The Significant Role of PA28αβ in CD8+ T Cell-Mediated Graft Rejection Contrasts with Its Negligible Impact on the Generation of MHC-I Ligands

The proteasome generates the majority of peptides presented on MHC class I molecules. The cleavage pattern of the proteasome has been shown to be changed via the proteasome activator (PA)28 alpha beta (PA28αβ). In particular, several immunogenic peptides have been reported to be PA28αβ-dependent. In contrast, we did not observe a major impact of PA28αβ on the generation of different major histocompatibility complex (MHC) classI ligands. PA28αβ-knockout mice infected with the lymphocytic choriomeningitis virus (LCMV) or vaccinia virus showed a normal cluster of differentiation (CD) 8 response and viral clearance. However, we observed that the adoptive transfer of wild-type cells into PA28αβ-knockout mice led to graft rejection, but not vice versa. Depletion experiments showed that the observed rejection was mediated by CD8+ cytotoxic T cells. These data indicate that PA28αβ might be involved in the development of the CD8+ T cell repertoire in the thymus. Taken together, our data suggest that PA28αβ is a crucial factor determining T cell selection and, therefore, impacts graft acceptance.

A Comprehensive Overview of the Clinical Relevance and Treatment Options for Antibody-mediated Rejection Associated With Non-HLA Antibodies

Although solid organ transplant results have improved significantly in recent decades, a pivotal cause of impaired long-term outcome is the development of antibody-mediated rejection (AMR), a condition characterized by the presence of donor-specific antibodies to HLA or non-HLA antigens. Highly HLA-sensitized recipients are treated with desensitization protocols to rescue the transplantation. These and other therapies are also applied for the treatment of AMR. Therapeutic protocols include removal of antibodies, depletion of plasma and B cells, inhibition of the complement cascade, and suppression of the T-cell-dependent antibody response. As mounting evidence illustrates the importance of non-HLA antibodies in transplant outcome, there is a need to evaluate the efficacy of treatment protocols on non-HLA antibody levels and graft function. Many reviews have been recently published that provide an overview of the literature describing the association of non-HLA antibodies with rejection in transplantation, whereas an overview of the treatment options for non-HLA AMR is still lacking. In this review, we will therefore provide such an overview. Most reports showed positive effects of non-HLA antibody clearance on graft function. However, monitoring non-HLA antibody levels after treatment along with standardization of therapies is needed to optimally treat solid organ transplant recipients.

Curcumin Blunts IL-6 Dependent Endothelial-to-Mesenchymal Transition to Alleviate Renal Allograft Fibrosis Through Autophagy Activation

Fibrosis contributes to graft loss in chronic renal allograft injury. Endothelial-to-mesenchymal transition (EndMT) plays an important role in the development of fibrosis following kidney transplantation. Autophagy plays an important role in the homeostasis of diverse cell types including endothelial cells. Here we demonstrate that inhibition of autophagy by treatment with 3-methyladenine (3-MA) or by silencing autophagy-related (ATG)5 promoted interleukin (IL)-6-dependent EndMT in human umbilical vein endothelial cells (HUVECs) and human renal glomerular endothelial cells (HRGECs), and autophagy inactivation was associated with EndMT in patients with chronic allograft dysfunction. IL-6 level was significantly higher in the culture medium of HUVECs transfected with ATG5 siRNA or treated with 3-MA compared to the respective control groups. IL-6 application induced EndMT in HUVECs and HRGECs, whereas antibody-mediated neutralization of IL-6 suppressed EndMT induced by ATG5 silencing. The protective role of curcumin (Cur) against allograft fibrosis was confirmed in a rat kidney transplantation model of F344 donors to Lewis recipients. Curcumin-a natural polyphenol compound with known antifibrotic effects in various tissues-alleviated IL-6-induced EndMT and promoted autophagy in the allografted organ and in HUVECs. This is the first demonstration of the role of autophagy in renal allograft fibrosis; our findings indicate that curcumin can alleviate chronic renal allograft injury by suppressing IL-6-dependent EndMT via activation of autophagy.

CD161a-positive natural killer (NK) cells and α-smooth muscle actin-positive myofibroblasts were upregulated by extrarenal DPP4 in a rat model of acute renal rejection

AIMS

Systemic inhibition of dipeptidyl peptidase 4 (DPP4) showed a protective effect in several transplant models. Here we assessed the specific role of extrarenal DPP4 in renal transplant rejection.

METHODS

Kidneys from wildtype (wt) F344 rats were either transplanted in wt Dark Agouti or congenic rats not expressing DPP4. The remaining, not transplanted donor kidney served as healthy controls. To investigate early inflammatory events rats were sacrificed 3 days after transplantation and kidneys were evaluated for inflammatory cells, capillary rarefaction, proliferation, apoptosis and myofibroblasts by immunohistochemistry.

RESULTS

Capillary ERG-1-positive endothelial cells were significantly more abundant in renal cortex when transplanted into DPP4 deficient compared to wt recipients. In contrast, TGF-ß and myofibroblasts were reduced by more than 25% in kidneys transplanted into DPP4 deficient compared to wt recipients. Numbers of CD161a-positive NK-cells were significantly lower in allografts in DPP4 deficient compared to wt recipients. Numbers of all other investigated immune cells were not affected by the lack of extrarenal DPP4.

CONCLUSION

In early transplant rejection extrarenal DPP4 is involved in the recruitment of NK-cells and early fibrosis. Beneficial effects were less pronounced than reported for systemic DPP4 inhibition, indicating that renal DPP4 is an important player in transplantation-mediated injury.

