Assessment of DNA vaccine encoding Toxoplasma gondii microneme complete gene and IL-12 as adjuvant in BALB/c mice

Document Type: Original Article


1 Department of Parasitology and Entomology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran

2 Department of Medical Parasitology, Faculty of Medicine, Zahedan University of Medical Sciences, Zahedan, Iran

3 Nursing Department, Basic Sciences faculty, Hamedan Branch, Islamic Azad University, Hamedan, Iran

4 Blood Transfusion Research Center, High Institute for Research and Education in Transfusion Medicine, Tehran, Iran


Objective(s): Toxoplasma gondii is an obligate intracellular protozoan parasite that causes toxoplasmosis in humans and animals. Micronemes (MICs) are effective candidates for DNA vaccine.
Materials and Methods: In this study, we evaluated the immune response of BALB/c mice against MIC3 gene of Toxoplasma gondii and interleukin 12 (IL-12) as DNA vaccine. The MIC3 gene was cloned into the PTZ57R/T vector before sub-cloning in pcDNA3. Recombinant pc-MIC3 was transformed into Escherichia coli (TOP10 strain). The pc-MIC3 plasmid was then transfected into Chinese Hamster Ovary (CHO) cells, and the expression of the MIC3 gene was evaluated by SDS-PAGE and Western blotting. Sixty female BALB/c mice were divided into 6 groups. Each group received 3 intramuscular immunizations on days 0, 21st and 42nd using one of the following stimulants: phosphate-buffered saline, pcDNA3, pCAGGS-IL12, pc-MIC3 (100 µg), pc-MIC3 (50 µg), or combined pCAGGS-IL12 (50 µg) and pc-MIC3 (50 µg). The enzyme-linked immunosorbent assays was applied to evaluate  interferon gamma (IFN-γ) and IL-4 cytokines excretion of lymphocytes stimulated with tachyzoites lysate antigen, as well as the total levels of immunoglobulin G (IgG), IgG2a and IgG1 in immunized mice sera.
Results: Our results showed that mice challenged with pc-MIC3 (100 µg) had the highest longevity and quantity of immunoglobulin. Moreover, the highest expression level of IFN-γ was found in mice injected with combined pcMIC3 and pCAGGS-IL12 (P<0.05).
Conclusion: The MIC3 gene can be an efficient DNA vaccine candidate against toxoplasmosis. While, the single-gene vaccine can confer partial protection to mice against toxoplasmosis, the multigene vaccine can significantly enhance immune responses.


Main Subjects

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