Long-term functional islet mass and metabolic function after xenoislet transplantation in primates

BACKGROUND

Pancreatic islet transplantation (PIT) is an attractive alternative for patients with type I diabetes mellitus. PIT is not yet an effective clinical reality due in part to the high incidence of rejection and early loss of functional islet mass. In addition, current immunosuppressive drugs have toxic effects on islets and increase the risk of morbidity and mortality. In the present study, the effects of PIT on glycemic parameters were assessed in spontaneously diabetic primates.

METHODS

Five insulinopenic nonhuman primates (three Macacca fascicularis, one Ceropithecus aethiops, and one Macacca mulatta) were studied. All required twice-daily treatment with 4-10 U of insulin. For immunosuppression, the animals received anti-CD3-immunotoxin (100 microg/kg(initially infused 2 hr before transplantation and again on day +1), cyclosporine (CsA) (20 mg/kg(i.v./2 hr before transplantation), cyclosporine microemulsion (Neoral) 60 mg/kg/b.i.d. on days +1 to +3 with dose adjusted by blood levels, and methylprednisolone (15 mg/kg day 0 to +3). Three recipients were given islets from a single donor (M mulatta). The islets were prepared by a semiautomated technique using Liberase. A mean of 13,136 islet equivalents/kg was infused into the portal vein. Two animals (M fascicularis and M mulatta) were used as a diabetic, nontransplanted control. Several metabolic parameters were evaluated.

RESULTS

All monkeys that underwent transplantation experienced reversal of diabetes mellitus with normalization of all diabetic glycemic parameters. In the nontransplanted primates given the same immunosuppression but no PIT, diabetic metabolic parameters were unchanged after 9 months of follow-up. In contrast, all three PIT recipients established fasting and nonfasting euglycemia within 1-2 weeks, and none required exogenous insulin after day 10. Normal intravenous glucose tolerance tests were observed at day 15, and no significant differences in the glucose disappearance rate (Kg) were observed at days 15, 45, 190, and 365 days after transplantation. The acute insulin response to glucose indicated no significant reduction of functional islet mass.

CONCLUSIONS

PIT in severely insulinopenic type I diabetes mellitus primates resulted in restoration of normal glycemic parameters and durable islet mass. Operational tolerance was achieved with only 4 days of drug administration, sparing the animals from chronic exposure to potentially diabetogenic immunosuppressive drugs. These results offer an exciting new potential for type I diabetes mellitus treatment.

Role of ERCP in asymptomatic orthotopic liver transplant patients with abnormal liver enzymes

OBJECTIVE

The safety and efficacy of endoscopic retrograde cholangiopancreatography (ERCP) in the evaluation and management of biliary tract complications after orthotopic liver transplantation (OLT) have been previously demonstrated. However, the role of ERCP in evaluating asymptomatic OLT patients with abnormal liver enzymes with a previously normal biliary tree remains poorly defined. We sought to assess the utility of ERCP in this subset of patients.

METHODS

A retrospective analysis of-asymptomatic OLT patients with abnormal liver enzymes evaluated by ERCP was undertaken. In addition to ERCP, all these patients had a diagnostic abdominal Doppler ultrasound, and a percutaneous liver biopsy. All patients had choledochocholedochostomy at the time of transplant and normal T-tube cholangiograms 3 months postoperatively. A radiologist, blinded to clinical findings, interpreted the ultrasound as normal, biliary dilation, or vascular abnormalities. The same radiologist interpreted ERCP findings. A pathologist, blinded to clinical findings, graded liver biopsies as normal, diagnostic, or abnormal but nondiagnostic.

RESULTS

Twenty-two patients underwent 23 ERCPs. Twenty-two of the 23 ERCPs were normal (96%), and one abnormal ERCP finding did not explain the liver enzyme abnormality. Liver biopsy was diagnostic in 13 of 22 (57%) and in each case the ERCP was normal. The remaining 10 liver biopsies were abnormal but nondiagnostic. Ultrasound was abnormal in five of 22 cases, but in the three cases suggesting biliary dilation, the ERCP was interpreted as normal.

CONCLUSION

Routine use of ERCP in evaluation of asymptomatic OLT patients with liver function test abnormalities and normal cholangiograms at 3 months was not diagnostically useful. In this subset of patients, liver biopsy was usually abnormal and frequently diagnostic and should be the initial invasive diagnostic procedure.

