Integration of Islet/Beta-Cell Transplants with Host Tissue Using Biomaterial Platforms

Cell-based therapies are emerging for type I diabetes mellitus (T1D), an autoimmune disease characterized by the destruction of insulin-producing pancreatic β-cells, as a means to provide long-term restoration of glycemic control. Biomaterial scaffolds provide an opportunity to enhance the manufacturing and transplantation of islets or stem cell-derived β-cells. In contrast to encapsulation strategies that prevent host contact with the graft, recent approaches aim to integrate the transplant with the host to facilitate glucose sensing and insulin distribution, while also needing to modulate the immune response. Scaffolds can provide a supportive niche for cells either during the manufacturing process or following transplantation at extrahepatic sites. Scaffolds are being functionalized to deliver oxygen, angiogenic, anti-inflammatory, or trophic factors, and may facilitate cotransplantation of cells that can enhance engraftment or modulate immune responses. This local engineering of the transplant environment can complement systemic approaches for maximizing β-cell function or modulating immune responses leading to rejection. This review discusses the various scaffold platforms and design parameters that have been identified for the manufacture of human pluripotent stem cell-derived β-cells, and the transplantation of islets/β-cells to maintain normal blood glucose levels.

JAK3 inhibitor-based immunosuppression in allogeneic islet transplantation in cynomolgus monkeys

Islet transplantation is efficacious to prevent severe hypoglycemia and glycemic liability of selected patients of type 1 diabetes. However, since calcineurin inhibitor (CNI) causes β-cell and nephrotoxicity, alternative drug(s) with similar potency and safety profile to CNI will be highly desirable. Here we tested whether JAK3 inhibitor, tofacitinib could be used instead of tacrolimus in CIT07 immunosuppression regimen in cynomolgus nonhuman primate (NHP) model. Five independent streptozotocin (STZ)-induced diabetic monkeys were transplanted with MHC-mismatched allogeneic islets and three animals were further re-transplanted upon insufficient glycemic control or early islet graft rejection. After islet transplantation, blood glucose levels were quickly stabilized and maximal islet graft survival as measured by serum C-peptide concentration was >330, 98, >134, 31, or 22 days, respectively, after transplantation (median survival day; 98 days). Cellular and humoral immune responses were efficiently suppressed by JAK3 inhibitor-based immunosuppression during the follow-up periods. Although intermittent increases of the genome copy number of cynomolgus cytomegalovirus (CMV) were detected by quantitative real-time PCR analyses, serious infections or posttransplant lymphoproliferative disease (PTLD) was not found in all animals. Taken together, we have shown that JAK3 inhibitor could be used in replacement of tacrolimus in a highly translatable NHP islet transplantation model and these results suggest that JAK3 inhibitor will be potentially incorporated in human allogeneic islet transplantation.

Efficacy of a medication adherence enhancing intervention in transplantation: The MAESTRO-Tx trial

BACKGROUND

Well-designed randomized controlled trials (RCTs) testing efficacy of post-transplant medication adherence enhancing interventions and clinical outcomes are scarce.

METHODS

This randomized controlled trial enrolled adult heart, liver, and lung transplant recipients who were >1 year post-transplant and on tacrolimus twice daily (convenience sample) (visit 1). After a 3-month run-in period, patients were randomly assigned 1:1 to intervention group (IG) or control group (CG) (visit 2), followed by a 6-month intervention (visits 2-4) and a 6-month adherence follow-up period (visit 5). All patients used electronic monitoring for 15 months for adherence measurement, generating a daily binary adherence score per patient. Post-intervention 5-year clinical event-free survival (mortality or retransplantation) was evaluated. The IG received staged multicomponent tailored behavioral interventions (visits 2-4) building on social cognitive theory and trans-theoretical model (e.g., electronic monitoring feedback, motivational interviewing). The CG received usual care and attended visits 1-5 only. Intention-to-treat analysis used generalized estimating equation modeling and Kaplan-Meier survival analysis.

RESULTS

Of 247 patients, 205 were randomly assigned (103 IG, 102 CG). At baseline, average daily proportions of patients with correct dosing (82.6% IG, 78.4% CG) and timing adherence (75.8% IG, 72.2% CG) were comparable. The IG had a 16% higher dosing adherence post-intervention (95.1% IG, 79.1% CG; p < 0.001), resulting in odds of adherence being 5 times higher in the IG than in the CG (odds ratio 5.17, 95% confidence interval 2.86-9.38). This effect was sustained at end of follow-up (similar results for timing adherence). In the IG, 5-year clinical event-free survival was 82.5% vs 72.5% in the CG (p = 0.18).

CONCLUSION

Our intervention was efficacious in improving adherence and sustainable. Further research should investigate clinical impact, cost-effectiveness, and scalability.

Use of Basiliximab and Daclizumab in Kidney Transplantation

Kidney transplantation represents a major medical victory in patients with whom dialysis and medical therapy have failed. To increase survival rates and optimize the use of limited organs, both patient care and immunosuppression therapy must be improved. Reduction in rejection episodes or severity of rejection may ultimately improve long-term allograft survival. Traditional engineered monoclonal antibodies have been associated with severe cytokine release reactions and an increased risk of opportunistic infections. Basiliximab and daclizumab are chimeric and humanized monoclonal antibodies that inhibit thymus-dependent lymphocyte proliferation. Interleukin 2 also affects the proliferation of natural killer cells, macrophages and monocytes, bursa-equivalent lymphocytes, epidermal dendritic cells, and lymphokine-activated killer cells. Interleukin-2 receptor antagonists have been shown to reduce the incidence of acute rejection without increasing the incidence of opportunistic infections or malignancy. Further studies are needed to evaluate the overall effect of these agents on long-term patient and allograft survival.

Evaluation of an Immunosuppressant Side Effect Instrument

Background

Clinicians continue to be compelled to evaluate the impact of immunosuppressive medication side effects on the quality of life of transplant recipients. We were asked to develop an instrument to measure side effects in immunosuppressed transplant recipients.

Objective

To construct an instrument that measures the impact and severity of side effects of immunosuppressive medications used in transplantation and to assess the reliability and validity of the newly developed instrument called the Memphis Survey.

Design

The instrument was constructed by a panel of physicians, nurses, and pharmacists with experience in treating transplant recipients. A small group of kidney transplant recipients (n=13) provided pilot data for refining and testing the instrument. A national sample of kidney, liver, and heart transplant recipients (n=505) provided data that were used to further develop the instrument.

Analysis

Factor analysis was used to determine the psychological dimensions underlying the instrument and to guide the construction of scales from the survey items. The instrument scales were then computed from the dataset of 505 transplant recipients to quantify the impact of immunosuppressant side effects on the quality of life of transplant recipients.

Results and Conclusion

Analyses showed the final instrument scales to be valid and reliable. Exploratory analysis suggests the need for further testing of the instrument to determine gender differences.

[Pharmacogenetics: a promising tool to personalize immunosuppressive therapy in renal transplantation]

Renal transplantation is the gold standard therapy for patients affected by end stage renal disease. It is a clinical condition characterized by severe biological/biochemical alterations that requires renal replacement therapy to ensure patients survival. In most cases, it is followed by a significant improvement of patients quality of life, reduction in medical expenses and prolongation of life. However, to reach these positive clinical effects, patients need to take several immunosuppressive medications (calcineurin inhibitors, mTOR inhibitors and antimetabolites) characterized by a narrow therapeutic index, that, in some cases, could cause important adverse effects. To avoid toxicities and adverse drug reactions, immunosuppressors should be correctly administered, according to the blood trough levels. Nevertheless, in most of the times, this methodology to adjust drug doses gives inadequate and non-reproducible results. Additionally, as largely described, inherited differences in drug metabolism and disposition and genetic variability in therapeutic targets (e.g. receptors) need to be taken into account because of their role in modulating drug effects and toxicities. Therefore, worldwide researchers are working together to identify biomarkers, useful to personalize therapy based on genetic characteristics of patients. In this context, we believe that the omics techniques could represent a future powerful instruments that, whether employed routinely, could help to reach this objective.

