Expression of tumour necrosis factor (TNF) ligand superfamily co-stimulatory molecules CD30L, CD27L, OX40L, and 4-1BBL in murine hearts with acute myocarditis caused by Coxsackievirus B3

OX40 and 4-1BB downregulate Kaposi’s sarcoma-associated herpesvirus replication in lymphatic endothelial cells, but 4-1BB and not OX40 inhibits viral replication in B-cells

Kaposi’s sarcoma-associated herpesvirus (KSHV) belongs to the human gammaherpesvirus subfamily and is associated with malignancies of endothelial origin (Kaposi’s sarcoma, KS) and B-cell origin [primary effusion lymphoma (PEL) and multicentric Castleman’s disease (MCD)]. Viral lytic replication is known to be required for KS and MCD. As KSHV-related tumours mostly develop in human subjects when the immune system is compromised by immunosuppressive regimen, human immunodeficiency virus infection or some genetic deficiencies, KSHV-specific immune responses are believed to be important in the control of KSHV replication. However, analysis of the roles of immune cells in viral pathogenesis has been difficult due to the lack of an adequate animal model. Recently, congenital OX40 deficiency, as determined by genome-wide exome sequencing, was shown to be associated with aggressive childhood KS in a patient, suggesting that disrupted OX40–OX40L interactions might be implicated in disease development. Here, we report that interaction of recombinant OX40 protein with OX40L expressed on endothelial cells severely impaired KSHV lytic replication. Furthermore, 4-1BB–4-1BBL interactions were also capable of efficiently inhibiting viral replication in B-cells and endothelial cells. To the best of our knowledge, this is the first direct evidence that ligation of tumour necrosis factor superfamily members and their cognate receptors is important for the control of viral lytic replication. These data are likely to pave the way for the development of KSHV-specific therapies for KS and MCD, in which viral lytic replication is a disease-determining factor.

Involvement of the 4-1BB/4-1BBL pathway in control of monocyte numbers by invariant NKT cells

4-1BB is expressed on invariant (i)NKT cells, but its role is unclear. We showed previously that iNKT cells are involved in control of monocyte numbers during influenza A virus (IAV) infection and now question the role of the 4-1BB costimulatory pathway in the cross-talk between these cells. We found that iNKT cells and monocytes interact to promote expression of 4-1BB and 4-1BBL, respectively. Blockade of 4-1BB/L pathway under resting coculture conditions increased apoptosis of iNKT cells and monocytes. However, activation of iNKT cells overrides this survival signal, causing marked apoptosis of monocytes independent of 4-1BB/L. Blocking 4-1BBL in alpha-galactosylceramide-activated iNKT-monocyte cocultures reduced iNKT proliferation and abrogated monocytic IL-12 production. In vivo, expression of 4-1BB and 4-1BBL is increased on iNKT cells and Ly6C(hi) monocytes, respectively, during IAV infection, and there were lower frequencies of apoptosing Ly6C(hi) monocytes in the blood of iNKT knockout mice and higher numbers of monocytes in lungs compared with infected wild-type mice. Adoptive transfer of iNKT cells into the lungs of these mice reduced lung Ly6C(hi) monocytes levels, even when iNKT cells were preincubated with 4-1BB blocking Abs. These findings suggest that under resting conditions, 4-1BB/L engagement during iNKT-monocyte interaction promotes survival of these cells. When iNKT cells are activated, whether by alpha-galactosylceramide or during IAV infection, iNKT cells induced apoptosis of monocytes via a 4-1BB/L-independent mechanism, reducing monocyte numbers. 4-1BB/L costimulation amplified monocyte-mediated proliferation of iNKT cells, indirectly providing a method for monocytes to control their own numbers during infection.

The effect of CD137-CD137 ligand interaction on phospholipase C signaling pathway in human endothelial cells

We previously reported the emerging role of CD137-CD137L interaction in inflammation and atherosclerosis. The mechanism of CD137-CD137L interaction may be related to a variety of signaling pathways. The most important signaling pathway involves the activation of phospholipase C(PLC) which induces the diacylglycerol-protein kinase C(DAG-PKC) and the inositol trisphosphate-intracellular free calcium (IP3-[Ca(2+)]i) pathway. In the current study, we investigated whether CD137-CD137L interaction can stimulate the PLC signaling pathway in human umbilical vein endothelial cells (HUVEC). The diacylglycerol (DAG) and inositol trisphosphate (IP3) levels in HUVEC were measured by radioenzymatic assay. The activity of protein kinase (PKC) was detected by its ability to transfer phosphate from [γ-(32)P]ATP to lysine-rich histone. The [Ca(2+)]i concentrations were measured by flow cytometric analysis. The DAG level and PKC activity were increased in a concentration-dependent, biphasic manner in HUVEC induced by anti-CD137. PKC activity was mainly in the cytosol at rest, and then translocated to the membrane when stimulated by anti-CD137. Similarly, rapid IP3 formation induced by anti-CD137 coincided with the peak of the DAG level. Moreover, anti-CD137 induced peak [Ca(2+)]i responses including the rapid transient phase and the sustained phase. However, anti-CD137L suppressed the activation of the DAG-PKC and IP3-[Ca(2+)]i signaling pathway, which was stimulated by anti-CD137 in HUVEC. In conclusion, the data suggested that CD137-CD137L interaction induces robust activation of the PLC signaling pathway in HUVEC.

