Myocarditogenic epitopes and autoimmune myocarditis.

Experimental autoimmune myocarditis is provoked by immunization with cardiac myosin. This animal model finally develops into dilated cardiomyopathy through repetitive myosin injections. To identify the myocardiogenic epitope, therefore, it is imperative not only to understand the mechanism of induction, but also to produce specific therapies, such as a blocking therapy to suppress the autoimmune process. Thus, we attempted to identify the myocarditogenic epitope using recombinant peptides. Beta-cardiac myosin heavy chain (CMHC) was amplified from rat mRNA by a reverse transcription polymerase chain reaction method. The PCR primers were designed to narrow the epitopic amino acid portion from each N-terminal to C-terminal site. These PCR products were cloned into an E. coli expression vector to produce fusion proteins consisting of a Histidine-tag and a myosin peptide. The segment of amplified CMHC including the epitopic amino acid sequence to provoke moderate myocarditis in vivo was reported previously. Each peptide solution was emulsified in an equal volume of complete Freund's adjuvant and given as an immunization to 7-week-old rats. On day 21 after immunization, the rats were sacrificed, and the fresh heart was observed pathologically. Through this immunization, we could restrict the myocardiogenic site. Lastly, this peptide was found to be located on residues from 1,124 to 1,153. Using ELISA, the antibodies against myocarditogenic peptides were easily identified. Whether or not the antibody productivity is linked to myocarditogenecity is discussed.