Cryptococcal infection in non-HIV immunosuppressed patients - Three case reports in a nephrology setting

Unveiling new features of the human pathogen Cryptococcus neoformans through the reconstruction and exploitation of a dedicated genome-scale metabolic model

Cryptococcus neoformans is notorious for causing severe pulmonary and central nervous system infections, particularly in immunocompromised patients. High mortality rates, associated with its tropism and adaptation to the brain microenvironment and its drug resistance profile, make this pathogen a public health threat and a World Health Organization (WHO) priority. This study presents the first reconstructed genome-scale metabolic model (GSMM), iRV890, for C. neoformans var. grubii, which comprises 890 genes, 2598 reactions, and 2047 metabolites across four compartments. The GSMM iRV890 model was reconstructed using the open-source software tool merlin 4.0.2, is openly available in the well-established systems biology markup language (SBML) format and underwent validation using experimental data for specific growth and glucose consumption rates, and 222 nitrogen and carbon assimilation sources, with a 85 % prediction rate. Based on the comparison with GSMMs available for other pathogenic yeasts, unique metabolic features were predicted for C. neoformans, including key pathways shaping dynamics between C. neoformans and human host, as well as its underlying adaptions to the brain environment. Finally, the 96 predicted essential genes from the validated model are investigated as potential novel antifungal drug targets-including Erg4, Chs1, Fol1, and Fas1-which represent promising candidates for targeted drug development due to their absence in human cells.

Reconstruction and exploitation of a dedicated Genome-Scale Metabolic Model of the human pathogen C. neoformans

C. neoformans is notorious for causing severe pulmonary and central nervous system infections, particularly in immunocompromised patients. High mortality rates, associated with its tropism and adaptation to the brain microenvironment and its drug resistance profile, makes this pathogen a public health threat and a World Health Organization (WHO) priority. In this study, we reconstructed GSMM iRV890 for C. neoformans var. grubii , providing a promising platform for the comprehensive understanding of the unique metabolic features of C. neoformans , and subsequently shedding light on its complex tropism for the brain microenvironment and potentially informing the discovery of new drug targets. The GSMM iRV890 model is openly available in the SBML format, and underwent validation using experimental data for nitrogen and carbon assimilation, as well as specific growth and glucose consumption rates. Based on the comparison with GSMMs available for other pathogenic yeasts, unique metabolic features were predicted for C. neoformans , including key pathways shaping the dynamics between C. neoformans and the human host, and underlying its adaptation to the brain environment. Finally, predicted essential genes from the validated model are explored herein as potential novel antifungal drug targets.

'When Cryptococcus strikes and lupus is found': a unique covert unveiling of systemic lupus erythematosus presenting as subacute meningitis

Cryptococcal neoformans is a rare fungal pathogen that has been associated with immunocompromised individuals. Due to its rare occurrence, clinicians have a low index of suspicion for diagnosis, which can lead to increased morbidity and mortality. We present an 81-year-old fully functional woman with no known predisposing risk factors or previous immunocompromising conditions who was found to have cryptococcal meningitis on cerebrospinal fluid analysis in the setting of newly diagnosed uncontrolled type 2 diabetes and systemic lupus erythematosus (SLE).

Atypical Presentation of Pediatric Systemic Lupus Erythematosus Complicated by Cryptococcal Meningitis

Background

Cryptococcus is an opportunistic fungal pathogen that leads to life-threatening infections. Cryptococcal infections are mainly reported in HIV patients and less commonly encountered in non-HIV immunocompromised host. Cryptococcus neoformans (C. neoformans) is the most common Cryptococcus species causing diseases in humans which can be presented as pulmonary, meningitis, cutaneous, and/or disseminated cryptococcosis. Case Presentation. A 12-year-old female girl from Cairo, Egypt, presented to the pediatric hospital with signs of systemic lupus erythematosus (SLE). She had an aggressive lupus nephritis course for which corticosteroids, mycophenolate mofetil, and cyclophosphamide were prescribed, and the child gradually improved and was discharged. Two months later, the patient exhibited skin lesions involved both in her legs, massive ulcers were developed and extended rapidly through the entire legs followed by deterioration in her conscious level, and signs of meningitis were documented. Cerebrospinal fluid (CSF) examination and microbiological workup were confirmatory for C. neoformans infection, and mental and motor functions were rapidly deteriorated. Treatment with amphotericin B in addition to supportive treatment and close follow-up of the patient's medical condition result in obvious clinical improvement and patient discharge with minimal residual weakness in her legs after almost a one-month duration. After six months, the patient was brought to the emergency department complaining of repeated attacks of seizures, a lumbar puncture was performed, and culture results were again confirmatory for C. neoformans. An intensive course of antifungal therapy was prescribed which was successful, evident by resolution of the signs and symptoms of infection in addition to negative culture results and negative sepsis biomarkers. The child clinically improved, but unfortunately, gradual optic nerve degeneration and brain cell atrophy as a sequel of severe and longstanding cryptococcal infection resulted in her death after almost one year from her first attack.

