IgM and IgG Epitope Mapping of the Porin Outer Membrane Protein-2a from <em>Brucela abortus</em>: Potential Biomarkers for Detecting Exposure to Brucellosis

Brucellosis is one of the most serious zoonotic diseases worldwide, affecting both human and animal health. In humans, the disease often presents with diverse and nonspecific symptoms, making laboratory confirmation essential for accurate diagnosis and effective treatment. However, traditional diagnostic methods, including serological tests, suffer from limitations such as low sensitivity and high false-positive rates, underscoring the need for improved diagnostic strategies. This underscores the need for improved assays that enable rapid and reliable laboratory detection. In this study, we performed comprehensive IgM and IgG epitope mapping of the Omp-2a protein using sera from Brucella-infected patients. We identified epitopes, created chimeric peptides, and tested their diagnostic value with ELISA. Materials and Methods: The IgM and IgG epitopes of the Omp-2a protein were identified through SPOT synthesis on cellulose membranes, utilizing sera obtained from seropositive individuals. Potential cross-reactive epitopes were screened using peptide database searches and ELISA. Long, chimeric, multi-epitope peptides were synthesized and tested using ELISA on sera from 40 patients to evaluate their diagnostic performance. Results: Three major IgM and seven IgG linear B-cell epitopes were identified. None of the selected epitopes showed cross-reactivity with proteins from other significant human pathogenic organisms, as determined by analysis of peptide databases. Six peptide epitopes were confirmed using peptide-ELISA. Two chimeric peptides (50 and 60 amino acids) containing Brucella-specific IgM and IgG epitopes demonstrated high diagnostic performance, with a sensitivity of 99.96% and a specificity of 100%. Conclusion: Our study identified and validated IgM and IgG epitopes of the transmembrane Omp-2a protein from Brucella abortus. The use of these specific epitopes as biomarkers presents a promising strategy for developing accurate serological assays, potentially enhancing Brucellosis diagnosis and facilitating better monitoring of infection-induced immunity.