Safety,pharmacokinetics, and pharmacodynamic activity of obinutuzumab,a type 2 anti‐CD20 monoclonal antibody for the desensitization of candidates for renal transplant

The limited effectiveness of rituximab plus intravenous immunoglobulin (IVIG) in desensitization may be due to incomplete B cell depletion. Obinutuzumab is a type 2 anti‐CD20 antibody that induces increased B cell depletion relative to rituximab and may therefore be more effective for desensitization. This open‐label phase 1b study assessed the safety, pharmacokinetics, and pharmacodynamics of obinutuzumab in highly sensitized patients with end‐stage renal disease. Patients received 1 (day 1, n = 5) or 2 (days 1 and 15; n = 20) infusions of 1000‐mg obinutuzumab followed by 2 doses of IVIG on days 22 and 43. Eleven patients received additional obinutuzumab doses at the time of transplant and/or at week 24. The median follow‐up duration was 9.4 months. Obinutuzumab was well tolerated, and most adverse events were grade 1‐2 in severity. There were 11 serious adverse events (SAEs) in 9 patients (36%); 10 of these SAEs were infections and 4 occurred after kidney transplant. Obinutuzumab plus IVIG resulted in profound peripheral B cell depletion and appeared to reduce B cells in retroperitoneal lymph nodes. Reductions in anti‐HLA antibodies, number of unacceptable antigens, and the calculated panel reactive antibody score as centrally assessed using single‐antigen bead assay were limited and not clinically meaningful for most patients (NCT02586051).     

Histopathologic features of transplant glomerulopathy associated with response to therapy with intravenous immune globulin and rituximab

Transplant glomerulopathy (TG) is associated with poor long‐term allograft survival and is often accompanied by microcirculation inflammation. Histopathologic scoring may inform prognosis and help guide therapy. We retrospectively assessed 33 patients with biopsy‐proven TG. All biopsies were given a glomerulitis (g) and peritubular capillaritis (ptc) score. We determined allograft survival and serum creatinine stability in three different score groups: g < 2 and ≥ 2, ptc < 2 and ≥ 2, and (g + ptc) < 4 and ≥ 4. We assessed the impact of treatment with intravenous immune globulin (IVIG) and rituximab on outcomes. Graft survival and serum creatinine stability did not differ in each of the histopathologic score groups. Higher‐score groups were associated with the presence of concomitant antibody‐mediated rejection and were more likely to receive IVIG and rituximab. Treatment with IVIG and rituximab resulted in stability of serum creatinine within the higher‐score groups, but not in the lower‐score groups. Stabilization of serum creatinine was associated with an improvement in donor‐specific antibody. Histopathologic scoring in kidney allograft biopsies with TG may help guide treatment. The combination of IVIG and rituximab appears to be beneficial in patients whose biopsies have moderate or severe microvascular injury.     

Pre‐existing donor‐specific antibodies are detrimental to kidney allograft only when persistent after transplantation

Donor‐specific antibodies (DSA) increase the risk of allograft rejection and graft failure. They may be present before transplant or develop de novo after transplantation. Here, we studied the evolution of preformed DSA and their impact on graft outcome in kidney transplant recipients. Using the Luminex Single Antigen assay, we analyzed the sera on the day of transplantation of 239 patients who received a kidney transplant. Thirty‐seven patients (15.5%) had pre‐existing DSA detected the day of transplantation. After 5 years, the pre‐existing DSA disappeared in 22 patients whereas they persisted in 12. Variables associated with DSA persistence were age <50 years (P = 0.009), a history of previous transplantation (P = 0.039), the presence of class II DSA (P = 0.009), an MFI of preformed DSA >3500 (P < 0.001), and the presence of two or more DSA (P < 0.001). DSA persistence was associated with a higher risk of graft loss and antibody‐mediated rejection. Previously undetected preformed DSA are deleterious to graft survival only when they persist after transplantation.     

