Timing of CMV‐specific effector memory T cells predicts viral replication and survival after allogeneic hematopoietic stem cell transplantation

The aim of this study was to characterize timing, kinetic, and magnitude of CMV‐specific immune response after hematopoietic stem cell transplantation (HSCT) and its ability to predict CMV replication and clinical outcomes. Using cell surface and intracellular cytokine staining by flow cytometry, CMV‐specific T‐cell response was measured in blood, while CMV viral load and chimerism were determined by real‐time PCR. Patients that reconstituted CMV‐specific T‐cell response within 6 weeks after Allo‐SCT showed a more robust immune response (CD8⁺: 0.7 cells/μl vs. 0.3/μl; P‐value = 0.01), less incidence of CMV replication (33% vs. 89.5%; P‐value = 0.007), reduced viral loads (1.81 log copies/ml vs. 0 copies/ml; P‐value = 0.04), and better overall survival (72%; CI: 0.53–0.96 vs. 42% CI: 0.24–0.71; P‐value = 0.07) than patients with a delayed immune reconstitution. Viremic patients had significantly higher transplant‐related mortality than nonviremic patients after 1 year (33% CI: 0.15–0.52 vs. 0% CI: 0.05–0.34; P‐value = 0.01). Risk factors independently associated with viral replication were receptor pretransplant CMV‐positive serostatus (P‐value = 0.02) and acquiring CMV‐specific T‐cell response after 6 weeks post‐transplantation (P‐value = 0.009). In conclusion, timing of acquiring a positive CMV‐specific T‐cell immune response after transplantation may identify patients with different risk for viral replication and different clinical outcomes, including survival.     

Viral load,CMV‐specific T‐cell immune response and cytomegalovirus disease in solid organ transplant recipients at higher risk for cytomegalovirus infection during preemptive therapy

Despite advances in prevention, cytomegalovirus (CMV) recurrence is an important challenge in high‐risk organ recipients. The present study prospectively evaluates the impact of CMV‐specific T‐cell immune response and secondary prophylaxis on the risk of recurrence in a cohort of CMV high‐risk organ recipients and whether it is possible to determine a safe standardized viral load value below which CMV disease is unlikely. Thirty‐nine recipients were included. Thirty‐six had primary infections, and 88.9% recurred. Rate and duration of recurrent CMV infection was similar in patients with and without secondary prophylaxis: 57.9% vs. 53.6%, P = 0.770 and 16 vs. 15 days, P = 0.786, respectively. The only factor independently associated with no episodes of CMV recurrence was the acquisition of CMV‐specific T‐cell immune response (OR: 0.151, 95% CI: 0.028–0.815; P = 0.028). Cytomegalovirus diseases (N = 5) occurred in patients with CMV viral load above 1500 IU/ml who did not follow the planned monitorization schedule. Our observations suggest that episodes of recurrent CMV infection are common after preemptive therapy despite secondary prophylaxis and that CMV‐specific T‐cell immune response is associated with a decreased risk of recurrent infections. Preemptive therapy may be safe in patients at high risk for CMV infection with strict close monitoring of the CMV viral load.     

Virus‐specific T‐cell therapy in solid organ transplantation

This article reviews the current state of T‐cell therapy as therapeutic option for virus‐associated diseases against the background of the most common viral complications and their standard treatment regimens after SOT. The available data of clinical T‐cell trials in SOT are summarized. References to the hematopoietic stem cell transplantation are made if applicable data in SOT are not available and their content was considered likewise valid for cell therapy in SOT. Moreover, aspects of different manufacturing approaches including beneficial product characteristics and the importance of GMP compliance are addressed.     

Costimulatory blockade with mTor inhibition abrogates effector T‐cell responses allowing regulatory T‐cell survival in renal transplantation

