The main effects of the proteolytic digestion of the Asian (A 2) strain of influenza virus were a loss of the characteristic surface morphology and a change in density. The untreated virus was found to have a density of 1·204 g./cm.3 on a sucrose gradient, but after protease action the density was 1·168 g./cm.3. The density change was correlated with a change in particle mass as indicated by a fall in sedimentation coefficient (S20) from the normal 788 Svedbergs to 562 Svedbergs.
From the data obtained with the protease-treated and control virus preparations it was calculated that the changes observed could be accounted for by a loss of 35 to 40 % of the particle mass. The action of the protease appeared to be confined to the surface of the virus. Concomitantly with the destruction of the haemagglutinating activity there was a release of neuraminidase activity, and on a density gradient this could be separated from the residual virus and was located at the top of the gradient tube. In addition to the changes described, there appeared to be a destruction of the virus V antigen.
AminoffD.1961; Methods for the quantitative estimation of TV-acetyl neuraminic acid and their application to hydrolysates of sialomucoids. Biochem. J 81:384
BradstreetC. M. P., TaylorC. D. E.1962; Technique of complement fixation test applicable to the diagnosis of virus diseases. Monthly Bull. Publ Hlth. Lab. Service 21:96
CleelandR., SuggJ. Y.1963; Inactivation of haemagglutinating capacity of type A influenza by trypsin treatment (28209). Proc. Soc. exp. Biol. Med 112:913
FrommhagenL. H., KnightC. A., FreemanN. K.1959; The ribonucleic acid, lipid and poly-saccharide constituents of influenza virus preparations. Virology 8:176
International Critical Tables1927 New York: McGraw-Hill and Co. Inc;
MayronE. W., RobertB., WinzlerR. J., RafelsonM. E.1961; Studies on the neuraminidase of influenza vims. (1) Separation and some properties of the enzyme from Asian and PR 8 strains. Archs Biochem. Biophys 92:475