Mycophenolate mofetil, microemulsion cyclosporine, and prednisone as primary immunosuppression for pediatric liver transplant recipients

Chronic rejection of the liver: the role of immunosuppression

Liver transplantation is now widely recognised as an effective treatment option for patients with advanced liver disease. Many units now achieve greater than 85% survival at 1 year, with the majority of patients having a high quality of life. The maintenance of a high quality of life requires careful clinical management to ensure that the continued maintenance of excellent liver graft function is not achieved at the expense of immunosuppressive drug complications or morbidity. Acute liver rejection will occur in between 30 to 45% of patients, although with modern immunosuppressive protocols, usually combining one of the calcineurin agents, either cyclosporin or tacrolimus, with both azathioprine and corticosteroids (prednisolone) ensures that relatively few grafts are lost from severe acute rejection. While the incidence and severity of acute rejection may be one factor in raising the risk of chronic rejection, it may not be the principal one in many patients. It is important to recognise that the frequency of rejection also varies with the primary underlying liver disease, with patients with hepatitis B or alcoholic liver disease having relatively low rejection rates, compared with patients with primary biliary cirrhosis (PBC) or primary sclerosing cholangitis (PSC), which range between 20 to 70%. Chronic rejection will account for some 5% of grafts lost in the first 3 to 5 years. Indeed, there is some evidence that the incidence of chronic rejection is actually declining over the past few years. While the reason for this apparent decline is uncertain, and it could relate to better immunosuppression management, or more likely to the growing recognition that chronic graft dysfunction may be due to recurrent liver disease, such as autoimmune hepatitis, PBC, PSC, or recurrent hepatitis C. The differentiation of recurrent primary liver disease from chronic rejection can prove to be very difficult in clinical practice. Thus, the clinician must carefully monitor liver and graft function, evaluate any biochemical changes, and try to reach a clear diagnosis before considering any modification of immunosuppressive schedules.

Long term management of liver transplant rejection in children

The current management of hepatic allograft rejection after liver transplantation in children requires effective baseline immunosuppression to prevent rejection and rapid diagnosis and treatment to manage acute rejection episodes. The subsequent impact on chronic rejection is dependent on the combination of adequate prevention and the treatment of acute rejection. Tacrolimus is a macrolide lactone that inhibits the signal transduction of interleukin-2 (IL-2) via calcineurin inhibition. Introduced in 1989, tacrolimus was first used in the salvage of refractory acute or chronic rejection under cyclosporin or to rescue patients with significant cyclosporin-related complications. The majority of paediatric transplant centres use a combination of steroids with tacrolimus as a basic immunosuppressant regimen following paediatric liver transplantation. This combination has allowed the acute cellular rejection-free rate to increase to between 30 and 60%, while lowering the rate of refractory rejection to less than 5%. Corticosteroid-resistant rejection is commonly treated with monoclonal (muromonab CD3) or polyclonal preparations. Although most episodes of acute cellular rejection occur during the first 6 weeks after liver transplant, the appearance of late acute liver allograft rejection must raise the question of noncompliance, especially in the adolescent population. Chronic rejection is becoming increasingly rare under tacrolimus-based immunosuppression. Tacrolimus is effective in reversing refractory acute cellular rejection or early chronic rejection in patients initially treated with cyclosporin-based regimens. Patients with a history of noncompliance as well as children with autoimmune liver disease are at risk of chronic rejection. Retransplantation therapy for chronic rejection has, fortunately, become more rare in the tacrolimus era with only 3% of retransplants being performed for this indication. Newer immunosuppressive agents are further modifying the long term management of liver allograft rejection. These include mycophenolate mofetil, rapamycin and IL-2 antibodies such as daclizumab. The development of these agents is allowing patient-specific immunosuppressive management to minimise rejection as well as the complications related to immunosuppression.

