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Studies on the budding process of a temperature-sensitive mutant of murine leukemia virus with a scanning electron
Abstract:
The scanning electron microscope was used to study the budding process of the wild-type Moloney murine leukemia virus and one of its temperature-sensitive mutants, designated ts 3. A considerably larger number of budding particles was observed on TB cells infected with ts 3 at the nonpermissive temperature (39 C) than at the permissive temperature (34 C). No apparent difference was noted between the number of particles on ts 3-infected cells at (34 C) and wild-type-infected cells at 34 or 39 C. Virions were detected at the cell membrane of ts 3-infected cells at 39 C as early as 8 h postinfection. Virion density increased progressively up to 48 h after which no increase was observed. An average of 1,600 virus particles was observed at the cell surface at the peak of virus production. The distribution of these on the cell membrane appeared to be random. The maximum proportion of the cell surface occupied by the viral particles did not exceed 10%. After temperature shift from 39 to 34 C, approximately 90% of the particles had dissociated from the cell membrane within 1 h.
Insights
Moloney murine leukemia virus budding is temperature-sensitive. A mutant (ts 3) showed increased viral particle budding at nonpermissive temperatures, which rapidly reversed upon temperature shift.
Area of Science:
- Virology
- Microbiology
- Cell Biology
Background:
- Moloney murine leukemia virus (MMLV) is a retrovirus.
- Understanding viral budding is crucial for controlling retroviral infections.
- Temperature-sensitive mutants offer insights into viral replication dynamics.
Purpose of the Study:
- To investigate the effect of temperature on MMLV budding.
- To characterize the behavior of a temperature-sensitive MMLV mutant (ts 3).
- To analyze virion assembly and release at the cellular level.
Main Methods:
- Scanning electron microscopy (SEM) was employed.
- Wild-type MMLV and ts 3 mutant infections were studied.
- Cells were observed at permissive (34 C) and nonpermissive (39 C) temperatures.
Main Results:
- ts 3 mutant exhibited significantly more budding at 39 C compared to 34 C.
- No difference in budding was observed between ts 3 at 34 C and wild-type MMLV.
- Virions appeared on cell membranes as early as 8 hours post-infection at 39 C.
- A temperature shift from 39 C to 34 C caused rapid dissociation of ~90% of viral particles.
Conclusions:
- MMLV budding is regulated by temperature, with ts 3 showing a clear defect at nonpermissive temperatures.
- The ts 3 mutant's budding process is reversible upon a shift to permissive temperatures.
- SEM is effective in visualizing and quantifying viral budding events.
