• Vaccine Name: T. gondii DNA vaccine pVAX-CDPK1 with pVAX-IL7-IL15
• Target Pathogen: Toxoplasma gondii
• Target Disease: Toxoplasmosis
• Type: DNA vaccine
• Status: Research
• Host Species for Licensed Use: Human
• Antigen: CDPK1 (Chen et al., 2016): calcium-dependent protein kinase 1: involved in the regulation of the parasite’s life cycle at stages dependent on microneme secretion, the key regulator of calcium dependent exocytosis, acts in calcium-dependent secretion of specialized organelles called micronemes, which play a critical role in direct parasite motility, host-cell invasion, and egress (Chen et al., 2014)
• CDPK1 gene engineering:
  • Type: DNA vaccine construction
  • Description: CDPK1 was amplified by RT-PCR using a forward primer introducing Kpn I recognition sites and a reverse primer introducing Xba I recognition sites. The amplified CDPK1 was purified and was inserted into the pVAX I vector and generated plasmid pVAX-CDPK1.(Chen et al., 2014)
  • Detailed Gene Information: Click Here.
• Immunization Route: Intramuscular injection (i.m.)
• Description: T. gondii DNA vaccine encoding CDPK1 as antigin and IL-7 and IL-15 as adjuvants using pVAX I vector. (Chen et al., 2016)

Mouse Response

• Host Strain: Specific-pathogen-free (SPF) grade Kunming mice (Chen et al., 2016)
• Host age: 6–10 weeks (Chen et al., 2016)
• Host gender: female (Chen et al., 2016)
• Vaccination Protocol: Mice were randomly divided into six groups (30 mice each). Three vaccination groups were immunized three times at 2-week intervals with 100 μg plasmid dissolved in 100 μl sterile PBS (pVAX-CDPK1, pVAX-IL-7-IL-15, or pVAX-CDPK1 + pVAX-IL-7-IL-15). Another two groups of mice were injected with empty pVAX I vector or PBS respectively as negative control, and one group of mice was not inoculated to constitute blank control. (Chen et al., 2016)
• Immune Response: Humoral: Specific total IgG antibodies were detected in the experimental group, with the highest antibody levels in the group of pVAX-CDPK1 + pVAX-IL-7-IL-15 (CDPK1.7.15) in contrast to PBS, pVAX I or blank control (p < 0.05), and the antibody levels increased with successive DNA immunizations. Immunization with pVAX-CDPK1 induced a higher IgG2a/IgG1 ratio compared to the pVAX-IL-7-IL-15 alone immunized animals, and co-injection of pVAX-CDPK1 with pVAX-IL-7-IL-15 induced the highest IgG2a/IgG1 ratio. (Chen et al., 2016)
  Cellular: Mice immunized with pVAX-CDPK1 + pVAX-IL-7-IL-15 generated significantly higher lymphocytes proliferative response (SI) and levels of IFN-γ and IL-2 compared with mice immunized with pVAX-CDPK1 or pVAX-IL-7-IL-15 alone (p < 0.05). IL-4 and IL-10 levels increased in pVAX-CDPK1, pVAX-IL-7-IL-15 and pVAX-CDPK1 + pVAX-IL-7-IL-15 groups compared to the control groups (p < 0.05). The percentages of CD3+CD8+CD4- T cells and CD3+CD4+CD8– T cells in pVAX-CDPK1, pVAX-IL-7-IL-15 and pVAX-CDPK1 + pVAX-IL-7-IL-15 groups were significantly increased compared to the controls. CD8+ and CD4+ T cell profiles were also significantly altered in theses groups in terms of IFN-γ expression compared to all controls (p < 0.05). There were no difference between changes in CD8+ and CD4+ T cell profiles in terms of IFN-γ secretion (p > 0.05). (Chen et al., 2016)
• Challenge Protocol: 10 mice per group were challenged intraperitoneally with 1 × 10^3 tachyzoites of virulent T. gondii (RH strain). The survival periods were recorded until a fatal outcome for all animals. The other 10 mice per group were inoculated orally with 10 cysts of cyst T. gondii (PRU strain) 14 days after the last immunization. The cysts in their brains were counted 30 days post challenge. (Chen et al., 2016)
• Efficacy: RH: immunized mice showed a prolonged survival time compared to mice receiving the controls (all these mice died within 9 days, p > 0.05), with 14.13 ± 3.85 days in the group of pVAX-CDPK1, 11.73 ± 1.83 days in the group of pVAX-IL-7-IL-15 and 18.07 ± 5.43 days in the group of pVAX-CDPK1 + pVAX-IL-7-IL-15 (p < 0.05). (Chen et al., 2016)
  PRU:Immunization with pVAX-CDPK1, pVAX-IL-7-IL-15 and pVAX-CDPK1 + pVAX-IL-7-IL-15 induced reduction in average parasite burden significantly by 46.0%, 45.0% and 73.5% respectively (p < 0.05) in comparison with the control groups (p < 0.05). (Chen et al., 2016)