|Year : 2020 | Volume
| Issue : 2 | Page : 130-135
Effect of De novo donor-specific antibodies on graft function in renal allograft recipients
Ravi Kumar Singh1, Ashwani Gupta1, Vinant Bhargava1, Anurag Gupta1, Vaibhav Tiwari1, Manish Malik1, AK Bhalla1, DS Rana1, Monika Jain2
1 Institute of Renal Sciences, Sir Ganga Ram Hospital, New Delhi, India
2 HLA and Immunogenetics Laboratory, Sir Ganga Ram Hospital, New Delhi, India
|Date of Submission||22-Jan-2020|
|Date of Acceptance||17-May-2020|
|Date of Web Publication||06-Jul-2020|
Dr. Ravi Kumar Singh
Institute of Renal Sciences, Sir Ganga Ram Hospital, New Delhi
Source of Support: None, Conflict of Interest: None
Background: De novo formation of donor-specific antibodies (DSA) against donor human leukocyte antigens (HLAs) class I and II has been recognized as one of the major risk factors for reduced allograft survival. This study aimed to detect the de novo DSA in renal transplanted recipients and their association with graft function. Methods: This was a retro-prospective observational study conducted from July 2017 to March 2019. The patients with pretransplant DSA-negative renal allograft and those who fulfilled the inclusion criteria were enrolled. Posttransplant, HLA-specific antibodies were tested using a panel reactive antibody (PRA) screen and a positive PRA screen was further tested by Luminex crossmatch assay. Posttransplant biochemical data were assessed for 6-, 12-, and 18-month follow-ups. Results: A total of 72 patients were included in this study, of which 63 were diagnosed as de novo DSA negative, and nine were diagnosed as de novo DSA positive. At 18-month follow-up, in the patients with de novo DSA positive, 55.55% patients showed positive DSA levels for HLA Class II, 33.33% patients showed border-line DSA levels for HLA Class II, and 11.11% patients showed border-line DSA levels for HLA Class I (P < 0.001). Proteinuria was high in de novo DSA-positive patients than de novo DSA negative while serum creatinine, estimated glomerular filtration rate, and tacrolimus level were comparable between groups at 6-, 12-, 18-month follow-up periods. Conclusion: The incidence of de novo DSA was developed in 12.5% of patients; however, there was no significant graft dysfunction.
Keywords: Antibodies, graft, human leukocyte antigen, kidney transplant, Luminex assay
|How to cite this article:|
Singh RK, Gupta A, Bhargava V, Gupta A, Tiwari V, Malik M, Bhalla A K, Rana D S, Jain M. Effect of De novo donor-specific antibodies on graft function in renal allograft recipients. Indian J Transplant 2020;14:130-5
|How to cite this URL:|
Singh RK, Gupta A, Bhargava V, Gupta A, Tiwari V, Malik M, Bhalla A K, Rana D S, Jain M. Effect of De novo donor-specific antibodies on graft function in renal allograft recipients. Indian J Transplant [serial online] 2020 [cited 2020 Aug 5];14:130-5. Available from: http://www.ijtonline.in/text.asp?2020/14/2/130/289047
| Introduction|| |
Chronic antibody-mediated rejection (cAMR) is the most common cause of late allograft failure. The mechanism of cAMR is unclear and is still under investigation. It is caused by the development of antibodies that do not preexist but develop after transplantation and are directed against foreign human leukocyte antigens (HLAs) class I and II antigens, known as de novo donor-specific antibodies (DSA). According to the majority of the studies, approximately 15%–20% of the kidney-transplanted adults develop de novo DSA.,,,,, In studies, patients with DSA show significantly higher proteinuria and this seems to be an important factor determining rapid glomerular filtration rate (GFR) decline and responsiveness to therapy.
The levels of DSA can be immunologically monitored by directly cross-matching recipient sera with donor lymphocytes using complement-dependent lymphocytotoxicity, flow cytometry, or Luminex assay. The posttransplant monitoring can be useful to guide immunotherapy and permit early interventions like increasing doses of mycophenolate mofetil  and maintaining proper tacrolimus levels.
