Insect Cell-Expressed Major Ragweed Allergen Amb a 1.01 Exhibits Similar Allergenic Properties to Its Natural Counterpart from Common Ragweed Pollen

Common ragweed pollen allergy has become a health burden worldwide. One of the major allergens in ragweed allergy is Amb a 1, which is responsible for over 90% of the IgE response in ragweed-allergic patients. The major allergen isoform Amb a 1.01 is the most allergenic isoform in ragweed pollen. So far, no recombinant Amb a 1.01 with similar allergenic properties to its natural counterpart (nAmb a 1.01) has been produced. Hence, this study aimed to produce a recombinant Amb a 1.01 with similar properties to the natural isoform for improved ragweed allergy management. Amb a 1.01 was expressed in insect cells using a codon-optimized DNA construct with a removable N-terminal His-Tag (rAmb a 1.01). The recombinant protein was purified by affinity chromatography and physicochemically characterized. The rAmb a 1.01 was compared to nAmb a 1.01 in terms of the IgE binding (enzyme-linked immunosorbent assay (ELISA), immunoblot) and allergenic activity (mediator release assay) in well-characterized ragweed-allergic patients. The rAmb a 1.01 exhibited similar IgE reactivity to nAmb a 1.01 in different IgE-binding assays (i.e., IgE immunoblot, ELISA, quantitative ImmunoCAP inhibition measurements). Furthermore, the rAmb a 1.01 showed comparable dose-dependent allergenic activity to nAmb a 1.01 regarding basophil activation. Overall, the results showed the successful expression of an rAmb a 1.01 with comparable characteristics to the corresponding natural isoform. Our findings provide the basis for an improvement in ragweed allergy research, diagnosis, and immunotherapy.

Complex IgE sensitization patterns in ragweed allergic patients: Implications for diagnosis and specific immunotherapy

Background

Ragweed (Ambrosia artemisiifolia) is one of the most important allergen sources, worldwide, causing severe respiratory allergic reactions in late summer and fall, in sensitized patients. Amb a 1 has been considered as the most important allergen in ragweed but 12 ragweed pollen allergens are known. The aim of our study was to investigate IgE reactivity profiles of ragweed allergic patients and to associate them with clinical symptoms.

Methods

IgE sensitization profiles from clinically well‐characterized ragweed allergic patients (n = 150) were analyzed using immunoblotted ragweed pollen extract. Immunoblot inhibition experiments were performed with two Amb a 1 isoforms and CCD markers and basophil activation experiments were performed with IgE serum before and after depletion of Amb a 1‐specific IgE.

Results

By IgE‐immunoblotting 19 different IgE reactivity patterns with and without Amb a 1‐sensitization were found. The majority of patients (>95%) suffered from rhino‐conjunctivitis, around 60% reported asthma‐like symptoms and about 25% had skin reactions. Patients with complex IgE sensitization profiles tended to have more clinical symptoms. Serum with and without Amb a 1‐specific IgE induced basophil activation.

Conclusions

Ragweed pollen allergic patients exhibit complex IgE reactivity profiles to ragweed allergens including Amb a 1 isoforms and cross‐reactive carbohydrates indicating the importance of Amb a 1 isoforms and additional allergens for diagnosis and allergen‐specific immunotherapy of ragweed allergy.