IgM and IgG Epitope Mapping of the Porin Outer Membrane Protein-2a from Brucella abortus: Potential Biomarkers for Detecting Exposure to Brucellosis.

Brucellosis is a globally prevalent zoonotic disease affecting both humans and animals. Its nonspecific clinical manifestations often complicate diagnosis, underscoring the need for reliable laboratory confirmation. Traditional serological assays, though widely used, suffer from limitations such as inconsistent sensitivity and false-positive results. To address these challenges, this study mapped IgM and IgG epitopes of the Brucella Omp-2a protein using sera from infected patients. Epitope identification was performed through SPOT synthesis on cellulose membranes, followed by assessment of potential cross-reactivity using peptide database analysis and ELISA validation. Three major IgM and seven IgG linear B-cell epitopes were identified, six of which demonstrated strong reactivity in peptide-ELISA. Importantly, no significant cross-reactivity with proteins from other human pathogens was detected. Two chimeric multi-epitope peptides, composed of 50 and 60 amino acids and integrating Brucella-specific IgM and IgG epitopes, exhibited excellent diagnostic performance in ELISA, achieving near 100% sensitivity and specificity. These findings support the potential of synthetic peptides as reliable and cost-effective alternatives to native antigens in serological assays. Further validation in larger, geographically diverse cohorts will be essential to confirm their diagnostic robustness and facilitate their integration into routine brucellosis diagnostics.