Neonatal innate immunity response in invasive candidiasis.

Infections caused by Candida spp. are frequent in critically hospitalized patients, especially among premature neonates, representing one of the most common healthcare-related infections. Although there is considerable production of current knowledge about the mechanisms of immune response, aspects involved in the newborn's innate defense are not fully understood. The aim of this study was to describe the innate immune mechanisms involved in the defense of neonates against invasive candidiasis. This is an integrative literature review from the Scopus, Scifinder, Medline, Web of Science databases and the electronic libraries ScienceDirect and Scielo, in the period between 2002 and 2020, with rescue based on primary descriptor Immunity Innate plus secondary descriptors Candidiasis Invasive AND Infant Newborn. We have observed the involvement of various mechanisms in the neonatal response against invasive candidiasis, including the recognition, signaling, recruitment, and initiation of an effective immune response. These mechanisms encompass the presence of antimicrobial peptides, phagocytosis, synthesis of reactive oxygen species, inflammatory mediators, and complex cell signaling systems mediated by Pattern Recognition Receptors (PRRs). With this study, it is expected to contribute to the expansion of knowledge about the immunological mechanisms involved in the innate immune response of the newborn against disseminated infections caused by Candida species, and in the same sense, highlight the importance of this knowledge as a reflex in the decrease in mortality in the neonatal period.

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.

Candida Cell-Surface-Specific Monoclonal Antibodies Protect Mice against Candida auris Invasive Infection.

Candida auris is a multidrug-resistant fungal pathogen that can cause disseminated bloodstream infections with up to 60% mortality in susceptible populations. Of the three major classes of antifungal drugs, most C. auris isolates show high resistance to azoles and polyenes, with some clinical isolates showing resistance to all three drug classes. We reported in this study a novel approach to treating C. auris disseminated infections through passive transfer of monoclonal antibodies (mAbs) targeting cell surface antigens with high homology in medically important Candida species. Using an established A/J mouse model of disseminated infection that mimics human candidiasis, we showed that C3.1, a mAb that targets ß-1,2-mannotriose (ß-Man3), significantly extended survival and reduced fungal burdens in target organs, compared to control mice. We also demonstrated that two peptide-specific mAbs, 6H1 and 9F2, which target hyphal wall protein 1 (Hwp1) and phosphoglycerate kinase 1 (Pgk1), respectively, also provided significantly enhanced survival and reduction of fungal burdens. Finally, we showed that passive transfer of a 6H1+9F2 cocktail induced significantly enhanced protection, compared to treatment with either mAb individually. Our data demonstrate the utility of ß-Man3- and peptide-specific mAbs as an effective alternative to antifungals against medically important Candida species including multidrug-resistant C. auris.

Impact of mTOR signaling pathway on CD8+ T cell immunity through Eomesodermin in response to invasive candidiasis.

BACKGROUND: We investigated the effect of the mammalian target of rapamycin (mTOR) pathway on CD8+ T cell immunity through Eomesodermin (Eomes) in intensive care unit (ICU) patients with invasive candidiasis (IC) and in a mouse model. METHODS: We evaluated quantitative changes in parameters of the mTOR/phosphorylated ribosomal S6 kinase (pS6K) pathway and immune system at the onset of infection in ICU patients. The study was registered on 28 February 2017 at chictr.org.cn (ChiCTR-ROC-17010750). We also used a mouse model of Candida infection and constructed T-cell-specific mTOR and T-cell-specific tuberous sclerosis complex (TSC) 1 conditional knockout mice to elucidate the molecular mechanisms. RESULTS: We enrolled 88 patients, including 8 with IC. The IC group had lower CD8+ T cell counts, higher serum levels of mTOR, pS6K, Eomes and interleukin (IL)-6. The mouse model with IC showed results consistent in the clinical study. The CD8+ T cell immune response to IC seemed to be weakened in TSC1 knockout mice compared with wild-type IC mice, demonstrating that mTOR activation resulted in the impaired CD8+ T cell immunity in IC. CONCLUSIONS: In IC, the mTOR activation may play a vital role in impaired CD8+ T cell immunity through enhancing expression of Eomes. The study was registered on 28 February 2017 at chictr.org.cn (identifier ChiCTR-ROC-17010750).

