Recovery of transforming EBV from non-producer cells after superinfection with non-transforming P3HR-1 EBV

Epstein-Barr virus stimulates torque teno virus replication: a possible relationship to multiple sclerosis

Viral infections have been implicated in the pathogenesis of multiple sclerosis. Epstein-Barr virus (EBV) has frequently been investigated as a possible candidate and torque teno virus (TTV) has also been discussed in this context. Nevertheless, mechanistic aspects remain unresolved. We report viral replication, as measured by genome amplification, as well as quantitative PCR of two TTV-HD14 isolates isolated from multiple sclerosis brain in a series of EBV-positive and -negative lymphoblastoid and Burkitt's lymphoma cell lines. Our results demonstrate the replication of both transfected TTV genomes up to day 21 post transfection in all the evaluated cell lines. Quantitative amplification indicates statistically significant enhanced TTV replication in the EBV-positive cell lines, including the EBV-converted BJAB line, in comparison to the EBV-negative Burkitt's lymphoma cell line BJAB. This suggests a helper effect of EBV infections in the replication of TTV. The present study provides information on a possible interaction of EBV and TTV in the etiology and progression of multiple sclerosis.

Episomal replication timing of gamma-herpesviruses in latently infected cells

This study addresses the timing of gammaherpesviral episomal DNA replication with respect to the cell cycle. For the first time we analyzed a rhadinovirus, the prototype Herpesvirus saimiri (HVS), and compared it to the lymphocryptovirus Epstein-Barr virus (EBV). Newly synthesized DNA of latently infected B- or T-cells was first BrdU-labeled; then we sorted the cells corresponding to cell cycle phases G(0/1), G(2/M), and S (4 fractions S(1)-S(4)) and performed anti-BrdU chromatin immunoprecipitation. Next, DNA of different viral gene loci was quantitatively detected together with cellular control genes of known replication time. The sensitive technique is further enhanced by an internal coprecipitation standard for increased precision. Both gammaherpesviruses replicated very early in S-phase, together with cellular euchromatin. Our work suggests that early S-phase DNA replication is a general characteristic of episomal herpesviral genomes.

Molecular virology of Epstein-Barr virus

Epstein-Barr virus (EBV) interacts with its host in three distinct ways in a highly regulated fashion: (i) EBV infects human B lymphocytes and induces proliferation of the infected cells, (ii) it enters into a latent phase in vivo that follows the proliferative phase, and (iii) it can be reactivated giving rise to the production of infectious progeny for reinfection of cells of the same type or transmission of the virus to another individual. In healthy people, these processes take place simultaneously in different anatomical and functional compartments and are linked to each other in a highly dynamic steady-state equilibrium. The development of a genetic system has paved the way for the dissection of those processes at a molecular level that can be studied in vitro, i.e. B-cell immortalization and the lytic cycle leading to production of infectious progeny. Polymerase chain reaction analyses coupled to fluorescent-activated cell sorting has on the other hand allowed a descriptive analysis of the virus-host interaction in peripheral blood cells as well as in tonsillar B cells in vivo. This paper is aimed at compiling our present knowledge on the process of B-cell immortalization in vitro as well as in vivo latency, and attempts to integrate this knowledge into the framework of the viral life cycle in vivo.

Identification of a naturally occurring recombinant Epstein-Barr virus isolate from New Guinea that encodes both type 1 and type 2 nuclear antigen sequences

In this report we describe an Epstein-Barr virus isolate, derived from the peripheral blood lymphocytes of a healthy adult from Papua New Guinea, that is a recombinant of the two major Epstein-Barr virus types, encoding type 1 Epstein-Barr nuclear antigen 2 (EBNA2) sequences, and type 2 EBNA3, EBNA4, and EBNA6 sequences.

Effects of defective interfering viruses on virus replication and pathogenesis in vitro and in vivo

DI viruses and defective viruses generally are widespread in nature. Laboratory studies show that they can sometimes exert powerful disease-modulating effects (either attenuation or intensification of symptoms). Their role in nature remains largely unexplored, despite recent suggestive evidence for their importance in a number of systems.

