CD40 expression on graft infiltrates and parenchymal CD154 (CD40L) induction in human chronic renal allograft rejection

The Inhibition of CD40/CD154 Costimulatory Signaling in the Prevention of Renal Transplant Rejection in Nonhuman Primates: A Systematic Review and Meta Analysis

The prevention of allograft transplant rejection by inhibition of the CD40/CD40L costimulatory pathway has been described in several species. We searched pubmed for studies reporting the prevention of kidney transplant rejection in nonhuman primates utilizing either anti CD40 or anti CD40L (CD154) treatment. Inclusion of data required treatment with anti CD40 or anti CD154 as monotherapy treatment arms, full text available, studies conducted in nonhuman primate species, the transplant was renal transplantation, sufficient duration of treatment to assess long term rejection, and the reporting of individual graft survival or survival duration. Eleven publications were included in the study. Rejection free survival was calculated using the Kaplan-Meier (KM) life test methods to estimate the survival functions. The 95% CI for the medians was also calculated. A log-rank test was used to test the equality of the survival curves between control and treatment arms (CD40 and CD154). The hazard ratio for CD154 compared to CD40 and 95% CI was calculated using a Cox proportional-hazards model including treatment as the covariate to assess the magnitude of the treatment effect. Both anti CD40 and anti CD154 treatments prevented acute and long term graft rejection. The median (95% CI) rejection free survival was 131 days (84,169 days) in the anti CD40 treated animals and 352 days (173,710 days) in the anti CD154 treated animals. Median survival in the untreated animals was 6 days. The inhibition of transplant rejection was more durable in the anti CD154 group compared to the anti CD40 group after cessation of treatment. The median (95% CI) rejection free survival after cessation of treatment was 60 days (21,80 days) in the anti CD40 treated animals and 230 days (84,552 days) in the anti CD154 treated animals.

Review: Ischemia Reperfusion Injury-A Translational Perspective in Organ Transplantation

Thanks to the development of new, more potent and selective immunosuppressive drugs together with advances in surgical techniques, organ transplantation has emerged from an experimental surgery over fifty years ago to being the treatment of choice for many end-stage organ diseases, with over 139,000 organ transplants performed worldwide in 2019. Inherent to the transplantation procedure is the fact that the donor organ is subjected to blood flow cessation and ischemia during harvesting, which is followed by preservation and reperfusion of the organ once transplanted into the recipient. Consequently, ischemia/reperfusion induces a significant injury to the graft with activation of the immune response in the recipient and deleterious effect on the graft. The purpose of this review is to discuss and shed new light on the pathways involved in ischemia/reperfusion injury (IRI) that act at different stages during the donation process, surgery, and immediate post-transplant period. Here, we present strategies that combine various treatments targeted at different mechanistic pathways during several time points to prevent graft loss secondary to the inflammation caused by IRI.

Association of soluble CD40 levels with -1 C > T CD40 polymorphism and chronic kidney disease in systemic lupus erythematosus

Background

CD40 is a transmembrane protein mainly expressed on the antigen‐presenting cells surface. CD40 plays a crucial role in immunoglobulin class switching and antibodies production. Genetic polymorphisms in the CD40 gene have been associated with increased risk of systemic lupus erythematosus (SLE) in several populations. This study aimed to evaluate the association of CD40 polymorphisms (−1 C > T, rs1883832 and 6,048 G > T, rs4810485) with SLE susceptibility, as well as with mRNA expression and soluble CD40 (sCD40) levels.

Methods

The study included 293 patients with SLE and 294 control subjects (CS). Genotyping was performed by PCR‐RFLP method. CD40 mRNA expression was determined by quantitative real‐time PCR, and ELISA quantified sCD40 levels.

Results

The CD40 polymorphisms −1 C > T and 6,048 G > T were associated with SLE susceptibility. There was no difference between CD40 mRNA expression and CD40 polymorphisms. The sCD40 levels were lower in SLE patients with TT haplotype, whereas higher sCD40 levels were associated with damage and impaired renal function according to SLICC and KDIGO. The sCD40 levels were negatively correlated with eGFR.

Conclusion

The CD40 gene polymorphisms increase the risk of SLE in the western Mexican population. The sCD40 levels are associated with −1 C > T polymorphism and chronic kidney disease.

Cardiotonic Steroids and the Sodium Trade Balance: New Insights into Trade-Off Mechanisms Mediated by the Na⁺/K⁺-ATPase

In 1972 Neal Bricker presented the "trade-off" hypothesis in which he detailed the role of physiological adaptation processes in mediating some of the pathophysiology associated with declines in renal function. In the late 1990's Xie and Askari published seminal studies indicating that the Na⁺/K⁺-ATPase (NKA) was not only an ion pump, but also a signal transducer that interacts with several signaling partners. Since this discovery, numerous studies from multiple laboratories have shown that the NKA is a central player in mediating some of these long-term "trade-offs" of the physiological adaptation processes which Bricker originally proposed in the 1970's. In fact, NKA ligands such as cardiotonic steroids (CTS), have been shown to signal through NKA, and consequently been implicated in mediating both adaptive and maladaptive responses to volume overload such as fibrosis and oxidative stress. In this review we will emphasize the role the NKA plays in this "trade-off" with respect to CTS signaling and its implication in inflammation and fibrosis in target organs including the heart, kidney, and vasculature. As inflammation and fibrosis exhibit key roles in the pathogenesis of a number of clinical disorders such as chronic kidney disease, heart failure, atherosclerosis, obesity, preeclampsia, and aging, this review will also highlight the role of newly discovered NKA signaling partners in mediating some of these conditions.