Immunosuppressive effects of erythropoietin on human alloreactive T cells

Correction of anemia with erythropoietin (EPO) is associated with improved kidney transplant outcomes. Emerging evidence, predominantly from animal models, indicates that these observations may be erythropoiesis-independent and that EPO exhibits immunosuppressive properties. We examined the effects of EPO on human T-cell alloimmunity by first documenting that CD4(+) and CD8(+) T cells express EPO receptor (EPO-R) on their surfaces. In mixed lymphocyte reactions, EPO induced a dose-dependent decrease in allogeneic CD4(+) T-cell proliferation (EPO 1000 U/ml: 44.6%±22.9% of vehicle, P<0.05; 2000 U/ml: 11.1%±4% of vehicle, P<0.001) without inducing cell death. The effects required signals transmitted directly through the EPO-R expressed on T cells, resulting in diminished Th1 differentiation without effects on regulatory T-cell induction. Mechanistic studies revealed that EPO prevented IL-2-induced proliferation by uncoupling IL-2 receptor signaling, inhibiting phosphorylation of the intracellular intermediaries AKT and extracellular signal-regulated kinase that are known to mediate T-cell expansion. EPO treatment reduced expansion of human naïve CD4(+) T cells after adoptive transfer into NOD scid γc(null) mouse recipients, verifying the effects in vivo. Although activated T cells expressed CD131, an alternative EPO receptor, addition of a specific CD131 agonist peptide, ARA290, did not alter T-cell proliferation or cytokine production. Our findings link EPO-R signaling on T cells to inhibition of T-cell immunity, providing one mechanism that could explain the observed protective effects of EPO in kidney transplant recipients.

Sibling donor and recipient immune modulation with atorvastatin for the prophylaxis of acute graft-versus-host disease

PURPOSE

Graft-versus-host disease (GVHD) is major cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT). Atorvastatin is a potent immunomodulatory agent that holds promise as a novel and safe agent for acute GVHD prophylaxis.

PATIENTS AND METHODS

We conducted a phase II trial to evaluate the safety and efficacy of atorvastatin administration for GVHD prophylaxis in both adult donors and recipients of matched sibling allogeneic HCT. Atorvastatin (40 mg per day orally) was administered to sibling donors, starting 14 to 28 days before the anticipated first day of stem-cell collection. In HCT recipients (n = 30), GVHD prophylaxis consisted of tacrolimus, short-course methotrexate, and atorvastatin (40 mg per day orally).

RESULTS

Atorvastatin administration in healthy donors and recipients was not associated with any grade 3 to 4 adverse events. Cumulative incidence rates of grade 2 to 4 acute GVHD at days +100 and +180 were 3.3% (95% CI, 0.2% to 14.8%) and 11.1% (95% CI, 2.7% to 26.4%), respectively. One-year cumulative incidence of chronic GVHD was 52.3% (95% CI, 27.6% to 72.1%). Viral and fungal infections were infrequent. One-year cumulative incidences of nonrelapse mortality and relapse were 9.8% (95% CI, 1.4% to 28%) and 25.4% (95% CI, 10.9% to 42.9%), respectively. One-year overall survival and progression-free survival were 74% (95% CI, 58% to 96%) and 65% (95% CI, 48% to 87%), respectively. Compared with baseline, atorvastatin administration in sibling donors was associated with a trend toward increased mean plasma interleukin-10 concentrations (5.6 v 7.1 pg/mL; P = .06).

CONCLUSION

A novel two-pronged strategy of atorvastatin administration in both donors and recipients of matched sibling allogeneic HCT seems to be a feasible, safe, and potentially effective strategy to prevent acute GVHD.

Systemic immunoregulatory and proteogenomic effects of tacrolimus to sirolimus conversion in liver transplant recipients

Immunosuppression (IS) withdrawal from calcineurin inhibitors is only possible in ≈ 20% of liver transplant recipients. However, mammalian target of rapamycin inhibitors (e.g., sirolimus; SRL) appear to be more immunoregulatory and might promote a tolerant state for withdrawal. Our aim was to determine whether systemic (i.e., blood, marrow, and allograft) signatures of immunoregulation are promoted by conversion from tacrolimus (TAC) to SRL. We therefore performed the following serial assays before and after SRL conversion in liver transplant recipients to test for enhanced markers of immunoregulation: (1) flow-cytometry immunophenotyping of peripheral blood mononuclear cells (PBMCs) and bone marrow aspirates for regulatory T cells (Tregs) (e.g., CD4(+) CD25(+++) FOXP3(+) ) and regulatory dendritic cells (DCregs) (immunoglobulin-like transcript 3(+) /4(+) ); (2) liver biopsy immunohistochemical staining (e.g., FOXP3:CD3 and CD4:CD8 ratios) and immunophenotyping of biopsy-derived Tregs after growth in culture; (3) effects of pre- versus postconversion sera on Treg generation in mixed lymphocyte reactions; (4) peripheral blood nonspecific CD4 responses; and (5) peripheral blood gene transcripts and proteomic profiles. We successfully converted 20 nonimmune, nonviremic recipients (age, 57.2 ± 8.0; 3.5 ± 2.1 years post-liver transplantation) from TAC to SRL for renal dysfunction. Our results demonstrated significant increases in Tregs in PBMCs and marrow and DCregs in PBMCs (P < 0.01) after conversion. In biopsy staining, FOXP3:CD3 and CD4:CD8 ratios were significantly higher after conversion and a number of biopsy cultures developed new or higher FOXP3(+) cell growth. Nonspecific CD4 responses did not change. Both pre- and postconversion sera inhibited mixed lymphocyte reactions, although only TAC sera suppressed Treg generation. Finally, 289 novel genes and 22 proteins, several important in immunoregulatory pathways, were expressed after conversion.

CONCLUSIONS

TAC to SRL conversion increases systemic Tregs, DCregs, and immunoregulatory proteogenomic signatures in liver transplant recipients and may therefore facilitate IS minimization or withdrawal.

Feasibility of localized immunosuppression: 3. Preliminary evaluation of organosilicone constructs designed for sustained drug release in a cell transplant environment using dexamethasone

As part of our ongoing effort to develop biohybrid devices for pancreatic islet transplantation, we are interested in establishing the feasibility of a localized immune-suppressive approach to avoid or minimize the undesirable side effects of existing systemic treatments. Since biohybrid devices can also incorporate biocompatible scaffold constructs to provide a support environment for the transplanted cells that enhances their engraftment and long-term function, we are particularly interested in an approach that would use the same three-dimensional construct, or part of the same construct, to also provide sustained release of therapeutic agents to modulate the inflammatory and immune responses locally. Within this framework, here, we report preliminary results obtained during the investigation of the suitability of organosilicone constructs for providing sustained localized drug release using small, matrix-type polydimethylsiloxane (PDMS) disks and dexamethasone as a model hydrophobic drug. Following a short burst, long-term steady sustained release was observed under in vitro conditions at levels of 0.1-0.5 microg/day/disk with a profile in excellent agreement with that predicted by the Higuchi equation. To verify that therapeutic levels can be achieved, suppression of LPS-induced activation has been shown in THP-1 cells with disks that have been pre-soaked for up to 28 days. These preliminary results prove the feasibility of this approach where an integral part of the biomaterial construct used to enhance cell engraftment and long-term function also serves to provide sustained local drug release.

