Co-stimulatory blockade in the treatment of murine systemic lupus erythematosus (SLE)

Population Pharmacokinetics and Exposure-Response for Dapirolizumab Pegol From a Phase 2b Trial in Patients With Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a systemic, autoimmune disease characterized by chronic inflammation and organ damage. Dapirolizumab pegol inhibits CD40 ligand (CD40L) and is currently undergoing phase 3 trials for the treatment of SLE. To describe the pharmacokinetic characteristics of dapirolizumab pegol and the relationship between exposure and probability of achieving a British Isles Lupus Assessment Group-based Composite Lupus Assessment (BICLA) response, a population pharmacokinetic (popPK) model and an exposure-response model were developed, based on results of the phase 2b trial (RISE; NCT02804763) of dapirolizumab pegol in SLE. Dapirolizumab pegol pharmacokinetics were found to be dose proportional and well described by a 2-compartment model with first-order elimination from the central compartment. In the popPK model, body weight was the only significant covariate. The average concentration of dapirolizumab pegol, derived from the popPK model, was incorporated into the exposure-response model. Overall, the exposure-response model showed that treatment with dapirolizumab pegol increased the probability of transitioning from BICLA "Nonresponder" to "Responder." No significant covariates on BICLA responder status were identified. Notably, the half maximal effective concentration was greater for the transition from "Responder" to "Nonresponder" (150 µg/mL) than the transition from "Nonresponder" to "Responder" (12 µg/mL), indicating that sustained dapirolizumab pegol concentrations may be required to maintain BICLA response. In conclusion, dapirolizumab pegol pharmacokinetics were as expected for a PEGylated molecule and results from the exposure-response model indicate that a favorable dapirolizumab pegol effect was identified for both BICLA "Nonresponder" to "Responder" and "Responder" to "Nonresponder" transition probabilities.

CDP7657, an anti-CD40L antibody lacking an Fc domain, inhibits CD40L-dependent immune responses without thrombotic complications: an in vivo study

INTRODUCTION

CD40 ligand (CD40L) blockade has demonstrated efficacy in experimental autoimmune models. However, clinical trials of hu5c8, an anti-human CD40L IgG1 antibody, in systemic lupus erythematosus (SLE) were halted due to an increased incidence of thrombotic events. This study evaluated CDP7657, a high affinity PEGylated monovalent Fab' anti-CD40L antibody fragment, to assess whether an Fc-deficient molecule retains efficacy while avoiding the increased risk of thrombotic events observed with hu5c8.

METHODS

The potency and cross-reactivity of CDP7657 was assessed in in vitro assays employing human and non-human primate leukocytes, and the capacity of different antibody formats to activate platelets in vitro was assessed using aggregometry and dense granule release assays. Given the important role CD40L plays in regulating humoral immunity, in vivo efficacy was assessed by investigating the capacity of Cynomolgus monkeys to generate immune responses to the tetanus toxoid antigen while the potential to induce thrombotic events in vivo was evaluated after repeat dosing of antibodies to Rhesus monkeys. A PEGylated anti-mouse CD40L was generated to assess efficacy in the New Zealand Black/White (NZB/W) mouse model of SLE.

RESULTS

CDP7657 dose-dependently inhibited antigen-specific immune responses to tetanus toxoid in Cynomolgus monkeys, and in contrast to hu5c8, there was no evidence of pulmonary thrombovasculopathy in Rhesus monkeys. Aglycosyl hu5c8, which lacks Fc receptor binding function, also failed to induce thrombotic events in Rhesus monkeys. In vitro experiments confirmed that antibody constructs lacking an Fc, including CDP7657, did not induce human or monkey platelet activation. A PEGylated monovalent Fab' anti-mouse CD40L antibody also inhibited disease activity in the NZB/W mouse model of SLE after administration using a therapeutic dosing regimen where mice received antibodies only after they had displayed severe proteinuria.

CONCLUSIONS

These findings demonstrate for the first time that anti-CD40L antibodies lacking a functional Fc region do not induce thrombotic events in Rhesus monkeys and fail to activate platelets in vitro but, nevertheless retain pharmacological activity and support the investigation of CDP7657 as a potential therapy for systemic lupus erythematosus and other autoimmune diseases.

