Abstract: There is disclosed an antigenic peptide that comprises at least 15 amino acids having the sequence Ala Glu Pro Lys X Ala Glu Pro Lys X Ala Glu Pro Lys X, wherein X is Pro or Ser. This peptide is useful in an ELISA assay to detect antibodies specific to T. cruzi infection and Chagas disease. This peptide is further useful in a vaccine composition for immunizing an individual to prevent Chagas disease upon exposure to T. cruzi.