The role of EBV in post-transplant malignancies: a review

B cells under influence: transformation of B cells by Epstein-Barr virus

Epstein-Barr virus (EBV) is an extremely successful virus, infecting more than 90% of the human population worldwide. After primary infection, the virus persists for the life of the host, usually as a harmless passenger residing in B cells. However, EBV can transform B cells, which can result in the development of malignant lymphomas. Intriguingly, the three main types of EBV-associated B-cell lymphoma - that is, Burkitt lymphoma, Hodgkin lymphoma and post-transplant lymphomas - seem to derive from germinal-centre B cells or atypical survivors of the germinal-centre reaction in most, if not all, cases, indicating that EBV-infected germinal-centre B cells are at particular risk for malignant transformation.

Epstein-Barr virus infection in colorectal neoplasms associated with inflammatory bowel disease: detection of the virus in lymphomas but not in adenocarcinomas

Epstein-Barr virus (EBV) is associated with several lymphoid and epithelial human malignancies. The latter include gastric adenocarcinomas, while sporadic colorectal adenocarcinomas (CRCs) have been reported to be EBV-negative. Recently, increased numbers of EBV-infected B lymphocytes have been detected in intestinal mucosal samples affected by ulcerative colitis (UC) and, to a lesser extent, Crohn's disease (CD). Both CRC and colorectal non-Hodgkin's lymphoma (NHL) are recognized complications of inflammatory bowel disease (IBD), but it is unclear to what extent EBV contributes to the development of these neoplasms. Seventeen cases of IBD-associated CRC and nine cases of IBD-associated colorectal NHL were therefore studied for the presence of EBV by in situ hybridization. EBV-positive cases were further studied for the expression of the EBV-encoded nuclear antigen (EBNA) 2 and the latent membrane protein (LMP) 1 of EBV by immunohistochemistry. Four out of seven cases of colorectal NHL associated with UC were shown to be EBV-positive. In addition, two of two colorectal NHLs developing in patients with CD were EBV-positive. Of the EBV-positive lymphomas, three displayed a pattern of EBV latent gene expression consistent with type I latency (EBNA2(-)/LMP1(-)), two a type II pattern (EBNA2(-)/LMP1(+)), and one a type III pattern (EBNA2(+)/LMP1(+)). These findings suggest that EBV infection is involved in the pathogenesis of a proportion of colorectal NHLs developing in IBD. Iatrogenic immunosuppression may contribute to the development of these lymphomas. By contrast, all 17 IBD-associated CRCs were EBV-negative, including a case of CRC occurring synchronously with an EBV-positive NHL. In conjunction with previous reports on sporadic CRCs, this suggests that EBV is not involved in the pathogenesis of CRC.

Epstein-Barr virus and the B cell: a secret romance

Infection by the Epstein-Barr virus (EBV) in immunocompetent individuals seems mainly confined to antigen-experienced memory B cells. However, a recent report shows that EBV(+) post-transplant lymphoproliferative disease might arise not only from memory B cells but also from nai;ve and germinal center (GC) B cells. Intriguingly, some of the EBV-positive B-cell clones seem to carry non-functional Ig-V-region genes as a result of deleterious somatic mutations acquired during the GC reaction. Given that such GC B cells are destined to die by apoptosis in the absence of EBV, these findings suggest that transformation by EBV might bypass negative selection of B cells within GCs.

A novel porcine gammaherpesvirus

A novel porcine gammaherpesvirus was detected in the blood of domestic pigs by PCR. With degenerate-primer PCR and subsequent long-distance PCR approaches a 60-kbp genome stretch was amplified. Sequence analysis revealed the presence of the gammaherpesvirus ORFs 03 to 46 as well as a putative chemokine receptor and a v-bcl-2 gene. The 60-kbp sequence was compared with the corresponding sequence of the porcine lymphotropic herpesvirus 1 (PLHV-1) published recently and the sequence of PLHV-2, which was amplified from porcine tonsil. Considerable sequence differences (amino acid identities: 49-89%) were found between the novel virus and PLHV-1 as well as PLHV-2, which were very closely related to each other (amino acid identities: 85-98%). The novel virus had essentially the same genome organization as PLHV-1 and -2 and was therefore designated PLHV-3. Like PLHV-1 and -2, PLHV-3 was frequently found in the blood and in lymphoid organs of domestic and feral pigs from different geographic locations. In the blood, the PLHVs were detected predominantly in B-cells. Indication for latent as well as productive PLHV-3 infection was found in the porcine B-cell line L23. It can be concluded that the PLHVs are widespread and are likely to cause a persistent B-lymphotropic infection. Since PLHV-1 has been implicated in the development of porcine posttransplantation lymphoproliferative disease, all porcine lymphotropic gammaherpesviruses are of concern when pigs are used as donors in xenotransplantation.

