Distinct "Immunoallertypes" of Disease and High Frequencies of Sensitization in Non-Cystic Fibrosis Bronchiectasis.

RATIONALE: Allergic sensitization is associated with poor clinical outcomes in asthma, chronic obstructive pulmonary disease, and cystic fibrosis; however, its presence, frequency, and clinical significance in non-cystic fibrosis bronchiectasis remain unclear. OBJECTIVES: To determine the frequency and geographic variability that exists in a sensitization pattern to common and specific allergens, including house dust mite and fungi, and to correlate such patterns to airway immune-inflammatory status and clinical outcomes in bronchiectasis. METHODS: Patients with bronchiectasis were recruited in Asia (Singapore and Malaysia) and the United Kingdom (Scotland) (n = 238), forming the Cohort of Asian and Matched European Bronchiectasis, which matched recruited patients on age, sex, and bronchiectasis severity. Specific IgE response against a range of common allergens was determined, combined with airway immune-inflammatory status and correlated to clinical outcomes. Clinically relevant patient clusters, based on sensitization pattern and airway immune profiles ("immunoallertypes"), were determined. MEASUREMENTS AND MAIN RESULTS: A high frequency of sensitization to multiple allergens was detected in bronchiectasis, exceeding that in a comparator cohort with allergic rhinitis (n = 149). Sensitization was associated with poor clinical outcomes, including decreased pulmonary function and more severe disease. "Sensitized bronchiectasis" was classified into two immunoallertypes: one fungal driven and proinflammatory, the other house dust mite driven and chemokine dominant, with the former demonstrating poorer clinical outcome. CONCLUSIONS: Allergic sensitization occurs at high frequency in patients with bronchiectasis recruited from different global centers. Improving endophenotyping of sensitized bronchiectasis, a clinically significant state, and a "treatable trait" permits therapeutic intervention in appropriate patients, and may allow improved stratification in future bronchiectasis research and clinical trials.

NMR structure and IgE epitopes of Blo t 21, a major dust mite allergen from Blomia tropicalis.

Blo t 21 is a paralogue of the group 5 allergen, Blo t 5, a major allergen from the dust mite Blomia tropicalis. Blo t 21 has moderate sequence identity (40.7%) to Blo t 5 and low to moderate cross-reactivity to Blo t 5. In B. tropicalis, the most prevalent and allergenic allergens are in the order of Blo t 21, Blo t 5, and Blo t 7. Here, we determined the NMR solution structure of Blo t 21, which represents the first structure of the group 21 dust mite allergen. The structure of Blo t 21 closely resembles the structures of Blo t 5 and Der p 5, comprising three anti-parallel α-helices arranged in a helical bundle. Using site-directed mutagenesis and specific IgE binding ELISA, Blo t 21 was found to contain both conserved and unique charged IgE epitope residues at the L2 loop region and on helix α3. Cross-inhibition assays confirmed that Blo t 21 has a low to moderate cross-reactivity with Blo t 5 and Der p 5 and represents a novel group of major allergen in B. tropicalis. In addition to group 5 allergens, Blo t 21 has also a low to moderate cross-reactivity with group 21 allergens from Dermatophagoides mites, confirming that B. tropicalis is a major and distinct source of dust mite allergens.

Mite component-specific IgE repertoire and phenotypes of allergic disease in childhood: the tropical perspective.

Sensitization to perennial aeroallergens correlates with the risk of persistent asthma (AS) in children. In tropical Singapore, multiple codominant species of mites abound in the indoor environment, and preferential species-specific sensitization has been associated with different phenotypes of allergic disease. We investigated the pattern of mite component-specific IgE (mcsIgE) in children with different phenotypes of clinical allergic disease in an environment with multiple mite species exposure. A prospective evaluation of newly diagnosed patients with clinical diagnosis of allergic rhinitis (AR), atopic dermatitis (AD), or AS and sensitization to one or more aeroallergens were performed. Sera were tested for specific IgE against an extensive panel of Dermatophagoides pteronyssinus and Blomia tropicalis allergens. A total of 253 children were included, mean age 7.3 yr, 79% fulfilled criteria for AR, 46% AS, 71% AD, and 31% for all three. Sensitization to one or both mites was observed in 91% of children, 89% were sensitized to D. pteronyssinus, and 70% to B. tropicalis. The most common mite allergens recognized by these atopic children were Der p 1 (64%), Der p 2 (71%), Blo t 5 (45%), Blo t 7 (44%), and Blo t 21 (56%). Specific IgE responses to an increased number of distinct mite allergens correlated with the complexity of the allergic phenotype. In multivariate analysis, an increased risk for the multi-systemic phenotype (AR + AS + AD) was associated with sensitization to an increased repertoire of mite components (three or more) (OR 4.3, 95% CI 2.1-8.8, p = 0.001) and a positive parental history of AS (OR 2.4, 95% CI 1.2-2.9, p = 0.013). A highly pleiomorphic IgE response to the prevalent indoor mites is associated with the presence of a multi-systemic allergic phenotype in childhood in a tropical environment.

Crystal structure of Der f 7, a dust mite allergen from Dermatophagoides farinae.

BACKGROUND: Der f 7 is the group 7 allergen from the dust mite Dermatophagoides farinae, homologous to the major allergen Der p 7 from D. pteronyssinus. Monoclonal antibody that bind to residues Leu48 and Phe50 was found to inhibit IgE binding to residue Asp159, which is important for the cross-reactivity between Der f 7 and Der p 7. METHODOLOGY/PRINCIPAL FINDINGS: Here, we report the crystal structure of Der f 7 that shows an elongated and curved molecule consisting of two anti-parallel ß-sheets--one 4-stranded and the other 5-stranded--that wrap around a long C-terminal helix. The overall fold of Der f 7 is similar to Der p 7 but key difference was found in the ß1-ß2 loop region. In Der f 7, Leu48 and Phe50 are in close proximity to Asp159, explaining why monoclonal antibody binding to Leu48 and Phe50 can inhibit IgE binding to Asp159. Both Der f 7 and Der p 7 bind weakly to polymyxin B via a similar binding site that is formed by the N-terminal helix, the 4-stranded ß-sheet and the C-terminal helix. The thermal stability of Der f 7 is significantly lower than that of Der p 7, and the stabilities of both allergens are highly depend on pH. CONCLUSION/SIGNIFICANCE: Der f 7 is homologous to Der p 7 in terms of the amino acid sequence and overall 3D structure but with significant differences in the region proximal to the IgE epitope and in thermal stability. The crystal structure of Der f 7 provides a basis for studying the function and allergenicity of this group of allergens.