An EBV membrane protein expressed in immortalized lymphocytes transforms established rodent cells

A conserved domain of the Epstein-Barr virus nuclear antigens 3A and 3C binds to a discrete domain of Jkappa

EBNA-3C can affect the LMP-1 promoter in both a positive and a negative manner through distinct DNA sequence elements. The viral transactivator EBNA-2 normally binds DNA indirectly via Jkappa to activate transcription, but this activation is prevented in the presence of EBNA-3C. The DNA element recognized by Jkappa is both required and sufficient for this inhibition. Jkappa clones isolated in a yeast two-hybrid screen using EBNA-3C as bait allowed us to delineate the sequences of both proteins mediating the interaction. Two isoforms of Jkappa that differ in exon 1, Jkappa-1 and RBP-2N, interact with EBNA-3C, suggesting that exon 1 is not required for this interaction; indeed, clones with deletion of the N-terminal third of Jkappa interacted as efficiently with EBNA-3C as full-length Jkappa clones. A Jkappa domain as small as 56 amino acids was sufficient to bind to EBNA-3C. A 74-amino-acid domain of EBNA-3C, conserved in all three EBNA-3 family members, was sufficient to interact with Jkappa. A specific mutation in this conserved domain suppressed the ability of EBNA-3C to downregulate transcription. Accordingly, EBNA-3A was also able to interact with Jkappa and downregulate Jkappa-mediated transcription as efficiently as EBNA-3C. The ability of the EBNA-3 proteins to prevent Jkappa from binding to DNA in vitro and suppress transactivation via Jkappa DNA elements suggests that the EBNA-3 proteins act analogously to the Drosophila protein Hairless.

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.

Restricted expression of Kaposi sarcoma-associated herpesvirus (human herpesvirus 8) genes in Kaposi sarcoma

Kaposi sarcoma (KS) is the leading neoplasm of HIV-infected patients and is also found in several HIV-negative populations. Recently, DNA sequences from a novel herpesvirus, termed KS-associated herpesvirus (KSHV), or human herpesvirus 8 (HHV-8) have been identified within KS tissue from both HIV-positive and HIV-negative cases; infection with this agent has been proposed as a possible factor in the etiology or pathogenesis of the tumor. Here we have examined the pattern of KSHV/HHV-8 gene expression in KS and find it to be highly restricted. We identify and characterize two small transcripts that represent the bulk of the virus-specific RNA transcribed from over 120 kb of the KSHV genome in infected cells. One transcript is predicted to encode a small membrane protein; the other is an unusual polyadenylylated RNA that accumulates in the nucleus to high copy number. This pattern of viral gene expression suggests that most infected cells in KS are latently infected, with lytic viral replication likely restricted to a much smaller subpopulation of cells. These findings have implications for the therapeutic utility of currently available antiviral drugs targeted against the lytic replication cycle.

Inflammatory pseudotumor of the liver. Evidence for follicular dendritic reticulum cell proliferation associated with clonal Epstein-Barr virus

We describe an "inflammatory pseudotumor" of the liver that, which on detailed investigation, proved that the spindle-cell component of this lesion is derived from follicular dendritic reticulum cells (FDRC). This contention is supported by morphologic observations and by immunophenotype. The FDRC population contain Epstein-Barr virus (EBV). It is known that FDRC express the EBV receptor CD21. In this particular case, the FDRC contained clonal EBV genomes, EBV RNA (EBER) transcripts, and expressed EBV latent membrane protein (LMP1). DNA sequencing of PCR products showed three point mutations compared with the standard LMP1 sequence of the EBV strain B95-8. The findings in this case corroborate those of other investigators concerning the possible role of EBV in the development of some inflammatory pseudotumors, including the recent production of functionally active EBV-transformed FDRC-like cell lines. This association could prove instructive in delineating the histogenesis of these tumors and further assist in making prognostic and therapeutic decisions.

Interactions involving cyclosporine A, interleukin-6, and Epstein-Barr virus lead to the promotion of B-cell lymphoproliferative disease

Post-transplant patients undergoing prolonged Cyclosporine A (CsA) immunosuppressive therapy were reported to have an increased incidence of Epstein-Barr virus (EBV)-associated lymphoproliferative disorders. EBV-infected B cells cultured with CsA demonstrated increased EBV B-cell out-growth as compared to those cultured without CsA. Peripheral blood mononuclear cells (PBMC), following infection with EBV and CsA treatment, demonstrated increased IL-6 activity in the culture supernatant. The induction of IL-6 appeared to differ within the various lymphocyte populations. In monocytes and B cells, IL-6 expression was preferentially induced by EBV, and initiated by the binding of the two major virion glycoproteins, gp350 and gp220, to CD21, or a CD21-like receptor. Expression of IL-6 in T cells appeared to be due mainly to CsA. B cells also expressed IL-6 following EBV exposure, but not following CsA treatment. EBY-immortalized B-cell lines cultured with CsA exhibited both an increased number of cells expressing viral lytic-cycle antigens and increased amounts of lytic-cycle proteins. IL-6, which was induced by CsA in PBMC, was also capable of inducing the lytic viral cycle in several EBV-immortalized cells. When IL-6 was expressed, it was shown to act as an autocrine growth factor for B cells and to inhibit the immune system allowing for the promotion of B-cell tumors by impairing lymphokine-activated killer cells. Thus CsA treatment, in promoting both increased numbers of lytic EBV B cells and expression of the EBV paracrine growth factor, IL-6, within the microenvironment of EBV B:T cell and EBV B:monocyte interactions, may lead to increased EBV B-cell immortalization and ultimately result in the promotion of B-cell lymphomas in immunosuppressed patients.

Immunohistochemical expression of Epstein-Barr virus-encoded latent membrane protein (LMP-1) in paraffin sections of EBV-associated nasopharyngeal carcinoma in Spanish patients

Nasopharyngeal carcinoma (NPC) paraffin samples, from Spanish patients, of distinct histological types, including squamous cell carcinoma (10 cases), nonkeratinising carcinoma (12 cases) and undifferentiated carcinoma (29 cases) were analysed for Epstein-Barr virus (EBV) detection and EBV-encoded latent membrane protein (LMP-1) expression using a sensitive nested-polymerase chain reaction with four oligonucleotide primers specific for EBV genome (EB-1, 2, 3, 4) and immunohistochemistry by means of CS1-4 pool monoclonal antibody. EBV genome was detected regardless of histological type in 100% of samples with sufficient DNA quality to permit viral diagnosis (50 out of 51 cases), supporting the previous view that all types of NPC are variants of an EBV-associated malignancy. However LMP-1, an EBV-encoded oncogenic protein, was detected in 40 out of 51 samples (78.4%) and LMP-1 immunohistochemical expression was not apparently influenced by histological type, primary or metastatic site, clinical stage, age or sex. This high percentage of detection of LMP-1 in our cases supports a role for EBV in the pathogenesis of different types of NPC, but the lack of constant expression of LMP-1 in NPC remains unclear and various reasons are postulated to explain the absence of this oncogenic protein in some EBV-associated NPCs.