Genetically modified CD34+ cells as cellular vehicles for gene delivery into areas of angiogenesis in a rhesus model

To develop a cellular vehicle able to reach systemically disseminated areas of angiogenesis, we sought to exploit the natural tropism of circulating endothelial progenitor cells (EPCs). Primate CD34+ EPCs were genetically modified with high efficiency and minimal toxicity using a non-replicative herpes virus vector. These EPCs localized in a skin autograft model of angiogenesis in rhesus monkeys, and sustained the expression of a reporter gene for several weeks while circulating in the blood. In animals infused with autologous CD34+ EPCs transduced with a thymidine kinase-encoding herpes virus, skin autografts and subcutaneous Matrigel pellets impregnated with vascular growth factors underwent necrosis or accelerated regression after administration of ganciclovir. Importantly, the whole intervention was perfectly well tolerated. The accessibility, easy manipulation, lack of immunogenicity of the autologous CD34+ cell vehicles, and tropism for areas of angiogenesis render autologous CD34+ circulating endothelial progenitors as ideal candidates for exploration of their use as cellular vehicles when systemic gene delivery to those areas is required. Gene Therapy (2000) 7, 43-52.

Peritransplant tolerance induction in macaques: early events reflecting the unique synergy between immunotoxin and deoxyspergualin

BACKGROUND

Day of transplant T cell depletion with anti-CD3 immunotoxin or F(Ab)2 immunotoxin induces stable tolerance to renal allografts in rhesus monkeys given 15-deoxyspergualin (DSG), a NF-kappaB inhibitor that suppresses proinflammatory cytokine (PC) production. Because PC and NF-kappaB are involved in dendritic cell (DC) maturation, we asked if impaired DC maturation and Th2-type cytokine deviation might be related to the synergistic effect of DSG in this novel model.

METHODS

Immunosuppression was initiated 4 hr before transplanting a major histocompatibility complex mismatched renal allograft. Some groups received a supplemental 5-day course of cyclosporine A or DSG or a 15-day course of DSG. Peripheral lymph nodes were sequentially examined for presence of mature DC. In vitro effects of DSG on PC-induced maturation of DC were also examined.

RESULTS

Allografts survived without rejection in 87% of recipients given immunotoxin or F(Ab)2 immunotoxin with DSG x 15 days, in 50% with DSG x 5 days, and 0% with cyclosporine A. The longest DSG survivors are >1000 days with normal graft function and tolerance validated, including acceptance of challenge second donor kidneys without treatment. DSG-treated recipients were unique in developing polarized Th2-type plasma cytokines. In DSG recipients, mature DC were significantly reduced in day +5 lymph node biopsies, with complete repopulation by 30 days. In vitro studies verified an inhibitory effect of DSG on DC maturation.

CONCLUSIONS

The study suggests DSG arrests DC maturation. The unusual synergy of immunotoxin and DSG apparently involves coincidental reduction in lymph node T cell mass and mature DC, a transient circumstance favoring development of stable tolerance.

Anoikis, extracellular matrix, and apoptosis factors in isolated cell transplantation

BACKGROUND

Isolated cell transplantation (ICT) of pancreatic islets (PI), nerve tissue, hepatocytes, and other cells is an exciting new concept of transplantation. PI transplantation can be successful in reversing diabetes but, unlike whole pancreas, grafts have a unique and unexplained high failure rate, with over 60% loss by 3 to 6 months. We established that PI of rhesus monkeys have a high rate of death within 48 hours of isolation as a result of apoptosis, as measured with the Annexin V assay (Pharmingen, San Diego, Calif). In contrast, PI incompletely separated from the extracellular matrix (ECM) remained viable for prolonged periods in culture and performed superiorly in perifusion assays (insulin secretion of 4.6 +/- 0.8 times basal secretion).

METHODS

We studied the ability of the anti-AP Bcl-2 molecule, known to block anoikis (a mechanism of AP due to cell-ECM separation), to prevent apoptosis of isolated PI.

RESULTS

PI transduced with an adenovirus-Bcl-2 gene complex showed a high viability and a low AP rate in culture versus control rhesus PI.

CONCLUSION

In summary, PI protected from AP by a surrounding ECM mantle or by Adenovirol Vector (AdV) transduction of the Bcl-2 gene showed superior viability without AP in vitro and in vivo evidence of a preserved insulin secretion response to glucose.

