Post-infectious inflammatory response syndrome (PIIRS): Dissociation of T-cell-macrophage signaling in previously healthy individuals with cryptococcal fungal meningoencephalitis

Postpartum cryptococcosis in an HIV-negative patient

PURPOSE AND METHODS

We present an unusual case of an HIV-negative patient with postpartum pulmonary cryptococcosis and cryptococcemia.

RESULTS

The diagnostic methods and treatment of cryptococcosis in a postpartum patient are presented in this case report. Due to anaphylaxis to liposomal amphotericin B, desensitisation to the drug was performed.

CONCLUSION

We would like to raise awareness about rare infections such as cryptococcosis in pregnancy and the postpartum period. In addition, we were able to document a successful desensitisation to liposomal amphotericin B.

Immunological Predictors of Post Infectious Inflammatory Response Syndrome in HIV-Negative Immunocompetent Cryptococcal Meningitis

Objective

This research aims to study the correlation between serum immune factors and post-infectious inflammatory response syndrome (PIIRS) in immunocompetent cryptococcal meningitis (CM), and explore whether serum immune factors could be used to predict the development of PIIRS.

Methods

A cohort of 30 patients with PIIRS and 87 patients without PIIRS was selected from 347 CM patients. We analyzed the general clinical information and immunological indexes (cytokines, complement, immunoglobulin, inflammation, related cytological and biochemical indexes). Spearman correlation analysis and principal component analysis were used to explore the effects of the variables on PIIRS. Additionally, the variables were identified by a random forest-based classifier for predicting the development of PIIRS. The clinical value of predictors was verified by survival analysis.

Results

Compared with patients without PIIRS, patients with PIIRS had lower baseline serum interleukin-6 (IL-6, P = 0.006), immunoglobulin M (IgM, P = 0.004), and a higher baseline neutrophil ratio (P <0.001). The baseline neutrophil ratio (r = 0.359, P = 0.001), IgM (r = −0.272, P = 0.025), and IL-6 (r = −0.259, P = 0.027) were significantly correlated with PIIRS. Combining principal component analysis and random forest results, neutrophil ratio, neutrophil count, IgM, IL-6, and D-dimer were useful predictors. The accuracy of random forest prediction was 75.00%, AUC, and sensitivity were 0.76 and 70%, respectively. Further survival analysis of the time from treatment to PIIRS revealed that the development of PIIRS was associated with IgM (more than 98 days of treatment) and neutrophil ratio/count.

Conclusion

Baseline neutrophils ratio, neutrophil count, IgM, IL-6, and D-dimer may be clinically useful predictors of PIIRS in HIV-negative immunocompetent CM patients.

Post-Infectious Inflammatory Response Syndrome in an HIV-Negative Immunocompetent Elderly Patient With Cryptococcal Meningitis: A Case Report and Literature Review

We report a previously healthy 82-year-old male with cryptococcal meningitis (CM) who represented neurological deterioration due to post-infectious inflammatory response syndrome (PIIRS) occurring in 4 months after initial antifungal therapy. He was treated with corticosteroids for 2 months and recovered clinically. However, the clinical manifestation, cerebrospinal fluid (CSF), and brain magnetic resonance imaging (MRI) results got worse again on the next day after corticosteroid withdrawal. The analysis of inflammatory cytokines and culture on CSF, as well as brain MRI, still suggested a diagnosis of PIIRS. Therefore, corticosteroid therapy was used again and he subsequently obtained a complete resolution of symptoms.

Fungal CNS Infections in Africa: The Neuroimmunology of Cryptococcal Meningitis

Cryptococcal meningitis (CM) is the leading cause of central nervous system (CNS) fungal infections in humans, with the majority of cases reported from the African continent. This is partly due to the high burden of HIV infection in the region and reduced access to standard-of-care including optimal sterilising antifungal drug treatments. As such, CM is responsible for 10-15% of all HIV-related mortality, with a large proportion being preventable. Immunity to the causative agent of CM, Cryptococcus neoformans, is only partially understood. IFNγ producing CD4⁺ T-cells are required for the activation of myeloid cells, especially macrophages, to enable fungal killing and clearance. However, macrophages may also act as a reservoir of the fungal yeast cells, shielding them from host immune detection thus promoting latent infection or persistent chronic inflammation. In this chapter, we review the epidemiology and pathogenesis of CNS fungal infections in Africa, with a major focus on CM, and the antifungal immune pathways operating to protect against C. neoformans infection. We also highlight the areas of research and policy that require prioritisation to help reduce the burden of CNS fungal diseases in Africa.

Cryptococcal Meningitis and Post-Infectious Inflammatory Response Syndrome in a Patient With X-Linked Hyper IgM Syndrome: A Case Report and Review of the Literature

The hyper IgM syndromes are a rare group of primary immunodeficiency. The X-linked Hyper IgM syndrome (HIGM), due to a gene defect in CD40L, is the commonest variant; it is characterized by an increased susceptibility to a narrow spectrum of opportunistic infection. A few cases of HIGM patients with Cryptococcal meningoencephalitis (CM) have been described in the literature. Herein we report the case of a young male diagnosed in infancy with HIGM who developed CM complicated by a post-infectious inflammatory response syndrome (PIIRS), despite regular immunoglobulin replacement therapy and appropriate antimicrobial prophylaxis. The patient was admitted because of a headache and CM was diagnosed through detection of Cryptococcus neoformans in the cerebrospinal fluid. Despite the antifungal therapy resulting to negative CSF culture, the patient exhibited persistent headaches and developed diplopia. An analysis of inflammatory cytokines on CSF, as well as the brain MRI, suggested a diagnosis of PIIRS. Therefore, a prolonged corticosteroids therapy was started obtaining a complete resolution of symptoms without any relapse.

