory element, IL-10. In the finale, we classified divergent neuroimmune key signatures in CSF by gender, survival, and intragender-specific survival among people with HIV-associated cryptococcal meningitis. These intragender-specific survival associated-neuroimmune signatures, suggests the discrete role of gender immune regulating mechanisms as the possible targets for interventions to advance therapy to improve survival among people with HIV-associated cryptococcal meningitis.

Recurrence of Symptoms Following Cryptococcal Meningitis: Characterizing a Diagnostic Conundrum With Multiple Etiologies

BACKGROUND

Cryptococcal meningitis is a common cause of AIDS-related mortality. Although symptom recurrence after initial treatment is common, the etiology is often difficult to decipher. We sought to summarize characteristics, etiologies, and outcomes among persons with second-episode symptomatic recurrence.

METHODS

We prospectively enrolled Ugandans with cryptococcal meningitis and obtained patient characteristics, antiretroviral therapy (ART) and cryptococcosis histories, clinical outcomes, and cerebrospinal fluid (CSF) analysis results. We independently adjudicated cases of second-episode meningitis to categorize patients as (1) microbiological relapse, (2) paradoxical immune reconstitution inflammatory syndrome (IRIS), (3) persistent elevated intracranial pressure (ICP) only, or (4) persistent symptoms only, along with controls of primary cryptococcal meningitis. We compared groups with chi-square or Kruskal-Wallis tests as appropriate.

RESULTS

724 participants were included (n = 607 primary episode, 81 relapse, 28 paradoxical IRIS, 2 persistently elevated ICP, 6 persistent symptoms). Participants with culture-positive relapse had lower CD4 (25 cells/μL; IQR: 9-76) and lower CSF white blood cell (WBC; 4 cells/μL; IQR: 4-85) counts than paradoxical IRIS (CD4: 78 cells/μL; IQR: 47-142; WBC: 45 cells/μL; IQR: 8-128). Among those with CSF WBC <5 cells/μL, 86% (43/50) had relapse. Among those with CD4 counts <50 cells/μL, 91% (39/43) had relapse. Eighteen-week mortality (from current symptom onset) was 47% among first episodes of cryptococcal meningitis, 31% in culture-positive relapses, and 14% in paradoxical IRIS.

CONCLUSIONS

Poor immune reconstitution was noted more often in relapse than IRIS as evidenced by lower CSF WBC and blood CD4 counts. These easily obtained laboratory values should prompt initiation of antifungal treatment while awaiting culture results.

CLINICAL TRIALS REGISTRATION

NCT01802385.

Efficacy and safety of lenalidomide in HIV-associated cryptococcal meningitis patients with persistent intracranial inflammation: an open-label, single-arm, prospective interventional study

BACKGROUND

Patients with human immunodeficiency virus-associated cryptococcal meningitis (HIV-CM) have persistent intracranial inflammation despite negative cerebrospinal fluid (CSF) fungal cultures after optimal treatment for CM, which could be devastating for the central nervous system. However, a definitive treatment strategy for persistent intracranial inflammation despite optimal antifungal therapies is undefined.

METHODS

We identified 14 HIV-CM patients with persistent intracranial inflammation and conducted a 24-week, prospective, interventional study. All participants received lenalidomide (25 mg, p.o.) on days 1 to 21 of a 28-day cycle. Follow-up lasted for 24 weeks with visits at baseline and weeks 4, 8, 12, and 24. The primary endpoint was the change in clinical manifestations, routine CSF parameters, and MRI findings after lenalidomide treatment. An exploratory analysis was made on changes in cytokine levels in CSF. Safety and efficacy analyses were undertaken in patients who received at least one dose of lenalidomide.

RESULTS

Of 14 participants, 11 patients completed the 24 weeks of follow-up. Rapid clinical remission following lenalidomide therapy was observed. Clinical manifestations (fever, headache, altered mentation) were reversed fully by week-4 and remained stable during follow-up. A significant reduction in white blood cell (WBC) count in CSF was noted occurred at week-4 (P = 0.009). The median protein concentration in CSF decreased from 1.4 (0.7-3.2) g/L at baseline to 0.9 (0.6-1.4) at week-4 (P = 0.004). The median albumin concentration in CSF decreased from 79.2 (48.4-149.8) mg/L at baseline to 55.3 (38.3-89.0) mg/L at week-4 (P = 0.011). The WBC count, protein level, and albumin level in CSF remained stable and approached a normal range through week-24. There was no significant change in immunoglobulin-G, intracranial pressure (ICP), or chloride-ion concentration at each visit. Brain MRI demonstrated multiple lesions to be absorbed post-therapy. Levels of tumor necrosis factor-α granulocyte colony stimulating factor, interleukin (IL)-6, and IL-17A decreased significantly during 24-week follow-up. Two (14.3%) patients had mild skin rash, which resolved spontaneously. Lenalidomide-related serious adverse events were not observed.

CONCLUSION

Lenalidomide could improve persistent intracranial inflammation in HIV-CM patients significantly and was well tolerated without serious adverse events observed. And the additional randomized controlled study is required to further validate the finding.

Sterile Cerebrospinal Fluid Culture at Cryptococcal Meningitis Diagnosis Is Associated with High Mortality

Cryptococcus is the leading cause of AIDS-related meningitis in sub-Saharan Africa. The clinical implications of a sterile cerebrospinal fluid (CSF) culture among individuals diagnosed with cryptococcal meningitis using CSF cryptococcal antigen (CrAg) are unclear. We prospectively enrolled 765 HIV-positive Ugandans with first-episode cryptococcal meningitis from November 2010 to May 2017. All persons were treated with amphotericin-based induction therapy. We grouped participants by tertile of baseline CSF quantitative Cryptococcus culture burden and compared clinical characteristics, CSF immune profiles, and 18-week mortality. We found 55 (7%) CSF CrAg-positive participants with sterile CSF cultures. Compared to the non-sterile groups, participants with sterile CSF cultures had higher CD4 counts, lower CSF opening pressures, and were more frequently receiving ART. By 18 weeks, 47% [26/55] died in the sterile culture group versus 35% [83/235] in the low culture tertile, 46% [107/234] in the middle tertile, and 56% [135/241] in the high tertile (p < 0.001). The sterile group had higher levels of CSF interferon-gamma (IFN-γ), IFN-α, interleukin (IL)-6, IL-17, G-CSF, GM-CSF, and chemokine CXCL2 compared with non-sterile groups. Despite persons with sterile CSF cultures having higher CD4 counts, lower CSF opening pressures, and CSF cytokine profiles associated with better Cryptococcus control (e.g., IFN-γ predominant), mortality was similar to those with higher fungal burdens. This unexpected finding challenges the traditional paradigm that increasing CSF fungal burdens are associated with increased mortality but is consistent with a damage-response framework model.

