Wayne R. Thomas

Indoor allergens and asthma:Report of the Third International Workshop

In parallel with changes in lifestyle over the last 50 years (sedentary living in warm houses with extensive furnishing and low ventilation rates), there has been a progressive increase in the prevalence and morbidity of asthma in many parts of the world. The increase has been in perennial rather than seasonal asthma, and a large proportion of the patients are sensitized to one or more of the allergens found predominantly inside houses, that is, indoor allergens. The Third International Workshop on Indoor Allergens and Asthma was designed to discuss recent progress in basic and clinical research in this area, to formulate recommendations for allergen-specific management of asthma, and to consider future research directions. As with the two previous workshops, discussion topics included biology; allergen immunochemistry; molecular biology and immune response; epidemiology of asthma; and the role of allergen avoidance, a, 2 Because of dramatic progress in recent years, the Third International Workshop was expanded to cover not only house dust mite allergens but also allergens from cat, dog, and cockroach, for which immunochemical and epidemiologic data are available. Over the past 5 years there have been significant advances in several areas of research on indoor allergens, including: (1) cloning and expression of recombinant allergens, 3-7 (2) analysis of T-cell responses to indoor allergens, derivation of T-cell clones, and analysis of T-cell epitope specificity and cytokine profiles, s, 9 (3) investigation of the dose-response relationship between exposure to mite, cat, and cockroach allergens and sensitization, 1°-13 and (4) epidemiologic studies on indoor allergens as risk factors for the symptoms of asthma and bronchial hyperreactivity (BHR)? 4-17 Better definition of the allergens has made it possible to analyze their structure and biologic function and to define epitopes recognized by antibodies or T cells. Information obtained from those studies has provided exciting possibilities for developing new vaccines for safe and effective immunotherapy. 9, 18. 19 Studies of T-cell responses to dust mites have confirmed the dominance of T-helper cell (Tin) responses in allergic individuals.

Microarrayed allergen molecules: diagnostic gatekeepers for allergy treatment

Type I allergy is an immunoglobulin E (IgE)‐mediated hypersensitivity disease affecting more than 25% of the population. Currently, diagnosis of allergy is performed by provocation testing and IgE serology using allergen extracts. This process defines allergen‐containing sources but cannot identify the disease‐eliciting allergenic molecules. We have applied microarray technology to develop a miniaturized allergy test containing 94 purified allergen molecules that represent the most common allergen sources. The allergen microarray allows the determination and monitoring of allergic patients’ IgE reactivity profiles to large numbers of disease‐causing allergens by using single measurements and minute amounts of serum. This method may change established practice in allergy diagnosis, prevention, and therapy. In addition, microarrayed antigens may be applied to the diagnosis of autoimmune and infectious diseases.

Characterization and immunobiology of house dust mite allergens

The examination of house dust mite extracts has indicated that over 30 different proteins can induce IgE antibody in patients allergic to the house dust mite. There are however dominant specificities especially the group 1 and 2 allergens which can account for much of the allergenicity of extracts. Of the 19 denominated allergens, the major IgE binding has been reported for the group 1, 2, 3, 9, 11, 14 and 15 allergens. The high-molecular-weight group 11, 14 and 15 allergens have only recently been described and although high IgE binding has been anticipated from immunoblotting, there is a need for considerable corroboration. Similarly, the study of the group 3 and 9 serine protease allergens has been incomplete. The group 4, 5, 7 and 8 allergens have shown intermediate IgE binding and the group 10 tropomyosins are of interest because of their potential cross-reactivity with allergen from disparate species. Although the progress with the production of recombinant group 1 allergens has been recent, many of the allergens can be produced as high IgE-binding polypeptides. The tertiary structure of the group 2 allergens has been determined from recombinant proteins and they are an excellent model for the investigation of modified allergens. An unexpected property of the group 1, 2 and 3 allergens has been the high degree of polymorphism found by cDNA analysis. It has however been possible to identify sequences to represent the variation in the natural allergens. The group 7 and 14 allergens show secondary modifications which vary in different extracts creating batch variation. While some estimate of the importance of allergens can be obtained from IgE binding, few analyses of T-cell responses have been made and these regulate both the development of, and the protection from sensitization.

