• Vaccine Name: T. gondii DNA vaccine pVAX-CDPK1 with pVAX-IL21-IL15
• Target Pathogen: Toxoplasma gondii
• Target Disease: Toxoplasmosis
• Type: DNA vaccine
• Status: Research
• Host Species for Licensed Use: Human
• Antigen: CDPK1: 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 antigen and IL-21 and IL-15 as adjuvants using pVAX I vector. (Chen et al., 2014)

Mouse Response

• Host Strain: Kunming mice (Chen et al., 2014)
• Host age: Six to eight week old (Chen et al., 2014)
• Host gender: female (Chen et al., 2014)
• Vaccination Protocol: Six groups (35 mice in each group) were intramuscularly injected twice at 2-week intervals in three immunizations (at weeks 0, 2 and 4) with 100 μg pVAX-CDPK1 DNA in 100 μl sterile PBS, 100 μg pVAX-CDPK1 + pVAX-IL-21-IL-15 DNA in 100 μl sterile PBS, 100 μg pVAX/IL-21/IL-15 DNA in 100 μl sterile PBS, 100 μg the empty vector pVAX, PBS (100 μl/each), respectively, and one group of mice was not inoculated to constitute blank control. (Chen et al., 2014)
• Immune Response: Humoral: A significant antibody responses corresponding to total antibodies including IgG, IgG1and IgG2a (P < 0.05) were induced in pVAX-CDPK1, pVAX-IL-21-IL-15 and pVAX-CDPK1 plus pVAX-IL-21-IL-15 groups compared to the controls. The highest antibody levels were observed in pVAX-IL-21-IL-15 and pVAX-CDPK1 co-injection group. There was a predominance of IgG2a over IgG1, and co-injection of pVAX-IL-21-IL-15 with pVAX-CDPK1 significantly increased the ratio (P < 0.05). (Chen et al., 2014)
  Cellular: Stimulation index in spleen cells from mice immunized with pVAX-CDPK1 or pVAX-IL-21-IL-15 alone was significantly higher compared to the controls, and the level of splenocyte proliferation was further increased (P < 0.05) in mice co-injected pVAX-IL-21-IL-15 and pVAX-CDPK1. The percentage of CD3 + CD8 + CD4-T cells and CD3 + CD4 + CD8-T cells were significantly increased in all immunized mice compared with the controls, and the most increase presented in pVAX-CDPK1 plus pVAX-IL-21-IL-15 co-injection group. IFN-γ and IL-2 significantly increased in all immunized mice, and the largest amounts of both two cytokines were produced in pVAX-CDPK1 and pVAX-IL-21-IL-15 co-injection group compared to the controls (P < 0.05). Small amounts of IL-4 and IL-10 were secreted from splenocytes stimulated by TLA in vitro in all immunized mice compared to the control groups (P < 0.05). (Chen et al., 2014)
• Challenge Protocol: Two weeks after the last immunization, 15 mice per group were challenged intraperitoneally (IP) with 1 × 10^3 tachyzoites of the RH strain. The survival time for each mouse and the percentages of mice survived were recorded until a fatal outcome for all animals. In addition, 10 mice per group were inoculated orally with 20 cysts of the PRU strain at day 14th after the third immunization, and observed mice daily for mortality. Four weeks after the PRU strain challenge, surviving mice were sacrificed. 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. (Chen et al., 2014)
• Efficacy: RH: Mice immunized with pVAX-CDPK1 (17.3 ± 4.3 days) or pVAX/IL-21/IL-15 (12.0 ± 2.0 days) significantly prolonged survival time after challenge in comparison to mice in control groups. There was significant difference of survival time between the two groups (P < 0.05). Co-injection with pVAX-CDPK1 and pVAX/IL-21/IL-15 enhanced the survival time of the immunized mice (19.2 ± 5.1 days) in contrast to the group of pVAX-CDPK1 or pVAX/IL-21/IL-15 (P < 0.05). (Chen et al., 2014)
  PRU: The immunized groups challenged with PRU strain cysts showed a significant reduction in the number of cysts in the brain (P < 0.05) (Chen et al., 2014)