Defective viral DNA in Epstein-Barr virus-associated oral hairy leukoplakia

Defective Epstein-Barr virus (EBV) has a deleted and rearranged genome (termed het DNA) that disrupts latency and induces standard EBV to replicate in vitro. We used the polymerase chain reaction to detect, in 2 of 10 patient samples, the junction of abnormally juxtaposed EBV DNA fragments BamHI W and Z, a genomic rearrangement responsible for the biologic activity of het DNA. By sequence analysis, the junction in wild-type defective DNA appears to be similar but not identical to the recombination in the DNA of laboratory strain P3HR-1. The presence of this marker for het DNA in the epithelial lesions of two patients suggests a role for defective EBV in a human pathologic process.

Detection of a second widespread strain of Epstein-Barr virus

The prevalence of Epstein-Barr virus (EBV) type B, which was previously found mainly in equatorial Africa, was investigated with the polymerase chain reaction in a population of healthy adults in Memphis, Tennessee. EBV was detected in the throat washings of 34 (22%) of 157 randomly selected donors, 14 (41%) of whom had type B virus and 17 (50%) type A; 3 donors (9%) had both strains. 18 additional adults with human immunodeficiency virus (HIV-1) infection and 6 severely immunocompromised children were also investigated. Results indicated that type B EBV is widespread in nature and may be reactivated by immunodeficiency.

The transforming prototype of Epstein-Barr virus (B95-8) is also a lytic virus

The B95-8 isolate of the Epstein-Barr virus (EBV) has been described as a non-lytic transforming virus. We have performed experiments in order to determine if the B95-8 EBV is capable of super-infecting and replicating in EBV-genome-positive non-producer lymphoblastoid cells. Using concentrates of B95-8 EBV, prepared from 6 different B95-8 cell lines treated with 12-O-tetradecanoylphorbol-13-acetate (TPA), we demonstrated that virus concentrates could transform human or cotton-top tamarin B-lymphocytes and also lytically replicate in Raji cells, inducing EBV antigens and infectious virus. While the virus obtained from B95-8 super-infected Raji cells was able to transform cord-blood lymphocytes (CBLs) and super-infect Raji cells, transformation was abortive, with cell cultures only growing for up to 6 weeks. Transformation titers of the B95-8 virus concentrates ranged from 10(5) to greater than 10(8) transforming units/ml; early antigen (EA) induction ranged from 1% to 50% after superinfection of Raji cells, depending on the virus stock used, as determined by immunofluorescence. Southern blot analysis was carried out on the DNA prepared from B95-8 cells and virion DNA. The results were consistent with the published EcoRI restriction pattern for B95-8 EBV. The issue of whether the B95-8 cells produce virions with a dual biological phenotype or, rather, 2 biologically distinct viruses, is addressed.

Purification and characterization of the Epstein-Barr virus nuclear antigen 2 using monoclonal antipeptide antibodies

The Epstein-Barr virus (EBV) nuclear antigen 2 (EBNA-2) is the only one of the EBNA proteins to have been implicated as an EBV-encoded transforming protein. More detailed studies of this protein have been hampered by the lack of EBNA-2-specific monoclonal antibodies (MAbs) and of purified protein. To overcome these problems, we isolated 5 hybridomas producing MAbs reactive with an 18 residue synthetic peptide corresponding to the carboxyterminus of EBNA-2. Four of the 5 MAbs were specifically reactive with EBNA-2 in its denatured form on immunoblots. The 5th antibody (115E) was reactive with the native form of EBNA-2. By using a one-step immunoaffinity purification method with 115E cross-linked to protein-A-Sepharose, we purified EBNA-2 to homogeneity, i.e., more than 1,200-fold, from Burkitt lymphoma cell extracts. A major 32-kDa associated protein and a less abundant 17-kDa protein were co-purified with EBNA-2. Immunoprecipitation with 115E from 35S-methionine-labelled cell extracts showed that the 32-kDa protein co-precipitated with EBNA-2 from EBV-positive cells, but was not detectable in immunoprecipitates of EBV-negative cells. When the immunoprecipitates or the purified proteins were immunoblotted with EBV-immune sera, only EBNA-2 was reactive, indicating that the associated proteins are of cellular origin. Immunoprecipitation of cells labelled with 32P-orthophosphate showed that EBNA-2, but not the associated proteins, is a phosphoprotein. The expression level of EBNA-2 varied between different EBV-carrying cell lines, as measured by a 2-site ELISA based on antibody 115E. In indirect immunofluorescence, the 115E MAb gave an EBNA-2-specific characteristic granular staining pattern. These characteristics of EBNA-2 resemble those of other viral transforming proteins.

