Immunologic suppression mediated by genetically modified hepatocytes expressing secreted allo-MHC class I molecules

Long-term results of combined heart and kidney transplantation: a French multicenter study

BACKGROUND

Outcomes in recipients who have undergone combined heart and kidney transplantation have mainly been addressed in small, single-center studies. We studied long-term results of combined heart and kidney transplantation in a large multicenter cohort.

METHODS

Between 1984 and 2007, 67 consecutive patients (61 men and 6 women) from 3 French centers underwent combined heart and kidney transplantation. At transplantation, 38 (57%) were receiving dialysis. All patients received immediate triple immunosuppression therapy (anti-calcineurin, steroids, azathioprine, or mycophenolate).

RESULTS

Overall actuarial survival rates were 62.0%, 60.3%, 53.3%, and 46.5% at 1, 3, 5, and 10 years, respectively. These rates were similar to those observed in 2981 isolated heart recipients at the 3 participating centers during the same period (respectively, 71.0%, 65.2%, 60.1%, and 47.2%, p = 0.6). Survival tended to improve during the last decade (1996 to 2007) and reached 71.1%, 67.5%, and 60% at 1, 3, and 5 years. Cardiac allograft rejection requiring treatment occurred in 12 (17.9%). Coronary artery vasculopathy developed in 3 (9.3%). Kidney allograft rejection occurred in 9 (13.4%). Kidney graft survival was 95.9% at 1, 3, 5, and 10 years.

CONCLUSIONS

Long-term survival rates in a large cohort of combined heart and kidney recipients are similar to those of isolated heart recipients in France. The rates of acute heart and kidney rejection and angiographic coronary artery vasculopathy were low in this patient population.

Lower Incidence of Bronchiolitis Obliterans in Pediatric Liver−Lung Transplant Recipients With Cystic Fibrosis

BACKGROUND

Simultaneous liver-lung transplantation is an infrequent but technically feasible procedure in patients with end-stage lung disease and advanced liver disease. We characterize the outcomes of pediatric patients who underwent this procedure at our institution.

METHODS

We performed a retrospective, case-control study and reviewed the medical records of all patients referred to our transplant program from its inception. Seven patients were listed for simultaneous liver-lung transplant. The five patients who survived to transplant were matched to 13 controls who underwent isolated bilateral sequential lung transplant for underlying diagnosis, age at time of transplant, gender, and era of transplant. Outcome measures included patient and graft survival, occurrence of bronchiolitis obliterans (BO), and episodes of rejection.

RESULTS

Of the five study patients who underwent liver-lung transplant, one died of multiorgan failure 11 days after transplant compared with 9 of 13 controls who died. The median survival for the study patients was 89 months (range, 0-112 months) compared with the controls, who had a median survival of 34 months (range, 0-118 months). The remaining four patients had bronchiolitis obliterans syndrome scores of 0 compared with 5 of 13 control patients (P=0.02). The rate of acute rejection per 100 patient days was 0.012 for the study patients compared with 0.11 for the controls (P=0.025).

CONCLUSIONS

Simultaneous liver-lung transplantation is a technically feasible procedure with excellent long-term outcomes. The surviving study subjects remain free from bronchiolitis obliterans syndrome. These results suggest that the transplanted liver may bestow immunologic privilege to the lung allograft.

Study of the impact of liver transplantation on the outcome of intestinal grafts in children

BACKGROUND

Successful small bowel transplantation remains a challenge due to the septic and immune content of the gut. The possible beneficial role of the liver was assessed in pediatric recipients of isolated intestinal and liver intestinal combined transplantation, receiving the same immunosuppressive therapy.

METHODS

Fifteen children who underwent small bowel transplantation (seven SbTx) or combined liver-small bowel transplantation (eight LSbTx) at a single center between 1994 and 1998 were retrospectively reviewed and compared with fifteen controls (eight normal and seven appendicitis as inflammatory control). Transplant and patient survival, acute rejection episodes were analyzed and compared. Epithelial apoptotic body counts (ABC) and NF-kB (p65), Caspase-3 and Bax intestinal immunostaining from days 0 to 20 after transplantation were assessed.

