Long-term antibiotic exposure promotes mortality after systemic fungal infection by driving lymphocyte dysfunction and systemic escape of commensal bacteria.

Antibiotics are a modifiable iatrogenic risk factor for the most common human nosocomial fungal infection, invasive candidiasis, yet the underlying mechanisms remain elusive. We found that antibiotics enhanced the susceptibility to murine invasive candidiasis due to impaired lymphocyte-dependent IL-17A- and GM-CSF-mediated antifungal immunity within the gut. This led to non-inflammatory bacterial escape and systemic bacterial co-infection, which could be ameliorated by IL-17A or GM-CSF immunotherapy. Vancomycin alone similarly enhanced the susceptibility to invasive fungal infection and systemic bacterial co-infection. Mechanistically, vancomycin reduced the frequency of gut Th17 cells associated with impaired proliferation and RORγt expression. Vancomycin's effects on Th17 cells were indirect, manifesting only in vivo in the presence of dysbiosis. In humans, antibiotics were associated with an increased risk of invasive candidiasis and death after invasive candidiasis. Our work highlights the importance of antibiotic stewardship in protecting vulnerable patients from life-threatening infections and provides mechanistic insights into a controllable iatrogenic risk factor for invasive candidiasis.

An Acquired and Endogenous Glycocalyx Forms a Bidirectional "Don't Eat" and "Don't Eat Me" Barrier to Phagocytosis.

Macrophages continuously survey their environment in search of pathogens or apoptotic corpses or debris. Targets intended for clearance expose ligands that initiate their phagocytosis ("eat me" signals), while others avoid phagocytosis by displaying inhibitory ligands ("don't eat me" signals). We report that such ligands can be obscured by the glycosaminoglycans and glycoproteins that coat pathogenic as well as malignant phagocytic targets. In addition, a reciprocal barrier of self-synthesized or acquired glycocalyx components on the macrophage surface shrouds phagocytic receptors, curtailing their ability to engage particles. The coating layers of macrophages and their targets hinder phagocytosis by both steric and electrostatic means. Their removal by enzymatic means is shown to markedly enhance phagocytic efficiency. In particular, we show that the removal of mucins, which are overexpressed in cancer cells, facilitates their clearance. These results shed light on the physical barriers that modulate phagocytosis, which have been heretofore underappreciated. VIDEO ABSTRACT.

IL-17C/IL-17RE: Emergence of a Unique Axis in TH17 Biology.

Therapeutic targeting of IL-17A and its receptor IL-17RA with antibodies has turned out to be a tremendous success in the treatment of several autoimmune conditions. As the IL-17 cytokine family consists of six members (IL-17A to F), it is intriguing to elucidate the biological function of these five other molecules to identify more potential targets. In the past decade, IL-17C has emerged as quite a unique member of this pro-inflammatory cytokine group. In contrast to the well-described IL-17A and IL-17F, IL-17C is upregulated at very early timepoints of several disease settings. Also, the cellular source of the homodimeric cytokine differs from the other members of the family: Epithelial rather than hematopoietic cells were identified as the producers of IL-17C, while its receptor IL-17RE is expressed on TH17 cells as well as the epithelial cells themselves. Numerous investigations led to the current understanding that IL-17C (a) maintains an autocrine loop in the epithelium reinforcing innate immune barriers and (b) stimulates highly inflammatory TH17 cells. Functionally, the IL-17C/RE axis has been described to be involved in the pathogenesis of several diseases ranging from infectious and autoimmune conditions to cancer development and progression. This body of evidence has paved the way for the first clinical trials attempting to neutralize IL-17C in patients. Here, we review the latest knowledge about identification, regulation, and function of the IL-17C/IL-17receptor E pathway in inflammation and immunity, with a focus on the mechanisms underlying tissue injury. We also discuss the rationale for the translation of these findings into new therapeutic approaches in patients with immune-mediated disease.

Chronic Disseminated Candidiasis During Hematological Malignancies: An Immune Reconstitution Inflammatory Syndrome With Expansion of Pathogen-Specific T Helper Type 1 Cells.

