Staphylococcus aureus directly activates eosinophils via platelet-activating factor receptor

Eosinophils as drivers of bacterial immunomodulation and persistence

Traditionally, eosinophils have been linked to parasitic infections and pathological disease states. However, emerging literature has unveiled a more nuanced and intricate role for these cells, demonstrating their key functions in maintaining mucosal homeostasis. Eosinophils exhibit diverse phenotypes and exert multifaceted effects during infections, ranging from promoting pathogen persistence to triggering allergic reactions. Our investigations primarily focus on Bordetella spp., with particular emphasis on Bordetella bronchiseptica, a natural murine pathogen that induces diseases in mice akin to pertussis in humans. Recent findings from our published work have unveiled a striking interaction between B. bronchiseptica and eosinophils, facilitated by the btrS-mediated mechanism. This interaction serves to enhance pathogen persistence while concurrently delaying adaptive immune responses. Notably, this role of eosinophils is only noted in the absence of a functional btrS signaling pathway, indicating that wild-type B. bronchiseptica, and possibly other Bordetella spp., possess such adeptness in manipulating eosinophils that the true function of these cells remains obscured during infection. In this review, we present the mounting evidence pointing toward eosinophils as targets of bacterial exploitation, facilitating pathogen persistence and fostering chronic infections in diverse mucosal sites, including the lungs, gut, and skin. We underscore the pivotal role of the master regulator of Bordetella pathogenesis, the sigma factor BtrS, in orchestrating eosinophil-dependent immunomodulation within the context of pulmonary infection. These putative convergent strategies of targeting eosinophils offer promising avenues for the development of novel therapeutics targeting respiratory and other mucosal pathogens.

IL-10+ regulatory B cells mitigate atopic dermatitis by suppressing eosinophil activation

Atopic dermatitis (AD) presents significant therapeutic challenges due to its poorly understood etiology. Eosinophilia, a hallmark of allergic inflammation, is implicated in AD pathogenesis. Interleukin-10 (IL-10)-producing regulatory B (Breg) cells exhibit potent anti-inflammatory effects. However, their role in controlling AD-related eosinophilia is not well understood. To investigate the impact of eosinophils on AD, we employed IL-5Rα-deficient (Il5ra-/-) mice, which lack functional eosinophils. Induction of AD in these mice resulted in attenuated disease symptoms, underscoring the critical role of eosinophils in AD development. Additionally, the adoptive transfer of purified Breg cells into mice with AD significantly alleviated disease severity. Mechanistic studies revealed that IL-10 produced by Breg cells directly inhibits eosinophil activation and infiltration into the skin. In vitro experiments further confirmed that Breg cells inhibited eosinophil peroxidase secretion in an IL-10-dependent manner. Our collective findings demonstrate that IL-10 from Breg cells alleviates AD by suppressing eosinophil activation and tissue infiltration. This study elucidates a novel regulatory mechanism of Breg cells, providing a foundation for future Breg-mediated therapeutic strategies for AD.

Bordetella spp. block eosinophil recruitment to suppress the generation of early mucosal protection

Bordetella spp. are respiratory pathogens equipped with immune evasion mechanisms. We previously characterized a Bordetella bronchiseptica mutant (RB50ΔbtrS) that fails to suppress host responses, leading to rapid clearance and long-lasting immunity against reinfection. This work revealed eosinophils as an exclusive requirement for RB50ΔbtrS clearance. We also show that RB50ΔbtrS promotes eosinophil-mediated B/T cell recruitment and inducible bronchus-associated lymphoid tissue (iBALT) formation, with eosinophils being present throughout iBALT for Th17 and immunoglobulin A (IgA) responses. Finally, we provide evidence that XCL1 is critical for iBALT formation but not maintenance, proposing a novel role for eosinophils as facilitators of adaptive immunity against B. bronchiseptica. RB50ΔbtrS being incapable of suppressing eosinophil effector functions illuminates active, bacterial targeting of eosinophils to achieve successful persistence and reinfection. Overall, our discoveries contribute to understanding cellular mechanisms for use in future vaccines and therapies against Bordetella spp. and extension to other mucosal pathogens.