Elimination of alpha-gal xenoreactive epitope: alpha-galactosidase treatment of porcine heart valves

BACKGROUND AND AIM OF THE STUDY

Porcine heart valves are among the most widely used tissue valves in clinical heart valve implantation. However, immunologic responses have been implicated as potential causes of the limited durability of xenograft heart valves. The study aim was to determine the effectiveness of alpha-galactosidase treatment used to degrade the major xenoreactive antigens found in xenograft heart valves.

METHODS

Fresh porcine heart valves and pericardium treated with alpha-galactosidase were studied to evaluate the xenoreactive galactose (alpha1,3) galactose (alpha-gal) antigen. Removal of the alpha-gal epitope from the porcine heart valve was monitored via 3,3'-diaminobenzidine staining intensity, while the removal of alpha-gal from N-glycans on porcine heart valves treated with recombinant alpha-galactosidase was determined either qualitatively or quantitatively by mass fingerprinting using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The porcine pericardium was used for monitoring the change in mechanical properties after alpha-galactosidase treatment. In addition, the biomechanical modification property of collagen fiber rearrangement on tissue was assessed using transmission electron microscopy (TEM).

RESULTS

Following a 24-h incubation at pH 7.2, 4 degrees C, employing 0.1 U/ml of Bacteroides thetaiotaomicron-derived recombinant alpha-galactosidase, the enzyme effectively removed the alpha-gal epitopes expressed on porcine heart valves. The identification type of alpha-gal N-glycan on fresh aortic valve, aortic wall, pulmonary valve, and pulmonary wall was 7.1%, 10.3%, 6% and 8%, respectively. In the presence of alpha-galactosidase treatment, alpha-gal-containing N-glycans were converted into alpha-gal-negative N-glycans. Likewise, alpha-gal-containing N-glycans were not detected when MALDI-TOF MS quantitative analysis was used. Furthermore, no significant difference was observed in the mechanical properties and findings from TEM in alpha-galactosidase-treated porcine pericardial tissue when compared to fresh porcine pericardium.

CONCLUSION

Alpha-galactosidase can effectively remove the alpha-gal epitope from porcine heart valves and pericardium. This may possibly alleviate harmful xenoreactive immunologic responses by alpha-gal, without adversely affecting the biomechanical properties of the alpha-galactosidase-processed tissue.

Modelling and optimal control of immune response of renal transplant recipients

We consider the increasingly important and highly complex immunological control problem: control of the dynamics of immunosuppression for organ transplant recipients. The goal in this problem is to maintain the delicate balance between over-suppression (where opportunistic latent viruses threaten the patient) and under-suppression (where rejection of the transplanted organ is probable). First, a mathematical model is formulated to describe the immune response to both viral infection and introduction of a donor kidney in a renal transplant recipient. Some numerical results are given to qualitatively validate and demonstrate that this initial model exhibits appropriate characteristics of primary infection and reactivation for immunosuppressed transplant recipients. In addition, we develop a computational framework for designing adaptive optimal treatment regimes with partial observations and low-frequency sampling, where the state estimates are obtained by solving a second deterministic optimal tracking problem. Numerical results are given to illustrate the feasibility of this method in obtaining optimal treatment regimes with a balance between under-suppression and over-suppression of the immune system.

Immunosuppression regimens to address alloantibodies in transplant recipients

The purpose of immunosuppression in patients receiving a solid organ transplant is to prevent both acute and chronic rejection, while avoiding the complications of immunodeficiency such as infections and malignancy. Over the last 50 years, immunosuppressive agents have been developed and put into clinical practice to achieve this purpose. The majority of immunosuppressive agents developed during this time have focused on suppressing the T cells. T cell centric immunosuppressive development was a result of the early belief that the T cell caused an allograft to fail. However, emerging evidence from the use of new laboratory techniques has caused the field to reexamine this T cell centric view and focus on the role of the B cells. Today, humoral immunity is thought to be the major cause of allograft loss. As a result, newer immunosuppressive agents are being introduced to deplete the B cell populations in a patient's immune system. However, not all patients may need these immunosuppressive agents. It is only when patients are at high risk for donor specific anti-HLA antibody (DSA) development or when DSAs are present that these immunosuppressive agents may be necessary. This review will focus on the new agents and immunosuppressive regimens that may serve the high-risk subpopulations of solid organ transplant recipients who have or who develop DSA.

[Pregnancy under immunosuppression]

The desire to have children and pregnancy itself are important topics in the treatment of patients under immunosuppression. In this review the risks of frequently prescribed immunosuppressants are discussed regarding the safety of mother and child during and after pregnancy. Knowledge of the specific risks of immunosuppressants in pregnancy is important to balance the therapy between the patients' desire to be treated most effectively and to deliver a healthy child after an uncomplicated pregnancy. Generally, an interdisciplinary approach is advisable in treating and counseling immunosuppressed patients with a desire to have children and during pregnancy.

The latest developments in synthetic peptides with immunoregulatory activities

In the past few years, many researches have provided us with much data demonstrating the abilities of synthetic peptides to impact immune response in vitro and in vivo. These peptides were designed according to the structure of some important protein molecules which play a key role in immune response, so they act with specific targets. The class I and II MHC-derived peptides inhibit the TCR recognition of antigen peptide-MHC complex. Rationally designed CD80 and CD154-binding peptides block the interaction between cell surface costimulatory molecules on antigen-presenting cells (APCs) and T cells. Some peptides were designed to inhibit the activities of cell signal proteins, including JNK, NF-κB and NFAT. Some peptide antagonists competitively bind to important cytokines and inhibit their activities, such as TNF-α, TGF-β and IL-1β inhibitory peptides. Adhesion molecule ICAM-1 derived peptides block the T cell adhesion and activation. These immunoregulatory peptides showed therapeutic effect in several animal models, including collagen-induced arthritis (CIA), autoimmune cystitis model, murine skin transplant model and cardiac allograft model. These results give us important implications for the development of a novel therapy for immune mediated diseases.

[Pharmacogenetics, a valuable aid to therapeutic monitoring of immunosuppressives and antiretrovirals]

Although very effective, some drugs have considerable side effects and are characterized by a relatively narrow therapeutic index. It is therefore sometimes required to regularly check their blood concentration in order to find the best compromise between optimal therapeutic efficacy and reduced toxicity. A therapeutic drug monitoring (TDM) is applied for immunosuppressants used in solid organ transplantation and for antiretrovirals used in the treatment of HIV infections. A first improvement of conventional TDM consists in trying to understand the origin of the inter-individual variability at the pharmacokinetic level in order to anticipate it and to propose individualized dose adjustment according to each patient's genetic characteristics. A complementary improvement consists in measuring the active biological dose of the drug directly in target tissues (lymphocytes for both pharmacological classes considered) and in studying genetic and other factors, influencing this parameter. In complement to conventional TDM, pharmacogenetics therefore allows a better individualization of drug therapy.