House dust-mite allergens

Dermatophagoides pteronyssinus and D. farinae are the major source of HDM allergens, although Euroglyphus mayrtei, in temperate regions, and Blomia tropicalis, in tropical and subtropical areas, can be important. D. microcerus in Europe and D. siboney in the Caribbean have been occasionally studied. Lepidoglyphus destructor is the source of important occupational allergens, which in some locations can contribute to house-dust allergy (1). The results of immunoblotting studies of the allergens in extracts of the mites have differed in detail, but the broad picture shows both complexity and the existence of some dominant specificities. Western blotting using sera selected on the basis of high antimite IgE has revealed 32 different IgE-binding bands with molecular weights from 11 to over 100 K (2, 3). Most sera recognized a unique combination of 6-10 bands. Of the 32 bands, nine were recognized at high frequency. A subsequent study found that most sera reacted to 1-7 bands, although some did have a broader reactivity (4). This pattern is consistent with several similar studies using either D. pteronyssinus or D. farinae extracts (5-8). Although the blotting studies have provided a snapshot, their limitations should be recognized. The concentration of allergens varies from extract to extract, and blotting procedures can have sharp dose-response characteristics. Some allergens, such as Der p 2, have their IgE-binding activity enhanced by denaturation (9), while others. W. R. Thomas, W. Smith

Interactions between Innate Antiviral and Atopic Immunoinflammatory Pathways Precipitate and Sustain Asthma Exacerbations in Children

Severe asthma exacerbations in children requiring hospitalization are typically associated with viral infection and occur almost exclusively among atopics, but the significance of these comorbidities is unknown. We hypothesized that underlying interactions between immunoinflammatory pathways related to responses to aeroallergen and virus are involved, and that evidence of these interactions is detectable in circulating cells during exacerbations. To address this hypothesis we used a genomics-based approach involving profiling of PBMC subpopulations collected during exacerbation vs convalescence by microarray and flow cytometry. We demonstrate that circulating T cells manifest the postactivated “exhausted” phenotype during exacerbations, whereas monocyte/dendritic cell populations display up-regulated CCR2 expression accompanied by phenotypic changes that have strong potential for enhancing local inflammation after their recruitment to the atopic lung. Notably, up-regulation of FcεR1, which is known to markedly amplify capacity for allergen uptake/presentation to Th2 effector cells via IgE-mediated allergen capture, and secondarily programming of IL-4/IL-13-dependent IL-13R+ alternatively activated macrophages that have been demonstrated in experimental settings to be a potent source of autocrine IL-13 production. We additionally show that this disease-associated activation profile can be reproduced in vitro by cytokine exposure of atopic monocytes, and furthermore that IFN-α can exert both positive and negative roles in the process. Our findings suggest that respiratory viral infection in atopic children may initiate an atopy-dependent cascade that amplifies and sustains airway inflammation initiated by innate antiviral immunity via harnessing underlying atopy-associated mechanisms. These interactions may account for the unique susceptibility of atopics to severe viral-induced asthma exacerbations.

Component-resolved diagnosis of house-dust mite allergy with purified natural and recombinant mite allergens

Background Mites belong to the most frequent and potent allergen sources. Immunotherapy with mite allergen extracts is frequently performed if allergen avoidance is not possible or successful. However, highly controversial results have been reported for mite‐specific immunotherapy.

House dust mite allergens in asthma and allergy

IgE antibodies in house dust mite (HDM) allergy follow a predictable pattern. Half are directed against two dominant allergens and the remainder largely against four midpotency allergens. This hierarchical pattern is not changed by the titre of the IgE response or severity of disease. The structures of these allergens are known and they can be produced as authentic recombinant allergens. There is also evidence that the allergenicity is augmented by the biological activity of the key allergens, validating them as targets for vaccination. Collectively, these developments should facilitate the development of new diagnostics, improve immunotherapy and allow vaccination with defined reagents. Highly purified recombinant polypeptides representing the important mite allergens are now available so that informative and reproducible experiments can be performed with mite allergens in place of poorly defined and variable extracts.

Inhalant allergen‐specific T‐cell reactivity is detectable in close to 100% of atopic and normal individuals: covert responses are unmasked by serum‐free medium

Background It is widely held that in vitro T cell responses to allergens are more prominent in atopic than in normal individuals, though this conclusion is based upon culture techniques which fail to detect proliferative responses in a significant minority of atopies and many normals.

Cloning and expression of DNA coding for the major house dust mite allergen Der p 1 in Escherichia coli.

A cDNA clone coding for the major house dust mite allergen Der p 1 was isolated from a lambda gt 11 library. Its sequence correlates with known amino acid sequences of Der p 1 and it produces a fusion protein which reacts with rabbit anti-Der p 1 antiserum.

Variability of IgE reactivity profiles among European mite allergic patients

Background  House dust mites (HDM) Dermatophagoides pteronyssinus are a frequent indoor allergen source. Our aim was to determine the frequencies of IgE reactivity to purified HDM allergen molecules in mite allergic patients from different parts of Europe in order to establish an allergen panel for diagnosis of HDM allergy.