The advent of novel immunosuppressive strategies in renal transplantation, with immunomodulatory properties, might facilitate long‐term allograft survival. T‐cell depletion, costimulation‐blockade and mTor inhibition have been shown to favour anti‐donor hyporesponsiveness. Recently, the combination of rATG, belatacept (Bela) and sirolimus (SRL) has been used in kidney transplantation, showing very low incidence of acute rejection and excellent 12‐month graft and patient survival. Herein, we have analysed the 1‐year evolution of memory/effector and regulatory T cells and assessed the donor‐specific T‐cell alloimmune response in a group of these patients and compared with others treated with a calcineurin‐inhibitor(CNI)‐based (rATG/tacrolimus/MMF), and two other Bela‐based regimens (rATG/Bela/MMF and basiliximab/Bela/MMF/steroids). During the first year after transplantation, patients receiving rATG/Bela/SRL had significantly higher percentage of Tregs upon the memory T‐cell compartment and showed a potent anti‐donor suppressive activity. In an in vitro naive and memory/effector T‐cell co‐culture, the combination of costimulation‐blockade and SRL could abrogate both antigen‐specific T‐cell responses as efficiently as using a CNI drug. The combination of T‐cell depletion, costimulation‐blockade and mTor inhibition seems to be able to allow Treg survival and inhibit donor‐specific alloreactive effector immune responses after kidney transplantation in humans.     

Uremia‐associated immunological aging is stably imprinted in the T‐cell system and not reversed by kidney transplantation

The uremia‐induced inflammatory environment in end‐stage renal disease (ESRD) patients is associated with premature T‐cell aging resulting in a defective T‐cell immunity. As kidney transplantation (KTx) reduces the pro‐inflammatory environment, we hypothesized that KTx would rejuvenate the aged T‐cell system. As aging parameters, we determined in 70 KTx recipients the differentiation status by immunophenotyping, thymic output by the T‐cell receptor excision circle (TREC) content together with CD31⁺ naïve T‐cell numbers and the relative telomere length (RTL) as a measure for proliferative history at pre‐KTx, 3, 6 and 12 months post‐KTx. In addition, T‐cell function was determined by measuring the proliferative capacity and percentages of cytokine‐producing cells. Directly post‐KTx, memory T‐cell numbers were diminished but restored to pre‐KTx values at 12 months, except for CD4⁺EM T cells. The RTL of (memory) CD4⁺ and CD8⁺ T cells did not change. In contrast, TREC content and CD31⁺ naïve T‐cell numbers were stable post‐KTx although the RTL of naïve CD4⁺ and CD8⁺ T cells decreased implying homeostatic proliferation of naïve cells, in response to a temporary decrease in memory cells. The T‐cell function was not improved post‐KTx. Our findings demonstrate that the uremia‐associated aged phenotype is stably imprinted in the T‐cell system and not reversed by KTx.     

Risk factors for impaired CD4+ T‐cell reconstitution following rabbit antithymocyte globulin treatment in kidney transplantation

To describe long‐term CD4⁺ T‐cell reconstitution after rabbit antithymocyte globulin (rATG) treatment and identify predictive factors following kidney transplantation. A single‐center retrospective study analyzed lymphocyte subsets in rATG‐treated kidney transplant recipients (1986–2009). 589 patients were analyzed (maximum follow‐up 21 years). A comparator group (n = 298) received an anti‐IL‐2 receptor monoclonal antibody. CD4⁺ T‐cell lymphopenia (<200/mm³) was present in 48.5%, 9.2%, 6.7%,2.0%, and 0% of patients at one, three, five, 10, and 20 years post‐transplant, respectively. CD4⁺ T‐cell count increased during the first 10 years but remained below the pretransplant count even after 20 years. At 1, 3, and 6 months post‐transplant, mean CD4⁺ T‐cell count was significantly lower in patients with CD4⁺ T‐cell lymphopenia at 12 months versus patients without lymphopenia. On multivariate analyses, significant independent predictors for long‐term impaired CD4 T‐cell reconstitution were recipient age, pretransplant CD4⁺ T‐cell count, 12‐month CD4⁺ T‐cell count, and tacrolimus or MMF therapy. Recipient age >40 years was identified as a cutoff point. CD4⁺ T‐cell reconstitution following rATG treatment remains impaired even after 21 years. Most risk factors for long‐term impaired CD4⁺ T‐cell reconstitution may be evaluated pretransplant or are modifiable post‐transplant.     