Differential requirement for CD70 and CD80/CD86 in dendritic cell-mediated activation of tumor-tolerized CD8 T cells

A major obstacle to efficacious T cell-based cancer immunotherapy is the tolerizing-tumor microenvironment that rapidly inactivates tumor-infiltrating lymphocytes. In an autochthonous model of prostate cancer, we have previously shown that intratumoral injection of Ag-loaded dendritic cells (DCs) delays T cell tolerance induction as well as refunctionalizes already tolerized T cells in the tumor tissue. In this study, we have defined molecular interactions that mediate the effects of DCs. We show that pretreating Ag-loaded DCs with anti-CD70 Ab abolishes the ability of DCs to delay tumor-mediated T cell tolerance induction, whereas interfering with 4-1BBL, CD80, CD86, or both CD80 and CD86 had no significant effect. In contrast, CD80(-/-) or CD80(-/-)CD86(-/-) DCs failed to reactivate already tolerized T cells in the tumor tissue, whereas interfering with CD70 and 4-1BBL had no effect. Furthermore, despite a high level of programmed death 1 expression by tumor-infiltrating T cells and programmed death ligand 1 expression in the prostate, disrupting programmed death 1/programmed death ligand 1 interaction did not enhance T cell function in this model. These findings reveal dynamic requirements for costimulatory signals to overcome tumor-induced tolerance and have significant implications for developing more effective cancer immunotherapies.

T-cell intrinsic effects of GITR and 4-1BB during viral infection and cancer immunotherapy

GITR [glucocorticoid inducible tumor necrosis factor receptor (TNFR)-related protein] and 4-1BB are costimulatory TNFR family members that are expressed on regulatory and effector T cells as well as on other cells of the immune system. Here we discuss the role of GITR and 4-1BB on T cells during viral infections and in cancer immunotherapy. Systemic treatment with agonistic anti-4-1BB antibody leads to a number of immune system abnormalities, and clinical trials of anti-4-1BB have been terminated. However, other modes of 4-1BB ligation may be less toxic. To date, similar toxicities have not been reported for anti-GITR treatment of mice, although anti-GITR antibodies can exacerbate mouse autoimmune models. Intrinsic effects of GITR and 4-1BB on effector T cells appear to predominate over their effects on other cell types in some models. Despite their similarities in enhancing T-cell survival, 4-1BB and GITR are clearly not redundant, and both pathways are required for maximal CD8(+) T-cell responses and mouse survival following severe respiratory influenza infection. GITR uses TNFR-associated factor (TRAF) 2 and TRAF5, whereas 4-1BB recruits TRAF1 and TRAF2 to mediate survival signaling in T cells. The differential use of signaling adapters combined with their differential expression may explain the non-redundant roles of GITR and 4-1BB in the immune system.

The role of costimulatory receptors of the tumour necrosis factor receptor family in atherosclerosis

Atherosclerosis is a chronic inflammatory disease that is mediated by both the innate and adaptive immune responses. T lymphocytes, that together with B cells are the cellular effectors of the adaptive immune system, are currently endowed with crucial roles in the development and progression of atherosclerosis. Costimulatory receptors are a class of molecules expressed by T lymphocytes that regulate the activation of T cells and the generation of effector T-cell responses. In this review we present the roles of costimulatory receptors of the tumour necrosis factor receptor (TNFR) superfamily in atherosclerosis and discuss the implications for future therapies that could be used to specifically modulate the immune response of pathogenic T cells in this disease.

Expression of CD137 in the cerebral artery after experimental subarachnoid hemorrhage in rats: a pilot study

Inflammation and immunity play a crucial role in the pathogenesis of cerebral vasospasm after subarachnoid hemorrhage (SAH). CD137 is recognized as an independent costimulatory molecule of T cells and activator of monocytes. A growing body of evidence indicates that CD137 is vital for inflammation and immunity. Therefore, this study aimed to investigate the expression of CD137 in the basilar artery in a rat SAH model and to clarify the potential role of CD137 in cerebral vasospasm. A total of 107 rats were randomly divided into four groups: control group; day 3, day 5, and day 7 groups. Day 3, day 5, and day 7 groups were all SAH groups. The animals in SAH groups were subjected to injection of autologous blood into cisterna magna twice on day 0 and day 2 and were sacrificed on days 3, 5, and 7, respectively. Cross-sectional area of basilar artery was measured and the CD137 expression was assessed by quantitative real-time PCR, Western blot and immunohistochemistry. The cross-sectional area of basilar artery was found to be 57,944±5581μm(2) in control group, 26,100±2639μm(2) in day 3, 19,723±2412μm(2) in day 5, and 28,800±2980μm(2) in day 7 group, respectively. The basilar artery exhibited vasospasm after SAH and became more severe on day 5. The elevated mRNA and protein of CD137 were detected after SAH and peaked on day 5. CD137 is increasingly expressed in a parallel time course to the development of cerebral vasospasm in a rat experimental model of SAH. These findings indicate the possible role of CD137 in the pathogenesis of cerebral vasospasm after SAH.

Nasal cardiac myosin peptide treatment and OX40 blockade protect mice from acute and chronic virally-induced myocarditis

Myocarditis poses a severe health problem, can lead to dilated cardiomyopathy (DCM) and death, and is thought to be triggered by infections. Enteroviruses such as Coxsackie virus B3 (CVB3) have been implicated as a culprit, since they can cause acute and chronic heart disease in susceptible mice. CVB was detected in human cardiac myocytes in some cases, whereas acute CVB infection was thought to have caused death. Here we studied, whether nasal administration of cardiac myosin (CM) major histocompatibility class (MHC) II peptides CM₉₄₇-₉₆₀ and CM₇₃₅-₇₄₇ and OX40 blockade would be able to ameliorate immunopathology and heart disease in BALB/C mice infected with CVB3. We found that nasal CM-peptide prophylactic treatment significantly reduced myocarditis and mortality by enhancing Treg and IL-10 induction and that blockade of OX40 signaling could reduce heart inflammation when administered late during pathogenesis. Altogether, these results chart the way for novel prevention and intervention strategies for viral myocarditis.

