Traumatic brain injury does not disrupt costimulatory blockade-induced immunological tolerance to glial-restricted progenitor allografts.

BACKGROUND: Cell transplantation-based treatments for neurological disease are promising, yet graft rejection remains a major barrier to successful regenerative therapies. Our group and others have shown that long-lasting tolerance of transplanted stem cells can be achieved in the brain with systemic application of monoclonal antibodies blocking co-stimulation signaling. However, it is unknown if subsequent injury and the blood-brain barrier breach could expose the transplanted cells to systemic immune system spurring fulminant rejection and fatal encephalitis. Therefore, we investigated whether delayed traumatic brain injury (TBI) could trigger graft rejection. METHODS: Glial-restricted precursor cells (GRPs) were intracerebroventricularly transplanted in immunocompetent neonatal mice and co-stimulation blockade (CoB) was applied 0, 2, 4, and 6 days post-grafting. Bioluminescence imaging (BLI) was performed to monitor the grafted cell survival. Mice were subjected to TBI 12 weeks post-transplantation. MRI and open-field test were performed to assess the brain damage and behavioral change, respectively. The animals were decapitated at week 16 post-transplantation, and the brains were harvested. The survival and distribution of grafted cells were verified from brain sections. Hematoxylin and eosin staining (HE) was performed to observe TBI-induced brain legion, and neuroinflammation was evaluated immunohistochemically. RESULTS: BLI showed that grafted GRPs were rejected within 4 weeks after transplantation without CoB, while CoB administration resulted in long-term survival of allografts. BLI signal had a steep rise following TBI and subsequently declined but remained higher than the preinjury level. Open-field test showed TBI-induced anxiety for all animals but neither CoB nor GRP transplantation intensified the symptom. HE and MRI demonstrated a reduction in TBI-induced lesion volume in GRP-transplanted mice compared with non-transplanted mice. Brain sections further validated the survival of grafted GRPs and showed more GRPs surrounding the injured tissue. Furthermore, the brains of post-TBI shiverer mice had increased activation of microglia and astrocytes compared to post-TBI wildtype mice, but infiltration of CD45+ leukocytes remained low. CONCLUSIONS: CoB induces sustained immunological tolerance towards allografted cerebral GRPs which is not disrupted following TBI, and unexpectedly TBI may enhance GRPs engraftment and contribute to post-injury brain tissue repair.

Peptide Blocking CTLA-4 and B7-1 Interaction.

Discovery of the B7 family immune checkpoints such as CTLA-4 (CD152), PD-1 (CD279), as well as their ligands B7-1 (CD80), B7-2 (CD86), B7-H1 (PD-L1, CD274), and B7-DC (PD-L2, CD273), has opened new possibilities for cancer immunotherapy using monoclonal antibodies (mAb). The blockade of inhibitory receptors (CTLA-4 and PD-1) with specific mAb results in the activation of cancer patients' T lymphocytes and tumor rejection. However, the use of mAb in clinics has several limitations including side effects and cost of treatment. The development of new low-molecular compounds that block immune checkpoints' functional activity can help to overcome some of these limitations. In this paper, we describe a synthetic peptide (p344) containing 14 amino acids that specifically interact with CTLA-4 protein. A 3D computer model suggests that this peptide binds to the 99MYPPPY104 loop of CTLA-4 protein and potentially blocks the contact of CTLA-4 receptor with B7-1 ligand. Experimental data confirm the peptide-specific interaction with CTLA-4 and its ability to partially block CTLA-4/B7-1 binding. The identified synthetic peptide can be used for the development of novel immune checkpoint inhibitors that can block CTLA-4 functional activity for cancer immunotherapy.

Immune Checkpoint PD-1/PD-L1 CTLA-4/CD80 are Blocked by Rhus verniciflua Stokes and its Active Compounds.

The bark of Rhus verniciflua Stokes (RVS) has been used to treat cancer in Korean herbal medicine. When we screened for PD-1 and CTLA-4 immune checkpoint inhibitors (PD-1/PD-L1 CTLA-4/CD80) from around 800 herbal extracts using competitive Enzyme-Linked Immunosorbent Assay (ELISA), we found that RVS blocked both the PD-1/PD-L1 and the CTLA-4/CD80 interactions. To identify the active compounds from RVS, we performed bioactivity-guided fractionation, and the ethyl acetate (EtOAc) fraction of RVS proved to be the most effective at blocking the PD-1/PD-L1 and CTLA-4/CD80 interactions. In addition, we isolated and identified 20 major compounds in the EtOAc fraction of RVS and then examined the blocking effects of these 20 compounds on PD-1/PD-L1 and CTLA-4/CD80. Among them, four compounds [eriodictyol (7) > fisetin (9) > quercetin (18) > liquiritigenin (13)] blocked the interaction of PD-1/PD-L1 on competitive ELISA. In addition, four different compounds [protocatechuic acid (2) > caffeic acid (19) > taxifolin (5) > butin (6)] blocked the interaction of CTLA-4/CD80. Our findings suggest that RVS and its components could be used as a potential immune checkpoint inhibitor blockade and could be developed for immuno-oncological therapeutics.

