A complete set of overlapping cosmid clones of M-ABA virus derived from nasopharyngeal carcinoma and its similarity to other Epstein-Barr virus isolates

Is the Epstein-Barr Virus Involved in Hodgkin's Disease?

EBV genomes, in clonal episomal form, were detected in 7 out of 17 cases of Hodgkin's disease (HD) and in a single case of non-Hodgkin's lymphoma which occurred in a patient after therapeutic treatment for HD. The experimental data presented imply that a clonal cell population, harboring the EBV genome, must be present in EBV-positive HD. In light of this finding we are attempting to reconsider the abundant literature on this lymphoproliferative disorder, and suggest a reevaluation of the possibility that EBV could be etiologically involved in HD.

Shedding dynamics of Epstein-Barr virus: A type 1 carcinogen

Epstein Barr virus (EBV) is one of the ubiquitous viral carcinogens found in humans and successfully infects more than 90% of the world population. The spectrum of EBV-related pathology ranges from asymptomatic primary infection to grave B- and T-cell malignancies. EBV triggers lymphoproliferative disorders after allogeneic stem cell transplantation, which contributes to higher mortality rates. Although the transmission of EBV primarily occurs from an infected host to a naive host through viral shedding from the oropharynx, increasing evidence points to considerable amount of shedding in other anatomical sites such as cervix, anal mucosa, breast milk and respiratory tract. It is impossible to eradicate the prevalence of EBV-related malignancies and other pathologies without preventing viral shedding. However, a detail analysis of the multifaceted nature of EBV shedding is not available in the literature. Thus, this review focuses on elucidating the key elements of the shedding dynamics of this carcinogenic virus.

Detection of EBV, HBV, HCV, HIV-1, HTLV-I and -II, and SMRV in human and other primate cell lines

The high prevalence of contaminated cell cultures suggests that viral contaminations might be distributed among cultures. We investigated more than 460 primate cell lines for Epstein-Barr (EBV), hepatitis B (HBV), hepatitis C (HCV), human immunodeficiency virus type 1 (HIV-1), human T-cell leukemia/lymphoma virus I and II (HTLV-I/-II), and squirrel monkey retrovirus (SMRV) infections for risk assessment. None of the cell lines were infected with HCV, HIV-1, or HTLV-I/-II. However, one cell line displayed reverse transcriptase activity. Thirty-nine cell lines harbored EBV DNA sequences. Studies on the lytic phase of EBV revealed that five cell lines produce EBV particles and six further cell lines produced EBV upon stimulation. One cell line contained an integrated HBV genome fragment but showed no virus production. Six cell lines were SMRV-infected. Newly established cell lines should be tested for EBV infections to detect B-lymphoblastoid cell lines (B-LCL). B-LCLs established with EBV from cell line B95-8 should be tested for SMRV infections.

The latent origin of replication of Epstein-Barr virus directs viral genomes to active regions of the nucleus

The Epstein-Barr virus efficiently infects human B cells. The EBV genome is maintained extrachromosomally and replicates synchronously with the host's chromosomes. The latent origin of replication (oriP) guarantees plasmid stability by mediating two basic functions: replication and segregation of the viral genome. While the segregation process of EBV genomes is well understood, little is known about its chromatin association and nuclear distribution during interphase. Here, we analyzed the nuclear localization of EBV genomes and the role of functional oriP domains FR and DS for basic functions such as the transformation of primary cells, their role in targeting EBV genomes to distinct nuclear regions, and their association with epigenetic domains. Fluorescence in situ hybridization visualized the localization of extrachromosomal EBV genomes in the regions adjacent to chromatin-dense territories called the perichromatin. Further, immunofluorescence experiments demonstrated a preference of the viral genome for histone 3 lysine 4-trimethylated (H3K4me3) and histone 3 lysine 9-acetylated (H3K9ac) nuclear regions. To determine the role of FR and DS for establishment and subnuclear localization of EBV genomes, we transformed primary human B lymphocytes with recombinant mini-EBV genomes containing different oriP mutants. The loss of DS results in a slightly increased association in H3K27me3 domains. This study demonstrates that EBV genomes or oriP-based extrachromosomal vector systems are integrated into the higher order nuclear organization. We found that viral genomes are not randomly distributed in the nucleus. FR but not DS is crucial for the localization of EBV in perichromatic regions that are enriched for H3K4me3 and H3K9ac, which are hallmarks of transcriptionally active regions.

Features distinguishing Epstein-Barr virus infections of epithelial cells and B cells: viral genome expression, genome maintenance, and genome amplification

Epstein-Barr virus (EBV) is associated with malignant diseases of lymphoid and epithelial cell origin. The tropism of EBV is due to B-cell-restricted expression of CD21, the major receptor molecule for the virus. However, efficient infection of CD21- epithelial cells can be achieved via transfer from EBV-coated B cells. We compare and contrast here the early events following in vitro infection of primary B cells and epithelial cells. Using sensitive, quantitative reverse transcription-PCR assays for several latent and lytic transcripts and two-color immunofluorescence staining to analyze expression at the single cell level, we confirmed and extended previous reports indicating that the two cell types support different patterns of transcription. Furthermore, whereas infection of B cells with one or two copies of EBV resulted in rapid amplification of the viral genome to >20 copies per cell, such amplification was not normally observed after infection of primary epithelial cells or undifferentiated epithelial lines. In epithelial cells, EBNA1 expression was detected in only ca. 40% of EBER+ cells, and the EBV genome was subsequently lost during prolonged culture. One exception was that infection of AGS, a gastric carcinoma line, resulted in maintenance of EBNA1 expression and amplification of the EBV episome. In contrast to B cells, where amplification of the EBV episome occurred even with a replication-defective BZLF1-knockout virus, amplification in AGS cells was dependent upon early lytic cycle gene expression. These data highlight the influence of the host cell on the outcome of EBV infection with regard to genome expression, amplification, and maintenance.

Three restricted forms of Epstein-Barr virus latency counteracting apoptosis in c-myc-expressing Burkitt lymphoma cells

Epstein-Barr virus (EBV), a human herpesvirus, transforms B cell growth in vitro through expressing six virus-coded Epstein-Barr nuclear antigens (EBNAs) and two latent membrane proteins (LMPs). In many EBV-associated tumors, however, viral antigen expression is more restricted, and the aetiological role of the virus is unclear. For example, endemic Burkitt lymphoma (BL) classically presents as a monoclonal, c-myc-translocation-positive tumor in which every cell carries EBV as an EBNA1-only (Latency I) infection; such homogeneity among EBV-positive cells, and the lack of EBV-negative comparators, hampers attempts to understand EBV's role in BL pathogenesis. Here, we describe an endemic BL that was unusually heterogeneous at the single-cell level and, in early passage culture, yielded a range of cellular clones, all with the same c-myc translocation but differing in EBV status. Rare EBV-negative cells were isolated alongside EBV-positive cells displaying one of three forms of restricted latency: (i) conventional Latency I expressing EBNA1 only from a WT virus genome, (ii) Wp-restricted latency expressing EBNAs 1, 3A, 3B, 3C, and -LP only from an EBNA2-deleted genome, and (iii) a previously undescribed EBNA2(+)/LMP1(-) latency in which all six EBNAs are expressed again in the absence of the LMPs. Interclonal comparisons showed that each form of EBV infection was associated with a specific degree of protection from apoptosis. Our work suggests that EBV acts as an antiapoptotic rather than a growth-promoting agent in BL by selecting among three transcriptional programs, all of which, unlike the full virus growth-transforming program, remain compatible with high c-myc expression.

