Epstein-Barr virus-associated lymphoproliferative disorders in immunocompromised individuals

EBV Association with Lymphomas and Carcinomas in the Oral Compartment

Epstein-Barr virus (EBV) is an oncogenic human herpesvirus infecting approximately 90% of the world's population. The oral cavity serves a central role in the life cycle, transmission, and pathogenesis of EBV. Transmitted to a new host via saliva, EBV circulates between cellular compartments within oral lymphoid tissues. Epithelial cells primarily support productive viral replication, while B lymphocytes support viral latency and reactivation. EBV infections are typically asymptomatic and benign; however, the latent virus is associated with multiple lymphomas and carcinomas arising in the oral cavity. EBV association with cancer is complex as histologically similar cancers often test negative for the virus. However, the presence of EBV is associated with distinct features in certain cancers. The intrinsic ability of EBV to immortalize B-lymphocytes, via manipulation of survival and growth signaling, further implicates the virus as an oncogenic cofactor. A distinct mutational profile and burden have been observed in EBV-positive compared to EBV-negative tumors, suggesting that viral infection can drive alternative pathways that converge on oncogenesis. Taken together, EBV is also an important prognostic biomarker that can direct alternative therapeutic approaches. Here, we discuss the prevalence of EBV in oral malignancies and the EBV-dependent mechanisms associated with tumorigenesis.

A systematic review of primary gastric diffuse large B-cell lymphoma: Clinical diagnosis, staging, treatment and prognostic factors

Primary gastric lymphoma (PGL) is a rare clinical entity accounting for the majority of extra-nodal non-Hodgkin lymphoma (EN-NHL). The most common histological subtype is the primary gastric diffuse large B-cell lymphoma (PG-DLBCL) with a media age of 50-60 years old, mostly in male. Pathogenesis is often related to some bacterial infection such as Helicobacter pylori (H. pylori) infection. However, due to various available staging system, there is still no consensus on the staging of PG-DLBCL. The international prognostic index (IPI) is the most valuable used for the stratification of almost all subtype of NHL and as well as for PG-DLBCL. As for treatment strategies, surgery, chemotherapy, radiation therapy and antibiotic therapy in various combinations have been applied in clinical treatment. There are a few well-known prognostic factors and some of them may constitute prognostic models. Due to the increasing incidence of this neoplasm, it is necessary for clinicians to make deep insight of the diagnosis, staging, treatment and prognostic factors of PG-DLBCL.

Surgery for Non-Hodgkin's Lymphoma

Non-Hodgkin lymphomas (NHLs) are a diverse group of blood cancers derived from lymphocytes that vary significantly in their severity. Surgery is not often used as a treatment because of the efficacy of chemotherapy, biological therapy, radiotherapy and hematopoietic stem cell transplantation. We reviewed the natural history and possible role of surgery for NHL. Surgery may be useful in confirming or refuting an equivocal radiological diagnosis through biopsy, removing symptomatic limited disease from an affected organ and in splenectomy for primary splenic lymphoma. Emergency abdominal surgery for acute complications of NHL provides palliation and diagnosis. There is as yet no consensus as to the optimum treatment for symptomatic limited disease affecting an organ and timing of chemotherapy perioperatively. Prospective randomized trials are required.

Determination of EBV serostatus prior to kidney transplantation: comparison of VIDAS®, LIAISON® and immunofluorescence assays

Immunosuppression following solid organ transplantation reduces T cell-mediated immune control of Epstein-Barr Virus (EBV), which may then drive development of post-transplant lymphoproliferative disease. Serology plays a key role in determination of risk of outgrowth of such lesions following transplantation. The study compared the VIDAS(®) (bioMérieux) and LIAISON(®) (DiaSorin) enzyme immunoassays (EIAs) and immunofluorescence assays (IFA; MBL-Bion) in the kidney transplantation setting. Sera from 100 live kidney donors [51 males; age range 20-82 years (mean 51.2 years)] and 100 cadaveric kidney recipients [70 males; age range 17-77 years (mean 51.0 years)] were tested. Overall proportional agreement ranged from 96% to 100% for VIDAS(®) and LIAISON(®). Sensitivity ranged from 91% to 100% and 92% to 100% for VIDAS(®)/IFA and LIAISON(®)/IFA, respectively. The VIDAS(®) and LIAISON(®) approaches gave similar results. Such automated random access EIAs are well suited to busy clinical virology laboratories and rapid determination of donor and recipient EBV serostatus prior to transplantation.

Synthesis and biological activity of the nucleoside analogs based on polyfluoroalkyl-substituted 1,2,3-triazoles

This paper offers the results of a synthesis and study of cytotoxicity and the anti-Epstein-Barr virus (EBV) activity of new 2-deoxy-2-chloro-pyranosyl derivatives of 4-tosyl-5-trifluoromethyl-1,2,3-triazole obtained via the addition reaction of the corresponding 2-N-chlorotriazole to the double bond of 3,4,6-tri-O-acetyl-D-glucal. Nucleoside mimetics, derivatives of 4-tosyl-5-polyfluoroalkyl-1,2,3-triazoles containing fragments of 3-chloro-tetrahydrofuran, 3-chloro-tetrahydropyran, tetrahydropyran, dihydrofuran, dihydropyran, or acyclic substituents, were also studied. Evaluation of cytotoxicity (trypan blue and MTT methods) and anti-EBV activity (polymerase chain reaction (PCR) method) showed high selectivity indices for the compounds 4a, 4b, 5b, 6, and 8. A total of 15 novel compounds were examined in this study.

The Epstein-Barr virus nuclear antigen-1 promotes genomic instability via induction of reactive oxygen species

The Epstein-Barr virus (EBV) nuclear antigen (EBNA)-1 is the only viral protein expressed in all EBV-carrying malignancies, but its contribution to oncogenesis has remained enigmatic. We show that EBNA-1 induces chromosomal aberrations, DNA double-strand breaks, and engagement of the DNA damage response (DDR). These signs of genomic instability are associated with the production of reactive oxygen species (ROS) and are reversed by antioxidants. The catalytic subunit of the leukocyte NADPH oxidase, NOX2/gp91(phox), is transcriptionally activated in EBNA-1-expressing cells, whereas inactivation of the enzyme by chemical inhibitors or RNAi halts ROS production and DDR. These findings highlight a novel function of EBNA-1 and a possible mechanism by which expression of this viral protein could contribute to malignant transformation and tumor progression.

Cyclosporin A up-regulates and activates protein kinase C-zeta in EBV-infected and EBV-transformed human B-cells

BACKGROUND

Protein Kinase C (PKC) is a family of enzymes that plays a key role in cell signaling pathways leading to cellular activation and proliferation. Conventional PKC (cPKC) is dependent on calcium for activation. We have proposed that cyclosporin A (CsA), despite being a calcineurin inhibitor, will activate PKC in B cells, thus promoting Epstein-Barr virus (EBV)-induced transformation. Here we show that CsA promoted atypical PKC isoform PKC-zeta in B cells.

