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Biomedical subjects

L O Arthur

Publications and source records attributed to L O Arthur.

At least 109 records · Page 6Linked to original sources
PubMed1980

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. DNA binding by CAP proteins was sensitive to heat or addition of sodium dodecyl sulphate (SDS) and was neutralized by pre-incubation of CAP with anti-MMTV p14, but not by anti-MMTV p27, p10 or anti-mouse casein. Incubation of CAP with dsDNA led to unwinding of the double helix as measured by its increased sensitivity to S1 nuclease digestion. This activity was also linear over a several-fold concentration of A particle protein and was heat labile. It was not inhibited by pre-incubation of CAP with either anti-MMTV p14 or with anti-MMTV, anti-MMTV p27 and anti-MMTV p10. DNA unwinding was inhibited by anti-A particle antiserum and to a lesser extent by anti-CAP p20-18.

Animals↗
PubMed1980

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. The neutralization was immunoglobulin G mediated, and the antibodies of C3H/HeN mammary tumor-bearing mice were type specific and capable of distinguishing C3H and GR/N MMTVs from RIII and C3H/HeNf MMTVs. Precipitating antibodies were detected in sera from RIII and GR/N tumor-bearing mice, GR/N non-tumor-bearing mice, and six of the feral mice, although these same sera did not neutralize the Kirsten sarcoma virus (C3H MMTV) pseudotype. The results of this study and of a previous study demonstrate that C3H/HeN mammary tumor-bearing mice develop three functionally distinct antibody populations: (i) group-specific virus-precipitating antibodies; (ii) type-specific virus-neutralizing antibodies; and (iii) type-specific cytotoxic antibodies.

Animals↗
PubMed1980

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. All of the monoclonal antibodies were directed against the envelope glycoprotein gp52. Three of the hybrid cell lines produced immunoglobulins of the immunoglobulin M subclass and three produced immunoglobulin G2a. The monoclonal antibodies showed limited charge heterogeneity in light and heavy chains when analyzed by high-resolution, two-dimensional gel electrophoresis. Three serologically distinct specificities were observed when these ascites fluids were tested against different strains of MMTV. The antigenic determinants detected were the following: (i) a type-specific determinant unique to the C3H strain of MMTV; (ii) class-specific determinants shared between C3H and GR MMTVs; and (iii) a group-specific determinant found on C3H, GR, RIII, and the endogenous C3H (C3Hf) MMTVs. Because monoclonal antibodies recognize single antigenic determinants, these results demonstrate for the first time that the three patterns of antigenic reactivity for MMTV are related to individual determinants on the gp52 molecule and also clearly show that one strain of MMTV can be distinguished from other strains.

Animals↗
PubMed1979

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.i.m.; about 0.06 VP/cell) In A204 cell cultures. At higher p.i.m. (about 600 to 6000 VP/cell) newly synthesized virus was detected within 4 days post infection. Although virus production was cumulative following primary infection, after subculture of infected cultures MPVM production was greater during active cell division. Using synchronization techniques, MPMV replication in persistently infected cultures was found to be cell cycle-dependent. The major internal antigen, p27, was synthesized in G2 and newly synthesized virus particles were released predominantly during mitosis and early G1. Colcemid arrest of cells during mitosis inhibited subsequent MPMV release. Consequently, production of extracellular virus depends upon the progression of cells through the mitotic stage. These data, which provided a basic understanding of the virus-host relationship that occurs in primate cells productively infected with MPMV, were used as a guideline for isolating MPMV-like viruses from experimentally and naturally infected Rhesus monkey.

Animals↗
PubMed1979

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. Sera from mammary tumor-bearing mice and mammary tumors from C3H/HeN and C3H/HeNf mice competed in both the gp52 and the p10 assays. Although these radioimmunoassays detected predominantly group-specific antigenic determinants in C3H/HeN and C3H/HeNf tumor extracts, type specificity was also found with gp52. Absorption of the anti-MMTV serum with C3H/HeNf tumor extracts removed all antibodies directed against p10 and decreased the anti-gp52 titer approximately 30-fold. When this absorbed antiserum was used at limiting dilution in the gp52 radioimmunoassay, C3H/HeN tumor extracts gave complete competition, whereas no competition was found with C3H/HeNf tumor extracts.

