Highly conserved exposed immunogenic peptides of Omp34 against Acinetobacter baumannii: An innovative approach

Omp34, also known as Omp34kDa or Omp33-36 is a virulence factor associated with A. baumannii metabolic fitness or its adherence and invasion to human epithelial cells. This protein is also introduced as a specific antigen which could induce strong antibody responses. In the present in silico study, recent vaccine design strategies such as 'antigen minimization' and 'high epitope density' were invoked to design a soluble immunogen with higher antigenicity. As an advantage, the tools employed in the current study are easily available. Exposed peptides in linear B-cell epitopes were predicted and their conservancy and immunogenicity were evaluated. In this regard, constructs were designed by removal of inappropriate regions. Based on the obtained results the external loops (L1-L7) were exclusively considered of which L3, L6 and L7 were the most appropriate of which the most appropriate were in L3>L6>L7 order while L2 was assigned as an inappropriate peptide. The final construct, named Omp34-4, encompasses three copies of L3, two copies of L6 and L7 and one copy of L1, L4 and L5. The designed construct is predicted to be a soluble antigen with enhanced epitope density and antigenicity. Omp34 is present in >1600 strains of A. baumannii with ≥98% identity. So, it could be applicable in diagnostic kits and an immunotherapy choice against A. baumannii. It could be presumed that co-administration of Omp34-4 and a recently designed OmpA-derived antigen could confer sufficient protection against A. baumannii-associated infections. In vitro and in vivo experiments are needed to confirm all these data. The innovative approach could be generalized to vaccine designs focused on OMPs.