Proteomic characterization of HIV-modulated membrane receptors, kinases and signaling proteins involved in novel angiogenic pathways

Background

Kaposi's sarcoma (KS), hemangioma, and other angioproliferative diseases are highly prevalent in HIV-infected individuals. While KS is etiologically linked to the human herpesvirus-8 (HHV8) infection, HIV-patients without HHV-8 and those infected with unrelated viruses also develop angiopathies. Further, HIV-Tat can activate protein-tyrosine-kinase (PTK-activity) of the vascular endothelial growth factor receptor involved in stimulating angiogenic processes. However, Tat by itself or HHV8-genes alone cannot induce angiogenesis in vivo unless specific proteins/enzymes are produced synchronously by different cell-types. We therefore tested a hypothesis that chronic HIV-replication in non-endothelial cells may produce novel factors that provoke angiogenic pathways.

Methods

Genome-wide proteins from HIV-infected and uninfected T-lymphocytes were tested by subtractive proteomics analyses at various stages of virus and cell growth in vitro over a period of two years. Several thousand differentially regulated proteins were identified by mass spectrometry (MS) and >200 proteins were confirmed in multiple gels. Each protein was scrutinized extensively by protein-interaction-pathways, bioinformatics, and statistical analyses.

Results

By functional categorization, 31 proteins were identified to be associated with various signaling events involved in angiogenesis. 88% proteins were located in the plasma membrane or extracellular matrix and >90% were found to be essential for regeneration, neovascularization and angiogenic processes during embryonic development.

Conclusion

Chronic HIV-infection of T-cells produces membrane receptor-PTKs, serine-threonine kinases, growth factors, adhesion molecules and many diffusible signaling proteins that have not been previously reported in HIV-infected cells. Each protein has been associated with endothelial cell-growth, morphogenesis, sprouting, microvessel-formation and other biological processes involved in angiogenesis (p = 10^-4 to 10^-12). Bioinformatics analyses suggest that overproduction of PTKs and other kinases in HIV-infected cells has suppressed VEGF/VEGFR-PTK expression and promoted VEGFR-independent pathways. This unique mechanism is similar to that observed in neovascularization and angiogenesis during embryogenesis. Validation of clinically relevant proteins by gene-silencing and translational studies in vivo would identify specific targets that can be used for early diagnosis of angiogenic disorders and future development of inhibitors of angiopathies. This is the first comprehensive study to demonstrate that HIV-infection alone, without any co-infection or treatment, can induce numerous "embryonic" proteins and kinases capable of generating novel VEGF-independent angiogenic pathways.

Immune regulation by 4-1BB and 4-1BBL: complexities and challenges

SUMMARY

The tumor necrosis factor receptor family member 4-1BB plays a key role in the survival of activated and memory CD8(+) T cells. Depending on the disease model, 4-1BB can participate at different stages and influence different aspects of the immune response, likely due to the differential expression of receptor and ligand relative to other costimulatory molecules. Studies comparing mild versus severe influenza infection of mice suggest that the immune system uses inducible receptors such as 4-1BB to prolong the immune response when pathogens take longer to clear. The expression of 4-1BB on diverse cell types, evidence for bidirectional as well as receptor-independent signaling by 4-1BBL, the unexpected hyperproliferation of 4-1BB-deficient T cells, and complex effects of agonistic anti-4-1BB therapy have revealed additional roles for the 4-1BB/4-1BBL receptor/ligand pair in the immune system. In this review, we discuss these diverse roles of 4-1BB and its ligand in the immune response, exploring possible mechanisms for the observed complexities and implications for therapeutic applications of 4-1BB/4-1BBL.

CD137-CD137 Ligand Interactions in Inflammation

The main stream of CD137 studies has been directed to the function of CD137 in CD8⁺ T-cell immunity, including its anti-tumor activity, and paradoxically the immunosuppressive activity of CD137, which proves to be of a great therapeutic potential for animal models of a variety of autoimmune and inflammatory diseases. Recent studies, however, add complexes to the biology of CD137. Accumulating is evidence supporting that there exists a bidirectional signal transduction pathway for the CD137 receptor and its ligand (CD137L). CD137/CD137L interactions are involved in the network of hematopoietic and nonhematopoietic cells in addition to the well characterized antigen-presenting cell-T cell interactions. Signaling through CD137L plays a critical role in the differentiation of myeloid cells and their cellular activities, suggesting that CD137L signals trigger and sustain inflammation. The overall consequence might be that the amplified inflammation by CD137L enhances the T-cell activity together with CD137 signals by upregulating costimulatory molecules, MHC molecules, cell adhesion molecules, cytokines, and chemokines. Solving this outstanding issue is urgent and will have an important clinical implication.

Attenuation of experimental autoimmune myocarditis by blocking T cell activation through 4-1BB pathway

4-1BB, a member of the tumor necrosis factor receptor (TNFR) family, binds the 4-1BB ligand (4-1BBL), works as a costimulatory molecule, and regulates T cell-mediated immune responses. Although inflammation is an essential pathological feature of myocarditis, the role of 4-1BB in experimental autoimmune myocarditis (EAM) remains unclear. Lewis rats were immunized on day 0 with purified porcine cardiac myosin to establish EAM. 4-1BB-immunoglobulin (4-1BBIg) was administered intraperitoneally (n=6) a total of 9 times (3 times per week). Rats were killed on day 21 to study effects of 4-1BB/4-1BBL pathway blockade. For controls, isotype-matched human IgG was administered in other EAM rats (n=6). Histologic and echocardiographic examination showed development of EAM attenuated by 4-1BBIg. Suppression of mRNA expression for IL-1alpha, IL-1beta, IL-4, IL-6, and TNF-alpha was noted in the heart tissue treated with 4-1BBIg. Treatment with 4-1BBIg reduced production of Th1-type cytokines, and inhibited T cell proliferation in vitro. In the 4-1BB signaling pathway in splenocytes, 4-1BBIg suppressed JNK, p38, and IkappaB activity but not that of ERK1/2. Blockade of T cell activation through the 4-1BB/4-1BBL pathway regulates development of EAM; therefore, 4-1BB may be an effective target for treating myocarditis.

