# Toxoplasma gondii C2 Domain Protein Deletion Mutant as a Promising Vaccine Against Toxoplasmosis in Mice

## TL;DR

A new vaccine candidate for toxoplasmosis was developed using a modified parasite that is less harmful and triggers strong immune responses in mice.

## Contribution

A C2 domain protein deletion mutant of Toxoplasma gondii is shown to be a promising live attenuated vaccine candidate.

## Key findings

- Deleting the TGME49_203240 gene reduces T. gondii virulence and tissue cyst formation in mice.
- ME49Δ203240 vaccination protects mice against lethal T. gondii strains and boosts immune responses.
- The mutant elicits high IgG antibodies and key cytokines like IFN-γ, TNF-α, and IL-12.

## Abstract

Toxoplasma gondii (T. gondii), a parasitic protozoan capable of infecting nearly all warm‐blooded animals, causes significant economic losses in livestock and poses a significant threat to both animal and public health. Despite its impact, no ideal vaccine is currently available to prevent toxoplasmosis. Vesicular transport plays a crucial role in the life cycle of T. gondii, and proteins involved in this process – such as those containing C2 domains – may serve as novel targets for the development of live attenuated vaccines. In this study, we evaluated the feasibility of a C2 domain‐containing protein (TGME49_203240) as a live attenuated vaccine candidate. Our findings suggest that TGME49_203240 may be involved in vesicular transport and that it is essential for T. gondii growth. Deletion of TGME49_203240 reduced parasite virulence and impaired tissue cyst formation in mice. Moreover, mice vaccinated with ME49Δ203240 were protected against the lethal challenge of the tachyzoites of T. gondii I, II, III strains and cysts of II strain. In addition, the ME49Δ203240 strain elicited robust immune responses, including the production of high levels of specific IgG antibodies and key cytokines (IFN‐γ, TNF‐α and IL‐12). These findings highlight TGME49_203240 as a promising target for the development of a live attenuated vaccine against T. gondii.

Without TGME49_203240, a C2 domain‐containing protein, the virulence of T. gondii is much weakened. Immunisation of mice with the ME49Δ203240 strain produces a Th1‐biased immune response against reinfection by the T. gondii I, II and III strains.