Peptide mimicry breaks the heart
Myocarditis, a prolonged chronic inflammation of heart muscle, can eventually progress to inflammatory cardiomyopathy, a serious condition associated with heart failure. Activated T helper (TH) cells that recognize myosin heavy chain 6–derived peptides are thought to play a central role in this pathogenesis. Using a mouse model of myocarditis, Gil-Cruz et al. found that cardiac myosin–reactive TH cells are initially primed by myosin-peptide mimics derived from commensal Bacteroides species in the gut (see the Perspective by Epelman). Unlike heathy controls, human myocarditis patients also showed detectable immune reactivity to both Bacteroides and cardiac myosin antigens. Treatment with antibiotics dampened inflammatory responses and prevented lethal heart disease.
Abstract
Myocarditis can develop into inflammatory cardiomyopathy through chronic stimulation of myosin heavy chain 6–specific T helper (TH)1 and TH17 cells. However, mechanisms governing the cardiotoxicity programming of heart-specific T cells have remained elusive. Using a mouse model of spontaneous autoimmune myocarditis, we show that progression of myocarditis to lethal heart disease depends on cardiac myosin–specific TH17 cells imprinted in the intestine by a commensal Bacteroides species peptide mimic. Both the successful prevention of lethal disease in mice by antibiotic therapy and the significantly elevated Bacteroides-specific CD4+ T cell and B cell responses observed in human myocarditis patients suggest that mimic peptides from commensal bacteria can promote inflammatory cardiomyopathy in genetically susceptible individuals. The ability to restrain cardiotoxic T cells through manipulation of the microbiome thereby transforms inflammatory cardiomyopathy into a targetable disease.
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