Competition between skin antimicrobial peptides and commensal bacteria in type 2 inflammation enables survival of S. aureus

During inflammation, the skin deploys antimicrobial peptides (AMPs) yet during allergic inflammation it becomes more susceptible to Staphylococcus aureus. To understand this contradiction, single-cell sequencing of Il4ra^-/- mice combined with skin microbiome analysis reveals that lower production of AMPs from interleukin-4 receptor α (IL-4Rα) activation selectively inhibits survival of antibiotic-producing strains of coagulase-negative Staphylococcus (CoNS). Diminished AMPs under conditions of T helper type 2 (Th2) inflammation enable expansion of CoNS strains without antibiotic activity and increase Staphylococcus aureus (S. aureus), recapitulating the microbiome on humans with atopic dermatitis. This response is rescued in Camp^-/- mice or after topical steroids, since further inhibition of AMPs enables survival of antibiotic-producing CoNS strains. In conditions of Th17 inflammation, a higher expression of host AMPs is sufficient to directly inhibit S. aureus survival. These results show that antimicrobials produced by the host and commensal bacteria each act to control S. aureus on the skin.

Clinical Potential of Eosinophil-Derived Neurotoxin in Asthma Management

The assessment and management of patients with asthma is challenging because of the complexity of the underlying inflammatory mechanisms and heterogeneity of their clinical presentation. Optimizing disease management requires therapy individualization that should rely on reliable biomarkers to unravel the phenotypes and endotypes of asthma. The secretory activity and turnover of eosinophils, as assessed by measuring eosinophil-derived proteins, may provide an accurate and complementary tool that mirrors the eosinophil activation status. Emerging evidence suggests that eosinophil-derived neurotoxin has considerable potential as a precision medicine biomarker. In this review, we explore the suitability of eosinophil-derived neurotoxin as a biomarker in asthma management, with particular emphasis on its clinical significance in the management of both pediatric and adult populations.

Translating the biology of β common receptor-engaging cytokines into clinical medicine

The family of cytokines that comprises IL-3, IL-5, and GM-CSF was discovered over 30 years ago, and their biological activities and resulting impact in clinical medicine has continued to expand ever since. Originally identified as bone marrow growth factors capable of acting on hemopoietic progenitor cells to induce their proliferation and differentiation into mature blood cells, these cytokines are also recognized as key mediators of inflammation and the pathobiology of diverse immunologic diseases. This increased understanding of the functional repertoire of IL-3, IL-5, and GM-CSF has led to an explosion of interest in modulating their functions for clinical management. Key to the successful clinical translation of this knowledge is the recognition that these cytokines act by engaging distinct dimeric receptors and that they share a common signaling subunit called β-common or βc. The structural determination of how IL-3, IL-5, and GM-CSF interact with their receptors and linking this to their differential biological functions on effector cells has unveiled new paradigms of cell signaling. This knowledge has paved the way for novel mAbs and other molecules as selective or pan inhibitors for use in different clinical settings.

Serum Levels of Eosinophil-Derived Neurotoxin, Platelet-Activating Factor and Vascular Endothelial Growth Factor in Adult Patients with Atopic Dermatitis-A Pilot Study

Atopic dermatitis (AD) is a chronic, highly pruritic, relapsing-remitting inflammatory skin disease. The etiology of AD has not been fully explained yet and complex interactions of various small molecules are still being taken into account. The aim of this research was to investigate the serum eosinophil-derived neurotoxin (EDN), platelet activating factor (PAF) and vascular endothelial growth factor (VEGF) concentrations in relation to the disease severity and pruritus intensity in adult patients with AD. This pilot study was performed on 30 participants (15 patients with AD and 15 healthy controls). Blood samples were taken to examine the serum levels of EDN, PAF and VEGF using the enzyme-linked immunosorbent assay (ELISA) test. The severity of disease was assessed by the Scoring Atopic Dermatitis (SCORAD) index. The intensity of pruritus, as a subjective symptom, was determined by the Visual Analogue Scale (VAS). Obtained results revealed that the EDN (p = 0.016) and VEGF (p = 0.032), but not PAF (p = 0.841) concentrations were significantly higher in patients with AD compared with those of the control group. There was positive correlation between the EDN level and the SCORAD index in patients with AD (r = -0.9, p = 0.037) which was not found for the PAF and VEGF levels. Circulating EDN, PAF and VEGF levels were not significantly correlated with the severity of pruritus. Our results suggest that the END and VEGF serum levels are significantly increased in patients with AD compared to control group. Moreover, EDN might be useful to reflect the severity of symptoms.

