Detection of Epstein-Barr virus (EBV) DNA sequences using in situ hybridization

Immunofluorescent evaluation of DNA repair synthesis using interactive laser cytometry

An improved differential fluorescence analysis technique which employs scanning laser cytometry for the detection of two DNA binding fluorochromes was used to quantitate both total DNA and cellular incorporation of the base analogue, bromodeoxyuridine (BrdUrd), into UV- or methyl methane sulphonate (MMS)-treated DNA. In this procedure DNA containing BrdUrd was partially denatured and immunolabeled by binding anti-BrdUrd monoclonal IgG to incorporated BrdUrd. Anti-BrdUrd was detected with a secondary fluorochrome-labeled polyclonal anti-IgG. Cells were counterstained with propidium iodide to allow the determination of total DNA. Fluorescence was determined using the Meridian ACAS 570 Scanning Laser Cytometer. The computer-analyzed images were generated from monodisperse populations of UV- or MMS-treated cells, allowing the evaluation of DNA synthesis associated with excision repair and of total DNA content in single cells. These data were compared with 3H-thymidine incorporation occurring as a function of excision repair. The analysis of DNA synthesis with this technique is consistent, relatively simple, and rapid with excellent sensitivity and provides a viable method for determining cycling vs. non-cycling cells, total cellular DNA, and excision repair-associated DNA synthesis of individual cells within heterogeneous cell populations.

Detection of Epstein-Barr virus in lymphoid tissues of patients with infectious mononucleosis by in situ hybridization

Although the immunological response during infectious mononucleosis (IMN) has been studied in detail, little is known about the spread of Epstein-Barr virus (EBV) in lymphoid organs or the topographical distribution of the infected cells. In this study, EBV was detected in 11 lymph nodes, 4 tonsils, and 1 spleen of 16 patients with IMN. The predominant cell type positive for the EBV genome was identified as small lymphocytes localized chiefly within typical T areas, preferentially in perifollicular and interfollicular regions of the lymph node. A few endothelia of epithelioid venules were also found to be positive. Furthermore, a small number of sinus lining cells of lymph nodes exhibited labelling. Altogether, only a small number of cells, not exceeding 1 per cent of all cells, were infected with EBV. Our results show that only a small number of lymphocytes carry the EBV and that besides B lymphocytes, other cell constituents of lymphatic tissues are infected by EBV during IMN.

Formation of intranuclear replication compartments of Epstein-Barr virus with redistribution of BZLF1 and BMRF1 gene products

The localizations of the Epstein-Barr virus immediate-early transcriptional activator BZLF1 protein ZEBRA, of the BMRF1 early antigen diffuse component (EA-D), and of viral DNA replication were studied in the Burkitt's lymphoma cell line Akata treated with anti-human immunoglobulin antibodies. Prompt and sequential appearance of ZEBRA, EA-D, and viral DNA was observed in about 70% of the cells. At early times after activation, ZEBRA had a diffuse intranuclear distribution, but later it was concentrated in globular regions within the nucleus. EA-D appeared first in a finely stippled pattern and then in a diffuse pattern. At late times, EA-D concentrated in globular regions similar to those with ZEBRA. Double staining for ZEBRA and EA-D revealed that ZEBRA followed the morphological changes of EA-D with a 1-2 hr delay and that both finally coalesced in the same structures, where in situ hybridization localized replicating viral DNA. The redistribution of both ZEBRA and EA-D to these compartments depended upon the replication of lytic viral DNA. These findings indicate that these globular regions are sites for viral replication and that transcription of EBV late genes may be regulated in these structures.

Detection of Epstein-Barr virus genomes in AIDS related lymphomas: sensitivity and specificity of in situ hybridisation compared with Southern blotting

Eighteen cases of AIDS related, non-Hodgkin's lymphomas were examined for the presence of Epstein-Barr virus (EBV) genomes using in situ hybridisation with a 35S-labelled probe. The results were compared with those obtained independently by Southern blot analysis with a 32P-labelled probe of frozen tissue from the same tumours. Technically satisfactory results were obtained with both methods in 15 lymphomas. EBV DNA was detected in seven of 15 (47%) cases by in situ hybridisation and in eight of 15 (53%) cases by Southern blotting (including all the cases positive by in situ hybridisation). The results of EBV DNA detection by the two techniques were identical in 14 of 15 (93%) cases. In situ hybridisation gave no false positive results. This study shows that the sensitivity and specificity of in situ hybridisation for the detection of EBV genomes in AIDS related lymphomas approaches that of Southern blotting, even when using routinely processed archival, paraffin wax embedded material.