Epstein-Barr virus seronegativity is a risk factor for late-onset posttransplant lymphoroliferative disorder in adult renal allograft recipients

BACKGROUND

Posttransplant lymphoproliferative disorder (PTLD) remains a difficult management issue; therefore, many studies focus on the identification of risk factors to allow for preventive strategies. We investigated risk factors for PTLD in the adult renal transplant setting.

METHODS

A single-center, matched case-control study design was used. Cases were identified from patients who underwent a first renal transplant between January 1, 1985, and December 1, 2001. Two controls were chosen per case, matched (+/-1 year) by date of transplant and graft survival. Clinical and demographic data were ascertained from medical records. Pretransplant serology for Epstein-Barr virus (EBV) and cytomegalovirus was confirmed on frozen, stored sera. Statistical analysis included univariate and multivariable examination of putative risk factors using conditional logistic regression.

RESULTS

Twenty cases of PTLD were identified, an incidence of 2.4%. Median time from transplant to diagnosis was 55 months (range, 3-168 months), with 16 cases of late-onset PTLD (>1 year posttransplant). The only significant risk in univariate analysis was EBV-negative status at transplant (risk ratio 6.0, P=0.03). In multivariable analysis, EBV-negative status remained significant (adjusted risk ratio 8.9, P=0.01). The risk related to EBV status held true when late cases were analyzed separately (adjusted risk ratio 7.1, P=0.03).

CONCLUSIONS

Pretransplant EBV-seronegative status is a strong risk for development of PTLD in adult renal allograft recipients, even in late disease. These results indicate that primary infection with EBV may have a pathogenic role in some cases of late PTLD.

Pathogenic roles for Epstein-Barr virus (EBV) gene products in EBV-associated proliferative disorders

Epstein-Barr virus (EBV) is associated with a still growing spectrum of clinical disorders, ranging from acute and chronic inflammatory diseases to lymphoid and epithelial malignancies. Based on a combination of in vitro and in vivo findings, EBV is thought to contribute in the pathogenesis of these diseases. The different EBV gene expression patterns in the various disorders, suggest different EBV-mediated pathogenic mechanisms. In the following pages, an overview of the biology of EBV-infection is given and functional aspects of EBV-proteins are discussed and their putative role in the various EBV-associated disorders is described. EBV gene expression patterns and possible pathogenic mechanisms are discussed. In addition, expression of the cellular genes upregulated by EBV in vitro is discussed, and a comparison with the in vivo situation is made.

Epstein-Barr virus and post-transplant lymphoproliferative disease

There is convincing evidence that Epstein-Barr virus (EBV) is associated with post-transplant lymphoproliferative disease (PTLD). Primary EBV infection following transplantation occurs in as many as 90% of cases of PTLD in children and pretransplant EBV seronegativity is a recognized risk factor for developing PTLD. Other risk factors include young age at the time of transplant, the type of transplant that the recipient receives and the type and intensity of immunosuppression. The clinical presentation is often nonspecific and tissue biopsy is necessary to establish the diagnosis. There appears to be a correlation between PTLD and EBV viral load measured by polymerase chain reaction (PCR) of the peripheral blood and quantitative PCR may be a useful guide in the management of PTLD. Antiviral drugs and cytomegalovirus-immunoglobulin G may have a role in preventing PTLD. Because PTLD results from functional over-immunosuppression, the initial treatment is reduction of immunosuppression. Antiviral agents, interferon, immuno-based monoclonal therapy, cell-based therapy and chemotherapy also have a potential role in treating this disorder. At the present time there is no standardized approach to the evaluation and treatment of PTLD.

