Innate and adaptive immunity in allergic airway disease

PURPOSE OF REVIEW

This article explores recent findings on the involvement of innate immunity in allergic airways disease, concentrating on allergic rhinitis.

RECENT FINDINGS

We speculate on the ways in which environmental influences act to initiate inflammation and on how these may have altered in recent decades. Improved understanding of the mechanisms involved may reveal future possibilities for therapy.

SUMMARY

The complex nature of immunity - both innate and acquired - in airways disease has implications for prevention and for therapy and requires further elucidation.

Early-life exposure to sibling modifies the relationship between CD14 polymorphisms and allergic sensitization

BACKGROUND

Markers of microbial exposure are thought to be associated with risk of allergic sensitization; however, the associations are inconsistent and may be related to gene-environment interactions.

OBJECTIVE

To examine the relationship between polymorphisms in the CD14 gene and allergic sensitization and whether sibling exposure, as a marker of microbial exposure, modified this relationship.

METHODS

We used data from the Tasmanian Longitudinal Health Study and the Melbourne Atopy Cohort Study. Two CD14 polymorphisms were genotyped. Allergic sensitization was defined by a positive response to a skin prick test. Sibling exposure was measured as cumulative exposure to siblings before age 6 months, 2 and 4 years. Logistic regression and multi-level mixed-effects logistic regression were used to examine the associations. Effect estimates across the cohorts were pooled using random-effects meta-analysis.

RESULTS

CD14 SNPs were not individually associated with allergic sensitization in either cohort. In TAHS, cumulative sibling exposure before age 6 months, 2 and 4 years was each associated with a reduced risk of allergic sensitization at age 45 years. A similar effect was observed in MACS. Meta-analysis across the two cohorts showed consistent evidence of an interaction between cumulative sibling exposure before 6 months and the rs5744455-SNP (P = 0.001) but not with the rs2569190-SNP (P = 0.60). The pooled meta-analysis showed that the odds of sensitization with increasing cumulative exposure to sibling before 6 months of age was 20.9% smaller in those with the rs5744455-C-allele than the T-allele (OR = 0.83 vs 1.05, respectively).

CONCLUSION AND CLINICAL RELEVANCE

Cumulative sibling exposure reduced the risk of sensitization from childhood to middle age in genetically susceptible individuals.

International Consensus Statement on Allergy and Rhinology: Allergic Rhinitis

BACKGROUND

Critical examination of the quality and validity of available allergic rhinitis (AR) literature is necessary to improve understanding and to appropriately translate this knowledge to clinical care of the AR patient. To evaluate the existing AR literature, international multidisciplinary experts with an interest in AR have produced the International Consensus statement on Allergy and Rhinology: Allergic Rhinitis (ICAR:AR).

METHODS

Using previously described methodology, specific topics were developed relating to AR. Each topic was assigned a literature review, evidence-based review (EBR), or evidence-based review with recommendations (EBRR) format as dictated by available evidence and purpose within the ICAR:AR document. Following iterative reviews of each topic, the ICAR:AR document was synthesized and reviewed by all authors for consensus.

RESULTS

The ICAR:AR document addresses over 100 individual topics related to AR, including diagnosis, pathophysiology, epidemiology, disease burden, risk factors for the development of AR, allergy testing modalities, treatment, and other conditions/comorbidities associated with AR.

CONCLUSION

This critical review of the AR literature has identified several strengths; providers can be confident that treatment decisions are supported by rigorous studies. However, there are also substantial gaps in the AR literature. These knowledge gaps should be viewed as opportunities for improvement, as often the things that we teach and the medicine that we practice are not based on the best quality evidence. This document aims to highlight the strengths and weaknesses of the AR literature to identify areas for future AR research and improved understanding.

Rhinitis in Swiss adults is associated with asthma and early life factors, but not second hand tobacco smoke or obesity

BACKGROUND

Second hand tobacco smoke (SHS) and overweight/obesity are risk factors for asthma and lower airway respiratory symptoms. We investigated whether SHS or overweight/obesity were also associated with allergic or non-allergic rhinitis.

METHODS

Cross-sectional data were obtained during the second SAPALDIA Study. Interviewer administered questionnaires were completed by 8047 participants from 8 communities in Switzerland. Blood was collected from 5841 participants and tested for allergen specific IgE. Allergic rhinitis was defined as nasal symptoms with detectable IgE. Data were analysed by multinomial logistic regression with four outcome categories defined according to the presence or absence of rhinitis and/or atopy.