Belatacept in kidney transplantation and its limitations.

INTRODUCTION: Since the approval of belatacept in 2011 for use in the setting of de novo kidney transplantation, this CD80/86 - CD28 co-stimulation blocker has been shown to be a valuable treatment option for maintenance immunosuppression. Areas covered: In this setting, belatacept has been associated with superior glomerular filtration rate as compared to calcineurin inhibitor-based treatments because of the absence of nephrotoxicity. Additionally, belatacept avoids the cardiovascular side effects (e.g. hypertension and dyslipidemia) caused by a CNI-based-regimen. Nevertheless, belatacept-treated recipients have a higher rate of acute rejections and a higher risk of lymphoproliferative disorders. Expert opinion: Data suggest a benefit from early conversion vs. late conversion of belatacept in a conversion setting following CNI-related toxicity. Randomized studies are currently comparing belatacept to tacrolimus, instead of cyclosporine, as was done in the Belatacept Evaluation of Nephroprotection and Efficacy as a First-line Immunosuppression Trial (BENEFIT). The benefits and limitations of belatacept seem to be the same when tacrolimus is used instead of cyclosporine. Finally, we also report in this review on the immunological data available so far that explain belatacept's limitations and the higher rate of acute rejection. The goal is to find the optimal immunosuppressive strategy to improve efficacy and safety at post-transplantation.

Costimulation Blockade in Kidney Transplantation: An Update.

In the setting of solid-organ transplantation, calcineurin inhibitor (CNI)-based therapy remains the cornerstone of immunosuppression. However, long-term use of CNIs is associated with some degree of nephrotoxicity. This has led to exploring the blockade of some costimulation pathways as an efficient immunosuppressive tool instead of using CNIs. The only agent already in clinical use and approved by the health authorities for kidney transplant patients is belatacept (Nulojix), a fusion protein that interferes with cytotoxic T lymphocyte-associated protein 4. Belatacept has been demonstrated to be as efficient as cyclosporine-based immunosuppression and is associated with significantly better renal function, that is, no nephrotoxicity. However, in the immediate posttransplant period, significantly more mild/moderate episodes of acute rejection have been reported, favored by the fact that cytotoxic T lymphocyte-associated protein pathway has an inhibitory effect on the alloimmune response; thereby its inhibition is detrimental in this regard. This has led to the development of antibodies that target CD28. The most advanced is FR104, it has shown promise in nonhuman primate models of autoimmune diseases and allotransplantation. In addition, research into blocking the CD40-CD154 pathway is underway. A phase II study testing ASK1240, that is, anti-CD40 antibody has been completed, and the results are pending.

Regulatory T Cell-Dependent and -Independent Mechanisms of Immune Suppression by CD28/B7 and CD40/CD40L Costimulation Blockade.

Blocking of costimulatory CD28/B7 and CD40/CD40L interactions is an experimental approach to immune suppression and tolerance induction. We previously reported that administration of a combination of CTLA-4Ig and MR1 (anti-CD40L mAb) for blockade of these interactions induces tolerance in a fully mismatched allogeneic splenocyte transfer model in mice. We now used this model to study whether regulatory T cells (Tregs) contribute to immune suppression and why both pathways have to be blocked simultaneously. Mice were injected with allogeneic splenocytes, CD4(+) T cells, or CD8(+) T cells and treated with MR1 mAb and different doses of CTLA-4Ig. The graft-versus-host reaction of CD4(+) T cells, but not of CD8(+) T cells, was inhibited by MR1. CTLA-4Ig was needed to cover CD8(+) T cells but had only a weak effect on CD4(+) T cells. Consequently, only the combination provided full protection when splenocytes were transferred. Importantly, MR1 and low-dose CTLA-4Ig treatment resulted in a relative increase in Tregs, and immune suppressive efficacy was abolished in the absence of Tregs. High-dose CTLA-4Ig treatment, in contrast, prevented Treg expansion and activity, and in combination with MR1 completely inhibited CD4(+) and CD8(+) T cell activation in a Treg-independent manner. In conclusion, MR1 and CTLA-4Ig act synergistically as they target different T cell populations. The contribution of Tregs to immune suppression by costimulation blockade depends on the concentration of CTLA-4Ig and thus on the degree of available CD28 costimulation.

B7-1 Blockade Does Not Improve Post-Transplant Nephrotic Syndrome Caused by Recurrent FSGS.