Evidence suggests that the presence of preexisting DSA can cause hyperacute rejection, accelerated acute rejection and graft loss ,, whereas de novo DSA leads to increased acute rejection, cAMR, and allograft failure.,,, In spite of that, some results showed that patients with persistent DSA do not develop damage to the graft. However, there is a discrepancy between the exact properties of de novo DSA and its effect on AMR and graft outcome. A systematic review of the observational study reported that de novo DSA is responsible for the increased risks of graft failure and poor renal transplant outcomes. Nevertheless, inconclusive results exist in literature due to factors such as heterogeneity. To our knowledge, the present study is the first Indian study to evaluate the association between de novo DSA and graft failure. Therefore, the present study aimed to detect the de novo DSA in renal transplant recipients and determine its effect on renal allograft function up to 18 months posttransplant.
| Methods|| |
This was a retro-prospective observational study conducted at the Sir Ganga Ram Hospital, New Delhi, India, from July 2017 to March 2019. The study protocol was approved by the Institutional Ethics Committee and the study procedure was in accordance with the principles of the Declaration of Helsinki. Written informed consent was obtained from all participants.
For retrospective analysis, the inclusion criteria included patients with renal transplant surgery within 6 months of the date of approval of the study, having live donor from family, with pretransplant workup details, with no episodes of rejection in the last 6 months and willing to give informed consent for the study. Similarly, patients with more than 18 years of age and who had live donors from family were included prospectively. Patients with pretransplant DSA positive, posttransplant graft dysfunction secondary to the biopsy-proven recurrence of primary disease, calcineurin inhibitors toxicity, polyomavirus nephropathy or interstitial nephritis, posttransplant graft dysfunction due to urinary tract obstruction or pyelonephritis and who were unwilling to give consent for the study were excluded.
All patients received induction as per their immunological risk profile and received standard triple drug immunosuppression, i.e., tacrolimus, mycophenolate mofetil, and prednisolone.
Posttransplant, the patient's serum samples were tested for the presence of the HLA-specific antibodies using panel reactive antibody (PRA) screen. The positive PRA screen was further tested by Luminex crossmatch assay. The reactions with mean fluorescence intensity (MFI) <1000, 1000–2000, and > 2000 were considered negative, borderline, and positive, respectively. Complement fixation of the DSA was not determined. The levels of DSA were measured at 6-, 12-, and 18 months posttransplant. PRA screen and DSA Luminex crossmatch was done in all patients posttransplant at 6 months interval as per the study protocol. Depending on the DSA levels observed at follow-up, they were divided into two groups, DSA positive and DSA negative.
Posttransplant clinical characteristics along with laboratory data including serum creatinine, estimated GFR (eGFR), proteinuria, and tacrolimus level were assessed for 6-, 12-, and 18 months. The levels of serum creatinine were measured by the Jaffe kinetics methods. The eGFR was calculated by the chronic kidney disease and modification of diet in renal disease (CKD MDRD) (4 Points) method using the creatinine values. Proteinuria was determined as a protein/creatinine ratio (mg/mg) from spot urine samples. Non-adherence was recorded by routine (every 3rd month) multidisciplinary patient/parents consulting through clinicians and psychologists.
Graft kidney biopsy was performed only when there was graft dysfunction. Graft dysfunction was diagnosed if serum creatinine increased to ≥25% from baseline or proteinuria ≥0.5 g per day without a known cause. Graft loss was defined by the need to return to dialysis.
The 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. The study has been approved by Institutional ethics committee of Sir Ganga Ram Hospital, New Delhi (EC/07/17/1200).
Statistical analyses were performed using SPSS version 23.0. The numerical variables were presented as mean (standard deviation [SD]) and categorical variables were expressed as number (percentage). Categorical variables were compared with the Chi-square test. Continuous variables were compared with independent sample T-test (for normally distributed data). Statistical significance was defined as P < 0.05.
| Results|| |
A total of 76 patients, who underwent a renal transplant, were enrolled in this study. Out of 76 patients, four patients died within 6 months of transplant, hence they were excluded. Of the remaining 72 patients, 63 (87.50%) were diagnosed as de novo DSA negative, and 9 (12.50%) were diagnosed as de novo DSA positive at 18-month follow-up. The mean age of de novo DSA negative and positive recipients was 40.94 years and 34.67 years, respectively. The number of men and women in de novo DSA-negative group was 51 (80.95%) and 12 (19.04%), respectively, while the number of men and women in de novo DSA-positive group was 7 (77.77%) and 2 (22.22%), respectively [Table 1]. The demographic characteristics of the donor are summarized in [Table 2].