Bortezomib limits renal allograft interstitial fibrosis by inhibiting NF-κB/TNF-α/Akt/mTOR/P70S6K/Smurf2 pathway via IκBα protein stabilization

Chronic allograft dysfunction is a major cause of late graft failure after kidney transplantation. One of the histological changes is interstitial fibrosis, which is associated with epithelial-mesenchymal transition. Bortezomib has been reported to prevent the progression of fibrosis in organs. We used rat renal transplantation model and human kidney 2 cell line treated with tumor necrosis factor-α (TNF-α) to examine their response to bortezomib. To explore the mechanism behind it, we assessed the previously studied TNF-α/protein kinase B (Akt)/Smad ubiquitin regulatory factor 2 (Smurf2) signaling and performed RNA sequencing. Our results suggested that bortezomib could attenuate the TNF-α-induced epithelial-mesenchymal transition and renal allograft interstitial fibrosis in vitro and in vivo. In addition to blocking Akt/mammalian target of rapamycin (mTOR)/p70S6 kinase/Smurf2 signaling, bortezomib's effect on the epithelial-mesenchymal transition was associated with inhibition of nuclear factor kappa B (NF-κB) pathway by stabilizing inhibitor of NF-κB. The study highlighted the therapeutic potential of bortezomib on renal allograft interstitial fibrosis. Such an effect may result from inhibition of NF-κB/TNF-α/Akt/mTOR/p70S6 kinase/Smurf2 signaling via stabilizing protein of inhibitor of NF-κB.

Use of De Novo mTOR Inhibitors in Hypersensitized Kidney Transplant Recipients: Experience From Clinical Practice

BACKGROUND

It is commonly believed that mTOR inhibitors (mTORi) should not be used in high-immunological risk kidney transplant recipients due to a perceived increased risk of rejection. However, almost all trials that examined the association of optimal-dose mTORi with calcineurin inhibitor (CNI) have excluded hypersensitized recipients from enrollment.

METHODS

To shed light on this issue, we examined 71 consecutive patients with a baseline calculated panel reactive antibody (cPRA) ≥50% that underwent kidney transplantation from June 2013 to December 2016 in our unit. Immunosuppression was based on CNI (tacrolimus), steroids and alternatively mycophenolic acid (MPA; n = 38), or mTORi (either everolimus or sirolimus, n = 33, target trough levels 3-8 ng/mL).

RESULTS

Demographic and immunological risk profiles were similar, and almost 90% of patients in both groups received induction with lymphocyte-depleting agents. Cox-regression analysis of rejection-free survival revealed better results for mTORi versus MPA in terms of biopsy-proven acute rejection (hazard ratio [confidence interval], 0.32 [0.11-0.90], P = 0.031 at univariable analysis and 0.34 [0.11-0.95], P = 0.040 at multivariable analysis). There were no differences in 1-year renal function, Banff chronicity score at 3- and 12-month protocol biopsy and development of de novo donor-specific antibodies. Tacrolimus trough levels along the first year were not different between groups (12-mo levels were 8.72 ± 2.93 and 7.85 ± 3.07 ng/mL for MPA and mTORi group respectively, P = 0.277).

CONCLUSIONS

This single-center retrospective cohort analysis suggests that in hypersensitized kidney transplant recipients receiving tacrolimus-based immunosuppressive therapy similar clinical outcomes may be obtained using mTOR inhibitors compared to mycophenolate.

Recent insights how combined inhibition of immuno/proteasome subunits enables therapeutic efficacy

The proteasome is a multicatalytic protease in the cytosol and nucleus of all eukaryotic cells that controls numerous cellular processes through regulated protein degradation. Proteasome inhibitors have significantly improved the survival of multiple myeloma patients. However, clinically approved proteasome inhibitors have failed to show efficacy against solid tumors, neither alone nor in combination with other therapies. Targeting the immunoproteasome with selective inhibitors has been therapeutically effective in preclinical models for several autoimmune diseases and colon cancer. Moreover, immunoproteasome inhibitors prevented the chronic rejection of allogeneic organ transplants. In recent years, it has become apparent that inhibition of one single active center of the proteasome is insufficient to achieve therapeutic benefits. In this review we summarize the latest insights how targeting multiple catalytically active proteasome subunits can interfere with disease progression in autoimmunity, growth of solid tumors, and allograft rejection.

Impact of Mesenchymal Stromal Cells and Their Extracellular Vesicles in a Rat Model of Kidney Rejection

Background

Mesenchymal stromal cells (MSCs) from different sources possess great therapeutic potential due to their immunomodulatory properties associated with allograft tolerance. However, a crucial role in this activity resides in extracellular vesicles (EVs) and signaling molecules secreted by cells. This study aimed to evaluate the immunomodulatory properties of donor and recipient MSCs isolated from adipose tissue (AD) or bone marrow (BM) and their EVs on kidney outcome in a rat kidney transplant model.

Methods

The heterotopic-kidney-transplant Fisher-to-Lewis rat model (F-L) was performed to study mixed cellular and humoral rejection. After kidney transplantation, Lewis recipients were assigned to 10 groups; two control groups; four groups received autologous MSCs (either AD- or BM- MSC) or EVs (derived from both cell types); and four groups received donor-derived MSCs or EVs. AD and BM-EVs were purified by ultracentrifugation. Autologous cell therapies were administered three times intravenously; immediately after kidney transplantation, 4 and 8 weeks, whereas donor-derived cell therapies were administered once intravenously immediately after transplantation. Survival and renal function were monitored. Twelve weeks after kidney transplantation grafts were harvested, infiltrating lymphocytes were analyzed by flow cytometry and histological lesions were characterized.

Results

Autologous AD- and BM-MSCs, but not their EVs, prolonged graft and recipient survival in a rat model of kidney rejection. Autologous AD- and BM-MSCs significantly improved renal function during the first 4 weeks after transplantation. The amelioration of graft function could be associated with an improvement in tubular damage, as well as in T, and NK cell infiltration. On the other side, the application of donor-derived AD-MSC was harmful, and all rats died before the end of the protocol. AD-EVs did not accelerate the rejection. Contrary to autologous MSCs results, the single dose of donor-derived BM-MSCs is not enough to ameliorate kidney graft damage.