First-in-human trial of the safety, pharmacokinetics and immunogenicity of a PEGylated anti-CD40L antibody fragment (CDP7657) in healthy individuals and patients with systemic lupus erythematosus

OBJECTIVE

The objective of this paper is to investigate the safety, pharmacokinetics (PK) and immunogenicity of CDP7657, a PEGylated anti-CD40L antibody fragment, in healthy individuals and patients with systemic lupus erythematosus (SLE).

METHODS

This randomized, double-blind, single-dose, dose-escalation phase I study consisted of two parts. In part 1, 28 healthy individuals received CDP7657 IV (0.004-5 mg/kg) or placebo. In part 2, 17 patients with SLE received CDP7657 IV (5-60 mg/kg) or placebo. The CDP7657:placebo ratio was 3:1.

RESULTS

Adverse events (AEs) were reported by 76% of healthy individuals and 100% of patients with SLE treated with CDP7657; most were mild or moderate in intensity. Two healthy individuals reported serious AEs (SAEs), one of which was considered treatment related (infusion-related reaction; 5 mg/kg cohort). One patient with SLE (60 mg/kg cohort) experienced three SAEs, one of which was considered treatment related (herpes zoster infection). No thromboembolic events were reported. CPD7657 exposure increased in a dose-proportional manner. Low anti-CDP7657 antibody titres were detected in the majority of CDP7657-treated participants with no apparent impact on the PK of CDP7657.

CONCLUSION

Single doses of CDP7657 showed predictable PK in healthy individuals and patients with SLE and were well tolerated, with no safety signals of concern. These findings support further investigation of CDP7657 as a therapy for SLE.

CD40 gene silencing reduces the progression of experimental lupus nephritis modulating local milieu and systemic mechanisms

Lupus nephritis (LN) is an autoimmune disorder in which co-stimulatory signals have been involved. Here we tested a cholesterol-conjugated-anti-CD40-siRNA in dendritic cells (DC) in vitro and in a model of LPS to check its potency and tissue distribution. Then, we report the effects of Chol-siRNA in an experimental model of mice with established lupus nephritis. Our in vitro studies in DC show a 100% intracellular delivery of Chol-siRNA, with a significant reduction in CD40 after LPS stimuli. In vivo in ICR mice, the CD40-mRNA suppressive effects of our Chol-siRNA on renal tissue were remarkably sustained over a 5 days after a single preliminary dose of Chol-siRNA. The intra-peritoneal administration of Chol-siRNA to NZB/WF1 mice resulted in a reduction of anti-DNA antibody titers, and histopathological renal scores as compared to untreated animals. The higher dose of Chol-siRNA prevented the progression of proteinuria as effectively as cyclophosphamide, whereas the lower dose was as effective as CTLA4. Chol-siRNA markedly reduced insterstitial CD3+ and plasma cell infiltrates as well as glomerular deposits of IgG and C3. Circulating soluble CD40 and activated splenic lymphocyte subsets were also strikingly reduced by Chol-siRNA. Our data show the potency of our compound for the therapeutic use of anti-CD40-siRNA in human LN and other autoimmune disorders.

Novel therapeutic agents in clinical development for systemic lupus erythematosus

Conventional immunosuppressive therapies have radically transformed patient survival in systemic lupus erythematosus (SLE), but their use is associated with considerable toxicity and a substantial proportion of patients remain refractory to treatment. A more comprehensive understanding of the complexity of SLE immunopathogenesis has evolved over the past decade and has led to the testing of several biologic agents in clinical trials. There is a clear need for new therapeutic agents that overcome these issues, and biologic agents offer exciting prospects as future SLE therapies.An array of promising new therapies are currently emerging or are under development including B-cell depletion therapies, agents targeting B-cell survival factors, blockade of T-cell co-stimulation and anti-cytokine therapies, such as monoclonal antibodies against interleukin-6 and interferon-α.

T cells interact with T cells via CD40-CD154 to promote autoimmunity in type 1 diabetes

We have investigated the role of CD40 signaling in islet-reactive, diabetogenic CD4(+) Th1 T-cell clones. Using multispectral flow cytometry, we showed that CD40 and CD154 are co-expressed and form complexes on the surface of activated T cells. We also demonstrate that activated Tcells can transactivate CD4(+) CD40(+) T cells through the CD40-CD154 pathway. To investigate the role of CD40 signaling on Th1 cells, we used the diabetogenic clone BDC-5.2.9 retrovirally transduced with a truncated form of the CD40 molecule to produce a CD40 dominant-negative T-cell clone. Upon challenge with antigen in vitro, the production of IFN-γ by BDC-5.2.9 CD40DN was greatly reduced and, in vivo, the dominant-negative variant was unable to induce diabetes. Transduction with the CD40DN vector was also effective in preventing transfer of disease by primary NOD CD4(+) T cells. Ex vivo analysis of pancreatic infiltrates after transfer of BDC-5.2.9 CD40DN cells revealed an overall reduction of cell numbers and cytokine production by both T cells and macrophages. These data indicate that CD40 is an important signaling molecule on autoreactive CD4(+) T cells and contributes to their pathogenic effector function.

