The invention concerns variants of JL7 antigens that are suitable for detecting antibodies against Trypanosoma cruzi (causing Chagas disease) in an isolated biological sample. These antigens comprise a JL7 specific amino acid sequence, said JL7 specific sequence consisting of two copies of SEQ ID NO. 2, wherein each of said two copies has an amino acid identity of at least 90% to SEQ ID NO.2 and wherein no further Trypanosoma cruzi specific amino acid sequences are present in said polypeptide. The invention also concerns a composition of polypeptides useful for the detection of antibodies against Trypanosoma cruzi that comprises the above characterized JL7 antigen along with at least one of T. cruzi polypeptides 1F8, Cruzipain, KMP-11 and PAR-2. Moreover, it relates to a method for producing JL7 antigen as well as to diagnostic methods for detecting T. cruzi antibodies using the JL7 polypeptide. In addition, the invention concerns a reagent kit comprising said JL7 polypeptides or composition of Trypanosoma cruzi polypeptides.