Children at risk for asthma: home allergen levels, lymphocyte proliferation, and wheeze

Prenatal blood metals, per- and polyfluoroalkyl substances and antigen- or mitogen-stimulated cord blood lymphocyte proliferation and cytokine secretion

BACKGROUND

Evidence suggests that prenatal per- and polyfluoroalkyl substances (PFAS) and metals, two classes of chemicals found ubiquitously in human populations, influence immune system development and response.

OBJECTIVE

We evaluated whether first trimester blood PFAS and metals were associated with antigen- or mitogen-stimulated cord blood lymphocyte proliferation and cytokine secretion.

METHODS

We measured six PFAS, as well as six nonessential and four essential metals, in first trimester blood from participants in the longitudinal pre-birth Project Viva cohort, recruited between 1999 and 2000 in eastern Massachusetts. We measured antigen- or mitogen-stimulated cord blood mononuclear cell proliferation responses (n = 269-314) and cytokine secretion (n = 217-302). We used covariate-adjusted least absolute shrinkage and selection operator (LASSO) for variable selection and multivariable regression to estimate associations with the immune markers.

RESULTS

Each ng/mL of MeFOSAA was associated with a 3.6% (1.4, 5.8) higher lymphocyte proliferation response after stimulation with egg antigen, as well as 0.8 (0.7, 1.0) reduced odds of having IFN-γ detected in response to dust mite. Each ng/g increment of cesium was associated with 27.8% (-45.1, -4.9) lower IL-10 levels in response to dust mite. Each ng/g increment of mercury was associated with 12.0% (1.3, 23.8) higher IL-13 levels in response to mitogen PHA. Each ng/g increment of selenium and zinc was associated with 0.2% (0.01, 0.4) and 0.01% (0.002, 0.02) higher TNF-α in response to mitogen PHA, respectively.

CONCLUSIONS

Prenatal metals and PFAS influence cord blood lymphocyte proliferation and cytokine secretion in ways that may increase risk for atopic disease in childhood.

EAACI Molecular Allergology User's Guide 2.0

Since the discovery of immunoglobulin E (IgE) as a mediator of allergic diseases in 1967, our knowledge about the immunological mechanisms of IgE-mediated allergies has remarkably increased. In addition to understanding the immune response and clinical symptoms, allergy diagnosis and management depend strongly on the precise identification of the elicitors of the IgE-mediated allergic reaction. In the past four decades, innovations in bioscience and technology have facilitated the identification and production of well-defined, highly pure molecules for component-resolved diagnosis (CRD), allowing a personalized diagnosis and management of the allergic disease for individual patients. The first edition of the "EAACI Molecular Allergology User's Guide" (MAUG) in 2016 rapidly became a key reference for clinicians, scientists, and interested readers with a background in allergology, immunology, biology, and medicine. Nevertheless, the field of molecular allergology is moving fast, and after 6 years, a new EAACI Taskforce was established to provide an updated document. The Molecular Allergology User's Guide 2.0 summarizes state-of-the-art information on allergen molecules, their clinical relevance, and their application in diagnostic algorithms for clinical practice. It is designed for both, clinicians and scientists, guiding health care professionals through the overwhelming list of different allergen molecules available for testing. Further, it provides diagnostic algorithms on the clinical relevance of allergenic molecules and gives an overview of their biology, the basic mechanisms of test formats, and the application of tests to measure allergen exposure.

IgE reactivity patterns in Asian and central European cockroach-sensitized patients reveal differences in primary sensitizing allergen sources

Background

The prevalence of cockroach (CR) sensitization and its relevance as a trigger of allergy symptoms differs greatly in different geographic areas.

Objective

This study aimed to compare molecular IgE reactivity profiles in CR-sensitized patients with perennial allergy symptoms from Hong Kong (HK) and Austria and identify the main primary sensitizers.

Methods

IgE sensitization was assessed by skin prick test and/or IgE reactivity with CR extract. Molecular IgE reactivity profiles were analyzed via multiplex assay for sensitization to allergens and extracts from CR, house dust mite (HDM), shellfish, and 3 additional insect species.

Results

HDM was the main primary sensitizer in both cohorts. In the HK group, genuine sensitization to CR was found in 45%, but none of the patients in the Austrian cohort was truly sensitized to that allergen source. Most patients from HK were cross-sensitized to other insects and/or shellfish, presumably by broad reactivity to tropomyosin and arginine kinase. About half of Austrian subjects lacked IgE to these pan-allergens, indicating co- but not cross-sensitization to insects and/or shellfish. Regarding IgE recognition frequencies, arginine kinases (64% HK, 10% Austria) and tropomyosins (42% HK, 15% Austria) were most frequently recognized; Bla g 4 (lipocalin) was detected in HK patients only (42%). Tropomyosin (Per a 7) was significantly more frequently recognized in patients with asthma. Sera from HDM-sensitized subjects from HK showed a higher proportion of sensitization to minor mite allergens.

Conclusion

Molecular profiling identified differences between CR-sensitized allergic patients from HK and Austria in terms of primary sensitizers and molecular IgE reactivity patterns. Tropomyosin from American cockroach (Per a 7) was shown to be significantly associated with asthma symptoms and might be suitable as biomarker for more severe respiratory allergy symptoms.

Cockroach exposure and its allergy sensitization in asthma patients

Asthma is a heterogeneous disease with distinct phenotypes. Serum tIgE, SSIgE and SPT are the methods of evaluating allergen sensitization. The present study evaluates the exposure and sensitization to cockroach (Periplaneta americana) antigens in asthma patients in a metropolitan city of India. The study enrolled 200 consecutive bronchial asthma patients, diagnosed as per GINA guidelines. As per history of exposure to cockroaches, the patients are divided in two groups as exposed and non-exposed asthmatic. All the enrolled subjects underwent SPT against common aeroallergens including cockroach, spirometry and estimation of tIgE level and SSIgE against cockroach. Out of 200 asthma patients, a total of 114 (57%) asthmatic were found SPT positive against one of the common aeroallergens, of which 68 (34%) showed SPT sensitivity against cockroach. A total of 103 (51.5%) patients were found exposed to cockroaches. In the cockroach exposed group, the mean serum tIgE was found significantly higher than the non-exposed group (569.31±224.64 vs 479.29±237 IU/ml; p=0.007). The mean SSIgE against cockroach in exposed groups was found not significant than non-expose group (4.87±11.19 vs 4.11±8.39 KUA/L; p=0.589). The mean tIgE was also not significant in atopic compared to non-atopic asthmatic (553.25±218.12 IU/ml vs 489.1±251.16 IU/ml; p=0.056). The mean SSIgE against cockroach was 5.66±10.45 KUA/L for atopic and 2.96±8.98 KUA/L for non-atopic (p=0.054). The airway obstruction was almost the same in both groups.  Asthmatic patients who were exposed to cockroach and atopic had high tIgE, SSIgE levels and SPT positivity against cockroach antigen compared to non-exposed patients.

The Persistence of Escherichia coli Infection in German Cockroaches (Blattodea: Blattellidae) Varies Between Host Developmental Stages and is Influenced by the Gut Microbiota

The German cockroach, Blatella germanica (L.), is a suspected vector of several enteric bacterial pathogens, including Escherichia coli, among livestock and humans. However, little is known about the factors that influence bacterial transmission by cockroaches. Here, we orally infected B. germanica with various laboratory and field strains of E. coli and examined bacterial titers over time to shed new light on the factors that influence the dynamics of infection. Our results reveal that a laboratory strain of E. coli is largely cleared within 48 h while one field isolate can persist in a majority of cockroaches (80-100%) for longer than 3 d with minimal impact on cockroach longevity. We also find that the ability to clear some strains of E. coli is greater in cockroach nymphs than adults. Notably, no differential expression of the antimicrobial gene lysozyme was observed between nymphs and adults or in infected groups. However, clearance of E. coli was significantly reduced in gnotobiotic cockroaches that were reared in the absence of environmental bacteria, suggesting a protective role for the microbiota against exogenous bacterial pathogens. Together, these results demonstrate that the interactions between cockroaches and enteric bacterial pathogens are highly dynamic and influenced by a combination of microbial, host, and environmental parameters. Such factors may affect the disease transmission capacity of cockroaches in nature and should be further considered in both lab and field studies.