PPARγ expression is increased in systemic lupus erythematosus patients and represses CD40/CD40L signaling pathway

Systemic lupus erythematosus (SLE) is a heterogeneous disease involving several immune cell types and pro-inflammatory signals, including the one triggered by binding of CD40L to the receptor CD40. Peroxisome-proliferator activated receptor gamma (PPARγ) is a transcription factor with anti-inflammatory properties. Here we investigated whether CD40 and PPARγ could exert opposite effects in the immune response and the possible implications for SLE. Increased PPARγ mRNA levels were detected by real-time PCR in patients with active SLE, compared to patients with inactive SLE PPARγ/GAPDH mRNA = 2.21 ± 0.49 vs. 0.57 ± 0.14, respectively (p < 0.05) or patients with infectious diseases and healthy subjects (p < 0.05). This finding was independent of the corticosteroid therapy. We further explored these observations in human THP1 and in SLE patient-derived macrophages, where activation of CD40 by CD40L promoted augmented PPARγ gene transcription compared to non-stimulated cells (PPARγ/GAPDH mRNA = 1.14 ± 0.38 vs. 0.14 ± 0.01, respectively; p < 0.05). This phenomenon occurred specifically upon CD40 activation, since lipopolysaccharide treatment did not induce a similar response. In addition, increased activity of PPARγ was also detected after CD40 activation, since higher PPARγ-dependent transcription of CD36 transcription was observed. Furthermore, CD40L-stimulated transcription of CD80 gene was elevated in cells treated with PPARγ-specific small interfering RNA (small interfering RNA, siRNA) compared to cells treated with CD40L alone (CD80/GAPDH mRNA = 0.11 ± 0.04 vs. 0.05 ± 0.02, respectively; p < 0.05), suggesting a regulatory role for PPARγ on the CD40/CD40L pathway. Altogether, our findings outline a novel mechanism through which PPARγ regulates the inflammatory signal initiated by activation of CD40, with important implications for the understanding of immunological mechanisms underlying SLE and the development of new treatment strategies.

Interferon-γ-dependent inhibition of B cell activation by bone marrow-derived mesenchymal stem cells in a murine model of systemic lupus erythematosus

OBJECTIVE

Bone marrow-derived mesenchymal stem cells (BM-MSCs) are multipotent cells characterized by immunomodulatory properties and are therefore considered a promising tool for the treatment of immune-mediated diseases. This study was undertaken to assess the influence of murine BM-MSCs on the activation of B cells in (NZB × NZW)F(1) mice as an animal model of systemic lupus erythematosus (SLE).

METHODS

We evaluated the in vitro effects of BM-MSCs on the proliferation and differentiation to plasma cells of splenic mature B cell subsets, namely follicular and marginal zone B cells isolated from (NZB × NZW)F(1) mice. Lupus mice were also treated with BM-MSCs, and serum autoantibodies, proteinuria, histologic changes in the kidney, and survival rates were monitored.

RESULTS

BM-MSCs inhibited antigen-dependent proliferation and differentiation to plasma cells of follicular and marginal zone B cells in vitro. This inhibitory effect was dependent on interferon-γ (IFNγ) and was mediated by cell-to-cell contact, involving the programmed death 1 (PD-1)/PD ligand pathway. In vivo treatment with BM-MSCs did not affect the levels of anti-double-stranded DNA antibodies or proteinuria. However, a reduction in glomerular immune complex deposition, lymphocytic infiltration, and glomerular proliferation was observed.

CONCLUSION

Our findings indicate that BM-MSCs affect B cell receptor-dependent activation of both follicular and marginal zone B cells from lupus mice. This inhibitory effect is IFNγ-dependent and cell contact-dependent. MSCs in vivo do not affect the production of autoantibodies, the level of proteinuria, or the mortality rates. Nonetheless, the significant improvement in histologic findings in the kidney supports the potential role of MSCs in the prevention of glomerular damage.