Two strains of Epstein-Barr virus (B95-8 and a P3HR-1 subclone) that lack defective genomes induce early antigen and cause abortive infection of Raji cells

The heterogeneity of Epstein-Barr virus (EBV) obtained from P3HR-1 cells has permitted derivation of a distinct subclone of P3HR-1 (L. Heston, M. Rabson, N. Brown, and G. Miller, Nature (London) 295:160-163, 1982). We have analyzed the biologic properties and genomic structure of this subclonal virus (clone 13) compared with those of parental P3HR-1 and B95-8 viruses. Synthesis of EBV compared with those of parental P3HR-1 and B95-8 viruses. Synthesis of EBV proteins in Raji cells superinfected with virus derived from P3HR-1, clone 13, and B95-8 was analyzed both by fluorography of radiolabeled proteins and by immunoblotting. Highly concentrated preparations of clone 13 and B95-8 virus induced most of the spectrum of EBV proteins in Raji cells with the exception of the 145,000-, 140,000-, and 110,000-molecular-weight proteins, which were either undetectable or reduced. Moreover, both clone 13 and B95-8 viruses also induced the same patterns of early antigen diffuse components as the parental P3HR-1 virus did. However, only P3HR-1 virus could induce EBV DNA synthesis in superinfected Raji cells, as determined both by buoyant density centrifugation and by in situ cytohybridization with biotinylated recombinant EBV DNA probes. Defective heterogeneous molecules present in P3HR-1 virus have been implicated in early antigen induction after superinfection of Raji cells. Therefore, Southern blots of clone 13, P3HR-1, and B95-8 viruses were hybridized to recombinant EBV fragments representing the sequences contained within the defective molecules in P3HR-1. The parental P3HR-1 contained the previously described defective molecules. No evidence for defective molecules was found in clone 13 or B95-8 viruses. These data indicate that concentrated preparations of both clone 13 and B95-8 viruses can induce abortive infection in Raji cells, but while the defective molecules are not needed for induction of early antigen diffuse components, they may be required for the induction of viral DNA synthesis.

Lymphoblastoid cell lines and Burkitt-lymphoma-derived cell lines differ in the expression of a second Epstein-Barr virus encoded nuclear antigen

Twenty-seven Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines and 27 EBV-carrying Burkitt-lymphoma-derived lines were analyzed for expression of the second EBV-encoded nuclear antigen (EBNA-2) by immunoblotting and anticomplement immunofluorescence with EBNA-2-specific sera. While all lymphoblastoid cell lines expressed EBNA-2, only 10 of the 27 BL lines were EBNA-2-positive. Comparison of the EBNA-2 coding BamHI W-, Y- and H-fragments of EBV-DNA in the different cell lines by restriction enzyme analysis suggests that EBNA-2 negativity is due either to sequence diversity or to a deletion in the BamHI WYH region.

