Brief resolved unexplained events: practical evaluation and management in the emergency department.

In a 2016 clinical practice guideline, the American Academy of Pediatrics (AAP) created and introduced the term brief resolved unexplained event (BRUE). This guideline defined specific criteria for diagnosis of BRUE and provided a set of guidelines for evaluation of these infants as well as characteristics that indicate a BRUE will have a low risk for a repeat event or a serious underlying disorder. This issue reviews the definition and broad differential diagnosis of a BRUE, highlights the criteria for risk stratification of infants who experience a BRUE, summarizes the management recommendations for patients with a lower-risk BRUE, and examines the available literature that evaluates the impact of the AAP guidelines in the years since its publication.

Chronic Occupational Mold Exposure Drives Expansion of Aspergillus-Reactive Type 1 and Type 2 T-Helper Cell Responses.

Occupational mold exposure can lead to Aspergillus-associated allergic diseases including asthma and hypersensitivity pneumonitis. Elevated IL-17 levels or disbalanced T-helper (Th) cell expansion were previously linked to Aspergillus-associated allergic diseases, whereas alterations to the Th cell repertoire in healthy occupationally exposed subjects are scarcely studied. Therefore, we employed functional immunoassays to compare Th cell responses to A. fumigatus antigens in organic farmers, a cohort frequently exposed to environmental molds, and non-occupationally exposed controls. Organic farmers harbored significantly higher A. fumigatus-specific Th-cell frequencies than controls, with comparable expansion of Th1- and Th2-cell frequencies but only slightly elevated Th17-cell frequencies. Accordingly, Aspergillus antigen-induced Th1 and Th2 cytokine levels were strongly elevated, whereas induction of IL-17A was minimal. Additionally, increased levels of some innate immune cell-derived cytokines were found in samples from organic farmers. Antigen-induced cytokine release combined with Aspergillus-specific Th-cell frequencies resulted in high classification accuracy between organic farmers and controls. Aspf22, CatB, and CipC elicited the strongest differences in Th1 and Th2 responses between the two cohorts, suggesting these antigens as potential candidates for future bio-effect monitoring approaches. Overall, we found that occupationally exposed agricultural workers display a largely balanced co-expansion of Th1 and Th2 immunity with only minor changes in Th17 responses.

Development of a Simple and Robust Whole Blood Assay with Dual Co-Stimulation to Quantify the Release of T-Cellular Signature Cytokines in Response to Aspergillus fumigatus Antigens.

Deeper understanding of mold-induced cytokine signatures could promote advances in the diagnosis and treatment of invasive mycoses and mold-associated hypersensitivity syndromes. Currently, most T-cellular immunoassays in medical mycology require the isolation of mononuclear cells and have limited robustness and practicability, hampering their broader applicability in clinical practice. Therefore, we developed a simple, cost-efficient whole blood (WB) assay with dual α-CD28 and α-CD49d co-stimulation to quantify cytokine secretion in response to Aspergillus fumigatus antigens. Dual co-stimulation strongly enhanced A. fumigatus-induced release of T-cellular signature cytokines detectable by enzyme-linked immunosorbent assay (ELISA) or a multiplex cytokine assay. Furthermore, T-cell-dependent activation and cytokine response of innate immune cells was captured by the assay. The protocol consistently showed little technical variation and high robustness to pre-analytic delays of up to 8 h. Stimulation with an A. fumigatus lysate elicited at least 7-fold greater median concentrations of key T-helper cell signature cytokines, including IL-17 and the type 2 T-helper cell cytokines IL-4 and IL-5 in WB samples from patients with Aspergillus-associated lung pathologies versus patients with non-mold-related lung diseases, suggesting high discriminatory power of the assay. These results position WB-ELISA with dual co-stimulation as a simple, accurate, and robust immunoassay for translational applications, encouraging further evaluation as a platform to monitor host immunity to opportunistic pathogens.

