DNA binding and unwinding activities associated with intracytoplasmic a particles isolated from mouse mammary tumors.

Intracytoplasmic A particles (CAP), previously identified as probably cytoplasmic nucleocapsid precursor structures to mouse mammary tumour virus (MMTV), possess both DNA binding and DNA unwinding activities, CAP proteins bind to both single-stranded (ss)- and double-stranded (ds)DNA, with the ssDNA slightly preferred. This activity was linear over a 30-fold concentration of A particle protein and was not affected by NaCl concentrations as high as 0.6 M or pH changes over a wide range.

Monoclonal antibodies identify individual determinants on mouse mammary tumor virus glycoprotein gp52 with group, class, or type specificity.

Hybrid cell lines producing monoclonal antibodies against the C3H strain of mouse mammary tumor virus (C3H MMTV) were prepared by the fusion of mouse myeloma cells with the lymphocytes of BALB/c mice that were immunized with C3H MMTV. Approximately 10% of the hybrid cells initially plated after cell fusion produced immunoglobulins that reacted in antibody-binding assays with C3H MMTV; 40 of these cells were cloned, and 6 eventually yielded stable cell lines. High concentrations of monoclonal antibodies (5 to 20 mg/ml) were obtained from serum and ascites fluid of syngeneic mice inoculated with the hybrid cells.

C3H/HeN mammary tumor-bearing mice develop type-specific neutralizing antibodies and group-specific precipitating antibodies for the mouse mammary tumor virus.

The development of mouse mammary tumor virus (MMTV)-neutralizing antibodies in various strains of mice was measured by their ability to neutralize the focus-forming capacity of a Kirsten sarcoma virus (C3H MMTV) pseudotype containing the MMTV envelope glycoprotein gp52. C3H/HeN, but not GR/N and RIII, mammary tumor-bearing mice were found to develop neutralizing antibodies to this pseudotype. In addition, non-tumor-bearing C3H/HeN, GR/N, RIII, NIH Swiss, C57BL/6, and BALB/c mice and 13 feral mice were also negative for neutralizing antibodies.

Establishment of a C3Hf mammary tumor cell line expressing endogenous mouse mammary tumor virus: antigenic and genetic relationships of this virus with highly oncogenic mouse mammary tumor viruses.

A single-cell clone of C3Hf mammary tumor cells (clone 14) was developed into a continuous cell line expressing high levels of endogenous mouse mammary tumor virus (MMTV) with less than 0.1% murine leukemia virus expression. Comparison of the C3Hf MMTV protein profile on sodium dodecyl sulfatepolyacrylamide gel electrophoresis with that of C3H MMTV revealed that the protein content of the two viruses was quite similar.

Mice with spontaneous mammary tumors develop type-specific neutralizing and cytotoxic antibodies against the mouse mammary tumor virus envelope protein gp52.

Sera from C3H mammary tumor-bearing mice contain cytotoxic antibodies for mouse mammary tumor virus (MMTV)-producing cells, based on (51)Cr release in a complement-dependent serum cytotoxicity assay. The cytotoxic antibodies could be absorbed by purified C3H MMTV gp52 and C3H MMTV-infected cat cells (C3H [MMTV] CrFK) containing cell surface MMTV gp52. However, purified MMTV p27 and uninfected CrFK cat cells were negative.

Characterization of infection and replication of Mason-Pfizer monkey virus in human cell cultures.

Human cells derived from both normal and neoplastic tissues can be infected by Mason-Pfizer monkey virus (MPMV) without accompanying cytopathology. Infection of cell cultures such as human rhabdomyosarcoma (A204) results in a persistenly infected cell line which can be subcultured over 30 sequential culture passages without significant change in phenotype properties according to reverse, transcriptase (RT), MPMV p27 antigen content, virus particle count and infectivity titre. Productive virus infections were established at relatively low virus particle (VP) input multiplicities (p.

Immunological characterization of mouse mammary tumor virus p10 and its presence in mammary tumors and sera of tumor-bearing mice.