Pharmacokinetics of mycophenolate mofetil in stable pediatric liver transplant recipients receiving mycophenolate mofetil and cyclosporine

There are few pharmacokinetic data for mycophenolate mofetil (MMF) when used in combination with cyclosporine (CsA) in pediatric liver transplant recipients. The aim of this study was to assess the pharmacokinetics of MMF in stable pediatric liver transplant patients and estimate the dose of MMF required to provide a mycophenolic acid (MPA) exposure similar to that observed in adult liver transplant recipients receiving the recommended dose of MMF (target area under the plasma concentration-time curve from 0 to 12 hours [AUC(0-12)] for MPA of 29 mug.hour/mL in the immediate posttransplantation period and 58 microg x hour/mL after 6 months). A 12-hour pharmacokinetic profile was collected for 8 pediatric patients (mean age 20.9 months) on stable doses of MMF and CsA who had received a liver transplant > or = 6 months prior to entry and who had started on MMF within 2 weeks of transplantation. Mean MMF dosage was 285 mg/m(2) (range, 200-424 mg/m(2)). Of 8 patients, 7 had a MPA AUC(0-12) (range, 11.0-37.2 microg x hour/mL) well below the target. One patient had an AUC(0-12) > or = 58 microg x hour/mL but was considered an outlier and was excluded from analyses. Mean MPA AUC(0-12) and maximum plasma concentration values were 22.7 +/- 10.5 microg x hour/mL and 7.23 +/- 3.27 microg/mL, respectively; values normalized to 600 mg/m(2) (the approved pediatric dose in renal transplantation) were 47.0 +/- 21.8 microg x hour/mL and 14.5 +/- 4.21 microg/mL. In conclusion, assuming that MPA exhibits linear pharmacokinetics, when used in combination with CsA, a MMF dose of 740 mg/m(2) twice daily would be recommended in pediatric liver transplant recipients to achieve MPA exposures similar to those observed in adult liver transplant recipients. This finding should be confirmed by a prospective trial.

Autoimmune hepatitis in children: diagnosis, pathology and treatment

Autoimmune hepatitis (AIH) is characterized by progressive inflammation of the liver and destruction of liver parenchyma. Rare in absolute terms, it is nevertheless an important cause of noninfectious chronic liver disease in children. In many ways, the diagnosis and treatment of children with AIH has changed little over the last 10 years. However, in recent years, steady progress in defining the genetic, immunologic and potential environmental triggers that underlie this disease, in addition to increasing experience with a wider array of therapeutic agents, promises to expand our understanding and ability to treat AIH effectively. This review will summarize the current clinical and pathophysiological understanding of AIH in children, along with therapeutic options.

Current issues in pediatric transplantation

Pediatric solid organ transplantation is so successful that >80% of children will survive to become teenagers and adults. Therefore, it is essential that these children maintain a good quality life, free of significant long-term side effects. While intensive immunosuppressive regimens (containing CsA, tacrolimus, MMF, and steroids) effectively reduce acute or chronic rejection, they can produce long-term side effects including viral infection, renal dysfunction, hypertension, and stunting. The development of effective methods of diagnosis, prevention, and treatment of CMV means that this is no longer a significant cause of mortality, but morbidity remains high. In contrast, infection rates of EBV remain high in EBV-negative pre-transplant patients. However, pre-emptive reduction of immunosuppression or treatment with rituximab or adoptive T-cell therapy is effective in preventing/treating post-transplant lymphoproliferative disease. Recent protocols have concentrated on reducing CsA immunosuppression, to prevent unacceptable cosmetic effects, and to reduce the hypertension, hyperlipidemia, and nephrotoxicity. Both CsA and tacrolimus cause a 30% reduction in renal function, with 4-5% of patients developing severe chronic renal failure. The use of IL-2 inhibitors for induction therapy with low-dose calcineurin inhibitors, in combination with renal-sparing drugs such as MMF or sirolimus for maintenance immunosuppression, should prevent significant renal dysfunction in the future. The concept of steroid-free immunosuppression with IL-2 inhibitors, tacrolimus, and MMF is an attractive option, which may reduce stunting and renal dysfunction. However, these regimens may be associated with the increased development of de-novo autoimmune hepatitis in 2-3% of children. The most important challenge to long-term survival in transplanted children is the management of non-adherence and other adolescent issues, particularly when transferring to adult units, as this is the time when many successful transplant survivors lose their grafts.

