Targeted mapping and utilization of the perihepatic surface for therapeutic beta cell replacement and retrieval in diabetic non-human primates.

Introduction: Successful diabetes reversal using pancreatic islet transplantation by various groups illustrates the significant achievements made in cell-based diabetes therapy. While clinically, intraportal islet delivery is almost exclusively used, it is not without obstacles, including instant blood-mediated inflammatory reaction (IBMIR), relative hypoxia, and loss of function over time, therefore hindering long-term success. Here we demonstrate the perihepatic surface of non-human primates (NHPs) as a potential islet delivery site maximizing favorable characteristics, including proximity to a dense vascular network for adequate oxygenation while avoiding IBMIR exposure, maintenance of portal insulin delivery, and relative ease of accessibility through minimally invasive surgery or percutaneous means. In addition, we demonstrate a targeted mapping technique of the perihepatic surface, allowing for the testing of multiple experimental conditions, including a semi-synthetic hydrogel as a possible three-dimensional framework to improve islet viability. Methods: Perihepatic allo-islet cell transplants were performed in immunosuppressed cynomolgus macaques using a targeted mapping technique to test multiple conditions for biocompatibility. Transplant conditions included islets or carriers (including hydrogel, autologous plasma, and media) alone or in various combinations. Necropsy was performed at day 30, and histopathology was performed to assess biocompatibility, immune response, and islet viability. Subsequently, single-injection perihepatic allo-islet transplant was performed in immunosuppressed diabetic cynomolgus macaques. Metabolic assessments were measured frequently (i.e., blood glucose, insulin, C-peptide) until final graft retrieval for histopathology. Results: Targeted mapping biocompatibility studies demonstrated mild inflammatory changes with islet-plasma constructs; however, significant inflammatory cell infiltration and fibrosis were seen surrounding sites with the hydrogel carrier affecting islet viability. In diabetic NHPs, perihepatic islet transplant using an autologous plasma carrier demonstrated prolonged function up to 6 months with improvements in blood glucose, exogenous insulin requirements, and HbA1c. Histopathology of these islets was associated with mild peri-islet mononuclear cell infiltration without evidence of rejection. Discussion: The perihepatic surface serves as a viable site for islet cell transplantation demonstrating sustained islet function through 6 months. The targeted mapping approach allows for the testing of multiple conditions simultaneously to evaluate immune response to biomaterials at this site. Compared to traditional intraportal injection, the perihepatic site is a minimally invasive approach that allows the possibility for graft recovery and avoids IBMIR.

Anti-C5 Antibody Tesidolumab Reduces Early Antibody-mediated Rejection and Prolongs Survival in Renal Xenotransplantation.

OBJECTIVE: Pig-to-primate renal xenotransplantation is plagued by early antibody-mediated graft loss which precludes clinical application of renal xenotransplantation. We evaluated whether temporary complement inhibition with anti-C5 antibody Tesidolumab could minimize the impact of early antibody-mediated rejection in rhesus monkeys receiving pig kidneys receiving costimulatory blockade-based immunosuppression. METHODS: Double (Gal and Sda) and triple xenoantigen (Gal, Sda, and SLA I) pigs were created using CRISPR/Cas. Kidneys from DKO and TKO pigs were transplanted into rhesus monkeys that had the least reactive crossmatches. Recipients received anti-C5 antibody weekly for 70 days, and T cell depletion, anti-CD154, mycophenolic acid, and steroids as baseline immunosuppression (n = 7). Control recipients did not receive anti-C5 therapy (n = 10). RESULTS: Temporary anti-C5 therapy reduced early graft loss secondary to antibody-mediated rejection and improved graft survival (P < 0.01). Deleting class I MHC (SLA I) in donor pigs did not ameliorate early antibody-mediated rejection (table). Anti-C5 therapy did not allow for the use of tacrolimus instead of anti-CD154 (table), prolonging survival to a maximum of 62 days. CONCLUSION: Inhibition of the C5 complement subunit prolongs renal xenotransplant survival in a pig to non-human primate model.

Blockade of BAFF Reshapes the Hepatic B Cell Receptor Repertoire and Attenuates Autoantibody Production in Cholestatic Liver Disease.

