Epitope Prediction and Structural Analysis of Outer Membrane Protein A (AbOmpA) as a Vaccine Candidate against Multidrug-Resistant Acinetobacter baumannii

Acinetobacter baumannii is a Gram-negative opportunistic microorganism and a member of the ESKAPE pathogens, recognized as a major contributor to multidrug-resistant (MDR) infections worldwide. The increasing prevalence of MDR A. baumannii strains has severely restricted therapeutic options and raised significant global health concerns, particularly in regions with insufficient infection control measures. Among the potential solutions, vaccination offers an effective means of preventing infection by activating host immune responses. In this study, we investigated the outer membrane protein A of A. baumannii (AbOmpA), its predominant surface protein, due to its relevance as a vaccine target: (1) AbOmpA is strongly immunogenic and critical for bacterial survival, (2) it is continuously expressed during the bacterial life cycle, and (3) its surface accessibility facilitates host immune recognition. Through comparative sequence alignment, 3D structural modeling, and in silico epitope prediction, we identified several conserved B- and T-cell epitopes within AbOmpA that are potentially cross-reactive across multiple MDR A. baumannii strains. Collectively, these findings highlight AbOmpA as a compelling antigen candidate for broad-spectrum vaccine development and provide a foundation for novel strategies to combat MDR A. baumannii infections.