• Vaccine Name: RH-AMA1KO
• Target Pathogen: Toxoplasma gondii
• Target Disease: Toxoplasmosis
• Type: Live, attenuated vaccine
• Status: Research
• Host Species for Licensed Use: Human
• Antigen: Live, attenuated T. gondii RH strain with AMA1 knockout (Lagal et al., 2015)
• Immunization Route: Intraperitoneal injection (i.p.)
• Description: T. gondii Live, attenuated vaccine using RH strain with AMA1 knockout (Lagal et al., 2015)

Mouse Response

• Host Strain: BALB/c, CD-1, or C57BL/6J (Lagal et al., 2015)
• Vaccination Protocol: Viable parasites (2.5 × 10^2 to 10^6) were injected i.p. or subcutaneously into mice in a 100-μl volume of phosphate-buffered saline (PBS). (Lagal et al., 2015)
• Challenge Protocol: RH: Naive and AMA1KO-injected mice received an i.p. injection of 10^3 (C57BL/6J) or 10^5 (BALB/c, CD-1) AMA1+ parasites 6.5 to 15 weeks after the first injection. (Lagal et al., 2015)
  Chronic: 10^3 Me49 tachyzoites were injected in BALB/c mice that had been inoculated with 10^5 AMA1KO tachyzoites 8 weeks earlier. (Lagal et al., 2015)
• Efficacy: BALB/c: When challenged with 10^5 AMA1+ type I parasites, BALB/c naive mice died within 6 days, while mice injected with either 10^5 or 10^6 AMA1KO parasites 8 to 10 weeks earlier survived over the assay period of 60 days. The protection went down to 18% when a lower AMA1KO dose (10^3 AMA1KO parasites) was first injected. Immunity lasting more than 8 months for BALB/c mice immunized with 10^5 AMA1KO tachyzoites, which resisted the challenge from 10^5 virulent tachyzoites. 60% of BALB/c mice immunized with 10^5 AMA1KO parasites and challenged 8 weeks later with 10^3 type II ME49 tachyzoites gave negative results by qPCR for the presence of parasites in their brain whereas 100% of the nonimmunized mice gave positive results. (Lagal et al., 2015)
  C57BL/6J: A rather long-lasting immunity was conferred to C57BL/6J mice immunized with 2.5 × 10^2 and 1.5 × 10^3 AMA1KO tachyzoites, which resisted challenge from 10^3 AMA1+ tachyzoites. (Lagal et al., 2015)
  CD-1: CD-1 mice immunized with 10^4 or 10^6 AMA1KO parasites survived challenge with 10^5 AMA1+ tachyzoites. (Lagal et al., 2015)