Intracellular Interferon-γ Staining Analysis of Donor-Specific T-Cell Responses in Liver Transplant Recipients

Barcelona Consensus on Biomarker-Based Immunosuppressive Drugs Management in Solid Organ Transplantation

With current treatment regimens, a relatively high proportion of transplant recipients experience underimmunosuppression or overimmunosuppression. Recently, several promising biomarkers have been identified for determining patient alloreactivity, which help in assessing the risk of rejection and personal response to the drug; others correlate with graft dysfunction and clinical outcome, offering a realistic opportunity for personalized immunosuppression. This consensus document aims to help tailor immunosuppression to the needs of the individual patient. It examines current knowledge on biomarkers associated with patient risk stratification and immunosuppression requirements that have been generally accepted as promising. It is based on a comprehensive review of the literature and the expert opinion of the Biomarker Working Group of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology. The quality of evidence was systematically weighted, and the strength of recommendations was rated according to the GRADE system. Three types of biomarkers are discussed: (1) those associated with the risk of rejection (alloreactivity/tolerance), (2) those reflecting individual response to immunosuppressants, and (3) those associated with graft dysfunction. Analytical aspects of biomarker measurement and novel pharmacokinetic-pharmacodynamic models accessible to the transplant community are also addressed. Conventional pharmacokinetic biomarkers may be used in combination with those discussed in this article to achieve better outcomes and improve long-term graft survival. Our group of experts has made recommendations for the most appropriate analysis of a proposed panel of preliminary biomarkers, most of which are currently under clinical evaluation in ongoing multicentre clinical trials. A section of Next Steps was also included, in which the Expert Committee is committed to sharing this knowledge with the Transplant Community in the form of triennial updates.

T-Cell Cytokines as Predictive Markers of the Risk of Allograft Rejection

Over the last decade, several biomarkers and surrogate markers have surfaced as promising predictive markers of risk of rejection in solid organ transplantation. The monitoring of these markers can help to improve graft and recipient care by personalizing immunomodulatory therapies. The complex immune system response against an implanted graft can change during long-term follow-up, and the dynamic balance between effector and regulatory T-cell populations is a crucial factor in antidonor response, risk of rejection, and immunosuppression requirements. Therefore, at any time before and after transplantation, T-effector activity, which is associated with increased production and release of proinflammatory cytokines, can be a surrogate marker of the risk of rejection and need for immunosuppression. In addition, immunosuppressive drugs may have a different effect in each individual patient. The pharmacokinetics and pharmacodynamics of these drugs show high interpatient variability, and pharmacodynamic markers, strongly associated with the specific mechanism of action, can potentially be used to measure individual susceptibility to a specific immunosuppressive agent. The monitoring of a panel of valid biomarkers can improve patient stratification and the selection of immunosuppressive drugs. After transplantation, therapy can be adjusted based on the prediction of rejection episodes (maintained alloreactivity), the prognosis of allograft damage, and the individual's response to the drugs. This review will focus on current data indicating that changes in the T-cell production of the intracellular cytokines interferon-γ and interleukin-2 could be used to predict the risk of rejection and to guide immunosuppressive therapy in transplant recipients.

Alloreactive T Cells to Identify Risk HLA Alleles for Retransplantation After Acute Accelerated Steroid-Resistant Rejection

The risk of rejection by cellular alloreactivity to the transplant donor is not routinely assessed. Here we analyzed alloreactive T cells in kidney transplant recipients and report how their detection may have helped to prevent rejection of a second kidney graft in a patient with a history of acute accelerated steroid-resistant nonhumoral rejection. Alloreactive CD4 and CD8 T cells were quantified using a flow-cytometric mixed lymphocyte reaction assay based on interferon-γ induction. A group of 16 nonrejecting transplant recipients did not show any alloreactive T-cell immunity to their respective donors, whereas alloreactivity to third-party controls was detectable. In the patient with rejection, HLA-specific antibodies were not detectable before and shortly after rejection, but after transplantation the patient showed exceptionally high frequencies of alloreactive T cells against 2 of 11 HLA-typed controls (0.604% and 0.791% alloreactive CD4 T cells and 0.792% and 0.978% alloreactive CD8 T cells) who shared HLA alleles (HLA-A*24, -B*44, -C*02, -DQB1*5) with the kidney donor. These HLA alleles were subsequently excluded for allocation of a second graft. No alloreactive T cells were observed toward the second kidney donor, and this transplantation was performed successfully. Thus, shared HLA alleles between the donor and third-party controls may suggest that alloreactive T cells had contributed to rejection of the first graft. The rejecting patient highlights that determination of cellular alloreactivity before transplantation may be applied to identify unacceptable mismatches and to reduce the risk for acute cellular rejection episodes.

