Immunogenicity and protective efficacy of a Toxoplasma gondii glycoprotein-enriched fraction in mice

Toxoplasma gondii remains a significant parasitic pathogen with limited effective vaccines against its acute virulent form. This study aimed to evaluate the protective and immunological efficacy of a total glycoprotein-based vaccine isolated from T. gondii tachyzoites against infection with the virulent RH strain in Swiss albino mice. A glycoprotein-enriched fraction was isolated from T. gondii tachyzoites using Concanavalin A affinity column chromatography. Mice were divided into four groups (n = 12/group): group I received three subcutaneous doses of 25 μg total isolated glycoproteins emulsified in Freund's adjuvant; goup II received adjuvant only; group III served as control positive (infected, non-vaccinated); Group IV served as control negative. Two weeks after the final dose, groups I-III were challenged intraperitoneally with 2500 tachyzoites of the RH strain. Survival, parasite load, antibody responses, cytokine levels (IFN-γ, IL-12, IL-17), histopathological changes, and CD4⁺/CD8⁺ cell infiltration were evaluated. Vaccinated mice (group I) showed a 60 % survival rate, with significantly prolonged survival (13.77 ± 0.878 days) compared to controls. Parasite load in peritoneal fluid and liver was reduced by 99.8 % and 98.6 %, respectively. Vaccination induced a significant increase in antigen-specific IgG and pro-inflammatory cytokines (IFN-γ, IL-12, and IL-17), suggesting a potent Th1/Th17-mediated immune response. Histopathological and immunohistochemical analyses confirmed reduced tissue damage, absence of tachyzoites, and enhanced CD4+/CD8+ T-cell infiltration in the vaccinated group. In conclusion, the glycoprotein-based fraction provided significant protection against acute toxoplasmosis, demonstrating potential for further development as a subunit vaccine candidate.