Reduction of ischemia-reperfusion injury of the liver by in vivo adenovirus-mediated gene transfer of the antiapoptotic Bcl-2 gene

OBJECTIVE

To examine the possibility of reducing ischemia-reperfusion injury (I/R injury) to the mouse liver by in vivo adenovirus-mediated gene transfer of the antiapoptotic human Bcl-2 gene.

SUMMARY BACKGROUND DATA

Ischemia-reperfusion injury has been demonstrated in a number of clinically relevant diseases such as myocardial infarction, cerebrovascular disease, sepsis, peripheral vascular disease, and organ transplantation. In this regard, apoptosis plays a central role.

METHODS

Normal C57BL/6 mice were used. An adenovirus (deltaE1) vector containing the human Bcl-2 gene was developed in the authors' laboratory. An adenovirus vector encoding an irrelevant gene (beta-galactosidase, AdCMVLacZ) was used as a control. Taking advantage of the hepatotropic properties of adenovirus vectors, gene transfer was performed with 1 x 10(9) plaque-forming units by intravenous tail injection, 48 hours before the ischemic injury. Ischemic-reperfusion injury was induced by temporal and segmental occlusion of hepatic blood flow. Aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase activity was measured using standard assays. Liver biopsies were obtained before and 6 hours after I/R injury for morphologic assessment, and apoptosis was determined in situ with a histochemical assay.

RESULTS

The expression of AdCMVhBcl-2 vector was confirmed by reverse transcription-polymerase chain reaction and functionally validated in apoptotic studies in endothelial cells. Expression of the Bcl-2 gene protects against I/R injury, as shown by a significant decrease in transaminases (p < 0.05) and necrosis and apoptosis (p < 0.001), and permanent survival (p < 0.0001), compared with sham-operated animals and animals treated with AdCMVLacZ.

CONCLUSIONS

Genetic modification of the liver to induce cytoprotection has potential applications to prevent I/R injury to the liver in surgical interventions, including liver transplantation.

Adenovirus-mediated gene expression in vivo is enhanced by the antiapoptotic bcl-2 gene

An adenovirus vector encoding the human Bcl-2 gene (hBcl-2) was derived. In vivo expression of hBcl-2 in murine livers enhanced and prolonged adenovirus-mediated gene expression. Furthermore, in the hBcl-2-treated group a significant reduction in the apoptosis induced by the adenovirus vector was observed. Thus, the cytoprotection of the vector-infected cells with antiapoptotic genes appears promising for successful in vivo gene therapy.

Anoikis, extracellular matrix, and apoptosis factors in isolated cell transplantation

BACKGROUND

Isolated cell transplantation (ICT) of pancreatic islets (PI), nerve tissue, hepatocytes, and other cells is an exciting new concept of transplantation. PI transplantation can be successful in reversing diabetes but, unlike whole pancreas, grafts have a unique and unexplained high failure rate, with over 60% loss by 3 to 6 months. We established that PI of rhesus monkeys have a high rate of death within 48 hours of isolation as a result of apoptosis, as measured with the Annexin V assay (Pharmingen, San Diego, Calif). In contrast, PI incompletely separated from the extracellular matrix (ECM) remained viable for prolonged periods in culture and performed superiorly in perifusion assays (insulin secretion of 4.6 +/- 0.8 times basal secretion).

METHODS

We studied the ability of the anti-AP Bcl-2 molecule, known to block anoikis (a mechanism of AP due to cell-ECM separation), to prevent apoptosis of isolated PI.

RESULTS

PI transduced with an adenovirus-Bcl-2 gene complex showed a high viability and a low AP rate in culture versus control rhesus PI.

CONCLUSION

In summary, PI protected from AP by a surrounding ECM mantle or by Adenovirol Vector (AdV) transduction of the Bcl-2 gene showed superior viability without AP in vitro and in vivo evidence of a preserved insulin secretion response to glucose.

Tolerability and side effects of anti-CD3-immunotoxin in preclinical testing in kidney and pancreatic islet transplant recipients

INTRODUCTION

Anti-CD3-immunotoxin (alpha-CD3-IT) promotes allograft tolerance in nonhuman primates owing to efficient depletion of sessile and circulating T cells. Common side effects of vascular leak syndrome, hepatotoxicity, and nephrotoxicity have limited tolerability of other immunotoxins. We report on preclinical studies of alpha-CD3-IT-related side effects.

