Development of a monoclonal antibody-based sandwich ELISA for detection and quantification of the major cat allergen Fel d 1.

Felis domesticus allergen 1 (Fel d 1), the primary allergen produced by cats, is a key trigger of various allergic symptoms in humans, such as rhinitis, conjunctivitis, and asthma. In this study, a recombinant Fel d 1 protein composed of chain 2 and chain 1 was successfully produced in E. coli, based on a previously reported fusion construct that closely approximates the native allergen. Two antibodies, 2A7 and 6B1, were selected for further study due to their high specificity and complementary epitope recognition. A dual-antibody sandwich ELISA was established using 2A7 as the capture antibody and HRP-conjugated 6B1 as the detection antibody. The assay showed a detection range of 10-500 ng/mL with a sensitivity of 1 ng/mL. Application to feline saliva and fur samples revealed detectable Fel d 1 levels, and results correlated well with commercial kits. Epitope mapping identified distinct α-helical regions targeted by 2A7 and 6B1, and sequence analysis of their variable regions confirmed diverse V(D)J gene usage. This study provides a valuable antibody pair and a sensitive ELISA method for Fel d 1 quantification, with potential applications in allergen exposure assessment and diagnostic development. SCIENTIFIC SECTION: Immunology, Antibodies, and Diagnostics.