• Vaccine Name: T. gondii GRA17 mutant vaccine
• Target Pathogen: Toxoplasma gondii
• Target Disease: Toxoplasmosis
• Type: Live, attenuated vaccine
• Status: Research
• Host Species for Licensed Use: Human
• Antigen: GRA17 (Wang et al., 2017)
• GRA17 gene engineering:
  • Type: DNA vaccine construction
  • Description: Deleted gene
  • Detailed Gene Information: Click Here.
• Immunization Route: Intraperitoneal injection (i.p.)
• Description: T. gondii attenuated vaccine: used CRISPR-Cas9 method to delete GRA17 gene in T. gondii RH strain (Wang et al., 2017)

Mouse Response

• Host Strain: Kunming mice (Wang et al., 2017)
• Host gender: female and male (Wang et al., 2017)
• Vaccination Protocol: Mice were immunized with 5 × 10^4 ΔGRA17 tachyzoites or mock-immunized in a volume of 200 µl PBS intraperitoneally (i.p.) (Wang et al., 2017)
• Immune Response: Humoral: Higher IgG and IgG2a levels at day 28 postimmunization. Increased IgG1 level at 70 days postimmunization. (Wang et al., 2017)
  Cellular: Significantly higher levels of Th1-type cytokines (IFN-γ, IL-2, and IL-12) and significant increase in the level of Th2-type cytokine (IL-10) (Wang et al., 2017)
• Challenge Protocol: The efficacy of ΔGRA17 was tested against acute, latent, and congenital infections in mice 70 days after vaccination.
  Acute: mice were challenged with 1 × 10^3 RH tachyzoites of T. gondii RH, ToxoDB#9 PYS, or ToxoDB#9 TgC7 strain.
  Chronic mice werechallenged with 20 Pru cysts.
  Congenital: female mice were mated to males on a 2:1 ratio 70 days post vaccination. Compared between five groups: (A) ΔGRA17-immunized and orally gavaged with 10 tissue cysts of Pru on day 12 of gestation, (B) ΔGRA17-immunized and i.p. inoculated with 200 RH tachyzoites on day 18 of gestation, (C) non-immunized, and orally gavaged with 10 tissue cysts of Pru on day 12 of gestation, (D) non-immunized and i.p. inoculated with 200 RH tachyzoites on day 18 of gestation, and (E) non-immunized and uninfected.
  (Wang et al., 2017)
• Efficacy: Acute: All immunized mice survived the challenge, whereas all challenged naïve mice died within 10 dpi. Significantly higher levels of IFN-γ and IL-12 in the sera and peritoneal washes in non-immunized and infected mice than in the immunized and infected, and non-immunized and uninfected mice.
  Chronic: All ΔGRA17-immunized mice survived compared to 40% survival of non-immunized and infected mice. Immunized mice had significantly less cyst burden (53 ± 15 cysts/brain compared to 4,296 ± 687 cysts/brain) (P < 0.05). Brain cysts were not found in 4 out of 10 (40%) immunized mice.
  Congenital: The mean sizes of viable pups born to immunized and infected mice were similar to pups born to non-immunized and uninfected mice and in both groups, and no abortions were observed. The mean litter sizes of viable neonates born to non-immunized and infected mice were significantly reduced, and abortions were observed. Five days after birth, the survival rate and mean BW of pups born to non-immunized and uninfected, and immunized and infected mice were significantly higher than that from non-immunized and infected mice. Non-immunized and infected dams showed clinical signs of toxoplasmosis, whereas immunized and infected, and non-immunized and uninfected dams did not show any clinical signs. T. gondii DNA was found in all examined non-immunized and infected dams, but not in any of the 10 examined pups. However, parasites DNA was detected in some aborted fetuses. The pups from the immunized and infected mice had equivalent mean BW and survival rate to that from non-immunized and uninfected dams on day 35 of age.
  (Wang et al., 2017)