METHODS

Normal rhesus monkeys received a kidney transplant and alpha-CD3-IT alone (on day -to +2) or in combination with brief peritransplant adjunctive immunosuppressive therapy. Some received donor CD34+ cells. Blood chemistries, complete blood count, weight, liver, and kidney biopsies were examined for immunotoxin-related changes. Five spontaneously diabetic primates also received alpha-CD3-IT, three of whom had a pancreas islet transplant.

RESULTS

The main side effect of alpha-CD3-IT, vascular leak syndrome, was entirely prevented by adjunctive immunosuppressive therapy. Renal and liver function tests and biopsies revealed a lack of nephrotoxicity and hepatotoxicity. All had transient weight loss (14+/-5%). Without infusion of donor CD34+ cells, 97% had full weight recovery. Of those given donor CD34+ cells, 50% were euthanized for wasting.

CONCLUSIONS

Side effects of alpha-CD3-IT are manageable and should not prevent therapeutic application.

Reversal of naturally occuring diabetes in primates by unmodified islet xenografts without chronic immunosuppression

BACKGROUND

Isolated pancreatic islet transplantation (IPITx) is an attractive alternative for treatment of insulin-dependent diabetes mellitus (IDDM). However, IPITx has been difficult to implement clinically because islets frequently fail to function, have a high incidence of rejection, and are susceptible to autoimmune recurrence and damage by chronic immunosuppressive therapy. Tolerance induction may be a rational approach to resolve several of these limitations. Because anti-CD3 immunotoxin (IT) has been successful in promoting stable primate kidney transplant tolerance in our experience, we considered that tolerance induction with IT might be duplicated in IPITx.

MATERIALS AND METHODS

Three monkeys with spontaneous IDDM (two Macaca fascicularis and one Ceropithecus aethiops) were treated with xenogeneic pancreatic islets (Macaca mulatta). Intrahepatic islet transplantation was performed at a mean of 13136+/-3860 islet equivalents/kg. Islet xenograft acceptance was accomplished by tolerance induction with two injections of IT given on day 0 at 2 hr before transplantation and on day +1, respectively. IT treatment was supplemented with cyclosporine and steroids administered on days 0 through 4. No additional immunosuppression was given thereafter. Two additional control macaques with spontaneous IDDM received the immunosuppressive protocol without islet infusion.

RESULTS

All recipients were restored to stable euglycemia, off exogenous insulin, within 1-2 weeks after transplantation. Glucose tolerance, C-peptide, and glycosylated hemoglobin tests confirmed the restoration of normal glucose homeostasis after islet transplantation. All three islet recipients have remained euglycemic at 410, 255, and 100 days of follow-up despite recovery of peripheral T cells to normal levels. In contrast, none of the controls presented changes in the diabetic status 4 and 8 months after treatment.

CONCLUSIONS

These results represent the first demonstration in nonhuman primates of stable, long-term acceptance of nonencapsulated xenogeneic islets off all immunosuppression, suggesting operational tolerance. The findings have potential implications for islet transplantation as well as improved and more cost-effective therapy for IDDM.

Genetic modification of liver grafts with an adenoviral vector encoding the Bcl-2 gene improves organ preservation

BACKGROUND

Liver function after transplantation is determined by the quality of the donor organ and the influences of preservation, flush, and reperfusion injury. In this regard, cell death (apoptosis) plays an important role in organ preservation and rejection. Therefore, we examined the possibility of genetic modification of the liver graft with a recombinant adenovirus vector encoding the Bcl-2 gene to reduce apoptosis during the preservation time.

METHODS

Liver grafts from C57B1/6 mice were procured and preserved using standard techniques. A replication defective adenovirus vector (deltaE1) containing the human Bcl-2 gene (AdCMVhBcl-2) was developed in our laboratory. An adenovirus vector encoding an irrelevant gene (Escherichia coli beta-galactosidase) was used as a control. Each mouse received 1 x 10(9) plaque forming units administered i.v. 48 hr before the liver procurement. Analyses of liver enzyme activities were determined in the preservation solution. Apoptosis in liver biopsies was determined by DNA fragmentation with an in situ histochemical assay.