Rezafungin: a novel antifungal for the treatment of invasive candidiasis.

Rezafungin is a novel echinocandin with exceptional stability and solubility and a uniquely long half-life allowing for front-loaded drug exposure with once-weekly dosing. Rezafungin has been shown comparable to other echinocandins, with activity against Candida spp. and Aspergillus spp. including subsets of echinocandin-resistant Candida auris and azole-resistant Aspergillus isolates. Available clinical data show robust safety and promising efficacy. Phase III trials will provide data on efficacy of rezafungin for the treatment of candidemia and invasive candidiasis and for the prevention of invasive fungal disease in blood and bone marrow transplant recipients. Rezafungin is a promising new candidate in the antifungal arsenal that opens up clinical possibilities based on its impressive half-life, such as early hospital discharge for stable patients and use as prophylaxis in immunocompromised patients.

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.

Neutrophils From Patients With Invasive Candidiasis Are Inhibited by Candida albicans Biofilms.

Invasive candidiasis frequently involves medical device placement. On the surfaces of these devices, Candida can form biofilms and proliferate in adherent layers of fungal cells surrounded by a protective extracellular matrix. Due in part to this extracellular matrix, biofilms resist host defenses and antifungal drugs. Previous work (using neutrophils from healthy donors) found that one mechanism employed to resist host defenses involves the inhibition of neutrophil extracellular traps (NET) formation. NETs contain nuclear DNA, as well as antimicrobial proteins that can ensnare pathogens too large or aggregated to be effectively killed by phagocytosis. Given that these neutrophil structures are anticipated to have activity against the large aggregates of C. albicans biofilms, understanding the role of this inhibition in patients could provide insight into new treatment strategies. However, prior work has not included patients. Here, we examine NET formation by neutrophils collected from patients with invasive candidiasis. When compared to neutrophils from healthy participants, we show that patient neutrophils exhibit a heightened background level of NET release and respond to a positive stimulus by producing 100% more NETs. However, despite these physiologic differences, patient neutrophil responses to C. albicans were similar to healthy neutrophils. For both groups, planktonic cells induce strong NET release and biofilms inhibit NET formation. These results show that a mechanism of immune evasion for fungal biofilms translates to the clinical setting.

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.

Human inborn errors of immunity underlying superficial or invasive candidiasis.

Candida species, including C. albicans in particular, can cause superficial or invasive disease, often in patients with known acquired immunodeficiencies or iatrogenic conditions. The molecular and cellular basis of these infections in patients with such risk factors remained largely elusive, until the study of inborn errors of immunity clarified the basis of the corresponding inherited and "idiopathic" infections. Superficial candidiasis, also known as chronic mucocutaneous candidiasis (CMC), can be caused by inborn errors of IL-17 immunity. Invasive candidiasis can be caused by inborn errors of CARD9 immunity. In this chapter, we review both groups of inborn errors of immunity, and discuss the contribution of these studies to the deciphering of the critical mechanisms of anti-Candida immunity in patients with other conditions.

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.

Rezafungin treatment in mouse models of invasive candidiasis and aspergillosis: Insights on the PK/PD pharmacometrics of rezafungin efficacy.

Rezafungin acetate is a novel echinocandin in clinical development for prevention and treatment of invasive fungal infections. Rezafungin is differentiated by a pharmacokinetic/pharmacodynamic (PK/PD) profile that includes a long half-life allowing once-weekly administration, front-loaded plasma drug exposures associated with antifungal efficacy, and penetration into deep-seated infections, such as intra-abdominal abscesses. In this series of in vivo studies, rezafungin demonstrated efficacy in the treatment of neutropenic mouse models of disseminated candidiasis, including infection caused by azole-resistant Candida albicans, and aspergillosis. These results contribute to a growing body of evidence demonstrating the antifungal efficacy and potential utility of rezafungin in the treatment of invasive fungal infections.

Microbiological Laboratory Testing in the Diagnosis of Fungal Infections in Pulmonary and Critical Care Practice. An Official American Thoracic Society Clinical Practice Guideline.

