Abstract
Toxoplasma gondii can infect all warm-blooded animals including human beings. T. gondii dense granule protein 16 (TgGRA16) as a crucial virulence factor could modulate the host gene expression. Here, a DNA vaccine expressing TgGRA16 was constructed to explore the protective efficacy against T. gondii infection in Kunming mice. The immune responses induced by pVAX-GRA16 were also evaluated. Mice immunized with pVAX-GRA16 could elicit higher levels of specific IgG antibody and strong cellular response compared to those in controls. The DNA vaccination significantly increased the levels of cytokines (IFN-γ, IL-2, IL-4, and IL-10) and the percentages of CD4+ and CD8+ T cells in mice. After lethal challenge, mice immunized with pVAX-GRA16 (8.4 ± 0.78 days) did not show a significant longer survival time than that in controls (7.1 ± 0.30 days) (p > 0.05). However, in chronic toxoplasmosis model (administration of 10 brain cysts of PRU strain orally), numbers of tissue cysts in mice immunized with pVAX-GRA16 were significantly reduced compared to those in controls (p < 0.05) and the rate of reduction could reach 43.89%. The results indicated that the TgGRA16 would be a promising vaccine candidate for further development of effective epitope-based vaccines against chronic T. gondii infection in mice.
Highlights
Toxoplasma gondii, an apicomplexan parasite, can infect any nucleated cells of almost all warm-blood mammals including humans and birds [1,2,3]
Specific green fluorescence was observed in HEK293 cells transfected with the eukaryotic recombinant plasmid pVAX-GRA16, but not OD, 450 nm Negative control phosphate-buffered saline (PBS)
Toxoplasmosis is a zoonotic disease with worldwide distribution [26]
Summary
Toxoplasma gondii, an apicomplexan parasite, can infect any nucleated cells of almost all warm-blood mammals including humans and birds [1,2,3]. One-third of the global human beings are considered T. gondii seropositive [2, 4]. T. gondii infections in immunocompetent people are asymptomatic. For people with immunodeficiency, such as AIDS patients and transplant recipients, T. gondii infection can lead to encephalitis, ophthalmopathy, or even death [4,5,6]. Pregnant women primarily infected with Toxoplasma could result in miscarriage, ocular complications, and severe neonatal malformations in the fetus [7, 8]. Toxoplasmosis occurring in animals can cause abortion and neonatal loss which can lead to significant economic losses to animal husbandry [9,10,11]
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