House dust endotoxin and allergic sensitization in children

Radiation-Detoxified Form of Endotoxin Effectively Activates Th1 Responses and Attenuates Ragweed-Induced Th2-Type Airway Inflammation in Mice

Urbanization with reduced microbial exposure is associated with an increased burden of asthma and atopic symptoms. Conversely, environmental exposure to endotoxins in childhood can protect against the development of allergies. Our study aimed to investigate whether the renaturation of the indoor environment with aerosolized radiation-detoxified lipopolysaccharide (RD-LPS) has a preventative effect against the development of ragweed-induced Th2-type airway inflammation. To explore this, cages of six-week-old BALB/c mice were treated daily with aerosolized native LPS (N-LPS) or RD-LPS. After a 10-week treatment period, mice were sensitized and challenged with ragweed pollen extract, and inflammatory cell infiltration into the airways was observed. As dendritic cells (DCs) play a crucial role in the polarization of T-cell responses, in our in vitro experiments, the effects of N-LPS and RD-LPS were compared on human monocyte-derived DCs (moDCs). Mice in RD-LPS-rich milieu developed significantly less allergic airway inflammation than mice in N-LPS-rich or common environments. The results of our in vitro experiments demonstrate that RD-LPS-exposed moDCs have a higher Th1-polarizing capacity than moDCs exposed to N-LPS. Consequently, we suppose that the aerosolized, non-toxic RD-LPS applied in early life for the renaturation of urban indoors may be suitable for the prevention of Th2-mediated allergies in childhood.

A Cross-Sectional Study to Evaluate the Alteration of Cytokine Expression and Activation of Inflammatory Pathway in Response to NOD1 and NOD2 Signal in Leprosy

Introduction

Leprae bacilli are identified as foreign by pattern recognition receptors (PRRs) present in the microbes but absent in the host. The Nucleotide oligomerization domain (NOD)-like receptor (NLR) family comprises the nucleotide-binding oligomerisation domain (NOD1 and NOD2) proteins, which are two well-known PRRs. The objectives of this study were to study the expression of cytoplasmic NOD1 and NOD2 in the pathogenesis of leprosy and the serum level of expressed cytokines and to measure the messenger Ribonucleic Acid (mRNA) expression.

Methods

Clinically suspected Hansen's patients were analysed for 4 years. Newly diagnosed leprosy patients were considered leprosy disease control (LDC). The cases with active or new lesions and an increase in Bacteriological index (BI) by at least 2 + after 12 months of completion of Multidrug therapy (MDT) were considered leprosy disease relapse (LDR) cases. Age- and sex-matched healthy individuals served as our control group (healthy control (HC)). enzyme-linked immunosorbent assay (ELISA) was performed to measure the concentration of five human cytokines in serum, including three pro-inflammatory cytokines (Tumor necrosis factor (TNF)-α, Interferon gamma (IFN-γ) and IL-6), one anti-inflammatory cytokine (IL-10) and one chemokine (IL-8). Quantitative expression of receptor genes (NOD1 and NOD2) and cytokine genes (TNF-α, IFN-γ, IL-6, IL-10 and IL-8) was evaluated by quantitative real-time polymerase chain reaction (PCR) (qRT-PCR). We studied NOD1 and NOD2 expression in the tissues through fluorescence immunohistochemistry. Differential NLR intracellular expression on peripheral blood monocytes (PBMs) and their response to stimulation with specific ligands (lipopolysaccharide (LPS) and muramyl dipeptide (MDP)) were studied.

Results

A significant difference in the expression of the NOD1 gene was observed in unstimulated monocytes of the LDC and LDR cases when compared to HC. The NOD2 transcript level was significantly higher in stimulated monocytes from LDC and LDR patients than in similarly stimulated cells from HC. The LDC patients had a significantly higher level of pro-inflammatory cytokines as compared to the HC.

Conclusion

In conclusion, this study has demonstrated the expression of both cytokines and chemokines in response to NLR activation in the skin of leprosy patients.

Exposure to household dust, allergens, and endotoxin and allergy-related outcomes alternation in the general U.S. population

It has been widely reported that the general population was at an increased risk of allergy diseases, which probably be related with household allergens exposure. However, the difference of local and systemic allergic reactions exposure to allergens has not been reported in the general population previously. The data of 1094 U.S. adults from the National Health and Nutrition Examination Survey (NHANES) 2005-2006 data bank were analyzed. Dust, allergens (Bia g 1, Bia g 2, Can f 1, Feld 1, Derp 1, Mus m 1, Rat n 1, Alternaria alternate, and Aspergillus fumigatus), and endotoxin, were measured to estimate sensitizing source exposure. And allergy-related outcomes indicators including hay fever, sneezing, allergic rhinitis (AR), immunoglobulin E (IgE), and allergic sensitization, were evaluzted to estimate local and systemic allergic reactions. Multiple linear regression and logistic regression models were used to examine the associations of sensitizer and allergy-related outcomes. The mean or median concentration of dust and endotoxin were 0.66 g and 12.98 EU/mg dust. The Derp 1, Mus m 1, Rat n 1, Alternaria alternate, and Aspergillus fumigatus were the main allergens in the dust, with the concentrations of 30.66 ng/g dust, 30.73 ng/g dust, 5.94 ng/g dust, 5.20 ng/g dust, and 207.68 μg/g dust, respectively. The prevalence of AR was 34.2% among the general population. After controlling for sociodemographic factors, we found that the allergens, such as Can f 1 and Feld 1, were positively associated with AR. The prevalence of allergic sensitization was about 20%. Dust and endotoxin were found positively associated with allergic sensitization, while Bia g 2, Rat n 1, Alternaria alternate, and Aspergillus fumigatus were inversely associated with that. Dust and endotoxin probably be associated with higher risk of local allergic reactions, while some allergens, such as Bia g 2, Rat n 1, Alternaria alternate, and Aspergillus fumigatus probably be associated with lower risk of systemic allergic reactions.

IL-6 prevents Th2 cell polarization by promoting SOCS3-dependent suppression of IL-2 signaling

Defective interleukin-6 (IL-6) signaling has been associated with Th2 bias and elevated IgE levels. However, the underlying mechanism by which IL-6 prevents the development of Th2-driven diseases remains unknown. Using a model of house dust mite (HDM)-induced Th2 cell differentiation and allergic airway inflammation, we showed that IL-6 signaling in allergen-specific T cells was required to prevent Th2 cell differentiation and the subsequent IgE response and allergic inflammation. Th2 cell lineage commitment required strong sustained IL-2 signaling. We found that IL-6 turned off IL-2 signaling during early T-cell activation and thus inhibited Th2 priming. Mechanistically, IL-6-driven inhibition of IL-2 signaling in responding T cells was mediated by upregulation of Suppressor Of Cytokine Signaling 3 (SOCS3). This mechanism could be mimicked by pharmacological Janus Kinase-1 (JAK1) inhibition. Collectively, our results identify an unrecognized mechanism that prevents the development of unwanted Th2 cell responses and associated diseases and outline potential preventive interventions.

Understanding the development of Th2 cell-driven allergic airway disease in early life

Allergic diseases, including atopic dermatitis, allergic rhinitis, asthma, and food allergy, are caused by abnormal responses to relatively harmless foreign proteins called allergens found in pollen, fungal spores, house dust mites (HDM), animal dander, or certain foods. In particular, the activation of allergen-specific helper T cells towards a type 2 (Th2) phenotype during the first encounters with the allergen, also known as the sensitization phase, is the leading cause of the subsequent development of allergic disease. Infants and children are especially prone to developing Th2 cell responses after initial contact with allergens. But in addition, the rates of allergic sensitization and the development of allergic diseases among children are increasing in the industrialized world and have been associated with living in urban settings. Particularly for respiratory allergies, greater susceptibility to developing allergic Th2 cell responses has been shown in children living in urban environments containing low levels of microbial contaminants, principally bacterial endotoxins [lipopolysaccharide (LPS)], in the causative aeroallergens. This review highlights the current understanding of the factors that balance Th2 cell immunity to environmental allergens, with a particular focus on the determinants that program conventional dendritic cells (cDCs) toward or away from a Th2 stimulatory function. In this context, it discusses transcription factor-guided functional specialization of type-2 cDCs (cDC2s) and how the integration of signals derived from the environment drives this process. In addition, it analyzes observational and mechanistic studies supporting an essential role for innate sensing of microbial-derived products contained in aeroallergens in modulating allergic Th2 cell immune responses. Finally, this review examines whether hyporesponsiveness to microbial stimulation, particularly to LPS, is a risk factor for the induction of Th2 cell responses and allergic sensitization during infancy and early childhood and the potential factors that may affect early-age response to LPS and other environmental microbial components.

