|Year : 2020 | Volume
| Issue : 2 | Page : 175-181
Role of donor-specific antibodies in immunological assessment for kidney transplant: A report of ten cases in a cost-limited set-up
Joyita Bharati1, Deepesh Benjamin Kenwar2, Sarabpreet Singh2, Ritambhra Nada3, Harbir Singh Kohli1, Manish Rathi1, Ashish Sharma2, Ranjana Walker Minz4, Raja Ramachandran1
1 Department of Nephrology, Post Graduate Institute of Medical Education and Research, Chandigarh, India
2 Department of Renal Transplant Surgery, Post Graduate Institute of Medical Education and Research, Chandigarh, India
3 Department of Histopathology, Post Graduate Institute of Medical Education and Research, Chandigarh, India
4 Department of Immunopathology, Post Graduate Institute of Medical Education and Research, Chandigarh, India
|Date of Submission||05-Sep-2019|
|Date of Acceptance||15-Mar-2020|
|Date of Web Publication||06-Jul-2020|
Dr. Raja Ramachandran
Department of Nephrology, Post Graduate Institute of Medical Education and Research, Chandigarh
Source of Support: None, Conflict of Interest: None
Sensitized patients, who constitute a considerable proportion of kidney-transplant recipients, often have poor allograft outcomes. Only cell-based complement-dependent cytotoxicity (CDC) assays are typically used to quantify donor-specific antibodies (DSAs) in patients in developing nations, owing to financial restraints. We report the clinical outcomes of ten sensitized patients who were stratified and managed based on Luminex single-antigen beads (SAB) method for the DSA detection in a cost-limited set-up. Sensitization events included a history of blood transfusion, multiple pregnancies, and previous allograft loss. Anti-human leukocyte antigen antibodies, measured by SAB and reported as mean fluorescence intensity (MFI), were considered positive if the value was > 1000 MFI for single antigen. Three best approaches, (1) cadaveric transplants using virtual cross-match for kidney allocation in five patients, (2) desensitization before living donor transplants for four donor–recipient pairs with immunological incompatibility (high DSAs but cross-match compatible), and (3) combined kidney paired exchange with desensitization for one donor–recipient pair with cross-match incompatibility (positive CDC cross-match), resulted in successful allograft outcomes in all the 10 patients during follow-up (range: 3–55 months). DSA by SAB to assess pretransplant immunological risk (in a sensitized recipient) is useful even in cost-limited settings, largely due to reduction of posttransplant rejection rates and avoidance of mortality while on the waitlist.
Keywords: Allograft survival, desensitization, donor-specific antibodies, kidney transplant
|How to cite this article:|
Bharati J, Kenwar DB, Singh S, Nada R, Kohli HS, Rathi M, Sharma A, Minz RW, Ramachandran R. Role of donor-specific antibodies in immunological assessment for kidney transplant: A report of ten cases in a cost-limited set-up. Indian J Transplant 2020;14:175-81
|How to cite this URL:|
Bharati J, Kenwar DB, Singh S, Nada R, Kohli HS, Rathi M, Sharma A, Minz RW, Ramachandran R. Role of donor-specific antibodies in immunological assessment for kidney transplant: A report of ten cases in a cost-limited set-up. Indian J Transplant [serial online] 2020 [cited 2021 Apr 14];14:175-81. Available from: https://www.ijtonline.in/text.asp?2020/14/2/175/289040
| Introduction|| |
Pretransplant immunological testing is an assessment of donor–recipient histocompatibility, which predominantly includes human leukocyte antigen (HLA) alloimmunization. Presence of pretransplant anti-HLA antibodies is associated with increased risk of allograft failure. Sensitization is the process by which a person develops anti-HLA antibodies on exposure to nonself-HLA antigens. Patients with kidney-transplant prospects are often sensitized with anti-HLA alloantibodies, owing to exposure to blood transfusion, pregnancy, previous kidney transplant, and infections (cross-reactive antigens). Transplant recipients are usually stratified as “high risk,” “intermediate risk,” or “low risk” based on the presence of pretransplant donor-specific antibodies (DSAs), which determine their risk for early allograft rejection. Irrespective of alloimmunization, in developing/underdeveloped countries, the immunological work-up in most centers (including ours) is limited to complement-dependent cytotoxicity (CDC) cross-match alone. Using this approach, we found high early rejection rates (26%) at our center. Notably, a considerable proportion (78%) of the patients with rejection had sensitization events in the form of blood transfusion. Detection of anti-HLA antibodies by single-antigen beads (SAB) Luminex-assay, although expensive, is more sensitive and specific allowing better risk stratification of recipients, particularly those exposed to sensitization events. The cost of DSA (by SAB) for both Class I and Class II HLA antibodies is 15,000 INR at our center. High acute rejection rates and increased exposure to sensitizing episodes (>40% of our patients), along with continued dependency on only CDC is likely to yield poor long-term results. In the current manuscript, we report ten patients with a history of sensitization events that were managed using DSA (measured by SAB)-based risk assessment and describe its implications in a cost-limited setting.