Cryptococcal Immune Reconstitution Inflammatory Syndrome: From Clinical Studies to Animal Experiments

Cryptococcus neoformans is an encapsulated pathogenic fungus that initially infects the lung but can migrate to the central nervous system (CNS), resulting in meningoencephalitis. The organism causes the CNS infection primarily in immunocompromised individuals including HIV/AIDS patients, but also, rarely, in immunocompetent individuals. In HIV/AIDS patients, limited inflammation in the CNS, due to impaired cellular immunity, cannot efficiently clear a C. neoformans infection. Antiretroviral therapy (ART) can rapidly restore cellular immunity in HIV/AIDS patients. Paradoxically, ART induces an exaggerated inflammatory response, termed immune reconstitution inflammatory syndrome (IRIS), in some HIV/AIDS patients co-infected with C. neoformans. A similar excessive inflammation, referred to as post-infectious inflammatory response syndrome (PIIRS), is also frequently seen in previously healthy individuals suffering from cryptococcal meningoencephalitis. Cryptococcal IRIS and PIIRS are life-threatening complications that kill up to one-third of affected people. In this review, we summarize the inflammatory responses in the CNS during HIV-associated cryptococcal meningoencephalitis. We overview the current understanding of cryptococcal IRIS developed in HIV/AIDS patients and cryptococcal PIIRS occurring in HIV-uninfected individuals. We also describe currently available animal models that closely mimic aspects of cryptococcal IRIS observed in HIV/AIDS patients.

Double Trouble: Concomitant Unmasking and Paradoxical Immune Reconstitution Inflammatory Syndrome in a Patient with Newly Diagnosed HIV

Immune reconstitution inflammatory syndrome (IRIS) is a complication encountered in patients with HIV due to immune function recovery following the initiation of antiretroviral therapy. IRIS can be divided into two forms: paradoxical (recurrence of clinical signs of a previously treated opportunistic infection) and unmasking (uncovering of a previously undiagnosed and asymptomatic infection). We present the rare case of a 48-year-old man diagnosed with AIDS after presenting with cryptococcal meningitis who, shortly after initiation of ART, developed both unmasking IRIS due to Mycobacterium avium complex (MAC), and subsequently paradoxical IRIS to his prior cryptococcal meningitis infection. To our knowledge, cases in the medical literature describing “double IRIS” remain scarce.

The Effect of Early vs. Deferred Antiretroviral Therapy Initiation in HIV-Infected Patients With Cryptococcal Meningitis: A Multicenter Prospective Randomized Controlled Analysis in China

Background: The optimal timing for initiation of antiretroviral therapy (ART) in HIV-positive patients with cryptococcal meningitis (CM) has not, as yet, been compellingly elucidated, as research data concerning mortality risk and the occurrence of immune reconstitution inflammatory syndrome (IRIS) in this population remains inconsistent and controversial. Method: The present multicenter randomized clinical trial was conducted in China in patients who presented with confirmed HIV/CM, and who were ART-naïve. Subjects were randomized and stratified into either an early-ART group (ART initiated 2-5 weeks after initiation of antifungal therapy), or a deferred-ART group (ART initiated 5 weeks after initiation of antifungal therapy). Intention-to-treat, and per-protocol analyses of data for these groups were conducted for this study. Result: The probability of survival was found to not be statistically different between patients who started ART between 2-5 weeks of CM therapy initiation (14/47, 29.8%) vs. those initiating ART until 5 weeks after CM therapy initiation (10/55, 18.2%) (p = 0.144). However, initiating ART within 4 weeks after the diagnosis and antifungal treatment of CM resulted in a higher mortality compared with deferring ART initiation until 6 weeks (p = 0.042). The incidence of IRIS did not differ significantly between the early-ART group and the deferred-ART group (6.4 and 7.3%, respectively; p = 0.872). The percentage of patients with severe (grade 3 or 4) adverse events was high in both treatment arms (55.3% in the early-ART group and 41.8% in the deferred-ART group; p=0.183), and there were significantly more grade 4 adverse events in the early-ART group (20 vs. 13; p = 0.042). Conclusion: Although ART initiation from 2 to 5 weeks after initiation of antifungal therapy was not significantly associated with high cumulative mortality or IRIS event rates in HIV/CM patients compared with ART initiation 5 weeks after initiation of antifungal therapy, we found that initiating ART within 4 weeks after CM antifungal treatment resulted in a higher mortality compared with deferring ART initiation until 6 weeks. In addition, we observed that there were significantly more grade 4 adverse events in the early-ART group. Our results support the deferred initiation of ART in HIV-associated CM. Clinical Trials Registration: www.ClinicalTrials.gov, identifier: ChiCTR1900021195.

Reimagining the future of African brain health: Perspectives for basic research on the pathogenesis of cryptococcal meningitis

Cryptococcal meningitis is a fatal opportunistic infection of the brain and a leading cause of neurological damage and death in immunocompromised individuals. This neglected fungal disease of the brain is a huge burden on the health systems of developing countries, especially in Sub-Saharan Africa, where up to 25% of people living with HIV/AIDS succumb to it. Cryptococcal fungal cells have a predilection for the brain and they are capable of traversing the blood brain barrier and invade the brain where they cause infection, inflammation and a disruption of normal brain function. A robust host neuroimmune response is critical for pathogen clearance and survival, and a good understanding of the mechanisms underlying its development in the host is critical for the development of effective treatments. However, past basic research studies have been focussed on the characteristics of the fungus and its effect on the peripheral immune system; with little attention paid to how it interacts with brain immune cells. This mini review briefly discusses the paucity of basic research data on the neuroimmune response to cryptococcal infection, raises pertinent questions on how the brain cells respond to the fungal infection, and thereafter discusses models, techniques and advanced technologies that could be useful for carrying out high-throughput research on the pathogenesis of cryptococcal meningitis.

Cryptococcal meningoencephalitis: time for action

Cryptococcal meningoencephalitis was first described over a century ago. This fungal infection is preventable and treatable yet continues to be associated with excessive morbidity and mortality. The largest burden of disease resides in people living with HIV in low-income and middle-income countries. In this group, mortality with the best antifungal induction regimen (7 days of amphotericin B deoxycholate [1·0 mg/kg per day] and flucytosine [100·0 mg/kg per day]) in a clinical trial setting was 24% at 10 weeks. The world is now at an inflection point in terms of recognition, research, and action to address the burden of morbidity and mortality from cryptococcal meningoencephalitis. However, the scope of interventional programmes needs to increase, with particular attention to implementation science that is specific to individual countries. This Review summarises causes of excessive mortality, interventions with proven survival benefit, and gaps in knowledge and practice that contribute to the ongoing high death toll from cryptococcal meningoencephalitis. TRANSLATIONS: For the Vietnamese and Chichewa translations of the abstract see Supplementary Materials section.

