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Molecular cloning of infectious viral DNA from ecotropic neurotropic wild mouse retrovirus
Abstract:
Among a mixture of amphotropic and ecotropic murine leukemia viruses (MuLVs) isolated from paralyzed wild mice, only N-tropic ecotropic MuLV, cloned by cell culture techniques, has been shown to induce paralysis after reinjection into susceptible mice (M. B. Gardner, Curr. Top. Microbiol. Immunol. 79:215-239, 1978). The viral DNA genome of one of these neurotropic MuLVs (Cas-Br-E) has been cloned in Charon 21A at the SalI site. One clone, designated NE-8, was studied in more detail. A restriction endonuclease map of this cloned DNA was derived. Cloned viral DNA microinjected into NIH 3T3 cells produced infectious MuLV which was characterized as XC+, ecotropic, and N-tropic. The virus that was recovered after the microinjection of NE-8 DNA was also injected into susceptible SIM.S and NIH Swiss mice and was found to induce lower limb paralysis in these animals. These results make it highly unlikely that other agents (which might have escaped detection and separation from ecotropic MuLV by the techniques previously used) play a role in the etiology of this disease and clearly indicate that the ecotropic MuLV genome harbors sequences responsible for this paralysis. The availability of this clone DNA would now allow us to map these sequences on the genome.
Insights
Neurotropic ecotropic murine leukemia virus (MuLV) DNA cloned from paralyzed mice induces paralysis. This finding confirms the MuLV genome harbors paralysis-causing sequences, enabling further genetic mapping.
Area of Science:
- Virology
- Molecular Biology
- Neuroscience
Background:
- Paralysis in wild mice is associated with a mixture of retroviruses, including murine leukemia viruses (MuLVs).
- Previous studies identified N-tropic ecotropic MuLV as the causative agent of paralysis after reinjection into susceptible mice.
Purpose of the Study:
- To clone the viral DNA genome of a neurotropic MuLV (Cas-Br-E) responsible for inducing paralysis.
- To confirm that the ecotropic MuLV genome contains the specific sequences that cause paralysis.
Main Methods:
- Cloning of the Cas-Br-E MuLV DNA genome using Charon 21A vector at the SalI site.
- Restriction endonuclease mapping of the cloned viral DNA (NE-8).
- Microinjection of cloned viral DNA into NIH 3T3 cells to produce infectious MuLV.
Main Results:
- Infectious, XC-positive, ecotropic, N-tropic MuLV was recovered after microinjection of the NE-8 clone.
- This recovered virus induced lower limb paralysis when injected into susceptible SIM.S and NIH Swiss mice.
- The results strongly implicate ecotropic MuLV as the sole etiological agent, excluding other potential factors.
Conclusions:
- The ecotropic MuLV genome harbors the genetic sequences responsible for inducing paralysis.
- The availability of the cloned viral DNA (NE-8) facilitates the precise mapping of these neurovirulence-associated sequences.
- This research provides definitive evidence for the role of ecotropic MuLV in the etiology of paralysis observed in these mice.