Detection of a nuclear, EBNA-type antigen in apparently EBNA-negative Herpesvirus papio (HVP)-transformed lymphoid lines by the acid-fixed nuclear binding technique

Characterization of the Cyno-EBV LMP1 homologue and comparison with LMP1s of EBV and other EBV-like viruses

EBV latent membrane protein 1 (LMP1) is essential for EBV-mediated transformation and has been associated with several cases of malignancies. EBV-like viruses in Cynomolgus monkeys (Macaca fascicularis) have been associated with high lymphoma rates in immunosuppressed monkeys. In the study, the entire coding region of the Cyno-EBV LMP1 gene was cloned, sequenced and expressed in human embryonic kidney (HEK) cells 293. The Cyno-EBV LMP1 homologue sequence predicted a 588 amino acid (a.a.) protein with a short 19 a.a. N-terminus, six transmembrane domains and a long carboxy tail of 404 a.a. The protein contained a series of seven 9 a.a.-tandem repeats and two 20 a.a.-repeats, which harbored two potential TRAF binding motifs, PxQxT/S. These repeats shared no homology with the repeats in any other LMP1. However, the proline-rich sequence GPxxPx(6) found within the 11 a.a.-repeats of EBV LMP1 was conserved in Cyno-EBV carboxy tail and contained two consensus JAK/STAT sequences PxxPxP. A cluster of eight histidine residues was found in proximity to the last transmembrane domain of Cyno-EBV LMP1 and was exploited as a natural protein tag in expression studies. Western blot analysis revealed a major polypeptide of 110 kDa. Comparative functional studies showed that Cyno-EBV LMP1 expressed in HEK 293 cells shares the same ability as EBV LMP1 to induce NFkappaB driven CAT activity.

Simian homologues of Epstein-Barr virus

Gamma-herpesviruses closely related to the Epstein-Barr virus (EBV) are known to naturally infect Old World non-human primates and are classified in the same lymphocryptovirus (LCV) genera. LCV infecting humans and Old World primates share similar biology, and recent studies have demonstrated that these viruses share a similar repertoire of viral genes. Surprisingly, the latent infection genes associated with cell growth transformation demonstrate the most striking sequence divergence, but the functional mechanisms for these genes are generally well conserved. The recent discovery of LCVs naturally infecting New World primates has rewritten the old paradigm of LCV host range restriction to humans and Old World non-human primates, so that these viruses are more widespread than previously believed. However, the New World LCV genome has significant and interesting differences from EBV and other Old World LCVs despite similar biological properties. Thus, the simian homologues of EBV can provide an important animal model for studying LCV pathogenesis, and the similarities and differences that have evolved among these related viruses can provide a unique perspective towards a better understanding of EBV.

Initiation points for cellular deoxyribonucleic acid replication in human lymphoid cells converted by Epstein-Barr virus

Replicon size was estimated in two Epstein-Barr virus (EBV)-negative human lymphoma lines, BJAB and Ramos, and four EBV-positive lines derived from the former ones by infection (conversion) with two viral strains, B95-8 and P3HR-1. Logarithmic cultures were pulse-labeled with [3H]thymidine, and the deoxyribonucleic acid was spread on microscopic slides and autoradiographed by the method of Huberman and Riggs. After developing, replication forks were visualized as silver grain tracks on the autoradiograms. Average replicon size was estimated by scoring the number of replication forks per constant length of deoxyribonucleic acid and by measuring distances between centers of adjacent tracks, followed by detailed statistical analyses. Three of the four EBV-converted cell lines, BJAB/B95-8, Ra/B95-8, and Ra/HRIK, were found to have significantly shorter replicons (41, 21, 54% shorter, respectively), i.e., more initiation points, than their EBV-negative parents. BJAB/HRIK had replicons which were only slightly shorter (11%) than those of BJAB. However, analysis of track length demonstrated that extensive track fusion occurred during the labeling of BJAB/ HRIK, implying that its true average replicon size is shorter than the observed value. The results indicate that in analogy to simian virus 40, EBV activates new initiation points for cellular DNA replication in EBV-transformed cells.

