Precision medicine in patients with allergic diseases: Airway diseases and atopic dermatitis-PRACTALL document of the European Academy of Allergy and Clinical Immunology and the American Academy of Allergy, Asthma & Immunology

In this consensus document we summarize the current knowledge on major asthma, rhinitis, and atopic dermatitis endotypes under the auspices of the PRACTALL collaboration platform. PRACTALL is an initiative of the European Academy of Allergy and Clinical Immunology and the American Academy of Allergy, Asthma & Immunology aiming to harmonize the European and American approaches to best allergy practice and science. Precision medicine is of broad relevance for the management of asthma, rhinitis, and atopic dermatitis in the context of a better selection of treatment responders, risk prediction, and design of disease-modifying strategies. Progress has been made in profiling the type 2 immune response-driven asthma. The endotype driven approach for non-type 2 immune response asthma, rhinitis, and atopic dermatitis is lagging behind. Validation and qualification of biomarkers are needed to facilitate their translation into pathway-specific diagnostic tests. Wide consensus between academia, governmental regulators, and industry for further development and application of precision medicine in management of allergic diseases is of utmost importance. Improved knowledge of disease pathogenesis together with defining validated and qualified biomarkers are key approaches to precision medicine.

Multiple regulatory variants located in cell type-specific enhancers within the PKP2 locus form major risk and protective haplotypes for canine atopic dermatitis in German shepherd dogs.

BACKGROUND Canine atopic dermatitis (CAD) is a chronic inflammatory skin disease triggered by allergic reactions involving IgE antibodies directed towards environmental allergens. We previously identified a ~1.5 Mb locus on canine chromosome 27 associated with CAD in German shepherd dogs (GSDs). Fine-mapping indicated association closest to the PKP2 gene encoding plakophilin 2. RESULTS Additional genotyping and association analyses in GSDs combined with control dogs from five breeds with low-risk for CAD revealed the top SNP 27:19,086,778 (p = 1.4 × 10(-7)) and a rare ~48 kb risk haplotype overlapping the PKP2 gene and shared only with other high-risk CAD breeds. We selected altogether nine SNPs (four top-associated in GSDs and five within the ~48 kb risk haplotype) that spanned ~280 kb forming one risk haplotype carried by 35 % of the GSD cases and 10 % of the GSD controls (OR = 5.1, p = 5.9 × 10(-5)), and another haplotype present in 85 % of the GSD cases and 98 % of the GSD controls and conferring a protective effect against CAD in GSDs (OR = 0.14, p = 0.0032). Eight of these SNPs were analyzed for transcriptional regulation using reporter assays where all tested regions exerted regulatory effects on transcription in epithelial and/or immune cell lines, and seven SNPs showed allelic differences. The DNA fragment with the top-associated SNP 27:19,086,778 displayed the highest activity in keratinocytes with 11-fold induction of transcription by the risk allele versus 8-fold by the control allele (pdifference = 0.003), and also mapped close (~3 kb) to an ENCODE skin-specific enhancer region. CONCLUSIONS Our experiments indicate that multiple CAD-associated genetic variants located in cell type-specific enhancers are involved in gene regulation in different cells and tissues. No single causative variant alone, but rather multiple variants combined in a risk haplotype likely contribute to an altered expression of the PKP2 gene, and possibly nearby genes, in immune and epithelial cells, and predispose GSDs to CAD.

