Evaluation of the immune response in BALB/c mice induced by a novel DNA vaccine expressing GRA14 against Toxoplasma gondii

Toxoplasma gondii can cause severe and even fatal disease in human beings and animals. Effective vaccines may contribute to control toxoplasmosis. GRA14, a novel secreted dense granule protein of T. gondii, has been proposed as a vaccine candidate due to its intervacuolar transport and unique topology in the parasitophorous vacuole membrane. In this study, we constructed a DNA vaccine encoding GRA14 of T. gondii. BALB/c mice were immunized intramuscularly three times at 2 week intervals and challenged with T. gondii RH strain 5 weeks later. The immune responses were evaluated using lymphocyte proliferation assay, cytokine and antibody measurements. In addition, the survival times and parasite load of mice challenged with the virulent T. gondii RH strain were evaluated. The results showed that the mice immunized with pcGRA14 induced both enhanced specific humoral and Th1 cellular immune responses, and also mice immunized with the pcGRA14 showed an increased survival time and decreased parasite load compared with control groups (P<.05). The results indicated, for the first time, that the GRA14 is a potential DNA vaccine against toxoplasmosis.