The regulatory role of eosinophils in viral, bacterial, and fungal infections

Eosinophils are innate immune cells typically associated with allergic and parasitic diseases. However, in recent years, eosinophils have also been ascribed a role in keeping homeostasis and in fighting several infectious diseases. Indeed, these cells circulate as mature cells in the blood and can be quickly recruited to the infected tissue. Moreover, eosinophils have all the necessary cellular equipment such as pattern recognition receptors (PRRs), pro-inflammatory cytokines, anti-bacterial proteins, and DNA traps to fight pathogens and promote an efficient immune response. This review summarizes some of the updated information on the role of eosinophils' direct and indirect mediated interactions with pathogens.

Host-informed therapies for the treatment of pneumococcal pneumonia

Over the past two decades, traditional antimicrobial strategies have lost efficacy due to a rapid rise in antibiotic resistance and limited success in developing new antibiotics. Rather than relying on therapeutics solely targeting the bacterial pathogen, therapies are emerging that simultaneously focus on host responses. Here, we describe the most promising 'host-informed therapies' (HITs) in two categories: those that aid patients with fully functional immune systems, and those that aid patients with perturbed immune processes. Using Streptococcus pneumoniae, the leading cause of bacterial pneumonia, as a case study, we show HITs as an attractive option for supplementing infection management. However, to broaden their applicability and design new strategies, targeted research and clinical trials will be essential.

Eosinophils and Bacteria, the Beginning of a Story

Eosinophils are granulocytes primarily associated with TH2 responses to parasites or immune hyper-reactive states, such as asthma, allergies, or eosinophilic esophagitis. However, it does not make sense from an evolutionary standpoint to maintain a cell type that is only specific for parasitic infections and that otherwise is somehow harmful to the host. In recent years, there has been a shift in the perception of these cells. Eosinophils have recently been recognized as regulators of immune homeostasis and suppressors of over-reactive pro-inflammatory responses by secreting specific molecules that dampen the immune response. Their role during parasitic infections has been well investigated, and their versatility during immune responses to helminths includes antigen presentation as well as modulation of T cell responses. Although it is known that eosinophils can present antigens during viral infections, there are still many mechanistic aspects of the involvement of eosinophils during viral infections that remain to be elucidated. However, are eosinophils able to respond to bacterial infections? Recent literature indicates that Helicobacter pylori triggers TH2 responses mediated by eosinophils; this promotes anti-inflammatory responses that might be involved in the long-term persistent infection caused by this pathogen. Apparently and on the contrary, in the respiratory tract, eosinophils promote TH17 pro-inflammatory responses during Bordetella bronchiseptica infection, and they are, in fact, critical for early clearance of bacteria from the respiratory tract. However, eosinophils are also intertwined with microbiota, and up to now, it is not clear if microbiota regulates eosinophils or vice versa, or how this connection influences immune responses. In this review, we highlight the current knowledge of eosinophils as regulators of pro and anti-inflammatory responses in the context of both infection and naïve conditions. We propose questions and future directions that might open novel research avenues in the future.

Topical therapy of atopic dermatitis with a focus on pimecrolimus

Atopic dermatitis (AD) is a chronic and relapsing, inflammatory skin disease characterized by impaired skin barrier function and immune system dysregulation that results in dryness, skin microbiome dysbiosis and intense pruritus. It is highly heterogeneous, and its management is demanding. Patients with AD are at greater risk of comorbidities such as attention-deficit hyperactivity disorder as well as other atopic diseases. Early-onset AD cases typically improve or resolve in late childhood; however, it is proposed that the prevalence of persistent or adult-onset AD is higher than previously thought. Basic therapy consists of emollient application and trigger avoidance, and when insufficient, topical corticosteroids (TCS) are the first-line treatment. However, corticophobia/steroid aversion and TCS side-effects, particularly on sensitive skin areas, lead to low compliance and insufficient disease control. Several long- and short-term randomized controlled and daily practice studies have demonstrated that topical calcineurin inhibitors, such as pimecrolimus, have similar anti-inflammatory effects to low-to-medium strength TCS, reduce pruritus and improve the quality of life of patients. In addition, pimecrolimus does not cause skin atrophy, is steroid-sparing and has a good safety profile, with no evidence for an increased risk of malignancies or skin infections. In general, pimecrolimus cream is well-accepted and well-tolerated, encouraging patient adherence and leading to its use by many physicians as a preferred therapy for children and sensitive skin areas.