An objective definition for clinical suspicion of T‐cell‐mediated rejection after liver transplantation

A uniform definition of clinical suspicion of T‐cell‐mediated rejection (TCMR) in liver transplantation (LT) is needed to homogenize clinical decisions, especially within randomized trials. This multicenter study included a total of 470 primary LT recipients. The derivation cohort consisted of 142 patients who had clinically driven liver biopsies at any time after LT. The external validation cohort included 328 patients who underwent protocol biopsies at day 7‐10 after LT. The rates of moderate‐severe histological TCMR were 33.8% in the derivation cohort and 43.6% in the validation cohort. Independent predictors (ie, risk factors) of moderate‐severe TCMR in the derivation cohort were as follows: serum bilirubin >4 mg/dL (OR=5.83; P<.001), rising bilirubin within the 4 days prior to liver biopsy (OR=4.57; P=.003), and blood eosinophils count >0.1×10⁹/L (OR=3.81; P=.004). In the validation cohort, the number of risk factors was an independent predictor of moderate‐severe TCMR (OR=1.74; P=.001), after controlling for hepatitis C status. The number of risk factors paralleled the rates of moderate‐severe TCMR in the derivation and validation cohorts (P<.001 in both comparisons). In conclusion, increased serum bilirubin, rising bilirubin and eosinophilia are validated risk factors for moderate‐severe histological TCMR and could be used as objective criteria to select candidates for liver biopsy.     

Impact of cyclosporine‐A concentration in T‐cell replete haploidentical allogeneic stem cell transplantation

This paper aims to study whether cyclosporine‐A (CSA) levels have an impact on the clinical outcome of patients with T‐cell replete haploidentical allogeneic hematopoietic stem cell transplantation (allo‐HSCT). We analyzed 140 consecutive patients who had been given T‐cell replete haploidentical allo‐HSCT in our institute to assess the effect of CSA concentration in the early stages of allo‐HSCT on clinical outcomes, such as hematopoietic recovery, acute graft vs host disease (aGVHD), infection, disease‐free survival (DFS), and overall survival (OS). The median concentrations of CSA in the blood in the 1st, 2nd, 3rd, and 4th week after allo‐HSCT were 218, 235, 263, and 270 ng/mL, respectively. Additionally, 46%, 40%, 27%, and 18% of the patients had CSA blood levels below 200 ng/mL during those weeks. In total, 39 patients developed aGVHD (grade II‐IV), for a cumulative incidence of 27.8%, at a median of 32 days. Patients having a low CSA concentration (below 200 ng/mL) in the 3rd week had a higher cumulative incidence of grade II‐IV aGVHD (P = .02). In addition, multivariate logistic regression analysis showed that low CSA concentration (below 200 ng/mL) in the 3rd week was an independent risk factor of grade II‐IV aGVHD (P = .02; odds ratio = 2.66; 95% CI, 1.15‐6.17). However, CSA levels during the first 4 weeks did not have a significant impact on the patients’ hematopoietic recovery, infection, DFS, and OS. Our data indicated that adequate management of CSA levels during the peri‐engraftment period might improve clinical outcomes for those with T‐cell replete haploidentical allo‐HSCT.     

CMV specific T cell immune response in hepatitis C negative kidney transplant recipients receiving transplant from hepatitis C viremic donors and hepatitis C aviremic donors

Kidney transplants (KT) from hepatitis C (HCV) viremic donors to HCV negative recipients has shown promising renal outcomes, however, high incidence of cytomegalovirus (CMV) viremia were reported. We performed a prospective cohort study of 52 HCV negative KT recipients from Methodist University Hospital including 41 receiving transplants from HCV aviremic donors and 11 from HCV viremic donors. CMV specific CD4+ and CD8 + T cell immunity was measured by intracellular flow cytometry assay. Primary outcome was the development of positive CMV specific CD4+ and CD8 + T cell immune response in the entire cohort and each subgroup. The association between donor HCV status and CMV specific CD4+ and CD8 + T cell immune response was analyzed by Cox proportional hazard models. Mean recipient age was 48 ± 13 years, with 73% male and 82% African American. Positive CMV specific CD4+ and CD8 + T cell immune response was found in 53% and 47% of the cohort at 1 month, 65% and 70% at 2 months, 80% and 75% at 4 months, 89% and 87% at 6 months, and 94% and 94% at 9 months post-transplant, respectively. There was no significant difference in the incidence of positive CMV specific T cell immune response between recipients of transplants from HCV aviremic donors compared to HCV viremic donors in unadjusted (for CD8+: HR = 1.169, 95%CI: 0.521–2.623; for CD4+: HR = 1.208, 95%CI: 0.543–2.689) and adjusted (for CD8+: HR = 1.072, 95%CI: 0.458–2.507; for CD4+: HR = 1.210, 95%CI: 0.526–2.784) Cox regression analyses. HCV viremia in donors was not associated with impaired development of CMV specific T cell immunity in this cohort.     