Targeted disruption of Cd40 in a genetically hypertensive rat model attenuates renal fibrosis and proteinuria, independent of blood pressure

High blood pressure is a common cause of chronic kidney disease. Because CD40, a member of the tumor necrosis factor receptor family, has been linked to the progression of kidney disease in ischemic nephropathy, we studied the role of Cd40 in the development of hypertensive renal disease. The Cd40 gene was mutated in the Dahl S genetically hypertensive rat with renal disease by targeted-gene disruption using zinc-finger nuclease technology. These rats were then given low (0.3%) and high (2%) salt diets and compared. The resultant Cd40 mutants had significantly reduced levels of both urinary protein excretion (41.8 ± 3.1 mg/24 h vs. 103.7 ± 4.3 mg/24 h) and plasma creatinine (0.36 ± 0.05 mg/dl vs. 1.15 ± 0.19 mg/dl), with significantly higher creatinine clearance compared with the control S rats (3.04 ± 0.48 ml/min vs. 0.93 ± 0.15 ml/min), indicating renoprotection was conferred by mutation of the Cd40 locus. Furthermore, the Cd40 mutants had a significant attenuation in renal fibrosis, which persisted on the high salt diet. However, there was no difference in systolic blood pressure between the control and Cd40 mutant rats. Thus, these data serve as the first evidence for a direct link between Cd40 and hypertensive nephropathy. Hence, renal fibrosis is one of the underlying mechanisms by which Cd40 plays a crucial role in the development of hypertensive renal disease.

Blockade of CD40-TRAF2,3 or CD40-TRAF6 is sufficient to inhibit pro-inflammatory responses in non-haematopoietic cells

Inhibition of the CD40-CD154 pathway controls inflammatory disorders. Unfortunately, administration of anti-CD154 monoclonal antibodies causes thromboembolism. Blockade of signalling downstream of CD40 may represent an approach to treat CD40-driven inflammatory disorders. Blocking tumour necrosis factor receptor-associated factor 6 (TRAF6) signalling downstream of CD40 in MHC II(+) cells diminishes inflammation. However, CD40-TRAF6 blockade may cause immunosuppression. We examined the role of CD40-TRAF2,3 and CD40-TRAF6 signalling in the development of pro-inflammatory responses in human non-haematopoietic and monocytic cells. Human aortic endothelial cells, aortic smooth muscle cells, renal proximal tubule epithelial cells, renal mesangial cells and monocytic cells were transduced with retroviral vectors that encode wild-type CD40, CD40 with a mutation that prevents TRAF2,3 recruitment (ΔT2,3), TRAF6 recruitment (ΔT6) or both TRAF2,3 plus TRAF6 recruitment (ΔT2,3,6). Non-haematopoietic cells that expressed CD40 ΔT2,3 exhibited marked inhibition in CD154-induced up-regulation of vascular cell adhesion molecule 1, intercellular adhesion molecule 1 (ICAM-1), monocyte chemotactic protein 1 (MCP-1), tissue factor and matrix metalloproteinase 9. Similar results were obtained with cells that expressed CD40 ΔT6. Although both mutations impaired ICAM-1 up-regulation in monocytic cells, only expression of CD40 ΔT6 reduced MCP-1 and tissue factor up-regulation in these cells. Treatment of endothelial and smooth muscle cells with cell-permeable peptides that block CD40-TRAF2,3 or CD40-TRAF6 signalling impaired pro-inflammatory responses. In contrast, while the CD40-TRAF2,3 blocking peptide did not reduce CD154-induced dendritic cell maturation, the CD40-TRAF6 blocking peptide impaired this response. Hence, preventing CD40-TRAF2,3 or CD40-TRAF6 interaction inhibits pro-inflammatory responses in human non-haematopoietic cells. In contrast to inhibition of CD40-TRAF6 signalling, inhibition of CD40-TRAF2,3 signalling did not impair dendritic cell maturation. Blocking CD40-TRAF2,3 signalling may control CD40-CD154-dependent inflammatory disorders.

Costimulatory pathways in kidney transplantation: pathogenetic role, clinical significance and new therapeutic opportunities

Costimulatory pathways play a key role in immunity, providing the second signal required for a full activation of adaptive immune response. Different costimulatory families (CD28, TNF-related, adhesion and TIM molecules), characterized by structural and functional analogies, have been described. Costimulatory molecules modulate T cell activation, B cell function, Ig production, cytokine release and many other processes, including atherosclerosis. Patients suffering from renal diseases present significant alterations of the costimulatory pathways, which might make them particularly liable to infections. These alterations are further pronounced in patients undergoing kidney transplantation. In these patients, different costimulatory patterns have been related to distinct clinical features. The importance that costimulation has gained during the last years has led to development of several pharmacological approaches to modulate this critical step in the immune activation. Different drugs, mainly monoclonal antibodies targeting various costimulatory molecules (i.e. anti-CD80, CTLA-4 fusion proteins, anti-CD154, anti-CD40, etc.) were designed and tested in both experimental and clinical studies. The results of these studies highlighted some criticisms, but also some promising findings and now costimulatory blockade is considered a suitable strategy, with belatacept (a CTLA-4 fusion protein) being approved as the first costimulatory blocker for use in renal transplantation. In this review, we summarize the current knowledge on costimulatory pathways in the setting of kidney transplantation. We describe the principal costimulatory molecule families, their role and clinical significance in patients undergoing renal transplantation and the new therapeutic approaches that have been developed to modulate the costimulatory pathways.

