Heterogeneous Epstein-Barr virus latent gene expression in AIDS-associated lymphomas and in type I Burkitt's lymphoma cell lines.

Epstein-Barr virus (EBV) is associated with lymphoma in immunocompromised patients. This study provides evidence that the expression of EBV nuclear antigen-3 genes can be directed from the F promoter in different type I Burkitt's lymphoma cell lines and in some lymphomas from human immunodeficiency virus-infected patients. This expression occurs predominantly after induction of the EBV lytic cycle.

Remarkable application of serum EBV EBER-1 in monitoring response of nasopharyngeal cancer patients to salvage chemotherapy.

Nineteen consecutive patients with metastatic or recurrent nasopharyngeal cancer (NPC) receiving combination chemotherapy were monitored for EBV DNA in their serum. EBV DNA (EBER-1) concentration in serum was measured before, during, and after chemotherapy. Thirteen patients had additional multiple prechemotherapy readings. There was a significant lead time from first detection of serum EBER-1 to clinical recurrence in 62% of patients by a mean of 17.4 weeks (range: 8-74.5 weeks; mean = 28.2 weeks if confined to the 8 patients with significant lead time). The median EBER-1 concentration was significantly higher in those with distant metastasis as compared to those with loco-regional recurrence only (17,468 vs. 684 pg/mL serum; p = 0.046, Mann-Whitney U test). Among the 13 patients who responded to chemotherapy, 4 exhibited clinical complete remission (CR) who were only found in the group with EBER-1 DNA drop to background level, while the magnitude of EBER-1 drop did not discriminate partial remission (PR) and stable disease (SD) patients clearly. Subsequent profile of EBER-1 DNA showed concordance with clinical course of either continuous remission or later progression. EBER-1 DNA in serum can become a useful adjunctive surrogate marker to monitor chemotherapeutic response in NPC patients with distant metastasis or advanced local recurrence.

Antibody responses to recombinant Epstein-Barr virus antigens in nasopharyngeal carcinoma patients: complementary test of ZEBRA protein and early antigens p54 and p138.

Serological tests based on the antibodies directed against the Epstein-Barr virus early antigen (EA) and viral capsid antigen (VCA), which have been recognized as tumor markers for nasopharyngeal carcinoma (NPC), are routinely used to help in the diagnosis of this malignancy. The detection of these antibodies reveals very low titers, found only in a small proportion of young compared with older NPC patients. This is a problem for the diagnosis of NPC, especially among Maghrebians, among whom young people are also affected, and emphasizes the necessity to search for more reliable markers. The present study reports results of immunoglobulin G (IgG) and IgA responses of NPC patients to recombinant EA antigens p54 (BMRF1) and p138 (BALF2), VCA complex antigens p18 (BFRF3) and p23 (BLRF2), and EBNA antigen p72 (BKRF1). Our results show that IgA-EA-p54 and -p138 (IgA-EA-p54+138) antibodies have a diagnostic value for detection of NPC (70%), compared with IgA-VCA-p18+23 and IgA-EBNA-p72, which have limited diagnostic value, especially in young patients. It is also noteworthy that IgA-EA-p54+138 can detect a high percentage (64%) of NPC cases negative by immunofluorescence. These results, however, clearly show that a single test cannot achieve the objective of detecting all NPC patients, and it seems advisable to combine different tests for the diagnosis of NPC. The combination of IgG-ZEBRA with IgA-EA-p54+138 improved the sensitivity of detection of NPC to 95% in the overall NPC population. The use of IgA-EA-p54+138 in combination with IgG-ZEBRA will facilitate detailed studies on the pattern of antibody response, which may result in the development of useful serological markers to guide the treatment of NPC.

Induction of cyclooxygenase-2 by Epstein-Barr virus latent membrane protein 1 is involved in vascular endothelial growth factor production in nasopharyngeal carcinoma cells.