Response of elevated Epstein-Barr virus DNA levels to therapeutic changes in pediatric liver transplant patients: 56-month follow up and outcome

BACKGROUND

Posttransplant lymphoproliferative disease (PTLD) is a serious complications after liver transplantation. Epstein-Barr virus (EBV) load measured by quantitative competitive polymerase chain reaction (PCR) has been used as an early marker for the development of PTLD and a guide for initiating preemptive therapy. The aim of this study is to report the results of EBV DNA PCR screening in a transplant population and to examine the risk factors for developing elevated EBV DNA PCR and the effect of interventions for reducing EBV DNA levels.

METHODS

Medical records of 44 children who underwent liver transplantation and EBV DNA PCR screening during a 3-year period were reviewed, and the patients were prospectively followed up for another 2 years. Eleven patients who developed elevated EBV DNA PCR levels, defined as >/=40 genomes/105 peripheral blood lymphocytes (PBL) in pretransplant EBV-seronegative patients and >/=200 genomes/105 PBL in pretransplant-seropositive patients, were treated. The initial intervention was reduction of immunosuppression and initiation of anti-viral therapy in all patients, with administration of cytomegalovirus immunoglobulin (CMV-IgG) in two patients. CMV-IgG was then given to five of the patients who did not respond to the initial intervention.

RESULTS

The initial intervention resulted in the reduction of EBV DNA PCR levels to below threshold values in 4 of 11 patients. Five patients who did not respond to the initial interventions were subsequently given intravenous CMV-IgG. The EBV DNA PCR level fell in all five of these patients during the course of treatment with CMV-IgG, with a significant reduction (to threshold levels or by two dilutions) in four of the five patients. No episodes of graft rejection were observed.

CONCLUSION

Eleven patients (25%) developed elevated EBV DNA PCR after liver transplantation. There were no identifiable risk factors for developing elevated EBV DNA PCR. A combination of reducing immunosuppression, adding antiviral agents, and initiating CMV-IgG resulted in a significant reduction of EBV DNA levels in nine (82%) patients during the follow-up period.

Inhibition of EBV-induced lymphoproliferation by CD4(+) T cells specific for an MHC class II promiscuous epitope

Posttransplant lymphoproliferative disorder (PTLD) and B cell lymphomas induced by EBV continue to be a major life-threatening complication in transplant patients. The establishment and enhancement of T cell immunity to EBV before transplantation and immunosuppressive therapy could help diminish these complications, but the lack of an effective vaccine has limited this prophylactic approach. We describe here the identification of a peptide epitope from the EBV EBNA2 Ag that is capable of inducing in vitro CD4(+) T cell responses that inhibit the EBV-mediated B lymphocyte proliferation associated with PTLD. Most significantly, T cell responses to the EBNA2 epitope were found to be restricted by numerous MHC class II alleles (DR1, DR7, DR16, DR52, DQ2, and DQ7), indicating that this peptide is highly promiscuous and would be recognized by a large proportion (>50%) of the general population. These results are relevant for the design of a simple, inexpensive and widely applicable peptide-based vaccine to prevent PTLD in solid organ transplant patients.

Epstein-Barr virus reactivation after superinfection of the BJAB-B1 and P3HR-1 cell lines with cytomegalovirus

BACKGROUND

Studies examining herpesvirus-herpesvirus (cytomegalovirus (CMV)-Epstein-Barr virus (EBV)) interactions are limited, and many of the studies have been clinical observations suggesting such an interaction exists. This report aims to examine the in vitro susceptibilities of BJAB-B1 and P3HR-1 cells (EBV positive Burkitt's lymphoma B-cell lines) to a CMV superinfection; and show that EBV reactivation occurs after CMV superinfects these cell lines.

RESULTS

The BJAB-B1 and P3HR-1 cells were observed to be susceptible to a CMV superinfection by detecting the major immediate early (MIE) viral transcript and protein (p52) expression. The BZLF1 transcript was observed in both cell lines superinfected with CMV, indicating EBV reactivation. BZLF1 protein was observed in the BJAB-B1 cells. Antigen detection was not performed in the P3HR-1 cells.

CONCLUSION

The results from the in vitro superinfections support the in vivo studies suggesting a CMV infection is related to an EBV reactivation and suggests that CMV may be important as a co-factor in EBV pathogenesis in the immunocompromised patient.