FSGS is a common glomerular disorder that has a high propensity for recurrence after kidney transplant. The pathophysiology of FSGS is unknown, but podocytes seem to be the target of one or several circulating factors that lead to cytoskeleton reorganization and proteinuria. Research on podocytes has identified B7-1 as an important factor in podocyte biology and a new therapeutic target in renal disease. Indeed, in four patients with recurrent FSGS after transplant, treatment with the B7-1 blocker abatacept was associated with proteinuria remission. Here, we prospectively treated nine patients with recurrent FSGS after transplant using either abatacept or belatacept, a B7-1 blocker with higher affinity, and did not induce proteinuria remission. Furthermore, we did not detect B7-1 expression by immunofluorescence in podocytes of biopsy specimens from these or other kidney grafts or podocytes of native kidney biopsy specimens. In conclusion, B7-1 blockade did not induce FSGS remission after transplant in our study.

MPGES-1-derived PGE2 suppresses CD80 expression on tumor-associated phagocytes to inhibit anti-tumor immune responses in breast cancer.

Prostaglandin E2 (PGE2) favors multiple aspects of tumor development and immune evasion. Therefore, microsomal prostaglandin E synthase (mPGES-1/-2), is a potential target for cancer therapy. We explored whether inhibiting mPGES-1 in human and mouse models of breast cancer affects tumor-associated immunity. A new model of breast tumor spheroid killing by human PBMCs was developed. In this model, tumor killing required CD80 expression by tumor-associated phagocytes to trigger cytotoxic T cell activation. Pharmacological mPGES-1 inhibition increased CD80 expression, whereas addition of PGE2, a prostaglandin E2 receptor 2 (EP2) agonist, or activation of signaling downstream of EP2 reduced CD80 expression. Genetic ablation of mPGES-1 resulted in markedly reduced tumor growth in PyMT mice. Macrophages of mPGES-1(-/-) PyMT mice indeed expressed elevated levels of CD80 compared to their wildtype counterparts. CD80 expression in tumor-spheroid infiltrating mPGES-1(-/-) macrophages translated into antigen-specific cytotoxic T cell activation. In conclusion, mPGES-1 inhibition elevates CD80 expression by tumor-associated phagocytes to restrict tumor growth. We propose that mPGES-1 inhibition in combination with immune cell activation might be part of a therapeutic strategy to overcome the immunosuppressive tumor microenvironment.

Personalized medicine in rheumatoid arthritis: is the glass half full or half empty?

The care of patients with rheumatoid arthritis (RA) has been revolutionized since the 1990s. Strict monitoring and disease control based on measurement of signs and symptoms towards a target of low disease activity have improved outcome of patients enormously. As a result of treatment strategies based upon individualized measurement of disease activity, the clinical view of RA has changed from a destructive autoimmune disease (with a median joint damage of >10 Sharp units per year) to a condition in which significant damage can be prevented in the majority of patients. Moreover, a large number of targeted therapies (tumour necrosis factor, IL6, CD80/CD86 and CD20 inhibitors) have become available to better treat the underlying disease process. However, identification of the underlying pathways that drive the disease process in an individual patient has been relatively unsuccessful, implying that no predictive factors have been identified to guide the choice of a specific treatment. Distinct subsets of RA patients have been identified, based on the presence or absence of anticitrullinated protein antibodies (ACPAs). These two subsets are associated with different environmental and genetic risk factors, histology and disease outcome (a more destructive disease course with more persistent joint inflammation is observed when ACPAs are present). Therefore, it is recommended that treatment should be guided towards a more consistently low level of disease activity in the presence of ACPAs than in the absence of the antibodies.

Abatacept in B7-1-positive proteinuric kidney disease.

Abatacept (cytotoxic T-lymphocyte-associated antigen 4-immunoglobulin fusion protein [CTLA-4-Ig]) is a costimulatory inhibitor that targets B7-1 (CD80). The present report describes five patients who had focal segmental glomerulosclerosis (FSGS) (four with recurrent FSGS after transplantation and one with primary FSGS) and proteinuria with B7-1 immunostaining of podocytes in kidney-biopsy specimens. Abatacept induced partial or complete remissions of proteinuria in these patients, suggesting that B7-1 may be a useful biomarker for the treatment of some glomerulopathies. Our data indicate that abatacept may stabilize ß1-integrin activation in podocytes and reduce proteinuria in patients with B7-1-positive glomerular disease.

B7-1/B7-2 blockade overrides the activation of protective CD8 T cells stimulated in the absence of Foxp3+ regulatory T cells.

