Tuesday, August 27, 2013

Donor Cancer Transmission in Kidney Transplantation: A Systematic Review

Transplantation of any biological material from a donor to a host will carry some inherent risk of disease transmission. Our aims were to summarize the totality of the published evidence about donor cancer transmission among kidney transplant recipients and to determine the cancer-specific survival of these patients. We systematically reviewed all case reports, case series and registry studies that described the outcomes of kidney transplant recipients with donor cancer transmission published to December 2012. A total of 69 studies with 104 donor-transmitted cancer cases were identified. The most common transmitted cancer types were renal cancer (n = 20, 19%), followed by melanoma (n = 18, 17%), lymphoma (n = 15, 14%) and lung cancer (n = 9, 9%). Patients with melanoma and lung cancers had the worst prognosis, with less than 50% of recipients surviving after 24 months from transplantation. Recipients with transmitted renal cancers had the best outcomes, with over 70% of recipients surviving for at least 24 months after transplantation. Overall, the risk of donor transmission of cancer appears low, but there is a high likelihood of reporting bias. Our findings support the current recommendations for rejecting organs from donors with a history of melanoma and lung cancer, but suggest that the use of donor kidneys with a history of small, incidental renal cell cancer may be reasonable (read more)

Toward eliminating HLA class I expression to generate universal cells from allogeneic donors

Long-term engraftment of allogeneic cells necessitates eluding immune-mediated rejection, which is currently achieved by matching for human leukocyte antigen (HLA) expression, immunosuppression, and/or delivery of donor-derived cells to sanctuary sites. Genetic engineering provides an alternative approach to avoid clearance of cells that are recognized as "non-self" by the recipient. To this end, we developed designer zinc finger nucleases and employed a "hit-and-run" approach to genetic editing for selective elimination of HLA expression. Electro-transfer of mRNA species coding for these engineered nucleases completely disrupted expression of HLA-A on human T cells, including CD19-specific T cells. The HLA-AnegT-cell pools can be enriched and evade lysis by HLA-restricted cytotoxic T-cell clones. Recognition by natural killer cells of cells that had lost HLA expression was circumvented by enforced expression of nonclassical HLA molecules. Furthermore, we demonstrate that zinc finger nucleases can eliminate HLA-A expression from embryonic stem cells, which broadens the applicability of this strategy beyond infusing HLA-disparate immune cells. These findings establish that clinically appealing cell types derived from donors with disparate HLA expression can be genetically edited to evade an immune response and provide a foundation whereby cells from a single donor can be administered to multiple recipients (read more)

Wednesday, August 21, 2013

Basiliximab/Low-Dose Rabbit Anti-Thymocyte Globulin Induces B Cell Depletion and Regeneration, Which Associates with a High Incidence of De Novo Donor-Specific Anti-HLA Antibody Development

In this single-center matched-cohort study, we evaluated the phenotype of repopulating B cells and its correlation with donor-specific anti-HLA Ab development and long-term graft function in 16 renal transplant recipients and 32 age- and gender-matched controls induced with alemtuzumab or basiliximab (Bas)/low-dose rabbit anti-thymocyte globulin (rATG), respectively. Alemtuzumab, but not Bas/rATG, profoundly depleted peripheral B cells in the first 2 mo posttransplantation. Early posttransplant, naive B cells were significantly depleted, whereas Ag-experienced and memory B cells were partially spared. Transitional B cells transiently increased 2 mo posttransplant. At month 6 posttransplant, pregerminal center B cells emerged, a process promoted by increased BAFF serum levels. Thereafter, B cell counts increased progressively, mainly due to expansion of naive B cells. Conversely, Bas/rATG did not modify the B cell phenotype throughout the follow-up period. Alemtuzumab was associated with a higher incidence of de novo DSA compared with Bas/rATG. DSA development was predicted by changes in the B cell compartment and correlated with worse long-term graft function. Thus, alemtuzumab-induced B cell depletion/reconstitution may promote chronic humoral responses against the graft (read more)

Wednesday, August 14, 2013

Higher Risk of Kidney Graft Failure in the Presence of Anti-Angiotensin II Type-1 Receptor Antibodies