Successful multidisciplinary treatment of refractory cytomegalovirus infection after living donor liver transplantation using mixed lymphocyte reactions: report of a case

A 52-year-old Japanese male underwent ABO-incompatible living donor liver transplantation for acute-on-chronic hepatitis B infection. Fifty-one months later, he became feverish and a cytomegalovirus (CMV) infection was diagnosed. A dramatically high CMV pp65 antigen (C10/C11) load (2,412) was measured, which did not respond to ganciclovir and immune globulin treatment, and increased further to 5,353. The next treatment strategy was the reduction of immunosuppressants, but to simply reduce immunosuppressants can lead to graft loss. Therefore, before using this strategy, responses to alloantigens were evaluated using a carboxyfluorescein-diacetate-succimidyl ester-labeled mixed lymphocyte reaction (CFSE-MLR). Only limited CD4(+) and CD8(+) T-cell proliferation was observed, suggesting the patient was hyporesponsive. After reducing tacrolimus levels from 3-4 ng/mL to <1.5-1.8 ng/mL, the fever dropped immediately and C10/C11 disappeared after 2 months. In conclusion, CFSE-MLR could be a useful tool for the treatment of refractory infectious disease after transplantation and, importantly, for checking a patient's immunosuppressive state beyond the perioperative period.

High proportion of CD95(+) and CD38(+) in cultured CD8(+) T cells predicts acute rejection and infection, respectively, in kidney recipients

The aim of this study was to find noninvasive T-cell markers able to predict rejection or infection risk after kidney transplantation. We prospectively examined T-lymphocyte subsets after cell culture stimulation (according to CD38, CD69, CD95, CD40L, and CD25 expression) in 79 first graft recipients from four centers, before and after transplantation. Patients were followed up for one year. Patients who rejected within month-1 (n=10) showed high pre-transplantation and week-1 post-transplantation percentages of CD95(+), in CD4(+) and CD8(+) T-cells (P<0.001 for all comparisons). These biomarkers conferred independent risk for early rejection (HR:5.05, P=0.061 and HR:75.31, P=0.004; respectively). The cut-off values were able to accurately discriminate between rejectors and non-rejectors and Kaplan-Meier curves showed significantly different free-of-rejection time rates (P<0.005). Patients who rejected after the month-1 (n=4) had a higher percentage of post-transplantation CD69(+) in CD8(+) T-cells than non-rejectors (P=0.002). Finally, patients with infection (n=41) previously showed higher percentage of CD38(+) in CD8(+) T-cells at all post-transplantation times evaluated, being this increase more marked in viral infections. A cut-off of 59% CD38(+) in CD8(+) T-cells at week-1, week-2 and month-2 reached 100% sensitivity for the detection of subsequent viral infections. In conclusion, predictive biomarkers of rejection and infection risk after transplantation were detected that could be useful for the personalized care of kidney recipients.

Intracellular IFN-γ and IL-2 expression monitoring as surrogate markers of the risk of acute rejection and personal drug response in de novo liver transplant recipients

Biomarker monitoring is needed in transplantation to reflect individual response to immunosuppressive drugs and graft outcome. We evaluated intracellular expression and soluble production of interferon-(IFN)-γ and interleukin-(IL)-2 as predictive biomarkers of acute rejection (AR) and personal drug response. Pharmacokinetic-pharmacodynamic profiles were determined in 47 de novo liver recipients treated with tacrolimus, mycophenolate mofetil and prednisone. Of the 47 patients, AR occurred in nine. There were no differences in drug concentrations between rejectors and non-rejectors. A pre-transplantation cut-off value of 55.80% for %CD8(+)-IFN-γ(+) identified patients at high risk of AR with a sensitivity of 75% and a specificity of 82%. In the first week post-transplantation, patients with a % inhibition for soluble IFN-γ, %CD8(+)-IFN-γ(+) and %CD8(+)-IL2(+) lower than 40% developed AR, showing low susceptibility to immunosuppressive drugs. Therefore, effector-T-cell response monitoring may help physicians to identify personal response to treatment and patients at high risk of AR.