CCR2 Signaling Promotes Brain Infiltration of Inflammatory Monocytes and Contributes to Neuropathology during Cryptococcal Meningoencephalitis

Cryptococcal meningoencephalitis (CM) is a leading cause of central nervous system (CNS) infection-related mortality worldwide, with surviving patients often developing neurological deficiencies. While CNS inflammation has been implicated in the pathogenesis of CM, little is known about the relative contribution of the specific inflammatory/immune pathways to CNS pathology versus fungal clearance. Increased cerebrospinal fluid level of C-C chemokine receptor 2 (CCR2) ligand CCL2 is associated with disease deterioration in patients with CM. Using a murine model, we investigated the role of the CCR2 pathway in the development of CNS inflammation and pathology during CM. We found that CCR2-deficient mice exhibited improved 28-day survival and alleviated neurological disease scores despite a brain fungal burden higher than that of the WT mice. Reduced CM pathology in CCR2-deficient mice was accompanied by markedly decreased neuronal cell death around cryptococcal microcysts and restored expression of genes involved in neurotransmission, connectivity, and neuronal cell structure in the brains. Results show that CCR2 axis is the major pathway recruiting CD45hiCD11b+Ly6C+ inflammatory monocyte to the brain and indirectly modulates the accumulation of CD4+ T cells and CD8+ T cells. In particular, CCR2 axis promotes recruitment of interferon gamma (IFN-γ)-producing CD4+ T cells and classical activation of myeloid cells. In this context, CCR2 deletion limits the immune network dysregulation we see in CM and attenuates neuropathology. Thus, the CCR2 axis is a potential target for interventions aimed to limit inflammatory CNS pathology in CM patients. IMPORTANCE Cryptococcal meningoencephalitis (CM) causes nearly 200,000 deaths worldwide each year, and survivors frequently develop long-lasting neurological sequelae. The high rate of mortality and neurologic sequelae in CM patients indicate that antifungal therapies alone are often insufficient to control disease progression. Here, we reveal that CM disease progression in mice is accompanied by inflammatory monocytes infiltration at the periphery of the infected foci that overlap locally perturbed neuronal function and death. Importantly, we identified that CCR2 signaling is a critical pathway driving neuroinflammation, especially inflammatory monocyte recruitment, as well as CNS pathology and mortality in CM mice. Our results imply that targeting the CCR2 pathway may be beneficial as a therapy complementary to antifungal drug treatment, helping to reduce CNS damage and mortality in CM patients.

High Levels of TNF-α and TIM-3 as a Biomarker of Immune Reconstitution Inflammatory Syndrome in People with HIV Infection

Immune reconstitution inflammatory syndrome (IRIS) is an exacerbated immune response that can occur to HIV+ patients after initiating antiretroviral therapy (ART). IRIS pathogenesis is unclear, but dysfunctional and exhausted cells have been reported in IRIS patients, and the TIM-3/Gal-9 axis has been associated with chronic phases of viral infection. This study aimed to evaluate the soluble levels of TIM-3 and Gal-9 and their relationship with IRIS development. TIM-3, Gal-9, TNF-α, IFN-γ, IL-6, TNFR1, TNFR2, E-cadherin, ADAM10, and ADAM17 were measured to search for IRIS-associated biomarkers in plasma samples from 0-, 4-, 8-, 12-, and 24-weeks after ART initiation of 61 HIV+ patients (15 patients developed IRIS, and 46 did not). We found that patients who developed IRIS had higher levels of TIM-3 [median 4806, IQR: 3206-6182] at the time of the IRIS events, compared to any other follow-up time evaluated in these patients or compared with a control group of patients who did not develop IRIS. Similarly, IRIS patients had a higher TNF-α level [median 10.89, IQR: 8.36-12.34] at IRIS events than any other follow-up time evaluated. Other molecules related to the TIM-3 and TNF-α pathway (Gal-9, IL-6, IFN-γ, TNFR1, TNFR2, ADAM-10, and ADAM-17) did not change during the IRIS events. In conclusion, our data suggest that a high level of soluble TIM-3 and TNF-α could be used as an IRIS biomarker.

Cryptococcal meningitis: a review for emergency clinicians

INTRODUCTION

Cryptococcal Meningitis (CM) remains a high-risk clinical condition, and many patients require emergency department (ED) management for complications and stabilization.

OBJECTIVE

This narrative review provides an evidence-based summary of the current data for the emergency medicine evaluation and management of CM.

DISCUSSION

This review evaluates the diagnosis, management, and empiric treatment of suspected CM in the ED. CM can easily evade diagnosis with a subacute presentation, and should be considered in any patient with a headache, neurological deficit, or who is immunocompromised. As a definitive diagnosis of CM will not be made in the ED, management of a patient with suspected CM includes prompt diagnostic testing and initiation of empiric treatment. Multiple types of newer Cryptococcal antigen tests provide high sensitivity and specificity both in serum and cerebrospinal fluid (CSF). Patients should be treated empirically for bacterial, fungal, and viral meningitis, specifically with amphotericin B and flucytosine for presumed CM. Additionally, appropriate resuscitation and supportive care, including advanced airway management, management of increased intracranial pressure (ICP), antipyretics, intravenous fluids, and isolation, should be initiated. Antiretroviral therapy (ART) should not be initiated in the ED for those found or known to be HIV-positive for risk of immune reconstitution inflammatory syndrome (IRIS).

CONCLUSIONS

CM remains a rare clinical presentation, but carries significant morbidity and mortality. Physicians must rapidly diagnose these patients while evaluating for other diseases and complications. Early consultation with an infectious disease specialist is imperative, as is initiating symptomatic care.

Cryptococcosis

Cryptococcosis is an invasive fungal infection of global significance caused by yeasts of the genus Cryptococcus. The prevalence of HIV in certain areas of the world and the expanding population of immunocompromised patients contribute to the ongoing global disease burden. Point-of-care serologic testing has allowed for more rapid diagnosis and implementation of screening programs in resource-limited settings. Management involves therapy aimed at reduction in fungal burden, maintenance of intracranial pressure, and optimization of host immunity. Despite diagnostic and therapeutic advances, cryptococcosis continues to be a disease with unacceptably high incidence and mortality, particularly in resource-limited settings.

Cryptococcal Immune Reconstitution Inflammatory Syndrome: From Blood and Cerebrospinal Fluid Biomarkers to Treatment Approaches

Immune reconstitution inflammatory syndrome (IRIS) presents as an exaggerated immune reaction that occurs during dysregulated immune restoration in immunocompromised patients in late-stage human immunodeficiency virus (HIV) infection who have commenced antiretroviral treatments (ART). Virtually any opportunistic pathogen can provoke this type of immune restoration disorder. In this review, we focus on recent developments in the identification of risk factors for Cryptococcal IRIS and on advancements in our understanding of C-IRIS immunopathogenesis. We overview new findings in blood and cerebrospinal fluid which can potentially be useful in the prediction and diagnosis of cryptococcal meningitis IRIS (CM-IRIS). We assess current therapeutic regimens and novel treatment approaches to combat CM-IRIS. We discuss the utility of biomarkers for clinical monitoring and adjusting treatment modalities in acquired immunodeficiency syndrome (AIDS) patients co-infected with Cryptococcus who have initiated ART.