Conclusion

EVs treatments did not exert any benefit in our experimental settings. In the autologous setting, BM-MSCs prompted as a potentially promising therapy to improve kidney graft outcomes in rats with chronic mixed rejection. In the donor-derived setting, AD-MSC accelerated progression to end-stage kidney disease. Further experiments are required to adjust timing and dose for better long-term outcomes.

Pretransplant Desensitization with Costimulation Blockade and Proteasome Inhibitor Reduces DSA and Delays Antibody-Mediated Rejection in Highly Sensitized Nonhuman Primate Kidney Transplant Recipients

BACKGROUND

Patients with broad HLA sensitization have poor access to donor organs, high mortality while waiting for kidney transplant, and inferior graft survival. Although desensitization strategies permit transplantation via lowering of donor-specific antibodies, the B cell-response axis from germinal center activation to plasma cell differentiation remains intact.

METHODS

To investigate targeting the germinal center response and plasma cells as a desensitization strategy, we sensitized maximally MHC-mismatched rhesus pairs with two sequential skin transplants. We administered a proteasome inhibitor (carfilzomib) and costimulation blockade agent (belatacept) to six animals weekly for 1 month; four controls received no treatment. We analyzed blood, lymph node, bone marrow cells, and serum before desensitization, after desensitization, and after kidney transplantation.

RESULTS

The group receiving carfilzomib and belatacept exhibited significantly reduced levels of donor-specific antibodies (P=0.05) and bone marrow plasma cells (P=0.02) compared with controls, with a trend toward reduced lymph node T follicular helper cells (P=0.06). Compared with controls, carfilzomib- and belatacept-treated animals had significantly prolonged graft survival (P=0.02), and renal biopsy at 1 month showed significantly reduced antibody-mediated rejection scores (P=0.02). However, four of five animals with long-term graft survival showed gradual rebound of donor-specific antibodies and antibody-mediated rejection.

CONCLUSIONS

Desensitization using proteasome inhibition and costimulation blockade reduces bone marrow plasma cells, disorganizes germinal center responses, reduces donor-specific antibody levels, and prolongs allograft survival in highly sensitized nonhuman primates. Most animals experienced antibody-mediated rejection with humoral-response rebound, suggesting desensitization must be maintained after transplantation using ongoing suppression of the B cell response.

Bortezomib attenuates renal interstitial fibrosis in kidney transplantation via regulating the EMT induced by TNF-α-Smurf1-Akt-mTOR-P70S6K pathway

Allograft interstitial fibrosis was characterized by massive extracellular matrix deposition caused by activated fibroblasts and myofibroblasts. Epithelial‐mesenchymal transition (EMT) is recognized as an important source of myofibroblasts contributing to the pathogenesis of allograft interstitial fibrosis. Smad ubiquitination regulatory factor 1 (Smurf1) has been recently reported to be involved in the progression of EMT. Our study was to detect the effect of Bortezomib and Smurf1 in the EMT and allograft interstitial fibrosis. Biomarkers of EMT, as well as Smurf1, were examined in human proximal tubular epithelial cells (HK‐2) treated with tumour necrosis factor‐alpha (TNF‐α) in various doses or at various time points by Western Blotting or qRT‐PCR. We knockdown or overexpressed Smurf1 in HK‐2 cells. Furthermore, rat renal transplant model was established and intervened by Bortezomib. Allograft tissues from human and rats were also collected and prepared for HE, Masson's trichrome, immunohistochemical staining and western blotting assays. As a result, we found that TNF‐α significantly promoted the development of EMT in a time‐dependent and dose‐dependent manner through Smurf1/Akt/mTOR/P70S6K signalling pathway. More importantly, Bortezomib alleviated the progression of EMT and allograft interstitial fibrosis in vivo and in vitro by inhibiting the production of TNF‐α and expression of Smurf1. In conclusion, Smurf1 plays a critical role in the development of EMT induced by TNF‐α. Bortezomib can attenuate the Sumrf1‐mediated progression of EMT and renal allograft interstitial fibrosis, which could be suggested as a novel choice for the prevention and treatment of renal allograft interstitial fibrosis.

Immunoproteasome inhibition induces plasma cell apoptosis and preserves kidney allografts by activating the unfolded protein response and suppressing plasma cell survival factors

Chronic antibody-mediated rejection is the leading cause of allograft dysfunction and loss after kidney transplantation, and current immunosuppressive regimens fail to target the plasma cells that produce alloantibodies. We previously showed that treatment with the immunoproteasome inhibitor ONX 0914 prevented the expansion of plasma cells and prevented chronic allograft nephropathy and organ failure after kidney transplantation in rats, but the mechanism has remained elusive. In the current study, we confirmed a long-term reduction in alloantibody production and improvements in allograft histology in rats treated with ONX 0914 or with the broad-spectrum proteasome inhibitor bortezomib. Plasma cells from allotransplanted rats expressed immunoproteasomes at high levels. Immunoproteasome inhibition with ONX 0914 led to ubiquitin-conjugate accumulation, activation of the unfolded protein response, and induction of apoptosis in plasma cells. In addition, ONX 0914 suppressed the expression of adhesion molecules (VLA-4 and LFA-1), plasma cell survival factors (APRIL and IL-6), and IFN-γ-inducible chemokines in bone marrow, while the APRIL receptor BCMA, the IL-6 receptor, and the chemokine receptors CXCR4 and CXCR3 were down-regulated on plasma cells. Taken together, immunoproteasome inhibition blocked alloantibody production by inducing apoptosis of plasma cells through activating the unfolded protein response and suppressing plasma cell survival factors in the bone marrow.