Visualization of episomal and integrated Epstein-Barr virus DNA by fiber fluorescencein situ hybridization

For many Epstein-Barr virus (EBV)-associated malignancies, it is still a matter of controversy whether infected cells harbor episomal or chromosomally integrated EBV genomes or both. It is well established that the expression of EBV genes per se carries oncogenic potential, but the discrimination between episomal and integrated forms is of great relevance because integration events can contribute to the oncogenic properties of EBV, whereas host cells that exclusively harbor viral episomes may not carry the risks mediated by chromosomal integration. This notion prompted us to establish a reliable technique that not only allows to unequivocally discriminate episomal from integrated EBV DNA, but also provides detailed insights into the genomic organization of the virus. Here, we show that dynamic molecular combing of host cell DNA combined with fluorescence in situ hybridization (FISH) using EBV-specific DNA probes facilitate unambiguous discrimination of episomal from integrated viral DNA. Furthermore, the detection of highly elongated internal repeat 1 (IR1) sequences provides evidence that this method permits detection of major genomic alterations within the EBV genome. Thus, fiber FISH may also provide valuable insights into the genomic organization of viral genomes other than EBV.

Epstein-Barr virus-induced B-cell transformation: quantitating events from virus binding to cell outgrowth

Epstein-Barr virus (EBV) infection and growth activation of human B cells is central to virus biology and disease pathogenesis, but is poorly understood in quantitative terms. Here, using virus at defined m.o.i., the different stages of this process at the single-cell level are followed in vitro. Virus binding to the B-cell surface, assayed by quantitative PCR, is highly efficient, particularly at the low m.o.i. values that most likely reflect physiologic events in vivo. However, only 10-15 % of bound virus genomes reach the cell nucleus, as visualized by sensitive fluorescence in situ hybridization (FISH) assay; viral genomes acquired per cell nucleus range from 1 to >10, depending on the m.o.i. Thereafter, despite differences in initial genome load, almost all nuclear genome-positive cells then go on to express the virus-encoded nuclear antigen EBNA2, upregulate the cell activation antigen CD23 and transit the cell cycle. EBNA2-positive cells in the first cycle post-infection then grow out to lymphoblastoid cell lines (LCLs) just as efficiently as do cells limiting-diluted from already established LCLs. This study therefore identifies EBV genome delivery to the nucleus as a key rate-limiting step in B-cell transformation, and highlights the remarkable efficiency with which a single virus genome, having reached the nucleus, then drives the transformation programme.

Epstein-Barr virus encoded BALF1 gene is transcribed in Burkitt's lymphoma cell lines and in nasopharyngeal carcinoma's biopsies

BACKGROUND

The Epstein-Barr virus (EBV) encodes two anti-apoptotic cellular Bcl2 homologs, BALF1 and BHRF1. BHRF1 has an anti-apoptotic activity but is rarely expressed in nasopharyngeal carcinoma (NPC). However, BALF1 is not yet well characterized.

OBJECTIVES

The objective of the study was to characterize BALF1 gene. First, the search of its transcriptional expression in EBV-positive B cell lines, EBV-positive Burkitt's lymphoma's cell lines and nasopharyngeal carcinoma's biopsies. Second, the examination of its anti-apoptotic activity in serum dependent assays.

STUDY DESIGN

We first analysed the transcriptional expression of BALF1 by reverse transcriptase DNA polymerase chain reaction (RT-PCR) method. For the analysis of its anti-apoptotic activity, we transfected NIH3T3 cells with pBABE-BALF1 expression plasmid and studied serum dependence of these transfectants.

RESULTS

BALF1 expression was detected in the latent stage and increased more significantly during the lytic phase in IgG-treated AKATA and TPA-SB-treated P3HR1-TK negative cell lines. As its expression was not affected by the inhibitor of viral DNA synthesis, this gene does not belong to late gene family. When analysed its transcription in Burkitt's lymphoma (BL)-derived cell lines and NPC biopsies, all BL-derived cell lines and more than 80% of NPC biopsies transcribed this gene. The study of serum dependence of BALF1-transfected NIH3T3 cells showed: with 10% of serum, BALF1 transfectants grew significantly more higher cell density than vector alone transfected NIH3T3 cell lines and with 1% of serum, BALF1 transfectants were capable of growing, but with about 40% reduced rate in comparison with those with 10% serum, while vector alone transfected NIH3T3 cells could not almost grow.

CONCLUSION

BALF1 gene was transcribed in EBV-associated tumor cells. BALF1 could render cells to serum independent. These results suggest that BALF1 gene could play its role in EBV oncogenesis.

The reading frame BPLF1 of Epstein-Barr virus: a homologue of herpes simplex virus protein VP16

The open reading frame BPLF1 of Epstein-Barr virus (EBV) shows homology to the Herpes simplex virus 1 (HSV1) protein VP16. This protein is a structural tegument component playing a pivotal role for HSV replication as trans-activator of viral immediate-early genes. An EBV gene with a comparable function has not been described so far. However, computer analysis indicated that BPLF1 may be a tegument protein homologous to VP16. This is the first report on the characterisation of the BPLF1 gene, its transcription, and expression of its gene product in vitro and in vivo. Using RT-PCR and Northern blot assays we demonstrated that the BPLF1 gene belongs to the class of late lytic cycle genes of EBV. Besides a full length transcript of 9.5 kb also a polyadenylated transcript of approximately 3 kb is synthesised. However, no consensus splice sites could be identified. Northern blot experiments using partially overlapping probes and sequencing of a BPLF1-specific cDNA revealed 1,550 nucleotides of the BPLF1 transcript, collinear in sequence with the viral genome from position 64547 to 66097. A recombinant Western blot assay detected BPLF1-specific antibodies in seropositive individuals, in particular in cases with elevated viral replication like infectious mononucleosis, chronic active infection, and nasopharyngeal carcinoma. This demonstrated expression of the BPLF1 protein in vivo. Thus, experimental data and computer analysis strongly support the hypothesis of BPLF1 being a tegument protein of the EBV homologous to VP16 of HSV1 and ORF22 of Varicella zoster virus.

Lytic cycle gene regulation of Epstein-Barr virus

Episomal reporter plasmids containing the Epstein-Barr virus (EBV) oriP sequence stably transfected into Akata Burkitt's lymphoma cells were used to analyze EBV lytic cycle gene regulation. First, we found that the Zp promoter of EBV, but not the Rp promoter, can be activated in the absence of protein synthesis in these oriP plasmids, casting doubt on the immediate early status of Rp. An additional level of regulation of Zp was implied by analysis of a mutation of the ZV element. Second, our analysis of late lytic cycle promoters revealed that the correct relative timing, dependence on ori lyt in cis, and sensitivity to inhibitors of DNA replication were reconstituted on the oriP plasmids. Late promoter luciferase activity from oriP plasmids also incorporating replication-competent ori lyt was phosphonoacetic acid sensitive, a hallmark of EBV late genes. A minimal ori lyt, which only replicates weakly, was sufficient to confer late timing of expression specifically on late promoters. Finally, deletion analysis of EBV late promoter sequences upstream of the transcription start site confirmed that sequences between -49 and +30 are sufficient for late gene expression, which is dependent on ori lyt in cis. However, the TATT version of the TATA box found in many late genes was not essential for late expression.

BAMHI DNA fragment H-polymorphism of Epstein-Barr virus is associated with the mutations present in an 89 BP sequence localized in EBNA2 gene

To characterize the genotypes of Epstein-Barr virus (EBV) isolate present in North Africa, viruses were isolated from B-lymphoblastoid cell lines established from the saliva of both Algerian Nasopharyngeal Carcinoma (NPC) patients and EBV-positive normal individuals, Algerian Burkitt's lymphoma cell lines, and NPC biopsies. By nucleotide sequence analysis, we showed that there were two specific missense mutations in an 89 bp region of EBNA2 gene at position 49390-49479 of the EBV genome: a mutation at 49449 (C-->A) and another mutation at 49444 (T-->C), changing their amino acid sequence. The first mutation was found in all B cell lines established from the saliva and 50% of BL cell lines, as well as the W91 cell line, while the second mutation was found in EBV isolates from NPC biopsies, BL cell lines and the M-ABA isolate. A PCR-RFLP analysis on the BamHI DNA fragment H showed that the Hl-H2-polymorphism was specifically associated with M-ABA-like mutation, while H-polymorphism was linked with W91-like mutation. The latter was not identified in NPC biopsies, but was found rather in saliva from NPC patients, normal individuals and BL cell lines. The M-ABA-like mutation, on the other hand, was found in 100% of NPC biopsies and some BL cell lines. This suggests that EBV with H1-H2-polymorphism is tightly implicated in NPC development in North Africa rather than EBV with H-polymorphism.