Clinical monitoring in the form of urine routine examination, proteinuria estimation, and tacrolimus level estimation was done along with DSA testing at every 6 months interval for 18 months posttransplant. Before transplantation, all patients were tested and found to have no preformed DSA.
[Figure 1]a shows pretransplant DSA levels. At follow-up after 6 months, the de novo DSA-negative group showed no presence of DSA for HLA class I and II in 62 patients (98.41%), and one patient (1.58%) showed border-line DSA for HLA class I and II. However, in de novo DSA-positive group, four patients (44.44%) showed DSA positive for HLA class II, three patients (33.33%) showed no presence of DSA for HLA class I and II, one patient (11.11%) showed borderline DSA for HLA class II and one patient (11.11%) showed border-line DSA for HLA class I. There was a significant difference in the DSA levels between de novo DSA-negative and de novo DSA-positive groups at 6-month follow-up (P < 0.001) [Figure 1]b.
|Figure 1: DSA levels at (a) pretransplant, (b) 6 months, (c) 12 months and (d) 18 months. BO: Borderline, NEG: Negative; POS: Positive|
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At 12-month follow-up, all the de novo DSA-negative patients showed no presence of DSA for HLA class I and II. While in de novo DSA-positive patients, six patients (66.66%) showed positive DSA for HLA class II, two patients (22.22%) showed border-line DSA for HLA class II, and one patient (11.11%) showed border-line DSA for HLA class I. The difference in the DSA levels between de novo DSA-negative and de novo DSA-positive groups was significant at 12-month follow-up (P < 0.001) [Figure 1]c.
All the de novo DSA-negative patients showed no presence of DSA for HLA class I and II at 18-month follow-up. In patients of de novo DSA-positive group, five patients (55.55%) showed positive DSA for HLA class II, three patients (33.33%) showed border-line DSA for HLA class II, and one patient (11.11%) showed border-line DSA for HLA class I. There was a significant difference in the DSA levels between de novo DSA-negative and de novo DSA-positive groups at 18-month follow-up (P < 0.001) [Figure 1]d. The mean MFI level of de novo DSA-positive patients was 2241 while for de novo DSA negative 518 [Table 3].
|Table 3: Mean fluorescence intensity level of de novo dsa positive patients|
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The mean levels of serum creatinine (mg/dL) in de novo DSA-negative and de novo DSA-positive groups at 1 week, 6-, 12-, and 18-month follow-ups were 1.19 and 1.31, 1.41, and 1.24, 1.49, and 1.27, and 1.41 and 1.51, respectively. The mean eGFR (mL/min/1.73 m2) in de novo DSA-negative and de novo DSA-positive groups at 1 week, 6-, 12-, and 18-month follow-ups were 76.83 and 72.92, 58.83 and 66.37, 54.80 and 67.47, and 58.04 and 56.48, respectively. The mean tacrolimus (ng/mL) in the de novo DSA-negative and de novo DSA-positive groups at 1 week, 6-, 12-, and 18-month follow-ups were, 7.46 and 6.23, 7.62 and 6.40, 7.56 and 6.93, and 6.87 and 6.05, respectively. The mean urinary protein to creatinine ratio (mg/mmol) in the de novo DSA-negative and de novo DSA-positive groups at 1 week, 6-, 12-, and 18-month follow-ups were 0.29 and 0.03, 0.33 and 0.17, 0.31 and 0.22, and 0.30 and 0.31, respectively [Table 4].
| Discussion|| |
Previous studies showed that patients who developed de novo DSA after kidney transplantation, have developed chronic allograft dysfunction., However, there is a lack of evidence-based data, suggesting the incidence of de novo DSA and its association with graft failure. The present retro-prospective observational study assessed the prevalence of de novo DSA in renal transplant recipients and their correlation with graft functions. In this study, a total of 72 patients were screened for the presence of de novo DSA at every 6 months interval for the duration of 18-month follow-up. The principal finding of this study was the development of de novo DSA level in 12.50% patients after 18-month follow-up. However, there was no association between de novo DSA level and graft dysfunction. As described by Fotheringham et al., de novo DSA development first causes increased proteinuria and later on results into graft dysfunction.
