Development and Characterization of a Fully Human Recombinant MPO ‐ ANCA Monoclonal Antibody as Candidate Quality Control Material

AIM: MPO-ANCA detection suffers prominent inter-assay variability due to a shortage of standardized, sustainable quality control (QC) materials. Existing patient-pooled sera have limited supply, while chimeric monoclonal antibodies fail to fully mimic human autoantibodies. This study aimed to construct a fully human recombinant MPO-ANCA monoclonal antibody and systematically characterize its analytical performance as a candidate QC material for multi-platform MPO-ANCA immunoassay evaluation. METHODS: A human anti-MPO scFv phage display library was constructed using peripheral blood mononuclear cells obtained from MPO-ANCA-positive patients. Following antigen-specific biopanning and screening, the candidate clone H042 was selected and converted into a full-length human IgG1 monoclonal antibody. We verified its structural integrity, antigen specificity, pANCA immunofluorescence pattern, quantitative linearity, thermal/freeze-thaw stability, and cross-kit performance across enzyme-linked immunosorbent assay (ELISA), chemiluminescence immunoassay (CLIA), multiplex flow immunoassay, and indirect immunofluorescence assay (IIFA) from multiple mainstream manufacturers. RESULTS: Purified H042 exhibited intact IgG structure, strong MPO binding affinity, and no cross-reactivity with PR3/GBM. It presented typical pANCA staining in IIFA and showed predictable quantitative response. H042 retained > 89% residual activity under accelerated thermal and repeated freeze-thaw stress. Notably, H042 yielded consistent qualitative positivity on all tested kits of four mainstream methodologies without false-negative signals, despite inter-platform signal intensity differences. CONCLUSION: The fully human monoclonal antibody H042 demonstrated favorable structural integrity, MPO specificity, and broad detectability across the evaluated commercial assay platforms. These characteristics support its potential as a scalable recombinant candidate QC material and an auxiliary tool for MPO-ANCA assay harmonization and laboratory quality assurance.