Epstein-Barr virus-associated peripheral T-cell and NK-cell proliferative disease/lymphoma: clinicopathologic, serologic, and molecular analysis

Peripheral T-cell proliferative disease/lymphoma is a group of diseases which exhibits heterogeneity in clinical manifestations, pathological findings and outcomes. They are highly associated with the Epstein-Barr virus (EBV) infection. It is likely that EBV plays an important role in the tumorigenesis. From January 1997 through April 2000, we identified 100 patients. One hundred healthy age- and sex- matched controls were selected. Serologic tests for the EBV infection and the study of EBV genomes in circulating non-T cells (CD3- cells), T cells (CD3+ cells), and T-cell subsets (CD4+ and CD8+ cells) were performed. The main features were prolonged fever, weight loss, hepatosplenomegaly, lymphadenopathy, multiorgan involvement, anemia, and high serum alkaline phosphatase and lactate dehydrogenase. Fifty-one patients had an aggressive course and died; median survival was 21 months. Chemotherapy was not effective in improving survival. Anti-viral capsid antigen-IgG and anti-early antigen-IgG were significantly elevated, whereas there was no significant difference in anti-EBV nuclear antigen. EBV internal repeat-1 region (IR-1) in the peripheral blood CD3+ cells was detected in 65% of the patients but in none of the controls. For the CD3- cells, EBV IR-1 was detected in 88% of the patients and 50% of the controls. Among twenty-five patients whose CD3+ cells were positive for EBV IR-1, 6 (24%) showed EBV IR-1 in only CD4+ cells, 6 (24%) in only CD8+ cells, and 13 (52%) in both CD4+ and CD8+ cells. The 30-bp deletion variant of the EBV latent membrane protein-1 gene was significantly higher in the patients than in the controls. These data support the chronic infective process. The EBV which is dormant in non-T cells may infect T cells and contribute to the pathogenesis of disease in a select group of patients.

Role of Epstein-Barr virus DNA load monitoring in prevention and early detection of post-transplant lymphoproliferative disease

Posttransplant lymphoproliferative disease (PTLD) is a severe and life-threatening complication after stem cell or solid-organ transplantation, virtually always associated with presence of Epstein-Barr virus (EBV) in the proliferating cells. PTLD is probably caused by the iatrogenically impaired T-cell response allowing outgrowth of EBV-positive B-cells. Quantitative EBV DNA load monitoring is a minimally invasive technique increasingly recognized as a valuable tool in posttransplant patient management. In this review, we focus on the clinical utility of EBV DNA load monitoring in the peripheral blood of transplant recipients using PCR and we discuss the currently most-widely used techniques and their value and limitations in predicting and diagnosing PTLD. Options for EBV DNA load-guided pre-emptive therapy and application of monitoring EBV DNA load dynamics in the prediction of clinical response after therapy are described. Origins of elevated EBV DNA loads in immunosuppressed patients and recent insights in the EBV life cycle in the immuncompromised host are discussed. Finally, a standardization of methodology, clinical specimen type, and cut-off values is proposed. This is essential for comparisons between different institutes and more adequate patient management.

Epstein-Barr virus-negative precursor B cell lymphoblastic lymphoma after liver transplantation: a unique form of posttransplant lymphoproliferative disease

BACKGROUND

We report a liver transplant patient with Epstein-Barr virus-negative, precursor B cell lymphoblastic lymphoma diagnosed 6 months after transplantation.

PATIENT

The patient was a 13-year-old boy with acute, fulminant hepatic failure of unknown etiology who underwent cadaveric liver transplantation.

RESULTS

Six months after the transplant, the patient developed non-tender cervical lymphadenopathy 2 days after a reduction in prednisone dosage. The adenopathy worsened despite withdrawal of immunosuppression, and a biopsy showed precursor B cell lymphoblastic lymphoma. All investigations for Epstein-Barr virus were negative. The patient responded well to chemotherapy and is currently in complete remission 24 months after diagnosis.

CONCLUSIONS

Precursor B cell lymphoblastic lymphoma has not been previously reported as a form of posttransplant lymphoproliferative disease. We discuss this unique form of posttransplant lymphoproliferative disease and briefly review the clinical and pathological spectrum of posttransplant lymphoproliferative disease.

