Bioinformatics-driven design and protective efficacy assessment of a multi-epitope vaccine for Toxoplasma gondii

Abstract

Introduction Toxoplasma gondii can cause toxoplasmosis. It is an important type of pathogen within the broad category of emerging and re-emerging zoonoses. As an infectious disease featuring a complex multi-host transmission cycle, it poses an increasingly severe threat to global public health. No licensed vaccines are currently available for pets and humans, and thus a novel high-efficiency vaccine is urgently required. Methods Six antigens (GRA1, MIC17A, OWP2, LEA880, LEA870, and a hypothetical protein LEA530) representing different stages of the parasite lifecycle were selected from ToxoDB. T-cell and B-cell epitopes were predicted using immunoinformatics tools and screened based on antigenicity, allergenicity, and toxicity. The multi-epitope peptide (MEP1) was evaluated using molecular docking with Toll-like receptor 4 (TLR4) and immune simulation. The optimized sequence was expressed in HEK293T cells as a recombinant plasmid (MEP1-pcDNA3.1) and further evaluated in BALB/c mice. Results MEP1 contained 13 cytotoxic T lymphocyte epitopes, 16 helper T lymphocyte epitopes, and 12 B-cell epitopes, with a length of 732 amino acids and a predicted molecular weight of 75.73 kDa. The antigenicity score was 0.7343, and structural modeling indicated stable secondary and tertiary conformations. Molecular docking suggested strong binding affinity to TLR4. Immune simulation predicted increased B-cell and T-cell responses following vaccination. In vivo, MEP1-pcDNA3.1 immunization significantly increased serum IFN-γ levels (526.81 pg/mL) compared with PBS and pcDNA3.1 controls. Splenocyte proliferation was significantly enhanced in the MEP1-pcDNA3.1 group (SI = 1.58 ± 0.21) compared with PBS (1.10 ± 0.09) and pcDNA3.1 (1.12 ± 0.04) groups (P < 0.01). Following challenge with 5 × 10³ tachyzoites of the PLK strain, survival was markedly prolonged in vaccinated mice, whereas all control mice died within 2–4 days. Conclusion This study demonstrates an immunoinformatics-guided multi-epitope vaccine strategy against T. gondii, supported by in vivo immunogenicity and partial protective efficacy in a mouse model.