Effects of in vivo administration of anti-B7-1/B7-2 monoclonal antibodies on the survival of mice with chronic ongoing myocarditis caused by Coxsackievirus B3

Expression of CD80 and CD86 on B cells during coxsackievirus B3-induced acute myocarditis

Introduction

The pathogenesis of viral myocarditis (VMC) is unclear, but many studies have shown that VMC is associated with an excessive immune response. CD80 and CD86 are important costimulatory molecules that play a critical role in autoimmunity. However, whether CD80+/CD86+ B cells participate in the pathogenesis of acute VMC is unknown.

Material and methods

Male C57BL/6 mice were infected by intraperitoneal injection with coxsackievirus B3 (CVB3) to establish a VMC model. Control mice were administered phosphate-buffered saline intraperitoneally. At one week and two weeks post injection, histopathological changes in heart tissue were assessed with haematoxylin and eosin staining. The frequency of splenic CD80+/CD86+ B cells was measured with flow cytometry.

Results

The frequency of CD80+ B cells was significantly increased in VMC, while the frequency of CD86+ B cells was significantly decreased. Furthermore, the frequency of CD80+ B cells related to the severity of VMC.

Conclusions

These data show that CD80+/CD86+B cells are involved in the pathogenesis of VMC, with CD80+B cells being more important than CD86+B cells.

Intricacies of cardiac damage in coxsackievirus B3 infection: implications for therapy

Heart disease is the leading cause of death in humans, and myocarditis is one predominant cause of heart failure in young adults. Patients affected with myocarditis can develop dilated cardiomyopathy (DCM), a common reason for heart transplantation, which to date is the only viable option for combatting DCM. Myocarditis/DCM patients show antibodies to coxsackievirus B (CVB)3 and cardiac antigens, suggesting a role for CVB-mediated autoimmunity in the disease pathogenesis; however, a direct causal link remains to be determined clinically. Experimentally, myocarditis can be induced in susceptible strains of mice using the human isolates of CVB3, and the disease pathogenesis of postinfectious myocarditis resembles that of human disease, making the observations made in animals relevant to humans. In this review, we discuss the complex nature of CVB3-induced myocarditis as it relates to the damage caused by both the virus and the host's response to infection. Based on recent data we obtained in the mouse model of CVB3 infection, we provide evidence to suggest that CVB3 infection accompanies the generation of cardiac myosin-specific CD4 T cells that can transfer the disease to naïve recipients. The therapeutic implications of these observations are also discussed.

Amelioration of myocarditis by statin through inhibiting cross-talk between antigen presenting cells and lymphocytes in rats

Statins, inhibitors of 3-hydroxy-3-methylglutary-coenzyme A (HMG-CoA) reductase, have been recognized as a new type of immunomodulator and reported to have anti-inflammatory effect. To investigate the effect of simvastatin, a lipophilic statin, on myocarditis, we explored whether simvastatin is able to inhibit experimental autoimmune myocarditis (EAM) and adoptive transfer of EAM in rats. We found that administration of simvastatin not only interfered with the development of EAM, but also inhibited the transfer. Antigen presenting cells (APCs) were proved to be important for the development of EAM. The ability of myocarditic splenocytes to transfer myocarditis was enhanced after co-culture with APCs. During co-culture of the myocarditic splenocytes and the APCs, simvastatin not only decreased percentages of CD28 expression in CD4-positive myocarditic splenocytes, and CD80 and CD86 expressions in APCs, but also inhibited the production of tumor necrosis factor (TNF)-partial differential in the CD4-positive myocarditic splenocytes and the APCs. These results indicate that simvastatin was able to ameliorate EAM through the inhibition of cross-talk between lymphocytes and APCs, suggesting beneficial role of simvastatin in the treatment of autoimmune myocarditis.

Critical contribution of CD28-CD80/CD86 costimulatory pathway to protection from Trypanosoma cruzi infection

The CD28-CD80/CD86-mediated T-cell costimulatory pathway has been variably implicated in infectious immunity. In this study, we investigated the role of this costimulatory pathway in resistance to Trypanosoma cruzi infection by using CD28-deficient mice and blocking antibodies against CD80 and CD86. CD28-deficient mice exhibited markedly exacerbated T. cruzi infection, as evidenced by unrelenting parasitemia and 100% mortality after infection with doses that are nonlethal in wild-type mice. The blockade of both CD80 and CD86 by administering specific monoclonal antibodies also exacerbated T. cruzi infection in wild-type mice. Splenocytes from T. cruzi-infected, CD28-deficient mice exhibited greatly impaired gamma interferon production in response to T. cruzi antigen stimulation in vitro compared to those from infected wild-type mice. The induction of T. cruzi antigen-specific CD8(+) T cells was also impaired in T. cruzi-infected, CD28-deficient mice. In addition to these defects in natural protection against T. cruzi infection, CD28-deficient mice were also defective in the induction of CD8(+)-T-cell-mediated protective immunity against T. cruzi infection by DNA vaccination. These results demonstrate, for the first time, a critical contribution of the CD28-CD80/CD86 costimulatory pathway not only to natural protection against primary T. cruzi infection but also to DNA vaccine-induced protective immunity to Chagas' disease.

[Neonatal enterovirus myocarditis]

Enterovirus infections in neonates are difficult to diagnose. Diphasic pattern and possibly fatal myocarditis must be anticipated.