Tumor outgrowth in peripheral blood mononuclear cell-injected SCID mice is not associated with early Epstein-Barr virus reactivation

Epstein-Barr virus (EBV)-positive B-cell lymphoproliferative disease develops in severe combined immunodeficient (SCID) mice inoculated with peripheral blood mononuclear cells (PBMC) from EBV(+) individuals (SCID/hu mice). In this study, we investigated the contribution of EBV reactivation and de novo infection of B lymphocytes to tumor outgrowth in SCID/hu mice. Evaluation of BZLF-1, an early EBV activation transcript, in cells recovered from the mouse peritoneal cavity within 16 days following PBMC transfer did not reveal EBV reactivation, while BZLF-1 expression was only detected in tumor masses or in vitro established lymphoblastoid cell lines. To confirm these data by a different strategy, we coinjected PBMC from seropositive donors with purified B cells from seronegative donors of different sex. Fluorescence in situ hydridization analysis of the resulting tumor masses disclosed that the overwhelming majority of lymphoma cells originated from the seropositive donor, implying that no substantial in vivo production and transmission of virus had occurred. Further, treatment of SCID/hu mice with ganciclovir did not prevent lymphoma development. Our results suggest that in the SCID/hu mouse, early EBV replication and secondary infection of bystander B cells does not occur, and that the direct outgrowth of the transformed B lymphocytes present within the PBMC inoculum is the predominant mechanism, which leads to lymphoma generation in this experimental model.

MedB-1, a human tumor cell line derived from a primary mediastinal large B-cell lymphoma

Primary mediastinal B-cell lymphoma is a locally highly aggressive but poorly disseminating tumor composed of medium sized or large cells most probably of thymic medullary origin. It has a mature B-cell phenotype, typically lacks immunoglobulin expression and has variable defects in expression of HLA-molecules. We present here a cell line, MedB-1, derived from such a tumor. As is frequently found in mediastinal B-cell lymphomas in situ, MedB-1 is CD10(-), CD19(+), CD21(-), CD22(+), CD23(+), CD25(-), CD37(+), CD38(-), CD39(+), CD40(+), CD54(+), CD95(+). Like the parental tumor, MedB-1 lacks HLA-A,B,C alpha-chains and beta(2)microglobulin and expresses HLA-D molecules at decreased levels. Both parental tumor and MedB-1 cells are clonally related as shown by immunoglobulin heavy chain gene rearrangement analysis. Unlike the parental tumor tissue, the MedB-1 cell line cytoplasmically expresses IgG/kappa in a very small subset of cells under standard culture conditions. MedB-1 does not contain any Epstein-Barr virus DNA. In a tissue adhesion assay MedB-1 cells showed an extensive binding to the medullary region of normal thymus. Altogether, MedB-1 is a suitable tool for functional and molecular analysis of this distinct lymphoma entity.

Lymphoproliferative disorders in children with primary immunodeficiencies: immunological status may be more predictive of the outcome than other criteria

AIMS

Lymphoproliferative disorders (LPDs) are a severe complication in primary immunodeficiency and post-transplant patients. In primary immunodeficiency patients, LPDs are not well-known and, thus, we tried to evaluate their distinctive features and to determine prognostic factors predictive of clinical outcome by comparison with LPDs in post-transplant children.

METHODS AND RESULTS

Clinical records and histopathology of 18 LPDs occurring in primary immunodeficieny children were compared with those of 10 LPDs in post-transplant children, together with results of in-situ hybridization for the detection of Epstein-Barr virus (EBV)-RNA and molecular biological techniques. LPDs were frequently extranodal, EBV-associated, and were more commonly pleomorphic in primary immunodeficiency than in post-transplant patients. A low T-cell count and abnormal T-cell function indicated bad prognosis in both groups. Polymorphic LPDs (PLPDs) were most frequent (n = 19), whereas lymphomas were rare (n = 7), and pseudo-tumoral lymphoid hyperplasias (n = 2) were observed only in primary immunodeficiency. Comparative p53/bcl-2 staining revealed a p53 overexpression in lymphomas compared with PLPDs; CD20/CD79a showed a similar staining in lymphomas, whereas PLPD expressed mainly CD20. TCR and IgH rearrangements did not help in distinguishing PLPDs from lymphomas, but detection of IgH clonality by Southern blot indicated poor prognosis, whereas oligoclonality by Southern blot regardless of PCR clonality and especially a polyclonal profile by Southern blot and PCR indicated a relatively good prognosis.

CONCLUSIONS

This study documents the pleomorphism of LPDs in primary immunodeficiency compared to post-transplant children, even if some LPDs are similar in both groups (PLPDs). No criteria are useful enough to ascertain the diagnosis of malignancy in this series. Some molecular biological criteria help to predict the clinical outcome which, nevertheless, seems to depend more on the degree of immunosuppression and on T-lymphocyte presence and function.

Detection of Epstein-Barr virus in Hodgkin-Reed-Sternberg cells : no evidence for the persistence of integrated viral fragments inLatent membrane protein-1 (LMP-1)-negative classical Hodgkin's disease

Classical Hodgkin's disease (HD) is associated with Epstein-Barr virus (EBV) infection. Although in developing countries EBV can be demonstrated in Hodgkin-Reed-Sternberg (H-RS) cells in up to 95% of HD cases, in industrialized countries only about 50% of HD cases are associated with EBV. An open question remains whether EBV in the EBV-negative cases has escaped detection by standard screening procedures due to deletions in the viral genome associated with integration of viral fragments into the host cell genome. We, among others, recently described this phenomenon in Burkitt's lymphoma cells. To investigate whether H-RS cells in latent membrane protein-1 (LMP-1)-negative HD cases harbor fragments of the EBV genome, we combined fluorescence in situ hybridization (FISH) using a set of six overlapping DNA probes spanning the whole EBV genome with immunophenotyping of fresh frozen lymphoma sections. Results in the eight cases analyzed were as follows: in three LMP-1-positive cases, FISH analysis yielded specific signals for each EBV DNA probe in H-RS cells, which had been identified by morphology and CD30 staining. In contrast, none of the EBV DNA probes hybridized to the H-RS cells in the five LMP-1-negative cases. Thus, there is no evidence for the presence of fragments of the viral genome integrated into the host cell genome in the LMP-1-negative cases. Furthermore, in the LMP-1-positive cases analyzed, no large deletions in the viral genome were detected. These results show that, in classical HD, LMP-1-negative cases do not harbor EBV DNA within the H-RS cells. Whether, in these cases, a still unknown virus contributes to the transformation and maintenance of the malignant phenotype remains to be established.