Systemic Inflammation Associated with Immune Reconstitution Inflammatory Syndrome in Persons Living with HIV

Antiretroviral therapy (ART) has represented a major advancement in the care of people living with HIV (PLWHH), resulting in significant reductions in morbidity and mortality through immune reconstitution and attenuation of homeostatic disruption. Importantly, restoration of immune function in PLWH with opportunistic infections occasionally leads to an intense and uncontrolled cytokine storm following ART initiation known as immune reconstitution inflammatory syndrome (IRIS). IRIS occurrence is associated with the severe and rapid clinical deterioration that results in significant morbidity and mortality. Here, we detail the determinants underlying IRIS development in PLWH, compiling the available knowledge in the field to highlight details of the inflammatory responses in IRIS associated with the most commonly reported opportunistic pathogens. This review also highlights gaps in the understanding of IRIS pathogenesis and summarizes therapeutic strategies that have been used for IRIS.

Residual immune dysfunction under antiretroviral therapy

The usage of combination antiretroviral therapy in people with HIV (PWH) has incited profound improvement in morbidity and mortality. Yet, PWH may not experience full restoration of immune function which can manifest with non-AIDS comorbidities that frequently associate with residual inflammation and can imperil quality of life or longevity. In this review, we discuss the pathogenesis underlying chronic inflammation and residual immune dysfunction in PWH, as well as potential therapeutic interventions to ameliorate them and prevent incidence or progression of non-AIDS comorbidities. Current evidence advocates that early diagnosis and prompt initiation of therapy at high CD4 counts may represent the best available approach for an improved immune recovery in PWH.

Clinical features and treatment outcomes of human immunodeficiency virus-associated cryptococcal meningitis: a 2-year retrospective analysis

BACKGROUND

Cryptococcal meningitis (CM) is one of the most common opportunistic infections caused by Cryptococcus neoformans in human immunodeficiency virus (HIV)-infected patients, and is complicated with significant morbidity and mortality. This study retrospectively analyzed the clinical features, characteristics, treatment, and outcomes of first-diagnosed HIV-associated CM after 2-years of follow-up.

METHODS

Data from all patients (n = 101) of HIV-associated CM hospitalized in Shanghai Public Health Clinical Center from September 2013 to December 2016 were collected and analyzed using logistic regression to identify clinical and microbiological factors associated with mortality.

RESULTS

Of the 101 patients, 86/99 (86.9%) of patients had CD4 count <50 cells/mm, 57/101 (56.4%) were diagnosed at ≥14 days from the onset to diagnosis, 42/99 (42.4%) had normal cerebrospinal fluid (CSF) cell counts and biochemical examination, 30/101 (29.7%) had concomitant Pneumocystis (carinii) jiroveci pneumonia (PCP) on admission and 37/92 (40.2%) were complicated with cryptococcal pneumonia, 50/74 (67.6%) had abnormalities shown on intracranial imaging, amongst whom 24/50 (48.0%) had more than one lesion. The median time to negative CSF Indian ink staining was 8.50 months (interquartile range, 3.25-12.00 months). Patients who initiated antiretroviral therapy (ART) before admission had a shorter time to negative CSF Indian ink compared with ART-naïve patients (7 vs. 12 months, χ = 15.53, P < 0.001). All-cause mortality at 2 weeks, 8 weeks, and 2 years was 10.1% (10/99), 18.9% (18/95), and 20.7% (19/92), respectively. Coinfection with PCP on admission (adjusted odds ratio [AOR], 3.933; 95% confidence interval [CI], 1.166-13.269, P = 0.027) and altered mental status (AOR, 9.574; 95% CI, 2.548-35.974, P = 0.001) were associated with higher mortality at 8 weeks.

CONCLUSION

This study described the clinical features and outcomes of first diagnosed HIV-associated CM with 2-year follow-up data. Altered mental status and coinfection with PCP predicted mortality in HIV-associated CM.

Cytokine profiling of extracellular vesicles isolated from plasma in myalgic encephalomyelitis/chronic fatigue syndrome: a pilot study

BACKGROUND

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a debilitating disease of unknown etiology lasting for a minimum of 6 months but usually for many years, with features including fatigue, cognitive impairment, myalgias, post-exertional malaise, and immune system dysfunction. Dysregulation of cytokine signaling could give rise to many of these symptoms. Cytokines are present in both plasma and extracellular vesicles, but little investigation of EVs in ME/CFS has been reported. Therefore, we aimed to characterize the content of extracellular vesicles (EVs) isolated from plasma (including circulating cytokine/chemokine profiling) from individuals with ME/CFS and healthy controls.

METHODS

We included 35 ME/CFS patients and 35 controls matched for age, sex and BMI. EVs were enriched from plasma by using a polymer-based precipitation method and characterized by Nanoparticle Tracking Analysis (NTA), Transmission Electron Microscopy (TEM) and immunoblotting. A 45-plex immunoassay was used to determine cytokine levels in both plasma and isolated EVs from a subset of 19 patients and controls. Linear regression, principal component analysis and inter-cytokine correlations were analyzed.

RESULTS

ME/CFS individuals had significantly higher levels of EVs that ranged from 30 to 130 nm in size as compared to controls, but the mean size for total extracellular vesicles did not differ between groups. The enrichment of typical EV markers CD63, CD81, TSG101 and HSP70 was confirmed by Western blot analysis and the morphology assessed by TEM showed a homogeneous population of vesicles in both groups. Comparison of cytokine concentrations in plasma and isolated EVs of cases and controls yielded no significant differences. Cytokine-cytokine correlations in plasma revealed a significant higher number of interactions in ME/CFS cases along with 13 inverse correlations that were mainly driven by the Interferon gamma-induced protein 10 (IP-10), whereas in the plasma of controls, no inverse relationships were found across any of the cytokines. Network analysis in EVs from controls showed 2.5 times more significant inter-cytokine interactions than in the ME/CFS group, and both groups presented a unique negative association.

CONCLUSIONS

Elevated levels of 30-130 nm EVs were found in plasma from ME/CFS patients and inter-cytokine correlations revealed unusual regulatory relationships among cytokines in the ME/CFS group that were different from the control group in both plasma and EVs. These disturbances in cytokine networks are further evidence of immune dysregulation in ME/CFS.