Clinical relevance of the de novo production of anti‐HLA antibodies following intestinal and multivisceral transplantation

Despite a negative pretransplant cross‐match, intestinal transplant recipients can mount humoral immune responses soon after transplantation. Moreover, the development of donor‐specific anti‐HLA antibodies (DSAs) is associated with severe graft injury. Between June 2000 and August 2011, 30 patients (median age 37.6 ± 9.8 years) received isolated intestinal transplantations (ITX, n = 18) or multivisceral transplantations (MVTXs, n = 12) at our center. We screened for human leukocyte antigen (HLA) antibodies pre‐ and post‐transplant. If patients produced DSAs, treatment with plasmapheresis and intravenous immunoglobulin (IVIG) was initiated. In the event of DSA persistence and/or treatment‐refractory rejection, rituximab and/or bortezomib were added. Ten patients developed DSAs and simultaneously showed significant signs of rejection. These patients received plasmapheresis and IVIG. Eight patients additionally received rituximab, and two patients were treated with bortezomib. DSA values decreased upon antirejection therapy in 8 of the 10 patients. The development of DSAs following ITX is often associated with acute rejection. We observed that the number of mismatched antigens and epitopes correlates with the probability of developing de novo DSAs. Early diagnosis and therapy, including B‐cell depletion and plasma cell inhibition, are crucial to preventing further graft injury.     

Early findings of prospective anti‐HLA donor specific antibodies monitoring study in pancreas transplantation: Indiana University Health Experience

The significance of donor‐specific antibodies (DSA) is not well known in the setting of pancreas transplantation. Since December 2009, we prospectively followed pancreas transplant patients with single‐antigen‐luminex‐bead testing at one, two, three, six, and then every six months for the first two yr. Thirty‐five of the 92 patients that underwent pancreas transplantation (13 pancreas‐alone [PTA], 20 with a kidney [SPK], and two after a kidney [PAK]) agreed to participate in study. Median age at transplant was 45 yr and follow‐up was 23 months. Majority were Caucasian (n = 33) and male (n = 18). Rabbit anti‐thymocyte globulin induction was used. Median HLA‐mismatch was 4.2 ± 1.1. Eight patients (7SPK, 1PAK) developed post‐transplant DSA at median follow‐up of 76 d (26–119), 1 SPK had pre‐formed DSA. Seven patients had both class I and class II DSA, one with class I and one with class II only. Mean peak class I DSA‐MFI was 3529 (±1456); class II DSA‐MFI was 5734 (±3204) whereas cumulative DSA MFI (CI + CII) was 9264 (±4233). No difference was observed in the patient and donor demographics among patients with and without DSA. One patient in non‐DSA group developed acute cellular rejection of pancreas. From our data it appears that post‐transplant DSA in pancreas allograft recipients may not impact the early‐pancreatic allograft outcomes. The utility of prospective DSA monitoring in pancreatic transplant patients needs further evaluation and long‐term follow‐up.     

Desensitizing the broadly human leukocyte antigen-sensitized patient awaiting deceased donor kidney transplantation

For broadly human leukocyte antigen-sensitized patients (HS; calculated panel-reactive antibody >80%), options for deceased donor (DD) transplantation are extremely limited. Data from United Network for Organ Sharing (2000-2009) indicate that <10% of HS patients are transplanted each year. Immune modulation of HS patients using intravenous immunoglobulin (IVIG) and rituximab has shown promise in reducing donor-specific antibody (DSA) titers and improving the chances for successful transplantation for patients awaiting DD transplants. Critical to the success of desensitization with IVIG + rituximab is a coherent antibody-testing strategy aimed at detection of DSA reductions and identification of crossmatch parameters that are associated with a low likelihood of antibody-mediated rejection posttransplant. Here, we discuss data that examine the efficacy of IVIG + rituximab in reducing DSA levels and improving chances for a successful DD transplantation. Patient and graft survival data are also presented as is an analysis of the safety of IVIG + rituximab in sensitized patients.     