Regulation of Epstein-Barr virus promoters in oral epithelial cells and lymphocytes

Hairy leukoplakia (HL) is a proliferative lesion of the tongue that supports abundant Epstein-Barr virus (EBV) replication. Previous work showed high-level expression of the EBV BMRF2 gene in HL. To characterize the regulation of BMRF2 expression in HL, we mapped the 5' ends of the BMRF1 and BMRF2 transcripts and showed that BMRF2 is expressed from a novel internal promoter within the BMRF1 coding region. Mechanisms of BMRF2 regulation were compared in oral epithelial cells and B lymphocytes, as were those of BMRF1 and BDLF3, early and late EBV transcripts, respectively, that are also known to be expressed in HL. Basal activity of the putative BMRF2 promoter was 10-fold higher in HSC-3 epithelial cells than in B lymphocytes. The BMRF2 and the BDLF3 promoters were responsive to induction by phorbol ester, but unlike the BMRF1 promoter, they were not responsive to BZLF1 transactivation. By mutational analysis, the major activity of the BMRF2 promoter mapped to a 50-bp region, which includes a TATA-like element and a GC box. The BMRF2 promoter may be regulated differentially from the BMRF1 promoter and more closely resembles that of BDLF3. This novel BMRF2 promoter likely belongs to a class of viral promoters that is more responsive to mechanisms known to induce epithelial cell differentiation, consistent with its high level of expression in HL.

Inflammatory myofibroblastic tumor with HMGIC rearrangement

Inflammatory pseudotumors or inflammatory myofibroblastic tumors (IMT) are lesions of extreme heterogeneity showing a highly variable mixture of bland-looking spindle cells, inflammatory cells, and collagen fibers. We describe our results of molecular cytogenetic and rapid amplification of cDNA ends (RACE-PCR) studies on an IMT characterized by a translocation involving 12q15. Chromosomal aberrations involving this region are very frequent among other benign tumors, such as lipomas, uterine leiomyomas, or pulmonary chondroid hamartomas. Recently, we have shown that, by these structural chromosomal aberrations, the HMGIC gene is affected. Fluorescence in situ hybridization (FISH) analysis and 3' RACE-PCR on cells of the present case of an inflammatory myofibroblastic tumor indicated an intragenic rearrangement of HMGIC, resulting in an aberrant transcript of that gene. Clonal cytogenetic aberrations have been described in very few cases of IMT. The results presented herein indicate that this case of IMT represents a true benign mesenchymal neoplasm associated with, or due to, a rearrangement of HMGIC.

Intron retention may regulate expression of Epstein-Barr virus nuclear antigen 3 family genes

The nuclear antigen 3 family genes (EBNA-3, EBNA-4, and EBNA-6) of Epstein-Barr virus (EBV) are important for EBV-induced immortalization and survival of B lymphocytes. However, little is known about how the expression of these genes is regulated. Each of the EBNA-3, EBNA-4, and EBNA-6 genes consists of two exons separated by a small intron. Reverse transcriptase PCR assays revealed that the vast majority of the EBNA-3, EBNA-4, and EBNA-6 mRNA, expressed in transfected and EBV-infected B cells, retained intron sequences. Northern blot and S1 protection assays confirmed that most of the EBNA-3 mRNA contained intron. Examination of deletion mutants of EBNA-3 indicated that the EBNA-3 protein was not necessary for intron retention and that there was no splicing silencing element encoded in the EBNA-3 mRNA. Cell fractionation and RNA gradient analysis revealed that the unspliced EBNA 3 family mRNAs were transported into the cytoplasm and associated with the polysomes. However, Western blot analysis of FLAG-epitope tagged EBNA-3 gave no indication of the presence of splice variant protein forms of EBNA-3. In contrast, transiently transfected cells expressing EBNA-3 revealed a sixfold increase in EBNA-3 protein expression from the genomic EBNA-3 gene compared to EBNA-3 cDNA. These data show that the intronic sequences can influence EBNA-3 protein expression and suggest that intron retention may provide a means for the fine-tuning of expression of the individual EBNA 3 family genes.

Different distribution of H1-H2 Epstein-Barr virus variant in oropharyngeal virus and in biopsies of Hodgkin's disease and in nasopharyngeal carcinoma from Algeria

In a previous study of Epstein-Barr virus (EBV) strains in North African nasopharyngeal carcinoma (N PC) biopsies, we have found that the viral strain present was of A/F/W'-I'/Xhol kept/H1-H2 type, while the strain associated with Chinese NPC was the A/"f"/W'I'/Xhol lost/H type. Using the restriction fragment length polymorphism (RFLP) and PCR-RFLP methods, the present study analyzed the H1-H2 variant in different clinical samples from Algeria, including the saliva of healthy EBV-positive individuals and patients with NPC or Hodgkin's disease (HD), as well as HD biopsies and lymphoblastoid cell lines (LCLs) established from the oropharyngeal virus-infected cells. Our results demonstrate that, in contrast to the H1-H2 variant found in NPC biopsies, the H genotype was dominant in HD biopsies. Moreover, H genotype was also dominant in the oropharynx of healthy EBV-positive individuals, of patients with NPC and with HD. Our results clearly indicate that in North Africa the EBV strain present of NPC biopsies is different from that shed in the oropharynx. This may suggest a specific distribution of the H1-H2 variant in the NPC epithelial tumor, whereas the H genotype is dominant in HD biopsies and in the oropharynx. The specific association of both viral strains with these 2 distinct diseases in North Africa may reflect a difference in tumorigenicity.

Role of Rta in the translation of bicistronic BZLF1 of Epstein-Barr virus

The BZLF1 gene of Epstein-Barr virus (EBV), which encodes a transcription factor, Zta, is transcribed into monocistronic and bicistronic mRNAs from two different promoters during the immediate-early stage of the EBV lytic cycle. It is generally accepted that the Zta protein translated from the monocistronic mRNA profoundly influences the activation of the EBV lytic cycle. In this study, we constructed a plasmid, pCMV-RZLUC, which can transcribe a bicistronic mRNA consisting of BRLF1 and a BZLF1-luc fusion gene under latent conditions. P3HR1 cells transfected with this plasmid produce a luciferase activity which is approximately 17-fold higher than the activity exhibited by pRZLUC, a plasmid incapable of transcribing the bicistronic mRNA. Genetic analyses indicated that mutations in BRLF1 not only can decrease the translation of the fusion gene from the bicistronic mRNA but can also be complemented by a functional BRLF1 gene in cis. This observation implies that the product of BRLF1, Rta, is involved in the translation of the downstream gene. Results presented herein also demonstrate that these mutations cannot be complemented in trans with a plasmid overexpressing Rta, suggesting that the amount of Rta in the vicinity of the intercistronic region may be crucial for the translation. Furthermore, our results correspond to those of previous investigations indicating that the Zta protein can be translated from the bicistronic mRNA and that, similar to the translation of bicistronic ZLUC, mutations in BRLF1 also hinder the translation of Zta from the BRLF1-BZLF1 bicistronic mRNA. Translation of Zta from the bicistronic mRNA may play an essential role in the activation of the EBV lytic cycle.

Functional analysis of the p53 protein in AIDS-related non-Hodgkin's lymphomas and polymorphic lymphoproliferations

Alteration of the tumour suppressor gene p53 is frequent in AIDS-related non-Hodgkin's lymphomas (AIDS-NHL), particularly in Burkitt's or Burkitt's-like lymphomas (BL/BLL). Since mechanisms of inactivation other than mutations have been advanced, the transcriptional activity of the p53 protein was studied in a functional assay in yeast in a series of AIDS-NHL lesions and compared with their morphology, immunohistochemistry (IHC) and single-strand conformation polymorphism (SSCP) analysis detection of other p53 abnormalities, Epstein-Barr virus (EBV) status, MDM-2 oncoprotein expression and c-MYC rearrangement. Polymorphic lymphoproliferations (PL), identified as precursors of NHL in HIV-patients, were also analysed in attempt to detect p53 modifications related to clonal progression. The functional assay detected p53 mutants in 40% (12/ 30) of the tumours: 50% (6/12) of BL/BLL, 40% (4/10) of diffuse large cell lymphomas (DLCL) and 25% (2/8) of PL. An oligoclonal or monoclonal population was identified in the two PL cases with mutant p53. An accumulation of the p53 protein was detected by IHC in 26% (8/30) of the tumours (five BL/BLL and three DLCL) and was associated with positive functional assay. In the 20 lesions tested by both of the screening methods for mutations, a p53 mutant pattern was detected in 55% of cases (11/20) and in 25% of cases (5/ 20) respectively with the functional assay and SSCP analysis of exons 5-8. There was no inverse correlation between the detection of EBV genome and the presence of p53 mutations and no overexpression of MDM-2 protein for the whole series. In conclusion, the functional assay was more sensitive than IHC and SSCP for the detection of p53 mutations in tumour samples. The mutations identified in AIDS-NHL lesions inactivate the p53 protein and in PL they could represent a selection of an aggressive clone.

