Retrovirus-mediated gene transfer of tumor necrosis factor alpha into colon carcinoma cells generates a growth inhibition

Retrovirus-mediated gene transfer was employed to introduce two different cDNAs of the human tumor necrosis factor alpha gene (TNF) into colon carcinoma cell lines either sensitive (LoVo) or resistant (LS174T) to the external addition of TNF. The TNF variants differed in their 5'-sequences (HTNF: authentic TNF cDNA, SPTNF: TNF cDNA with a signal sequence of the IgG heavy chain). The integration of TNF-specific DNA into the genomic DNA, the expression of TNF-specific mRNA and the translation into TNF protein was shown by Southern-, Northern- and Western analysis with TNF-specific DNA- and RNA probes and anti-TNF-antibodies, respectively. Neomycin selected tumor cell clones expressed biologically active TNF up to 40 pg/ml. As shown in a growth assay, both variants of TNF caused an up to 80% growth inhibition in colon carcinoma cells. Furthermore, the cells constitutively producing TNF had a distinguishable morphological appearance and a reduced colony growth in soft agar compared to the parental cells. The subcutaneous injection of 1 x 10(6) TNF-expressing tumor cells into nude mice resulted in a reduced tumor progression in comparison to the controls.

Rapid method of total RNA mini-preparation from eucaryotic cells

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Molecular cloning of a type D retrovirus from human cells (PMFV) and its homology to simian acquired immunodeficiency type D retroviruses

Unintegrated circular proviral DNA of a type D retrovirus (PMFV) isolated from a permanent human cell line was molecularly cloned in the bacteriophage vector L47.1 and subcloned in the plasmid vector pGEM-2. A restriction endonuclease map of PMFV DNA was established using 10 different enzymes for single and multiple digestions of closed circular and cloned DNA molecules. By restriction endonuclease analysis cloned PMFV DNA represented full-length viral DNA with one long terminal repeat (LTR). The comparison of the physical map of cloned PMFV to those of other cloned type D retroviruses revealed closest homology to the map of retrovirus D/New England (pD398) and SAIDS retrovirus type 1 (SRV-1). The relatedness of PMFV to further type D retroviruses (Mason-Pfizer monkey virus, MPMV; SAIDS retrovirus type 2, SRV-2) was also demonstrated by cross-hybridization of cloned DNAs under different stringencies (i) using full-length genomic probes of PMFV, MPMV, and SRV-2 and (ii) by DNA sequence analysis of regions of the group specific antigen (gag) protease (prt), polymerase (pol), and envelope (env) genes.

A radioimmunoassay detecting the bovine leukaemia virus transmembrane protein gp30 and anti-gp30 antibodies in the serum of cattle

By means of SDS PAGE we isolated from virus-infected foetal lamb kidney (FLK) cells a relatively homogenous envelope transmembrane protein gp30 of bovine leukaemia virus (BLV). As shown by a partial sequence analysis of the N-terminus of this protein, our gp30 preparation contained only traces (less than 5%) of p24 gag protein: Rabbit anti-gp30 serum did not cross react with the BLV proteins gp51, p12, p15(1), p15(2), and p10 but reacted weakly with the p24 polypeptide. 125I-labelled gp30 (chloramine-T) was precipitated with the serum of BLV-infected cattle. Nonlabelled preparation of gp30 competitively inhibited the reaction of 125I-labelled gp30 with the natural antibodies. We investigated 193 cattle sera by liquid phase radioimmunoassays (RIA) using 125I-gp30, gp51 and p24 antigens. Sixteen noninfected cattle sera were negative in all tests. The 177 serum samples of BLV-infected animals were examined to the diagnostic value of the three tests. Of these, 175 were positive in gp51 RIA, 172 in p24 RIA and 164 in gp30 RIA. In all three tests, 159 sera were positive while 18 sera, mostly coming from animals with normal leukocyte counts, were positive only either with gp51 or p24, or were double positive with either gp51/p24 or gp51/gp30. We conclude that the gp51 RIA is superior to both the gp30 and the p24 RIA and that the gp30 RIA will be useful for investigating the role of gp30 in virus pathogenicity.

