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

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.

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.

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.

Unexpected exacerbation of cryptococcal meningitis after unilateral adrenalectomy in a PMAH patient: a case report and literature review

BACKGROUND

Primary bilateral macronodular adrenal hyperplasia (PMAH) combined with infection by an opportunistic pathogen is complicated. Clinical evidence on managing PMAH patients with infections by opportunistic pathogens is insufficient.

CASE PRESENTATION

A 66-year-old male was admitted with bilateral adrenal masses and was diagnosed with PMAH. Fever and disturbance of consciousness appeared after laparoscopic left adrenalectomy. Cryptococcal meningitis was confirmed by cerebrospinal fluid (CSF) culture. The exacerbation of his medical condition was suspected to result from immune reconstitution inflammatory syndrome (IRIS), and he had been treated with antifungal therapy and glucocorticoid replacement, but he responded poorly and eventually died of multiorgan failure. We summarized the clinical observations of 12 Cushing's syndrome (CS) patients infected by Cryptococcus. Seven out of nine patients who were treated for cryptococcus infection before receiving CS survived, while three patients treated for cryptococcus infection after CS treatment developed signs of IRIS and eventually died.

CONCLUSION

Cushing's syndrome, complicated with cryptococcal infection, has a high mortality rate, mainly when IRIS emerges. Carefully identifying the presence of the suspected infection, and controlling cryptococcal infection before removing the culprit adrenals could be the rational choice.

T cell infiltration into the brain triggers pulmonary dysfunction in murine Cryptococcus-associated IRIS

Cryptococcus-associated immune reconstitution inflammatory syndrome (C-IRIS) is a condition frequently occurring in immunocompromised patients receiving antiretroviral therapy. C-IRIS patients exhibit many critical symptoms, including pulmonary distress, potentially complicating the progression and recovery from this condition. Here, utilizing our previously established mouse model of unmasking C-IRIS (CnH99 preinfection and adoptive transfer of CD4⁺ T cells), we demonstrated that pulmonary dysfunction associated with the C-IRIS condition in mice could be attributed to the infiltration of CD4⁺ T cells into the brain via the CCL8-CCR5 axis, which triggers the nucleus tractus solitarius (NTS) neuronal damage and neuronal disconnection via upregulated ephrin B3 and semaphorin 6B in CD4⁺ T cells. Our findings provide unique insight into the mechanism behind pulmonary dysfunction in C-IRIS and nominate potential therapeutic targets for treatment.

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.

Cryptococcus escapes host immunity: What do we know?

Cryptococcus is an invasive fungus that seriously endangers human life and health, with a complex and well-established immune-escaping mechanism that interferes with the function of the host immune system. Cryptococcus can attenuate the host’s correct recognition of the fungal antigen and escape the immune response mediated by host phagocytes, innate lymphoid cells, T lymphocytes, B lymphocytes with antibodies, and peripheral cytokines. In addition, the capsule, melanin, dormancy, Titan cells, biofilm, and other related structures of Cryptococcus are also involved in the process of escaping the host’s immunity, as well as enhancing the ability of Cryptococcus to infect the host.

Outcome of Lenalidomide Treatment for Cognitive Impairment Caused by Immune Reconstitution Inflammatory Syndrome in Patients with HIV-Related Cryptococcal Meningitis

Purpose

Cognitive impairment associated with human immunodeficiency virus (HIV)-related cryptococcal meningitis (HCM) in the context of immune reconstitution inflammatory syndrome is difficult to address. This study was a follow-up of lenalidomide treatment outcomes in patients with HCM and cognitive impairment after complete cryptococcal clearance.

Patients and Methods

Seven HCM patients with neuroinflammation and cognitive impairment after complete cryptococcal clearance were enrolled in this prospective study. Neurocognitive assessment, clinical examination and cerebrospinal fluid (CSF) assays were performed before and after lenalidomide treatment.