BACKGROUND: Chronic disseminated candidiasis (CDC) is a rare disease that mostly occurs after chemotherapy-induced prolonged neutropenia in patients with hematological malignancies. It is believed to ensue from Candida colonization, breach of the intestinal epithelial barrier, and venous translocation to organs. Fungal blood or liver biopsy cultures are generally negative, suggesting the absence of an ongoing invasive fungal disease. METHODS: To unravel the contribution of the immune system to CDC pathogenesis, we undertook a prospective multicentric exploratory study in 44 CDC patients at diagnosis and 44 matched controls. RESULTS: Analysis of Candida-specific T-cell responses using enzyme-linked immunospot assays revealed higher numbers of interferon (IFN)γ-producing T cells reactive to mp65 or candidin in 27 CDC cases compared with 33 controls. Increased plasma levels of soluble CD25, interleukin (IL)-6, IL-1ß, tumor necrosis factor-α, and IL-10 and lower levels of IL-2 were observed in CDC patients versus controls. Neutrophilia and higher levels of CD4 and CD8 T-cell activation were found in CDC patients as well as increased proportions of CXCR3-expressing TCRγδ +Vδ2+ cells. CONCLUSIONS: The expansion of Candida-specific IFNγ-producing T cells together with features of T-cell activation and systemic inflammation identified here support the view that CDC belongs to the broad spectrum of fungal-associated immune reconstitution inflammatory syndromes.

Candida-reactive T cells for the diagnosis of invasive Candida infection of the lumbar vertebral spine.

Invasive Candida infection is the fourth most common bloodstream infection. Blood cultures are the current gold standard diagnostic method, however, false negatives remain a clinical challenge. We developed a new technique measuring Candida-reactive T cells as diagnostic read-out for invasive Candida infection. In a pilot study, we followed the treatment course of a patient with an invasive Candida infection of the lumbar vertebral spine. We present the case of a 56-year-old patient with HIV-associated Burkitt lymphoma who developed septic shock during chemotherapy-induced neutropenia. For the first time, we provide flow cytometry-based diagnostics with Candida-reactive T cells for invasive candidiasis with comprehensive MRI imaging. The Candida-reactive T cell assay has potential to complement current diagnostic assays for invasive Candida infection and thus to support targeted treatment.

Opportunistic Fungal Infections in Critical Care Units.

Fungal infections are rare compared with bacterial infections, but they are on the increase in critical care units. Diagnosis can be difficult, resulting in increased mortality. Immunocompromised patients are at higher risk for fungal infections, including organ transplant, oncology, and HIV/AIDS patients. Fatigue and fever are common symptoms that require critical care nurses to remain vigilant in assessment to identify at-risk patients and promote use of timely cultures and appropriate treatments for fungal infections. Critical care nurses can contribute to decreasing risk for fungal infections by controlling glucose levels, decreasing the use of invasive lines, and preventing unnecessary antibiotic use.

Immunological Identification of Fungal Species.

Immunodetection is described in this chapter as a technique for producing specific antibodies for antigen detection of the major human fungal pathogens. In the case of Candida spp., heat-killed cells are used to immunize mice over a couple of weeks and then splenocytes are isolated and further fused with myelomas to easily propagate the antibodies produced in the mice. The resulting antibodies follow a purification process where antibody levels and concentrations are determined. Fungal cells are also lysed to obtain whole cell extracts as a prior step for identification of antigens using immunoprecipitation. Finally, this method permits the production of specific antibodies against fungi and the identification of the respective antigens in an in vivo model.

Reduced PICD in Monocytes Mounts Altered Neonate Immune Response to Candida albicans.

