淋巴细胞凋亡与p53蛋白表达关系的研究

培养B95-8细胞,分离EB病毒,转染外周血和扁桃体淋巴细胞,建立永生化的LCLs和TLCL细胞株; 带有wt P₅₃基因的LCLs在DNA损伤剂——顺铂处理前未检出p53蛋白,经顺铂处理后,LCLs随作用时间延长细胞存活率明显下降、p53蛋白水平升高、DNA电泳显出梯状带;含mt P₅₃基因的淋巴瘤细胞在顺铂处理前可检出高浓度的p53蛋白,经顺铂处理后,细胞存活率与p53蛋白并无明显改变.这些结果表明：顺铂引起细胞DNA损伤、激活wt p53蛋白的表达、继而wt p53蛋白又促进了DNA损伤细胞凋亡.     

Glycoprotein 110, the Epstein-Barr virus homolog of herpes simplex virus glycoprotein B, is essential for Epstein-Barr virus replication in vivo.

The Epstein-Barr virus (EBV) glycoprotein gp110 has substantial amino acid homology to gB of herpes simplex virus but localizes differently within infected cells and is essentially undetectable in virions. To investigate whether gp110, like gB, is essential for EBV infection, a selectable marker was inserted within the gp110 reading frame, BALF4, and the resulting null mutant EBV stain, B95-110HYG, was recovered in lymphoblastoid cell lines (LCLs). While LCLs infected with the parental virus B95-8 expressed the gp110 protein product following productive cycle induction, neither full-length gp110 nor the predicted gp110 truncation product was detectable in B95-110HYG LCLs. Infectious virus could not be recovered from B95-110HYG LCLs unless gp110 was provided in trans. Rescued B95-110HYG virus latently infected and growth transformed primary B lymphocytes. Thus, gp110 is required for the production of transforming virus but not for the maintenance of transformation of primary B lymphocytes by EBV.     

An Epstein-Barr virus that expresses only the first 231 LMP1 amino acids efficiently initiates primary B-lymphocyte growth transformation

An Epstein-Barr virus (EBV) recombinant (MS231) that expresses the first 231 amino acids (aa) of LMP1 and is truncated 155 aa before the carboxyl terminus transformed resting B lymphocytes into lymphoblastoid cell lines (LCLs) only when the infected cells were grown on fibroblast feeder cells (K. M. Kaye et al., J. Virol. 69:675-683, 1995). Higher-titer MS231 virus has now been compared to wild-type (WT) EBV recombinants for the ability to cause resting primary B-lymphocyte transformation. Unexpectedly, MS231 is as potent as WT EBV recombinants in causing infected B lymphocytes to proliferate in culture for up to 5 weeks. When more than one transforming event is initiated in a microwell, the MS231 recombinant supports efficient long-term LCL outgrowth and fibroblast feeder cells are not required. However, with limited virus input, MS231-infected cells differed in their growth from WT virus-infected cells as early as 6 weeks after infection. In contrast to WT virus-infected cells, most MS231-infected cells could not be grown into long-term LCLs. Thus, the LMP1 amino-terminal 231 aa are sufficient for initial growth transformation but the carboxyl-terminal 155 aa are necessary for efficient long-term outgrowth. Despite the absence of the carboxyl-terminal 155 aa, MS231- and WT-transformed LCLs are similar in latent EBV gene expression, in ICAM-1 and CD23 expression, and in NF-kappaB and c-jun N-terminal kinase activation. MS231 recombinant-infected LCLs, however, require 16- to 64-fold higher cell density than WT-infected LCLs for regrowth after limiting dilution. These data indicate that the LMP1 carboxyl-terminal 155 aa are important for growth at lower cell density and appear to reduce dependence on paracrine growth factors.     

Epstein-Barr virus recombinants with specifically mutated BCRF1 genes.