CcpA- and Shm2-Pulsed Myeloid Dendritic Cells Induce T-Cell Activation and Enhance the Neutrophilic Oxidative Burst Response to Aspergillus fumigatus.

Aspergillus fumigatus causes life-threatening opportunistic infections in immunocompromised patients. As therapeutic outcomes of invasive aspergillosis (IA) are often unsatisfactory, the development of targeted immunotherapy remains an important goal. Linking the innate and adaptive immune system, dendritic cells are pivotal in anti-Aspergillus defense and have generated interest as a potential immunotherapeutic approach in IA. While monocyte-derived dendritic cells (moDCs) require ex vivo differentiation, antigen-pulsed primary myeloid dendritic cells (mDCs) may present a more immediate platform for immunotherapy. To that end, we compared the response patterns and cellular interactions of human primary mDCs and moDCs pulsed with an A. fumigatus lysate and two A. fumigatus proteins (CcpA and Shm2) in a serum-free, GMP-compliant medium. CcpA and Shm2 triggered significant upregulation of maturation markers in mDCs and, to a lesser extent, moDCs. Furthermore, both A. fumigatus proteins elicited the release of an array of key pro-inflammatory cytokines including TNF-α, IL-1ß, IL-6, IL-8, and CCL3 from both DC populations. Compared to moDCs, CcpA- and Shm2-pulsed mDCs exhibited greater expression of MHC class II antigens and stimulated stronger proliferation and IFN-γ secretion from autologous CD4+ and CD8+ T-cells. Moreover, supernatants of CcpA- and Shm2-pulsed mDCs significantly enhanced the oxidative burst in allogeneic neutrophils co-cultured with A. fumigatus germ tubes. Taken together, our in vitro data suggest that ex vivo CcpA- and Shm2-pulsed primary mDCs have the potential to be developed into an immunotherapeutic approach to tackle IA.

T-Cell Immune Surveillance in Allogenic Stem Cell Transplant Recipients: Are Whole Blood-Based Assays Ready to Challenge ELISPOT?

We compared the feasibility of 4 cytomegalovirus (CMV)- and Aspergillus-reactive T-cell immunoassay protocols in allogenic stem cell transplant recipients. While enzyme-linked immunospot performed best overall, logistically advantageous whole blood-based assays performed comparably in patients with less severe lymphocytopenia. CMV-induced interferon-gamma responses correlated strongly across all protocols and showed high concordance with serology.

Triple RNA-Seq Reveals Synergy in a Human Virus-Fungus Co-infection Model.

High-throughput RNA sequencing (RNA-seq) is routinely applied to study diverse biological processes; however, when performed separately on interacting organisms, systemic noise intrinsic to RNA extraction, library preparation, and sequencing hampers the identification of cross-species interaction nodes. Here, we develop triple RNA-seq to simultaneously detect transcriptomes of monocyte-derived dendritic cells (moDCs) infected with the frequently co-occurring pulmonary pathogens Aspergillus fumigatus and human cytomegalovirus (CMV). Comparing expression patterns after co-infection with those after single infections, our data reveal synergistic effects and mutual interferences between host responses to the two pathogens. For example, CMV attenuates the fungus-mediated activation of pro-inflammatory cytokines through NF-κB (nuclear factor κB) and NFAT (nuclear factor of activated T cells) cascades, while A. fumigatus impairs viral clearance by counteracting viral nucleic acid-induced activation of type I interferon signaling. Together, the analytical power of triple RNA-seq proposes molecular hubs in the differential moDC response to fungal/viral single infection or co-infection that contribute to our understanding of the etiology and, potentially, clearance of post-transplant infections.

Evaluating Changes in Diagnostic Accuracy of Ultrasound for Appendicitis: Does Practice Make Perfect?