CASE REPORT

A 14-day-old girl had presented a heart failure after an initial episode of gastroenteritis and supraventricular tachycardia. Investigation demonstrated global myocardial dysfunction. Diagnosis of neonatal enterovirus myocarditis was made by polymerase chain reaction detection of viral genome. Heart failure was controlled with medical treatment.

CONCLUSION

Enterovirus myocarditis is typically a biphasic illness. Rapid diagnosis of enteroviral infection in neonatal period may be made by polymerase chain reaction detection of viral genome. There is anecdoctal evidence that immunoglobulin infusions may improve outcome.

Role of Fas/FasL pathway in the activation of infiltrating cells in murine acute myocarditis caused by Coxsackievirus B3

OBJECTIVES

This study was designed to investigate the roles of Fas/FasL pathway in myocardial damage in murine acute myocarditis caused by Coxsackie virus B3 (CVB3).

BACKGROUND

Cardiac myocyte apoptosis rarely occurs in murine acute myocarditis caused by CVB3. Fas/FasL belong to the tumor necrosis factor receptor/ligand superfamily of costimulatory molecules and are known to play a critical role in the induction of apoptosis, as well as in the cytotoxicty mediated by T-cells and natural killer cells.

METHODS

We first analyzed the expression of Fas on cardiac myocytes in vivo and in vitro. Second, we examined the development of myocardial damage, in C3H/He mice treated with an anti-FasL monoclonal antibody (mAb), and in C3H/He-lpr/lpr mice and C3H/He-gld/gld mice infected with CVB3. Third, to investigate the effects of anti-FasL mAb treatment on the activation of the infiltrating cells, we examined the expression of interferon (IFN)-gamma and interleukin (IL)-2 as activation markers in the heart of mice by semiquantitative polymerase chain reaction.

RESULTS

Fas was markedly induced on cardiac myocytes with acute myocarditis. Myocardial inflammation was decreased in mice treated with anti-Fas L mAb, C3H/He-lpr/lpr mice and C3H/He-gld/gld mice. Anti-FasL mAb-treatment also decreased the expression of IFN-gamma, IL-2, inducible nitric oxide synthase and CVB3 genomes in myocardial tissue.

CONCLUSIONS

Our findings strongly suggested that the Fas/FasL pathway played a critical role in the development of massive myocardial necrosis through activation of infiltrating cells, and raise the possibility of immunotherapy by blocking the Fas/FasL pathway to prevent myocardial damage and improve the prognosis of patients with viral myocarditis.

Restricted usage of T-cell receptor Vgamma-Vdelta genes and expression of costimulatory molecules in Takayasu's arteritis

To further investigate the immunological mechanisms involved in Takayasu's arteritis, we analyzed the T-cell receptor (TCR) Vgamma and Vdelta gene usage by infiltrating gammadelta T-cells and the expression of costimulatory molecules B7-1, B7-2, CD40, CD27 ligand (CD27L), CD30L, OX40L in the arterial tissue of a patient with Takayasu's arteritis. We found that the repertoires of TCR Vgamma as well as Vdelta gene transcripts of the infiltrating cells were restricted as compared with those of peripheral blood lymphocytes from a patient with Takayasu's arteritis. This strongly suggests that gammadelta T-cells as well as alphabeta T-cells, as we previously reported, were specifically involved in the pathogenesis of Takayasu's arteritis. We also found that B7-1, B7-2, CD40, CD27L, CD30L, and OX40L were expressed in the arterial tissue, suggesting the roles for these costimulatory molecules in T-cell-mediated vascular injury in Takayasu's arteritis. Our findings strongly support the involvement of T-cell-mediated immunological mechanisms in the pathogenesis of Takayasu's arteritis.

Expression of tumour necrosis factor (TNF) receptor/ligand superfamily co-stimulatory molecules CD40, CD30L, CD27L, and OX40L in murine hearts with chronic ongoing myocarditis caused by coxsackie virus B3

T-cell-mediated myocardial damage has been shown to be involved in acute myocarditis and dilated cardiomyopathy. It is necessary for T-cells to receive a co-stimulatory signal as well as the main signal through the T-cell receptor for antigen-specific T-cell activation to occur. To investigate the roles of the co-stimulatory molecules CD40/CD40L, CD30/CD30L, CD27/CD27L, and OX40/OX40L, which belong to the tumour necrosis factor (TNF) receptor/ligand superfamily, in the development of chronic ongoing myocarditis, the expression of CD40, CD30L, CD27L, and OX40L was analysed in the hearts of A/J mice with myocarditis induced by Coxsackie virus B3 (CVB3). The expression of CD40L, CD30, CD27, and OX40 was also examined on the infiltrating cells. Furthermore, the induction of CD40, CD30L, CD27L, and OX40L was evaluated on cultured cardiac myocytes treated with interferon (IFN)-gamma. CVB3-induced myocarditis resulted in the induction of CD40 and CD30L on the surface of cardiac myocytes. Induction of CD40 and CD30L on cardiac myocytes was confirmed by treatment with IFN-gamma in vitro. CD27L and OX40L were expressed on cardiac myocytes in vivo and in vitro. The expression of CD27L and OX40L on cardiac myocytes was increased, at least partly, by CVB3-induced myocarditis in vivo. Many infiltrating cells expressed CD27 and OX40, whereas much smaller numbers expressed CD40L and CD30. The induction of these molecules, especially CD40 and CD30L, on cardiac myocytes strongly suggests that cardiac myocytes may co-stimulate T-cells and induce cytokine production by T-cells and humoral immune responses. This may play an important role in the pathogenesis of the resulting myocardial damage.