Epstein-Barr virus (EBV) recombinants with specifically mutated BCRF1 genes were constructed and compared with wild-type BCRF1 recombinants derived in parallel for the ability to initiate and maintain latent infection and growth transformation in primary human B lymphocytes. A stop codon insertion after codon 116 of the 170-codon BCRF1 open reading frame or deletion of the entire gene had no effect on latent infection, B-lymphocyte proliferation into long-term lymphoblastoid cell lines (LCLs), or virus replication. LCLs infected with the stop codon recombinant were indistinguishable from wild-type recombinant-infected LCLs in tumorigenicity in SCID mice. However, mutant BCRF1 recombinant-infected cells differed from wild-type recombinant-infected cells in their inability to block gamma interferon release in cultures of permissively infected LCLs incubated with autologous human peripheral blood mononuclear cells. This is the first functional assay for BCRF1 expression from the EBV genome. BCRF1 probably plays a key role in modulating the specific and nonspecific host responses to EBV infection.     

Human B-lymphoid cell lines.

The collective efforts during almost three decades by hematologists, tumor biologists and immunologists have provided a collection of established human hematopoietic cell lines, representing most of the hematopoietic cell lineages. The representativity of cell lines derived from the B cell differentiation lineage, however, is the most impressive. Human B-lymphoid cell lines are extensively used world wide as models in studies of various aspects of B cell biology and as tools in research on the etiology, pathogenesis and the biology of leukemia and lymphoma. Lymphoblastoid cell lines (LCL) carrying the Epstein-Barr Virus (EBV) are of particular importance. These lines can be established spontaneously from blood and lymphoid tissue from any EBV positive individual by special techniques, and from all individuals by EBV infection of peripheral blood B cells by EBV infection in vitro. At spontaneous establishment B cells, latently infected by EBV in vivo, will release EBV which subsequently infects normal EBV-negative B cells and immortalizes them into LCL cells, but direct outgrowth of the latently infected B cells as LCLs has also been documented. The target B cells for the EBV infection in vitro are not fully defined-most are mature B cells but also pro-B and pre-B and some B-blasts can be infected. Apart from their capacity for infinite growth, LCL cells have non-malignant properties, e. g. they are diploid, do not grow in agarose and do not form tumors upon inoculation subcutaneously in nude mice. LCLs have a phenotype corresponding to activated B cells (B-blasts) and have been used as "the E. Coli" of eukaryotic cells for about two decades. LCLs are derived at a high frequency also from tumor biopsies of EBV positive patients with leukemia and lymphoma. However, tumor cell lines are available from most of the B cell lineage-derived leukemias, B-lymphomas and myeloma. The frequency of successful establishment has been particularly high from EBV positive Burkitt's lymphoma (BL). From EBV genome negative BL and other B-lymphoma and B-leukemia biopsies the frequency of successful, spontaneous establishment is low (5-10%), and such lines have, with rare exceptions, been derived from pleural effusions and ascitis of patients with advanced, chemotherapy resistant, disease. Many of the cell lines therefore do not represent the clinically most common types of leukemia and lymphoma. No authentic malignant cell lines have been established from chronic lymphocytic leukemia (CLL), prolymphocytic leukemia (PLL) and Waldenstr?m's disease.(ABSTRACT TRUNCATED AT 400 WORDS)     

Epstein-Barr virus-induced transformation of B cells for the diagnosis of genetic metabolic disorders--enumerative conditions for cryopreservation

Epstein-Barr virus (EBV) infection in vitro causes transformation of B cells and generates B lymphoblastoid cell lines (LCLs). These LCLs have been widely used for the diagnostic of several genetic metabolic disorders. However, up to now, efficiency of LCL generation has been based on misleading subjective analysis. In this study, quantitative analyses have been performed to indicate efficiency of B-cell transformation to measuring human lysosomal acid hydrolases associated with: GM1-gangliosidosis type I, Gaucher disease and mucopolysaccharidosis type I. Peripheral blood mononuclear cells were isolated from 13 subjects, and LCLs were produced by culturing them with EBV for 12 days. Activities of the enzymes beta-galactosidase, beta-glucosidase and alpha-iduronidase were measured before and after cryopreservation in liquid nitrogen for 30 days. Efficiency of the B-cell transformation was screened every 4 days by the enumeration of cell proliferation, cell counts and changes in granularity estimated by flow cytometry. We observed the generation of 13 LCLs. Cell transformation was confirmed by the gradual increase of cellular clusters, cell size and granularity. In addition, we determined that the activity of the enzymes mentioned above did not change following cryopreservation. These data suggest that our enumerative approach for screening of EBV-LCLs is efficient for the enzymatic determination of human lysosomal acid hydrolases and may thus replace misleading subjective analyses.     