Effect of CD40 and sCD40L on renal function and survival in patients with renal artery stenosis

Activation of the CD40 receptor on the proximal tubular epithelium of the kidney results in fibrosis and inflammation in experimental models of kidney injury. Soluble CD40 ligand is released by activated platelets. The role of CD40-soluble CD40 ligand in patients with ischemic renal disease is unknown. Plasma levels of CD40 and soluble CD40 ligand were measured by enzyme-linked immunosorbent assay in a single center cohort of 60 patients with renal artery stenosis recruited from Salford Royal Hospital, Manchester, United Kingdom. A natural log transformation of CD40 and soluble CD40 ligand was performed to normalize the data. Estimated glomerular filtration rate was used as the primary indicator of renal function. By univariate analysis, low baseline levels of circulating CD40 (R(2)=0.06; P<0.05) and baseline creatinine (R(2)=0.08; P=0.022) were associated with loss of kidney function at 1-year follow-up, whereas soluble CD40 ligand was not (R(2)=0.02; P=ns). In a multiple linear regression model, CD40 (P<0.02) and baseline creatinine (P<0.01) continued to be significantly associated with a decline in renal function (model R(2)=0.17; P<0.005). Baseline CD40 levels were somewhat lower in patients who died during follow-up (survivors, 7.3±0.9 pg/mL, n=48 versus nonsurvivors, 6.7±1.0 pg/mL, n=12; P=0.06). The CD40/soluble CD40 ligand signaling cascade may be a novel mechanism contributing to the development and progression of renal injury in patients with atherosclerotic renal artery stenosis.

In vivo therapeutic efficacy of intra-renal CD40 silencing in a model of humoral acute rejection

The humoral branch of the immune response has an important role in acute and chronic allograft dysfunction. The CD40/CD40L costimulatory pathway is crucial in B- and T- alloresponse. Our group has developed a new small interfering RNA (siRNA) molecule against CD40 that effectively inhibits its expression. The aim of the present study was to prevent rejection in an acute vascular rejection model of kidney transplant by intra-graft gene silencing with anti-CD40 siRNA (siCD40), associated or not with sub-therapeutic rapamycin. Four groups were designed: unspecific siRNA as control; sub-therapeutic rapamycin; siCD40; and combination therapy. Long-surviving rats were found only in both siCD40-treated groups. The CD40 mRNA was overexpressed in control grafts but treatment with siCD40 decreased its expression. Recipient spleen CD40+ B-lymphocytes were reduced in both siCD40-treated groups. Moreover, CD40 silencing reduced donor-specific antibodies, graft complement deposition and immune-inflammatory mediators. The characteristic histological features of humoral rejection were not found in siCD40-treated grafts, which showed a more cellular histological pattern. Therefore, the intra-renal effective blockade of the CD40/CD40L signal reduces the graft inflammation as well as the incidence of humoral vascular acute rejection, finally changing the type of rejection from humoral to cellular.

CD40L proinflammatory and profibrotic effects on proximal tubular epithelial cells: role of NF-kappaB and lyn

Chronic allograft nephropathy (CAN) is the main cause of renal graft loss, but its pathogenic mechanisms are still unclear. Immune system activation has been suggested as a key event in the development of CAN. CD40 is a co-stimulatory protein whose expression is upregulated in proximal tubular epithelial cells (PTEC) in acute rejection. This receptor interacts with CD40L, expressed by activated T cells. CD40L induces the production by PTEC of different proinflammatory cytokines, but very little is known of its profibrotic effects. The aim of this study was to investigate the effect of CD40/CD40L interaction on PTEC expression of plasminogen activator inhibitor-1 (PAI-1), a powerful profibrotic mediator, and monocyte chemoattractant protein-1 (MCP-1), a proinflammatory cytokine, and to investigate the signaling pathways that lead to these effects. Soluble CD40L induced a time-dependent increase in both PAI-1 and MCP-1 gene expression and protein production in PTEC. CD40 cross-linking on PTEC caused TNF-R-associated factors 2 and 6 membrane translocation. This event led to NF-kappaB activation, through the NF-kappaB-inducing kinase, and to a significant increase in the phosphorylation of lyn, a src-related tyrosine kinase. Lyn, upon phosphorylation, became strictly associated with caveolin-1, a scaffolding protein enriched in caveolae. Lyn inhibition did not have any effect on CD40L-induced NF-kappaB activation and MCP-1 expression but abolished PAI-1 induction. On the contrary, NF-kappaB inhibition significantly reduced only MCP-1 expression. In conclusion, CD40L could play a key role in the pathogenesis of CAN through PAI-1 induction. CD40L profibrotic and proinflammatory effects are mediated by different signaling pathways, suggesting that drugs that inhibit inflammation may not be equally effective in reducing fibrosis.