Biochemical and immunological characterization of structural proteins from retrovirus-D/New England and comparison to Mason-Pfizer monkey virus and permanent human fibroblast virus

Biochemical and immunological properties of retrovirus-D/New England (here referred as R-D/NE) recently isolated at the New England Regional Primate Research Center, Southborough, Ma, from a rhesus monkey with acquired immune deficiency syndrome were investigated and compared to the prototype type D retroviruses Mason-Pfizer monkey virus (MPMV) and permanent human fibroblast virus (PMFV) isolated from a breast carcinoma of a rhesus monkey and a continuous human cell line, respectively. The polypeptide composition of R-D/NE propagated in a human lymphoid B cell line (Raji cells) has been investigated using SDS-polyacrylamide gel electrophoresis. Staining with Coomassie blue and labelling with 14C amino acids revealed seven viral polypeptides with molecular weights of 4,000, 10,000, 12,000, 15,000, 18,000, 27,000, and 80,000 Da which were also shared by MPMV and PMFV. The 80,000 Da protein was shown to be a glycoprotein by incorporation of 3H glucosamine. The 18,000 Da protein was identified as a phosphoprotein of R-D/NE. p18 structural proteins of MPMV and PMFV represent phosphoproteins of their respective viruses as well. All three phosphorylated proteins contain O-phosphoserine as major phosphoamino acid. The comparison of tryptic peptide maps of the major internal structural proteins of R-D/NE, MPMV, and PMFV revealed a striking similarity among p 10/p 12 and p 15. proteins. A minor difference was detected among the tryptic peptide digests of p 4 and p 27 proteins. Antiserum against p 15 of MPMV showed a significantly weaker binding to R-D/NE than to MPMV and PMFV at high dilutions.

Isolation and characterization of covalently closed circular proviral DNA molecules of several type D retroviruses isolated from human cell lines

Infection of a human lymphoblastoid B cell line (Raji cells) with type D retroviruses, originally isolated either from subhuman primates (MPMV, LV) or from permanent human cell lines (PMFV, HeLaV, HEp-2V) led to the production of type D retrovirus particles. Subsequent cocultivation of uninfected and virus-producing Raji cells was employed for the generation of sufficient amounts of covalently closed circular DNA molecules (cccDNA). Highest amounts of cccDNA were obtained after cocultivation of virus-producing Raji cells and homologous uninfected cells at a ratio of 1 to 3 for 72 hr. The cccDNAs of type D retroviruses migrated at about 4.3 kbp compared to lambda DNA/HindIII markers. Digestion of cccDNAs with restriction endonucleases which have one recognition site generated molecules of approximately 8 kbp. The restriction endonuclease site analysis of the cccDNA of type D retroviruses revealed a genomic heterogeneity among the different isolates.

Structural components of bovine leukemia virus: further biochemical and immunological characterization of major structural proteins and glycoproteins

Proteins from bovine leukemia virus (BLV) were investigated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis in the presence and absence of 14C amino acids. Virus grown either in fetal lamb kidney (FLK) or bat lung (BL) cells revealed seven major proteins designated p10, p12, p15(1), p15(2), p24, gp30, and gp64. By tryptic peptide analysis, N-terminal amino acid analysis and radioimmunoassay it could be shown that p10, a basic protein with hydrophobic properties, is a cleavage product of p15(2), the acidic and slightly hydrophobic phosphoprotein of BLV. The structural protein p12 was shown to be a phosphorylated protein identifying it as a second major viral protein to contain phosphorous. Investigation of [3H]glucosamine incorporation, N-terminal amino acid analysis and hydrophobic properties by chloroform-methanol extraction confirmed properties of gp30 and gp64 predicted by nucleotide sequence data. The two p15 proteins have been characterized in more detail.