On the role of the immunoproteasome in transplant rejection

The immunoproteasome is expressed in cells of hematopoietic origin and is induced during inflammation by IFN-γ. Targeting the immunoproteasome with selective inhibitors has been shown to be therapeutically effective in pre-clinical models for autoimmune diseases, colitis-associated cancer formation, and transplantation. Immunoproteasome inhibition prevents activation and proliferation of lymphocytes, lowers MHC class I cell surface expression, reduces the expression of cytokines of activated immune cells, and curtails  T helper 1 and 17 cell differentiation. This might explain the in vivo efficacy of immunoproteasome inhibition in different pre-clinical disease models for autoimmunity, cancer, and transplantation. In this review, we summarize the effect of immunoproteasome inhibition in different animal models for transplantation.

De Novo Donor-Specific Antibody Formation in Tacrolimus-Based, Mycophenolate Versus Mammalian Target of Rapamycin Immunosuppressive Regimens

OBJECTIVES

De novo donor-specific antibody formation posttransplant is associated with decreased graft survival. It is not known whether mammalian target of rapamycin inhibitors may be advantageous or detrimental compared with mycophenolate in the prevention of de novo donor-specific antibody formation.

MATERIALS AND METHODS

We compared 66 kidney and kidney-pancreas transplant recipients who received tacrolimus, mammalian target of rapamycin inhibitor, and prednisone (group 1; 36 of whom received everolimus and 30 of whom received sirolimus) versus 132 patients who received tacrolimus, mycophenolate, and prednisone (group 2) matched for age, sex, race, and type/timing of transplant from 2007 to 2012.

RESULTS

Rates of de novo donor-specific antibody formation were comparable between groups at 1, 6, and 12 months (16.7%, 25.8%, and 28.8% for group 1 vs 9.8%, 15.2%, and 22.0% for group 2). There were no significant differences in class (I, II, or mixed), strength (mean fluorescence intensity) of de novo donor-specific antibody, glomerular filtration rate, proteinuria levels, or acute rejection between the groups. In those with de novo donor-specific antibody by 6 months, acute rejection was more common versus those without de novo donor-specific antibody formation (24.3% vs 5.6% at 6 mo; P = .002), with rates of 27.0% versus 6.8% at 1 year (P = .001) and 40.7% versus 11.3% at 2 years (P < .001). An associated reduction in glomerular filtration rate also occurred.

CONCLUSIONS

Mammalian target of rapamycin inhibitors were neither protective nor permissive for de novo donor-specific antibody formation versus mycophenolate when used with clinically relevant tacrolimus dosing regimens.

Targeting B Cells and Plasma Cells in Glomerular Diseases: Translational Perspectives

The unique contributions of memory B cells and plasma cells in kidney diseases remain unclear. In this review, we evaluate the clinical experience with treatments directed at B cells, such as rituximab, and at plasma cells, such as proteasome inhibition, to shed light on the role of these two B lineage compartments in glomerular diseases. Specifically, analysis of these targeted interventions in diseases such as ANCA-associated vasculitis, SLE, and antibody-mediated transplant rejection permits insight into the pathogenetic effect of these cells. Notwithstanding the limitations of preclinical models and clinical studies (heterogeneous populations, among others), the data suggest that memory B and plasma cells represent two engines of autoimmunity, with variable involvement in these diseases. Whereas memory B cells and plasma cells appear to be key in ANCA-associated vasculitis and antibody-mediated transplant rejection, respectively, SLE seems likely to be driven by both autoimmune compartments. These conclusions have implications for the future development of targeted therapeutics in immune-mediated renal disease.

Amelioration of autoimmunity with an inhibitor selectively targeting all active centres of the immunoproteasome

BACKGROUND AND PURPOSE

Multicatalytic endopeptidase complex-like-1 (β2i), low molecular mass polypeptide (LMP) 2 (β1i) and LMP7 (β5i) are the proteolytically active subunits of the immunoproteasome, a special type of proteasome mainly expressed in haematopoietic cells. Targeting LMP7 has been shown to be therapeutically effective in preclinical models of autoimmune diseases. In this study, we investigated the selectivity and biological activity of LU-005i, a recently described inhibitor of the immunoproteasome.

EXPERIMENTAL APPROACH

The specificity of LU-005i and other immunoproteasome-selective inhibitors was characterized using fluorogenic peptide substrates. The effect of proteasome inhibition on cytokine release was investigated in endotoxin-stimulated mouse splenocytes or human peripheral blood mononuclear cells (PBMCs). The effect of proteasome inhibition on inflammatory bowel disease in the dextran sulfate sodium (DSS)-induced colitis model was assessed by measuring weight loss and colon length.

KEY RESULTS

LU-005i is the first human and mouse immunoproteasome-selective inhibitor that targets all three proteolytically active immunoproteasome subunits. LU-005i inhibited cytokine secretion from endotoxin-stimulated mouse splenocytes or human PBMCs. Furthermore, differentiation of naïve T helper cells to T helper 17 cells was impaired in the presence of LU-005i. Additionally, LU-005i ameliorated DSS-induced colitis.

CONCLUSION AND IMPLICATIONS

This study with a novel pan-immunoproteasome inhibitor substantiates that the immunoproteasome is a promising drug target for the treatment of inflammatory diseases and that exclusive inhibition of LMP7 is not necessary for therapeutic effectiveness. Our results will promote the design of new generations of immunoproteasome inhibitors with optimal therapeutic efficacy for clinical use in the treatment of autoimmunity and cancer.

Inhibition of JAK3 and PKC via Immunosuppressive Drugs Tofacitinib and Sotrastaurin Inhibits Proliferation of Human B Lymphocytes In Vitro

BACKGROUND

Antibody-mediated response in solid organ transplantation is critical for graft dysfunction and loss. The use of immunosuppressive agents partially inhibits the B-lymphocyte response leading to a risk of acute and chronic antibody-mediated rejection. This study evaluated the impact of JAK3 and PKC inhibitors tofacitinib (Tofa) and sotrastaurin (STN), respectively, on B-cell proliferation, apoptosis, and activation in vitro.