Morphologic differences between latent membrane protein-1 (LMP-1)-positive and negative tumour cells in Epstein-Barr virus (EBV)-related childhood Hodgkin's disease. A morphometric study

The values of five cellular morphometric parameters (longest and shortest cytoplasmic axis, cellular circumference, area and roundness coefficient) were compared between 20 Latent Membrane Protein 1 (LMP-1)-positive and an equal number of LMP-1-negative Reed-Sternberg and Hodgkin (HRS) cells for each of 13 cases of Hodgkin's disease (HD) occurring in children (aged 3-15 years); the presence of Epstein-Barr virus (EBV) encoded EBER mRNAs had previously been detected in all cases using RNA in situ hybridisation (RISH), while the presence of LMP-1 was immunohistochemically detected using the alkaline phosphatase-antialkaline phosphatase (APAAP) method. The longest and shortest axis, circumference and area were larger in LMP-1-positive than in LMP-1 negative HRS cells, while the roundness coefficient of LMP-positive HRS cells was smaller than that of LMP-1 negative cells. All differences were statistically highly significant when univariate (paired comparisons) t-test were used. Multivariate analysis (Hotelling's T2 test) showed all differences (except the roundness coefficient) to be significant both at the 5% and 1% level of significance. These results provide a numerical basis for the alteration brought by the expression of LMP-1 in the cellular skeleton of tumour (HRS) cells in EBV-related childhood HD cases.

Follicular dendritic cell tumor of the liver. Evidence for an Epstein-Barr virus-related clonal proliferation of follicular dendritic cells

Tumors of the follicular dendritic cell are uncommon, and most occur as primary lymph node tumors. We report a case of primary follicular dendritic cell tumor of the liver that was initially reported as an inflammatory pseudotumor. The neoplasm recurred as two separate tumor masses 30 months after complete resection of the "hepatic inflammatory pseudotumor." It showed a wide spectrum of morphologic features ranging from areas with fascicles of very bland spindle cells amidst a background population of lymphocytes, reminiscent of inflammatory pseudotumor, to areas of dispersed sheets of highly pleomorphic tumor cells with a relative paucity of reactive inflammatory cells. The diagnosis was confirmed by positive immunohistochemical staining with CD21, CD35, R4/23, and Ki-M4 and by ultrastructural demonstration of convoluted interdigitating cell processes joined by desmosomes. The background lymphocytes were oligoclonal, CD8-positive T cells. In situ hybridization for Epstein-Barr virus (EBV)-encoded RNA was positive in the tumor cells in the original and recurrent tumors. More importantly, the cells showed identical episomal clonal EBV on Southern blot analysis, implying that the initial and recurrent tumors are due to clonal proliferation of EBV-positive neoplastic follicular dendritic cells. The tumor cells expressed latent membrane protein but not EBV-encoded nuclear antigen 2 (EBNA2) or ZEBRA. Such gene expression is very similar to that of Hodgkin's disease and nasopharyngeal carcinoma. The strong expression of latent membrane protein restricted to the tumor cells and the clonality of the EBV suggest that the virus may be involved in the pathogenesis of this tumor and not present merely as a "bystander."

A pathologic study of Hodgkin's disease in Korea and its association with Epstein-Barr virus infection

BACKGROUND

The incidence of Hodgkin's disease (HD) in Korea and other Asian countries is much lower than in western countries and its association with the Epstein-Barr virus has not been well characterized.

METHODS

We evaluated the clinical, morphologic, and immunohistochemical features of 87 patients with Hodgkin's disease and also analyzed patients for Epstein-Barr virus (EBV) using in situ hybridization for EBV DNA, RNA, and latent membrane protein (LMP1).

RESULTS

There were 68 males and 19 females, with a mean age of 38 years. Mixed cellularity was the most prevalent subtype. Expression of EBV RNA (EBER:EBV-encoded RNA) was detected in 60 of 87 cases (69%): 1 of 1 (100%) with lymphocyte predominance, nodular; 4 of 7 (57%) with lymphocyte predominance, diffuse; 10 of 17 (59%) with nodular sclerosis; 38 of 51 (75%) with mixed cellularity; and 7 of 11 (64%) with lymphocyte depletion. Positivity was higher in advanced clinical stages; 4 of 7 patients (57%) with Stage I; 6 of 12 patients (50%) with Stage II: 7 of 9 patients (75%) with Stage III; and 5 of 5 patients (100%) with Stage IV HD EBV DNA was detected in 9 of 25 cases tested (36%). LMP1 was seen in 39 of 87 cases (45%). EBER and LMP1 positivity were higher in children and older adults than in adults aged between 15-50 years. Immediate early mRNAs (BHLF:Bam H-fragment, lower strand frame) was seen in a single patient.

CONCLUSIONS

HD in Korea showed a high incidence of mixed cellularity subtype and a high prevalence of EBV. EBV was detected in all subtypes, including a case of nodular lymphocytic predominance, and in all age groups, and showed correlation with mixed cellularity subtype and higher clinical stage. The expression of EBER and LMP were more frequently seen in children and older adults, suggesting a lowered immune surveillance in those age groups or a different pathophysiology of HD among different age groups.

Epstein-Barr virus in non-Hodgkin's lymphomas of the upper respiratory tract: association with sinonasal localization and expression of NK and/or T-cell antigens by tumour cells

Fifty-five cases of non-Hodgkin's lymphoma (NHL) of the upper respiratory tract, comprising 27 sinonasal (SN) and 28 Waldeyer's ring (WR) NHL, were investigated for expression of Epstein-Barr virus (EBV)-encoded EBER transcripts and latent membrane protein-1 (LMP-1) by RNA in-situ hybridization (RISH) and immunohistochemistry, respectively. Thirty-two cases were B-cell tumours (10 SNHLs and 22 WRNHLs) and 23 cases expressed natural killer (NK) and/or T-cell antigens (17 SNHLs and 6 WRNHLs). EBER transcripts were detected in tumour cells in 19 lymphomas expressing NK and/or T-cell antigens (16/17 SHNHLs and 3/6 WRNHLs) but in only 2/32 B-NHLs (1/10 SNHLs and 1/22 WRNHLs). LMP-1 expression was found in tumour cells in the 19 EBER-positive tumours expressing NK and/or T-cell antigens but in none of the B-cell lymphomas. All the LMP-1-positive lymphomas expressed the CD30 molecule in tumour cells. These results indicate that in lymphomas of the upper respiratory tract, EBV is strongly associated with sinonasal localization and expression of NK and/or T-cell antigens by tumour cells. EBV can also be detected in some cases of WRNHLs expressing NK and/or T-cell antigens, whereas it is rarely found in B-cell SNHLs and WRNHLs. Furthermore, the detection of the LMP-1 protein in tumour cells in most SNHLs and some WRNHLs expressing NK and/or T-cell antigens, in view of the LMP-1 transforming potential, suggests that EBV may play a role in the pathogenesis of these lymphomas.

Regulation of Epstein-Barr virus latency by latent membrane protein 2

Like other herpesviruses, Epstein-Barr virus persists in its host through its ability to establish a latent infection that periodically reactivates. Latent membrane protein 2A (LMP2A) regulates reactivation from latency by interfering with normal B cell signal transduction processes, and may define a new class of regulators of herpesvirus latency.

