OBJECTIVETo identify the candidate auto-antigen of rheumatic heart disease as a molecular marker for this disease.

METHODSThe total RNA of the heart tissue of patients with rheumatic heart disease was extracted and reverse-transcribed into long cDNA to construct the phage expression library. The library was screened using the serum from patients with active rheumatic fever, and the positive clone was identified and analyzed by bioinformatics and expressed in vitro. The expressed products were evaluated with Western blotting and its cross-reactivity was assessed.

RESULTSThe phage expression library of the heart tissue of patients with rheumatic heart disease was constructed, with the titer of the primary library of 3.3×10(6) pfu/ml, recombinant rate of 99%, and 81% of the inserted segments were larger than 1 kb. An auto-antigen RHDAG1 was identified by screening, which was homologous to keratin 18. RHDAG1 was detected in the serum of patients with active rheumatic fever and of those with rheumatic heart disease, but not in the serum of healthy subjects.

CONCLUSIONPhage display library can be an effective strategy to screen the auto-antigens of rheumatic heart disease. The auto-antigen RHDAG1 can be a candidate molecular biomarker of rheumatic heart disease and/or rheumatic fever.