Design and testing of a humanized porcine donor for xenotransplantation.

Recent human decedent model studies1,2 and compassionate xenograft use3 have explored the promise of porcine organs for human transplantation. To proceed to human studies, a clinically ready porcine donor must be engineered and its xenograft successfully tested in nonhuman primates. Here we describe the design, creation and long-term life-supporting function of kidney grafts from a genetically engineered porcine donor transplanted into a cynomolgus monkey model. The porcine donor was engineered to carry 69 genomic edits, eliminating glycan antigens, overexpressing human transgenes and inactivating porcine endogenous retroviruses. In vitro functional analyses showed that the edited kidney endothelial cells modulated inflammation to an extent that was indistinguishable from that of human endothelial cells, suggesting that these edited cells acquired a high level of human immune compatibility. When transplanted into cynomolgus monkeys, the kidneys with three glycan antigen knockouts alone experienced poor graft survival, whereas those with glycan antigen knockouts and human transgene expression demonstrated significantly longer survival time, suggesting the benefit of human transgene expression in vivo. These results show that preclinical studies of renal xenotransplantation could be successfully conducted in nonhuman primates and bring us closer to clinical trials of genetically engineered porcine renal grafts.

Prophylactic bilateral nephrectomy and preemptive kidney transplantation for Denys-Drash syndrome prior to development of kidney failure.

BACKGROUND  : Nephropathy in Denys-Drash syndrome (DDS) develops within a few months of birth, often progressing to kidney failure. Wilms tumors also develop at an early age with a high rate of incidence. When a patient does not have Wilms tumor but develops kidney failure, prophylactic bilateral nephrectomy, and kidney transplantation (KTX) is an optimal approach owing to the high risk of Wilms tumor development. In the case presented here, prophylactic bilateral nephrectomy and KTX were performed in a patient who had not developed Wilms tumor or kidney failure. However, the treatment option is controversial as it involves the removal of a tumor-free kidney and performing KTX in the absence of kidney failure. CASE DIAGNOSIS/TREATMENT: We present the case of a 7-year-old boy, born at 38 weeks gestation. Examinations at the age of 1 year revealed severe proteinuria and abnormal internal and external genitalia. Genetic testing identified a missense mutation in exon 9 of the WT1 gene, leading to the diagnosis of DDS. At the age of 6 years, he had not yet developed Wilms tumor and had grown to a size that allowed him to safely undergo a KTX. His kidney function was slowly deteriorating (chronic kidney disease (CKD) stage 3), but he had not yet developed kidney failure. Two treatment options were considered for this patient: observation until the development of kidney failure or prophylactic bilateral nephrectomy with KTX to avoid Wilms tumor development. After a detailed explanation of options to the patient and family, they decided to proceed with prophylactic bilateral nephrectomy and KTX. At the latest follow-up 4 months after KTX, the patient's kidney functioned well without proteinuria. CONCLUSION: We performed prophylactic bilateral nephrectomy with KTX on a DDS patient who had not developed kidney failure or Wilms tumor by the age of 7 years. Although the risk of development of Wilms tumor in such a patient is unclear, this treatment may be an optimal approach for patients who are physically able to undergo KTX, considering the potentially lethal nature of Wilms tumor in CKD patients.

Longitudinal mortality risks and kidney functional outcomes in Japanese living kidney donors.

