Bacterial protein domains with a novel Ig-like fold target human CEACAM receptors.

Streptococcus agalactiae, also known as group B Streptococcus (GBS), is the major cause of neonatal sepsis in humans. A critical step to infection is adhesion of bacteria to epithelial surfaces. GBS adhesins have been identified to bind extracellular matrix components and cellular receptors. However, several putative adhesins have no host binding partner characterised. We report here that surface-expressed ß protein of GBS binds to human CEACAM1 and CEACAM5 receptors. A crystal structure of the complex showed that an IgSF domain in ß represents a novel Ig-fold subtype called IgI3, in which unique features allow binding to CEACAM1. Bioinformatic assessment revealed that this newly identified IgI3 fold is not exclusively present in GBS but is predicted to be present in adhesins from other clinically important human pathogens. In agreement with this prediction, we found that CEACAM1 binds to an IgI3 domain found in an adhesin from a different streptococcal species. Overall, our results indicate that the IgI3 fold could provide a broadly applied mechanism for bacteria to target CEACAMs.

BRAF V600E is associated with higher incidence of second cancers in adults with Langerhans cell histiocytosis.

In this retrospective study, BRAF mutation status did not correlate with disease extent or (event-free) survival in 156 adults with Langerhans cell histiocytosis. BRAFV600E was associated with an increased incidence of second malignancies, often comprising hematological cancers, which may be clonally related.

De-escalation of axillary treatment in the event of a positive sentinel lymph node biopsy in cT1-2 N0 breast cancer treated with mastectomy: nationwide registry study (BOOG 2013-07).

BACKGROUND: Trials have demonstrated the safety of omitting completion axillary lymph node dissection in patients with cT1-2 N0 breast cancer operated with breast-conserving surgery who have limited metastatic burden in the sentinel lymph node. The aim of this registry study was to provide insight into the oncological safety of omitting completion axillary treatment in patients operated with mastectomy who have limited-volume sentinel lymph node metastasis. METHODS: Women diagnosed in 2013-2014 with unilateral cT1-2 N0 breast cancer treated with mastectomy, with one to three sentinel lymph node metastases (pN1mi-pN1a), were identified from the Netherlands Cancer Registry, and classified by axillary treatment: no completion axillary treatment, completion axillary lymph node dissection, regional radiotherapy, or completion axillary lymph node dissection followed by regional radiotherapy. The primary endpoint was 5-year regional recurrence rate. Secondary endpoints included recurrence-free interval and overall survival, among others. RESULTS: In total, 1090 patients were included (no completion axillary treatment, 219 (20.1%); completion axillary lymph node dissection, 437 (40.1%); regional radiotherapy, 327 (30.0%); completion axillary lymph node dissection and regional radiotherapy, 107 (9.8%)). Patients in the group without completion axillary treatment had more favourable tumour characteristics and were older. The overall 5-year regional recurrence rate was 1.3%, and did not differ significantly between the groups. The recurrence-free interval was also comparable among groups. The group of patients who did not undergo completion axillary treatment had statistically significantly worse 5-year overall survival, owing to a higher percentage of non-cancer deaths. CONCLUSION: In this registry study of patients with cT1-2 N0 breast cancer treated with mastectomy, with low-volume sentinel lymph node metastasis, the 5-year regional recurrence rate was low and comparable between patients with and without completion axillary treatment.

Toward Understanding How Staphylococcal Protein A Inhibits IgG-Mediated Phagocytosis.

IgG molecules are crucial for the human immune response against bacterial infections. IgGs can trigger phagocytosis by innate immune cells, like neutrophils. To do so, IgGs should bind to the bacterial surface via their variable Fab regions and interact with Fcγ receptors and complement C1 via the constant Fc domain. C1 binding to IgG-labeled bacteria activates the complement cascade, which results in bacterial decoration with C3-derived molecules that are recognized by complement receptors on neutrophils. Next to FcγRs and complement receptors on the membrane, neutrophils also express the intracellular neonatal Fc receptor (FcRn). We previously reported that staphylococcal protein A (SpA), a key immune-evasion protein of Staphylococcus aureus, potently blocks IgG-mediated complement activation and killing of S. aureus by interfering with IgG hexamer formation. SpA is also known to block IgG-mediated phagocytosis in absence of complement, but the mechanism behind it remains unclear. In this study, we demonstrate that SpA blocks IgG-mediated phagocytosis and killing of S. aureus and that it inhibits the interaction of IgGs with FcγRs (FcγRIIa and FcγRIIIb, but not FcγRI) and FcRn. Furthermore, our data show that multiple SpA domains are needed to effectively block IgG1-mediated phagocytosis. This provides a rationale for the fact that SpA from S. aureus contains four to five repeats. Taken together, our study elucidates the molecular mechanism by which SpA blocks IgG-mediated phagocytosis and supports the idea that in addition to FcγRs, the intracellular FcRn is also prevented from binding IgG by SpA.