The clinical details of the ten patients with a history of sensitization event who underwent living or cadaveric transplant using DSA (SAB) for risk assessment at our center are described below. Sensitization events included a history of blood transfusion, multiple pregnancies, and previous allograft loss. The number, time, and type of sensitization events per patient are shown in [Table 1]. After an audit of acute rejection rate, our current practice for all patients with prior sensitizing events includes additional pretransplant immunological testing by flow cytometry cross-match (FCXM) and DSA (SAB). Median channel shift of > 120 and > 55 was the threshold cutoffs for positive B-cell and T-cell FCXM, respectively. Anti-HLA antibodies, measured by SAB and reported as mean fluorescence intensity (MFI), were considered positive if the value was > 1000 MFI for single antigen. In the presence of > 1 DSA of > 5000 MFI and/or positive CDC cross-match, transplant in the donor–recipient pair is considered unacceptable at our center. For those with > 1 DSAs between 1000 and 5000 MFI with a negative FXCM and CDC cross-match, options for kidney paired exchange and desensitization followed by transplant are explained to the patient. Patient details are shown in [Table 1].
| Case Scenario 1: Cadaveric Transplant Using Virtual Cross-Match for Allocation|| |
Five patients with a history of prior sensitization events and positive anti-HLA antibodies (as defined above) were enrolled in the deceased donor registry of our center. Cadaveric donor HLA typing was performed for all these transplants (the cost of HLA typing of donor was borne by the hospital), and a virtual cross-match with the recipients' DSA (SAB) was done. Transplant was performed if the virtual cross-match was negative, i.e., single-antigen DSAs were <1000 MFI. Patient #5 had previous kidney allograft loss due to acute thrombotic microangiopathy (no identified etiology). Patients #1–4 had exposure to blood transfusion in the preceding 2 years of transplant evaluation [Table 1]. Further, patient #4 had three successful pregnancies. The posttransplant course was uneventful in four of the five patients, and serum creatinine decreased to <1.5 mg/dl in all patients. Patient #3 was given methylprednisolone pulses (500 mg for 3 days) for acute cellular rejection (Grade IA) on day 15 posttransplant to which she responded with a reduction of serum creatinine from 1.6 to 0.9 mg/dl. Patient #2 had a recurrence of focal segmental glomerulosclerosis (proteinuria 6 g/day and electron microscopy suggestive of foot process effacement) on day 4 posttransplant, for which was successfully treated with seven sessions of plasma exchange performed. Her nadir serum creatinine was 1.0 mg/dl on day 8 posttransplant and proteinuria reduced to 1 g/day. Posttransplant anti-HLA antibodies were not routinely monitored in any patient. Patient #4 died after 3 months of the transplant due to a cardiac cause; however, her serum creatinine was 0.8 mg/dl until 2 days before her demise.