Cyclooxygenase-2 (COX-2) is an inducible form of COX and is overexpressed in diverse tumors, raising the possibility of a role for COX-2 in carcinogenesis. In addition, COX-2 contributes to angiogenesis. The Epstein-Barr virus (EBV) oncoprotein, latent membrane protein 1 (LMP1), is detected in at least 70% of nasopharyngeal carcinoma (NPC) and all EBV-infected preinvasive nasopharyngeal lesions. We found that in specimens of LMP1-positive NPC, COX-2 is frequently expressed, whereas LMP1-negative NPC rarely express the enzyme. We next found that expression of LMP1 in EBV-negative nasopharyngeal epithelial cells induced COX-2 expression. Coexpression of IkappaBalpha(S32A/S36A), which is not phosphorylated and prevents NF-kappaB activation, with LMP1 showed that NF-kappaB is essential for induction of COX-2 by LMP1. We also demonstrate that NF-kappaB is involved in LMP1-induced cox-2 promoter activity with the use of reporter assays. Two major regions of LMP1, designated CTAR1 and CTAR2, are signal-transducing domains of LMP1. Constructs expressing either CTAR1 or CTAR2 induce COX-2 but to a lesser extent than wild-type LMP1, consistent with the ability of both regions to activate NF-kappaB. Furthermore, we demonstrate that LMP1-induced COX-2 is functional because LMP1 increased production of prostaglandin E(2) in a COX-2-dependent manner. Finally, we demonstrate that LMP1 increased production of vascular endothelial growth factor (VEGF). Treatment of LMP1-expressing cells with the COX-2-specific inhibitor (NS-398) dramatically decreased production of VEGF, suggesting that LMP1-induced VEGF production is mediated, at least in part, by COX-2. These results suggest that COX-2 induction by LMP1 may play a role in angiogenesis in NPC.

Association of Epstein-Barr virus with human mammary carcinoma. Pros and cons.

The Epstein-Barr virus (EBV) is associated with the development of different malignancies. In the last few years, EBV has been detected in a subset of breast tumors. The EBV genome was detected by PCR and Southern-blot analysis and identification of the infected cells was determined using different in situ methods. EBV has detected more frequently in steroid hormone receptors negative tumors, in high histological SBR grade tumors and furthermore, the EBV genome was also observed in metastatic lymph nodes, along with EBV detection in the primary tumor. Opposing results are discussed.

Transforming growth factor beta 1 stimulates expression of the Epstein-Barr virus BZLF1 immediate-early gene product ZEBRA by an indirect mechanism which requires the MAPK kinase pathway.

Disruption of Epstein-Barr virus (EBV) latency is mediated by ZEBRA, the protein product of the immediate-early EBV gene, BZLF1. In vitro, phorbol 12-myristate 13-acetate (PMA), a potent activator of protein kinase C (PKC), induces reactivation of EBV. However, the physiological stimuli responsible for the disruption of viral latency are not well characterized. Transforming growth factor beta 1 (TGF-beta1) has also been shown to trigger the reactivation of EBV in Burkitt lymphoma cell lines; however, the effect of TGF-beta1 on ZEBRA expression has not been reported. To further understand this phenomenon, we have investigated the effect of TGF-beta1 on ZEBRA expression. Our results indicate that the treatment of different EBV-positive Burkitt's lymphoma cell lines with TGF-beta1 induces a time-dependent activation of BZLF1 transcription with a corresponding increase in the production of the protein ZEBRA. TGF-beta1 has been shown to exert its effects through a wide range of intracellular routes; in the present study, we have explored these pathways. Transient expression of Smad proteins on their own had no effect on ZEBRA expression. A specific inhibitor of p38 mitogen-activated protein kinase (MAPK), SB203580, did not affect TGF-beta1-induced ZEBRA expression, whereas treatment with the MAPK/ERK kinase inhibitors, PD98059 and U0126, dramatically decreased this induction. This suggests that TGF-beta1 effect on BZLF1 expression requires the MAPK pathway. However, in Raji and B95-8 cells additional routes can be used, as (i) the inhibition of ZEBRA induction by PD98059 or U0126 was incomplete, whereas these inhibitors completely abolished PMA-induced ZEBRA expression, (ii) TGF-beta1 induction of ZEBRA expression occurs in PKC-depleted cells, (iii) in Raji and in B95-8 cells, the effect of TGF-beta1 and PMA are additive. Transient transfection of the EBV-negative B-cell line DG75 with a BZLF1 promoter-fusion construct (Zp-CAT) showed that under conditions where the BZLF1 promoter is activated by PMA treatment, TGF-beta1 had no significant effect on the expression of the chloramphenicol acetyltransferase gene. Furthermore, TGF-beta1 induction of BZLF1 transcripts is dependent on de novo protein synthesis, which suggests that TGF-beta1 induces BZLF1 expression by an indirect mechanism.