OBJECTIVES: Previous studies suggested that living kidney donors do not have a higher risk of death or kidney failure than the general population. However, living kidney donor risk is controversial. Furthermore, only a few studies have evaluated long-term kidney function after kidney donation. METHODS: This study evaluated Japanese kidney donor' long-term outcomes, including mortality and kidney function. From 1965 to 2015, 230 donors (76 males, 154 females, and a median age of 54) were enrolled in this study. The median observation period was 11.0 (range, 0.3-41.0) years. RESULTS: In total, 215 donors were still alive, and 15 had died. Causes of death included malignancies, cardiovascular disease, pneumonia, suicide, gastrointestinal bleeding, and kidney failure. Actual donor survival rates at 10, 20, and 30 years were 95.3%, 90.7%, and 80.9%, respectively. These values were comparable to age- and gender-matched expected survival. Long-term kidney function after donation was evaluated in 211 donors with serum creatinine data. Two donors developed kidney failure 24 and 26 years post-donation, respectively. The percentage of donors whose estimated glomerular filtration rate (eGFR) remained ≥45 mL/min/1.73 m2 at 10, 20, and 30 years after donation were 84.2%, 73.0%, and 63.9%, respectively. Survival rates of donors with eGFR <45 mL/min/1.73 m2 were comparable to those in persons with eGFR >45 mL/min/1.73 m2. CONCLUSION: Our findings revealed that kidney donors did not have a higher long-term risk of death than the general population. Although some donors showed decreased kidney function after donation, kidney function did not impact their survival.

TNX-1500, a crystallizable fragment-modified anti-CD154 antibody, prolongs nonhuman primate renal allograft survival.

The blockade of the CD154-CD40 pathway with anti-CD154 monoclonal antibody has been a promising immunomodulatory approach to prevent allograft rejection. However, clinical trials of immunoglobulin G1 antibodies targeting this pathway revealed thrombogenic properties, which were subsequently shown to be mediated by crystallizable fragment (Fc)-gamma receptor IIa-dependent platelet activation. To prevent thromboembolic complications, an immunoglobulin G4 anti-CD154 monoclonal antibody, TNX-1500, which retains the fragment antigen binding region of ruplizumab (humanized 5c8, BG9588), was modified by protein engineering to decrease Fc binding to Fc-gamma receptor IIa while retaining certain other effector functions and pharmacokinetics comparable with natural antibodies. Here, we report that TNX-1500 treatment is not associated with platelet activation in vitro and consistently inhibits kidney allograft rejection in vivo without clinical or histologic evidence of prothrombotic phenomena. We conclude that TNX-1500 retains efficacy similar to that of 5c8 to prevent kidney allograft rejection while avoiding previously identified pathway-associated thromboembolic complications.

Kidney transplantation from triple-knockout pigs expressing multiple human proteins in cynomolgus macaques.

Porcine cells devoid of three major carbohydrate xenoantigens, αGal, Neu5GC, and SDa (TKO) exhibit markedly reduced binding of human natural antibodies. Therefore, it is anticipated that TKO pigs will be better donors for human xenotransplantation. However, previous studies on TKO pigs using old world monkeys (OWMs) have been disappointing because of higher anti-TKO pig antibodies in OWMs than humans. Here, we show that long-term survival of renal xenografts from TKO pigs that express additional human transgenes (hTGs) can be achieved in cynomolgus monkeys. Kidney xenografts from TKO-hTG pigs were transplanted into eight cynomolgus recipients without pre-screening for low anti-pig antibody titers. Two recipients of TKO-hTG xenografts with low expression of human complement regulatory proteins (CRPs) (TKO-A) survived for 2 and 61 days, whereas six recipients of TKO-hTG xenografts with high CRP expression (TKO-B) survived for 15, 20, 71, 135, 265, and 316 days. Prolonged CD4+ T cell depletion and low anti-pig antibody titers, which were previously reported important for long-term survival of αGal knock-out (GTKO) xenografts, were not always required for long-term survival of TKO-hTG renal xenografts. This study indicates that OWMs such as cynomolgus monkeys can be used as a relevant model for clinical application of xenotransplantation using TKO pigs.

Clinical trials for renal allograft tolerance induction through combined hematopoietic stem cell transplantation: A narrative review.

During the last four decades, development of effective immunosuppressants has significantly improved short-term results of organ transplantation. However, long-term results have not been satisfactory due to chronic rejection or complications caused by immunosuppressive drugs. Therefore, induction of immunological tolerance of the transplanted organ is considered essential to improve the long-term results. Despite numerous tolerance strategies that have been successful in murine models, inducing hematopoietic chimerism through donor hematopoietic stem cell transplantation is the only method that reproducibly induces kidney allograft tolerance in nonhuman primates or humans. Combining kidney and hematopoietic stem cell transplantation to achieve allograft tolerance has now been attempted with different chimerism strategies. This review summarizes the status of current clinical trials on the induction of allograft tolerance. We also summarize recent studies to extend the chimerism approach to deceased donor transplant recipients.