Defects in biliary transport proteins, MDR3 in humans and Mdr2 in mice, can lead to a spectrum of cholestatic liver disorders. Although B cell disorders and the aberrant Ab production are the leading extrahepatic manifestations of cholestatic liver diseases, the mechanism underlying this phenomenon is incompletely understood. Using mice with deficiency of Mdr2 that progressively develop cholestatic liver disease, we investigated the contributions of BAFF to aberrant IgG autoantibody production and hepatic fibrosis. In Mdr2-/- mice, hepatic B lymphocytes constitutively produced IgG during fibrosis progression, which correlated with elevated serum levels of BAFF, antinuclear Abs (ANA) and immune complexes. The elevated BAFF and ANA titers were also detected in human patients with primary sclerosing cholangitis and hepatobiliary cholangiopathies. Consistent with the higher BAFF levels, liver-specific selection of the focused BCR IgH repertoire was found on hepatic B cells in Mdr2-/- mice. Interestingly, the administration of anti-BAFF mAb in Mdr2-/- mice altered the BCR repertoire on hepatic B lymphocytes and resulted in reduced ANA and immune complex titers. However, anti-BAFF treatment did not attenuate hepatic fibrosis as measured by collagen deposition, hepatic expressions of collagen-1a, α-smooth muscle actin, and mononuclear cell infiltration (CD11b+ Ly-6chi monocytes and CD11b+ Gr1+ neutrophils). Importantly, depletion of B cells by anti-CD20 mAb reduced both hepatic fibrosis and serum levels of ANA and immune complexes. Our findings implicate B cells as the potential therapeutic targets for hepatic fibrosis and targeting BAFF specifically for attenuating the autoantibody production associated with cholestatic liver disease.

Brief exposure to hyperglycemia activates dendritic cells in vitro and in vivo.

Dendritic cells are key players in regulating immunity. These cells both activate and inhibit the immune response depending on their cellular environment. Their response to hyperglycemia, a condition common amongst diabetics wherein glucose is abnormally elevated, remains to be elucidated. In this study, the phenotype and immune response of dendritic cells exposed to hyperglycemia were characterized in vitro and in vivo using the streptozotocin-induced diabetes model. Dendritic cells were shown to be sensitive to hyperglycemia both during and after differentiation from bone marrow precursor cells. Dendritic cell behavior under hyperglycemic conditions was found to vary by phenotype, among which, tolerogenic dendritic cells were particularly sensitive. Expression of the costimulatory molecule CD86 was found to reliably increase when dendritic cells were exposed to hyperglycemia. Additionally, hydrogel-based delivery of the anti-inflammatory molecule interleukin-10 was shown to partially inhibit these effects in vivo.

Non-invasive early detection of acute transplant rejection via nanosensors of granzyme B activity.

The early detection of the onset of transplant rejection is critical for the long-term survival of patients. The diagnostic gold standard for detecting transplant rejection involves a core biopsy, which is invasive, has limited predictive power and carries a morbidity risk. Here, we show that nanoparticles conjugated with a peptide substrate specific for the serine protease granzyme B, which is produced by recipient T cells during the onset of acute cellular rejection, can serve as a non-invasive biomarker of early rejection. When administered systemically in mouse models of skin graft rejection, these nanosensors preferentially accumulate in allograft tissue, where they are cleaved by granzyme B, releasing a fluorescent reporter that filters into the recipient's urine. Urinalysis then discriminates the onset of rejection with high sensitivity and specificity before features of rejection are apparent in grafted tissues. Moreover, in mice treated with subtherapeutic levels of immunosuppressive drugs, the reporter signals in urine can be detected before graft failure. This method may enable routine monitoring of allograft status without the need for biopsies.

Long-term survival of pig-to-rhesus macaque renal xenografts is dependent on CD4 T cell depletion.

The shortage of available organs remains the greatest barrier to expanding access to transplant. Despite advances in genetic editing and immunosuppression, survival in experimental models of kidney xenotransplant has generally been limited to <100 days. We found that pretransplant selection of recipients with low titers of anti-pig antibodies significantly improved survival in a pig-to-rhesus macaque kidney transplant model (6 days vs median survival time 235 days). Immunosuppression included transient pan-T cell depletion and an anti-CD154-based maintenance regimen. Selective depletion of CD4+ T cells but not CD8+ T cells resulted in long-term survival (median survival time >400 days vs 6 days). These studies suggested that CD4+ T cells may have a more prominent role in xenograft rejection compared with CD8+ T cells. Although animals that received selective depletion of CD8+ T cells showed signs of early cellular rejection (marked CD4+ infiltrates), animals receiving selective CD4+ depletion exhibited normal biopsy results until late, when signs of chronic antibody rejection were present. In vitro study results suggested that rhesus CD4+ T cells required the presence of SLA class II to mount an effective proliferative response. The combination of low pretransplant anti-pig antibody and CD4 depletion resulted in consistent, long-term xenograft survival.