Reports have associated non-HLA antibodies, specifically those against angiotensin II type-1 receptor (AT1R), with antibody-mediated kidney graft rejection. However, association of anti-AT1R with graft failure had not been demonstrated. We tested anti-AT1R and donor-specific HLA antibodies (DSA) in pre- and posttransplant sera from 351 consecutive kidney recipients: 134 with biopsy-proven rejection and/or lesions (abnormal biopsy group [ABG]) and 217 control group (CG) patients. The ABG's rate of anti-AT1R was significantly higher than the CG's (18% vs. 6%, p < 0.001). Moreover, 79% of ABG patients with anti-AT1R lost their grafts (vs. 0%, CG), anti-AT1R levels in 58% of those failed grafts increasing posttransplant. With anti-AT1R detectable before DSA, time to graft failure was 31 months—but 63 months with DSA detectable before anti-AT1R. Patients with both anti-AT1R and DSA had lower graft survival than those with DSA alone (log-rank p = 0.007). Multivariate analysis showed that de novo anti-AT1R was an independent predictor of graft failure in the ABG, alone (HR: 6.6), and in the entire population (HR: 5.4). In conclusion, this study found significant association of anti-AT1R with graft failure. Further study is needed to establish causality between anti-AT1R and graft failure and, thus, the importance of routine anti-AT1R monitoring and therapeutic targeting (read more)

Tuesday, August 13, 2013

Increased T Cell Glucose Uptake Reflects Acute Rejection in Lung Grafts

Although T cells are required for acute lung rejection, other graft–infiltrating cells such as neutrophils accumulate in allografts and are also high glucose utilizers. Positron emission tomography (PET) with the glucose probe [18F]fluorodeoxyglucose ([18F]FDG) has been employed to image solid organ acute rejection, but the sources of glucose utilization remain undefined. Using a mouse model of orthotopic lung transplantation, we analyzed glucose probe uptake in the grafts of syngeneic and allogeneic recipients with or without immunosuppression treatment. Pulmonary microPET scans demonstrated significantly higher [18F]FDG uptake in rejecting allografts when compared to transplanted lungs of either immunosuppressed or syngeneic recipients. [18F]FDG uptake was also markedly attenuated following T cell depletion therapy in lung recipients with ongoing acute rejection. Flow cytometric analysis using the fluorescent deoxyglucose analog 2-NBDG revealed that T cells, and in particular CD8+ T cells, were the largest glucose utilizers in acutely rejecting lung grafts followed by neutrophils and antigen-presenting cells. These data indicate that imaging modalities tailored toward assessing T cell metabolism may be useful in identifying acute rejection in lung recipients (read more)

Thursday, August 8, 2013

Overall and Cause-Specific Mortality in Transplant Recipients with a Pretransplantation Cancer History

Background: It is unclear to what extent cancer history affects posttransplantation mortality in solid organ transplant recipients. Methods: We identified a Swedish population-based cohort of solid organ transplant recipients in the National Patient Register 1970 to 2008 and linked it to the Cancer and Cause-of-Death Register. Overall and cause-specific mortality was estimated using Cox regression. Results: Of 10,448 eligible recipients, 416 (4%) had a prior malignancy unrelated to the indication for transplantation diagnosed 2 months or more before surgery (median, 5.7 years). Mortality among cancer history recipients was 30% increased after transplantation, compared with other recipients (adjusted hazard ratio [HR], 1.3; 95% confidence interval [CI], 1.1–1.5; P<0.001), driven by cancer-specific death with no increase in cardiovascular, infectious, or other noncancer mortality. An increased rate of death due to cancer history was primarily observed among nonkidney recipients (adjusted HRnonkidney, 1.8; 95% CI, 1.3–2.5; HRkidney, 1.2; 95% CI, 1.0–1.4). Rates were greatest for patients with waiting times of 5 years or less but persisted with waiting times more than 10 years among kidney and nonkidney recipients with prior aggressive cancer types (gastrointestinal, breast, kidney/urothelial, and hematologic malignancies). Conclusion: We conclude that organ transplant recipients with cancer history are at a moderately increased rate of death after transplantation, driven primarily by death due to cancer recurrence (read more)

Polyreactive Antibodies Developing Amidst Humoral Rejection of Human Kidney Grafts Bind Apoptotic Cells and Activate Complement