Results

After lenalidomide treatment, the Montreal Cognitive Assessment [week (W) 0 (median [interquartile range]: 23.0 (13.0–24.0) vs W24: 26.0 (24.0–28.00), P=0.018] and International HIV Dementia Scale scores [W0: 9.0 (2.5–10.5) vs W24: 11.0 (10.00–12.0), P=0.028] improved significantly, mainly in the domain of memory function. There was no significant difference in the Center for Epidemiological Research Depression scores for anxiety and depression before and after treatment. Further stratified analyses revealed that the patients with cognitive improvement group had higher levels of CSF white blood cells [94.0 (44.0–180.0) vs 0 (0–1.5), P=0.032], CSF protein [4.9 (3.0–6.6) vs 0.6 (0.5–0.7), P=0.034], CSF albumin [318.5 (190.9–346.5) vs 33.5 (30.4–46.2), P=0.034], and CSF IgG [160.5 (73.8–256. 0) vs 4.7 (4.3–7.4), P=0.034] but a lower CSF glucose level [2.4 (2.0–2.7) vs 2.8 (2.8–3.9), P=0.032] than the patients with cognitive non-improvement group before treatment. CSF inflammatory cytokines of the growth-related oncogene, interleukin [IL]-10, granulocyte-colony stimulating factor, IL-6, IL-8, complement factor H, tumor necrosis factor-α, and α-2 macroglobulin were obviously decreased in patients with cognitive improvement group after lenalidomide treatment.

Conclusion

Lenalidomide potentially reduces cognitive impairment caused by immune reconstitution inflammatory syndrome in patients with HCM after cryptococcal clearance by inhibiting intracranial inflammation.

Multi-locus sequence typing reveals genotypic similarity in Nigerian Cryptococcus neoformans AFLP1/VNI of environmental and clinical origin

IntroductionPigeon droppings are among the major environmental sources of Cryptococcus neoformans AFLP1/VNI, from where the organism infects susceptible humans and animals resulting in cryptococcosis. Until now, C. neoformans AFLP1B/VNII was the only molecular type reported in Nigeria. Effective clinical treatment of this infection has occasionally been stymied by the emergence of antifungal non-susceptible, and resistant strains of C. neoformans AFLP1/VNI.Hypothesis/Gap StatementPigeon droppings harbour C. neoformans and HIV/AIDS patients are among the susceptible population to develop cryptococcal infection. Epidemiological data on cryptococcal prevalence is limited in Nigeria.AimTo investigate the environmental prevalence of C. neoformans in South-eastern Nigeria and compare the isolates with other lineages by using molecular and microbiological tools.MethodologyA total of 500 pigeon droppings and 300 blood samples of HIV/AIDS patients were collected, respectively, from five market squares and three tertiary healthcare centres within the Nsukka area of South-eastern Nigeria. The antifungal susceptibility of the C. neoformans isolates to amphotericin B, fluconazole, 5-fluorocytosine, itraconazole, voriconazole, posaconazole, and isavuconazole was investigated based on the CLSI M27-A3 protocol. Yeasts were identified by MALDI-TOF MS, thereafter Cryptococcus MLST was performed according to the International Society for Human and Animal Mycology (ISHAM) consensus scheme.Results C. neoformans was recovered from 6 (1.2 %) pigeon droppings and 6 (2 %) blood cultures of HIV/AIDS patients. Molecular analyses indicated that all cryptococcal isolates belong to serotype A and the AFLP1/VNI molecular type with sequence type (ST)32. Infection with C. neoformans was independent of sex and age of the patients investigated. All C. neoformans isolates were susceptible to the seven antifungal agents.ConclusionThis is the first report on the prevalence of C. neoformans AFLP1/VNI (ST32) in environmental and clinical samples from Nigeria. The antifungal susceptibility indicates that antifungal resistance by C. neoformans is yet a rare occurrence in Nigeria.