Objectives: Plasma cell-rich acute rejection is an aggressive form of acute rejection that occurs late after transplant and is usually resistant to standard antirejection therapy. This study reports the safety, efficacy, and outcomes of plasma cell-rich acute rejection after treatment with bortezomib, a proteasome inhibitor, in 10 patients after a first living-related renal transplant.
Materials and Methods: Plasma cell-rich acute rejection was diagnosed using the 2007 Banff classification. The treatment protocol for plasma cell-rich acute rejection included methylprednisolone (500 mg/kg), 7 sessions of plasmapheresis, antithymocyte globulin (3-5 mg/kg/day for 10 days), rituximab (2 doses at 375 mg/m2), and bortezomib (1 cycle at 1.3 mg/m2).
Results: The mean age of recipients and donors was 23.70 ± 11.39 and 37.30 ± 12.82 years, respectively. The mean time to plasma cell-rich acute rejection was 3.1 ± 2.5 years. The mean serum creatinine level at rejection was 4.8 ± 2.7 mg/dL. After treatment, serum creatinine decreased to 3.3 ± 1.8 mg/dL. Serum creatinine levels at 1-year and 2-year follow-up were 3.0 ± 2.3 and 3.3 ± 0.9 mg/dL, respectively. There was 1 graft failure due to recurrence of glomerulonephritis/de novo glomerulonephritis. No significant adverse effects were noted in the patients. Bortezomib successfully reverted plasma cell-rich acute rejection and stabilized graft function, with patients showing 2-year graft survival after rejection of 90%.
Conclusion: Bortezomib-based treatment was successful in reverting plasma cell-rich acute rejection and stabilizing graft function, with graft survival of 90% at 2 years. Further studies with large cohorts and randomized trials with or without bortezomib will help in better evaluation of its efficacy, safety, and outcomes.
Key words : Bortezomib, Graft survival, Plasma cells
Plasma cell-rich acute rejection (PCAR) is an aggressive form of acute rejection that typically develops beyond 6 months after transplant.1-5 Recent studies have found that it is associated with donor-specific antibodies (DSA) in a significant number of cases.6-9 The definition of PCAR is not completely standardized, with most studies categorizing acute rejection episodes as PCAR when plasma cells account for > 10% of the graft-infiltrating cells. Other studies have used a cut-off value of 20% of plasma cells.4 Plasma cell-rich acute rejection is a rare form of acute rejection, with reported prevalence rates of 2% to 14% in biopsy-proven rejection.1-9
Plasma cell-rich acute rejection may represent a late variant of acute antibody-mediated rejection (AMR), which could be classified separately from acute cellular rejection (ACR) and treated accordingly.7,8 The management of PCAR is not uniformly standardized due to its rarity in clinical experience. Typically, PCAR episodes are steroid resistant in nature and may respond at least transiently to antithymocyte globulin and are associated with poor graft survival compared with classical ACR.10-12 However, with the use of aggressive treatment protocols aimed at removing and neutralizing antibody components of the rejection, better outcomes have been reported.6,7 This study retrospectively analyzed the use of a specific anti-plasma cell agent, bortezomib (a proteasome inhibitor), for treatment of PCAR in terms of safety, efficacy, and outcomes in 10 patients with a first living-related renal transplant.
Materials and Methods
Between January and June 2014, 10 patients who were diagnosed with PCAR on renal allograft biopsies were treated with bortezomib. Historic and current serum results at the time of PCAR were tested for the presence of anti-human leucocyte antigen (HLA) antibodies by Luminex technology (Luminex, Austin, TX, USA). The value of 1000 mean fluorescence intensity was taken as a cut-off for positive results. Renal graft biopsies were reported and graded using the Banff 1997 classification and its revisions, including the Banff 2013 updates.13,14 Infiltrates were designated as plasma cell-rich when plasma cells accounted for ≥ 10% of the graft-infiltrating cells. The plasma cells were counted manually per 1000 mononuclear cells in the densely infiltrated interstitial spaces in randomly selected high-power fields (×400).