Staphylococcal protein A inhibits complement activation by interfering with IgG hexamer formation.

Immunoglobulin (Ig) G molecules are essential players in the human immune response against bacterial infections. An important effector of IgG-dependent immunity is the induction of complement activation, a reaction that triggers a variety of responses that help kill bacteria. Antibody-dependent complement activation is promoted by the organization of target-bound IgGs into hexamers that are held together via noncovalent Fc-Fc interactions. Here we show that staphylococcal protein A (SpA), an important virulence factor and vaccine candidate of Staphylococcus aureus, effectively blocks IgG hexamerization and subsequent complement activation. Using native mass spectrometry and high-speed atomic force microscopy, we demonstrate that SpA blocks IgG hexamerization through competitive binding to the Fc-Fc interaction interface on IgG monomers. In concordance, we show that SpA interferes with the formation of (IgG)6:C1q complexes and prevents downstream complement activation on the surface of S. aureus. Finally, we demonstrate that IgG3 antibodies against S. aureus can potently induce complement activation and opsonophagocytic killing even in the presence of SpA. Together, our findings identify SpA as an immune evasion protein that specifically blocks IgG hexamerization.

C1q binding to surface-bound IgG is stabilized by C1r2s2 proteases.

Complement is an important effector mechanism for antibody-mediated clearance of infections and tumor cells. Upon binding to target cells, the antibody's constant (Fc) domain recruits complement component C1 to initiate a proteolytic cascade that generates lytic pores and stimulates phagocytosis. The C1 complex (C1qr2s2) consists of the large recognition protein C1q and a heterotetramer of proteases C1r and C1s (C1r2s2). While interactions between C1 and IgG-Fc are believed to be mediated by the globular heads of C1q, we here find that C1r2s2 proteases affect the capacity of C1q to form an avid complex with surface-bound IgG molecules (on various 2,4-dinitrophenol [DNP]-coated surfaces and pathogenic Staphylococcus aureus). The extent to which C1r2s2 contributes to C1q-IgG stability strongly differs between human IgG subclasses. Using antibody engineering of monoclonal IgG, we reveal that hexamer-enhancing mutations improve C1q-IgG stability, both in the absence and presence of C1r2s2 In addition, hexamer-enhanced IgGs targeting S. aureus mediate improved complement-dependent phagocytosis by human neutrophils. Altogether, these molecular insights into complement binding to surface-bound IgGs could be important for optimal design of antibody therapies.

Effects of cylindrospermopsin, chlorpyrifos and their combination in a SH-SY5Y cell model concerning developmental neurotoxicity.

The cyanotoxin cylindrospermopsin (CYN) has been postulated to cause neurotoxicity, although the studies in this concern are very few. In addition, some studies in vitro indicate its possible effects on development. Furthermore, pesticides can be present in the same environmental samples as cyanotoxins. Therefore, chlorpyrifos (CPF) has been one of the most common pesticides used worldwide. The aim of this report was to study the effects of CYN, isolated and in combination with CPF, in a developmental neurotoxicity in vitro model. The human neuroblastoma SH-SY5Y cell line was exposed during 6 days of differentiation to both toxics to study their effects on cell viability and neurite outgrowth. To further evaluate effects of both toxicants on cholinergic signaling, their agonistic and antagonistic activities on the α7 homomeric nicotinic acetylcholine receptor (nAChR) were studied upon acute exposure. Moreover, a transcriptomic analysis by qPCR was performed after 6 days of CYN-exposure during differentiation. The results showed a concentration-dependent decrease on both cell viability and neurite outgrowth for both toxics isolated, leading to effective concentration 20 (EC20) values of 0.35 µM and 0.097 µM for CYN on cell viability and neurite outgrowth, respectively, and 100 µM and 58 µM for CPF, while the combination demonstrated no significant variations. In addition, 95 µM and 285 µM CPF demonstrated to act as an antagonist to nicotine on the nAChR, although CYN up to 2.4 µM had no effect on the efficacy of these receptors. Additionally, the EC20 for CYN (0.097 µM) on neurite outgrowth downregulated expression of the 5 genes NTNG2 (netrin G2), KCNJ11 (potassium channel), SLC18A3 (vesicular acetylcholine transporter), APOE (apolipoprotein E), and SEMA6B (semaphorin 6B), that are all important for neuronal development. Thus, this study points out the importance of studying the effects of CYN in terms of neurotoxicity and developmental neurotoxicity.

