Heterogenous Induction of Blocking Antibodies against Ragweed Allergen Molecules by Allergen Extract-Based Immunotherapy Vaccines.

Currently, allergen-specific immunotherapy (AIT) for ragweed allergy is still based on natural allergen extracts. This study aimed to analyse the ability of four commercially available AIT vaccines (CLUSTOID, TYRO-SIT, POLLINEX Quattro Plus and Diater Depot) regarding their ability to induce IgG antibodies against ragweed pollen allergens in rabbits. Accordingly, the IgG reactivity of AIT-induced rabbit sera was tested for ten different ragweed pollen allergens (Amb a 1, 3, 4, 5, 6, 8, 9, 10, 11 and 12) by an ELISA. Furthermore, the ability of rabbit AIT-specific sera to block allergic patients' IgE binding to relevant ragweed allergens (Amb a 1, 4, 6, 8 and 11) and to inhibit allergen-induced basophil activation was evaluated by an IgE inhibition ELISA and a mediator release assay. Only two AIT vaccines (Diater Depot > CLUSTOID) induced relevant IgG antibody levels to the major ragweed allergen Amb a 1. The IgG responses induced by the AIT vaccines against the other ragweed allergens were low and highly heterogeneous. Interestingly, the kinetics of IgG responses were different among the AIT vaccines and even within one AIT vaccine (Diater Depot) for Amb a 1 (long-lasting) versus Amb a 8 and Amb a 11 (short-lived). This could be due to variations in allergen contents, the immunogenicity of the allergens, and different immunization protocols. The IgE inhibition experiments showed that rabbit AIT-specific sera containing high allergen-specific IgG levels were able to inhibit patients' IgE binding and prevent the mediator release with Diater Depot. The high levels of allergen-specific IgG levels were associated with their ability to prevent the recognition of allergens by patients' IgE and allergen-induced basophil activation, indicating that the measurement of allergen-induced IgG could be a useful surrogate marker for the immunological efficacy of vaccines. Accordingly, the results of our study may be helpful for the selection of personalized AIT vaccination strategies for ragweed-allergic patients.

Prenatal Factors in the Development of Allergic Diseases.

Allergic diseases are showing increasing prevalence in Western societies. They are characterized by a heightened reactivity towards otherwise harmless environmental stimuli. Allergic diseases showing a wide range of severity of symptoms have a significant impact on the quality of life of affected individuals. This study aims to highlight the mechanisms that induce these reactions, how they progress, and which prenatal factors influence their development. Most frequently, the reaction is mediated by immunoglobulin E (IgE) produced by B cells, which binds to the surface of mast cells and basophils and triggers an inflammatory response. The antibody response is triggered by a shift in T-cell immune response. The symptoms often start in early childhood with eczema or atopic dermatitis and progress to allergic asthma in adolescence. An important determinant of allergic diseases seems to be parental, especially maternal history of allergy. Around 30% of children of allergic mothers develop allergic sensitization in childhood. Genes involved in the regulation of the epithelial barrier function and the T-cell response were found to affect the predisposition to developing allergic disorders. Cord blood IgE was found to be a promising predictor of allergic disease development. Fetal B cells produce IgE starting at the 20th gestation week. These fetal B cells could be sensitized together with mast cells by maternal IgE and IgE-allergen complexes crossing the placental barrier via the low-affinity IgE receptor. Various factors were found to facilitate these sensitizations, including pesticides, drugs, exposure to cigarette smoke and maternal uncontrolled asthma. Prenatal exposure to microbial infections and maternal IgG appeared to play a role in the regulation of T-cell response, indicating a protective effect against allergy development. Additional preventive factors were dietary intake of vitamin D and omega 3 fatty acids as well as decreased maternal IgE levels. The effect of exposure to food allergens during pregnancy was inconclusive, with studies having found both sensitizing and protective effects. In conclusion, prenatal factors including genetics, epigenetics and fetal environmental factors have an important role in the development of allergic disorders in later life. Children with a genetic predisposition are at risk when exposed to cigarette smoke as well as increased maternal IgE in the prenatal period. Maternal diet during pregnancy and immunization against certain allergens could help in the prevention of allergy in predisposed children.