N-glycan in cockroach allergen regulates human basophil function

INTRODUCTION

Cockroach allergen exposure elicits cockroach sensitization and poses an increased risk for asthma. However, the major components in cockroach allergen and the mechanisms underlying the induction of cockroach allergen-induced allergy and asthma remain largely elusive. We sought to examine the role of cockroach-associated glycan in regulating human basophil function.

METHODS

N-linked glycans from naturally purified cockroach allergen Bla g 2 were characterized by MALDI-TOF mass spectrometry. Binding of cockroach allergen to serum IgE from cockroach allergic subjects was determined by solid-phase binding immunoassays. Role of cockroach associated glycan in histamine release and IL-4 production from human basophils was examined. Expression of C-type lectin receptors (CLRs) and their role in mediating glycan-uptake in the basophils was also investigated.

RESULTS

MALDI-TOF mass spectrometric analysis of N-glycan from Bla g 2 showed complex hybrid-types of glycans that terminated with mannose, galactose, and/or N-acetyl glucosamine (GlcNAc). Deglycosylated Bla g 2 showed reduced binding to IgE and was less capable of inducing histamine release from human basophils. In contrast, N-glycan derived from Bla g 2 significantly inhibited histamine release and IL-4 production from basophils passively sensitized with serum from cockroach allergic subjects. An analysis of CLRs revealed the expression of DC-SIGN and DCIR, but not MRC1 and dectin-1, in human basophils. Neutralizing antibody to DCIR, but not DC-SIGN, significantly inhibited Bla g 2 uptake by human basophils. A dose-dependent bindings of cockroach allergen to DCIR was also observed.

CONCLUSIONS

These observations indicate a previously unrecognized role for cockroach allergen-associated glycans in allergen-induced immune reactions, and DCIR may play a role in mediating the regulation of glycan on basophil function.

Cockroach allergen exposure and plasma cytokines among children in a tropical environment

BACKGROUND

Little is known about the effects of socioeconomic status or cockroach allergen on immune responses in school-age children, particularly in tropical environments.

OBJECTIVE

To examine whether cockroach allergen and/or socioeconomic status is associated with plasma cytokine levels in Puerto Rican children.

METHODS

This was a cross-sectional study of 532 children (6-14 years old) with (n = 272) and without (n = 260) asthma in San Juan (Puerto Rico). House dust allergens (cockroach [Bla g 2], dust mite [Der p 1], cat dander [Fel d 1], dog dander [Can f 1], and mouse urinary protein [Mus m 1]) were quantified using monoclonal antibody arrays. A panel of 14 cytokines (interleukin [IL]-1β, IL-4, IL-6, IL-10, IL-17A, IL-17F, IL-21, IL-22, IL-23, IL-25, IL-31, IL-33, interferon-γ, and tumor necrosis factor-α) was measured in plasma samples. Low household income was defined as less than $15,000 per year (below the median income for Puerto Rico in 2008-2009). Linear regression was used for the analysis of cockroach allergen and plasma cytokines.

RESULTS

In a multivariable analysis adjusting for low income and other allergen levels, cockroach allergen was significantly associated with decreased IL-17A and with increased levels of 8 cytokines (IL-4, IL-10, IL-17F, IL-21, IL-25, IL-31, interferon-γ, and tumor necrosis factor-α). After stratifying this analysis by cockroach allergy (ie, having a cockroach positive immunoglobulin E reaction), our findings remained largely unchanged for children sensitized to cockroach but became weaker and statistically nonsignificant for non-sensitized children.

CONCLUSION

Cockroach allergen has broad effects on adaptive immune responses in school-age children in a tropical environment, particularly in those sensitized to cockroach.

A single intervention for cockroach control reduces cockroach exposure and asthma morbidity in children

BACKGROUND

Exposure to cockroaches is an important asthma trigger, particularly for children with asthma living in inner cities. Integrated pest management is the recommended approach to cockroach abatement; however, it is costly and difficult to implement. The impact of reducing cockroach exposure on asthma outcomes is not known.

OBJECTIVE

We sought to test the use of a single intervention, insecticidal bait, to reduce cockroach exposure in the home of children with asthma in New Orleans and to examine the impact of cockroach reduction on asthma outcomes.

METHODS

One hundred two children aged 5 to 17 years with moderate to severe asthma were enrolled in a 12-month randomized controlled trial testing the use of insecticidal bait on cockroach counts and asthma morbidity. Homes were visited 6 times and asthma symptoms were assessed every 2 months.

RESULTS

After adjustment, intervention homes had significantly fewer cockroaches than did control homes (mean change in cockroaches trapped, 13.14; 95% CI, 6.88-19.39; P < .01). Children in control homes had more asthma symptoms and unscheduled health care utilization in the previous 2 weeks (1.82, 95% CI, 0.14-3.50, P = .03; 1.17, 95% CI, 0.11-2.24, P = .03, respectively) and a higher proportion of children with FEV₁ of less than 80% predicted (odds ratio, 5.74; 95% CI, 1.60-20.57; P = .01) compared with children living in intervention homes.

CONCLUSIONS

Previous research has demonstrated improvement in asthma health outcomes using multifaceted interventions. The strategic placement of insecticidal bait, which is inexpensive, has low toxicity, and is widely available, resulted in sustained cockroach elimination over 12 months and was associated with improved asthma outcomes. This single intervention may be an alternative to multifaceted interventions currently recommended to improve asthma morbidity.

EAACI Molecular Allergology User's Guide

The availability of allergen molecules ('components') from several protein families has advanced our understanding of immunoglobulin E (IgE)-mediated responses and enabled 'component-resolved diagnosis' (CRD). The European Academy of Allergy and Clinical Immunology (EAACI) Molecular Allergology User's Guide (MAUG) provides comprehensive information on important allergens and describes the diagnostic options using CRD. Part A of the EAACI MAUG introduces allergen molecules, families, composition of extracts, databases, and diagnostic IgE, skin, and basophil tests. Singleplex and multiplex IgE assays with components improve both sensitivity for low-abundance allergens and analytical specificity; IgE to individual allergens can yield information on clinical risks and distinguish cross-reactivity from true primary sensitization. Part B discusses the clinical and molecular aspects of IgE-mediated allergies to foods (including nuts, seeds, legumes, fruits, vegetables, cereal grains, milk, egg, meat, fish, and shellfish), inhalants (pollen, mold spores, mites, and animal dander), and Hymenoptera venom. Diagnostic algorithms and short case histories provide useful information for the clinical workup of allergic individuals targeted for CRD. Part C covers protein families containing ubiquitous, highly cross-reactive panallergens from plant (lipid transfer proteins, polcalcins, PR-10, profilins) and animal sources (lipocalins, parvalbumins, serum albumins, tropomyosins) and explains their diagnostic and clinical utility. Part D lists 100 important allergen molecules. In conclusion, IgE-mediated reactions and allergic diseases, including allergic rhinoconjunctivitis, asthma, food reactions, and insect sting reactions, are discussed from a novel molecular perspective. The EAACI MAUG documents the rapid progression of molecular allergology from basic research to its integration into clinical practice, a quantum leap in the management of allergic patients.

A systematic review of associations between environmental exposures and development of asthma in children aged up to 9 years

OBJECTIVES

Childhood asthma is a complex condition where many environmental factors are implicated in causation. The aim of this study was to complete a systematic review of the literature describing associations between environmental exposures and the development of asthma in young children.

SETTING

A systematic review of the literature up to November 2013 was conducted using key words agreed by the research team. Abstracts were screened and potentially eligible papers reviewed. Papers describing associations between exposures and exacerbation of pre-existing asthma were not included. Papers were placed into the following predefined categories: secondhand smoke (SHS), inhaled chemicals, damp housing/mould, inhaled allergens, air pollution, domestic combustion, dietary exposures, respiratory virus infection and medications.

