Expression of virus-specific, thymus-specific and tumour-specific antigens in lymphoblastoid cell lines derived from Marek's disease lymphomas

Adenine and deazaadenine nucleoside and deoxynucleoside analogues: inhibition of viral replication of sheep MVV (in vitro model for HIV) and bovine BHV-1

A series of N(6)-cycloalkyl-2',3'-dideoxyadenosine derivatives has been prepared by coupling of 2,6-dichloropurine to protected 2,3-dideoxyribose, followed by reaction with appropriate cycloalkylamines. Synthesized compounds, along with other purine nucleoside analogues previously synthesized in our laboratory, have been tested for their antiviral activity against Bovine herpesvirus 1 (BHV-1) and sheep Maedi/Visna Virus (MVV), the latter being an in vitro and in vivo model of Human Immunodeficiency Virus (HIV). All compounds showed good antireplicative activity against MVV, with the N(6)-cycloheptyl-2',3'-dideoxyadenosine (5b) being the most active [effective concentration (EC(50)) causing 50% reduction of cytopatic effects (CPE)=27 nM]. All compounds showed also a from low to very low cell toxicity, resulting in a cytotoxic dose 50 (CD(50))/EC(50) ratio in some cases higher than 1000.

Antibody directed against Marek's disease-associated tumor surface antigen can be eluted from Marek's disease tumor cells

Antibody directed against Marek's disease-associated tumor surface antigen (MATSA) was eluted from tumor cells of lymphomas and peripheral blood lymphocytes that were isolated from Marek's disease virus-infected chickens. Feather follicular Marek's disease virus (MDV) antigen could not be demonstrated with this antibody by indirect immunofluorescent (IF) staining. Monoclonal antibody directed against MATSA could completely block the activity of eluted antibody and vice versa. By indirect IF staining using eluted antibody and fluorescein isothiocyanate (FITC) labelled antichicken globulin conjugate. MATSA-bearing cells were detected in MDV infected and herpes virus of turkey (HVT) vaccinated birds. Blocking of immunoglobulin molecules present on B-cells by anti-chicken globulin is critical in this test.

Partial transcription map of Marek's disease herpesvirus in lytically infected cells and lymphoblastoid cell lines

Marek's disease herpesvirus (MDV) can cause either a productive-restrictive or lytic infection, a latent infection or can transform thymus-derived lymphocytes. RNA was extracted from infected chicken embryo fibroblasts (CEF) or from lymphoblastoid tumour cell lines. Some of the infected CEF were treated with 200 micrograms/ml cycloheximide to identify immediate early (IE) transcripts, and others with 1 microM 1-(2-fluoro-2-deoxy-B-D-arabinofuranosyl)-5-methyluracil (FMAU), an inhibitor of herpesvirus DNA synthesis to identify early transcripts. An extensive Northern blot analysis was carried out using DNA probes spanning almost the complete MDV genome. In the lytically infected CEF at least 66 discrete transcripts were detected, ranging in size from 9.1 kb to 0.6 kb. Eleven IE transcripts were identified, of which 8 were mapped in the genome segment consisting of the IRL, IRS, US and TRS. Six transcripts were identified as early genes. In the MD lymphoblastoid cell lines MDCC-HPI, a non-producer cell line, and MDCC-CU41, a non-expression cell line, 4 and 7 transcripts were detected, respectively. These RNAs were transcribed from IE genes located mainly in the repeat sequences flanking UL and US and in US. Treatment of the lymphoblastoid cell lines with 20 micrograms/ml 5-iodo-2-deoxyuridine resulted in the additional transcription of 1 RNA species in HPI and 9 in CU41. Most of the transcripts present in lytically infected cells were also detected in MDCC-CU36, a cell line with a high percentage of antigen-positive cells (expression cell line).

Demonstration of chicken fetal antigen (CFA) on normal splenic lymphocytes, Marek's disease lymphoblastoid cell lines and other neoplasms

Chicken fetal antigen (CFA) was detected on normal splenic lymphocytes and a direct relationship was observed between the percentage of CFA-positive cells and the age of the donor. The fetal antigen was also detected on lymphoblastoid tumor cells and cell lines induced by known avian oncogenic viruses (Marek's disease virus and avian leukosis virus), and on spontaneously occurring adenocarcinoma cells. The fetal antigen appears to be distinct from Marek's disease tumor-associated surface antigen.