NKG2D receptor signaling enhances cytolytic activity by virus-specific CD8+ T cells: evidence for a protective role in virus-induced encephalitis

Inoculation with the neurotropic JHM strain of mouse hepatitis virus (JHMV) into the central nervous system (CNS) of mice results in an acute encephalitis associated with an immune-mediated demyelinating disease. During acute disease, infiltrating CD8(+) T cells secrete gamma interferon (IFN-gamma) that controls replication in oligodendrocytes, while infected astrocytes and microglia are susceptible to perforin-mediated lysis. The present study was undertaken to reveal the functional contributions of the activating NKG2D receptor in host defense and disease following JHMV infection. NKG2D ligands RAE-1, MULT1, and H60 were expressed within the CNS following JHMV infection. The immunophenotyping of infiltrating cells revealed that NKG2D was expressed on approximately 90% of infiltrating CD8(+) T cells during acute and chronic disease. Blocking NKG2D following JHMV infection resulted in increased mortality that correlated with increased viral titers within the CNS. Anti-NKG2D treatment did not alter T-cell infiltration into the CNS or the generation of virus-specific CD8(+) T cells, and the expression of IFN-gamma was not affected. However, cytotoxic T-lymphocyte (CTL) activity was dependent on NKG2D expression, because anti-NKG2D treatment resulted in a dramatic reduction in lytic activity by virus-specific CD8(+) T cells. Blocking NKG2D during chronic disease did not affect either T-cell or macrophage infiltration or the severity of demyelination, indicating that NKG2D does not contribute to virus-induced demyelination. These findings demonstrate a functional role for NKG2D in host defense during acute viral encephalitis by selectively enhancing CTL activity by infiltrating virus-specific CD8(+) T cells.

Glycogen synthase kinase 3beta inhibition reduces the development of nonseptic shock induced by zymosan in mice

Glycogen synthase kinase 3 has recently been identified as a ubiquitous serine-threonine protein kinase that participates in a multitude of cellular processes and plays an important role in the pathophysiology of a number of diseases. In the present study, we have investigated the effects of 4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione (TDZD-8), a glycogen synthase kinase 3beta inhibitor, on the development of nonseptic shock caused by zymosan (dose, 500 mg/kg i.p. suspension in saline) in mice. Organ failure and systemic inflammation in mice was assessed 18 h after administration of zymosan and/or TDZD-8; another group of mice was monitored for 12 days (for clinical score and mortality). Treatment of mice with TDZD-8 (dose, 10 mg/kg i.p., 1 and 6 h after zymosan administration) attenuated the peritoneal exudation and the migration of polymorphonuclear cells caused by zymosan. TDZD-8 also attenuated the lung, liver, and pancreatic injury, the renal dysfunction caused by zymosan, and the increase in myeloperoxidase activity caused by zymosan in the lung and in the intestine. Immunohistochemical analysis for inducible nitric oxide synthase, nitrotyrosine, poly(ADP-ribose), CD30, CD30 ligand, and Fas ligand revealed positive staining in lung and intestinal tissues obtained from zymosan-injected mice. The degree of staining for inducible nitric oxide synthase, nitrotyrosine, poly(ADP-ribose), CD30, CD30 ligand, and Fas ligand were markedly reduced in tissue sections obtained from zymosan-injected mice that had received TDZD-8. This study provides the first evidence that TDZD-8 attenuates the degree of zymosan-induced, nonseptic shock in mice.

Neutralizing anti-4-1BBL treatment improves cardiac function in viral myocarditis

Coxsackievirus B3 (CVB3) is the most common causative agent of infectious myocarditis. Chronic inflammation, loss of contractile tissue, and maladaptive remodeling all contribute to dilated cardiomyopathy and heart failure. The 4-1BB receptor is a costimulatory molecule expressed by T cells and cardiomyocytes. We infected mice with CVB3 to examine if virus infection triggers 4-1BB activation and whether inhibition of this pathway will reduce inflammation and improve heart function. Echocardiography was performed on days 3, 9, 30 and at 10 weeks post-infection (pi) and ejection fraction (EF), left ventricular (LV) wall thickness, contractility, and internal cardiac dimensions were measured. At day 9, reduced rate of wall thickening (30+/-17 vs 70+/-19%), increased LV wall thickness (0.15+/-0.04 vs 0.09+/-0.01 cm in diastole and 0.19+/-0.04 vs 0.15+/-0.02 cm in systole), and reduced cardiac volume (0.013+/-0.004 vs 0.023+/-0.003 ml in diastole and 0.004+/-0.002 ml vs 0.007+/-0.001 ml in systole) were observed in infected hearts as compared with shams. At 14 days pi, CVB3-infected mice were randomly assigned to receive either anti-4-1BBL neutralizing (M522) or control antibodies (Ab) for 8 weeks. Cardiac damage, fibrosis, and inflammation were assessed by histological stains and immunohistochemistry. Polymerase chain reaction (PCR) was utilized to detect matrix metalloproteinase (MMP)-2, MMP-9, and MMP-12 expressions. At 10 weeks pi, M522 treatment improved LV wall thickening rate (-10+/-13 vs -49+/-16%, expressed as percentage change from baseline) and reduced diastolic LV posterior wall thickness (17+/-10 vs 57+/-47%, expressed as percentage change from baseline), cardiac damage as assessed by histological scores (0 vs 1.3+/-1.5), fibrosis by collagen volume fraction (3.2+/-0.6 vs 4.9+/-2.2%), overall inflammation (5.9+/-1.3 vs 8.5+/-4.1%), and T-cell infiltration (1.3+/-0.9 vs 4.3+/-3.8%) as compared to control. MMP-12 was highly increased during acute and chronic myocarditis, but was significantly decreased by M522 treatment. Thus, long-term inhibition of the 4-1BB pathway reduces cardiac damage, remodeling, and inflammation during viral myocarditis.

