In silico Evaluation, Cloning, and Expression of Omp22 as a Promising Vaccine Candidate against Acinetobacter baumannii

Introduction: There is currently no approved vaccine available for Acinetobacter baumannii, an important agent of nosocomial infections. Recently, Omp22 from A. baumannii has been identified as a vaccine candidate that stimulates effective immune responses in mice. However, limited data is available about this protein. This study aimed to comprehensively analyze the immunoinformatic properties of Omp22 and its expression in vitro. Methods: The protein sequence of Omp22 was scanned for subcellular localization, antigenicity, allergenicity, homology to human proteome, physiochemical characteristics, linear and conformational B-cell epitopes, MHC binding sites, tertiary structure prediction, and molecular dockings. Additionally, the gene encoding omp22 was cloned into the pET-28a (+) vector and the expression level was optimized. Results: Omp22 (22.48 kDa, pI of 9.30) belongs to the outer membrane proteins superfamily without transmembrane helices. Omp22 was predicted to be a non-allergenic antigen with appropriate stability. Two linear B-cell epitopes were identified, as well as 108 MHC-I and 50 MHC-II binding sites. Three conformational B-cell epitopes were identified through 3D structure prediction, and molecular docking analysis showed desirable interactions in the docked complexes. The optimized expression of the recombinant Omp22 was successfully achieved. Conclusion: This study represents a significant step towards developing an Omp22-based vaccine candidate against A. baumannii. However, further experimental analyses are still needed.