Comparative in silico analyses of proteins involved in serum resistance as promising vaccine candidates against Acinetobacter baumannii

Introduction: Acinetobacter baumannii as a Gram-negative coccobacillus has become a major cause of hospital-acquired infections. The virulence factors involved in serum resistance are important targets in the development of an effective vaccine against this pathogen. Our aim in this project was in silico analyses of A. baumannii proteins involved in serum resistance which could potentially be used as efficient vaccines. Methods: Based on computational procedures, we evaluated all A. baumannii proteins involved in serum resistance, namely AbOmpA, PKF, PLD , PBP 7/8, CipA and Tuf SurA1, as vaccine candidates. Subcellular localization, sequence conservation, domain prediction and 3D modelings were analyzed by online tools. Moreover, the prevalence of serum resistance factors in 5 strains of A. baumannii was characterized. The MHC-binding sites of class I and II were detected. Linear and conformational B cell epitopes were analyzed by 2 prediction servers. Results: The MetaLocGramN server showed that AbOmpA, PKF, PBP7/8, phospholipase D, CipA, Tuf and SurA1 were outer membrane protein (56.32%), extracellular protein (58.74%), extracellular protein (52.59%), cytoplasmic protein (45.08%), extracellular protein (53.8%), Cytoplasmic protein (96.36%) and extracellular protein (58.23%), respectively. The OMD of AbOmpA, PKF, PBP7/8 and phospholipase D, CipA, Tuf and SurA1 were 0.060, 0.076, 0.08, 0.101, 0.09, 0.06 and 0.103, respectively. The numbers of immunogenic linear and conformational epitopes with high score (P ≥ 0.6), extracted from beta-barrel of AbOmpA were 6 and 4; whereas these values for PKF were 10 and 4, respectively. Conclusion: The in silico analyses and reverse vaccinology criteria showed that AbOmpA and PKF had better attributes as vaccine targets and they could be considered as promising vaccine candidates against A. baumannii.