Malignant lymphomas induced by an Epstein-Barr virus-related herpesvirus from Macaca arctoides--a rabbit model

Animal models for Epstein-Barr virus (EBV) are restricted to some species of new-world monkeys which develop malignant lymphoid tumours or benign lymphoproliferative diseases after virus inoculation. Similar pathological features were induced in rabbits by the EBV-related herpesvirus of Macaca arctoides (HVMA). In this study 17 of 32 rabbits infected with varying amounts of HVMA produced from MAL-1 cells developed lymphoproliferative disorders. In 13 rabbits high-grade malignant lymphomas were detected, 4 rabbits revealed the histopathological feature of lymphoid hyperplasia. These lymphoproliferations were shown to be associated with HVMA by PCR and by the expression of EBV-like RNAs (EBER) in 14 and 10 cases, respectively. The homology in the polymerase gene region between DNA from EBV and HVMA, and from HVMA and the malignant tissue was found to be 94.8% and 100%, respectively. All the infected animals produced antibodies to antigens corresponding to early and late EBV proteins. By studying the HVMA expression in MAL-1 cells EBV-like proteins expressed in latency (EBNA1 and EBNA2) and in the lytic cycle (VCA, EA) were detected. Our findings suggested that HVMA caused a symptomatic infection in rabbits with pathological features that fit the conditions of an animal model suitable for testing antiviral drugs and vaccines against EBV.

Plasmid origin of replication of herpesvirus papio: DNA sequence and enhancer function

Herpesvirus papio (HVP) is a lymphotropic virus of baboons which is related to Epstein-Barr virus (EBV) and produces latent infection. The nucleotide sequence of the 5,775-base-pair (bp) EcoRI K fragment of HVP, which has previously been shown to confer the ability to replicate autonomously, has been determined. Within this DNA fragment is a region which bears structural and sequence similarity to the ori-P region of EBV. The HVP ori-P region has a 10- by 26-bp tandem array which is related to the 20- by 30-bp tandem array from the EBV ori-P region. In HVP there is an intervening region of 764 bp followed by five partial copies of the 26-bp monomer. Both the EBV and HVP 3' regions have the potential to form dyad structures which, however, differ in arrangement. We also demonstrate that a transcriptional enhancer which requires transactivation by a virus-encoded factor is present in the HVP ori-P.

Epstein-Barr virus-related herpesvirus from a rhesus monkey (Macaca mulatta) with malignant lymphoma

A herpesvirus (RhEBV) was isolated from a lymphoblastoid cell line (LCL) that became established from a malignant lymphoma in a rhesus monkey. The predominant cell marker in the LCL was that of B lymphocytes. RhEBV-induced viral capsid (VCA) and nuclear antigens (NA) in the LCL were serologically related to similar antigens known to be induced by human Epstein-Barr virus (EBV). RhEBV was of nonhuman primate origin and was clearly differentiated from EBV in the anti-complement immunofluorescence reaction using human and non-human primate sera with antibodies to the NA induced by the respective viruses. While human sera reacted with NA induced by both EBV and RhEBV, monkey sera failed to recognize the NA induced by EBV. RhEBV-induced NA was present in nearly all the cells of a suspension prepared from the tumor tissue mass, but not in the monolayer fibroblasts derived from the tumor tissue or in the blood and lymph-node lymphocytes of clinically healthy animals. RhEBV induced in vitro transformation and establishment of LCLs from peripheral blood lymphocytes of normal rhesus and cynomolgus monkeys but not from those of 6 other non-human primate species tested. The LCLs, with predominant B-lymphocyte markers, established after treatment with RhEBV, all had evidence of the virus infection since nearly all cells in the culture expressed the virus-induced NA.

Human T-cell leukemia virus-associated nuclear antigen (HTLV-NA)

Replication-competent retroviruses are not known to encode or induce nuclear antigens that are immunogenic in their natural hosts. We describe here the detection of a human T-lymphotropic virus (type I and type II) associated nuclear antigen (HTLV-NA) by an anticomplement immunofluorescence assay. Antibody to HTLV-NA is detected in 18 of 68 (26%) HTLV-I seropositives.

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.