Antibodies to the Epstein-Barr virus transactivator protein (ZEBRA) as a valuable biomarker in young patients with nasopharyngeal carcinoma.

Epstein-Barr virus (EBV)-associated nasopharyngeal carcinoma (NPC) generally occurs in adults, especially in high-prevalence populations such as the Chinese and Eskimos. In Maghrebian populations, young patients affected with this malignancy represent 25% of the total NPC cases. In adults with NPC, relatively high titers of IgA antibodies to the EBV viral capsid antigen (VCA) and early antigen (EA) represent important markers. However, nearly 50% of young NPC patients are negative for IgA-anti-VCA and -EA or exhibit very low titers of these antibodies. We report here that 92% of sera from young NPC patients negative for IgA-EA and 89% of those negative for IgA-VCA were positive for IgG antibodies to the EBV transactivator protein (ZEBRA) at very high titers. Our results show that in young patients with NPC these antibodies represent the most reliable marker for diagnosis and prognosis, particularly when compared with conventional NPC markers, i.e., IgA-VCA (58%) and anti-EA (25%). The titers of IgG-ZEBRA antibodies increased along with lymph node involvement only in the young patient group, suggesting a prognostic value of this marker in this patient group.

Dimerization of the Epstein-Barr virus ZEBRA protein in the yeast two-hybrid system. Comparison Of a ZEBRA variant with the B95-8 form.

Epstein-Barr virus (EBV) is a herpes virus associated with several human tumors. The EBV protein, ZEBRA, is a transactivator of the basic leucine zipper family (bZip). It binds to specific sequences on DNA and is able to interact with cellular proteins such as p53. The interaction of the ZEBRA protein with its cognate DNA sequences is stable as long as the dimerization domain is functional. Recent work from this laboratory identified a ZEBRA variant (Z206) with a single amino acid change at residue 206. An alanine is substituted for a serine, and this replacement is present in 72% of nasopharyngeal carcinoma from Europe and North Africa. As amino acid 206 lies within the dimerization domain it could be instrumental in interactions with other proteins. The yeast two-hybrid system was used to study ZEBRA-protein interactions. As ZEBRA by itself is a transactivator in yeast, it cannot be used directly in this assay. This paper describes modifications in ZEBRA amino acid sequences, rendering it usable in the yeast two-hybrid assay. We compared the dimerization capacity of the Z206 variant to that of ZEBRA from B95-8 (Z95) and observed that reporter gene activity with Z206 was consistently lower than that of Z95 (P < 0.05). Furthermore, no interaction was found to occur between either form of ZEBRA (Z206 or Z95) and the tumor suppressor, p53 in the yeast two-hybrid system.

Detection of Epstein-Barr virus in invasive breast cancers.

BACKGROUND: Epstein-Barr virus (EBV) may be a cofactor in the development of different malignancies, including several types of carcinomas. In this study, we investigated the presence of EBV in human breast cancers. METHODS: We used tissues from 100 consecutive primary invasive breast carcinomas, as well as 30 healthy tissues adjacent to a subset of the tumors. DNA was amplified by use of the polymerase chain reaction (PCR), with the primers covering three different regions of the EBV genome. Southern blot analysis was performed by use of a labeled EBV BamHI W restriction fragment as the probe. Infected cells were identified by means of immunohistochemical staining, using monoclonal antibodies directed against the EBV nuclear protein EBNA-1. RESULTS: We were able to detect the EBV genome by PCR in 51% of the tumors, whereas, in 90% of the cases studied, the virus was not detected in healthy tissue adjacent to the tumor (P<.001). The presence of the EBV genome in breast tumors was confirmed by Southern blot analysis. The observed EBNA-1 expression was restricted to a fraction (5%-30%) of tumor epithelial cells. Moreover, no immunohistochemical staining was observed in tumors that were negative for EBV by PCR. EBV was detected more frequently in breast tumors that were hormone-receptor negative (P =.01) and those of high histologic grade (P =.03). EBV detection in primary tumors varied by nodal status (P =.01), largely because of the difference between subjects with more than three lymph nodes versus less than or equal to three lymph nodes involved (72% versus 44%). CONCLUSIONS: Our results demonstrated the presence of the EBV genome in a large subset of breast cancers. The virus was restricted to tumor cells and was more frequently associated with the most aggressive tumors. EBV may be a cofactor in the development of some breast cancers.

