The Immunogenic and Immunoprotective Activities of Recombinant Chimeric Proteins Containing AMA1 Antigen Fragments

Toxoplasmosis, one of the most common parasitoses worldwide, is potentially dangerous for individuals with a weakened immune system, but specific immunoprophylaxis intended for humans is still lacking. Thus, efforts have been made to create an efficient universal vaccine for both animals and humans to overcome the shortcomings of currently used treatment methods and protect all hosts against toxoplasmosis. The current work represents a relatively new approach to vaccine development based on recombinant chimeric antigens. In the present research, three tetravalent chimeric proteins containing different portions of the parasite's AMA1 antigen-AMA1-SAG2-GRA1-ROP1 (ASGR), AMA1-SAG2-GRA1-ROP1 (ASGR) and AMA1-SAG2-GRA1-ROP1 (ASGR)-were tested for their immunogenic and immunoprotective capacities. All tested proteins were immunogenic, as evidenced by the triggering of specific humoral and cellular immune responses in vaccinated C3H/HeOuJ mice, defined by the production of specific IgG (IgG1/IgG2a) antibodies in vivo and synthesis of key Th1/Th2 cytokines by lysate antigen-stimulated splenocytes in vitro. Although all tested preparations provided partial protection against chronic toxoplasmosis in immunized and -challenged mice, the intensity of the generated immunoprotection depended on the fragment of the AMA1 antigen incorporated into the chimeric antigen's structure.