Non-Specific Lipid Transfer Protein Amb a 6 Is a Source-Specific Important Allergenic Molecule in Ragweed Pollen.

Pollen from common ragweed is an important allergen source worldwide and especially in western and southern Romania. More than 100 million patients suffer from symptoms of respiratory allergy (e.g., rhinitis, asthma) to ragweed pollen. Among the eleven characterized allergens, Amb a 6 is a non-specific lipid transfer protein (nsLTP). nsLTPs are structurally stable proteins in pollen and food from different unrelated plants capable of inducing severe reactions. The goal of this study was to produce Amb a 6 as a recombinant and structurally folded protein (rAmb a 6) and to characterize its physicochemical and immunological features. rAmb a 6 was expressed in Spodoptera frugiperda Sf9 cells as a secreted protein and characterized by mass spectrometry and circular dichroism (CD) spectroscopy regarding molecular mass and fold, respectively. The IgE-binding frequency towards the purified protein was evaluated using sera from 150 clinically well-characterized ragweed-allergic patients. The allergenic activities of rAmb a 6 and the nsLTP from the weed Parietaria judaica (Par j 2) were evaluated in basophil activation assays. rAmb a 6-specific IgE reactivity was associated with clinical features. Pure rAmb a 6 was obtained by insect cell expression. Its deduced molecular weight corresponded to that determined by mass spectrometry (i.e., 10,963 Da). rAmb a 6 formed oligomers as determined by SDS-PAGE under non-reducing conditions. According to multiple sequence comparisons, Amb a 6 was a distinct nsLTP with less than 40% sequence identity to currently known plant nsLTP allergens, except for nsLTP from Helianthus (i.e., 52%). rAmb a 6 is an important ragweed allergen recognized by 30% of ragweed pollen allergic patients. For certain patients, rAmb a 6-specific IgE levels were higher than those specific for the major ragweed allergen Amb a 1 and analysis also showed a higher allergenic activity in the basophil activation test. rAmb a 6-positive patients suffered mainly from respiratory symptoms. The assumption that Amb a 6 is a source-specific ragweed allergen is supported by the finding that none of the patients showing rAmb a 6-induced basophil activation reacted with Par j 2 and only one rAmb a 6-sensitized patient had a history of plant food allergy. Immunization of rabbits with rAmb a 6 induced IgG antibodies which strongly inhibited IgE binding to rAmb a 6. Our results demonstrate that Amb a 6 is an important source-specific ragweed pollen allergen that should be considered for diagnosis and allergen-specific immunotherapy of ragweed pollen allergy.

Cross-Reactivity of Ragweed Pollen Calcium-Binding Proteins and IgE Sensitization in a Ragweed-Allergic Population from Western Romania.

Ragweed pollen allergy is the most common seasonal allergy in western Romania. Prolonged exposure to ragweed pollen may induce sensitization to pan-allergens such as calcium-binding proteins (polcalcins) and progression to more severe symptoms. We aimed to detect IgE sensitization to recombinant Amb a 9 and Amb a 10 in a Romanian population, to assess their potential clinical relevance and cross-reactivity, as well as to investigate the relation with clinical symptoms. rAmb a 9 and rAmb a 10 produced in Escherichia coli were used to detect specific IgE in sera from 87 clinically characterized ragweed-allergic patients in ELISA, for basophil activation experiments and rabbit immunization. Rabbit rAmb a 9- and rAmb a 10-specific sera were used to detect possible cross-reactivity with rArt v 5 and reactivity towards ragweed and mugwort pollen extracts. The results showed an IgE reactivity of 25% to rAmb a 9 and 35% to rAmb a 10. rAmb a 10 induced basophil degranulation in three out of four patients tested. Moreover, polcalcin-negative patients reported significantly more skin symptoms, whereas polcalcin-positive patients tended to report more respiratory symptoms. Furthermore, both rabbit antisera showed low reactivity towards extracts and showed high reactivity to rArt v 5, suggesting strong cross-reactivity. Our study indicated that recombinant ragweed polcalcins might be considered for molecular diagnosis.