PARTICIPANTS

Children aged up to 9 years.

PRIMARY OUTCOMES

Diagnosed asthma and wheeze.

RESULTS

14,691 abstracts were identified, 207 papers reviewed and 135 included in the present review of which 15 were systematic reviews, 6 were meta-analyses and 14 were intervention studies. There was consistent evidence linking exposures to SHS, inhaled chemicals, mould, ambient air pollutants, some deficiencies in maternal diet and respiratory viruses to an increased risk for asthma (OR typically increased by 1.5-2.0). There was less consistent evidence linking exposures to pets, breast feeding and infant dietary exposures to asthma risk, and although there were consistent associations between exposures to antibiotics and paracetamol in early life, these associations might reflect reverse causation. There was good evidence that exposures to house dust mites (in isolation) was not associated with asthma risk. Evidence from observational and intervention studies suggest that interactions between exposures were important to asthma causation, where the effect size was typically 1.5-3.0.

CONCLUSIONS

There are many publications reporting associations between environmental exposures and modest changes in risk for asthma in young children, and this review highlights the complex interactions between exposures that further increase risk.

Reprint of: Perinatal and early childhood environmental factors influencing allergic asthma immunopathogenesis

BACKGROUND

The prevalence of asthma has increased dramatically over the past several decades. While hereditary factors are highly important, the rapid rise outstrips the pace of genomic variation. Great emphasis has been placed on potential modifiable early life exposures leading to childhood asthma.

METHODS

We reviewed the recent medical literature for important studies discussing the role of the perinatal and early childhood exposures and the inception of childhood asthma.

RESULTS AND DISCUSSION

Early life exposure to allergens (house dust mite (HDM), furred pets, cockroach, rodent and mold), air pollution (nitrogen dioxide (NO2), ozone (O3), volatile organic compounds (VOCs), and particulate matter (PM)) and viral respiratory tract infections (Respiratory syncytial virus (RSV) and human rhinovirus (hRV)) has been implicated in the development of asthma in high risk children. Conversely, exposure to microbial diversity in the perinatal period may diminish the development of atopy and asthma symptoms.

Perinatal and early childhood environmental factors influencing allergic asthma immunopathogenesis

BACKGROUND

The prevalence of asthma has increased dramatically over the past several decades. While hereditary factors are highly important, the rapid rise outstrips the pace of genomic variation. Great emphasis has been placed on potential modifiable early life exposures leading to childhood asthma.

METHODS

We reviewed the recent medical literature for important studies discussing the role of the perinatal and early childhood exposures and the inception of childhood asthma.

RESULTS AND DISCUSSION

Early life exposure to allergens (house dust mite (HDM), furred pets, cockroach, rodent and mold), air pollution (nitrogen dioxide (NO(2)), ozone (O(3)), volatile organic compounds (VOCs), and particulate matter (PM)) and viral respiratory tract infections (Respiratory syncytial virus (RSV) and human rhinovirus (hRV)) has been implicated in the development of asthma in high risk children. Conversely, exposure to microbial diversity in the perinatal period may diminish the development of atopy and asthma symptoms.

Determinants of sensitization to allergen in infants and young children

Atopic sensitization is a complex phenomenon that changes dynamically with age throughout childhood; its prevalence increases with age in young children. Additionally, with increasing age, the prevalence of sensitization to inhalant allergens and the prevalence of polysensitization to allergens increase. It is also well established that the development of atopic sensitization is the result of a complex interplay of genetic and environmental factors. However, there is considerable heterogeneity in the literature in terms of the effect of different environmental exposures in young children on the subsequent risk of atopic sensitization and allergic diseases. Previous studies on the relationship, in early life, between pet ownership, sex, exposure to secondhand smoke, exposure to traffic-related air pollution components, and atopic sensitization have yielded different results. Recent studies have highlighted the importance of gene-environment interactions, especially during early childhood, on the risk of subsequent atopic sensitization and allergic diseases. Therefore, pediatricians should consider the genetic and environmental determinants of atopic sensitization in infants and young children when diagnosing and treating patients with allergic diseases. Determining ways in which early exposure to these risk factors in young children may be reduced could be beneficial in preventing the likelihood of developing atopic sensitization.

Recombinant allergens for diagnosis of cockroach allergy

Molecular cloning of cockroach allergens and their expression as recombinant proteins have allowed a better understanding of the mechanisms of cockroach allergic disease. Recombinant cockroach allergens have been used for skin testing or in vitro methods to measure IgE antibody levels in serum. Early studies evaluating selected U.S. patients revealed that a cocktail of four cockroach allergens, Bla g 1, Bla g 2, Bla g 4, and Bla g 5, would identify 95 % of cockroach allergic patients. More recent studies pointed to an important role of sensitization to tropomyosin among certain populations, and suggested that a cocktail of five allergens Bla g 1 and/or Per a 1, Bla g 2, Bla g 4, Bla g 5, and Bla g 7, and/or Per a 7, would be expected to diagnose 50- 64 % of cockroach-allergic patients worldwide. Variation in IgE reactivity profiles could be in part due to IgE responses to cross-reactive homologous allergens from different origins. The availability of purified natural or recombinant cockroach allergens provides the capacity to improve diagnosis of cockroach allergy and to develop novel forms of immunotherapy for cockroach-allergic patients.

Treatment with pyranopyran-1, 8-dione attenuates airway responses in cockroach allergen sensitized asthma in mice

Chronic allergic asthma is characterized by Th2-typed inflammation, and contributes to airway remodeling and the deterioration of lung function. Viticis Fructus (VF) has long been used in China and Korea as a traditional herbal remedy for treating various inflammatory diseases. Previously, we have isolated a novel phytochemical, pyranopyran-1, 8-dione (PPY), from VF. This study was conducted to evaluate the ability of PPY to prevent airway inflammation and to attenuate airway responses in a cockroach allergen-induced asthma model in mice. The mice sensitized to and challenged with cockroach allergen were treated with oral administration of PPY. The infiltration of total cells, eosinophils and lymphocytes into the BAL fluid was significantly inhibited in cockroach allergen-induced asthma mice treated with PPY (1, 2, or 10 mg/kg). Th2 cytokines and chemokine, such as IL-4, IL-5, IL-13 and eotaxin in BAL fluid were also reduced to normal levels following treatment with PPY. In addition, the levels of IgE were also markedly suppressed after PPY treatment. Histopathological examination demonstrated that PPY substantially inhibited eosinophil infiltration into the airway, goblet cell hyperplasia and smooth muscle hypertrophy. Taken together, these results demonstrate that PPY possesses a potent efficacy on controlling allergic asthma response such as airway inflammation and remodeling.

Environmental assessment and exposure reduction of cockroaches: a practice parameter

This parameter was developed by the Joint Task Force on Practice Parameters, representing the American Academy of Allergy, Asthma & Immunology (AAAAI); the American College of Allergy, Asthma & Immunology (ACAAI); and the Joint Council of Allergy, Asthma & Immunology. The AAAAI and the ACAAI have jointly accepted responsibility for establishing "Environmental assessment and remediation: a practice parameter." This is a complete and comprehensive document at the current time. The medical environment is a changing environment, and not all recommendations will be appropriate for all patients. Because this document incorporated the efforts of many participants, no single person, including those who served on the Joint Task Force, is authorized to provide an official AAAAI or ACAAI interpretation of these practice parameters. Any request for information about or an interpretation of these practice parameters by the AAAAI or ACAAI should be directed to the Executive Offices of the AAAAI, the ACAAI, and the Joint Council of Allergy, Asthma & Immunology. These parameters are not designed for use by pharmaceutical companies in drug promotion. The findings and conclusions in this manuscript are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention (CDC).