Conclusion

Cryptococcal infection among non-HIV patients is a rare disease but can result in advanced medical complications which may be fatal. The disease should be suspected to be reliably diagnosed. Cryptococcus infection can be presented as a skin lesion which, if not treated properly at an earlier time, can result in dissemination and life-threatening consequences. Amphotericin B can be used effectively in cryptococcosis management in the settings where flucytosine is not available. Signs of cryptococcal meningitis can be manifested again after a period of remission and clinical cure which signifies the latency of Cryptococcus in the central nervous system. The second activation of Cryptococcus after its latency is usually life-threatening and mostly fatal.

Cryptococcus neoformans Induces MCP-1 Release and Delays the Death of Human Mast Cells

Cryptococcosis, caused by the basidiomycete Cryptococcus neoformans, is a life-threatening disease affecting approximately one million people per year worldwide. Infection can occur when C. neoformans cells are inhaled by immunocompromised people. In order to establish infection, the yeast must bypass recognition and clearance by immune cells guarding the tissue. Using in vitro infections, we characterized the role of mast cells (MCs) in cryptococcosis. We found that MCs recognize C. neoformans and release inflammatory mediators such as tryptase and cytokines. From the latter group MCs released mainly CCL-2/MCP-1, a strong chemoattractant for monocytic cells. We demonstrated that supernatants of infected MCs recruit monocytes but not neutrophils. During infection with C. neoformans, MCs have a limited ability to kill the yeast depending on the serotype. C. neoformans, in turn, modulates the lifespan of MCs both, by presence of its polysaccharide capsule and by secreting soluble modulators. Taken together, MCs might have important contributions to fungal clearance during early stages of cryptocococis where these cells regulate recruitment of monocytes to mucosal tissues.

Cryptococcosis in Renal Transplant Recipients: A Single-Center Experience

BACKGROUND

In solid organ transplant patients, 8% of invasive fungal infections are attributed to Cryptococcus. The aim of this study was to determine the frequency, risk factors, clinical characteristics, and outcome of kidney transplant recipients (TR) infected with Cryptococcus.

CASE SERIES

Between 2007 and 2014, a total of 500 kidney transplantations were performed at São João Hospital, in Porto, Portugal. Six infections by C. neoformans were reported, an incidence of 1.2% (3 disseminated, 2 meningeal, and 1 cutaneous). Patients were 65-72 years of age and 4 of 6 were male, compared with all kidney TR, among whom the mean age was 51.1 years and 60% were male. Three cases of crytococcosis occurred within the first 6 months after transplantation; 3 patients had cytomegalovirus infection and leukopenia, and 2 patients' immunosuppression had been increased in the last 6 months. Meningitis presented with headache, fever, and acute mental confusion; pulmonary involvement presented with respiratory insufficiency and infiltrative or nodular lung lesions; and cutaneous infections presented as cellulitis or skin abscess. Blood cultures for C. neoformans were positive in 3 cases; all of these patients had positive cryptococcal antigen of 1:128 to 1:8192. Five patients received liposomal amphotericin B for 9-21 days, followed by fluconazole. Four patients lost their grafts, and one patients died after a persistent vegetative state due to cryptococcal meningitis.

CONCLUSIONS

This small case series led to suspicion of an association between cryptococcosis and older age, renal dysfunction, cytomegalovirus infection, and intensification of immunosuppression after rejection episodes. In our series, cryptococcosis was associated with poor graft outcome.

Cryptococcal meningitis in systemic lupus erythematosus patients: pooled analysis and systematic review

Cryptococcal meningitis is an important fungal infection among systemic lupus erythematosus patients. We conducted a pooled analysis and systematic review to describe the epidemiological and clinical profile of cryptococcal meningitis in systemic lupus erythematosus patients. From two hospitals in China and nine literature databases, cases and prevalence data were collected for pooled analysis and meta-analysis, respectively. Categorical variables of cases were compared using a χ²-test on the statistical program of SAS. A multiple regression analysis was performed to ascertain independent predictors significantly correlated with prognosis. Meta-analysis was conducted by the statistical program of R. The prevalence of cryptococcal meningitis in systemic lupus erythematosus patients was 0.5%. Patients were predominantly females and adults. A prednisone equivalent of more than 30 mg/day before infection was associated with higher mortality (odds ratio (OR)=9.69 (1.54, 60.73)). In all, 36.8–38.9% patients showed low lupus activity when they developed the crytococcal infection. Moreover, 38.2% of the patients were misdiagnosed. The estimated case-fatality rate was 23.6%. Our results suggest that more emphasis should be placed to further understand lupus-related cryptococcal meningitis and to develop better prophylaxis and management strategies to combat this condition.

Pulmonary Cryptococcosis in HIV- sero-negative patients: case series from India

Pulmonary cryptococcosis is likely to be misdiagnosed due to relatively non-specific clinical and radiological features. It is more frequently associated with immuno-suppressed conditions especially acquired immuno-deficiency syndrome (AIDS) and pulmonary tuberculosis (PTB). Four cases of pulmonary cryptococcosis were diagnosed over a period of eleven years. All patients in this case series were human immune-deficiency virus (HIV)-negative. The predisposing factors in these patients were diabetes mellitus (DM), acute lymphoblastic leukaemia (ALL), post-partum and pregnancy in one each of the patients. Relapse was seen in two cases. All the patients survived due to strict follow-up. Pulmonary cryptococcosis is common in non-AIDS patients and it warrants rapid diagnosis, treatment and follow-up to prevent relapse.