The mean age of the patients with de novo DSA negative and de novo DSA positive was 40.94 and 34.67 years, respectively, and the majority of patients were men. On the other line, the previous two studies have reported a similar distribution of age and sex.,
Several studies have reported the incidence rate of de novo DSA in renal transplant recipients. A retrospective study of 505 patients evaluated a rate of de novo DSA in 18.2% of patients. Another single-center study monitored the development of DSA after transplantation using bead-based flow-cytometry assays. In that study, out of 72 renal transplant recipients, 16 (22.2%) developed DSA after transplantation. Wiebe et al. found that 15% of patients developed DSA at a mean of 4.6 ± 3.0 years posttransplant. A considerable wide range was observed in the incidence of de novo DSA which may be due to the diversity of methods used to detect the anti-HLA antibodies., A study done by Worthington et al. evaluated renal transplant outcome in 235 recipients which were negative for DSA before and after transplantation, 51.7% of the graft failure group produced DSA compared with 1.6% of the control group. They highlighted that not only HLA Class II-specific antibodies play an important role in graft failure but also associated with chronic rejection. A 6-month follow-up study on the significance of the anti-HLA class on renal response demonstrated that HLA class I DSA are more injurious to the graft compared to HLA Class II. This might be due to the level of expression of HLA Class II on the arterial site. In this study, patients with de novo DSA positive, 55.55% showed positive DSA levels for HLA Class II, 33.33% patients showed border-line DSA levels for HLA Class II, and 11.11% patients showed border-line DSA levels for HLA class I at 18-month follow-up. This might be because of Luminex assay has high sensitivity and specificity in order to detect low and transient HLA antibodies which is an advantage over other assays. During the 18-month follow-up period, one patient out of 63 patients from DSA-negative group showed transient borderline DSA positivity at 6-month follow-up; however, it disappeared at 12-month follow-up and remain DSA negative at 18-month follow-up as well. This can be attributable to the fact that some DSA can be transient; this underlies the importance of follow-up testing and clinical correlation.
A retrospective study of the pediatric population evaluated renal function. It was observed that serum creatinine level was significantly increased in patients with de novo DSA at the end of the follow-up compared with the values at discharge and at the time of first DSA appearance (P < 0.05). Likewise, DeVos et al. reported that patients with renal transplant developed DSA postoperatively and is associated with an increased rate of acute rejection episodes, higher serum creatinine, and worst graft survival. According to Kim et al., there were also a large number of patients without DSA, generating an average decline in GFR over time and therefore allows analysis of deviation from this trend in DSA-positive patients.
However, in the present analysis, there was no significant difference in the levels of serum creatinine and eGFR between patients with de novo DSA negative and de novo DSA positive during the follow-up. Zachary et al. reported that the evolution of renal function including serum creatinine, eGFR, and proteinuria of the DSA-positive group did not show a significant difference compared to non-DSA during the 1st-year posttransplant.
This study reported comparable tacrolimus levels between de novo DSA-negative and de novo DSA-positive patients at 6-, 12-, 18-month follow-up periods, which was in accordance with the previous study. This finding suggests that the tacrolimus trough level was an independent predictor of DSA development after kidney transplant.
The limitation of our study was the inclusion of a very small number of patients that cannot be extrapolated to a larger population belonging to diverse geographical and ethnic groups. Therefore, a future large scale study is needed to verify the results.
| Conclusion|| |
De novo DSA level was developed in 12.5% of patients with renal allograft after 18-month follow-up. However, there was no association between de novo DSA and its impact on graft function in patients with renal transplantation.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]