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Journal of Clinical Microbiology, July 2005, p. 3540-3543, Vol. 43, No. 7
0095-1137/05/$08.00+0 doi:10.1128/JCM.43.7.3540-3543.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
| CASE REPORT |
Bone Marrow Transplant Program, Barbara Ann Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, Michigan 48201
Received 27 January 2005/ Returned for modification 24 February 2005/ Accepted 1 March 2005
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Case 1. A 1-year-old female with malignant osteopetrosis received a conditioning regimen with high-dose cyclophosphamide and rabbit antithymocyte globulin (ATG), at a dose of 5 mg/kg of body weight/day, for 4 days followed by an HLA-matched unrelated-donor umbilical cord transplant. Immunosuppression after transplantation consisted of cyclosporine, methotrexate, and corticosteroids. The patient did not receive any additional immunosuppression besides graft-versus-host disease (GvHD) prophylaxis with cyclosporine. On day 49, she developed low-grade fever, dyspnea, and rash. The fever, dyspnea, and rash persisted even after treatment with empirical antibiotic therapy and initiation of steroids for presumptive acute GvHD. The patient subsequently deteriorated and required mechanical ventilation. Bronchoalveolar lavage fluid was used in viral and bacterial cultures and Epstein-Barr virus (EBV)-PCR. Empirical antiviral therapy with ganciclovir was started. The patient further deteriorated and died on day 54 as a result of multiorgan failure. Autopsy findings revealed extensive multiorgan involvement, including the lungs, kidneys, liver, and multiple lymph nodes, and microscopy showed disseminated polymorphous B cells (posttransplant lymphoproliferative disease [PTLD]). These cells stained strongly positive for EBER, a nontranslated RNA (Fig. 1). PCR and EBV serology results, which were consistent with the diagnosis of PTLD, were subsequently available.
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FIG. 1. Histopathology of excised tissue from a patient with PTLD involving the liver, showing a large cellular infiltrate consisting of diffuse large immunoblasts with plasmacytoid features demonstrating EBV by use of immunohistochemical staining for EBER. Magnification, x400.
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FIG. 2. Histopathology of excised tissue taken at autopsy from a patient with PTLD involving the liver, showing a large cellular infiltrate consisting of diffuse large immunoblasts with plasmacytoid features demonstrating EBV by use of immunohistochemical staining for EBER. Magnification, x400.
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FIG. 3. Histopathology of excised tissue from a patient with PTLD involving the lymph node, showing a mixed infiltrate of lymphocytes and diffuse large immunoblasts with plasmacytoid features. Magnification, x400.
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PTLD is a well-recognized complication occurring in patients with T-cell immune deficiencies (5). In the transplant setting, EBV-LPD in the majority of cases is a reactivation of the infected B cells that harbor the virus (5). It is characterized by the expression of eight viral genes, six of which encode nuclear proteins (EBNA-1, -2, -3A, -3B, -3C, and -LP) and two of which encode latent membrane proteins, LMP-1 and -2 (5). There are also two nontranslated RNAs (EBER-1 and EBER-2), which can be identified by histological staining of infected cells (5). Reactivation occurs after an appropriate stimulus, subsequent production of virions, and proliferation (5). This reactivation occurs secondarily to the suppression of cellular immunity after stem cell transplant (5). The pathogenesis seems to be an expansion of transformed cells that proliferate in the absence of T-cell immunity (10).
The NK-cell activity usually controls the proliferation of B cells via two target antigens, EBNA-2 and LMP-1 (5). CTL can usually eliminate the B cells in which the viral replication has been initiated and prevent further proliferation (5).
The risk for developing EBV-LPD is increased after solid-organ or bone marrow transplantation and usually occurs within the first 2 years, during T-cell function impairment (10). Primary EBV infection occurs in as many as 90% of PTLD patients, making seronegativity in the recipient a risk factor for the development of PTLD (10). PTLD has been reported to occur in both allogeneic and autologous BMTs (10). The reported incidence of PTLD in the bone marrow transplantation setting is 1%, with the majority occurring after allogeneic stem cell transplants (7). Clinical features of PTLD are usually nonspecific and may include fever, malaise, fatigue, lymphadenopathy, and diarrhea (7). PTLD can involve every organ system and may present as either localized or disseminated disease. PTLD may be rapidly progressive or may wax and wane for several weeks to months (7). Here, we discuss the clinical characteristics, time to development of PTLD, treatment, and outcome for a subgroup of patients.
Between March 1999 and January 2001, a total of 539 patients received allogeneic (154 patients) and autologous (385 patients) BMTs at the Karmanos Cancer Institute of Wayne State University. Of the 539 patients, 23 received a conditioning regimen of ATG, with either horse or rabbit being the source. We report here on three patients who received rabbit ATG (Tables 1 and 2). All three patients had positive skin tests to horse ATG, and rabbit ATG was substituted. The three patients who received rabbit ATG went on to develop PTLD after their BMTs. There were no cases of PTLD following conditioning with equine ATG. PTLD occurred at a median of 70 days post-BMT (with a range of 60 to 90 days). The median dose of rabbit ATG was 5 mg/kg/dose (with a range of 2.5 to 10 mg/kg/dose). The diagnosis was based on EBV-PCR and EBV DNA quantification (Table 3), and immunohistochemical staining for EBER was included in this study. An autopsy was performed on each patient, and organs were sectioned and stained for EBER. Flow cytometry analysis was performed in one case.