[Epstein-Barr virus and Burkitt's lymphoma]. / Le virus d'Epstein-Barr et le lymphome de Burkitt.

Burkitt's lymphoma has the highest incidence of any childhood cancer in equatorial Africa. Geographic distribution appears to be related to climatic conditions and coincides with areas of endemic malaria. These tumors are characterized by reciprocal translocation from chromosome 8 at or near the c-myc locus to either the immunoglobulin chain locus on chromosome 14 (80 p. 100 of cases) or one of the light chain loci on chromosome 2 or 22. As a result of this translocation, transcription of the protooncogene c-myc is activated. Deregulation of c-myc could play a major role in onset and development of the tumor. Study of Burkitt's lymphoma led to the discovery of the first association between viral infection and tumor development in humans. The Epstein-Barr virus is contained in all endemic Burkitt's lymphoma cells, thus implicating it as a likely etiologic factor. Viral expression is reduced essentially to small non-coding RNA, non-polyadenilates, and EBERs (10(6) copies per cell) and a nuclear protein EBNA1 which is indispensable for maintenance of the Epstein-Barr virus genome in infected cells. Expression of EBNA in transgenes leads to lymphoma in mice and could play a role in the expression of the c-myc gene involved in translocations.

Amino-acid change in the Epstein-Barr-virus ZEBRA protein in undifferentiated nasopharyngeal carcinomas from Europe and North Africa.

Different Epstein-Barr-virus(EBV) variants were found to be associated with nasopharyngeal carcinoma (NPC). The type-C variant lacks the BamHI site between the BamHI W1* and I* regions and the type-f variant has an extra BamHI site in the BamHI F fragment. The BNLF1 gene (which encodes the LMP1 protein) from a nude-mouse-passaged CAO strain and from NPC biopsies from Taiwanese patients also exhibits variations resulting in structural and functional differences in the protein. The BZLF1 gene encodes the ZEBRA protein which triggers the EBV lytic cycle. A difference has been observed in 8 amino acids in the ZEBRA sequence in B95-8 (Z95) and P3HR1 (ZP3) cell lines. EBV found in NPC biopsies and peripheral-blood cells from Asians was predominantly of the ZP3 type (72%), while 81% of samples from different EBV-associated diseases and peripheral-blood cells from North Africa or Europe were of the Z95 type. We found that an alanine 206 had been replaced by a serine in the Z95 sequence in 72% of the NPC biopsies from European and North African patients. The Zser206 variant is found in a significantly lower percentage (p < 0.001) of other EBV-positive tissues from individuals in the same region (10-33%). In contrast, a 30-bp deletion is observed near the 3' end of the LMP1 gene in the majority of EBV (86%) from NPC and peripheral-blood cells from Asians, whereas a significantly lower percentage (p < 0.001) of NPC biopsies from European and North African patients (56%) have this deletion, as do lymphocytes from control individuals from the same region (36 and 55% respectively).

Sequence variations in EBNA-1 may dictate restriction of tissue distribution of Epstein-Barr virus in normal and tumour cells.

In seropositive individuals Epstein-Barr virus (EBV) establishes a virus reservoir in peripheral blood lymphocytes (PBLs). Transmission from one individual to another occurs via saliva due to a lytic (virion productive) phase of infection in the oropharynx. EBNA-1 is responsible for maintaining viral episomes in the host cell and could, therefore, also affect the persistence of the virus in different cell lineages. Based on sequence analysis of EBNA-1 we now demonstrate that (i) in addition to the prototype EBNA-1 (identical to the B95.8 virus EBNA-1), EBV in normal individuals encompasses multiple EBNA-1 subtypes, both in PBLs and in oral secretions; (ii) although EBV with prototype EBNA-1 is the predominant virus in normal individuals, it is very rarely associated with either nasopharyngeal carcinoma (NPC) or Burkitt's lymphoma (BL); (iii) EBV with an EBNA-1 subtype (V-val) frequently associated with NPC is also selectively detected in oral secretions and not in PBLs; (iv) EBV with the EBNA-1 subtype V-pro is restricted to PBLs, while a mutated version of this subtype is present in BL, but not in NPC. These findings suggest that the variations in EBNA-1 may be relevant to the ability of EBV to persist in different cell types, and hence relevant to its oncogenic potential.

Interleukin (IL)-10 and IL-6 are produced in vivo by non-Hodgkin's lymphoma cells and act as cooperative growth factors.

