Detection and analysis of HLA class I and class II specific alloantibodies in the sera of dialysis recipients waiting for a renal retransplantation

Superiority of Single-Antigen Bead Study in Donor-Specific Antibodies: Determination in Highly Sensitized Patients

OBJECTIVES

The presence of donor-specific antibodies against HLA before kidney transplant has been variably associated with decreased long-term graft survival. Data on the association between pretransplant donor-specific antibodies and rejection and cause of graft failure in recipients of donor kidneys are scarce.

MATERIALS AND METHODS

For this study of HLA antibody levels, we analyzed serum samples from 76 patients (48 women and 28 men) who were prepared for kidney transplant at the Baskent University İstanbul Hospital between 2017 and 2022. Levels were determined by using Lifecodes panel reactive antibody class I and II identification kits and Lifecodes LSA class I and II identification kits by the Luminex assay method.

RESULTS

Multiple antigen tests showed more than 70% sensitization detected against both class I and class II antigens in our patient group. When some samples were reevaluated with the single-antigen bead method, desensitization values were shown to be considerably reduced compared with values from multiple antigen methods.

CONCLUSIONS

The single-antigen-coated bead method can be useful in determining the risk of donor-specific antibodies in highly sensitized patients.

Chimeric HLA antibody receptor T cells for targeted therapy of antibody-mediated rejection in transplantation

The presence of donor-specific antibodies (DSA), mainly against HLA, increases the risk of allograft rejection. Moreover, antibody-mediated rejection (ABMR) remains an important barrier to optimal long-term outcomes after solid organ transplantation. The development of chimeric autoantibody receptor T lymphocytes has been postulated for targeted therapy of autoimmune diseases. We aimed to develop a targeted therapy for DSA desensitization and ABMR, generating T cells with a chimeric HLA antibody receptor (CHAR) that specifically eliminates DSA-producing B cells. We have genetically engineered an HLA-A2-specific CHAR (A2-CHAR) and transduced it into human T cells. Then, we have performed in vitro experiments such as cytokine measurement, effector cell activation, and cytotoxicity against anti-HLA-A2 antibody-expressing target cells. In addition, we have performed A2-CHAR-Tc cytotoxic assays in an immunodeficient mouse model. A2-CHAR expressing T cells could selectively eliminate HLA-A2 antibody-producing B cells in vitro. The cytotoxic capacity of A2-CHAR expressing T cells mainly depended on Granzyme B release. In the NSG mouse model, A2-CHAR-T cells could identify and eradicate HLA-A2 antibody-producing B cells even when those cells are localized in the bone marrow. This ability is effector:target ratio dependent. CHAR technology generates potent and functional human cytotoxic T cells to target alloreactive HLA class I antibody-producing B cells. Thus, we consider that CHAR technology may be used as a selective desensitization protocol or an ABMR therapy in transplantation.

Study Design: HLA-A*02-Chimeric Antigen Receptor Regulatory T Cells in Renal Transplantation

Introduction

Cell therapy with regulatory T cells (Tregs) in solid organ transplantation is a promising approach for the prevention of graft rejection and induction of immunologic tolerance. Previous clinical studies have demonstrated the safety of Tregs in renal transplant recipients. Antigen-specific Tregs, such as chimeric antigen receptor (CAR)-Tregs, are expected to be more efficacious than polyclonal Tregs in homing to the target antigen. We have developed an autologous cell therapy (TX200-TR101) where a human leukocyte antigen (HLA) class I molecule A^∗02 (HLA-A^∗02)-CAR is introduced into autologous naive Tregs from a patient with HLA-A^∗02-negative end-stage renal disease (ESRD) awaiting an HLA-A^∗02-positive donor kidney.

Methods

This article describes the design of the STEADFAST study, a first-in-human, phase I/IIa, multicenter, open-label, single-ascending dose, dose-ranging study to assess TX200-TR101 in living-donor renal transplant recipients. Up to 15 transplant recipients will receive TX200-TR101 and will be followed up for a total of 84 weeks post-transplant, alongside a control cohort of up to 6 transplant recipients. All transplant recipients will receive a standard of care immunosuppressive regimen, with the intent of intensified tapering of the regimen in the TX200-TR101 cohort.

Results

The primary end point is the incidence and severity of treatment-emergent adverse events (AEs) within 28 days post–TX200-TR101 infusion. Other end points include additional safety parameters, clinical and renal outcome parameters, and the evaluation of biomarkers.