Endotoxin concentration and persistent eczema in early childhood

Although endotoxin concentration in the environment is negatively associated with atopic dermatitis (AD) onset in early childhood, the association between endotoxin concentration in the environment and eczema resolution in children with preexisting eczema is unclear. The aim of this study was to evaluate the association between endotoxin concentration in house dust and eczema persistence in young children. The authors used data from children participating in JECS (Japan Environment and Children's Study). In children who had AD or AD-like lesions at the age of 1 year, the authors investigated the association between the prevalence of eczema at the age of 3 years and endotoxin concentration (categorized by quartiles) in the dust on children's mattresses at the ages of 1.5 and 3 years. This study included 605 children. Eczema was significantly less prevalent among children whose mattresses were in the second and third quartiles of endotoxin concentration when they were 18 months old than among children whose mattresses were in the first quartile (adjusted odds ratio, 0.57 [95% confidence interval, 0.35-0.93] and adjusted odds ratio, 0.49 [95% confidence interval, 0.29-0.83], respectively). Moreover, of the children with eczema at age 3 years, those whose mattresses had endotoxin concentrations in the first quartile had significantly worse sleep disturbance caused by itchy rash (>1 time per week) than did those whose mattresses were in the third and fourth quartiles (20.0% vs 3.3% and 3.7%, both p values < 0.01). The findings indicate that low endotoxin exposure is associated with a higher prevalence of persistent eczema during early childhood.

Fooling TLR4 to promote fungal virulence

The invasive fungal pathogen Cryptococcus neoformans promotes type 2 immunity to escape host defenses by unknown mechanisms. In a recent issue of Nature, Dang and colleagues identify a secreted fungal protein that triggers TLR4 signaling and supports a type 2 permissive environment and C. neoformans growth.

Construction for Health; Reversing the Impacts

The health of humans and the planet are the most vital contemporary issues and essential components of the Sustainable Development Goals (SDGs). Scientists and professionals strive for integrated, evolving, healthy, and sustainable solutions encompassing biodiversity and industrial ecology, while offering viable economic attainments. The building industry, especially construction, is an extensive economic counterpart that largely influences health on various levels. On a practical scale, most direct or indirect impacts on health are related to conventional construction systems (CCSs), particularly their materialisations and implementation methods. Therefore, from a global perspective, emerging technologies or remodelled methods to accomplish sustainable use, reuse, and recycling, and improving the planet’s health to ensure the wellbeing of its inhabitants, are crucial. The current research is part of a broader study on “programmable construction systems” (PCSs), concentrating on “programmable construction materials” (PCMs) for health. Therefore, issues are reviewed, relevancies are addressed, and health-oriented concepts are discussed. Example concepts of formulation and the simplified toolkit creations follow the problems’ sources in a case study, providing insight into the resulting multiscale impacts on real-life practices. The results prove the method’s potential and validate its simplicity and applicability through an abstract examination of a newly built case study. Finally, the summarised outcomes of other extensive studies on societal preferences also confirm the feasibility of the hypothesis (i.e., the healthy materialisation) also from a social perspective.

GM-CSF production by non-classical monocytes controls antagonistic LPS-driven functions in allergic inflammation

Lipopolysaccharide (LPS) can either promote or prevent T helper 2 (Th2) cell allergic responses. However, the underlying mechanism remains unknown. We show here that LPS activity switches from pro-pathogenic to protective depending on the production of granulocyte-macrophage colony-stimulating factor (GM-CSF) by non-classical monocytes. In the absence of GM-CSF, LPS can favor pathogenic Th2 cell responses by supporting the trafficking of lung-migratory dendritic cells (mDC2s) into the lung-draining lymph node. However, when non-classical monocytes produce GM-CSF, LPS and GM-CSF synergize to differentiate monocyte-derived DCs from classical Ly6Chi monocytes that instruct mDC2s for Th2 cell suppression. Importantly, only allergens with cysteine protease activity trigger GM-CSF production by non-classical monocytes. Hence, the therapeutic effect of LPS is restricted to allergens with this enzymatic activity. Treatment with GM-CSF, however, restores the protective effects of LPS. Thus, GM-CSF produced by non-classical monocytes acts as a rheostat that fine-tunes the pathogenic and therapeutic functions of LPS.

Novel acute hypersensitivity pneumonitis model induced by airway mycosis and high dose lipopolysaccharide

BACKGROUND

Inhalation of fungal spores is a strong risk factor for severe asthma and experimentally leads to development of airway mycosis and asthma-like disease in mice. However, in addition to fungal spores, humans are simultaneously exposed to other inflammatory agents such as lipopolysaccharide (LPS), with uncertain relevance to disease expression. To determine how high dose inhalation of LPS influences the expression of allergic airway disease induced by the allergenic mold Aspergillus niger (A. niger).

METHODS

C57BL/6J mice were intranasally challenged with the viable spores of A. niger with and without 1 μg of LPS over two weeks. Changes in airway hyperreactivity, airway and lung inflammatory cell recruitment, antigen-specific immunoglobulins, and histopathology were determined.

RESULTS

In comparison to mice challenged only with A. niger, addition of LPS (1 μg) to A. niger abrogated airway hyperresponsiveness and strongly attenuated airway eosinophilia, PAS+ goblet cells and TH2 responses while enhancing TH1 and TH17 cell recruitment to lung. Addition of LPS resulted in more severe, diffuse lung inflammation with scattered, loosely-formed parenchymal granulomas, but failed to alter fungus-induced IgE and IgG antibodies.

CONCLUSIONS

In contrast to the strongly allergic lung phenotype induced by fungal spores alone, addition of a relatively high dose of LPS abrogates asthma-like features, replacing them with a phenotype more consistent with acute hypersensitivity pneumonitis (HP). These findings extend the already established link between airway mycosis and asthma to HP and describe a robust model for further dissecting the pathophysiology of HP.

Birch Pollen Induces Toll-Like Receptor 4-Dependent Dendritic Cell Activation Favoring T Cell Responses

Seasonal exposure to birch pollen (BP) is a major cause of pollinosis. The specific role of Toll-like receptor 4 (TLR4) in BP-induced allergic inflammation and the identification of key factors in birch pollen extracts (BPE) initiating this process remain to be explored. This study aimed to examine (i) the importance of TLR4 for dendritic cell (DC) activation by BPE, (ii) the extent of the contribution of BPE-derived lipopolysaccharide (LPS) and other potential TLR4 adjuvant(s) in BPE, and (iii) the relevance of the TLR4-dependent activation of BPE-stimulated DCs in the initiation of an adaptive immune response. In vitro, activation of murine bone marrow-derived DCs (BMDCs) and human monocyte-derived DCs by BPE or the equivalent LPS (nLPS) was analyzed by flow cytometry. Polymyxin B (PMB), a TLR4 antagonist and TLR4-deficient BMDCs were used to investigate the TLR4 signaling in DC activation. The immunostimulatory activity of BPE was compared to protein-/lipid-depleted BPE-fractions. In co-cultures of BPE-pulsed BMDCs and Bet v 1-specific hybridoma T cells, the influence of the TLR4-dependent DC activation on T cell activation was analyzed. In vivo immunization of IL-4 reporter mice was conducted to study BPE-induced Th2 polarization upon PMB pre-treatment. Murine and human DC activation induced by either BPE or nLPS was inhibited by the TLR4 antagonist or by PMB, and abrogated in TLR4-deficient BMDCs compared to wild-type BMDCs. The lipid-free but not the protein-free fraction showed a reduced capacity to activate the TLR4 signaling and murine DCs. In human DCs, nLPS only partially reproduced the BPE-induced activation intensity. BPE-primed BMDCs efficiently stimulated T cell activation, which was repressed by the TLR4 antagonist or PMB, and the addition of nLPS to Bet v 1 did not reproduce the effect of BPE. In vivo, immunization with BPE induced a significant Th2 polarization, whereas administration of BPE pre-incubated with PMB showed a decreased tendency. These findings suggest that TLR4 is a major pathway by which BPE triggers DC activation that is involved in the initiation of adaptive immune responses. Further characterization of these BP-derived TLR4 adjuvants could provide new candidates for therapeutic strategies targeting specific mechanisms in BP-induced allergic inflammation.

