CD4+TEM cells drive the progression from acute myocarditis to dilated cardiomyopathy in CVB3-induced BALB/c mice.

Acute viral myocarditis can progress to chronic myocarditis leading to dilated cardiomyopathy (DCM). Persistent CD4+ T-cell-mediated autoimmunity triggered by infection plays a critical role in this progression. Increasing evidence demonstrates that effector memory CD4+T (CD4+TEM) cells, a subset of memory CD4+ T cells, are crucial pathogenic mediators of many autoimmune diseases. However, the role of CD4+TEM cells during the progression from acute viral myocarditis to DCM remains unknown. In this study, we observed an increase in CD4+TEM cells both in the periphery and the heart, and memory CD4+ T cells were the predominant sources of IL-17A and IFN-γ among inflamed heart-infiltrating CD4+ T cells during the progression from acute myocarditis to chronic myocarditis and DCM in CVB3-induced BALB/c mice. Moreover, splenic CD4+TEM cells sorted from DCM mice induced by CVB3 were found to respond to cardiac self-antigens ex vivo. Additionally, adoptive transfer experiments substantiated their pathogenic impact, inducing sustained myocardial inflammation, tissue fibrosis, cardiac injury, and impairment of cardiac systolic function in vivo. Our findings illustrate that long-lived CD4+TEM cells are important contributors to the progression from acute viral myocarditis into DCM.

Cardiac macrophages undergo dynamic changes after coxsackievirus B3 infection and promote the progression of myocarditis.

Although most patients with acute viral myocarditis recover spontaneously, some patients progress to heart failure. Perturbations in innate immunity may partially explain the heterogeneity of clinical outcomes. As the most abundant immune cells in the heart, cardiac macrophages have heterogeneous origins, including embryonic-derived resident macrophages (ResMϕs) and monocyte-derived macrophages (MoMFs). However, the time course change and role of cardiac macrophage subsets has not been fully explored. In the present study, we found that BALB/c mice had prolonged MoMF accumulation and low proportions of ResMϕs that could not be restored to normal levels. MoMFs of BALB/c mice generally exhibit an M1-dominant functional phenotype. Moreover, the preferential depletion of MoMF by a C-C chemokine receptor type 2 (CCR2) inhibitor resulted in improved acute myocarditis and chronic fibrosis, as well as the recovery of ResMϕs number and reduced CD4+ T cell expansion. Hence, immunomodulatory therapy that targets the balance among cardiac macrophages and modulates their function is expected to prevent the progression of cardiac injury to overt heart failure and improve adverse outcomes.

The absence of B cells disrupts splenic and myocardial Treg homeostasis in coxsackievirus B3-induced myocarditis.

Although B cells are essential for humoral immunity and show noteworthy immunomodulatory activity through antibody-independent functions, the role of B cells in regulating Treg cell responses remains controversial. Tregs (CD4+CD25+Foxp3+) are considered to play an immunoprotective role in viral myocarditis (VMC) by controlling autoimmune effector T cells. Here, we proved that B-cell knockout can not only lead to significant reductions in Tregs in the spleen, blood, and heart of VMC mice but also decrease the activation and immune function of splenic Tregs, which was reversed by adoptive transfer of B cells; the transcription levels of TGF-ß and Foxp3 in the myocardium were also significantly reduced. B-cell depletion by anti-CD20 impaired the anti-inflammatory function of splenic Tregs and the homeostasis of myocardial Tregs population. Moreover, B cells can convert CD4+CD25- T cells into Foxp3+ and Foxp3-, two functionally suppressive Treg subgroups. Although the reduction in myocardial inflammation in BKO mice indicates that B cells may play a proinflammatory role, the beneficial side of B cells cannot be ignored, that is, to control autoimmunity by maintaining Treg numbers. The results observed in the animal model of VMC highlight the potential harm of rituximab in the nonselective depletion of B cells in clinical applications.

The abnormal distribution of peripheral B1 cells and transition B cells in patients with idiopathic dilated cardiomyopathy: a pilot study.

