Impact of preexisting circulating effector T cells on the outcome of ABO-incompatible adult LDLT

Strategies for ABO Incompatible Liver Transplantation

Liver transplantation (LT) is a definitive treatment for the decompensated liver cirrhosis and fulminant liver failure. With limited availability of cadaveric liver allograft, ABO incompatible (ABOi) living donor liver transplantation (LDLT) plays an important part in further expansion of donor pool. Over the years, with the introduction of Rituximab and improving desensitisation protocol, outcomes of ABOi LDLT are on par with ABO compatible LT. However, ABOi LDLT protocol varies markedly from centre to centre. Intravenous Rituximab followed by plasmapheresis or immunoadsorption effectively reduce ABO isoagglutinins titre before transplant, thereby reducing the risk of antibody mediated rejection in the post-transplant period. Local infusion therapy and splenectomy are not used routinely at most of the centres in Rituximab era. Post-transplant immunosuppression usually consists of standard triple drug regime, and tacrolimus trough levels are targeted at higher level compared to ABO compatible LT. Introduction of newer therapies like Belatacept and Obinutuzumab hold promise to further improve outcomes and reduce the risk of antibody mediated rejection related complications. ABOi LT in emergency situations like acute liver failure and deceased donor LT is challenging due to limited time period for desensitisation protocol before transplant, and available evidence are still limited but encouraging.

Challenge to ABO blood type barrier in living donor liver transplantation

ABO incompatible living donor liver transplantation has the potential to expand the donor pool for patients with end stage liver diseases on the expense of challenges to overcome immunological barriers across blood type. There is a profound impact of age on incidence and severity of antibody mediated rejection (AMR). Even children older than 1 year have chances of AMR; children aged 8 years or older have risks of hepatic necrosis similar to adult liver recipients. The mechanism of AMR is based on circulatory disturbances secondary to inflammation and injury of the vascular endothelium caused by an antibody-antigen-complement reaction. The strategy to overcome ABO blood type barrier is based on both pre-transplant desensitization and adequate treatment of this phenomenon. Nowadays, rituximab is the standard means of desensitization but unfortunately an insufficient aid to treat AMR. Because of low incidence (less than 5% in the rituximab era), in practice of AMR only some case reports about the treatment of clinical AMR are available in the literature. Initial experiences revealed that the proteasome inhibitor, bortezomib might be a promising treatment based on its capacity to deplete plasma cell agents. Although ABO blood type barrier has been counteracted in 95% of patients by applying "rituximab-desensitization", many issues, such as prediction of high-risk patients of infection and AMR and secure treatment strategies for evoked AMR, remain to be resolved.

Adult Living Donor Liver Transplantation Across ABO-Incompatibility

The objective of this study was to evaluate the results of adult ABO-incompatible living donor liver transplantation (LDLT).ABO-incompatible LDLT is an aggressive treatment that crosses the blood-typing barrier for saving lives from liver diseases. Although graft and patient survival have been improved recently by various treatments, the results of adult ABO-incompatible LDLT require further evaluation.Two regimens were designed based on isoagglutinin IgG and IgM titers and the time course of immunological reactions at this institute. When isoagglutinin IgG and IgM titers were ≤64, liver transplantation was directly performed and rituximab (375 mg/m) was administrated on postoperative day 1 (regimen I). When isoagglutinin titers were >64, rituximab (375 mg/m) was administered preoperatively with or without plasmapheresis and boosted on postoperative day 1 (regimen II). Immunosuppression was achieved by administration of mycophenolate mofetil, tacrolimus, and steroids.Forty-six adult ABO-incompatible and 340 ABO-compatible LDLTs were performed from 2006 to 2013. The Model for End-Stage Liver Disease scores for ABO-incompatible recipients ranged from 7 to 40, with a median of 14. The graft-to-recipient weight ratio ranged from 0.61% to 1.61% with a median of 0.91%. The 1-, 3-, and 5-year survival rates were 81.7%, 75.7%, and 71.0%, respectively, for ABO-incompatible LDLT recipients, compared to 81.0%, 75.2%, and 71.5% for ABO-C recipients (P = 0.912). The biliary complication rate was higher in ABO-incompatible LDLT recipients than in the ABO-compatible recipients (50.0% vs 29.7%, P = 0.009).In the rituximab era, the blood type barrier can be crossed to achieve adult ABO-incompatible LDLT with survival rates comparable to those of ABO-compatible LDLT, but with more biliary complications.