Eosinophilic lung disease as a sequela of MSSA pneumonia

Eosinophilic lung diseases are a rare group of lung disorders with multiple known and unknown aetiologies and the diagnosis is often challenging. We present a case of a young man who was admitted with pneumonia due to methicillin-sensitive Staphylococcus aureus and was discharged on antibiotics. He presented to the emergency department approximately 2 weeks after discharge with high-grade fever, cough and shortness of breath associated with serum and bronchoalveolar lavage eosinophilia. He was then treated with steroids with complete resolution of disease process.

Role of specific IgE on staphylococcal enterotoxin B in chronic rhinosinusitis severity

OBJECTIVE

To investigate the clinical significance of specific IgE-staphylococcal enterotoxin B (IgE-SEB) in CRS (chronic rhinosinusitis).

DESIGN

Retrospective analysis of patients who were positive for specific IgE-staphylococcal enterotoxin B.

SETTING

Tertiary rhinology clinic.

PARTICIPANTS

A total of 965 patients who were tested for specific IgE-staphylococcal enterotoxin B from December 2016 to December 2017.

MAIN OUTCOME MEASURES

We retrospectively reviewed the records of 965 patients who were tested for specific IgE-staphylococcal enterotoxin B from December 2016 to December 2017. Patient demographics, titre-specific IgE to staphylococcal enterotoxin B levels, MAST, serologic test and medical records were reviewed.

RESULTS

IgE-SEB (KU/L) was higher in CRS patients than non-CRS patients (0.13 ± 0.37 vs 0.08 ± 0.22, respectively; P-value: .044), and the IgE-SEB (+, ≥0.35) rate was also higher (10.06% vs 4.46%, respectively; P-value: .030). IgE-SEB (KU/L) was higher in the CRS group than in the fungal sinusitis group (0.13 ± 0.37 vs 0.03 ± 0.05, respectively; P-value: <.001), and the IgE-SEB (+, ≥0.35) rate was also higher (10.06% vs 0%, respectively; P-value: .015). Between the CRSsNP (chronic rhinosinusitis without nasal polyps) and CRSwNP (chronic rhinosinusitis with nasal polyps) groups, there were no differences in IgE-SEB (KU/L) or IgE-SEB (+) rates. IgE-SEB positivity was not associated with the presence of polyps, concomitant asthma or postoperative recurrence. As the values of IgE-SEB (KU/L) and the IgE-SEB (+, >0.1) rate increased, the CRS severity also increased.

CONCLUSIONS

IgE-SEB showed a positive correlation with Lund-Mackay CT severity score, but not with postoperative recurrence or nasal polyps. Further studies are needed to obtain clear evidence that IgE-SEB can be considered as an independent CRS endotype.

Eosinophilia and reduced STAT3 signaling affect neutrophil cell death in autosomal-dominant Hyper-IgE syndrome

The autosomal-dominant hyper-IgE syndrome (HIES), caused by mutations in STAT3, is a rare primary immunodeficiency that predisposes to mucocutaneous candidiasis and staphylococcal skin and lung infections. This infection phenotype is suggestive of defects in neutrophils, but data on neutrophil functions in HIES are inconsistent. This study was undertaken to functionally characterize neutrophils in STAT3-deficient HIES patients and to analyze whether the patients` eosinophilia affects the neutrophil phenotype in S. aureus infection. Neutrophil functions and cell death kinetics were studied in eight STAT3-deficient patients. Moreover, the response of STAT3-deficient neutrophils to S. aureus and the impact of autologous eosinophils on pathogen-induced cell death were analyzed. No specific aberrations in neutrophil functions were detected within this cohort. However, the half-life of STAT3-deficient neutrophils ex vivo was reduced, which was partially attributable to the presence of eosinophils. Increased S. aureus-induced cell lysis, dependent on the staphylococcal virulence controlling accessory gene regulator (agr)-locus, was observed in STAT3-deficient neutrophils and upon addition of eosinophils. Accelerated neutrophil cell death kinetics may underlie the reported variability in neutrophil function testing in HIES. Increased S. aureus-induced lysis of STAT3-deficient neutrophils might affect pathogen control and contribute to tissue destruction during staphylococcal infections in HIES.

Staphylococcal enterotoxin IgE sensitization in late-onset severe eosinophilic asthma in the elderly

BACKGROUND

Asthma in the elderly (aged ≥ 65 years old) is a significant concern with high morbidity, but the pathophysiology remains unclear particularly in late-onset asthma. Recent studies suggest staphylococcal enterotoxin IgE (SE-IgE) sensitization to be a risk factor for asthma in general populations; however, the associations have not been examined in late-onset elderly asthma.

