Multi-epitope DnaK peptide vaccine against S.Typhi: An in silico approach

Salmonella is one of the key global causes of food and water borne enteric infections, responsible for significant morbidity and mortality worldwide especially in developing countries. Currently available vaccines against typhoid are moderately effective with several side effects and not efficacious against all Salmonella serovars. Due to limitations of these vaccines and emerging threats of multidrug resistance, developing an effective vaccine against these infections has increasingly become a priority. Heat shock proteins (Hsps), being evolutionarily conserved, represent dominant antigens in the host immune response. In continuation of our earlier studies on the development of S. Typhi DnaK and GroEL vaccine candidates, highly efficacious against Salmonella and multiple pathogens, in the present study, we have designed multi-epitope vaccine candidates common to multiple serovars of Salmonella using bioinformatics approach. Implementing various immunoinformatics tools such as IEDB, EpiJen, BCPRED, ElliPro and VaxiJen, led to the identification of many immunogenic B and T cell epitopes. The 3-D structure model of DnaK was generated to predict conformational B-cell epitopes using ElliPro server. Most promising T cell epitopes (29 CTLs, 18 T-helper cells) were selected based on their binding efficiency with commonly occurring MHC alleles. Finally we narrowed down to 5 protective antigenic peptides (PAPs), comprising highly conserved, antigenic and immunogenic B /T cell epitopes, least homologous with human host. These PAPs were predicted to be non-allergenic by allergenicity prediction tools (SORTALLER and AllerHunter). Hence, these immunogenic epitopes can be used for prophylactic or therapeutic usages specifically to defeat antibiotic-resistant Salmonella. These antigens have been reported for the first time and their conserved nature endow them as potential future vaccine candidates against other multiple pathogens as well.