Antibody mediated rejection (AMR) is associated with a variety of graft-reactive antibodies following kidney transplant. To characterize these antibodies, we immortalized 107 B cell clones from a patient with AMR. In a previous study, we showed that six clones were reacting to multiple self-antigens as well as to HLA and MICA for two of them, thus displaying a pattern of polyreactivity. We show here that all six polyreactive clones also reacted to apoptotic but not viable cells. More generally we observed a nearly perfect overlap between polyreactivity and reactivity to apoptotic cells. Functionally, polyreactive antibodies can activate complement, resulting in the deposition of C3d and C4d at the surface of target cells. Testing the serum of 88 kidney transplant recipients revealed a significantly higher IgG reactivity to apoptotic cells in AMR patients than in patients with stable graft function. Moreover, total IgG purified from AMR patients had increased complement activating properties compared to IgG from non-AMR patients. Overall, our studies show the development of polyreactive antibodies cross-reactive to apoptotic cells during AMR. Further studies are now warranted to determine their contribution to the detection of C4d in graft biopsies as well as their role in the pathophysiology of AMR (read more)
Hypogammaglobulinemia has been described after solid organ transplantation and has been associated with increased risk of infections. The aim of the study was to evaluate the rate of severe hypogammaglobulinemia and its relationship with the risk of infections during the first year posttransplantation. Eighteen studies (1756 patients) that evaluated hypogammaglobulinemia and posttransplant infections were included. The data were pooled using the DerSimonian and Laird random-effects model. Q statistic method was used to assess statistical heterogeneity. Within the first year posttransplantation, the rate of hypogammaglobulinemia (IgG < 700 mg/dL) was 45% (95% CI: 0.34–0.55; Q = 330.1, p < 0.0001), the rate of mild hypogammaglobulinemia (IgG = 400–700 mg/dL) was 39% (95% CI: 0.22–0.56; Q = 210.09, p < 0.0001) and the rate of severe hypogammaglobulinemia (IgG < 400 mg/dL) was 15% (95% CI: 0.08–0.22; Q = 50.15, p < 0.0001). The rate of hypogammaglobulinemia by allograft type: heart 49% (21%–78%; Q = 131.16, p < 0.0001); kidney 40% (30%–49%; Q = 24.55, p = 0.0002); liver 16% (0.001%–35%; Q = 14.31, p = 0.0002) and lung 63% (53%–74%; Q = 6.85, p = 0.08). The odds of respiratory infection (OR = 4.83; 95% CI: 1.66–14.05; p = 0.004; I2 = 0%), CMV (OR = 2.40; 95% CI: 1.16–4.96; p = 0.02; I2 = 26.66%), Aspergillus (OR = 8.19; 95% CI: 2.38–28.21; p = 0.0009; I2 = 17.02%) and other fungal infections (OR = 3.69; 95% CI: 1.11–12.33; p = 0.03; I2 = 0%) for patients with IgG <400 mg/dL were higher than the odds for patients with IgG >400 mg/dL. The odds for 1-year all-cause mortality for severe hypogammaglobulinemia group was 21.91 times higher than those for IgG >400 mg/dL group (95% CI: 2.49–192.55; p = 0.005; I2 = 0%). Severe hypogammaglobulinemia during the first year posttransplantation significantly increased the risk of CMV, fungal and respiratory infections, and was associated with higher 1-year all-cause mortality (read more)

Pretransplant Sensitization Against Angiotensin II Type 1 Receptor Is a Risk Factor for Acute Rejection and Graft Loss

The angiotensin II type 1 receptor (AT1R) is an emerging target of functional non-HLA antibodies (Ab). We examined the potential of determining the degree of presensitization against AT1R as a risk factor for graft survival and acute rejection (AR). The study included 599 kidney recipients between 1998 and 2007. Serum samples were analyzed in a blinded fashion for anti-AT1R antibodies (AT1R-Abs) using a quantitative solid-phase assay. A threshold of AT1R-Ab levels was statistically determined at 10 U based on the time to graft failure. An extended Cox model determined risk factors for occurrence of graft failure and a first AR episode. AT1R-Abs >10 U were detected in 283 patients (47.2%) before transplantation. Patients who had a level of AT1R-Abs >10 U had a 2.6-fold higher risk of graft failure from 3 years posttransplantation onwards (p = 0.0005) and a 1.9-fold higher risk of experiencing an AR episode within the first 4 months of transplantation (p = 0.0393). Antibody-mediated rejection (AMR) accounted for 1/3 of AR, whereby 71.4% of them were associated with >10 U of pretransplant AT1R-Abs. Pretransplant anti-AT1R-Abs are an independent risk factor for long-term graft loss in association with a higher risk of early AR episodes (read more and editorial)