Human-specific staphylococcal virulence factors enhance pathogenicity in a humanised zebrafish C5a receptor model.

Staphylococcus aureus infects ∼30% of the human population and causes a spectrum of pathologies ranging from mild skin infections to life-threatening invasive diseases. The strict host specificity of its virulence factors has severely limited the accuracy of in vivo models for the development of vaccines and therapeutics. To resolve this, we generated a humanised zebrafish model and determined that neutrophil-specific expression of the human C5a receptor conferred susceptibility to the S. aureus toxins PVL and HlgCB, leading to reduced neutrophil numbers at the site of infection and increased infection-associated mortality. These results show that humanised zebrafish provide a valuable platform to study the contribution of human-specific S. aureus virulence factors to infection in vivo that could facilitate the development of novel therapeutic approaches and essential vaccines.

Ultra-low-dose CT versus chest X-ray for patients suspected of pulmonary disease at the emergency department: a multicentre randomised clinical trial.

BACKGROUND: Chest CT displays chest pathology better than chest X-ray (CXR). We evaluated the effects on health outcomes of replacing CXR by ultra-low-dose chest-CT (ULDCT) in the diagnostic work-up of patients suspected of non-traumatic pulmonary disease at the emergency department. METHODS: Pragmatic, multicentre, non-inferiority randomised clinical trial in patients suspected of non-traumatic pulmonary disease at the emergency department. Between 31 January 2017 and 31 May 2018, every month, participating centres were randomly allocated to using ULDCT or CXR. Primary outcome was functional health at 28 days, measured by the Short Form (SF)-12 physical component summary scale score (PCS score), non-inferiority margin was set at 1 point. Secondary outcomes included hospital admission, hospital length of stay (LOS) and patients in follow-up because of incidental findings. RESULTS: 2418 consecutive patients (ULDCT: 1208 and CXR: 1210) were included. Mean SF-12 PCS score at 28 days was 37.0 for ULDCT and 35.9 for CXR (difference 1.1; 95% lower CI: 0.003). After ULDCT, 638/1208 (52.7%) patients were admitted (median LOS of 4.8 days; IQR 2.1-8.8) compared with 659/1210 (54.5%) patients after CXR (median LOS 4.6 days; IQR 2.1-8.8). More ULDCT patients were in follow-up because of incidental findings: 26 (2.2%) versus 4 (0.3%). CONCLUSIONS: Short-term functional health was comparable between ULDCT and CXR, as were hospital admissions and LOS, but more incidental findings were found in the ULDCT group. Our trial does not support routine use of ULDCT in the work-up of patients suspected of non-traumatic pulmonary disease at the emergency department. TRIAL REGISTRATION NUMBER: NTR6163.

Pilot Study: Short Term Impact of Radiation Therapy on Bone Mineral Density and Bone Metabolism.