Xenoantigen Deletion and Chemical Immunosuppression Can Prolong Renal Xenograft Survival.

OBJECTIVE: Xenotransplantation using pig organs could end the donor organ shortage for transplantation, but humans have xenoreactive antibodies that cause early graft rejection. Genome editing can eliminate xenoantigens in donor pigs to minimize the impact of these xenoantibodies. Here we determine whether an improved cross-match and chemical immunosuppression could result in prolonged kidney xenograft survival in a pig-to-rhesus preclinical model. METHODS: Double xenoantigen (Gal and Sda) knockout (DKO) pigs were created using CRISPR/Cas. Serum from rhesus monkeys (n = 43) was cross-matched with cells from the DKO pigs. Kidneys from the DKO pigs were transplanted into rhesus monkeys (n = 6) that had the least reactive cross-matches. The rhesus recipients were immunosuppressed with anti-CD4 and anti-CD8 T-cell depletion, anti-CD154, mycophenolic acid, and steroids. RESULTS: Rhesus antibody binding to DKO cells is reduced, but all still have positive CDC and flow cross-match. Three grafts were rejected early at 5, 6, and 6 days. Longer survival was achieved in recipients with survival to 35, 100, and 435 days. Each of the 3 early graft losses was secondary to IgM antibody-mediated rejection. The 435-day graft loss occurred secondary to IgG antibody-mediated rejection. CONCLUSIONS: Reducing xenoantigens in donor pigs and chemical immunosuppression can be used to achieve prolonged renal xenograft survival in a preclinical model, suggesting that if a negative cross-match can be obtained for humans then prolonged survival could be achieved.

Transplantation Versus Resection for Hilar Cholangiocarcinoma: An Argument for Shifting Treatment Paradigms for Resectable Disease.

OBJECTIVE: To investigate the influence of type of surgery (transplant vs resection) on overall survival (OS) in patients with hilar cholangiocarcinoma (H-CCA). BACKGROUND: Outcomes after resection for H-CCA are poor, yet transplantation is currently only reserved for well-selected patients with unresectable disease. METHODS: All patients with H-CCA who underwent resection from 2000 to 2015 at 10 institutions were included. Three institutions additionally had active H-CCA transplant protocols with similar selection criteria over similar time periods. RESULTS: Of 304 patients with suspected H-CCA, 234 underwent attempted resection and 70 were enrolled in a transplant protocol. Excluding incomplete/R2 resections (n = 43), patients who were enrolled, but did not undergo transplant (n = 24), and transplants without confirmed H-CCA diagnoses (n = 5), 191 patients underwent curative-intent resection and 41 curative-intent transplant. Compared with resection, transplant patients were younger (52 vs 65 years; P < 0.001), and more frequently had primary sclerosing cholangitis (PSC; 61% vs 2%; P < 0.001) and received chemotherapy and/or radiation (98% vs 57%; P < 0.001). Groups were otherwise similar in demographics and comorbidities. Patients who underwent transplant for confirmed H-CCA diagnosis had improved OS compared with resection (3-year: 72% vs 33%; 5-year: 64% vs 18%; P < 0.001). Among patients who underwent resection for tumors <3 cm with lymph-node negative disease, and excluding PSC patients, transplant was still associated with improved OS (3-year: 54% vs 44%; 5-year: 54% vs 29%; P = 0.03). Transplant remained associated with improved survival on intention-to-treat analysis, even after accounting for tumor size, lymph node status, and PSC (P = 0.049). CONCLUSIONS: Resection for hilar cholangiocarcinoma that meets criteria for transplantation (<3 cm, lymph-node negative disease) is associated with substantially decreased survival compared to transplant for the same criteria with unresectable disease. Prospective trials are needed and justified.

Alloimmunity But Not Viral Immunity Promotes Allograft Loss in a Mouse Model of Polyomavirus-Associated Allograft Injury.