Animals↗
PubMed1979

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. Absorption of the sera with GR (MMTV) CrFK cells also removed all of the cytotoxicity, whereas absorption with RIII (MMTV) CrFK cells was negative, even though all three infected cat cells contained equivalent amounts of gp52. The same C3H cytotoxic sera also neutralized the focus-forming capacity of a C3H MMTV pseudotype of Kirsten sarcoma virus containing MMTV gp52. In contrast, sera from mammary tumor-bearing GR and RIII mice did not neutralize the pseudotype. Furthermore, neutralization could be achieved only by anti-gp52 but not by anti-gp36, -p27, -p14, or -p10 C3H MMTV sera. The gp52's of C3H, GR, and RIII MMTV could also be distinguished by using a type-specific competition radioimmunoassay employing (125)I-gp52 of C3H MMTV and a hyperimmune rabbit anti-C3H MMTV serum. To demonstrate these differences directly, we studied the primary structure of gp52 on the surface of the C3H, GR, and RIII (MMTV) CrFK cells. Two-dimensional tryptic peptide maps of the cell surface lactoper-oxidase-catalyzed iodinated gp52's revealed a greater number of peptides common to the gp52's of C3H and GR MMTVs than to RIII MMTV gp52. These results demonstrate that gp52 is a major target antigen for both cytotoxic and neutralizing antibodies, that the cell surface and virion-associated gp52's of C3H, GR, and RIII MMTV contain both group- and type-specific determinants, and that C3H and GR MMTV gp52's are antigenically more related to each other than to RIII MMTV gp52. Furthermore, C3H mammary tumor-bearing mice develop type-specific antibodies capable of recognizing unique gp52 determinants and, therefore, are able to distinguish the gp52 of C3H MMTV from the gp52's of GR and RIII MMTV.

Animals↗
PubMed1979

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. However, oligonucleotide fingerprints obtained of MMTV 70S RNA revealed that approximately 20% of the large oligonucleotides examined were unique to each virus. The oligonucleotide fingerprint indicated that although the viruses were similar, they differed in their genetic content. The differences in the two viruses extended to immunological differences in the major envelope glycoprotein, gp52. C3Hf MMTV competed only partially in a homologous radioimmunoassay for gp52 of C3H MMTV, whereas C3H MMTV gave complete competition, indicating that gp52 of C3H MMTV contained type-specific determinants not present on gp52 of C3Hf MMTV. Comparison of C3Hf MMTV with highly oncogenic C3H, GR, and RIII MMTVs in a homologous C3H MMTV gp52 assay gave two patterns of reactivity: complete competition by GR and C3H MMTV and incomplete competition by C3Hf and RIII MMTV. Absorption of anti-C3H MMTV serum by either C3Hf MMTV or RIII MMTV removed all antibodies against both viruses but not against GR and C3H MMTVs. These results indicate that C3H and GR MMTVs are more closely related to each other than to RIII and C3Hf MMTVs.

Animals↗
PubMed1978

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. In addition, shared antigenic determinants between intracytoplasmic A particles and MMTV p27, p20 and p10 were demonstrated. MMTV p14 did not cross-react with the low-molecular-weight DNA-binding proteins of MuLV or of type-C or -D viruses of higher mammals.

Animals↗
PubMed1978

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 (1.2 X 10(8) particles/mouse), reached and optimum at 1.3 X 10(5) particles/mouse, and decreased with virus dilution.

Adenocarcinoma↗
PubMed1978

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. Although the major structural proteins of MPMV and SMRV competed with equal efficiency in this assay, type B and type C oncornavirus proteins lacked detectable reactivity. Antibodies reactive with the major structural proteins of both MPMV and SMRV were observed in sera of several normal rhesus monkeys with known prior exposure to MPMV-infected animals. These findings demonstrate the ability of sera from naturally immunized primates to recognize broadly reactive interspecies antigenic determinants shared by the major structural proteins of type D oncornaviruses, and they suggest possible horizontal transmission of MPMV among rhesus monkeys. Although sera from a number of squirrel monkeys contained antibody to SMRV p35, the possibility that this latter reactivity was due to endogenous virus activation rather than horizontal transmission cannot be ruled out.

Animals↗