Epitope prediction and immunogenicity assessment of Leishmania donovani TryS protein as a potential vaccine candidate.

Leishmaniasis, a vector-borne tropical disease, is caused by the bite of Leishmania-infected sand flies. Currently, chemotherapy is the only available option because of the absence of any approved vaccine. Vaccines are considered decisive for the complete eradication of the disease. In this study, we have designed a multiepitope-based vaccine and evaluated its potential immunogenicity using immunoinformatic tools. We selected Leishmania donovani trypanothione synthetase (LdTryS) for the development and analysis of potential immunogenic epitopes. A total of 4 CTL, 3 HTL and 2 LBL epitopes were identified from LdTryS. The immunogenicity, toxicity, and allergenicity of the vaccine construct, comprising all the selected epitopes joined by a linker sequence and adjuvant at the N-terminal, were assessed. Furthermore, LdTryS was also included in the immune simulation. Molecular docking and MD simulations were performed between LdTryS and TLR9, given the high antibody titers observed against the vaccine construct. The results confirmed stable docking of the complex, with localized flexibility observed during molecular dynamics simulations. In addition, MTT assay of LdTryS showed no toxicity in human THP-1 cells, with cell viability always being over 90% even at the maximum concentration tested (20 µg), implying that the protein is safe for subsequent in-vitro and in-vivo validation. Further in vitro or in vivo studies are needed to validate the immunoinformatic predictions for LdTryS.