The role of heart binding antibodies in rheumatic fever

Review of microbial infections and the immune response to cardiac antigens

Heart disease is the most prevalent cause of morbidity and mortality in rich countries. Multiple pathogens are epidemiologically linked to human heart disease, and autoinflammatory responses to heart-specific epitopes revealed to the host's immune system (e.g., due to the cytopathic effects of cardiotropic viruses) or attacked by autoaggresive lymphocytes activated by mimicking peptides present in bacteria may be causative in the pathogenesis of chronic inflammatory cardiomyopathy. The experimental system of murine chronic autoimmune myocarditis has been used to analyze aspects of the host immune response. This review presents insights gained by use of this murine model system into molecular mechanisms governing activation of autoaggressive lymphocytes, target organ susceptibility, and cardiopathogenic epitope mapping and discusses mimicking endogenous epitopes found in pathogens.

Chlamydia infections and heart disease linked through antigenic mimicry

Chlamydia infections are epidemiologically linked to human heart disease. A peptide from the murine heart muscle-specific alpha myosin heavy chain that has sequence homology to the 60-kilodalton cysteine-rich outer membrane proteins of Chlamydia pneumoniae, C. psittaci, and C. trachomatis was shown to induce autoimmune inflammatory heart disease in mice. Injection of the homologous Chlamydia peptides into mice also induced perivascular inflammation, fibrotic changes, and blood vessel occlusion in the heart, as well as triggering T and B cell reactivity to the homologous endogenous heart muscle-specific peptide. Chlamydia DNA functioned as an adjuvant in the triggering of peptide-induced inflammatory heart disease. Infection with C. trachomatis led to the production of autoantibodies to heart muscle-specific epitopes. Thus, Chlamydia-mediated heart disease is induced by antigenic mimicry of a heart muscle-specific protein.

Heart-specific autoantibodies following murine coxsackievirus B3 myocarditis

The sera from A.SW/SnJ mice infected with Coxsackievirus B3 (CB3) were tested on normal mouse tissue by indirect immunofluorescence. Heart-reactive antibodies were found. Absorption studies with organ extracts showed some of these autoantibodies to be heart-specific. Additional antibodies were crossreactive with skeletal muscle and kidney. These findings suggest a role for autoimmunity in the pathogenesis of murine CB3-induced myocarditis. This study establishes an animal model for the study of the humoral autoimmune response in human viral myocarditis.

Murine monoclonal antibodies reactive with human heart and group A streptococcal membrane antigens

Ten selected murine hybridoma cell lines that produce monoclonal antibodies against M type 5 Streptococcus pyogenes and human heart antigen were isolated. All of the monoclonal antibodies studied were determined to be the immunoglobulin M isotype. The antibodies were characterized on the basis of their reactions with Triton X-100-extracted whole human heart antigens, sodium dodecyl sulfate-extracted sarcolemmal antigens, and whole streptococci or their membranes. Enzyme-linked immunosorbent assays and Western immunoblotting techniques were used to compare the reactivity of the monoclonal antibodies. All 10 of the antibodies were first selected for their reactivity with Triton X-100-extracted heart antigens and whole group A, M type 5 streptococci. These antibodies were then divided into two categories: strong reactors or weak reactors with human sarcolemmal and streptococcal membranes. Among the strong reactors, two different types of monoclonal antibodies were observed on the basis of their immunobanding patterns with sarcolemmal and streptococcal membranes on Western blots. Monoclonal antibodies that were strong reactors with sarcolemmal and group A streptococcal membrane antigen were directed against a determinant on a family of proteins. The major reactants of sarcolemmal extracts were high-molecular-weight proteins near 200,000. Some monoclonal antibodies demonstrated more specificity for the heart than did others when reacted with separated Triton X-100-extracted tissue antigens from the heart, kidney, and skeletal muscle. One of the monoclonal antibodies that reacted with group A streptococci reacted with a Triton X-100-extracted heart antigen ca. 40,000 daltons in size. None of these monoclonal antibodies opsonized type 5 Streptococcus pyogenes, and in enzyme-linked immunosorbent assays most of the antibodies were found to react to a lesser degree with other groups of streptococci. Monoclonal antibody was used to probe normal and rheumatic sarcolemma for differences in reactivity. Although the rheumatic heart reacted more intensely, no major differences between the immunobanding patterns of normal and rheumatic hearts were observed.