Design and validation of a chimeric vaccine against Trypanosoma evansi ISG75: An in silico study

Vaccination remains the most effective practical approach for controlling the spread of infections and alleviating the adverse health effects of diseases. Surra, caused by Trypanosoma evansi , affects various hosts, enabling the disease's continual transmission between its wildlife reservoir and domesticated or working animals. Furthermore, parasites utilize mechanisms such as antigenic variation to circumvent both innate and adaptive immune responses, thereby complicating the development and effectiveness of an anti-trypanosome vaccine. We used an in silico method to design a novel vaccine consisting of a chimeric protein that incorporates predicted epitopes of Invariant Surface Glycoprotein 75 (ISG75) of T. evansi to stimulate an immune response against the parasitic infection. The assessment of predictions was conducted utilizing VaxiJen and ANTIGENpro to facilitate the identification of four epitopes with antigenic properties. In the selected ISG75 sequences, we obtained scores between 0.7 and 1.4 on VaxiJen and between 0.15 and 0.57 with ANTIGENpro. The analysis of immunoinformatics, physicochemical characteristics of the chimeric protein, and molecular simulations indicate that the multiepitope vaccine may be efficacious and appropriate for in vitro evaluation, aiming to develop a peptide vaccine against T. evansi infection. Supplementary validation analyses utilizing ProSA and ERRAT affirmed the structural integrity of the chimeric model, while molecular interaction assessments conducted with ClusPro and BIOVIA Discovery Studio Visualizer bolstered its conformational stability and receptor-ligand compatibility, thereby enhancing its viability as a promising immunogenic construct. The effectiveness of ISG75 as a vaccine candidate has been validated by multiple previous in silico experimental trials. Consequently, we propose an alternative multiepitope ISG75 vaccine for immunization against T. evansi . No chimeric protein has previously been evaluated against any salivarian trypanosomes.