Cryopreservation of adult human hepatocytes obtained from resected liver biopsies

Isolated human hepatocytes have been shown to represent a valuable in vitro model to investigate the metabolism and cytotoxicity of xenobiotics. In addition, human hepatocyte transplantation and artificial liver support systems using isolated human hepatocytes are currently investigated as treatment for acute and chronic hepatic failure. In this regard, human hepatocyte banking by cryopreservation would be of great interest. In the present study, freshly isolated hepatocytes from resected liver biopsies of 28 separate donors (viability: 88 +/- 2%; plating efficiency: 79 +/- 5%) were cryopreserved using two different protocols, stepwise freezing (SF) or progressive freezing (PF), in combination (PF(+), SF(+)) or not (PF(-), SF(-)) with a 30 min preincubation in culture medium at 37 degrees C. Total recovery was higher after PF (38 +/- 3%) than after SF (12 +/- 2%). Preincubation prior to SF had no effect on plating efficiency of thawed hepatocytes (SF(-): 38 +/- 6% versus SF(+): 46 +/- 7%) while preincubation prior to PF increased plating efficiency of thawed hepatocytes (PF(-): 42 +/- 6% versus PF(+): 64 +/- 4%, p < 0.05). In attached cultured human cryopreserved/thawed hepatocytes (CH) from the PF(+) group, albumin production and glutathione content were not significantly different from those of the freshly isolated hepatocyte (FIH) cultures. Cells in CH monolayers appeared smaller than cells in FIH monolayers. In addition, the pattern of cytochrome P450- and UDP-glucuronosyl transferase-dependent isoenzyme activities and GST activity were different, suggesting a variability in the resistance to cryopreservation of the various liver hepatocyte populations. Taken all together, the results of the present study suggest that recovery of human hepatocytes after isolation prior to progressive freezing should allow human hepatocyte banking for use in pharmacotoxicology and cell therapy research purposes.     

In vitro regulation of IgA subclass production. III. Selective transformation of IgA1 producing cells by Epstein-Barr virus

In past experiments, using limited dilution analysis, we have demonstrated that a high percentage of immunoglobulin-secreting clones derived from Epstein-Barr virus- (EBV) stimulated lymphocytes secrete IgA. To further characterize the IgA produced by these clones, the IgA subclass of supernatants from clones stimulated 4 to 6 wk previously with EBV was determined by radioimmunoassay. All of 17 IgA-producing clones secreted IgA1; none secreted IgA2. Because we have shown that surface IgM+ (sIgM+) B cells are an enriched source of IgA2 plasma cell precursors, panning techniques were used to purify sIgM+ B cells from tonsils. Of 103 clones derived from these sIgM+ B cells, 102 secreted IgA1 and only one secreted IgA2. The relative absence of IgA2-producing clones could not be attributed to an absence of EBV receptors on IgA2 cells. A mean of 84 +/- 4% of freshly isolated IgA2 B cells and 78 +/- 6% of IgA1 B cells could be stained with a monoclonal antibody binding the EBV receptor; and there was no failure of EBV to infect IgA2 plasma cells precursors. Of IgA2 plasma cells derived from peripheral blood lymphocytes stimulated 7 days previously with EBV, 54 +/- 7% were positive for the EBV nuclear antigen, compared with 54 +/- 18% of IgA1 plasma cells from the same cultures. Seven days after EBV stimulation, a mean of 25% of the total IgA plasma cells were positive for cytoplasmic IgA2, whereas by 21 days after stimulation only 7% were positive for IgA2. This shift in the proportions of IgA1 and IgA2 plasma cells could be attributed to a failure of the IgA2 plasma cell number to increase after 10 days in culture. There was no evidence for selective suppression of IgA2 production by T cells or selective lysis of IgA2 plasma cells by infectious EBV particles. These results demonstrate that although precursors for both IgA1- and IgA2-producing cells can be stimulated to differentiate in response to EBV, there is preferential transformation of IgA1-producing cells.     