Unexpected case of cryptococcal meningoencephalitis in a patient with long-standing well-controlled HIV infection

Cryptococcal meningoencephalitis (CM) classically occurs in individuals with advanced HIV infection, solid organ transplants, or other immunocompromising conditions. We report a case of fatal CM in a 78-year-old woman with well-controlled HIV infection who had delayed diagnosis, persistently elevated intracranial pressure and pleocytosis of the cerebrospinal fluid. Initial suspicion for CM was low due to her relatively high CD4⁺ T cell counts, which likely contributed to greater inflammation.

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.

Resistance and Tolerance to Cryptococcal Infection: An Intricate Balance That Controls the Development of Disease

Cryptococcus neoformans is a ubiquitous environmental yeast and a leading cause of invasive fungal infection in humans. The most recent estimate of global disease burden includes over 200,000 cases of cryptococcal meningitis each year. Cryptococcus neoformans expresses several virulence factors that may have originally evolved to protect against environmental threats, and human infection may be an unintended consequence of these acquired defenses. Traditionally, C. neoformans has been viewed as a purely opportunistic pathogen that targets severely immune compromised hosts; however, during the past decade the spectrum of susceptible individuals has grown considerably. In addition, the closely related strain Cryptococcus gattii has recently emerged in North America and preferentially targets individuals with intact immunity. In parallel to the changing epidemiology of cryptococcosis, an increasing role for host immunity in the pathogenesis of severe disease has been elucidated. Initially, the HIV/AIDS epidemic revealed the capacity of C. neoformans to cause host damage in the absence of adaptive immunity. Subsequently, the development and clinical implementation of highly active antiretroviral treatment (HAART) led to recognition of an immune reconstitution inflammatory syndrome (IRIS) in a subset of HIV+ individuals, demonstrating the pathological role of host immunity in disease. A post-infectious inflammatory syndrome (PIIRS) characterized by abnormal T cell-macrophage activation has also been documented in HIV-negative individuals following antifungal therapy. These novel clinical conditions illustrate the highly complex host-pathogen relationship that underlies severe cryptococcal disease and the intricate balance between tolerance and resistance that is necessary for effective resolution. In this article, we will review current knowledge of the interactions between cryptococci and mammalian hosts that result in a tolerant phenotype. Future investigations in this area have potential for translation into improved therapies for affected individuals.

CD4+ T Cells Orchestrate Lethal Immune Pathology despite Fungal Clearance during Cryptococcus neoformans Meningoencephalitis

Cryptococcus neoformans is a major fungal pathogen that disseminates to the central nervous system (CNS) to cause fatal meningoencephalitis, but little is known about immune responses within this immune-privileged site. CD4⁺ T cells have demonstrated roles in anticryptococcal defenses, but increasing evidence suggests that they may contribute to clinical deterioration and pathology in both HIV-positive (HIV+) and non-HIV patients who develop immune reconstitution inflammatory syndrome (IRIS) and post-infectious inflammatory response syndrome (PIIRS), respectively. Here we report a novel murine model of cryptococcal meningoencephalitis and a potential damaging role of T cells in disseminated cryptococcal CNS infection. In this model, fungal burdens plateaued in the infected brain by day 7 postinfection, but activation of microglia and accumulation of CD45^hi leukocytes was significantly delayed relative to fungal growth and did not peak until day 21. The inflammatory leukocyte infiltrate consisted predominantly of gamma interferon (IFN-γ)-producing CD4⁺ T cells, conventionally believed to promote fungal clearance and recovery. However, more than 50% of mice succumbed to infection and neurological dysfunction between days 21 and 35 despite a 100-fold reduction in fungal burdens. Depletion of CD4⁺ cells significantly impaired IFN-γ production, CD8⁺ T cell and myeloid cell accumulation, and fungal clearance from the CNS but prevented the development of clinical symptoms and mortality. These findings conclusively demonstrate that although CD4⁺ T cells are necessary to control fungal growth, they can also promote significant immunopathology and mortality during CNS infection. The results from this model may provide important guidance for development and use of anti-inflammatory therapies to minimize CNS injury in patients with severe cryptococcal infections.

CNS infection with the fungal pathogen Cryptococcus neoformans often results in debilitating brain injury and has a high mortality rate despite antifungal treatment. Treatment is complicated by the fact that immune responses needed to eliminate infection are also thought to drive CNS damage in a subset of both HIV+ and non-HIV patients. Thus, physicians need to balance efforts to enhance patients’ immune responses and promote microbiological control with anti-inflammatory therapy to protect the CNS. Here we report a novel model of cryptococcal meningoencephalitis demonstrating that fungal growth within the CNS does not immediately cause symptomatic disease. Rather, accumulation of antifungal immune cells critically mediates CNS injury and mortality. This model demonstrates that antifungal immune responses in the CNS can cause detrimental pathology and addresses the urgent need for animal models to investigate the specific cellular and molecular mechanisms underlying cryptococcal disease in order to better treat patients with CNS infections.