Mycophenolate mofetil for renal dysfunction after pediatric liver transplantation

BACKGROUND

Cyclosporine A (CsA) and tacrolimus (Tac) provide effective immunosuppression after orthotopic liver transplantation (OLT) but can cause renal dysfunction that may progress to end-stage renal failure (ESRF). Mycophenolate mofetil (MMF) is a newer immunosuppressant that does not affect renal function. Its long-term use in children with renal dysfunction after OLT has not yet been fully evaluated.

METHODS

A retrospective analysis was performed of all children begun on MMF for renal dysfunction and followed up for at least 1 year. Renal dysfunction was defined as calculated glomerular filtration rate (cGFR) of less than 65 mL/min/1.73 m2. cGFR and liver function were measured before and after transfer. Data were analyzed using the Wilcoxon signed rank test.

RESULTS

Forty-eight children (23 males) began MMF at a median age of 11.1 (0.9-18.1) years and at a median of 4.0 (0.3-12.4) years postOLT. Median baseline cGFR was 54 (range 29-65) mL/min/1.73 m2. Immunosuppression after transfer was MMF monotherapy in 36, MMF with steroids, in 4 and MMF with low-dose CsA or Tac in 8. In 44 (92%) patients, there was a statistically significant increase to a median cGFR of 69 (28-114) mL/min/1.73 m2 by 1 month and a further increase to a median cGFR of 77 (24-105) mL/min/1.73 m2 by 2 months of MMF treatment, after which time cGFR was maintained. Children aged less than 3 years at OLT or who were less than 5 years postOLT when MMF was begun demonstrated greater increases in cGFR. Four children with a median baseline cGFR of 34 (range 31-49) mL/min/1.73 m2 did not respond and progressed to ESRF. Mild side effects occurred in seven (15%) and gastrointestinal bleeding requiring discontinuation of MMF in one (2%). Liver function abnormalities occurred in seven (15%): transient transaminitis in three, acute rejection in two, and chronic rejection in two, of whom one required retransplantation.

CONCLUSIONS

In 92% children with renal dysfunction after OLT, MMF treatment provided safe and effective immunosuppression and allowed CsA or Tac to be discontinued or reduced, leading to improvement of renal function. The improvement was greatest in younger children and those who began MMF early postOLT. Side effects were uncommon. Additional steroid cover during the transfer to MMF should be considered to prevent liver-allograft rejection.

Renal function outcome in pediatric liver transplant recipients

The orthotopic liver transplantation (OLT) allows survival of children followed for severe hepatic injury, provided that the immunosuppressive treatment is prolonged. The nephrotoxicity of cyclosporine predicts the long-term outcome of the adult patients receiving a liver transplant. The aim of this study was to determine the long-term outcome of renal function in children receiving OLT. This study included 12 children, with a median for age of 7.1 yr (2-15 yr) at the time of OLT. The duration of follow-up was at least 4 yr, being 7 yr in 10 patients and more than 10 yr in seven. Renal function was evaluated with the serum level of creatinine, calculated glomerular filtration rate (cGFR), and measurement of glomerular filtration rate using chrome 51 ethylenediaminetetraacetate ((51)Cr EDTA) clearance performed at least once during follow-up. The doses and the serum concentrations (C(0)) of cyclosporine were reported at each study time. The cGFR decreased significantly 2 yr after the OLT [median (range): 106 mL/min/1.73 m(2) (71-150) at the time of OLT vs. 85 mL/min/1.73 m(2) (57-128) 2 yr after the OLT, p = 0.03], and decreased again between 7 and 10 yr after OLT [median (range): 99 mL/min/1.73 m(2) (76-125) 7 yr after OLT vs. 81 mL/min/1.73 m(2) (66-140) 10 yr after OLT, p = 0.04]. Six patients developed chronic renal failure (cGFR from 57 to 80 mL/min/1.73 m(2)) 2 yr after OLT associated with high doses of cyclosporine [median (range): 8.8 mg/kg/day (3.5-13)]. The cGFR overestimated renal function by 16% compared with the isotopic measurement of GFR (p = 0.03). Using the (51)Cr EDTA measurement, six of seven patients followed up more than 10 yr after OLT presented mild (n = 3) or moderate (n = 3) chronic renal failure. In our study, the majority of OLT recipients developed a chronic renal failure 10 yr after transplantation. Cyclosporine seems to be the most important factor responsible for the impairment of renal function. The use of the mycophenolate mofetil, a new immunosuppressive agent, allowing a reduction in the dose of cyclosporine, could minimize renal dysfunction. While awaiting the results of a prospective long-term study, close drug monitoring is advised.

