Siglec-8 Signals Through a Non-Canonical Pathway to Cause Human Eosinophil Death In Vitro

Sialic acid-binding immunoglobulin-like lectin (Siglec)-8 is a glycan-binding receptor bearing immunoreceptor tyrosine-based inhibitory and switch motifs (ITIM and ITSM, respectively) that is selectively expressed on eosinophils, mast cells, and, to a lesser extent, basophils. Previous work has shown that engagement of Siglec-8 on IL-5–primed eosinophils causes cell death via CD11b/CD18 integrin–mediated adhesion and NADPH oxidase activity and identified signaling molecules linking adhesion, reactive oxygen species (ROS) production, and cell death. However, the proximal signaling cascade activated directly by Siglec-8 engagement has remained elusive. Most members of the Siglec family possess similar cytoplasmic signaling motifs and recruit the protein tyrosine phosphatases SHP-1/2, consistent with ITIM-mediated signaling, to dampen cellular activation. However, the dependence of Siglec-8 function in eosinophils on these phosphatases has not been studied. Using Siglec-8 antibody engagement and pharmacological inhibition in conjunction with assays to measure cell-surface upregulation and conformational activation of CD11b integrin, ROS production, and cell death, we sought to identify molecules involved in Siglec-8 signaling and determine the stage of the process in which each molecule plays a role. We demonstrate here that the enzymatic activities of Src family kinases (SFKs), Syk, SHIP1, PAK1, MEK1, ERK1/2, PLC, PKC, acid sphingomyelinase/ceramidase, and Btk are all necessary for Siglec-8–induced eosinophil cell death, with no apparent role for SHP-1/2, SHIP2, or c-Raf. While most of these signaling molecules are necessary for Siglec-8–induced upregulation of CD11b integrin at the eosinophil cell surface, Btk is phosphorylated and activated later in the signaling cascade and is instead necessary for CD11b activation. In contrast, SFKs and ERK1/2 are phosphorylated far earlier in the process, consistent with their role in augmenting cell-surface levels of CD11b. In addition, pretreatment of eosinophils with latrunculin B or jasplakinolide revealed that actin filament disassembly is necessary and sufficient for surface CD11b integrin upregulation and that actin polymerization is necessary for downstream ROS production. These results show that Siglec-8 signals through an unanticipated set of signaling molecules in IL-5–primed eosinophils to induce cell death and challenges the expectation that ITIM-bearing Siglecs signal through inhibitory pathways involving protein tyrosine phosphatases to achieve their downstream functions.

Relevance of tissue eosinophilia in subdural hematomata

Chronic subdural hematomata (CSDH) are treated by evacuation. Recurrence occurs in 3-20% of cases, but the factors determining its occurrence have not been determined. Having observed that eosinophil cell infiltrates are often present in the outer membrane of CSDH, our aim was to determine whether such infiltrates are associated with risk of recurrence. Histological sections of the resections from 72 patients with primary CSDH (Mean age 73.4) and 16 with recurrent CSDH (Mean age 72.1) stained with H&E were graded by blinded observers for eosinophilic cell infiltrates using a semiquantitative 0 to 3 scale. The risk of recurrence requiring reoperation (RrR) in primary CSDH was 11.1%, and 12.5% in recurrent CSDH (meaning third surgery was required). A dense (grades 2 or 3) eosinophilic infiltrate was present in 22.2% of primary CSDH; the RrR was 0% in these cases, as compared with 14.8% in cases with sparse (grades 0-1) eosinophilic infiltrate. Among recurrent CSDH cases, 12.5% (2/15) showed a dense eosinophilic infiltrate; the RrR was also 0%, contrasting with 14.3% in those with sparse eosinophilic infiltrate. We conclude that eosinophils either play a role or are a marker of a process leading to stabilizing CSDH, making them less prone to rebleeding. Abstract not previously publishedLearning ObjectivesDescribe the risk of recurrence following surgical evacuation of chronic subdural hematomataRecognize the variable presence of eosinophils in chronic subdural hematomataCite the presence of eosinophils is predictive of absence of recurrence

Using Blood Eosinophil Count as a Biomarker to Guide Corticosteroid Treatment for Chronic Obstructive Pulmonary Disease

Treating patients hospitalised with acute exacerbations of chronic obstructive pulmonary disease (COPD) usually involves administering systemic corticosteroids. The many unwanted side effects associated with this treatment have led to increased interest in minimising the accumulated corticosteroid dose necessary to treat exacerbations. Studies have shown that short-term treatment with corticosteroids is preferred, and recent trials have shown that biomarkers can be used to further reduce exposure to corticosteroids. Interestingly, high eosinophil counts in patients with acute exacerbations of COPD are indicative of an eosinophilic phenotype with a distinct response to treatment with corticosteroids. In addition, post-hoc analysis of randomised control trials have shown that higher blood eosinophil counts at the start of the study predict a greater response to inhaled corticosteroids in stable COPD. In this review, we examine the studies on this topic, describe how blood eosinophil cell count may be used as a biomarker to guide treatment with corticosteroids, and identify some relevant challenges.