RESULTS

Immunohistochemical analysis and RT-PCR confirmed the expression of hBcl-2 in the grafts. Grafts from livers expressing hBcl-2 showed significant reduction of the aspartame amino transferase (AST) and lactate dehydrogenase (LDH) release compared with grafts from the control groups. After rewarming, significant cytoprotection was also observed in grafts from animals treated with AdCMVhBcl-2. Histological analysis correlated with the hepatocellular injury determined with transaminases and LDH in the preservation solution. Significant reduction in the number of apoptotic cells was observed in grafts expressing hBcl-2.

CONCLUSIONS

We have demonstrated a novel approach to reducing the preservation injury to liver grafts with the human Bcl-2 gene. This approach may allow a longer preservation time, potentially reduce the incidence of primary nonfunction, decrease the immunogenicity of the cold injured organ, and increase the safer use of "marginal" liver grafts.

Immunoregulatory role of CD8alpha in the veto effect

BACKGROUND

Allogeneic bone marrow cell (allo-BMC) infusion induces tolerance to incompatible renal allografts in rhesus macaques after depletion of peripheral T lymphocytes with cytolytic anti-T cell antibodies. The tolerogenic effect of allo-BMC, ascribed to a veto mechanism, associates with specific functional deletion of antidonor cytotoxic T lymphocyte precursor (CTLp), and is dependent on a CD8+ donor BMC subset. In previous studies, the CD8 molecule was implicated by loss of suppression after blocking interaction between CD8 on allo-BMC and major histocompatibility complex class Ialpha3 domain on CTLp. CD8 cross-linking on BMC induced secretion of active transforming growth factor-beta1 (TGF-beta1), suggesting a regulatory mechanism(s) operating via a CD8-mediated signaling pathway.

METHODS

CD8 on rhesus cells was cross-linked using IgG-conjugated beads, and TGF-beta1 mRNA and protein were quantified. CD8+ cells were tested for veto activity by mixed lymphocyte reaction (MLR)-induced cell-mediated lymphocytotoxicity (CML) assay. Activated rhesus T cells exposed to TGF-beta1 were examined for apoptosis by TdT-mediated end-labeling and annexin staining.

RESULTS

CD8 cross-linking induces accumulation of TGF-beta1 mRNA and protein. Both CD3- CD8+CD16+ and CD3+ CD8+CD16- subsets of allo-BMC up-regulate TGF-beta1 mRNA after CD8 cross-linking, and exhibit veto activity. The CD3-CD8+CD16+ subset expresses more TGF-beta1 mRNA and increased veto activity at low BMC/CTLp ratios. Exposure of activated T cells to TGF-beta1 induces apoptosis.

CONCLUSIONS

CD8+ allo-BMC are enriched for veto activity and activation via CD8 induces TGF-beta1 mRNA and protein accumulation. These results agree with the hypothesis that paracrine TGF-beta1 may be involved in peripheral deletion of alloreactive CTLp by CD8+ allo-BMC. We suggest that TGF-beta1 overexpression by donor lymphohematopoietic cells may enhance tolerance induction.

Race: a critical factor in organ donation, patient referral and selection, and orthotopic liver transplantation?

The influence of ethnic origin on organ donation and renal allograft survival after renal transplantation has been controversial. Several large studies have reported inferior renal allograft survival in black recipients, whereas others have reported equal survival. However, the issue of race as it relates to organ donation, patient referral, and patient selection in orthotopic liver transplantation has not been investigated. We retrospectively reviewed our results of organ donation, patient referral and selection, and orthotopic liver transplantation since 1989. Because of a concerted educational effort by this organ procurement organization, the percentage of black donors has increased from 6.1% in 1988 to 21.9% in 1996. Since the inception of the Liver Transplant Program in 1989, 844 patients have been referred to our transplant center for organ transplant evaluation. Disproportionately fewer black patients (119; 14.1%) were referred for liver transplantation than white patients (725; 85.9%) based on the prevalence of end-stage liver disease in these populations. The acceptance rate for listing for transplantation was similar between the two groups. The percentage of patient referrals who actually underwent transplantation was similar across racial lines (43% black v 42% white patients). However, it appeared that black patients were referred for liver transplantation at a later stage and were more critically ill at the time of referral. Nevertheless, the patient and graft survival were similar between black and white patients. The 1- and 3-year survival rates in white recipients was 88% and 81%, respectively, versus 96% and 84% in black recipients. Within this organ procurement organization, black donation has increased over the past 10 years. Unfortunately, there may be a selection bias at the level of referral for liver transplantation. However, once patients are referred to this center for liver transplantation, the rate of transplantation and survival is similar between white and black patients.