BACKGROUND: The interplay between viral infection and alloimmunity is known to influence the fate of transplanted organs. Clarifying how local virus-associated inflammation/injury and antiviral immunity can alter host alloimmune responses in transplantation remains a critical question. METHODS: We used a mouse model of polyomavirus (PyV) infection and kidney transplantation to investigate the roles of direct viral pathology, the antiviral immune response, and alloimmunity in the pathogenesis of PyV-associated allograft injury. We have previously shown that an effective primary T cell response is required in PyV-associated graft injury. RESULTS: Here we show that the transfer of primed antidonor, but not antiviral, T cells results in PyV-associated allograft injury. In further studies, we use a surrogate minor antigen model (ovalbumin) and show that only antidonor specific T cells and not antiviral specific T cells are sufficient to mediate injury. Lastly, we demonstrate that local but not systemic virus-mediated inflammation and injury within the graft itself are required. CONCLUSIONS: These data suggest that in this mouse model, the predominant mechanism of allograft injury in PyV-associated injury is due to an augmented alloimmune T cell response driven by virus-induced inflammation/injury within the graft. These studies highlight the important interplay between viral infection and alloimmunity in a model system.

Hospitalization Among Individuals Waitlisted For Kidney Transplant.

BACKGROUND: For patients waitlisted for a deceased-donor kidney, hospitalization is associated with a lower likelihood of transplantation and worse posttransplant outcomes. However, individual-, neighborhood-, and regional-level risk factors for hospitalization throughout the waitlist period and specific causes of hospitalization in this population are unknown. METHODS: We used United States Renal Data System Medicare-linked data on patients waitlisted between 2005 and 2013 with continuous enrollment in Medicare parts A and B (n = 53 810) to examine the association between annual hospitalization rate and a variety of demographic, clinical, and social factors. We used multilevel multivariable ordinal logistic regression to estimate odds ratios. RESULTS: Factors associated with significantly increased hospitalization rates among waitlisted individuals included older age, female sex, more years on dialysis before waitlisting, tobacco use, panel-reactive antibody greater than 0, public insurance or no insurance at end-stage renal disease diagnosis, more regional acute care hospital beds, and urban residence (all P < 0.05). Among patients dialysis-dependent when waitlisted, individuals with arteriovenous fistulas were significantly less likely than individuals with indwelling catheters or grafts to be hospitalized (odds ratios, 0.79 and 0.82, respectively, both P < 0.001). The most common causes of hospitalization were complications related to devices, implants, and grafts; hypertension; and sepsis. CONCLUSIONS: Individual- and regional-level variables were significantly associated with hospitalization while waitlisted, suggesting that personal, health system, and geographic factors may impact patients' risk. Conditions related to dialysis access and comorbidities were common hospitalization causes, underscoring the importance proper access management and care for additional chronic health conditions.

Interruption of OX40L signaling prevents costimulation blockade-resistant allograft rejection.

The potential of costimulation blockade to serve as a novel transplant immunosuppression strategy has been explored for over 20 years, culminating in the recent clinical approval of belatacept for renal transplant patients. Despite improving long-term graft function and survival compared with calcineurin inhibitors, clinical acceptance of belatacept has been hindered by elevated rates of acute rejection. We examined the signaling pathways required to activate costimulation blockade-resistant alloreactive T cells and identified the OX40/OX40L secondary costimulatory pathway as a promising target. We next sought to improve the clinical efficacy of traditional costimulation blockade using belatacept by coupling it with anti-OX40L. Using a murine transplant model, we demonstrate that combined blockade enhances the suppression of alloreactive T cell proliferation and effector functions including both cytokine release and cytotoxic degranulation. We also show that anti-OX40L may be particularly useful in targeting alloreactive memory T cell responses that are relatively unaffected by traditional costimulation blockade regimens. Finally, we translated this therapy to a clinically relevant nonhuman primate renal transplant model, validating the efficacy of this regimen in a potentially novel steroid- and calcineurin inhibitor-free immunosuppression regimen.

Waitlist Hospital Admissions Predict Resource Utilization and Survival After Renal Transplantation.