Long-term MHC class II presentation of the EBV lytic protein BHRF1 by EBV latently infected b cells following capture of BHRF1 antigen

Although T lymphocytes are considered essential for the control of EBV infection, it remains uncertain how this control occurs. We previously reported unexpected killing of EBV-transformed B-lymphoblastoid cells (LCLs) that did not express BHRF1 by CD4+ T cells specific for BHRF1, an EBV lytic cycle protein. Using LCLs transformed with an EBV mutant, in which the BHRF1 gene was deleted, we showed that killing of latently infected cells through the recognition of a protein produced during the lytic cycle is due to transfer of BHRF1 from lytically infected to latently infected cells, which occurs in culture. Accordingly, LCLs efficiently presented exogenous BHRF1 protein. Furthermore, we present evidence for persistence of captured BHRF1 Ag for several days. Due to this long-term persistence, repeated loading of suboptimal amounts of BHRF1 led to accumulation of BHRF1 Ags in LCLs and, ultimately, to their optimal recognition by BHRF1-specific CD4+ T cells. These results unveil an MHC class II-dependent pathway that could be important for the control of EBV latent infection through recognition of lytic cycle Ags.     

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.     

Relationship between immunoglobulin production and immortalization by Epstein Barr virus

After infection with Epstein Barr virus (EBV), human B lymphocytes actively secrete immunoglobulin (Ig) and are immortalized to become long-term cell lines. In these studies, we investigated the relationship between these virally induced processes utilizing limiting dilution culture techniques, and asked whether all B cells stimulated by EBV to secrete Ig are also immortalized. The activation of B cells by EBV resulting in Ig production and immortalization involved a single precursor cell, required live viral particles, and was independent of immunity to EBV by the lymphocyte donor. However, the precursor frequency of B cells activated to secrete Ig (mean 4.7%) was higher than the precursor frequency of B cells activated to long-term in vitro growth (mean 2.1%). When examined at a single cell level, it appeared that although the vast majority of the immortalized B cells also secrete Ig, only approximately 50% of the B cell precursors induced by EBV to secrete Ig go on to form long-term cell lines. In addition, although immortalized B cell clones producing all major classes of Ig were detected, IgM-committed precursors were more likely to become immortal than were precursors committed to IgG or IgA production. In contrast to these findings in B cells freshly infected with EBV, Ig production was almost always associated with evidence of long-term growth when B cells from previously established EBV-induced B cell lines were tested in identical limiting dilution cultures. Thus, after infection with EBV, human B cells can either become transiently activated to proliferate and to secrete Ig, or become transformed into long-term cell lines most of which produce Ig.     

Epstein-Barr virus lytic infection is required for efficient production of the angiogenesis factor vascular endothelial growth factor in lymphoblastoid cell lines

Although Epstein-Barr virus (EBV)-associated malignancies are primarily composed of cells with one of the latent forms of EBV infection, a small subset of tumor cells containing the lytic form of infection is often observed. Whether the rare lytically infected tumor cells contribute to the growth of the latently infected tumor cells is unclear. Here we have investigated whether the lytically infected subset of early-passage lymphoblastoid cell lines (LCLs) could potentially contribute to tumor growth through the production of angiogenesis factors. We demonstrate that supernatants from early-passage LCLs infected with BZLF1-deleted virus (Z-KO LCLs) are highly impaired in promoting endothelial cell tube formation in vitro compared to wild-type (WT) LCL supernatants. Furthermore, expression of the BZLF1 gene product in trans in Z-KO LCLs restored angiogenic capacity. The supernatants of Z-KO LCLs, as well as supernatants from LCLs derived with a BRLF1-deleted virus (R-KO LCLs), contained much less vascular endothelial growth factor (VEGF) in comparison to WT LCLs. BZLF1 gene expression in Z-KO LCLs restored the VEGF level in the supernatant. However, the cellular level of VEGF mRNA was similar in Z-KO, R-KO, and WT LCLs, suggesting that lytic infection may enhance VEGF translation or secretion. Interestingly, a portion of the vasculature in LCL tumors in SCID mice was derived from the human LCLs. These results suggest that lytically infected cells may contribute to the growth of EBV-associated malignancies by enhancing angiogenesis. In addition, as VEGF is a pleiotropic factor with effects other than angiogenesis, lytically induced VEGF secretion may potentially contribute to viral pathogenesis.     