GABAergic drugs and sexual behaviour in the rabbit: evidence for species-specific effects

The effects of gamma-amino butyric acid (GABA)-ergic drugs on male rabbit sexual behaviour have been evaluated. The GABA(A) agonist 4,5,6,7-tetrahydroxixazolo-5,4c-pyridin-3-ol (THIP), the GABA(B) agonist R-baclofen and the GABA antagonists picrotoxin and bicuculline were used. Injection of THIP, 20 mg/kg, s.c. produced a complete suppression of sexual behaviour and R-baclofen, 2.5 mg/kg, s.c. a significant inhibition. Intraperitoneal injections produced effects at higher doses than did s.c. injections. The inhibition produced by R-baclofen was associated with strong motor effects as shown by the water escape test. It is probable, therefore, that the reduced sexual behaviour observed after treatment with this drug is a consequence of sedative or muscle relaxant effects. By contrast, the dose of THIP that inhibited sexual behaviour had no effect on the water escape test. These results show that the GABA(A) agonist inhibits sexual behaviour in the male rabbit independent of effects on the motor system. The GABA antagonists had marginal or no effects on sexual behaviour. When these data are compared to previous results in the rat, substantial differences are seen. As there are differences between the effects on rat and rabbit sexual behaviour by other types of drugs, it appears that drug action on sexual behaviour cannot be generalized from one species to another.

Peritransplant tolerance induction with anti-CD3-immunotoxin: a matter of proinflammatory cytokine control

BACKGROUND

Tolerance is gaining momentum as an approach to reduce lifelong immunosuppressive therapy while improving transplant longevity. Anti-CD3 immunotoxin (IT), FN18-CRM9, has potential to induce tolerance owing to its exceptional ability to deplete sessile lymph node T cells. However, if initiated at the time of transplantation, alpha-CD3-IT alone elicits a proinflammatory cytokine response, precluding establishment of tolerance.

METHODS

Four groups of rhesus monkeys received kidney allografts and immunosuppression. Three groups received alpha-CD3-IT alone or alpha-CD3-IT supplemented with 15-deoxyspergualin (DSG) and/or methylprednisolone (MP). One group received alpha-CD3-monoclonal antibody with DSG and MP. Cytokines were measured by enzyme-linked immunosorbent assay.

RESULTS

Supplementing peritransplant alpha-CD3-IT treatment with a brief course of DSG and MP promoted rejection-free kidney allograft acceptance in 75% of macaques followed for up to 550 days. Among those given alpha-CD3-IT alone or with MP, none were long-term survivors. Tolerance developed after alpha-CD3-IT, DSG, and MP treatment, but not when the unconjugated a-CD3 monoclonal antibody was substituted for IT. Systemic production of proinflammatory cytokines interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha induced after peritransplant alpha-CD3-IT was prevented only in animals given DSG. Despite high levels of interleukin (IL)-12 in the first month after transplant, tolerant recipients exhibited IL-12 resistance, as evidenced by baseline plasma levels of IFN-gamma but elevated IL-4. DSG was shown to inhibit IL-12-driven IFN-gamma production by a mechanism associated with inhibition of nuclear factor kappa-B.

CONCLUSIONS

In this model, peritransplant induction of tolerance is promoted by efficient elimination of sessile lymph node T cells and control of the proinflammatory IFN-gamma response by a mechanism that appears to involve resistance to IL-12.

Application of a Fas ligand encoding a recombinant adenovirus vector for prolongation of transgene expression

An adenovirus vector encoding murine Fas ligand (mFasL) under an inducible control was derived. In vivo ectopic expression of mFasL in murine livers induced an inflammatory cellular infiltration. Furthermore, ectopic expression of mFasL by myocytes did not allow prolonged vector-mediated transgene expression. Thus, ectopic expression of functional mFasL in vector-transduced cells does not appear to confer, by itself, an immunoprivileged site sufficient to mitigate adenovirus vector immunogenicity.