Mouse mammary tumor virus (MMTV) p10 and gp52 were purified and used as radiolabeled antigens in sensitive radioimmunoassays. These radioimmunoassays were specific for MMTV proteins since detergent-disrupted MMTV from C3H/HeN, RIII, and GR/N mice gave complete competition, whereas C3H/HeNf liver extracts and other lysed retroviruses did not. Both gp52 and p10 are coded by the viral genome, since MMTV grown in a heterologous cell line (feline kidney cells) competed in these assays.

Immunological characterization of the low-molecular-weight DNA binding protein of mouse mammary tumor virus.

p14, a low-molecular-weight MMTV protein previously identified as having DNA-binding properties and encoded by the gag region of the MMTV genome, was purified by affinity chromatography on DNA-sepharose. Immunological characterization of the purified protein showed that MMTV p14 shares no cross-reactivity with gp52, gp36 and p10, antigens associated with the MMTV envelope, nor with p27 antigen found in the virion core. Purified MMTV p14 did show cross-reactivity with purified intracytoplasmic A particles, supporting the concept that A particles are morphological precursors to MMTV cores.

Case of tumour rickets.

A 10-year-old boy, with widespread soft tissue tumours of bone, developed hypophosphataemic rickets due to impaired renal tubular reabsorption of phosphate. Biopsy of the largest tumour showed a nonosteogenic fibroma. We believe this boy is another example of 'tumour rickets', as other causes of rickets were excluded clinically and biochemically.

Prevalence of murine mammary tumor virus antibody and antigens in normal and tumor-bearing feral mice.

Approximately 20% of normal male and female feral mice (Mus musculus) from areas with populations having either high [Lake Casitas (LC) and La Puente] or low (Bouquet Canyon) spontaneous lymphoma incidence expressed murine mammary tumor virus (MuMTV) gp52 in specific tissues. Sera from a low percentage (6%) of mice from the same trapping areas contained precipitating antibody specific for MuMTV. Although moderate to high levels of MuMTV gp52 were expressed in mammary tumor tissues of 3 of 7 LC mice and 3 of 3 (C57BL/10ScSn X LC)F1 mice, the same animals showed no detectable MuMTV-precipitating antibody.

[Chronic infection caused by the simian Mason-Pfizer virus in primate cell cultures].

Cell cultures of monkey prepuce (Rhfs) and African green monkey kidney (BSC-1) were infected once with simian Mason-Pfizer virus (MPV) and virus expression in the course of establishment of chronic infection was studied. The productive infection was characterized by changes in the cell metabolism (DNA synthesis increased 2-3-fold as early as the "zero" passage), the appearance of gs-antigen, formation of virions of type D and high activity of RNA-dependent DNA-polymerase. Multinuclear giant cells appeared only in the infected Rhfs cell culture most sensitive to MPV.

Primate retroviruses: immunological cross-reactivity between major structural proteins of new and old world primate virus isolates.

The major 35,000-molecular-weight internal antigen (p35) of the squirrel monkey retrovirus (SMRV) was isolated and partially characterized. Immunological analysis of SMRV p35 led to the demonstration of antigenic determinants common to SMRV and the Mason-Pfizer monkey virus (MPMV). A broadly reactive competition immunoassay was developed utilizing antiserum to MPMV to precipitate 125I-labeled SMRV p35.

Oncogenicity of murine mammary tumor virus produced in tissue culture: brief communication.

Murine mammary tumor virus (MuMTV), produced from a glucocorticoid-stimulated C3H mouse mammary adenocarcinoma cell line, was free of murine leukemia virus and oncogenic for weanling BALB/c mice. Adenocarcinomas were induced by MuMTV as early as 136 days post inoculation and with as low as 5 X 10(3) virus particles/mouse. Tumor incidence did not correlate directly with virus dose; rather, it was low at higher MuMTV concentrations (1.

Gene order of the mouse mammary tumor virus glycoproteins.

Immunochemical and tryptic peptide mapping techniques were used to show that the mouse mammary tumor virus (MMTV) envelope glycoproteins gp52 and gp36 are distinct components derived from a common glycosylated precursor polypeptide of 75,000 daltons (gPr75). Because both gp52 and gp36 are derived from a common precursor polypeptide and therefore have a common initiation site, we have been able to determine their gene order within the viral genome. The gene order was deduced from three different types of experiments.