Combined Treatment with CD40 Costimulation Blockade, T-Cell Depletion, Low-Dose Irradiation, and Donor Bone Marrow Transfusion in Limb Allograft Survival

To determine the efficacy of a regimen based on CD40 costimulation blockade and donor bone marrow in the limb allograft model, C57Bl/6 mice received limb allografts from Balb/c mice and either no treatment or a combination of MR1 (anti-CD40 ligand monoclonal antibody), CD4+ and CD8+ T-cell-depleting antibodies, low-dose irradiation, and bone marrow transfusion from Balb/c donors for 1 or 2 weeks. Recipients treated for 1 week showed rejection at 38.2 +/- 5.4 (mean +/- SEM) days, while those treated for 2 weeks had allograft survival of 56.5 +/- 9.9, with a range up to 91 days. Histology demonstrated rejection which was less cell-mediated and suggestive of transplant vasculopathy. Differential rejection of skin occurred first. Thus, a combined regimen based on CD40 costimulatory blockade and donor marrow significantly prolonged allograft survival. However, tolerance was not achieved, and histology suggests chronic rejection as a possible cause of allograft loss.

Prolonged limb allograft survival with CD40 costimulation blockade, T-cell depletion, and megadose donor bone-marrow transfusion

The purpose of this study was to determine the efficacy of a treatment regimen consisting of CD 40 costimulation blockade, T-cell depletion, and megadose donor bone marrow transfusion in the limb allograft model. C57Bl/6 mice underwent limb transplantation from Balb/c mice and received MR1 (anti-CD 40 ligand monoclonal antibody), and CD4(+) and CD8(+) T cell-depleting antibodies with and without 120 x 10(6) donor bone-marrow transfusion. Recipients treated only with antibodies showed rejection at 51.4+/-17 (mean+/-SEM) days, while those who also received donor bone marrow had allograft survival of 67+/-16.4 days, with a range up to 91 days. Treated specimens with rejection had less lymphocytic infiltration than untreated controls. Recipients of donor bone marrow also demonstrated early mixed chimerism, which disappeared after 1 month. While allograft survival was prolonged, tolerance was not achieved, and the mechanism of rejection was more consistent with a chronic process.

Efficacy and safety of ABI793, a novel human anti-human CD154 monoclonal antibody, in cynomolgus monkey renal allotransplantation

BACKGROUND

Anti-CD154 monoclonal antibodies (mAbs) cause long-term graft survival in preclinical allotransplantation experiments. This is the first report on the efficacy and safety of ABI793, a novel human anti-human CD154 mAb, in Cynomolgus renal transplant recipients.

METHODS

ABI793 (human immunoglobulin-G1:kappa) was derived from a hybridoma generated after immunization of human immunoglobulin transgenic mice (HuMAb-Mouse, Medarex Inc., Annandale, NJ). Cynomolgus monkey recipients of major histocompatibility complex-mismatched, life-supporting renal allografts were treated repeatedly with intravenous ABI793 for a 3-month period posttransplantation. Graft function was monitored by serum creatinine, and rejection was confirmed histologically.

RESULTS

ABI793 binds to human, Cynomolgus and Rhesus monkey CD154; it inhibits dose dependently in vitro CD154:CD40 binding and human mixed lymphocyte reaction. ABI793 is comparable to the mouse anti-human CD154 mAbs 5c8 and 24-31 with respect to affinity, inhibitory capacity, and species specificity; however, ABI793 binds to a different CD154 epitope. With 20 mg/kg of ABI793, five of nine recipients showed substantially prolonged graft survival after cessation of treatment, whereas four of nine recipients were killed because of high serum creatinine while still receiving treatment. ABI793 treatment was associated with episodes of severe acute tubular necrosis (which was unrelated to rejection and responded to fluid and diuretic treatment) and a decrease in platelet numbers. Chronic and acute thromboembolic vascular lesions with hemorrhages were observed in the lung and brain of two allograft recipients. None of these side effects were observed in animals that underwent autotransplantation, thus excluding direct toxicity of ABI793.

CONCLUSIONS

ABI793 treatment effectively prevents graft rejection in Cynomolgus monkeys. Evidence for rare thromboembolic events, as also previously observed with different anti-human CD154 mAbs, suggests that thromboembolic complications may be a class effect of anti-CD154 mAbs, unrelated to their epitope specificity.

Reduced CD40L Expression on ex vivo Activated CD4+ T-Lymphocytes from Patients with Excellent Renal Allograft Function Measured with a Rapid Whole Blood Flow Cytometry Procedure

BACKGROUND

The CD40-CD40L (CD154) costimulatory pathway plays a critical role in the pathogenesis of kidney allograft rejection. In renal transplant biopsies, CD4+CD40L+ graft-infiltrating cells were detected during chronic rejection in contrast to acute rejection episodes. Using a rapid noninvasive FACS procedure, we were able to demonstrate CD40L upregulation in peripheral blood of patients with chronic renal allograft dysfunction.

MATERIALS AND METHODS

Whole blood from recipients of renal allografts was stimulated with PMA and ionomycin and measured by flow cytometry. Patients were assigned to three groups based on transplant function. Group 1: 26 patients with excellent renal transplant function; group 2: 28 patients with impaired transplant function; group 3: 14 patients with chronic allograft dysfunction and group 4: 8 healthy controls.