Background: Fungal infections are of increasing incidence and importance in immunocompromised and immunocompetent patients. Timely diagnosis relies on appropriate use of laboratory testing in susceptible patients.Methods: The relevant literature related to diagnosis of invasive pulmonary aspergillosis, invasive candidiasis, and the common endemic mycoses was systematically reviewed. Meta-analysis was performed when appropriate. Recommendations were developed using the Grading of Recommendations Assessment, Development, and Evaluation approach.Results: This guideline includes specific recommendations on the use of galactomannan testing in serum and BAL and for the diagnosis of invasive pulmonary aspergillosis, the role of PCR in the diagnosis of invasive pulmonary aspergillosis, the role of ß-d-glucan assays in the diagnosis of invasive candidiasis, and the application of serology and antigen testing in the diagnosis of the endemic mycoses.Conclusions: Rapid, accurate diagnosis of fungal infections relies on appropriate application of laboratory testing, including antigen testing, serological testing, and PCR-based assays.

Commensal Candida albicans Positively Calibrates Systemic Th17 Immunological Responses.

Mucosal barriers are densely colonized by pathobiont microbes such as Candida albicans, capable of invasive disseminated infection. However, systemic infections occur infrequently in healthy individuals, suggesting that pathobiont commensalism may elicit host benefits. We show that intestinal colonization with C. albicans drives systemic expansion of fungal-specific Th17 CD4+ T cells and IL-17 responsiveness by circulating neutrophils, which synergistically protect against C. albicans invasive infection. Protection conferred by commensal C. albicans requires persistent fungal colonization and extends to other extracellular invasive pathogens such as Staphylococcus aureus. However, commensal C. albicans does not protect against intracellular influenza virus infection and exacerbates allergic airway inflammation susceptibility, indicating that positively calibrating systemic Th17 responses is not uniformly beneficial. Thus, systemic Th17 inflammation driven by CD4+ T cells responsive to tonic stimulation by commensal C. albicans improves host defense against extracellular pathogens, but with potentially harmful immunological consequences.

Association of Immune Cell Subtypes and Phenotype With Subsequent Invasive Candidiasis in Patients With Abdominal Sepsis.

BACKGROUND: In nonneutropenic intensive care unit (ICU) patients, current risk stratification scores lack specificity to reliably predict the risk of a prospective invasive candidiasis (IC). We aimed to explore possible associations of distinct immunological markers with different degrees of Candida affection in patients with abdominal sepsis. METHODS: The presented explorative, noninterventional diagnosis study recruited patients admitted to the surgical ICU at Heidelberg University Hospital with abdominal sepsis. Over 5 days, we determined white blood cell count, 1,3-ß-D-glucan, and HLA-DR expression; the amount of Th1, Th17, regulatory T, T helper, and cytotoxic T cells; Dectin-1 and TLR2-expression; the amount of T, B, and NK cells; the ex vivo secretion of IL-8 upon stimulation with LPS, flagellin, and zymosan; and the distribution of distinct T-cell cytokines in a daily manner. On day 21, patients' Candida infection status was stratified in no colonization or IC, colonization or IC. RESULTS: A total of 26 patients were included. On day 21, five patients showed no colonization or IC, in 13 patients a colonization was detected, and eight patients were diagnosed with IC. On study inclusion, the stratification groups showed comparable values in standard laboratory parameters and morbidity scores. Decreased B and NK cell counts, as well as reduced IL-8 secretion after ex vivo stimulation with LPS or flagellin seemed to be associated with a higher risk of subsequent Candida colonization. Even lower values could distinguish the therapy-relevant difference between prospective IC from colonization alone. CONCLUSIONS: We were able to show distinct immune system impairments in early abdominal sepsis by specific immune-based measurements. A possible association of these impairments with a subsequent Candida affection is shown.

Prospective evaluation of lymphocyte subtyping for the diagnosis of invasive candidiasis in non-neutropenic critically ill patients.