Biologics in the treatment of systemic lupus erythematosus

PURPOSE OF REVIEW

The pathogenesis of systemic lupus erythematosus (SLE) involves aberrancy in multiple components of the immune system including B cells, T cells, cytokines and growth factors. Therapeutic agents targeting these mediators selectively have been tested for the treatment of SLE. This review summarizes the recent advances in the fast expanding field of these biological therapies.

RECENT FINDINGS

The two large phase 2/3 randomized placebo-controlled trials of B-cell depletion, using anti-CD20 antibody, rituximab, in SLE, reported unexpected negative results. On the contrary, two large phase 3 trials of belimumab, the monoclonal antibody against B-lymphocyte stimulator (BLyS), showed significant clinical benefit. Response rates were 57.6 and 43.2% for 10 mg/kg belimumab, compared with 43.6 and 33.8% for placebo in BLISS-52 and BLISS-76, respectively. Studies of a co-stimulation blocker (abatacept), tumor necrosis factor inhibitor (infliximab), and interleukin-6 inhibitor (tocilizumab) were either negative (abatacept) or were associated with high rates of adverse events. Studies of T cell and interferon inhibition remain in the early development phase.

SUMMARY

Despite the enthusiasm in the field of biologic therapies, the majority of these new modalities have fallen short of expectations for various reasons. Only belimumab has recently met its primary outcome in two phase 3 trials.

CD40/CD40L signaling and its implication in health and disease

CD40, a transmembrane receptor of the tumor necrosis factor gene superfamily is expressed on a variety of cells, such as monocytes, B-cells, antigen presenting cells, endothelial, smooth muscle cells, and fibroblasts. The interaction between CD40 and CD40 ligand (CD40L) enhances the expression of cytokines, chemokines, matrix metalloproteinases, growth factors, and adhesion molecules, mainly through the stimulation of nuclear factor kappa B. The aim of this review is to summarize the molecular and cellular characteristics of CD40 and CD40L, the mechanisms that regulate their expression, the cellular responses they stimulate and finally their implication in the pathophysiology of inflammatory and autoimmune diseases.

T cell CD40LG gene expression and the production of IgG by autologous B cells in systemic lupus erythematosus

CD40 ligand (CD40LG), encoded on the X chromosome, has been reported to be overexpressed on lupus T cells. Herein, we investigated the effect of DNA demethylation on T cell CD40LG expression and the production of IgG by autologous B cells in lupus. We found normal human T cells transfected with CD40LG induced autologous B cell activation and plasma cell differentiation. Both female lupus CD4+ T cells and demethylating agents treated CD4+ T cells overexpressed CD40LG mRNA. Further, lupus T cells from both genders or demethylated CD4+ T cells from healthy women overstimulated autologous B cells, and this could be reversed with anti-CD40LG Ab in only females. We demonstrated that female lupus CD4+ T cells and demethylated CD4+ T cells express high level of CD40LG and overstimulate B cells to produce IgG. This is due to DNA demethylation and thereby reactivation of the inactive X chromosome in female.

B cells flying solo

Systemic autoimmunity such as systemic lupus erythematosus (SLE) is associated with the loss of B-cell tolerance, B-cell dysregulation and autoantibody production. While some autoantibodies may contribute to the pathology seen with SLE, numerous studies have shown that dysregulation of T-cell function is another critical aspect driving disease. The positive results obtained in clinical trials using T-cell- or B-cell-specific treatments have suggested that cooperation between T and B cells probably underlies disease progression in many patients. A similar cooperative mechanism seemed to explain SLE developing in mice overexpressing the B-cell-activating factor from the tumor necrosis factor family (BAFF). However, surprisingly, T-cell-deficient BAFF transgenic (Tg) mice develop SLE similar to T-cell-sufficient BAFF Tg mice, and the disease was linked to innate activation of B cells and production of proinflammatory autoantibody isotypes. In conclusion, dysregulated innate activation of B cells alone can drive disease independently of T cells, and as such this aspect represents a new pathogenic mechanism in autoimmunity.