A systematic review of treatments for atopic dermatitis

Atopic dermatitis is a very common inflammatory skin disease, particularly in children. A systematic review of randomised controlled trials of treatments for atopic dermatitis (AD) was carried out to assess how many trials exist, what they cover, what they do not cover, the research gaps, provide a 'blue print' for future Cochrane Reviews and assist those making treatment recommendations by summarising the available RCT evidence, using descriptive statistics. The Cochrane Collaboration systematic review process formed the basis of the methodology, from which over 4000 studies were located via electronic database searches and hand searching of journals. A total of 292 trials were finally included covering 9 treatment groups and over 48 individual treatments. There are lots of trials covering lots of interventions but gaps are evident. However, there is evidence of a benefit in the treatment of atopic dermatitis with topical corticosteroids, psychological approaches, UV light, ascomycin derivatives, topical tacrolimus and oral cyclosporin. Treatments that show limited evidence of a benefit include non-sedatory antihistamines, topical doxepin, the oral antibiotic Cefadroxil on clinically infected AD, the topical antibacterial Mupirocin on clinically uninfected AD, Chinese herbs, hypnotherapy and biofeedback, massage therapy, dietary manipulation, house dust mite reduction, patient education, emollients, allergen antibody complexes of house dust mite and thymic extracts. Treatments that show no evidence of benefit include sedatory antihistamines, oral sodium cromoglycate, oral antibiotics on clinically uninfected AD, topical antibacterials, topical antifungals, aromatherapy essential oils, borage oil, fish oil, evening primrose oil, enzyme-free clothes detergent, cotton clothing, house dust mite hyposensitisation, salt baths, topical coal tar, topical cyclosporin and platelet-activating-factor antagonist. When interpreting the conclusions of this thesis it is important to understand that lack of evidence does not equal lack of efficacy, particularly considering the interventions that are commonly in use today to treat atopic dermatitis that have not been subjected to RCTs, such as occlusive dressings, water softening devices and stress management among many others.

Atopic Dermatitis

A 10-year-old girl with atopic dermatitis reports itching that has recently become relentless, resulting in sleep loss. Her mother has been reluctant to treat the girl with topical corticosteroids, because she was told that they damage the skin, but she is exhausted and wants relief for her child. How should the problem be managed?

How epidemiology has challenged 3 prevailing concepts about atopic dermatitis

We challenge 3 prevailing concepts in understanding atopic dermatitis using data from epidemiologic studies. First, we show that although atopy is associated with atopic dermatitis to some degree, its importance is not likely to be a simple causeand- effect relationship, especially at a population level. Our epidemiologic data do not exclude a contributory role for IgEmediated immunologic processes, especially in those with existing and severe disease. Second, evidence is presented that does not support a straightforward inverse relationship between infections and atopic dermatitis risk. A link, if present, is likely to be more complex, depending critically on the timing and type of infectious exposure. Third, recent evidence suggests that the risk of subsequent childhood asthma is not increased in children with early atopic dermatitis who are not also early wheezers, suggesting a comanifestation of phenotypes rather than a progressive atopic march. Collectively, these observations underline the importance of epidemiologic studies conducted at a population level to gain a more balanced understanding of the enigma of atopic dermatitis.

New treatments for atopic dermatitis

Atopic dermatitis now affects 15% to 20% of chil­ dren in developed countries, and prevalence in cities in developing countries undergoing rapid demographic changes is quickly following suit.1 Most cases of atopic dermatitis in a given community are mild, but children with moderate to severe disease can have continuous itching and associated loss of sleep. The social stigma of a visible skin disease can also be soul destroying for both patient and family. A few studies have suggested that some degree of prevention of the disease is possible,2 although these measures have not been taken up widely. In the absence of any treatment that is known to alter the clinical course of the disease, most treatment is aimed at reducing symp­ toms and signs. After a relative lull of almost 40 years, new drugs—tacrolimus and pimecrolimus—have appeared that offer different approaches to managing this miserable disease. Do they work? Are they safe? And how do they compare with existing treatments?

Skin microbiome before development of atopic dermatitis: Early colonization with commensal staphylococci at 2 months is associated with a lower risk of atopic dermatitis at 1 year

Background: Disease flares of established atopic dermatitis (AD) are generally associated with a low-diversity skin microbiota and Staphylococcus aureus dominance. The temporal transition of the skin microbiome between early infancy and the dysbiosis of established AD is unknown. Methods: We randomly selected 50 children from the Cork Babies After SCOPE: Evaluating the Longitudinal Impact Using Neurological and Nutritional Endpoints (BASELINE) longitudinal birth cohort for microbiome sampling at 3 points in the first 6 months of life at 4 skin sites relevant to AD: the antecubital and popliteal fossae, nasal tip, and cheek. We identified 10 infants with AD and compared them with 10 randomly selected control infants with no AD. We performed bacterial 16S ribosomal RNA sequencing and analysis directly from clinical samples. Results: Bacterial community structures and diversity shifted over time, suggesting that age strongly affects the skin microbiome in infants. Unlike established AD, these patients with infantile AD did not have noticeably dysbiotic communities before or with disease and were not colonized by S aureus. In comparing patients and control subjects, infants who had affected skin at month 12 had statistically significant differences in bacterial communities on the antecubital fossa at month 2 compared with infants who were unaffected at month 12. In particular, commensal staphylococci were significantly less abundant in infants affected at month 12, suggesting that this genus might protect against the later development of AD. Conclusions: This study suggests that 12-month-old infants with AD were not colonized with S aureus before having AD. Additional studies are needed to confirm whether colonization with commensal staphylococci modulates skin immunity and attenuates development of AD.