BACKGROUND: Ultrasound (US) is the preferred method of initial evaluation for appendicitis in pediatrics. However, limited accuracy of US for appendicitis is an obstacle to implementation of US-first protocols at facilities less experienced with US. OBJECTIVES: The primary objective was to demonstrate changes in diagnostic accuracy of US for appendicitis over time, after implementation of an US-first protocol. Secondary objectives included evaluating trends in utilization and factors associated with accuracy of US. METHODS: We reviewed 5 years of pediatric emergency department encounters that included US evaluations for appendicitis. The primary outcome was conclusive US (fully visualized normal appendix or unequivocal appendicitis) vs. equivocal US (partially visualized or nonvisualized appendix). We also analyzed rates of conclusive US over time; accuracy, sensitivity, and specificity of US for appendicitis; and associations of US accuracy with patient gender, body mass index, and ultrasonographer's experience. RESULTS: A conclusive US report was found in 267 of 1058 encounters (25.2%); overall accuracy rate was 24.5%. Over 5 years, the diagnostic accuracy of US for appendicitis improved significantly from 13.9% to 31.5% (p = 0.001). Overall sensitivity was 80.7% and specificity was 77.6%. Male gender and dedicated US of the appendix were significantly associated with conclusive US (ps < 0.001). Higher body mass index was significantly associated with equivocal US (p < 0.001). Ultrasonographer experience was not significantly associated with conclusive US (p = 0.22). CONCLUSIONS: An US-first imaging protocol for appendicitis in children shows chronologic improvement in diagnostic accuracy. This may provide encouragement to facilities using computed tomography-based diagnostic protocols to implement US-first protocols to reduce childhood radiation exposure.

In Vitro Evaluation of Radiolabeled Amphotericin B for Molecular Imaging of Mold Infections.

Invasive pulmonary aspergillosis and mucormycosis are life-threatening complications in immunocompromised patients. A rapid diagnosis followed by early antifungal treatment is essential for patient survival. Given the limited spectrum of biomarkers for invasive mold infections, recent studies have proposed the use of radiolabeled siderophores or antibodies as molecular probes to increase the specificity of radiological findings by nuclear imaging modalities. While holding enormous diagnostic potential, most of the currently available molecular probes are tailored to the detection of Aspergillus species, and their cost-intensive and sophisticated implementation restricts their accessibility at less specialized centers. In order to develop cost-efficient and broadly applicable tracers for pulmonary mold infections, this study established streamlined and high-yielding protocols to radiolabel amphotericin B (AMB) with the gamma emitter technetium-99m (99mTc-AMB) and the positron emitter gallium-68 (68Ga-AMB). The radiochemical purity of the resulting tracers consistently exceeded 99%, and both probes displayed excellent stability in human serum (>98% after 60 to 240 min at 37°C). The uptake kinetics by representative mold pathogens were assessed in an in vitro Transwell assay using infected endothelial cell layers. Both tracers accumulated intensively and specifically in Transwell inserts infected with Aspergillus fumigatus, Rhizopus arrhizus, and other clinically relevant mold pathogens compared with their accumulation in uninfected inserts and inserts infected with bacterial controls. Inoculum-dependent enrichment was confirmed by gamma counting and autoradiographic imaging. Taken together, this pilot in vitro study proposes 99mTc-AMB and 68Ga-AMB to be facile, stable, and specific probes, meriting further preclinical in vivo evaluation of radiolabeled amphotericin B for molecular imaging in invasive mycoses.

Impact of immunosuppressive and antifungal drugs on PBMC- and whole blood-based flow cytometric CD154+ Aspergillus fumigatus specific T-cell quantification.