Mechanisms underlying B-cell tolerance induction by antigen-immunoglobulin G gene transfer

Previous studies on the mechanisms underlying tolerance induction in diabetes have mainly focused on T cells, however B cells also have an important role in diabetes. Based on our previous studies that splenocytes, transduced with glutamic acid decarboxylase (GAD) 65 fused to immunoglobulin (Ig) G carrier, reduced antibody-mediated response in non-obese diabetic (NOD) mice, here we examined the mechanisms underlying B-cell tolerance in this system. We found that GAD-IgG-transduced splenocytes did not reduce CD40 expression on B-cells in NOD mice, but they did downregulate CD40 ligand (CD40L) expression. Furthermore, anti-CD40L injection reduced autoantibody levels in NOD mice and in vitro experiments demonstrated that CD40L blockade reduced the antigenpresenting capability of B-cells. In conclusion, the results of this study suggest that downregulation of CD40L may be one mechanism underlying the induction of B-cell tolerance in GAD-IgG-treated NOD mice.

BAFF and MyD88 signals promote a lupuslike disease independent of T cells

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by the production of autoantibodies. However, the underlying cause of disease appears to relate to defects in T cell tolerance or T cell help to B cells. Transgenic (Tg) mice overexpressing the cytokine B cell–activating factor of the tumor necrosis factor family (BAFF) develop an autoimmune disorder similar to SLE and show impaired B cell tolerance and altered T cell differentiation. We generated BAFF Tg mice that were completely deficient in T cells, and, surprisingly, these mice developed an SLE-like disease indistinguishable from that of BAFF Tg mice. Autoimmunity in BAFF Tg mice did, however, require B cell–intrinsic signals through the Toll-like receptor (TLR)–associated signaling adaptor MyD88, which controlled the production of proinflammatory autoantibody isotypes. TLR7/9 activation strongly up-regulated expression of transmembrane activator and calcium modulator and cyclophilin ligand interactor (TACI), which is a receptor for BAFF involved in B cell responses to T cell–independent antigens. Moreover, BAFF enhanced TLR7/9 expression on B cells and TLR-mediated production of autoantibodies. Therefore, autoimmunity in BAFF Tg mice results from altered B cell tolerance, but requires TLR signaling and is independent of T cell help. It is possible that SLE patients with elevated levels of BAFF show a similar basis for disease.

Sulfamethoxazole and its metabolite nitroso sulfamethoxazole stimulate dendritic cell costimulatory signaling

Different signals in addition to the antigenic signal are required to initiate an immunological reaction. In the context of sulfamethoxazole allergy, the Ag is thought to be derived from its toxic nitroso metabolite, but little is known about the costimulatory signals, including those associated with dendritic cell maturation. In this study, we demonstrate increased CD40 expression, but not CD80, CD83, or CD86, with dendritic cell surfaces exposed to sulfamethoxazole (250-500 microM) and the protein-reactive metabolite nitroso sulfamethoxazole (1-10 microM). Increased CD40 expression was not associated with apoptosis or necrosis, or glutathione depletion. Covalently modified intracellular proteins were detected when sulfamethoxazole was incubated with dendritic cells. Importantly, the enzyme inhibitor 1-aminobenzotriazole prevented the increase in CD40 expression with sulfamethoxazole, but not with nitroso sulfamethoxazole or LPS. The enzymes CYP2C9, CYP2C8, and myeloperoxidase catalyzed the conversion of sulfamethoxazole to sulfamethoxazole hydroxylamine. Myeloperoxidase was expressed at high levels in dendritic cells. Nitroso sulfamethoxazole immunogenicity was inhibited in mice with a blocking anti-CD40L Ab. In addition, when a primary nitroso sulfamethoxazole-specific T cell response using drug-naive human cells was generated, the magnitude of the response was enhanced when cultures were exposed to a stimulatory anti-CD40 Ab. Finally, increased CD40 expression was 5-fold higher on nitroso sulfamethoxazole-treated dendritic cells from an HIV-positive allergic patient compared with volunteers. These data provide evidence of a link between localized metabolism, dendritic cell activation, and drug immunogenicity.

B cell targeted therapy in autoimmunity

Autoimmunity results from a break in self-tolerance involving humoral and/or cell-mediated immune mechanisms. Part of the pathological consequence of a failure in central and/or peripheral tolerance, results from survival and activation of self-reactive B cells. Such B cells produce tissue-damaging pathogenic autoantibodies, and subsequent formation of complement-fixing immune complexes that contribute to tissue damage. Current pharmacological strategies for treating autoimmune diseases involve global use of broad-acting immunosuppressants that with long term use have associated toxicities. The present drive in drug development is towards therapies that target a specific biological pathway or pathogenic cell population. This review focuses on some of the emerging therapies based on co-stimulation blockers, and compounds which contribute to a specific B cells depletion, based on studies in animal models and human clinical studies.