Th17 cells and tissue remodeling in atopic and contact dermatitis

BACKGROUND: Eczematous skin lesions of atopic dermatitis (AD) as well as allergic and irritant contact dermatitis (ACD, ICD) are characterized by the same typical clinical signs, although due to different causes. In both AD and ACD, the presence of T helper 17 cells which play an important role in host defense, has been reported. Furthermore, IL-17 is involved in tissue repair and remodeling. This study aimed to investigate IL-17 expression in acute eczematous skin lesions and correlate it with markers of remodeling in AD, ACD, and ICD. METHODS: Skin specimens were taken from positive patch test reactions to aeroallergens, contact allergens, and irritants at days 2, 3, and 4. Inflammatory cells as well as the expression of cytokines and extracellular matrix proteins were evaluated by immunofluorescence staining and confocal microscopy. RESULTS: Allergic contact dermatitis and ICD were characterized by IFN-γ expression, whereas in AD lesions, IL-13 expression and high numbers of eosinophils were the prominent phenotype. Expression of IL-17, but also IL-21 and IL-22, was observed in all eczema subtypes. The number of IL-22+ T cells correlated with the number of eosinophils. Markers of remodeling such as MMP-9, procollagen-3, and tenascin C were observed in all acute eczematous lesions, while a correlation of IL-17+ T cell numbers with tenascin C-expressing cells and MMP-9+ eosinophils was apparent. CONCLUSION: The expression of IL-17 and related cytokines, such as IL-22, was demonstrated in acute eczematous lesions independent of their pathogenesis. Our results suggest a potential role for IL-17 in remodeling of the skin.

Atopic Manifestations: Dermatitis, Allergic Rhinitis and Asthma in Patients With Hypogammaglobulinemia

Background: Most of the hypogammaglobulinemic patients have a clinical history in favor of allergic respiratory disease. Nevertheless, in these patients the importance and prevalence of atopic disorders have not been completely explained. Objectives: This study was aimed to evaluate atopic manifestations (dermatitis, allergic rhinitis and asthma) and pulmonary function in patients with hypogammaglobulinemia. Patients and Methods: We used the international study of asthma and allergies in childhood (ISAAC) questionnaire in forty-five patients diagnosed with hypogammaglobulinemia and spirometry was done in 41 patients older than 5 years. Results: Spirometry results were normal in 21 (51%), and showed obstructive in 15 (37%) and restrictive pattern in 5 (12%) of the 41 patients who were evaluated. By the end of the study, asthma was diagnosed in nine (20%) patients and other atopies (rhinitis and dermatitis) identified in 10 (22%), and four (9%), respectively. Conclusions: Atopic conditions should be investigated in the hypogammaglobulinemic patients and the prevalence in these patients may be higher than in normal population. Also, it is recommended to perform a pulmonary function test as a routine procedure in patients with hypogammaglobulinemia and atopy should be assessed in these patients.

Evaluation of skin sensitivity in dogs bearing allergic dermatitis to standardized allergenic extract of house dust and storage mites

The objective of the study was to evaluate whether allergenic extracts of five house dust and storage mite species standardized for humans might be used for the diagnosis of canine atopic dermatitis (CAD). Extracts of Dermatophagoides pteronyssinus (Pyroglyphidae), D. farinae (Pyroglyphidae), Blomia tropicalis (Glycyphagidae), Lepidoglyphus destructor (Glycyphagidae) and Tyrophagus putrescentiae (Acaridae) were evaluated by intradermal testing in 20 healthy dogs (control) and 25 dogs with allergic dermatitis. A significant difference in the response was observed between the two groups (p<0.05). Only one dog (5%) in the control group reacted to the intradermal test, whereas 14 dogs (56%) in the allergic group were positive for at least one extract (odds ratio = 24.2). Most of the positive reactions observed in the allergic group occurred against the extracts of T. putrescentiae or L. destructor, each inducing reactions in 10 dogs (40%). D. farinae, D. pteronyssinus e B. tropicalis extracts induced reactions in 7 (28%), 3 (12%) and 3 (12%) dogs, respectively. The allergenic extracts standardized for humans evaluated in the present study may be used as a tool to complement the diagnosis of the disease, as well as to select potential allergen candidates for allergen-specific immunotherapy.