An Epstein-Barr virus (EBV)-determined nuclear antigen (EBNA5) partly encoded by the transformation-associated Bam WYH region of EBV DNA: preferential expression in lymphoblastoid cell lines

Four peptides were synthesized on the basis of amino acid sequences deduced from a highly spliced transcript encoded by the Bam W, Y, and H fragments of the Epstein-Barr virus (EBV) genome [Bodescot, M., Chambraud, J. B., Farrell, P. J. & Perricaudet, M. (1984) EMBO J. 3, 1913-1917]. Rabbit antisera against three of the four peptides identified a nuclear polypeptide that varied between 22 and 70 kDa in molecular size. Four of 20 EBV-positive human sera contained antibodies against this polypeptide. Since this is the fifth EBV-determined nuclear antigen (EBNA) discovered in growth-transformed cells, it is designated EBNA5. The antigen was detected in virus nonproducer lines (less than 0.01% EBV early antigen expression) and is thus not dependent on the viral cycle. It was differentially expressed depending on the origin of the lines. All 10 lymphoblastoid cell lines tested expressed EBNA5, but it could not be detected in 10 of 11 EBV-carrying Burkitt lymphoma lines. Infection of tonsillar lymphocytes with the B95-8 strain of EBV induced six EBNA5-specific polypeptides that varied between 41 and 70 kDa in molecular size with regular increments of 6 kDa. This may be due to the fact that the EBNA5 coding sequence includes the Bam W internal repeat. Parallel infection of the EBV-negative Burkitt lymphoma line Ramos with the same viral substrain did not induce detectable levels of EBNA5, nor was this antigen present in permanently EBV-converted Ramos sublines. These findings imply that the expression of the viral genome varies among B cells having different phenotypes.

Transformation by Epstein-Barr virus requires DNA sequences in the region of BamHI fragments Y and H

Eight independent recombinant Epstein-Barr virus genomes, each of which was a transforming strain, were made by superinfecting cell lines containing Epstein-Barr virus DNA (Raji or B95-8 strain) with a nontransforming virus (P3HR1 strain). A knowledge of the constitution of each transforming recombinant allowed the localization of the defect in the genome of the nontransforming parent to a 12-megadalton sequence within the EcoRI A fragment. Within this region, the nontransforming virus has a deletion of the BamHI Y fragment and about half of the sequences in the adjacent BamHI H fragment. The present data suggest that this deletion is responsible for the nontransforming phenotype. Furthermore, mapping a deletion in one of the recombinant genomes allowed the conclusion that a sequence (comprising about 20% of the Epstein-Barr virus genome) from the center of BamHI-D to BamHI-I' is not necessary for the maintenance of transformation by Epstein-Barr virus.

Characterization of a second Epstein-Barr virus-determined nuclear antigen associated with the BamHI WYH region of EBV DNA

The Epstein-Barr virus-determined nuclear antigen (EBNA) is the only known virally-determined component that is regularly associated with EBV-transformed cells. A main component of EBNA, herein designated EBNA-1, has been conclusively localized to the BamHI K fragment of the viral genome. EBNA-1 is present in all EBV-carrying cell lines so far studied. Our current study deals with a second component. We have found that the EBNA reaction detected by anti-complement immunofluorescence (ACIF) in Burkitt lymphoma lines Daudi, Jijoye, and P3HR-1 could be completely removed by preabsorption of sera with any one of these 3 lines, when tested against any other of them. The same absorbed sera still gave a brilliant nuclear staining against other EBV-carrying lines, e.g. Raji or B95-8. The 3 lines in the first category carry EBV genomes that have deletions in the BamHI WYH region of the EBV genome. This region is intact in the second group of lines. This result is interpreted as showing the existence of 2 different ACIF-stainable EBV-determined nuclear antigens, one of which is associated with the BamHI WYH region. We designate this antigen as EBNA-2. We found that the two different EBNAs are different with regard to their association with metaphase chromosomes. In lines positive for both EBNA subtypes, metaphase chromosomes gave brilliant EBNA-1 staining, but could not be stained for EBNA-2, indicating differences in chromatin association of the two EBNAs. An 86 kd polypeptide was identified by immunoblotting of DNA-binding proteins from EBV-transformed lymphoid cell lines. EBV-specificity of the polypeptide was demonstrated by the presence of antibodies against this polypeptide in antisera from a population of EBV-seropositive donors, but not from seronegative donors, by the presence of the polypeptide itself in EBV-carrying but not in EBV-negative cell lines and by the appearance of antibodies against this polypeptide during the course of infectious mononucleosis (IM). The polypeptide was absent from the EBV-carrying P3HR-1, Daudi and Jijoye cell lines, which suggested that it may be encoded by the BamHI WYH region that is deleted from the viral substrains carried by these lines.

