Overview of immunosuppression in liver transplantation

Toward immunosuppressive effects on liver transplantation in rat model: tacrolimus loaded poly(ethylene glycol)-poly(D,L-lactide) nanoparticle with longer survival time

In this study, tacrolimus (FK506) was encapsulated into a biodegradable poly(ethylene glycol)-poly(D,L-lactide) (MPEG-PLA) block copolymer using a double emulsion-solvent evaporation technique. Drug loading (DL) and encapsulation efficiency (EE) can be changed by varying the mass ratio of FK506/MPEG-PLA. Furthermore, transmission electron microscope (TEM) and Malvern Zetasizer were used to investigate the properties of FK506/MPEG-PLA nanoparticles (DL=9.5%), which were monodisperse (PDI=0.100 ± 0.023) with a mean particle size of 90.5 ± 1.5 nm. Compared with FK506 capsule, in vitro release profile showed that FK506/MPEG-PLA nanoparticles exhibited sustained release. Meanwhile, the higher concentration and longer retention time in plasma were also confirmed in vivo. We further preliminarily evaluated immunosuppressive effect on liver transplantation in rat model. The survival time of the rat administrated FK506/MPEG-PLA nanoparticles was obviously prolonged than that of the control group administrated FK506 capsule.

Neurologic complications after liver transplantation

Neurologic complications are relatively common after solid organ transplantation and affect 15%-30% of liver transplant recipients. Etiology is often related to immunosuppressant neurotoxicity and opportunistic infections. Most common complications include seizures and encephalopathy, and occurrence of central pontine myelinolysis is relatively specific for liver transplant recipients. Delayed allograft function may precipitate hepatic encephalopathy and neurotoxicity of calcineurin inhibitors typically manifests with tremor, headaches and encephalopathy. Reduction of neurotoxic immunosuppressants or conversion to an alternative medication usually result in clinical improvement. Standard preventive and diagnostic protocols have helped to reduce the prevalence of opportunistic central nervous system (CNS) infections, but viral and fungal CNS infections still affect 1% of liver transplant recipients, and the morbidity and mortality in the affected patients remain fairly high. Critical illness myopathy may also affect up to 7% of liver transplant recipients. Liver insufficiency is also associated with various neurologic disorders which may improve or resolve after successful liver transplantation. Accurate diagnosis and timely intervention are essential to improve outcomes, while advances in clinical management and extended post-transplant survival are increasingly shifting the focus to chronic post-transplant complications which are often encountered in a community hospital and an outpatient setting.

Current status of immunosuppression in liver transplantation

With advancements in immunosuppressive strategies and availability of better immunosuppressive agents, survival rate following liver transplantation has improved significantly in the recent times. Besides improvements in surgical techniques, the most important factor that has contributed to this better outcome is the progress made in the field of immunosuppression. Over the last several years, the trend has changed to tailored immunosuppression with the aim of achieving optimal graft function while avoiding its undesirable side effects. Induction agents are no longer used routinely and the aim is to provide minimal immunosuppression in the maintenance phase. The present review discusses the various types of immunosuppressive agents, their mechanism of action, clinical utility, advantages and disadvantages, and their side effects in short and long-term. It also discusses about tailoring immunosuppression in presence of various situations such as renal dysfunction, metabolic syndrome, hepatitis C recurrence, cytomegalovirus infections and so on. The issue of chronic kidney disease and the available renal sparing immunosuppressive strategies has been particularly stressed upon. Finally, it discusses about the practical aspects of various immunosuppression regimens including drug monitoring.

Immunomodulating options for liver transplant patients

Much has changed since the early years of liver transplantation. Improvements in post-transplant survival are largely due to more selective and less toxic immunosuppression regimens and advances in operative and perioperative care. This has allowed liver transplantation to become an extremely successful treatment option for patients with endstage liver disease. Beginning with cyclosporine, a cyclic endecapeptide of fungal origin and the first of the calcineurin inhibitors to find widespread use, immunosuppressive regimens have evolved to include additional calcineurin inhibitors, steroids, mTOR inhibitors, antimetabolites and antibodies, mostly targeting T-cell activation. This review will present currently available immunosuppressive agents used in the perioperative period of liver transplantation, as well as maintenance treatments, tailoring therapeutic strategies for specific populations, and advances in immune monitoring and tolerance.