RESULTS

The median percentage +/- SEM of CD4+/CD40L+ cells stimulated ex vivo at 10 ng/ml PMA was as follows: group 1: 28.3 +/- 4.1%; group 2: 18.4 +/- 2.4%; group 3: 50.1 +/- 5.0% and group 4: 40.4 +/- 3.4%. Subdivisions of groups 2 and 3 resulted in different CD40L expression patterns. Patients with increased serum creatinine since the initial phase after transplantation (groups 2a and 3a) revealed a higher percentage of CD4+CD40L+ cells than patients showing a gradual increase over time (groups 2b and 3b). Consequently, patients of group 3a exhibited a significantly reduced transplant function compared with those of group 3b.

CONCLUSION

After PMA + ionomycin stimulation, patients with excellent kidney graft function displayed significantly reduced expression of CD40L surface molecules on CD4+ cells early after transplantation. Those with a chronic dysfunction of the renal graft showed significantly more CD4+ cells expressing CD40L compared to the other transplanted groups. These results demonstrate that the percentage of CD4+CD40L+ cells stimulated ex vivo in peripheral blood may be a valuable marker for chronic allograft nephropathy.

Analysis of intragraft gene and protein expression of the costimulatory molecules, CD80, CD86 and CD154, in orthotopic liver transplant recipients

CD40-CD154 and/or CD28-CD80/86 costimulatory blockade induces long-term allograft survival in numerous animal models. Studies examining the expression of costimulatory molecules during acute cellular rejection (ACR) have been limited to renal and cardiac allografts. The aim of this study was to describe the relationship between intragraft costimulatory molecule expression in OLT recipients and ACR. Forty-five liver biopsies were obtained at reperfusion and day 7. Gene and protein expression of CD80, CD86 and CD154 were analyzed by RT-PCR and immunohistochemistry. CD154 protein expression was present in 13 of 18 patients with a RAI score of 4, but in only two of 14 patients with a RAI score of <4. There was a strong association between the RAI score and the presence of CD80 and CD154 immunoreactivity. CD86 protein expression did not correlate with the severity of ACR. In reperfusion biopsies CD154, but not CD80 or CD86, protein expression correlated with the total ischaemic time. There was no association between expression of costimulatory molecule genes and ACR. In conclusion, we have demonstrated an association between CD154 and CD80 protein expression and ACR in orthotopic liver allografts.

Long-term limb allograft survival using anti-CD40L antibody in a murine model

BACKGROUND

Costimulation blockade has been shown to be effective in achieving donor-specific immune unresponsiveness in models of organ transplantation. This study represents the first application of blockade of the CD40 costimulatory pathway to a murine model of limb allotransplantation.

METHODS

Eighteen Balb/c mice (H-2K(d)) were randomized to four groups. The control group (n=5) received syngeneic limb transplants from Balb/c donors. The experimental groups were recipients of limb allografts from C57Bl/6 mice (H-2K(b)) and received either no treatment (n=5) or treatment with MR1 (hamster antimouse CD40 ligand monoclonal antibody) 500 microg intraperitoneally (IP) on days 0, 2, 4, 6, 14, 28, and 60 (n=5). A fourth group received myocutaneous allografts from C57Bl/6 donors and the same treatment with MR1 (n=5).

RESULTS

Untreated limb allografts were rejected at a mean of 9.6+/-1.1 days postoperatively. MR1-treated limb allografts underwent rejection of the skin component at a mean of 75+/-25 days whereas the musculoskeletal component survived to a mean of 222+/-84 days with two allografts surviving more than 10 months (P<0.001). The MR1-treated myocutaneous allografts were rejected after 16.2+/-2 days. All groups demonstrated acute rejection on histology except the treated limb allograft group, which was more suggestive of a chronic process. No chimerism was detected in this group by flow cytometry.

CONCLUSIONS

CD40 costimulatory blockade significantly prolonged limb-allograft survival, and the bone-marrow component may have played an important role. Tolerance was not achieved, and histologic evaluation suggested chronic rejection as a possible cause of allograft loss.

A novel CD154 monoclonal antibody in acute and chronic rat vascularized cardiac allograft rejection

BACKGROUND

The CD40-CD154 interaction is critically important in the cell-mediated immune responses. Blockade of this costimulatory pathway has been shown to prevent acute allograft rejection in murine, as well as nonhuman primate models. However, the role of the CD40-CD154 pathway in the development of chronic rejection and the effects of CD154 targeting on progression of chronic rejection have not been evaluated.

METHODS

We examined the effect of AH.F5, a new hamster anti-rat CD154 monoclonal antibody, in a fully allogeneic acute(u) into Lewis [LEW] (RT11) and chronic [WF.1L (RT1l) into LEW (RT1l)] vascularized cardiac allograft rejection model. In the chronic model, the antibody was evaluated for prevention (starting day of transplant) and interruption of progression (starting day 30 or 60 after transplant) of chronic vasculopathy. Graft survival, morphology, and immunohistology were evaluated.

