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

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. 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. 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. 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.