Postoperative rebound of antiblood type antibodies and antibody‐mediated rejection after ABO‐incompatible living‐related kidney transplantation

The purpose of this study is to examine whether postoperative antiblood type antibody rebound is attributed to kidney allograft rejection in ABO blood type‐incompatible (ABO‐I) living‐related kidney transplantation (KTx). A total of 191 ABO‐I recipients who received ABO‐I living‐related KTx between 2001 and 2013 were divided into two groups: Group 1 consisted of low rebound [(≦1:32), N = 170] and Group 2 consisted of high rebound [(≧1:64), N = 21], according to the levels of the rebounded antiblood type antibodies within 1 year after transplantation. No prophylactic treatment for rejection was administered for elevated antiblood type antibodies, regardless of the levels of the rebounded antibodies. Within 1 year after transplantation, T‐cell‐mediated rejection was observed in 13 of 170 recipients (13/170, 8%) in Group 1 and in 2 of 21 recipients (2/21, 10%) in Group 2 (Groups 1 vs. 2, P = 0.432). Antibody‐mediated rejection was observed in 15 of 170 recipients (15/170, 9%) and 2 of 21 recipients (2/21, 10%) in Groups 1 and 2, respectively (P = 0.898). In this study, we found no correlation between the postoperative antiblood type antibody rebound and the incidence of acute rejection. We concluded that no treatment is necessary for rebounded antiblood type antibodies.     

Clinical impact of preformed donor‐specific denatured class I HLA antibodies after kidney transplantation

Class I single‐antigen flow beads (SAFB) carry native and denatured human leukocyte antigen (HLA) molecules. Using a cohort of 179 class I HLA‐sensitized kidney recipients, we described incidence and clinical relevance of preformed denatured HLA donor‐specific antibodies (DSA) using two different assays: an acid‐treated SAFB assay (anti‐dHLA DSA) and the iBeads assays (SAFB+/iBeads‐ DSA). Eighty‐five class I DSA were found in 67 patients (median mean fluorescence intensity [MFI] of 1729 [range 520–13 882]). Anti‐dHLA and SAFB+/iBeads‐ DSA represented 11% and 18% of class I DSA and were mainly low MFI DSA (500–1000 MFI). Concordance between these two assays was good (90%). None of the patients with only class I anti‐dHLA DSA or only SAFB+/iBeads‐ DSA developed acute clinical antibody‐mediated rejection in the first‐year post‐transplantation, and their five‐yr death‐censored graft survival was similar to that of patients without DSA. Moreover, all these patients displayed a negative current T‐cell flow cytometry cross‐match. Therefore, both anti‐dHLA DSA and SAFB+/iBeads‐ DSA appear irrelevant, which could explain the good outcome observed in some patients with preformed class I DSA.     

Urgent desensitization in patients bridged to heart transplantation under extracorporeal membrane oxygenation support: A preliminary experience

Antihuman leukocyte antigen (HLA) antibodies restrict the access to cardiac allografts. Desensitization therapy is a major challenge in patients with cardiogenic shock waiting for urgent heart transplantation (HT). We retrospectively reviewed six patients (mean age of 37.5 years [16–70]) who underwent plasmapheresis (PP) under extracorporeal membrane oxygenation (ECMO) before transplant between January 2017 and September 2018. The average duration of follow‐up was 25 months [20–32]. Mean fluorescence intensity (MFI) of HLA‐specific antibodies was reported as follows: score 4 for MFI < 1000, score 6 for 1000 < MFI < 3000 and score 8 for MFI > 3000. The mean duration of ECMO support was 29 days [1–74] and 6.8 [1–29] PP sessions were performed per patient before transplant. The mean number of HLA‐specific antibodies before HT was 9.6 for score 6 [4–13] and 5.8 for score 8 [1–12]. Four patients had major complications after transplantation (2 hemorrhagic shocks, 5 infectious events). Mean MFI reduction rate was 94% [79–100] for Class I and 44.2% for Class II [0–83]. Hospital survival was 100%, and early antibody‐mediated rejection was diagnosed in one patient at 7 days after HT. Plasmapheresis under ECMO support was associated with favorable early outcomes in highly sensitized candidates for urgent heart transplantation.     