RESULTS

The prevalence of allergic rhinitis was 885 (15.2%) and non-allergic rhinitis 323 (5.5%). The risk of allergic rhinitis was increased in subjects with physician diagnosed asthma (Relative Risk Ratio 6.81; 95%CI 5.39, 8.6), maternal atopy (1.56; 1.27, 1.92) and paternal atopy (1.41; 1.11, 1.79). Older subjects were at lower risk (0.96; 0.95,0.97 per year), as were those raised on a farm (0.64; 0.49,0.84), with older siblings (0.92; 0.86,0.97 per sib) or from rural areas. The risk of non-allergic rhinitis was also increased in subjects with physician diagnosed asthma (4.02; 2.86, 5.67), reduced in males (0.59; 0.46, 0.77), but not associated with upbringing on a farm or older siblings. There were no significant associations of SHS or overweight/obesity with either form of rhinitis.

CONCLUSIONS

Allergic and non-allergic rhinitis have different risk factors apart from asthma. There are significant regional variations within Switzerland, which are not explained by the factors examined.

Replication of genomewide associations with allergic sensitization and allergic rhinitis

BACKGROUND

Three genomewide metastudies have recently reported associations with self-reported allergic rhinitis and allergic sensitization. The three studies together identified a set of 37 loci but showed low concordance. This study investigates the reproducibility of the detected single nucleotide polymorphism (SNP) associations in an extensively characterized longitudinal cohort, BAMSE.

METHODS

Phenotypic evaluation of allergic rhinitis (AR) and allergic sensitization was performed on 2153 children from BAMSE at 8 and 16 years of age. Allele frequencies of 39 SNPs were investigated for association with the exact allergic phenotypes of the metastudies. Odds ratios and false discovery rates were calculated, and the impact of asthma was evaluated. The cases were also evaluated for age at onset effects (≤ or >8 years of age).

RESULTS

Association tests of the 39 SNPs identified 12 SNPs with P-values < 0.05 and Q-values < 0.10. Two of the four loci (TLR6-TLR1 and HLA-DQA1-HLA-DQB1) identified in all three original studies were also identified in this study. Three SNPs located in the TLR6-TLR1 locus had the lowest P-values and Q-values < 0.1 when using a well-defined AR phenotype. Two loci showed significant age at onset effects, but the effect of asthma on the associations was very limited.

CONCLUSION

The TLR6-TLR1 locus is likely to have a central role in the development of allergic disease. The association between genetic variation in the SSTR1-MIPOL1 and TSLP-SLC25A46 loci and age at onset is the first report of age at onset effects in allergic rhinitis.

CD14 polymorphisms, microbial exposure and allergic diseases: a systematic review of gene-environment interactions

Asthma and allergy may develop as a result of interactions between environmental factors and the genetic characteristics of an individual. This review aims to summarize the available evidence for, and potential effects of, an interaction between polymorphisms of the CD14 gene and exposure to microbes on the risk of asthma and allergic diseases. We searched PubMed, MEDLINE and Global Health databases, finding 12 articles which met inclusion criteria. Most studies reported a significant interaction between CD14 polymorphisms and microbial exposure. When stratified by age at microbial exposure (early life vs adult life), there was evidence of a protective effect of gene-environment interaction against atopy in children, but not adults. We also found different effects of interaction depending on the type of microbial exposures. There was no strong evidence for asthma and eczema. Future studies should consider a three-way interaction between CD14 gene polymorphisms, microbial exposures and the age of exposure.

The link between parental allergy and offspring allergic and nonallergic rhinitis

BACKGROUND

Parental allergy-related disease increases the risk for rhinitis, but it remains unknown how different phenotypes of parental allergy affect this risk. The aim of this study was to investigate how parental hay fever, asthma, and eczema affect the risk of allergic rhinitis (AR) and nonallergic rhinitis (NAR) at 8 years of age.

METHODS

Information on 2413 children from a population-based birth cohort was used combining questionnaire data and IgE to inhalant allergens. Logistic regression was used to estimate the association between parental allergy-related disease and AR and NAR. In addition, cluster analysis was used to search for latent phenotypes of heredity likely to be associated with AR and NAR.