A putative transforming gene of Jijoye virus differs from that of Epstein-Barr virus prototypes

The P3HR-1 strain of Epstein-Barr virus (EBV), a nontransforming clonal derivative of Jijoye (EBV), is characterized by a deletion of 6.6 kb involving part of the BamHI-W repeats and the adjacent region including the NotI repeats. In the transforming parental Jijoye virus this region differs from the corresponding regions in B95-8 or M-ABA virus. The HindIII-B fragments which carry this region from both Jijoye and prototype M-ABA (EBV) viruses have been cloned and subclones have been constructed which contain the left-hand part of HindIII-B from the HindIII to the BglII site (BglII-delta C fragment). By restriction enzyme analysis the inserts were found to be of equal size (6.3 kb) but to differ in their restriction enzyme pattern. Heteroduplexes formed under stringent conditions in the presence of T4 gene 32 protein revealed a substitution loop of 1750 +/- 200 nucleotides. Heteroduplex formation under nonstringent conditions showed that the substituted sequences are partially homologous to each other, with the regions of nonhomology confined to three distinct areas of 100 to 200 nucleotides. The partial homology observed between both regions indicates that they have evolved from a common ancestor. By hybridization of a Jijoye virus subclone containing only sequences of the substituted region to Northern blots a 2.8-kb polyadenylated transcript was detected indicating that the substituted region is expressed in Jijoye cells.

Epstein-Barr virus (P3HR-1) defective DNA codes for components of both the early antigen and viral capsid antigen complexes

A set of lambda phages containing overlapping fragments of Epstein-Barr virus (EBV) defective DNA has been cloned from P3HR-1-superinfected Raji cells. Mapping data obtained using these cloned DNA fragments confirmed the structure of P3HR-1 defective DNA previously deduced directly from virion DNA (M.-S. Cho, G. W. Bornkamm, and H. zur Hausen, 1984, J. Virol., in press). The ability of the cloned defective DNA fragments to induce EBV antigens in transfected baby hamster kidney (BHK) cells was tested using indirect immunofluorescence assays. Up to 5% of those cells receiving a defective DNA fragment BamHI-W'C' transiently expressed a de novo nuclear antigen which was identified as being a component of the EAD complex by its reactivity with characterized EBV-positive human sera. A 20-kb clone of P3HR-1 defective DNA (EcoRI-C1) was found to induce the synthesis of a component of the VCA complex. One percent of cells transfected with this clone showed cytoplasmic fluorescence when tested with either VCA+ human sera or EBV anti-VCA monoclonal antibody. Subcloning of the EcoRI-C1 fragment localized the VCA gene to a 4.1-kb segment which maps within the BamHI-A fragment of the standard genome. This segment contains a single large open reading frame of 2.6 kb (B. Barrell, A. Bankier, R. Baer, P. Biggin, P. Deininger, P. Farrell, T. Gibson, G. Hatfull, G. Hudson, S. Stachwell, and C. Sequin, 1984, Nature (London), in press). None of the defective DNA clones were capable of inducing EBV-specific nuclear antigens (EBNAs) which is consistent with the absence of the known EBNA coding regions from the defective genome.

Structure of defective DNA molecules in Epstein-Barr virus preparations from P3HR-1 cells