RESULTS

In the acute rejection model, anti-CD154 therapy alone prevented acute allograft rejection and resulted in 50% long-term allograft survival (>200 days) and donor-specific tolerance. In recipients treated with anti-CD154 monoclonal antibody in combination with a short course of cyclosporine, 100% of allografts survived long-term and all recipients achieved donor-specific tolerance. In the chronic rejection model, allografts from animals treated with the anti-CD154 antibody had a statistically significant lower score of graft arteriosclerosis and fibrosis in both the prevention and 30-day interruption groups when compared with control allografts. In addition, immunohistochemistry showed a decrease in intragraft mononuclear cell infiltration and activation.

CONCLUSION

A new anti-CD154 antibody not only prevents acute allograft rejection, but also inhibits and interrupts the development of chronic rejection. In the acute rejection model cyclosporine acts synergistically with anti-CD154 therapy to prolong allograft survival and induce tolerance. In the chronic rejection model relatively early initiation of therapy is essential to prevent progression of chronic allograft vasculopathy and fibrosis.

CD154 is expressed during treatment with calcineurin inhibitors after organ transplantation

BACKGROUND

CD154 (CD40 ligand) monoclonal antibody prevents allograft rejection in rodents and monkeys. Inasmuch as calcineurin inhibitors (CI) inhibit CD154 expression by pharmacologic agents in vitro, we investigated whether CD154 is also inhibited by CI in vivo and in vitro during allogeneic stimulation.

METHODS

CD154 expression was determined by immunohistochemistry and flow cytometry in human lymph nodes and spleen sections from rhesus monkeys with or without CI treatment. The effect of CI on induction of CD154 expression was studied by stimulating lymphocytes with phorbol 12-myristate 13-acetate (PMA) and ionomycin or with allogeneic monocyte-derived mature dendritic cells.

RESULTS

Lymph nodes from patients with or without CI cyclosporine (CsA) or FK506 (FK) treatment showed comparable CD154 expression, which was present on the cell surface of T cells. CD154-expressing cells were also present in spleens from monkeys treated with CsA in comparable numbers to those in the nontreated group. Moreover, in several liver transplant rejection biopsies taken during CI therapy CD154-expressing cells were observed. In vitro, CsA and FK strongly inhibited induction of CD154 expression on peripheral blood mononuclear cells by pharmacologic stimuli. Maximum inhibition was found at 50 ng/ml CsA and 20 ng/ml FK. CD154 expression induced by dendritic cells in peripheral blood mononuclear cells or spleen cells was also almost completely inhibited by CsA.

CONCLUSION

Although CI strongly suppressed pharmacologic and allogeneic induction of CD154 expression on T cells in vitro at concentrations at approximately clinical trough levels, CD154 is prominently expressed during CI therapy in lymphoid tissue and (sporadically) in liver allografts. This suggests that the CD154-CD40 pathway remains functional during CI therapy, which may contribute to allograft rejections in the clinical setting.

Costimulatory blockade prevents early rejection, promotes lymphocyte apoptosis, and inhibits the upregulation of intragraft interleukin-6 in an orthotopic liver transplant model in the rat

Costimulatory pathways have a pivotal role in the T-cell response to alloantigen. The role of costimulatory blockade with anti-CD154 in orthotopic liver transplantation (OLT) has not been examined previously. This study aims to investigate effects of anti-CD154 and CTLA4-immunoglobulin (Ig) in the early post-OLT period using a major histocompatibility complex-disparate fully arterialized OLT model in the rat. Lewis rats underwent OLT with Dark Agouti liver allografts. Recipients were randomized to receive (1) isotype control, (2) anti-CD154, (3) CTLA4-Ig, or (4) cyclosporine A (CyA). Rats were killed day 8, and specimens were obtained for histological examination, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling, immunohistochemistry, and quantitative reverse-transcriptase polymerase chain reaction. An additional five transplant recipients were treated with anti-CD154 for 14 days postoperatively to assess long-term allograft survival. All isotype control animals died on or before day 6 of acute rejection. Apart from four deaths caused by nonimmunologic causes, all treated recipients survived to day 8. The median survival of rats treated for 14 days with anti-CD154 was greater than 150 days. Serum aspartate aminotransferase and bilirubin levels normalized by day 3 in the CyA group and day 5 in transplant recipients treated with costimulatory blockade. Histologically, there was no difference between isotype controls and CTLA4-Ig-treated animals, whereas anti-CD154-treated transplant recipients had a lower Banff score. CD4+ and CD8+ T-cell infiltrates were prominent in transplant recipients treated with costimulatory blockade. Intragraft analysis showed an increase in lymphocyte apoptosis, Fas ligand messenger RNA expression, and reduction in interleukin-6 gene expression in transplant recipients treated with costimulatory blockade. Costimulatory blockade did not alter intragraft gene expression of other mediators of T-cell priming, differentiation, and effector function compared with isotype control animals. In conclusion, costimulatory blockade prevented acute rejection, enabled long-term survival, and increased intragraft lymphocyte apoptosis in a high-responding rat OLT model.