Vesicoureteral reflux treatment following kidney transplantation potentially prevents graft function deterioration and allows long-term graft survival.

OBJECTIVES: The impact of vesicoureteral reflux post-kidney transplantation on graft survival remains unclear, and guidelines on appropriate vesicoureteral reflux management post-kidney transplantation are lacking. For this reason, we conducted a retrospective study on the impact of vesicoureteral reflux and its treatment on graft survival. METHODS: We evaluated 347 consecutive kidney transplantation recipients, who also underwent a ureteroneocystostomy, between 1996 and 2012. RESULTS: Vesicoureteral reflux was diagnosed in 55 cases (15.9%), with a median post-kidney transplantation duration of 50 months (range 0-172 months). Among these, 22 were monitored, 17 underwent transurethral collagen injections, and 16 received a ureteroneocystostomy. The 10-year graft survival rate was significantly lower in recipients with vesicoureteral reflux (68.9%) than in those without vesicoureteral reflux (84.4%) (P = 0.0165). Moreover, among the vesicoureteral reflux recipients, the 10-year graft survival rate was significantly higher in those whose vesicoureteral reflux was cured (80.1%) than in those whose vesicoureteral reflux persisted (53.6%) (P = 0.0062). Multivariate analysis showed that vesicoureteral reflux was significantly associated with both overall and death-censored graft loss (odds ratio 3.737 and 3.685; P = 0.0015 and P = 0.0052, respectively). Lastly, the incidence of interstitial fibrosis and tubular atrophy was higher in recipients with vesicoureteral reflux than in those without vesicoureteral reflux (P = 0.0009). CONCLUSIONS: Post-kidney transplantation vesicoureteral reflux has a negative impact on long-term graft survival, and that treatment prevents graft deterioration. From the perspective of maintaining long-term graft function in kidney recipients, vesicoureteral reflux may be one of the most important complications to be addressed.

Phase I, multicenter, dose-escalation study of avadomide in adult Japanese patients with advanced malignancies.

Non-Hodgkin lymphoma (NHL) treated with chemoimmunotherapy has limited efficacy in some patients, resulting in relapsed or refractory disease. Avadomide (CC-122) is a novel cereblon-binding agent that exhibits antilymphoma and immune-modulation activities with a biological profile distinct from similar agents, such as lenalidomide. This phase I multicenter study evaluated avadomide in Japanese patients with advanced solid tumors or NHL. Fourteen patients with NHL and one with a solid tumor (esophageal carcinoma), were enrolled in four dose-escalation cohorts using a 3 + 3 design. Primary endpoints included safety, dose-limiting toxicities (DLT), maximum-tolerated dose and/or recommended phase II dose (RP2D), and pharmacokinetics. Secondary endpoints included overall response rate (ORR) and duration of response. One patient with NHL experienced DLT, which included face edema, pharyngeal edema, and tumor flare (all grade 1) that led to a dose reduction. Eleven patients had grade ≥3 treatment-emergent adverse events, most frequently decreased neutrophil count (33%) and decreased lymphocyte count (20%). The ORR in patients with NHL (n = 13) was 54%, including four complete and three partial responses. The best response for the solid tumor patient was progressive disease. Avadomide dose intensity was consistent across cohorts, and the 3-mg dose given five consecutive days/week was established as the RP2D. This phase I study identified a tolerable dose of avadomide, with an acceptable toxicity profile and clinically meaningful efficacy in Japanese patients with previously treated NHL.

Acute kidney injury caused by systemic Neisseria gonorrhoeae infection after successful kidney transplantation.

Neisseria gonorrhoeae is one of the microbes that can causes male urethritis. This microbe is most likely to be transmitted via sexual intercourse. In men, the representative infection sites are the urethra, and oral mucosa but gonococcemia is rere. We present a case of gonococcemia in a 47-year-old male successful kidney recipient. He temporarily lost his graft function due to acute kidney injury followed by sepsis; however, short-course intermittent hemodialysis and long-term intensive ceftriaxone inoculation saved his life and his graft function.

