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

Sara Ayazian Mavi; Mohammad Hossein Modarressi; Mehdi Mohebali; Saeedeh Shojaee; Hojjat Zeraati; Aref Teimouri; Hossein Keshavarz

doi:10.2147/IDR.S209270

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

Infect Drug Resist. 2019 Aug 15:12:2519-2530. doi: 10.2147/IDR.S209270. eCollection 2019.

Authors

Sara Ayazian Mavi¹, Mohammad Hossein Modarressi², Mehdi Mohebali^{1

3}, Saeedeh Shojaee¹, Hojjat Zeraati⁴, Aref Teimouri^{1

5}, Hossein Keshavarz^{1

3}

Affiliations

¹ Department of Medical Parasitology and Mycology, Tehran University of Medical Sciences, Tehran, Iran.
² Department of Medical Genetics, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
³ Center for Research of Endemic Parasites of Iran, Tehran University of Medical Sciences, Tehran, Iran.
⁴ Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
⁵ Students Scientific Research Center, Tehran University of Medical Sciences, Tehran, Iran.

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.

Keywords: BALB/c mice; CpG-ODN adjuvant; DNA vaccine; GRA7; RH strain; SAG1; Toxoplasma gondii; pVitro2-neo-mcs.