Demonstration of HHV‐6 antigens in biopsies of kidney transplant recipients with cytomegalovirus infection

The activation of human herpesvirus‐6 (HHV‐6) commonly coexists with that of cytomegalovirus (CMV) in organ transplant recipients. No data exist of HHV‐6 in renal allografts, whereas persistent CMV in the kidney associates with poor outcome and histopathologic changes. We examined HHV‐6 and CMV antigens from kidney transplants with previous CMV infection. HHV‐6 and CMV pp65 antigens were demonstrated by monoclonal antibodies and immunohistochemistry from 22 kidney transplants with previous CMV infection. CMV was diagnosed by antigenemia tests and/or viral cultures. HHV‐6 antigens were found in 7/22 biopsies 18–1330 days after CMV infection, in infiltrating leukocytes in six, and in tubular epithelial cells in two patients. CMV infections were treated, and no virus could be detected from urine or blood thereafter, or at the time of the biopsy. Only 1/7 of these biopsies demonstrated also CMV antigens, whereas CMV antigens were found in 6/15 of the biopsies with no HHV‐6. HHV‐6 in the graft was associated with previous acute rejections, but not with any histopathological changes or reduced renal function. In conclusion, HHV‐6 was a common finding in late renal allograft biopsies of patients with previous CMV infection, but its significance remains to be elucidated.     

Reversing donor‐specific antibody responses and antibody‐mediated rejection with bortezomib and belatacept in mice and kidney transplant recipients

Active antibody‐mediated rejection (AMR) is a potentially devastating complication and consistently effective treatment remains elusive. We hypothesized that the reversal of acute AMR requires rapid elimination of antibody‐secreting plasma cells (PC) with a proteasome inhibitor, bortezomib, followed by the sustained inhibition of PC generation with CTLA4‐Ig or belatacept (B/B). We show in mice that B/B therapy selectively depleted mature PC producing donor‐specific antibodies (DSA) and reduced DSA, when administered after primary and secondary DSA responses had been established. A pilot investigation was initiated to treat six consecutive patients with active AMR with B/B. Compassionate use of this regimen was initiated for the first patient who developed early, severe acute AMR that did not respond to steroids, plasmapheresis, and intravenous immunoglobulin after his third kidney transplant. B/B treatment resulted in a rapid reversal of AMR, leading us to treat five additional patients who also resolved their acute AMR episode and had sustained disappearance of circulating DSA for ≤30 months. This study provides a proof‐of‐principle demonstration that mouse models can identify mechanistically rational therapies for the clinic. Follow‐up investigations with a more stringent clinical design are warranted to test whether B/B improves on the standard of care for the treatment of acute AMR.     

The possible critical role of T‐cell help in DSA‐mediated graft loss

In this review, we discuss a possible central role of T‐cell help in severe forms of graft damage mediated by donor‐specific HLA antibodies (DSA). Some kidney transplant recipients with pretransplant DSA show a high graft failure rate, whereas in other patients DSA do not harm the transplanted kidney and in most cases, disappear shortly after transplantation. Analyzing 80 desensitized highly immunized kidney transplant recipients and another multicenter cohort of 385 patients with pretransplant HLA antibodies, we reported recently that an ongoing T‐cell help from an activated immune system, as measured by an increased level of soluble CD30 in serum, might be necessary for the DSA to exert a deleterious effect. Patients positive for both pretransplant DSA and sCD30 appear to require special measures, such as the elimination of DSA from the circulation, potent immunosuppression, good HLA‐matching, and intense post‐transplant monitoring, whereas exclusion of DSA‐positive patients from transplantation in the absence of high sCD30 may not be justified in all cases, even if the pretransplant DSA are strong and complement‐activating.     

