Design of Multiepitope Vaccine Construct Against Non-typhoidal Salmonellosis and its Characterization Using Immunoinformatics Approach

Non-typhoidal salmonellosis (NTS) is a food-borne zoonotic disease of human and veterinary importance. Besides enteric infections, most often it leads to invasive systemic bacteremia in immunocompromised patients leading to mortality. Emergence of antimicrobial-resistant species warrant the development of newer preventive approaches against NTS. Here, we adopted an in-silico approach to design a multiepitope-based peptide vaccine which will likely enhance the body’s immune response against most commonly isolated serovars (Salmonella Typhimurium, Salmonella Enteritidis and Salmonella Dublin) causing NTS. Using computational tools, we screened the B- cell, MHC-1 and MHC-2 epitopes of the highly conserved outer membrane proteins (OMPs)- OmpC, OmpD and OmpF. By further immunoinformatic processing, for enhanced vaccine efficacy, nineteen most promising epitopes were selected based on their antigenicity. Epitopes were assembled with help of molecular linkers to create a multivalent recombinant protein and then named as NTSVax. Safety assessment of the construct showed zero allergenicity and toxicity. To increase its immunogenicity, synthetic adjuvants RS09 and TpD were added to the C and N terminal ends respectively. Tertiary structure of the vaccine construct, refined at multiple stages, was shown to have 99.7% of residues in favoured regions of Ramachandran plot. The vaccine’s efficacy was further screened via molecular dynamics and immune simulations by docking the complex against human toll like receptors (TLR-1 & 4). Then the peptide sequence was reverse translated and its nucleotide sequence encoding NTSVax was cloned in a plasmid for bulk expression in E. coli.