METHODS

Human B cells isolated from peripheral blood of healthy volunteers were cocultured with CD40 ligand-transfected fibroblasts as feeder cells in the presence of interleukin (IL) 2, IL-10, and IL-21. The cocultures were treated with immunosuppressants Tofa, STN, and rapamycin (as a control), to analyze the proliferation and apoptosis of B cells by means of Cyquant and flow cytometry, respectively. CD27 and IgG staining were applied to evaluate whether treatments modified the activation of B cells.

RESULTS

Tofa and STN were able to inhibit B-cell proliferation to the same extent as rapamycin, without inducing cell apoptosis. After 6 days in coculture with feeder cells, all B cells showed CD27 memory B-cell phenotype. None of the immunosuppressive treatments modified the proportion between class-switched and non-class-switched memory B cells observed in nontreated cultures. The high predominance of CD27⁺CD24⁺ phenotype was not modified by any immunosuppressive treatment.

CONCLUSIONS

Our results show that Tofa and STN can suppress B-cell antibody responses to an extent similar to rapamycin, in vitro; therefore these compounds may be a useful therapy against antibody-mediated rejection in transplantation.

Drug-induced modulation of T lymphocytes as a potential mechanism of susceptibility to infections in patients with multiple myeloma during bortezomib therapy

Bortezomib is effective in the therapy of multiple myeloma (MM), but causes infections that are different from those associated with conventional chemotherapy. It is important to identify the risk factors that facilitate infections associated with bortezomib therapy. In the present report, we sought to (1) define the features of the infections associated with this therapy and (2) identify the immune mechanisms responsible for the observed susceptibility to these infections. We first retrospectively analyzed the clinical data of 143 patients who had received bortezomib therapy for MM. We then prospectively assessed the modulation of T lymphocyte status during this therapy, and evaluated potential relationships between infections and T lymphocyte changes. The infection rates peaked during the first cycle of bortezomib therapy (47.6 %) in patients with MM (p < 0.05 vs. subsequent cycles). Bortezomib therapy was associated with higher incidence rates of viral and fungal infections (15.8 %, p < 0.05 vs. conventional chemotherapy). In addition, patients with the IgG immunophenotype showed higher bacterial and viral infection rates (respectively, p = 0.008 and 0.009). The T lymphocyte numbers significantly decreased after bortezomib therapy (p < 0.05), and the same was true for the Th1/Th2 ratio (p < 0.01). Patients with MM who have decreased lymphocyte counts, while on bortezomib therapy are more likely to develop bacterial or viral infections. In addition, an imbalance in T lymphocyte subsets is also associated with bacterial or viral infections in these patients.

Pilot conversion trial from mycophenolic acid to everolimus in ABO-incompatible kidney-transplant recipients with BK viruria and/or viremia

Immunosuppression using everolimus (EVR) plus low-dose tacrolimus (Tac) is commonly used in organ transplantation. EVR has potential antiviral effects. Herein, the long-term outcomes and impacts of Tac-EVR on the BK virus are reported in ABO-incompatible kidney-transplant recipients. The initial immunosuppressive regimen combined steroids, Tac, and mycophenolic acid (MPA). At a median of 141 (34-529) days post-transplantation, seven stable ABO-incompatible kidney-transplant recipients were converted from MPA to EVR because of active BK replication, and compared with a reference group of fourteen ABO-incompatible patients receiving classical Tac plus MPA. At 1 month before conversion, at 1, 3 months after, and at last follow-up, clinical and biological parameters were monitored. The median time from conversion to the last follow-up was 784 (398-866) days. Conversion to EVR caused no change to rejection episodes or immunological status (isoagglutinin titers, anti-HLA antibodies). At last follow-up, median eGFR was similar in the Tac-MPA versus Tac-EVR group (40 [range: 14-56] vs. 54.5 ml/min/1.73 m(2) [range: 0-128], P = 0.07). The major adverse event was dyslipidemia. Interestingly, conversion from MPA to EVR decreased BK viral load in five patients. ABO-incompatible kidney-transplant recipients with an active BK virus infection may benefit from conversion to EVR.

Hepatitis B virus reactivation in patients with multiple myeloma receiving bortezomib-containing regimens followed by autologous stem cell transplant

To investigate hepatitis B virus (HBV) reactivation and survival in patients with multiple myeloma (MM) receiving bortezomib-containing regimens, we analyzed 139 patients with MM receiving bortezomib-containing regimens in our hospital. Twenty-seven/139 patients were hepatitis B surface antigen positive (HBsAg+) with nine having DNA levels > 500 IU/mL, including four > 1000 IU/mL. All but five HBsAg+ patients were treated with lamivudine or entecavir before chemotherapy until at least 6 months after chemotherapy or autologous stem cell transplant (ASCT). HBV reactivation occurred in six HBsAg+ patients and two HBsAg- patients, including six who received ASCT. Overall survival and progression-free survival of HBsAg- patients were significantly longer than for HBsAg+ patients (both p < 0.01). From these results, we confirmed that the incidence of HBV reactivation was notable in patients with MM receiving bortezomib-containing regimens, especially those who underwent ASCT. HBsAg+ patients with MM had a poorer prognosis than HBsAg- patients. Prophylactic treatment should be prescribed to all patients with HBsAg+ MM for a minimum duration of 12 months.