Th1-Dependent Cryptococcus-Associated Immune Reconstitution Inflammatory Syndrome Model With Brain Damage

Cryptococcus-associated immune reconstitution inflammatory syndrome (C-IRIS) is identified upon immune reconstitution in immunocompromised patients, who have previously contracted an infection of Cryptococcus neoformans (Cn). C-IRIS can be lethal but how the immune system triggers life-threatening outcomes in patients is still poorly understood. Here, we establish a mouse model for C-IRIS with Cn serotype A strain H99, which is highly virulent and the most intensively studied. C-IRIS in mice is induced by the adoptive transfer of CD4+ T cells in immunocompromised Rag1-deficient mice infected with a low inoculum of Cn. The mice with C-IRIS exhibit symptoms which mimic clinical presentations of C-IRIS. This C-IRIS model is Th1-dependent and shows host mortality. This model is characterized with minimal lung injury, but infiltration of Th1 cells in the brain. C-IRIS mice also exhibited brain swelling with resemblance to edema and upregulation of aquaporin-4, a critical protein that regulates water flux in the brain in a Th1-dependent fashion. Our C-IRIS model may be used to advance our understanding of the paradoxical inflammatory phenomenon of C-IRIS in the context of neuroinflammation.

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.

Case Report: A Case of Severe Cryptococcal Immune Reconstitution Inflammatory Syndrome Presenting with Brain and Intradural Abscesses in an HIV Patient

Clinical worsening or new manifestation of cryptococcal disease following initiation of anti-retroviral therapy (ART) in an HIV patient is a hallmark of cryptococcal immune reconstitution inflammatory syndrome (C-IRIS). However, it can be difficult to distinguish IRIS from worsening or new infection. Here, we present a case of severe C-IRIS involving multiple cerebellar, spinal, and intradural abscesses and spinal arachnoiditis 7 months after ART initiation in an AIDS patient with uncertain prior ART compliance. He had multiple prior episodes of cryptococcal meningitis with complications necessitating ventriculoperitoneal shunt placement and was on suppressive fluconazole when he developed worsening brain manifestations. He received empiric anti-cryptococcal re-induction without improvement. All cerebrospinal fluid cultures remained sterile, with negative Cryptococcus PCR testing, and his condition continued to worsen prior to corticosteroid initiation. Ultimately, C-IRIS was diagnosed by brain biopsy. This case demonstrates an extreme in severity of C-IRIS and in the timeline of presentation after ART initiation.

Chemokine receptor CXCR3 is required for lethal brain pathology but not pathogen clearance during cryptococcal meningoencephalitis

Cryptococcal meningoencephalitis (CM) is the major cause of infection-related neurological death, typically seen in immunocompromised patients. However, T cell-driven inflammatory response has been increasingly implicated in lethal central nervous system (CNS) immunopathology in human patients and murine models. Here, we report marked up-regulation of the chemokine receptor CXCR3 axis in human patients and mice with CM. CXCR3 deletion in mice improves survival, diminishes neurological deficits, and limits neuronal damage without suppressing fungal clearance. CD4+ T cell accumulation and TH1 skewing are reduced in the CNS but not spleens of infected CXCR3-/- mice. Adoptive transfer of WT, but not CXCR3-/- CD4+ T cells, into CXCR3-/- mice phenocopies the pathology of infected WT mice. Collectively, we found that CXCR3+CD4+ T cells drive lethal CNS pathology but are not required for fungal clearance during CM. The CXCR3 pathway shows potential as a therapeutic target or for biomarker discovery to limit CNS inflammatory damages.

Pathogen and host genetics underpinning cryptococcal disease

Cryptococcosis is a severe fungal disease causing 220,000 cases of cryptococcal meningitis yearly. The etiological agents of cryptococcosis are taxonomically grouped into at least two species complexes belonging to the genus Cryptococcus. All of these yeasts are environmentally ubiquitous fungi (often found in soil, leaves and decaying wood, tree hollows, and associated with bird feces especially pigeon guano). Infection in a range of animals including humans begins following inhalation of spores or aerosolized yeasts. Recent advances provide fundamental insights into the factors from both the pathogen and its hosts which influence pathogenesis and disease. The complex interactions leading to disease in mammalian hosts have also updated from the availability of better genomic tools and datasets. In this review, we discuss recent genetic research on Cryptococcus, covering the epidemiology, ecology, and evolution of Cryptococcus pathogenic species. We also discuss the insights into the host immune response obtained from the latest genetic modified host models as well as insights from monogenic disorders in humans. Finally we highlight outstanding questions that can be answered in the near future using bioinformatics and genomic tools.

New Insights Into Cryptococcus Spp. Biology and Cryptococcal Meningitis

PURPOSE OF REVIEW

Defective cell-mediated immunity is a major risk factor for cryptococcosis, a fatal disease if untreated. Cryptococcal meningitis (CM), the main presentation of disseminated disease, occurs through hematogenous spread to the brain from primary pulmonary foci, facilitated by yeast virulence factors. We revisit remarkable recent improvements in the prevention, diagnosis and management of CM.

RECENT FINDINGS

Cryptococcal antigen (CrAg), main capsular polysaccharide of Cryptococcus spp. is detectable in blood and cerebrospinal fluid of infected patients with point of care lateral flow assays. Recent World Health Organization guidelines recommend 7-day amphotericin B plus flucytosine, then 7-day high dose (1200 mg/day) fluconazole for induction treatment of HIV-associated CM. Management of raised intracranial pressure, a consequence of CM, should rely mainly on daily therapeutic lumbar punctures until normalisation. In HIV-associated CM, following introduction of antifungal therapy, (re)initiation of antiretroviral therapy should be delayed by 4-6 weeks to prevent immune reconstitution inflammatory syndrome, common in CM. CM is a fatal disease whose diagnosis has recently been simplified. Treatment should always include antifungal combination therapy and management of raised intracranial pressure. Screening for immune deficiency should be mandatory in all patients with cryptococcosis.

CD200R1 regulates eosinophilia during pulmonary fungal infection in mice

CD200 receptor 1(CD200R1) signalling limits myeloid cell responses and reduces autoimmunity, alloimmunity and viral‐mediated immunopathology, but has never been examined in the context of eosinophilic inflammation. Susceptibility to lung fungal infection is associated with T‐helper 2 (Th2) cytokine dominated responses and strong eosinophilic pathology. Blockade of CD200R1 enhances type I cytokine responses in many infectious and non‐infectious settings and so may promote a more protective response to fungal infection. By contrast, we demonstrate that, rather than promoting type I cytokine responses, CD200R1 blockade enhanced eosinophilia in a mouse model of Cryptococcus neoformans infection, whereas CD200R1 agonism reduced lung eosinophilia – with neither strategy completely altering fungal burden. Thus, we reveal a surprising disconnect between pulmonary eosinophilia and cryptococcal burden and dissemination. This research has 2 important implications. Firstly, a lack of CD200R1 signalling enhances immune responses regardless of cytokine polarisation, and secondly reducing eosinophils does not allow protective immunity to develop in susceptible fungal system. Therefore, agonists of CD200R1 may be beneficial for eosinophilic pathologies.