Pharmacokinetics and pharmacodynamics of dasatinib in the chronic phase of newly diagnosed chronic myeloid leukemia.

PURPOSE: Dasatinib is a novel, oral, multi-targeted kinase inhibitor of breakpoint cluster region-abelson (BCR-ABL) and Src family kinases. The study investigated pharmacokinetic (PK) and pharmacodynamic (PD) analyses of dasatinib in 51 newly diagnosed, chronic phase, chronic myeloid leukemia patients. METHODS: The dasatinib concentration required to inhibit 50 % of the CrkL (CT10 regulator of kinase like) phosphorylation in bone marrow CD34+ cells (half maximal (50 %) inhibitory concentration (IC50)CD34+cells) was calculated from each patient's dose-response curve using flow cytometry. PK parameters were obtained from the population pharmacokinetic analysis of dasatinib concentrations in plasma on day 28 after administration. RESULTS: Early molecular responses were not significantly associated with PK or PD (IC50 CD34+cells) parameters. However, the PK/PD parameter-time above IC50 CD34+cells-significantly correlated with BCR-ABL transcript level at 3 months (correlation coefficient (CC) = -0.292, P = 0.0375) and the reduction of BCR-ABL level at 1 or 3 months (CC = -0.404, P = 0.00328 and CC = -0.356, P = 0.0104, respectively). Patients with more than 12.6 h at time above IC50 CD34+cells achieved a molecular response of 3.0 log reduction at 3 months and those more than 12.8 h achieved a deep molecular response less than 4.0 log reduction at 6 months at a significantly high rate (P = 0.013, odds ratio = 4.8 and P = 0.024, odds ratio = 4.3, respectively). CONCLUSION: These results suggest that the anti-leukemic activity of dasatinib exhibits in a time-dependent manner and that exposure for more than 12.8 h at time above IC50 CD34+cells could significantly improve prognosis.

A case of endocapillary proliferative glomerulonephritis with macrophages phagocytosing monoclonal immunoglobulin lambda light chain.

Multiple myeloma (MM) is a plasma-cell neoplasm that can cause renal disorders. Renal lesions in MM can present with a very rare pathological manifestation involving a specific monoclonal immunoglobulin (Ig). We report the case of a 33-year-old woman who had edema, fatigue, elevated serum creatinine levels, hypoalbuminemia, and hypercholesterolemia. She had persistent hematuria and proteinuria lasting 3 years. Serum protein electrophoresis showed an M-spike, and serum immunofixation demonstrated the presence of monoclonal IgG λ. She had proteinuria in the nephrotic range, and a monoclonal λ fragment was present on urine immunofixation. Renal biopsy showed proliferative glomerulonephritis with λ light chain and C3c deposition and inflammatory cell infiltration with CD68. Macrophage lysosomes contained λ light chains, suggesting their partial phagocytosis. She was diagnosed with symptomatic MM and was treated with bortezomib and dexamethasone and an autologous peripheral stem cell transplant conditioned with intravenous melphalan. She achieved a partial response with decreased serum monoclonal protein and improved renal function. This case may be categorized as a monoclonal gammopathy-associated proliferative glomerulonephritis. The biopsy finding of partially phagocytosed Ig λ light chains by macrophages is very rare; this pathological condition is similar to crystal-storing histiocytosis.

Neutralizing antibody responses and cellular responses against SARS-CoV-2 Omicron subvariants after mRNA SARS-CoV-2 vaccination in kidney transplant recipients.