Microbial diversity in homes and the risk of allergic rhinitis and inhalant atopy in two European birth cohorts

BACKGROUND

Microbial exposures in early childhood direct the development of the immune system and their diversity may influence the risk of allergy development. We aimed to determine whether the indoor microbial diversity at early-life is associated with the development of allergic rhinitis and inhalant atopy.

METHODS

The study population included children within two birth cohorts: Finnish rural-suburban LUKAS (N = 312), and German urban LISA from Munich and Leipzig study centers (N = 248). The indoor microbiota diversity (Chao1 richness and Shannon entropy) was characterized from floor dust samples collected at the child age of 2-3 months by Illumina MiSeq sequencing of bacterial and fungal DNA amplicons. Allergic rhinitis and inhalant atopy were determined at the age of 10 years and analyzed using logistic regression models.

RESULTS

High bacterial richness (aOR 0.19, 95%CI 0.09-0.42 for middle and aOR 0.12, 95%CI 0.05-0.29 for highest vs. lowest tertile) and Shannon entropy were associated with lower risk of allergic rhinitis in LISA, and similar trend was seen in LUKAS. We observed some significant associations between bacterial and fungal diversity measured and the risk of inhalant atopy, but the associations were inconsistent between the two cohorts. High bacterial diversity tended to be associated with increased risk of inhalant atopy in rural areas, but lower risk in more urban areas. Fungal diversity tended to be associated with increased risk of inhalant atopy only in LISA.

CONCLUSIONS

Our study suggests that a higher bacterial diversity may reduce the risk of allergic rhinitis later in childhood. The environment-dependent heterogeneity in the associations with inhalant atopy - visible here as inconsistent results between two differing cohorts - suggests that specific constituents of the diversity may be relevant.

Particle Resuspension Dynamics in the Infant Near-Floor Microenvironment

Carpet dust contains microbial and chemical material that can impact early childhood health. Infants may be exposed to greater quantities of resuspended dust, given their close proximity to floor surfaces. Chamber experiments with a robotic infant were integrated with a material balance model to provide new fundamental insights into the size-dependency of infant crawling-induced particle resuspension and exposure. The robotic infant was exposed to resuspended particle concentrations from 10⁵ to 10⁶ m^-3 in the near-floor (NF) microzone during crawling, with concentrations generally decreasing following vacuum cleaning of the carpets. A pronounced vertical variation in particle concentrations was observed between the NF microzone and bulk air. Resuspension fractions for crawling are similar to those for adult walking, with values ranging from 10^-6 to 10^-1 and increasing with particle size. Meaningful amounts of dust are resuspended during crawling, with emission rates of 0.1 to 2 × 10⁴ μg h^-1. Size-resolved inhalation intake fractions ranged from 5 to 8 × 10³ inhaled particles per million resuspended particles, demonstrating that a significant fraction of resuspended particles can be inhaled. A new exposure metric, the dust-to-breathing zone transport efficiency, was introduced to characterize the overall probability of a settled particle being resuspended and delivered to the respiratory airways. Values ranged from less than 0.1 to over 200 inhaled particles per million settled particles, increased with particle size, and varied by over 2 orders of magnitude among 12 carpet types.

Global differences in atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disorder, with a highly variable prevalence worldwide. Recent evidence, however, has shown an increase in prevalence in the Asia Pacific region. Nevertheless, most of the published literature has focused mainly on Western populations, and only few clinical trials have included subgroups of other ethnic populations. Reasons for the observed ethnic and geographical differences in AD are not well established. This calls into question the need for a better understanding of AD pathogenesis and inter-ethnic differences in clinical and immuno-phenotypes. These differences may reflect inherent variability in disease mechanisms between populations, which in turn may impact upon treatment responses such as biologics that are currently tailored mainly to a specific immuno-phenotype (T-helper type 2 dominant). In this article, we reviewed existing literature on the prevalence of AD globally, highlighting differences, if any, in the clinical and immuno-phenotypes of AD between different ethnicities. We discussed genetic and environmental factors that affect AD in different populations and therapeutic considerations. Our review highlights AD as a disease with ethnic-dependent clinical and immunological heterogeneity and calls for greater inclusion of ethnic diversity in future research in order to develop targeted treatments.

House dust endotoxin, asthma and allergic sensitization through childhood into adolescence

Background

House dust endotoxin may have beneficial effects on allergic sensitization and asthma in children. Evidence is scarce for adolescents and most studies so far have been cross‐sectional and limited to a single exposure measurement.

Objective

We assessed associations of house dust endotoxin with asthma and allergic sensitization from birth to age 17 years longitudinally taking into account exposure early in life and at primary school age.

Methods

We used data of 854 participants of the prospective Dutch PIAMA birth cohort study with house dust endotoxin measurements at 3 months and/or 5‐6 years and data on asthma and/or allergic sensitization from at least one of 11 follow‐ups until age 17. We assessed overall and age‐specific associations of the prevalence of asthma and sensitization with mattress and living room floor dust concentrations (per gram of dust) and loads (per m² of sampling surface).

Results

Higher living room floor dust endotoxin concentrations at 3 months were associated with lower odds of asthma until age 4 [odds ratio (95% confidence interval) ranging from 0.70 (0.51‐0.97) at age 1 to 0.76 (0.57‐1.00) at age 3 per interquartile range increase], but not thereafter in children of allergic mothers. Higher living room floor dust endotoxin at 5‐6 years was associated with higher odds of sensitization at 8‐16 years [eg odds ratio (95% confidence interval) 1.70 (1.17‐2.47) per interquartile range increase in endotoxin load].

Conclusions and clinical relevance

House dust endotoxin may have beneficial effects on asthma in preschool children of allergic mothers, which do not persist into adolescence. Beneficial associations with allergic sensitization could not be confirmed.

The External Exposome and Food Allergy

PURPOSE OF REVIEW

The recent increase in childhood food allergy prevalence strongly suggests that environmental exposures are contributing to food allergy development. This review summarizes current knowledge about the role of the external exposome in food allergy.

RECENT FINDINGS

There is growing evidence that environmental exposure to food antigens in house dust through non-oral routes contributes to food sensitization and allergy. Co-exposure to environmental adjuvants in house dust, such as microbial products and fungal allergens, may also facilitate allergic sensitization. While a high-microbe environment is associated with decreased atopy, studies are mixed on whether endotoxin exposure protects against food sensitization. Several chemicals and air pollutants have been associated with food sensitization, but their role in food allergy remains understudied. Children are exposed to numerous environmental agents that can influence food allergy risk. Further studies are needed to identify the key early-life exposures that promote or inhibit food allergy development.

Household airborne endotoxin associated with asthma and allergy in elementary school-age children: a case-control study in Kaohsiung, Taiwan

To evaluate the association between the presence of asthma and allergy, and airborne endotoxin in homes of school-age children in Kaohsiung City, Taiwan, with a case-control study design by matching the age and class exposure. Data collection of home visits included an interviewer-administered questionnaire and air sampling of participants' homes for endotoxin, bacteria, and fungi, as well as temperature and relative humidity measurements. Endotoxin was detected in all air samples with a median value of 0.67 EU m^-3. In the adjusted logistic regression model, household airborne endotoxin was associated with higher prevalence of asthma and allergy; OR = 4.88 (95% CI 1.16-20.55) for Q3 (between 0.67 and 1.97 EU m ^-3) vs. Q1 (< 0.31 EU m ^-3), with statistical significance. Airborne fungi were associated with higher prevalence of asthma and allergy; OR = 4.47 (95% CI 1.13-17.69) for Q3 (between 314 and 699 CFU m ^-3) vs. Q1 (< 159 CFU m ^-3) in adjusted logistic regression models. Airborne endotoxin and fungi were significantly associated with children's asthma and allergy.