Dissecting genetic control of autoimmunity in NOD congenic mice

My lab investigates genetic control of autoimmune disease and autoimmune phenotypes using a series of nonobese diabetic (NOD) congenic mice. NOD congenic mice have regions from B6/B10 introgressed onto the NOD genetic background, which reduces the severity/incidence of autoimmune diabetes. We have demonstrated, however, that while diabetes is reduced, other autoimmune phenotypes and diseases arise in NOD congenic mice. Mapping the genomic regions responsible for these phenotypes has produced novel insights into genetic control of autoimmunity. This review will illustrate some of the genetically controlled phenotypes we have investigated, which shed light upon autoimmune features relevant to human type 1 diabetes, systemic lupus erythematosus, and primary biliary cirrhosis.

Modulating protective and pathogenic CD4+ subsets via CD137 in type 1 diabetes

CD137 (TNFRSF9) is an activation-inducible T-cell costimulatory molecule and a member of the tumor necrosis factor (TNF) receptor superfamily. Cd137 is also a candidate gene (in the Idd9.3 interval) for autoimmune diabetes in NOD mice. Here, we demonstrate that anti-CD137 treatment protects NOD mice from diabetes. Anti-CD137-treated mice are not protected from insulitis and still harbor pathogenic T-cells, as demonstrated by transfer studies. Transfer of CD4(+), but not CD8(+), cells from anti-CD137-treated pre-diabetic NOD mice into NOD-scid mice delayed diabetes onset. Anti-CD137 treatment significantly increased the number of CD4(+)CD25(+) cells, which demonstrated intracellular Foxp3 expression and in vitro suppressive activity. The CD4(+)CD25(+) cell subset from anti-CD137-treated mice transferred complete protection from diabetes, whereas the CD4(+)CD25(-) cell subset offered no significant protection. Anti-CD137 treatment of NOD-scid recipients of diabetic spleen cells, however, hastened the onset of disease, showing that the effect of anti-CD137 treatment depends on the balance of pathogenic and protective cells. These results support a critical role for CD137 acting in the early phase of autoimmune diabetes to enhance regulatory cell production. Disease-associated CD137 alleles are likely ineffectual at stimulating a regulatory T-cell population sufficient to prevent disease.

Increased Soluble 4-1BB Ligand (4-1BBL) Levels in Peripheral Blood of Patients with Multiple Sclerosis

4-1BB ligand (4-1BBL; CD137L) is a member of the tumour necrosis factor superfamily expressed primarily on antigen presenting cells such as B cells, macrophages and dendritic cells. Its engagement with the receptor 4-1BB (CD137) has been shown to promote T-cell activation and regulate proliferation and survival of T cells. The role of the costimulatory molecule in multiple sclerosis (MS) remains unclear. In this study, the expression of 4-1BBL and soluble 4-1BBL (s4-1BBL) protein levels were analysed in peripheral blood of MS patients. Compared with healthy controls, MS patients had an increase in both plasma s4-1BBL protein levels and expression of 4-1BBL in CD14(+) monocytes. In contrast, myelin basic protein-reactive T-cell proliferation was not found to be inhibited by the use of an anti-4-1BBL antibody. The elevated s4-1BBL protein levels in the MS patients may function as a self-regulatory mechanism of 4-1BB/4-1BBL interaction and costimulation.

4-1 BB stimulation inhibits allergen-specific immunoglobulin E production and airway hyper-reactivity but partially suppresses bronchial eosinophilic inflammation in a mouse asthma model

BACKGROUND

4-1 BB, a member of the tumour necrosis factor receptor superfamily, functions as a co-stimulatory molecule. Recently, stimulation of the 4-1 BB pathway was shown to suppress antigen-specific CD4(+) T cell and subsequent T cell-dependent humoral immune responses.

OBJECTIVE

We examined the effect of agonistic anti-4-1 BB monoclonal antibody (mAb) treatment on allergic asthma, in which allergen-specific type 2 helper T cells (Th2) have been shown to play an important role.

METHODS

BALB/c mice were systemically sensitized with intraperitoneal injections of ovalbumin (OVA) and alum on days 0 and 14, and then challenged with inhaled OVA on days 28, 29 and 30. In test groups, the agonistic anti-4-1 BB mAb was administered at the time of initial systemic sensitization with OVA. On day 31, mice were challenged with inhaled methacholine, and enhanced pause was measured as an index of airway hyper-responsiveness (AHR). Levels of OVA-specific IgE in serum, and levels of various cytokines in bronchoalveolar lavage (BAL) fluids were measured. The severity of airway inflammation was determined by differential cell counts in BAL fluids and histopathologic lung analysis. To evaluate local immunity, we cultured lymphocytes from draining perihilar lymph nodes and evaluated the proliferative response to OVA and the levels of IL-5 in the culture supernatant. In addition, the functional mechanism of 4-1 BB stimulation was evaluated in splenocytes obtained at day 7 after systemic OVA sensitization.

RESULTS

We found that treatment with the anti-4-1 BB mAb significantly decreased AHR and the production of allergen-specific IgE. Bronchial inflammation, however, had only partially improved and the levels of IL-4 and IL-5 in BAL fluids showed only a small degree of reduction compared with the control Ig-treated mice. Thoracic lymphocytes from anti-4-1 BB-treated mice showed significant suppression of OVA-induced proliferation and IL-5 production. In anti-4-1 BB-treated mice, splenocytes exhibited poor proliferation and marked apoptosis 7 days after systemic OVA challenge.