Despite the risk of complications, high dose radiation therapy is increasingly utilized in the management of selected bone malignancies. In this study, we investigate the impact of moderate to high dose radiation (over 50 Gy) on bone metabolism and structure. Between 2015 and 2018, patients with a primary malignant bone tumor of the sacrum that were either treated with high dose definitive radiation only or a combination of moderate to high dose radiation and surgery were prospectively enrolled at a single institution. Quantitative CTs were performed before and after radiation to determine changes in volumetric bone mineral density (BMD) of the irradiated and non-irradiated spine. Bone histomorphometry was performed on biopsies of the irradiated sacrum and the non-irradiated iliac crest of surgical patients using a quadruple tetracycline labeling protocol. In total, 9 patients were enrolled. Two patients received radiation only (median dose 78.3 Gy) and 7 patients received a combination of preoperative radiation (median dose 50.4 Gy), followed by surgery. Volumetric BMD of the non-irradiated lumbar spine did not change significantly after radiation, while the BMD of the irradiated sacrum did (pre-radiation median: 108.0 mg/cm3 (IQR 91.8-167.1); post-radiation median: 75.3 mg/cm3 (IQR 57.1-110.2); p = 0.010). The cancellous bone of the non-irradiated iliac crest had a stable bone formation rate, while the irradiated sacrum showed a significant decrease in bone formation rate [pre-radiation median: 0.005 mm3/mm2/year (IQR 0.003-0.009), post-radiation median: 0.001 mm3/mm2/year (IQR 0.001-0.001); p = 0.043]. Similar effects were seen in the cancellous and endocortical envelopes. This pilot study shows a decrease of volumetric BMD and bone formation rate after high-dose radiation therapy. Further studies with larger cohorts and other endpoints are needed to get more insight into the effect of radiation on bone. Level of evidence: IV.

A network analysis of depressive symptoms and metabolomics.

BACKGROUND: Depression is associated with metabolic alterations including lipid dysregulation, whereby associations may vary across individual symptoms. Evaluating these associations using a network perspective yields a more complete insight than single outcome-single predictor models. METHODS: We used data from the Netherlands Study of Depression and Anxiety (N = 2498) and leveraged networks capturing associations between 30 depressive symptoms (Inventory of Depressive Symptomatology) and 46 metabolites. Analyses involved 4 steps: creating a network with Mixed Graphical Models; calculating centrality measures; bootstrapping for stability testing; validating central, stable associations by extra covariate-adjustment; and validation using another data wave collected 6 years later. RESULTS: The network yielded 28 symptom-metabolite associations. There were 15 highly-central variables (8 symptoms, 7 metabolites), and 3 stable links involving the symptoms Low energy (fatigue), and Hypersomnia. Specifically, fatigue showed consistent associations with higher mean diameter for VLDL particles and lower estimated degree of (fatty acid) unsaturation. These remained present after adjustment for lifestyle and health-related factors and using another data wave. CONCLUSIONS: The somatic symptoms Fatigue and Hypersomnia and cholesterol and fatty acid measures showed central, stable, and consistent relationships in our network. The present analyses showed how metabolic alterations are more consistently linked to specific symptom profiles.

Preservation of the Pectoral Fascia in Mastectomy With Immediate Reconstruction: A Nationwide Survey.

INTRODUCTION: Pectoral fascia (PF) removal during mastectomy still seems to be the standard procedure. However, preservation of the PF might improve postoperative and cosmetic outcomes, without compromising oncological safety. Here, we report on a national survey among Dutch plastic surgeons and oncological breast surgeons to evaluate their techniques and opinions regarding the PF. MATERIALS AND METHODS: A survey based study was performed in the Netherlands, in which both plastic surgeons and oncological breast surgeons were included, each receiving a different version of the survey. The surveys were distributed to 460 and 150 e-mail addresses, respectively. RESULTS: A total of 68 responses were included from more than half of all Dutch medical centers. The results of this study indicate that circa one in five plastic surgeons and breast surgeons routinely preserve the PF during mastectomies and even more surgeons preserve the PF in specific cases. The surgical techniques and opinions regarding PF preservation widely differ between surgeons. CONCLUSIONS: Preservation of the PF does occur in a substantial part of the Dutch medical centers and techniques and opinions are contradictory. Future studies on this topic should clarify the effect of PF preservation on oncological safety, complication rates, postoperative pain, cosmetic outcomes, and patient satisfaction.

Long Term Health Related Quality of Life After Acute Type B Aortic Dissection: a Cross Sectional Survey Study.