Epstein-Barr virus BMRF-2 and BDLF-3 expression in hairy leukoplakia

Hairy leukoplakia (HL) is a lesion found on the side of the tongue of immunocompromised individuals, including those with human immunodeficiency virus (HIV) infection. The lesion has unique histopathologic features and is characterised by high-level Epstein-Barr virus (EBV) replication, multiple EBV strains, and extensive inter- and intra-strain recombination. Expression of EBV genes spanning the entire viral life cycle from latency-associated genes to late, replicative genes has been detected in the lesion. HL thus provides a unique opportunity to study EBV expression in oral epithelium, and to study expression of novel EBV genes. We therefore constructed a cDNA library from an HL biopsy and detected expression of two genes not previously described in vivo: BMRF-2 and BDLF-3. Sequence analysis of the cDNAs revealed few amino acid changes from the B95-8 sequence. Expression of both genes was localized to the lower prickle cell layer of the tongue epithelium. BMRF-2 protein expression was primarily detected in the cell nuclei of the upper prickle cell layer. BDLF-3 protein expression was observed in the peri-nuclear space and Golgi compartment. The function of these proteins is currently under investigation.

Strict Lymphotropism of Epstein-Barr Virus During Acute Infectious Mononucleosis in Nonimmunocompromised Individuals

Previous investigations of exfoliated oropharyngeal cells from individuals suffering from infectious mononucleosis (IM) suggested that the oropharyngeal epithelia are the primary target and also the site of life-long persistence of the Epstein-Barr virus (EBV). This concept was widely accepted. However, the investigation of histological sections with more sensitive EBV detection techniques has drawn this concept into doubt since EBV proved to be constantly absent in normal epithelial cells. To elucidate the discrepancy, throat washings and peripheral mononuclear blood cells from 16 patients suffering from IM were investigated for EBV-DNA and EBV gene products employing highly sensitive in situ hybridization, immunocytochemistry, and polymerase chain reaction. Although all patients exhibited latently infected B lymphocytes in peripheral blood, samples of exfoliated oropharyngeal cells were constantly EBV-negative with the exception of three cases. In these cases, the patients additionally suffered from purulent ulcerating tonsillitis, EBV-infected B cells, but no EBV-infected epithelial cells were detectable. These findings support the view that recirculating lymphocytes of B-cell origin, but not epithelial cells are the initial target of EBV during primary infection and that B cells also represent the site of life-long viral persistence.

AIDS-related primary brain lymphomas: histopathologic and immunohistochemical study of 51 cases. The French Study Group for HIV-Associated Tumors

Fifty-one cases of acquired immunodeficiency syndrome (AIDS)-related primary brain lymphomas (AR-PBL) were investigated for clinical characteristics; human immunodeficiency virus (HIV)-associated disorders; histopathologic features; immunophenotype; Epstein-Barr virus (EBV) infection; and, when frozen tissue was available, oncogene rearrangements. AR-PBL occurred late in the course of AIDS and were usually associated with other systemic or cerebral disorders and with a low level of CD4 lymphocytes. All cases were high grade lymphomas according to the Working Formulation or updated Kiel classification, and often displayed a multifocal pattern. Thirty cases were classified as immunoblastic with plasmacytic differentiation, 18 cases were large cell lymphomas with an immunoblastic component or centroblastic polymorphic lymphomas, and 2 were small noncleaved non-Burkitt lymphomas (Working Formulation). This latter category is classified as Burkitt's-like lymphoma in the REAL nomenclature. One case could not be classified because of necrosis. AR-PBL showed a high level expression of activation and adhesion molecules. The presence of EBV was detected in most cases, and, when PCR was used, this was a constant finding. bcl-2 oncoprotein and latent membrane protein-1 (LMP-1) were strongly expressed. None of the tested cases expressed p53, or were rearranged for bcl-2 or c-myc oncogenes. This study confirms the immunophenotypic specificity of AR-PBL, which may reflect the special immune status of the brain.

Synergy between human immunodeficiency virus type 1 and Epstein-Barr virus in T lymphoblastoid cell lines

CR2 (CD21), the EBV receptor, was detected on three of four CD4-positive cell lines by indirect fluorescent labeling, and its corresponding mRNA was found by use of the reverse transcription-based polymerase chain reaction. To determine whether CR2 on CD4-positive cells was functional, their ability to be infected by EBV was analyzed. EBV DNA, EBV nuclear antigen 2 (EBNA-2A), and EBV-encoded small RNA (EBER1) transcripts could be detected in CR2-expressing CD4-positive cells following infection by the B95.8 strain of EBV. Analysis of the terminal region showed the EBV genome remained linear following infection, and copy number decreased with time. Since CD4-positive cell lines are targets for HIV-1 infection, the effects of EBV infection on HIV-1 expression were analyzed. HIV-1 replication was upregulated when CD4-positive cells were coinfected with EBV strain B95.8 but not P3HR-1K. These results suggested that EBNA-2 is involved in upregulation of HIV-1 expression in T lymphoblastoid cell lines. To test this hypothesis an EBNA-2-expression vector was transfected into T lymphoblastoid cell lines and HIV-1 expression measured. First, trans-activation of HIV-1 long terminal repeat (LTR) by Tat was enhanced by EBNA-2 type 1 expression. trans-Activation of the HIV-1 LTR by Tat was also enhanced when CD4-positive cells were infected by EBV (strain B95.8) encoding an intact EBNA-2, but not by P3HR-1K with a deleted EBNA-2. In addition, CD4-positive cell clones stably expressing EBNA-2 supported enhanced HIV-1 replication as measured by accumulation of reverse transcriptase activity and syncytium induction. This provides direct evidence that EBV infection can enhance HIV-1 replication in T cells. Whether this in vitro phenomenon contributes to disease progression in vivo remains to be determined.

Characteristics of EBV-infected cells in HIV-related lymphadenopathy: implications for the pathogenesis of EBV-associated and EBV-unrelated lymphomas of HIV-seropositive individuals

The present study was performed with the aim of better defining the possible role of Epstein-Barr-virus (EBV)-infected cells in the pathogenesis of HIV-related lymphadenopathy syndrome (LAS). In addition, since LAS has been considered as a pre-lymphomatous lesion, we also wished to elucidate the possible contribution of EBV-carrying cells present in LAS tissues to the development of HIV-associated malignant lymphomas. To this end, we have characterized EBV-infected cells in LAS lymph nodes in terms of EBV DNA prevalence, tissue distribution in relation to HIV-carrying cells, virus sub-type, expression of latent and replicative antigens, and presence of clonal EBV episomes. When compared with HIV-unrelated lymphadenopathies (4/10, 40%), LAS showed a higher prevalence of EBV DNA (14/20, 70%). Comparable values of EBV prevalence were detected in LAS with follicular hyperplasia (12/16, 75%) and with follicular involution (4/4, 100%). All EBV+ non-neoplastic lymph nodes from HIV-seronegative patients carried type-I EBV, whereas LAS specimens showed almost equivalent distribution of the 2 EBV sub-types. Of the 14 EBV-carrying LAS, 4 (29%) were positive by Southern-blot analysis for the BamHI-W region of the virus genome but negative for the presence of monoclonal EBV episomes. In situ hybridization revealed a remarkably higher load of EBV-infected cells in LAS than in HIV-unrelated lymphadenopathies. In LAS lymph nodes, EBV-carrying cells were identified as isolated, cytologically normal elements, sometimes with immunoblastic morphology, usually scattered throughout the interfollicular areas. By contrast, the expression of HIV p24 was restricted to germinal center cells. All the EBV+ LAS samples were negative for the expression of EBV-encoded latent (LMP-1 and EBNA-2) and replicative proteins (BZLF-1, BHLF-1, EA-D, EA-R and VCA). In addition, amplification of the immunoglobulin heavy-chain genes using 2 different polymerase-chain-reaction protocols showed evidence of B-cell clonal expansion in 2/20 (10%) LAS, one EBV- case, and one sample with low numbers of EBV-infected cells. These results suggest that (i) EBV-carrying cells are probably not involved in the development of LAS, either directly or indirectly; (ii) type-2-EBV-infected cells are present in LAS lymph nodes from the early phases of HIV infection; (iii) EBV-carrying LAS per se probably does not constitute a lesion at high risk for subsequent development of EBV+ lymphomas; (iv) it is unlikely that a high viral load or strong EBV-mediated antigenic stimulation plays a contributory role in the development of EBV-unrelated lymphomas of HIV-seropositive individuals.