RESULTS

Graft and patient survivals at 5 years were respectively 75% and 75% in LSbTx; 43% and 57% in SbTx (NS). Histological analysis showed higher ABC in LSbTx intestinal mucosa (P = 0.05 on day 5, P < 0.01 thereafter). Immunostaining of biopsies on day 0 after reperfusion showed different expression of NF-kB, Caspase-3 and Bax on endothelial (P < 0.05 for NF-kB and Bax), mononuclear (P < 0.05 for Bax) and epithelial cells in LSbTx and SbTx.

CONCLUSIONS

Our results suggest a protective role of the liver toward intestinal transplantation even in absence of significative difference, probably due to the small number of children. Early changes in NF-kB immunostaining in the biopsies sampled on day 0, pointed to a possible beneficial effect of the liver in the very early phase following transplantation, perhaps through the differential control of ischemia-reperfusion.

Prolongation of long-term kidney graft survival by a simultaneous liver transplant: the liver does it, and the heart does it too

BACKGROUND

Whereas some authors reported that kidney transplants were protected from rejection by simultaneous liver grafts, other authors failed to obtain evidence for a kidney graft-protective role for the liver.

METHODS

The survival rate of 383 kidney grafts in recipients of combined kidney-liver transplants performed between 1985 and 2000 and reported to the international Collaborative Transplant Study (CTS) was analyzed and compared retrospectively with that of a matched group of control patients who were transplanted with kidneys only. In addition, 105 combined kidney-heart transplants performed during the same time period were analyzed.

RESULTS

At 1 year, the survival rate of kidney grafts in recipients of kidney-liver transplants was significantly lower than that in kidney only recipients (P<0.0001). Subsequently, however, kidneys in kidney-liver recipients fared much better so that the success rates were virtually identical after 8 years of follow-up (62.1+/-3.5% vs. 61.9+/-2.3%, P=ns). Half-life times after the first posttransplant year were 27.6 and 14.5 years for combined or single kidney grafts, respectively, and the projected 20-year graft survival rates were 46% and 35%, respectively. The 8-year survival rate of kidney grafts in recipients of combined kidney-heart recipients was 63.5+/-6.2%, the associated half-life time 31.6 years, and the projected 20-year graft survival rate 49%.

CONCLUSIONS

The long-term kidney graft survival rate is higher in recipients of combined kidney-liver transplants than in recipients of kidney grafts only. Because the success rate is equally high in recipients of combined kidney-heart transplants, it is necessary to reexamine the hypothesis that the liver possesses a unique capacity of protecting a simultaneous kidney graft from rejection.

Hepatocyte expression of soluble donor MHC class I antigen via gene transfer inhibits multiple aspects of the antidonor immune response in fully sensitized rat transplant recipients

Sensitized organ transplant recipients face an increased risk of hyperacute rejection (HAR) due to donor major histocompatibility complex (MHC) class I antigen (Ag) preexposure. We recently reported a novel donor-specific strategy to address this problem, whereby soluble donor MHC class I Ag gene therapy prevented HAR of heart allografts in passively sensitized rats. Here, we tested this same approach in presensitized rat recipients with a fully preactivated humoral and cellular immune response. Our gene therapy method involved liposomal transfection of cultured recipient (Lewis-RT1.A(1)) hepatocytes with DNA encoding secretable donor MHC class I Ag, RT1.A(a). Control-transfected or RT1.A(a)-transfected hepatocytes were implanted intrasplenically into Lewis rats presensitized with three skin transplants. Subsequently, antidonor antibody, cytotoxic T lymphocyte (CTL), and helper T lymphocyte (HTL) assays were performed. Additionally, the effectiveness of our gene therapy on the prevention of ACI (RT1(a)) heart HAR was evaluated. Results indicated that soluble MHC not only decreased cytotoxic antibody levels, but also suppressed antidonor CTL and HTL responses; furthermore, HAR of heart allografts was prevented in all recipients. Therefore, soluble donor MHC class I gene therapy can inhibit multiple aspects of the primed antidonor immune response in actively presensitized rats. Development of this strategy in presensitized humans could improve organ transplant outcome.

