In silico and in vivo Investigations of the Immunoreactivity of Klebsiella pneumoniae OmpA Protein as a Vaccine Candidate

Background: The growing threat of antibiotic resistance and Klebsiella pneumoniae infection in healthcare settings highlights the urgent need for innovative solutions, such as vaccines, to address these challenges. This study sought to assess the potential of using K. pneumoniae outer membrane protein A (OmpA) as a vaccine candidate through both in silico and in vivo analyses. Methods: The study examined the OmpA protein sequence for subcellular localization, antigenicity, allergenicity, similarity to the human proteome, physicochemical properties, B-cell epitopes, MHC binding sites, tertiary structure predictions, molecular docking, and immune response simulations. The ompA gene was cloned into the pET-28a (+) vector, expressed, purified and confirmed using Western blotting analysis. IgG levels in the serum of the immunized mice were measured using ELISA with dilutions ranging from 1:100 to 1:6400, targeting recombinant outer membrane protein A (rOmpA) and K. pneumoniae ATCC 13883. The sensitivity and specificity of the ELISA method were also assessed. Results: The bioinformatics analysis identified rOmpA as a promising vaccine candidate. The immunized group demonstrated significant production of specific total IgG antibodies against rOmpA and K. pneumoniae ATCC1 13883, as compared to the control group (p < 0.0001). The titers of antibodies produced in response to bacterial exposure did not show any significant difference when compared to the anti-rOmpA antibodies (p > 0.05). The ELISA test sensitivity was 1:3200, and the antibodies in the serum could accurately recognize K. pneumoniae cells. Conclusion: This study is a significant advancement in the development of a potential vaccine against K. pneumoniae that relies on OmpA. Nevertheless, additional experimental analyses are required.