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Characterization of infectious oncornaviruses from MOPC-460 plasmacytomas: their relation to A-type particles
Abstract:
MOPC-460 mouse plasmacytoma cells produce intracellular A-type particles and extracellular oncornavirus-like particles ("myeloma-associated virus," abbreviated MAV). The genomes of these two particles are closely related. During attempts to establish infections with MOPC-460 extracellular particles, we isolated ecotropic and xenotropic infectious forms of murine leukemia virus. We have investigated the relation of these isolates to A-type particles and to MAV by nucleic acid hybridization. Using complementary DNA probes prepared from the two isolates, we found that these infectious murine leukemia viruses differ from A-type particles and from MAV. Moreover, we found that MAV is the predominant extracellular component: the ecotropic and xenotropic forms of murine leukemia virus were present at only low levels (less than 5%) in MAV preparations. Neither the SC-1 cells infected with ectropic murine leukemia virus nor the mink cells infected with xenotropic murine leukemia virus showed any A-type particles in their cytoplasm when examined by electron microscopy. Our inability to demonstrate infection by the A-type particle-related component, MAV, suggests that these may be defective.
Insights
Researchers investigated murine leukemia virus isolates from MOPC-460 cells. Nucleic acid hybridization revealed infectious murine leukemia viruses differ from A-type particles and myeloma-associated virus (MAV), suggesting MAV may be defective.
Area of Science:
- Virology
- Molecular Biology
- Oncology
Background:
- MOPC-460 mouse plasmacytoma cells produce intracellular A-type particles and extracellular myeloma-associated virus (MAV).
- The genomes of A-type particles and MAV are closely related.
- Attempts to infect cells with MOPC-460 extracellular particles yielded ecotropic and xenotropic murine leukemia virus isolates.
Purpose of the Study:
- To investigate the relationship between A-type particles, MAV, and isolated infectious murine leukemia viruses.
- To determine if isolated murine leukemia viruses are related to MAV or A-type particles.
- To assess the potential defectiveness of MAV.
Main Methods:
- Nucleic acid hybridization using complementary DNA probes derived from ecotropic and xenotropic murine leukemia virus isolates.
- Electron microscopy to examine A-type particle presence in infected cells.
Main Results:
- Infectious murine leukemia viruses were found to differ genetically from A-type particles and MAV.
- MAV was the predominant extracellular component, with ecotropic and xenotropic murine leukemia viruses present at low levels (<5%).
- No A-type particles were observed in the cytoplasm of SC-1 or mink cells infected with the respective murine leukemia virus isolates.
Conclusions:
- The isolated infectious murine leukemia viruses are distinct from MAV and A-type particles.
- MAV represents the primary extracellular viral component, with infectious murine leukemia viruses at low abundance.
- The inability to demonstrate infection by MAV suggests it may be a defective virus.