Antibodies in the sera of acute rheumatic fever patients bind to human cardiac tropomyosin.

Previous work from this laboratory has demonstrated the occurrence of heart reactive antibodies (HRA) in the sera of acute rheumatic fever (ARF) patients which bound primarily to the sarcolemmal sheath of cardiac myofibres. While many investigators have reported the presence of antibodies to myosin in the sera of ARF patients, the question of whether these sera also contain antibodies to other cytoskeletal proteins has not been addressed. In this study, crude human sarcolemmal sheaths were extracted with 3 M KCl and partially purified using a DEAE cellulose column and a step gradient of NaCl. Maximum reactivity with ARF sera was seen with a protein fraction eluted with 0.3 M NaCl. Using FPLC, a single polypeptide of 38 kDa reacted in ELISA preferentially with ARF sera when compared to sera from patients with uncomplicated streptococcal infections and acute post-streptococcal glomerulonephritis (APSGN). A comparison of the N-terminal sequence of the purified protein and competitive inhibition assays indicated that the reactive sarcolemmal antigen was human cardiac tropomyosin.