OBJECTIVE

We aimed to examine the associations of SE-IgE sensitization with late-onset asthma in the elderly, using a database of elderly asthma cohort study.

METHODS

A total of 249 elderly patients with asthma and 98 controls were analysed. At baseline, patients were assessed for demographics, atopy, induced sputum profiles and comorbidities including chronic rhinosinusitis (CRS). Serum total IgE and SE-IgE levels were measured. Asthma severity was assessed on the basis of asthma outcomes during a 12-month follow-up period.

RESULTS

At baseline, serum SE-IgE concentrations were significantly higher in patients with asthma than in controls [median 0.16 (interquartile range 0.04-0.53) vs. 0.10 (0.01-0.19), P < 0.001]. Elderly asthma patients with high SE-IgE levels had specific characteristics of having more severe asthma, sputum eosinophilia and CRS, compared to those with lower SE-IgE levels. In multivariate logistic regression analyses, the associations between serum SE-IgE concentrations and severe asthma were significant, independently of covariables [SE-IgE-high (≥ 0.35 kU/L) vs. negative (< 0.10 kU/L) group: odds ratio 7.47, 95% confidence interval 1.86-30.03, P = 0.005]. Multiple correspondence analyses also showed that high serum SE-IgE level had close relationships with severe asthma, CRS and sputum eosinophilia together.

CONCLUSIONS AND CLINICAL RELEVANCE

This is the first report on the significant associations of SE-IgE sensitization with late-onset asthma in the elderly, particularly severe eosinophilic asthma with CRS comorbidity. Our findings indicate a potential implication of SE in the high morbidity burden of elderly asthma and suggest clues to the pathogenesis of severe late-onset eosinophilic asthma in the elderly.

Bacterial exploitation of phosphorylcholine mimicry suppresses inflammation to promote airway infection

Regulation of neutrophil activity is critical for immune evasion among extracellular pathogens, yet the mechanisms by which many bacteria disrupt phagocyte function remain unclear. Here, we have shown that the respiratory pathogen Streptococcus pneumoniae disables neutrophils by exploiting molecular mimicry to degrade platelet-activating factor (PAF), a host-derived inflammatory phospholipid. Using mass spectrometry and murine upper airway infection models, we demonstrated that phosphorylcholine (ChoP) moieties that are shared by PAF and the bacterial cell wall allow S. pneumoniae to leverage a ChoP-remodeling enzyme (Pce) to remove PAF from the airway. S. pneumoniae-mediated PAF deprivation impaired viability, activation, and bactericidal capacity among responding neutrophils. In the absence of Pce, neutrophils rapidly cleared S. pneumoniae from the airway and impeded invasive disease and transmission between mice. Abrogation of PAF signaling rendered Pce dispensable for S. pneumoniae persistence, reinforcing that this enzyme deprives neutrophils of essential PAF-mediated stimulation. Accordingly, exogenous activation of neutrophils overwhelmed Pce-mediated phagocyte disruption. Haemophilus influenzae also uses an enzyme, GlpQ, to hydrolyze ChoP and subvert PAF function, suggesting that mimicry-driven immune evasion is a common paradigm among respiratory pathogens. These results identify a mechanism by which shared molecular structures enable microbial enzymes to subvert host lipid signaling, suppress inflammation, and ensure bacterial persistence at the mucosa.

The CD48 receptor mediates Staphylococcus aureus human and murine eosinophil activation

BACKGROUND

Allergy is characterized by eosinophilia and an increased susceptibility to microbial infection. Atopic dermatitis (AD) is typically associated with Staphylococcus aureus (SA) colonization. Some of the mechanisms by which SA and its exotoxins interact with eosinophils remain elusive. CD48, a glycosylphosphatidylinositol-anchored receptor belonging to the CD2 family, participates in mast cells-SA stimulating cross-talk, facilitates the formation of the mast cell/eosinophils effector unit and as expressed by eosinophils, mediates experimental asthma.

OBJECTIVE

To investigate the role of CD48 expressed on human peripheral blood and mouse bone marrow-derived eosinophils (BMEos) in their interaction with heat-killed SA and its three exotoxins, Staphylococcal enterotoxin B (SEB), protein A (PtA) and peptidoglycan (PGN).