Neurologic Complications of Human Immunodeficiency Virus Infection

PURPOSE OF REVIEW

Widespread use of antiretroviral therapy (ART) has led to near-normal life expectancy in people with human immunodeficiency virus (HIV) infection. However, neurologic complications of HIV remain common; can affect any part of the neuraxis; and are due to direct effects of the virus, immunosuppression because of untreated HIV infection, aberrant immune responses in the setting of ART initiation, and ART toxicities.

RECENT FINDINGS

HIV-associated neurocognitive disorder (HAND) remains one of the most common neurologic complications of HIV encountered today, but milder forms predominate in people on ART. No specific treatments for HAND exist, but small trials and epidemiologic evidence suggest paroxetine, intranasal insulin, and maraviroc may have utility in its treatment; further trials of these agents are ongoing. Widespread ART use has decreased the incidence of central nervous system opportunistic infections, but prognosis often remains poor in those who develop opportunistic infections. High-titer positive serum cryptococcal antigen is strongly predictive of cryptococcal meningitis and provides a tool to enhance diagnosis in areas with limited resources. HIV is an independent risk factor for stroke, and accelerated aging associated with HIV infection results in neurologic diseases of older age occurring at much younger ages in individuals infected with HIV. Ongoing HIV replication in the CSF despite peripheral virologic suppression may contribute to the development of HAND and may not improve despite adjusting the ART regimen to increase central nervous system penetrance.

SUMMARY

Neurologists are likely to encounter patients infected with HIV in clinical practice. This article reviews the presentation, diagnosis, and management of the most common neurologic conditions associated with HIV infection and ART.

Diagnosis and Management of Central Nervous System Cryptococcal Infections in HIV-Infected Adults

Cryptococcal meningitis persists as a significant source of morbidity and mortality in persons with HIV/AIDS, particularly in sub-Saharan Africa. Despite increasing access to antiretrovirals, persons presenting with advanced HIV disease remains common, and Cryptococcus remains the most frequent etiology of adult meningitis. We performed a literature review and herein present the most up-to-date information on the diagnosis and management of cryptococcosis. Recent advances have dramatically improved the accessibility of timely and affordable diagnostics. The optimal initial antifungal management has been newly updated after the completion of a landmark clinical trial. Beyond antifungals, the control of intracranial pressure and mitigation of toxicities remain hallmarks of effective treatment. Cryptococcal meningitis continues to present challenging complications and continued research is needed.

Immune Reconstitution Disorders: Spotlight on Interferons

Three decades of research in hematopoietic stem cell transplantation and HIV/AIDS fields have shaped a picture of immune restoration disorders. This manuscript overviews the molecular biology of interferon networks, the molecular pathogenesis of immune reconstitution inflammatory syndrome, and post-hematopoietic stem cell transplantation immune restoration disorders (IRD). It also summarizes the effects of thymic involution on T cell diversity, and the results of the assessment of diagnostic biomarkers of IRD, and tested targeted immunomodulatory treatments.

HIV-Associated Cryptococcal Immune Reconstitution Inflammatory Syndrome Is Associated with Aberrant T Cell Function and Increased Cytokine Responses

Cryptococcal meningitis remains a significant opportunistic infection among HIV-infected patients, contributing 15-20% of HIV-related mortality. A complication of initiating antiretroviral therapy (ART) following opportunistic infection is immune reconstitution inflammatory syndrome (IRIS). IRIS afflicts 10-30% of HIV-infected patients with cryptococcal meningitis (CM), but its immunopathogenesis is poorly understood. We compared circulating T cell memory subsets and cytokine responses among 17 HIV-infected Ugandans with CM: 11 with and 6 without CM-IRIS. At meningitis diagnosis, stimulation with cryptococcal capsule component, glucuronoxylomannan (GXM) elicited consistently lower frequencies of CD4⁺ and CD8⁺ T cell memory subsets expressing intracellular cytokines (IL-2, IFN-γ, and IL-17) among subjects who subsequently developed CM-IRIS. After ART initiation, T cells evolved to show a decreased CD8⁺ central memory phenotype. At the onset of CM-IRIS, stimulation more frequently generated polyfunctional IL-2⁺/IL-17⁺ CD4⁺ T cells in patients with CM-IRIS. Moreover, CD8⁺ central and effector memory T cells from CM-IRIS subjects also demonstrated more robust IL-2 responses to antigenic stimulation vs. controls. Thus, ART during CM elicits distinct differences in T cell cytokine production in response to cryptococcal antigens both prior to and during the development of IRIS, suggesting an immunologic foundation for the development of this morbid complication of CM infection.

Cryptococcosis in solid organ transplantation-Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the diagnosis, prevention, and management of cryptococcosis in the pre- and post-transplant period. The current update now includes a discussion of cryptococcosis, which is the third most common invasive fungal infection in SOT recipients. Infection often occurs a year after transplantation; however, early infections occur and donor-derived infections have been described within 3 months after transplant. There are two main species that cause infection, Cryptococcus neoformans and C gattii. Clinical onset may be insidious, but headaches, fevers, and mental status changes should warrant diagnostic testing. The lateral flow cryptococcal antigen assay is now the preferred test from serum and cerebrospinal fluid due to its rapidity, accuracy, and cost. A lumbar puncture with measurement of opening pressure is recommended for patients with suspected or proven cryptococcosis. Lipid amphotericin B plus 5-flucytosine is used as initial treatment of meningitis, disseminated infection, and moderate-to-severe pulmonary infection, followed by fluconazole as consolidation therapy. Fluconazole is effective for mild-to-moderate pulmonary infection. Immunosuppression reduction as part of management may lead to immune reconstitution syndrome that may resemble active disease.

Association Between Plasma Antibody Responses and Risk for Cryptococcus-Associated Immune Reconstitution Inflammatory Syndrome

Background

Initiation of antiretroviral therapy (ART) in human immunodeficiency virus (HIV)-infected individuals with cryptococcal meningitis places them at risk for Cryptococcus-associated immune reconstitution inflammatory syndrome (C-IRIS). The relationship between antibody immunity and C-IRIS risk has not been investigated.

Methods

We compared plasma levels of immunoglobulins, C. neoformans glucuronoxylomannan (GXM) capsule-specific and laminarin (Lam)-binding IgM and IgG, and percentages of peripheral blood total and memory B cells between 27 HIV-infected patients with CM who developed C-IRIS and 63 who did not, and evaluated associations of these parameters with risk of C-IRIS.

Results

Prior to initiation of ART, plasma IgM, Lam-binding IgM (Lam-IgM), Lam-IgG, and GXM-IgM levels were significantly lower in patients who developed C-IRIS than those who did not. Multivariate analysis revealed significant inverse associations between C-IRIS and IgM (P = .0003), Lam-IgM (P = .0005), Lam-IgG (P = .002), and GXM-IgM (P = .002) independent of age, sex, HIV viral load, CD4+ T-cell count, and cerebrospinal fluid fungal burden. There were no associations between C-IRIS and total or memory B cells.

