Evaluation of histogenesis of B-lymphocytes in pediatric EBV-related post-transplant lymphoproliferative disorders

Proteoglycan expression correlates with the phenotype of malignant and non-malignant EBV-positive B-cell lines

The involvement of proteoglycans (PGs) in EBV-host interactions and lymphomagenesis remains poorly investigated. In this study, expression of major proteoglycans (syndecan-1, glypican-1, perlecan, versican, brevican, aggrecan, NG2, serglycin, decorin, biglycan, lumican, CD44), heparan sulphate (HS) metabolic system (EXT1/2, NDST1/2, GLCE, HS2ST1, HS3ST1/2, HS6ST1/2, SULF1/2, HPSE) and extracellular matrix (ECM) components (collagen 1A1, fibronectin, elastin) in primary B cells and EBV carrying cell lines with different phenotypes, patterns of EBV-host cell interaction and viral latency stages (type I-III) was investigated. Primary B cells expressed a wide repertoire of PGs (dominated by serglycin and CD44) and ECM components. Lymphoblastoid EBV+ B cell lines (LCLs) showed specific PG expression with down-regulation of CD44 and ECM components and up-regulation of serglycin and perlecan/HSPG2. For Burkitt's lymphoma cells (BL), serglycin was down-regulated in BL type III cells and perlecan in type I BL cells. The biosynthetic machinery for HS was active in all cell lines, with some tendency to be down-regulated in BL cells. 5'-aza-dC and/or Trichostatin A resulted in transcriptional upregulation of the genes, suggesting that low expression of ECM components, proteoglycan core proteins and HS biosynthetic system is due to epigenetic suppression in type I cells. Taken together, our data show that proteoglycans are expressed in primary B lymphocytes whereas they are not or only partly expressed in EBV-carrying cell lines, depending on their latency type program.

Suppression of HLA expression by lentivirus-mediated gene transfer of siRNA cassettes and in vivo chemoselection to enhance hematopoietic stem cell transplantation

Current approaches for hematopoietic stem cell (HSC) and organ transplantation are limited by donor and host-mediated immune responses to allo-antigens. Application of these therapies is limited by the toxicity of preparative and post-transplant immunosuppressive regimens and a shortage of appropriate HLA-matched donors. We have been exploring two complementary approaches for genetically modifying donor cells that achieve long-term suppression of cellular proteins that elicit host immune responses to mismatched donor antigens, and provide a selective advantage to genetically engineered donor cells after transplantation. The first approach is based on recent advances that make feasible targeted down-regulation of HLA expression. Suppression of HLA expression could help to overcome limitations imposed by extensive HLA polymorphisms that restrict the availability of suitable donors. Accordingly, we have recently investigated whether knockdown of HLA by RNA interference (RNAi) enables allogeneic cells to evade immune recognition. For efficient and stable delivery of short hairpin-type RNAi constructs (shRNA), we employed lentivirus-based gene transfer vectors that integrate into genomic DNA, thereby permanently modifying transduced donor cells. Lentivirus-mediated delivery of shRNA targeting pan-Class I and allele-specific HLA achieved efficient and dose-dependent reduction in surface expression of HLA in human cells, and enhanced resistance to allo-reactive T lymphocyte-mediated cytotoxicity, while avoiding non-MHC restricted killing. Complementary strategies for genetic engineering of HSC that would provide a selective advantage for transplanted donor cells and enable successful engraftment with less toxic preparative and immunosuppressive regimens would increase the numbers of individuals to whom HLA suppression therapy could be offered. Our second strategy is to provide a mechanism for in vivo selection of genetically modified HSC and other donor cells. We have uniquely combined transplantation during the neonatal period, when tolerance may be more readily achieved, with a positive selection strategy for in vivo amplification of drug-resistant donor HSC. This model system enables the evaluation of mechanisms of tolerance induction to neo-antigens, and allogeneic stem cells during immune ontogeny. HSC are transduced ex vivo by lentivirus-mediated gene transfer of P140K-O(6)-methylguanine-methyltransferase (MGMT(P140K)). The MGMT(P140K) DNA repair enzyme confers resistance to benzylguanine, an inhibitor of endogenous MGMT, and to chloroethylating agents such as BCNU. In vivo chemoselection enables enrichment of donor cells at the stem cell level. Using complementary approaches of in vivo chemoselection and RNAi-induced silencing of HLA expression may enable the generation of histocompatibility-enhanced, and eventually, perhaps "universally" compatible cellular grafts.