Although T cell activation has been classically described to require distinct, positive stimulation signals that include B7-1 (CD80) and B7-2 (CD86) costimulation, overriding suppression signals that avert immune-mediated host injury are equally important. How these opposing stimulation and suppression signals work together remains incompletely defined. Our recent studies demonstrate that CD8 Teff activation in response to cognate peptide stimulation is actively suppressed by the Foxp3(+) subset of CD4 cells, called Tregs. Here, we show that the elimination of Treg suppression does not bypass the requirement for positive B7-1/B7-2 costimulation. The expansion, IFN-γ cytokine production, cytolytic, and protective features of antigen-specific CD8 T cells stimulated with purified cognate peptide in Treg-ablated mice were each neutralized effectively by CTLA-4-Ig that blocks B7-1/B7-2. In turn, given the efficiency whereby CTLA-4-Ig overrides the effects of Treg ablation, the role of Foxp3(+) cell-intrinsic CTLA-4 in mitigating CD8 Teff activation was also investigated. With the use of mixed chimera mice that contain CTLA-4-deficient Tregs exclusively after the ablation of WT Foxp3(+) cells, a critical role for Treg CTLA-4 in suppressing the expansion, cytokine production, cytotoxicity, and protective features of peptide-stimulated CD8 T cells is revealed. Thus, the activation of protective CD8 T cells requires positive B7-1/B7-2 costimulation even when suppression by Tregs and in particular, Treg-intrinsic CTLA-4 is circumvented.

Galiximab (anti-CD80)-induced growth inhibition and prolongation of survival in vivo of B-NHL tumor xenografts and potentiation by the combination with fludarabine.

Galiximab is a primatized monoclonal antibody that targets CD80 expressed on malignant B cells and is being studied in the clinic as a potential treatment for follicular NHL. We have recently reported that galiximab signals B-NHL cells in vitro and inhibits cell growth and sensitizes resistant tumor cells to apoptosis by chemotherapeutic drugs. This study was designed to validate the in vitro findings in in vivo in mice. Thus, we examined in vivo the antitumor activity of galiximab used alone and in combination with chemotherapeutic agents in SCID mice bearing human lymphoma xenografts. The in vivo antitumor effects of galiximab used alone and in combination with fludarabine or doxorubicin were determined in solid and disseminated human B-lymphoma tumors grown in SCID mice. Galiximab monotherapy in vivo demonstrated significant antitumor activity in a Raji lymphoma solid tumor model and in an SKW disseminated lymphoma tumor model. There was significant inhibition in tumor growth and prolongation of survival. In vitro, galiximab sensitized Raji cells to apoptosis by both fludarabine and doxorubicin. Tumor growth inhibition was significantly enhanced when the mice were treated with the combination of galiximab and fludarabine. These findings support the potential clinical application of galiximab in combination with chemotherapeutic drugs for the treatment of CD80-expressing hematological malignancies.

Co-stimulatory molecules as targets for treatment of lupus.

Co-stimulatory molecules help to regulate interactions between T cells and antigen-presenting cells and may play an important role in the pathogenesis of lupus. Both work in murine models and some early studies in human lupus support further examination of these molecules as therapeutic targets. Complexities of lupus clinical trial variables may have hampered progress in this area but recent developments in the field may make interventional trials more feasible in the near future. To date biologics which provide direct blockade of interactions between CD40 and CD154, B7RP-1 and ICOS, and CD80 or CD86 with CD28 have been assessed in multicenter clinical trials. These data will be reviewed and critiqued.

[Effect of CD80-scFv on recognition of CD80 molecule and proliferation of different tumor cells in vitro].

AIM: To prepare CD80-scFv in CHO cells and investigate its effect on the recognition and proliferation of different tumor cells. METHODS: The CD80-scFv was purified from culture supernatant without fetal calf serum (FCS) by IMAC affinity chromatography, and then bound to CD80 molecule on the Daudi, U251, A375 and 8266 cells detected by flow cytometry. Different concentrations of CD80-scFv were added in the training system of different tumor cells, and we analyzed the influence on the proliferation of these cells by MTT assay. With 8266 cells which expressed CD80 highly and were treated by mitomycin firstly as the APC, and human PBMC as the effect cells, we analyzed the influence of the CD80-scFv on the proliferation of PBMC by blocking the co-stimulatory signal. RESULTS: The concentration of CD80-scFv purified from FCS was about 6.67 mg/L and the binding rate of CD80-scFv with Daudi, U251, A375, 8266 and U266 were 96.8%, 39.6%, 20.5%, 99.9% and 3.8%, respectively. CD80-scFv suppressed the proliferation of Daudi and 8266 cells which expressed CD80 highly, and the inhibition rate of Daudi and 8266 cells cultured with CD80-scFv (the final concentration was 25 µg/mL) was 24.04% and 24.16%, respectively. Additionally, the antibody suppressed the proliferation of PBMC by blocking the co-stimulatory signal mediated by CD80-CD28. CONCLUSION: CD80-scFv can recognize CD80 molecule and suppress the proliferation of tumor cells which express CD80 highly.