MATERIALS AND METHODS

Western-blot was used to assay PKC-zeta protein level in EBV-B cells. Confocal microscopy was used to assay PKC-zeta translocation from cytosol to cell membrane, a known process of PKC activation.

RESULTS

CsA (500 ng/mL) time dependently increased PKC-zeta from control of 7055 units to 7145, 10,805, 10,914, and 12,705 units, respectively, after 15 min, 1 h, 12 h, and 24 h of incubation in EBV-transformed human B-cell line (LCL). CsA increased PKC-zeta expression was inhibited 50% by Vit.E (40 microM) indicating that this effect may be due to oxidative stress induced by CsA. Indeed, after oxidant H(2)O(2) (0.1 mM) treatment, PKC-zeta protein level in LCL cells increased 124%, 257%, 349%, and 359% after 15 min, 1 h, 12 h, and 24 h of culture compared with control. Addition of Vit.E (40 microM) in H(2)O(2) (0.1 mM) treatment and then with Vit.E in the culture decreased PKC-zeta level in LCL cells 26%, 20%, 41%, and 60% after 15 min, 1 h, 12 h, and 24 h of culture. In confocal microscopy in Jurkat T cell line, phorbol 12-myristate 13-acetate (PMA) activated cPKC isoform PKCalpha after 30 min treatment and activated PKC-zeta after 60 min treatment. CsA inhibited PMA activation of PKC-alpha, but not PKC-zeta. CsA alone did not activate PKC-alpha or PKC-zeta in Jurkat T cells. In LCL and in EBV-infected human B-cells, PMA stimulated PKC-alpha activation after 30 min treatment and stimulated PKC-zeta activation after 60 min treatment. CsA inhibited PMA activation of PKC-alpha, but not PKC-zeta. In addition, CsA activated PKC-zeta in the EBV-transformed and EBV-infected human B cells.

CONCLUSION

These experiments show that CsA-induced oxidative stress caused PKC-zeta up-regulation in LCL cells, and show the differential effect of CsA in the PKC signaling pathways in T cells versus B cells. CsA-induced PKC-zeta activation may be an important signaling step in EBV-induced post-transplant lymphoproliferative disorders.

Dithiocarbamates and viral IL-10 collaborate in the immortalization and evasion of immune response in EBV-infected human B lymphocytes

Epstein-Barr virus (EBV) is implicated in the development of a number of human malignancies including several subtypes of non-Hodgkin lymphoma (NHL) [G. Pallesen, S.J. Hamilton-Dutoit, X. Zhou, The association of Epstein-Barr virus (EBV) with T cell lymphoproliferations and Hodgkin's disease: two new developments in the EBV Field, Adv. Cancer Res. 62 (1993) 179-239]. Lymphoproliferative disease and NHL occurring in severely immunosuppressed individuals almost always involve EBV and have been extensively studied and modeled in vitro. EBV has also been causally associated with some cases of NHL occurring in otherwise immunocompetent individuals. However, a direct role for EBV in the pathogenesis of neoplasms developing in the presence of an otherwise competent immune system has not been established. We investigated potential interactions between dithiocarbamates (DTC), an important class of thiono-sulfur compounds, and EBV leading to immortalization of human B lymphocytes and evasion of cell-mediated immune response in culture. Primary lymphocyte cultures employing wild-type and recombinant EBV mutants were used to assess the respective roles of DTC and viral genes in lymphocyte transformation and survival. Pretreatment of EBV-infected human B lymphocytes with DTC directly enhanced transformation in the absence of T cells (5 nM) and independently increased survival of transformed cells in the presence of competent autologous T cells (10 nM). Both DTC-induced transformation and immortalization of EBV-infected B lymphocytes were dependent on the expression of viral IL-10. These results provide a biological basis for studying collaborations between chemical and virus that alter lymphocyte biology, and provide a rationale for further molecular epidemiology studies to better understand the potential influence of these interactions on the development of NHL and perhaps other viral-associated malignancies.

Primary diffuse large B-cell lymphoma of the stomach

The stomach is the extranodal site most commonly involved by non-Hodgkin lymphomas. Diffuse large B-cell lymphoma is the most common histotype category arising in this organ. This is an aggressive lymphoma usually presenting as limited disease, being associated or not to Helicobacter pylori infection and mucosa-associated lymphoid tissue-type areas. Histopathological characteristics are similar to those reported for other diffuse large B-cell lymphomas. It occurs more frequently in males with a median age ranging between 50 and 60 years. With an adequate therapeutic strategy, its prognosis is good, with a 5-year overall survival near to 90%. Conservative treatment with anthracycline-containing chemotherapy, followed or not by involved-field radiotherapy has replaced gastrectomy as standard approach against this malignancy. Several questions on the best treatment remain unanswered. Among others, the role of rituximab, consolidation radiotherapy as well as of more conservative approaches like H. pylori-eradicating antibiotic therapy should be better defined.

Adoptive transfer of Epstein-Barr virus-specific cytotoxic T-lymphocytes for the treatment of angiocentric lymphomas

Angiocentric lymphoma, known as natural killer (NK)/T-cell non-Hodgkin's lymphoma, has been reported to be associated with the Epstein-Barr virus (EBV). We performed adoptive transfer of EBV-specific polyclonal T-cell lines in 3 patients with extranodal NK/T-cell lymphoma, nasal type, and evaluated the treatment for safety, immunologic reconstitution, and clinical outcomes. The tissue samples collected from the 3 patients were confirmed by polymerase chain reaction analysis to be EBV positive. In the cases of the first and second patients, EBV-transformed B-lymphoblastoid cell lines (LCLs) and T-cell lines were generated from peripheral lymphocytes of HLA-matched sibling donors. The third patient's T-cell lines were induced with autologous lymphocytes. Polyclonal T-cell infusion was carried out after high-dose radiotherapy because active relapsed disease remained in all of the patients. The first patient received 4 weekly infusions of 2 3 10(7) cells/m(2), and the second and third patients underwent treatment with 2 cycles of infusions of the same dosage. All T-cell lines showed >60% NK activity, cytotoxic T-lymphocyte (CTL) responses of >40% against autologous LCLs, and no CTL activity against patient-derived lymphoblasts. The level of cytotoxicity increased substantially in all patients after cell infusion. The 2 patients who received T-cell therapy twice had stabilized disease for more than 3 years. These safe treatments exhibited no severe inflammatory response, and no serious toxicity developed during T-cell therapy. Our findings demonstrate that adoptively transferred cells may provide reconstitution of EBV-specific CTL responses in patients with active relapsed angiocentric lymphoma. These results provide a rationale for the immunotherapy of angiocentric lymphoma.