DNA of herpesvirus pan, a third member of the Epstein-Barr virus-Herpesvirus papio group

The DNA of herpesvirus pan, a primate B-lymphotropic herpesvirus, shares about 40% well-conserved sequence relatedness with Epstein-Barr virus (EBV) and herpesvirus papio DNAs. Labeled cloned fragments from the EBV recombinant DNA library were cross hybridized to blots of EcoRI, XbaI, and BamHI restriction endonuclease fragments of herpesvirus pan DNA to identify and map homologous sequences in the herpesvirus pan genome. Regions of colinear homology were demonstrated between 6 x 10(6) daltons and 108 x 10(6) daltons in the DNAs. The structural organization of herpesvirus pan DNA was similar to the format of Epstein-Barr virus and herpesvirus papio DNAs. The DNA consists of two domains of largely unique sequence complexity, a segment US of 9 x 10(6) daltons and a segment UL of 88 x 10(6) daltons. US and UL are separated by a variable number of tandem repetitions of a sequence IR (2 x 10(6) daltons). There was homology between DNA which mapped at 26 to 28 x 10(6) daltons and 93 to 95 x 10(6) daltons in UL. The terminal reiteration component, TR, of herpesvirus pan DNA and sequences which mapped to the left of 6 x 10(6) daltons and to the right of 108 x 10(6) daltons had no detectable homology with the corresponding regions of Epstein-Barr virus DNA.

Complement-fixing antibodies to human cytomegalovirus induced early nuclear antigens in mononucleosis

Early nuclear antigen (CMNA) induced by human cytomegalovirus (HCMV) was extracted from infected human embryonic fibroblast cells and purified by ds DNA Sephadex chromatography. The purified antigen was added to acid-fixed preparations from human embryonic fibroblasts and these in vitro converted nuclei were exposed to human sera to estimate the antibodies to CMNA by anti-complement immunofluorescence staining. Serial serum samples were obtained from eight patients suffering from acute HCMV infection (mononucleosis), from nine patients with Epstein-Barr virus (EBV) mononucleosis, and from 20 healthy persons who had been shown to possess antibodies to HCMV late antigens. Acute HCMV infection is characterized by the presence of anti-CMNA antibodies at high titer (1:16 - 1:32) together with the elevated level of IgG antibodies to anti-HCMV-late antigens. During convalescence the anti-CMNA titer decreased to a lower level which was maintained for long period. The anti-CMNA antibodies were also regularly detected in sera of persons possessing antibodies to HCMV late antigens but without any sign of acute HCMV infection. It is concluded that antibodies to CMNA are not transitory and their presence even at high titer (1:16 - 1:32) in a serum sample cannot be taken as a presumptive evidence of acute virus infection. This method seems to be valuable for measuring antibodies to nuclear DnA-binding antigens induced by other viruses.

Initiation points for cellular deoxyribonucleic acid replication in human lymphoid cells converted by Epstein-Barr virus

Replicon size was estimated in two Epstein-Barr virus (EBV)-negative human lymphoma lines, BJAB and Ramos, and four EBV-positive lines derived from the former ones by infection (conversion) with two viral strains, B95-8 and P3HR-1. Logarithmic cultures were pulse-labeled with [3H]thymidine, and the deoxyribonucleic acid was spread on microscopic slides and autoradiographed by the method of Huberman and Riggs. After developing, replication forks were visualized as silver grain tracks on the autoradiograms. Average replicon size was estimated by scoring the number of replication forks per constant length of deoxyribonucleic acid and by measuring distances between centers of adjacent tracks, followed by detailed statistical analyses. Three of the four EBV-converted cell lines, BJAB/B95-8, Ra/B95-8, and Ra/HRIK, were found to have significantly shorter replicons (41, 21, 54% shorter, respectively), i.e., more initiation points, than their EBV-negative parents. BJAB/HRIK had replicons which were only slightly shorter (11%) than those of BJAB. However, analysis of track length demonstrated that extensive track fusion occurred during the labeling of BJAB/ HRIK, implying that its true average replicon size is shorter than the observed value. The results indicate that in analogy to simian virus 40, EBV activates new initiation points for cellular DNA replication in EBV-transformed cells.

No activation of new initiation points for deoxyribonucleic acid replication in BALB/c 3T3 cells transformed by Kirsten sarcoma virus

BALB/c 3T3 cells were transformed by Kirsten sarcoma virus, and five clones were isolated in soft agar. Average replicon sizes of the transformed cell lines were estimated by the method of fiber-autoradiography (J. A. Huberman and A. D. Riggs, J. Mol. Biol.32:327-341, 1968) and found to be the same size as the nontransformed 3T3 cells, analyzed in parallel. The results indicate that, unlike simian virus 40 and Epstein-Barr virus, Kirsten sarcoma virus does not activate new initiation points for cellular deoxyribonucleic acid replication in murine sarcoma virus-transformed BALB/c 3T3 cells.