Tuesday, August 6, 2013

Indications for intestinal transplantation: recognizing the scope and limits of total parenteral nutrition

Total parenteral nutrition (TPN) is currently the treatment of choice for patients with intestinal failure. Intestinal failure in adults is mostly due to short bowel syndrome, which is most often caused by ischemia and Crohn's disease. However, TPN fails in a substantial number of cases. For patients with TPN failure, intestinal transplantation (ITx) may be offered as a treatment. TPN failure is considered to be present either if nutrition itself is not possible or if complications of TPN occur. These complications can, for example, originate from recurrent line infections or thrombosis. As TPN is usually a lifelong therapy and is associated with substantial impairment of the quality of life, the tolerance of each patient to this procedure is another important consideration in the decision making about whether to perform transplantation. The survival rates of intestinal transplant recipients have now reached the same level as that of recipients of other solid organ transplants. A five-yr survival of up to 80% has been reported in specialized centers, whereas registry data show rates of <80%. Although in about one-third of patients, isolated ITx is sufficient, patients with concurrent liver disease (mostly due to TPN) benefit from combined intestinal and liver transplantation. In some cases, multivisceral transplantation is necessary. Here, we review the current indications for ITx with a special focus on TPN (read more)

Alternatives to islet transplantation: future cell sources of beta-like cells

Cell transplantation is a treatment option for diabetes, metabolic liver disease in children, and leukemia. Except for the latter indication, solid organ transplantation is one of the available therapies but can be replaced by cell transplantation. However, due to the limited amount of cells that can be transplanted and due to rejection, results of cell transplants are still inferior to solid organ transplantation; there is a general shortage of donor organs, and cell isolation is limited to organs which cannot be transplanted as a whole for anatomic reasons. Therefore, alternatives to islets and beta cells are needed. There are some cells which can be generated from the recipient and would not be rejected; still, immunosuppression would be required to prevent reoccurrence of type I diabetes unless durable tolerance to beta cells could be induced. Generating beta cells for transplant from the recipient would help to overcome the lack of available organs. Moreover, understanding the underlying mechanisms of differentiation of these cells into beta-like cells would deepen our understanding of both pathophysiology and development of diabetes mellitus type I. This article examines embryonal stem cells, induced pluripotent cells, mesenchymal stromal cells, and hepatocytes as potential alternatives to beta-cell transplantation (read more)

Thursday, August 1, 2013

A Validated Model for Predicting Outcome after Liver Transplantation: Implications on Transplanting the Extremely Sick

Given the organ shortage, there is a need to optimize outcome after liver transplantation (LT). We defined post-transplant hospital length of stay > 60 days (LOS>60) as a surrogate of suboptimal outcome. In the first phase of the study, a “Study cohort” (SC) of 643 patients was used to identify risk factors and construct a mathematical model to identify recipients with anticipated inferior results. In the second phase, a cohort of 417 patients was used for validation of the model (“Validation Cohort”- VC). In the SC, 65 patients (10.1%) had LOS > 60 days. One- and three-year patient/graft survival rates were 81.9%/76.1% and 73.4%/67.4%, respectively. Patient and graft survival of those with LOS >60 days were inferior (p < 0.0001) while transplant cost was greater (3.42 RU vs. 1 RU, p < 0.0001). In a multivariable analysis, pre-transplant dialysis (p< 0.001), mechanical ventilation (p< 0.015), MELD (p<0.003) and age (p<0.009) were predictors of LOS > 60 days {ROC curve - 0.75 (95% CI [0.70, 0.81]}. In the VC, 53 patients (12.7%) were expected to have adverse outcome by the model. These patients had longer LOS (p < 0.0001), higher cost (< 0.0001) and inferior patient and graft survival (p< 0.007) (read more)