Epstein-Barr virus (EBV), isolated from P3HR-1 cells, induces early antigen and viral capsid antigen upon infection of human B-lymphoblasts. The strong early antigen- and viral capsid antigen-inducing activity is only observed in P3HR-1 virus preparations harboring particles with defective genomes, suggesting that this biological activity is directly associated with the defective DNA population. After infection of EBV genome-carrying Raji or EBV genome-negative BJAB cells, defective genomes of P3HR-1 EBV DNA are replicated in excess, depending on the multiplicity of infecting EBV particles. Hybridization of the DNA from such infected cells with 32P-labeled EBV DNA after HindIII cleavage reveals six hypermolar fragments. Mapping of these fragments shows that they form one defective genome unit containing four nonadjacent regions (alpha, beta, gamma, and delta) of the nondefective P3HR-1 EBV DNA. Two of the segments (alpha and beta) contain ca. 17 and 13 megadaltons, respectively, from the terminal regions of the P3HR-1 genome, whereas the two smaller segments (gamma and delta) contain ca. 3.7 and 3.0 megadaltons, respectively, originating from the central portion of the genome. In the defective molecule, the regions gamma and delta are present in the opposite orientation compared with nondefective P3HR-1 EBV DNA. Tandem concatemers are formed by fusion of the alpha and beta regions. Our model suggests that tandem concatemers of three defective genome units can be packaged into virions in P3HR-1 cells.

Identification of a rare Epstein-Barr virus variant that enhances early antigen expression in Raji cells

Early antigens (EAs) are made when the P3J-HR-1 strain of Epstein-Barr virus (EBV) infects cells that already harbor latent EB viral genomes. We wished to identify EBV genes that might participate in induction of EAs. We have recently isolated from the HR-1 line EB viral variants that are unable to induce EAs. We have now isolated a clone of HR-1 cells that releases virus with the capacity to induce EA. We compared the genome of the EB variant that possesses the capacity to induce EA with that of a variant that is unable to induce EA and with parental stock that was the source of both different biotypes of EBV. The variant that is able to induce EA contains, in molar or greater quantities, additional fragments of EBV DNA not found in the variant that lacks that capacity. These same DNA fragments are present in submolar quantities in the parental DNA, indicating that they represent a subpopulation in the parental viral DNA mixture. We thus provide evidence that EA induction is brought about by unusual forms of EBV DNA that are likely to act by regulating expression of the genome.

Non-immortalizing P3J-HR-1 Epstein-Barr virus: a deletion mutant of its transforming parent, Jijoye

The P3J-HR-1 strain of Epstein-Barr virus (EBV) fails to immortalize human lymphocytes. We wished to understand the nature of the genomic alterations which correlated with the loss of this ability. As a first step, the heterogeneity of DNA molecules in the P3J-HR-1 line was eliminated by cell cloning. Then a physical map was prepared of virion DNA from one cell clone, designated FF452-3. By comparison with the genomes of two EBVs, B95-8 and FF41, which are competent to immortalize lymphocytes, we identified a total of eight modifications of BamHI and EcoRI restriction endonuclease fragments of EBV (FF452-3) DNA consisting of insertions, deletions, or loss of a restriction endonuclease recognition site. To determine which of these alterations might be responsible for the loss of transforming phenotype, we examined homologous DNA fragments of the Jijoye strain of EBV, the progenitor of the HR-1 strain which still retains the ability to immortalize lymphocytes. We also studied viral DNA in lymphocytes transformed in vitro by Jijoye virus. Six of the eight alterations were found both in Jijoye and in clonal HR-1 DNA and were presumably genomic traits characteristic of this lineage of EBV. A small deletion in the BamHI-K fragment of HR-1 DNA was not found in Jijoye virion DNA, but this deletion was present in intracellular Jijoye DNA. Thus only one major genomic lesion in HR-1 DNA, a deletion of at least 2.4 x 10(6) molecular weight of DNA from a fused BamHI-H-Y fragment, consistently distinguished Jijoye DNA from its non-immortalizing P3J-HR-1 derivative. This deletion is likely to affect EBV genes which are directly or indirectly involved in immortalizing lymphocytes.

