High-affinity recombinant antibodies enable a sensitive MRGPRX2-specific ELISA for detecting allergic rhinitis and chronic spontaneous urticaria

Mas-related G-protein-coupled receptor X2 (MRGPRX2) plays a critical role in mast cell activation and the mediation of pseudo-allergic reactions, and its detection in peripheral blood is important for investigating mast cell–related disorders such as allergic rhinitis (AR), chronic spontaneous urticaria (CSU), and asthma. However, existing assays based on polyclonal and hybridoma-derived monoclonal antibodies suffer from limitations in accuracy, reproducibility, and standardization, highlighting the need for alternative antibody strategies. In this study, animals were immunized with a rationally selected MRGPRX2 peptide identified using the IEDB Analysis Resource, and sequence-defined recombinant monoclonal antibodies were generated. A sandwich ELISA was subsequently established and validated using serum samples from patients with AR, CSU, and healthy controls (Chinese Clinical Trial Registry: ChiCTR2400082024, ChiCTR2400094130). The peptide spanning residues 289–330 was identified as an optimal immunogen, and six recombinant antibodies were obtained, among which optimal capture–detection pairs exhibited high affinity as confirmed by surface plasmon resonance and Western blot analysis. The developed ELISA demonstrated excellent linearity over the concentration range of 1.5625–200 ng/mL (y = 82.772x − 9.6566, R² = 0.9996), with satisfactory recovery (83.82–115.60%), low imprecision (within-run CV = 3.9%, between-run CV = 5.8%), and a detection limit of 0.981 ng/mL. In addition, the assay showed good stability and specificity. Serum MRGPRX2 levels were significantly elevated in patients with AR and CSU compared with healthy controls. Collectively, these results demonstrate that the recombinant antibody–based ELISA provides a sensitive, specific, stable, and reproducible platform for circulating MRGPRX2 detection, with promising potential for clinical and translational applications in mast cell–related disorders.