Comparison of microbiota and allergen profile in house dust from homes of allergic and non-allergic subjects- results from the GUSTO study

Background

The prevalence of allergic diseases, such as asthma, allergic rhinitis, eczema and food allergy, has been increasing worldwide, as shown in a large number of studies, including the International Study of Asthma and Allergies in Childhood (ISAAC). However, there is significant variation in the prevalence of these diseases in different regions, suggesting that there may be location-specific factors such as environment and microbial exposure affecting allergic disease prevalence. Hence, in this study we determine if there is a difference in microbiota composition and allergen concentration of household dust collected from the homes of non-allergic and allergic subjects from the Growing Up in Singapore Towards Healthy Outcomes (GUSTO) cohort.

Methods

From the Growing Up in Singapore Towards Healthy Outcomes (GUSTO) cohort, 25 allergic subjects and 25 non-allergic subjects were selected at the year 5.5 follow up. Definitions of allergic outcomes were standardized in the questionnaires administered at 3, 6, 9, 12, 15, 18, 24, 36, 48 and 60 months to ensure consistency during interviews and home visits. Allergen sensitization was determined by skin prick testing (SPT) at 18, 36 and 60 months. Dust samples were collected from the subject’s bed, sofa, and play area. DNA extraction was carried out and V3-V4 hypervariable regions of bacterial 16S rRNA gene were sequenced. Protein extraction was performed and allergens assayed by using multiplex assay and ELISA.

Results

The most abundant phyla in house dust were Actinobacteria (29.8%), Firmicutes (27.7%), and Proteobacteria (22.4%). Although there were no differences in bacteria abundance and diversity between house dust samples of allergic and non-allergic subjects, the relative abundance of Anaplasmataceae, Bacteroidaceae, and Leptospiraceae were significantly higher in dust samples of allergic subjects as compared to non-allergic subjects in 2 or more locations. The concentration of Der p 1 was significantly lower in bed dust samples of allergic subjects (Median [Interquartile range], 174 ng/g [115–299 ng/g]) as compared to non-allergic subjects (309 ng/g [201–400 ng/g]; P < 0.05). The concentration of tropomyosin was significantly higher in sofa dust samples of allergic subjects (175 ng/g [145–284 ng/g] as compared to non-allergic subjects (116 ng/g [52.8–170 ng/g]; P < 0.05).

Conclusion

In conclusion, we found a differential microbiota and allergen profile between homes of allergic and non-allergic subjects.

Trial registration

NCT01174875 Registered 1 July 2010, retrospectively registered.

Electronic supplementary material

The online version of this article (10.1186/s40413-018-0212-5) contains supplementary material, which is available to authorized users.

Artemisia pollen is the main vector for airborne endotoxin

BACKGROUND

Endotoxin (LPS) released from gram-negative bacteria causes strong immunologic and inflammatory effects and, when airborne, can contribute to respiratory conditions, such as allergic asthma.

OBJECTIVES

We sought to identify the source of airborne endotoxin and the effect of this endotoxin on allergic sensitization.

METHODS

We determined LPS levels in outdoor air on a daily basis for 4 consecutive years in Munich (Germany) and Davos (Switzerland). Air was sampled as particulate matter (PM) greater than 10 μm (PM > 10) and PM between 2.5 and 10 μm. LPS levels were determined by using the recombinant Factor C assay.

RESULTS

More than 60% of the annual endotoxin exposure was detected in the PM > 10 fraction, showing that bacteria do not aerosolize as independent units or aggregates but adhered to large particles. In Munich 70% of annual exposure was detected between June 12th and August 28th. Multivariate modeling showed that endotoxin levels could be explained by phenological parameters (ie, plant growth). Indeed, days with high airborne endotoxin levels correlated well with the amount of Artemisia pollen in the air. Pollen collected from plants across Europe (100 locations) showed that the highest levels of endotoxin were detected on Artemisia vulgaris (mugwort) pollen, with little on other pollen. Microbiome analysis showed that LPS concentrations on mugwort pollen were related to the presence of Pseudomonas species and Pantoea species communities. In a mouse model of allergic disease, the presence of LPS on mugwort pollen was needed for allergic sensitization.

CONCLUSIONS

The majority of airborne endotoxin stems from bacteria dispersed with pollen of only one plant: mugwort. This LPS was essential for inducing inflammation of the lung and allergic sensitization.

The association between endotoxin in house dust with atopy and exercise-induced bronchospasm in children with asthma

BACKGROUND

Studies have reported protective and adverse associations between microbial exposure and childhood asthma. However, among children with asthma the relationships between endotoxin and exercise-induced bronchospasm (EIB) is less clear.

OBJECTIVE

We investigated the association between exposure to endotoxin in house dust with atopy and EIB in children with asthma.

METHODS

A cross-sectional survey was conducted among schoolchildren (aged 7-17 years) in the province of Saskatchewan, Canada. A subpopulation with asthma (n = 116) were identified from 335 participants using a validated asthma algorithm. We determined atopy among the asthma subpopulation by skin prick testing (SPT) while EIB was evaluated using exercise challenge testing (ECT). Dust samples were collected from mattress and play area floors, and endotoxin was measured in dust extracts. Logistic regression analyses were used to explore associations between endotoxin with atopy and EIB.

RESULTS

Among the 116 children with asthma, 99 completed SPT and all had completed ECT. Of these, 71/99 (71.7%) were atopic and 26/116 (22.4%) had EIB. Exposure to high play area endotoxin concentration [adjusted odds ratio (aOR) = 0.15, 95% CI: 0.03-0.85] and load (aOR = 0.11, 95% CI: 0.02-0.73) were negatively associated with atopy. In contrast, EIB was positively associated with high mattress endotoxin concentration (aOR = 6.01, 95% CI: 1.20-30.13).

CONCLUSION

Indoor microbial endotoxin exposure has varied associations with atopy and exercise-induced bronchospasm among children with asthma.

Environmental determinants of allergy and asthma in early life

Allergic disease prevalence has increased significantly in recent decades. Primary prevention efforts are being guided by study of the exposome (or collective environmental exposures beginning during the prenatal period) to identify modifiable factors that affect allergic disease risk. In this review we explore the evidence supporting a relationship between key components of the external exposome in the prenatal and early-life periods and their effect on atopy development focused on microbial, allergen, and air pollution exposures. The abundance and diversity of microbial exposures during the first months and years of life have been linked with risk of allergic sensitization and disease. Indoor environmental allergen exposure during early life can also affect disease development, depending on the allergen type, dose, and timing of exposure. Recent evidence supports the role of ambient air pollution in allergic disease inception. The lack of clarity in the literature surrounding the relationship between environment and atopy reflects the complex interplay between cumulative environmental factors and genetic susceptibility, such that no one factor dictates disease development in all subjects. Understanding the effect of the summation of environmental exposures throughout a child's development is needed to identify cost-effective interventions that reduce atopy risk in children.

Diet Matters: Endotoxin in the Diet Impacts the Level of Allergic Sensitization in Germ-Free Mice

Germ-free animals have been used to define the vital role of commensal bacteria on the maturation of the host immune system. However, the role of bacterial residues in diet in this setting is poorly understood. Here we investigated the effect of bacterial contamination in sterile diet on the level of allergic sensitization in germ-free mice. Sterile grain-based diets ST1 and R03 were tested for the level of bacterial contamination. ST1 contained higher amount of bacterial DNA, approximately ten times more endotoxin, and induced higher, TLR4-dependent, cytokine production in dendritic cells compared to R03. In a germ-free mouse model of sensitization to the major birch pollen allergen Bet v 1, feeding on ST1 for at least two generations was associated with decreased production of allergen-specific IgE and IgG1 antibodies in sera in comparison to R03. Furthermore, reduced levels of allergen-specific and ConA-induced cytokines IL-4, IL-5 and IL-13 accompanied by increased levels of IFN-γ were detected in splenocytes cultures of these mice. Our results show that contamination of experimental diet with bacterial residues, such as endotoxin, significantly affects the development of allergic sensitization in germ-free mice. Therefore, careful selection of sterile food is critical for the outcomes of germ-free or gnotobiotic experimental models of immune-deviated diseases.

