• Vaccine Name: T. gondii DNA vaccine pVAX-GRA24 + pVAX-GRA25 + pVAX-MIC6
• Target Pathogen: Toxoplasma gondii
• Target Disease: Toxoplasmosis
• Type: DNA vaccine
• Status: Research
• Host Species for Licensed Use: Human
• Antigen: GRA24(Xu et al., 2019), GRA25(Xu et al., 2019), MIC6 (Xu et al., 2019)
• MIC6 gene engineering:
  • Type: DNA vaccine construction
  • Description: MIC6 was PCR amplified and was cloned in pGEM-T easy vector, generated pGEM-MIC6. The MIC6 fragment was cleaved by BamHI/XhoI from pGEM-MIC6 and cloned into the BamHI/XhoI sites of pVAXI. (Xu et al., 2019)
  • Detailed Gene Information: Click Here.
• GRA24 gene engineering:
  • Type: DNA vaccine construction
  • Description: GRA24 was PCR amplified and was cloned in pMD-18 T vector, generated pMD-GRA24. The GRA24 fragment was cleaved by KpnI/XbaI from pMD-GRA24 and cloned into the KpnI/XbaI sites of pVAXI. (Xu et al., 2019)
  • Detailed Gene Information: Click Here.
• Immunization Route: Intramuscular injection (i.m.)
• Description: T. gondii DNA vaccine using three pVAX I plasmids encoding GRA24, GRA25, and MIC6 respectively(Xu et al., 2019)

Mouse Response

• Host Strain: Kunming mice (Xu et al., 2019)
• Vaccination Protocol: Eight groups (30 Kunming mice per group) were used for this study, consisting of five experimental and three control groups. Mice in the experimental groups were immunized three times (2-week intervals) with 100 μL (1 μg/μL) of pVAX-GRA24, pVAX-GRA25, pVAX-MIC6, pVAX-GRA24 + pVAX-GRA25 or pVAX-GRA24 + pVAX-GRA25 + pVAX-MIC6 plasmids by intramuscular injection into the quadriceps, respectively. Control groups included mice injected with 100 μL empty pVAX I vector (1 μg/μL), 1× PBS or blank control, respectively. (Xu et al., 2019)
• Immune Response: Humoral: Highest antibodies titer was observed in pVAX-GRA24 + pVAX-GRA25 + pVAX-MIC6 group. Also, boosting with pVAX-GRA24 and pVAX-GRA25 increased the IgG titer induced by pVAX-GRA24 or pVAX-GRA25. The levels of IgG titer in the pVAX-GRA24, pVAX-GRA25 or pVAX-MIC6 groups were significantly higher (p < 0.05) than those in the three control groups. Higher IgG2a to IgG1 ratio.
  Cellular: Highest levels of IL-2, IFN-γ, IL-12 and IL-23 in co-injected mice. The percentages of CD3+CD4+CD8− and CD3+CD8+CD4− T lymphocytes were significantly increased in all experimental groups. pVAX-GRA24 + pVAX-GRA25 showed higher percentage than single plasmid group, whereas pVAX-GRA24 + pVAX-GRA25 + pVAX-MIC6 group showed the highest percentage. Higher SI in all experimental groups.
  (Xu et al., 2019)
• Challenge Protocol: Two weeks after the third booster vaccine dose, 10 mice from all groups were challenged intraperitoneally with 1 × 10^3 tachyzoites of the virulent RH strain, and the survival periods were recorded daily until all mice were dead. Meanwhile, another 10 mice per group were challenged with a non-lethal dose of 20 cysts of the Pru strain. Then, 4 weeks after the challenge, the surviving mice were sacrificed via cervical dislocation, and the mean number of cysts per brain was determined by counting three samples of 10 μL aliquots of each homogenized brain under an optical microscope. (Xu et al., 2019)
• Efficacy: Mice immunized with pVAX-GRA24 (8.1 ± 0.5 days), pVAX-GRA25 (9.4 ± 0.7 days), pVAX-MIC6 (11.5 ± 0.8 days), pVAX-GRA24 + pVAX-GRA25 (13.8 ± 0.9 days) and with pVAX-GRA24 + pVAX-GRA25 + pVAX-MIC6 (18.7 ± 1.3 days) had a significantly longer survival time compared to the three control groups. The mice in the three control groups died within 6 days after challenge. (Xu et al., 2019)
  The number of cysts in the mouse brain was reduced significantly in the pVAX-GRA24 (29.03%), pVAX-GRA25 (40.88%), pVAX-MIC6 (37.70%), pVAX-GRA24 + pVAX-GRA25 (48.06%) and pVAX-GRA24 + pVAX-GRA25 + pVAX-MIC6 (55.37%) groups, compared to the control group (p < 0.05). There was no apparent reduction of brain cysts among the three control groups. (Xu et al., 2019)