Immunofluorescent staining of nuclear antigen in lymphoid cells transformed by Herpesvirus papio (HVP)

An improved fixation method for antigen detection in lymphoblastoid cells is described. Herpesvirus papio nuclear antigen (HUPNA) could be stained in several transformed lymphoid cell lines by anti-complement immunofluorescence (ACIF). Antibody to HUPNA was detected in many human sera containing antibodies to Epstein-Barr virus capsid and nuclear antigen (EBNA). Rheumatoid arthritis sera showed a high incidence of both anti-EBNA and anti-HUPNA antibodies.

Colinearity between the DNAs of Epstein-Barr virus and herpesvirus papio

Epstein Barr virus (EBV) and herpesvirus papio (HVPapio) DNAs share a common format and 40% homology. Labeled cloned fragments of EBV DNA were hybridized to blots of XbaI, EcoRI, HindIII, and SalI fragments of HVPapio DNA. EBV fragments which mapped from 2 x 10(6) to 54 x 10(6) and from 59 x 10(6) to 106 x 10(6) daltons hybridized to fragments at identical map positions in HVPapio DNA. Regions of nonhomology were demonstrated at 0 x 10(6) to 2 x 10(6), 54 x 10(6) to 59 10(6), and 106 x 10(6) to 115 x 10(6) daltons.

Herpesvirus papio DNA is similar in organization to Epstein-Barr virus DNA

EcoRI, HindII, SalI, nd XbaI restriction endonuclease maps of herpesvirus papio (HVPapio) DNA were derived by determining the fragment sizes and the linkage relationships between fragments generated by the different enzymes. The data indicate that HVPapio DNA has a single molecular arrangement which is similar to that of Epstein-Barr virus DNA. The size of the DNA was 110 X 10(6) to 114 X 10(6) daltons. Restriction fragments from both ends varied in the number of repeats of a 4 X 10(5)-dalton sequence, TR, and hybridized to each other. This suggests that there is an identical repeating unit, TR, at both ends of the DNA. There were usually six tandem repetitions (range, 1 to 11) of a 2 X 10(6)-dalton sequence, IR, within the DNA. IR separated the DNA into two domains of largely unique sequence complexity, a 9 X 10(6)-dalton segment, Us, and an 88 X 10(6)-dalton segment, UL. There was homology between DNA fragments which mapped at 25 X 10(6) to 29 X 10(6) to 91 X 10(6) to 95 X 10(6) daltons in UL.

Purification and biochemical characterization of the Epstein-Barr virus-determined nuclear antigen and an associated protein with a 53,000-dalton subunit

The Epstein-Barr virus-determined nuclear antigen (EBNA) was purified 700-fold to apparent homogeneity from Raji and Namalwa cell extracts by a three-step procedure involving heat treatment, DNA-cellulose chromatography, and hydroxyapatite chromatography. Acid-fixed nuclear binding and complement fixation were used to monitor antigenic specificity. Purified EBNA was also capable of specifically inhibiting the regular anticomplement immunofluorescence reaction for EBNA against Raji target cells. The purified antigen had a molecular weight of 170,000 to 200,000. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis, it yielded a single 48,000-dalton (48K) monomer. An EBNA-associated protein was also purified from the same cell extract. It had a molecular weight of about 200,000 and yielded a single 53K protein band by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The same protein was also found in Epstein-Barr virus negative B-cell lymphoma lines. The two types of protein were characterized by amino acid composition and peptide mapping. The results showed that the 53K and 48K protein components have no long regions in common; this excludes that the smaller product arises by breakdown of the larger product. Residue distributions were different, but an excess of hydrophilic residues was found in both proteins, suggesting a certain overall similarity in properties. 53K components from different cell lines appeared to differ somewhat. Epstein-Barr virus-positive lines carry two 53K components, one of which may be a slightly modified 53K product. Immunocomplexing assay showed that the 48K, but not the 53K, protein carries EBNA specificity. In mixtures, the 53K protein is co-precipitated with the 48K protein. The data suggest that EBNA may form a complex with the 53K proten within the cell.