Domestic exposure to endotoxin and respiratory morbidity in former smokers with COPD

Indoor air pollution has been linked to adverse chronic obstructive pulmonary disease (COPD) health, but specific causative agents have not yet been identified. We evaluated the role of indoor endotoxin exposure upon respiratory health in former smokers with COPD. Eighty-four adults with moderate to severe COPD were followed longitudinally and indoor air and dust samples collected at baseline, 3 and 6 months. Respiratory outcomes were repeatedly assessed at each time point. The associations between endotoxin exposure in air and settled dust and health outcomes were explored using generalizing estimating equations in multivariate models accounting for confounders. Dust endotoxin concentrations in the main living area were highest in spring and lowest in fall, while airborne endotoxins remained steady across seasons. Airborne and dust endotoxin concentrations were weakly correlated with one another (rs  = +0.24, P = 0.005). Endotoxin concentrations were not significantly associated with respiratory symptoms, rescue medication use, quality of life, or severe exacerbations. In vitro whole-blood assays of the pro-inflammatory capacity of PM10 filters with and without endotoxin depletion demonstrated that the endotoxin component of indoor air pollution was not the primary trigger for interleukin-1β release. Our findings support that endotoxin is not the major driver in the adverse effects of indoor PM upon COPD morbidity.

Role of lipopolysaccharide (LPS) in asthma and other pulmonary conditions

Endotoxin significantly contaminates house dust and is an enhancing factor for asthma severity. Natural exposure to endotoxin in early life could influence immune development and protect from the risk of developing atopy. This article will focus on published data showing that home environmental contamination by endotoxin can participate in chronic airways diseases, in particular asthma.

The association of residential mold exposure and adenotonsillar hypertrophy in children living in damp environments

BACKGROUND

There are many consequences of mold exposure related to respiratory system health of children This retrospective cohort study aims to find the association between adenoid hypertrophy and mold exposure in children living in damp environments.

METHODS

Children with history of recurrent respiratory tract infections were enrolled in the study between June 2012 and June 2013 and were followed up for adenoid hypertrophy from June 2013 to June 2016. One hundred and forty two children were residents of moldy houses and 242 were living in normal houses. Skin prick test results for 60 common allergens, vitamin D levels, IgE levels, age, presence of comorbidities such as urticaria, atopic dermatitis, allergic conjunctivitis, allergic rhinitis, asthma, frequency of upper respiratory tract infections and lower respiratory tract infections, were evaluated in both groups.

RESULTS

A total of 384 children (mean age ± standard deviation = 53.37 ± 36 months; 198 males and 186 females) were included. The children were classified into 2 groups (1)Children living normal houses (n = 242) (2); Children living in damp houses (n = 142) according to mold exposure. Children with adenoid hypertrophy (p < 0,001) and higher IgE levels (p < 0,001) were more common in mold exposed group. Lower respiratory tract infections were more common in children with mold exposure (p < 0,05). Bivariate correlation analysis showed no significant association between IgE levels and adenoid hypertrophy. Multiple linear regression analysis was performed to evaluate IgE levels, vitamin D levels, and presence of adenoid as independent variables; age as dependent variable among two groups and was found statistically significant (p < 0,001). Dermatophagoid sensitive group living in damp houses had a significant increase in adenoid hypertrophy (p = 0,01). Housedustmite sensitive children with recurrent lower respiratory tract infection and upper respiratory tract infection were mainly residents of damp houses (p < 0,001). Allergic comorbidities were significantly more in damp environment group (p < 0,001), but there was no significant increase in any of the subgroups.

CONCLUSIONS

Children with mold exposure had significantly increased adenoid hypertrophy regardless of their atopic nature, however, they may have become more sensitized due to other environmental triggers and genetic factors. In damp environments, sensitization to dermatophagoids, was significantly increased in children with adenoid hypertrophy. During the period of infancy, when children were mostly vitamin D supplemented, they were not sensitized and had normal adenoids. As children with recurrent respiratory tract infections grow, they tend to have lower vitamin D levels, become more atopic and tend to have adenoid hypertrophy.

Particulate matter properties and health effects: consistency of epidemiological and toxicological studies

Identifying the ambient particulate matter (PM) fractions or constituents, critically involved in eliciting adverse health effects, is crucial to the implementation of more cost-efficient abatement strategies to improve air quality. This review focuses on the importance of different particle properties for PM-induced effects, and whether there is consistency in the results from epidemiological and experimental studies. An evident problem for such comparisons is that epidemiological and experimental data on the effects of specific components of ambient PM are limited. Despite this, some conclusions can be drawn. With respect to the importance of the PM size-fractions, experimental and epidemiological studies are somewhat conflicting, but there seems to be a certain consistency in that the coarse fraction (PM10-2.5) has an effect that should not be neglected. Better exposure characterization may improve the consistency between the results from experimental and epidemiological studies, in particular for ultrafine particles. Experimental data indicate that surface area is an important metric, but composition may play an even greater role in eliciting effects. The consistency between epidemiological and experimental findings for specific PM-components appears most convincing for metals, which seem to be important for the development of both pulmonary and cardiovascular disease. Metals may also be involved in PM-induced allergic sensitization, but the epidemiological evidence for this is scarce. Soluble organic compounds appear to be implicated in PM-induced allergy and cancer, but the data from epidemiological studies are insufficient for any conclusions. The present review suggests that there may be a need for improvements in research designs. In particular, there is a need for better exposure assessments in epidemiological investigations, whereas experimental data would benefit from an improved comparability of studies. Combined experimental and epidemiological investigations may also help answer some of the unresolved issues.

Synergistic Effect of Dermatophagoides farinae and Lipopolysaccharides in Human Middle ear Epithelial Cells

Purpose

Although the concept of "one airway, one disease," which includes the middle ear space as part of the united airway is well recognized, the role of allergens in otitis media with effusion (OME) is not clearly understood. We aimed to investigate the effect of the interaction between Dermatophagoides farinae (Der f) and lipopolysaccharide (LPS) on the induction of epithelial inflammatory response in vitro.

Methods

Primary human middle ear epithelial cells were exposed to Der f, LPS, or both in different sequences, and the magnitude of the immunologic responses was compared. The mRNA expressiona of mucin (MUC) 4, 5AC, 5B, 8, GM-CSF, TNF-α, TLR4, and MD-2 were evaluated using real-time PCR. MUC levels before and after siRNA-mediated knockout of TLR4 and MD-2 were assessed. Lastly, the involved cell signaling pathway was evaluated.

Results

The expressiona of cytokines, and the MUC 4, 5AC, 5B, and 8 genes were augmented by pretreatment with Der f followed by LPS; however, reverse treatment or combined treatment did not induce the same magnitude of response. Increased MUC expression was decreased by TLR4 knockdown, but not by MD-2 knockdown. The signal intensity of MUC 8 was higher in MD-2 over-expressed cells than in those exposed to LPS only. The translocation of nuclear factor-κB was observed in cells pretreated with Der f followed by LPS.

Conclusions

When Der f treatment preceded LPS exposure, Der f and LPS acted synergistically in the induction of pro-inflammatory cytokines and the MUC gene, suggesting an important role in the development of OME in patients with concealed allergy airway sensitization.

Allergen-Associated Immunomodulators: Modifying Allergy Outcome

The prevalence of allergies is increasing since mid twentieth century; however the underlying causes of this increase are not fully clear. Understanding the mechanism by which a harmless protein becomes an allergen provides us with the basis to prevent and treat these diseases. Although most studies on allergen immunogenicity have traditionally focused on structural properties of the proteins, it is increasingly clear that allergenicity cannot be determined only based on structural features of the allergenic proteins. In fact, allergens do not encounter human facings as isolated molecules but contained in complex mixtures of proteins, carbohydrates and lipids, such as pollen grains or foods. As a result, attention has lately been directed to examine whether allergen-associated molecules exhibit immune-regulatory properties. The present review aims to illustrate some examples of how non-protein molecules accompanying the allergen can modulate allergic responses.

Early indoor aeroallergen exposure is not associated with development of sensitization or allergic rhinitis in high-risk children

RATIONALE

Allergen exposure is associated with the development of allergic sensitization in childhood as reflected by global variations in sensitization patterns. However, there is little evidence to support a direct association.

OBJECTIVES

To investigate the association between perinatal aeroallergen exposure and sensitization and rhinitis to such allergens later in childhood.

METHODS

Allergic sensitization to cat, dog, and house dust mites was diagnosed longitudinally using skin prick tests and specific IgE measurements at ½, 1½, 4, 6, and 13 years in 399 children from the Copenhagen Prospective Study on Asthma in Childhood2000 birth cohort. Rhinitis was diagnosed at 7 and 13 years. Allergen exposure was defined as dog or cat in the home during the 3rd trimester of pregnancy or the first year of life and as allergen levels of dog, cat, and house dust mite in bed dust samples at 1 year. Associations between exposure and outcomes were analyzed by logistic regression and stratified for eczema status and test method (skin prick test and specific IgE).