T cell re-targeting to EBV antigens following TCR gene transfer: CD28-containing receptors mediate enhanced antigen-specific IFNγ production

EBV is associated with a broad range of malignancies. Adoptive immunotherapy of these tumors with EBV-specific CTL proved useful. We generated a panel of primary human T cells specific to various EBV antigens (i.e. Epstein-Barr nuclear antigen 3A, 3B and BamHI-M leftward reading frame) via transfer of modified TCR genes that are either coupled to CD3zeta or Fc(epsilon)RIgamma. TCR-transduced T cells from 20-60% of donors (total number of 25) demonstrated specific lysis of EBV peptide-loaded target cells, whereas lymphoblastoid cell lines expressing native EBV antigens were not killed by any of the EBV-specific T cell populations. This non-responsiveness, confirmed at the level of nuclear factor of activated T cells activation, is not due to receptor configuration since identical receptor formats specific for melanoma antigens successfully re-targeted T cells to native melanoma cells. In an effort to generate a more potent receptor, we introduced a CD28 domain into one of the EBV-specific TCR. This TCR did not affect the cytotoxic response of re-targeted T cells, but dramatically enhanced antigen-specific IFNgamma production. We therefore conclude that these novel CD28-containing EBV-specific TCRs provide a basis for further development of TCR gene transfer to treat EBV-induced diseases.

Anticancer effect of curcumin on human B cell non-Hodgkin's lymphoma

To explore the anticancer effect of curcumin on human B cell non-Hodgkin's lymphoma and compare its effects on human B cell non-Hodgkin's lymphoma cells and normal peripheral blood mononuclear cells (NPBMNCs). MTT assay was used to study the effect of curcumin on the growth of Raji cells and NPBMNCs. The effect of curcumin on the apoptosis of Raji cells and NPBMNC were studied by flow cytometry and TDT-mediated dUTP nick and labeling (TUNEL). The effect of curcumin on the cell cycle of Raji cells were examined by propidium iodide staining flow cytometry. The results showed that curcumin strongly inhibited proliferation of Raji cells, 24 h IC50 for Raji cells was 22.8 +/- 1.82 micromol/L and curcumin induced Raji cell apoptosis in a time- and dose-dependent manner. Raji cells treated with curcumin showed G0/G1 or G2/M phase increase and S phase decrease. However, curcumin did not demonstrate apparent proliferation inhibition and apoptosis induction in NPBMNCs. It was concluded that curcumin is able to inhibit the proliferation of Raji cells by regulating the cell cycle and inducing the cell apoptosis. Morever, curcumin has low toxicity on NPBMNCs but can selectively induce apoptosis in Raji cells.

Dendritic cells pulsed with polyomavirus BK antigen induce ex vivo polyoma BK virus-specific cytotoxic T-cell lines in seropositive healthy individuals and renal transplant recipients

Polyoma BK virus (BKV)-associated interstitial nephritis has emerged as a relevant complication of immunocompromise after kidney transplantation, leading to reduced survival of the renal allograft. The limitations of current antiviral treatment and the high probability of rejection in kidney graft recipients when control of viral replication is attempted by reduction of immunosuppression warrant further efforts to develop alternative therapeutic tools. Cellular immunotherapy has proved to be a successful approach for prevention and/or treatment of other viral complications in the immunocompromised host. For assessing the feasibility of translating this strategy to the prevention of BKV-associated disease, a procedure for ex vivo reactivation of BKV-specific cytotoxic T cells (CTL) was developed from BKV-seropositive healthy donors and allograft recipients through stimulation with dendritic cells pulsed with inactivated BKV. The CTL lines thus obtained showed BKV specificity, as an efficient lysis of BKV-infected targets was accompanied by little or no reactivity against mock-infected autologous or allogeneic targets. In vitro killing of allogeneic BKV-infected targets, likely as a result of populations of TCRgammadelta+/CD3+ displaying MHC class I unrestricted cytotoxicity, was also displayed. Application of this culture system may allow a preemptive therapy approach to BKV-related complications in transplant recipients, based on CTL treatment guided by BKV DNA levels.

Epstein–Barr virus oncogenesis and the ubiquitin–proteasome system

Epstein-Barr virus (EBV), a human herpesvirus associated with lymphoid and epithelial cell tumors, encodes several proteins that exploit the ubiquitin-proteasome system to regulate latency and allow the persistence of infected cells in immunocompetent hosts. Further modifications of ubiquitin-dependent proteolysis by activated cellular oncogenes contribute to malignant transformation. A detailed understanding of these processes may lead to the development of new therapeutic strategies for EBV-associated cancers.

Vitamin E inhibits cyclosporin A and H2O2 promoted Epstein-Barr virus (EBV) transformation of human B cells as assayed by EBV oncogene LMP1 expression

BACKGROUND

We have previously shown that oxidative stress induced by H2O2 or cyclosporin A (CsA) can promote Epstein-Barr virus (EBV) transformation of human B cells as analyzed by colony formation, cell number, and by 3H-thymidine incorporation. In this report, we used EBV oncogene LMP1 as a marker to analyze H2O2 or CsA promotion of EBV transformation of human B cells and to test whether antioxidant vitamin E could inhibit H2O2 or CsA promoted LMP1 expression in the EBV-infected cells.

MATERIALS AND METHODS

Human splenocytes were prepared by centrifugation and plating technique to provide a greater than 80% pure preparation of B cells and were used for EBV infection. The EBV infected cells were treated with H2O2 (0.1 mM, 10 min), or with CsA (500 ng/ml) with or with out vitamin E (40 microM). The cells were cultured for up to 4 weeks. Samples were taken every week and were stained with phycoerythrin-conjugated mouse anti-LMP1 monoclonal antibody to assay LMP1 positive population by flow cytometry.

RESULTS

In EBV-infected cells, the LMP1-positive cell population reached 14% after 4 weeks of culture. CsA or H2O2 treatment promoted LMP1 positive population to 43% and 41% after 4 weeks of culture. Vitamin E (40 microM) completely inhibited LMP1 expression in EBV-infected cells and in CsA- or H2O2-treated cells.

CONCLUSION

In agreement with our previous observation, CsA or H2O2 can promote EBV transformation of human B cells. This oxidative stress induced promotion of EBV transformation can be blocked by antioxidant Vitamin E. This finding may have future therapeutic implications for post-transplant lymphoproliferative disorder.

Intestinal non-Hodgkin's lymphoma: a multicenter prospective clinical study from the German Study Group on Intestinal non-Hodgkin's Lymphoma

PURPOSE

Intestinal non-Hodgkin's lymphomas are not well characterized. We therefore studied prospectively their clinical features and response to standardized therapy.