METHODS

Eosinophils were obtained from human peripheral blood and BM of WT and CD48-/- mice. SA was heat killed and eosinophils-SA/exotoxins interactions were analyzed by confocal microscopy, adhesion and degranulation, cell viability, cytokine release and cell signalling. In addition, peritonitis was induced by SEB injection into CD48-/- and WT mice. CD48 expression was studied in AD patients' skin and as expressed on their leucocytes in the peripheral blood.

RESULTS

We provide evidence for the recognition and direct physical interaction between eosinophils and SA/exotoxins. Skin of AD patients showed a striking increase of eosinophil-associated CD48 expression while on peripheral blood leucocytes it was down-regulated. SA/exotoxins enhanced CD48 eosinophil expression, bound to CD48 and caused eosinophil activation and signal transduction. These effects were significantly decreased by blocking CD48 on human eosinophils or in BMEos from CD48-/- mice. We have also explored the role of CD48 in a SEB-induced peritonitis model in CD48-/- mice by evaluating inflammatory peritoneal cells, eosinophil numbers and activation.

CONCLUSIONS

These data demonstrate the important role of CD48 in SA/exotoxins-eosinophil activating interactions that can take place during allergic responses and indicate CD48 as a novel therapeutic target for allergy and especially of AD.

NOX2-derived ROS-mediated surface translocation of BLT1 is essential for exocytosis in human eosinophils induced by LTB4

BACKGROUND

Leukotriene B4 (LTB4) is a proinflammatory lipid mediator that elicits eosinophil exocytosis, leading to allergic inflammation. However, the detailed intracellular signaling mechanisms of eosinophil exocytosis induced by LTB4 are poorly understood. Herein, we report that NADPH oxidase (NOX)2-derived reactive oxygen species (ROS)-mediated BLT1 migration to the cell surface is required for exocytosis in human eosinophils induced by LTB4.

METHODS

Peripheral blood eosinophils were purified and stimulated for up to 60 min with LTB4. The signaling role of NOX2-derived ROS in BLT1-dependent exocytosis in LTB4-stimulated eosinophils was investigated.

RESULTS

Stimulating eosinophils with LTB4 induced intracellular ROS production and surface upregulation of the exocytosis marker protein CD63 via BLT1-mediated signaling. LTB4 induced p47(phox) phosphorylation and 91(phox) expression required for NOX2 activation in a BLT1-dependent manner. Pretreatment with NOX2 inhibitors, but not mitochondria inhibitor, prevented LTB4-induced ROS generation and exocytosis. At 30 min after stimulation with LTB4, BLT1 expression at the cell surface was upregulated. LTB4-triggered surface upregulation of BLT1 was also blocked by inhibition of ROS generation with NOX2 inhibitors. Moreover, stimulation for 30 min with LTB4 resulted in the interaction of BLT1 with NOX2 by immunoprecipitation. LTB4-induced ROS generation, surface upregulation of BLT1 and exocytosis was also inhibited by pretreatment with a lipid raft disruptor, protein kinase C inhibitor, or Src kinase inhibitor.

CONCLUSION

These results suggest that NOX2-derived ROS-mediated BLT1 trafficking to the cell surface plays a key role in the exocytosis of human eosinophils induced by LTB4.

Gut-adipose tissue axis in hepatic fat accumulation in humans

BACKGROUND & AIMS

Recent evidence suggests that in animals gut microbiota composition (GMC) affects the onset and progression of hepatic fat accumulation. The aim of this study was to investigate in humans whether subjects with high hepatic fat content (HHFC) differ in their GMC from those with low hepatic fat content (LHFC), and whether these differences are associated with body composition, biomarkers and abdominal adipose tissue inflammation.

METHODS

Hepatic fat content (HFC) was measured using proton magnetic resonance spectroscopy ((1)H MRS). Fecal GMC was profiled by 16S rRNA fluorescence in situ hybridization and flow cytometry. Adipose tissue gene expression was analyzed using Affymetrix microarrays and quantitative PCR.

RESULTS

The HHFC group had unfavorable GMC described by lower amount of Faecalibacterium prausnitzii (FPrau) (p<0.05) and relatively higher Enterobacteria than the LHFC group. Metabolically dysbiotic GMC associated with HOMA-IR and triglycerides (p<0.05 for both). Several inflammation-related adipose tissue genes were differentially expressed and correlated with HFC (p<0.05). In addition, the expression of certain genes correlated with GMC dysbiosis, i.e., low FPrau-to-Bacteroides ratio.