Immunohistochemistry was carried out for CD20, CD138, and kappa and lambda light chains using monoclonal antibodies (DAKO, Glostrup, Denmark). Hematoxylin and eosin-stained preparations were used for plasma cell counting. C4d staining was performed by immunofluorescence on frozen sections with monoclonal antibody against complement protein C4d (Quidel Corporation, San Diego, CA, USA). C4d positivity was interpreted and reported according to Banff 2001 criteria.15
All patients were routinely screened for bacterial and viral infections when indicated. Bacterial screening included routine urine, blood, and tuberculosis cultures. The viral markers included Epstein-Barr virus, cytomegalovirus, and polyomavirus infections by standard polymerase chain reaction methodology.
The treatment protocol for PCAR consisted of intravenous methylprednisolone (500 mg/kg for 3 days), plasmapheresis on alternate days (7 sessions), antithymocyte globulin (3-5 mg/kg/day for 10 days), 2 doses of rituximab (375 mg/m2 on days 1 and 7), and 1 cycle of bortezomib (1.3 mg/m2 on days 1, 4, 8, and 11).
Data were analyzed using Statistical Package for Social Sciences version 10.0 (SPSS Inc., Chicago, IL, USA). Results are expressed as mean and standard deviation for continuous variables and numbers with percentages for categorical variables.
The demographic and HLA matching results for the study population are shown in Table 1. The mean age of recipients was 23.70 ± 11.39 years, and mean age of donors was 37.30 ± 12.82 years. The mean HLA match was 3.50 ± 0.97. Pretransplant crossmatch by microcytotoxicity assays for T and B cells and flow T-cell immunoglobulin and B-cell immunoglobulin were negative in all cases. Biopsy findings, serum creatinine levels, and immunosuppression regimens are shown in Table 2. Previous acute rejection episodes were detected in 3 patients (30%). The Banff types of rejections were 1A in 2 patients (20%), 2A in 2 patients (20%), and 1B in 6 patients (60%).
The mean plasma cell percentage was 31.28 ± 10.5%, the mean percentage of CD20-positive cells was 22.4 ± 7.6%, and mean percentage of CD138-positive cells was 30.2 ± 8.4%. All plasma cell infiltrates were polyclonal on light-chain immunohistochemistry. Testing of freshly frozen tissue for C4d staining was done for 6 samples and found to be positive in 2 samples. The mean time from transplant to development of PCAR was 3.1 ± 2.5 years.
The mean serum creatinine level before devel-opment of PCAR was 1.47 ± 0.4 mg/dL. The mean serum creatinine at the time of PCAR was 4.9 ± 2.7 mg/dL. Treatment outcomes are shown in Table 3. Serum creatinine after treatment of PCAR declined to a mean of 3.3 ± 1.8 mg/dL. Mean serum creatinine at 1-year follow-up was 3.0 ± 2.3 mg/dL; at 2 years, it was 3.3 ± 0.9 mg/dL. The mean estimated glomerular filtration rate at time of PCAR was 20.31 ± 0.49 mL/min, which increased to 29.8 ± 9.85 mL/min after treatment. The mean estimated glomerular filtration rate at 1-year follow-up was 30.7 ± 12.7 mL/min; at 2-year follow-up, it was 28.7 ± 11.2 mL/min.
Donor-specific antibody positivity statuses before and after treatment are shown in Table 4. All 10 patients were positive for DSA, 20% were positive for HLA class I, and 80% were class II positive. The mean fluorescence intensity of class I antibodies was 4018 ± 1265, whereas that for class II was 5355 ± 2921.
All patients had interstitial fibrosis tubular atrophy (IFTA) of moderate and severe degree on biopsy at PCAR. Graft survival at 2 years was 90%. None of the patients experienced neutropenia or bortezomib-induced peripheral neuropathy. During follow-up, none of the patients developed Epstein-Barr virus, cytomegalovirus, or polyomavirus infections. Tuberculosis was not found in any patient, but 4 patients developed urinary tract infection.
Currently, there is no standardized care for patients with PCAR.1-6 This is mainly due to the rarity of the lesion and ambiguity in the precise classification of PCAR.16 Traditionally, it was considered a type of ACR; however, more recent studies have found increasing components of AMR in this type of graft pathology.3,6,17 Thus, in the majority of cases, PCAR represents a combination of both T-cell-mediated acute rejection and AMR.1-5 The treatment protocols for PCAR have also evolved with this evolution in understanding of the pathogenesis of the process. Up to now, the emphasis of treatment lay on elimination of and neutralization of antibodies from the sera of recipients. Use of specific anti-B-cell therapy has also been reported.6 However, no study is available on the use of proteasome inhibitors in this setting.