Investigating cockroach allergens: aiming to improve diagnosis and treatment of cockroach allergic patients

Cockroach allergy is an important health problem associated with the development of asthma, as a consequence of chronic exposure to low levels of allergens in susceptible individuals. In the last 20 years, progress in understanding the disease has been possible, thanks to the identification and molecular cloning of cockroach allergens and their expression as recombinant proteins. Assays for assessment of environmental allergen exposure have been developed and used to measure Bla g 1 and Bla g 2, as markers of cockroach exposure. IgE antibodies to cockroach extracts and to specific purified allergens have been measured to assess sensitization and analyze association with exposure and disease. With the development of the field of structural biology and the expression of recombinant cockroach allergens, insights into allergen structure, function, epitope mapping and allergen-antibody interactions have provided further understanding of mechanisms of cockroach allergic disease at the molecular level. This information will contribute to develop new approaches to allergen avoidance and to improve diagnosis and therapy of cockroach allergy.

Functional profiling of the gut microbiome in disease-associated inflammation

The microbial residents of the human gut are a major factor in the development and lifelong maintenance of health. The gut microbiota differs to a large degree from person to person and has an important influence on health and disease due to its interaction with the human immune system. Its overall composition and microbial ecology have been implicated in many autoimmune diseases, and it represents a particularly important area for translational research as a new target for diagnostics and therapeutics in complex inflammatory conditions. Determining the biomolecular mechanisms by which altered microbial communities contribute to human disease will be an important outcome of current functional studies of the human microbiome. In this review, we discuss functional profiling of the human microbiome using metagenomic and metatranscriptomic approaches, focusing on the implications for inflammatory conditions such as inflammatory bowel disease and rheumatoid arthritis. Common themes in gut microbial ecology have emerged among these diverse diseases, but they have not yet been linked to targetable mechanisms such as microbial gene and genome composition, pathway and transcript activity, and metabolism. Combining these microbial activities with host gene, transcript and metabolic information will be necessary to understand how and why these complex interacting systems are altered in disease-associated inflammation.

Role of cockroach proteases in allergic disease

Allergic asthma is on the rise in developed countries, and cockroach exposure is a major risk factor for the development of asthma. In recent years, a number of studies have investigated the importance of allergen-associated proteases in modulating allergic airway inflammation. Many of the studies have suggested the importance of allergen-associated proteases as having a direct role on airway epithelial cells and dendritic cells. In most cases, activation of the protease activated receptor (PAR)-2 has been implicated as a mechanism behind the potent allergenicity associated with cockroaches. In this review, we focus on recent evidence linking cockroach proteases to activation of a variety of cells important in allergic airway inflammation and the role of PAR-2 in this process. We will highlight recent data exploring the potential mechanisms involved in the biological effects of the allergen.

Analysis of T cell responses to the major allergens from German cockroach: epitope specificity and relationship to IgE production

Bla g allergens are major targets of IgE responses associated with cockroach allergies. However, little is known about corresponding T cell responses, despite their potential involvement in immunopathology and the clinical efficacy of specific immunotherapy. Bioinformatic predictions of the capacity of Bla g 1, 2, 4, 5, 6, and 7 peptides to bind HLA-DR, -DP, and -DQ molecules, and PBMC responses from 30 allergic donors, identified 25 T cell epitopes. Five immunodominant epitopes accounted for more than half of the response. Bla g 5, the most dominant allergen, accounted for 65% of the response, and Bla g 6 accounted for 20%. Bla g 5 induced both IL-5 and IFN-γ responses, whereas Bla g 6 induced mostly IL-5, and, conversely, Bla g 2 induced only IFN-γ. Thus, responses to allergens within a source are independently regulated, suggesting a critical role for the allergen itself, and not extraneous stimulation from other allergens or copresented immunomodulators. In comparing Ab with T cell responses for several donor/allergen combinations, we detected IgE titers in the absence of detectable T cell responses, suggesting that unlinked T cell-B cell help might support development of IgE responses. Finally, specific immunotherapy resulted in IL-5 down modulation, which was not associated with development of IFN-γ or IL-10 responses to any of the Bla g-derived peptides. In summary, the characteristics of T cell responses to Bla g allergens appear uncorrelated with IgE responses. Monitoring these responses may therefore yield important information relevant to understanding cockroach allergies and their treatment.

Cord blood versus age 5 mononuclear cell proliferation on IgE and asthma

BACKGROUND

Fetal immune responses following exposure of mothers to allergens during pregnancy may influence the subsequent risk of childhood asthma. However, the association of allergen-induced cord blood mononuclear cell (CBMC) proliferation and cytokine production with later allergic immune responses and asthma has been controversial. Our objective was to compare indoor allergen-induced CBMC with age 5 peripheral blood mononuclear cell (PBMC) proliferation and determine which may be associated with age 5 allergic immune responses and asthma in an inner city cohort.

METHODS

As part of an ongoing cohort study of the Columbia Center for Children's Environmental Health (CCCEH), CBMCs and age 5 PBMCs were cultured with cockroach, mouse, and dust mite protein extracts. CBMC proliferation and cytokine (IL-5 and IFN-gamma) responses, and age 5 PBMC proliferation responses, were compared to anti-cockroach, anti-mouse, and anti-dust mite IgE levels, wheeze, cough, eczema and asthma.

RESULTS

Correlations between CBMC and age 5 PBMC proliferation in response to cockroach, mouse, and dust mite antigens were nonsignificant. Cockroach-, mouse-, and dust mite-induced CBMC proliferation and cytokine responses were not associated with allergen-specific IgE at ages 2, 3, and 5, or with asthma and eczema at age 5. However, after adjusting for potential confounders, age 5 cockroach-induced PBMC proliferation was associated with anti-cockroach IgE, total IgE, and asthma (p < 0.05).

CONCLUSION

In contrast to allergen-induced CBMC proliferation, age 5 cockroach-induced PBMC proliferation was associated with age 5 specific and total IgE, and asthma, in an inner-city cohort where cockroach allergens are prevalent and exposure can be high.

A TLR2 agonist in German cockroach frass activates MMP-9 release and is protective against allergic inflammation in mice

The role of TLR2 in modulating experimentally induced asthma is not fully understood. We recently identified that German cockroach (GC) frass contains a TLR2 ligand allowing us to investigate the role of a TLR2 agonist in a complex real world allergen in mediating allergic airway inflammation. GC frass exposure significantly increased airway inflammation, airway hyperresponsiveness and serum IgE levels in wild-type mice; however the same exposure in TLR2-deficient mice resulted in greatly exaggerated serum IgE and eosinophilia but diminished airway neutrophilia, suggesting a protective role for TLR2. Since GC frass inhalation usually induces airway neutrophilia, we queried the effect of neutrophil depletion on airway responses. Inhibition of neutrophil recruitment into the airways of naive wild-type mice before intratracheal inhalation of GC frass resulted in significantly increased levels of serum IgE and eosinophilia. Neutrophils are a rich source of MMP-9, and we found that MMP-9 levels were significantly increased in the airways of mice following exposure to GC frass. Importantly the levels of MMP-9 were significantly decreased in neutrophil-depleted and TLR2-deficient mice after exposure to GC frass, suggesting that TLR2 regulated MMP-9 release from neutrophils. Functionally, MMP-9-deficient mice had more acute allergic inflammation than wild-type mice, suggesting that MMP-9 was protective against experimentally induced asthma. These data suggest that TLR2 activation of neutrophils leads to release of MMP-9 which decreases allergic responses to GC frass. This suggests a protective role for TLR2 activation and MMP-9 release in the context of experimentally induced asthma in mice.

The role of indoor allergens in the development of asthma

PURPOSE OF REVIEW

Asthma prevalence has markedly increased over the past 30 years. Although atopy and exposure to environmental allergens are known to exacerbate asthma, recent literature supports a causal role of indoor allergens in disease development.

RECENT FINDINGS

High-risk birth cohorts continue to point to atopy as the main risk factor for developing asthma. Exposure to perennial allergens has also been linked to the development of asthma, though with less consistency. Intervention at the level of allergen exposure and allergic immune response is promising.