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

Hodgkin's disease represents a phenotypically and genotypically heterogeneous lymphoma of CD30-positive tumour cells. Infection of the putative tumour cell population with Epstein-Barr virus (EBV) represents the most common genetic abnormality detectable in HD, yet the role of EBV in the pathogenesis of HD is only poorly understood. In virus-associated HD cases, monoclonal EBV genomes are detectable in all Hodgkin and Reed-Sternberg (HRS) cells, indicating that EBV infection takes place before expansion of the HRS cell population and, by implication, supporting the concept of a monoclonal origin of HRS cells. EBV infection does not define a distinct subgroup of HD but is detectable in different histotypes and in HRS cells expressing lymphocyte differentiation antigens of different cell lineages. Through the EBV-encoded protein, LMP1, the virus may superimpose an activated phenotype on genotypically immature lymphocytes. EBV-induced modulation of the cytokine expression pattern of HRS cells may contribute to the local inhibition of EBV-specific immunity observed in EBV-positive cases.

The ecology and pathology of Epstein-Barr virus

Epstein-Barr virus achieves its ubiquitous and uniform epidemiological distribution by a dual strategy of latency to guarantee lifelong persistence and intermittent replication to guarantee transmission. These two functions appear to dictate residence in different cell types: latency in B lymphocytes and replication in epithelial cells. Both of these cell compartments are potential sites for EBV-associated malignancies.

Epstein-Barr virus is detected in undifferentiated nasopharyngeal carcinoma but not in lymphoepithelioma-like carcinoma of the urinary bladder

The Epstein-Barr virus (EBV) is associated with nasopharyngeal carcinoma (NPC) and with lymphoepithelioma-like carcinomas developing in certain anatomic sites. In this study, an in situ hybridization was used to identify EBV-encoded ribonucleic acid (RNA) (EBER1) transcripts in 32 of 45 cases of NPC but not in any of the 11 lymphoepithelioma-like carcinomas developing in the urinary bladder. EBER1 was most commonly detected in those NPCs having undifferentiated or nonkeratinizing squamous histology rather than the keratinizing squamous cell subtype of NPC. The EBV-encoded latent membrane protein 1 (LMP1) was expressed focally in only seven of 21 EBER1-positive NPCs by an immunohistochemical technique. These findings imply that EBER1 hybridization is more sensitive than LMP1 immunohistochemistry on paraffin sections in detecting carcinoma-associated virus. Previous in vitro studies have suggested that LMP1 expression might be a function of differentiation, but this study of naturally infected NPCs showed no strong correlation between LMP1 positivity and degree of tumor differentiation, albeit a limited spectrum of differentiation that could be examined. In two cases in which frozen tissue was available, the NPCs were monoclonal with respect to viral DNA structure, implying that the virus was present before malignant transformation. Unlike NPCs, the lymphoepithelioma-like carcinomas of the bladder were uniformly EBV negative, lending further evidence to the growing body of literature linking EBV with lymphoepithelial carcinomas of foregut-derived tissues but not with similar-appearing tumors developing in other anatomic sites.

In situ detection of Epstein-Barr virus in non-small cell lung carcinomas

Epstein-Barr virus (EBV) is strongly associated with nasopharyngeal carcinoma and lymphoepithelioma-like carcinomas (LELC) of foregut-derived organs. Recently this group of EBV-associated carcinomas has been expanded by the identification of the virus in conventional adenocarcinomas of the stomach. In situ hybridization (ISH) using a sensitive digoxigenin-labelled EBER RNA probe was performed on 167 consecutive unselected primary non-small cell lung carcinomas, to determine the frequency of EBV association in these tumours. Nine cases (5.4 per cent) showed strong EBER signals in the tumour cell nuclei. By immunohistochemistry, four of the EBER-positive tumours showed patchy expression of the viral latent membrane protein (LMP-1) and none showed any expression of the EBV nuclear antigen 2 (EBNA2). Morphologically, all the positive tumours were LELC, whereas no conventional type of non-small cell lung carcinoma showed EBV association. The LELC presented a morphological spectrum from undifferentiated to squamoid or glandular differentiation. The patients showed a male to female ratio of 8:1. The mean age at presentation was 48 years. Smoking was not a risk factor. All patients were alive at follow-up periods of 23-52 months. Southern blot analysis performed on eight of the nine positive tumours showed a clonal episomal form of EBV, suggesting the clonal expansion of an infected tumour cell early in oncogenesis. These characteristics of the EBV-associated lung tumours justify their consideration as a distinct clinicopathological entity.

Lymphoepithelial carcinoma of the salivary gland: in situ detection of Epstein-Barr virus

AIM

To examine the role of Epstein-Barr virus (EBV) in lymphoepithelial carcinoma of the salivary gland in Hong Kong Chinese.

METHODS

Ten cases of lymphoepithelial carcinoma of the salivary gland (eight parotid and two submandibular) were examined. In situ hybridisation was used to localise EBER RNA, immunohistochemical methods to detect expression of latent membrane protein 1 (LMP-1) in EBV positive tumours, and Southern blot analysis to examine the clonality of EBV in the two cases where frozen tissue was available.

RESULTS

None of the cases had a history of Sjögren's syndrome or histological evidence of a benign lymphoepithelial lesion. The IgA antibody titre against EBV viral capsid antigen was elevated in four cases. All cases were EBV positive by in situ hybridisation, with a strong uniform positive signal in the epithelial cells, and all cases expressed LMP-1. Southern blot analysis revealed that the clonal episomal form of the virus was present. Two of the three female patients in this series also developed carcinoma of cervix. One of these carcinomas had histological features of a lymphoepithelioma-like carcinoma but was EBV negative.

CONCLUSIONS

A consistent association between EBV and lymphoepithelial carcinoma of the salivary gland was found. The presence of the virus in a clonal episomal form, and the expression of LMP-1 viral oncoprotein is further evidence of the role of EBV in the oncogenesis of this tumour.

Epstein-Barr virus-associated leiomyosarcomas in liver transplantation recipients. Origin from either donor or recipient tissue

BACKGROUND

Leiomyosarcoma, a mesenchymal malignancy with smooth muscle differentiation, is extremely rare in children. Immunosuppression, due to either antirejection medication in organ transplantation recipients or human immunodeficiency virus infection (HIV), appears to constitute a predisposition.

METHODS

Two cases of leiomyosarcoma in pediatric liver transplantation recipients were investigated and compared clinically with respect to site of origin and course of the disease and pathologically by routine histology and electron microscopy, by forensic DNA methodology for origin from donor or recipient tissue, and by EBER-1 in situ hybridization for evidence of latent Epstein-Barr virus (EBV) infection.

RESULTS

A 9-year-old male developed a high grade, poorly differentiated leiomyosarcoma in his allografted liver 2 years after transplantation, and despite antineoplastic chemotherapy, he died of metastatic disease. The genotype of his tumor indicated an origin from allografted tissue. A 12-year-old female had a low grade retroperitoneal leiomyosarcoma involving the superior mesenteric vein. After resection, she remained disease free without chemotherapy. The genotype of her tumor indicated an origin from native tissue. In both tumors, latent EBV infection was documented.