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.

Relationship between IgE Levels Specific for Ragweed Pollen Extract, Amb a 1 and Cross-Reactive Allergen Molecules.

Ragweed (Ambrosia artemisiifolia) pollen is a major endemic allergen source responsible for severe allergic manifestations in IgE-sensitized allergic patients. It contains the major allergen Amb a 1 and cross-reactive allergen molecules, such as the cytoskeletal protein profilin, Amb a 8 and calcium-binding allergens Amb a 9 and Amb a 10. To assess the importance of Amb a 1, profilin and calcium-binding allergen, the IgE reactivity profiles of clinically well-characterized 150 ragweed pollen-allergic patients were analysed regarding specific IgE levels for Amb a 1 and cross-reactive allergen molecules by quantitative ImmunoCAP measurements, IgE ELISA and by basophil activation experiments. By quantifying allergen-specific IgE levels we found that Amb a 1-specific IgE levels accounted for more than 50% of ragweed pollen-specific IgE in the majority of ragweed pollen-allergic patients. However, approximately 20% of patients were sensitized to profilin and the calcium-binding allergens, Amb a 9 and Amb a 10, respectively. As shown by IgE inhibition experiments, Amb a 8 showed extensive cross-reactivity with profilins from birch (Bet v 2), timothy grass (Phl p 12) and mugwort pollen (Art v 4) and was identified as a highly allergenic molecule by basophil activation testing. Our study indicates that molecular diagnosis performed by the quantification of specific IgE to Amb a 1, Amb a 8, Amb a 9 and Amb a 10 is useful to diagnose genuine sensitization to ragweed pollen and to identify patients who are sensitized to highly cross-reactive allergen molecules present in pollen from unrelated plants, in order to enable precision medicine-based approaches for the treatment and prevention of pollen allergy in areas with complex pollen sensitization.

Ragweed Major Allergen Amb a 11 Recombinant Production and Clinical Implications.

Ragweed pollen is highly allergenic and elicits type I hypersensitivity reactions in the exposed populations. Amb a 11 is a recently discovered component of this pollen, and its biological role in allergy is still being researched. In our study, ragweed allergy patients were recruited prospectively over a three-year period; a comprehensive questionnaire was administered, and sera were collected and stored. The production of recombinant Amb a 11 was achieved in parallel with patients' recruitment. The gene coding for mature protein was inserted in E. coli and in Sf9 Spodoptera frugiperda cells. The recombinant allergens (designated eAmb a 11 and iAmb a 11) were tested for His-tag presence in Western blot. IgE reactivity was evaluated in 150 patients' sera for both recombinant allergen forms in ELISA, with 5 positive sera being tested further by hRBL (humanized rat basophilic leukemia) hexosaminidase release assay. Both allergen forms were proven to be IgE-reactive His-tagged proteins, with an extensive overlap of positive sera (92 toward the former recombinant allergen, 100 toward the latter) and an overall Amb a 11 sensitization prevalence estimated at 68.67%. The hRBL mediator release assay revealed a significant, slightly weaker effect of recombinant allergens when compared with nAmb a 1. Sensitization to this major allergen appears to be associated with more severe asthma symptoms (OR = 4.71, 95% CI = 1.81-12.21). In conclusion, recombinant Amb a 11 is a bona fide allergen, which is IgE-reactive and an inducer of hRBL degranulation. It is an important IgE-reactive component from ragweed pollen, with high IgE sensitization prevalence in the sample population and allergenicity of the recombinant allergen comparable to Amb a 1.

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.