The in vivo production of interleukin (IL)-10, IL-6, IL-2, and tumor necrosis factor (TNF)-alpha in tumor samples was investigated by immunohistochemistry in 54 non-Hodgkin's lymphomas (NHLs). Respectively, 55, 89, 23, and 29% of tumor samples were found positive for IL-10, IL-6, IL-2, and TNF-alpha expression by immunohistochemistry. Using reverse transcription-PCR, the mRNA of IL-10 and IL-6 were detectable in all samples tested and in 90 and 34% of the samples for TNF-alpha and IL-2, respectively. In 13 patients, fresh tumor tissue was available for B NHL cell purification with Dynabeads. IL-10, IL-6, IL-2, and TNF-alpha were detectable in the supernatant of 38, 100, 0, and 23% of purified tumor cell preparations (PTCPs), respectively. All patients with detectable IL-10 in culture had increased serum IL-10. IL-6 production by tumor cells and serum IL-6 levels were also found to be highly correlated (P < 0.0001). This suggests that tumor cells are a major source of serum IL-1O and IL-6 in these patients. Exogenous IL-10, IL-6, IL-2, and TNF-alpha significantly enhanced the [3H]thymidine uptake in 13 of 13 (100%), 5 of 13 (38%), 9 of 13 (69%), and 2 of 10 (20%) PTCPs costimulated with anti-CD40, respectively. IL-2, IL-6, and TNF-alpha synergized with IL-10 in 54, 23, and 30% of PTCPs. The combination of IL-10, IL-2, and IL-6 induced the maximal level of proliferation in 12 (92%) of 13 PTCPs. CD40 ligand mRNA expression was also detectable in vivo using reverse transcription-PCR in 28 of the 29 (97%) tumor samples tested, including 11 of those tested for [3H]thymidine incorporation. These results show that IL-1O, IL-6, IL-2, and TNF-alpha are produced in NHL tumors and may cooperate in vivo to increase NHL cell proliferation.

Serum interleukin-10 in acquired immunodeficiency syndrome lymphoma patients. Seroco-Hemoco Study Group.

Interleukin-10 (IL-10) has multiple effects on lymphoid development, particularly as a stimulant of activated B-cell proliferation and differentiation. It is thought that IL-10 might play a role in the development of B lymphoid malignancies based on the observation that lymphomatous tissues from HIV+ patients contain numerous cells containing IL-10 mRNA as well as IL-10 protein. The aim of this study using an Elisa test was to analyze IL-10 in the serum of 18 HIV+ patients with non Hodgkin's B lymphoma (NHL) and compared the presence of this cytokine in the serum of 18 HIV+ patients without NHL. In this comparative study we also considered the different parameters such as the mode of contamination, sex, age and number of CD4 cells. 44% of the patients with HIV-related NHL had significant levels of IL-10 (> or = 12 pg/ml) in their serum, in comparison to the patients without NHL who did not show detectable serum IL-10.

Transcriptional analysis of the Epstein-Barr virus interleukin-10 homologue during the lytic cycle.

The Epstein-Barr virus (EBV) open reading frame (ORF) BCRF1, expressed in the late phase of the viral cycle, encodes a homologue of human interleukin-10 (hIL-10). Unspliced, 3' co-terminal transcripts of 0.8 and 1.6 kb from O-tetradecanoylphorbol 13-acetate (TPA)-treated B95-8 cells have been described but other results indicated the existence of uncharacterized transcript(s) initiated upstream of the 1.6 kb BCRF1 mRNA. Here we describe two additional large transcripts of the BCRF1 ORF, a possibly spliced product of 3.5 kb and an unspliced product of 4.5 kb. The time course of the expression of BCRF1 transcripts and of the secreted protein from Akata cells were also determined.

Qualitative analysis of the expression of Epstein-Barr virus lytic genes in nasopharyngeal carcinoma biopsies.