CONCLUSIONS

Neoplastic smooth muscle proliferation in immunosuppressed liver transplantation recipients is analogous to the more common posttransplantation lymphoproliferative disorder in involving transformation of either engrafted donor tissue or recipient tissue elsewhere in the body, in displaying a wide spectrum of histologic differentiation, grade and clinical behavior, and in exhibiting evidence of latent EBV infection.

Pathogenesis and classification of primary central nervous system lymphoma: an update

Primary central nervous system lymphoma has undergone a remarkable increase in incidence over the last decade, both in immunosuppressed and immunocompetent individuals. Its clinicopathologic evaluation requires knowledge of current hematopathologic systems for lymphoma classification, as well as specific understanding of unique central nervous system determinants. In immunocompromised individuals, the tumor has a constant association with Epstein-Barr virus. The form of Epstein-Barr virus in these tumors appears to be predominantly latent, however, the precise mechanism relating virus to tumor pathogenesis is still unclear. In immunocompetent patients, risk factors and oncogenic associations are completely unknown. Critical to the formation of these tumors is the trafficking of B-cells, whether pre- or post-transformation, across the blood-brain barrier. These B-cell migrations may require perturbations to the barrier that originate in or around neural parenchyma, such as localized injury or infection.

Detection of an Epstein-Barr-virus variant in T-cell-lymphoma tissues identical to the distinct strain observed in nasopharyngeal carcinoma in the Taiwanese population

An EBV variant has been identified in NPC tissues in Taiwan. This EBV variant contains a point mutation in exon I of the LMP I gene. This mutation results in the loss of an XhoI site at nt 169,426, which is present in strain B95-8. In addition, this variant contains a 30-bp deletion in exon 3 of the gene. The recent demonstration of the prevalence of EBV-containing nasal and peripheral T-cell lymphoma in this region drove us to evaluate the presence of this NPC-EBV strain in 7 cases of T-cell lymphoma, as well as in 48 NPC tissues, 2 cases of Hodgkin's disease and I B-cell lymphoma. Four samples of normal lymph node tissue, 40 of normal nasopharynx tissue and 78 throat washings of healthy individuals were included for comparison. We used sequence-specific primers and the polymerase chain reaction (PCR) method to amplify LMP I gene fragments containing these variations. Mutations were then confirmed by restriction-enzyme digestion and the DNA sequencing analysis. Our results showed that 57 of 58 tumor-tissues samples were EBV-positive. Among them, 56, including 6 T-cell-lymphoma samples, belonged to the NPC strain. This strain of EBV was also present in 92% of EBV-positive normal nasopharynx tissues and in 84% of EBV-positive throat washings of the healthy individuals tested. These results suggest that the NPC-EBV strain is prominently present in Taiwan.

Clonal proliferations of cells infected with Epstein-Barr virus in preinvasive lesions related to nasopharyngeal carcinoma

BACKGROUND

The Epstein-Barr virus (EBV) is consistently detected in patients with nasopharyngeal carcinoma. To determine whether EBV infection is an early, initiating event in the development of this malignant tumor, we screened nasopharyngeal-biopsy samples, most of which were archival, for preinvasive lesions, including dysplasia and carcinoma in situ. Preinvasive lesions were found in 11 samples, which were tested for the presence of EBV.

METHODS

EBV infection was detected with in situ hybridization for EBV-encoded RNAs (EBERs) and by immunohistochemical staining for latent membrane protein 1 (LMP-1). The larger samples were also tested for the EBV genome with the use of Southern blotting. The expression of specific EBV RNAs was determined by the amplification of complementary DNA with the polymerase chain reaction.

RESULTS

Evidence of EBV infection was detected in all 11 tissue samples with dysplasia or carcinoma in situ. EBERs were identified in all eight samples tested, and LMP-1 was detected in all six of the tested samples. Six of the seven samples tested for the EBV termini contained clonal EBV DNA: Transcription of the latent EBV gene products, EBV nuclear antigen 1, LMP-1, LMP-2A, and the BamHI-A fragment, was detected in most of the samples. Viral proteins characteristic of lytic lesions were not detected.

CONCLUSIONS

Preinvasive lesions of the nasopharynx are infected with EBV. The EBV DNA is clonal, indicating that the lesions represent a focal cellular growth that arose from a single EBV-infected cell and that EBV infection is an early, possibly initiating event in the development of nasopharyngeal carcinoma. Preinvasive lesions contain EBV RNAs that are characteristic of latent infection but not the viral proteins that are characteristic of lytic infection. The detection of the EBV-transforming gene, LMP-1, in all the neoplastic cells suggests that its expression is essential for preinvasive epithelial proliferations associated with nasopharyngeal carcinoma.

Tumorigenicity of EBNA2-transfected cells

The Epstein-Barr virus nuclear antigen 2 (EBNA2) gene is thought to be important for transformation by Epstein-Barr virus (EBV), but the mechanism of this transformation is little understood. Here, to examine the transforming ability of EBNA2, we transfected a rat fibroblast cell line F2408 with a recombinant EBNA2 expression plasmid and examined cell morphology, colony formation in soft agar, and tumorigenicity in nude mice. The morphology of transfected clones was similar to those of untransfected cells, but two of seven clones grew in soft agar, and four clones of seven clones reproducibly formed tumors in nude mice. These four clones showed EBNA2 expression, but non-tumorigenic clones did not. These results indicate that the expression of EBNA2 is correlated with tumorigenicity.

Down-regulation of Epstein-Barr virus nuclear antigen 1 in Reed-Sternberg cells of Hodgkin's disease

AIMS

To demonstrate Epstein-Barr virus (EBV) encoded nuclear antigen 1 (EBNA-1) gene expression in EBV associated disorders using a new monoclonal antibody (1H4-1) on routinely processed tissues.

METHODS

The pressure cooker antigen retrieval method was used for the immunohistochemical demonstration of EBNA-1 gene expression in formalin fixed, EBV positive tissues from Hodgkin's disease, infectious mononucleosis, HIV associated non-Hodgkin's lymphomas, post-transplant lymphomas, and undifferentiated nasopharyngeal carcinoma (NPC). EBV encoded EBNA-2, latent membrane protein 1 (LMP-1) and BZLF-1 gene expression was also examined using commercially available monoclonal antibodies.

RESULTS

Of the 34 EBER in situ hybridisation positive cases of Hodgkin's disease examined, none expressed EBNA-1 in the Reed-Sternberg cells. These cells were nevertheless strongly LMP-1 positive in all cases. Strong EBNA-1 staining was seen in all cases of EBER positive HIV associated non-Hodgkin's lymphoma (five of five), nasopharyngeal carcinoma (five of five), infectious mononucleosis (three of three), and post-transplant lymphoma (one of one). These cases also expressed LMP-1, EBNA-2 and BZLF-1, but at differing levels.

CONCLUSION

The pressure cooker antigen retrieval procedure is a sensitive and reliable adjunct to immunohistochemistry, especially with antibodies which are otherwise ineffective on routinely processed tissues. The EBNA-1 gene is not expressed at detectable levels in the malignant cells of Hodgkin's disease, but is consistently expressed in other EBV associated disorders. This finding has important implications for the role of EBNA-1 in the biology of EBV.