Flow cytometric quantification of CD154+ mould specific T-cells in antigen-stimulated peripheral blood mononuclear cells (PBMCs) or whole blood has been described as a supportive biomarker to diagnose invasive mould infections and to monitor therapeutic outcomes. As patients at risk frequently receive immunosuppressive and antifungal medication, this study compared the matrix-dependent impact of representative drugs on CD154+ T-cell detection rates. PBMCs and whole blood samples from healthy adults were pre-treated with therapeutic concentrations of liposomal amphotericin B, voriconazole, posaconazole, cyclosporine A (CsA) or prednisolone. Samples were then stimulated with an Aspergillus fumigatus lysate or a viral antigen cocktail (CPI) and assessed for CD154+ T-helper cell frequencies. Specific T-cell detection rates and technical assay properties remained largely unaffected by exposure of both matrices to the studied antifungals. By contrast, CsA and prednisolone pre-treatment of isolated PBMCs and whole blood adversely impacted specific T-cell detection rates and caused elevated inter-replicate variation. Unexpectedly, the whole blood-based protocol that uses additional α-CD49d co-stimulation was less susceptible to CsA and prednisolone despite prolonged drug exposure in the test tube. Accordingly, addition of α-CD49d during PBMC stimulation partially attenuated the impact of immunosuppressive drugs on test performance. Translating these results into the clinical setting, false-negative results of CD154+ antigen-specific T-cell quantification need to be considered in patients receiving T-cell-active immunosuppressive medication. Optimized co-stimulation regimes with α-CD49d could contribute to an improved feasibility of functional T-cell assays in immunocompromised patient populations.

Development and evaluation of a whole blood-based approach for flow cytometric quantification of CD154+ mould-reactive T cells.

CD154+ mould-reactive T cells were proposed as a novel biomarker in the diagnosis of invasive mycoses. As PBMC-based protocols for flow cytometric quantification of these cells are logistically challenging and susceptible to preanalytic delays, this study evaluated and optimized a whole blood-based method for the detection of mould-reactive T cells. Blood collection tubes containing costimulatory antibodies and Aspergillus fumigatus mycelial lysates were inoculated with heparinized whole blood from healthy adults, and detection rates of CD154+/CD4+A. fumigatus reactive T cells were compared with PBMC-based detection using samples from the same donors. In contrast to the PBMC-based method, double costimulation with αCD28 and αCD49d was crucial for reliable whole blood stimulation. Optimizing stimulation schemes for both matrixes, significantly higher specific T-cell detection rates were achieved by the whole blood-based method, whereas the unspecific background stimulation remained low. MHC II-dependent CD154+ upregulation was demonstrated for both matrixes. Excellent correlation and reproducible conversion factors between whole blood and PBMC-based results were observed. Using frozen ready-to-use test tubes containing costimulatory antibodies and lysates, detection rates of specific T cells were comparable to freshly prepared blood collection tubes. The optimized whole blood-based protocol was also used to detect Rhizopus arrhizus and Rhizomucor pusillus reactive T cells, resulting in 1.5- to 2.7-fold higher detection rates compared with PBMC-based measurement. In summary, the whole blood protocol is a robust, highly sensitive, and cost-effective method for mould-reactive T-cell quantification, allowing for point-of-care sample stimulation and contributing to better assay standardization in multi-centre evaluation of mould reactive T-cell quantification.

Evaluation of Aspergillus and Mucorales specific T-cells and peripheral blood mononuclear cell cytokine signatures as biomarkers of environmental mold exposure.

Mold specific T-cells have been described as a supportive biomarker to monitor invasive mycoses and mold exposure. This study comparatively evaluated frequencies and cytokine profiles of Aspergillus fumigatus and Mucorales reactive T-cells depending on environmental mold exposure. Peripheral blood mononuclear cells (PBMCs) obtained from 35 healthy donors were stimulated with mycelial lysates of A. fumigatus and three human pathogenic Mucorales species. CD154+ specific T-cells were quantified by flow cytometry. In a second cohort of 20 additional donors, flow cytometry was complemented by 13-plex cytokine assays. Mold exposure of the subjects was determined using a previously established questionnaire. Highly exposed subjects exhibited significantly greater CD154+A. fumigatus and Mucorales specific naïve and memory T-helper cell frequencies. Significant correlation (r = 0.48 - 0.79) was found between A. fumigatus and Mucorales specific T-cell numbers. Logistic regression analyses revealed that combined analysis of mold specific T-cell frequencies and selected cytokine markers (A. fumigatus: IL-5 and TNF-α, R. arrhizus: IL-17A and IL-13) significantly improves classification performance, resulting in 75-90 % predictive power using 10-fold cross-validation. In conclusion, mold specific T-cell frequencies and their cytokine signatures offer promising potential in the assessment of environmental mold exposure. The cytokines identified in this pilot study should be validated in the clinical setting, e. g. in patients with hypersensitivity pneumonitis.

