In silico identification of B- and T-cell epitopes on OMPLA and LsrC from Salmonella typhi for peptide-based subunit vaccine design

Typhoid, caused by Salmonella typhi, has been the most common human illness. In the present study, peptide-based subunit vaccine was developed from OMPLA and LsrC against S. typhi. We adopted sequence, 3-D structure and fold level in silico analysis to predict B-cell and T-cell epitopes. The 3-D structure was determined for OMPLA and LsrC by homology modeling and the modeled structure was validated. One T-cell epitope from OMPLA (WQLSNSKES, 99.5%) and one from LsrC (FIPNQTGTG, 75.31%) binds to maximum number of MHC class I and class II alleles. They also specifically bind to HLA alleles, namely, A*0201, A*0204, B*2705, DRB1*0101 and DRB1*0401. Molecular dynamics simulation of DRB1*0401-epitope complex indicated that they are stable and flexible. Taken together, the results indicate that OMPLA and LsrC are more suitable vaccine candidates against typhoid. Similar epitopes from other human pathogens were identified, which may provide useful information for vaccine development.