Colorectal neoplasia in ulcerative colitis-recent advances

It is recognized that ulcerative colitis (UC) predisposes to the development of colorectal adenocarcinoma (CRC), and the molecular pathway for this process differs from that for sporadic CRCs. However, several important details regarding the risk factors for and the molecular changes underlying UC-related colorectal carcinogenesis have only come to light lately. First, recent data suggest environmental factors related to long-standing inflammation contribute more to this increased cancer risk than an inherited susceptibility. Second, molecular changes that may represent the first steps in the development of neoplasia are being increasingly identified in non-dysplastic, colitic mucosa. Third, there is now good evidence suggesting that UC-related CRC may develop along more than one molecular pathway. These emerging data will hopefully contribute to attempts to prevent the development of UC-related CRC, e.g. through refining surveillance programmes. Details of the molecular heterogeneity of UC-related dysplasia and CRC may also help develop reliable tools for diagnosing the former and for predicting the behaviour of the latter. Finally, there is increasing awareness of non-epithelial colorectal malignancies which are associated with UC and may potentially increase in incidence with changes in the medical management of this inflammatory disease.

Induction of the Epstein-Barr virus thymidine kinase gene with concomitant nucleoside antivirals as a therapeutic strategy for Epstein-Barr virus-associated malignancies

Lymphoproliferative diseases (LPDs) associated with the Epstein-Barr virus (EBV) include non-Hodgkin lymphomas, which occur in the setting of immunosuppression, including that induced by human immunodeficiency virus, and posttransplant lymphoproliferative disorders. These LPDs are characterized by actively proliferating, latently infected EBV-positive B lymphocytes and often follow a rapidly progressive fatal clinical course. Pharmacologic treatment for herpesvirus infections has targeted the virus-specific enzyme, thymidine kinase (TK), with nucleoside analogs. The lack of viral TK expression in EBV-positive tumors, caused by viral latency, however, makes antiviral therapy alone ineffective as an antineoplastic therapy. Arginine butyrate selectively activates the EBV TK gene in latently infected EBV-positive tumor cells. We have developed a strategy for treatment of EBV-associated lymphomas using pharmacologic induction of the latent viral TK gene and enzyme in tumor cells using arginine butyrate, followed by treatment with ganciclovir. A phase I/II trial, using an intrapatient dose escalation of arginine butyrate combined with ganciclovir, is underway. This combination therapy has produced complete clinical responses in 5 of 10 previously refractory patients, with partial responses occurring in 2 additional patients. This virus-targeted antitumor strategy may provide a new therapeutic approach to EBV-associated neoplasms.

Epstein--Barr virus post-transplant lymphoproliferative disease and virus-specific therapy: pharmacological re-activation of viral target genes with arginine butyrate

Lymphoproliferative disorders associated with the Epstein-Barr virus (EBV) include non-Hodgkin's lymphoma, Hodgkin's lymphoma, and "post-transplant lymphoproliferative disorders" (PTLD), which occur with immunosuppression after marrow and organ transplantation. PTLD is characterized by actively proliferating, latently infected EBV(+) B-lymphocytes, and often manifests a rapidly progressive fatal clinical course if the immunosuppression cannot be reversed. Lung transplant recipients are a subset of patients at special risk for developing PTLD. The incidence of PTLD development in these patients has been estimated at 5--10%. Whereas immunologic and antiviral therapy have been moderately effective for treating EBV-associated infections in the lytic phase, they have been less useful in the more common latent phase of the disease. One common treatment for herpesvirus infections has targeted the virus-specific enzyme thymidine kinase (TK). The lack of viral TK expression in EBV(+) tumor cells, due to viral latency, makes anti-viral therapy alone ineffective as an anti-neoplastic therapy, however. We have developed a strategy for the treatment of EBV-associated lymphomas/PTLD using pharmacologic induction of the latent viral TK gene and enzyme in the tumor cells, followed by treatment with ganciclovir. Arginine butyrate selectively activates the EBV TK gene in latently EBV-infected human lymphoid cells and tumor cells. A Phase I/II trial has been initiated, employing an intra-patient dose escalation of arginine butyrate combined with ganciclovir. In six patients with EBV-associated lymphomas or PTLD, all of which were resistant to conventional radiation and/or chemotherapy, this combination produced complete clinical responses in four of six patients, with a partial response occurring in a fifth patient. Pathologic examination in two of three patients demonstrated complete necrosis of the EBV lymphoma, with no residual disease, following a single three-week course of the combination therapy. Possible side-effects of the therapy included nausea and reversible lethargy at the highest doses. One patient suffered acute liver failure, thought to be secondary to release of FasL from the necrotic tumor. Analysis of patient-derived tumor cells in culture demonstrated that arginine butyrate produced selective induction of the EBV TK gene, which then conferred sensitivity to ganciclovir, resulting in tumor apoptosis. Additional patient accrual is sought for further evaluation of this therapy.