PATIENTS AND METHODS

Fifty-six patients with primary intestinal lymphoma were included in a prospective, nonrandomized multicenter study. Lymphoma resection was recommended and staging was performed according to the Ann Arbor classification. Patients were scheduled to receive six cycles of cyclophosphamide, doxorubicin, vincristine, and prednisolone (CHOP) chemotherapy, and at stages EIII to EIV, they received additional involved-field radiotherapy. Corticosteroids were used in patients who could not receive chemotherapy.

RESULTS

Thirty-five patients had intestinal T-cell lymphoma (ITCL), 21 patients had intestinal B-cell lymphoma (IBCL; 18 diffuse large-cell lymphomas, two marginal-cell lymphomas, and one follicle-center lymphoma). Thirty-four patients at stages EI to EII (14 ITCL and 20 IBCL) and nine patients at stages EIII to EIV (all ITCL) received chemotherapy. No patient in stages EIII to EIV received radiotherapy, because death occurred in 12 of 14 patients. Two-year cumulative survival in patients with IBCL was 94% (95% CI, 82% to 100%) and higher than in patients with ITCL (28% [95% CI, 13% to 43%]; P <.0001), even when only stages EI to EII were considered (ITCL, 37.5% [95% CI, 16.5% to 58.5%]; P <.0001). IBCL patients compared with ITCL patients were at lower lymphoma stages (P <.01), had higher Karnofsky status (P <.005), had intestinal perforation less often (P <.05), required emergency operation less often (P <.05), received CHOP (P <.05) more often, and reached complete remission (P <.0005) more frequently.

CONCLUSION

IBCL patients at stages EI and EII respond well to chemotherapy, but the prognosis and treatment of ITCL patients is unsatisfactory.

Reconstitution of the latent T-lymphocyte response to Epstein-Barr virus is coincident with long-term recovery from posttransplant lymphoma after adoptive immunotherapy

BACKGROUND

Adoptive transfer of Epstein-Barr virus (EBV)-specific cytotoxic T lymphocytes (CTLs) has been used to treat EBV-induced posttransplant lymphoproliferative disease (PTLD) in solid-organ recipients. This study defines, in detail, the temporal relationship between adoptive transfer and the clinical response, EBV DNA load, and CTL response to EBV latent and lytic antigens in a patient with a subcutaneous PTLD presentation treated with adoptive transfer of autologous CTL.

METHODS

A heart transplant patient developed multiple subcutaneous PTLD deposits and was treated with a total of six doses (20 x 106 CTL per dose) of cultured autologous polyclonal EBV-specific CTL by adoptive transfer.

RESULTS

Complete regression occurred after the sixth CTL dose, and the patient has remained disease-free from 47 weeks to the present (136 weeks). Real-time polymerase chain reaction analysis showed a reduction in viral load after therapy. Enzyme-linked immunospot analysis using defined EBV CTL epitopes showed that the CTL precursor frequency (pCTL) toward a lytic antigen epitope was elevated early in the course of disease but tended to decrease to lower levels after long-term regression of PTLD. The most dramatic result was seen in relation to three latent CTL epitopes studied. Long-term regression of PTLD was characterized by high pCTL toward the latent antigens.

CONCLUSIONS

Increased pCTL reactivity to latent EBV CTL epitopes is coincident with recovery from disease after adoptive transfer of autologous CTL. Furthermore, the results are compatible with the belief that activation of a sustained CTL response to EBV latent epitopes is protective and may be a characteristic of patients in long-term remission from PTLD.

The ubiquitin/proteasome system in Epstein-Barr virus latency and associated malignancies

Epstein-Barr virus (EBV) is a human herpesvirus associated with lymphoid and epithelial malignancies. Three viral proteins, the EBV nuclear antigen 1 and the latent membrane proteins-1 and -2A, regulate viral latency by manipulating ubiquitin-dependent proteolysis. The activation of cellular oncogenes is instrumental for the progression of EBV infected cells to full malignancy. Constitutively activation of c-myc correlates with decreased proteasomal activity and upregulation of compensatory proteolytic pathways in Burkitt's lymphomas. Knowledge of these multiple strategies of interference with regulated proteolysis may provide new clues for the treatment of EBV-associated malignancies.

Manipulation of immune responses by Epstein–Barr virus

Epstein-Barr virus (EBV) infects and persists for life in the majority of the human population. Persistence is achieved through a combination of strictly regulated programs of latent infection in B-cells and chronic reactivation of virus replication in lymphoid tissue and mucosal surfaces. The resulting multiple patterns of virus-host interaction have selected unique strategies of immune escape. T-cell mediated immunity plays a central role in the control of EBV latency and several immune escape mechanism that protect the virus at this stage of its life circle have been characterized in details. In contrast, the contribution of innate immunity and the immune regulation of productive infection are largely unexplored areas that may yield important clues on the establishment and maintenance of EBV persistence. This review summarizes well known and emerging mechanisms of EBV immune escape that may reveal new strategies of immunoregulation and promote new approaches to the prophylaxis and treatment of EBV associated diseases.

Redox control of EBV infection: prevention by thiol-dependent modulation of functional CD21/EBV receptor expression

CD21 serves as a receptor for the Epstein-Barr virus (EBV). In this report, surface expression of CD21 on B and T cells was shown to be suppressed by a thiol-antioxidant, N-acetylcysteine (NAC), in a dose- and time-dependent manner. In contrast, expression of other surface markers, CD25 and CD4 for T cells and CD19 and surface IgM for B cells, was not affected by NAC. When an EBV-negative B-cell line B104 was treated with NAC, the cells were not susceptible to infection with B95-8-derived EBV. The effect of NAC was shown to be irrelevant to the transcriptional levels of CD21 mRNA and the intracellular glutathione levels. Immunoprecipitation study revealed that NAC causes a loss of anti-CD21 monoclonal antibody (HB5) binding to both membrane and soluble CD21, suggesting that NAC modulates the structure of CD21. Other thiol-antioxidants, such as 2-mercaptoethanol, pyrrolidine dithiocarbamate, and glutathione, showed similar effect to NAC on CD21 expression. These results suggest the possible modulation of EBV infection via thiol-dependent redox control of CD21, and thiol-antioxidants may be good candidates for controlling EBV infection.

Generation of autologous Epstein-Barr virus-specific cytotoxic T cells for adoptive immunotherapy in solid organ transplant recipients

BACKGROUND

Epstein-Barr virus (EBV)-driven posttransplant lymphoproliferative disorders (PTLD) affect 2%-27% of solid organ transplant (SOT) recipients. Adoptive immunotherapy may have therapeutic potential in this setting, but there is little experience in generating autologous EBV-specific cytotoxic T-cell lymphocytes (EBV-CTLs) from SOT recipients, and their efficacy and persistence in an immunosuppressed environment is unknown.

