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BIOCHEMICAL STUDIES ON THE VIRUS AND THE INCLUSION BODIES OF SILKWORM JAUNDICE
1Department of Animal and Plant Pathology of The Rockefeller Institute for Medical Research, Princeton, New Jersey.
Abstract:
Silkworm jaundice virus is stable only between pH 5 and about pH 9. The fact that polyhedral bodies retain virus activity after exposure to hydrogen ion concentrations as high as pH 2 is regarded as being due to the protection of virus occluded within the bodies. Further evidence on this point is furnished by experiments on the activity of the polyhedra when treated with antiformin-formalin and when treated with 1 per cent sodium dodecyl sulfate. Free jaundice virus is inactivated by 36 per cent urea, 36 per cent guanidine, or 1 per cent sodium dodecyl sulfate. A purified preparation, active at a concentration of 10(-12) gm. per cc., consisting essentially of a nucleoprotein component having a sedimentation constant of 17 S, a particle diameter of 10 mmicro, and a molecular weight of about 300,000, was obtained from the polyhedra-free blood of jaundiced silkworms. However, a component having a sedimentation constant of 16 S was demonstrated in the blood of normal worms. This component, the material from diseased blood, and polyhedral bodies, were found to contain serologically related material. Absorption of material from diseased blood with antiserum induced by a preparation from normal blood yielded a substance having a sedimentation constant of 17 S, which reacted strongly only with antiserum to material from diseased blood. This fact, and especially the fact that the inoculation of normal blood does not produce jaundice, demonstrates that a difference must exist between the purified material from diseased worms and that from normal ones. Chemical analyses of the purified virus material and of the polyhedral bodies also showed certain differences, although both probably represent nucleoproteins. Examination by means of the electron microscope showed further differences.
Insights
Silkworm jaundice virus is protected within polyhedral bodies, but free virus is inactivated by chemicals. Purified virus from diseased silkworms differs from normal components, indicating a distinct viral entity.
Area of Science:
- Virology
- Biochemistry
- Molecular Biology
Background:
- Silkworm jaundice virus exhibits stability within a specific pH range (5-9).
- Polyhedral bodies protect the virus from harsh conditions, such as low pH.
- Free silkworm jaundice virus is susceptible to inactivation by various chemical agents.
Purpose of the Study:
- To investigate the protective role of polyhedral bodies against silkworm jaundice virus inactivation.
- To characterize the biophysical and biochemical properties of the virus.
- To differentiate the viral components in diseased silkworms from those in normal silkworms.
Main Methods:
- Exposure of virus and polyhedral bodies to varying pH levels and chemical treatments (urea, guanidine, sodium dodecyl sulfate).
- Purification of viral nucleoprotein from silkworm blood.
- Sedimentation analysis (ultracentrifugation) to determine sedimentation constants.
- Serological testing using antisera.
- Electron microscopy and chemical analysis.
Main Results:
- Polyhedral bodies shield the virus from inactivation at low pH (pH 2).
- Free virus is inactivated by 36% urea, 36% guanidine, and 1% sodium dodecyl sulfate.
- A purified nucleoprotein component (17 S, 10 nm diameter, 300,000 MW) was isolated from diseased silkworms.
- A distinct component (16 S) was found in normal silkworm blood.
- Both diseased and normal components, along with polyhedral bodies, showed serological relatedness.
- Purified virus from diseased worms demonstrated unique characteristics compared to normal components, confirmed by serology, chemical analysis, and electron microscopy.
Conclusions:
- Polyhedral bodies are crucial for the stability and protection of silkworm jaundice virus.
- A distinct viral nucleoprotein is responsible for jaundice in silkworms, differing from components in healthy individuals.
- These findings contribute to understanding the virus's structure, stability, and pathogenicity.
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