Computational Design of Different Epitope-Based Vaccines Against Salmonella typhi

Salmonella is a gram-negative bacterium belonging to the Enterobacteriaceae family. One of the major known serotypes of this bacterium is Salmonella typhi. This pathogen is the main cause of diseases in humans and livestock. It is transmitted from animals to humans through the consumption of contaminated food. At the moment, one way to prevent this illness is using the live attenuated Ty21a vaccine. To eliminate the side effects of the vaccine and improve its safety, it is important to use epitope subunit vaccines. In this study, a wide range of accurate online servers have been used to predict the epitopes of OmpA, OmpC and OmpF antigens of Salmonella typhi. The T-cell (MHCI and MHCII) and B-cell epitopes share a degree of overlap between these tools. The highest scores were chosen for the study. Further analysis of their antigenicity and resistance to digestive compounds was performed by VaxiJen Servers and Protein Digest Servers. Eventually, the resultant epitopes that had desired antigenicity (≥ 1) and showed the highest resistance to digestive compounds were selected. Using these epitopes (MHCI, MHCII and B cell) two different structures (antigenic structure and digestion-resistant structure) were designed by rigid linkers. These structures were based on the highest antigenicity ranking of epitopes and the highest resistance of epitopes to digestive compounds, respectively. Given that this pathogen is primarily transmitted through contaminated foods, oral vaccines are essential in this regard. Therefore, these structures can be considered as suitable candidates for subunit vaccines.