Pyrrolidine dithiocarbamate reduces the progression of total kidney volume and cyst enlargement in experimental polycystic kidney disease

Heterocyclic dithiocarbamates have anti‐inflammatory and anti‐proliferative effects in rodent models of chronic kidney disease. In this study, we tested the hypothesis that pyrrolidine dithiocarbamate (PDTC) reduces the progression of polycystic kidney disease (PKD). Male Lewis polycystic kidney (LPK) rats (an ortholog of Nek8/NPHP9) received intraperitoneal injections of either saline vehicle or PDTC (40 mg/kg once or twice daily) from postnatal weeks 4 until 11. By serial magnetic resonance imaging at weeks 5 and 10, the relative within‐rat increase in total kidney volume and cyst volume were 1.3‐fold (P =0.01) and 1.4‐fold (P < 0.01) greater, respectively, in LPK + Vehicle compared to the LPK + PDTC(40 mg/kg twice daily) group. At week 11 in LPK rats, PDTC attenuated the increase in kidney weight to body weight ratio by 25% (P < 0.01) and proteinuria by 66% (P < 0.05 vs. LPK + Vehicle) but did not improve renal dysfunction. By quantitative whole‐slide image analysis, PDTC did not alter interstitial CD68+ cell accumulation, interstitial fibrosis, or renal cell proliferation in LPK rats at week 11. The phosphorylated form of the nuclear factor (NF)‐κB subunit, p105, was increased in cystic epithelial cells of LPK rats, but was not altered by PDTC. Moreover, PDTC did not significantly alter nuclear expression of the p50 subunit or NF‐κB (p65)‐DNA binding. Kidney enlargement in LPK rats was resistant to chronic treatment with a proteasome inhibitor, bortezomib. In conclusion, PDTC reduced renal cystic enlargement and proteinuria but lacked anti‐inflammatory effects in LPK rats.

Lewis polycystic kidney rats were treated with pyrrolidine dithiocarbamate (PDTC) from weeks 4 to 11. Quantitative analysis of serial magnetic resonance images indicated that over time, the change in total kidney volume was 1.3‐fold higher in PDTC‐treated than in vehicle‐treated rats. PDTC treatment also decreased kidney weight to body weight ratio, renal cystic volume, and proteinuria.

Soluble DPP4 originates in part from bone marrow cells and not from the kidney

Dipeptidyl peptidase 4 (DPP4) is known to inactivate incretins as well as important chemokines and neuropeptides. DPP4 is expressed as a transmembrane protein but also occurs as a soluble enzyme circulating in the blood. However, the origin of the soluble DPP4 (sDPP4) is still unknown. In this study, DPP4 activity was quantified in plasma and extracted from different rat organs. Then, in order to see if the kidney or the bone marrow was the source of sDPP4, kidney or bone marrow transplantation was performed between wildtype (wt) Dark Agouti (DA) and DPP4 deficient congenic rats (n=6-9). Kidney was verified to have the highest DPP4 activity, followed by spleen and lung. In the following three weeks after successful kidney transplantation only transient trace plasma DPP4 activity was detected in DPP4 deficient rats receiving wt kidneys. In addition, DPP4 activity was not diminished in DA wt rats receiving DPP4 deficient kidneys. Both findings indicated that sDPP4 did not originate from the kidney. In contrast, 43±14% (compared to wt) sDPP4 activity was detected in the plasma of DPP4 deficient DA rats that were reconstituted with wt bone marrow cells. Not only leukocyte but also macrophage subpopulations express DPP4 in bone marrow as well as in blood as assessed by flow cytometry. Thus, bone marrow derived cells but not the kidney represent at least one source of sDPP4. And leukocyte or macrophage subpopulations could be potential candidates.

Bortezomib in late antibody-mediated kidney transplant rejection (BORTEJECT Study): study protocol for a randomized controlled trial

Background

Despite major advances in transplant medicine, improvements in long-term kidney allograft survival have not been commensurate with those observed shortly after transplantation. The formation of donor-specific antibodies (DSA) and ongoing antibody-mediated rejection (AMR) processes may critically contribute to late graft loss. However, appropriate treatment for late AMR has not yet been defined. There is accumulating evidence that the proteasome inhibitor bortezomib may substantially affect the function and integrity of alloantibody-secreting plasma cells. The impact of this agent on the course of late AMR has not so far been systematically investigated.

Methods/design

The BORTEJECT Study is a randomized controlled trial designed to clarify the impact of intravenous bortezomib on the course of late AMR. In this single-center study (nephrological outpatient service, Medical University Vienna) we plan an initial cross-sectional DSA screening of 1,000 kidney transplant recipients (functioning graft at ≥180 days; estimated glomerular filtration rate (eGFR) >20 ml/minute/1.73 m²). DSA-positive recipients will be subjected to kidney allograft biopsy to detect morphological features consistent with AMR. Forty-four patients with biopsy-proven AMR will then be included in a double-blind placebo-controlled intervention trial (1:1 randomization stratified for eGFR and the presence of T-cell-mediated rejection). Patients in the active group will receive two cycles of bortezomib (4 × 1.3 mg/m² over 2 weeks; 3-month interval between cycles). The primary end point will be the course of eGFR over 24 months (intention-to-treat analysis). The sample size was calculated according to the assumption of a 5 ml/minute/1.73 m² difference in eGFR slope (per year) between the two groups (alpha: 0.05; power: 0.8). Secondary endpoints will be DSA levels, protein excretion, measured glomerular filtration rate, transplant and patient survival, and the development of acute and chronic morphological lesions in 24-month protocol biopsies.

Discussion

The impact of anti-humoral treatment on the course of late AMR has not yet been systematically investigated. Based on the hypothesis that proteasome inhibition improves the outcome of DSA-positive late AMR, we suggest that our trial has the potential to provide solid evidence towards the treatment of this type of rejection.

Trial registration

Clinicaltrials.gov: NCT01873157.