RESULTS

At age 8 years, 13.8% of the children had AR, while 6.4% had NAR. Parental isolated hay fever increased the odds of AR (OR 2.2, 95% CI 1.6-3.2), whereas isolated asthma or eczema did not. The odds of NAR increased when one parent had two or more allergy-related diseases. In the cluster analysis, the highest proportion of AR, 37.5%, was seen in a cluster where both parents had hay fever and pollen allergy and that of NAR, 11.0%, in a cluster where one parent had hay fever, pollen allergy, and eczema.

CONCLUSIONS

Parental allergy-related disease may be an important risk factor for NAR as well as AR, and the risk is comparable for maternal and paternal allergy. Parental hay fever seems to be the dominating hereditary risk factor for AR.

The pathophysiology of the hygiene hypothesis

There has been a considerable increase in the diagnosis of allergic diseases over the last decades. Prevalence of allergies in high-income countries and urban areas appears higher than in rural environments. While environmental factors like pollution or nutrition can be important, it is more likely that in the end they have a small association with allergies. Childhood infections and exposure to certain microbial antigens on the other hand seem to present a strong negative correlation with allergies, and therefore the increase of the allergic burden in the Western world has been frequently related to a decline of childhood infections giving birth to the "Hygiene Hypothesis". We address the issue with emphasis on the associated pathophysiology tightrope walking between the skepticism of the critics, which cast doubt on it, and the pilgrims' belief of having discovered allergy's Holy Grail.

Prevalence of asthma and allergies in children from the Greek-Cypriot and Turkish-Cypriot communities in Cyprus: a bi-communal cross-sectional study

Background

The Greek-Cypriot (G/C) and Turkish-Cypriot (T/C) communities have lived apart since 1974, with the former presumably adopting a more westernized way of life. We estimated the prevalence of asthma and allergies among children in the two communities and investigated differences in socio-demographic and lifestyle risk factors.

Methods

The ISAAC questionnaire was completed by 10156 children aged 7–8 and 13–14 years. Relative differences in asthma and allergic symptoms between the two communities were expressed as odds ratios (OR), estimated in multivariable logistic regression models before and after adjusting for participants’ risk characteristics.

Results

In contrast to our original speculation, consistently lower prevalence rates were observed for respiratory outcomes (but not eczema) among G/C compared to T/C children in both age-groups. For instance, the prevalence of current wheeze among 7–8 year-olds was 8.7% vs 11.4% (OR = 0.74, 95%, CI: 0.61, 0.90) and of current rhinoconjuctivitis 2.6% vs 4.9% (OR = 0.52, 95% CI: 0.37, 0.71). Surprisingly, the proportion reporting family history of allergy was almost double in the G/C community. With the exception of early life nursery attendance, several protective factors were more prevalent amongst T/C, such as bedroom sharing, less urbanized environment and exposure to farm animals. In contrast, exposure to tobacco smoke was more frequent in the T/C community. Controlling for risk factors did not account for the observed lower prevalence of current wheeze (in the younger age-group) and rhinoconjuctivitis (in both age-groups) among G/C children while differences in the prevalence of eczema between the two communities were no longer statistically significant.

Conclusions

A mixed picture of potential risk factors was observed in the two communities of Cyprus, not consistently favoring one over the other community since, for example, bedroom sharing and rural living but also exposure to tobacco smoke were more common among T/C children. Investigated risk factors do not fully account for the lower prevalence of asthma and allergies among G/C children, especially against a background of higher family history of allergy in this community.

Management of patients with atopic dermatitis: the role of emollient therapy

Atopic dermatitis is a common inflammatory skin disorder that afflicts a growing number of young children. Genetic, immune, and environmental factors interact in a complex fashion to contribute to disease expression. The compromised stratum corneum found in atopic dermatitis leads to skin barrier dysfunction, which results in aggravation of symptoms by aeroallergens, microbes, and other insults. Infants—whose immune system and epidermal barrier are still developing—display a higher frequency of atopic dermatitis. Management of patients with atopic dermatitis includes maintaining optimal skin care, avoiding allergic triggers, and routinely using emollients to maintain a hydrated stratum corneum and to improve barrier function. Flares of atopic dermatitis are often managed with courses of topical corticosteroids or calcineurin inhibitors. This paper discusses the role of emollients in the management of atopic dermatitis, with particular emphasis on infants and young children.