Blood dendritic cell levels associated with impaired IL‐12 production and T‐cell deficiency in patients with kidney disease: implications for post‐transplant viral infections

Reduced pretransplant blood myeloid dendritic cell (mDC) levels are associated with post‐transplant BK viremia and cytomegalovirus (CMV) disease after kidney transplantation. To elucidate potential mechanisms by which mDC levels might influence these outcomes, we studied the association of mDC levels with mDC IL‐12 production and T‐cell level/function. Peripheral blood (PB) was studied in three groups: (i) end stage renal disease patients on hemodialysis (HD; n = 81); (ii) chronic kidney disease stage IV‐V patients presenting for kidney transplant evaluation or the day of transplantation (Eval/Tx; n = 323); and (iii) healthy controls (HC; n = 22). Along with a statistically significant reduction in mDC levels, reduced CD8⁺ T‐cell levels were also demonstrated in the kidney disease groups compared with HC. Reduced PB mDC and monocyte‐derived DC (MoDC) IL‐12 production was observed after in vitro LPS stimulation in the HD versus HC groups. Finally, ELISpot assays demonstrated less robust CD3⁺ INF‐γ responses by MoDCs pulsed with CMV pp65 peptide from HD patients compared with HC. PB mDC level deficiency in patients with kidney disease is associated with deficient IL‐12 production and T‐cell level/function, which may explain the known correlation of CD8⁺ T‐cell lymphopenia with deficient post‐transplant antiviral responses.     

Comparative analysis of post‐transplant lymphoproliferative disorder after kidney transplantation versus hematopoietic stem cell transplantation

Post‐transplant lymphoproliferative disorder (PTLD) is a major complication caused by immune‐suppression after transplantation. Survival outcome is known to be poor and the characteristics are not fully understood because of its rare incidence. This single center retrospective study enrolled 41 adult PTLD patients after kidney‐transplantation (KT, n = 28) and hematopoietic stem cell transplantation (HSCT, n = 13) from 1992 to 2012. We compared the characteristics and estimated the survival outcomes according to several factors [age‐adjusted‐IPI (aaIPI), pathologic subtype, viral status, extranodal manifestation] and added some significant parameters to aaIPI scoring system. Post‐HSCT‐PTLD patients were younger and showed earlier onset, and viral status was more frequently identified. Ten‐year OS of the entire group was 44% but the 10‐year OS was not significantly different between post‐KT‐PTLD and post‐HSCT‐PTLD (39% vs. 56%, P = 0.860). The time onset of PTLD and viral statuses were not meaningful, however, aaIPI, age > 50, extranodal manifestation and monomorphic subtype were predictive for OS. We used those factors for PTLD‐specific scoring which showed intermediate‐risk (HR = 7.1, P = 0.019) and high‐risk (HR = 16.5, P = 0.001) presented worse OS compared to low‐risk subgroup. Although the treatment strategies were heterogenous, this study showed comprehensive PTLD data between KT versus HSCT, and our PTLD‐specific scoring might be validated by another larger studies.     

Human leukocyte antigen selected allogeneic mesenchymal stromal cell therapy in renal transplantation: The Neptune study,a phase I single‐center study

Mesenchymal stromal cells (MSC) hold promise as a novel immune‐modulatory therapy in organ transplantation. First clinical studies have used autologous MSCs; however, the use of allogeneic "off‐the‐shelf" MSCs is more sustainable for broad clinical implementation, although with the risk of causing sensitization. We investigated safety and feasibility of allogeneic MSCs in renal transplantation, using a matching strategy that prevented repeated mismatches. Ten patients received two doses of 1.5 × 10⁶/kg allogeneic MSCs 6 months after transplantation in a single‐center nonrandomized phase Ib trial, followed by lowering of tacrolimus (trough level 3 ng/mL) in combination with everolimus and prednisone. Primary end point was safety, measured by biopsy proven acute rejection (BPAR) and graft loss 12 months after transplantation. Immune monitoring was performed before and after infusion. No BPAR or graft loss occurred and renal function remained stable. One patient retrospectively had DSAs against MSCs, formed before infusion. No major alterations in T and B cell populations or plasma cytokines were observed upon MSC infusion. Administration of HLA selected allogeneic MSCs combined with low‐dose tacrolimus 6 months after transplantation is safe at least in the first year after renal transplantation. This sets the stage to further explore the efficacy of third‐party MSCs in renal transplantation.     