Impact of pretransplant donor‐specific antibodies on kidney allograft recipients with negative flow cytometry cross‐matches

The Luminex test can detect low levels of donor‐specific antibody (DSA) that cannot be detected by flow‐cytometric cross‐matching (FCXM) in kidney transplantation (KT). This study evaluated the impact of DSA on clinical outcomes in KT recipients negative on FCXM. Of 575 consecutive patients who underwent living donor KT between January 2013 and July 2016, 494 (85.9%) were DSA‐negative and 81 (14.1%) were DSA‐positive. Although rates of acute cellular rejection (ACR) at 1 year were similar in the 2 groups (P = .54), the incidence of antibody‐mediated rejection (ABMR) was significantly higher in the DSA‐positive group (P < .01). There was no statistically significant association between rejection‐free graft survival (RFGS) rates and pretransplant class I DSA. However, evaluation of pretransplant class II DSA showed that RFGS rates were significantly lower in patients with mean fluorescence intensity (MFI) >3000 than in patients with DSA‐negative (P < .01). On multivariate analyses, class II DSA MFI ≥5000 was a significant risk factor for acute rejection (hazard ratio, 7.48; P < .01). These findings suggested that pretransplant DSA alone did not affect graft survival in KT recipients without desensitization. However, class II DSA MFI >5000 was an independent predictor of acute rejection in DSA‐positive patients.     

Intravenous immunoglobulins and rituximab therapy for severe transplant glomerulopathy in chronic antibody‐mediated rejection: a pilot study

Outcome of patients with transplant glomerulopathy (TG) is poor. Using B‐cell targeting molecules represent a rational strategy to treat TG during chronic antibody‐mediated rejection. In this pilot study, 21 patients with this diagnosis received four doses of intravenous immunoglobulins and two doses of rituximab (IVIG/RTX group). They were retrospectively compared with a untreated control group of 10 patients. At 24 months post‐biopsy, graft survival was similar and poor between the treated and the untreated group, 47% vs. 40%, respectively, p = 0.69. This absence of response of IVIG/RTX treatment was observed, regardless the phenotype of TG. Baseline estimated glomerular filtration rate (eGFR) and decline in eGFR during the first six months after the treatment were risk factors associated with 24‐month graft survival. The IVIG/RTX therapy had a modest effect on the kinetics of donor‐specific alloantibodies at M24, compared to the untreated group, not associated with an improvement in graft survival. The mean number of adverse events per patient was higher in the IVIG/RTX group than in the control group (p = 0.03). Taken together, IVIG/RTX treatment for severe TG during chronic antibody‐mediated rejection does not seem to change the natural history of TG and is associated with a high incidence of adverse events.     

Effects of different sensitization events on HLA alloimmunization in renal transplant cases; a retrospective observation in 1066 cases

BackgroundPatients awaiting solid organ transplantation may develop anti-HLA antibodies after sensitization events such as transfusions, pregnancies, or previous transplantations. However, the effects of a particular sensitization event on HLA alloimmunization have not been well studied in parallel using cell-based assays and solid-phase assays. In this study, we evaluated and compare how different sensitization events affect the HLA antibody screening (HLA-Ab) and donor specific antibody (DSA) status in solid renal organ transplantation patients.MethodsHLA antibody (HLA-Ab) screening tests like complement-dependent cytotoxicity crossmatch (CDC-XM), flow cytometry crossmatch (FC-XM) and Luminex panel-reactive antibody (L-PRA) were performed in all 1066 patients (635 males and 431 females). If any of these tests turned out to be positive, a Luminex single antigen bead (L-SAB) assay was performed for DSA identification. Test positive rates and antibody strengths were analyzed according to the different sensitization events and gender.ResultsIn this study, HLA-Ab screening tests positive rates (L-PRA, FC-XM and CDC-XM) were significantly higher in patients with previous transplantation (73.91%, 100% and 56.52% p < 0.001), previous pregnancy (57.46%, 70.14% and 18.85% p < 0.001) or blood transfusion (27.33%, 35.55% and 7.33% p < 0.001) compared with patients without a sensitizing event (6.17%, 13.58% and 1.09). In this study, re-transplantation group showed significantly stronger antibody strength (DSA) than non sensitized group (class I and II MFI 11418.04, 17,837.78 vs class I and II MFI 2659, 3329; P < 0.001) and those with single sensitization events of transfusion (class I and II MFI 11418.04, 17,837.78 vs class I and II MFI 5790.26, 6004.16; P < 0.001) or pregnancy (class I & II MFI 11418, 17,837 vs class I and II MFI 8631.71, 7253.29; P < 0.001).ConclusionsPregnancy and blood transfused had high allo-immunization rate for class I HLA antigens. While re-transplantation patients had high allo-immunization rate for both the HLA classes (HLA- class I and HLA- class II). Re-transplantation group showed significantly stronger antibody strength, followed by pregnancy and then transfusion.     

