• Vaccine Name: T. gondii DNA vaccine pIRESneo/ROP18/PLP1
• Target Pathogen: Toxoplasma gondii
• Target Disease: Toxoplasmosis
• Type: DNA vaccine
• Status: Research
• Host Species for Licensed Use: Human
• Antigen: ROP18 (Chen et al., 2018); TgPLP1 (Chen et al., 2018)
• ROP18 gene engineering:
  • Type: DNA vaccine construction
  • Description: Amplified by PCR using a forward primer introducing Sma I recognition sites and a reverse primer introducing Xba I recognition sites. (Chen et al., 2018) The amplified ROP18 was cloned into the pGEM-T Easy vector (Promega) and was sequenced. The ROP18 fragment was cleaved by SmaI/XbaI from pGEM-ROP18, purified, and then cloned into the SmaI/XbaI sites of pIRESneo, generating recombinant plasmid pIRESneo/ROP18. The purified TgPLP1 was cloned into pIRESneo/ROP18 and formed pIRESneo/ROP18/PLP1. (Yan et al., 2012)
  • Detailed Gene Information: Click Here.
• PLP1 gene engineering:
  • Type: DNA vaccine construction
  • Description: Amplified by PCR using a forward primer introducing Cla I recognition sites and a reverse primer introducing BamH I recognition sites. (Chen et al., 2018) The amplified TgPLP1 was digested, purified, and cloned into pIRESneo/ROP18 and formed pIRESneo/ROP18/PLP1. (Yan et al., 2012)
  • Detailed Gene Information: Click Here.
• Immunization Route: Intramuscular injection (i.m.)
• Description: T. gondii DNA vaccine encoding ROP18 and TgPLP1 as antigin using pIRESneo vector. pVAX I plasmids encoding IL-18 are codelivered as adjuvant. (Chen et al., 2018)

Mouse Response

• Host Strain: Specific-pathogen-free (SPF) Kunming mice (Chen et al., 2018)
• Host age: 6-7 weeks old (Chen et al., 2018)
• Host gender: female (Chen et al., 2018)
• Vaccination Protocol: Eight groups of mice (30 mice/group) were vaccinated intramuscularly with 100 μg of plasmid dissolved in 100 μl of sterile PBS. The experimental groups received pIRESneo/ROP18/PLP1 + pVAX/IL-18, pIRESneo/ROP18/PLP1, pVAX/PLP1, or pVAX/ROP18 respectively. Injection of pVAX/IL-18, PBS, empty pIRESneo vector, or empty pVAX1 vector was performed as controls. All of the mice were boosted twice at 2-week intervals. (Chen et al., 2018)
• Immune Response: Humoral: Immunization with PBS, pVAXI, pIRESneo, or pVAX/IL-18 alone (four control groups) did not produce an antibody response, which was significantly different (P < 0.05) from the response observed in the four experimental groups. Significant differences were observed between the mice treated with pROP18/PLP1 or pROP18/PLP1 + pVAX/IL-18 and mice treated with pVAX/ROP18 (P < 0.05). (Chen et al., 2018)
  Cellular: The lymphocyte proliferative response in mice injected with pROP18/PLP1 or pROP18/PLP1 + pVAX/IL-18 was significantly higher than that in control mice (P < 0.05). Th1-type cytokines (IFN-γ, IL-2 and IL-12) were induced at significantly higher levels by ROP18/PLP1 fusion protein (P < 0.05) than by ROP18 or PLP1 alone. Compared to mice immunized with pROP18/PLP1 + pVAX/IL-18, mice immunized with pROP18/PLP1 had than significantly lower IL-2, IL-12 and IFN-γ levels (P < 0.05) but significantly higher IL-4 and IL-10 levels (P < 0.05). (Chen et al., 2018)
• Challenge Protocol: Two weeks after the last stimulation, 12 mice per group were randomly chosen for intragastric administration of 80 T. gondii PRU cysts, and survival was monitored daily. Another 8 mice per group were orally infected with 20 PRU tissue cysts, and brain cysts were counted at 6 weeks post-infection. (Chen et al., 2018)
• Efficacy: Acute infection: the survival time was significantly longer (P < 0.05) in mice vaccinated with pROP18/PLP1 (44 ± 2.9 days) or pROP18/PLP1 + pVAX/IL-18 (47 ± 2.9 days) than in control mice (≤36 days). (Chen et al., 2018)
  Chronic infection: brain cyst burden was significantly lower (P < 0.05) in mice immunized with pROP18/PLP1 + pVAX/IL-18 or pROP18/PLP1 than in control mice. (Chen et al., 2018)