Conclusion

The STEADFAST study represents the next frontier in adoptive cell therapies. TX200-TR101 holds great potential to prevent immune-mediated graft rejection and induce immunologic tolerance after HLA-A^∗02-mismatched renal transplantation.

Analysis of Panel Reactive Antibodies in Renal Transplant Recipients Detected by Luminex: A Single-Center Experience

OBJECTIVES

The role of panel reactive antibody has gained universal acceptance in solid-organ transplant. This parameter is used to gauge the level of sensitization of prospective solid-organ recipients. More than one-third of patients on wait lists for kidney transplant are sensitized. Most have previously formed donor-specific and non-donor-specific serum antibodies and/or positive crossmatch by complement-dependent cytotoxicity and/or flow cytometry. We present the rate of positivity at our institution for human leukocyte antigen antibodies and describe the condensation of antibodies in human leukocyte antigens for renal pretransplant recipients.

MATERIALS AND METHODS

Between January 2011 and December 2012, six hundred twenty consecutive renal transplant recipients on the wait list at the Baskent University were evaluated for this retrospective study. Panel reactive antibody screening and definition tests were studied with Luminex assays for the combination of class I (A, B, C) and class II antigens (DR, DQ).

RESULTS

We found a panel reactive antibody screening positivity in 20.4% of our patients on renal transplant waiting list. Panel reactive antibody defining tests were meaningful in 12.2% of the whole list. We observed that only panel reactive antibody class I positivity was seen in 2.2%, only panel reactive antibody class II positivity was seen in 2.7%, and both panel reactive antibody class I and class II positivities were seen in 7.2% of the defining tests.

CONCLUSIONS

The estimated risk of sensitization for patients with a living donor is determined from the combined results of the crossmatch with the donor and those of the recipient's panel reactive and donor-specific antibodies. Compared with complement-dependent cytotoxicity crossmatch, Luminex assays provide greater sensitivity and specificity in detection of donor-specific antibodies.

Kidney retransplantation: removal or persistence of the previous failed allograft?

A significant percentage of patients with failed renal graft are candidates for retransplantation. The outcomes of retransplantation are poorer than those of primary transplantation and sensitization is documented to be a major reason. The management of a failed allograft that is not immediately symptomatic is still very controversial. The aim of this study was to determine the impact of the failed allograft nephrectomy on a subsequent transplantation and its importance in the sensitization. We performed a retrospective analysis of the local prospective transplantation registry of the outcome of 126 second kidney transplantations among 2438 transplantations performed in our unit between June 1980 and March 2013, comparing those who underwent allograft nephrectomy prior to retransplantation with those who retained the failed graft. Primary endpoints were graft and patient survival. The levels of panel-reactive antibodies (PRA) and rate of acute rejections on retransplantation outcomes were also studied. Among the 126 patients who underwent a second renal transplantation, 76 (60.3%) had a prior graft nephrectomy (Group A), whereas 50 (39.7%) kept their failed graft (Group B). Group A showed significantly more positive PRA levels when compared with the other group (38% vs 10%; P < .001), as measured before the most recent transplantation, and a higher rate of acute rejection (19% vs 5.6%; P = .016). There were 28 (36%) renal allograft losses for Group A and 18 (36%) for those who had not had transplantectomy (P = not significant [NS]). One-, 3-, and 5-year graft survival rates were 96.6%, 90.7%, and 83.4%, respectively, in Group A and 95%, 82%, and 68.4%, respectively, in Group B, with no statistical differences (P = .19). Five-year actuarial patient survival rates in the 2 groups was 89.3% and 82.8%, respectively (P = .55). Multivariate analysis showed that PRA level and delayed graft function (DGF) had a statistically significant influence on graft survival (P = .028; odds ratio [OR] = 1.029; and P = .024; OR = 8.6), irrespective of whether the patient had graft nephrectomy or not. The allosensitization indicated by PRA increases after transplantectomy and leads to a higher incidence of acute rejection after retransplantation. Nephrectomy of failed allograft does not seem to significantly influence the survival of a subsequent graft. The decision to remove or retain a failed graft in the context of retransplantation should thus be based on known clinical indications for the procedure.