Successful use of anti-CD20 monoclonal antibody (rituximab) for ABO-incompatible living-related liver transplantation

BACKGROUND

Humoral rejection after ABO-incompatible liver transplantation often causes graft loss and a life-threatening situation. We used rituximab, which can eliminate B cells highly selectively, as an additional therapy for ABO-incompatible living-related liver transplantation.

CASES

Patient 1 was a 1-year-old girl with biliary atresia. Her blood type was O, and the donor's was A. She underwent two plasma exchanges before liver transplantation and had triple immunosuppressants (mycophenolate mofetil, tacrolimus, and methylprednisolone). She was diagnosed with humoral rejection by needle biopsy on postoperative day 6. Rituximab was used for 3 days at 375, 187, and 187 mg/m(2) and successfully reduced the antibody titer, transaminase, and CD19(+) cells count in peripheral blood lymphocytes. The patient has not had any severe rejection, infection, or serious complications 2 years posttransplantation. Patient 2 was a 42-year-old woman with primary biliary cirrhosis. The blood type was O, and the donor's was B. She received three plasma exchanges, triple immunosuppressants, splenectomy, intraarterial anticoagulant therapy, and rituximab (375 mg/m(2) immediately after transplantation). The titer and CD19(+) cells count remained persistently low throughout the recovery course. She did not develop humoral rejection 1 year after transplantation.

CONCLUSIONS

Rituximab efficiently reduces anti-ABO antibody titer by selectively eliminating B cells and is safe and effective against humoral rejection after ABO-incompatible liver transplantation.

Current status of liver transplantation

Liver transplantation is accepted therapy for acute or chronic liver failure. Survival after LT has improved significantly in developed countries and this has increased the awareness of this treatment modality in the developing world. Successful LT in both children and adults have now been reported from India. Chronic liver failure secondary to cholestatic liver disease in the most frequent indication for LT, with biliary with atresia as the single commonest cause. Innovative techniques such as reduced size, splint, and living donor liver transplantation are being applied more often to decrease long waiting times and reduce associated morbidity and mortality. Early postoperative complications include primary graft failure, venous thrombosis, rejection, biliary complications and infections. Late complication includes CMV or EBV infections, side effects of immunosuppression, post transplantation lymphoproliferative disease and late biliary strictures. Most children achieve good quality of life. There are still many lessons to learn and there are future challenges such as the ever increasing problems of donor scarcity and the search for potent but less toxic immunosuppressive agents.

Strategies for optimizing immunosuppression in adolescent transplant recipients: a focus on liver transplantation