The ZIIR element of the Epstein-Barr virus BZLF1 promoter plays a central role in establishment and maintenance of viral latency

The Epstein-Barr virus (EBV) BZLF1 gene encodes the immediate-early (IE) protein Zta, which plays a central role in regulating the switch between viral latency and lytic replication. A silencing element, ZIIR, is located between the ZID and ZII positive regulatory elements in the BZLF1 promoter Zp. We report here the phenotypes of variants of EBV strain B95.8 containing base substitution mutations in this ZIIR element. HEK293 cells infected with ZIIR mutant (ZIIRmt) virus produced at least 20-fold more viral IE Zta and Rta and early (E) EAD protein than did cells infected with the parental wild-type (WT) virus, leading to viral DNA replication and production of infectious virus. However, ZIIR mutant virus was 1/10 as efficient as WT virus in establishing proliferating B-cell clones following infection of human primary blood B cells. The ZIIRmt-infected lymphoblastoid cell lines (LCLs) that did grow out exhibited a phenotype similar to the one observed in 293 cells, including marked overproduction of IE and E gene products relative to WT-infected LCLs and lytic replication of the viral genome. Incubation of the ZIIRmt-infected LCLs with the chemical inducer 12-O-tetradecanoyl-phorbol-13-acetate (TPA) led to much greater activation of Zp than did the same treatment of WT- or ZVmt-infected LCLs. Furthermore, a protein kinase C (PKC) inhibitor, bis-indolylmaleimide, eliminated this activation by TPA. Thus, we conclude that ZIIR is a potent silencing element of Zp; it plays a key role in establishment and maintenance of EBV latency by inhibiting activation of Zp through the PKC signal transduction pathway.     

Latent Membrane Protein LMP2A Impairs Recognition of EBV-Infected Cells by CD8+ T Cells

The common pathogen Epstein-Barr virus (EBV) transforms normal human B cells and can cause cancer. Latent membrane protein 2A (LMP2A) of EBV supports activation and proliferation of infected B cells and is expressed in many types of EBV-associated cancer. It is not clear how latent EBV infection and cancer escape elimination by host immunity, and it is unknown whether LMP2A can influence the interaction of EBV-infected cells with the immune system. We infected primary B cells with EBV deleted for LMP2A, and established lymphoblastoid cell lines (LCLs). We found that CD8+ T cell clones showed higher reactivity against LMP2A-deficient LCLs compared to LCLs infected with complete EBV. We identified several potential mediators of this immunomodulatory effect. In the absence of LMP2A, expression of some EBV latent antigens was elevated, and cell surface expression of MHC class I was marginally increased. LMP2A-deficient LCLs produced lower amounts of IL-10, although this did not directly affect CD8+ T cell recognition. Deletion of LMP2A led to several changes in the cell surface immunophenotype of LCLs. Specifically, the agonistic NKG2D ligands MICA and ULBP4 were increased. Blocking experiments showed that NKG2D activation contributed to LCL recognition by CD8+ T cell clones. Our results demonstrate that LMP2A reduces the reactivity of CD8+ T cells against EBV-infected cells, and we identify several relevant mechanisms.     

Phenotype, frequency, and EBV responsiveness of human marrow B and pre-B cells

We have purified subpopulations of B lineage cells from human adult (rib) bone marrow by cell sorting and panning. Limiting dilution analysis was then used for a clonal analysis of cells able to secrete IgG, IgA, or IgM spontaneously or after infection with EBV. Nonproliferating, high rate IgG or IgA producers occurred at frequencies of about one per 1000 marrow mononuclear cells. Their frequency and Ig production was unaffected by EBV, and they appeared not to express EBNA after exposure to EBV. These cells were Ia+, B1+, and over 85% expressed sIg of the IgM/D (up to 75%) and/or IgG/A isotypes (40 to 60%). B cells committed to the secretion of IgM represent 2 to 10% of marrow B lymphocytes. They were found to be Ia+/B1+/B2+/CALLA- and C3b receptor (CR3)-cells, and most (greater than 90%) required infection with EBV and proliferation to develop into IgM-producing lymphocytes. Thirty to 40% of these cells did not express Ig (H or L chain) on their surface, and therefore resembled pre-B cells at the beginning of the 4- to 5-wk culture period. Proliferating pre-B cells from adult human marrow have been described, but their conversion into IgM-producing cells has not been formally demonstrated. Although EBV induces IgM production, the expression of EBNA, and several rounds of cell division in these cells, the induction of stable (greater than 5 wk) growth transformation represents a rare event in these pre-B cells: in several thousand limiting dilution wells, not a single culture of sIg-cells showed stable growth transformation. The dichotomy between EBV-induced high-rate IgM responses and absent growth transformation discriminates activation and transformation as distinct aspects of EBV-induced B cell "responses", and suggests that cellular properties play critical roles for viral transformation. We propose a model in which cellular target genes for transforming sequences in the EBV genome are transiently expressed during B cell differentiation.     