[Small-diameter portosystemic shunts: indications and limitations]

Low diameter porto-systemic shunts for the treatment of portal hypertension bleeding have emerged as a consequence of the technical development of vascular grafts (PTFE) that allow the use of a narrow lumen. The experience with this kind of operation at the Instituto Nacional de la Nutrición Salvador Zubirán, Mexico City during a 6-year period is reported. There were twenty-seven patients with good liver function (Child-Pugh A-B) were operated or electively, average Age 47.5 years (range 17-71), twenty three patients with liver cirrhosis, one with portal fibrosis and three with idiopathic portal hypertension. Operative mortality: 4%. Rebleeding: 14%. Postoperative encephalopathy was observed in 14 of 27, three of them being grade III-IV (11%). In the remaining 11 cases, it was mild and easily controlled. Postoperative angiography showed shunt patency in 81% of the cases; in 33% of the cases, portal vein diameter reduction was shown, as well as two cases with portal vein thrombosis. In 77% of the cases, adequate postoperative quality of life was observed. Survival (Kaplan-Meier): 86% at 12 months and 56% at 60 months. These kinds of shunts are a good alternate choice for patients considered for surgery, in which other portal blood flow preserving procedures (selective shunts, devascularization with transection) are not feasible.

Tacrolimus (FK506) and mycophenolate mofetil combination therapy versus tacrolimus in adult liver transplantation

BACKGROUND

Mycophenolate mofetil (MMF) prolongs allograft survival in experimental animals, prevents acute rejection in humans, and has recently been approved for use in renal transplantation in combination with cyclosporine. Tacrolimus (Prograf) has been shown to be effective for the prevention and treatment of allograft rejection in liver transplantation. However, there has been limited experience with the combination of tacrolimus and MMF in liver transplantation.

METHODS

This retrospective pilot study examined the results in 130 primary, consecutive, adult liver transplants under two separate immunosuppressive protocols. Patients in the study group received MMF (1 g p.o. b.i.d.), tacrolimus (0.1 mg/kg p.o. b.i.d.), and a standard steroid taper. MMF was also tapered and then discontinued within 3 months of transplantation. A historical control received tacrolimus (0.15 mg/kg p.o. b.i.d.) and the same steroid taper.

RESULTS

Pretransplant demographics, including creatinine, were not significantly different between the groups. The 6-month patient and graft survivals of 96.3% (control) versus 92.0% (study) were not significantly different. The incidence of acute rejection was 45.0% in the control group versus 26.0% in the study group (P = 0.03). The study group had a lower incidence of rejection (mean episodes/patient +/- SEM): 0.28+/-0.07 vs. 0.61+/-0.10 (P = 0.007). All of the study group members responded to high-dose steroids. In the control group, three patients required monoclonal antibody therapy and two patients required the addition of MMF. The incidence of cytomegalovirus was similar in the study group and the control group (13.8% vs. 10.0%, P = NS). Early renal function was better preserved in the tacrolimus/MMF group (mean creatinine +/- SEM): 1.09 mg/dl +/- 0.05 vs. 1.51 mg/dl +/- 0.08 at 30 days, P = 0.0001. The study design required dosing with less tacrolimus (mean mg/day +/- SEM), which was achieved at 1 week (23.2+/-0.7 vs. 13.5+/-0.5); 1 month (18.7+/-0.8 vs. 11.4+/-0.5); 3 months (14.5+/-0.6 vs. 9+/-0.5); and 6 months (11.6+/-0.6 vs. 8.2+/-0.6); P = 0.0001, for all time points.

CONCLUSION

Combination therapy with tacrolimus and MMF may significantly reduce the incidence of acute liver allograft rejection, allow a significant reduction in tacrolimus dosage, and decrease the incidence of nephrotoxicity. Long-term analysis will be necessary to assess any increased risk of opportunistic infections.

Free tryptophan as an indicator of brain serotonin synthesis in infants

This study confirms observations made in a former study of plasma of preterm and term newborn infants with intrauterine malnutrition during the first month of life and extends to the lactational period. The free fraction of L-tryptophan, the precursor amino acid of brain serotonin synthesis, is significantly elevated up to 3 months of age. According to previous results, which demonstrated that L-tryptophan and serotonin synthesis are increased in the brain of gestationally malnourished rats, the present data in humans malnourished early in life strongly suggest that the elevation of the free fraction of L-tryptophan in plasma provides an increased amount of the precursor molecule to pass across the blood-brain barrier and activates the synthesis of brain serotonin. Because serotonin has been found to have a possible neurotrophic role in the fetal brain, any alteration of its metabolism in this period could reflect as a permanent change in brain neurogenesis. The data suggest that the free fraction of plasma L-tryptophan may be an indirect marker of changes in brain serotonin synthesis in these patients. Additional data on the functional relevance of the brain serotonergic system in humans are required to support this hypothesis.