BACKGROUND: Invasive fungal infections with Candida albicans (C. albicans) occur frequently in extremely low birthweight (ELBW) infants and are associated with poor outcome. Phagocytosis of C.albicans initializes apoptosis in monocytes (phagocytosis induced cell death, PICD). PICD is reduced in neonatal cord blood monocytes (CBMO). HYPOTHESIS: Phagocytosis of C. albicans causes PICD which differs between neonatal monocytes (CBMO) and adult peripheral blood monocytes (PBMO) due to lower stimulation of TLR-mediated immune responses. METHODS: The ability to phagocytose C. albicans, expression of TLRs, the induction of apoptosis (assessment of sub-G1 and nick-strand breaks) were analyzed by FACS. TLR signalling was induced by agonists such as lipopolysaccharide (LPS), Pam3Cys, FSL-1 and Zymosan and blocked (neutralizing TLR2 antibodies and MYD88 inhibitor). RESULTS: Phagocytic indices of PBMO and CBMO were similar. Following stimulation with agonists and C. albicans induced up-regulation of TLR2 and consecutive phosphorylation of MAP kinase P38 and expression of TNF-α, which were stronger on PBMO compared to CBMO (p < 0.005). Downstream, TLR2 signalling initiated caspase-3-dependent PICD which was found reduced in CBMO (p < 0.05 vs PBMO). CONCLUSION: Our data suggest direct involvement of TLR2-signalling in C. albicans-induced PICD in monocytes and an alteration of this pathway in CBMO.

Invasive fungal sinusitis in the pediatric population: Systematic review with quantitative synthesis of the literature.

BACKGROUND: Invasive fungal sinusitis (IFS) represents an often fatal condition within the pediatric population. In an effort to characterize demographics, treatment modalities, and prognostic factors, we performed a systematic review. METHODS: We systematically reviewed EMBASE, Medline, TRIPdatabase, SCOPUS and the Cochrane database for invasive fungal nasal and sinus infections limited to individuals <18 years of age. Case series including 3 or more patients were included. Demographics, treatment and outcomes were analyzed using R Gui statistical software. RESULTS: Twelve studies met inclusion criteria (103 patients). There was male preponderance of 48.5% with median age of 11 years old. Majority of patients had underlying leukemia (44.6%). Aspergillus was the predominant organism (47%). Isolated nasal findings occurred in 14% of patients and nasal findings occurred in 49% overall. Absolute neutrophil count (ANC) of immunocompromised patients was below 600 in most patients (99%). Average and median length of neutropenia was 2 weeks. All patients were prescribed amphoterocin with 50% as single medicinal therapy. Surgery occurred in 82.8% of cases. The mortality rate was 46%. Univariate analysis identified presenting with facial pain as a negative predictor of overall mortality (OR 0.296, 95% CI: 0.104-0.843, p < 0.05). CONCLUSION: Mortality remains high in pediatric patients with IFS. An ANC of <600 occurred in the majority of immunocompromised patients at a duration of 2 weeks. Presenting with facial pain was a negative predictor of mortality. Many studies label this condition as invasive fungal sinusitis; however, approximately one seventh presented with only nasal findings and half overall had nasal involvement.

Targeting CBLB as a potential therapeutic approach for disseminated candidiasis.

Disseminated candidiasis has become one of the leading causes of hospital-acquired blood stream infections with high mobility and mortality. However, the molecular basis of host defense against disseminated candidiasis remains elusive, and treatment options are limited. Here we report that the E3 ubiquitin ligase CBLB directs polyubiquitination of dectin-1 and dectin-2, two key pattern-recognition receptors for sensing Candida albicans, and their downstream kinase SYK, thus inhibiting dectin-1- and dectin-2-mediated innate immune responses. CBLB deficiency or inactivation protects mice from systemic infection with a lethal dose of C. albicans, and deficiency of dectin-1, dectin-2, or both in Cblb(-/-) mice abrogates this protection. Notably, silencing the Cblb gene in vivo protects mice from lethal systemic C. albicans infection. Our data reveal that CBLB is crucial for homeostatic control of innate immune responses mediated by dectin-1 and dectin-2. Our data also indicate that CBLB represents a potential therapeutic target for protection from disseminated candidiasis.