Epstein-Barr virus genomes in lymphoid cells: activation in mitosis and chromosomal location

Biotin-labeled Epstein-Barr virus (EBV)-specific DNA probes have been used to detect viral genomes by in situ hybridization. Immunocytochemically amplified signals produced by the hybridized probe allow visualization of viral DNA even in cells previously reported to contain only one or two EBV genomes. In EBV producer lymphoid cell lines, such as B95-8, P3HR-1, or Daudi, activation of latent EBV DNA could be observed in mitotic cells; in non-virus-producing cells of these same lines, EBV was found to be present in low copy numbers. Noninducible cell lines such as IB4, AW-Ramos, and Namalwa exhibited low but clearly positive hybridization. Unexpectedly, significant variations in the amounts of EBV DNA per cell were observed between individual cells of these lines. The EBV DNA in the cloned IB4 cell line was localized to chromosome 4 in metaphase cells, but in the noncloned converted line AW-Ramos, the location of integrated viral DNA was essentially random.

Nucleic acid probes in clinical microbiology

The infectious disease applications of nucleic acid probe have been described. In addition, the basic procedures of nucleic acid probe technology have been discussed, as have the factors affecting implementation of probe technology in diagnostic laboratories. Despite the questions raised, nucleic acid probes will become part of the diagnostic laboratory in the near future. Commercial interests are developing and marketing new probes, reagents, and kits which will expedite the employment of this technology. High-volume reference laboratories will first use probes as part of a battery of tests which will include ELISA and monoclonal antibody methods. In all probability, probes will replace methods: that have proven to be ineffective, difficult, or costly such as culturing for some enteric pathogens and Legionella, that require long incubation periods, such as mycobacteria, or that have high costs and low yields, such as virology.

In situ hybridization of immunoglobulin-specific RNA in single cells of the B lymphocyte lineage with radiolabelled DNA probes

A method for in situ hybridization has been developed which detects immunoglobulin-specific mRNA transcripts in single murine B lymphocytes with radiolabelled, immunoglobulin gene-specific single-stranded DNA probes. The method has been applied to myeloma and hybridoma cells and to B lymphocytes at various stages of their maturation from small, resting B cells to Ig-secreting plasma cells. A critical step in the procedure is the treatment of the cells with pronase. The various cell types have been found to be differently susceptible to this treatment. Single-stranded DNA probes of different lengths, i.e., between 26 and 1000 bp, have been employed in the hybridization. The number of silver grains over a cell increases proportionally with the length of the probe and with its concentration in the hybridization reaction. The kinetics of the increase of mu-heavy chain-specific RNA molecules in single cells and the appearance of 'switched', gamma-heavy chain-expressing cells are shown after stimulation of murine B cells with lipopolysaccharide.

Effects of DNA synthesis inhibitors on early antigen expression following primary infection or superinfection by Epstein-Barr virus

Seven lymphoid cell lines previously characterized with respect to their resident Epstein-Barr virus (EBV) genome content were infected or superinfected with concentrated EBV from supernatant of the P3HR-1 cell line. Immunofluorescence assays were conducted on smears 48 hours after infection, using human sera containing antibodies to EBV early antigen (EA). Two EBV nuclear antigen (EBNA) negative cell lines containing no detectable resident EBV DNA and five EBNA positive cell lines containing EBV genomes were tested. The cell lines did not spontaneously express EBV EA (i.e., they were non-producers). All cell lines responded to infection or superinfection with EBV by expressing EA. Treatment of the cell lines with arabinosylcytosine (Ara-C) 10 micrograms/ml, at the time of infection resulted in significant decreases in the number of cells expressing detectable EA after drug treatment in all cell lines (72 +/- 5 percent inhibition of EA expression). Experiments were also conducted with hydroxyurea (HU) and phosphonoacetic acid (PAA). It was found that treatment with HU (100 micrograms/ml) inhibited EA production in cell lines containing EBV genome copies by 81 percent as compared to the superinfected cultures receiving no drug. In primary infection of EBNA negative cell lines, HU had minimal effects. PAA (100 micrograms/ml), on the other hand, had very little effect on EA expression following superinfection of cell lines harboring the EBV genome, but reduced the EA expression after primary infection of EBNA negative cell lines by 70 to 80 percent. All drugs were used at concentrations having little effect on RNA and protein synthesis. However, HU and Ara-C significantly reduced DNA synthesis and cell division in the treated cultures.