Although the mRNA SARS-CoV-2 vaccine has improved the mortality rate in the general population, its efficacy against rapidly mutating virus strains, especially in kidney transplant recipients, remains unclear. We examined the anti-SARS-CoV-2 spike protein IgG antibody and neutralizing antibody titers and cellular immunity against B.1.1, BA.1, and BA.5 antigens in 73 uninfected kidney recipients and 16 uninfected healthy controls who received three doses of an mRNA SARS-CoV-2 vaccine. The IgG antibody titers were significantly lower in recipients than in healthy controls. Similarly, neutralizing antibody titers against three viral variants were significantly lower in recipients. When the virus was mutated, the neutralizing antibody titers decreased significantly in both groups. In cellular immunity analysis, the number of spike-specific CD8 + non-naïve T cells against three variants significantly decreased in recipients. Conversely, the frequency of spike-specific Th2 CD4 + T-cells in recipients was higher than that in healthy controls. Nineteen recipients and six healthy controls also received a bivalent omicron-containing booster vaccine, leading to increase IgG and neutralizing antibody titers in both groups. After that, eleven recipients and five healthy controls received XBB.1.5 monovalent vaccines, increasing the neutralizing antibody titers against not only XBB.1.5, but also EG.5.1 and BA.2.86 antigens in kidney recipients. Although kidney recipients did not gain sufficient immunity against Omicron BA.5 with the third dose of vaccine, humoral response against mutant SARS-CoV-2 lineages significantly increased after bivalent Omicron-containing booster vaccine and the XBB.1.5 monovalent vaccine. Therefore, it is important for kidney recipients to continue to administer updated vaccines.

Long-term clinicopathological impact of calcineurin inhibitor cessation without specific cytoreductive induction in kidney transplantation.

Calcineurin inhibitors (CNIs) have considerably improved renal allograft survival. However, their chronic use has various adverse effects, including hypertension, hyperlipidemia, and nephrotoxicity. We conducted a retrospective study of kidney transplant recipients using a CNI withdrawal protocol. Eleven of 13 patients who had stable graft function on triple-drug therapy including a cyclosporine (CsA) were enrolled in this study. The dose of CsA was reduced by 20% every two wks until complete withdrawal. The mean period between the baseline and last biopsies was 97 (range: 21-123) months. No patient had an acute rejection episode during follow-up. Progression of interstitial fibrosis and tubular atrophy was seen in five and six cases, respectively. Arteriolar hyalinosis improved in three cases, but worsened in four. No patient lost his graft during the study. The mean serum creatinine level was 1.30 ± 0.26 mg/dL at baseline and stable for 10 yr after elimination (1.26 ± 0.11 mg/dL). At the end of the study, four of the eleven patients had reduced their antihypertensive drugs, and one patient had stopped hyperlipidemia treatment. CNI withdrawal can be implemented safely in stable renal transplant recipients and might lead to improved patient outcomes. Additional specific evidence of CNI nephrotoxicity should be elucidated.

Synthesis and characterization of molecular hexagons and rhomboids and subsequent encapsulation of Keggin-type polyoxometalates by molecular hexagons.

Structural control among hexagonal (trimer), rhomboidal (dimer), and infinite-chain supramolecular complexes with three different supporting ligands of ethylenediamine (en), N,N,N',N'-tetramethylethylenediamine (en*), and 1,2-bis(diphenyl)phosphinoethane (dppe) [(en)Pd(L)]3(OTf)6 1t·OTf, [(en*)Pd(L)]2(PF6)4 2d·PF6, and [(dppe)Pd(L)(OTf)2]∞ 3·OTf (OTf = trifluoromethane sulfonate; L = 1,3-bis(4-pyridylethynyl)benzene) in the solid and solution states was investigated. The encapsulation of a large Keggin-type polyoxometalate [α-PW12O40](3-) by these complexes was also examined. As the steric bulkiness of the supporting ligands increased in the order of en < en* < dppe, the hexagonal, rhomboidal, and infinite-chain structures were obtained, as confirmed by X-ray crystallography. In solution, equilibrium between the molecular hexagon (1t·OTf/2t·PF6) and the molecular rhomboid (1d·OTf/2d·PF6) was observed in the en/en* ligand systems, whereas 3·OTf with the dppe ligand did not exhibit equilibrium and instead existed as a single species. These phenomena were established by cold-spray ionization mass spectroscopy (CSI-MS) and (1)H diffusion ordered NMR spectroscopy (DOSY). The addition of the highly negatively charged Keggin-type phosphododecatungstate [α-PW12O40](3-) to a solution of 2t/2d·PF6 resulted in the encapsulation of the tungstate species in the cavity of the molecular hexagon to form {[(en*)Pd(L)]3[⊃α-PW12O40]}(PF6)3 2t·[α-PW12O40](3-), as confirmed by a combination of (1)H and (31)P DOSY and CSI-MS spectral data.