SUMMARY

The current model of atopic asthma, the predominant phenotype, incorporates genetic and environmental factors in the development of disease. Although genetic factors are less malleable, the environmental component lends itself to analysis and modification.For many, the development of asthma starts with allergen exposure leading to atopic sensitization and subsequent disease. Several studies support the progression from exposure to sensitization with the potential of extremely high levels of exposure leading to tolerance. Likewise, the progression from atopy to asthma is well documented,especially in genetically predisposed children. Recent intervention trials confirm these findings and begin to show promise for the prevention of asthma by interrupting the allergen exposure==>allergen sensitization==>atopic asthma pathway.

Early-life co-administration of cockroach allergen and endotoxin augments pulmonary and systemic responses

BACKGROUND

Environmental exposures to cockroach allergen and endotoxin are recognized epidemiological risk factors for the early development of allergies and asthma in children. Because of this, it is important to examine the role of early-life concurrent inhalation exposures to cockroach allergen and endotoxin in the pathogenesis of allergic airways disease.

OBJECTIVE

We examined the effects of repeated concomitant endotoxin and cockroach allergen inhalation on the pulmonary and systemic immune responses of newborn and juvenile mice.

METHODS

C3H/HeBFeJ mice were exposed to inhaled endotoxin and cockroach allergen via intranasal instillation from day 2 to 21 after birth, and systemic and pulmonary responses were examined in serum, bronchoalveolar lavage fluid, and lung tissue.

RESULTS

Cockroach allergen exposures induced pulmonary eosinophilic inflammation, total and allergen-specific IgE, IgG(1), and IgG(2a) production, and alveolar remodelling. Co-exposures with endotoxin and cockroach allergen significantly increased serum IgE and IgG(1), lung inflammation, and alveolar wall thickness, and decreased airspace volume density. Importantly, compared with exposures with individual substances, the responses to co-exposures were more than additive.

CONCLUSIONS

Repeated inhalation exposures of neonatal and juvenile mice to endotoxin and cockroach allergen increased the pulmonary inflammatory and systemic immune responses in a synergistic manner and enhanced alveolar remodelling in the developing lung. These data underscore the importance of evaluating the effect of multiple, concurrent environmental exposures, and of using an experimental model that incorporates clinically relevant timing and route of exposures.

Violence and Asthma: A Review

Recent research shows that exposure to community violence is, directly and indirectly, associated with asthma. This article reviews the findings on the impact of violence on asthma, and the pathways for the association of violence and asthma are suggested: 1) exposure to violence is directly associated with asthma, mainly through dysregulation of sympathetic-adrenal-medullary (SAM) and hypothalamic-pituitary-adrenal (HPA) axis, 2) exposure to violence is associated with the change of susceptibility of outdoor air pollution on asthma, probably through the change of an immune response, and 3) behavioral change due to exposure to violence (e.g. keeping children indoors) leads to more exposure to indoor pollutants. The suggested framework may be useful to develop health policy on asthma in high-violence communities.

Rodent allergen in Los Angeles inner city homes of children with asthma

Recent studies have examined the presence of mouse allergen in inner city children with asthma. Researchers have found high levels of rodent allergen in homes sampled in the northeast and midwest United States, but there has been considerable variation between cities, and there have been few studies conducted in western states. We evaluated the frequency of rodent sightings and detectable mouse allergen and the housing conditions associated with these outcomes in inner city homes in Los Angeles. Two hundred and two families of school children, ages 6-16 living in inner city neighborhoods, participated in the study. Families were predominantly Latino (94%), and Spanish speaking (92%). At study entry, parents completed a home assessment questionnaire, and staff conducted a home evaluation and collected kitchen dust, which was analyzed for the presence of mouse allergen. Fifty-one percent of homes had detectable allergen in kitchen dust. All 33 families who reported the presence of rodents had detectable allergen in the home and were also more likely to have increased levels of allergen compared to those who did not report rodents. Unwashed dishes or food crumbs, lack of a working vacuum, and a caretaker report of a smoker in the home were all significantly associated with a greater risk of rodent sightings or detectable allergen (P<0.05). Detached homes were significantly more likely to have detectable allergen. The prevalence of allergen is common enough that it may have public health implications for asthmatic children, and detectable allergen was not routinely identified based on rodent sightings. Many of the predictors of rodent allergen are amenable to low-cost interventions that can be integrated with other measures to reduce exposure to indoor allergens.

Differences in susceptibility to German cockroach frass and its associated proteases in induced allergic inflammation in mice

Background

Cockroach exposure is a major risk factor for the development of asthma. Inhalation of fecal remnants (frass) is the likely sensitizing agent; however isolated frass has not been tested for its ability to induce experimental asthma in mice.

Methods

Mice (Balb/c or C57Bl/6) were sensitized and challenged with GC frass or GC frass devoid of proteases and measurements of airway inflammation and hyperresponsiveness were performed (interleukin (IL)-5, -13, and interferon gamma (IFNγ) levels in bronchoalveolar lavage fluid, serum IgE levels, airway hyperresponsiveness, cellular infiltration, and mucin production).

Results

Sensitization and challenge of Balb/c mice with GC frass resulted in increased airway inflammation and hyperresponsiveness. C57Bl/6 mice were not susceptible to this model of sensitization; however they were sensitized to GC frass using a more aggressive sensitization and challenge protocol. In mice that were sensitized by inhalation, the active serine proteases in GC frass played a role in airway hyperresponsiveness as these mice had less airway hyperresponsiveness to acetylcholine and less mucin production. Proteases did not play a role in mediating the allergic inflammation in mice sensitized via intraperitoneal injection.

Conclusion

While both strains of mice were able to induce experimental asthma following GC frass sensitization and challenge, the active serine proteases in GC frass only play a role in airway hyperresponsiveness in Balb/c mice that were susceptible to sensitization via inhalation. The differences in the method of sensitization suggest genetic differences between strains of mice.

Fetal cord blood: aspects of heightened immune responses

Neonatal immune responses have been associated with the development of atopy in childhood. We assessed in cord blood mononuclear cells (CBMC) whether increased allergen/mitogen-induced lymphoproliferation (LP) is associated with pro-allergic Th2 cytokine IL-13 or Th1 cytokine IFN-gamma secretion. We determined whether LP to one allergen is related to heightened lymphocyte function to other allergens/mitogen. CBMC from 135 neonates were stimulated with house dust mite (Derf1), cockroach, ovalbumin, or mitogen. LP to one allergen was associated with significantly increased LP to other allergens/mitogen. Increased Derf1-LP was associated with increased Derf1-induced IL-13 secretion (r = 0.21, p = 0.01). After adjusting for neonatal gender, race, and maternal smoking, Derf1-LP remained associated with Derf1-IL-13 (OR 3.08, 95% CI 1.56-6.10). Increased mitogen-induced proliferation was associated with increased mitogen-induced IL-13 secretion (r = 0.37, p < 0.001). For some individuals, a predisposition to a heightened immune response is already evident at birth. Whether this phenotype results in atopy in childhood warrants further investigation.

German cockroach frass proteases cleave pro-matrix metalloproteinase-9

Matrix metalloproteinase (MMP)-9, secreted as pro-MMP-9, is cleaved by serine proteases at the N-terminus to generate active MMP-9. Pro-MMP-9 has been found in the bronchoalveolar lavage fluid of patients with asthma. Because many inhaled aeroallergens contain active proteases, the authors sought to determine whether German cockroach (GC) fecal remnants (frass) and house dust mite (HDM) were able to cleave pro-MMP-9. Treatment of recombinant human (rh) pro-MMP-9 with GC frass resulted in a dose- and time-dependent cleavage. This was abrogated by pretreating frass with an inhibitor of serine, but not cysteine protease activity. GC frass also induced cleavage of pro-MMP-9 from primary human neutrophils dependent on the active serine proteases in GC frass. HDM was less potent at cleaving pro-MMP-9. Alpha1-antitrypsin (A1AT), a naturally occurring protease inhibitor, attenuated GC frass-induced cleavage of pro-MMP-9. A1AT partially inactivated the serine protease activity in GC frass, while GC frass cleaved A1AT in a dose- and time-dependent manner. These data suggest that GC frass-derived serine proteases could regulate the activity of MMP-9 and that A1AT may play an important role in modulating GC frass activity in vivo. These data suggest a mechanism by which inhalation of GC frass could regulate airway remodeling through the activation of pro-MMP-9.