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TABLE 1. Patient characteristics
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TABLE 2. Disease status of patientsa
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TABLE 3. EBV test results
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Multiple risk factors for the development of PTLD, in addition to immunosuppression, have been implicated in previous reports (12). Primary EBV infection is responsible for up to 90% of the cases occurring in the first 3 to 4 months after transplantation, eliminating previous infection as a risk factor for the development of LPD (20). The intensity and type of immunosuppression along with the development of chronic GvHD are known risk factors (20). Infection with cytomegalovirus has also been found to be a risk factor independent of immunosuppression (20). Other risk factors for allogeneic BMT patients include the use of T-cell-depleted grafts either in vivo or ex vivo, unrelated or HLA-mismatched donor, chronic GvHD, degree of immunosuppression therapy, and the use of either ATG therapy or monoclonal anti-T-cell antibodies (13). Nash et al. reported their experience with hematopoietic stem cell transplantation for severe autoimmune disease and the risk of developing EBV-PTLD in patients who received rabbit ATG (11) (the patient from case 2 is included in this subset of patients). Other risk factors in solid-organ transplant include EBV seronegativity, the number of rejection episodes requiring the use of OKT3, and the organ transplanted (2).
Here we have described three patients whose conditioning regimens included rabbit ATG. In two cases, the transplant was from an unrelated allogeneic donor, and in one case, the transplant was from a CD34+-selected autologous transplant. To date there have been 10 cases of autologous transplant-associated PTLD. Since PTLD results from immunosuppression, the initial approach with all of our patients was to withdraw immunosuppression. The withdrawal of immunosuppression alone can result in a response rate of 20 to 50% with a regression of the patient's PTLD (14). The problem with the withdrawal of immunosuppression in earlier stages is graft rejection or increased GvHD in the allogeneic setting. The efficacy of treatment with antiviral agents is unclear at this time. Since EBV-PTLD is associated with a latent cycle of EBV infection and B-cell proliferation is independent of viral replication, these agents currently play little role in the treatment of established PTLD. However, they could possibly play a role in the prophylaxis of EBV-PTLD (21). Only one patient in this report was treated with antiviral therapy, with no significant impact on survival. Chemotherapy has been used in cases refractory to withdrawal of immunosuppression, and complete remissions have been reported with the use of multidrug chemotherapy. Up to 70% of the patients from a previous study achieved a disease-free interval of 19 months (22). Rituximab has been used as a single agent and in combination with good response (9). One patient in our group was treated with multiagent chemotherapy without response. At the time of treatment of these patients, rituximab was not considered a therapeutic modality. Donor lymphocyte infusion has been reported to be effective in at least one patient after an allogeneic transplant (9). We treated the CD34+-selected autologous transplant patient with unselected autologous peripheral blood progenitor cells without success. EBV-generated CTL have been reported as a successful treatment for PTLD. They can be generated in vitro by the stimulation of T cells with EBV-transformed B cells; subsequently, clones of EBV-specific T cells can be generated to relatively high numbers. The infusion of these expanded T cells has been shown to be effective in the management and prophylaxis of EBV-PTLD (1, 4, 6). Several reports testify to the utilization of this procedure; however, the time involved to generate cell lines (weeks to months) and the expense limit this treatment modality (1, 4, 6).
Recently, there have been several approaches used to monitor and prevent EBV reactivation following bone marrow transplantation (17). Molecular monitoring of the EBV load in the peripheral blood using quantitative real-time PCR for EBV reactivation was one of those approaches (4). In that study, patients were treated preemptively with rituximab for viral loads that were greater than 1,000 genome equivalents/ml (8). Our current practice is to monitor these patients by EBV-PCR and to treat preemptively with rituximab for viral DNA levels that are >1,000 genome equivalents/ml.
We have presented three cases of EBV-LPD associated with rabbit ATG in the conditioning regimen. Rabbit ATG was used in this setting after the occurrence of a severe skin reaction from equine ATG. There was no other substitute for equine ATG besides rabbit ATG at our institution at the time patients were being treated with this conditioning regimen. One case occurred in an autologous BMT setting, and two cases occurred in an allogeneic BMT setting. Since no cases of EBV-LPD occurred in the equine ATG-conditioned group, we can speculate that rabbit ATG causes a much more potent T-cell depletion (Table 3). The number of T-cell subsets for the rabbit ATG-conditioned group of patients was significantly lower (CD4 and CD8) than that for the equine ATG-conditioned group, as was previously reported by Nash. The diagnosis of LPD should be considered for patients receiving prolonged immunosuppression or for patients receiving in vivo or ex vivo T-cell depletion and in the differential diagnosis of any BMT patient presenting with adenopathy, unexplained fever, or respiratory distress.
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