Transplant glomerulopathy: the interaction of HLA antibodies and endothelium

Transplant glomerulopathy (TG) is a major cause of chronic graft dysfunction without effective therapy. Although the histological definition of TG is well characterized, the pathophysiological pathways leading to TG development are still poorly understood. Electron microscopy suggests an earlier appearance of TG and suggests that endothelial cell injury is the first sign of the disease. The pathogenic role of human leukocyte antigen (HLA) antibodies in endothelial cells has been described in acute vascular and humoral rejection. However the mechanisms and pathways of endothelial cell injury by HLA antibodies remain unclear. Despite the description of different causes of the morphological lesion of TG (hepatitis, thrombotic microangiopathy), the strong link between TG and chronic antibody mediated rejection suggests a major role for HLA antibodies in TG formation. In this review, we describe the effect of classes I or II HLA-antibodies in TG and especially the implication of donor specific antibodies (DSA). We update recent studies about endothelial cells and try to explain the different signals and intracellular pathways involved in the progression of TG.

Long-term gene therapy with thrombospondin 2 inhibits TGF-β activation, inflammation and angiogenesis in chronic allograft nephropathy

We recently identified Thrombospondin-2 (TSP-2) as a regulator of matrix remodelling and inflammation in experimental kidney disease by using TSP-2 null mice and successfully proved TSP-2 overexpression as a therapeutic concept in a short term glomerulonephritis model in the rat. In this current study, we investigated if long-term TSP-2 overexpression is also capable to ameliorate the progression of chronic kidney disease in the setting of the chronic allograft nephropathy F344-Lewis model in the rat. Two weeks after renal transplantation, two rat thigh muscles were transfected once only with either a TSP-2 overexpressing plasmid (n = 8) or a luciferase-expressing plasmid as control (n = 8). Rats were monitored for renal function, histological changes and gene expression in the graft for up to 30 weeks after transplantation. Unexpectedly, only in the TSP-2 treated group 2 rats died before the end of the experiment and renal function tended to be worsened in the TSP-2 group compared to the luciferase-treated controls. In addition, glomerular sclerosis and tubular interstitial injury as well as cortical fibronectin deposition was significantly increased in the TSP-2 treated kidneys despite reduced TGF-β activation and marked anti-inflammatory (macrophages, T-cells and B-cells) effects in this group. Long-term TSP-2 therapy impaired repair of renal endothelium, as demonstrated by significant higher glomerular and peritubular endothelial rarefaction and reduced endothelial cell proliferation in the transplanted kidneys from TSP-2 treated rats compared to controls. This TSP-2 effect was associated with decreased levels of renal VEGF but not VEGF1 receptor. In conclusion, despite its anti-inflammatory and TGF-β activation blocking effects, TSP-2 gene therapy did not ameliorate but rather worsened experimental chronic allograft nephropathy most likely via its anti-angiogenic properties on the renal microvasculature.

Injured kidney endothelium is only marginally repopulated by cells of extrarenal origin

The role of bone marrow marrow-derived cells after kidney endothelial injury is controversial. In this study, we investigated if and to what extent extrarenal cells incorporate into kidney endothelium after acute as well as during chronic endothelial injury. Fischer F-344 wt (wild type) rat kidney grafts were transplanted into R26- hPAP (human placental alkaline phosphatase) transgenic Fischer F-344 recipient rats to allow identification of extrarenal cells by specific antibody staining. A severe model of renal thrombotic microangiopathy was induced via graft perfusion with antiglomerular endothelial cell (GEN) antibody and resulted in eradication of 85% of the glomerular and 69% of the peritubular endothelium (GEN group). At week 4 after injury, renal endothelial healing as well as recovery of the kidney function was seen. Endothelial chimerism was evaluated by double staining for hPAP and endothelial markers RECA-1 or JG-12. Just 0.25% of the glomerular and 0.1% of the peritubular endothelium was recipient derived. In a second experiment, chronic endothelial injury was induced by combination of kidney transplantation with 5/6 nephrectomy (5/6 Nx group). After 14 wk, only 0.86% of the peritubular and 0.05% of the glomerular endothelium was of recipient origin. In summary, despite demonstration of extensive damage and loss as well as excellent regeneration, just a minority of extrarenal cells were incorporated into kidney endothelium in rat models of acute and chronic renal endothelial cell injury. Our results highlight that kidney endothelial regeneration after specific and severe injury is almost exclusively of renal origin.

IVIG and rituximab for treatment of chronic antibody-mediated rejection: a prospective study in paediatric renal transplantation with a 2-year follow-up

Chronic antibody-mediated rejection (AMR) is the major cause of late renal allograft loss. There is, however, no established treatment for this condition. We report the results of a prospective pilot study on an antihumoral therapy (AHT) consisting of high-dose intravenous immunoglobulin G (IVIG) and rituximab in 20 paediatric renal transplant recipients. Donor-specific HLA antibodies (HLA DSA) were quantified by Luminex-based bead array technology. Loss of eGFR decreased significantly from 7.6 ml/min/1.73 m² during 6 months prior to AHT to 2.1 ml/min/1.73 m² (P = 0.0013) during 6 months after AHT. Fourteen patients (70%) responded: nine of nine patients (100%) without and five of 11 (45%) with transplant glomerulopathy (P = 0.014). C4d positivity in PTC decreased from 40 ± 18.5% in the index biopsy to 11.6 ± 12.2% (P = 0.002) in the follow-up biopsy. In four of nine biopsies (44%) C4d staining turned negative. During 2 years of follow-up, the median loss of eGFR in each of the four 6-month periods remained significantly lower compared with prior to AHT. Class I DSA declined in response to AHT by 61% (p = 0.044), class II DSA by 63% (p = 0.033) 12 months after intervention. AHT with IVIG and rituximab significantly reduces or stabilizes the progressive loss of transplant function in paediatric patients with chronic AMR over an observation period of 2 years, apparently by lowering circulating DSA and reducing intrarenal complement activation.