The Epstein-Barr virus latent membrane protein 1 induces expression of the epidermal growth factor receptor

The Epstein-Barr virus (EBV)-encoded LMP1 protein is an important component of the process of transformation by EBV. LMP1 is essential for transformation of B lymphocytes, most likely because of its profound effects on cellular gene expression. Although LMP1 is expressed in the majority of nasopharyngeal carcinoma (NPC) tumors, the effect of LMP1 on cellular gene expression and its contribution to the development of malignancy in epithelial cells is largely unknown. In this study the effects of LMP1 on the expression and tyrosine kinase activity of the epidermal growth factor receptor (EGFR) were investigated in C33A human epithelial cells. Stable or transient expression of LMP1 in C33A cells increased expression of the EGFR at both the protein and mRNA levels. In contrast, expression of the EGFR was not induced by LMP1 in EBV-infected B lymphocytes. Stimulation of LMP1-expressing C33A cells with epidermal growth factor (EGF) caused rapid tyrosine phosphorylation of the EGFR (pp170) as well as several other proteins, including pp120, pp85, pp75, and pp55, indicating that the EGFR induced by LMP1 is functional. LMP1 also induced expression of the A20 gene in C33A epithelial cells. In C33A cells, LMP1 expression increased the proliferative response to EGF, as LMP1-expressing C33A cells continued to increase in number when plated in serum-free media supplemented with EGF, while the neo control cells exhibited very low levels of viability and did not proliferate. Immunoblot analysis of protein extracts from nude mouse-passaged NPC tumors also demonstrated that the EGFR is overexpressed in primary NPC tumors as well as those passaged in nude mice. This study suggests that the alteration in the growth patterns of C33A cells expressing LMP1 is a result of increased proliferative signals due to enhanced EGFR expression, as well as protection from cell death due to LMP1-induced A20 expression. The induction of EGFR and A20 by LMP1 may be an important component of EBV infection in epithelial cells and could contribute to the development of epithelial malignancies such as NPC.

The Epstein-Barr virus 3.5-kilobase latent membrane protein 1 mRNA initiates from a TATA-Less promoter within the first terminal repeat

The complete 5' sequence of the Epstein-Barr virus 3.5-kb latent membrane protein 1 (LMP1) mRNA, expressed in nasopharyngeal carcinoma, has been determined. The transcript initiates from heterogeneous start sites within the first terminal repeat (TR) of the viral genome. This region is TATA-less, consistent with heterogeneous starting, but contains multiple GC-rich elements which potentially interact with the Sp1 transcription factor. Expression of the 3.5-kb mRNA was consistently detected in nasopharyngeal carcinoma samples and in additional cell types, including a Burkitt's lymphoma. This is the first identification of an Epstein-Barr virus mRNA containing TR sequence and the first report of the ability of the TR to function as a transcriptional promoter.

Expression of LMP1 in epithelial cells leads to the activation of a select subset of NF-kappa B/Rel family proteins

This study demonstrates that the Epstein-Barr virus protein LMP1 activates a specific subset of NF-kappa B/Rel proteins in the C33 epithelial cell line. Western immunoblot analysis used to analyze the intracellular distribution and abundance of the proteins present in these complexes demonstrated that levels of the p50 and p52 proteins were significantly elevated in the nuclei of LMP1-expressing cells. The data also suggest that LMP1 facilitates the translocation of p50 to the nucleus and may affect the processing of the p100 and p105 precursor proteins or the stability of p52 and p50.

Evaluation of clonal immunoglobulin heavy chain rearrangements in Hodgkin's disease using the polymerase chain reaction (PCR)

We have correlated histologic type of Hodgkin's disease, degree of Hodgkin and Reed-Sternberg cell infiltration, percentage of Hodgkin and Reed-Sternberg cell positivity for latent membrane protein, immunophenotype of Hodgkin and Reed-Sternberg cells, and immunoglobulin heavy chain (IgH) gene rearrangements detected by polymerase chain reaction (PCR) in 56 unselected Hodgkin's disease cases. Two protocols were used for amplification of IgH gene using Fr2 or Fr3 V-region primers, in conjunction with nested primers directed to the JH region. PCR products were run on polyacrylamide gels. Immunohistochemical studies were performed on paraffin sections using monoclonal antibodies for CD20 and latent membrane protein, and polyclonal antibody to CD3. Using both primer combinations we detected a definitive clonal band in 23.2% of the Hodgkin's disease cases. Clonal IgH rearrangements were detected in 23.6% of nodular sclerosis type and in 28.5% of mixed cellularity type. Using a highly sensitive method such as PCR, more than 20% of unselected cases of Hodgkin's disease were found to contain B-cell clonal proliferations, but there was no correlation between histological and immunological parameters and molecular analysis results.

Immortalization of human primary B lymphocytes in vitro with DNA

Epstein-Barr virus (EBV) is a human DNA tumor virus that efficiently immortalizes human primary B lymphocytes in vitro. Although viral genes that are expressed in latently infected B lymphocytes have been shown to function in cellular growth control, their detailed genetic analysis has been cumbersome for two reasons. The viral genome is too large to permit genetic engineering and human primary B lymphocytes, the only targets for infection by EBV in vitro, are both intractable in culture and recalcitrant to DNA transfection. To overcome these obstacles, we have assembled all the essential genes of EBV on a single recombinant vector molecule in Escherichia coli. We show here that this mini-EBV plasmid can yield immortalized B cells upon transfer of its naked DNA into human primary B lymphocytes. Established cell lines carry recombinant vector DNA and cannot support virus production. Because this DNA can be easily manipulated in E. coli, mutant mini-EBVs as well as foreign genes can now be introduced and studied successfully in recipient B lymphocytes from any human donors. These mini-EBVs therefore are potentially useful for human gene therapy.

Epstein-Barr virus (EBV) in extranodal T-cell non-Hodgkin's lymphomas (T-NHL). Identification of nasal T-NHL as a distinct clinicopathological entity associated with EBV

T-cell Non-Hodgkin's lymphomas (T-NHL) can be defined as clonal malignant proliferations related phenotypically and functionally to normal T-cell populations of the lymphoid tissue. There is increasing evidence that T-NHL with similar morphology but originating from different sites differ in their clinical behaviour, immunophenotypic features, oncogene expression and relation with oncogenic viruses such as HTLV-I and EBV. Indeed, it has been shown that the prevalence of EBV in T-NHL is related to the site of origin. Thus, EBV was found in nearly all nasal T-NHL but only in a proportion of primary nodal, lung, gastrointestinal and Waldeyer's ring T-NHL while it was undetectable in most primary cutaneous T-NHL. Besides their constant association with EBV, nasal T-NHL display peculiar clinical, histological, immunophenotypic and genotypic features. They present clinically as lethal midline granuloma and histologically as pleomorphic malignant tumours variably associated with angiocentricity, angioinvasion and necrosis. Moreover, they frequently exhibit extensive loss of T-cell antigens, including CD3 and TCR alpha beta and gamma delta proteins, usually express the Natural Killer (NK)-related CD56 antigen and frequently show absence of clonal rearrangements of TCR beta, gamma and delta loci. Therefore, among T-NHL, nasal T-NHL can be regarded as a distinct clinicopathologic entity associated with EBV, which could be derived either from immature T-cells or from NK cells.