Adolescence is a difficult time for transplant recipients; they must learn to take responsibility for their own behavior and medication, and to balance their developing sexuality in a body that has been transformed by the adverse effects of immunosuppression. More than 80% of children survive transplantation to adolescence and adulthood, thus long-term outcome and tailoring of immunosuppression is of great importance. To date, the most experience with long-term immunosuppression regimens is cyclosporine, which is well tolerated and effective. Long-term adverse effects include hypertension, nephrotoxicity, and post-transplant lymphoproliferative disease (PTLD). The recent development of tacrolimus has improved the cosmetic adverse effects related to cyclosporine, but has similar rates of hypertension and nephrotoxicity, and possibly a higher rate of PTLD. There has been a recent, welcome development in renal sparing drugs, such as mycophenolate mofetil, which has no cosmetic adverse effects, does not require drug level monitoring and is thus particularly attractive to teenagers. Recent surveys demonstrate recovery of renal function with mycophenolate mofetil, if started prior to irreversible renal dysfunction. There are currently little published data on the use of sirolimus (rapamycin) in the pediatric population, but preliminary studies suggest that the future use of interleukin-2 receptor antibodies may be beneficial for immediate post-transplant induction of immunosuppression. It is important when planning immunosuppression for adolescents to consider the effects of drug therapy on both males and females in order to maintain fertility and to ensure safety in pregnancy. Noncompliance is a problem in this age group, but adequate practical measures and support should reduce noncompliance, and allow good, long-term graft function.

Therapy for acute rejection in pediatric organ transplant recipients

Despite the availability of potent immunosuppressive drugs, rejection after organ transplantation in children remains a serious concern, and may lead to significant morbidity, graft loss, and death of the patient. Acute graft rejection in pediatric recipients is first treated with methylprednisolone pulses, followed by progressive taper of corticosteroid doses. After control of the rejection episode, baseline immunosuppression has to be adjusted and closely monitored since rejection (especially late episodes, occurring more than 6 months after transplantation) may be due to a lack of compliance or sub-therapeutic drug concentrations. The management of corticosteroid resistant rejection is not standardized, and depends on the transplanted organ and previous immunosuppressive regimen. In patients experiencing corticosteroid resistant acute rejection while on a cyclosporine-based immunosuppressive regimen, cyclosporine is generally changed to tacrolimus. In case of tacrolimus-based immunosuppression, tacrolimus blood levels may be increased, and/or mycophenolate mofetil (which nowadays tends to replace azathioprine) or sirolimus may be added, although pharmacodynamic data and clinical studies with these agents are still scarce in pediatric recipients. The use of antithymocyte globulins or monoclonal anti-CD3 antibodies, muromonab CD3 (OKT3) is hampered by numerous adverse effects, including a significant risk of over-immunosuppression. These therapies are nowadays indicated in very selected cases. Other treatments such as plasmapheresis and high dose immunoglobulins may be useful in difficult cases. In patients with refractory rejection despite therapeutic escalation, the risks of over-immunosuppression, including opportunistic infections and malignancies (especially the Epstein-Barr virus related post-transplant lymphoproliferative disease) have to be balanced with the consequences of graft loss due to rejection. Detransplantation or retransplantation may, in some instances, be preferable to severe infectious or tumoral complications.

Mycophenolic acid pharmacokinetics in pediatric liver transplant recipients

The aim of this study is to study mycophenolic acid (MPA) pharmacokinetics in stable pediatric liver transplant recipients and determine which times best represent the area under the concentration versus time curve (AUC) of MPA plasma concentrations. MPA pharmacokinetic profiles were determined in 21 liver transplant recipients (age, 2 to 15 years; 12 boys) administered mycophenolate mofetil (MMF) for at least 6 months. Ten patients were coadministered cyclosporine A (CsA), and 11 patients were coadministered tacrolimus (Tac). Plasma MPA levels were analyzed by enzyme-multiplied immunoassay technique in blood samples at 0, 0.33, 0.67, 1.25, 2, 3.5, 5, and 7 hours after MMF administration. The AUC of plasma concentrations to 7 hours (AUC(0-7)) was calculated using the linear trapezoidal rule. MPA plasma trough concentration (C(0)), maximal concentration, and AUC(0-7) values ranged 9- to 14-fold at a median of 1.81 mg/L (range, 0.4 to 3.7 mg/L), 10.5 mg/L (range, 2.8 to 40.0 mg/L), and 30.2 mg/L.hr (range, 9.3 to 80.3 mg/L.hr), respectively. AUC(0-7) correlated significantly with MMF dose (r = 0.552; P =.010) and C(0) (r = 0.844; P <.001). Median AUC(0-7) (29.6 v 31.4 mg/L.hr; P =.918) was similar in children comedicated with CsA or Tac. Median MMF dose was greater in the CsA group (500 v 250 mg; P =.006). Consequently, median AUC(0-7) was significantly lower in the CsA group when equalized for dose and body weight (2.02 v 3.85 microg/L.hr per mg of MMF dose per kg of weight; P =.002). Variations of MPA pharmacokinetics in pediatric liver transplant recipients suggest that monitoring MPA plasma levels is required. C(0) correlates closely with AUC. Comedication with CsA increased MMF dosage requirements compared with children on Tac therapy.