Long-term outcome on kidney retransplantation: a review of 100 cases from a single center

Renal transplantation has become an effective form of treatment for end-stage renal failure. Unfortunately, as a consequence of immunological and nonimmunological pathogenic mechanisms, chronic allograft nephropathy is responsible for the loss of a large proportion of kidney grafts after several years and return to dialysis. We have reported herein our 24 years of experience with second kidney transplantations. Of 1,302 kidney transplantations between January 1983 and June 2007 performed in our transplantation center, 100 were second transplantations. Kidney retransplantation was performed in 74 men and 26 women of overall mean age of 35.4 +/- 12.6 years. Cadaveric donor grafts were transplanted in 92 patients, whereas the remaining 8 were living-related donor kidneys. At 1, 5, and 10 years after kidney transplantation, patient survival rates were 100%, 96%, and 92%, respectively, whereas graft survival rates were 85%, 72%, and 53%, respectively. Immunosuppressive therapy included induction therapy with polyclonal anti-lymphocyte antibodies (ALG/ATG) or (starting from 1999) monoclonal anti CD 25 antibody. Our results demonstrated good outcomes for kidney retransplantations with allocation based on anti- HLA antibody identification together with induction immunosuppression.

Influence of Donors' and Recipients' HLA Typing on Renal Function Immediately After Kidney Transplantation

BACKGROUND

The human leukocyte antigen (HLA) system is widely used as a strategy in the search for the etiology of renal function impairment.

OBJECTIVES

This study was carried out to detect the most common HLA alleles' distribution in kidney transplant in both donors and recipients, and clarify the association between HLA alleles and renal dysfunction immediately after transplantation.

PATIENTS AND METHODS

HLA-class I and II alleles typing by PCR-SSOP was performed on a total of 874 recipients aged 40.7 ± 13.8 (male/female: 562/279) and 874 donor aged 27.5 ± 5.3 (male/female: 683/110), between 2006 and 2009 in Baqiyatallah, hospital, Tehran, Iran. In this retrospective, cross sectional study, data were obtained from personal files. Donors aged 40.9 ± 13.6 years and male/female 390/195, while recipients had a mean age 27.5 ± 5.3 and male/female 523/83. Renal dysfunction defined as acute rejection, acute tubular necrosis and Delay graft function.

RESULTS

In this study common alleles at each of the loci for the human leukocyte antigen (HLA) class I (A, B, and C) and class II (DR and DQ) were A2 (n = 186, 33.8%), Bw6 (n = 196, 47.5%), Cw4 (n = 164, 39.7%), DR52 (n = 161, 29.6%), DQ3 (n = 101, 40.1%) for donors; while A2 (n = 200, 34%), BW6 (n = 235, 38.8%), Cw6 (n = 23, 15.2%), DR511 (n = 174, 30.4%), DQ1 (n = 99, 46.3%) for recipients. We detected a total of 139 case of renal dysfunction among RTRs. By the way only cold ischemic time (P = 0.03) and severe anemia (P = 0.000) were significantly associated with renal dysfunction early post kidney transplantation.

CONCLUSIONS

We can predict high risk groups before kidney transplantation and try to establish a screening program for the detection of genetic susceptibility to renal function impairment. HLA typing of the donors and recipients might influence the development of new treatment strategy.

Antibodies in transplantation: the effects of HLA and non-HLA antibody binding and mechanisms of injury

Until recently, allograft rejection was thought to be mediated primarily by alloreactive T cells. Consequently, immunosuppressive approaches focused on inhibition of T cell activation. While short-term graft survival has significantly improved and rejection rates have dropped, acute rejection has not been eliminated and chronic rejection remains the major threat to long-term graft survival. Increased attention to humoral immunity in experimental systems and in the clinic has revealed that donor specific antibodies (DSA) can mediate and promote acute and chronic rejection. Herein, we detail the effects of alloantibody, particularly HLA antibody, binding to graft vascular and other cells, and briefly summarize the experimental methods used to assess such outcomes.

Predictive factors of allosensitization after immunosuppressant withdrawal in recipients of long-term cultured islet cell grafts

BACKGROUND

Islet transplantation has been reported to induce allosensitization in the majority of type 1 diabetic recipients of fresh or shortly incubated islet grafts prepared from one to three donors.

METHODS

We examined the appearance of human leukocyte antigen (HLA) antibodies after withdrawal of immunosuppressants in 35 type 1 diabetic recipients of islet cell grafts prepared from a median of 6 donors (range, 2-11), cultured for longer periods, and characterized for their cellular composition. Immunosuppression consisted of antithymocyte globulin induction followed by mycophenolate mofetil plus calcineurin inhibitors (n=28, with 7 also receiving steroids) or sirolimus with (n=3) or without calcineurin inhibitors (n=4). Both the complement-dependent cytotoxicity (CDC) assay (class I) and the solid-phase flow-based Luminex method (class I and II) were used to identify HLA antibodies.

