Design and synthesis of RNA vaccines encoding SAG1 antigen of toxoplasma gondii and evaluation of immunogenicity and its protective efficacy against acute toxoplasmosis in BALB/c mice.

Toxoplasmosis represents a significant global health concern due to the limited availability of safe and effective vaccines and drugs. mRNA technology offers a promising approach for toxoplasmosis vaccine development, combining effectiveness with enhanced safety features. Unlike DNA vaccines, mRNA vaccines remain exclusively in the cytoplasm, eliminating the risk of genomic integration and malignant cell transformation. We designed an RNA-based vaccine encoding the T. gondii SAG1 gene and validated its protein expression in vitro using Western blotting and indirect fluorescent antibody testing (IFAT). Following intramuscular administration in BALB/c mice, we evaluated the resulting protective immune responses. Mice immunized with SAG1 mRNA exhibited robust immune responses involving both cellular and humoral immunity. Immunological analysis revealed elevated titers of T. gondii-specific IgG antibodies (P < 0.01), with predominant representation of the IgG2a subclass relative to IgG1. Cytokine analysis revealed elevation of IFN-γ and IL-4 levels (P < 0.05), indicating a mixed Th1/Th2 immune response with predominant Th1 activity. Following SAG1 mRNA immunization, there was a marked increase in the expression levels of three key inflammatory mediators: tumor necrosis factor-alpha (TNF-α), interleukin-1 (IL-1), and interleukin-6 (IL-6) (P < 0.01). No significant inflammatory or morphological changes were detected in hepatocytes post-vaccination. This immunological response was associated with significant alterations in mortality rates and parasite burdens in vaccinated mice (P < 0.001). Most importantly, mice vaccinated with SAG1 mRNA showed significantly enhanced protection against acute infection compared to those receiving the SAG1 DNA vaccine. Our findings suggest that the use of an mRNA-based platform for SAG1 delivery may provide a feasible strategy for vaccine development against T. gondii, supporting further investigation.