OBJECTIVE: To determine whether fitness for transplant can be determined by candidates' hospitalizations although waitlisted. BACKGROUND: Renal transplantation must increasingly serve a population of multiply comorbid patients in an environment defined by organ scarcity and premiums on value-based care. Determining those at excess risk for transplant is critical to these imperatives. METHODS: United States Renal Data Systems patient and claims data for all adult renal transplant recipients between 2000 and 2010 with continuous primary Medicare coverage for 1 year before and after transplantation were examined. Outcomes included readmissions within the first-year post-transplant and 3-year graft and patient survival. Chi-square statistics, Kaplan-Meier methods (log-rank test), and goodness of fit calculations (c-statistics) were performed for models of transplant outcome. RESULTS: Among 37,623 patients, the percentages of patients admitted for 0, 1 to 7, 8 to 14, or 15 or more days in the pretransplant year were 51%, 25%, 11%, and 13%. Overall readmission-free survival at 1 year was 31%. Heavily preadmitted patients were more likely to have a greater length of stay during their transplant admission, and had a greater service needs at discharge. Pretransplant admission strongly predicted more frequent post-transplant admission. Among all factors studied, preadmission was the strongest predictor of post-transplant death, and had a dose-dependent effect on both death and graft loss. CONCLUSIONS: In summary, hospitalization in the year before transplant is an objective, readily ascertainable, and powerful predictor of excess resource utilization and inferior outcome. Incorporation of a rolling assessment of patient hospitalization has potential policy implications for maximizing value in renal transplantation.

Nonhuman primate models of transplant tolerance: closer to the holy grail.

PURPOSE OF REVIEW: Transplantation tolerance, successful acceptance of an organ without the perils of immunosuppression, has been a central goal of transplant research. Many strategies to achieve this tolerance have been examined over the past three decades, culminating in several human trials of transplant tolerance. This progression from the 'benchtop to the clinic' has depended on the successful implementation of these tolerance strategies in nonhuman primates. This review will examine the described methods of transplant tolerance induction in nonhuman primates. RECENT FINDINGS: Although costimulatory blockade and mixed chimerism have an established record of achieving transplant tolerance in nonhuman primates, some of the most innovative recent techniques of tolerance induction have relied on cellular transfer. This review will fully examine the role of regulatory T-cell transfer and the use of mesenchymal stem/stromal cells to promote tolerance of organ allografts in nonhuman primates. SUMMARY: Use of translational nonhuman primate transplant models is a vital intermediate step to advance new approaches of transplant tolerance induction from the lab to the clinic. This review will explore numerous techniques of tolerance induction that have been piloted in primates, including depletional techniques, induction of mixed hematopoietic chimerism, costimulation blockade, and adoptive transfer of tolerogenic cell populations.

Preventing T cell rejection of pig xenografts.

Xenotransplantation is a potential solution to the limited supply of donor organs. While early barriers to xenograft acceptance, such as hyperacute rejection, are now largely avoided through genetic engineering, the next frontier in successful xenograft survival will require prevention of T cell-mediated rejection. Most successful immunosuppressive regimens in xenotransplantation utilize T cell depletion with antibody therapy. Additionally, the use of T cell costimulatory blockade - specifically blockade of the CD40-CD154 pathway - shows promise with several reports of long-term xenograft survival. Additional therapies, such as transgenic expression of T cell coinhibitory molecules or transfer of immunomodulatory cells to promote tolerance, may be necessary to achieve reliable long-term xenograft acceptance. Further studies in pre-clinical models are essential in order to optimize these regimens prior to trials in patients.

Pre-transplant antibody screening and anti-CD154 costimulation blockade promote long-term xenograft survival in a pig-to-primate kidney transplant model.

Xenotransplantation has the potential to alleviate the organ shortage that prevents many patients with end-stage renal disease from enjoying the benefits of kidney transplantation. Despite significant advances in other models, pig-to-primate kidney xenotransplantation has met limited success. Preformed anti-pig antibodies are an important component of the xenogeneic immune response. To address this, we screened a cohort of 34 rhesus macaques for anti-pig antibody levels. We then selected animals with both low and high titers of anti-pig antibodies to proceed with kidney transplant from galactose-α1,3-galactose knockout/CD55 transgenic pig donors. All animals received T-cell depletion followed by maintenance therapy with costimulation blockade (either anti-CD154 mAb or belatacept), mycophenolate mofetil, and steroid. The animal with the high titer of anti-pig antibody rejected the kidney xenograft within the first week. Low-titer animals treated with anti-CD154 antibody, but not belatacept exhibited prolonged kidney xenograft survival (>133 and >126 vs. 14 and 21 days, respectively). Long-term surviving animals treated with the anti-CD154-based regimen continue to have normal kidney function and preserved renal architecture without evidence of rejection on biopsies sampled at day 100. This description of the longest reported survival of pig-to-non-human primate kidney xenotransplantation, now >125 days, provides promise for further study and potential clinical translation.