RESULTS

Immunosuppressant withdrawal resulted in CDC positivity for class I antibodies in only 6% of patients. However, the majority became positive for class I antibodies (72%) or class II antibodies (72%) in the Luminex assay; positivity was not correlated to a higher number of donors or HLA mismatches, but with a lower β-cell purity; use of steroids reduced de novo positivity for Luminex class I antibodies.

CONCLUSION

Allosensitization to cultured human islet cell grafts was low when assessed by CDC assay but high in Luminex. No correlation was found with the number of donors but risk was higher for grafts with lower β-cell purity.

Impact of renal graft nephrectomy on second kidney transplant survival

PURPOSE

To determine the impact of non-functional renal graft nephrectomy on second kidney transplantation survival.

METHODS

We performed a retrospective study on patients managed in our department from April 1989 to April 2011. We compared the number of acute graft rejections and graft survival between patients undergoing second transplantation with (Group I) or without (Group II) prior graft nephrectomy.

RESULTS

A total of ninety-one patients received a second renal graft: 43 underwent graft nephrectomy and 48 kept their non-functional renal graft. There were 5 episodes of acute graft rejection in Group I and 12 in Group II (p = 0.3). Six (13.9 %) grafts failed in Group I and eight (16.6 %) in Group II. Five and 10 years actuarial graft survival in Group I were, respectively, 91 and 85 %, while in Group II were 82.7 % and 69 % (p = 0.2). PRA level and number of acute rejection episodes did not have a statistically significant influence on graft survival, whether the patient had a nephrectomy or not (p = 0.2).

CONCLUSION

Nephrectomy of a failed allograft did not significantly improve the survival of a subsequent graft. Graft nephrectomy should be indicated in case of graft-related pain or a chronic inflammation syndrome.

Renal retransplantation: a retrospective monocentric study

Approximately 10% to 20% of all annual renal transplantations are retransplantations and up to 20% of patients on waiting lists need a repeat kidney because of previous graft failure. The immunological risk is much greater among retransplanted patients than first-time kidney recipients. It is likely that retransplantation will become even more prevalent in the future. However, clinical studies or retrospective data are rare in this patient population. We retrospectively investigated 50 recipients after second or third renal transplantations in our center since 2001. Immunosuppression was performed with corticosteroids, mycophenolate mofetil (MMF), tacrolimus, and induction therapy with either thymoglobulin (2.5 mg/kg body weight; n = 27) or 20 mg basiliximab on days 0 and 4 (n = 22) after renal transplantation; 1 patient was treated with antithymoglobulin Fresenius after combined liver-kidney transplantation. Acute rejection occurred in 12 recipients (44.4%) after thymoglobulin and in 7 recipients (31.8%) after basiliximab induction therapy (P < .05). In 4 (14.8%) thymoglobulin- and 5 (22.7%) basiliximab-treated recipients, vascular rejections were observed (P = NS). Patients with basiliximab treatment showed improved renal function at 1 year after transplantation: serum creatinine 134.3 mumol/L versus 199.6 mumol/L in the thymoglobulin group (P < .05). Over the observation period the renal function remained stable or improved in both groups if rejection treatment was successful. However, allograft failure was higher in the basiliximab-treated group, namely, 18.1% versus 14.8% in thymoglobulin-treated patients, but the difference did not reach statistical significance. In 3 (11.1%) thymoglobulin- and 4 (18.2%) basiliximab-treated patients cytomegalovirus (CMV) infections complicated the follow-up (P = NS). In the follow-up period of 5 years, no malignant diseases were seen in either group. Three basiliximab-treated recipients died in the first year due to sepsis or cardiovascular complications. Two thymoglobulin-treated patients developed BK virus nephropathy in the follow-up period. In conclusion, we observed a high immunological risk and rejection risk among retransplanted kidney recipients in our center. Particularly, severe vascular rejections with a harmful long-term impact on allograft function were observed in this population. Induction treatment seems to be successful to reduce risk and achieve better results. Single-shot thymoglobulin may be preferable to reduce severe vascular rejection and prevent allograft failure than basiliximab with the same infection rate.