OBJECTIVE: Acute type B aortic dissection (ATBD) is a rare yet serious cardiovascular event that potentially has an impact on health related quality of life (HRQoL). However, long term follow up data on this topic are scarce. This study aimed to review the long term HRQoL among patients treated for ATBD. METHODS: In this multicentre, cross sectional survey study, consecutive treated patients with ATBD between 2007 and 2017 in four referral centres in the Netherlands were retrospectively included and baseline data were collected. Between 2019 and 2021 the 36 Item Short Form Survey (SF-36) was sent to all surviving patients (n = 263) and was compared with validated SF-36 scores in the Dutch general population stratified by age and sex. RESULTS: In total, 144 of 263 surviving patients completed the SF-36 (response rate 55%). Median (IQR) age was 68 (61, 76) years at completion of the questionnaire, and 40% (n = 58) were female. Initial treatment was medical in 55% (n = 79), endovascular in 41% (n = 59), and surgical in 4% (n = 6) of ATBD patients. Median follow up time was 6.1 (range 1.7-13.9; IQR 4.0, 9.0) years. Compared with the general population, patients scored significantly worse on six of eight SF-36 subdomains, particularly physical domains. Apart from bodily pain, there were no substantial differences in HRQoL between male and female ATBD patients. Compared with sex matched normative data, females scored significantly worse on five of eight subdomains, whereas males scored significantly lower on six subdomains. Younger patients aged 41-60 years seemed more severely impaired in HRQoL compared with the age matched general population. Treatment strategy did not influence HRQoL outcomes. Follow up time was associated with better Physical and Mental Component Summary scores. CONCLUSION: Long term HRQoL was impaired in ATBD patients compared with the Dutch general population, especially regarding physical status. This warrants more attention for HRQoL during clinical follow up. Rehabilitation programmes including exercise and physical support might improve HRQoL and increase patients' health understanding.

Improved LC-MS identification of short homologous peptides using sequence-specific retention time predictors.

Peptides are an important group of compounds contributing to the desired, as well as the undesired taste of a food product. Their taste impressions can include aspects of sweetness, bitterness, savoury, umami and many other impressions depending on the amino acids present as well as their sequence. Identification of short peptides in foods is challenging. We developed a method to assign identities to short peptides including homologous structures, i.e. peptides containing the same amino acids with a different sequence order, by accurate prediction of the retention times during reversed phase separation. To train the method, a large set of well-defined short peptides with systematic variations in the amino acid sequence was prepared by a novel synthesis strategy called 'swapped-sequence synthesis'. Additionally, several proteins were enzymatically digested to yield short peptides. Experimental retention times were determined after reversed phase separation and peptide MS2 data was acquired using a high-resolution mass spectrometer operated in data-dependent acquisition mode (DDA). A support vector regression model was trained using a combination of existing sequence-independent peptide descriptors and a newly derived set of selected amino acid index derived sequence-specific peptide (ASP) descriptors. The model was trained and validated using the experimental retention times of the 713 small food-relevant peptides prepared. Whilst selecting the most useful ASP descriptors for our model, special attention was given to predict the retention time differences between homologous peptide structures. Inclusion of ASP descriptors greatly improved the ability to accurately predict retention times, including retention time differences between 157 homologous peptide pairs. The final prediction model had a goodness-of-fit (Q2) of 0.94; moreover for 93% of the short peptides, the elution order was correctly predicted.

Mid-regional proadrenomedullin, C-terminal proendothelin-1 values, and disease course are not different in critically ill SARS-CoV-2 pneumonia patients with obesity.

BACKGROUND/OBJECTIVES: Patients affected by obesity and Coronavirus disease 2019, the disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), appear to have a higher risk for intensive care (ICU) admission. A state of low-grade chronic inflammation in obesity has been suggested as one of the underlying mechanisms. We investigated whether obesity is associated with differences in new inflammatory biomarkers mid-regional proadrenomedullin (MR-proADM), C-terminal proendothelin-1 (CT-proET-1), and clinical outcomes in critically ill patients with SARS-CoV-2 pneumonia. SUBJECTS/METHODS: A total of 105 critically ill patients with SARS-CoV-2 pneumonia were divided in patients with obesity (body mass index (BMI) ≥ 30 kg/m2, n = 42) and patients without obesity (BMI < 30 kg/m2, n = 63) and studied in a retrospective observational cohort study. MR-proADM, CT-proET-1 concentrations, and conventional markers of white blood count (WBC), C-reactive protein (CRP), and procalcitonin (PCT) were collected during the first 7 days. RESULTS: BMI was 33.5 (32-36.1) and 26.2 (24.7-27.8) kg/m2 in the group with and without obesity. There were no significant differences in concentrations MR-proADM, CT-proET-1, WBC, CRP, and PCT at baseline and the next 6 days between patients with and without obesity. Only MR-proADM changed significantly over time (p = 0.039). Also, BMI did not correlate with inflammatory biomarkers (MR-proADM rho = 0.150, p = 0.125, CT-proET-1 rho = 0.179, p = 0.067, WBC rho = -0.044, p = 0.654, CRP rho = 0.057, p = 0.564, PCT rho = 0.022, p = 0.842). Finally, no significant differences in time on a ventilator, ICU length of stay, and 28-day mortality between patients with or without obesity were observed. CONCLUSIONS: In critically ill patients with confirmed SARS-CoV-2 pneumonia, obesity was not associated with differences in MR-proADM, and CT-proET-1, or impaired outcome. TRIAL REGISTRATION: Netherlands Trial Register, NL8460.