| Case Scenario 2: Living Donor Transplant Using Desensitization|| |
Four patients with the previous history of failed renal allograft and positive anti-HLA antibodies underwent living donor transplant. The cause of allograft failure in all the four patients was rejection (cellular or antibody-mediated) occurring after the 1st year of transplantation. Allograft survival ranged between 5 and 13 years. One patient with his elder sister as the donor had negative DSA, FXCM, and CDC cross-match in addition to zero mismatches on HLA typing. Other three of the four patients (patients #7–9) underwent desensitization for the reduction of antibodies (DSAs) using plasmapheresis (centrifugal apheresis technique; 40 ml/kg plasma removal each session; replacement with albumin; for 7 sessions) and low-dose intravenous immunoglobulin at 100 mg/kg at the last plasma exchange session. Desensitization was done in these three patients because of positive DSAs (1000–5000 MFI) in all and positive T-cell and B-cell FXCM, additionally, in one patient (patient #9). These patients were also enrolled in the kidney paired exchange program; however, as the chances of benefiting from such a program at a single center are less likely, desensitization with the same donor opted after patient consent. All these three patients had negative DSAs after desensitization. Furthermore, all the four patients received anti-thymoglobulin (ATG), at 1 mg/kg over 3 days, as the induction agent, and were continued on tacrolimus, mycophenolate mofetil, and prednisolone as maintenance immunosuppression. Desensitization therapy was not continued in the immediate posttransplant period in any patient. Serum creatinine reduced to <1.5 mg/dl posttransplant over 1–2 weeks in all the patients with none of them developing biopsy-proven acute rejection. Posttransplant DSAs at 3 months remained negative in all four patients.
| Case Scenario 3: Living Donor Transplant Using Kidney Paired Exchange Combined With Desensitization|| |
Patient #10 was on maintenance hemodialysis for 2 years with a poorly functioning arteriovenous fistula. He was sensitized due to multiple blood transfusions with positive anti-HLA antibodies for Class I and II HLA antigens. The transplant was unacceptable with his wife as the only potential donor as the CDC cross-match was positive with multiple positive SAB-DSAs. His chances for cadaveric transplant were poor and remote, owing to his numerous positive anti-HLA antibodies. While he was put on the deceased donor registry list, another donor–recipient pair with ABO incompatibility (ABOi) was identified from our center's kidney pair exchange program. A possible swap of donors was planned after written informed consent from the patients, as there was blood group compatibility across the pairs. While CDC of both the donor–recipient pairs was negative, B-cell FCXM of patient #10 was borderline positive. Besides, the patient #10 had positive DSA for a single antigen (HLA* A-24:02) to his intended swap donor too. Desensitization was done using rituximab (375 mg/m2 single dose on day 15 of transplant) and plasma exchange (7 sessions, using the same technique as described above) for the patient# 10 after which his DSA reduced from 12,192 to 1091 MFI. Tacrolimus (0.1 mg/kg/day) and mycophenolate mofetil (1 g/day) were also started simultaneously from the day 15 of transplant. Pretransplant CDC cross-match after desensitization was negative, and with an acceptable low-strength DSA of 1091 MFI, this patient–donor pair underwent operation simultaneously with the other ABO and HLA compatible donor–recipient pair. He was induced with ATG (3 mg/kg) and had a nadir serum creatinine of 1.4 mg/dl on postoperative day 12. Desensitization was not continued in the immediate posttransplant period. At 1 month following transplantation, he developed a rise in serum creatinine to 1.9 mg/dl, with an increase in DSA titer to 4000 MFI. Kidney allograft biopsy, done at the same time, did not reveal rejection. However, because of raised DSA, as per the current recommendation, plasmapheresis (5 sessions, using the same technique as described above) was done following which DSA fell to 1800 MFI. His serum creatinine remained < 1.5 mg/dl until his last visit at 1-year posttransplant.
| Discussion|| |
Kidney transplant in sensitized patients is hindered on account of the unacceptable match and poor allograft outcome. We describe ten patients with positive anti-HLA antibodies (SAB) who underwent successful transplants with an immunologically favorable donor in a cost-limited setting. We used three best approaches to transplant these sensitized patients, namely cadaveric transplants using virtual cross-match for kidney allocation, desensitization before living donor transplants for donor–recipient pairs with immunological incompatibility (high DSAs but cross-match compatible), and kidney paired exchange combined with desensitization for a donor–recipient pair with cross-match incompatibility (positive CDC cross-match). The strategy, as mentioned above, led to a successful transplant of the sensitized patients.
Kidney transplantation leads to better survival and quality of life in patients with end-stage renal disease as compared to being on dialysis. Sensitized patients, comprising up to one-third of the patients on the waitlist, are infrequently transplanted due to issues in finding compatible donors. They were previously identified based on panel reactive antibody (PRA) using cell-based assays. However, due to the lack of reliability of this method and the poor outcomes related to the presence of pretransplant DSAs, it is prudent to use newer techniques of DSA detection. Using an appropriate assessment of pretransplant DSAs and desensitization in the presence of DSAs, survival is better than being on the waitlist or receiving an incompatible transplant.