Remission of lymphoma after withdrawal of methotrexate in rheumatoid arthritis: relationship with type of latent Epstein-Barr virus infection

Rheumatoid arthritis (RA) is associated with an increased risk of developing lymphoma. Although the pathogenesis is still unclear, the increased risk appears to be related to the high inflammatory activity of RA, immunosuppressive agents, or Epstein-Barr virus (EBV) infection. We investigated the relationship between EBV latent infection and methotrexate (MTX)-associated lymphoma in RA patients. Nine patients were diagnosed with non-Hodgkin's lymphoma (NHL) during MTX treatment for RA in a multicenter study. The pathologic findings were consistent with diffuse large B-cell lymphoma in 8 patients and peripheral T-cell lymphoma, unspecified in 1. EBV infection was detected in 3 patients by in situ hybridization. Among all 9 patients who were initially treated by MTX withdrawal alone, 2 obtained spontaneous complete response (CR), 1 had partial response, 2 had stable disease (SD), and 4 had progressive disease. Both patients who had a CR and 1 who had SD were positive for EBV. Further examination of the latent EBV infection patterns revealed that 2 patients who obtained a CR had latency Type III, and the other with SD had latency Type II. These results demonstrate that immunodeficiency caused by MTX treatment is associated with the development of EBV-related NHL in RA patients. In patients who were treated by MTX for RA and developed NHL, remission can be observed following MTX withdrawal especially in NHL with latency Type III EBV infection. The analysis of EBV infection, including the latency types, is useful to decide the optimum therapeutic strategy.

Impact of Epstein-Barr virus in monomorphic B-cell posttransplant lymphoproliferative disorders: a histogenetic study

The heterogeneity of the posttransplant lymphoproliferative disorders (PTLDs) is well recognized. However, in contrast to other immunodeficiency-associated lymphomas or diffuse large B-cell lymphomas in general, studies of the histogenetic spectrum of the large category of monomorphic B-cell cases have been more limited, produced conflicting results, and have paid little attention to the impact of Epstein-Barr virus (EBV). Therefore, 30 monomorphic B-cell PTLD from 27 patients were analyzed using EBER in situ hybridization for EBV and a panel of antibodies directed against CD20, CD3/bcl-6, CD10, MUM-1/IRF4, CD138, and bcl-2. The results were correlated with the histopathologic features and clinical outcome. All PTLD were CD20 with 23% CD10, 53% bcl-6, 67% MUM-1/IRF4, 13% CD138, 83% bcl-2 and 67% EBV. 30% of the PTLD had a germinal center (GC) profile (CD10, bcl-6, MUM-1/IRF4, CD138), 53% a "late GC/early post-GC" profile (CD10, bcl-6, MUM-1/IRF4, CD138), 13% a post-GC profile (CD10, bcl-6, MUM-1/IRF4, CD138) and 3% an indeterminate profile (all markers negative). EBV positivity was associated with MUM-1/IRF4 expression (P=0.005) and with a non-GC phenotype (P=0.01). All CD138 cases were EBV. The cases with a GC phenotype were the most likely to resemble transformed GC cells (P=0.023). No statistically significant survival differences could be documented between those with a GC versus non-GC phenotype. These results highlight the broad histogenetic spectrum of monomorphic B-cell PTLD. They demonstrate the association of EBV positivity with a non-GC phenotype and suggest that EBV PTLD are more like lymphomas that arise in immunocompetent individuals. The lack of a demonstrable correlation with survival may relate to the relatively small number of cases studied.

Monomorphic Epstein-Barr virus (EBV)-associated large B-cell posttransplant lymphoproliferative disorder presenting as a tongue ulcer in a pancreatic transplant patient

Posttransplant lymphoproliferative disorders are a group of lymphoid proliferations and lymphomas that develop as a consequence of immunosuppression in recipients of solid organ or bone marrow allografts. We describe an unusual oral presentation of posttransplant Epstein-Barr virus-associated diffuse large B-cell lymphoma in a 45-year-old woman after pancreatic transplant.

Treatment of Epstein-Barr virus--associated lymphoproliferative disorder (EBV-PTLD) and pure red cell aplasia (PRCA) with Rituximab following unrelated cord blood transplantation: a case report and literature review

OBJECTIVE

We report the first case of EBV-PTLD and pure red cell aplasia (PRCA) after an unrelated cord blood transplant in China, who was successfully treated with Rituximab.

METHODS

Case report and literature review.

RESULTS

A 5-year-old girl with CML underwent a major ABO-incompatible HLA-identical unrelated cord blood transplantation (U-CBT) in January 2003. The post transplant course was complicated by PRCA. She presented on day +75 with fever, followed by rapid enlargement of tonsils, and a cluster of lymph nodes in the cervical and submandibular regions. A cervical lymph node biopsy revealed the histopathologic findings consistent with PTLD. The immunoblasts were shown to contain EBV viral genomic DNA by PCR, and immunocytochemistry study for the latent membrane protein 1 (LMP-1) and in situ hybridization for Epstein-Barr encoded RNAs1 (EBER1) were both positive. She responded rapidly to Rituximab and achieved complete resolution of clinical findings and symptoms of both EBV-PTLD and PRCA.

CONCLUSION

EBV-PTLD may occur with increasing frequency due to the increasing numbers of transplant recipients, transplant physician should be aware of this life-threatening complication. Rituximab alone may be an effective therapeutic strategy for patients who develop EBV-PTLD and PRCA after U-CBT.