Towards global consensus on outcome measures for atopic eczema research: results of the HOME II meeting

The use of nonstandardized and inadequately validated outcome measures in atopic eczema trials is a major obstacle to practising evidence-based dermatology. The Harmonising Outcome Measures for Eczema (HOME) initiative is an international multiprofessional group dedicated to atopic eczema outcomes research. In June 2011, the HOME initiative conducted a consensus study involving 43 individuals from 10 countries, representing different stakeholders (patients, clinicians, methodologists, pharmaceutical industry) to determine core outcome domains for atopic eczema trials, to define quality criteria for atopic eczema outcome measures and to prioritize topics for atopic eczema outcomes research. Delegates were given evidence-based information, followed by structured group discussion and anonymous consensus voting. Consensus was achieved to include clinical signs, symptoms, long-term control of flares and quality of life into the core set of outcome domains for atopic eczema trials. The HOME initiative strongly recommends including and reporting these core outcome domains as primary or secondary endpoints in all future atopic eczema trials. Measures of these core outcome domains need to be valid, sensitive to change and feasible. Prioritized topics of the HOME initiative are the identification/development of the most appropriate instruments for the four core outcome domains. HOME is open to anyone with an interest in atopic eczema outcomes research.

Characterization of canine dendritic cells in healthy, atopic, and non-allergic inflamed skin

Atopic dermatitis in humans and dogs is a chronic relapsing allergic skin disease. Dogs show a spontaneous disease similar to the human counterpart and represent a model to improve our understanding of the immunological mechanisms, the pathogenesis of the disease, and new therapy development. The aim of the study was to determine the frequency and phenotype of dendritic cells (DC) in the epidermis and dermis of healthy, canine atopic dermatitis lesional, and non-allergic inflammatory skin to further validate the model and to obtain insights into the contribution of DC to the pathogenesis of skin diseases in dogs. We first characterized canine skin DC using flow-cytometric analysis of isolated skin DC combined with an immunohistochemical approach. A major population of canine skin dendritic cells was identified as CD1c(+)CD11c(+)CD14(-)CD80(+)MHCII(+)MAC387(-) cells, with dermal DC but not Langerhans cells expressing CD11b. In the epidermis of lesional canine atopic dermatitis and non-allergic inflammatory skin, we found significantly more dendritic cells compared with nonlesional and control skin. Only in canine atopic dermatitis skin did we find a subset of dendritic cells positive for IgE, in the epidermis and the dermis. Under all inflammatory conditions, dermal dendritic cells expressed more CD14 and CD206. MAC387(+) putative macrophages were absent in healthy but present in inflamed skin, in particular during non-allergic diseases. This study permits a phenotypic identification and differentiation of canine skin dendritic cells and has identified markers and changes in dendritic cells and macrophage populations related to allergic and non-allergic inflammatory conditions. Our data suggest the participation of dendritic cells in the pathogenesis of canine atopic dermatitis similar to human atopic dermatitis and further validate the only non-murine spontaneous animal model for this disease.

Dermatophagoides farinae-specific immunotherapy in atopic dogs with hypersensitivity to multiple allergens: a randomised, double blind, placebo-controlled study

A randomised, placebo-controlled, double blind study was conducted on 25 dogs that had atopic dermatitis, together with skin test reactivity and elevated serum IgE to Dermatophagoides farinae (Df) and at least one additional allergen. Dogs were treated with either a Df-restricted immunotherapy solution (n=14) or a placebo (n=11) and evaluated 6 weeks and 3, 5, 7 and 9 months after the initiation of treatment using a clinical scoring system (SASSAD) and pruritus analogue scale scores. The Df-restricted solution and the placebo had an equal effect on both pruritus and the skin manifestations (P>0.05). The results of this study indicate that in dogs with atopic dermatitis based on hypersensitivity to environmental allergens in addition to D. farinae, Df-restricted immunotherapy is insufficient to control the disease. Consequently, a solution for allergen-specific immunotherapy should remain customised.