CONCLUSION

These results suggest that stimulation of the 4-1 BB pathway effectively suppresses some features of allergic asthma, including allergen-specific IgE production and AHR, through deletion of allergen-specific Th2 cells. However, we found that bronchial allergic inflammation was not strictly mediated by suppression of the Th2 immune response in this murine model of asthma. Despite these somewhat contradictory effects, intervention in the 4-1 BB pathway might provide a potential novel immunotherapeutic approach for treatment of allergic asthma.

Immunotherapy targeting 4-1BB and its ligand

T-cell activation in the absence of costimulation is futile because T-cells deprived of costimulatory signals enter a state of unresponsiveness or anergy. The interaction of 4-1BB and 4-1BB ligand (4-1BBL) activates an important costimulatory pathway with diverse and important roles in immune regulation. Signals relayed through 4-1BB generate strong CD8(+) T-cell responses rather than CD4(+) T-cell responses; this action results in cytokine induction and promotes T-cell survival. In recent years, 4-1BB-mediated immune regulation has gained great significance because of the seemingly contradictory dual roles of agonistic anti-4-1BB in vivo disease models. To date, agonistic 4-1BB monoclonal antibody has shown therapeutic potential against a variety of tumors, CD4(+) T-cell-mediated autoimmune diseases, and chronic graft-versus-host disease. In addition, blockade of 4-1BB/4-1BBL interaction has produced therapeutic effects against coxsackievirus-induced myocardial inflammation, herpetic stromal keratitis, and graft rejection. We propose that the dual roles of agonistic anti-4-1BB--an enhanced effector function and a suppressor function--are mediated by a novel CD11c(+)CD8(+) T-cell population.

Effect of the angiotensin II receptor blocker olmesartan on the development of murine acute myocarditis caused by coxsackievirus B3

Ang II (Angiotensin II) has been shown to play a pivotal role in the pathophysiology of various organs, especially the cardiovascular system. The effects of ARBs (Ang II receptor blockers) in the treatment of hypertension, congestive heart failure and myocardial fibrosis have been analysed extensively in human trials, as well as animal models, and the focus of interest is now directed to its pleiotropic effects, especially on inflammatory disorders. To investigate the effects of a new ARB, olmesartan, on immune-mediated myocardial injury, the protective effects of olmesartan on the development of murine acute myocarditis caused by CVB3 (coxsackievirus B3) were analysed. Olmesartan and a non-specific vasodilator hydralazine lowered systolic blood pressure of mice on day 7 after virus inoculation to a similar extent. Olmesartan significantly decreased myocardial inflammation compared with controls, whereas hydralazine significantly increased this. Olmesartan significantly decreased the expression of IFN-γ (interferon-γ), FasL (Fas ligand), iNOS (inducible nitric oxide synthase) and PFP (pore-forming protein) in myocardial tissue, indicating that olmesartan suppressed the activation of infiltrating killer lymphocytes. Olmesartan also decreased the expression of CVB3 genomes in myocardial tissue as well as serum levels of 8-OHdG (8-hydroxy-2′-deoxyguanosine), a biomarker of oxidative-stress-induced DNA damage. The findings suggest that olmesartan prevents myocardial damage and may improve the prognosis of patients with acute myocarditis; however, further investigations are needed before clinical use.

Genetic control of anti-Sm autoantibody production in NOD congenic mice narrowed to the Idd9.3 region

Anti-Smith (anti-Sm) autoantibodies are directed to proteins in the small-nuclear ribonucleoprotein (snRNP) family and are considered specific for systemic lupus erythematosus (SLE) in both humans and mice. We previously established that NOD.c3c4 mice, carrying B6 and B10 congenic segments from chromosomes 3 to 4 on an nonobese diabetic (NOD) background, and NOD.Idd9R28 mice, carrying a B10 segment on c4 alone, developed significant penetrance of anti-Sm antibody production. Here we determine autoantibody incidence in additional NOD.Idd9 congenic strains and use a congenic mapping approach to narrow the interval necessary for enhanced autoantibody production to a approximately 5.6-Mb region containing insulin-dependent diabetes (Idd)9.3. The Idd9.3 interval contains the candidate molecule cluster of differentiation (CD)137, which is a member of the tumor necrosis factor (TNF) receptor superfamily, functions as an inducible costimulator of T cells, and controls T-B interactions. The NOD and B10 CD137 alleles have sequence polymorphisms and different functional effects on T cells; the NOD CD137 allele mediates weaker T cell proliferative responses and decreased interleukin (IL)-2 production after CD137-mediated costimulation. Our work establishes CD137 as a candidate gene for control of autoantibody production in NOD.Idd9.3 congenic mice.

TNF/TNFR family members in costimulation of T cell responses

Several members of the tumor necrosis factor receptor (TNFR) family function after initial T cell activation to sustain T cell responses. This review focuses on CD27, 4-1BB (CD137), OX40 (CD134), HVEM, CD30, and GITR, all of which can have costimulatory effects on T cells. The effects of these costimulatory TNFR family members can often be functionally, temporally, or spatially segregated from those of CD28 and from each other. The sequential and transient regulation of T cell activation/survival signals by different costimulators may function to allow longevity of the response while maintaining tight control of T cell survival. Depending on the disease condition, stimulation via costimulatory TNF family members can exacerbate or ameliorate disease. Despite these complexities, stimulation or blockade of TNFR family costimulators shows promise for several therapeutic applications, including cancer, infectious disease, transplantation, and autoimmunity.