RESULTS

We found no association between dog or cat exposure in perinatal life and sensitization or rhinitis during childhood. Similarly, there was no association between levels of allergens in bed dust samples and sensitization or rhinitis during childhood.

CONCLUSION

Perinatal indoor aeroallergen exposure does not seem to affect development of allergic sensitization or rhinitis during childhood questioning the relevance of allergen avoidance as a preventive measure. Other factors such as timing of allergen exposure or other environmental adjuvants may contribute in a more complex pathway to sensitization.

Seasonal variation in airborne endotoxin levels in indoor environments with different micro-environmental factors in Seoul, South Korea

This study evaluated the variation over a year in airborne endotoxin levels in the indoor environment of five university laboratories in Seoul, South Korea, and examined the micro-environmental factors that influenced endotoxin levels. These included temperature, relative humidity, CO2, CO, illumination, and wind velocity. A total of 174 air samples were collected and analyzed using the kinetic limulus amebocyte lysate assay. Endotoxin levels ranged from <0.001 to 8.90EU/m(3), with an overall geometric mean of 0.240EU/m(3). Endotoxin levels showed significantly negative correlation with temperature (r=-0.529, p<0.001), CO2 (r=-0.213, p<0.001) and illumination (r=-0.538, p<0.001). Endotoxin levels tended to be higher in winter. Endotoxin levels in laboratories with rabbits were significantly higher than those of laboratories with mice. Multivariate regression analysis showed that the environmental factors affecting endotoxin levels were temperature (coefficient=-0.388, p<0.001) and illumination (coefficient=-0.370, p<0.001). Strategies aimed at reducing airborne endotoxin levels in the indoor environments may be most effective if they focus on illumination.

What can reunification of East and West Germany tell us about the cause of the allergy epidemic?

The increase of allergies in East Germany--reaching West German prevalence shortly after the reunification--is considered a model for the allergy epidemic in the western world. Whether such a pattern was observed in all comparison studies and for all allergic manifestations is not known because a complete overview is missing. Hints about possible causal factors for the allergy epidemic could be gained by identifying known risk factors, which explain the observed pattern of allergy development in Germany. Again, an overview about these efforts is missing. We identified 14 cross-sectional studies conducted after 1989 and calculated prevalence ratios (West/East) for asthma, hayfever, eczema and allergic sensitization. Additionally, a tabular overview about the explanatory power of risk factors hypothesized in the nineties and covering outdoor exposure, indoor factors, early childhood influences, nutrition as well as awareness is given. At the time of the German reunification, the prevalence ratio West/East was largest for hayfever and sensitization to birch pollen, less pronounced for the other phenotypes and even less than one for atopic eczema. Hayfever and sensitization to birch pollen also showed the steepest increase in East Germany afterwards. Single-room heating with fossil fuels and living as only child in a family were identified as explaining up to 23.5% of the excess trend in East compared to the trend in West. Hayfever as most typical atopic disease showed the difference in allergy pattern between East and West Germany clearest. Risk factors identified for these phenotypes are completely different (single child) or even act in the opposite direction (single-room heating) from classical risk factors for airway diseases. This might be the most important lesson from the West/East German experience. It already stimulated many other studies focussing on protective factors such as microbial stimulation.

Determinants of house dust, endotoxin, and β-(1→3)-D-glucan in homes of Danish children

Little is known about the geographic variation and determinants of bacterial endotoxin and β-(1,3)-D-glucan in Danish house dust. In a population of 317 children, we: (i) described loads and concentrations of floor dust, endotoxin, and β-(1→3)-D-glucan and (ii) their correlations and (iii) assessed their determinants; (iv) Finally, we compared our findings with previous European studies. Bedroom floor dust was analyzed for endotoxin content by the kinetic limulus amoebocyte lysate assay and for β-(1→3)-D-glucan by the inhibition enzyme immunoassay. The parents answered questions regarding potential determinants. We found: geometric means (geometric standard deviations) 186 mg/m(2) (4.3) for dust; 5.46 × 10(3) EU/m(2) (8.0) and 31.1 × 10(3) EU/g (2.6) for endotoxin; and 142 μg/m(2) (14.3) and 0.71 × 10(3) μg/g (7.3) for β-(1→3)-D-glucan. High correlations (r > 0.75) were found between floor dust and endotoxin and β-(1→3)-D-glucan loads, while endotoxin and β-(1→3)-D-glucan concentrations were moderately correlated (r = 0.36-0.41) with the dust load. Having a carpet was positively associated with dust load and with endotoxin and β-(1→3)-D-glucan concentrations. Pet keeping, dwelling type, and dwelling location were determinants of endotoxin concentrations. No other determinants were associated with β-(1→3)-D-glucan concentrations. Compared with other European studies, we found lower β-(1→3)-D-glucan loads and concentrations but higher endotoxin loads and concentrations suggesting a geographically determined different composition of Danish floor dust compared with other European regions.

Exposure to household endotoxin and total and allergen-specific IgE in the US population

BACKGROUND

Although endotoxin has strong pro-inflammatory properties, endotoxin-allergy relationship in adults and children have been inconsistent.

OBJECTIVES

We investigated the association between household endotoxin levels and total immunoglobulin E (IgE) or specific IgE in the US general population, classified into three age ranges: children/adolescent, adults, and older adults.

METHODS

We analyzed the 2005-2006 National Health and Nutrition Examination Surveys. A total of 5220 participants for whom serum IgE and household endotoxin data were available was included in the analyses.

RESULTS

Exposure to endotoxin reduced the risk for allergic sensitization, especially in specific IgE to plants (OR in Quartile 3 = 0.58; 95% CI = 0.44-0.76) and pets (OR in Quartile 3 = 0.62; 95% CI = 0.41-0.92), for children/adolescents. In contrast, the risk among adults and older adults increased with increasing endotoxin levels.

CONCLUSIONS

Our findings suggest that the effect of endotoxin on allergic reaction is likely to depend on age.

Comparison of endotoxin levels in cow's milk samples derived from farms and shops

The observations on the protective effect of bacterial endotoxin in farm-derived cow's milk on childhood asthma and allergy are contradictory. The aim of this study was to determine the endotoxin levels in 'farm-derived whole raw' and 'processed shop' sources of cow's milk, and to test how the temperature and storing conditions might alter their endotoxin concentrations. Milk was collected from farms and shops. The level of endotoxin was measured by micro (gel-clot) Limulus amebocyte lysate test expressed as EU/ml. The concentration ranges of endotoxin were much higher and more widely scattered in the samples of whole raw farm milk than in the processed shop milk. Cold storage or heating increased the endotoxin concentrations in all samples of farm milk, but not in the processed shop milk. These results show that elevated levels of endotoxin in raw farm milk samples can occur from the cowshed or be formed during storage. In processed shop milk, storage does not cause any changes in the amount of endotoxin. Therefore, it is consistent that the handling and storage of raw milk alters the endotoxin concentrations, which may explain previous contradictory findings regarding the beneficial modulating effects on innate immunity toward allergy prevention in early childhood.

Marine aerosol as a possible source for endotoxins in coastal areas

Marine aerosols, that are very common in the highly populated coastal cities and communities, may contain biological constituents. Some of this biological fraction of marine aerosols, such as cyanobacteria and plankton debris, may influence human health by inflammation and allergic reactions when inhaled. In this study we identify and compare sources for endotoxins sampled on filters in an on-shore and more-inland site. Filter analysis included endotoxin content, total bacteria, gram-negative bacteria and cyanobacteria genome concentrations as well as ion content in order to identify possible sources for the endotoxins. Satellite images of chlorophyll-a levels and back trajectory analysis were used to further study the cyanobacteria blooms in the sea, close to the trajectory of the sampled air. The highest endotoxin concentrations found in the shoreline site were during winter (3.23±0.17 EU/m(3)), together with the highest cyanobacteria genome (1065.5 genome/m(3)). The elevated endotoxin concentrations were significantly correlated with cyanobacterial levels scaled to the presence of marine aerosol (r=0.90), as well as to chlorophyll-a (r=0.96). Filters sampled further inland showed lower and non-significant correlation between endotoxin and cyanobacteria (r=0.70, P value=0.19), suggesting decrease in marine-originated endotoxin, with possible contributions from other sources of gram-negative non-cyanobacteria. We conclude that marine cyanobacteria may be a dominant contributor to elevated endotoxin levels in coastal areas.

