High Levels of Protection Against Acute and Chronic Toxoplasmosis in Institute of Cancer Research Mice with a Novel Low-Temperature Inactivated Toxoplasma gondii Candidate Vaccine Adjuvanted with HA201/HA203.

Toxoplasma gondii is a highly complex protozoan parasite that poses significant health risks to humans and livestock. Traditional inactivated vaccines have simple preparation and high safety characteristics, but the protection is insufficient. This study aimed to find a new way to prepare an inactivated vaccine and find a suitable adjuvant to evaluate the immunoprotection. Inactivated vaccine (IVAC) was prepared by a novel low-temperature inactivation method, and different adjuvants were selected to evaluate the immune response. To assess immune protection, cytokines and other quantifiable factors associated with protection were examined, and then acute and chronic immune-protected experiments were carried out. IVAC has good integrity and biosafety. Immunizing mice with the adjuvant vaccine resulted in increased immunoglobulin G antibody and interferon-gamma levels, indicating the induction of a mixed Th1/Th2 immune response. Most notably, vaccination significantly improved the survival rate of mice. The IVAC can achieve a 10% protection rate, and the protection rate with adjuvant HA201 and HA203 can reach 50% and 70%, respectively. We found a new method to prepare IVAC and identified two adjuvants that could improve survival rates by 40-60%. These results provide valuable insights for future research on the Toxoplasma vaccine.