Co-stimulatory blockade and tolerance induction in transplantation

Recipients of organ and tissue transplants require lifelong immunosuppression to prevent rejection. Better understanding of the processes culminating in allograft rejection has led to novel approaches to modulating the immune response. Co-stimulatory signals between antigen-presenting and -responding cells are essential for a normal alloimmune response, and blockade of these pathways during initial graft-host interaction may be used to ameliorate or prevent a destructive response from proceeding. A large number of experimental studies now support this concept, and early clinical trials have been initiated. Despite some early difficulties and many unanswered questions, co-stimulatory blockade has major potential as a future immune-modulating mechanism for use in clinical transplantation.

Tubular lesions and tubular cell adhesion molecules for the prognosis of lupus nephritis

BACKGROUND

To assess the prognostic value of tubular lesions and cell adhesion molecules' expression, a retrospective study with immunohistochemistry was performed on 152 patients presenting lupus nephritis from January 1985 to December 1999.

METHODS

The following clinical parameters were recorded: age, sex, race, time of systemic lupus erythematosus (SLE) diagnosis, time of the biopsy, proteinuria, creatininemia, and renal function at the end of follow-up. All biopsies were re-evaluated according to a tubular grading, an inflammatory grading, the percentage of sclerosed glomeruli, the percentage of crescents, and the current WHO classification. Immunohistochemistry was performed with anti-CD40, anti-CD44, and anti-intercellular adhesion molecule-1 (anti-ICAM-1) antibodies.

RESULTS

Patients were 136 women (89.5%) and 16 men with a mean age of 31.2 years +/- 12.8 at the time of biopsy. The mean follow-up period was 94.3 months +/- 64.1. Eighty-eight biopsies (58%) showed various degrees of tubular atrophy. Males (P = 0.001) and tubular grading (P = 0.0001) were linked with renal survival in univariate and multivariate analysis. CD40 (P = 0.01) and ICAM-1 (P = 0.001) tubular expressions were linked with renal survival. ICAM-1 tubular expression provided additional information for the prognosis of the patients with biopsies showing tubular atrophy (P = 0.005) or not (P = 0.05).

CONCLUSIONS

Our study shows that tubular lesions are good indicator of lupus nephritis outcome. Furthermore, tubular expression of cell adhesion molecules like ICAM-1 and CD40 also serves to predict the outcome.

Cell-cell contacts with epithelial cells modulate the phenotype of human macrophages

Interactions of macrophages with epithelium represent one of the pathways involved in regulating local immune mechanisms. We studied the effect of cell-cell contact with an epithelial monolayer on the phenotype of macrophages. Human monocytes and THP-1 macrophages were co-cultured with monolayers of human bronchial epithelial cells (HBECs), the alveolar type II-like cell line A549, renal adenocarcinoma epithelial cells (RA), and the lung fibroblast strain HFL-1. The expression of CD11b, CD14, CD54, and HLA-DR was measured by immunocytochemistry and flow cytometry and showed epithelial cell induction of CD54 and HLA-DR in monocytes and of all antigens in THP-1 cells. Co-culture with fibroblasts did not change the phenotype of macrophages. Separation by a filter insert inhibited most of the effects. Culture supernatants did not induce prominent phenotypic changes. Cell-cell contacts with epithelium appear to be of importance in regulating the phenotype of macrophages.

Analysis of the CD40/CD40L role in the sustenance of alloreactive antibody production

CD40 ligand (CD40L) is important for T/B lymphocyte interaction. To understand the cellular basis of humoral allosensitization we, therefore: (1) measured CD40L protein and gene expression in sensitized and non-sensitized uremic unactivated peripheral CD4+ T lymphocytes; (2) studied the impact of blocking the CD40/CD40L pathway on alloreactive antibody (allo-Ab) production by engrafted sensitized PBLs into severe combined immunodeficient (SCID) mice after in vitro preactivation with IL2/LPs/HLA class II allopeptides and adjuvants as a potent stimulus to produce allo-Ab (Shoker et al. Transplantation 1999;68;1188); and (3) studied the modifying effect of CD40/CD40L blockade on T helper type I and II cytokine gene expression in the respective mice spleen. The CD40L protein was measured by flow cytometry and the gene expression was measured by quantitative RT-PCR. Alloreactive antibodies (alo-Abs) produced by sensitized PBLs engrafted into SCID mice with and without blockade of the CD40 receptor were measured by the PRA-STAT ELISA method. The modifying effects of CD40 blocking on allo-Ab production and cytokine gene expression by the engrafted cells measured by RT-PCR were then compared. There was no detectable CD40L protein expression in either the uremic or the control groups. The CD40L gene expression of 0.04 +/- 0.02 attomoles (aM) in the sensitized group was significantly higher than in the non-sensitized patients (0.009 +/- 0.007 aM, P < 0.0001) or the control CD4+ T cells (0.016 +/- 0.004 aM, P < 0.001). Blockade of the CD40 receptor abrogated the production of allo-Ab antibodies by the engrafted sensitized cells in 60% of the tested mice (n = 10); decreased the mean +/- S.D. optic density of allo-Ab to 0.1 +/- 0.13 and the mean +/- S.D. PRA to 12 + 16). In the presence of the control Ab, allo-Ab production in SCID sera was present in 100% of the 10 SCID mice tested; the mean +/- S.D. PRA was 75 +/- 20, and the mean + S.D. OD activity was 0.412 +/- 0.17. All cytokine genes were, otherwise, expressed in the presence or absence of CD40 blockade. The results suggest a potential role of an enhanced CD40/CD40L interaction in the sustenance of alloreactive antibody production without significant deviation to T helper-like I or II responses. Blocking the CD40/CD40L pathway may have a potential therapeutic benefit to treat sensitized uremic patients.