METHODS

EBV-CTLs were generated from eight SOT recipients, using weekly stimulations with autologous lymphoblastoid cell lines (LCLs) and interleukin-2. CTL phenotype and function were evaluated in the presence of therapeutic concentration of cyclosporin A or FK506.

RESULTS

In all cases, CTLs expanded with normal kinetics. The majority was CD3+CD8+ (mean, 76%), with less than 3% of natural killer cells. All ex vivo-generated CTLs produced significantly higher killing of autologous LCLs than of HLA-mismatched LCLs (mean, 56% vs. 14% at 20:1 ratio). No lysis of autologous or allogeneic PHA blasts was observed. The CTL expansion rate was reduced in a concentration-dependent manner in the presence of immunosuppressive drugs; however, neither lytic activity nor phenotype was affected.

CONCLUSIONS

Using methods that are approved for clinical application, EBV-CTLs can be generated from SOT recipients, even those with frank lymphoma, or who are receiving immunosuppressive drugs. These CTLs retain their function in the presence of immunosuppressive agents. Although in vivo efficacy, safety, and persistence can be assessed only in clinical trials, our results suggest that CTLs can be effective for the treatment of PTLD, even when immunosuppression cannot be reduced because of the high risk of graft rejection.

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.

DNA sequence heterogeneity within the Epstein-Barr virus family of repeats in the latent origin of replication

To detect the presence of variability in the tandemly repeated sequences of the Epstein-Barr virus latent origin of replication, we analyzed the length of the family of repeats in 14 lymphoblastoid and Burkitt's lymphoma cell lines by PCR amplification. The gel electrophoresis analysis of the PCR products revealed a broad banding pattern, characteristic of each line, consisting of several fragments, sometimes smeared, of variable length. This finding was interpreted as a result of the hairpin-like structures generated by the palindrome within the family of repeats, able to originate artefacts. Since the banding pattern was different only in strictly non-correlated cell lines, we supposed that the sequence of the repeat units was polymorphic. We therefore sequenced the family of repeats in three healthy bone marrow derived lymphoblastoid cell lines carrying an endogenous EBV as well as in a B95-8 infected cell line as control. The sequence analysis revealed that each line is different both in the number and in the sequence of repeats. At the 3' end of the family of repeats the B95-8 virus was found to have a 252 bp region missing in the GenBank standard sequence. This one is probably a partial sequence since it was shorter than the control specimens obtained from different sources of B95-8 DNA analyzed by Southern blot hybridization. The length analysis of the family of repeats can be used to characterize EBV strains by PCR.

Role of cytotoxic T lymphocytes in Epstein-Barr virus-associated diseases

Adaptation of persistent infection within the cells of the immune system is a unique characteristic of gamma herpes viruses. A classic example of this is Epstein-Barr virus (EBV), which may have co-evolved with Homo sapiens over millions of years, thus achieving a balance between viral persistence and immune control. In this review, we present an overview of virus and the host immune system interactions that regulate the life-long host-virus relationship in healthy virus carriers and EBV-associated diseases. Extensive analysis of cytotoxic T lymphocyte-mediated immune responses in healthy virus carriers has revealed unique mechanisms used by EBV to maintain a benign persistent state in vivo. On the other hand, this relationship in EBV-associated diseases favors the escape of the virus from the hostile effects of the immune response. This escape is achieved by either down-regulating the expression of highly immunogenic antigens of the virus or by direct modulation of the host cytotoxic T lymphocyte response by virus-encoded proteins.

Functional CD4(+) and CD8(+) T-cell responses induced by autologous mitomycin C treated Epstein-Barr virus transformed lymphoblastoid cell lines

Epstein-Barr virus (EBV) gene expression in tumor cells of posttransplant lymphoproliferative disorder (PTLD) patients resembles that of EBV transformed B-cell lines (LCL). EBV-specific cytotoxic T-lymphocytes can be generated by stimulating peripheral blood lymphocytes with autologous LCL. We describe a standardized method for the growth inactivation and cryopreservation of LCL for optimal T-cell stimulation and analyzed the function and phenotype of responding T-cells. LCL growth was completely blocked by mitomycin C treatment (McLCL) and McLCL could be cryopreserved while retaining excellent APC function. McLCL stimulated both CD4(+) and CD8(+) T-cells as measured by HLA-DR and CD25 expression using FACS analysis. EBV-specific CTL activity and T-cell proliferation were induced and immunocytochemical staining showed CD4(+) and (granzyme B positive) CD8(+) T-cells rosetting with McLCL. Granzymes A and B, IFN-gamma, and IL-6 were detected at significant levels in the supernatant. Thus, ex vivo T-cell activation with cryopreserved McLCL results in activation of both CD4(+) and CD8(+) T-cells producing a Th1-like cytokine profile, making this a suitable protocol for adoptive therapy of PTLD.

Binding of the Epstein-Barr virus major envelope glycoprotein gp350 results in the upregulation of the TNF-alpha gene expression in monocytic cells via NF-kappaB involving PKC, PI3-K and tyrosine kinases

Epstein-Barr virus (EBV) is a human herpesvirus that interacts with various immunocompetent cells that carry the EBV receptor (CD21/CR2). EBV binds to CR2 through its major envelope glycoprotein 350 (gp350). Previously we had demonstrated that EBV and other human herpesviruses are capable of modulating cytokine synthesis through the deregulated expression of cytokine genes interleukin-1 (IL-1), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and interleukin-2 (IL-2). Here we show that, in contrast to infectious EBV, purified recombinant gp350 upregulates TNF-alpha gene expression in human monocyte/macrophages (M/M) as well as in a monocytoid cell line, U937. Our results also demonstrate that this increased expression is due to both enhanced transcription and stability of TNF-alpha mRNA in gp350-treated cells. The specificity of this effect is evidenced by the fact that pre-incubation of cells with anti-CR2 monoclonal antibody OKB7, which blocks binding of gp350 to CR2, inhibits the above mentioned effects of gp350. Furthermore, we demonstrate that activation of TNF-alpha by gp350 is mediated by NF-kappaB through signal transduction pathways involving PKC, PI3-K and tyrosine kinases. To our knowledge this is the first report describing the modulation of TNF-alpha gene expression by the EBV-gp350 molecule following its interaction with the viral receptor CR2 on cells of the monocytic lineage.

Risk of lymphoid neoplasia after cardiothoracic transplantation. a cohort study of the relation to Epstein-Barr virus

BACKGROUND

Organ transplantation is associated with a greatly increased risk of Epstein-Barr virus (EBV)-associated lymphoproliferative disease (LPD), which is often fatal. There has been little epidemiological analysis, however, of the risk factors for LPD in transplant patients and none on whether the risks of non-EBV-associated lymphoid neoplasms are also increased.

METHODS

The risk of lymphoid neoplasia was assessed in a cohort of 1563 patients who underwent cardiothoracic transplantation at Harefield Hospital, UK from 1980 to 1994 and were followed until December 1995. EBV antibody was assessed in the patients before transplantation, and lymphoid neoplasms were assessed for EBV RNA and latent EBV gene expression.