Use of an adenoviral vector to express soluble donor-major histocompatibility complex molecules capable of suppressing the immune response in rat transplant recipients

There is an accumulating body of evidence indicating that soluble major histocompatibility complex (sMHC) molecules have donor-specific immunosuppressive properties. One classic, but still unproven, theory is that production of sMHC by liver transplants induces a potent immunosuppressive effect. To mimic this possible effect, we have developed a replication deficient adenovirus (Ad-RQ) to express high levels of donor sMHC class I molecules (sRT1.A(a)) in the liver. Ad-RQ produced sRT1.A(a) was measured by enzyme-linked immunosorbent assay (ELISA) after in vitro infection of Lewis (RT1(l)) hepatocytes, and in vivo following intravenous virus injection into Lewis rats. Results indicated high sRT1.A(a) expression in Lewis hepatocyte cultures and, in vivo, high expression was also demonstrated and maintained for at least 1 week. A strong immunosuppressive potential of sMHC in vivo was revealed by prolongation of cardiac (ACI, RT1(a)) heart allograft survival in high-responder Lewis rat recipients treated with Ad-RQ alone. Furthermore, limiting dilution cytotoxic T-lymphocyte precursor (CTLp) analysis of lymphocytes from Ad-RQ-treated Lewis recipients receiving an ACI heart transplant indicated a marked decrease in antidonor CTLp frequency. In conclusion, our results demonstrate that viral vectors can be used effectively to express high levels of sMHC molecules, and their immunosuppressive effect, without concurrent immunosuppression, is sufficiently potent to prolong heart transplant survival.

Association of CD8+ natural killer T cells in the liver with neonatal tolerance phenomenon

BACKGROUND

Neonatal tolerance is a very interesting phenomenon, because even allogeneic skin grafts are not rejected in these mice at the adult stage. However, the underlying mechanism remains unclear.

METHODS

In this study we prepared such tolerant C57BL/6 (B6) mice (H-2b) by the injection of allogeneic lymphocytes of BALB/c origin (H-2d) at the neonatal stage.

RESULTS

The total number of liver lymphocytes in these tolerant mice was found to increase when it was examined at the adult stage. Nevertheless, the retention of allogeneic lymphocytes that were injected at the neonatal stage was highest in the spleen. It is speculated that these allogeneic lymphocytes stimulate the hepatic immune system via the portal vein and that such stimulation maintains the tolerance phenomenon. Indeed, these tolerant mice showed elevated levels of IL-2R beta+ CD3int cells (i.e., extrathymic T cells) and NK1.1+ CD3int cells (i.e., NKT cells) in the liver. Even more interestingly, the number and proportion of CD8+ NKT cells, which are usually a minor population in normal mice, increased among NKT cells in the liver of tolerant mice. This became much more prominent when tolerant mice were grafted with allogeneic (H-2d) skin.

CONCLUSION

In conjunction with additional data from a cell-transfer experiment and a splenectomy experiment, our results suggest that CD8+ NKT cells in the liver of tolerant mice might be intimately associated with the neonatal tolerance phenomenon.

Immunologic considerations for therapeutic strategies utilizing allogeneic hepatocytes: hepatocyte-expressed membrane-bound major histocompatibility complex class I antigen sensitizes while soluble antigen suppresses the immune response in rats