Enhancement of CD4 and CD8 immunity by anti-CD137 (4-1BB) monoclonal antibodies during hepatitis C vaccination with recombinant adenovirus

The induction of protective or therapeutic cellular immunity against hepatitis C virus (HCV) is a difficult goal. In a previous work we showed that immunization with a recombinant adenovirus encoding HCV-NS3 (RAdNS3) could partially protect mice from challenge with a vaccinia virus encoding HCV antigens. We sought to investigate whether systemic administration of an immunostimulatory monoclonal antibody directed against the lymphocyte surface molecule CD137 could enhance the immunity elicited by RAdNS3. It was found that treatment with anti-CD137 mAb after the administration of a suboptimal dose of RAdNS3 enhanced cytotoxic and T helper cell responses against HCV NS3. Importantly, the ability of RAdNS3 to induce protective immunity against challenge with a recombinant vaccinia virus expressing HCV proteins was markedly augmented. Thus, combination of immunostimulatory anti-CD137 mAb with recombinant adenoviruses expressing HCV proteins might be useful in strategies of immunization against HCV.

Cross-Linking of 4-1BB Activates TCR-Signaling Pathways in CD8+ T Lymphocytes

Cross-linking of 4-1BB, a member of the TNFR family, increased tyrosine phosphorylation of TCR-signaling molecules such as CD3epsilon, CD3zeta, Lck, the linker for activation of T cells, and SH2 domain-containing leukocyte phosphoprotein of 76 kDa (SLP-76). In addition, incubation of activated CD8+ T cells with p815 cells expressing 4-1BBL led to redistribution of the lipid raft domains and Lck, protein kinase C-theta;, SLP-76, and phospholipase C-gamma1 (PLC-gamma1) on the T cell membranes to the areas of contact with the p815 cells and recruitment of 4-1BB, TNFR-associated factor 2, and phospho-tyrosine proteins to the raft domains. 4-1BB ligation also caused translocation of TNFR-associated factor 2, protein kinase C-theta;, PLC-gamma1, and SLP-76 to detergent-insoluble compartments in the CD8+ T cells, and cross-linking of 4-1BB increased intracellular Ca2+ levels apparently by activating PLC-gamma1. The redistribution of lipid rafts and Lck, as well as translocation of PLC-gamma1, and degradation of IkappaB-alpha in response to 4-1BB were inhibited by disrupting the formation of lipid rafts with methyl-beta-cyclodextrin. These findings demonstrate that 4-1BB is a T cell costimulatory receptor that activates TCR-signaling pathways in CD8+ T cells.

Role of T cell costimulation in anti-viral immunity

Members of both the CD28 and TNFR families can have costimulatory roles in T cell activation. Gene targeted mice as well as in vivo blocking experiments have established distinct roles for CD28/B7; ICOS/ICOSL; CD27/CD70; 4-1BB/4-1BBL and OX40/OX40L during viral infection. Many issues remain to be addressed, including the timing and location of the interactions, the possibility of partial redundancy between related family members and the molecular basis for the specific phenotypes observed in the different gene targeted mice.

Autoimmune myocarditis: cellular mediators of cardiac dysfunction

Immune mediators play a critical role in the pathogenesis and outcomes of a number of cardiac diseases. This review summarizes recent findings on the composition of the inflammatory infiltrate and the role of different types and subtypes of immune cells and their products in mediating cardiac dysfunction in experimental autoimmune myocarditis (EAM). CD4+ T cells are required for initiation of myocarditis and their numbers in the heart infiltrate correlate with systolic dysfunction during disease progression. Other immune cells, including CD8+ T cells, granulocytes, and mast cells, can directly affect cardiomyocyte function. When regulatory mechanisms fail, the local damage leads to cardiomyocyte death, replacement fibrosis and overall cardiac dysfunction. EAM provides insights into the role of the immune system in the development of dilated cardiomyopathy (DCM) and heart failure and may serve as a general paradigm for autoimmune organ-specific tissue damage.

Links between type I interferons and the genetic basis of disease in mouse lupus

Systemic lupus erythematosus (SLE), like other autoimmune diseases, is a complex genetic trait with contributions from both major histocompatibility complex (MHC) genes and multiple non-MHC genes. Most of the contributing genes have yet to be identified. Studies of mouse models of lupus have provided important insight into the immunopathogenesis of lupus-like IgG autoantibody production and lupus nephritis, and genetic analyses of these mice are helping to unravel the complex and heterogeneous genetic basis of disease. Recent studies in both human SLE and mouse models of lupus have emphasized a potential role of type I interferons (IFN-alpha/beta) in the initiation and perpetuation of disease. There is now increasing interest in genes that affect IFN-alpha/beta expression-activity and IFN-regulated target genes that may be involved in the disease process. One example is interferon-inducible gene 202 (Ifi202), which has been identified as a major candidate susceptibility gene in the New Zealand hybrid model of lupus. Studies suggest that increased expression of this transcription factor leads to lupus through inhibition of lymphocyte apoptosis, although its effects on immune function are extremely complex and have yet to be fully defined. This review will focus on the genetic basis of disease in mouse lupus with a special emphasis on those genetic contributions that may affect IFN-alpha/beta activity and those that may be target genes of IFN-alpha/beta action.

Marek's disease is a natural model for lymphomas overexpressing Hodgkin's disease antigen (CD30)

Animal models are essential for elucidating the molecular mechanisms of carcinogenesis. Hodgkin's and many diverse non-Hodgkin's lymphomas overexpress the Hodgkin's disease antigen CD30 (CD30(hi)), a tumor necrosis factor receptor II family member. Here we show that chicken Marek's disease (MD) lymphoma cells are also CD30(hi) and are a unique natural model for CD30(hi) lymphoma. Chicken CD30 resembles an ancestral form, and we identify a previously undescribed potential cytoplasmic signaling domain conserved in chicken, human, and mouse CD30. Our phylogeneic analysis defines a relationship between the structures of human and mouse CD30 and confirms that mouse CD30 represents the ancestral mammalian gene structure. CD30 expression by MD virus (MDV)-transformed lymphocytes correlates with expression of the MDV Meq putative oncogene (a c-Jun homologue) in vivo. The chicken CD30 promoter has 15 predicted high-stringency Meq-binding transcription factor recognition motifs, and Meq enhances transcription from the CD30 promoter in vitro. Plasma proteomics identified a soluble form of CD30. CD30 overexpression is evolutionarily conserved and defines one class of neoplastic transformation events, regardless of etiology. We propose that CD30 is a component of a critical intracellular signaling pathway perturbed in neoplastic transformation. Specific anti-CD30 Igs occurred after infection of genetically MD-resistant chickens with oncogenic MDV, suggesting immunity to CD30 could play a role in MD lymphoma regression.