Tetrandrine attenuates dendritic cell-mediated alloimmune responses and prolongs graft survival in mice

Tetrandrine, a bisbenzylisoquinoline alkaloid, has significant immunosuppressive effects; however, the effects of tetrandrine on dendritic cells (DCs) and the associated immune reactions are unclear. In this study, we investigated the effects of tetrandrine on DCs and the effects of the tetrandrine-treated DCs on alloimmune reactions in vitro and graft survival in vivo. Tetrandrine significantly downregulated the expression of CD80 and CD86 of DCs and increased their secretion of IL-10 (p = 0.0001). Mixed leukocyte reaction showed that tetrandrine inhibited dendritic-cell allo-stimulatory activity, which was reversed by the anti-IL-10 treatment. An in vivo study demonstrated that tetrandrine-treated DCs prolonged the survival time of skin grafts in mice compared to control (p = 0.005) and decreased cellular infiltration of the graft in the histopathological study. The data suggest that tetrandrine-treated DCs cause immunosuppression and protect skin grafts from rejection. The tetrandrine-induced immunosuppression seems to be partially due to increased IL-10 secretion.

Minimizing the risk of posttransplant malignancy

Recent improvements in immunosuppressive therapies have reduced the incidence of acute rejection and increased patient survival. These agents may however contribute to higher rates of mortality due to an increased risk of cardiovascular disease or malignancy. Transplant patients are immunocompromised with a reduced ability to combat the development of malignancy. The higher risk for the activity of oncoviruses may also contribute to the higher incidence and determine specific tumor types. Some immunosuppressants seem to have direct oncogenic effects. In vitro data have demonstrated that calcineurin inhibitors (CNIs) may show direct effects on tumor growth and the development of metastases. In contrast, mTOR inhibitors have demonstrated anti-tumoral properties in vitro and perhaps potent anti-angiogenic effects thereby. Recent studies and registry analyses have confirmed that mTOR inhibitors are associated with a reduced incidence of malignancies. UNOS data demonstrated that an mTOR inhibitor, with or without a CNI, is associated with a reduced incidence of tumors compared to regimens without mTOR inhibitors. The Rapamune Maintenance Regimen study demonstrated that patients receiving sirolimus-based, CNI-free therapy after CsA withdrawal at 3 months showed a reduced incidence of malignancy at 5 years posttransplant, compared with those who continued on a regimen that included CsA. In the CONVERT study, patients converted to sirolimus revealed a significantly lower malignancy rate at 24 months (3.1%) compared with those who continued CNI-based therapy (9.8%, P < .001). The elimination of CNIs and the introduction of sirolimus may, therefore, have a role to reduce the risk of cancer among posttransplant patients.

Long-Term Beneficial Effect of Tacrolimus Conversion on Renal Transplant Recipients

OBJECTIVE

Acute rejection, chronic allograft nephropathy, and cyclosporine (CsA) toxicity remain serious problems for renal transplant recipients and may lead to graft loss. We retrospectively analyzed 34 patients whose biopsies revealed acute and/or chronic allograft rejection, or CsA nephrotoxicity, and who converted from CsA to tacrolimus.

PATIENTS AND METHODS

From July 1996 through September 2003, CsA was converted to tacrolimus in 34 renal transplant recipients (26 male, 8 female) with renal biopsy at our hospital. Blood pressure and serum creatinine levels were checked monthly and serum cholesterol, triglyceride, and glutamic-pyruvic transaminase (GPT) levels were checked every three months.

RESULTS

A consistently stable and better function after conversion was obtained in a significant portion (24, 71%) of patients. A statistically significant decline in serum creatinine and an improvement in the glomerular filtration rate were found at 3 m, 6 m, 12 m, 36 m, and 72 m after tacrolimus conversion. In 85.7% (12/14) of patients with acute rejection and in 35.7% (5/14) of patients with chronic allograft nephropathy (concomitant with acute rejection in 5), improved or stabilized graft function was noted. In addition, the systolic blood pressure and diastolic BP dropped significantly (P<0.05), while there was no significant change in cholesterol, triglyceride, and GPT levels.

CONCLUSION

The beneficial effect of tacrolimus conversion on patients with acute rejection, chronic allograft nephropathy, or CsA nephrotoxicity was demonstrated in long-term follow up. The improvement in both renal function and blood pressure may be of paramount importance in reducing long-term cardiovascular morbidity and mortality.

Uncommon Side Effect of MMF in Renal Transplant Recipients

Mycophenolate mofetil (MMF) is a potent immunosuppressive agent used in renal transplantation. Gastrointestinal and hematological side effects are commonly observed, but hepatotoxicity has not been reported. In this study, we assessed MMF-related hepatotoxicity in renal transplant recipients. A total of 124 renal transplantation recipients (RTRs) were evaluated for elevated liver enzymes associated with MMF, and 79 patients were enrolled to the study. Patients used MMF 2 g/day. The patients who had progressive increase in liver enzymes after renal transplantation and their AST, ALT, GGT, ALP, bilirubin levels, hepatitis, cytomegalovirus (CMV), abdominal ultrasonography, duration of hepatotoxicity, and decreased dosage or withdrawal of MMF were recorded. Also, we evaluated their liver enzymes while the patients were on the waiting list. Of the 79 patients, 11 patients (13.9%) had a progressive increase in liver enzymes. The median (min-max) age of the patients with MMF-hepatotoxicity was 29 (19-54) and 72.7% of them were male. None of the patients had hepatitis B or C, CMV infection, or other possible causes for elevated liver enzymes and their abdominal ultrasonography were normal. High liver enzyme levels regressed after the withdrawal (n=6) or reduce dosage (n=5) of MMF. The median time of the increase in liver enzymes was 28 (4-70) days and after 50% reduction or withdrawal of MMF, returned to normal values in 16 (4-210) days. The median levels of ALT in waiting list (I), before (II), and after (III) reduction dosage or withdrawal of MMF were 22.0 (3-22), 222.0 (51-508), and 33.0 (21-64) U/L, respectively (p I-II=0.004,p I-II=0.013, andp II-III=0.005). There were no differences for ALP, GGT, total bilirubin, and direct bilirubin levels. Also, the correlation between recovery time of ALT and persistence time of ALT elevation before adjustment of MMF was significant (r=0.739, p=0.009). Consequently, after renal transplantation, hepatotoxicity can occur due to a lot of reason including MMF usage. If hepatotoxicity related to MMF is not considered, especially in the early period of renal transplantation, resolution of hepatotoxicity can be required long term.

The effects of immunosuppression on regulatory CD4(+)CD25(+) T cells: impact on immunosuppression selection in transplantation

During immune response and T-cell activation, both effector T cells and regulatory T(T(reg)) cells are activated and regulated simultaneously by both positive and negative pathways. CD4(+)CD25(+) T(reg) cells play a critical role in immune tolerance to self antigens as well as to allografts in some transplant settings. Effective immunosuppressive regimens significantly reduced the incidence of acute allograft rejection in patients following organ transplantation. However, the impact of immunosuppressive treatment on the potential induction of transplant tolerance has not been well determined. In this review we summarize the effects of immunosuppressive reagents on CD4(+)CD25(+) T(reg) cells in order to bring attention to this issue, which may affect the choice of immunosuppressive regimen in the clinical setting.

Costimulation blockade in autoimmunity and transplantation

Signaling through the costimulation receptors is a critical pathway in the regulation of T-cell activation. The selective costimulation inhibitor abatacept (cytotoxic T lymphocyte-associated antigen 4-Ig) binds to CD80 and CD86 on antigen-presenting cells, blocking interaction with CD28 on T cells, and is approved for the treatment of moderate to severe rheumatoid arthritis. Belatacept (LEA29Y), currently enrolling phase III trials in renal transplantation, was rationally designed from abatacept to bind with more avidity to CD86, providing the more potent immunosuppressive properties required for immunosuppression in transplantation. This review describes the relevant preclinical studies and summarizes recent clinical findings on these 2 molecules in autoimmune diseases and organ transplantation. Although both inhibit the CD28 costimulatory pathway, they are tailored for specific disease states--abatacept for autoimmune diseases and belatacept for transplantation.

