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Role of temperature-sensitive mutants in persistent infections initiated with vesicular stomatitis virus
Abstract:
Noncytocidal persistent infections at 37 C of mouse L cells (Lvsv) with infective B particles of vesicular stomatitis virus (VSV) could be established only in the presence of large numbers of defective interfering (DI) particles. Under these conditions, there was a rapid spontaneous selection of temperature-sensitive (ts) virus. At 10 days there was an increase to 17.8% in the frequency of ts clones in the virus population; by 17 days this frequency had reached 85.2%, and by 63 days 100% of the clones isolated were ts at 39.5 C, the nonpermissive temperature used. All 34 of the clones isolated from the 84-day fluid had an RNA-phenotype, and 8 clones that were tested all belonged to VSV complementation group I. When tested by an interference assay, Lvsv fluids did not contain significant numbers of DI particles (less than 1 DI/PFU). Furthermore, persistent infection of L cells at 37 C could be initiated under conditions in which few, if any, DI particles were present by using low input multiplicities (10(-4) and 10(-5) of a clonal isolate of an RNA-group I mutant obtained from Lvsv cells. On the basis of these and other results, a mechanism is proposed to explain the role of ts mutants in both the establishment and maintenance of the persistently infected state.
Insights
Persistent vesicular stomatitis virus (VSV) infections in mouse L cells rapidly select for temperature-sensitive (ts) mutants, with 100% of viral clones becoming ts over time. This suggests ts mutants play a key role in establishing and maintaining persistent infections.
Area of Science:
- Virology
- Cell Biology
- Molecular Biology
Background:
- Noncytocidal persistent infections can be established in mouse L cells using vesicular stomatitis virus (VSV).
- Defective interfering (DI) particles are often associated with persistent viral infections.
Purpose of the Study:
- To investigate the role of temperature-sensitive (ts) mutants in the establishment and maintenance of persistent VSV infections.
- To elucidate the mechanism by which ts mutants contribute to persistent viral states.
Main Methods:
- Establishing persistent VSV infections in mouse L cells at 37°C in the presence of DI particles.
- Monitoring the frequency of ts viral clones over time.
- Characterizing viral clones using RNA-phenotype and complementation assays.
- Initiating persistent infections with low multiplicities of ts mutants.
Main Results:
- Persistent VSV infections rapidly selected for ts mutants, reaching 100% frequency within 63 days.
- Isolated ts clones predominantly exhibited an RNA-phenotype and belonged to VSV complementation group I.
- Significant numbers of DI particles were not detected in the persistent infection fluids.
- Persistent infections could be initiated using low multiplicities of ts mutants even without high levels of DI particles.
Conclusions:
- Temperature-sensitive mutants are crucial for both the establishment and maintenance of persistent VSV infections in L cells.
- The selection and proliferation of ts mutants are a key feature of this persistent infection model.
- A proposed mechanism highlights the role of ts mutants in the dynamics of persistent viral infections.