Preparation and in vitro and in vivo characterization of cyclosporin A-loaded, PEGylated chitosan-modified, lipid-based nanoparticles

BACKGROUND AND METHODS

A new cyclosporin A-loaded, PEGylated chitosan-modified lipid-based nanoparticle was developed to improve upon the formulation of cyclosporin A. PEGylated chitosan, synthesized in three steps using mild reaction conditions, was used to modify the nanoparticles. Cyclosporin A-loaded, PEGylated chitosan-modified nanoparticles were prepared using an emulsification/solvent evaporation method. The drug content and encapsulation efficiency of the cyclosporin A-loaded, PEGylated chitosan-modified nanoparticles were measured by high-performance liquid chromatography. The average size of the nanoparticles was determined by transmission electron microscopy and dynamic light scattering. The pharmacokinetic behavior of the nanoparticles was investigated in rabbits after intravenous injection. Cyclosporin A concentrations in a whole blood sample were analyzed by high-performance liquid chromatography using tamoxifen as the internal standard. The pharmacokinetic parameters were calculated using the 3p87 software program.

RESULTS

Fourier transform infrared spectroscopy and nuclear magnetic resonance confirmed the structure of PEGylated chitosan. The drug content and encapsulation efficiency of the cyclosporin A-loaded, PEGylated chitosan-modified nanoparticles were 37.04% and 69.22%, respectively. The average size of the nanoparticles was 89.4 nm. The nanoparticles released 30% cyclosporin A-loaded in 48 hours in vitro, with no initial burst release. The mode of release in vitro was prone to bulk erosion. The in vivo results showed the biological half-life of the elimination phase (t(1/2β)) of the nanoparticles was 21 times longer than that of the cyclosporin A solution, and the area under the curve for the nanoparticles was 25.8 times greater than that of the cyclosporin A solution.

CONCLUSION

Modification of PEGylated chitosan prolonged the retention time of the nanoparticles in the circulatory system and improved the bioavailability of cyclosporin A.

Safety and efficacy of four steroid-minimization protocols in liver transplant recipients: 3-year follow-up in a single center

OBJECTIVE

To evaluate the safety and efficacy of steroid-minimization therapy in liver transplantation (LT) recipients with hepatitis B virus-related diseases in China.

METHODS

From March 2000 to June 2007, 502 adult LT recipients, mostly with hepatitis B (HBV)-related diseases, were enrolled in our study. Four study groups were setup according to the steroid-minimization protocols: tacrolimus (TAC) with 6 months steroids withdrawal (6M SW), TAC with 3 months SW (3M SW), TAC with 14 days SW (14d SW), and TAC with basiliximab induction and steroids avoidance (Bas SA). All patients were followed up for at least 36 months after LT.

RESULTS

There were no significant differences in the overall 3-year survival rates of the patients and graft, and chronic rejection among the four groups (P = 0.092, P = 0.113 and P = 0.684, respectively). There was also no difference in acute rejection within 12 months after LT (P = 0.514). The 3-year recurrence rates of HBV infection and hepatocellular carcinoma (HCC) after LT were significantly different among all the groups (lowest in TAC/Bas SA group; P = 0.037 and P = 0.029, respectively). The overall incidence of infection was significantly higher in the 6M SW group (62.2% vs 56.1% in 3M SW, 30.5% in 14d SW, 20.5% in Bas SA; P < 0.01). By the end of the 3-year follow-up, more than 90% of the surviving patients could safely receive TAC monotherapy.

CONCLUSION

Bas SA immunosuppressive protocol can be achieved safely in LT and reduce HBV infection and HCC recurrence and side effects of steroids after LT.