Unintegrated viral DNA sequences in a hamster tumor induced by bovine papilloma virus

A fibrosarcoma was induced in a hamster by bovine papilloma virus type 2 (BPV2). The content of BPV2 DNA sequences was measured by DNA-DNA and cRNA-DNA hybridizations. The tumor contained approximately 300 BPV2 genome equivalents per cell. Southern blot hybridization indicated that the viral DNA was in free form, the entire genome most likely being present. In situ hybridization with BPV2 cRNA showed that multiple genome copies were present in each cell. Neither virus particles nor virus coat antigens could be detected in the tumor. A cell line was established from the fibrosarcoma, and the cells contained multiple copies of the BPV2 genome. The latter was in free form, and all of the DNA sequences appeared to be present in multiple copies and in all cells. An extensive search failed to reveal the presence of virus or viral antigens.

Nucleic acid spot hybridization: rapid quantitative screening of lymphoid cell lines for Epstein-Barr viral DNA

A simple nucleic acid hybridization method to screen numerous samples of eukaryotic cells rapidly for their Epstein-Barr virus (EBV) DNA content is described. Whole cells are spotted on nitrocellulose filters and their DNA is denatured and fixed to the filter. The resultant DNA spots are hybridized to nick-translated EBV DNA and the extent of hybridization is monitored by autoradiography and scintillation counting. Statistical analysis of serial dilutions of cells permits their viral genome content to be estimated quantitatively by reference to a known standard, such as Raji cells or an artificial mixture of pure viral DNA and uninfected lymphocytes. The sensitivity of the method is between 5 and 50 pg of viral DNA. With this method we are able to select subclones that are high produces of EBV DNA and to identify the optimal time for harvest of EBV DNA from cultured cells. Spot hybridization should permit any cell population or fluid to be screened for the presence of a DNA sequence for which a radioisotopically labeled probe is available.

Abortive expression of the Epstein-Barr virus (EBV) cycle in a variety of EBV DNA-containing cell lines, as reflected by nucleic acid hybridization in situ

A variety of Epstein-Barr virus (EBV) DNA-containing cell lines have been tested for the expression of the EBV-associated antigens EBNA (nuclear antigen), EA (early antigen), and VCA (viral capsid antigen), and for the presence of cells containing disproportionate amounts of EBV DNA. The antigen tests utilized immunofluorescence and 125I-labelled antibodies combined with autoradiography. EBV-DNA was detected by in situ hybridization with 3H-labelled EBV RNA complementary to P3HR-1 EBV DNA (P-EBVcRNA). The P-EBVcRNA has been shown to represent the majority of the P3HR-1 EBV DNA sequences. It was concluded that EBV DNA-containing cell lines can be divided into those that express only EBNA, those that express EBNA and EA and those that express EBNA, EA and VCA and also contain cells that undergo disproportionate EBV DNA synthesis. Consequently, in some cell lines there is an abortive expression of the EBV cycle in that some cells spontaneously express EA but fail to continue further to viral DNA synthesis. A similar pattern can be found after experimental induction of the EBV cycle, suggesting that related mechanisms govern the spontaneous expression of the EBV cycle and the extent of its inducibility.

Somatic cell hybrids between human lymphoma cell lines. V. IdUrd inducibility and P3HR-1 superinfectability of Daudi/HeLa (DAD) and Daudi/P3HR-1 (DIP-1) cell lines

We have studied two types of somatic cell hybrid with regard to expression of the Epstein-Barr virus (EBV) cycle and its regulation. The first, DIP-1, a hybrid formed between two human lymphoma EBV producers (Daudi and P3HR-1), contained EBV DNA, expressed the virus-determined nuclear antigen (EBNA), andwas a producer of the EBV-associated antigens EA (early antigen) and VCA (viral capsid antigen). The second, DAD, a hybrid series of clones formed between Daudi and a HeLa cell derivative (D98), differed with regard to the expression of EBNA, EA, VCA and the content of EBV DNA. EA was regularly induced in the EBV DNA-containing hybrids following treatment with iododeoxyuridine (IdUrd). This induction was greater in lines spontaneously expressing EA. In two hybrids, DIP-1 and DAD10, VCA and virus DNA synthesis were also induced in the presence of IdUrd, the latter being detected by in situ hybridization with P3HR-1 EBV complementary RNA. Finally, while DIP-1 was superinfectable by the P3HR-1 EBV strain, the DAD series of hybrids were refractory to P3HR-1 superinfection and lacked EBV receptors.