In silico design of an epitope-based vaccine against choline binding protein A of Streptococcus pneumoniae

Abstract Streptococcus pneumoniae (Pneumococcus) accounts for a major global health burden that causes bacterial pneumonia, sepsis, otitis media, and meningitis. It is responsible for great morbidity and mortality globally. Available pneumonia vaccines are either carbohydrate-based vaccines or not protective against specific serotypes. Besides, antibiotic resistance to pneumococci justifies further attention to explore new vaccine candidates. The invariant peptide-based vaccines are not only immunogenic for all age groups but also protective against all serotypes of pneumococci. Initially, we searched for potential vaccine candidates of pneumococcus through literature mining. We found Choline binding protein A (CbpA) as a potential immunogenic extracellular protein. Next we applied the immunoinformatic approach to design a multi-epitope based vaccine (MEV) candidate of CbpA against pneumococcus. Furthermore, the protein sequence revealed the immunogenic T-cell epitopes of CbpA. The affinity between the T-cell epitope and MHC molecule was evaluated by Molecular docking (MD) analyses. We found a single 15-mer T-cell epitope (AMATGWLQYNGSWYY), which has not only affinity for both MHC class I and class II but also has the highest population coverage. Besides, the B-cell and IFNγ-inducing epitopes were also selected. All the peptides were assessed for conservancy, allergenicity, immunogenicity, and hydrophobicity. Finally, we assembled the best T-cell, B-cell, and IFNγ-inducing epitopes to make an MEV. The docking and MD simulation study revealed a strong affinity between the MEV and Toll-like receptors. Therefore, we propose that MEV of CbpA could be a novel vaccine candidate, which may induce both humoral and cellular immune responses to non-serotype-specific pneumococcus.