Characterization of 5'-upstream sequence of the latent membrane protein 1 (LMP-1) gene of an Epstein-Barr virus identified in nasopharyngeal carcinoma tissues

Sequence variations of the 5'-upstream region of latent membrane protein 1 (LMP-1) in two Epstein-Barr virus (EBV) strains have been reported before (Chen et al., 1992). To investigate the effect of these variations on gene expression, we constructed a series of deletion plasmids encompassing positions -950 to +20 of the LMP-1 promoter region and tested for the ability to drive chloramphenicol acetyltransferase (CAT) gene expression in C33A cells. Results showed that the promoter activities of constructs from NPC strain were 3-fold lower than the corresponding constructs from the B95-8 strain. In addition, the region between -54 and +20 contained the basic, constitutive promoter activity for both strains. Sequence analysis of this region indicated that an activating transcription factor (ATF) binding site, TGACGTAG, which is present in B95-8 strain was changed to TCTCGTAG in NPC strain. A chimeric plasmid study suggested that these sequence variations in the ATF binding site may contribute to the 3-fold increase of CAT activity observed for B95-8 strain. Furthermore, the activity of the promoter constructs was not activated by EBV-encoded nuclear antigen 2 (EBNA-2) in C33A cells. However, the promoter activities were upregulated in B-lymphocyte cells such as CG3 and CA46 cells. The biological significance of this difference in promoter activity of LMP-1 gene between two strains and the involvement of the cellular factors were discussed.

Detection of Epstein-Barr virus DNA in cerebrospinal fluid for diagnosis of AIDS-related central nervous system lymphoma

The diagnostic utility of Epstein-Barr virus (EBV) DNA detection in cerebrospinal fluid for the diagnosis of central nervous system lymphoma was evaluated with two different PCR assays to test a collection of cerebrospinal fluid samples from 24 AIDS patients with central nervous system disorders. A PCR assay amplifying a fragment from the BamHI-W region had the highest clinical and analytic sensitivity. The BamHI-W PCR assay detected EBV DNA in cerebrospinal fluid from 83% (5 of 6) of patients with pathologically proven primary central nervous system lymphoma and 7% (1 of 16) of controls with autopsy-proven nonlymphomatous central nervous system disorders. EBV DNA was also detected in one patient with autopsy-proven systemic lymphoma involving the central nervous system and one patient with probable primary central nervous system lymphoma. EBV DNA was detected consistently when central nervous system lymphoma involved meningeal surfaces. PCR for EBV in cerebrospinal fluid appears to be useful for diagnosis of AIDS-related central nervous system lymphoma, but additional studies are required to better define the sensitivity of the assay and to understand the significance of a positive test in the absence of lymphoma.

Induction of CD44 expression by the Epstein-Barr virus latent membrane protein LMP1 is associated with lymphoma dissemination

Epstein-Barr Virus (EBV) is implicated in the pathogenesis of endemic Burkitt's lymphoma (BL), B-cell lymphomas occurring under immunosuppression, nasopharyngeal carcinoma and Hodgkin's disease. Two distinct patterns of latent EBV gene expression occur in EBV-associated lymphomas. BLs typically display expression of the nuclear antigen EBNAI only, whereas EBV-associated, non-Burkitt B-cell lymphomas express at least 9 latent viral genes (6 EBNAs and 3 latent membrane proteins), reminiscent of in vitro EBV-immortalized lymphoblastoid cell lines (LCL). BLs are characterized by local, extra-nodal growth, whereas EBV-associated B-cell lymphomas often disseminate to peripheral lymphoid tissue. We show here that BL cells forming local tumors after xenotransplantation into SCID mice disseminate to lymphoid tissue following introduction of the latent membrane protein I (LMP 1) gene. Introduction of LMP 1 into BL cells induced expression of CD44 on the cell surface, a molecule implicated in enhanced lymphoid tumor growth and dissemination. Introduction of CD44 into LMP 1-/CD44-BL cells was observed to confer the disseminated tumor growth pattern associated with LMP 1 expression. Taken together our results show that expression of LMP 1 may regulate expression of CD44 and play an important role in the behavior of EBV-based lymphomas.

Stimulation of NF-kappa B-mediated transcription by mutant derivatives of the latent membrane protein of Epstein-Barr virus

The latent membrane protein (LMP) of Epstein-Barr virus contributes to the immortalizing activity of the virus in primary, human B lymphocytes, but its mechanism of function is unknown. LMP is expressed at the plasma membrane and may act by influencing the signalling pathways of infected cells. LMP increases transcription of reporter plasmids that are responsive to members of the NF-kappa B/Rel family of transcription factors (M.-L. Hammarskjold and M. C. Simurda, J. Virol. 66:6496-6501, 1992, and A. Krikos, C. D. Laherty, and V. M. Dixit, J. Biol. Chem. 267:17971-17976, 1992). We measured the stimulation of the activity of a reporter plasmid by LMP in Jurkat and 293 cells in transfection experiments. Expression of LMP stimulated plasmids that contained kappa B enhancer elements but not plasmids that lacked the elements. In 293 cells, expression of the NF-kappa B inhibitor, I kappa B-alpha, reduced the stimulatory activity of LMP. We used deletional analysis to map the domains of LMP that are required for its activity in 293 cells. Wild-type LMP stimulated NF-kappa B by a factor of 20 to 30, while mutant derivatives of LMP that lack oncogenic activity stimulated NF-kappa B by a factor of 3. The multiple membrane-spanning segments together with the carboxy-terminal 55 amino acid residues of LMP were required for its maximal stimulatory function. Residues within its cytoplasmic amino terminus were not required for LMP's stimulation of NF-kappa B. We tested also for stimulation of NF-kappa B activity in cell lines known to support phenotypic changes mediated by expression of LMP. LMP stimulated little NF-kappa B activity in HEp2 cells and no detectable NF-kappa B activity in BALB/3T3 cells. The LMP stimulation of NF-kappa B factors that occurs in some cell lines provides a useful and biochemically tractable assay for determining the function of LMP.

[Hodgkin disease: recent histological and biological data]

Recent histologic, immunophenotypic and genotypic data have restricted the concept of Hodgkin's disease (HD) to the type 2 and 3 of Rye classification. This classification should be revised since the lymphocyte-predominance type has been shown to include the nodular paragranuloma which is a B-cell lymphoma, cases which have been confused with T-cell-rich large B-cell non Hodgkin's lymphoma (NHL) and cases which should be reclassified among the mixed cellularity group. Further more, most types 4 are now regarded as anaplastic large cell NHL. Immunophenotypic and genotypic studies support the heterogeneous nature of Reed-Sternberg and Hodgkin's (RSH) cells since they could be derived from B, T or null lymphocytes. In 50% of cases, RSH cells harbour the Epstein-Barr virus genome and express a viral protein, the latent membrane protein, which could play an oncogenic role in HD. Finally, RSH cells produce a wide range of cytokines that could stimulate their proliferation and explain the marked cellular reaction that is observed in HD.