RESULTS

Thirty cases of LPD occurred during follow-up. One lymphoma of unknown EBV status occurred. There were also six cases of EBV-negative non-Hodgkin's lymphoma (EBV-negative NHL), a highly significant excess over expectations from the general population rates of NHL (standardized incidence ratio 10.2 [95% confidence interval, 4.6-22.8]). The risk of LPD was significantly 10-fold raised in individuals who were EBV seronegative before transplantation; independently of this, it decreased steeply with age at transplantation and was greatest in the first year after transplantation. The risk was significantly raised in young seronegative recipients if the donor was older than the recipient. EBV-negative NHL occurred entirely in men 45 years old and older who were EBV seropositive before transplantation, and risk was not related to duration since transplantation.

CONCLUSIONS

The risk factors found for LPD accord with EBV etiology and with greater hazard from primary infection than from reactivation. A second non-Hodgkin's lymphoid neoplasm, not related to EBV, seems also to be a consequence of transplantation and immunosuppression but is unlikely to be due to first infection by a ubiquitous agent. Its etiology and prevention need investigation separately from LPD.

A repetitive sequence of Epstein-Barr virus nuclear antigen 6 comprises overlapping T cell epitopes which induce HLA-DR-restricted CD4(+) T lymphocytes

Most human adults carry the Epstein-Barr virus (EBV) and develop immunological memory against the structural and the virus-encoded cellular proteins. The EBV nuclear antigen 6 (EBNA6) elicits cytotoxic T cell responses and it also maintains a persistent antibody response. The majority of sera from EBV-seropositive individuals reacts with a synthetic peptide, p63, comprising 21 amino acids of a repetitive region of EBNA6. CD4(+) T lymphocytes, with specificity for p63, could be recalled from the T cell repertoire of EBV carriers that expressed certain HLA-DR allotypes which were identified as good binders of p63 by an in vitro flow cytometric assay. Analysis of the HLA-DR/p63 interaction by molecular mechanics calculations indicated the presence of multiple overlapping epitopes which were predicted to bind in a HLA-DRB1 allo- and subtype-specific manner. Specific activation of p63-selected long-term CD4(+) T cell cultures resulted in a proliferative response, in the production of IL-2 and in the secretion of high levels of tumor necrosis factor as measured by bioassays. Proliferation and cytokine production of p63-specific T cells could be induced by p63-loaded HLA-DR-matched antigen-presenting cells and by B cells co-expressing relevant HLA-DR molecules and EBNA6. Our results show that peptides of an EBNA6 repeat region induce CD4(+) T cells which can react with EBNA6-carrying cells in many individuals. We suggest that these T(h) cells may be important in conditioning dendritic cells for initiation potent virus-specific immune responses, provide help for EBV-specific B cells, drive IgG isotype switch and support the sustained effector function of memory cytotoxic T lymphocytes.

Adenovirus vector pseudotyping in fiber-expressing cell lines: improved transduction of Epstein-Barr virus-transformed B cells

While adenovirus (Ad) gene delivery vectors are useful in many gene therapy applications, their broad tropism means that they cannot be directed to a specific target cell. There are also a number of cell types involved in human disease which are not transducible with standard Ad vectors, such as Epstein-Barr virus (EBV)-transformed B lymphocytes. Adenovirus binds to host cells via the viral fiber protein, and Ad vectors have previously been retargeted by modifying the fiber gene on the viral chromosome. This requires that the modified fiber be able to bind to the cell in which the vector is grown, which prevents truly specific vector targeting. We previously reported a gene delivery system based on a fiber gene-deleted Ad type 5 (Ad5) vector (Ad5.betagal.DeltaF) and packaging cells that express the viral fiber protein. Expression of different fibers in packaging cells will allow Ad retargeting without modifying the viral chromosome. Importantly, fiber proteins which can no longer bind to the producer cells can also be used. Using this approach, we generated for the first time pseudotyped Ad5.betagal.DeltaF particles containing either the wild-type Ad5 fiber protein or a chimeric fiber with the receptor-binding knob domain of the Ad3 fiber. Particles equipped with the chimeric fiber bound to the Ad3 receptor rather than the coxsackievirus-adenovirus receptor protein used by Ad5. EBV-transformed B lymphocytes were infected efficiently by the Ad3-pseudotyped particles but poorly by virus containing the Ad5 fiber protein. The strategy described here represents a broadly applicable method for targeting gene delivery to specific cell types.

Enhanced apoptosis mediates inhibition of EBV-transformed lymphoblastoid cell line proliferation by curcumin

BACKGROUND

Epstein-Barr virus (EBV)-associated B-cell lymphomas occur more frequently in immunodeficient states such as organ transplantation and HIV infection. We have previously reported that B cell immortalization with EBV was promoted by cyclosporin A (CyA) and that curcumin (Cur), a natural phenol with known antioxidant and antitumor properties, blocked EBV-induced B cell immortalization. In the following experiments we show that Cur inhibits the proliferation of EBV-transformed lymphoblastoid cell lines (LCL) via enhanced apoptosis.

METHODS

LCL were generated by infecting freshly isolated human B cells with EBV (B95-8) for 12 h and coculturing with predetermined optimal concentrations of CyA (500 ng/ml) for 4 weeks. LCL were then either frozen for future use or propagated for immediate experiments. These cells were then plated in 96-well plates with 20 microM Cur or 0.1% DMSO (vehicle control). The number of immortalized colonies/well, cell count, and (3)H uptake were used as an index of immortalization. To assess apoptosis rate LCL were cultured with 0.1% DMSO or Cur (20 microM) for 0, 18, and 42 h in culture flasks and then stained with MC540 and H33342, as markers for apoptosis, and analyzed by FACS.

RESULTS

A profound inhibition of proliferation was seen in the LCL with 20 microM curcumin compared to 0.1% DMSO control. The colony count reduced from 34.5 +/- 3.4 to 0/well (P = 0.005), cell number reduced from 101,250 +/- 12,093 to 3750 +/- 1500/well (P = 0.002), and (3)H uptake reduced from 40,889 +/- 3669 to 70 +/- 5.2/well (P = 0.001). The apoptosis rate of LCL in the DMSO control at 24.07 and 16.87% increased significantly with 20 microM Cur to 76.4 and 95.1% at 18 and 42 h, respectively (P = 0.02).

CONCLUSION

Cur is a potent inhibitor of EBV-transformed LCL. This effect appears to be mediated through enhanced apoptosis. A further investigation of this effect may be useful in prevention and therapy of B-cell lymphoma in immunodeficient patients.

