An Immunoinformatic Approach for a Multi-Epitope Vaccine Against Toxoplasma gondii.

Infection with the intracellular apicomplexan parasite Toxoplasma gondii causes severe and often fatal clinical outcomes worldwide, especially in patients with immunodeficiency, diabetes and in pregnant women and infants. Despite approximately one-third of the global population being infected with T. gondii, there is currently no effective vaccine available for humans. The objective was to develop a potential vaccine candidate for T. gondii, which would incorporate the B- and T-lymphocyte epitopes derived from three immunogenic antigens of the parasite. Initially, the immunodominant epitopes present in the SAG1, GRA6 and GRA7 proteins of T. gondii were identified. Following this, a multi-epitope vaccine was developed by integrating B-cell epitopes, CTL epitopes and HTL epitopes, with the addition of the 50S ribosomal protein L7/L12 serving as an adjuvant to enhance the immunogenic properties of the vaccine. All identified epitopes demonstrated characteristics of being antigenic, nonallergenic, nontoxic and lacking human homologues. Furthermore, the candidate vaccine exhibited immunogenicity, non-allergenicity and stability. Molecular docking studies indicated robust interactions between the vaccine construct and the TLR-4 immune receptor. Additionally, the stability of the formulated vaccine was confirmed through molecular dynamic simulations. In silico analyses suggested that the vaccine construct could effectively initiate primary immune responses; however, further laboratory evaluations are required to verify its efficacy and safety.