Regulatory T cells in kidney transplant recipients: the effect of induction immunosuppression therapy

BACKGROUND

Regulatory T cells have been suggested to down-regulate the alloimmune response. The aim of this prospective open study was to evaluate the effects of different inductive agents on peripheral blood regulatory T cells in kidney transplant patients and to analyse their association with short-term graft outcome.

METHODS

Regulatory and effector T cell numbers in peripheral blood were determined by flow cytometry in 71 prospectively followed kidney transplant recipients at postoperative day 0, 7, 14, 21, 28, 60 and 90. Patients were treated with a calcineurin inhibitor-based triple immunosuppression with polyclonal rabbit anti-thymocyte globulin (rATG, n = 28), basiliximab, the anti-CD25 monoclonal antibody (n = 18) or without induction (controls, n = 25). Flow cytometry data were correlated to rejection incidence.

RESULTS

Compared to controls, CD4(+)CD25(+)FoxP3(+) regulatory T-cell expansion among CD4(+) T cells was noticed in the rATG group at all post-transplant time-points by Day 14 (P < 0.001). A significant decrease in Treg frequency (P < 0.001) and concurrently a transient increase of CD4(+)CD25(low/-)FoxP3(+) population were observed in basiliximab-treated patients 7-60 days post-transplantation. Biopsy-proven acute rejection occurred in 16.7% of controls, 10.7% of the rATG group and in 11.1% of the basiliximab group. Higher CD4(+)FoxP3(+)/CD8(+)CD45RA(+)CD62L(-) ratios were observed repeatedly in those patients after basiliximab induction who were rejection free (P < 0.01).

CONCLUSIONS

In this study, the rATG induction therapy was associated with an expansion of regulatory cells. Sustained high CD4(+)FoxP3(+)/Teff ratios were associated with the absence of rejection after basiliximab induction.

Posttransplant bacteremia in adult living donor liver transplant recipients

Infectious complications such as bacteremia after living donor liver transplantation (LDLT) are associated with significant morbidity and mortality. We retrospectively analyzed the frequency and characteristics of posttransplant bacteremia in 181 adult LDLT recipients between April 2006 and November 2009, and we evaluated the risk factors for posttransplant bacteremia. One hundred seventeen episodes of bacteremia occurred in 62 of 181 recipients (34.3%) within 12 days (median) after transplantation (range = 1-71 days). The most frequently isolated pathogens were Pseudomonasaeruginosa (26 episodes), methicillin-resistant coagulase-negative staphylococci (22 episodes), and Enterococcus sp. (11 episodes). The overall survival rate at 1 year for patients with bacteremia (n = 62) was significantly lower than the rate for patients without bacteremia (n = 119; 69.6% versus 92.3%, respectively, P < 0.0001). Multivariate analysis showed that Child-Pugh class C (P = 0.0002), preoperative massive pleural effusion or ascites requiring drainage (P = 0.0384), postoperative cytomegalovirus infection (P = 0.0014), ABO incompatibility (P = 0.0188), and older donor age (P = 0.015) were independent risk factors for postoperative bacteremia. In conclusion, bacteremia occurred at a high rate after adult LDLT and induced a higher mortality rate in those who developed it. Infection control may play a pivotal role in improving early outcomes after LDLT.

Current progress in ABO-incompatible liver transplantation

BACKGROUND

ABO-incompatible (ABOi) living donor liver transplantation (LDLT) in adult patients has been controversial because of the high risk of antibody-mediated rejection (AMR) mediated by preformed anti-ABO antibodies. However, outcomes have recently improved owing to various treatment advances.

MATERIALS AND METHODS

This review article describes the history and current progress in ABOi liver transplantation, mainly from the viewpoint of the Japanese experience.

RESULTS

The typical clinical manifestations of AMR are hepatic necrosis and intrahepatic biliary complication. The outcomes of early ABOi LDLT were poor, especially in older children and adult cases. Since we first introduced portal vein infusion therapy into adult ABOi LDLT in 1998, local graft infusion therapy has emerged in Japan as a crucial breakthrough to overcome the ABO blood group barrier. From 2003, rituximab prophylaxis has been widely used with local graft infusion, and has resulted in markedly improved patient survival. The novel approach of intravenous immunoglobulin induction may become another option to suppress AMR. Continued patient enrollment and controlled trials will allow further validation of these treatments.

CONCLUSIONS

The outcome of ABOi LDLT is now similar to that of blood-type-matched transplantation in Japan. However, infection is the major cause of morbidity and mortality after ABOi LDLT. Thus, evaluation of the patients' immune status and adjustment of immunosuppression will be the way forward in the future.