BACKGROUND: The aberrant distribution of peripheral B cell subsets is associated with the pathogenesis of a variety of inflammatory and autoimmune diseases. However, the distribution of peripheral B cell subsets in patients with idiopathic dilated cardiomyopathy (DCM) remains to be elucidated. METHODS: Twenty-seven patients with idiopathic DCM (DCM group), 18 control patients with heart failure (HF group) and 21 healthy individuals (HC group) were included in this study. Peripheral B cell subsets were analysed using multicolour flow cytometry. The plasma ß1 adrenergic receptor (ß1-AR) autoantibody titre was determined using ELISA. Additionally, clinical features were also collected. RESULTS: Compared with the HF and HC groups, the percentage of B1 cells was significantly decreased, whereas the percentage of transitional B cells (Tr) was significantly increased in the DCM group. Notably, the percentage of B1 cells was significantly lower in patients with ß1-AR autoantibody-positive DCM than in ß1-AR autoantibody-negative patients. The correlation analysis showed that the percentage of B1 cells was negatively correlated with N-terminal pro-brain natriuretic peptide (NT-proBNP) levels and positively correlated with the left ventricular ejection fraction in patients with DCM. CONCLUSION: As shown in the present study, the percentage of B1 cells in the peripheral blood of patients with idiopathic DCM is abnormally decreased, especially in ß1-AR autoantibody-positive patients, while the percentage of Tr cells is significantly increased, indicating that B1 cells and Tr cells may be implicated in the pathogenesis of idiopathic DCM. The decrease in the percentage of B1 cells is directly related to the severity of DCM.

The Role of B Cells in Regulation of Th Cell Differentiation in Coxsackievirus B3-Induced Acute Myocarditis.

Viral myocarditis (VMC) is the major cause of sudden death in adolescents. To date, no effective treatment has been identified for VMC. Studies have shown that T helper (Th) cells such as Th1, Th2, Th17, and Th22 cells are involved in the pathogenesis of VMC. However, the role of B cells and their impact on Th cells in VMC is unclear. In this study, we investigated the role of B cells in Th cell differentiation in myocardial damage in an animal model of VMC. C57BL/6 mice were infected with Coxsackievirus B3 (CVB3) intraperitoneally or injected with phosphate-buffered saline as a control condition. At day 7, samples from these mice were analyzed by histology, ELISA, flow cytometry, and gene expression assays. We found that TNF-α-, IL-6-, and IL-17-producing B cell numbers were significantly increased, while IL-4-producing B cell population was significantly reduced in acute VMC. Furthermore, we performed B cell knockout (BKO), SCID, and SCID+B cells reconstitution experiments. We found that BKO alleviated the cardiac damage following CVB3 infection, may hamper the differentiation of Th1 and Th17 cells, may promote the differentiation of Th2 cells, and proved ineffective for the differentiation of Th22 cells. In contrast, SCID+B cells reconstitution experiment exacerbated the cardiac damage. Ex vivo studies further revealed that B cells promote the differentiation of Th1 and Th17 cells and inhibit the differentiation of Th2 cells. Our study shows that B cells are activated and have strong abilities of antigen presentation and producing cytokines in VMC; B cells not only play a pathogenic role in VMC independent of T cells but also promote Th1 and Th17 cell differentiation, and hamper Th2 cell differentiation in VMC.

Increased circulating interleukin 10-secreting B cells in patients with dilated cardiomyopathy.

OBJECTIVES: Regulatory B cells (Bregs) have recently been implicated in the pathogenesis of autoimmune diseases. However, their role in the pathogenesis of dilated cardiomyopathy (DCM) remains uncertain. We examined the levels of circulating interleukin 10 (IL-10)-secreting Bregs in patients with DCM. METHODS: The frequency of CD19+IL-10+-, CD19+CD5+-, CD19+CD5+CD1d+-, and CD19+CD5+CD1d+IL-10+-B cells in peripheral blood from DCM patients, heart failure (HF) control patients, and healthy controls (HCs) were analyzed by flow cytometry. RESULTS: DCM and HF control patients showed significantly elevated heart rate, increased left ventricular end-diastolic and left ventricular end-systolic diameters, higher levels of serum brain natriuretic peptide and reduced left ventricular ejection fraction, compared to subjects in the HC group. DCM patients showed significantly elevated levels of circulating CD19+IL-10+-, CD19+CD5+-, CD19+CD5+CD1d+-, and CD19+CD5+CD1d+IL-10+-B cells than HF control and HC patients (all P < 0.05). CONCLUSIONS: DCM patients exhibited elevated peripheral blood IL-10-secreting B cell levels, suggesting that IL-10-secreting B cells may play an important role in the pathogenesis of DCM.