The combined effects of zafirlukast, prednisone, and inhaled budesonide on IL-13 and IFN-gamma secretion

Therapy for asthma often includes the combined use of glucocorticoids and leukotriene receptor antagonists. The short-term, combined effects of these drugs on cytokine secretion and lymphocyte proliferation are ill-defined. The aim of this study was to analyze allergen and mitogen-induced cytokine secretion and lymphocyte proliferation in asthmatics and to determine the effect of combined therapy on these immune responses. Peripheral blood mononuclear cells were isolated from mild, persistent adult asthmatics (n = 28) and analyzed for cat allergen (Fel d 1) and mitogen (phytohemagglutinin) induced IL-13 and IFN-gamma secretion and lymphocyte proliferation. Samples were analyzed before and after 10 days of therapy with oral zafirlukast, prednisone (0.5 mg/kg/day), and inhaled budesonide (1600 mcg/day). Both Fel d 1 and mitogen stimulation resulted in IL-13 and IFN-gamma secretion. Combination drug therapy resulted in a significant decrease in allergen-induced IFN-gamma secretion (p = 0.018) and allergen-specific lymphocyte proliferation (p = 0.02), while IL-13 secretion was unchanged (p = 0.109). This study indicates a role for Th1 cytokines as well as Th2 cytokines in the allergic response.

Prenatal, perinatal, and heritable influences on cord blood immune responses

BACKGROUND

Maternal and perinatal environmental exposures, as well as inherited factors, may influence neonatal immune responses.

OBJECTIVE

To determine relations of maternal and perinatal exposures to antigen-specific cord blood lymphoproliferative responses.

METHODS

In 427 newborns from a Boston pregnancy/birth cohort, lymphoproliferative responses in cord blood mononuclear cells to stimulation with cockroach (Bla g 2), house dust mite (Der f 1), ovalbumin, and mitogen phytohemagglutinin were measured as stimulation index (SI). We used the Wilcoxon rank sum and chi2 tests to evaluate predictors of ovalbumin SI as a continuous ranked or dichotomous outcome. We used t test and Spearman correlation for univariate testing and linear regression to evaluate predictors of natural log-transformed Bla g 2, Der f 1, and phytohemagglutinin SI. Logistic multivariate regression was applied to evaluate predictors of Bla g 2, Der f 1, and phytohemagglutinin SI dichotomized at 2 or at the median for phytohemagglutinin.

RESULTS

Maternal smoking during pregnancy, inadequate or excessive maternal weight gain during pregnancy, neonate black race/ethnicity (compared with white), and Apgar score less than 8 were each independently associated with increased cord blood mononuclear cell proliferative responses to stimulation with Bla g 2 and/or Der f 1. Maternal history of asthma was associated only with increased lymphoproliferative response to ovalbumin stimulation.

CONCLUSIONS

Distinct fetal and perinatal exposures and black race/ethnicity may be associated with increased cord blood lymphoproliferative responses. The implications of these findings for future development of allergy or asthma are, as yet, unknown.

Associations of cord blood fatty acids with lymphocyte proliferation, IL-13, and IFN-gamma

BACKGROUND

N-3 and n-6 polyunsaturated fatty acids (PUFAs) have been hypothesized to have opposing influences on neonatal immune responses that might influence the risk of allergy or asthma. However, both n-3 eicosapentaenoic acid (EPA) and n-6 arachidonic acid (AA) are required for normal fetal development.

OBJECTIVE

We evaluated whether cord blood fatty acid levels were related to neonatal immune responses and whether n-3 and n-6 PUFA responses differed.

METHODS

We examined the relation of cord blood plasma n-3 and n-6 PUFAs (n = 192) to antigen- and mitogen-stimulated cord blood lymphocyte proliferation (n = 191) and cytokine (IL-13 and IFN-gamma; n = 167) secretion in a US birth cohort.

RESULTS

Higher levels of n-6 linoleic acid were correlated with higher IL-13 levels in response to Bla g 2 (cockroach, P = .009) and Der f 1 (dust mite, P = .02). Higher n-3 EPA and n-6 AA levels were each correlated with reduced lymphocyte proliferation and IFN-gamma levels in response to Bla g 2 and Der f 1 stimulation. Controlling for potential confounders, EPA and AA had similar independent effects on reduced allergen-stimulated IFN-gamma levels. If neonates had either EPA or AA levels in the highest quartile, their Der f 1 IFN-gamma levels were 90% lower (P = .0001) than those with both EPA and AA levels in the lowest 3 quartiles. Reduced AA/EPA ratio was associated with reduced allergen-stimulated IFN-gamma level.

CONCLUSION

Increased levels of fetal n-3 EPA and n-6 AA might have similar effects on attenuation of cord blood lymphocyte proliferation and IFN-gamma secretion.

CLINICAL IMPLICATIONS

The implications of these findings for allergy or asthma development are not yet known.

Exposure assessment implications for the design and implementation of the National Children's Study

Examining the influence of environmental exposures on various health indices is a critical component of the planned National Children's Study (NCS). An ideal strategy for the exposure monitoring component of the NCS is to measure indoor and outdoor concentrations and personal exposures of children to a variety of pollutants, including ambient particulate and gaseous pollutants, biologic agents, persistent organics, nonpersistent organics (e.g., pesticides), inorganic chemicals (e.g., metals), and others. However, because of the large sample size of the study (approximately 100,000 children), it is not feasible to assess every possible exposure of each child. We envision that cost-effective strategies for gathering the necessary exposure-related information with minimum burden to participants, such as broad administration of product-use questionnaires and diaries, would likely be considered in designing the exposure component of the NCS. In general a biologic (e.g., blood, urine, hair, saliva) measure could be the dosimeter of choice for many of the persistent and for some of the nonpersistent organic pollutants. Biologic specimens, such as blood, can also indicate long-term internal dose to various metals, including lead and mercury. Environmental measures, on the other hand, provide pathway/source-specific exposure estimates to many of the environmental agents, including those where biologic measurements are not currently feasible (e.g., for particulate matter and for some gaseous criteria pollutants). However, these may be burdensome and costly to either collect or analyze and may not actually indicate the absorbed dose. Thus, an important technical and logistical challenge for the NCS is to develop an appropriate study design with adequate statistical power that will permit detection of exposure-related health effects, based on an optimum set of exposure measurement methods. We anticipate that low-cost, low-burden methods such as questionnaires and screening type assessments of environmental and biologic samples could be employed, when exposures at different critical life stages of vulnerability can be reliably estimated by these simpler methods. However, when reliability and statistical power considerations dictate the need for collecting more specific exposure information, more extensive environmental, biologic, and personal exposure measurements should be obtained from various "validation" subsets of the NCS population that include children who are in different life stages. This strategy of differential exposure measurement design may allow the exposure-response relationships to be tested on the whole cohort by incorporating the information on the relationship between different types of exposure measures (i.e., ranging from simple to more complex) derived from the detailed validation subsamples.