Update on the treatment of lupus nephritis

Lupus nephritis (LN) is a major cause of morbidity and mortality in patients with systemic lupus erythematosus. Although the use of aggressive immunosuppression has improved both patient and renal survival over the past several decades, the optimal treatment of LN remains challenging. Improved outcomes have come at the expense of significant adverse effects owing to therapy. Moreover with long-term survival, the chronic adverse effects of effective therapies including risk of malignancy, atherosclerosis, infertility, and bone disease all become more important. Finally, some patients fail to achieve remission with standard cytotoxic therapy and others relapse when therapy is reduced. For these reasons, recent clinical trials have attempted to define alternate treatment protocols that appear to be efficacious in achieving and maintaining remission, but with less toxicity than standard regimens. This paper discusses established and newer treatment options for patients with proliferative and membranous LN, with an emphasis on the results of these recent clinical trials. We also review the experimental and human data regarding some of the novel targeted forms of therapy that are under investigation and in different phases of clinical trials.

Lack of correlation between the levels of soluble cytotoxic T-lymphocyte associated antigen-4 (CTLA-4) and the CT-60 genotypes

BACKGROUND

Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) plays a critical role in downregulation of antigen-activated immune response and polymorphisms at the CTLA-4 gene have been shown to be associated with several autoimmune diseases including type-1 diabetes (T1D). The etiological mutation was mapped to the CT60-A/G single nucleotide polymorphism (SNP) that is believed to control the processing and production of soluble CTLA-4 (sCTLA-4).

METHODS

We therefore determined sCTLA-4 protein levels in the sera from 82 T1D patients and 19 autoantibody positive (AbP) subjects and 117 autoantibody negative (AbN) controls using ELISA. The CT-60 SNP was genotyped for these samples by using PCR and restriction enzyme digestion of a 268 bp DNA segment containing the SNP. Genotyping of CT-60 SNP was confirmed by dye terminating sequencing reaction.

RESULTS

Higher levels of sCTLA-4 were observed in T1D (2.24 ng/ml) and AbP (mean = 2.17 ng/ml) subjects compared to AbN controls (mean = 1.69 ng/ml) with the differences between these subjects becoming significant with age (p = 0.02). However, we found no correlation between sCTLA-4 levels and the CTLA-4 CT-60 SNP genotypes.

CONCLUSION

Consistent with the higher serum sCTLA-4 levels observed in other autoimmune diseases, our results suggest that sCTLA-4 may be a risk factor for T1D. However, our results do not support the conclusion that the CT-60 SNP controls the expression of sCTLA-4.

Association of Epstein-Barr virus with systemic lupus erythematosus: effect modification by race, age, and cytotoxic T lymphocyte-associated antigen 4 genotype

OBJECTIVE

Epstein-Barr virus (EBV) is hypothesized to play a role in the development of systemic lupus erythematosus (SLE). Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) is important in regulating T cell-mediated immunity, encompassing the first line of response to viral infections, and genetic variation in CTLA-4 has been associated with SLE. This study examined the seroprevalence of EBV in a population-based study of SLE patients from the southeastern United States, and potential interactions with CTLA-4 polymorphisms were assessed.

METHODS

Cases comprised 230 subjects recently diagnosed as having SLE (144 African American and 86 white) from university and community-based clinics, and controls comprised 276 age-, sex-, and state-matched subjects (72 African American and 204 white) recruited from driver's license registries. Antibodies to EBV capsid antigen were determined by enzyme-linked immunosorbent assay, with results expressed as positive or negative using the international standardized ratio (ISR) (a ratio of the sample absorbance to a known standard). CTLA-4 genotypes were identified by polymerase chain reaction-based methods.