Meningitis patients with Angiostrongylus cantonensis may present without eosinophilia in the cerebrospinal fluid in northern Vietnam

Background Eosinophilic meningitis (EM) is a rare clinical syndrome caused by both infectious and noninfectious diseases. In tropical pacific countries, Angiostrongylus cantonensis is the most common cause. However, the EM definition varies in the literature, and its relation to parasitic meningitis (PM) remains unclear. Methodology/Principal findings Adult and adolescent patients of 13 years old or above with suspected central nervous system (CNS) infections with abnormal CSF findings were prospectively enrolled at a tertiary referral hospital in Hanoi, Vietnam from June 2012 to May 2014. Patients with EM or suspected PM (EM/PM) were defined by the presence of either ≥10% eosinophils or an absolute eosinophil cell counts of ≥10/mm3 in the CSF or blood eosinophilia (>16% of WBCs) without CSF eosinophils. In total 679 patients were enrolled: 7 (1.03%) had ≥10% CSF eosinophilia, 20 (2.95%) had ≥10/mm3 CSF eosinophilia, and 7 (1.03%) had >16% blood eosinophilia. The patients with ≥10% CSF eosinophilia were significantly younger (p = 0.017), had a lower body temperature (p = 0.036) than patients with ≥10/mm3 CSF eosinophilia among whom bacterial pathogens were detected in 72.2% (13/18) of those who were tested by culture and/or PCR. In contrast, the characteristics of the patients with >16% blood eosinophilia resembled those of patients with ≥10% CSF eosinophilia. We further conducted serological tests and real-time PCR to identify A. cantonensis. Serology or real-time PCR was positive in 3 (42.8%) patients with ≥10% CSF eosinophilia and 6 (85.7%) patients with >16% blood eosinophilia without CSF eosinophils but none of patients with ≥10/mm3 CSF eosinophilia. Conclusions The etiology of PM in northern Vietnam is A. cantonensis. The eosinophil percentage is a more reliable predictor of parasitic EM than absolute eosinophil count in the CSF. Patients with PM may present with a high percentage of eosinophils in the peripheral blood but not in the CSF.

Treatment with the anti-IgE monoclonal antibody omalizumab in women with asthma undergoing fertility treatment: a proof-of-concept study—The PRO-ART study protocol

IntroductionAsthma is associated with prolonged time to pregnancy and a higher need for fertility treatment. However, the mechanism underlying this association remains incompletely understood. Previous research points to asthma-driven systemic inflammation also affecting the reproductive organs and thereby fertility. The aim of this study was to determine if treatment with omalizumab prior to fertility treatment will increase pregnancy rate among women with asthma by decreasing the systemic asthma-related inflammation and, by that, to provide insight into the underlying mechanisms.Methods and analysisThis is an ongoing prospective multicentre randomised controlled trial planned to enrol 180 women with asthma recruited from fertility clinics in Denmark. The patients are randomised 1:1 to either omalizumab or placebo. The primary endpoint is the difference in pregnancy rate confirmed with ultrasound at gestational week 7 of pregnancy. The secondary endpoints are change in sputum and blood eosinophil cell count, change in biomarkers, change in microbiota, together with rate of pregnancy loss, frequency of malformations, pre-eclampsia, preterm birth, birth weight, small for gestational age and perinatal death between groups.Ethics and disseminationThe methods used in this study are of low risk, but if successful, our findings will have a large impact on a large group of patients as infertility and asthma are the most common chronic diseases among the young population. The study has been approved by the Ethics Committee–Danish national research ethics committee (H-18016605) and the Danish Medicines Agency (EudraCT no: 2018-001137-41) and the Danish Data Protection Agency (journal number: VD-2018486 and I-Suite number 6745). The test results will be published regardless of whether they are positive, negative or inconclusive. Publication in international peer-reviewed scientific journals is planned.Trial registration numberNCT03727971.

Should We Screen HIV-Positive Migrants for Strongyloidiasis?