Detection of Epstein-Barr virus DNA in anal scrapings from HIV-positive homosexual men

Epstein-Barr virus (EBV) can infect epithelial cells as well as B lymphocytes. Infection of the male and female genital tracts has recently been demonstrated, and it has been suggested that the virus may be sexually transmissible. In our study we investigated whether EBV can be found in the anal region of sexually active homosexual men. Anal scrapings from HIV-positive homosexual men and a heterosexual control population were investigated using the polymerase chain reaction (PCR) to screen for EBV DNA. EBV DNA was detected in 8 of 27 anal samples (29.6%) from the homosexual men and 3 of 34 samples (8.8%) from the heterosexual men. Our study shows that, like the genital tract, the anal region can harbour EBV subclinically. This finding suggests that the anal region may be a reservoir for EBV and that sexual transmission of this virus may be possible.

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.

Genotypic and immunohistological demonstration of the progression of an unusual reactive-like B-cell lymphoproliferative disorder to a high grade diffuse lymphoma

In the present study the clinical and pathological evolution of a reactive-like B-cell lymphoproliferative disorder with an unusually high content of T cells is described. Immunogenotypic analysis showed that the same phenotypically atypical B-cell clone, characterized by the unusual presence of an immunoglobulin (Ig)K gene rearrangement, with the heavy chain (IgH) gene in germline configuration, was invariantly present in all phases of the disease. The disorder showed an indolent course for a long period of time during which the clonal B-cell population coexisted with an abundant, reactive T-cell component in different locations of the disease. These findings, together with the observation of spontaneous progression and regression phases of the disorder and its responsiveness to corticosteroids, suggest that functional interactions between the B-cell clone and the polyclonal infiltrating T cells probably were involved in the pathogenesis of the disease. After the administration of the antiblastic treatment, a progressive reduction of the reactive T-cell component was observed with the concomitant evolution to a diffuse large cell (immunoblastic) B-cell lymphoma and the appearance of an IgH gene rearrangement. The biological characteristics and the clinical evolution of the case described here are similar to those reported for the so-called "T-cell-rich B-cell lymphomas" (TCRBCLs). These findings suggest that the T-cell-rich pattern may identify a group of B-cell lymphoproliferations with common pathogenetic mechanisms and clinical behavior.

New translocation t(2;13)(p12;q34) and rearrangement of the MLL gene in a childhood leukemia cell line

Here we report the case of a 7-month-old boy who presented with biphenotypic acute leukemia, but with leukemia cells of B-cell phenotype present at the time of relapse. Two cell lines were derived from bone marrow specimens obtained at relapse, and immunophenotyping and analysis of antigen receptor gene configuration revealed concordance between the patient's leukemic cells and the cell lines. Cell line PER-377 shows a new chromosomal abnormality, t(2;13)(p12;q34), a molecular rearrangement at chromosome band 11q23 in the absence of a cytogenetically detectable abnormality of this band, and deletion of the genes for IGK.

Immortalization of human B lymphocytes by a plasmid containing 71 kilobase pairs of Epstein-Barr virus DNA

We have assembled derivatives of Epstein-Barr Virus (EBV) that include 71 kbp of noncontiguous DNA sequences cloned into a prokaryotic F-factor plasmid. These mini-EBVs, when introduced into an EBV-containing lymphoblastoid cell, can be packaged by the endogenous helper virus. One such mini-EBV was found to have a single C residue deleted from its EBNA3a open reading frame. When packaged, this mini-EBV initiates proliferation of infected primary human B lymphocytes only in conjunction with a complementing helper virus. Proliferation of the infected cells, however, was maintained either alone by the mini-EBV containing the mutated EBNA3a open reading frame or alone by its derivative in which the EBNA3a open reading frame had been healed of its lesion by recombination with the helper virus. The mini-EBV with a wild-type EBNA3a open reading frame when packaged alone can both initiate and maintain proliferation upon infection of primary human B lymphocytes. These findings identify 41% of EBV DNA which is sufficient to immortalize primary human B lymphocytes and provide an assay to distinguish virus contributions to initiation or maintenance of cell proliferation or both. They also identify EBNA3a as a transforming gene, which contributes primarily to the initiation of cell proliferation.

Epstein-Barr virus genotypes in NPC biopsies from north Africa

The genotypes of Epstein-Barr virus (EBV) were investigated in North African nasopharyngeal carcinoma (NPC) biopsies, nasopharyngeal chronic inflammation (NCI) biopsies, and saliva of healthy individuals from Algeria and Tunisia where there is an intermediate incidence of NPC. The prevalence of A-type virus in NPC, NCI biopsies and saliva of healthy individuals was found in these regions by means of a PCR assay. Restriction enzyme polymorphism analysis by Southern blotting revealed that all North African EBV variants have a conserved restriction site on BamHI W'-I' and XhoI LMP gene. No additional BamHI enzyme site on the BamHI-F fragment was observed; however, the presence of an extra BamHI site on the BamHI-H fragment giving 2 HI and H2 fragment-like EBV M-ABA strains was found. All EBV strains present in NPC or NCI biopsies at all ages were homogeneous in these polymorphisms and no correlation was observed between the EBV genotypes from NPC patients and clinical stages of the cancer. These characteristics revealed a significant difference between the EBV variants common in Chinese NPC and those in North African NPC.

Preferential clustering of chromosomal breakpoints in Burkitt's lymphomas and L3 type acute lymphoblastic leukemias with a t(8;14) translocation

We have analyzed the type of MYC/IG heavy-chain locus (IGH) rearrangement present in 15 patients affected by t(8;14)-positive primary Burkitt's lymphoma or acute lymphoblastic leukemia of the L3 type in an attempt to map in detail the locations of the chromosome 8 and chromosome 14 breakpoints. The almost constant position of the chromosome 8 breakpoint (within or immediately 5' of the MYC gene) together with two distinct clusters of breakpoints on chromosome 14 resulted in two main types of MYC/IGH (present in 12 of 15 cases). In the first type (six cases), the MYC gene or at least its coding portion was joined with the JH region on chromosome 14, whereas in the second, present in another six cases, the MYC gene and the C alpha I region were juxtaposed. Physical linkage between the translocated MYC and a known enhancer element of the IGH locus is the common feature in the two types of rearrangement, suggesting that a high-level constitutive expression plays a prominent role in MYC activation. Interestingly, the chromosome 14 break site within the switch alpha 1 region, which has been only occasionally described in other cases, is present in 40% of our patients, suggesting the existence of preferential breakpoint cluster regions in cases of similar geographic origin.