Management of chronic rhinosinusitis

: Chronic rhinosinusitis (CRS) in children is difficult to treat, with resultant frequent recurrences and failures. There are controversies in the treatment, mirroring the debate over the exact etiology of this disorder. The available medical treatments are antibiotics, topical nasal corticosteroids, and nasal lavage with saline solutions; though, there is no general agreement on the efficacy of the latter. The new technique of balloon sinuplasty allows ventilation to the sinuses to be restored with minimal risk and trauma to the tissues, and initial outcome seems promising, being successful in most treated children. Concerning the surgical approach, adenoidectomy is among the most frequent surgical procedures performed on children, but its therapeutic effect is controversial, because randomized studies have failed to prove that adenoidectomy alone is sufficient in curing CRS. Instead, functional endoscopic sinus surgery is a minimally invasive technique which restores the sinus ostia patency and can re-establish ventilation and drainage through the natural pathways. It is important that the effectiveness of any treatment is also evaluated by patient-reported outcomes (PROs) that refer to all health-related reports coming from the patients, without any involvement or interpretations by physician or others. Among PROs, health-related quality of life (HRQL) is the one most widely known and used. HRQL can be measured by means of validated questionnaires, which provide scores proportional to the degree of well-being perceived by patients. Concerning diseases of the upper airway including RS, there are numerous instruments specifically designed for children and caregivers, which allow to assess the effects of treatments in a more extensive and complete manner.

Immunological approaches for tolerance induction in allergy

Allergy is the consequence of an inappropriate inflammatory immune response generated against harmless environmental antigens. In allergic disorders such as asthma and rhinitis, the Th2 mediated phenotype is a result of loss of peripheral tolerance mechanisms. In cases such as these, approaches such as immunotherapy attempt to treat the underlying cause of allergic disease by restoring tolerance. Immunotherapy initiates many complex mechanisms within the immune system that result in initiation of innate immunity, activation of both cellular and humoral B cell immunity, as well as triggering T regulatory subsets which are major players in the establishment of peripheral tolerance. Though studies clearly demonstrate immunotherapy to be efficacious, research to improve this treatment is ongoing. Investigation of allergenicity versus immunogenicity, native versus modified allergens, and the use of adjuvant and modality of dosing are all current strategies for immunotherapy advancement that will be reviewed in this article.

Allergic rhinitis

Allergic rhinitis is a costly disease associated with significant morbidity. It impacts the quality of life of millions of individuals, particularly in industrialized nations, and it is on the rise. Lost productivity and total healthcare expenditure exceeds several billion dollars annually in the United States, with an estimate of >$6 billion spent on prescription medications alone. It is also associated with asthma and other atopic conditions, sinusitis, otitis media, and sleep apnea. Primary care physicians should be well adept at recognizing and initiating empiric first-line therapy for chronic rhinitis. Allergen avoidance, topical nasal steroids, and antihistamines may be sufficient for some patients. In most cases, referral to a board-certified allergy specialist for skin testing and targeted management is indicated. It is essential to make sure that patients abstain from using antihistamines at least 1 week prior to reporting to the allergist for skin testing in order to avoid false-negative results. Traditional subcutaneous allergen immunotherapy, when performed by an experienced allergist, affords relief in >75% of cases. The growing armament of treatment options for refractory allergic rhinitis includes oral and sublingual immunotherapy, recombinant allergens, conjugated DNA vaccines, and anti-immunoglobulin E monoclonal antibody.

Prediction of the incidence and persistence of allergic rhinitis in adolescence: a prospective cohort study

BACKGROUND

Predictive models have rarely been used in allergy research and practice. However, they might support physicians in advising patients.

OBJECTIVE

The aim of this study was to create predictive models for the incidence and persistence of allergic rhinitis (AR) during adolescence.

METHODS

A prospective population-based cohort study was conducted starting at age 9 to 11 years. Potential risk factors for atopic diseases obtained at baseline in 2810 subjects were used to create predictive logistic regression models for the incidence and persistence of physician-diagnosed AR with current symptoms at age 15 to 18 years.

RESULTS

Positive skin prick test responses to outdoor allergens at baseline were the most important determinant for both the incidence and persistence of AR until follow-up. For the incidence of AR, positive skin prick test responses to indoor allergens, parental history of asthma, female sex, and not having been breast-fed exclusively for 2 or more months were additional statistically significant independent risk factors. Depending on the number of risk factors present, the probability of the incidence of AR increased from 2% (no risk factors present) to 72% (full model; 95% CI, 58% to 85%). The probability of persistence of AR ranged from 33% (no risk factors present) to 83% (full model; 95% CI, 70% to 97%).