Epstein-Barr virus nuclear protein 3C modulates transcription through interaction with the sequence-specific DNA-binding protein J kappa

The Epstein-Barr virus (EBV) nuclear protein 3C (EBNA 3C) is essential for EBV-mediated transformation of primary B lymphocytes, is turned on by EBNA 2, and regulates transcription of some of the viral and cellular genes which are regulated by EBNA 2. EBNA 2 is targeted to response elements by binding to the DNA sequence-specific, transcriptional repressor protein J kappa. We now show that EBNA 3C also binds to J kappa. EBNA 3C causes J kappa to not bind DNA or EBNA 2. J kappa DNA binding activity in EBV-transformed lymphoblastoid cells is consequently reduced. More than 10% of the EBNA 3C coimmunoprecipitated with J kappa from extracts of non-EBV-infected B lymphoblasts that had been stably converted to EBNA 3C expression. EBNA 3C in nuclear extracts from these cells (or in vitro-translated EBNA 3C) prevented J kappa from interacting with a high-affinity DNA binding site. Under conditions of transient overexpression in B lymphoblasts, EBNA 2 and EBNA 3C associated with J kappa and less EBNA 2 associated with J kappa when EBNA 3C was coexpressed in the same cell. EBNA 3C had no effect on the activity of a -512/+40 LMP1 promoter-CAT reporter construct that has two upstream J kappa sites, but it did inhibit EBNA 2 transactivation of this promoter. These data are compatible with a role for EBNA 3C as a "feedback" down modulator of EBNA 2-mediated transactivation. EBNA 3C could, in theory, also activate transcription by inhibiting the interaction of the J kappa repressor with its cognate DNA. The interaction of two viral transcriptional regulators with the same cell protein may reflect an unusually high level of complexity or stringency in target gene regulation.

Immunohistochemical demonstration of different latent membrane protein-1 epitopes of Epstein-Barr virus in lymphoproliferative diseases

AIM

To compare the immunoreactivity of monoclonal antibodies S12 and CS1-4, which recognise different epitopes of the Epstein-Barr virus (EBV) latent membrane protein-1 (LMP-1), in EBV associated benign and malignant lymphoproliferative disorders and control tissues processed using different methods.

RESULTS

Both monoclonal antibodies gave comparable results on frozen tissue sections and formalin fixed, paraffin wax embedded samples from cases with Hodgkin's disease and infectious mononucleosis. In all cases S12 stained more cells than CS1-4. For EBV associated B and T non-Hodgkin's lymphomas, frozen tissue sections yielded better LMP-1 staining results than formalin fixed material. Again, in all these cases S12 stained more cells and gave stronger results than CS1-4. For EBV negative tissues, both monoclonal antibodies showed cross-reactivity with melanocytic-like cells in the basal cell layer of the skin, synaptophysin-like staining in layers three and four of the cortex of the brain, and myelin-like staining in peripheral nerves and peripheral ganglion cells. Staining with S12 was always much stronger. Moreover, in contrast to CS1-4, S12 stained pancreatic islands in formalin fixed material but not in frozen tissue sections and sporadically stained solitary epithelial cells in the large bowel especially in formalin fixed tissue sections. CS1-4 also cross-reacted with myoepithelial cells around hair follicles and other adnexa of the skin.

CONCLUSION

The results indicate that for optimal detection of LMP-1, S12 yields better results than CS1-4 and that tissue processing is very important especially when B and T non-Hodgkin's lymphomas are examined.

Changes in tonsils and adenoids in children with posttransplant lymphoproliferative disorder: report of three cases with early involvement of Waldeyer's ring

Posttransplant lymphoproliferative disorder (PTLD) is an infrequent complication of transplantation in children, and this report emphasizes the value of tonsil and adenoid biopsy in the early management of this potentially life threatening condition. In all three cases biopsy specimens of tonsils and adenoids were diagnostic of polymorphic diffuse B-cell hyperplasia (PBCH). Immunophenotyping showed no immunoglobulin (Ig) light chain restriction, although immunoglobulin heavy chain (IgH) gene rearrangement was monoclonal in two cases. Despite an absence of serological evidence for acute Epstein-Barr virus (EBV) infection, EBV was detected in all cases by semiquantitative polymerase chain reaction (PCR) for EBV DNA, by in situ hybridization for EBV mRNA (EBER), and by immunoperoxidase for EBV latent membrane protein (LMP). All three patients were treated with reduced immunosuppression and acyclovir and are well (19, 28, and 28 months' follow-up) with no recurrence. Children without previous EBV exposure may develop PTLD localized to the tonsils/adenoids, and biopsy specimens of these tissues may permit early diagnosis and clinical intervention. Despite monoclonal gene rearrangement in two cases, overall features were not indicative of malignancy. Strong association with EBV is helpful in confirming the diagnosis of PTLD and is consistent with initial presentation in the tonsils/adenoids.

Contribution of Epstein-Barr virus to development of malignant lymphoma of the thyroid

Epstein-Barr virus (EBV)-related mRNA, their products and apoptosis were investigated in 32 cases of malignant lymphoma of the thyroid (MLT) and 30 cases of Hashimoto's thyroiditis (HT) by in situ hybridization, immunohistochemistry and nick end labeling method on routinely processed tissue sections. In MLT, EBV-encoded small RNA (EBER) were detected in three cases, consisting of a follicular, predominantly large cell type (FL), a diffuse, large cell type (DL) and a large cell, immunoblastic type (IBL). In EBER-positive cases, IBL that was positive for T cell marker, exhibited neither BamHl H Left Frame 1 (BHLF1) transcript, EBV-encoded latent membrane protein (LMP) nor BamHl Z Left Frame 1 (BZLF1) gene product (ZEBRA), whereas both BHLF1 and ZEBRA were found in a small portion of the tumor cells in the FL and DL that expressed B cell marker and LMP. Apoptotic cells were observed in only a few lymphocytes in HT, and in a few non-neoplastic lymphocytes and various numbers of lymphoma cells in MLT. The apoptotic cell ratio of MLT tended to be higher in lower grade lymphomas. These results suggest that EBV may participate in the malignant transformation from HT to MLT.

LMP-1 activates NF-kappa B by targeting the inhibitory molecule I kappa B alpha

LMP-1, an Epstein-Barr virus membrane protein expressed during latent infection, has oncogenic properties, as judged from its ability to transform B lymphocytes and rodent fibroblasts. LMP-1 induces the expression of bcl2, an oncogene which protects cells from apoptosis, as well as of genes encoding other proteins involved in cell regulation and growth control. The mechanisms by which LMP-1 upregulates these proteins is unknown, but it is plausible that LMP-1 modifies signal transduction pathways that result in the activation of one or more transcription factors that ultimately regulate transcription of oncogenic genes. NF-kappa B, a transcription factor controlling the expression of genes involved in cell activation and growth control, has been shown to be activated by LMP-1. The mechanism(s) regulating this activation remains unknown. Our data indicate that increased NF-kappa B DNA binding and functional activity are present in B-lymphoid cells stably or transiently expressing LMP-1. I kappa B alpha is selectively modified in LMP-1-expressing B cells. A phosphorylated form of I kappa B alpha and increased protein turnover-degradation correlate with increased NF-kappa B nuclear translocation. This results in increased transcription of NF-kappa B-dependent-genes, including those encoding p105 and I kappa B alpha (MAD3). These results indicate that LMP-1 activates NF-kappa B in B-cell lines by targeting I kappa B alpha. Identification of the pathways activated by LMP-1 to result in posttranslational modifications of I kappa B alpha will aid in determining the role of this virus-host cell protein interaction in Epstein-Barr virus-mediated oncogenesis.