Integration of Epstein Barr virus near the breakpoint of a translocation 11;19 in a Burkitt's lymphoma cell line

The physical state of Epstein Barr virus (EBV) DNA was analyzed in the Burkitt's lymphoma (BL) cell line BL60 and in the autologous EBV-immortalized lymphoblastoid cell line (LCL) IARC 277 by Gardella gel analysis, Southern blotting, and nonradioactive in situ hybridization to metaphase chromosomes. Although only episomal viral DNA was detected in the LCL, the 6-12 copies of EBV DNA in the BL cell line are integrated in one site of the host cell genome. The integration site is located near the breakpoint of a translocation 11;19 which is present in this cell line in addition to the BL-specific t(8;22).

High incidence of monoclonal EBV episomes in Hodgkin's disease and anaplastic large-cell KI-1-positive lymphomas in HIV-1-positive patients

A series of selected lymphoid malignancies (LMs) occurring in Italian HIV-1-infected (HIV+) patients, principally intravenous drug users, was investigated. In addition to small non-cleaved-cell (SNCC) and large-cell immunoblastic (LCI) non-Hodgkin's lymphomas (NHLs), a relatively high occurrence of anaplastic large-cell Ki-I-positive (ALC Ki-I+) lymphomas and Hodgkin's disease (HD) was observed, at variance with other reported series of HIV+ patients. Combined results of in situ hybridization and Southern-blot analyses, in conjunction with immunohistochemical detection of Epstein-Barr virus (EBV)-encoded latent membrane protein-I (LMP-I), showed an almost complete association of ALC Ki-I+ lymphomas and HD cases with EBV. The neoplastic cells of both these LMs also showed common immunophenotypic features such as frequent absence of B- and T-cell differentiation markers and expression of the Ki-I activation marker, while SNCC and LCI lymphomas were mainly of mature B-cell origin and Ki-I-. The concomitant high incidence of ALC Ki-I+ lymphomas and HD in a specific group of HIV+ patients, their almost complete association with EBV in clonal and episomal form and the great similarity in differentiation, activation and virological markers which they display suggest that these LMs are pathological variants of a continuous spectrum of HIV-I-associated disorders etiopathologically linked to EBV.

Expression of Epstein-Barr virus nuclear antigen 1,2A and 2B in the baculovirus expression system: serological evaluation of human antibodies to these proteins

The Epstein-Barr virus encoded nuclear antigens 1,2A, and 2B (EBNA 1, EBNA 2A, and EBNA 2B) were expressed in a baculovirus system. The full length recombinant proteins were recognized by polyclonal rabbit sera and by human sera. An immunofluorescence (IF) test for the differentiation between EBNA 1 and EBNA 2 antibodies in human sera was established with the expressed proteins. None of 55 sera of patients with infectious mononucleosis (IM) had anti-EBNA 1 antibodies while 36 of these sera had anti-EBNA 2A antibodies. Conversely, 47 of 51 sera from EBV-positive healthy carriers had anti-EBNA 1 antibodies and 18 of these sera had anti-EBNA 2A antibodies. The sensitivity and specificity of the EBNA 1 IF for the diagnosis of IM were higher as compared to conventional anti-complement immunofluorescence (ACIF). In the IF test differentiation between type A and type B EBV infection was only possible in sera from the IM patients. An immunoblot (IB) with low amounts of baculovirus expressed EBNA 2A and EBNA 2B antigen was carried out. Twenty-nine of 31 sera from IM patients or from healthy carriers with EBNA 2 antibodies reacted predominantly with EBNA 2A, whereas a known type B serum reacted strongly with EBNA 2B than with EBNA 2A.

Episomal and integrated copies of Epstein-Barr virus coexist in Burkitt lymphoma cell lines

The Epstein-Barr virus genome is present in more than 95% of the African cases of Burkitt lymphoma. In this tumor, the viral genome is usually maintained in multiple episomal copies. Viral integration has been described only for Namalwa, a cell line lacking episomes. In this study, we have addressed the question of whether integrated and episomal copies can coexist in Burkitt lymphoma cells. Gel electrophoresis was used to demonstrate the presence of episomal as well as free linear DNA in three Burkitt lymphoma cell lines. The numbers of episomal copies per cell were estimated to be 5 to 10 in BL36 and BL137 cells and below 1 in BL60 cells, indicating that BL60 does not represent a homogeneous cell population. Fluorescence in situ hybridization was combined with chromosomal banding to study the association of the viral DNA with metaphase chromosomes. A symmetrical pattern of signals at both chromatids located at the same chromosomal sites in many if not all metaphases was taken as evidence for viral integration. In each of the three cell lines, one site of integration was identified: at chromosome 11p15 in BL36 cells, at chromosome 1p34 in BL137 cells, and at the site of a reciprocal t(11;19) translocation in BL60 cells. Integrated, episomal and linear copies of Epstein-Barr virus DNA thus coexist in Burkitt lymphoma cells. The biological significance of viral integration in Burkitt lymphoma cells remains to be elucidated.

Down-regulation of integrated Epstein-Barr virus nuclear antigen 1 and 2 genes in a Burkitt lymphoma cell line after somatic cell fusion with autologous EBV-immortalized lymphoblastoid cells

Epstein Barr virus (EBV) latent gene expression was analyzed in somatic cell hybrids between an EBV-positive Burkitt lymphoma (BL) cell line (BL 60) and an autologous EBV-immortalized lymphoblastoid cell line (LCL, IARC 277). The EBV genomes carried by the parental cell lines differ in sequence and in their physical state. The BL 60 EBV genome is integrated into the host cell genome whereas the LCL IARC 277 carries exclusively episomal EBV molecules. The hybrid cells contain both EBV genomes and display the differentiation phenotype of the parental LCL with regard to growth characteristics and cell-surface antigen expression in vitro and in vivo. While the EBNA 1 and EBNA 2 gene expression of the LCL-derived EBV is maintained in these hybrid cells, the BL-60-derived EBNA 1 and EBNA 2 genes are transcriptionally down-regulated. Mapping of the genomic region surrounding the latent Cp promoter of the BL-60-derived EBV revealed an extensive deletion upstream of the Cp promoter including the enhancer element in the ori P region, the origin of latent viral replication (ori P), the coding sequences for the EBV latent membrane protein (LMP) and the EBV terminal protein (TP), and suggested that one viral-cellular junction sequence is located near the Cp promoter. Integration of EBV into the host cell genome together with the extensive deletion might be causally related with the altered latent gene expression pattern after introduction of a lymphoblastoid host-cell background by somatic cell fusion. Down-regulation of the BL-60-derived EBNA genes could be due to loss of regulatory sequences in the BL-derived EBV necessary for EBNA 1 and EBNA 2 transcription in the lymphoblastoid hybrid cells, but not in the parental BL cells.

Epstein-Barr virus (EBV) nuclear-antigen-2-induced up-regulation of CD21 and CD23 molecules is dependent on a permissive cellular context

The Epstein-Barr virus (EBV) induces unlimited growth of B lymphocytes in vitro, a phenomenon known as immortalization. The elucidation of the mechanisms by which EBV de-regulates B-cell proliferation in vitro will permit an understanding of how the virus contributes in vivo to the genesis of Burkitt's lymphoma (BL) and of lymphoproliferations in immunosuppressed patients. At present, no single EBV immortalizing gene has been identified, and the hypothesis has been made that many viral genes cooperate in establishing an autocrine loop of secretion leading to immortalization. Constitutive expression of B-cell surface molecules such as CD21 and CD23, specifically implicated in the control of B-cell proliferation, is indeed induced at the surface of immortalized B lymphocytes. The expression of the viral nuclear antigen 2 (EBNA2) has been shown to be in part responsible for CD21 and CD23 up-regulation, and EBNA2 is suspected to be a transactivator of cellular genes, although this point remains to be demonstrated. The role of EBNA2 gene, independently of other viral genes, has been investigated by transfection into B-lymphoma lines, but conflicting results have been reported. To further investigate its role in the regulation of CD21 and CD23 molecules, we have compared the effects of EBNA2 expression in 2 sets of B-lymphoma lines infected with P3HR1 EBV strain, and/or transfected with EBNA2 gene. We report here that: (i) EBNA2 expression is not a sufficient condition to induce CD21 and CD23 upregulation, EBNA2's effects are highly dependent on the cellular context, and moreover can be modified by infection with P3HR1 virus; (ii) EBNA2 induces activation of CD23 expression in a very particular way, namely, an increased quantity of CD23 steady-state RNA coding for the form A of the protein, which is not detectable at the cell surface but directly secreted.