Intragraft transcriptome level of CXCL9 as biomarker of acute cellular rejection after liver transplantation

BACKGROUND

Liver transplantation has been a life-saving and well-established treatment for acute liver failure and various end-stage liver diseases. However, acute cellular rejection (ACR) is one of the key factors that determine long-term graft function and survival after liver transplantation, and there are still no specific biomarkers available to monitor the alloimmune response. The aim of the present study was to identify molecular biomarkers for ACR in liver allograft.

METHODS

We analyzed the gene expression profile using an oligonucleotide microarray covering 44,000 human probes in 35 liver biopsy samples after living donor liver transplant, which consisted of 13 samples with ACR (ACR group; moderate/mild, 6/7), 13 samples with other dysfunctions (non-ACR group; recurrent hepatitis C / ischemia/reperfusion injury (IRI)/ nonspecific inflammation / small-for-size syndrome, 5/4/3/1), and 9 samples without liver dysfunction (protocol group). We selected 113 informative genes based on microarray results and adopted the network analysis to visualize key modulators in ACR. We selected 6 modulators (CXCL9, GZMB, CCL19, GBP2, LAIR1, and CDC25A) and confirmed the reproducibility in 23 independent biopsy samples and investigated the response to the rejection treatment in sequential samples.

RESULTS

Network analysis revealed the top three subnetworks, which had NF-κB, MAPK, and IFNG as central hubs. Among selected modulators, intragraft expression levels of CXCL9 mRNA was most upregulated and sensitive to alloimmune status.

CONCLUSION

Intragraft CXCL9 mRNA has a functionally important role in T-cell activation in liver allograft and serves as biomarker for ACR.

Mycophenolate mofetil inhibits hepatitis C virus replication in human hepatic cells

Hepatitis C virus (HCV) infection is the most common indication for liver transplantation and the major cause of graft failure. A widely used immunosuppressant, cyclosporine A (CsA), for people who receive organ transplantation, has been recognized to have the ability to inhibit HCV replication both in vivo and in vitro. In this study, we investigated the effects of several other immunosuppressants, including mycophenolate mofetil (MMF), rapamycin and FK506, on HCV replication in human hepatic cells. MMF treatment of hepatic cells before or during HCV infection significantly suppressed full cycle viral replication, as evidenced by decreased expression of HCV RNA, protein and production of infectious virus. In contrast, rapamycin and FK506 had little effect on HCV replication. Investigation of the mechanism(s) disclosed that the inhibition of HCV replication by MMF was mainly due to its depletion of guanosine, a purine nucleoside crucial for synthesis of guanosine triphosphate, which is required for HCV RNA replication. The supplement of exogenous guanosine could reverse most of anti-HCV effect of mycophenolate mofetil. These data indicate that MMF, through the depletion of guanosine, inhibits full cycle HCV JFH-1 replication in human hepatic cells. It is of interest to further determine whether MMF is indeed beneficial for HCV-infected transplant recipients in future clinical studies.

Analysis of infections in the first 3-month after living donor liver transplantation

AIM: To identify factors related to serious postoperative bacterial and fungal infections in the first 3 mo after living donor liver transplantation (LDLT).

METHODS: In the present study, the data of 207 patients from 2004 to 2011 were reviewed. The pre-, intra- and post-operative factors were statistically analyzed. All transplantations were approved by the ethics committee of West China Hospital, Sichuan University. Patients with definitely preoperative infections and infections within 48 h after transplantation were excluded from current study. All potential risk factors were analyzed using univariate analyses. Factors significant at a P < 0.10 in the univariate analyses were involved in the multivariate analyses. The diagnostic accuracy of the identified risk factors was evaluated using receiver operating curve.

