Identification of Amb t 18 as a novel allergenfrom Ambrosia trifida pollen

Yi-Fei Xu,¹ Ke Li,¹ Li-Xiang Zhu,^2,5 Ya-Li Cheng,⁴ Yong-Shi Yang,⁴ Zhi-Qiang Xu,² Jin-Lyu Sun,⁴ Ji-Fu Wei^1,3

Affiliations:
¹ Department of Pharmacy, The Affiliated Cancer Hospital of Nanjing Medical University, Jiangsu Cancer Hospital, Jiangsu Institute of Cancer Research, Nanjing, China
² Department of Pharmacy, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
³ National Vaccine Innovation Platform, Nanjing Medical University, Nanjing, China
⁴ Department of Allergy, State Key Laboratory of Complex Severe and Rare Diseases, Peking Union Medical College Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing, China
⁵ Department of Pharmacy, Shenzhen Children’s Hospital, Shenzhen, China

Yi-Fei Xu, Ke Li and Li-Xiang Zhu contributed equally to this work.

Abstract

Background: Ambrosia (ragweed) pollen is a major allergenic source, but Ambrosia trifida allergens remain understudied. Triosephosphate isomerase, a conserved pan-allergen in plants, has not been reported in weed pollen.
Objective: To identify and characterize the novel allergen (Amb t 18) and evaluated its clinical relevance.
Methods: Amb t 18 cDNA was cloned and expressed in E. coli. Natural (nAmb t 18) and recombinant (rAmb t 18) proteins were purified for structural analyses (CD spectra) and IgE-reactivity testing (ELISA/basophil activation). Cross-reactivity with homologs Pla a 7 and Tri a 31 was assessed through inhibition ELISA. Structural analyses included 3D modeling, sequence alignment, and phylogenetics.
Results: Natural and recombinant Amb t 18 exhibited similar CD spectra. Amb t 18 reacted with 35.1% (13/37) of serum samples, inhibited 17.56% of IgE-binding to pollen extracts, and activated basophils. In some sera, its IgE-binding activity exceeded that of ragweed pollen extracts. It shared 82% sequence identity with Pla a 7 and Tri a 31, grouped together in the phylogenetic tree. The recombinant Amb t 18 reacted with Pla a 7 or Tri a 31 IgE-positive sera from Platanus acerifolia or Triticum aestivum-allergic patients, rAmb t 18, rPla a 7, and rTri a 31 inhibited IgE binding to rAmb t 18 by 76.70%, 5.80%, and 21.94%, respectively.
Conclusions: Amb t 18 was identified as a novel Ambrosia trifida pollen allergen, the first of its type in ragweed pollen. These findings may aid in developing new diagnostic and therapeutic approaches for ragweed allergy.