OBJECTIVES: This study aimed to investigate the distinguishing ability of lymphocyte subtyping for Invasive candidiasis (IC) diagnosis and prognosis in non-neutropenic critically ill patients. METHODS: We assessed the quantitative changes in key parameters of lymphocyte subtyping at the onset of clinical signs of infection in non-neutropenic critically ill patients and their potential influence on diagnosis and outcome of IC. The primary outcome was 28-day mortality. RESULTS: Among the 182 consecutive critically ill patients, 22 (12.1%) were in the IC group. The CD28+CD8+ T-cell counts (AUC 0.863, 95%CI 0.804-0.909, P<0.001) had greater diagnostic value for IC than other parameters had. Adding CD28+CD8+ T to Candida score significantly improved the predictive value of Candida score (P=0.039). Multivariate logistic regression analysis identified CD28+CD8+ T-cell counts≤78 cells/mm3 (OR 24.544, 95%CI 6.461-93.236, P<0.001) as an independent predictor for IC diagnosis. CD28+CD8+ T-cell counts could also predict 28-day mortality. Kaplan-Meier survival analysis provided evidence that CD28+CD8+ T-cell count <144cells/mm3 (log-rank test; P=0.03) were associated with lower survival probabilities. CONCLUSIONS: CD28+CD8+ T-cell counts play an important role in early diagnosis of IC. Low counts are associated with early mortality in non-neutropenic critically ill patients. These results suggest the potential usefulness of measuring CD28+CD8+ T-cell lymphocyte levels in the early recognition and diagnosis of IC. TRIAL REGISTRATION: ChiCTR-ROC-17010750. Registered 28 February 2017.

Current antifungal drugs and immunotherapeutic approaches as promising strategies to treatment of fungal diseases.

Invasive candidiasis (IC) can affect individuals with various underlying diseases hospitalized in different parts of hospitals. In recent decades, IC has caused 27-55% mortality in general population. Although Candida albicans (C. albicans) is still the most common cause of IC, non-albicans infections such as C. krusei, C. glabrata, C. lusitaniae, C. tropicalis, and C. parapsilosis have been increased in recent years. Treatment of invasive fungal infections is challenging as the number of existing antifungals is limited and more problems include: toxicity, drug interactions, and drug resistance. These problems provide a clear rationale for the development of new immunotherapies to increase outcomes in patients with invasive fungal infections. Thus, the purpose of this paper is to complete review of the current and modern antifungal drugs in IC therapy and focus on the role of immunotherapy in preventing and controlling the disease. Therefore, we review the features of current research efforts directed towards devising safe and effective immunotherapeutic options for fungal infections, including work on antifungal vaccines, engineered T-cells, cytokines, monoclonal antibodies, and other agents.

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.

Biomarker-based strategy for early discontinuation of empirical antifungal treatment in critically ill patients: a randomized controlled trial.

PURPOSE: The aim of this study was to determine the impact of a biomarker-based strategy on early discontinuation of empirical antifungal treatment. METHODS: Prospective randomized controlled single-center unblinded study, performed in a mixed ICU. A total of 110 patients were randomly assigned to a strategy in which empirical antifungal treatment duration was determined by (1,3)-ß-D-glucan, mannan, and anti-mannan serum assays, performed on day 0 and day 4; or to a routine care strategy, based on international guidelines, which recommend 14 days of treatment. In the biomarker group, early stop recommendation was determined using an algorithm based on the results of biomarkers. The primary outcome was the percentage of survivors discontinuing empirical antifungal treatment early, defined as a discontinuation strictly before day 7. RESULTS: A total of 109 patients were analyzed (one patient withdraw consent). Empirical antifungal treatment was discontinued early in 29 out of 54 patients in the biomarker strategy group, compared with one patient out of 55 in the routine strategy group [54% vs 2%, p < 0.001, OR (95% CI) 62.6 (8.1-486)]. Total duration of antifungal treatment was significantly shorter in the biomarker strategy compared with routine strategy [median (IQR) 6 (4-13) vs 13 (12-14) days, p < 0.0001). No significant difference was found in the percentage of patients with subsequent proven invasive Candida infection, mechanical ventilation-free days, length of ICU stay, cost, and ICU mortality between the two study groups. CONCLUSIONS: The use of a biomarker-based strategy increased the percentage of early discontinuation of empirical antifungal treatment among critically ill patients with suspected invasive Candida infection. These results confirm previous findings suggesting that early discontinuation of empirical antifungal treatment had no negative impact on outcome. However, further studies are needed to confirm the safety of this strategy. This trial was registered at ClinicalTrials.gov, NCT02154178.