OmpA virulence factor, a promising conserved vaccine candidate against Acinetobacter baumannii, could trigger autoreactive immune responses in susceptible population.

The mechanism of epitope mimicry could have implications for the safety of vaccine development. OmpA is one of the most promising antigens of Acinetobacter baumannii. This property convinced us to investigate OmpA's potential to trigger autoimmune responses. To this end, BLAST searches were performed using the OmpA sequence and its overlapping peptides to find identical peptides in the human proteome. These peptides were analyzed for their epitopic and HLA binding properties. The population coverage was then calculated for the peptides. OmpA showed high identity among numerous strains of A. baumannii and had no similar counterparts in the human proteome. Three OmpA peptides (TKNYDSKI, LSLARANS, and GQEAAAPA) shared identity and similarity with human proteins. Amongst, LSLARANS, which was found in Isthmin-1, the one with the highest potential to induce autoimmune responses was identified. LSLARANS was found in a B-cell positive assay of OmpA and acted as an HLA binder (such as HLA-A*03:01). Approximately 18% of the world's population were determined to be more susceptible to probable A. baumannii-post-infection autoimmune disease, which could be rooted in OmpA similarity. Mutation sensitivity analyses indicated that the TKNYDSKI peptide is sensitive to engineering and modification. Given these circumstances, these peptides should be avoided in vaccine design efforts to reduce the risk of autoimmune responses.