Advances in diagnosing and managing antibody-mediated rejection

Antibody-mediated rejection (AMR) is a unique, significant, and often severe form of allograft rejection that is not amenable to treatment with standard immunosuppressive medications. Significant advances have occurred in our ability to predict patients at risk for, and to diagnose, AMR. These advances include the development of newer anti-human leukocyte antigen (HLA)-antibody detection techniques and assays for non-HLA antibodies associated with AMR. The pathophysiology of AMR suggests a prime role for antibodies, B cells and plasma cells, but other effector molecules, especially the complement system, point to potential targets that could modify the AMR process. An emerging and potentially larger problem is the development of chronic AMR (CAMR) resulting from de novo donor-specific anti-HLA antibodies (DSA) that emerge more than 100 days posttransplantation. Therapeutic options include: (1) High-dose intravenously administered immunoglobulin (IVIG), which has many potential benefits. (2) The use of IVIG + rituximab (anti-CD20, anti-B cell). (3) The combination of plasmapheresis (PP) + low-dose IVIG with or without rituximab. Data support the efficacy of all of the above approaches. Newer approaches to treating AMR include using the proteosome inhibitor (bortezomib), which induces apoptosis in plasma cells, and eculizumab (anti-C5, anticomplement monoclonal antibody).     

Treatment of chronic antibody mediated rejection with intravenous immunoglobulins and rituximab: A multicenter,prospective, randomized,double‐blind clinical trial

There are no approved treatments for chronic antibody mediated rejection (ABMR). We conducted a multicenter, prospective, randomized, placebo‐controlled, double‐blind clinical trial to evaluate efficacy and safety of intravenous immunoglobulins (IVIG) combined with rituximab (RTX) (EudraCT 2010‐023746‐67). Patients with transplant glomerulopathy and anti‐HLA donor‐specific antibodies (DSA) were eligible. Patients with estimated glomerular filtration rate (eGFR) <20 mL/min per 1.73m² and/or severe interstitial fibrosis/tubular atrophy were excluded. Patients were randomized to receive IVIG (4 doses of 0.5 g/kg) and RTX (375 mg/m²) or a wrapped isovolumetric saline infusion. Primary efficacy variable was the decline of eGFR at one year. Secondary efficacy variables included evolution of proteinuria, renal lesions, and DSA at 1 year. The planned sample size was 25 patients per group. During 2012‐2015, 25 patients were randomized (13 to the treatment and 12 to the placebo group). The planned patient enrollment was not achieved because of budgetary constraints and slow patient recruitment. There were no differences between the treatment and placebo groups in eGFR decline (?4.2 ± 14.4 vs. ?6.6 ± 12.0 mL/min per 1.73 m², P‐value = .475), increase of proteinuria (+0.9 ± 2.1 vs. +0.9 ± 2.1 g/day, P‐value = .378), Banff scores at one year and MFI of the immunodominant DSA. Safety was similar between groups. These data suggest that the combination of IVIG and RTX is not useful in patients displaying transplant glomerulopathy and DSA.     

ABO-incompatible living donor liver transplantation with high preoperative antibody titer: A case report