Sensitivity to Five Types of House Dust Mite in a Group of Allergic Egyptian Children

Background: The published data on house dust mite (HDM) sensitization from Egypt are scanty. We sought to investigate the sensitization to five different types of HDM among a group of allergic children in a trial to outline the most frequent sensitizing strains in the Cairo Province. Methods: We consecutively enrolled 100 asthmatic patients, aged 1-7 years, of whom 22 had concomitant skin allergy. Skin prick testing was performed using allergen extracts of Dermatophagoides pteronyssinus, Dermatophagoides farinae, Lepidoglyphus destructor, Tyrophagus putrescentiae, and Acarus siro. Results: Twenty-four patients (24%) were sensitized to one or more strains of HDM. Sensitization to one strain was revealed in 12% of the studied sample, while sensitization to two or three strains was detected in 8% and 4% respectively. Twelve percent of the enrolled children were sensitive to D. pteronyssinus, 11% to D. farinae, 7% to L. destructor, 6% to T. putrescentiae, and 4% to A. siro. Eight out of the 12 (66%) children sensitive to one strain had mild intermittent asthma, while five out of eight (62.5%) sensitive to two strains had moderate persistent asthma. All children sensitized to three strains of HDM had persistent rather than intermittent asthma. HDM sensitization did not correlate significantly to the history of sun exposure, bed mattresses and pillows, living in farms, or exposure to stored grains. The co-existence of atopic dermatitis tended to have a higher rate of HDM sensitization. Conclusion:D. pteronyssinus and D. farinae represent the most common sensitizing strains in the studied sample. Wider-scale population-based studies are needed to assess the prevalence of HDM allergy and its clinical correlates in our country.

Endotoxin levels in settled airborne dust in European schools: the HITEA school study

Indoor exposure to microbial agents is known to influence respiratory health. Besides home exposure, exposure in schools can affect respiratory health. In this study, we measured endotoxin in settled dust in primary schools in three European countries from three different geographical regions with different climates. Our aim was to characterize endotoxin levels in primary schools and evaluate associations with potential determinants. Endotoxin levels were repeatedly assessed in 23 schools in Spain (n = 7), the Netherlands (n = 10), and Finland (n = 6) using electrostatic dustfall collectors. In total, 645 measurements were taken in 237 classrooms. Endotoxin levels differed significantly between countries; Dutch schools had the highest levels, while Finnish schools showed the lowest levels. In each country, differences in endotoxin levels were observed between schools and over the sampling periods. Estimates improved after adjustment for sampling period. Factors affecting endotoxin levels in a school differed per country. In general, endotoxin levels were higher in lower grades and in classrooms with higher occupancy. School endotoxin levels may contribute significantly to total endotoxin exposure in children and teachers. As the correlation between the repeated measurements is reasonable, single endotoxin measurements form a reasonable basis for estimating annual endotoxin levels in schools.

Children's residential exposure to selected allergens and microbial indicators: endotoxins and (1→3)-β-D-glucans

OBJECTIVES

The study was aimed at assessment of exposure to endotoxins, (1→3)-β-D-glucans and mite, cockroach, cat, dog allergens present in settled dust in premises of children as agents which may be significantly correlated with the occurrence of allergic symptoms and diseases in children.

MATERIALS AND METHODS

The study covered 50 homes of one-or two-year-old children in Poland. Samples of settled dust were taken from the floor and the child's bed. The levels of (1→3)-β-D-glucans (floor), endotoxins (floor) and allergens of mite, cat, dog and cockroach (floor and bed) were analyzed.

RESULTS

Average geometric concentrations (geometric standard deviation) of endotoxins, (1→3)-β-D-glucans, Der p1, Fel d1, Can f1 and Bla g1 in children homes were on the floor 42 166.0 EU/g (3.2), 20 478.4 ng/g (2.38), 93.9 ng/g (6.58), 119.8 ng/g (13.0), 288.9 ng/g (3.4), 0.72 U/g (4.4) and in their beds (only allergens) 597.8 ng/g (14.2), 54.1 ng/g (4.4), 158.6 ng/g (3.1) 0.6 U/g (2.9), respectively. When the floor was covered with the carpet, higher concentrations of endotoxins, (1→3)-β-D-glucans and allergens (each type) were found in the settled dust (p < 0.05). The trend was opposite in case of allergens (except dog) analyzed from bed dust and significantly higher concentrations were found in the rooms with smooth floor (p < 0.05).

CONCLUSIONS

Among the analyzed factors only the type of floor significantly modified both the level of biological indicators and allergens. The results of this study could be the base for verifying a hypothesis that carpeting may have a protective role against high levels of cockroach, dog and cat allergens.

Indoor pollutant exposures modify the effect of airborne endotoxin on asthma in urban children

RATIONALE

The effect of endotoxin on asthma morbidity in urban populations is unclear.

OBJECTIVES

To determine if indoor pollutant exposure modifies the relationships between indoor airborne endotoxin and asthma health and morbidity.

METHODS

One hundred forty-six children and adolescents with persistent asthma underwent repeated clinical assessments at 0, 3, 6, 9, and 12 months. Home visits were conducted at the same time points for assessment of airborne nicotine, endotoxin, and nitrogen dioxide (NO2) concentrations. The effect of concomitant pollutant exposure on relationships between endotoxin and asthma outcomes were examined in stratified analyses and statistical models with interaction terms.

MEASUREMENTS AND MAIN RESULTS

Both air nicotine and NO2 concentrations modified the relationships between airborne endotoxin and asthma outcomes. Among children living in homes with no detectable air nicotine, higher endotoxin was inversely associated with acute visits and oral corticosteroid bursts, whereas among those in homes with detectable air nicotine, endotoxin was positively associated with these outcomes (interaction P value = 0.004 and 0.07, respectively). Among children living in homes with lower NO2 concentrations (<20 ppb), higher endotoxin was positively associated with acute visits, whereas among those living in homes with higher NO2 concentrations, endotoxin was negatively associated with acute visit (interaction P value = 0.05). NO2 also modified the effect of endotoxin on asthma symptom outcomes in a similar manner.

CONCLUSIONS

The effects of household airborne endotoxin exposure on asthma are modified by coexposure to air nicotine and NO2, and these pollutants have opposite effects on the relationships between endotoxin and asthma-related outcomes.

Innate immune response to LPS in airway epithelium is dependent on chronological age and antecedent exposures

The immune mechanisms for neonatal susceptibility to respiratory pathogens are poorly understood. Given that mucosal surfaces serve as a first line of host defense, we hypothesized that the innate immune response to infectious agents may be developmentally regulated in airway epithelium. To test this hypothesis, we determined whether the expression of IL-8 and IL-6 in airway epithelium after LPS exposure is dependent on chronological age. Tracheas from infant, juvenile, and adult rhesus monkeys were first exposed to LPS ex vivo, and then processed for air-liquid interface primary airway epithelial cell cultures and secondary LPS treatment in vitro. Compared with adult cultures, infant and juvenile cultures expressed significantly reduced concentrations of IL-8 after LPS treatment. IL-8 protein in cultures increased with animal age, whereas LPS-induced IL-6 protein was predominantly associated with juvenile cultures. Toll-like receptor (TLR) pathway RT-PCR arrays showed differential expressions of multiple mRNAs in infant cultures relative to adult cultures, including IL-1α, TLR10, and the peptidoglycan recognition protein PGLYRP2. To determine whether the age-dependent cytokine response to LPS is reflective of antecedent exposures, we assessed primary airway epithelial cell cultures established from juvenile monkeys housed in filtered air since birth. Filtered air-housed animal cultures exhibited LPS-induced IL-8 and IL-6 expression that was discordant with age-matched ambient air-housed animals. A single LPS aerosol in vivo also affected this cytokine profile. Cumulatively, our findings demonstrate that the innate immune response to LPS in airway epithelium is variable with age, and may be modulated by previous environmental exposures.

Factors associated with degree of atopy in Latino children in a nationwide pediatric sample: the Genes-environments and Admixture in Latino Asthmatics (GALA II) study

BACKGROUND

Atopy varies by ethnicity, even within Latino groups. This variation might be due to environmental, sociocultural, or genetic factors.