Herpesvirus papio: state and properties of intracellular viral DNA in baboon lymphoblastoid cell lines

Herpesvirus papio (HVP) is an indigenous B-lymphotropic virus of baboons (Papio sp.) present in latent form in baboon lymphoblastoid cell lines. It shares cross-reacting viral capsid and early antigens with the Epstein-Barr virus (EBV), and HVP DNA and EBV DNA show partial sequence homology. EBV-specific complementary RNA was employed here as a probe to investigate the physical state of the HVP DNA component in baboon lymphoblastoid cells after fractionation of cellular DNA by density gradient centrifugation. Five virus-producing cultures contained both free and integrated HVP DNA sequences while one non-producing cell line had two or three viral genome equivalents per cell in an apparently integrated form. Further analysis of one virus-producing line showed that the free HVP DNA fraction was composed of both linear and circular viral DNA. Contour length measurements of HVP circular DNA molecules by electron microscopy revealed that they were similar in length to the EBV circular DNA present in human lymphoblastoid cells.

Evidence for antigenic distinctness of the Epstein--Barr virus-determined nuclear antigen and the Herpesvirus papio-determined nuclear antigen

Previous serological evidence indicated that Epstein--Barr virus-determined nuclear antigen (EBNA) has cross reactive components with the herpesvirus papio-determined nuclear antigen (HUPNA) and, in addition, it has distinct components of its own, not present in HUPNA. In the present study, this hypothesis was studied by absorption experiments. Absorption of anti-EBNA positive human sera with EBNA abolished both anti-EBNA and anti-HUPNA reactivity. Absorption with HUPNA removed all anti-HUPNA reactivity but did not reduce anti-EBNA to any detectable degree, thus confirming the hypothesis.

Antibody responses to Herpesvirus papio antigens in baboons with lymphoma

An Epstein-Barr virus-related herpesvirus, termed Herpesvirus papio (HVP), was isolated from baboons (Papio hamadryas) at the Institute of Experimental Pathology and Therapy, Sukhumi, USSR, where there is a continuing outbreak of lymphoma. In the present study sera from diseased baboons and from age- and sex-matched control animals were examined for antibodies to HVP antigens. Results showed that animals with lymphoid disease had antibodies to HVP virus capsid, early, soluble, and nuclear antigens at higher frequencies and at higher titers than did control animals. Antibody titers were not age- or sex-related. No concordancy was detected for antibodies to soluble and nuclear antigens. The sera were also examined for antibodies to two other widely distributed viruses of hamadryas baboons, cytomegalovirus and foamy virus. The results of these studies did not indicate a disease-related role for either of these viruses.

Study of Epstein-Barr virus-determined nuclear antigen (EBNA) by chromatography on fixed cell nuclei

Low ionic strength (50 to 100 mM NaCl) and pH 6.0 were found to be optimal conditions for in vitro conversion of Epstein-Barr virus (EBV)-determined nuclear antigen (EBNA)-negative nuclei to EBNA-positive nuclei by addition of the complement-fixing (CF) antigen extracted from Raji cells. In vitro conversion of nuclei to EBNA-positively was sensitive to DNase but not to RNase treatment. This suggests that nuclear DNA is a specific target substance to which EBV-CF antigen binds. If nuclei were fixed with methanol/acetic acid and subsequently treated with 0.6 M NaCl, EBNA could be eluted from in vitro-converted Ramos nuclei with 0.3 and 0.4 M NaCl. The same conditions were also found to be optimal for the adsorption and elution of EBV-CF antigen in DNA-cellulose chromatography. This indicates that the DNA-binding properties of EBNA antigen can be studied by "chromatography" on fixed nuclei followed by the ACIF test. The obvious advantages of this method over chromatography on DNA-cellulose are its simplicity, the possibility of testing many samples in one experiment and, especially, the use of minimal amounts of material. Significant differences in elution patterns for EBNA were found when nuclei derived from different cell lines (Ramos, Raji, and P3HR-1) were converted in vitro to EBNA-positivity. EBNA is eluted from in vitro-converted nuclei of EBV genome-positive P3HR-1 cells at an almost 0.1 M higher concentration of NaCl than is necesssary for a similar degree of elution from nuclei of EBV genome-negative Ramos cells.