CONCLUSIONS

HHFC subjects differ unfavorably in their GMC from LHFC subjects. Adipose tissue inflammation may be an important link between GMC, metabolic disturbances, and hepatic fat accumulation.

Pediatric allergy and immunology in Japan

The Japanese Society of Pediatric Allergy and Clinical Immunology (JSPACI) was started in 1966 and currently has 3613 members as of August 1, 2012. The number of pediatricians specializing in allergies who have been certified by the Japanese Society of Allergology is 817. Among these, there are 125 training directors and training facilities for allergy and clinical immunology. The JSPACI first published an asthma guideline specific for children in 2000, and this has been revised every 3 yrs, contributing to better control of pediatric asthma. Food allergy management guidelines were first developed in 2005, which have helped to improve the care of food allergy patients. Among 514 pediatric training programs by the Japanese Society of Pediatrics, there are 312 facilities routinely performing oral food challenges. Among these, there were already 53 facilities performing oral immunotherapy at the end of 2011, treating 1400 cases of food allergy. The prevalence of pediatric allergic diseases has increased in Japan over the past 50 yrs. A number of International Study of Asthma and Allergies in Childhood surveys have been conducted in the past at specific times. The prevalence of wheezing among children aged 13-14 yrs in 2002 was 13.0%. Multi-year surveys found a 1.5- to 2-fold increase every 10 yrs until 2002. However, according to the latest data in 2012, asthma prevalence seems to have slightly decreased in Japan. Food allergy mainly associated with infantile atopic eczema among infants younger than 1 yr of age is the most common form as with other developed countries. The estimated food allergy prevalence based on data from several surveys is 5-10% among infants (0-6 yrs) and 1-2% among schoolchildren (6-15 yrs). A variety of patients suffering from primary deficiency syndrome have been actively analyzed. Previously, antibody defects and well-defined syndromes with immunodeficiency were analyzed, but recent research is focusing on not only acquired immune disorders but also on innate immune disorders. In contrast to the widespread use of oral immunotherapy, one immediate issue is to develop and reassess subcutaneous and sublingual immunotherapies for mite and Japanese cedar pollen antigens that have been disused in Japan since the 1990s.

Differential activation of eosinophils by bacteria associated with asthma

BACKGROUND

It has been suggested that there is a complex interaction between microbiota and various human diseases. Some bacteria have been reported to be involved in the inception and progression of asthma, and others in the protection against asthma. We know very little about the mechanisms by which bacteria do harm or good with regard to asthma. This study investigated whether bacteria exert differential effects on the functions of eosinophils, major effector cells in airway inflammation in asthma.

METHODS

Eosinophils were purified from healthy adult volunteers by Percoll density gradient centrifugation and negative immunomagnetic bead selection using anti-CD16 microbeads. Three kinds of heat-killed bacteria that have been implicated in asthma, namely Staphylococcus aureus (SA), Haemophilus influenzae (HI) and a Prevotella sp. (PS), were tested for their effects on the secretion of eosinophil-derived neurotoxin (EDN), the generation of superoxides and the production of cytokines/chemokines.

RESULTS

SA, but not HI or PS, induced significant EDN release in a dose-dependent manner. Superoxide generation was significantly enhanced by each of the bacterial species, but most strongly by SA, which induced significantly greater TNF-α production by eosinophils than either HI or PS. Conversely, interleukin 10, an anti-inflammatory cytokine, was more strongly induced by HI and PS than by SA.

CONCLUSIONS

Bacteria exert differential effects on eosinophils. Based on these results, SA may be involved in the exacerbation of, and HI and PS in the inhibition of, eosinophilic inflammation in asthma.

Microbial modulation of host immunity with the small molecule phosphorylcholine

All microorganisms dependent on persistence in a host for survival rely on either hiding from or modulating host responses to infection. The small molecule phosphorylcholine, or choline phosphate (ChoP), is used for both of these purposes by a wide array of bacterial and parasitic microbes. While the mechanisms underlying ChoP acquisition and expression are diverse, a unifying theme is the use of ChoP to reduce the immune response to infection, creating an advantage for ChoP-expressing microorganisms. In this minireview, we discuss several benefits of ChoP expression during infection as well as how the immune system fights back against ChoP-expressing pathogens.