Background: Strongyloides stercoralis, a nematode endemic in all (sub)tropical regions, can cause life-threatening disease, especially in immunosuppressed patients. Many countries with high HIV-prevalence rates are also highly S. stercoralis endemic, and co-infection may occur. Methods: Retrospective study based on serological testing for S. stercoralis in all HIV-infected migrants followed at the Institute of Tropical Medicine, Antwerp, Belgium. If untested, serologic testing was performed on stored samples, dating from the first HIV viral load determination. The epidemiological, clinical and laboratory features of patients with and without strongyloidiasis were retrieved from the electronic medical files. Results: Of the 2846 HIV patients in active follow-up, 723 (25.4%) had a migration background. Thirty-six patients (5.1%) were diagnosed with Strongyloides co-infection, including 29 during their medical evaluation and seven retrospectively. Patients had a median age of 35.3 years (IQR 30.3–44.4), 28 patients (78%) originated from Sub-Saharan Africa and median time in Belgium was 3.5 years (IQR 0.8–5.7). Symptoms compatible with strongyloidiasis were present in 17 (47%) patients, of whom two were diagnosed retrospectively. Eosinophilia (eosinophil cell count > 450/µL) was observed in 19 (53%) participants. Median CD4 level was 386 /µL (IQR 299–518) at diagnosis of co-infection. Of note, 8 (22%) patients with strongyloidiasis had no reported symptoms nor eosinophilia. None of the patients developed hyperinfection syndrome. There were no differences in age, gender, geographic origin, clinical presentation, CD4 level or viral load between patients with and without strongyloidiasis. Only eosinophilia was strongly correlated with the presence of Strongyloides in multivariate analysis (OR 10.74 (95% CI 5.19–22.25), p < 0.001); the positive likelihood ratio (LR+) of eosinophilia for strongyloidiasis was 5.38 (95% CI 3.66–7.91). Conclusion: Strongyloidiasis was diagnosed in 5.1% of HIV-infected migrants. Eosinophilia had good confirming power for the presence of the disease. However, a sizeable proportion (22%) of co-infected individuals were asymptomatic and had normal eosinophil count, supporting universal screening of all HIV-positive patients native to tropical countries.

Estimation of Eosinophil Cells in Cord Blood with References Based on Blood in Adults via Bayesian Measurement Error Modeling

Motivation Eosinophils are phagocytic white blood cells with a variety of roles in the immune system. In situations where actual counts are not available, high quality approximations of their cell proportions using indirect markers are critical. Results We develop a Bayesian measurement error model to estimate proportions of eosinophils in cord blood, using the cord blood DNA methylation profiles, based on markers of eosinophil cell heterogeneity in blood of adults. The proposed method can be directly extended to other cells across different reference panels. We demonstrate the method’s estimation accuracy using B cells and show that the findings support the proposed approach. The method has been incorporated into the estimateCellCounts function in the minfi package to estimate eosinophil cells proportions in cord blood. Availability estimateCellCounts function is implemented and available in Bioconductor package minfi. Supplementary information Supplementary data are available at Bioinformatics online.

144 Effect of sodium butyrate (SB) on growth performance and complete blood cell count in nursery pigs: Two facility study

A total of 344 weaned pigs (21 ± 2 d of age) were used at University of Arkansas (UA, n = 2 16) and University of Illinois at Urbana-Champaign (UIUC, n = 128) to evaluate increasing level of sodium butyrate (SB) on growth performance and complete blood cell count. Pigs at each facility were blocked by initial BW and randomly allotted to 1 of 4 dietary treatments with 9 replications/diet and 6 pigs/pen at UA; and 8 replications/diet and 4 pigs/pen at UIUC. Treatments included a control corn-soybean-meal based diet and 3 diets in which 0.05, 0.10, or 0.15% SB was added to the control diet. Feed was manufactured at each facility. Pigs were fed in 3 phases: 7 d, 14 d, and 14 d at UIUC and 7 d, 14 d, and 19 d at UA for phase 1, 2, and 3, respectively. At UA, blood was collected at the beginning of the experiment and at the end of each phase to determine complete blood cell count. Data for growth performance for both facilities were pooled and analysed as a RCBD using the Mixed procedure of SAS. Treatment was the fixed effect, and facility and facility by treatment interactions were random effects. Orthogonal contrasts were used to assess linear and quadratic responses to inclusion of increasing levels of SB in diets. Increasing dietary SB increased weight gain (quadratic, P < 0.05), ADFI (quadratic, P ≤ 0.05), and final BW (quadratic, P < 0.05). Total white blood cell and eosinophil cell count tended to increase with increasing SB (quadratic, P = 0.07 and P = 0.08, respectively). The lymphocyte cell count tended to decrease (linear, P = 0.09) with increasing SB. Results indicated that feeding SB during the nursery phase tended to alter blood cell count and improve growth performance.