Five patients with high anti-HLA antibodies due to previous sensitization events underwent successful cadaveric transplant after negative virtual cross-matches used for allocation. In the absence of information based on anti-HLA antibodies by SAB, these patients would not have received priority on the waitlist, given the lesser sensitivity and specificity of PRA alone in them. Moreover, transplantation in the absence or low levels of DSAs (detected by SAB assay) might have contributed to satisfactory allograft outcomes in these patients. The importance of pretransplant graft outcome prediction using DSAs measured by SAB assay was depicted in a study showing increased acute antibody-mediated rejection (AMR) and worse graft survival in patients with DSAs (by SAB) despite having negative CDC cross-match. While DSA > 6000 MFI was associated with the highest risk of AMR, there was a gradation of the risk for AMR and long-term graft survival based on levels of DSA titer above 465 MFI. The significance of preformed DSAs (measured using SAB) was also recently highlighted in a large retrospective study showing lower long-term graft survival in patients with preformed DSAs ≥3000 MFI who underwent living or deceased donor transplant. The finding that even weak DSA <3000 MFI was associated with worse graft survival is worthy of note.
In the presence of preformed DSAs, transplantation following desensitization has been a standard approach. However, the methods of detection of DSA and desensitization protocols vary across centers. Furthermore, the cutoff value for the strength of DSA (measured by SAB) to decide desensitization is challenging to standardize owing to inherent limitations of the method. Our desensitization protocol consists of plasmapheresis with or without rituximab based on previous studies., Four patients with sensitization from previous transplants received living donor transplants; three underwent desensitization to allow the least HLA incompatibility and one underwent HLA compatible transplant with his sister who had zero HLA mismatches with him. One patient with cross-match incompatibility with his only potential living donor was successfully transplanted using combined desensitization and kidney paired exchange approach. He was matched to the swapped donor with the least amount of incompatibility and underwent desensitization. In the absence of an HLA compatible donor in highly sensitized patients, desensitization to lower DSAs may be the only option for early transplant. Successful transplantation is possible these days owing to the availability of better techniques of anti-HLA antibody detection, effective therapies to lower down the antibodies, and better understanding of AMR. While the rates of acute AMR are higher in patients who underwent desensitization than nonsensitized patients, short-term graft survival seems to be promising. Furthermore, transplantation after desensitization protocols has been shown to improve survival of sensitized patients as compared to remaining on chronic dialysis., There was, however, a concern about the poor long-term success of desensitization protocols as observed in studies showing longer follow-up of sensitized patients who underwent transplant following desensitization. The association between the strength and number of DSAs with short-term and long-term allograft outcomes also needs to be standardized for different ethnicities and geographical distribution.
Newer treatment options such as immunoglobulin G-degrading enzyme of Streptococcus pyogenes may be more useful for highly sensitized HLA-incompatible patients. Nevertheless, on account of the possibility of rebound of DSAs and a higher risk of acute rejections, kidney paired exchange (ideally through national programs) should be the initial approach for highly sensitized patients. Using combined kidney paired exchange and desensitization, we were able to transplant a highly sensitized patient in a single-center kidney paired exchange program. This combined strategy was earlier reported to be successful by another center from our country  and across the world. Kidney paired exchange, particularly at a single center, is more effective for donor–recipient pair with comfortable to match ABOi and/or high HLA incompatibility where desensitization would fail or transplant is unacceptable.
We conclude that the use of newer DSA detection methods to characterize pretransplant immunological risk (in a sensitized recipient) can lead to earlier and better-matched transplant even in a cost-limited setting. The reduction of posttransplant rejection rates (and allograft survival) and avoidance of mortality while on the waitlist for transplant justify such assessment despite its costs, as aptly summarized – not to be “penny-wise and pound-foolish.”
Declaration of patient consent
The authors certify that patient consent has been taken for participation in the study and for publication of clinical details and images. Patients understand that the names, initials would not be published, and all standard protocols will be followed to conceal their identity.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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