Abstract
Toxoplasma gondii is an obligate intracellular parasite responsible for toxoplasmosis, which can cause severe disease in the fetus and immunocompromised individuals. Developing an effective vaccine is crucial to control this disease. Macrophage migration inhibitory factor (MIF) has gained substantial attention as a pivotal upstream cytokine to mediate innate and adaptive immune responses. Homologs of MIF have been discovered in many parasitic species, and one homolog of MIF has been isolated from the parasite Toxoplasma gondii. In this study, the recombinant Toxoplasma gondii MIF (rTgMIF) as a protein vaccine was expressed and evaluated by intramuscular injection in BALB/c mice. We divided the mice into different dose groups of vaccines, and all immunizations with purified rTgMIF protein were performed at 0, 2, and 4 weeks. The protective efficacy of vaccination was analyzed by antibody assays, cytokine measurements and lymphoproliferative assays, respectively. The results obtained indicated that the rTgMIF vaccine elicited strong humoral and cellular immune responses with high levels of IgG antibody and IFN-γ production compared to those of the controls, in addition to slight higher levels of IL-4 production. After vaccination, a stronger lymphoproliferative response was also noted. Additionally, the survival time of mice immunized with rTgMIF was longer than that of the mice in control groups after challenge infection with virulent T. gondii RH tachyzoites. Moreover, the number of brain tissue cysts in vaccinated mice was reduced by 62.26% compared with the control group. These findings demonstrated that recombinant TgMIF protein is a potential candidate for vaccine development against toxoplasmosis.
Highlights
Toxoplasma gondii is an obligate intracellular protozoan that belongs to the phylum Apicomplexa
The results revealed that most regions of the TgMIF protein were in hydrophilicity plots and flexible regions, and TgMIF exhibited ideal surface probability and an antigenic index that indicated it was a promising prospect for producing vaccines (Figure 1)
The recombinant TgMIF was expressed in E. coli and the soluble recombinant protein was purified by Ni2+-NTA agarose
Summary
Toxoplasma gondii is an obligate intracellular protozoan that belongs to the phylum Apicomplexa. This parasite can infect a wide range of warm-blooded mammals, including humans, livestock and birds. Vaccinations are considered to be an effective mean to prevent infection with the parasite. To date, inactivated and attenuated vaccines, subunit vaccines, DNA vaccines and recombinant protein vaccines have been developed to prevent infection by T. gondii. Toxovax R , the only available commercial vaccine, is based on the live-attenuated T. gondii S48 strain and is licensed only for use in sheep to avoid congenital toxoplasmosis (Buxton and Innes, 1995). It is imperative for us to develop a valuable and practical vaccine against toxoplasmosis, and an effective vaccine will be beneficial to the livestock industry by reducing economic losses (Qu et al, 2013)
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