A new humanized mouse model for autoimmune cardiomyopathy and its use to devise immunomodulation therapy.

Myocarditis is the principal cause of heart failure in young adults. Frequently triggered acutely by an episode of viral infection, its progression to dilated cardiomyopathy is associated with the development of auto-immunity, especially to human cardiac α-myosin (hCAM). Consistent with this, HLA genotype influences prevalence of the disease. Previous studies showed that humanised DQ8 transgenic non-obese diabetic mice spontaneously developed autoimmune cardiomyopathy, whereas the DR4 allele is over represented in patients and there is no association with diabetes. We therefore attempted to induce experimental autoimmune myocarditis in DR4 transgenic mice (DR4 mice) as a more relevant model of the human disease. DR4 mice were injected with purified hCAM or vehicle subcutaneously in complete Freund's adjuvant (CFA). After 3 weeks, anesthetized mice were subjected to cardiac ultrasonography, following which blood was obtained from the abdominal aorta under terminal anaesthesia. The hearts were then perfused fixed for histology and spleens were harvested for proliferation assay. Potential immunomodulatory peptides were predicted in silico. Peptides were then proven water soluble and effective in T-cell proliferation assays. For immunotherapy, mice were pre-dosed with escalating doses of mixtures of 3 each of 6 soluble hCAM-derived peptides (pools 1 and 2) according to an established protocol. DR4 mice did not develop spontaneous myocarditis. However, all mice immunized with hCAM developed high titres of both IgG1 and IgG2c antibodies. Consistent with this, splenic T-cell proliferation responses to hCAM significantly increased compared to un-immunized mice. DR4 mice immunized with hCAM failed to gain weight and by echocardiography showed a significant decline in cardiac output and fractional shortening and increase in diastolic dimension compared to those injected with PBS in CFA alone. 5/5 immunized vs 0/5 control mice showed cardiac inflammation based on histology. 3/5 immunized mice died if the experiment was prolonged for 6 weeks. Pre-treatment with hCAM derived peptide pools 1 or 2 blunted the T-cell proliferation response and pool 2 also decreased both IgG1 and IgG2c levels. Pools 1 and 2 significantly improved the left ventricular cardiac function by increasing the percentage of ejection fraction and fractional shortening. Pool 2 also significantly reduced cardiac inflammation. We have developed a novel, more relevant humanized mouse model of autoimmune cardiomyopathy and demonstrated its ability to validate the immunomodulatory activity of hCAM derived peptides. Further use of our approach should prove valuable in developing optimized, clinically applicable peptide cocktails to prevent the progression of myocarditis to dilated cardiomyopathy. [ABSTRACT FROM AUTHOR]