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. 2024 Dec 26;123(12):420.
doi: 10.1007/s00436-024-08435-3.

Vaccination with a DNA vaccine cocktail encoding TgROP2, TgROP5, TgROP9, TgROP16, TgROP17, and TgROP18 confers limited protection against Toxoplasma gondii in BALB/c mice

Rongqi Du #  1 , Jinling He #  1 , Jiali Meng #  2 , Dongchao Zhang  3   4   5 , Danruo Li  1 , Hui Wang  1 , Aili Fan  6 , Gang Xu  1 , Shuhui Ma  1 , Zonghui Zuo  1 , Qiqi Song  7 , Tianming Jin  8   9   10
Affiliations

Vaccination with a DNA vaccine cocktail encoding TgROP2, TgROP5, TgROP9, TgROP16, TgROP17, and TgROP18 confers limited protection against Toxoplasma gondii in BALB/c mice

Rongqi Du et al. Parasitol Res. .

Abstract

Toxoplasmosis is a foodborne zoonotic parasitic disease caused by Toxoplasma gondii, which seriously threatens to human health and causes economic losses. At present, there is no effective vaccine strategy for the prevention and control of toxoplasmosis. T. gondii rhoptry proteins (ROPs) are important proteins secreted by the parasite during the early stage of invasion into host cells. In this study, we constructed six individual plasmids (pVAX1-ROP2, pVAX1-ROP5, pVAX1-ROP9, pVAX1-ROP16, pVAX1-ROP17, and pVAX1-ROP18) encoding T. gondii rhoptry proteins and then used an equimolar amount of each as a vaccine cocktail. Following booster immunization, serum antibody levels, splenic lymphocyte proliferation, cytokine production, and survival time after infection with T. gondii RH strain were measured in immunized mice. The results showed that the mice immunized with the DNA vaccine cocktail developed a higher level of the specific anti-T. gondii IgG in serum and the cytokines such as IFN-γ, IL-2, IL-12, and IL-4 (P < 0.01). The stimulation index (SI) of spleen lymphocytes (P < 0.01), the frequencies of CD4+ T lymphocytes (P < 0.01), and the ratio of CD4+/CD8+ T lymphocytes (P < 0.05 or P < 0.01) in the vaccine-immunized mice were significantly increased compared to the control group. After challenge with the virulent T. gondii RH strain tachyzoites, the survival time of mice in the DNA vaccine cocktail group (18.1 ± 1.81 d) was significantly longer (P < 0.01) than that in the control group (8.4 ± 1.02 or 7.9 ± 0.83 d). The results indicated that the DNA vaccine cocktail could elicit strong humoral and cellular immune responses in mice and could also improve the resistance of mice to acute T. gondii infection.

Keywords: Toxoplasma gondii; DNA vaccine; Protective immunity; Rhoptry proteins.

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Conflict of interest statement

Declarations. Ethics approval: All animal housing and experiment protocol in this study conformed to the guidelines of the Ethics Committee of Tianjin Agricultural University (Approval number: 2022LLSC05) and striving to minimize suffering is our experimental principle. Consent to participate: Not applicable. Consent for publication: All the authors provided their consent for the publication of this manuscript. Competing interests: The authors declare no competing interests.

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