Long-Term Results in Recipients of Late Conversion to a Calcineurin Inhibitor-Free Regimen with Everolimus After Kidney Transplantation.

BACKGROUND: Conversion to a calcineurin inhibitor (CNI)-free regimen in cases of CNI nephrotoxicity (CNIT) is a strategy to improve the long-term outcomes of kidney transplantation. However, the long-term results of late conversion to a CNI-free regimen using everolimus (EVR) remain uncertain. METHODS: Nine kidney transplant recipients with biopsy-confirmed CNIT were enrolled. The median time of CNIT diagnosis was 9.0 years. All recipients underwent a conversion from CNI to EVR. We evaluated the clinical outcomes, development of donor-specific antibody (DSA), the incidence of rejection, alternative arteriolar hyalinosis (aah) scores, renal function changes, and T cell responses by mixed lymphocyte reaction (MLR) assay after conversion. RESULTS: The median follow-up after conversion was 5.4 years. Currently, 7 of 9 recipients have received a CNI-free regimen for 1.6 to 9.5 years. In the other 2 recipients, one experienced graft loss due to CNIT 3.8 years after conversion, and the other had to resume CNI due to acute T cell-mediated rejection (ATMR) a year after conversion. None of the recipients developed DSA. No rejection was observed in the kidney allograft histology except for the ATMR case. Moreover, improvement in aah scores was noted in one patient. Furthermore, serum creatinine levels were stable in recipients without proteinuria before the EVR add-on. In the MLR analysis, low responses against donors were observed in stable patients. CONCLUSIONS: Late conversion to an EVR-based regimen without CNI may be a promising therapeutic strategy against CNIT, particularly for recipients without proteinuria before the EVR add-on.

Clinical and molecular correlation defines activity of physiological pathways in life-sustaining kidney xenotransplantation.

Porcine kidney xenotransplantation is accelerating towards clinical translation. However, despite the demonstrated ability of porcine kidneys to remove metabolic waste products, questions remain about their ability to faithfully recapitulate renal endocrine functions after transplantation. Here we analyze xenograft growth and function of two kidney dependent endocrine pathways in seventeen cynomolgus macaques after kidney xenotransplantation from gene edited Yucatan minipigs. Xenograft growth, the renin-angiotensinogen aldosterone-system, and the calcium-vitamin D-parathyroid hormone axis are assessed using clinical chemistries data, renin activity and beta-C-terminal-telopeptide assays, kidney graft RNA-sequencing and serial ultrasonography. We demonstrate that xenografts transplanted from minipigs show only modest growth and do not substantially contribute to recipient RAAS pathway activity. However, parathyroid hormone-independent hypercalcemia and hypophosphatemia are observed, suggesting a need for close monitoring and timely intervention during human testing. Further study of these phenotypes is warranted in designing prospective clinical trials.

Use of Mixed Lymphocyte Reaction Assay to Evaluate Immune Tolerance before Kidney Transplantation with an Immunosuppression-Free Protocol following Hematopoietic Stem Cell Transplantation from the Same Donor.