Reduced IRF4 expression promotes lytic phenotype in Type 2 EBV-infected B cells

Humans are infected with two types of EBV (Type 1 (T1) and Type 2 (T2)) that differ substantially in their EBNA2 and EBNA 3A/B/C latency proteins and have different phenotypes in B cells. T1 EBV transforms B cells more efficiently than T2 EBV in vitro, and T2 EBV-infected B cells are more lytic. We previously showed that both increased NFATc1/c2 activity, and an NFAT-binding motif within the BZLF1 immediate-early promoter variant (Zp-V3) contained in all T2 strains, contribute to lytic infection in T2 EBV-infected B cells. Here we compare cellular and viral gene expression in early-passage lymphoblastoid cell lines (LCLs) infected with either T1 or T2 EBV strains. Using bulk RNA-seq, we show that T2 LCLs are readily distinguishable from T1 LCLs, with approximately 600 differentially expressed cellular genes. Gene Set Enrichment Analysis (GSEA) suggests that T2 LCLs have increased B-cell receptor (BCR) signaling, NFAT activation, and enhanced expression of epithelial-mesenchymal-transition-associated genes. T2 LCLs also have decreased RNA and protein expression of a cellular gene required for survival of T1 LCLs, IRF4. In addition to its essential role in plasma cell differentiation, IRF4 decreases BCR signaling. Knock-down of IRF4 in a T1 LCL (infected with the Zp-V3-containing Akata strain) induced lytic reactivation whereas over-expression of IRF4 in Burkitt lymphoma cells inhibited both NFATc1 and NFATc2 expression and lytic EBV reactivation. Single-cell RNA-seq confirmed that T2 LCLs have many more lytic cells compared to T1 LCLs and showed that lytically infected cells have both increased NFATc1, and decreased IRF4, compared to latently infected cells. These studies reveal numerous differences in cellular gene expression in B cells infected with T1 versus T2 EBV and suggest that decreased IRF4 contributes to both the latent and lytic phenotypes in cells with T2 EBV.     

Epstein-Barr virus nuclear antigen leader protein induces expression of thymus- and activation-regulated chemokine in B cells

Epstein-Barr virus (EBV) nuclear antigen leader protein (EBNA-LP) plays a critical role in transformation of primary B lymphocytes to continuously proliferating lymphoblastoid cell lines (LCLs). To identify cellular genes in B cells whose expression is regulated by EBNA-LP, we performed microarray expression profiling on an EBV-negative human B-cell line, BJAB cells, that were transduced by a retroviral vector expressing the EBV EBNA-LP (BJAB-LP cells) and on BJAB cells that were transduced with a control vector (BJAB-vec cells). Microarray analysis led to the identification of a cellular gene encoding the CC chemokine TARC as a novel target gene that was induced by EBNA-LP. The levels of TARC mRNA expression and TARC secretion were significantly up-regulated in BJAB-LP compared with BJAB-vec cells. Induction of TARC was also observed when a subline of BJAB cells was converted by a recombinant EBV. Among the EBV-infected B-cell lines with the latency III phenotype that were tested, the LCLs especially secreted significantly high levels of TARC. The level of TARC secretion appeared to correlate with the level of full-length EBNA-LP expression. These results indicate that EBV infection induces TARC expression in B cells and that EBNA-LP is one of the viral gene products responsible for the induction.