RESULTS: The serious bacterial and fungal infection rates were 14.01% and 4.35% respectively. Enterococcus faecium was the predominant bacterial pathogen, whereas Candida albicans was the most common fungal pathogen. Lung was the most common infection site for both bacterial and fungal infections. Recipient age older than 45 years, preoperative hyponatremia, intensive care unit stay longer than 9 d, postoperative bile leak and severe hyperglycemia were independent risk factors for postoperative bacterial infection. Massive red blood cells transfusion and postoperative bacterial infection may be related to postoperative fungal infection.

CONCLUSION: Predictive risk factors for bacterial and fungal infections were indentified in current study. Pre-, intra- and post-operative factors can cause postoperative bacterial and fungal infections after LDLT.

Calcineurin inhibitor minimisation versus continuation of calcineurin inhibitor treatment for liver transplant recipients

BACKGROUND

The therapeutic success of liver transplantation has been largely attributable to the development of effective immunosuppressive treatment regimens. In particular, calcineurin inhibitors were essential in reducing acute rejection and improving early survival. Currently, more than 90% of all liver transplant recipients are treated with the calcineurin inhibitor cyclosporine or tacrolimus. Unfortunately, calcineurin inhibitors cause adverse events, such as nephrotoxicity, and because of this, minimisation (reduction and withdrawal) regimens of calcineurin inhibitor have been developed and studied. However, the benefits and harms of these minimisation regimens are unclear.

OBJECTIVES

To assess the benefits and harms of calcineurin inhibitor minimisation for liver transplant recipients without substitution by another immunosuppressive agent.

SEARCH METHODS

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register (Gluud 2010), Cochrane Central Register of Controlled Clinical Trials (CENTRAL) in The Cochrane Library, MEDLINE (OvidSP), EMBASE (OvidSP), Science Citation Index Expanded (Royle 2003), and the World Health Organization (WHO) international clinical trials registry platform (www.who.int/ictrp) until August 2011. In addition, we searched bibliographies of relevant articles as well as US Food and Drug Administration (FDA) and European Medicines Agency (EMA) drug approval reviews for additional trials.

SELECTION CRITERIA

We planned to select all randomised clinical trials investigating calcineurin inhibitor reduction or withdrawal in liver transplant recipients, irrespective of blinding, publication status, or language. Quasi-randomised clinical studies and cohort studies that were obtained through the searches were considered only for the reporting of harms. Trials investigating substitution of one calcineurin inhibitor by another calcineurin inhibitor were excluded. Trials investigating calcineurin inhibitor withdrawal concurrently with switching over to a mammalian target of rapamycin (mTOR) inhibitor-based regimen (everolimus or sirolimus) or mycophenolate mofetil-based regimen are the subject of a separate review.

DATA COLLECTION AND ANALYSIS

Search strategies were used to obtain titles and abstracts of studies that were relevant for the review. Two authors independently scanned the references and assessed trial eligibility.

MAIN RESULTS

A total of 1299 references were identified by the searches. After removal of duplicates, 794 references were left. Out of these, two abstract reports of one ongoing randomised trial fulfilled the inclusion criteria of the review. This ongoing trial studies total withdrawal of immunosuppression in patients who receive a calcineurin inhibitor (cyclosporine or tacrolimus) or mycophenolate mofetil as the only immunosuppressive agent. The trial compares withdrawal of calcineurin inhibitor or mycophenolate mofetil with continuation of calcineurin inhibitor or mycophenolate mofetil. However, no trial results on the outcomes of interest to this review were available.

AUTHORS' CONCLUSIONS

This review shows that strategies regarding calcineurin inhibitor minimisation, that is, reduction or withdrawal, without substitution versus continuation of calcineurin inhibitor treatment lack evidence from randomised trials.More research with calcineurin inhibitor reduction and withdrawal regimens is needed to optimise dosing and timing of calcineurin inhibitor treatment in order to achieve optimal patient and graft survival with a minimum of adverse events.Specifically regarding calcineurin inhibitor reduction versus no reduction, we recommend that randomised trials evaluating calcineurin inhibitor reduction versus continuation of calcineurin inhibitor treatment are conducted.Regarding calcineurin inhibitor withdrawal, we recommend that mechanisms for tolerance and 'graft acceptance' are clarified, and patient groups likely to tolerate calcineurin inhibitor withdrawal are identified in order to select the right patients for total withdrawal of calcineurin inhibitors without substitution with another immunosuppressive drug. The randomised trials should only be performed in highly selected patients.