4-1BB cross-linking enhances the survival and cell cycle progression of CD4 T lymphocytes

4-1BB, a T cell co-stimulatory receptor, prolongs the survival and multiplication of CD4 T cells. Cross-linking 4-1BB stimulated expression of the anti-apoptotic genes bcl-XL and bcl-2, as well as of cyclins D2 and E, and inhibited expression of the cyclin-dependent kinase (cdk) inhibitor p27kip1. Ova-activated CD4 T cells of 4-1BB-deficient/DO11.10 TCR transgenic mice survived less well and underwent less expansion than cells of wild type DO11.10 TCR transgenic mice. These findings demonstrate that 4-1BB is a co-stimulatory molecule for CD4 T cell survival and expansion in vivo.

Blocking 4-1BB/4-1BB ligand interactions prevents herpetic stromal keratitis

Herpetic stromal keratitis (HSK) is a chronic inflammatory process in corneal stroma that results from recurrent HSV type 1 infection. We used the murine model of HSK to demonstrate the importance of the interaction between an inducible T cell costimulatory receptor, 4-1BB, and its ligand, 4-1BB ligand (4-1BBL), in the development of this disease. In BALB/c mice, HSK ordinarily induced by infection with the RE strain of herpes was prevented by blocking 4-1BB/4-1BBL interaction, either by deleting 4-1BB (in mutant 4-1BB(-/-) mice) or by introducing mAbs against 4-1BBL. The majority of T cells infiltrating the infected corneas were 4-1BB(+) activated effector cells that expressed cell surface markers CD44, CD25, and/or CD62L, as well as chemokine receptors CCR1, CCR2, and CCR5, and a limited number of TCR Vbeta chains (Vbeta8.1/8.2, Vbeta8.3, Vbeta10b, and Vbeta5.1/5.2, in order of abundance). Analysis of cell surface phenotypes showed that the failure to develop HSK in the 4-1BB(-/-) mice was associated with a reduced expression of CD62L at the time of T cell migration into the corneal stroma.

OX40 ligation on activated T cells enhances the control of Cryptococcus neoformans and reduces pulmonary eosinophilia

Pulmonary eosinophilia induced in C57BL/6 mice after Cryptococcus neoformans infection is driven by CD4(+) Th2 cells. The immunological mechanisms that protect against eosinophilia are not fully understood. Interaction of OX40 (CD134) and its ligand, OX40L, has been implicated in T cell activation and cell migration. Unlike CD28, OX40 is only expressed on T cells 1-2 days after Ag activation. Manipulation of this pathway would therefore target recently activated T cells, leaving the naive repertoire unaffected. In this study, we show that engagement of OX40 by an OX40L:Ig fusion protein drives IFN-gamma production by CD4(+) T cells and reduces eosinophilia and C. neoformans burden in the lung. Using gene-depleted mice, we show that reduction of eosinophilia and pathogen burden requires IL-12 and/or IFN-gamma. C. neoformans infection itself only partially induces OX40L expression by APCs. Provision of exogenous OX40L reveals a critical role of this pathway in the prevention of C. neoformans-induced eosinophilia.

New insights into the role of 4-1BB in immune responses: beyond CD8+ T cells

Since the discovery of 4-1BB 15 years ago, the receptor and its ligand (4-1BBL) have remained enigmatic molecules because of their highly regulated pattern of expression. Classically, 4-1BB is known to function as a costimulator for T cells and as a potent survival factor for CD8+ T cells. Recent studies highlight the participation of 4-1BB and its ligand 4-1BBL in a more complex network of immune cell responses and suggest that intervening in the 4-1BB costimulatory pathway might have some potential as a therapeutic approach to immune disorders.

Expression of tumor necrosis factor ligand superfamily costimulatory molecules CD27L, CD30L, OX40L and 4-1BBL in the heart of patients with acute myocarditis and dilated cardiomyopathy

BACKGROUND

T-cell-mediated myocardial damage is known to be involved in acute myocarditis and dilated cardiomyopathy. Recently, we found that tumor necrosis factor (TNF) ligand superfamily costimulatory molecules, especially 4-1BBL, played an important role in the myocardial damage of murine acute viral myocarditis.

METHODS AND RESULTS

To investigate the roles for CD27L, CD30L, OX40L and 4-1BBL, which belong to TNF ligand superfamily, in the development of acute myocarditis and dilated cardiomyopathy, we analyzed the expression of these antigens in the myocardial tissues of patients with acute myocarditis and dilated cardiomyopathy. We also examined expression of the receptors for these molecules, CD27, CD30, OX40 and 4-1BB, which belong to TNF receptor superfamily, on the infiltrating cells. Strong expression of CD27L, CD30L and 4-1BBL and weak to moderate expression of OX40L was found in the cardiac myocytes of patients with acute myocarditis. Moderate expression of CD27L, CD30L and 4-1BBL and weak expression of OX40L was found on the cardiac myocytes of patients with dilated cardiomyopathy. Most of the infiltrating cells expressed CD27, CD30 and 4-1BB and a part of the infiltrating cells expressed OX40.

CONCLUSIONS

Our findings suggest that expression of TNF ligand superfamily costimulatory molecules on cardiac myocytes may play a role in the cell-mediated myocardial damage in patients with acute myocarditis and dilated cardiomyopathy as in murine viral myocarditis.

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.