Deletion of the nontransforming Epstein-Barr virus strain P3HR-1 causes fusion of the large internal repeat to the DSL region

The nontransforming Epstein-Barr virus (EBV) strain P3HR-1 is known to have a deletion of sequences of the long unique region adjacent to the large internal repeats. The deleted region is believed to be required for initiation of transformation. To establish a more detailed map of the deletion in P3HR-1 virus, SalI-A of the transforming strain M-ABA and of P3HR-1 virus was cloned into the cosmid vector pHC79 and multiplied in Escherichia coli. The cleavage sites for BamHI, BglII, EcoRI, PstI, SacI, SacII, and XhoI were determined in the recombinant plasmid clones. Analysis of the boundary between large internal repeats and the long unique region showed that in M-ABA (EBV) the transition is different from that in B95-8 virus. The map established for SalI-A of P3HR-1 virus revealed that, in contrast to previous reports, the deletion has a size of 6.5 kilobase pairs. It involves the junction between large internal repeats and the long unique region and includes more than half of the rightmost large internal repeat. The site of the deletion in the long unique region is located between a SacI and a SacII site, about 200 base pairs apart from each other. The sequences neighboring the deletion in the long unique region showed homology to the nonrepeated sequences of the DS(R) (duplicated sequence, right) region. Sequences of the large internal repeat are thus fused to sequences of the DS(L) (duplicated sequence, left) region in P3HR-1 virus DNA under elimination of the DS(L) repeats. Jijoye, the parental Burkitt lymphoma cell line from which the P3HR-1 line is derived by single-cell cloning, is known to produce a transforming virus. Analysis of the Jijoye (EBV) genome with cloned M-ABA (EBV) probes specific for the sequences missing in P3HR-1 virus revealed that the sequences of M-ABA (EBV) BamHI-H2 are not represented in Jijoye (EBV). In Jijoye (EBV) the complete DS(L) region including the DS(L) repeats is, however, conserved. Further analysis of Jijoye (EBV) and of Jijoye virustransformed cell lines will be helpful to narrow down the region required for transformation.

Identification of Epstein-Barr virus strain differences with monoclonal antibody to a membrane glycoprotein

Two monoclonal antibodies directed against Epstein--Barr virus (EBV)-induced membrane antigens (MA) were isolated in this study. On of the monoclonal antibodies, designated 2F5.6, was an IgG2 which, as detected by membrane and fixed cell immunofluorescence, reacted with MA-positive lymphoblastoid cell lines that produced transforming EBV but not with the MA-positive P3HR-1 cell line that produced the lytic, nontransforming strain of this virus. This antibody precipitated the Mr 320,000/350,000 glycoprotein from B-95 virus infected cultures and the Mr 300,000 and 220,000/250,000 glycoproteins from Raji cells superinfected with P3HR-1 virus but did not precipitate any of these EBV-specific glycoproteins from the P3HR-1 cell line. In contrast, the second monoclonal antibody, IgM designated B10.3, reacted with all virus-producing cell lines including the P3HR-1 cell line. The identity of the glycoprotein that serves as the target for this antibody is still unknown. Neither antibody had neutralizing activity against the B-95 or P3HR-1 strain of EBV. These results indicated that the 2F5.6 monoclonal antibody was directed against an antigenic determinant on the major membrane glycoprotein which is common to transforming strains of EBV but absent from the lytic P3HR-1 stain whereas the B10.3 monoclonal antibody was directed against a group-specific EBV-induced membrane determinant.

Multiplicity-dependent biological and biochemical properties of Epstein-Barr virus (EBV) rescued from non-producer lines after superinfection with P3HR-1 EBV

Superinfection of lymphoblastoid cells of EBV non-producer lines with non-transforming P3HR-1 EBV leads to the rescue of transforming virus. At least part of the recovered molecules represent recombinant DNA between superinfecting P3HR-1 EBV and resident viral genomes (Fresen et al., 1979, 1980). With high titer stocks of superinfecting P3HR-1 EBV, viral particles with early antigen (EA)-inducing properties can be rescued, indicating that under these conditions of infection input viral genomes may become replicated. Sequential blot analysis with 32P-P3HR1-EBV DNA of intracellular viral DNA synthesized following infection reveals a multiplicity-dependent pattern. High particle inputs lead to preferential synthesis of certain fragments, independent of infection of either EBV genome-free or EBV genome carrier cells. This accumulation of specific viral sequences indicates defective replication of P3HR-1 EBV DNA.