Systems biological analyses reveal the hepatitis C virus (HCV)-specific regulation of hematopoietic development.

UNLABELLED: Chronic liver disease is characterized by the liver enrichment of myeloid dendritic cells (DCs). To assess the role of disease on myelopoiesis, we utilized a systems biology approach to study development in liver-resident cells expressing stem cell marker CD34. In patients with endstage liver disease, liver CD34+ cells were comprised of two subsets, designated CD34+CD146+ and CD34+CD146-, and hematopoietic function was restricted to CD34+CD146- cells. Liver CD34 frequencies were reduced during nonalcoholic steatohepatitis (NASH) and chronic hepatitis C virus (HCV) compared to alcohol liver disease (ALD), and this reduction correlated with viral load in the HCV cohort. To better understand the relationship between liver CD34+CD146+ and CD34+CD146- subsets and any effects of disease on CD34 development, we used gene expression profiling and computational modeling to compare each subset during ALD and HCV. For CD34+CD146+ cells, increased expression of endothelial cell genes including von Willebrand factor, VE-cadherin, and eNOS were observed when compared to CD34+CD146- cells, and minimal effects of ALD and HCV diseases on gene expression were observed. Importantly for CD34+CD146- cells, chronic HCV was associated with a distinct "imprint" of programs related to cell cycle, DNA repair, chemotaxis, development, and activation, with an emphasis on myeloid and B lymphocyte lineages. This HCV signature was further translated in side-by-side analyses, where HCV CD34+CD146- cells demonstrated superior hematopoietic growth, colony formation, and diversification compared to ALD and NASH when cultured identically. Disease-associated effects on hematopoiesis were also evident by phenotypic alterations in the expression of CD14, HLA-DR, and CD16 by myeloid progeny cells. CONCLUSION: Etiology drives progenitor fate within diseased tissues. The liver may be a useful source of hematopoietic cells for therapy, or as therapeutic targets.

Transplant versus resection for the management of hepatocellular carcinoma meeting Milan Criteria in the MELD exception era at a single institution in a UNOS region with short wait times.

BACKGROUND: Management of hepatocellular carcinoma (HCC) in the Model for End-Stage Liver Disease (MELD) exception era remains regionally variable. Outcomes were compared for patients undergoing transplant versus resection at a single institution in a UNOS region with short wait times for organ availability. METHODS: All patients who underwent resection of HCC from January 2000 to August 2012 and patients who underwent transplant post-January 2006, during the Milan Criteria (MC)-based MELD exception policy for HCC, were identified. Primary outcomes were overall survival (OS) and recurrence-free survival (RFS). RESULTS: Two hundred fifty-seven patients were analyzed, of whom 131 underwent transplant and 126 underwent resection. All transplant patients met MC; 45 (36%) resection patients met MC. Median follow-up time was 30 months. Median wait time to transplant was 55 days; no patients dropped off the waitlist while awaiting an organ. Among patients meeting MC, transplant demonstrated significantly greater 5-year OS (65.7% vs. 43.8%; P = 0.005) and RFS (85.3% vs. 22.7%; P < 0.001) versus resection. For patients with hepatitis C, transplant (n = 87) demonstrated significantly improved 5-year outcomes compared to patients meeting MC who underwent resection (n = 21; OS: 63.5% vs. 23.3%; P = 0.001; RFS: 83.5% vs. 23.7%; P < 0.001). CONCLUSION: In a region with short waitlist times for organ availability, liver transplant is associated with improved survival compared to resection for HCC within MC and should be considered for all patients meeting MC, particularly those with hepatitis C.

Secondary intervention after endovascular abdominal aortic aneurysm repair.