Selective shunts for portal hypertension: current role of a 21-year experience

The results of treatment of hemorrhagic portal hypertension with selective shunts over a 21-year period in a selected patient population are reported. Patients selected for surgical treatment had good cardiopulmonary and renal function, and most also had adequate liver function (141 Child-Pugh class A, 59 class B). Among 734 patients treated surgically for bleeding portal hypertension, 221 had selective shunts (168 distal splenorenal and 53 splenocaval shunts). Global operative mortality (in the 21-year period) was 14% and 12% for Child-Pugh A patients. Operative mortality in Child-Pugh A patients in the last 5 years was only 5%. The rate of rebleeding was 6%, rate of incapacitating encephalopathy was 5%, and rate of survival was 65% at 15 years (last 5 years: 88% at 1 year and 85% at 5 years). Good quality of life was demonstrated in 80% of surviving patients. Shunt patency was 94%. Postoperative portal blood flow changes occurred in 23% of cases (8% diameter reduction, 14% thrombosis). Compared with other forms of therapy (pharmacotherapy, sclerotherapy, and transjugular intrahepatic shunting), only liver transplantation offers similar results for these patients. In countries in which liver transplantation is not routinely performed, shunting with selective shunts is the treatment of choice for patients with good liver function.

Preclinical studies of allograft tolerance in rhesus monkeys: a novel anti-CD3-immunotoxin given peritransplant with donor bone marrow induces operational tolerance to kidney allografts

A major challenge in clinical transplantation today is to design a practical and effective protocol for tolerance induction compatible with cadaver organ transplantation. A preclinical rhesus monkey kidney allograft model using immediate peritransplant anti-CD3 immunotoxin (anti-CD3-IT) and donor bone marrow (DBM) is shown here to induce operational tolerance with prolonged graft survival in the absence of chronic immunosuppressive drugs. Bone marrow harvested from the kidney donor was depleted of mature alloantigen-presenting cells and T cells by removing DR(bright) cells and CD3(bright) cells, respectively. In outbred, major histocompatibility complex-incompatible donor-recipient pairs with high pretransplant mixed lymphocyte response and cytotoxic T lymphocyte precursor activity, four of six allografts survived for periods of 120 days to >1.5 years. Graft acceptance after peritransplant treatment followed robust elimination of both peripheral blood T cells and lymph node T cells. In most recipients given anti-CD3-IT and DBM infusion, anti-donor immunoglobulin G responses were completely inhibited. Microchimerism was observed in all recipients studied, including those not given DBM, but levels of microchimerism did not correlate with graft survival. Anti-CD3-IT induction in combination with modified DBM protocols such as the depletion of mature T cells and DR(bright) antigen-presenting cells may offer new opportunities to improve clinical tolerance protocols beyond those attempted in the clinic to date. Overall, these results with anti-CD3-IT show promise for development of cadaver transplant tolerance induction.

Dopamine and sexual behavior in the male rabbit

Male rabbits were treated with the dopamine releasing drug amphetamine or the dopamine D1/D2 receptor antagonist cis(Z)-flupenthixol. Amphetamine, 1 to 4 mg/kg, had no effect on sexual behavior. Flupenthixol, 2 mg/kg, reduced the proportion of rabbits that ejaculated and the number of ejaculations per test. Lower doses were ineffective. Castrated males were treated with both drugs at two intervals after castration, 19-21 and 27-29 days postcastration, respectively. Amphetamine was without effect while flupenthixol, 1 mg/kg, reduced sexual behavior at the test 19-21 days postcastration. At the second test, sexual behavior was almost completely absent in control animals. Therefore, no further reduction could be observed after treatment with flupenthixol. Another group of animals was castrated and given androgen replacement. Testosterone decanoate was injected once weekly at a dose of 3 mg/kg. This treatment maintained a stable, low sexual activity. In these animals, amphetamine was again ineffective whereas flupenthixol, 1 mg/kg, inhibited sexual behavior. Gross motor function was evaluated in a water escape test. Amphetamine was inactive, and the effective dose of flupenthixol was 10 mg/kg. This dose is far above the dose required for inhibiting sexual behavior. In sum, facilitated dopaminergic transmission does not seem to affect on sexual behavior in the male rabbit, whereas reduced dopaminergic activity disrupts this behavior.