Isolation and Properties of the Equine Encephalomyelitis Virus (Eastern Strain)

Abstract

A liponucleoprotein complex was isolated by ultracentrif-ugal procedures from extracts of chick embryos diseased with the equine encephalomyelitis virus (Eastern strain). The purified material behaves as the virus in the induction of the characteristic disease in animals. The quantity of material isolated represented 0.5 to 1% of the total protein of the chick embryo extracts. The degree of cone, with respect to protein was about 100 times, and 2000 times on the basis of wt. of embryo tissue extracted. The infectivity of the purified prepns. paralleled that of the crude extracts from which they were derived. In constitution the complex is 54% fat-solvent extractive of which 64% was phospho-lipid. 25% cholesterol and 18% fatty acid. The remainder behaved as protein and with it was associated 9.6% nucleic acid of the ribose type. In the whole complex 4% carbo-hydrate was present on the basis of a dextrose standard. Sedimentation velocity studies in the analytical ultra-centrifuge showed the purified prepn. to be of high homogeneity with respect to particle size as indicated by this method of examination. The mean sedimentation constant as determined on 30 prepns. was 265.5 X 10-13 with a standard of deviation of the mean of [plus or minus] 5.4 X 10-13. The specific volume in Ringer''s soln. was 0.839 by pyenometric measurement. From the sedimentation constant and the results of viscosity studies, calculations of the mol. wt. of the complex gave an approximate value of 152.000,000. The mean approx. 50% point infections unit of the purified virus in 17 studies was 10-13.2 gm., which corresponded to 250 molecules.