Hepatocyte transplantation for glycogen storage disease type Ib

Glycogen storage disease type I (GSD-I) is a group of autosomal recessive disorders with an incidence of 1 in 100,000. The two major subtypes are GSD-Ia, caused by a deficiency of glucose-6-phosphatase (G6Pase), and GSD-Ib, caused by a deficiency of glucose-6-phosphate transporter (G6PT). We report that a substantial improvement was achieved following several infusions of hepatocytes in a patient with GSD-Ib. Hepatocytes were isolated from the unused cadaveric whole livers of two donors. At the first transplantation, approximately 2 x 10(9) cells (2% of the estimated recipient's total hepatocytes) were infused. Seven days later 1 x 10(9) (1% of liver mass) cryopreserved hepatocytes from the same donor were infused, and an additional 3 x 10(9) (3% of liver mass) cells from the second donor were infused 1 month after the second transplantation. After the hepatocyte transplantation, the patient showed no hypoglycemic symptoms despite the discontinuation of cornstarch meals. Liver biopsies on posttransplantation days 20 and 250 showed a normal level of glucose-6-phosphatase activity in presolubilization assay that was very low before transplantation. This was the first and successful clinical hepatocyte transplantation in Korea. In this study, hepatocyte transplantation allowed a normal diet in a patient with GSD-Ib, with substantial improvement in their quality of life. Hepatocyte transplantation might be an alternative to liver transplantation and dietary therapy in GSD-Ib.

Pathophysiology of acute graft-versus-host disease: recent advances

Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative therapy for many malignant and nonmalignant hematologic diseases. Donor T cells from the allografts are critical for the success of this effective therapy. Unfortunately these T cells not only recognize and attack the disease cells/tissues but also the other normal tissues of the recipient as "foreign" or "nonself" and cause severe, immune-mediated toxicity, graft-versus-host disease (GVHD). Several insights into the complex pathophysiology of GVHD have been gained from recent experimental observations, which show that acute GVHD is a consequence of interactions between both the donor and the host innate and adaptive immune systems. These insights have identified a role for a variety of cytokines, chemokines, novel T-cell subsets (naĩve, memory, regulatory, and NKT cells) and for non-T cells of both the donor and the host (antigen presenting cells, delta T cells, B cells, and NK cells) in modulating the induction, severity, and maintenance of acute GVHD. This review will focus on the immunobiology of experimental acute GVHD with an emphasis on the recent observations.

A novel variant L263F in human inosine 5'-monophosphate dehydrogenase 2 is associated with diminished enzyme activity

BACKGROUND AND OBJECTIVE

Inosine 5'-monophosphate dehydrogenase 2 is required for purine synthesis in activated lymphocytes. Variants in the IMPDH2 gene may account for the large inter-individual variability in baseline enzyme activity, immunosuppressive efficacy and side effects in transplant recipients receiving mycophenolic acid. Therefore, the objective of this study was to identify and functionally characterize IMPDH2 variants.

METHODS

DNA samples from 152 solid organ transplant patients were screened at exons and exon/intron junctions of the IMPDH2 genes by PCR amplification followed by bidirectional direct DNA sequencing. Genetic variant was constructed by site-directed mutagenesis and transformed to an inosine 5'-monophosphate dehydrogenase-deficient strain of Escherichia coli h712. Proteins were purified to homogeneity and the enzymatic activity was measured by reduced nicotinamide adenine dinucleotide production.

RESULTS

Nine genetic variants were identified in the IMPDH2 gene, with frequencies of the rarer alleles ranging from 0.5 to 10.2%. A novel nonsynonymous variant L263F was identified, and the kinetic assay demonstrated that the inosine 5'-monophosphate dehydrogenase activity of L263F variant was decreased to 10% of the wild-type. The Ki for mycophenolic acid inhibition of the L263F variant was comparable with the wild-type, and the variant Km for inosine 5'-monophosphate and nicotinamide adenine dinucleotide did not change significantly.

CONCLUSIONS

IMPDH2 has low genetic diversity, but the nonsynonymous variant L263F has a significant impact on inosine 5'-monophosphate dehydrogenase activity. This novel functional variant may be one of the factors contributing to the inter-individual difference of baseline inosine 5'-monophosphate dehydrogenase activity as well as drug efficacy and adverse events in transplant patients.

Current concepts and perspectives of immunosuppression in organ transplantation

BACKGROUND

While early surgical success made organ transplantation possible in the 1950s and 1960s, the breakthrough in clinical organ transplantation was achieved through the discovery and invention of modern immunosuppressive agents in the early/mid-1980s. Especially during the 1990 s, a large array of immunosuppressants has expanded the armamentarium used to prevent and treat allograft rejection, resulting in an excellent short-term and an acceptable long-term outcome. However, these drugs have potent but still non-specific immunosuppressive properties and frequently show severe acute and chronic side effects, sometimes questioning the overall success.

CONCEPTS/TRENDS

As the "Holy-Grail" of the transplant community, the induction of "true donor-specific tolerance" has not been achieved yet; current immunosuppressive strategies, in particular in Europe, include "individually tailored immunosuppressive" protocols, mostly based on specific immunologic and non-immunologic risk factors. These protocols allow for optimal immunosuppressive protocols for each patient group according to their needs by choosing the most suitable, well-tolerated combination of agents and the most effective doses to avoid acute rejection episodes (incidence and severity) and minimise drug-related toxicity to reduce long-term drug-related morbidity and mortality. Nevertheless, transplant recipient are still being forced to take a life-long course of chemical immunosuppressive agents to keep their graft, knowing about the possible life-threatening side effects.

SUMMARY

We review current trends of immunosuppressive protocols in liver and kidney transplantation, focusing on calcineurin-inhibitor-sparing protocols, mammalian-target-of-rapamycin (mTOR) inhibitor based-protocols and corticosteroid-avoidance protocols, being aware of the fact, that most of these strategies could be applicable for other transplanted organs, too. Finally, we describe future trends and new developments that are rising on the horizon.

Sirolimus promotes tolerance for donor and recipient antigens after MHC class II disparate bone marrow transplantation in rats

OBJECTIVE

Mixed chimerism after allogeneic bone marrow transplantation (BMT) promotes immunologic tolerance. Graft-vs-host disease (GvHD) can occur when immunosuppressive control of the graft fails. Here we evaluate the influence of concurrent immunosuppression after irradiation-based induction therapy on development of tolerance and GvHD.

METHODS

Conditioning was performed by different doses of total body irradiation (TBI) in a major histocompatibility complex (MHC) class II disparate rat BMT model. Animals received subsequent immunosuppression with either cyclosporine A (CsA) or sirolimus. Nonresponsiveness toward donor and recipient antigens was demonstrated by development of mixed chimerism and/or GvHD.

RESULTS

Administration of 10 Gy of TBI prior to BMT alone was associated with severe GvHD. Induction therapy with 8 Gy of TBI alone led to graft rejection in the long-term. Two weeks of immunosuppression with CsA after 8 Gy of TBI resulted in transient chimerism, but was finally associated with a combination of fatal GvHD and graft rejection. Six gray of TBI with CsA treatment for 14 or 28 days caused only mild GvHD, but did not lead to stable chimerism. In contrast, treatment with sirolimus was associated with stable chimerism after 8 Gy of TBI (14-day course) and 6 Gy of TBI (28-day course) accompanied by a low incidence of GvHD.