Expanding the genetic and phenotypic spectrum of ACTA2-related vasculopathies in a Dutch cohort.

PURPOSE: Heterozygous pathogenic/likely pathogenic (P/LP) variants in the ACTA2 gene confer a high risk for thoracic aortic aneurysms and aortic dissections. This retrospective multicenter study elucidates the clinical outcome of ACTA2-related vasculopathies. METHODS: Index patients and relatives with a P/LP variant in ACTA2 were included. Data were collected through retrospective review of medical records using a standardized questionnaire. RESULTS: A total of 49 individuals from 28 families participated in our study. In total, 20 different ACTA2 variants were detected. Aortic events occurred in 65% of the cases (78.6% index patients and 47.6% relatives). Male sex and hypertension emerged as significantly associated with aortic events. Of 20 individuals, 5 had an aortic diameter of <45 mm (1.77 inches) at the time of the type A dissection. Mean age at first aortic event was 49.0 ± 12.4 years. Severe surgical complications for type A and type B dissection occurred in 25% and 16.7% of the cases and in-hospital mortality rates were 9.5% and 0%, respectively. CONCLUSION: P/LP ACTA2 variants are associated with an increased risk for an aortic event and age-related penetrance, which emphasizes the importance of early recognition of the disease. Caregivers should be aware of the risk for aortic dissections, even in individuals with aortic diameters within the normal range.

A cross-sectional study on fatigue, anxiety, and symptoms of depression and their relation with medical status in adult patients with Marfan syndrome. Psychological consequences in Marfan syndrome.

Marfan syndrome (MFS) is a connective tissue disorder affecting the cardiovascular, ocular, and skeletal system, which may be accompanied by psychological features. This study aimed to determine the prevalence of fatigue, anxiety, and symptoms of depression in MFS patients, and to assess the degree to which sociodemographic and clinical variables are associated with fatigue and psychological aspects. The prevalence of fatigue, anxiety, and symptoms of depression were assessed in two cohorts of MFS patients and compared with healthy controls. The checklist individual strength (CIS), and hospital anxiety and depression scale (HADS) questionnaires were utilized. Medical status was assessed (family history of MFS, aortic root dilatation >40 mm, previous aortic surgery, aortic dissection, chronic pain, skeletal involvement, and scoliosis). Severe fatigue was experienced by 37% of the total MFS cohort (n = 155). MFS patients scored significantly higher on the CIS questionnaire, concerning severe fatigue, as compared with the general Dutch population (p < 0.0001). There were no differences in HADS anxiety or depression scores. In older MFS patients, with a more severe cardiovascular phenotype, chronic pain, and a higher unemployment rate, significantly more symptoms of depression were observed, when compared with the general population (p = 0.027) or compared with younger MFS patients (p = 0.026). Multivariate analysis, showed that anxiety was associated with chronic pain (p = 0.022) and symptoms of depression with unemployment (p = 0.024). MFS patients report significantly more severe fatigue as compared with the general population. Since the cause of fatigue is unclear, more research may be needed. Psychological intervention, for example, cognitive behavioral therapy, may contribute to a reduction in psychological symptoms.

Signal inhibitory receptor on leukocytes-1 recognizes bacterial and endogenous amphipathic α-helical peptides.