Introduction and importanceABO-incompatible living donor liver transplantation (ABOi-LDLT) is essential for expanding the donor pool. ABOi-LDLT prognosis has improved since desensitization treatment with rituximab; however, patients with high antibody titers are considered to be at high risk of antibody mediated rejection (AMR). Nevertheless, the preoperative antibody titer cutoff levels that preclude ABOi-LDLT have not yet been determined. In this study, the highest preoperative antibody titer was 1:4096, and the recipient had good outcomes. There has been only one report of good outcomes with a preoperative antibody titer of more than 1:4096. We hypothesized that high preoperative antibody titers in ABOi-LDLT may not be associated with AMR in protocols involving rituximab.Case presentationThe recipient was a 22-year-old man with biliary atresia and underwent ABOi-LDLT (B to O). We administered 500 mg of rituximab 14 days prior and then 300 mg of rituximab one day prior to ABOi-LDLT. The recipients preoperative IgG antibody titer was 1:4096. Postoperative immunosuppressive protocol involved steroids, tacrolimus, and mycophenolate mofetil. The patient had satisfactory graft function three years following ABOi-LDLT.Clinical discussionThe antibody that is responsible for posttransplant AMR should be newly synthesized after transplantation as a result of sensitization by antigens on the vascular endothelial cells of the graft. In ABOi-LDLT, natural antibodies may not cause AMR.ConclusionsThe most important factor for preventing AMR in recipients undergoing ABOi-LDLT is the suppression of de novo antibodies. High preoperative antibody titers may not necessarily preclude ABOi-LDLT, provided that rituximab is used in desensitization.     

Acute antibody-mediated rejection in paediatric renal transplant recipients

Acute antibody-mediated rejections (aAMR) after renal transplantation are defined by rapidly deteriorating graft function, detection of donor-specific antibodies (DSA) and characteristic histological features. In adults, anti-rejection strategies comprise intravenous immunoglobulin (IVIG), steroid pulses, plasmapheresis and rituximab. Data of children with aAMR are scarce. We report four episodes of aAMR in three children (aged 10, 10 and 11 years respectively) occurring early after renal transplantation. Pre-transplant complement-dependent cytotoxicity crossmatches were negative; in the case of re-transplantation repeated antigens were excluded. Basic immunosuppression comprised cyclosporine A, MMF and steroids. All four rejection episodes were histologically proven and associated with acute renal failure. De novo DSAs were detected in two aAMRs; one patient was additionally tested positive for AT1-receptor antibodies. All aAMRs were treated with steroid pulses, tacrolimus, MMF, IVIG, plasmapheresis and one single dose of rituximab. Despite therapy one graft was lost; in the remaining three cases kidney function re-established within 1–8 weeks. At follow-up, 14, 15 and 22 months’ post-rejection their GFRs were 65, 88 and 105 ml/min/1.73 m² respectively. A combined therapy of steroid pulses, IVIG, plasmapheresis and rituximab is potentially effective in the treatment of aAMR in children.     

The Effect of Desensitization Protocols on Human Splenic B-Cell Populations In Vivo

Rituximab, intravenous immunoglobulin (IVIG) and rabbit antithymocyte globulin (rATG) all have been suggested to have an effect on antibody producing cells, however, supporting data are lacking. To assess the impact of these agents on splenic B‐cell populations in vivo, we retrospectively examined 25 spleens removed from patients treated with these agents as part of desensitization protocols in either ABO incompatible or positive crossmatch living donor kidney transplantation. These were compared to control (CTL) spleens removed for trauma. CTLs and spleens removed at transplant after multiple pretransplant plasmaphereses (PP) plus low‐dose IVIG showed similar large numbers of naïve B cells (CD20⁺ and CD79⁺), plasma cells (CD138⁺) and memory B cells (CD27⁺ cells). Adding rituximab to this PP/IVIG regimen reduced the number naïve B cells, but had no effect on memory or plasma cells. Combination treatment (PP/IVIG, rituximab and rATG) showed a trend toward the reduction of CD27⁺ cells, but again plasma cells were unchanged. We conclude that none of these protocols reduces splenic plasma cells in vivo. PP/low‐dose IVIG does not alter splenic B cells, but the addition of rituximab decreases mature B cells. Memory B cells may be affected by combination therapy including rATG and requires further study.     