CONCLUSIONS

In contrast to CsA, sirolimus facilitates development of tolerance after MHC class II disparate BMT and irradiation-based conditioning, with a low risk of GvHD. Therefore, sirolimus has promising characteristics for inclusion in immunosuppressive protocols.

Efficacy and safety of inhaled tacrolimus in rat lung transplantation

OBJECTIVE

Because acute rejection is the most important cause of chronic rejection in lung transplantation, the use of conventional systemic immunosuppression to improve long-term survival needs to be reassessed. The aim of this study was to investigate the efficacy and safety of inhaled tacrolimus for preventing acute rejection of rat lung allografts.

METHODS

Orthotopic left lung transplantation was performed in rats that were divided into 6 groups: control group received no treatment; groups 1.0-IM, 0.5-IM, and 0.3-IM received tacrolimus by intramuscular injection at 1.0, 0.5, and 0.3 mg/(kg.d), respectively; and groups 12-IT and 6-IT received 12 and 6 puffs of inhaled tacrolimus 3 times per day, respectively. Allografts were studied histologically. Whole blood and allograft tacrolimus concentrations were determined.

RESULTS

In groups 1.0-IM and 12-IT, histologic grade of the graft showed significantly less rejection than in the other groups. The blood tacrolimus concentration in group 12-IT (4.87 ng/mL) was significantly lower than that in group 1.0-IM (13.05 ng/mL, P = .0017) on postoperative day 7. Higher allograft tacrolimus concentrations were achieved in group 1.0-IM (478.0 ng/g) than in group 12-IT (270.4 ng/g, P = .009). Weight loss and diarrhea in group 12-IT were less severe than in the groups that received systemic tacrolimus. The proliferating cell nuclear antigen index in bronchus-associated lymphoid tissue cells was significantly lower in group 12-IT than in group 1.0-IM (P = .0209).

CONCLUSION

Local immunotherapy with inhaled tacrolimus has great potential for controlling pulmonary allograft rejection in clinical lung transplantation because it has fewer side effects than systemic immunosuppressive agents.

Prenatal transplantation of cytokine-stimulated marrow improves early chimerism in a resistant strain combination but results in poor long-term engraftment

OBJECTIVE

In the absence of immunodeficiency, only microchimerism (<0.1%) has been achieved in human fetal recipients or nonhuman primates following in utero hematopoietic cell transplantation (IUHCT). We hypothesized that enhanced long-term engraftment might be more reliably achieved in microchimeric systems if higher levels of chimerism existed during development of adaptive immunity. To evaluate this hypothesis, we stimulated the donor cells with vascular endothelial growth factor (VEGF) and stem cell factor (SCF) prior to IUHCT in a chimerism-resistant murine strain combination.

METHODS

Donor Balb/c marrow was cultured in media with or without VEGF and SCF supplementation for 12 hours prior to IUHCT into B6 fetuses at 14 days postcoitum (dpc). Donor cell phenotype, homing, and chimerism were assessed at short and long-term time points and transplanted animals received skin allografts at 8 weeks.

RESULTS

In pretreated allogeneic recipients, early chimerism rates were more than double that of controls (71% vs 33%, p = 0.01). These differences were associated with higher numbers of pretransplant donor cell colony-forming cells without change in donor cell homing. Despite prolonged skin allograft survival for pretreated recipients compared with controls (mean survival = 20.8 vs 8.2 days, p < 0.001), long-term engraftment was unchanged.

CONCLUSIONS

These findings demonstrate that higher levels of early chimerism in recipients of cytokine-stimulated marrow result in improved short-term chimerism and tolerance. Future studies are needed to confirm the existence of a "threshold" level of chimerism necessary to sustain long-term engraftment.

Modeling CTLA4-linked autoimmunity with RNA interference in mice

The CTLA4 gene is important for T lymphocyte-mediated immunoregulation and has been associated with several autoimmune diseases, in particular, type 1 diabetes. To model the impact of natural genetic variants of CTLA4, we constructed RNA interference (RNAi) "knockdown" mice through lentiviral transgenesis. Variegation of expression was observed in founders but proved surmountable because it reflected parental imprinting, with derepression by transmission from male lentigenics. Unlike the indiscriminate multiorgan autoimmune phenotype of the corresponding knockout mice, Ctla4 knockdown animals had a disease primarily focused on the pancreas, with rapid progression to diabetes. As with the human disease, the knockdown phenotype was tempered by genetic-modifier loci. RNAi should be more pertinent than gene ablation in modeling disease pathogenesis linked to a gene-dosage variation.

Molecular basis of posttransplant squamous cell carcinoma: the potential role of cyclosporine a in carcinogenesis

Cyclosporine (CSA) is a widely used immunosuppressive agent, predominantly for transplant patients. It is well recognized that transplant patients are prone to develop squamous carcinoma of the skin and mucosa, and this high incidence of squamous carcinoma in the transplant population cannot be explained by immunosuppression alone. We hypothesize that CSA may play a significant role in the transformation of normal epidermal squamous cells to carcinoma. CSA is a specific ligand for calcineurin, a ubiquitously expressed cellular serine/threonine phosphatase, that plays important roles in the immune system and cardiac muscles. Using global gene-profiling methods, we studied the short-time CSA effect on the squamous cell line (SCC-015) using Affymetrix human gene chips (Human U133, 2.0 plus chip). Multiple groups of genes were identified to be responsive to CSA treatment, including many genes of unknown functions. We then used reverse transcriptase-polymerase chain reaction and immunoblot analyses to selectively confirm the results from the chips analyses with emphasis on the regulatory molecules important for cellular functions of apoptosis, DNA damage repair, and cellular transformation. This global gene-profiling study indicated that CSA not only functions as an immunosuppressant on the immune system, but also activates/inhibits a wide array of genes important for cell-cycle regulation, apoptosis, and oncogene/tumor-suppressor activation. These functions of CSA on skin and mucosa systems at the molecular level are likely important in the pathogenesis of squamous carcinoma in transplant patients.

Modulation of graft-versus-host disease: role of regulatory T lymphocytes

Graft-versus-host (GVH) disease (GVHD) continues to be a major life-threatening complication after allogeneic bone marrow transplantation. Considerable progress has been made elucidating the pathophysiology of acute GVHD. Mature donor T cells transferred along with the marrow graft directly recognize antigenic differences on antigen-presenting cells of the host. Once activated, donor antihost-specific T cells can mediate tissue destruction. Interestingly, the failure to clonally delete autoreactive T cells in the thymus can also lead to an autoimmune syndrome mimicking the pathology of GVHD. Negative selection in the thymus may be compromised either by damage to the thymic epithelium (because of a direct attack by donor antihost alloreactive T cells) or by the use of immunosuppressive drugs that inhibit clonal deletion. An important component underlying GVHD mediated by either alloreactive or autoreactive T cells is the absence of a competent peripheral regulatory system. Studies in animal model systems clearly indicate that regulatory T cells play a vital role in down-regulating GVHD and are critically important for the establishment of active dominant tolerance to both allo- and self-major histocompatibility complex antigens. Although multiple populations of cells appear to participate in this process, CD4(+) regulatory T cells that innately express CD25(+) appear to orchestrate the regulatory control of the immune response. Evidence for regulatory T cells in clinical bone marrow transplantation, however, remains rudimentary. The recent identification that CD4(+)CD25(+) regulatory T cells preferentially express the Foxp3 nuclear transcription factor and the development of molecular reagents to isolate antigen-specific T cells have provided unique opportunities to explore immunoregulatory mechanisms after clinical marrow transplantation. Recent studies in recipients of clinical bone marrow transplantation suggest that antigen-specific CD4(+)CD25(+)Foxp3(+) T cells play a vital role in the regulatory control of GVH reactions mediated by both alloreactive and autoreactive lymphocytes. These regulatory T cells also appear to facilitate the establishment of donor antihost and donor antidonor (self) tolerance.