OBJECTIVE: Endovascular Abdominal Aortic Aneurysm Repair (EVAR) has been criticized because of the need for frequent secondary interventions (2ndINT) to maintain effective abdominal aortic aneurysm (AAA) exclusion. The study goal is to detail such interventions and determine their effect on clinical outcomes. METHODS: From January 1997 to December 2007, 832 patients underwent EVAR. Those requiring 2ndINT were stratified according to the indications and specific nature of 2ndINT and treatment. Study endpoints included freedom from 2ndINT, aneurysm-related and overall survival. RESULTS: There were 91 (11%) patients who underwent 131 2ndINT (mean follow-up 35 months). No demographic features (age, gender, etc) predicted the need for 2ndINT. Actuarial 5-year freedom from 2ndINT was 80%. Indications for 2ndINT included: sac rupture 5 (4%), graft migration/ type I endoleak 37 (28%), persistent type II endoleak 40 (38%), endotension with sac growth 5 (4%), and limb occlusion/kinking 24 (18%). The majority of 2ndINT were accomplished with an endovascular approach (76%) with a >80% initial success rate for all indications except type II endoleak in which the initial intervention was successful only 34% of the time. Initial 2ndINT were successful in 62% and 35 (38%) patients underwent more than one 2ndINT. Multivariate predictors of 2ndINT were AAA sac size >5.5cm (OR = 2.1, P = 0.004), and preprocedure coil embolization (hypogastric or inferior mesenteric artery) (OR = 2.1, P = 0.008). The actuarial survival was 70% at 5 years and the aneurysm-related survival was 97.5% with no difference in either parameter in patients who underwent 2ndINT compared with those who did not. CONCLUSIONS: Although 2ndINT are common after EVAR, most were addressed through an endovascular approach; technical success thereof varies widely with the specific indication for 2ndINT. Secondary intervention did not adversely affect aneurysm-related or overall actuarial 5-year survival.

Immunosuppressive and trafficking properties of donor splenic and bone marrow dendritic cells.

BACKGROUND: Infusion of donor dendritic cells (DC) has been shown to prolong allograft survival in a number of models. However, many regimens that utilize donor DC do not consistently produced tolerance or long-term allograft survival. We hypothesized that one factor limiting the therapeutic effect of donor DC is their relative inability to traffic to recipient peripheral lymph nodes and inhibit the function of resident alloreactive T cells. METHODS: Donor strain DC isolated from the spleens or bone marrow of Flt3L-treated mice were transferred intravenously into recipients at the time of skin grafting. Where indicated, recipients were treated with an anti-CD40L antibody and CTLA4-Ig. RESULTS: Infusion of donor DC together with costimulatory blockade promoted donor-specific prolongation of skin allograft survival in mice. Perhaps due to their more immature phenotype, bone marrow DC trafficked more effectively to the spleen, bone marrow, and thymus and were associated with significantly longer allograft survival than were splenic DC. Neither population of DC trafficked well to peripheral lymph nodes. Consistent with our hypothesis, splenic but not lymph node T cells from DC-treated recipients displayed donor-specific hyporesponsiveness in vitro. CONCLUSION: These data suggest that one factor contributing to rejection following treatment with donor DC plus costimulation blockade is the persistence of donor-reactive T cells within the recipient's secondary lymphoid structures. Strategies to improve DC trafficking to these structures may enhance their therapeutic effect.

Rational development of LEA29Y (belatacept), a high-affinity variant of CTLA4-Ig with potent immunosuppressive properties.

Current success in organ transplantation is dependent upon the use of calcineurin-inhibitor-based immunosuppressive regimens. Unfortunately, current immunotherapy targets molecules with ubiquitous expression resulting in devastating non-immune side effects. T-cell costimulation has been identified as a new potential immunosuppressive target. The best characterized pathway includes CD28, its homologue CTLA4 and their ligands CD80 and CD86. While an immunoglobulin fusion protein construct of CTLA4 suppressed rejection in rodents, it lacked efficacy in primate transplant models. In an attempt to increase the biologic potency of the parent molecule a novel, modified version of CTLA4-Ig, LEA29Y (belatacept), was constructed. Two amino acid substitutions (L104E and A29Y) gave rise to slower dissociation rates for both CD86 and CD80. The increased avidity resulted in a 10-fold increase in potency in vitro and significant prolongation of renal allograft survival in a pre-clinical primate model. The use of immunoselective biologics may provide effective maintenance immunosuppression while avoiding the collateral toxicities associated with conventional immunsuppressants.