Toxoplasma gondii: Identification and immune response against a group of proteins involved in cellular invasion

Toxoplasma gondii is an ubiquitous intracellular parasite, causative agent of toxoplasmosis, and a world- wide zoonosis for which an effective vaccine is needed. A group of proteins secreted by tachyzoites dur- ing host-cell invasion was isolated from the interaction medium. It induced the permeability of the cells as assessed by alpha-sarcin and consequently facilitated the entry of the parasite into the cells. SDS-PAGE of the purified proteins showed a pattern of four proteins of 67, 42, 32 and 27 kDa. MRC-5 cells incubated with the total protein and the different electroeluted bands endured a high cellular death in presence of alpha-sarcin. BALb/C mice immunized with the group of proteins had a mixed Th1/Th2 response and were protected upon challenge with the parasites.