Explaining variability in mycophenolic acid exposure to optimize mycophenolate mofetil dosing: a population pharmacokinetic meta-analysis of mycophenolic acid in renal transplant recipients

Large between- and within-patient variability has been observed in the pharmacokinetics of mycophenolic acid (MPA). However, conflicting results exist about the influence of patient characteristics that explain the variability in MPA exposure. This population pharmacokinetic meta-analysis of MPA in renal transplant recipients was performed to explore whether race, renal function, albumin level, delayed graft function, diabetes, and co-medication are determinants of total MPA exposure. A total of 13,346 MPA concentration-time data points from 468 renal transplant patients who participated in six clinical studies were combined and analyzed retrospectively. Sampling occasions ranged from day 1 after transplantation to 10 yr after transplantation. Concentration-time data were analyzed with nonlinear mixed-effect modeling. Exposure to total MPA, as determined by MPA clearance, significantly increased with increasing renal function, albumin level, and hemoglobin as well as decreasing cyclosporine predose level (P<0.001). These variables could explain 18% of the between-patient and 38% of the within-patient variability in MPA exposure. Differences in MPA exposure between patients with or without delayed graft function or between patients of different races are likely to be caused by the effect of renal function on MPA exposure. Diabetes did not have an effect on MPA exposure. The clinical implication is that a change in renal function or albumin level provides an indication for therapeutic drug monitoring as MPA exposure may be altered. Patients in whom cyclosporine and mycophenolate mofetil are combined may need higher mycophenolate mofetil doses, especially during the early phase after transplantation than currently recommended for optimal MPA exposure.

Cyclosporine exposure and calcineurin phosphatase activity in living-donor liver transplant patients: twice daily vs. once daily dosing

We have compared the pharmacokinetics and pharmacodynamics of cyclosporine between once- and twice-daily dosing regimens in de novo patients of living-donor liver transplantation (LDLT). A total of 14 patients were enrolled in this study, who had received cyclosporine microemulsion (Neoral) twice a day (BID, n = 5) or once daily in the morning (QD, n = 9) after transplantation. On postoperative day (POD) 6, the QD regimen significantly increased cyclosporine exposure; the blood concentration at 2 hours postdose (C2) and area under the concentration-time curve (AUC) for 4 hours (AUC(0-4)), compared with the BID regimen. Moreover, the area under the calcineurin (CaN) activity in peripheral blood mononuclear cells time-curve (AUA) for 12 hours (AUA(0-12)) and 24 hours (AUA(0-24)) were decreased by approximately 42 and 25% with the QD regimen relative to the BID regimen, respectively. The C2 level was significantly correlated with the AUC(0-4) (r2 = 0.95), which was negatively related to the AUA(0-12) with a large interindividual variability (r(2) = 0.59). However, a significant correlation was found between the AUA(0-12) or AUA(0-24) and CaN activity at trough time points. According to a maximum inhibitory effect attributable to the drug (E(max)) model, the mean estimates of E(max) and the C(b) value that gives a half-maximal effect (EC50) for CaN inhibition were not significantly different between the 2 groups, respectively. These findings suggest that a once daily morning administration of cyclosporine may improve oral absorption and help to provide an effective CaN inhibition early after LDLT. Furthermore, CaN activity at trough time points would be a single surrogate predictor for the overall CaN activity throughout dosing intervals following cyclosporine administration.

Efficacy and safety of low-dose valganciclovir in the prevention of cytomegalovirus disease in adult liver transplant recipients

The efficacy and safety of valganciclovir (VGCV) for cytomegalovirus (CMV) prophylaxis in liver transplant recipients has not been established. We retrospectively compared the efficacy and safety of low-dose oral VGCV (450 mg once daily for 90 days) and standard oral ganciclovir (1 g three times a day for 90 days, GCV) in preventing CMV disease in 109 adult liver transplant recipients who survived at least 1 month between January 2001 and April 2003 (49 GCV and 60 VGCV). The incidence of CMV disease at 1 year post-transplant was similar among patients treated with VGCV and GCV (3% and 4%, respectively). Three of the four CMV disease cases occurred in high-risk recipients with CMV serotype of donor+/recipient- (D+/R-) and all cases presented after completion of CMV prophylaxis, ranging 114-152 days post-transplant. Severe neutropenia was rare, and thrombocytopenia and anemia occurred at similar frequencies with both prophylaxis regimens. In conclusion, a 90-day regimen of low-dose oral VGCV has a similar efficacy and safety profile to high-dose oral GCV in adult liver transplant recipients. D+/R- liver transplant recipients remain at risk of developing CMV disease after completion of antiviral prophylaxis. Additional prospective studies with close monitoring for CMV viremia and drug resistance are needed to further establish the optimal dose and duration of VGCV in liver transplant recipients.

Protective antibody levels and dose requirements for IV 5% Nabi Hepatitis B immune globulin combined with lamivudine in liver transplantation for hepatitis B-induced end stage liver disease

Lamivudine combined with Hepatitis B immune globulin (HBIg) prevents post liver transplant (LT) HBV recurrence. The study was designed to assess the impact of lamivudine on hepatitis B antibody (anti-HBs) and dosage requirements of intravenous 5% HBIg (Nabi-HB) in the first 36 weeks post LT. Adults undergoing LT for chronic HBV received lamivudine prior to or at LT, and IV HBIg 20,000 IU on day of LT, 10,000 on days 1-7, weeks 4 and 8, and 5,000 every 4 weeks thereafter. Replicative status based on serum HBV DNA (> 5 pg/mL = replicator (R) or < or = 5 pg/mL = nonreplicator (N) was determined at initiation of lamivudine (R or N) and within 2 weeks of LT (r or n), resulting in 3 groups: Nn, Rn, and Rr. Between December 1999 and May 2001, 30 patients (10 Nn, 13 Rn, 6 Rr, and 1 unknown), mean age of 52 years underwent LT. HBsAg neutralization was achieved with anti-HBs > 300 IU/L during week 1 and > 200 IU/L during weeks 2-12. All but one patient were HBsAg-negative on last follow-up. Pre-LT suppression of HBV replication resulted in similar dose requirements and pK in the Rn and Nn groups within 1 week after LT. Comparatively, the Rr group had greater HBIg requirements during weeks 1-12 due to greater anti-HBs clearance and shortened t(1/2) during the entire 36-week follow-up. In conclusion, this study provides a rationale for the use of lower HBIg doses in HBV patients with suppressed replication undergoing LT.

Potential Mechanisms of Photopheresis in Hematopoietic Stem Cell Transplantation

Immune tolerance describes specific unresponsiveness to antigens. In clinical situations such as graft-versus-host disease it may be useful to capitalize on these pre-existing tolerance mechanisms to treat patients. Extracorporeal photopheresis is a pheresis treatment whereby the approximately 5 x 10(9) leukocytes are treated with a photoactivatable compound (8-methoxypsoralen) and UVA light, and immediately returned to the patient in a closed-loop, patient-connected system. This therapy induces apoptosis of virtually all the treated leukocytes. There is growing evidence that infusion of apoptotic cells may trigger certain tolerance mechanisms and, thus, be of therapeutic use in graft-versus-host disease. These apoptotic cells are taken up by phagocytes (antigen-presenting cells) in the body of the patient. Apoptotic cell engagement has been reported to induce several changes and functional activities in the engulfing antigen-presenting cell. These antigen-presenting cells: (1) decrease production of proinflammatory cytokines; (2) increase production of anti-inflammatory cytokines; (3) lower ability to stimulate T-cell responses; (4) delete CD8 T effector cells; and (5) induce regulatory T cells. Any and all of these mechanisms could explain the noted effect in graft-versus-host disease. It is still unclear which one or ones are truly responsible. Ongoing studies in animals and human trials will ultimately unravel these details.