We recently showed that BZLF1, the gene encoding the Epstein-Barr virus (EBV) ZEBRA protein, was expressed in all eight nasopharyngeal carcinoma (NPC) specimens studied. We present here studies on the expression of EBV lytic cycle genes in the same eight NPC biopsies to determine if production of the ZEBRA transactivator could lead to a complete productive cycle. The tumour lesions exhibit a number of different patterns of limited lytic gene expression. In three out of eight tumours neither BRLF1 nor BMLF1 expression could be detected. Otherwise BMLF1 mRNA was expressed in all the other specimens. Three specimens also expressed BRLF1. Two specimens not only exhibited BZLF1, BMLF1 and BRLF1 transcripts, but also expressed the late gene BLLF1 which encodes the membrane protein gp220. The early gene product BBLF2 could not be detected in any of the eight NPC. However, expression of the late gene encoding the lytic truncated form of LMP1 (D1LMP) was found in seven of the eight NPC biopsies. Thus, it could be suggested that the EBV abortive lytic cycle occurred in most of the NPC studied.

A possible prognostic role of immunoglobulin-G antibody against recombinant Epstein-Barr virus BZLF-1 transactivator protein ZEBRA in patients with nasopharyngeal carcinoma.

BACKGROUND: Epstein-Barr virus BZLF-1 replication activator (ZEBRA) is involved in the switch from viral latency to a productive cycle. Previous immunofluorescent study has shown that patients with nasopharyngeal carcinoma (NPC) have elevated immunoglobulin-G (IgG) antibody titres against recombinant ZEBRA protein (ZEBRA/IgG). METHODS: The prognostic role of ZEBRA/IgG was further investigated by enzyme-linked immunosorbent assay (ELISA) in 110 NPC patients under long period of clinical follow-up. RESULTS: Ninety-seven percent (85 of 88) of the patients with NPC had significantly higher ZEBRA/IgG titres (geometrical mean titre, i.e., GMT = 8397) than normal Chinese individuals (GMT = 233 and P < 0.0001). Based on Kaplan-Meier analysis, the actuarial survival in patients with high ZEBRA/IgG titres (25%) after radiotherapy was significantly lower than that of those with low (76%; P = 0.0008) or intermediate titres (62%; P = 0.0036), although the titres taken before treatment did not bear such a relationship. Subdividing the patients into either individual UICC or Ho's stages, those with late-stage disease (UICC Stage 4 and Ho's Stages 3 and 4) and with high ZEBRA/IgG titres also had poorer prognosis than those with disease of the same stages but who had low titres. Poor prognosis in those with high titres could be associated with a high risk of distant metastasis because consistent titre increase was found in the majority of patients who later developed distant metastasis either in the lung or liver. Only a minimal increase was found in patients with recurrence in the cervical lymph nodes. No consistent increase was observed, however, in patients whose disease was in remission or the majority of those with bone metastasis or local recurrence in the nasopharynx. CONCLUSION: The postradiotherapy ZEBRA/IgG titre could be a potentially useful marker for differentiating NPC patients with poor prognosis from those at high risk for the development of distant metastasis to the lung or liver.

Patterns of Epstein-Barr virus latent and replicative gene expression in Epstein-Barr virus B cell lymphoproliferative disorders after organ transplantation.

B cell lymphoproliferative disorders arising in organ transplant recipients (B cell posttransplant lymphoproliferative disorders [PTLD]) are generally associated with EBV. In previous reports, B cell PTLD were shown to express the full pattern of EBV latent genes, as in vitro-established lymphoblastoid cell lines. Although viral linear DNA was detected in 40% of lymphoproliferative disorders from immunocompromised hosts, immunophenotypic studies failed to detect late EBV replicative antigens. The aim of this study was to investigate the relationship of EBV latent gene expression in B cell PTLD to morphology, clonality, and immunophenotype, and to examine the replicative state of EBV in malignant cells. For this purpose, 9 cases of EBV-related B cell PTLD were analyzed. Immunoglobulin gene rearrangements were detected by Southern blot analysis. The presence of EBV was assessed by Southern blot and by in situ hybridization. B cell differentiation antigens, adhesion and activation molecules, and EBV latent and replicative gene expression were studied using immunohistochemistry techniques. We demonstrated that EBV-related B cell PTLD exhibited varying patterns of latent viral gene expression. Higher levels of adhesion molecules were detected in latent membrane protein 1 (LMP1) or LMP1 plus EBV nuclear antigen 2 (EBNA2)-positive tumors than in LMP1 and EBNA2-negative tumors. In contrast, there was no relationship between CD21 and CD23 expression and latent EBV phenotype. Activation of the EBV replicative cycle was highlighted by BamHI Z left frame 1 expression in 5 of 9 cases. Less frequent expression of late viral proteins suggested that the initiation of the EBV lytic cycle might not always lead to virions production.