Chicken thymocyte-specific antigens identified by monoclonal antibodies: characterization and distribution in normal tissues and in tumoral tissues from Marek's disease chicken

Monoclonal antibodies (MAbs) were obtained against purified thymocyte membrane extracts. Five MAbs TA3, TB1, TB6 (IgG1), TC4, and TA1 (IgG2a), were tested by immunofluorescence and by immunoperoxidase tests against normal cells from different organs, Marek's disease (MD) cell lines, and MD tumoral cells from chickens. Three of them, TA3, TB1, and TB6, reacted exclusively with lymphoid cells in both cortical and medullary areas of the thymus and with less than 8% bursa cells. They identified a protein of apparently 40 kD. The other two revealed antigenic determinants on most medullar thymocytes and some cortical thymocytes, and on some splenic and peripheral blood lymphocytes. They were positive with MD cell lines and cells deriving from MD tumors. TC4 and TA1 detected molecular masses of about 110 kD and 16 kD, respectively. No MAbs reacted with erythrocytes, bone marrow, liver, brain, and skin cells. Not all of the tested cells were stained after contact with an anti-chicken immunoglobulin serum. In this paper, we determine a specific antigen restricted to T cells from thymus and different markers belonging to the mature T cells. The latter are also present on MD cell lines and MD tumoral cells.

Identification of Marek's disease virus-specific antigens in Marek's disease lymphoblastoid cell lines using monoclonal antibody against virus-specific phosphorylated polypeptides

For identification of the antigens specific to Marek's disease virus (MDV) in virus-non-producer lymphoblastoid cell lines established from a tumor of Marek's disease (MD), hybridomas producing monoclonal antibodies (MAbs) against the antigens were isolated. Immunogens for preparation of the hybridomas were purified from the lysate of an MD-lymphoblastoid cell line, MSB1, by affinity chromatography coupled with chicken anti-MDV serum immunoglobulin G. Three of the MAbs obtained, MB1, MB2 and MB3, were specific to MDV by immunofluorescence test. An immunofluorescence test using MB2 antibody showed that immunofluorescence-positive cells in non-producer MD-lymphoblastoid line cells became detectable when the culture temperature was shifted from 41 degrees C to 33 degrees C or when treatment with 5-iodo-2-deoxyuridine (IUdR) was performed, indicating that the antigen reactive with MB2 antibody is an MDV-specific early antigen. This temperature shift or IUdR-treatment did not induce other MDV-specific antigens, such as late gene products of MDV, detected with MAbs. MB1 and MB2 antibodies immunoprecipitated 4 MDV-specific phosphorylated polypeptides with molecular weights (MWs) of 43,000 (43kd), 39kd, 36kd and 24kd from chick embryo fibroblasts productively infected with virulent MDV. In the place of 43kd, phosphorylated 44kd polypeptide was precipitated from avirulent MDV-infected fibroblasts. However, MB3 antibody did not precipitate any MDV-specific polypeptides from infected fibroblasts. These results suggest that the phosphorylated polypeptides are MDV-specific polypeptides predominantly expressed in non-producer MD-lymphoblastoid cell lines.

Marek's disease--a model for herpesvirus oncology

The article will review the salient features of pathogenesis of Marek's disease in terms of sequential events which occur from the time of virus entry to the development of frank lymphomas. A hypothesis will be presented which will offer a credible explanation for this specific sequence of changes. Then, various factors which influence the incidence of neoplasms will be identified and the possible mechanisms by which they are influential will be discussed. These include the variable oncogenic properties of different virus strains, the influence of host genotype, and immune responses.

