Background: House dust mites (HDMs) are the most important respiratory allergen sources. In temperate regions, the genus Dermatophagoides predominates, whereas in sub‐tropical and tropical regions, the genus Blomia is also of high importance. There is only limited IgE cross‐reactivity between Dermatophagoides and Blomia . Objective: To produce a chip containing purified microarrayed Blomia tropicalis (Blo t) and Dermatophagoides pteronyssinus allergens (Der p) capable of identifying patients with a genuine Blo t or Der p IgE sensitisation, co‐sensitisation and/or cross‐sensitisation. Methods: Chips containing seven purified Blo t and thirteen Der p allergens were generated by microarray technology and tested for IgE and IgG reactivity in HDM ‐sensitised patients from Blo t‐endemic (group 1: n = 115) and Blo t‐non‐endemic (group 2: n = 33) regions. IgE cross‐reactivity was analysed by IgE inhibition studies. Results: IgE levels to Blo t 2, Blo t 5, Blo t 10, Blo t 12 and Blo t 21 were significantly higher in HDM‐sensitised patients from Blo t‐endemic as compared to patients from Blo t‐non‐endemic regions, whereas the opposite was observed for IgE to Der p 2 and Der p 21 in patients from Blo t‐non‐endemic regions. An algorithm based on IgE reactivity profiles and allergen‐specific IgE levels capable of discriminating genuine sensitisation to Blo t and Der p or co‐sensitisation was established. In HDM‐sensitised patients from Blo t‐endemic regions, each of the aforementioned sensitisation profiles was observed, whereas in HDM‐sensitised patients from Blo t‐non‐endemic regions, only genuine sensitisations to Der p and co‐sensitisations to Blo t and Der p were observed. Conclusion: The algorithm based on microarrayed Blo t and Der p allergens for discrimination of Blo t and Der p sensitisation may support prescription of allergen‐specific immunotherapy. At minimum, it will be helpful in understanding disease aetiology and for fine resolution mapping of allergic reactivities in HDM sensitisation.

Der p 23 induces a high-frequency sensitization in allergic individuals. However, its allergenic activity and clinical impact are scarce. We aimed to evaluate the ability of rDer p 23 to induce allergic inflammation in a mouse model and to test IgE reactivity in humans. Female Balb/c mice were sensitized and challenged with rDer p 23 and Dermatophagoides pteronyssinus extract. Specific antibodies were determined by ELISA, inflammatory cell infiltration and goblet cells hyperplasia were evaluated by lung histology, and bronchial hyperreactivity (BHR) was assessed by the FinePoint RC System^TM and whole-body plethysmography (WBP). IgE reactivity was evaluated by ELISA, the basophils activation test (BAT) and the skin pick test (SPT) in humans. rDer p 23, produced in Escherichia coli, adopts a random coil structure, predominantly exists in a monomeric state, and exhibits high stability. rDer p 23-treated mice showed a significant increase in lung resistance and bronchial hyperreactivity, as well as in eosinophils, neutrophils, and T cell count in bronchoalveolar lavage fluid (BALF). Cytokine and antibodies profiles were biased to a Type-2 response. No significant difference was observed in group 2 Innate Lymphoid Cells (ILC-2s) in lung and regulatory T cells (Treg) in the spleen. In asthmatic individuals sensitized to D. pteronyssinus, serum IgE reactivity to rDer p 23 was 67.5%. BAT and SPT results were significantly higher in allergic patients. Our findings support the pro-allergenic role of rDer p 23 in the development of the pathological features of asthma.

Background: Allergic sensitization to cats and other furry animals is a major cause of asthma and allergic rhinitis in more than 200 million people worldwide. According to the frequency of IgE recognition, allergen‐specific IgE levels, and allergenic activity, Fel d 4 is a major allergen in the cat ( Felis domesticus ). The lipocalin allergen Fel d 4 is highly homologous to dog (Can f 6) and major horse (Equ c 1) allergens. Accordingly, IgE cross‐reactivity to these allergens contributes to polysensitization and allergic responses upon exposure to different animals. Methods: Fel d 4 was recombinantly produced in two systems, E. coli and Expi293F mammalian cells. Recombinant forms were characterized by circular dichroism and mass spectrometry. The Fel d 4 3D structure was determined using X‐ray crystallography. Immunoreactivity, epitope analyses, and cross‐reactive properties were assessed by ELISA and basophil release assays using allergic patients’ sera. Results: We reveal the rFel d 4 crystal structures and demonstrate that mammalian cells produce an N‐glycosylated recombinant Fel d 4 allergen. The C‐terminal regions of Fel d 4, Can f 6, and Equ c 1 constitute conformational IgE ‐epitope‐containing areas responsible for cross‐reactivity. Conclusion: Uncovering the IgE ‐binding sites of Fel d 4 and cross‐reactive allergens contributes to future rational design of active and passive allergen‐specific treatment forms.