Prevention of myosin-induced autoimmune myocarditis in mice by anti-L3T4 monoclonal antibody

Roles of Host Immunity in Viral Myocarditis and Dilated Cardiomyopathy

The pathogenesis of viral myocarditis includes both the direct damage mediated by viral infection and the indirect lesion resulted from host immune responses. Myocarditis can progress into dilated cardiomyopathy that is also associated with immunopathogenesis. T cell-mediated autoimmunity, antibody-mediated autoimmunity (autoantibodies), and innate immunity, working together, contribute to the development of myocarditis and dilated cardiomyopathy.

Mononuclear cell secretome protects from experimental autoimmune myocarditis

AIMS

Supernatants of serum-free cultured mononuclear cells (MNC) contain a mix of immunomodulating factors (secretome), which have been shown to attenuate detrimental inflammatory responses following myocardial ischaemia. Inflammatory dilated cardiomyopathy (iDCM) is a common cause of heart failure in young patients. Experimental autoimmune myocarditis (EAM) is a CD4+ T cell-dependent model, which mirrors important pathogenic aspects of iDCM. The aim of this study was to determine the influence of MNC secretome on myocardial inflammation in the EAM model.

METHODS AND RESULTS

BALB/c mice were immunized twice with an alpha myosin heavy chain peptide together with Complete Freund adjuvant. Supernatants from mouse mononuclear cells were collected, dialysed, and injected i.p. at Day 0, Day 7, or Day 14, respectively. Myocarditis severity, T cell responses, and autoantibody formation were assessed at Day 21. The impact of MNC secretome on CD4+ T cell function and viability was evaluated using in vitro proliferation and cell viability assays. A single high-dose application of MNC secretome, injected at Day 14 after the first immunization, effectively attenuated myocardial inflammation. Mechanistically, MNC secretome induced caspase-8-dependent apoptosis in autoreactive CD4+ T cells.

CONCLUSION

MNC secretome abrogated myocardial inflammation in a CD4+ T cell-dependent animal model of autoimmune myocarditis. This anti-inflammatory effect of MNC secretome suggests a novel and simple potential treatment concept for inflammatory heart diseases.

Infectious tolerance to ADP/ATP carrier peptides induced by anti-L3T4 monoclonal antibody in dilated cardiomyopathy mice

CD4 T cells are suspected to play an important role in the pathogenesis of dilated cardiomyopathy (DCM). This study sought to evaluate whether anti-L3T4 monoclonal antibody (McAb) could induce the infectious tolerance to the adenosine diphosphate (ADP)/adenosine triphosphate (ATP) carrier peptides to protect mice from DCM. BALB/c mice (n = 16) were immunized with the peptides derived from human ADP/ATP carrier on the 1st, 14th, 28th, 49th, and 79th days, and some of them (n = 6) were also injected with anti-L3T4 McAb on the -1st, 0, and 1st days. On the 180th day, the splenocytes (SC) from the McAb-treated group were transferred into the syngeneic recipients (n = 6) who were also immunized with the peptides in the same manner. The sham-immunized mice were taken as the controls (n = 10). Results showed that the serum antibody against the ADP/ATP carrier examined with ELISA was positive in all mice only immunized with the peptides (DCM group), while negative in the McAb-treated, the SC-transferred, and the Control groups. The mRNA expression of IFN-gamma, IL-2, and IL-4, especially IL-4 in T cells investigated using real-time quantitative PCR and the percentages of T helper 1 (Th1) and Th2 subsets, especially Th2 subset detected with Flow Cytometry were all increased in DCM group, accompanied by the cardiac histopathological changes like those in DCM. Such findings were not seen in the other three groups. It concluded that anti-L3T4 McAb could inhibit the occurrence of DCM induced by the ADP/ATP carrier peptides in mice, and this immune tolerance could be transferred to the syngeneic recipients.

Analysis of IgG subclass antibodies and expression of T-Cell receptor signaling molecules in anti-CD4 monoclonal antibody treated mice with autoimmune cardiomyopathy

T-cell immune abnormality in patients of dilated cardiomyopathy has been intensively studied over the past 10 years. In this study, we aim to focus on the molecular mechanism of T-cells in autoimmune cardiomyopathy mouse model by detecting the expression of three T-cell signaling molecules. Balb/C mice (n = 12) were immunized with the peptides derived from human ADP/ATP carrier on the 1st, 14th, 28th, 49th and 79th days, and half of them were also injected with anti-L3T4 McAb on the - 1st, 0 and 1st days. The sham-immunized mice were taken as the controls (n = 6). The main result shows that the antibody response of IgG subclasses such as IgG1, IgG2b and IgG3 were definitely blocked except IgG2a in CD4+ cell-depleted Balb/C mice. In addition, the average mRNA expression of p56lck, p59fyn and zap-70 were all found to be dramatically higher in the mice immunized with only ADP/ATP carrier peptides than in the control-group. At meantime, reduced levels of the protein kinases p56lck, p59fyn and zap-70 were clearly observed in anti-CD4 McAb immunized group compared with DCM group. We propose that the proliferation of T-cells was significantly inhibited in anti-CD4 treated mice and CD4+ T-cells may play a critical role in ADP/ATP carrier caused mouse DCM.

Effects of autoantibodies against β1-adrenoceptor in hepatitis virus myocarditis on action potential and L-type Ca2+ currents

AIM: To investigate the effects of autoantibodies against β₁-adrenoceptor in hepatitis virus myocarditis on action potential and L-type Ca²⁺ currents.

METHODS: Fifteen samples of autoantibodies against β₁-adrenoceptor positive sera of patients with hepatitis virus myocarditis were obtained and IgGs were purified by octanoic acid extraction. Binding of autoantibodies against β₁-adrenoceptor to guinea pig cardiac myocytes was examined by immunofluorescence. Using the patch clamp technique, the effects on the action potential and I_Ca-L of guinea pig cardiac myocytes caused by autoantibodies against β₁-adrenoceptor in the absence and presence of metoprolol were investigated. Cell toxicity was examined by observing cell morphology and permeability of cardiac myocytes to trypan blue.

RESULTS: The specific binding of autoantibodies against β₁-adrenoceptor to guinea pig cardiomyocytes was observed. Autoantibodies against β₁-adrenoceptor diluted at 1:80 prolonged APD₂₀, APD₅₀ and APD₉₀ by 39.2%, 29.1% and 15.2% respectively, and only by 7.2%, 5.3% and 4.1% correspondingly in the presence of 1 μmol/L metoprolol. Autoantibodies against β₁-adrenoceptor diluted at 1:80, 1:100 and 1:120 significantly increased the I_Ca-L peak current amplitude at 0 mV by 55.87 ± 4.39%, 46.33 ± 5.01% and 29.29 ± 4.97% in a concentration-dependent manner. In contrast, after blocking of β₁-adrenoceptors (1 μmol/L metoprolol), autoantibodies against β₁-adrenoceptor diluted at 1:80 induced a slight increase of I_Ca-L peak amplitude only by 6.81 ± 1.61%. A large number of cardiac myocytes exposed to high concentrations of autoantibodies against β₁-adrenoceptor (1:80 and 1:100) were turned into rounded cells highly permeable to trypan blue.

CONCLUSION: Autoantibodies against β₁-adrenoceptor may result in arrhythmias and/or impairment of myocardiums in HVM, which would be mediated by the enhancement of I_Ca-L.