Reflections on Epstein-Barr virus: some recently resolved old uncertainties

The change over recent decades in perceptions of the role of viruses in human cancer-causation is illustrated by the reception given to the discovery of Epstein-Barr virus (EBV) in 1964 compared to that of Kaposi's sarcoma herpesvirus (KSHV or HHV-8) in 1994. Very new data on EBV-like agents in New World monkeys is considered in relation to the antiquity of the association of proto-EBV with early anthropoids. Although the finding that individuals without B lymphocytes do not seem to be infected with EBV appears to have resolved the controversy regarding the permissive cell type producing infectious virus in the oropharynx, the presence of EBV in certain squamous and other epithelial cells raises continuing problems which are discussed. Among many recent successes of molecular biology applied to EBV, new information from such investigations on the genetic defect in X-linked lymphoproliferative syndrome now explains the cause of the disastrous pathological changes underlying the disease.Finally, current progress with vaccines against EBV is reviewed.

Clinical utility of viral quantification as a tool for disease monitoring

The possibility to detect viral DNA or RNA in a quantitative manner has already contributed significantly to the management and diagnosis of viral infections, as well as to the understanding of virus-host interactions. New developments in amplification techniques based on real-time detection, as well as automation of the whole process, will soon be introduced in a diagnostic laboratory setting, thereby enabling a rapid turnaround time to generate both quantitative and qualitative results. New guidelines for disease management, as well as extensive quality control and standardization programs must be introduced.

Immunotherapeutic strategies for EBV-associated malignancies

Advances in our understanding of the role of cytotoxic T lymphocytes (CTLs) in the control of Epstein-Barr virus (EBV)-associated malignancies and the overall biology of these diseases have led to the development of novel therapeutic strategies designed to specifically target viral antigens expressed in these malignancies. Long-term success of many of these strategies is constrained by the latency phenotypes adopted by different diseases. Adoptive transfer of polyclonal virus-specific CTLs has been used successfully to reverse the outgrowth of malignancies such as post-transplant lymphoproliferative disease (PTLD). On the other hand, limited viral gene expression in other EBV-associated malignancies such as Burkitt's lymphoma, Hodgkin's disease and nasopharyngeal carcinoma limits the efficacy of immunotherapeutic strategies used for PTLD. Preclinical studies based on specific targeting of viral antigens expressed in these malignancies have provided very encouraging results and thus are likely to serve as an important platform for the treatment of human patients.

Biology and disease associations of Epstein-Barr virus

Epstein-Barr virus (EBV) is a human herpesvirus which infects almost all of the world's population subclinically during childhood and thereafter remains in the body for life. The virus colonizes antibody-producing (B) cells, which, as relatively long-lived resting cells, are an ideal site for long-term residence. Here EBV evades recognition and destruction by cytotoxic T cells. EBV is passed to naive hosts in saliva, but how the virus gains access to this route of transmission is not entirely clear. EBV carries a set of latent genes that, when expressed in resting B cells, induce cell proliferation and thereby increase the chances of successful virus colonization of the B-cell system during primary infection and the establishment of persistence. However, if this cell proliferation is not controlled, or if it is accompanied by additional genetic events within the infected cell, it can lead to malignancy. Thus EBV acts as a step in the evolution of an ever-increasing list of malignancies which are broadly of lymphoid or epithelial cell origin. In some of these, such as B-lymphoproliferative disease in the immunocompromised host, the role of the virus is central and well defined; in others, such as Burkitt's lymphoma, essential cofactors have been identified which act in concert with EBV in the evolution of the malignant clone. However, in several diseases in which the presence of EBV has more recently been discovered, the role of the virus is unclear. This review describes recent views on the EBV life cycle and its interlinks with normal B-cell biology, and discusses how this interrelationship may be upset and result in EBV-associated disease.