Characterization of a multi-epitope peptide with selective MHC-binding capabilities encapsulated in PLGA nanoparticles as a novel vaccine candidate against Toxoplasma gondii infection.

No effective human vaccine against Toxoplasma gondii (T. gondii) has yet been developed; however, a protective vaccine using immunogenic peptides in a safe delivery vehicle system offers promise. Here, we employed bioinformatics to design a multimeric recombinant T. gondii vaccine using predicted T and B cell epitopes of SAG1, AMA1, ROP2, and GRA4 proteins based on their binding capabilities to common major histocompatibility complex (MHC) molecules. Furthermore, we encapsulated the expressed protein in poly lactic-co-glycolic acid (PLGA) nanoparticles as a delivery vehicle and also used alum as an adjuvant to determine the vaccine potency of this multimeric antigen. BALB/c mice were vaccinated and then challenged with T. gondii RH strain, and the survival rate and cytokine profiles were studied. Mice vaccinated with the multi-epitope-based vaccine, both with and without PLGA, had greater Th1 immune responses, survival rates, specific antibody titers, and IFN-γ and IL-2 levels than controls, while the alum-adsorbed vaccine stimulated a Th2-type humoral immune response.