RESULTS

In African Americans, EBV-IgA seroprevalence was strongly associated with SLE (odds ratio [OR] 5.6, 95% confidence interval [95% CI] 3.0-10.6). In whites, the modest association of SLE with EBV-IgA (OR 1.6) was modified by age, in that the strongest association was observed in those older than age 50 years (OR 4.1, 95% CI 1.6-10.4). The seroprevalence of EBV-IgM and that of EBV-IgG were not associated with SLE. Higher EBV-IgG absorbance ratios were observed in SLE patients, with a significant dose response across units of the ISR in African Americans (P < 0.0001). Allelic variation in the CTLA-4 gene promoter (-1661A/G) significantly modified the association between SLE and EBV-IgA (P = 0.03), with a stronger association among those with the -1661AA genotype.

CONCLUSION

These findings suggest that repeated or reactivated EBV infection, which results in increased EBV-IgA seroprevalence and higher IgG antibody titers, may be associated with SLE, and that the CTLA-4 genotype influences immune responsiveness to EBV in SLE patients. The observed patterns of effect modification by race, age, and CTLA-4 genotype should be examined in other studies and may help frame new hypotheses regarding the role of EBV in SLE etiology.

Mechanism of Action of Transmembrane Activator and Calcium Modulator Ligand Interactor-Ig in Murine Systemic Lupus Erythematosus

B cell-activating factor belonging to the TNF family (BAFF) blockade prevents the onset of disease in systemic lupus erythematosus (SLE)-prone NZB/NZW F(1) mice. To determine the mechanism of this effect, we administered a short course of TACI-Ig with and without six doses of CTLA4-Ig to 18- to 20-wk-old NZB/NZW F(1) mice and evaluated the effect on B and T cell subsets and on anti-dsDNA Ab-producing B cells. Even a brief exposure to TACI-Ig had a beneficial effect on murine SLE; CTLA4-Ig potentiated this effect. The combination of TACI-Ig and CTLA4-Ig resulted in a temporary decrease in serum IgG levels. However, after cessation of treatment, high titers of IgG anti-dsDNA Abs appeared in the serum and IgG Abs deposited in the kidneys. Despite the appearance of pathogenic autoantibodies, the onset of proteinuria was markedly delayed; this was associated with prolonged depletion of B cells past the T1 stage, a decrease in the size of the spleen and lymph nodes, and a decrease in the absolute number of activated and memory CD4(+) T cells. TACI-Ig treatment normalized serum levels of IgM that are markedly elevated in NZB/W F(1) mice; this appeared to be due to a prolonged effect on the ability of the splenic microenvironment to support short-lived IgM plasma cells. Finally, a short course of combination TACI-Ig and CTLA4-Ig prolonged life and even reversed proteinuria in aged NZB/W F(1) mice, suggesting that BAFF blockade may be an effective therapeutic strategy for active SLE.

CD40/CD154 interactions at the interface of tolerance and immunity

Development of the acquired immune response is dependent on the signaling of CD40 by its ligand, CD154. These molecules govern both the magnitude and quality of humoral- and cell-mediated immunity. A litany of studies have conclusively documented that blockade of this ligand-receptor pair can prevent, and also intervene in, the progression of antibody- and cell-mediated autoimmune diseases, and can instill long-lived allogeneic and xenogeneic graft tolerance. Many effector mechanisms of inflammation are abolished as a result of CD154 blockade, but we are now beginning to understand that CD154 blockade may, in some instances, engender long-lived, antigen-specific tolerance. In the context of transplantation tolerance, we present a hypothesis that alpha CD154 blockade is most effective at inducing long-lived allospecific tolerance if anergy and regulation can be elicited prior to the onslaught of inflammation that is induced by grafting (preemptive tolerance). This facet of alpha CD154-induced tolerance appears to co-opt the normal processes of peripheral tolerance induced by immature DCs and can be exploited to induce long-lived antigen-specific tolerance. The underlying science and the prospects for inducing long-lived antigen-specific tolerance in a model of allograft tolerance through CD154 blockade are presented and discussed.

The CD40/CD40L costimulatory pathway in inflammatory bowel disease

The CD154-CD40 ligand pair interaction plays a central role in both induction of the immune response and in immune effector functions. Indeed, many animal disease models and human autoimmune diseases have demonstrated a central role for CD154 expression. The expression of CD154 is very tightly regulated by the immune system through a number of non-redundant overlapping mechanisms that ensure its limited initial induction, along with its temporal maintenance and rapid elimination from the cell surface, and its functional neutralization by the release of soluble CD40. In this review, we discuss the current state of understanding of CD154 regulation during the activation of the immune system and describe numerous strategic mechanisms by which modulation of CD154-CD40 interactions may be applied to treat autoimmune disease.