Discussion

Antibody profiles that include plasma IgM, Lam-IgM, Lam-IgG, and/or GXM-IgM may have value in furthering our understanding of C-IRIS pathogenesis and hold promise as candidate biomarkers of C-IRIS risk.

Yeast Infections in Solid Organ Transplantation

Invasive candidiasis (IC) remains the most common invasive fungal infection following solid-organ transplant (SOT), but risk factors are evolving. Current challenges include infection due to drug resistant non-albicans and emerging novel species such as Candida auris. Preventive antifungal use in SOT needs to be re-examined in light of these current challenges. Cryptococcosis is the second most common IFI following SOT. Cryptococcus gattii is an emerging pathogen that can have reduced in-vitro susceptibility to antifungal agents. Cryptococcus associated IRIS in SOT is a clinical entity that warrants heightened awareness for timely recognition and management.

Understanding Pathogenesis and Care Challenges of Immune Reconstitution Inflammatory Syndrome in Fungal Infections

Immune deficiency of diverse etiology, including human immunodeficiency virus (HIV), antineoplastic agents, immunosuppressive agents used in solid organ recipients, immunomodulatory therapy, and other biologics, all promote invasive fungal infections. Subsequent voluntary or unintended immune recovery may induce an exaggerated inflammatory response defining immune reconstitution inflammatory syndrome (IRIS), which causes significant mortality and morbidity. Fungal-associated IRIS raises several diagnostic and management issues. Mostly studied with Cryptococcus, it has also been described with other major fungi implicated in human invasive fungal infections, such as Pneumocystis, Aspergillus, Candida, and Histoplasma. Furthermore, the understanding of IRIS pathogenesis remains in its infancy. This review summarizes current knowledge regarding the clinical characteristics of IRIS depending on fungal species and existing strategies to predict, prevent, and treat IRIS in this patient population, and tries to propose a common immunological background to fungal IRIS.

Shedding light on IRIS: from Pathophysiology to Treatment of Cryptococcal Meningitis and Immune Reconstitution Inflammatory Syndrome in HIV-Infected Individuals

OBJECTIVES

The aim of this work was to review current treatment options and propose alternatives for immune reconstitution inflammatory syndrome (IRIS) in HIV-infected individuals with cryptococcal meningitis (CM) (termed 'HIV-CM IRIS'). As a consequence of the immunocompromised state of these individuals, the initial immune response to CM is predominantly type 2 T helper (Th2) /Th17 rather than Th1, leading to inefficient fungal clearance at the time of antiretroviral initiation, and a subsequent overexaggeration of the Th1 response and life-threatening IRIS development.

METHODS

An article-based and clinical trial-based search was conducted to investigate HIV-CM IRIS pathophysiology and current treatment practices.

RESULTS

Guidelines for CM treatment, based on the Cryptococcal Optimal Antiretroviral Timing (COAT) trial, recommend delayed antiretroviral therapy (ART) following antifungal treatment. The approach aims to decrease fungal burden and allow immune balance restoration prior to ART initiation. If the initial immune balance is not restored, the fungal burden is not sufficiently reduced and there is a risk of developing IRIS post-ART, highlighted by a Th1 immune overcompensation, leading to increased mortality. The mainstay treatment for Th1-biased IRIS is corticosteroids; however, this treatment has been shown to correlate with increased mortality and significant associated adverse events. We emphasize targeting a more specific Th1 mechanism via the tumour necrosis factor (TNF)-α cytokine antagonist thalidomide, as it is the only TNF-α antagonist currently approved for use in infectious disease settings and has been shown to decrease Th1 overreaction, restoring immune balance in HIV-CM IRIS.

CONCLUSIONS

Although the side effects and limitations of thalidomide must be considered, it is currently being successfully used in infectious disease settings and warrants mainstream application as a therapeutic option for treatment of IRIS in HIV-infected patients with CM.

Ischemic stroke as a complication of cryptococcal meningitis and immune reconstitution inflammatory syndrome: a case report

Background

Cryptococcal meningitis remains the leading cause of adult meningitis in Sub-Saharan Africa. Immune Reconstitution Inflammatory Syndrome (IRIS) following anti-retroviral therapy (ART) initiation is an important complication. Here we report the first documented case of a IRIS reaction presenting as an ischemic stroke.

Case presentation

A 38 year old newly diagnosed HIV-infected, ART naive Malawian male presented to a tertiary referral hospital in Blantyre, Malawi with a 2 week history of headache. A diagnosis of cryptococcal meningitis was made and the patient was started on 1200 mg fluconazole once daily and flucytosine 25 mg/kg four times daily as part of the Advancing Cryptococcal Treatment for Africa (ACTA) clinical trial. There was an initial clinical and microbiological response to anti-fungal treatment and anti-retroviral therapy was started at week 4. The patient re-presented 16 days later with recurrence of headache, fever, and a sudden onset of left sided weakness in the context of rapid immune reconstitution; peripheral CD4 count had increased from a baseline of 29 cells/μl to 198 cells/μl. Recurrence of cryptococcal meningitis was excluded through CSF examination and fungal culture. Magnetic Resonance Imaging (MRI) of the brain demonstrated multi-focal DWI (diffusion weighted imaging) positive lesions consistent with an ischemic stroke. Given the temporal relationship to ART initiation, these MRI findings in the context of sterile CSF with raised CSF protein and a rapid immune reconstitution, following an earlier favorable response to treatment is most consistent with a paradoxical Immune Reconstitution Inflammatory Syndrome.

Conclusions

Stroke is an increasing cause of morbidity and mortality amongst HIV infected persons. Ischemic stroke is a recognized complication of cryptococcal meningitis in the acute phase and is thought to be mediated by an infectious vasculitis. This is the first time an ischemic stroke has been described as part of a paradoxical IRIS reaction. This report adds to the spectrum of clinical IRIS presentations recognized and highlights to clinicians the potential complications encountered at ART initiation in severely immunocompromised patients.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3386-0) contains supplementary material, which is available to authorized users.

The Damage-Response Framework as a Tool for the Physician-Scientist to Understand the Pathogenesis of Infectious Diseases

The Damage-Response Framework (DRF) is a powerful tool to inform research in infectious diseases. It can integrate clinical observation with microbiology and immunology to incorporate the role of the host response into the outcome of microbial pathogenesis. Although the role that microbial factors may play in the pathogenesis of infectious diseases is well recognized, the DRF brings the indispensable role of the host response to the fore. For example, inflammation may induce microbial control, but it can also produce host damage. On the other hand, insufficient inflammation may fail to induce sufficient microbial control. Each scenario may lead to the diagnosis of an infectious disease. Given the central role that the host response plays in the pathogenesis of infectious diseases, new strategies for treatment need to consider the nature of the host response as well as microbial factors.