IL-10-producing B cells involved in the pathogenesis of Coxsackie virus B3-induced acute viral myocarditis.

BACKGROUND: Interleukin-10 (IL-10)-producing B cells, a subset of regulatory B cells, play critical roles in autoimmune and infectious diseases. However, the role of IL-10-producing B cells in acute viral myocarditis (AVMC) remains unknown. METHODS: BALB/c mice were intraperitoneally (i. p.) infected with coxsackievirus B3 (CVB3) to establish AVMC models (AVMC group), while control mice (control group) were treated with phosphate-buffered saline (PBS) i. p. According to the time after injection, the AVMC group mice or control group mice were randomly separated into 1 week and 2 week subgroup. Myocardial histopathological changes were observed by hematoxylin and eosin staining and the frequency of splenic IL-10-producing B cells was measured by flow cytometry. RESULTS: Histopathologic examination of heart tissues showed that mice infected with CVB3 developed AVMC. Compared with control group, the frequency of splenic IL-10-producing B cells was increased significantly in the AVMC group, with the 1 week AVMC subgroup (3.58 ± 0.47%) higher than the 2 week AVMC subgroup (2.50 ± 0.42%) (all P < 0.05). CONCLUSIONS: IL-10-producing B cells are increased in CVB3-induced AVMC, indicating that IL-10-producing B cells may play an important role in the pathogenesis of CVB3-induced AVMC.

IL-22-producing Th22 cells play a protective role in CVB3-induced chronic myocarditis and dilated cardiomyopathy by inhibiting myocardial fibrosis.

BACKGROUND: A new subset of T helper (Th) cells, named IL-22-producing Th22 cells, was identified recently. Th22 cells have been implicated in immunity and inflammation. However, the role of these cells in the progression from acute viral myocarditis (AVMC) to dilated cardiomyopathy (DCM) and myocardial fibrosis remains unknown. METHODS: BALB/c mice were repeatedly i.p. infected with Coxsackie virus B3 (CVB3) to establish models of AVMC, chronic myocarditis and DCM. On week 2, 12 and 24 post initial injection, the percentage of splenic Th22 cells, the levels of plasma IL-22, cardiac IL-22 receptor (IL-22R) expression, and indicators of myocardial fibrosis were measured. Further, mice with AVMC and chronic myocarditis were treated with an anti-IL-22 neutralizing antibody (Ab). The collagen volume fraction (CVF), the percentage of splenic Th22 cells, plasma IL-22 levels, cardiac IL-22R expression and indicators of myocardial fibrosis were then monitored. RESULTS: Compared to control mice at the same time points, AVMC, chronic myocarditis and DCM mice have higher percentage of splenic Th22 cells, higher plasma IL-22 levels, increased cardiac IL-22R, as well as increased collagen typeI-A1 (COL1-A1), collagen type III-A1 (COL3-A1) and matrix metalloproteinase-9 (MMP9) expression. However, the expression of tissue inhibitor of metalloproteinase-1(TIMP-1) was decreased. Treatment of AVMC and chronic myocarditis mice with an anti-IL-22 Ab decreased the survival rate and exacerbated myocardial fibrosis. The percentage of splenic Th22 cells, plasma IL-22 levels and cardiac IL-22R expression also decreased in anti-IL-22 Ab treatment group as compared to IgG and PBS treated groups of AVMC and chronic myocarditis mice. Moreover, increased expression of COL1-A1, COL3-A1, MMP9 but decreased expression of TIMP-1 were observed in anti-IL-22 Ab mouse group. CONCLUSIONS: Th22 cells play an important role in the pathogenesis of CVB3-induced mouse chronic myocarditis and DCM. IL-22 is a myocardium-protective cytokine by inhibiting myocardial fibrosis. Therefore, Th 22 cells may be considered as potential therapeutic targets for DCM.