Identification of diagnostic peptides for Brucella melitensis using phage display technology

Brucellosis is a bacterial zoonotic disease that is widely endemic worldwide. A rapid and accurate diagnosis is essential in controlling and eradicating this disease. Nevertheless, the currently employed diagnostic tests have limited specificity, require prolonged antigen production, and pose challenges in culturing Brucella. To address these issues, phage display represents a promising approach for identifying and producing diagnostic peptides. This study aimed to identify Brucella spp.-derived peptides by mapping positive goat sera with peptide-displayed phage libraries and evaluating their potential utility in brucellosis serological diagnosis. Commercial peptide phage libraries and Brucella melitensis positive and negative sera were used to select antigenic peptides for diagnosis. A total of 26 reactive clones were identified, showing significantly higher reactivity compared with negative sera. The displayed peptide sequences were analyzed, and homology with numerous proteins involved in bacterial metabolism was found. To evaluate cross-reactivity against other bacteria, ELISA tests were performed using Salmonella Dublin rat hyperimmune sera, and five clones did not exhibit reactivity. Candidate clones can differentiate between seropositive and seronegative animals infected with brucellosis. Moreover, they demonstrate their usefulness in serological diagnosis while minimizing cross-reactions. These findings highlight the potential of phage-display-derived peptides as specific and cost-effective antigens for serological diagnosis of Brucellosis.