Assessment of the Immunogenicity and Protective Efficiency of a Novel Dual-Promoter Dna Vaccine, Harboring Sag1 and Gra7 Genes, From Rh Strain of Toxoplasma Gondii in Balb/C Mice Publisher



Ayazian Mavi S¹ ; Modarressi MH² ; Mohebali M^{1, 3} ; Shojaee S¹ ; Zeraati H⁴ ; Teimouri A^{1, 5} ; Keshavarz H^{1, 3}
Source: Infection and Drug Resistance Published:2019

Abstract

Background: Toxoplasmosis, a protozoan parasitic disease caused by Toxoplasma gondii, has been a serious human and veterinary medicine problem with global distribution. In the current study, we assessed immunogenicity and protective efficiency of a novel dual-promoter DNA vaccine, harboring SAG1 and GRA7 genes, from RH strain of Toxoplasma gondii (T. gondii) with or without CpG-ODN as adjuvant in a murine model. Methods: BALB/c mice were immunized intramuscularly with pVitro-SAG1-GRA7 alone and pVitro-SAG1-GRA7 with CpG-ODN three times at three-week intervals. Enzyme-linked immunosorbent assay (ELISA) was used to assess total IgG, IgG1 and IgG2a antibodies and gamma interferon (IFN-γ) and interleukin-10 (IL-10) cytokines in mice sera. Four weeks post final vaccination, MTT assay and lethal challenge-infection with 1×103 tachyzoites of T. gondii RH strain were carried out to assess stimulation index (SI) and mice survival time, respectively. Results: The IgG levels in mice immunized with multicomponent vaccines, including pVitro-SAG1–GRA7 alone and pVitro-SAG1–GRA7 with CpG-ODN, were significantly higher than those in control mice or single-gene DNA-vaccinated ones (P<0.05). Furthermore, level of IgG2a in mice receiving pVitro-SAG1–GRA7 with CpG-ODN was significantly higher than that in mice receiving pVitro-SAG1-GRA7 alone (P<0.05). The Toxoplasma lysate antigen (TLA)-stimulated lymphocytes from pVitro-SAG1-GRA7 with CpG-ODN group responded more dramatically than those from control groups or single-gene DNA-vaccinated groups (P<0.001). The pVitro-SAG1-GRA7 with CpG-ODN-vaccinated mice developed high levels of IgG2a and IFN-γ (P<0.001) and low levels of IgG1 and IL- 10, compared to control groups, suggesting a modulated immune response type Th1. In addition, survival time of the mice immunized with pVitro-SAG1-GRA7 with CpG-ODN was significantly extended, compared to controls (P<0.05); however, all mice died. Conclusion: The multivalent pVitro-SAG1-GRA7 DNA vaccine with CpG-ODN adjuvant is a promising vaccine candidate against toxoplasmosis. © 2019 Mavi et al.