Effect of recipient gender and donor‐specific antibodies on antibody‐mediated rejection after heart transplantation

Gender‐difference regarding antibody‐mediated rejection (AMR) after heart transplantation has been described. However, no study accounted for the presence of preformed donor‐specific antibodies (pfDSA), a known risk factor of AMR, more common among women than men. In a single‐institution 6‐year cohort (2010‐2015), time to AMR was assessed, comparing men with women by survival analysis with a 1‐year death‐censored follow‐up. All AMRs were biopsy proven. Confounding variables that were accounted for included mean intensity fluorescence (MFI) of pfDSA, recipient age, HLA‐, size‐ and sex‐mismatch. 463 patients were included. Overall incidence of AMR was 10.3% at 1 year. After adjusting for confounding variables, independent risk factors of AMR were female recipient gender (adjusted hazard‐ratio [adj. HR] = 1.78 [1.06‐2.99]), P = .03) and the presence of pfDSA (adj. HR = 3.20 [1.80‐5.70], P < .001). This association remained significant when considering pfDSA by their MFI; female recipient gender had an adj. HR = 2.2 (P = .026) and MFI of pfDSA (per 1 MFI‐increase) adj. HR = 1.0002 (P < .0001). In this cohort, women were at higher risk of AMR than men and this risk increase was additive to that of pfDSA. These findings may suggest a gender‐related difference in the severity of pfDSA.     

Impact of the Presence and Duration of Donor-Specific Antibodies on Renal Function

Background

Although anti-human leukocyte antigen (HLA) antibodies (DSA) is associated with graft loss, 3 things remain unclear: whether the duration and strength of DSA affect renal function; what mean fluorescence intensity (MFI) cut-off should be used; and whether the DSA effect is additive in case of multiple DSAs.

Methods

A study was made of 63 patients who received living donor kidney transplants with clonal deletion protocol and were followed up for 18 months with reduced doses of immunosuppressants. DSA was tested for monthly, using Luminex Mixed and Single Antigen beads (One Lambda, Inc., Canoga Park, CA, USA). Decrease of estimated glomerular filtration rate (eGFR) was obtained at baseline and 18 months after transplantation. Association of renal damage and DSAs was compared using several DSA models with several MFI cut-offs.

Results

Additive DSA models always showed better association with renal damage than comprehensive models. When calculating the DSA effect in additive models, “proxy-area under the curve” (AUC)—a triangular approximation of the actual AUC—showed better association with renal damage than did DSA duration (R² = 0.105 vs 0.087). Adjusting for other factors, 27% of the variation of GFR change was explained by proxy-AUC. No significant change of association occurred if the MFI cut-off level changed from 1000 to 3000.

Conclusion

Our results support the association of DSA with development of longitudinal renal damage. The clinical interpretation may be similar at MFI cut-offs of 1000, 2000, and 3000. An additive DSA effect may be expected in patients with multiple DSAs. Our study suggests the importance of frequently checking for DSA and reducing their MFI value to minimize renal damage by the antibodies.     

Desensitization protocol in highly HLA-sensitized and ABO-incompatible high titer kidney transplantation

Background

A positive crossmatch indicates the presence of donor-specific alloantibodies and is associated with a graft loss rate of >80%; anti-ABO blood group antibodies develop in response to exposure to foreign blood groups, resulting in immediate graft loss. However, a desensitization protocol for highly HLA-sensitized and ABO-incompatible high-titer kidney transplantation has not yet been established.

Methods

We treated 6 patients with high (≥1:512) anti-A/B antibody titers and 2 highly HLA-sensitized patients. Our immunosuppression protocol was initiated 1 month before surgery and included mycophenolate mofetil (1 g/d) and/or low-dose steroid (methylprednisolone 8 mg/d). Two doses of the anti-CD20 antibody rituximab (150 mg/m²) were administered 2 weeks before and on the day of transplantation. We performed antibody removal with 6–12 sessions of plasmapheresis (plasma exchange or double-filtration plasmapheresis) before transplantation. Splenectomy was also performed on the day of transplantation. Postoperative immunosuppression followed the same regimen as ABO-compatible cases, in which calcineurin inhibitors were initiated 3 days before transplantation, combined with 2 doses of basiliximab.

Results

Of the 8 patients, 7 subsequently underwent successful living-donor kidney transplantation. Follow-up of our recipients showed that the patient and graft survival rates were 100%. Acute cellular rejection and antibody-mediated rejection episodes occurred in 1 of the 7 recipients.

Conclusions

These findings suggest that our immunosuppression regimen consisting of rituximab infusions, splenectomy, plasmapheresis, and pharmacologic immunosuppression may prove to be effective as a desensitization protocol for highly HLA-sensitized and ABO-incompatible high-titer kidney transplantation.