Validation of a simplified in vitro Transwell® model of the alveolar surface to assess host immunity induced by different morphotypes of Aspergillus fumigatus.

Interactions between fungal pathogens such as Aspergillus fumigatus with host alveolar epithelium and innate immune cells are crucial in the defense against opportunistic fungal infections. In this study a simplified Transwell® system with a confluent layer of A549 cells acted as a model for the alveolar surface. A. fumigatus and dendritic cells were added to simulate the spatial and cellular complexity in the alveolus. Fungal growth into the lower chamber was validated by galactomannan assays. Addition of moDCs to the upper chamber led to a reduced GM signal and fungal growth, indicating moDC antifungal activity. Minimal cell death was documented by analyses of lactate dehydrogenase concentrations and pro-apoptotic gene expression. Measurement of trans-epithelial dextran blue movement confirmed tightness of the epithelial barrier even in presence of A. fumigatus. Cytokine measurements in supernatants from both chambers of the Transwell® system documented distinct response patterns during early and late stages of epithelial invasion, with A549 cells appearing to make a minimal contribution to cytokine release. Concentrations of cytokines in the lower chamber varied distinctly from the upper chamber, depending on the molecular weight of the cytokines. Low inter-assay variability of fungal biomarkers and cytokines was confirmed, highlighting that in vitro models closely mimicking conditions in the human lung can facilitate reproducible measurement of the dynamics of cytokine release and fungal penetration of host epithelia.

Susceptibility of A. fumigatus-specific T-cell assays to pre-analytic blood storage and PBMC cryopreservation greatly depends on readout platform and analytes.

Mould-specific T cells detectable by flow cytometry or ELISPOT were proposed as a novel biomarker in invasive aspergillosis. To define protocols facilitating sample shipment and longitudinal analysis, this study evaluated the susceptibility of different functional assays for A. fumigatus-specific T-cell quantification and characterisation to pre-analytic delays. PBMCs from 6 healthy donors were analysed after immediate isolation, after 6 hours whole blood storage or after cryopreservation using 3 different common media. Functional responses to A. fumigatus lysate stimulation were comparatively assessed by flow cytometry, ELISPOT and 14-plex cytokine assay. After 6 hours pre-analytic storage, all functional assays showed reduced detection rates, higher coefficients of variation (CV) and widely varying individual recovery indices of specific T-cell response. While cryopreservation resulted in sufficient yields and largely unaltered cellular composition, outcomes of functional readouts significantly differed from freshly processed samples. For CD154-based flow cytometry, only cryopreservation in RPMI supplemented with autologous serum resulted in satisfactory detection rates and CVs. For ELISPOT and cytokine secretion assays, none of the cryopreservation protocols provided sufficient concordance with immediately processed samples. Even using the same readout platform, individual analytes widely varied in their susceptibility to cryopreservation, highlighting that distinct optimisation is required depending on the downstream assay.

Comparative Analysis of Inflammatory Cytokine Release and Alveolar Epithelial Barrier Invasion in a Transwell® Bilayer Model of Mucormycosis.