Risk factors of bronchial hyperresponsiveness in children with wheezing-associated respiratory infection

The objectives of this study were to identify possible risk factors of bronchial hyperesponsiveness (BHR) in children up to 5 years of age with wheezing-associated respiratory infection (WARI), and to study the prevalence of BHR. Children up to 5 years of age with WARI were enrolled in the study. The parents or caregivers of children were asked about their demographic data and clinical histories. Physical examination and clinical score assessment were performed. Pulmonary function tests, i.e., tidal breathing flow volume (TBFV), were performed to measure tidal breathing parameters before and after salbutamol nebulization. If volume at peak tidal expiratory flow/expiratory tidal volume and time to peak expiratory flow/total expiratory time increased > or = 20%, or tidal expiratory flow at 25% of tidal volume/peak tidal expiratory flow increased > or = 20% after nebulization therapy, BHR was diagnosed. The number in the positive BHR group was used to calculate the prevalence of BHR, and clinical features were compared with those of the negative BHR group. Categorical data were analyzed for statistical significance (P < 0.05) by chi-square test or Fisher's exact test, or Student's t-test, as appropriate. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for those with statistical significance. One hundred and six wheezing children underwent pulmonary function tests before and after salbutamol nebulization. With the aforementioned criteria, 41 cases (38.7%) were diagnosed with BHR. History of reactive airway disease, (OR, 6.31; 95% CI, 1.68-25), maternal history of asthma (OR, 3.45; 95% CI, 1.34-9), breastfeeding less than 3 months (OR, 3.18; 95% CI, 1.26-8.12), and passive smoking (OR, 3; 95% CI, 1.15-7.62) were significant risk factors of BHR. The eosinophil count was significantly higher in the BHR (+) group particularly, in children 1-5 years of age (P < or = 0.01). Patchy infiltrates were more commonly found in patients with negative BHR but not statistically significant. In conclusion, a history of reactive airway disease, maternal history, breastfeeding less than 3 months, and passive smoking were significant risk factors for BHR.

TLR2 and TLR4 stimulation differentially induce cytokine secretion in human neonatal, adult, and murine mononuclear cells

Toll-like receptor 2 (TLR2) and TLR4 signaling may induce differential secretion of T helper 1 (Th1) and Th2 cytokines, potentially influencing the development of autoimmune or atopic diseases. To date, the influence of the type of stimulus, timing, and dose of TLR2 and TLR4 ligands on cytokine secretion has not been well established. We tested whether the innate stimuli peptidoglycan (Ppg, TLR2 agonist) and lipid A (LpA, TLR4 agonist) differentially affect the secretion of interleukin-13 (IL-13) (Th2) and interferon-gamma (IFN-gamma) (Th1). Further, we examined the influence of the maturity of the immune system, species, dose, and timing of stimuli in human cord and adult peripheral blood mononuclear cells (PBMC) and murine cells in vitro and in vivo. Stimulation with Ppg induced the secretion of both IL-13 and IFN-gamma, influenced by time and dose in neonates, adults, and mice. In contrast, stimulation with LpA induced primarily time-independent and dose-independent production of IFN-gamma. Pulmonary administration of Ppg in vivo in mice resulted in secretion of IL-13, whereas administration of LpA resulted in secretion of IFN-gamma in bronchoalveolar lavage (BAL). Therefore, TLR2 and TLR4 stimuli differentially influence IL-13 and IFN-gamma secretion in neonates, adults, and mice, supporting a critical role for innate stimuli in the modulation of cytokine responses.

A novel mouse model of experimental asthma

BACKGROUND

Animal models that mimic the pulmonary features observed in human asthma are important tools to study the mechanism(s) of allergen-induced asthma. Cockroach and dust mite allergens are two common allergens found in the 'inner city' environment. In this study, we examined the interaction between recombinant cockroach (r Bla g 2) and dust mite (r Der f 1) allergens in inbred mouse strain (A/J). The tested hypothesis was that there are enhanced effects of exposure to r Bla g 2 and r Der f 1 allergens in the airway inflammatory response in A/J mice.

METHODS

Five groups of mice (male, 6-8 weeks) were examined: vehicle (saline) controls; adjuvant (alum) controls; r Bla g 2 immunized (0.01-10 microg/mouse), r Der f 1 immunized (0.01-10 microg/mouse), and combined immunization with r Der f 1 (0.05 microg/mouse) and r Bla g 2 (0.0 5 microg/mouse). Mice were immunized at days 0 and 7, challenged by oro-tracheal inhalation with r Der f 1 and/or r Bla g 2 allergen at day 14, and were studied and sacrificed on day 17. Airway hyperreactivity was measured by peak airway pressure and airway pressure time index (APTI). Differential cell analysis and total proteins in bronchoalveolar lavage returns were used to assess airway inflammation and epithelial injury.

RESULTS

Dose-related statistically significant increases in peak pressure, APTI, total cells, eosinophils, epithelial cells, but not total proteins, were induced by r Bla g 2 challenge in r Bla g 2-immunized mice. Similar allergen-induced dose-related increases in airway total cells, eosinophils, epithelial cells and total proteins were observed in r Der f 1 immunized mice. Compared to either allergen alone, enhanced airway inflammation and epithelial damage, but not airway reactivity, were detected in the combined group.

CONCLUSION

This novel mouse model will allow investigation of the immunopathogenesis of human asthma and should provide insight into the common form of 'inner city asthma'.

Allergen-induced cytokine production, atopic disease, IgE, and wheeze in children

BACKGROUND

The early childhood allergen-induced immune responses associated with atopic disease and IgE production in early life are not well understood.

OBJECTIVE

We assessed the relationship of allergen-induced cytokine production by PBMCs to both atopic disease and to IgE increase in a cohort of children with a parental history of allergy or asthma (n = 112) at a median of 2 years of age. We examined cockroach (Bla g 1)-induced, house dust mite (Der f 1)-induced, and cat (Fel d 1)-induced cytokine secretion, including secretion of IFN-gamma, IL-13, IL-10, and TNF-alpha. We investigated whether distinct cytokine patterns associated with atopic disease can be detected in immune responses of children.

METHODS

PBMCs were isolated, and allergen-induced cytokine secretion was analyzed by means of ELISA. Atopic disease was defined as physician- or nurse-diagnosed eczema or hay fever. Increased IgE was defined as an IgE level of greater than 35 U/mL to dust mite, cockroach, cat, and egg white or a total IgE level of 60 U/mL or greater.

RESULTS

Compared with children without atopic disease, children with atopic disease had lower Der f 1 (P =.005) and Bla g 2 (P =.03) allergen-induced IFN-gamma levels. Compared with children without increased IgE (n = 95), those with increased IgE (n = 16) had higher Der f 1-induced (P =.006) and Fel d 1-induced (P =.005) IL-13 levels and lower Bla g 2-induced (P =.03) IFN-gamma levels. Compared with children with neither atopic disease nor repeated wheeze, children with both atopic disease and repeated wheeze had lower levels of allergen-induced IFN-gamma (P =.01 for Der f 1 and P =.02 for Bla g 2) cytokine secretion.

CONCLUSION

In young children at risk for asthma or allergy, decreased allergen-induced IFN-gamma secretion is associated with atopic disease and, in some cases, with increased IgE levels. Increased allergen-induced IL-13 secretion is most strongly associated with early life increase of IgE.

Allergenicity of recombinant Bla g 7, German cockroach tropomyosin

BACKGROUND

Cockroach infestation may sensitize and elicit allergic responses to genetically predisposed individuals. Invertebrate tropomyosins are a frequent cause of allergy and highly cross-reactive in nature. In this study, we aimed to produce recombinant German cockroach tropomyosin and investigate its allergenicity.

METHODS

German cockroach tropomyosin (Bla g 7) was cloned by reverse transcriptase polymerase chain reaction (RT-PCR). The cloned cDNA was over-expressed in Escherichia coli and purified by affinity chromatography using Ni-nitrilotriacetic (NTA) acid resin. The allergenicity of the recombinant tropomyosin was examined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The cloned Bla g 7 shared up to 91% amino acid sequence identity with other cockroach tropomyosins. ELISA showed a recombinant Bla g 7 sensitization rate of 16.2% to German cockroach allergic sera. Recombinant tropomyosin was able to inhibit 32.4% of the specific IgE binding to cockroach extract.

CONCLUSIONS

Tropomyosin represents a minor allergen in cockroach extracts. It is hoped that recombinant tropomyosin will be useful for further studies and clinical applications.

Pediatric allergy: a brief review of risk factors associated with developing allergic disease in childhood

OBJECTIVE

To briefly review some of the factors that have been implicated in the causation of the increased prevalence of allergic disease in children.