Prophylaxis and treatment of gastrointestinal complications following transplantation

Most transplant recipients will experience some type of gastrointestinal (GI) complication. These effects often are caused by infectious damage induced by a variety of opportunistic organisms, but they also may be due to mechanical injury during surgery or to metabolic or organ toxicity associated with immunosuppressive regimens. Although some of these GI complications can substantially impair quality of life or even carry significant mortality risk, many of them can be prevented, and most of them can be treated medically without the need to stop immunosuppression and expose the patient to the risk of rejection. Limiting the use of steroids, giving prophylactic antiviral and antifungal agents (particularly to patients at risk) and adopting a low threshold for endoscopy are among the most important measures that can be used to avoid GI complications after transplantation.

Management of the pediatric liver transplant patient

1. In pretransplant management, the prevention and treatment of malnutrition is essential for pediatric patients as malnutrition is associated with both increased pre- and posttransplant mortality. 2. Technical complications, particularly hepatic artery thrombosis, after pediatric liver transplantation are relatively common given the small size of the majority of the recipients. Early recognition is essential to reduce the associated increased risk for both patient and graft loss. 3. Immunosuppression regimens in children should aim to begin weaning of steroids within the first year after transplant because of their detrimental impact on growth. 4. Long-term immunosuppression strategies must focus on avoiding the risks of long-term immunosuppression, particularly nephrotoxicity, neurotoxicity, de novo malignancy, and late infections. 5. EBV-associated PTLD is a special problem for young pediatric liver recipients. Strategies for prevention and preemptive management are essential. 6. Noncompliance in teens is a particular problem and is associated not only with graft dysfunction, but also with graft loss and patient death. Recognizing teens at risk and providing intervention strategies require a multi-disciplinary approach.

Immunosuppressive drugs in paediatric liver transplantation

Orthotopic liver transplantation is established treatment for children with acute and chronic liver failure. Despite advances in pre- and postoperative management, innovative surgical techniques and new immunosuppressive drugs, acute and chronic rejection remains a problem. In addition, well established adverse effects of commonly used immunosuppressive drugs are no longer accept able. More potent, but less toxic, immunosuppressive agents have been developed and some novel compounds are now entering routine practice. Cyclosporin was the cornerstone of immunosuppressive therapy until the introduction of its novel pharmaceutical form (Neoral) with improved bioavailability, lower inter- and intraindividual pharmacokinetic variability and improved graft survival. Recently, tacrolimus, a macrolide drug with a similar mode of action, but much higher potency, was introduced and, at present, is the only agent which can successfully replace cyclosporin as a first-line immunosuppressive drug. Mycophenolate mofetil has recently been approved for use in adult and paediatric renal transplant recipients. It has a similar mode of action to cyclosporin and tacrolimus, but acts at a later stage of the T cell activation pathway. Administration with standard immunosuppressive drugs reduces the incidence of acute rejection and enables cyclosporin and tacrolimus dose reduction, thus reducing the risk of associated toxic effects. Phase I and II trials with sirolimus (rapamycin), a macrolide antibiotic, have shown comparable immunosuppressive action, when administered in conjunction with standard immunosuppressants. Further clinical trials need to be carried out to establish efficacy, tolerability and pharmacokinetics in paediatric transplant recipients. Monoclonal antibody therapy (daclizumab and basiliximab) is an exciting new development whereby T cell proliferation is inhibited by selective blockade of interleukin (IL)-2 receptors. Preliminary results, when used in combination with a standard immunosuppressive regimen, are good with respect to incidence of acute graft rejection, host immune response and adverse effects. FTY720 is a novel synthetic immunosuppressive compound which induces a reduction in peripheral blood lymphocyte count through apoptotic T cell death or accelerated trafficking of T cells into lymphatic tissues. Experimental animal studies demonstrated synergistic action in combination with low dose cyclosporin or tacrolimus, potentiating their immunosuppressive effects. Further studies are being carried out to determine its potential for application in organ transplantation. Despite this rapid development of novel compounds, it will take many years before they may become part of standard protocols in paediatric transplantation medicine. Further development and research of efficacy and tolerability of existing drugs is, therefore, vital.