Calcineurin inhibitor minimisation versus continuation of calcineurin inhibitor treatment for liver transplant recipients

BACKGROUND

The therapeutic success of liver transplantation has been largely attributable to the development of effective immunosuppressive treatment regimens. In particular, calcineurin inhibitors were essential in reducing acute rejection and improving early survival. Currently, more than 90% of all liver transplant recipients are treated with the calcineurin inhibitor cyclosporine or tacrolimus. Unfortunately, calcineurin inhibitors cause adverse events, such as nephrotoxicity, and because of this, minimisation (reduction and withdrawal) regimens of calcineurin inhibitor have been developed and studied. However, the benefits and harms of these minimisation regimens are unclear.

OBJECTIVES

To assess the benefits and harms of calcineurin inhibitor minimisation for liver transplant recipients without substitution by another immunosuppressive agent.

SEARCH METHODS

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register (Gluud 2010), Cochrane Central Register of Controlled Clinical Trials (CENTRAL) in The Cochrane Library, MEDLINE (OvidSP), EMBASE (OvidSP), Science Citation Index Expanded (Royle 2003), and the World Health Organization (WHO) international clinical trials registry platform (www.who.int/ictrp) until August 2011. In addition, we searched bibliographies of relevant articles as well as US Food and Drug Administration (FDA) and European Medicines Agency (EMA) drug approval reviews for additional trials.

SELECTION CRITERIA

We planned to select all randomised clinical trials investigating calcineurin inhibitor reduction or withdrawal in liver transplant recipients, irrespective of blinding, publication status, or language. Quasi-randomised clinical studies and cohort studies that were obtained through the searches were considered only for the reporting of harms. Trials investigating substitution of one calcineurin inhibitor by another calcineurin inhibitor were excluded. Trials investigating calcineurin inhibitor withdrawal concurrently with switching over to a mammalian target of rapamycin (mTOR) inhibitor-based regimen (everolimus or sirolimus) or mycophenolate mofetil-based regimen are the subject of a separate review.

DATA COLLECTION AND ANALYSIS

Search strategies were used to obtain titles and abstracts of studies that were relevant for the review. Two authors independently scanned the references and assessed trial eligibility.

MAIN RESULTS

A total of 1299 references were identified by the searches. After removal of duplicates, 794 references were left. Out of these, two abstract reports of one ongoing randomised trial fulfilled the inclusion criteria of the review. This ongoing trial studies total withdrawal of immunosuppression in patients who receive a calcineurin inhibitor (cyclosporine or tacrolimus) or mycophenolate mofetil as the only immunosuppressive agent. The trial compares withdrawal of calcineurin inhibitor or mycophenolate mofetil with continuation of calcineurin inhibitor or mycophenolate mofetil. However, no trial results on the outcomes of interest to this review were available.

AUTHORS' CONCLUSIONS

This review shows that strategies regarding calcineurin inhibitor minimisation, that is, reduction or withdrawal, without substitution versus continuation of calcineurin inhibitor treatment lack evidence from randomised trials.More research with calcineurin inhibitor reduction and withdrawal regimens is needed to optimise dosing and timing of calcineurin inhibitor treatment in order to achieve optimal patient and graft survival with a minimum of adverse events.Specifically regarding calcineurin inhibitor reduction versus no reduction, we recommend that randomised trials evaluating calcineurin inhibitor reduction versus continuation of calcineurin inhibitor treatment are conducted.Regarding calcineurin inhibitor withdrawal, we recommend that mechanisms for tolerance and 'graft acceptance' are clarified, and patient groups likely to tolerate calcineurin inhibitor withdrawal are identified in order to select the right patients for total withdrawal of calcineurin inhibitors without substitution with another immunosuppressive drug. The randomised trials should only be performed in highly selected patients.