Inhibition of CBLB protects from lethal Candida albicans sepsis.

Fungal infections claim an estimated 1.5 million lives each year. Mechanisms that protect from fungal infections are still elusive. Recognition of fungal pathogens relies on C-type lectin receptors (CLRs) and their downstream signaling kinase SYK. Here we report that the E3 ubiquitin ligase CBLB controls proximal CLR signaling in macrophages and dendritic cells. We show that CBLB associates with SYK and ubiquitinates SYK, dectin-1, and dectin-2 after fungal recognition. Functionally, CBLB deficiency results in increased inflammasome activation, enhanced reactive oxygen species production, and increased fungal killing. Genetic deletion of Cblb protects mice from morbidity caused by cutaneous infection and markedly improves survival after a lethal systemic infection with Candida albicans. On the basis of these findings, we engineered a cell-permeable CBLB inhibitory peptide that protects mice from lethal C. albicans infections. We thus describe a key role for Cblb in the regulation of innate antifungal immunity and establish a novel paradigm for the treatment of fungal sepsis.

Broad defects in the energy metabolism of leukocytes underlie immunoparalysis in sepsis.

The acute phase of sepsis is characterized by a strong inflammatory reaction. At later stages in some patients, immunoparalysis may be encountered, which is associated with a poor outcome. By transcriptional and metabolic profiling of human patients with sepsis, we found that a shift from oxidative phosphorylation to aerobic glycolysis was an important component of initial activation of host defense. Blocking metabolic pathways with metformin diminished cytokine production and increased mortality in systemic fungal infection in mice. In contrast, in leukocytes rendered tolerant by exposure to lipopolysaccharide or after isolation from patients with sepsis and immunoparalysis, a generalized metabolic defect at the level of both glycolysis and oxidative metabolism was apparent, which was restored after recovery of the patients. Finally, the immunometabolic defects in humans were partially restored by therapy with recombinant interferon-γ, which suggested that metabolic processes might represent a therapeutic target in sepsis.

Specificity of mannan antigen and anti-mannan antibody screening in patients with haematological malignancies at risk for fungal infection.

Combination of mannan antigen and anti-mannan antibody (Mn/A-Mn) testing has been reported a useful and specific strategy for diagnosis of invasive Candida infections (ICIs). We evaluated Mn/A-Mn as a screening tool in patients with haematological malignancies. This clinical prospective study was performed at the Division of Hematology, Medical University Graz, Austria between July and December 2012. Patients at risk for fungal infection were included into the study and twice weekly screened by Mn/A-Mn testing, yielding 650 samples. Of overall 67 patients 66 had no evidence for ICI. From those, 153/640 serum samples (23.9%) were positive for mannan Ab, and nine (1.4%) for Ag. Most false positive Ab results were observed among 375 samples from patients without haematopoietic stem cell transplantation (34.9% resulted positive). Combined specificity of Mn/A-Mn was 74.8%. Of 10 samples obtained in the single patient with candidemia, five were positive for mannan Ag (from the day of diagnosis up to 40 days after detection of candidemia) and none for Ab. In conclusion, mannan Ab screening yielded a high number of false positive results. While mannan Ag was found to be highly specific and may have potential for diagnostic driven testing, mannan Ab testing cannot be recommended based on our study results.

Common invasive fungal diseases: an overview of invasive candidiasis, aspergillosis, cryptococcosis, and Pneumocystis pneumonia.