Signal inhibitory receptor on leukocytes-1 (SIRL-1) is a negative regulator of myeloid cell function and dampens antimicrobial responses. We here show that different species of the genus Staphylococcus secrete SIRL-1-engaging factors. By screening a library of single-gene transposon mutants in Staphylococcus aureus, we identified these factors as phenol-soluble modulins (PSMs). PSMs are amphipathic α-helical peptides involved in multiple aspects of staphylococcal virulence and physiology. They are cytotoxic and activate the chemotactic formyl peptide receptor 2 (FPR2) on immune cells. Human cathelicidin LL-37 is also an amphipathic α-helical peptide with antimicrobial and chemotactic activities, structurally and functionally similar to α-type PSMs. We demonstrate that α-type PSMs from multiple staphylococcal species as well as human cathelicidin LL-37 activate SIRL-1, suggesting that SIRL-1 recognizes α-helical peptides with an amphipathic arrangement of hydrophobicity, although we were not able to show direct binding to SIRL-1. Upon rational peptide design, we identified artificial peptides in which the capacity to ligate SIRL-1 is segregated from cytotoxic and FPR2-activating properties, allowing specific engagement of SIRL-1. In conclusion, we propose staphylococcal PSMs and human LL-37 as a potential new class of natural ligands for SIRL-1.

Normal imaging findings after ascending aorta prosthesis implantation on 18F-Fluorodeoxyglucose Positron Emission Tomography with computed tomography.

BACKGROUND: To diagnose abnormal 18F-Fluorodeoxyglucose (18F-FDG) uptake in suspected endocarditis after aortic root and/or ascending aorta prosthesis (ARAP) implantation, it is important to first establish the normal periprosthetic uptake on positron emission tomography with computed tomography (PET/CT). METHODS: Patients with uncomplicated ARAP implantation were prospectively included and underwent 18F-FDG-PET/CT at either 12 (± 2) weeks (group 1) or 52 (± 8) weeks (group 2) after procedure. Uptake on three different locations of the prosthesis ("cranial anastomosis (CA)," "prosthetic heart valve (PHV)," "ascending aorta prosthesis (AAP)") was scored visually (none/low/intermediate/high) and quantitatively (maximum standardized uptake value (SUVmax) and target-to-background ratio (SUVratio). RESULTS: In total, 20 patients (group 1: n = 10, group 2: n = 10) (mean age 64±7 years, 70% male) were included. Both groups had similar visual uptake intensity for all measured areas (CA: mostly low-intermediate (16/20 (80%)), p = .17; PHV: low-intermediate (16/20 (80%)), p = .88; AAP: low-intermediate (19/20 (95%)), p = .48). SUVmax for CA was 5.6 [4.1-6.1] and 3.8 [3.1-5.9] (median [IQR], p = .19), and around PHV 5.0 [4.1-5.7] and 6.3 [4.6-7.1] (p = .11) for groups 1 and 2, respectively. SUVratio for CA was 2.8 [2.3-3.2] and 2.0 [1.7-2.6] (median [IQR], p = .07) and around PHV 2.5 [2.4-2.8] and 2.9 [2.3-3.5] (median [IQR], p = .26) for groups 1 and 2, respectively. CONCLUSION: No significant differences were observed between PET/CT findings at 3 months and 1 year after ARAP implantation, warranting caution in interpretation of PET/CT in the first year after implantation.

The Orphan Immune Receptor LILRB3 Modulates Fc Receptor-Mediated Functions of Neutrophils.

Neutrophils are critical to the generation of effective immune responses and for killing invading microbes. Paired immune receptors provide important mechanisms to modulate neutrophil activation thresholds and effector functions. Expression of the leukocyte Ig-like receptor (LILR)A6 (ILT8/CD85b) and LILRB3 (ILT5/CD85a) paired-receptor system on human neutrophils has remained unclear because of the lack of specific molecular tools. Additionally, there is little known of their possible functions in neutrophil biology. The objective of this study was to characterize expression of LILRA6/LILRB3 receptors during human neutrophil differentiation and activation, and to assess their roles in modulating Fc receptor-mediated effector functions. LILRB3, but not LILRA6, was detected in human neutrophil lysates following immunoprecipitation by mass spectrometry. We demonstrate high LILRB3 expression on the surface of resting neutrophils and release from the surface following neutrophil activation. Surface expression was recapitulated in a human PLB-985 cell model of neutrophil-like differentiation. Continuous ligation of LILRB3 inhibited key IgA-mediated effector functions, including production of reactive oxygen species, phagocytic uptake, and microbial killing. This suggests that LILRB3 provides an important checkpoint to control human neutrophil activation and their antimicrobial effector functions during resting and early-activation stages of the neutrophil life cycle.