Further characterization of Marek's disease virus-infected lymphocytes. I. In vivo infection

Previous reports from this laboratory identified bursa-derived lymphocytes (B cells) and non-B cells as the predominant cell types respectively involved in the early cytolytic and subsequent latent infection of chickens with Marek's disease virus (MDV). It was not known whether these differences were qualitative or quantitative or if the method for detection of latent infection (viral antigen production after 48 h of in vitro cultivation) was sensitive enough. To further define the cells involved in the various phases of MDV infection, we used monoclonal antibodies which specifically react with B cells, or T cells, or la-antigen-bearing cells. Dual fluorescence tests to detect surface markers and viral internal antigen (VIA) were conducted with infected spleen cells freshly collected from MDV-infected chickens or after in vitro cultivation of those cells. The same antibodies were also used for a rosetting procedure to yield fractions enriched or depleted of T cells, B cells or la-bearing cells. These were examined directly for viral DNA by in situ hybridization or dot blot DNA hybridization and for VIA cultivation. We learned that infected T cells also comprise part of the early cytolytic phase of MDV infection but constitute a minority population (approximately 2-3%) compared to B cells (83-92%) at 3 or 4 days post infection. Latently infected cells were definitively identified as mostly la-bearing T cells, although a few (2-4%) were B cells. Prior to in vitro cultivation, latently infected cells apparently had insufficient viral DNA for detection by in situ hybridization, but the more sensitive dot blot procedure revealed viral DNA in fractions later found positive by VIA expression after in vitro cultivation. Viral DNA replication in latently infected cells apparently had occurred after 48 h cultivation because in situ hybridization detected infected cells at that time. Treatment of cell cultures with iodo-deoxyuridine, 12-O-tetradecanoyl phorbol-13-acetate or n-butyrate failed to increase the number of spleen cells which expressed VIA.

Susceptibility of Marek's disease lymphoblastoid cell lines to infection with influenza and pseudorabies viruses and the protective effect of immunization with influenza virus-infected lymphoblastoid cells

The susceptibility of 3 lymphoblastoid cell lines (MDCC-MSB1, MDCC-HP1 and MDCC-RP1) derived from Marek's disease tumours to infection with influenza (AoPR8) and pseudorabies viruses was studied. MSB1 and HP1 were more susceptible to infection with influenza virus than was RP1. It was shown in the case of HP1, which was studied in greater detail, that although the majority of the cells synthesized influenza virus haemagglutinin when infected at high multiplicity, only a small proportion produced mature infectious particles. The results obtained from both high and low multiplicities of infection suggested that infection with AoPRs was abortive in the majority of the cells of all 3 cell lines. Infected cultures remained viable when subcultured over several days. All 3 cell lines were resistant to pseudorabies virus. The block in pseudorabies virus replication probably occurred after adsorption. Immunization of chickens with HP1 lymphoblastoid cells superinfected with influenza virus AoPR8 and inactivated with glutaraldehyde gave better protection against Marek's disease than immunization with uninfected HP1 cells.

Spontaneous and induced herpesvirus genome expression in Marek's disease tumor cell lines

We incubated 31 newly established Marek's disease tumor cell lines at 41 degrees C for 48 h after subculturing and then examined them to determine the spontaneous rates of expression of viral internal antigen(s), viral membrane antigen(s), and virus isolation. All but two of the lines were isolated from tumors induced by clone-purified Marek's disease virus strain JM-10, GA-5, RB-1B, and BC-1A in nine different genetic strains of chickens with defined histocompatibility antigens. The line-to-line variations in the rates of spontaneous expression for the antigens or virus rescue were great, but the levels of expression were very low in most cases. The median rates of expression for viral internal antigen, viral membrane antigen, and virus isolation were 32, 8, and 2 positive cells per 10(5) cells, respectively (ranges, 0 to 20,280, 0 to 22,990, and 0 to 220 positive cells per 10(5) cells, respectively). The ratio of viral internal antigen expression to virus isolation was extremely variable and often high, whereas the ratio of viral internal antigen to viral membrane antigen expression was more consistent and generally low. The virus strain which induced the cell line influenced the level of virus genome expression, but the cell genotype did not. Cell lines transformed by JM-10 virus, which exhibited low oncogenicity, had significantly (p less than 0.01) higher rates of expression than cell lines transformed by CA-5 and RB-1B viruses, which exhibited high oncogenicity. Treatment with iododeoxyuridine or incubation at 37 degrees C induced increased rates of expression in most lines but not in all lines. The degree of enhanced expression was inversely proportional to the rate of spontaneous expression.