Every year, Candida, Aspergillus, Cryptococcus and Pneumocystis infect an estimated two million individuals worldwide. Most are immunocompromised or critically ill. Candida is the most common fungal pathogen of the critically ill and of recipients of transplanted abdominal organs. In high-risk haemato-oncological patients, in contrast, the introduction of antifungal prophylaxis with fluconazole and later with mould-active posaconazole has led to a remarkable reduction of invasive candidiasis and is likely to have a similar effect on invasive aspergillosis. Invasive aspergillosis remains the dominant invasive fungal disease (IFD) of haemato-oncological patients and solid-organ transplant recipients and is increasingly found in individuals with exacerbated chronic obstructive pulmonary disease on corticosteroids. In the developed world, owing to antiretroviral therapy Pneumocystis pneumonia and cryptococcosis have become rare in patients with human immunodeficiency virus (HIV) and are mainly found in solid-organ transplant recipients or immunocompromised patients. In the developing world, cryptococcosis remains a common and highly lethal disease of HIV positive individuals. With invasive candidiasis and invasive aspergillosis, timely diagnosis is the principal challenge. The clinical presentation is nonspecific and current diagnostic tests lack sensitivity and specificity. The combination of several tests improves sensitivity, but not specificity. Standardised polymerase chain-reaction-based assays may be promising tools for more rapid and specific diagnosis of candidiasis and invasive aspergillosis. Nevertheless, initiation of treatment is often based solely on clinical suspicion. Empirical therapy, however, may lead to over-treatment of patients without IFD or it may miss its target in the case of resistance. Despite the success of antifungal prophylaxis in reducing the incidence of IFDs in haemato-oncological patients, there are a considerable number of breakthrough infections demonstrating not only fungal resistance but also the emergence of rare and often lethal fungal pathogens. Knowledge of the local epidemiology and antifungal resistance is therefore pivotal. Current trial-based guidelines leave major gaps in identifying those most at risk, who may benefit from prophylaxis. Ongoing searches for disease-associated genetic polymorphisms may contribute to the establishment of individual risk profiles and targeted prophylaxis.

Impaired RASGRF1/ERK-mediated GM-CSF response characterizes CARD9 deficiency in French-Canadians.

BACKGROUND: Caspase recruitment domain-containing protein 9 (CARD9) deficiency is an autosomal recessive primary immunodeficiency conferring human susceptibility to invasive fungal disease, including spontaneous central nervous system candidiasis (sCNSc). However, clinical characterization of sCNSc is variable, hindering its recognition. Furthermore, an in-depth understanding of the bases for this susceptibility has remained elusive. OBJECTIVES: We sought to comprehensively characterize sCNSc and to dissect the mechanisms by which a hypomorphic CARD9 mutation causes susceptibility to Candida species. METHODS: We describe the clinical and radiologic findings of sCNSc caused by CARD9 deficiency in a French-Canadian cohort. We performed genetic, cellular, and molecular analyses to further decipher its pathophysiology. RESULTS: In our French-Canadian series (n = 4) sCNSc had onset in adulthood (median, 38 years) and was often misinterpreted radiologically as brain malignancies; 1 patient had additional novel features (eg, endophthalmitis and osteomyelitis). CARD9 deficiency resulted from a hypomorphic p.Y91H mutation and allelic imbalance established in this population through founder effects. We demonstrate a consistent cellular phenotype of impaired GM-CSF responses. The ability of CARD9 to complex with B-cell CLL/lymphoma 10 (BCL10) and mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) is intact in our series, arguing against its involvement in susceptibility to fungi. Instead, we show that the p.Y91H mutation impairs the ability of CARD9 to complex with Ras protein-specific guanine nucleotide-releasing factor 1 (RASGRF1), leading to impaired activation of nuclear factor κB and extracellular signal-regulated kinase (ERK) in monocytes and subsequent GM-CSF responses. Successful treatment of a second patient with adjunctive GM-CSF bolsters the clinical relevance of these findings. CONCLUSIONS: Hypomorphic CARD9 deficiency caused by p.Y91H results in adult-onset disease with variable penetrance and expressivity. Our findings establish the CARD9/RASGRF1/ERK/GM-CSF axis as critical to the pathophysiology of sCNSc.

Association of cytokine gene polymorphisms with susceptibility to invasive candidiasis.