CONCLUSION

The course of AR over puberty can be predicted using risk factors that are easy to determine in childhood. Sensitization to outdoor allergens seems to play a much greater role for disease development than sensitization to indoor allergens. This might help pediatricians in advising patients.

Risk factors for wheezing, eczema and rhinoconjunctivitis in the previous 12 months among six-year-old children in Himeji City, Japan: food allergy, older siblings, day-care attendance and parental allergy history

BACKGROUND

The aim of this study was to clarify whether some environmental and genetic factors (food allergy, older siblings, early day-care attendance and parents' allergy history) are related to the development of allergic symptoms (wheezing in the previous 12 months [WP], eczema symptoms in the previous 12 months [EP], and rhinoconjunctivitis symptoms in the previous 12 months [RP]) in Japanese children.

METHODS

Using the modified version of the International Study on Asthma and Allergies in Childhood (ISSAC) questionnaire, we studied the prevalence of WP, EP and RP among six-year-old children attending 72 primary schools throughout Himeji City, Japan, during the two years from 2005 to 2006.

RESULTS

Food allergy and parents' history of allergy showed a significant relationship with the prevalence of WP, EP and RP. Day-care attendance in the first two years of life and presence of older siblings showed a significant inverse relationship with the prevalence of RP. However, neither day-care attendance nor presence of older siblings was related to the development of W and ER.

CONCLUSIONS

Among Japanese children, food allergy and parents' history of allergy are risk factors for WP, ES or RS. However, early day-care attendance and presence of older siblings might be protective factors against RS. Infections in early life may affect the prevalence of rhinoconjunctivitis in six-year-old children.

Developments in the field of allergy in 2009 through the eyes of Clinical and Experimental Allergy

In 2009 the journal published in the region of 200 papers including reviews, editorials, opinion pieces and original papers that ran the full gamut of allergic disease. It is instructive to take stock of this output to determine patterns of interest and where the cutting edge lies. We have surveyed the field of allergic disease as seen through the pages of Clinical and Experimental Allergy (CEA) highlighting trends, emphasizing notable observations and placing discoveries in the context of other key papers published during the year. The review is divided into similar sections as the journal. In the field of Asthma and Rhinitis CEA has contributed significantly to the debate about asthma phenotypes and expressed opinions about the cause of intrinsic asthma. It has also added its halfpennyworth to the hunt for meaningful biomarkers. In Mechanisms the considerable interest in T cell subsets including Th17 and T regulatory cells continues apace and the discipline of Epidemiology continues to invoke a steady stream of papers on risk factors for asthma with investigators still trying to explain the post-second world war epidemic of allergic disease. Experimental Models continue to make important contributions to our understanding of pathogenesis of allergic disease and in the Clinical Allergy section various angles on immunotherapy are explored. New allergens continue to be described in the allergens section to make those allergen chips even more complicated. A rich and vibrant year helpfully summarized by some of our associate editors.

Risk factors for allergic rhinitis in Costa Rican children with asthma

BACKGROUND

Risk factors for allergic rhinitis (AR) in asthmatics are likely distinct from those for AR or asthma alone. We sought to identify clinical and environmental risk factors for AR in children with asthma.

METHODS

We performed a cross-sectional study of 616 Costa Rican children aged 6-14 years with asthma. Candidate risk factors were drawn from questionnaire data, spirometry, methacholine challenge testing, skin testing, and serology. Two outcome measures, skin test reaction (STR)-positive AR and physician-diagnosed AR, were examined by logistic regression.

RESULTS

STR-positive AR had high prevalence (80%) in Costa Rican children with asthma, and its independent risk factors were nasal symptoms after exposure to dust or mold, parental history of AR, older age at asthma onset, oral steroid use in the past year, eosinophilia, and positive IgEs to dust mite and cockroach. Physician-diagnosed AR had lower prevalence (27%), and its independent risk factors were nasal symptoms after pollen exposure, STR to tree pollens, a parental history of AR, inhaled steroid and short-acting beta2 agonist use in the past year, household mold/mildew, and fewer older siblings. A physician's diagnosis was only 29.5% sensitive for STR-positive AR.

CONCLUSIONS

Risk factors for AR in children with asthma depend on the definition of AR. Indoor allergens drive risk for STR-positive AR. Outdoor allergens and home environmental conditions are risk factors for physician-diagnosed AR. We propose that children with asthma in Costa Rica and other Latin American nations undergo limited skin testing or specific IgE measurements to reduce the current under-diagnosis of AR.