Plasma total homocysteine and cardiovascular risk in patients submitted to liver transplantation

Patients submitted to orthotopic liver transplantation (OLT) show an increased rate of cardiovascular events. OLT subjects have high homocysteine (Hcy) levels, but no data are available on the association of Hcy with cardiovascular events. In a cross-sectional analysis, 230 subjects were studied at least 6 months after OLT (159 on cyclosporine, 71 on tacrolimus). Routine laboratory data and total Hcy were recorded, as well as the history of diabetes, hypertension, dyslipidemia, and overweight. Cardiovascular events occurring in a follow-up of 2-36 months were registered. OLT subjects had higher-than-normal Hcy (median 16.7 micromol/L, range 6.1-171.8) without difference between the 2 immunosuppressive agents. The prevalence of Hcy >15 micromol/L was also similar, and significantly correlated with creatinine levels. A total of 28 arterial events occurred in 25 patients during follow-up (11 in coronary arteries, 10 in peripheral arteries, and 7 in splanchnic arteries). Deep vein thromboses occurred in 2 patients, and splanchnic vein thromboses in 4 patients. Cardiovascular events were frequently associated to high Hcy and hypertension. Cox regression analysis showed that high Hcy was significantly associated with arterial events. The risk of any arterial event, coronary artery or peripheral artery event increased by nearly 10% for any increase in Hcy of 5 micromol/L. In conclusion, high Hcy may be involved in the pathogenesis of cardiovascular events in OLT patients. The usefulness of Hcy-lowering therapy remains to be verified.

Monitoring C2 level predicts exposure in maintenance lung transplant patients receiving the microemulsion formulation of cyclosporine (Neoral)

BACKGROUND

Dosing of the microemulsion formulation of cyclosporine (Neoral) is conventionally based on trough levels (C(0)). However, experience in renal transplantation has shown that cyclosporine exposure during the absorption phase (AUC(0-4)) is critical for optimizing immunosuppression, and that cyclosporine (CsA) concentration at 2 hours post-dose (C(2)) shows the closest correlation with AUC(0-4). This study evaluated whether C(2) values correlate more closely with AUC(0-4) than C(0) in lung transplant patients.

METHODS

Pharmacokinetic data were collected prospectively from 20 clinically stable adult lung allograft recipients receiving CsA, mycophenolate mofetil and steroids. Indications for transplantation were emphysema (n = 15), idiopathic fibrosis (n = 2), primary pulmonary hypertension (n = 1), cystic fibrosis (n = 1) and lymphangioleiomyomatosis LAM (n = 1). Blood samples were collected at 0, 1, 2, 3 and 4 hours after administration of CsA, and then AUC(0-4) was calculated. The Correlation between cyclosporine concentration at each time-point and AUC(0-4) was also calculated.

RESULTS

C(2) showed the closest correlation with AUC(0-4) (r(2) = 0.85). C(0) had the poorest correlation of all time-points (r(2) = 0.64). Two patients with radiologic signs of gastroparesis had no peak cyclosporine levels at all and were excluded from the correlation analysis. Mean AUC(0-4) was 3,700 ng . h/ml during Year 1 post-transplant, 2,400 ng . h/ml during Years 1 to 3, and 1,500 ng . h/ml thereafter. Mean C(2) values were 1.2 microg/ml during Year 1, 0.8 microg/ml during Years 1 to 3, and 0.5 microg/ml thereafter.

CONCLUSIONS

C(2) is the single time-point that correlates most closely with AUC(0-4) in lung transplant recipients without gastroparesis. It remains to be demonstrated whether monitoring CsA based on C(2) levels results in a lower incidence of rejection without additional toxicity.

Promotion of long-term heart allograft survival by combination of mobilized donor plasmacytoid dendritic cells and anti-CD154 monoclonal antibody

Infusion of donor immature dendritic cells (DC) can significantly prolong survival of organ allografts, and this is believed to be due to antigen recognition by T cells in the absence of co-stimulation. In this study we report that a single pre-operative infusion of donor-mobilized immature plasmacytoid dendritic cells (pDCs) is superior to that of other DC sub-sets in suppressing allograft rejection. The combination of pDC infusion with injection of anti-CD154 monoclonal antibody further inhibited graft rejection and, in 50% of the mice, led to indefinite graft survival. This finding suggests a role for the plasmacytoid DC sub-set in facilitating organ transplant survival and also in the treatment of autoimmune disorders.

Effect of Oral Vitamin E and C Therapy on Calcineurin Inhibitor Levels in Heart Transplant Recipients

BACKGROUND

A recent prospective trial demonstrated that oral vitamins C and E retard the early progression of transplant-associated coronary arteriosclerosis; as a result, a number of centers have added these agents to their maintenance regimens. This study reviewed the impact of vitamin E and C supplementation on calcineurin inhibitor trough concentrations.

METHODS

A retrospective chart review of the first 29 heart transplant patients prescribed anti-oxidant agents was performed. Twenty-two patients taking cyclosporin A (CsA) and 7 patients taking tacrolimus were prescribed vitamin C (500 mg twice a day) and vitamin E (400 IU twice a day). Serum chemistries and drug levels were measured before and after vitamin therapy was initiated.

RESULTS

The baseline CsA trough concentration (mean +/- SD) was 137 +/- 39 ng/ml and it declined to 99 +/- 54 ng/ml (p = 0.007) after anti-oxidant therapy was initiated. The average percentage decrease in the CsA trough concentration was 30%. No significant changes were seen in the patients taking tacrolimus.

CONCLUSIONS

These data demonstrate that supplementation with the anti-oxidant agents vitamin C and vitamin E decreases CsA concentrations but does not appear to effect tacrolimus concentrations. Although more detailed pharmacokinetic analysis is necessary to clarify the exact mechanism of this interaction, physicians who take care of transplant recipients should be aware that more frequent CsA concentration monitoring is warranted after initiating these anti-oxidant agents.

Peripheral nerve transplantation: the role of chemical acellularization in eliminating allograft antigenicity

This study tests the hypothesis that a chemically acellularized peripheral nerve allograft is as immunologically inactive as a peripheral nerve isograft. Cellular and acellular sciatic nerves were transplanted from BALB/c into C57BL/6 mice. C57BL/6 sciatic nerves were also transplanted into C57BL/6 recipients as isograft controls. Fourteen days post-transplantation, recipient splenocytes were isolated, stimulated with donor alloantigens, and IL-2, IL-4, IL-5, and gamma-IFN production was quantified using the ELISPOT technique. Cellular peripheral nerve allografts stimulated robust Th1 and Th2 systemic immune responses, whereas acellular peripheral nerve allografts elicited a response that is comparable to or lower than that quantified following peripheral nerve isograft transplantation. Chemical acellularization of peripheral nerve allografts dramatically reduces the cellular and humoral immunologic responses. These data indicate that chemically acellularized peripheral nerve constructs are relatively non-antigenic and may be a readily available source of nerve for peripheral nerve reconstruction.