Outcome of the risk‐stratified desensitization protocol in donor‐specific antibody‐positive living kidney transplant recipients: a retrospective study

Acceptable outcomes of donor‐specific antibody (DSA)‐positive living kidney transplantation (LKT) have recently been reported. However, LKT in crossmatch (XM)‐positive patients remains at high‐risk and requires an optimal desensitization protocol. We report our intermediate‐term outcomes of XM‐positive LKT vs. XM‐negative LKT in patients who underwent LKT between January 2012 and June 2015 in our institution. The rate of acute antibody‐mediated rejection (ABMR) within 90 days postoperation, graft function, and patient, and graft survival rates at 4 years were investigated. Patients were divided into three groups: XM?DSA? (n = 229), XM?DSA+ (n = 36), and XM + DSA+ (n = 15). The XM + DSA+ group patients underwent desensitization with high‐dose intravenous immunoglobulin, plasmapheresis, and rituximab. The rates of ABMR within 90 days in the XM?DSA?, XM?DSA+, and XM + DSA+ groups were 1.3%, 9.4%, and 60.0%, respectively (P < 0.001). There were no significant differences in the graft function throughout the observational period, the 4‐year patient or graft survival rates among three groups. This study showed that intermediate‐term outcomes of XM‐positive LKT were comparable to XM‐negative LKT. However, our current desensitization protocol cannot avert ABMR within 90 days, and XM positivity is still a significant risk factor for ABMR. Further refinement of the current desensitization regimen is required.     

De novo mTOR inhibitor‐based immunosuppression in ABO‐incompatible kidney transplantation

ABO‐incompatible (ABOi) kidney transplantation (KTx) has become an accepted therapeutic option in renal replacement therapy for patients without a blood group‐compatible living donor. Using different desensitization strategies, most centers apply B‐cell depletion with rituximab and maintenance immunosuppression (IS) with tacrolimus and mycophenolic acid. This high load of total IS leads to an increased rate of surgical complications and virus infections in ABOi patients. Our aim was to establish ABOi KTx using an immunosuppressive regimen, which is effective in preventing acute rejection without increasing the risk for viral infections. Therefore, we selected a de novo immunosuppressive protocol with low‐dose calcineurin inhibitor and the mTOR inhibitor everolimus for our ABOi program. Here, we report the first 25 patients with a complete three‐yr follow‐up treated with this regimen. Three‐yr patient survival and graft survival were 96% and 83%. The rate of acute T‐cell‐mediated rejections was low (12%). Cytomegalovirus (CMV) infection was evident in one patient only (4%). Surgical complications were common (40%), but mild in 80% of cases. We demonstrate that ABOi KTx with a de novo mTOR inhibitor‐based regimen is feasible without severe surgical or immunological complications and a low rate of viral infections.     

IL‐6 and IL‐10 in post‐transplant lymphoproliferative disorders development and maintenance: a longitudinal study of cytokine plasma levels and T‐cell subsets in 38 patients undergoing treatment

IL‐6 and IL‐10 have previously been implicated in the pathogenesis of post‐transplant lymphoproliferative disorders (PTLD) and, like peripheral lymphocyte populations, are markers of immune status that are amenable to study in vivo. Thus, we analyzed cytokine plasma levels as well as lymphocyte subsets in a longitudinal analysis of 38 adult transplant recipients undergoing treatment for PTLD. Pretherapeutically, we found significantly elevated IL‐6 (13.8 pg/ml) and IL‐10 plasma levels (54.7 pg/ml) – in the case of IL‐10, even higher in treatment nonresponders than in responders (116 vs. 14 pg/ml). Over time, however, IL‐10 levels did not correlate with the course of disease, whereas those of IL‐6 did, falling in responders and rising in nonresponders. These findings were independent of histological EBV‐status, treatment type, and total peripheral T‐cell counts, which were significantly reduced in patients with PTLD. Our observations support the idea that although IL‐10 is important for creating a permissive environment for post‐transplant lymphoma development, IL‐6 is associated with PTLD proliferation. The analysis of lymphocyte subsets further identified HLA‐DR+ CD8+ lymphocyte numbers as significantly different in non‐PTLD controls (33%), treatment responders (44%) and nonresponders (70%). Although the specificity of these cells is unclear, their increase might correlate with the impaired tumor‐specific cytotoxic‐T‐lymphocyte (CTL)‐response in PTLD.