Resistance to Chronic Toxoplasma gondii Infection Induced by a DNA Vaccine Expressing GRA16

Abstract EN

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.