The aim of this study was to investigate the role of cytokine genes in the susceptibility to Candida infection. A total of 275 consecutive patients diagnosed with Candida infection were selected between May 2010 and May 2011, along with 305 uninfected controls. Genotyping of the IL-1ß gene polymorphisms (IL1ß) rs1143634, IL1ßrs16944, IL8 rs4073, IL10 rs1800872, and IL10 rs1800896 was carried out using a 384-well plate format on the Sequenom MassARRAY platform. Patients with invasive Candida infections were more likely to have had an immunocompromised state, hematopoietic stem cell transplantation, solid organ transplant, solid tumor, chemotherapy within the past three months, neutropenia, surgery within the past 30 days, acute renal failure, liver failure, and/or median baseline serum creatinine. Conditional logistic regression analyses found that individuals with the rs1800896 GG genotype were associated with a higher risk of invasive Candida infections than those carrying the AA genotype (odds ratio = 0.61, 95% confidence interval = 0.37-0.94). From the results of this case-control study, we suggest that the cytokine IL-10 gene rs1800896 polymorphism might play a role in the etiology of invasive Candida infections.

Consensus guidelines for the treatment of yeast infections in the haematology, oncology and intensive care setting, 2014.

Pathogenic yeast forms are commonly associated with invasive fungal disease in the immunocompromised host, including patients with haematological malignancies and patients of haemopoietic stem cell transplants. Yeasts include the Candida spp., Cryptococcus spp., Pneumocystis jirovecii and some lesser-known pathogens. Candida species remain the most common cause of invasive yeast infections (and the most common human pathogenic fungi). These guidelines present evidence-based recommendations for the antifungal management of established, invasive yeast infections in adult and paediatric patients in the haematology/oncology setting. Consideration is also given to the critically ill patient in intensive care units, including the neonatal intensive care unit. Evidence for 'pre-emptive' or 'diagnostic-driven antifungal therapy' is also discussed. For the purposes of this paper, invasive yeast diseases are categorised under the headings of invasive candidiasis, cryptococcosis and uncommon yeast infections. Specific recommendations for the management of Pneumocystis jirovecii are presented in an accompanying article (see consensus guidelines by Cooley et al. appearing elsewhere in this supplement).

Breakthrough invasive fungal diseases during echinocandin treatment in high-risk hospitalized hematologic patients.

The frequency of breakthrough invasive fungal diseases (IFDs) during echinocandin therapy is unclear. We retrospectively analyzed 534 hematologic patients treated with echinocandin (caspofungin, N = 55; micafungin, N = 306; anidulafungin, N = 173). Four proven IFDs were found, caused by Candida parapsilosis (N = 2), C. parapsilosis and Candida glabrata (N = 1), and Fusarium species (N = 1). Four cases of possible IFDs were observed, all showing pulmonary infection. One case showed features suggestive of hepatosplenic candidiasis. Six of these eight cases had previously received the purine analog clofarabine. Breakthrough IFD during echinocandin treatment occurred infrequently (1.5 %), caused predominantly by Candida species. Clofarabine usage was an important risk factor.

CX3CR1-dependent renal macrophage survival promotes Candida control and host survival.

Systemic Candida albicans infection causes high morbidity and mortality and is associated with neutropenia; however, the roles of other innate immune cells in pathogenesis are poorly defined. Here, using a mouse model of systemic candidiasis, we found that resident macrophages accumulated in the kidney, the main target organ of infection, and formed direct contacts with the fungus in vivo mainly within the first few hours after infection. Macrophage accumulation and contact with Candida were both markedly reduced in mice lacking chemokine receptor CX3CR1, which was found almost exclusively on resident macrophages in uninfected kidneys. Infected Cx3cr1-/- mice uniformly succumbed to Candida-induced renal failure, but exhibited clearance of the fungus in all other organs tested. Renal macrophage deficiency in infected Cx3cr1-/- mice was due to reduced macrophage survival, not impaired proliferation, trafficking, or differentiation. In humans, the dysfunctional CX3CR1 allele CX3CR1-M280 was associated with increased risk of systemic candidiasis. Together, these data indicate that CX3CR1-mediated renal resident macrophage survival is a critical innate mechanism of early fungal control that influences host survival in systemic candidiasis.