Reverse vaccinology and immunoinformatics approaches driven designing of a novel multi-epitope mRNA vaccine against Toxoplasma gondii.

Toxoplasmosis is a zoonotic infectious disease caused by the intracellular apicomplexan parasite Toxoplasma gondii and primarily affects warm-blooded animals. Despite its global spread, the disease has limited therapeutic interventions. Chemotherapy can be used as a treatment, but there are potential side effects and contraindications. Despite several epitope-based in-silico vaccine studies, no mRNA-based vaccine has yet been explored. This study aims to design an mRNA vaccine using reverse vaccinology and immunoinformatics based on MIC1, MIC3, ROP29, and SAG1 proteins, which contribute to the attachment and activation processes of T. gondii. The selected epitopes achieved 100 % combined coverage worldwide. The favorable biophysical properties of the vaccine indicated its solubility and potential functional stability in the human body. The secondary and tertiary structural predictions of the refined vaccine revealed its well-stabilized configuration with a Ramachandran score of 80.9 % and a Z-score of -7.55. Docking analysis revealed a predicted high binding affinity toward TLR-2 and TLR-4 receptors. However, the lowest energy scores of -1000.5 kJ/mol and -1008.6 kJ/mol for TLR-2 and TLR-4, respectively, reflected highly favorable intermolecular interactions, which were further supported by MM-GBSA and molecular dynamics simulations. The vaccine showed cloning efficiency in Escherichia coli strains, and immune simulation predicted strong induction of B and T cells. Finally, the optimal and centroid structures of the designed mRNA vaccine were modelled. The vaccine developed in this study may serve as a probable future candidate against this parasite, reinforcing the need for additional in-vitro and in-vivo analyses.