The invention provides polypeptide fragments derived from TgAMA-1, nucleic acids that encode the polypeptide fragments, and TgAMA-binding polypeptides such as antibodies. Methods for using the polypeptide and nucleic acid molecules to produce vaccines are also provided. In addition the invention provides methods involving use of the polypeptides, nucleic acids, and binding polypeptides, such as antibodies, for the prevention and treatment of Toxoplasmosis.