This is the first study on the use of proteasome inhibitors in the treatment of PCAR. Previously, this agent has been used in the treatment of multiple myeloma and non-Hodgkin lymphoma.18 In the setting of kidney transplant, it has been used in desensitization protocols and the treatment of AMR.18-22 This drug induces plasma cell apoptosis and has been successfully used to decrease alloantibody levels and treat concurrent antibody and cell-mediated rejection processes.23 Because PCAR is associated with significant plasma cell infiltration and also with concomitant AMR in most cases, it is logical to hypothesize its efficacy in this form of rejection. However, no study on the use of proteasome inhibitors in the management of PCAR is currently available in the literature. We aimed to test this hypothesis in a small set of patients with PCAR. Although our study population did not achieve their baseline serum creatinine level, their graft function stabilized and only one patient lost the graft during the follow-up period. Stabilization of graft function has also been reported earlier by others.24 Inability to achieve baseline function may be explained by moderate IFTA in 80% of patients in our study. No significant correlation was found between the proportion of plasma cells and the individual or combined Banff IFTA scores on graft survival by others.2 The one graft lost developed recurrent/de novo focal segmental glomerulosclerosis. The results from this study are encouraging since 1- and 2-year graft survival rates of 90% are better than those reported in other series of PCAR treatment.1-3,6 Three studies analyzed short-term outcomes at 6 months and reported survival rates of 44%, 53%, and 58%, respectively.1-3 Our previous study reported 72% and 42% at 1 and 2 years.6 Compared with these studies, our present study showed markedly improved graft survival rates over longer follow-up.
All of our patients tested positive for HLA DSA, with class I in 20% and class II in 80% of cases. Earlier studies on PCAR lacked data on DSA in PCAR cases. Desvaux and associates found DSA to HLA and endothelial antigens in 8 of 12 patients tested.3 The increasing recognition and detection of DSA in PCAR have helped in better understanding of the underlying pathophysiology of the process and better treatment options. In addition, 2 of the 6 patients tested for C4d showed widespread positivity of this marker in peritubular capillaries. Similar findings have been reported by other investigators.3
Most patients (80%) in this series showed Banff type I rejection, mostly type IB (6 of 8 patients); only 2 patients showed vascular rejection (IIA). Others have also reported similar Banff types of rejection in PCAR. Desvaux and associates found 3 of 14 cases that belonged to the Banff borderline category.3 No correlation has been found between Banff acute rejection scores/grades and the number of plasma cells and PCAR.1-4
Bortezomib treatment was well tolerated in our study population. None of the patients showed neutropenia, thrombocytopenia, or peripheral neuropathy. There were also no infectious complications. Reports of adverse effects of bortezomib treatment have been published in other studies with repetitive cycles of treatment.24-26
This study has certain limitations. First, it was retrospective in nature; second, bortezomib was used as an add-on to the treatment regimen already being used for patients with PCAR.6
In conclusion, bortezomib-based treatment was successful in reverting PCAR, stabilizing graft function, and leading to graft survival of 90% at 2 years. A further study with a large cohort and a randomized trial with or without bortezomib will help in better evaluation of its efficacy, safety, and outcomes.
Volume : 17
Issue : 1
Pages : 42 - 46
DOI : 10.6002/ect.2017.0154
From the Departments of 1Transplant Immunology, 2Histopathology,
and 4Urology, Sindh Institute of Urology and Transplantation, Karachi, Pakistan
Acknowledgements: The authors have no sources of funding for this study and have no conflicts of interest to declare.
Corresponding author: Khawar Abbas, Department of Transplant Immunology, Sindh Institute of Urology and Transplantation, Karachi 74200, Pakistan
Phone: +92 21 99215752
Table 1. Demographic and HLA Matching of Recipients and Donors
Table 2. Immunohistological Characteristics of Plasma Cell-Rich Acute Rejection
Table 3. Posttreatment Outcomes of Patients With Plasma Cell-Rich Acute Rejection
Table 4. Donor-Specific Antibody Status in Patients with Plasma Cell-Rich Acute Rejection Before and After Treatment