Several cases of kidney transplantation after hematopoietic stem cell transplantation (HSCT) from the same donor for end-stage renal disease have been reported. In those cases, immunosuppressive drugs were discontinued since immune tolerance was supposed to be induced. Theoretically, the recipient's immune system recognizes the kidney allograft as its own tissue with the same human leukocyte antigen (HLA) profile, and the kidney allograft will not be rejected, even without the use of immunosuppressive agents. However, almost all recipients receive immunosuppressants in the early stages after kidney transplantation owing to concerns of acute rejection. Here, we report a successful case of post-HSCT kidney transplantation without the use of immunosuppressive drugs, in which a mixed lymphocyte reaction (MLR) assay was used to evaluate immune tolerance before kidney transplantation. The patient was a 25-year-old woman. Five years prior, she developed acute myeloid leukemia and underwent HLA-half-matched peripheral blood stem cell transplantation. Thereafter, she was in remission of the acute myeloid leukemia, but 1 year later, she developed renal graft-versus-host disease. Subsequently, the patient's renal function gradually deteriorated to end-stage renal failure, and she underwent kidney transplantation with the previous stem cell donor: her mother. HLA typing of donor and recipient showed a complete chimerism in the peripheral blood. The pretransplantation complement-dependent cytotoxic crossmatch and flow cytometric T-cell crossmatch results were both negative, and HLA antibody measurements were all negative. The MLR assay revealed no T-lymphocyte reaction to the donor; therefore, immunosuppressants were not used. Two years after transplantation, the patient's serum creatinine concentration was around 0.8 mg/dL (down from 4 mg/dL before transplantation). No abnormalities were observed in a renal biopsy performed after 3 months. Our study, along with others, indicates that immune tolerance to a donor develops in post-HSCT kidney transplantation from the same donor.

Analysis of T-cell alloantigen response via a direct pathway in kidney transplant recipients with donor-specific antibodies.

Donor-specific antibodies (DSAs) are the main cause of graft loss over time. The direct pathway of alloantigen recognition is important in the pathogenesis of acute rejection. Recent studies have suggested that the direct pathway also contributes to the pathogenesis of chronic injury. Nevertheless, there are no reports on T-cell alloantigen response via the direct pathway in kidney recipients with DSAs. We analyzed the T-cell alloantigen response via the direct pathway in kidney recipients with DSAs (DSA+) or without DSAs (DSA-). A mixed lymphocyte reaction assay was implemented to assess the direct pathway response. DSA+ patients showed significantly higher CD8+ and CD4+ T cell responses to donor cells than DSA- patients. Furthermore, proliferating CD4+ T cells showed a marked increase in Th1 and Th17 responses in DSA+ patients than in DSA- patients. In a comparison between anti-donor and third-party responses, the anti-donor CD8+ and CD4+ T cell response was significantly lower than the anti-third-party response. In contrast, the donor-specific hyporesponsiveness was absent in DSA+ patients. Our study demonstrated that DSA+ recipients have a greater potential for developing immune responses against the donor tissues via the direct alloantigen recognition pathway. These data contribute to an understanding of DSAs pathogenicity during kidney transplantation.

Selective Bcl-2 inhibition promotes hematopoietic chimerism and allograft tolerance without myelosuppression in nonhuman primates.

Hematopoietic stem cell transplantation (HSCT) has many potential applications beyond current standard indications, including treatment of autoimmune disease, gene therapy, and transplant tolerance induction. However, severe myelosuppression and other toxicities after myeloablative conditioning regimens have hampered wider clinical use. To achieve donor hematopoietic stem cell (HSC) engraftment, it appears essential to establish niches for the donor HSCs by depleting the host HSCs. To date, this has been achievable only by nonselective treatments such as irradiation or chemotherapeutic drugs. An approach that is capable of more selectively depleting host HSCs is needed to widen the clinical application of HSCT. Here, we show in a clinically relevant nonhuman primate model that selective inhibition of B cell lymphoma 2 (Bcl-2) promoted hematopoietic chimerism and renal allograft tolerance after partial deletion of HSCs and effective peripheral lymphocyte deletion while preserving myeloid cells and regulatory T cells. Although Bcl-2 inhibition alone was insufficient to induce hematopoietic chimerism, the addition of a Bcl-2 inhibitor resulted in promotion of hematopoietic chimerism and renal allograft tolerance despite using only half of the dose of total body irradiation previously required. Selective inhibition of Bcl-2 is therefore a promising approach to induce hematopoietic chimerism without myelosuppression and has the potential to render HSCT more feasible for a variety of clinical indications.