Effects of sotrastaurin, mycophenolic acid and everolimus on human B-lymphocyte function and activation

Humoral rejection processes may lead to allograft injury and subsequent dysfunction. Today, only one B-cell-specific agent is in clinical use and the effects of standard and new immunosuppressant substances on B-cell activation and function are not fully clarified. The impact of sotrastaurin, mycophenolic acid and everolimus on human B-lymphocyte function was assessed by analysing proliferation, apoptosis, CD80/CD86 expression and immunoglobulin and IL-10 production in primary stimulated B cells. In addition, B-cell co-cultures with pre-activated T cells were performed to evaluate the effect of the different immunosuppressive agents on T-cell-dependent immunoglobulin production. Sotrastaurin did not inhibit B-cell proliferation, CD80/CD86 expression, and IgG production and had only minor effects on IgM levels at the highest concentration administered. In contrast, mycophenolic acid and everolimus had strong effects on all B-cell functions in a dose-dependent manner. All immunosuppressive agents caused decreased immunoglobulin levels in T-cell-dependent B-cell cultures. The data provided here suggest that mycophenolic acid and everolimus, but not sotrastaurin, are potent inhibitors of human B-lymphocyte function and activation.

The novel combination of sirolimus and bortezomib prevents graft-versus-host disease but maintains the graft-versus-leukemia effect after allogeneic transplantation

BACKGROUND

We have previously shown that bortezomib induces a depletion of alloreactive T cells and allows the expansion of T cells with suppressive properties. In the current study, we analyzed the potential synergistic effect of bortezomib in conjunction with sirolimus in order to reduce-graft-versus-host disease without hampering graft-versus-leukemia effect in the allogeneic transplant setting.

DESIGN AND METHODS

We evaluated the effect of sirolimus, bortezomib or the combination of both in the proliferation and activation of in vitro stimulated T lymphocytes. Pathways involved in this synergy were also analyzed using Western blot assays. Finally, BALB/c mice receiving C57BL/6 allogeneic donor bone marrow with splenocytes were used to measure in vivo the effect of this novel combination on the risk of graft-versus-host disease.

RESULTS

The combination of both drugs synergistically inhibited both activation and proliferation of stimulated T cells. Also, the production of Th1 cytokines (IFN γ, IL-2 and TNF) was significantly inhibited. This effect was due, at least in part, to the inhibition of Erk and Akt phosphorylation. In vivo, the combination reduced the risk of graft-versus-host disease without hampering graft-versus-leukemia effect, as shown in mice receiving graft-versus-host disease prophylaxis with sirolimus plus bortezomib being infused with tumor WEHI cells plus C57BL/6 donor BM and splenocytes.

CONCLUSIONS

The current study reveals a synergistic effect of the combination sirolimus and bortezomib to prevent graft-versus-host disease while maintaining the graft-versus-leukemia effect.

Proteasome inhibitor treatment of antibody-mediated allograft rejection

PURPOSE OF REVIEW

Bortezomib is a first-in-class proteasome inhibitor that was originally Food and Drug Administration approved for the treatment of multiple myeloma. In the past few years, off-label use in solid organ transplant recipients has demonstrated its ability to provide plasma cell-targeted therapy in humans. The purpose of this review is to provide an update of recent basic science and clinical results with bortezomib in treating antibody-mediated rejection (AMR) that occurs in solid organ transplant recipients.

RECENT FINDINGS

Proteasome inhibitor therapy for AMR in kidney transplant recipients is effective both as primary and as rescue therapy. Optimal responses with proteasome inhibitor therapy are obtained when AMR is diagnosed promptly and early in the posttransplant period. However, proteasome inhibitor therapy for late AMR (i.e., occurring 6 months or later posttransplant) provides less predictable results, likely due to the existence of a substantial bone marrow niche-resident long-lived plasma cell population. Proteasome inhibitor therapy has also recently been shown to provide effective therapy for AMR in heart, and also, transplant recipients.

SUMMARY

Proteasome inhibitor therapy with bortezomib provides effective treatment for AMR in solid organ transplant recipients. As the first plasma cell-targeted therapy, proteasome inhibitor therapy provides the additional advantage of opening new possibilities for biologically defined plasma cell-targeted therapies.

Prevention and treatment of alloantibody-mediated kidney transplant rejection

Antibody-mediated rejection (AMR), which is commonly caused by preformed and/or de novo HLA alloantibodies, has evolved as a leading cause of early and late kidney allograft injury. In recent years, effective treatment strategies have been established to counteract the deleterious effects of humoral alloreactivity. One major therapeutic challenge is the barrier of a positive pretransplant lymphocytotoxic crossmatch. Several apheresis- and/or IVIG-based protocols have been shown to enable successful crossmatch conversion, including a strategy of peritransplant immunoadsorption for rapid crossmatch conversion immediately before deceased donor transplantation. While such protocols may increase transplant rates and allow for acceptable graft survival, at least in the short-term, it has become evident that, despite intense treatment, many patients still experience clinical or subclinical AMR. This reinforces the need for innovative strategies, such as complementary allocation programs to improve transplant outcomes. For acute AMR, various studies have suggested efficiency of plasmapheresis- or immunoadsorption-based protocols. There is, however, no established treatment for chronic AMR and the development of strategies to reverse or at least halt chronic active rejection remains a big challenge. Major improvements can be expected from studies evaluating innovative therapeutic concepts, such as proteasome inhibition or complement blocking agents.

Targeting B cells and antibody in transplantation

There has been increasing interest in the role played by B cells, plasma cells and their associated antibody in the immune response to an allograft, driven by the need to undertake antibody-incompatible transplantation and evidence suggesting that B cells play a role in acute cellular rejection and in acute and chronic antibody-mediated rejection. A number of immunosuppressive agents have emerged which target B cells, plasma cells and/or antibody, for example, the B cell-depleting CD20 antibody rituximab. This review describes recent developments in the use of such agents, our understanding of the role of B cells in alloimmunity and the application of this knowledge toward novel therapies in transplantation. It also considers the evidence to date suggesting that B cells may act as regulators of an alloimmune response. Thus, future attempts to target B cells will need to address the problem of how to inhibit effector B cells, while enhancing those with regulatory capacity.