Elevated tacrolimus trough levels in association with mycophenolate mofetil-induced diarrhea: a case report

The combination of tacrolimus (TAC) and mycophenolate mofetil (MMF) is frequently used for immunosuppression after organ transplantation (Tx), but the pharmacokinetics and interactions between the two drugs are poorly elucidated. We describe here the increase of TAC trough levels during MMF-induced diarrhea in a 8-yr-old boy after kidney Tx. Early dose reduction of TAC, together with short-term monitoring of TAC trough levels in the presence of diarrhea, is recommended.

B-cell dysfunction and depletion using mycophenolate mofetil in a pediatric combined liver and kidney graft recipient

The use of mycophenolate mofetil (MMF) in combination with cyclosporin A (CsA) and steroids is well established after kidney transplantation (Tx) in children. A 9-yr-old girl with primary hyperoxaluria type 1 and systemic oxalosis underwent a combined kidney and liver Tx at our institution. The post-operative immunosuppression consisted of CsA, prednisolone, and MMF. Four weeks post-transplant the girl suffered from a severe urinary tract infection caused by Pseudomonas aeruginosa, when the serum immunoglobulin G (IgG) concentration was found to be critically low (<1.53 g/L). Additionally, there was an isolated B-cell depletion (240/microL) at that time. In the following course, the B-cell count was significantly diminished until the MMF was stopped 13 weeks post-transplant. As a result of the very low serum IgG concentration, intravenous immunoglobulin (IVIG) substitution was necessary. There was no significant loss of immunoglobulins in the ascites and urine and no other medication with possible side-effects on B cells was given. We suggest that MMF can lead to suppressed IgG production by B cells and can cause a defective differentiation into mature B cells. In vitro studies demonstrated these effects of MMF on B cells, but no in vivo cases of this phenomenon have been reported. B-cell counts and serum IgG concentrations returned to normal values after discontinuing the MMF. As we can assume that the observed B-cell dysfunction and depletion were MMF related, we suggest that serum IgG concentrations should be monitored when MMF is used after solid-organ Tx.

Use of mycophenolate mofetil as rescue therapy after pediatric liver transplantation

BACKGROUND

Mycophenolate mofetil (MMF) has been increasingly used after liver transplantation (LT) in adults. We report our preliminary experience with MMF as rescue therapy after pediatric LT.

METHODS

A total of 19 children received MMF for 21 indications. Median age at LT was 30 months (range 7-149). The median initial oral dose of MMF was 23 mg/kg/day (range 12-43) orally. Median follow-up after initiation of MMF therapy was 642 days (range 229-1606).

RESULTS

1) EFFICACY: MMF was indicated for rejection or insufficient immunosuppression in 16 cases, with normalization of both liver function tests and liver histology in 10 (62%). MMF was successfully used in one patient with post-LT immmune hepatitis and one patient with corticodependence. In three patients with renal function impairment, MMF allowed reduction of cyclosporine A or tacrolimus blood levels, without subsequent rejection. 2) Tolerance: Six patients (32%) experienced eight side effects, mainly gastrointestinal and hematological, which resolved after cessation of MMF in five cases and dose reduction in three. One case of posttransplant lymphoproliferative disease (PTLD) occurred under MMF therapy (5.2%). Four patients had EBV primary infection, while under MMF therapy, without subsequent PTLD. Three patients had CMV primary infection, and five CMV reactivation, under MMF therapy. Seven remained asymptomatic, and one presented with CMV enteritis.