Management of Human Immunodeficiency Virus in the Emergency Department

Over the past 30 years, significant advances have transformed the landscape of human immunodeficiency virus (HIV) care in the emergency department. Diagnosis and management of HIV has improved, resulting in a decline in the incidence of acquired immunodeficiency syndrome (AIDS)-defining infections. Advances in pharmacology have led to fewer serious medication toxicities and more tolerable regimens. Emergency providers have played an increasingly important role in HIV screening and diagnosis of acute infection. Provision of postexposure prophylaxis is expanding from a focus on occupational exposure to include all high-risk cases.

HIV-associated opportunistic CNS infections: pathophysiology, diagnosis and treatment

Nearly 30 years after the advent of antiretroviral therapy (ART), CNS opportunistic infections remain a major cause of morbidity and mortality in HIV-positive individuals. Unknown HIV-positive disease status, antiretroviral drug resistance, poor drug compliance, and recreational drug abuse are factors that continue to influence the morbidity and mortality of infections. The clinical and radiographic pattern of CNS opportunistic infections is unique in the setting of HIV infection: opportunistic infections in HIV-positive patients often have characteristic clinical and radiological presentations that can differ from the presentation of opportunistic infections in immunocompetent patients and are often sufficient to establish the diagnosis. ART in the setting of these opportunistic infections can lead to a paradoxical worsening caused by an immune reconstitution inflammatory syndrome (IRIS). In this Review, we discuss several of the most common CNS opportunistic infections: cerebral toxoplasmosis, progressive multifocal leukoencephalopathy (PML), tuberculous meningitis, cryptococcal meningitis and cytomegalovirus infection, with an emphasis on clinical pearls, pathological findings, MRI findings and treatment. Moreover, we discuss the risk factors, pathophysiology and management of IRIS. We also summarize the challenges that remain in management of CNS opportunistic infections, which includes the lack of phase II and III clinical trials, absence of antimicrobials for infections such as PML, and controversy regarding the use of corticosteroids for treatment of IRIS.

Transcriptomic Predictors of Paradoxical Cryptococcosis-Associated Immune Reconstitution Inflammatory Syndrome

Background

Paradoxical cryptococcosis-associated immune reconstitution inflammatory syndrome (C-IRIS) affects ~25% of human immunodeficiency virus (HIV)-infected patients with cryptococcal meningitis (CM) after they commence antiretroviral therapy (ART) resulting in significant morbidity and mortality. Genomic studies in cryptococcal meningitis and C-IRIS are rarely performed.

Methods

We assessed whole blood transcriptomic profiles in 54 HIV-infected subjects with CM who developed C-IRIS (27) and compared the results with control subjects (27) who did not experience neurological deterioration over 24 weeks after ART initiation. Samples were analyzed by whole genome microarrays.

Results

The predictor screening algorithms identified the low expression of the components of interferon-driven antiviral defense pathways, such as interferon-inducible genes, and higher expression of transcripts that encode granulocyte-dependent proinflammatory response molecules as predictive biomarkers of subsequent C-IRIS. Subjects who developed early C-IRIS (occurred within 12 weeks of ART initiation) were characterized by upregulation of biomarker transcripts involved in innate immunity such as the inflammasome pathway, whereas those with late C-IRIS events (after 12 weeks of ART) were characterized by abnormal upregulation of transcripts expressed in T, B, and natural killer cells, such as IFNG, IL27, KLRB1, and others. The AIM2, BEX1, and C1QB were identified as novel biomarkers for both early and late C-IRIS events.

Conclusions

An inability to mount effective interferon-driven antiviral immune response, accompanied by a systemic granulocyte proinflammatory signature, prior to ART initiation, predisposes patients to the development of C-IRIS. Although early and late C-IRIS have seemingly similar clinical manifestations, they have different molecular phenotypes (as categorized by bioinformatics analysis) and are driven by contrasting inflammatory signaling cascades.

Understanding mechanisms underlying the pathology of immune reconstitution inflammatory syndrome (IRIS) by using animal models

Purpose of Review

Despite the increasing number of clinical reports on immune reconstitution inflammatory syndrome (IRIS), mechanistic understanding of IRIS is still largely limited. The main focus of this review is to summarize animal studies, which were performed to better understand the cellular and molecular mechanisms underlying the pathology of IRIS.

Recent Findings

Three IRIS animal models have been reported. They are Mycobacterial IRIS (M-IRIS), cryptococcal IRIS (C-IRIS) and Pneumocystis-IRIS. M-IRIS animal model suggested that, rather than lymphopenia itself, the failure to clear the pathogen by T cells results in excessive priming of the innate immune system. If this happens before T cell reconstitution, hosts likely suffer IRIS upon T cell reconstitution. Interestingly, T cells specific to self-antigens, not only pathogen-specific, could drive IRIS as well.

Summary

The mechanism to develop IRIS is quite complicated, including multiple layers of host immune responses; the innate immune system that detects pathogens and prime host immunity, and the adaptive immune system that is reconstituted but hyper-activated particularly through CD4⁺ T cells. Animal models of IRIS, although there are still small numbers of studies available, have already provided significant insights on the mechanistic understanding of IRIS.

Regulated Release of Cryptococcal Polysaccharide Drives Virulence and Suppresses Immune Cell Infiltration into the Central Nervous System

Cryptococcus neoformans is a common environmental yeast and opportunistic pathogen responsible for 15% of AIDS-related deaths worldwide. Mortality primarily results from meningoencephalitis, which occurs when fungal cells disseminate to the brain from the initial pulmonary infection site. A key C. neoformans virulence trait is the polysaccharide capsule. Capsule shields C. neoformans from immune-mediated recognition and destruction. The main capsule component, glucuronoxylomannan (GXM), is found both attached to the cell surface and free in the extracellular space (as exo-GXM). Exo-GXM accumulates in patient serum and cerebrospinal fluid at microgram/milliliter concentrations, has well-documented immunosuppressive properties, and correlates with poor patient outcomes. However, it is poorly understood whether exo-GXM release is regulated or the result of shedding during normal capsule turnover. We demonstrate that exo-GXM release is regulated by environmental cues and inversely correlates with surface capsule levels. We identified genes specifically involved in exo-GXM release that do not alter surface capsule thickness. The first mutant, the liv7Δ strain, released less GXM than wild-type cells when capsule was not induced. The second mutant, the cnag_00658Δ strain, released more exo-GXM under capsule-inducing conditions. Exo-GXM release observed in vitro correlated with polystyrene adherence, virulence, and fungal burden during murine infection. Additionally, we found that exo-GXM reduced cell size and capsule thickness under capsule-inducing conditions, potentially influencing dissemination. Finally, we demonstrated that exo-GXM prevents immune cell infiltration into the brain during disseminated infection and highly inflammatory intracranial infection. Our data suggest that exo-GXM performs a distinct role from capsule GXM during infection, altering cell size and suppressing inflammation.