Activation and adoptive transfer of Epstein-Barr virus-specific cytotoxic T cells in solid organ transplant patients with posttransplant lymphoproliferative disease

The treatment of Epstein-Barr virus (EBV)-associated lymphoproliferative disease (PTLD) in EBV seronegative solid organ transplant recipients who acquire their EBV infection after engraftment poses a considerable challenge because of underlying immunosuppression that inhibits the virus-specific cytotoxic T cell (CTL) response in vivo. We have developed a protocol for activating autologous EBV-specific CTL lines from these patients and show their potential use for immunotherapy against PTLD in solid organ transplant patients. Peripheral blood mononuclear cells from a panel of solid organ transplant recipients with and without active PTLD were used to assess EBV-specific memory CTL responses. The activation protocol involved cocultivation of peripheral blood mononuclear cells with an autologous lymphoblastoid cell line under conditions that favored expansion of virus-specific CTL and hindered the proliferation of allospecific T cells. These CTL consistently showed (i) strong EBV-specificity, including reactivity through defined epitopes in spite of concurrent immunosuppressive therapy, and (ii) no alloreactivity toward donor alloantigens. More importantly, adoptive transfer of these autologous CTLs into a single patient with active PTLD was coincident with a very significant regression of the PTLD. These results demonstrate that a potent EBV-specific memory response can be expanded from solid organ recipients who have acquired their primary EBV infection under high levels of immunosuppressive therapy and that these T cells may have therapeutic potential against PTLD.

Efficient gene delivery into epstein-barr virus (EBV)-transformed human B cells mediated by replication-defective herpes simplex virus-1 (HSV-1): A gene therapy model for EBV-related B cell malignancy

Subgroups of the B cell malignancies are known to be associated with Epstein-Barr virus (EBV) infection, especially in immunocompromised patients. These are fatal and refractory to conventional antineoplastic therapy. B cells are usually post-mitotic cells and even mitogen activated or transformed B cells have shown relative resistance against viral mediated gene transfer. To address this issue, we employed a replication-defective herpes simplex virus-1 (HSV-1) to mediate gene transfer into EBV-transformed B cells. The virus expresses the herpes simplex virus thymidine kinase (HSV-TK) and the E. coli lacZ reporter genes and is designated T0Z.1. We used the lymphoblastoid cell line SWEIG as a model for human EBV-related B cell malignancy. This cell line was established by in vitro EBV infection of primary human peripheral blood mononuclear cells. When SWEIG cells were infected with T0Z.1, X-gal staining revealed lacZ expression in more than 20% cells even at multiplicity of infection (MOI) as low as 1 and the expression persisted for at least one week. Ganciclovir (GCV) administration after T0Z.1 infection effectively decreased the number of the infected tumor cells in a dose-responsive manner. Viral toxicity was analyzed by cell proliferation assay (MTS assay) and found to be little even at 10 MOI infection. Three MOI of the virus yielded maximum antineoplastic effect and more than 50% tumor cells were killed by HSV-TK/GCV. These results suggest the potential utility of replication-defective HSV-1 for the treatment of EBV-related B cell malignancies.

An analysis of the prognostic significance of p53 status for squamous cell carcinoma of the oral cavity treated by radiotherapy

The status of the p53 gene in biopsy specimens was analyzed to determine whether it is predictive of the outcome of radiotherapy of squamous cell carcinomas of the oral cavity. Biopsy materials were obtained from 45 patients, and the p53 status of each patient was determined using a single-strand conformation polymorphism analysis. Fourteen of the patients were treated with radiation therapy alone; the other 31 patients underwent radiotherapy in combination with surgery or chemotherapy. Twenty-seven patients had tumors with wild-type p53 and 18 patients had a tumor with mutant p53. The initial tumor response was not significantly different between these two groups. Kaplan-Meier survival plots (log-rank test) showed that the probability of survival was not significantly different between two groups although the patients with mutant p53 had a tendency for longer survival (P = 0.2941). However, among the patients with stage III/IV tumors (n = 24), those with a wild-type p53 status tended to have longer survivals.

Functional differences between BHRF1, the Epstein-Barr virus-encoded Bcl-2 homologue, and Bcl-2 in human epithelial cells

BHRF1, a component of the restricted early antigen complex of the Epstein-Barr virus lytic cycle, encodes a 17-kDa protein with both sequence and functional homology to the antiapoptotic Bcl-2 oncogene. Recent work has suggested that BHRF1 behaves like Bcl-2 in protecting cells from apoptosis induced by a range of stimuli. In this study, the effect of BHRF1 and Bcl-2 on the growth and differentiation of the SCC12F human epithelial cell line was examined. The levels of stable transfected BHRF1 expression achievable in SCC12F cells was consistently lower than that obtained with Bcl-2. While both BHRF1 and Bcl-2 inhibited epithelial differentiation, the effect of Bcl-2 was more pronounced, resulting in an almost complete blockade of differentiation in organotypic raft cultures. However, BHRF1-expressing SCC12F cells proliferated at a much higher rate than SCC12F cells expressing Bcl-2, and this effect was supported by cell cycle analysis which demonstrated that BHRF1, but not Bcl-2, promotes rapid transit through the cell cycle. These data highlight important differences between BHRF1 and Bcl-2 and suggest that BHRF1 may function to promote the survival and proliferation of lytically infected cells. The proliferative properties of BHRF1 described in this study, together with the demonstration that other oncogenic gamma herpesviruses encode Bcl-2 homologues, suggests that these proteins may serve to increase the susceptibility of virus-infected cells to oncogenic transformation, thereby contributing to the development of virus-associated tumors.

Epstein-Barr virus in the pathogenesis of Hodgkin's disease

Epidemiologic and clinico-pathologic features of Hodgkin's disease suggest that an infectious agent may be involved in the pathogenesis of this puzzling disorder. Recently accumulated data provide direct evidence supporting a causal role of Epstein-Barr virus in a significant proportion of cases. In addition to allowing a better understanding of the complex pathogenesis of Hodgkin's disease, these virological advances, briefly reviewed herein, also constitute an important basis for the development of new therapeutic strategies.