Expression of the Epstein-Barr virus (EBV) latent membrane protein is tightly regulated, independently of EB nuclear antigen 2 and of EBV integration or copy number

In vivo, Epstein-Barr virus (EBV) is associated with human tumours and with lymphoproliferations in immunosuppressed patients. In vitro, EBV induces unlimited growth of normal B-lymphocytes, a phenomenon known as immortalization. A limited number of viral genes is expressed during this phenomenon and their relative role concerning the deregulation of cellular proliferation is still unclear. At present, the nuclear antigen EBNA2 and the membrane protein LMP are the two EBV proteins considered to be implicated in the immortalization process. Moreover, many data support the hypothesis that EBNA2 is the major inducer of LMP expression by transactivation; however, in some instances, expression of the two proteins is not correlated, suggesting the existence of complex interactions between EBV and its host-cell that influence viral gene regulation. In an attempt to study thoroughly these EBNA2/LMP interactions, it is important to evaluate whether EBNA2 is or is not a major inducer of LMP expression, and which other parameters can influence LMP expression. By analysing two sets of B-lymphoma lines either infected in vitro with EBV or stably transfected with EBNA2, we have demonstrated that (1) LMP expression can be absolutely independent of EBNA2 expression, (2) the level of LMP expression is very tightly regulated, and is independent of EBV genome status (integrated or episomal) and copy number. Our findings provide compelling evidence that LMP expression has to be related to that of cellular factors that remain to be identified.

The Epstein-Barr virus encoded membrane protein (LMP) induces phenotypic changes in epithelial cells

The Epstein-Barr virus (EBV)-encoded membrane protein, LMP, is expressed in a proportion of undifferentiated nasopharyngeal carcinomas (NPC). Previous studies have shown that the transfection of the gene encoding LMP into a human keratinocyte line, RHEK-1, induces morphological alterations and a reduced expression of cytokeratins. We have analyzed immunophenotypic changes in the RHEK-1 line following LMP-transfection and compared these changes with the phenotype of NPC biopsies. We demonstrate a downregulation of two epithelial markers, an epithelial glycoprotein (EGP) defined by the monoclonal antibody Ber-EP4 and the epithelial membrane antigen (EMA). Furthermore, a lymphocyte activation-associated antigen, CDw70 antigen, which was absent from the parental line was expressed in virtually all LMP-transfected cells, whereas no similar effect was seen with respect to the CD30 activation antigen. Nine EBV-positive human NPCs, six of which were LMP-positive expressed the EGP and EMA. The CDw70 antigen, which is not normally present in epithelial cells, was expressed in eight biopsies, whereas the CD30 antigen was not detectable. Our findings are in keeping with the notion that LMP expression may contribute to the immunophenotype of human NPCs.

Expression of B-type Epstein-Barr virus in HIV-infected patients and cardiac transplant recipients

In the present study, peripheral blood mononuclear cells (PBMCs) were obtained from HIV+ subjects as well as cardiac transplant recipients, and the presence of A- and B-type Epstein-Barr virus (EBV) was determined using the polymerase chain reaction (PCR). Of the HIV+ patients studied, 24% were found to be infected with A-type EBV, 27% with B-type EBV, and 39% with both A and B virus types. Analysis of PBMCs from cardiac transplant recipients revealed that 39% were infected with A-type EBV, 33% with B-type EBV, and 28% with both EBV types. These results demonstrate a higher prevalence of infection with B-type EBV in HIV+ patients, than had been found previously by an analysis of spontaneously generated lymphoblastoid cell lines. The data indicated that it is not HIV per se which is responsible for the high incidence of B-type EBV in HIV+ individuals.

Expression of Epstein-Barr virus membrane antigen gp350/220 in E. coli and in insect cells

The Epstein-Barr virus open reading frame BLLF1 encodes the major envelope glycoproteins gp350 and gp220. Fragments of the gp350/220 gene were expressed in Escherichia coli in order to define regions of the polypeptide chain reacting with human sera. The C-terminal half of the protein was sufficient for recognition by all VCA-positive sera tested. A membrane anchor truncated version of gp350/220 was expressed in insect cells using the baculovirus system. Proteins of different sizes were specifically detected in the cells while a glycosylated 220-kDa protein was secreted. The insect cells were tested for their suitability as tools for performing monospecific immunofluorescence.

EBV strain variation: geographical distribution and relation to disease state

The strains of Epstein-Barr virus (EBV) were characterized in epithelial and lymphoid malignancies from geographic regions with high or low incidence. The predominant strains in nasopharyngeal carcinoma (NPC) from regions with elevated incidence were EBV type 1 in southeast Asia and Mediterranean Africa. In Alaskan Eskimos, a distinct variant of EBV type 2 was found in NPC and carcinoma of the parotid gland. This strain contained polymorphisms characteristic of the Asian EBV type 1. The strains prevalent in southeast Asia and Mediterranean Africa were also found in NPC which developed in caucasian Americans. These variants were not detected in lymphomas which developed in central Africa, Mediterranean Africa, or continental United States. These results suggest that distinct EBV strains predominate in geographic areas with elevated incidence of NPC. The detection of these distinct strains in epithelial tumors from areas of low incidence may reflect an epithelial cell tropism or pathogenicity.

Expression of the Epstein-Barr virus latent membrane protein (LMP) in insect cells and detection of antibodies in human sera against this protein

Recombinant baculoviruses containing the complete LMP and truncated LMP genes were generated and high levels of the LMP proteins were expressed in Spadoptera Frugiperda insect cells. A specific rabbit antiserum directed against the N-terminal part of LMP was obtained by immunizing the rabbits with Escherichia coli-expressed trpE-N-terminal part of LMP fusion protein. A total of 127 human sera were studied for their immune response to the recombinant full-length LMP. In immunofluorescence analysis, all sera tested showed no detectable reaction with the recombinant full-length LMP. In immunoprecipitation-immunoblotting analysis, however, sera from patients with nasopharyngeal carcinoma (5/22), patients with Hodgkin's disease (16/27), patients with other diseases exhibiting high EA-IgG titers (3/52), and VCA-IgG-positive healthy individuals (2/26) were shown to contain antibodies against this recombinant LMP. The expressed LMP proteins provided a sufficient and economic source of the proteins for further serological and biological studies.

Phosphorylation of the Epstein-Barr virus nuclear antigen 2

A major in vivo phosphorylation site of the Epstein-Barr virus nuclear antigen 2 (EBNA-2) was found to be localized at the C-terminus of the protein. In vitro phosphorylation studies using casein kinase 1 (CK-1) and casein kinase 2 (CK-2) revealed that EBNA-2 is a substrate for CK-2, but not for CK-1. The CK-2 specific phosphorylation site was localized in the 140 C-terminal amino acids using a recombinant trpE-C-terminal fusion protein. In a similar experiment, the 58 N-terminal amino acids expressed as a recombinant trpE-fusion protein were not phosphorylated. Phosphorylation of a synthetic peptide corresponding to amino acids 464-476 of EBNA-2 as a substrate led to the incorporation of 0.69 mol phosphate/mol peptide indicating that only one of three potential phosphorylation sites within the peptide was modified. The most likely amino acid residues for phosphorylation by CK-2 are Ser469 and Ser470.