DATA SOURCES

MEDLINE search of original research and review articles related to the various risk factors considered responsible for the increased prevalence of allergic disease in children.

STUDY SELECTION

Author selected references.

CONCLUSIONS

It has been established that there is an increased prevalence of allergic disease, especially in children. Risk factors that are currently under investigation include: genetic atopic predisposition, early childhood allergen exposure and sensitization, occurrence of viral respiratory infections in young children, maternal smoking during pregnancy, poor dietary factors, lack of breast-feeding, childhood obesity, having a certain immunologic predisposition (Th2-prone), air pollution, and frequent immunizations in childhood. It is most likely that the occurrence of allergic disease will be found to be multifactorial.

Indoor allergen exposure in the development of allergy and asthma

Research evidence supports a causative relationship between indoor allergen exposure and the development of asthma. Epidemiologic studies demonstrate that exposure to indoor allergens, particularly house-dust mites and cockroaches and, to a lesser extent, animal allergens and mold, is a risk factor for the development of sensitization and perhaps respiratory symptoms. Sensitization to indoor allergen is clearly a major risk factor for the development of asthma and allergy. There is also epidemiologic and experimental evidence that, in sensitized subjects, higher exposure to indoor allergen causes morbidity. Most, but not all, prospective studies support the causative link between allergen exposure and asthma. Additional evidence comes from the prevention studies, in which reduction in indoor allergen exposure may lead to improvement in symptoms, pulmonary function, and bronchial hyperresponsiveness, and, if practiced, in early years of life, perhaps the development of asthma and allergy.

German cockroach extract increases bronchial epithelial cell interleukin-8 expression

BACKGROUND

Cockroach exposure has been recognized as a common trigger for asthma. While dust mite and Aspergillus fumigatus aeroallergens have been noted to have direct effects on airway epithelium, direct effects of cockroach proteins have not been determined.

OBJECTIVE

The purpose of this study was to investigate whether cockroach extract has a direct pro-inflammatory effect on airway epithelium.

METHODS

We examined the effect of crude German cockroach (Blattella germanica) extract on IL-8 expression in a human bronchial epithelial cell line (16HBE14o-cells) and primary human bronchial epithelial cells. Transcription from the IL-8 promoter and protein abundance were determined by reporter assay and enzyme-linked immunosorbent assay (ELISA), respectively. Endotoxin levels in the crude cockroach extracts were determined using the Limulus Amebocyte Lysate assay. Protease activity was assessed using Azocoll as a substrate.

RESULTS

We found that crude cockroach extract induced a synergistic increase in TNF-alpha-induced transcription from the IL-8 promoter. The synergistic effect was observed with as little as 0.3 micro g/mL of crude cockroach extract, while larger concentrations (30 micro g/mL) approximately doubled TNF-alpha-induced IL-8 promoter activity. Similar effects of cockroach extract on IL-8 protein abundance were observed in both 16HBE14o- and primary human bronchial epithelial cells. Addition of endotoxin at concentrations found in the cockroach extract had no effect on TNF-alpha-mediated IL-8 expression. The serine protease inhibitors aprotinin and phenylmethylsulphonyl fluoride abolished cockroach-induced synergy, while the cysteine protease inhibitors E64 and leupeptin had little effect. Measurement of protease activity using Azocoll as a substrate confirmed the presence of protease activity in cockroach extracts. Addition of recombinant Bla g 2, Bla g 3 and Bla g 5 had no effect on TNF-alpha-induced IL-8 promoter activation. Finally, cockroach extract also increased TNF-alpha-induced transcription from the IL-6 promoter.

CONCLUSIONS

German cockroach extract contains novel serine protease activity which has a direct pro-inflammatory effect on airway epithelial cells

High-level expression of immunoreactive recombinant cat allergen (Fel d 1): Targeting to antigen-presenting cells

BACKGROUND

Cat allergen Fel d 1 is a heterodimer encoded by 2 separate genes that has been difficult to produce as a fully immunoreactive molecule.

OBJECTIVE

We sought to engineer recombinant (r) Fel d 1 with IgE and IgG antibody binding comparable with that of the natural allergen that could be targeted to antigen-presenting cells.

METHODS

The rFel d 1 chains were coexpressed in baculovirus, either linked to the anti-CD64 antibody H22 (rFel d 1 H22(+)) or alone (rFel d 1 H22 (-)). Binding of expressed allergens to mouse and human antibodies was compared with that of natural (n) Fel d 1 by means of enzyme immunoassay and antigen-binding and inhibition RIAs. Binding of rFel d 1 H22 (+) to the CD64 receptor on leukocyte subpopulations and on the THP -1 cell line was analyzed by means of flow cytometry.

RESULTS

The baculovirus-expressed allergens migrated with molecular weights of 49 kd (rFel d 1 H22(+)) and 22 kd (rFel d 1 H22 (-)). The rFel d 1 inhibited IgG antibody binding to nFel d 1 by greater than 95% and showed identical dose-dependent inhibition curves. There was an excellent quantitative correlation between IgE and IgG antibody binding to rFel d 1 and nFel d 1 in sera from patients with cat allergy (IgE: n = 258, r = > 0.72,P <.001). The rFel d 1 H22(+) bound to monocytes but not to lymphocytes or neutrophils, and binding of rFel d 1 H22(+) to THP-1 cells was inhibited by a soluble CD64 fusion protein.

CONCLUSIONS

Recombinant Fel d 1 chains have been successfully coexpressed as mature proteins with comparable immunoreactivities to nFel d 1. The rFel d 1 can be targeted to antigen-presenting cells through CD64. These constructs will facilitate structural studies of Fel d 1 and the development of improved allergy diagnostics and therapeutics.

Daycare centers and schools as sources of exposure to mites, cockroach, and endotoxin in the city of São Paulo, Brazil

BACKGROUND

Public places, including schools, have been identified as sources of exposure to allergens derived from mites, cockroach, cat, and dog and to endotoxin.

OBJECTIVES

The purposes of this study were to assess and compare exposure to allergens and endotoxin in 4 types of public child-care facilities in Brazil and to investigate whether the presence of children and the performance of cleaning procedures could have an influence on allergen and endotoxin levels.

METHODS

We have analyzed dust from bedding, floors, chairs, and tables of daycare centers (DCs), preschools, kindergartens, and elementary schools (ESs). Major allergens from mites, cockroach, cat, and dog were quantitated by means of ELISA, and endotoxin content was determined by using the Limulus Amebocyte Lysate assay.

RESULTS

Group 1 mite allergens were greater than 2 microg/g in 67% of DC and preschool samples and in 8.9% and 2.2% of kindergarten and ES samples, respectively. The presence of bedding in DCs and preschools accounted for increased levels of mite allergens in these settings. Levels of Bla g 1 were higher in ES floors compared with those found in DC and preschool floors. Low levels (<1 microg/g) of Fel d 1 e Can f 1 were found in most samples. Levels of endotoxin in DCs and preschools were 3 times higher than in ESs.

CONCLUSIONS

DCs and schools in Brazil should be considered as important sources of exposure to dust mites and cockroach allergens and to endotoxin. Recommendations for mite allergen avoidance should include appropriate care of bedding in DCs and preschools.

The effect of allergen exposure in early childhood on the development of atopy

While there is good evidence for the association between allergen exposure and disease severity in sensitized individuals, and allergen exposure and development of sensitization, the relationship between allergen exposure and development of allergic disease is as yet unresolved. A protective effect of cat ownership on sensitization and allergic disease has been reported. The dose-response relationship between allergen exposure and sensitization may be different for different allergens (eg, linear for mite, bell-shaped for cat). Exposure to a high level of cat allergen may result in a modified Th2 response characterized by the presence of IgG4 antibody to cat proteins without IgE response, which could be regarded as a form of tolerance. The long-term prospective follow-up of well-defined cohorts with objective exposure and outcome measures will elucidate the complex relationship between environmental allergen exposures, sensitization, and asthma.