CONCLUSIONS

These preliminary results suggest that MMF is an effective and safe immunosuppressant in pediatric LT recipients. Its use is hampered by frequent gastrointestinal and hematological side-effects. MMF does not seem to increase the risk of PTLD nor CMV disease.

Liver transplantation. The pediatric challenge

Successful liver transplantation in a child is often a hard-won victory, requiring all the combined expertise of a dedicated pediatric transplant team. This article outlines the considerable challenges still facing pediatric liver transplant physicians and surgeons. In looking to the future, where should priorities lie to enhance the success already achieved? First, solutions to the donor shortage must be sought aggressively by increasing the use of from split-liver transplants, judicious application of living-donor programs, and increasing the donation rate, perhaps by innovative means. The major immunologic barriers, to successful xenotransplantation make it unlikely that this option will be tenable in the near future. Second, current immunosuppression is nonspecific, toxic, and unable to be individually adjusted to the patient's immune response. The goal of achieving donor-specific tolerance will require new consideration of induction protocols. Developing a clinically applicable method to measure the recipient's immunoreactivity is of paramount importance, for future studies of new immunosuppressive strategies and to address the immediate concern of long-term over-immunosuppression. The inclusion of pediatric patients in new protocols will require the ongoing insistence of pediatric transplant investigators. Third, the current immunosuppressive drugs have a long-term morbidity and mortality of their own. These long-term effects are particularly important in children who may well have decades of exposure to these therapies. There is now some understanding of their long-term renal toxicity and the risk of malignancy. New drugs may obviate renal toxicity, whereas the risk of malignancy is inherent in any nonspecific immunosuppressive regimen. Although progress is being made in preventing and recognizing PTLD, this entity remains an important ongoing concern. The global effect of long-term immunosuppression on the child's growth, development, and intellectual potential is unknown. Of particular concern is the potential for neurotoxicity from the calcineurin inhibitors. Fourth, recurrent disease and new diseases, perhaps potentiated by immunosuppressive drugs, must be considered. Already the recurrence of autoimmune disease and cryptogenic cirrhosis have been documented in pediatric patients. Now, a new lesion, a nonspecific hepatitis, sometimes with positive autoimmune markers, that may progress to cirrhosis has been recognized. It is not known whether this entity is an unusual form of rejection, an unrecognized viral infection, or a response to immunosuppressive drugs themselves. Finally, pediatric transplant recipients, like any other children, must be protected and nourished physically and mentally if they are to fulfill their potential. After liver transplantation the child's growth, intellectual functioning, and psychologic adaptation may all require special attention from parents, teachers, and physicians alike. There is limited understanding of how the enormous physical intervention of a liver transplantation affects a child's cognitive and psychologic function as the child progresses through life. The persons caring for these children have the difficult responsibility of providing services to evaluate these essential measures of children's health over the long term and to intervene if necessary. Part of the transplant physician's our duty to protect and advocate for children is to fight for equal access to health care. In most of the developing world, economic pressures make it impossible to consider liver transplantation a health care priority. In the United States and in other countries with the medical infrastructure to support liver transplantation, however, health care professionals must strive to be sure that the policies governing candidacy for transplantation and allocation of organs are applied justly and uniformly to all children whose lives are threatened by liver disease. In the current regulatory climate that increasingly takes medical decisions out of the hands of physicians, pediatricians must be even more prepared to protect the unique and often complicated needs of children both before and after transplantation. Only in this way can the challenges of the present and the future be met.

Overview of new immunosuppressive therapies

This review covers the new immunosuppressive drugs that have appeared in the past 5 years. It begins with the newest formulation (Neoral, Sandoz Pharmaceuticals, East Hanover, NJ, USA) of the clinically "mature" drug cyclosporin A and then reviews the literature on tacrolimus, sirolimus, and mycophenolate mofetil. In each case, the emphasis is on the evolution of experience with the drug and on the questions that the drug poses for pediatricians considering the risk-benefit ratio of the drug in children.