Distinct epitope structures of defensin‐like proteins linked to proline‐rich regions give rise to differences in their allergenic activity

Abstract

BackgroundArt v 1, Amb a 4, and Par h 1 are allergenic defensin-polyproline–linked proteins present in mugwort, ragweed, and feverfew pollen, respectively. We aimed to investigate the physicochemical and immunological features underlying the different allergenic capacities of those allergens.MethodsRecombinant defensin-polyproline–linked proteins were expressed in E. coli and physicochemically characterized in detail regarding identity, secondary structure, and aggregation status. Allergenic activity was assessed by mediator releases assay, serum IgE reactivity, and IgE inhibition ELISA using sera of patients from Austria, Canada, and Korea. Endolysosomal protein degradation and T-cell cross-reactivity were studied in vitro.ResultsDespite variations in the proline-rich region, similar secondary structure elements were observed in the defensin-like domains. Seventy-four percent and 52% of the Austrian and Canadian patients reacted to all three allergens, while Korean patients were almost exclusively sensitized to Art v 1. This was reflected by IgE inhibition assays demonstrating high cross-reactivity for Austrian, medium for Canadian, and low for Korean sera. In a subgroup of patients, IgE reactivity toward structurally altered Amb a 4 and Par h 1 was not changed suggesting involvement of linear epitopes. Immunologically relevant endolysosomal stability of the defensin-like domain was limited to Art v 1 and no T-cell cross-reactivity with Art v 125-36 was observed.ConclusionsDespite structural similarity, different IgE-binding profiles and proteolytic processing impacted the allergenic capacity of defensin-polyproline–linked molecules. Based on the fact that Amb a 4 demonstrated distinct IgE-binding epitopes, we suggest inclusion in molecule-based allergy diagnosis.

Artemisia pollen allergy in China: Component‐resolved diagnosis reveals allergic asthma patients have significant multiple allergen sensitization

“…From both sensitization frequencies and IgE titers, we can draw a general conclusion that three allergens qualify as major allergens in China: Art v 1, Art v 3, and Art an 7. These results are in line with those from Europe and our immunoblots of three widely recognized allergens in Northern China . Art v 1 and Art an 7 were consistently the most prevalent (more than 80%) in the three areas, indicating that these two allergens are biomarkers of Artemisia pollens inducing allergic reactions.…”

“…Art v 1 and Art an 7 were consistently the most prevalent (more than 80%) in the three areas, indicating that these two allergens are biomarkers of Artemisia pollens inducing allergic reactions. From the observations obtained from Shanxi and Shandong, we estimate the prevalence of Art v 1 at 84%‐93% in Northern China, which is quite similar to that of the mugwort‐allergic patients in Europe but higher than in North America . Median Art v 1 IgE value was also similar to those in Northern Europe.…”

Localization of Four Allergens in Artemisia Pollen by Immunofluorescent Antibodies

“…Antibody-producing hybridoma cells were screened by ELISA and later by Western blot with immunized pollen extracts, recombinant (r)Art v 1.0101 [2, 20] and Art v 3 allergen rArt v 3.0201 [21], to select specific monoclonal antibodies (mAbs). mAbs were purified by protein G column and isotype determination as described previously [22].…”

Future research trends in understanding the mechanisms underlying allergic diseases for improved patient care

“…30 Unequivocally, these authors [27][28][29][30] argue that it is a common misconception to regard allergens as generally harmless environmental substances. Allergens interact with innate immune receptors (eg, TLR4, 31 protease-activated receptor-2, 32 dectin-1 33 ), disrupt the integrity of membranes (eg, phospholipase A2, 34,35 defensins 36,37 ), or degrade connective tissues (eg, hyaluronidases 38 ). However, very few studies on why only susceptible individuals raise an allergic immune response have come forward.…”