During attempts at purification of horse-sickness virus for electron-microscopy from infected mouse brain extracts, it was found that a combination of polyethylene glycol precipitation of the virus, ultracentrifugation and zone electrophoresis gave promising results. The final purified material could not be regarded as pure on account of the presence of considerable normal brain components, but it contained particles not present in normal brain treated identically, which could be recognized as virus particles. The virus particles appear to have diameters of 70–80 mμ and are estimated to have 92 rod-shaped subunits radiating from a spherical body.
The authors wish to express their gratitude to Prof. A. Kipps and R. A. Alexander for their continued interest in this work.
The electron micrographs were taken by Mr L. G. Fowle of the Department of Physics, University of Cape Town.
This investigation was supported in part by a Public Health Service research grant AI 04044–02 from the National Institutes of Health, Bethesda, U.S.A.