Understanding the mechanisms of early invasion and epithelial defense in opportunistic mold infections is crucial for the evaluation of diagnostic biomarkers and novel treatment strategies. Recent studies revealed unique characteristics of the immunopathology of mucormycoses. We therefore adapted an alveolar Transwell® A549/HPAEC bilayer model for the assessment of epithelial barrier integrity and cytokine response to Rhizopus arrhizus, Rhizomucor pusillus, and Cunninghamella bertholletiae. Hyphal penetration of the alveolar barrier was validated by 18S ribosomal DNA detection in the endothelial compartment. Addition of dendritic cells (moDCs) to the alveolar compartment led to reduced fungal invasion and strongly enhanced pro-inflammatory cytokine response, whereas epithelial CCL2 and CCL5 release was reduced. Despite their phenotypic heterogeneity, the studied Mucorales species elicited the release of similar cytokine patterns by epithelial and dendritic cells. There were significantly elevated lactate dehydrogenase concentrations in the alveolar compartment and epithelial barrier permeability for dextran blue of different molecular weights in Mucorales-infected samples compared to Aspergillus fumigatus infection. Addition of monocyte-derived dendritic cells further aggravated LDH release and epithelial barrier permeability, highlighting the influence of the inflammatory response in mucormycosis-associated tissue damage. An important focus of this study was the evaluation of the reproducibility of readout parameters in independent experimental runs. Our results revealed consistently low coefficients of variation for cytokine concentrations and transcriptional levels of cytokine genes and cell integrity markers. As additional means of model validation, we confirmed that our bilayer model captures key principles of Mucorales biology such as accelerated growth in a hyperglycemic or ketoacidotic environment or reduced epithelial barrier invasion upon epithelial growth factor receptor blockade by gefitinib. Our findings indicate that the Transwell® bilayer model provides a reliable and reproducible tool for assessing host response in mucormycosis.

Intra- and inter-individual variability of Aspergillus fumigatus reactive T-cell frequencies in healthy volunteers in dependency of mould exposure in residential and working environment.

Invasive aspergillosis remains a deadly disease in immunocompromised patients, whereas the combination of an exaggerated immune response and continuous exposure lead to various hyperinflammatory diseases. This pilot study aimed to gain an overview of the intra- and inter-individual variability in Aspergillus fumigatus reactive T-helper cells in healthy adults and the correlation with environmental mould exposure. In this flow cytometric study, the frequencies of CD154+ A. fumigatus reactive T cells were evaluated in 70 healthy volunteers. All subjects completed a standardised questionnaire addressing their mould exposure. Subjects with intensive mould exposure in their professional or residential surrounding demonstrated considerably higher mean frequencies of A. fumigatus reactive T-helper and T-memory cells. Comparative evaluation of multiple measurements over time demonstrated relatively conserved reactive T-cell frequencies in the absence of major changes to the exposure profile, whereas those frequently exposed in professional environment or with changes to their risk score demonstrated a marked dependency of antigen reactive T-cell frequencies on recent mould exposure. This pilot study was the first to provide data on the intra-individual variability in A. fumigatus reactive T-cell frequencies and its linkage to mould encounter. Fungus reactive T cells are to be considered a valued tool for the assessment of environmental mould exposure.

ß-Catenin Does Not Confer Tumorigenicity When Introduced into Partially Transformed Human Mesenchymal Stem Cells.

Although osteosarcoma is the most common primary malignant bone tumor in children and adolescents, its cell of origin and the genetic alterations are unclear. Previous studies have shown that serially introducing hTERT, SV40 large TAg, and H-Ras transforms human mesenchymal stem cells into two distinct sarcomas cell populations, but they do not form osteoid. In this study, ß-catenin was introduced into mesenchymal stem cells already containing hTERT and SV40 large TAg to analyze if this resulted in a model which more closely recapitulated osteosarcoma. Results. Regardless of the level of induced ß-catenin expression in the stable transfectants, there were no marked differences induced in their phenotype or invasion and migration capacity. Perhaps more importantly, none of them formed tumors when injected into immunocompromised mice. Moreover, the resulting transformed cells could be induced to osteogenic and chondrogenic differentiation but not to adipogenic differentiation. Conclusions. ß-catenin, although fostering osteogenic differentiation, does not induce the malignant features and tumorigenicity conveyed by oncogenic H-RAS when introduced into partly transformed mesenchymal stem cells. This may have implications for the role of ß-catenin in osteosarcoma pathogenesis. It also may suggest that adipogenesis is an earlier branch point than osteogenesis and chondrogenesis in normal mesenchymal differentiation.