OBJECTIVE

We sought to examine risk factors for atopy within a nationwide study of US Latino children with and without asthma.

METHODS

Aeroallergen skin test responses were analyzed in 1830 US Latino subjects. Key determinants of atopy included country/region of origin, generation in the United States, acculturation, genetic ancestry, and site to which subjects migrated. Serial multivariate zero-inflated negative binomial regressions stratified by asthma status examined the association of each key determinant variable with the number of positive skin test responses. In addition, the independent effect of each key variable was determined by including all key variables in the final models.

RESULTS

In baseline analyses African ancestry was associated with 3 times (95% CI, 1.62-5.57) as many positive skin test responses in asthmatic participants and 3.26 times (95% CI, 1.02-10.39) as many positive skin test responses in control participants. Generation and recruitment site were also associated with atopy in crude models. In final models adjusted for key variables, asthmatic patients of Puerto Rican (exp[β] [95% CI], 1.31 [1.02-1.69]) and mixed (exp[β] [95% CI], 1.27 [1.03-1.56]) ethnicity had a greater probability of positive skin test responses compared with Mexican asthmatic patients. Ancestry associations were abrogated by recruitment site but not region of origin.

CONCLUSIONS

Puerto Rican ethnicity and mixed origin were associated with degree of atopy within US Latino children with asthma. African ancestry was not associated with degree of atopy after adjusting for recruitment site. Local environment variation, represented by site, was associated with degree of sensitization.

Indoor exposure to airborne endotoxin: a review of the literature on sampling and analysis methods

Assessment of exposure to airborne endotoxins has been studied for several years, especially in occupational environments, but a large number of procedures are used for sampling and analysis. This lack of standardization makes it very difficult to compare results and set internationally accepted threshold limit values (TLVs) or occupational exposure limits (OELs) for endotoxin exposure. This paper reviews the methods reported, using advanced bibliographical search techniques: 82 papers published from 2004 to the present were selected to analyze methods for the assessment of human exposure to airborne endotoxins, with particular reference to occupational settings, and to examine their performance and critical points. Only few studies have focused on the standardization of sampling and analysis methods. The European Committee for Standardization Guidelines coincide with the procedures most frequently applied, but this does not guarantee the best results in terms of recovery and reproducibility. The factor that mainly affects endotoxin measurements is the extraction method, the main concern being the presence in the samples of a fraction insoluble in aqueous media. If substantial differences in the proportions of this fraction in different environments are confirmed in the future, the contribution of insoluble endotoxins cannot be neglected.

Exposure to microbial agents in house dust and wheezing, atopic dermatitis and atopic sensitization in early childhood: a birth cohort study in rural areas

BACKGROUND

Early-life exposure to environmental microbial agents may be associated with development of wheezing and allergic diseases.

OBJECTIVE

To assess the association of microbial exposure in rural homes with the risk of asthma, wheezing, atopic dermatitis and sensitization.

METHODS

Birth cohorts of rural children (n = 1133), half from farmer families, were followed up from birth to 2 years of age by questionnaires in five European centres. Endotoxin and extracellular polysaccharides (EPS) of Penicillium and Aspergillus spp. were determined from living room floor and mother's mattress dust samples collected at 2 months of age. Specific IgE against 19 allergens was measured at 1 year of age. Discrete-time hazard models, generalized estimations equations (GEE) and logistic regression were used for statistical analyses.

RESULTS

The incidence of asthma was inversely associated with the amount of dust (adjusted odds ratio (aOR) 0.73, 95% CI 0.58-0.93) and the loads (units/m(2)) of EPS (aOR 0.75, 95% CI 0.55-1.04) and endotoxin (aOR 0.79, 95% CI 0.60-1.05) in the mother's mattress. Similar associations were seen with wheezing and with living room floor dust. The microbial markers were highly correlated and their effects could not be clearly separated. The inverse associations were seen especially among non-farmers. The risk of sensitization to inhalant allergens increased with increasing endotoxin exposure from mattress dust. No associations were observed with concentrations (units/g) or with atopic dermatitis.

CONCLUSION AND CLINICAL RELEVANCE

The amount and microbial content of house dust were inversely associated with asthma and wheezing, but due to high correlations between microbial agents and amount of dust, it was not possible to disentangle their individual effects. New ways to better measure and represent exposure to environmental microbes, including indexes of biodiversity, are needed especially among farmers.

The effects of various doses of bacterial lipopolysaccharide on the expression of CD63 and the release of histamine by basophils of atopic and non-atopic patients

OBJECTIVE

We tested the effect of various doses of bacterial lipopolysaccharide (LPS, endotoxin) on the expression of CD63 and the in vitro release of histamine by basophils stimulated with ragweed allergen in patients with or without ragweed and mite allergies.

METHODS

The peripheral blood of 11 patients with ragweed allergy, 10 patients with mite allergy and 14 control patients was incubated with ragweed allergen extract following pretreatment with varying doses of LPS. The expression of CD63 in basophils was measured by flow cytometry, and the release of histamine was determined by ELISA.

RESULTS

In the samples of patients with ragweed allergy that were exposed to specific allergen, only high doses of LPS significantly elevated the expression of CD63 (200 ng/ml; 1,000 EU/ml) and the release of histamine (2,000 ng/ml; 10,000 EU/ml). There was no effect of LPS in any other cases.

CONCLUSIONS

Bacterial LPS (endotoxin) concentrations higher than 200 ng/ml (1,000 EU/ml), which rarely occurs in nature, could only activate the basophils from atopic patients whilst in the presence of the specific allergen. Thus, the restoration of the urban, "microbe-poor" milieu with endotoxin (as LPS) can be a promising and harmless approach for allergy prevention.

Exposure assessment of residential mould, fungi and microbial components in relation to children's health: achievements and challenges

Each day we are exposed to a complex mixture of microbial agents and components in indoor environments. A major part of this mixture derives from fungal and bacterial origin. The impact between those microbial agents in the home environment in relation to respiratory health in children is still a major issue in research. There is little known about the causal agents that provoke or arrest the development of allergic respiratory disorders in children. Identification is complicated by the biodiversity and variability of microbial components in indoor air as well as the lack of validated and standardized exposure assessment methods. In this review, we aim to consider all important aspects in terms of research which may encounter an epidemiological study. Apart from the need for standardized exposure assessment methods which consider cost, handling and effort, especially for the participants, we suggest that a combination of different analysis methods such as chemical and molecular methods may have the potential to best describe the microbial milieu in indoor environments at present. Further, the impact of mould and moisture remediation activities on health is still heavily under investigated, especially in larger prospective cohorts of children and should be a topic of future research. Moreover, the exposure to mould and microbial agents might be embedded in a broader spectrum of children's health such as behavior and cognitive development.

Geographical variation and the determinants of domestic endotoxin levels in mattress dust in Europe

Endotoxin exposures have manifold effects on human health. The geographical variation and determinants of domestic endotoxin levels in Europe have not yet been extensively described. To investigate the geographical variation and determinants of domestic endotoxin concentrations in mattress dust in Europe using data collected in the European Community Respiratory Health Survey follow-up (ECRHS II). Endotoxin levels were measured in mattress dust from 974 ECRHS II participants from 22 study centers using an immunoassay. Information on demographic, lifestyle, and housing characteristics of the participants was obtained in face-to-face interviews. The median endotoxin concentration in mattress dust ranged from 772 endotoxin units per gram (EU/g) dust in Reykjavik, Iceland, to 4806 EU/g in Turin, Italy. High average outdoor summer temperature of study center, cat or dog keeping, a high household crowding index, and visible damp patches in the bedroom were significantly associated with a higher endotoxin concentrations in mattress dust. There is a large variability in domestic endotoxin levels across Europe. Average outdoor summer temperature of study center, which explains only 10% of the variation in domestic endotoxin level by center, is the strongest meteorological determinant. The observed variation needs to be taken into account when evaluating the health effects of endotoxin exposures in international contexts.

PRACTICAL IMPLICATIONS

The incoherent observations of the health effects of endotoxin may be partly owing to the geographical heterogeneity of endotoxin exposure. Therefore, the observed variation should be considered in further studies. Measurements of indoor endotoxin are recommended as an indicator for the level of exposures of individual domestic environments.