Hepatic differentiation of human embryonic stem cells is promoted by three-dimensional dynamic perfusion culture conditions

The developmental potential of human embryonic stem cells (hESCs) holds great promise to provide a source of human hepatocytes for use in drug discovery, toxicology, hepatitis research, and extracorporeal bioartificial liver support. There are, however, limitations to induce fully functional hepatocytes on conventional two-dimensional (2D) static culture. It had been shown that dynamic three-dimensional (3D) perfusion culture is superior to induce maturation in fetal hepatocytes and prolong hepatic functions of primary adult hepatocytes. We investigated the potential of using a four-compartment 3D perfusion culture to induce hepatic differentiation in hESC. Undifferentiated hESC were inoculated into hollow fiber-based 3D perfusion bioreactors with integral oxygenation. Hepatic differentiation was induced with a multistep growth factor cocktail protocol. Parallel controls were operated under equal perfusion conditions without the growth factor supplementations to allow for spontaneous differentiation, as well as in conventional 2D static conditions using growth factors. Metabolism, hepatocyte-specific gene expression, protein expression, and hepatic function were evaluated after 20 days. Significantly upregulated hepatic gene expression was observed in the hepatic differentiation 3D culture group. Ammonia metabolism activity and albumin production was observed in the 3D directed differentiation culture. Drug-induced cytochrome P450 gene expression was increased with rifampicin induction. Using flow cytometry analysis the mature hepatocyte marker asialoglycoprotein receptor was found on up to 30% of the cells in the 3D system with directed hepatic differentiation. Histological and immunohistochemical analysis revealed structural formation of hepatic and biliary marker-positive cells. In contrast to 2D culture, the 3D perfusion culture induced more functional maturation in hESC-derived hepatic cells. 3D perfusion bioreactor technologies may be useful for further studies on generating hESC-derived hepatic cells.

Immunosuppression armamentarium in 2010: mechanistic and clinical considerations

Effective immunosuppression is the key to successful organ transplantation, with success being defined as minimal rejection risk with concomitant minimal drug toxicities. Despite the general recognition of this fact, a paucity of appropriate clinical trials in children has contributed to lack of standardization of clinical management regimens, resulting in an extensive diversity of favored approaches. Nonetheless, although consensus has not been reached on the ideal approach to immunosuppression in pediatric transplantation, new drug therapies have contributed to a continuing improvement in graft and patient survival. Future clinical research must focus on diminishing the extensive burden of toxicities of these therapeutic agents in children.

Transplantation immunology: solid organ and bone marrow

Development of the field of organ and tissue transplantation has accelerated remarkably since the human MHC was discovered in 1967. Matching of donor and recipient for MHC antigens has been shown to have a significant positive effect on graft acceptance. The roles of the different components of the immune system involved in the tolerance or rejection of grafts and in graft-versus-host disease have been clarified. These components include antibodies, antigen-presenting cells, helper and cytotoxic T-cell subsets, immune cell-surface molecules, signaling mechanisms, and cytokines. The development of pharmacologic and biological agents that interfere with the alloimmune response has had a crucial role in the success of organ transplantation. Combinations of these agents work synergistically, leading to lower doses of immunosuppressive drugs and reduced toxicity. Reports of significant numbers of successful solid-organ transplantations include those of the kidneys, liver, heart, and lung. The use of bone marrow transplantation for hematologic diseases, particularly hematologic malignancies and primary immunodeficiencies, has become the treatment of choice in many of these conditions. Other sources of hematopoietic stem cells are also being used, and diverse immunosuppressive drug regimens of reduced intensity are being proposed to circumvent the mortality associated with the toxicity of these drugs. Gene therapy to correct inherited diseases by means of infusion of gene-modified autologous hematopoietic stem cells has shown efficacy in 2 forms of severe combined immunodeficiency, providing an alternative to allogeneic tissue transplantation.