Epstein-Barr Virus (EBV)-Specific Cytotoxic T Lymphocytes for the Treatment of Patients With EBV-Positive Relapsed Hodgkin's Disease

Adoptive transfer of Epstein-Barr virus (EBV)-specific cytotoxic T lymphocytes (CTLs) is effective prophylaxis and treatment of EBV-positive immunoblastic lymphoma in immunocompromised patients. In 50% of patients with Hodgkin's disease, the tumor cells are EBV antigen-positive and may therefore also be suitable targets for treatment with virus-specific CTLs. However, Hodgkin's disease may produce several inhibitory effects on immune induction and effector function in vivo, which may preclude the generation or effector function of CTLs reactive against EBV viral proteins, including those expressed by the tumor cells. We have investigated whether EBV-specific CTLs could be generated ex vivo from 13 patients with Hodgkin's disease: nine with active relapsed disease and four who were in clinical remission after a first or subsequent relapse. CTL lines were successfully generated from nine of 13 patients (five active disease, four remission). Although these lines had an abnormal pattern of expansion comparable to EBV-specific CTLs generated from normal donors, their phenotype was normal except for reduced expression of the zeta chain of the T-cell receptor (TCR). Their cytotoxicity was also compared to EBV-specific lines generated from normal donors and included activity against LMP2a, one of the three weakly immunogenic viral antigens expressed by Hodgkin's tumor cells. To assess the activity of the CTLs in vivo, they were gene-marked and infused into three patients with multiply relapsed disease. The CTLs persisted for more than 13 weeks postinfusion and retained their potent antiviral effects in vivo, thereby enhancing the patient immune response to EBV. This approach may therefore have value in the treatment of EBV-positive Hodgkin's disease.

Epstein-Barr virus EBNA3C represses Cp, the major promoter for EBNA expression, but has no effect on the promoter of the cell gene CD21

EBNA3C is a potent repressor of transcription when bound to DNA as a fusion with the DNA binding domain (DBD) of GALA. A survey of promoters has revealed that the wild-type, unfused EBNA3C can specifically repress expression from reporter plasmids containing the Epstein-Barr virus Cp latency-associated promoter. Repression of Cp activity required amino acids 207 to 368, which encompasses a region resembling a basic DBD adjacent to a leucine zipper DNA binding motif and a site which binds to the cellular factor CBF1/RBP-Jkappa. However, amino acids 207 to 368 are dispensable when the protein is bound to DNA as a fusion with the GAL4 DBD, thus implicating this region in DNA binding. Mutation of the CBF1/RBP-Jkappa binding site in EBNA3C abrogated repression, strongly suggesting that CBF1/RBP-Jkappa is necessary for targeting the viral protein to Cp. Consistent with this result, mutation of the EBNA2 response element (a CBF1/RBP-Jkappa binding site) in Cp also prevented significant repression. In addition, amino acids 346 to 543, which were previously defined as important for the repressor activity of the GAL4-EBNA3C fusion proteins, also appear to be necessary for the repression of Cp. Since repression by these fusions was not observed in all cell types, it seems likely that EBNA3C either depends on a corepressor which may interact with amino acids 346 to 543 or is modified in a cell-specific manner in order to repress. These data are consistent with EBNA3C contributing to the regulation of EBNA expression in latently infected B cells through CBF1/RBP-Jkappa and another factor, but this need not directly involve EBNA2. Finally, although it has been reported that EBNA3C can upregulate CD21 in some B cells, we were unable to demonstrate any effect of EBNA3C on reporter plasmids which contain the CD21 promoter.

Biology and adoptive cell therapy of Epstein-Barr virus-associated lymphoproliferative disorders in recipients of marrow allografts

Epstein-Barr virus (EBV) is an ubiquitous herpesvirus which is carried as a latent infection of B lymphocytes and salivary gland epithelial cells in over 90% of normal adults. Latently infected EBV-transformed B cells circulate at low frequency in the blood for the life of the host. These transformed B cells stimulate a heterogeneous and complex host cell response, ultimately leading to the development and maintenance of high frequencies of HLA-restricted T cells specific for the EBV-encoded nuclear antigens EBNA2-EBNA6 and the latency membrane proteins LMP-1 and LMP-2. Responses to latent EBV-encoded proteins are hierarchical with responses to certain epitopes predominating, dependent upon the HLA genotype of the host. Profound suppression of T-cell immunity may permit the emergence of polyclonal, oligoclonal or monoclonal EBV antigen-expressing lymphoproliferative disorders or malignant B-cell lymphomas expressing these latent EBV antigens. Adoptive transfer of small numbers of peripheral blood mononuclear cells or HLA-partially matched T cells from in vitro expanded EBV-specific T-cell lines derived from a seropositive marrow donor has induced durable regressions of bulky, widely metastatic monoclonal EBV lymphomas in a high proportion of cases. This review describes the current state of knowledge and hypothesis regarding the biology and immunology of EBV infection in the normal host, the features of donor, host and virus which contribute to the development of EBV-associated lymphoproliferative diseases and the mechanisms whereby they are controlled by adoptive transfer of immune T cells.

Killing Epstein-Barr virus-positive B lymphocytes by gene therapy: comparing the efficacy of cytosine deaminase and herpes simplex virus thymidine kinase

Epstein-Barr virus (EBV)-positive lymphomas are frequent among immunosuppressed patients. We have examined the feasibility of killing EBV-immortalized B lymphocytes by gene transfer involving the use of "suicide" genes whose expression in target cells renders them susceptible to killing by a prodrug. We examined two gene/prodrug pairs: the Escherichia coli cytosine deaminase (CD) gene with the prodrug 5-fluorocytosine (5-FC), and the herpes simplex virus thymidine kinase (HSV-TK) gene with the prodrug ganciclovir. Retroviral vectors and drug selection were used to obtain CD or HSV-TK expression in cells. Both the CD/5-FC and the HSV-TK/ganciclovir combinations yielded substantial killing of EBV-immortalized B lymphocytes in vitro, although the CD/5-FC regimen had a significantly greater therapeutic margin than the HSV-TK/ganciclovir combination. The CD/5-FC pair, but not the HSV-TK/ganciclovir pair, was shown to have a "bystander killing effect" in vitro. When only 30% of the cells expressed the suicide gene, scid mouse tumors regressed in both the CD/5-FC regimen and the HSV-TK/ganciclovir regimen, documenting an in vivo bystander effect with both regimens. However, a greater percentage of tumors completely regressed with the CD/5-FC regimen. Overall, the sum of our data indicates that the CD/5-FC combination is the more promising regimen for treatment of EBV-associated lymphomas in vivo.

Epstein-Barr virus associated Burkitt lymphoma in a heart transplant recipient

This report describes a case of Epstein-Barr [correction of Epstein Barr] Virus related post-transplantation B lymphoproliferative disease of unusual Burkitt lymphoma (BL) type in which combined cytotoxic agents (PACE BOM) successfully produced complete and long-term tumor remission.

Epstein-Barr virus nuclear antigen 2 and latent membrane protein independently transactivate p53 through induction of NF-kappaB activity

B-cell immortalization by Epstein-Barr virus (EBV) is dependent on permanent control of the cellular processes which normally regulate cell division and apoptosis, functions possessed by p53 in a number of normal cell types. In studies initiated to evaluate relationships between EBV latent genes and p53, p53 levels were found to increase approximately 10-fold 4 to 5 days after EBV infection of purified resting human B cells; the induced p53 was transcriptionally active. Latent membrane protein 1 and, to a lesser extent, EBV nuclear antigen 2 mediated the increase in p53 levels via activation of the NF-kappaB transcription factor.