Translational order of bovine leukemia virus gag and env gene-coded proteins

The translational orders of bovine leukemia virus (BLV) gag proteins and env proteins have been determined by the technique of pactamycin mapping. BLV-producing fetal lamb kidney (FLK) cells were pulse-labeled with 14C amino acids and [3H]glucosamine in the presence or absence of pactamycin which inhibits initiation of protein synthesis but not elongation. Viruses were harvested from the cell culture medium and viral proteins were analyzed by SDS-polyacrylamide gel electrophoresis. For each protein the " pactamycin ratio" was determined. The lower this ratio was for a given protein, the closer the protein would be to the amino terminus of the precursor polyprotein. From these experiments the following translational orders were derived: gag, NH2-p10-(p15(2) X p15(1)-p24-p12-COOH; and env, NH2- gp64 - gp30 -COOH. Investigation of isoelectric points of BLV proteins, a conserved property of retroviral proteins, supported the translational order of gag gene-coded proteins.

Bovine leukemia virus (BLV)--a structural model based on chemical crosslinking studies

Nearest neighbor relationships between lipid and protein as well as between high-molecular-weight viral RNA and protein were investigated in bovine leukemia virus (BLV) particles using chemical crosslinking reagents. Separation of dimethyl suberimidate (DMS) induced lipid-protein complexes by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the phosphoprotein pp 15 is linked to the lipid bilayer of the virus. By use of diepoxybutan (DEB) as crosslinking reagent p 12 and again pp 15 were found to be linked to the viral RNA. Based on these results and our previous data describing the spatial relationships of major structural proteins within BLV particles, a structural model of BLV is proposed.

Further evidence from tryptic peptide analysis for heterogeneity among type D retroviruses

Tryptic peptide analyses were performed on the major internal structural proteins of type D retroviruses isolated originally from subhuman primate species (MPMV, SMRV, LV) and from permanent human cell lines (HeLaV, HEp-2V, PMFV). The p25 peptide maps of MPMV, LV, PMFV and HEp-2V were very similar but showed a striking dissimilarity to the p25 map of HeLaV and the p35 map of SMRV. All type D viruses included in this study could be distinguished by peptide maps of at least two of their three low-molecular-weight proteins p10, p12 and p15. These studies further demonstrate the heterogeneity among type D retroviruses.

Type D retroviruses from human cells do not contain a minor glycoprotein shared by old world monkey type D viruses

The protein patterns of type D retroviruses isolated either from permanent human cells (HeLa virus, HeLa V, and HEp-2 virus, HEp-2V) or from spectacled langur (langur virus, LV), an Old World monkey, were investigated using sodium dodecyl sulfate polyacrylamide gel electrophoresis. Labeling with 14C-amino acids and 3H-glucosamine revealed for each of these isolates five polypeptides with molecular weights of 10,000, 12,000, 15,000, 25,000 and about 68,000 and identified the 68,000 D-protein as a glycoprotein. An additional glycoprotein with a molecular weight of 20,000 (gp20) was resolved in LV similarly as in previous studies with Mason-Pfizer monkey virus. However, in accordance with our recent analysis of a third type D isolate from human cells (PMFV), gp20 was not detectable in both HeLaV and HEp-2V regardless of the cell line in which they were grown. Thus, it appears that the type D virus isolates from human cells are slightly distinct from the presently known type D retroviruses of Old World monkeys. The relevance of this finding to the origin of the human isolates, however, remains to be shown.

The protein pattern of PMF virus, a type-D retrovirus from malignant permanent human cell lines

The protein pattern of a type-D retrovirus (PMFV) isolated from and propagated in human cell lines has been investigated using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Staining with Coomassie blue and labeling with 14C-leucine/14C-lysine revealed five viral polypeptides with molecular weights of 10,000, 12,000, 15,000, 25,000, and 68,000. The 68,000 D-protein was shown to be a glycoprotein by incorporation of 3H-glucosamine and the 15,000 D-protein was identified as a phosphoprotein. By comparing PMFV with the closely related Mason-Pfizer monkey virus (MPMV) in co-electrophoresis experiments no clear difference was detected in viral 14C-leucine/14C-lysine profiles. The viruses differ, however, with respect to their glycoprotein patterns. A glycoprotein corresponding to the gp20 of MPMV has not been detected in PMFV irrespective of the cell line used for propagation of viruses.