Re-evaluation of a transforming strain of Epstein-Barr virus from the Burkitt lymphoma cell line, Jijoye

The biological properties of Epstein-Barr virus (EBV) from a Burkitt lymphoma cell line, Jijoye, were examined. the synthesis of virus capsid antigen (VCA) and early antigen (EA) in Jijoye cells was markedly enhanced by shift-down of the temperature of incubation from 37 degrees C to 33 degrees C. Cultures of Jijoye cells at 33 degrees C released a large amount of transforming EBV (10(5.2) of 50% transforming doses/ml) into the culture fluid. However, no infectious virus was produced in all cultures at 37 degrees C during the course of this study. The EBV (Jijoye EBV) from Jijoye line was found to possess only transforming activity, but not EA-inducing activity. Jijoye EBV lacks adsorbing capacity to Jijoye cells, in contrast to P3HR-I EBV which can adsorb to Jijoye cells. The Jijoye cells were highly susceptible to superinfection with P3HR-I EBV as demonstrated by the induction of EA, VCA and infectious EBV. The EBV induced by the P3HR-I EBV superinfection of Jijoye cells has also transforming activity but neither EA-inducing activity nor adsorbing capacity to Jijoye cells.

Mitogenic effect of 12-0 tetradecanoyl phorbol 13-acetate on non-human primate mononuclear cells and in vitro interaction with Epstein-Barr virus transformation

12-0 tetradecanoyl phorbol 13-acetate (TPA), known to promote tumors in mice and also to enhance viral transformation as well as induction of viral antigens, was demonstrated to be mitogenic to peripheral blood mononuclear cells from rhesus monkeys and three species of marmosets. Even though mitogenic responses varied between species and within species, the mitogenic dose response due to TPA was comparable to the response of phytohemagglutinin (PHA-P). A significant synergistic effect of PHA-P and TPA on mononuclear cells from marmosets was evident when they were used together at optimal doses. TPA also increased the efficiency of in vitro transformation of marmoset lymphocytes by Epstein-Barr virus.

Differential inhibition of Epstein-Barr virus induction by the amino acid analogue, L-canavanine

The effect of an amino acid analogue, L-canavanine, on the synthesis of Epstein-Barr virus (EBV) antigens was investigated in lymphoblastoid cells. The analysis revealed that after infection of BJAB and NC-37 cells with P3HR-I EBV synthesis of early antigen (EA) was not affected by canavanine in concentrations up to 8.4 mM. The synthesis of EBV-determined nuclear antigen (EBNA) and of viral capsid antigen (VCA) was significantly inhibited at concentrations higher than 2.8 mM. Spontaneous induction of EA in P3HR-I cells was not affected by canavanine. On the other hand, EA induction by the tumor promoter TPA resulted in some viral antigen induction depending on the time period of TPA exposure. Pretreatment of the cells overnight with canavanine followed by washing and addition of the tumor promoter did not suppress EA induction by TPA. These data support the concept that EA induction by superinfection follows a different pathway from antigen induction by chemical inducers.

Differential inducibility of Epstein-Barr virus in cloned, non-producer Raji cells

Cells of the human lymphoblastoid non-producer line Raji were cloned in soft agar. Individual colonies were isolated and analyzed for their inducibility of the Epstein-Barr virus-associated early antigen (EA). The induction of EA by the tumor promoter TPA varied among the different cell clones. Clones with very high and very low inducibility of the resident Epstein-Barr virus genome were further analyzed. Constant differences in the inducibility of EA were observed after activation by tumor promoters, 5-iododeoxyuridine or antibodies to human IgM. Induction of EA synthesis by superinfection with Epstein-Barr virus from the P3HR-1 line, however, did not vary among the clones tested. No differences in expression of the Epstein-Barr virus-associated nuclear antigen (EBNA) were noted in cells of clones with high or low susceptibility to EA induction. DNA reassociation kinetics demonstrated that Raji cells with high susceptibility to EA induction contained a significantly higher number of Epstein-Barr virus genome equivalents per cell than cells with low susceptibility. Treatment of Raji cells with the tumor promoter TPA did not change the ratio of Epstein-Barr virus-specific DNA to cellular DNA.