Epstein-Barr virus as an agent of haematological disease

Epstein-Barr virus (EBV) encodes genes that permit its persistence in human B lymphocytes and genes that ensure its replication in epithelial cells. Immune restraints on the virus are usually so effective that most EBV infections are limited to a minute fraction of B lymphocytes and of epithelial cells. As a result, most EBV infections are never symptomatic. Occasionally, the virus causes disease, often with the cooperation of the immune system or other less characterized cofactors. Infectious mononucleosis, a generally self-limited lymphoproliferative illness common in adolescents and young adults, is due to primary EBV infection and to the brisk cellular immune response it elicits. Lymphoproliferative disorders of EBV-infected B cells arise almost exclusively when cellular immunity is grossly compromised. EBV-positive Burkitt's lymphoma contain a translocated and deregulated c-myc oncogene and EBV-positive non-Hodgkin's lymphomas are characterized by the presence of Reed-Sternberg's and Hodgkin's cells, features that have not been directly linked to EBV. Many recent observations, however, including evidence that virus infection precedes malignant transformation and is often associated with a characteristic pattern of viral gene expression, provide continued interest in the relationship between the virus and these haematological malignancies.

Epstein-Barr virus-associated gastric adenocarcinoma in Taiwan

Fifty-five gastric carcinoma tumors from Chinese patients in Taiwan, including 40 tubular type (one lymphoepthelioma-like carcinoma subtype), eight signet ring cell type, one papillary type, and six mucinous type gastric carcinomas, were investigated for the presence of Epstein-Barr virus (EBV) transcripts by in situ hybridization using fluorescein-conjugated EBV oligonucleotides for EBERs (Epstein-Barr virus early RNAs) expression and the polymerase chain reaction for viral DNA. Epstein-Barr virus was detected in six of 55 lesions (11%), a significantly lower proportion than has been observed in a North American series. Epstein-Barr virus involvement was more common among male patients. Epstein-Barr virus DNA and its EBERs were specifically present within gastric carcinoma and adjacent dysplastic cells but were absent in surrounding lymphocytes and normal gastric mucosa. Epstein-Barr virus DNA and EBERs were found in one sample of lymphoepithelioma-like carcinoma (LELC) and five specimens of typical gastric adenocarcinoma. Among the EBV-positive gastric adenocarcinomas, four were tubular type of varied differentiation and one was signet ring cell type. Furthermore, we evaluated the expression of the latent membrane protein (LMP) with monoclonal antibodies. We found that LMP was expressed in two EBV-positive samples. In addition, the presence of the EBV receptor was studied by probing samples with CD21 monoclonal antibody. Epstein-Barr virus receptor was not detected in any sample. Southern blot analysis indicated single clonal proliferation of tumor cells. These findings confirm and extend the results of Shibata et al. They also indicate that EBV infection might be related to oncogenesis not only in rare gastric cancers that resemble nasopharyngeal lymphoepithelioma but also in typical gastric adenocarcinoma.

The Epstein-Barr virus transforming protein LMP1 engages signaling proteins for the tumor necrosis factor receptor family

The cytoplasmic C-terminus of Epstein-Barr virus (EBV) latent infection membrane protein 1 (LMP1) is essential for B lymphocyte growth transformation and is now shown to interact with a novel human protein (LMP1-associated protein 1 [LAP1]). LAP1 is homologous to a murine protein, tumor necrosis factor receptor-associated factor 2 (TRAF2), implicated in growth signaling from the p80 TNFR. A second novel protein (EBI6), induced by EBV infection, is the human homolog of a second murine TNFR-associated protein (TRAF1). LMP1 expression causes LAP1 and EBI6 to localize to LMP1 clusters in lymphoblast plasma membranes, and LMP1 coimmunoprecipitates with these proteins. LAP1 binds to the p80 TNFR, CD40, and the lymphotoxin-beta receptor, while EBI6 associates with the p80 TNFR. The interaction of LMP1 with these TNFR family-associated proteins is further evidence for their role in signaling and links LMP1-mediated transformation to signal transduction from the TNFR family.

The Epstein-Barr virus LMP1 cytoplasmic carboxy terminus is essential for B-lymphocyte transformation; fibroblast cocultivation complements a critical function within the terminal 155 residues

Recombinant Epstein-Barr viruses (EBVs) were made with mutated latent membrane protein 1 (LMP1) genes that express only the LMP1 amino-terminal cytoplasmic and six transmembrane domains (MS187) or these domains and the first 44 amino acids of the 200-residue LMP1 carboxy-terminal domain (MS231). After infection of primary B lymphocytes with virus stocks having small numbers of recombinant virus and large numbers of P3HR-1 EBV which is transformation defective but wild type (WT) for LMP1, all lymphoblastoid cell lines (LCLs) that had MS187 or MS231 LMP1 also had WT LMP1 provided by the coinfecting P3HR-1 EBV. Lytic virus infection was induced in these coinfected LCLs, and primary B lymphocytes were infected. In over 200 second-generation LCLs, MS187 LMP1 was never present without WT LMP1. Screening of over 600 LCLs infected with virus from MS231 recombinant virus-infected LCLs identified two LCLs which were infected with an MS231 recombinant without WT LMP1. The MS231 recombinant virus could growth transform primary B lymphocytes when cells were grown on fibroblast feeders. Even after 6 months on fibroblast feeder layers, cells transformed by the MS231 recombinant virus died when transferred to medium without fibroblast feeder cells. These data indicate that the LMP1 carboxy terminus is essential for WT growth-transforming activity. The first 44 amino acids of the carboxy-terminal cytoplasmic domain probably include an essential effector of cell growth transformation, while a deletion of the rest of LMP1 can be complemented by growth on fibroblast feeder layers. LMP1 residues 232 to 386 therefore provide a growth factor-like effect for the transformation of B lymphocytes. This effect may be indicative of the broader role of LMP1 in cell growth transformation.

Characterization of the CD48 gene demonstrates a positive element that is specific to Epstein-Barr virus-immortalized B-cell lines and contains an essential NF-kappa B site

Epstein-Barr virus (EBV) infection of mature, resting B cells drives them to become lymphoblasts expressing high levels of cell surface molecules, such as CD48, characteristically expressed on normal activated B cells. Here, we report on the identification of an enhancer element in the CD48 gene which reproducibly confers strong transcriptional activity only in EBV-positive B-lymphoblastoid cell lines. The element is not activated upon infection of established EBV-negative B-cell lines, indicating that EBV fails to drive these cells to a fully lymphoblastoid phenotype. An NF-kappa B binding site is an essential component of the element but alone is not sufficient to account for the activity or the specificity of the element. We have detected a specific nuclear protein complex that binds to the element and show that NF-kappa B1 (p50) is a part of this complex. The EBV-encoded latent membrane protein 1 is capable of transactivating the isolated CD48 NF-kappa B site but not the intact element, suggesting that the latent membrane protein 1-driven activation of NF-kappa B/Rel must interact with other regulatory pathways to control expression of cellular genes as EBV drives resting B cells into the cell cycle.