Understanding the immunologic effects of hepatocytes is critical because of the potential to use these cells for bioartificial livers, as a vehicle for gene transfer, and as a means to induce donor-specific immunosuppression in organ transplantation. However, this understanding is complicated by the fact that hepatocytes express membrane-bound and soluble forms of major histocompatibility complex (MHC) class I antigen, each with the potential to induce different immune responses. In the present study we first determined the immunologic effect of normal donor-derived hepatocytes in a rat heart transplant model. We then used ex vivo hepatocyte gene transfer to examine the immunologic effects of different forms of hepatocyte-expressed MHC class I antigen. Results showed that intrasplenic injection of purified, donor-strain-specific hepatocytes into recipients primes alloimmunity, as evidenced by acceleration of heart allograft rejection. Interestingly, injection of autologous hepatocytes transfected ex vivo with DNA encoding only membrane-bound donor MHC class I antigen (RT1.A(a)) also accelerated allograft rejection. However, hepatocytes transfected to express only secreted donor MHC antigen prolonged transplant survival. Limiting-dilution analysis of lymphocytes from animals treated with hepatocytes producing only secreted alloantigen showed an antigen-specific reduction in cytotoxic T lymphocyte (CTL) and helper T lymphocyte (HTL) precursors. Further analysis of CTL populations by flow cytometry revealed a relatively high percentage of nonviable cells, implying that soluble antigen promotes allospecific CTL death. In summary, this study suggests that hepatocyte-expressed MHC class I molecules have opposing immunologic effects, with the membrane-bound antigen inducing immunologic sensitization, and the soluble antigen promoting donor-specific immunosuppression.

Effective use of donor MHC class I gene therapy in organ transplantation: prevention of antibody-mediated hyperacute heart allograft rejection in highly sensitized rat recipients

Immunologically sensitized recipients present one of the most critical problems in clinical organ transplantation today, since preformed antibodies rapidly destroy donor tissue expressing specific MHC class I antigens (Ag). Therefore, sensitized patients are either unable to receive a compatible organ, or experience a prolonged waiting period. In this study we examined the effectiveness of donor MHC class I gene therapy in preventing hyperacute rejection (HR) of rat heart allografts in passively sensitized recipients. Our gene therapy strategy to address this problem is based on the phenomenon that liver transplants, which resist antibody-mediated HR, produce soluble MHC class I Ag capable of neutralizing preformed antibodies and suppressing the immune response. To mimic this "liver effect," we used liposomes to transfect cultured recipient (Lewis-RT1.Al) hepatocytes with plasmid DNA encoding the soluble donor MHC class I Ag, RT1.Aa. Control or RT1.Aa-transfected hepatocytes were implanted intrasplenically into Lewis recipients 1 day prior to heterotopic ACI (RT1.Aa) heart transplantation and injection of 6 ml of anti-ACI hyperimmune serum (HIS). Results showed that nearly all recipients receiving ACI-specific HIS and control hepatocytes experienced HR, while none of the recipients receiving HIS and hepatocytes expressing soluble RT1.Aa developed HR. Furthermore, active immunosuppression by soluble RT1.Aa was evidenced by prolongation of allograft survival, compared with controls not receiving HIS. In summary, soluble donor-MHC class I Ag gene therapy can prevent antibody-mediated destruction associated with HR. Future development of a similar strategy in humans may significantly improve the results of clinical organ transplantation in immunologically sensitized recipients.

The metalloproteinase-mediated pathway is essential for generation of soluble HLA class I proteins by activated cells in vitro: proposed mechanism for soluble HLA release in transplant rejection

We and others have found donor-derived soluble beta2m-associated HLA class I proteins (sHLA/beta2m) in the serum of allograft recipients with acute and chronic rejection. Whether appearance of sHLA/beta2m and upregulated expression of donor cell-bound HLA/beta2m during allograft rejection are related events is unknown. Activation-induced upregulation of in vitro HLA/beta2m expression correlates with the surface expression of another form of HLA class I, namely beta2m-free HLA heavy chains (beta2m-free HC). We have shown that beta2m-free HC, but not beta2m-associated HC, are then cleaved by a specific membrane-bound metalloproteinase and released into supernatants as soluble 36 kDa proteins. We show now that activated peripheral blood lymphocytes produce predominantly the 36 kDa form of sHLA proteins which is present in supernatants as both beta2m-free HC and sHLA/beta2m. Importantly, the metalloprotease inhibitor BB-94 blocked not only the release of soluble beta2m-free HC, but also the appearance of sHLA/beta2m in cell supernatants. Low levels of 36 kDa beta2m-free HC were also present in human plasma of healthy donors. These data suggest an important role for the HLA class I-specific metalloproteinase in vivo in healthy individuals and during allograft rejection in the generation of soluble beta2m-free and beta2m-associated HLA proteins.