Subtractive proteomics and immunoinformatics approaches to explore Bartonella bacilliformis proteome (virulence factors) to design B and T cell multi-epitope subunit vaccine.

Bartonella bacilliformis a gram-negative facultative aerobe responsible for the Carrion's disease widely distributed in Ecuador, Peru, and Colombia with a high mortality rate when no specific treatment is received. B bacilliformis is transmitted by Sand fly (Lutzomyia verrucarum) to healthy individuals. Immunoinformatic and subtractive proteomics approaches were employed in this study to prioritize the best candidates for vaccine designing. These approaches resulted in five vaccine candidates, flagellar biosynthetic protein (Uniprot ID: A1UTU1), heme exporter protein C (UniProt ID: A1UU82), Cytochrome c-type biogenesis protein (Uniprot ID: A1URZ7), Hemin ABC transporter (Uniprot ID: A1US20) and Phosphatidate cytidylyltransferase (Uniprot ID: A1USE3). The mentioned proteins are antigenic and essential for pathogen survival. A range of immune-informatics tools was applied for the prediction of B and T cell epitopes for the vaccine candidate proteins. In-silico vaccine was constructed using carefully evaluated epitopes and consequently modeled for docking with human Toll-like receptor 4. TLR-4 agonist 50S ribosomal protein L7/L12 (UniproKB ID; P9WHE3) was linked to the vaccine as an adjuvant to boost immune response towards the vaccine. For stability evaluation of the vaccine-TLR-4 docked complex, MD simulations were performed. The final vaccine was back-translated and cloned in Eschericia coli to attain the maximal expression of the vaccine protein. The maximal expression was ensured, and the CAI score of 0.96 was reported. The current vaccine requires future experimental validation to confirm its effectiveness. The vaccine developed will be helpful to protect against B bacilliformis associated infections.