Interleukin-17 and CD40-ligand synergistically enhance cytokine and chemokine production by renal epithelial cells

Renal allograft rejection is characterized by an influx of inflammatory cells. Interaction between infiltrating T cells and resident parenchymal cells might play an important role in the ongoing inflammatory response. The present study demonstrates that CD40L, a product of activated T cells, is locally expressed in kidneys undergoing rejection. Furthermore, during rejection, CD40 expression not only is present on most graft infiltrating cells but also is increased on resident tubular epithelial cells (TEC). To obtain more detailed insight in the consequences of T cell/TEC interaction, we analyzed the production of chemokines, including interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1) and regulated upon activation, normal T cell expressed and secreted (RANTES), and the production of IL-6 by cultured human primary TEC in response to activation with CD40L in vitro. In addition, we studied the interaction with IL-17, a T-cell-specific cytokine previously demonstrated to be present during renal allograft rejection. The results, obtained by enzyme-linked immunosorbent assay, indicate that simultaneous activation of TEC with IL-17 and CD40L synergistically enhances production of IL-6 (2.1-fold higher than sum of single stimulations) and the chemokines IL-8 (15-fold) and RANTES (5.8-fold) as demonstrated by statistical analysis (P: < 0.05), whereas effects on MCP-1 (1.4-fold) are additive. Part of the synergy can be explained by increased CD40 expression on TEC upon IL-17 stimulation. The synergy is not unique for TEC, because similar responses were found with human synoviocytes and a foreskin fibroblast cell line (FS4). Stimulation of TEC with CD40L results in activation of NF-kappaB and induction of cytokine production by IL-17 and CD40L is prevented by addition of the NF-kappaB inhibitor pyrrolidine dithiocarbamate. These data suggest an important role for T cells in renal allograft rejection by acting on parenchymal cells via both soluble mediators and direct cellular contact.

Knowledge about transplantation tolerance gained in primates

Research in transplantation tolerance relies on application of successful strategies in a nonhuman-primate organ transplant model for preclinical testing. Three principal approaches are being evaluated: hematopoietic chimerism, lymphocyte depletion and costimulation blockade. Interactive work in these three areas has yielded much new information on mechanisms of tolerance and opened the door to pilot clinical trials. Clinical application of xenotransplantation is likely to depend on such strategies.

Heightened CD40 ligand gene expression in peripheral CD4+ T cells from patients with kidney allograft rejection

BACKGROUND

CD40 ligand (CD40L) gene expression is increased in rejecting allograft biopsies. We, therefore, tested the possibility that CD40L gene expression is heightened in peripheral CD4+ T cells during renal allograft rejection.

METHODS

CD40L gene expression in peripheral blood CD4+ T cells from two renal transplant groups was measured by quantitative reverse transcription-polymerase chain reaction (RT-PCR). Group 1: 20 patients with excellent renal transplant function; group 2: 25 patients with findings of acute and/or chronic allograft nephropathy (CAN); and group 3 of 12 normal controls. CD4+ cells were isolated by positive selection. The modifying effect of cyclosporine (CsA) and FK506 on CD40L gene expression was further tested in vitro in CD4+ T lymphocytes separated from pokeweed mitogen- (PWM) activated peripheral blood lymphocytes (PBL) preparations.

RESULTS

Mean+/-SD expressions of CD40L gene, in aM, in groups 1-3 were as follows: 0.0052+/-0.0094; 0.022+/-0.023 (P=0.0038 vs. group 2); and 0.014+/-0.005. Levels of CD40L gene expression correlated significantly with acute rejection Banff 97 score (R2=0.44, P=0.0004) and severity of intertubular capillary changes (ITCC) (R2=0.33, P=0.011). After in vitro activation, CD40L gene expression increased by approximately 4-fold and the addition of CsA or FK506 diminished CD40L gene expression to a base level.

CONCLUSION

Peripheral CD4+ T cell CD40L gene expression increases significantly in acute rejection and CAN and may serve as a non-invasive method to monitor allograft function and determine the biological response to CsA and FK506.

The role of costimulatory molecules as targets for new immunosuppressives in transplantation

T-cell costimulation is critical for all T-cell-mediated immune responses that are responsible for endpoints such as allograft rejection or autoimmune disease. Recent experimental data elucidate specific pathways for T-cell activation and negative regulatory mechanisms via unique costimulatory molecules. These data have implications for the development of novel therapeutic strategies to prevent graft rejection and improve long-term graft survival in transplant patients, and to treat autoimmune diseases in humans.

Blockade of costimulatory pathways of T-cell activation: the solution to acute and chronic rejection?

Understanding of how antigen-specific signals and costimulatory molecules are involved in T-cell activation has resulted in new strategies to interfere with allograft rejection. The present review focuses on the role of two receptor-ligand pairs: CD28 and cytotoxic T lymphocyte associated antigen-4, which interact with the B7 ligands (CD80, CD86); and CD40, which interacts with the CD40L (CD154). On the basis of the extensive tissue distribution of CD40, it is likely that the CD40/CD40L system plays a much broader role.