Biophysical Properties of Preparations of Pr8 Influenza Virus

Abstract

The biophysical properties of several preparations of PR8 influenza virus have been studied. Electron micrographs showed slightly irregular, circular particles with an average diameter of 115 mµ and a standard deviation of the distribution of diameters of 15 per cent. The specific volume was determined with a pycnometer to be 0.79. The sedimentation rate was found to vary inversely with the concentration of virus. The extrapolated value for one preparation was 722 Svedberg units and the value for another preparation was 658 units. Sedimentation studies in sucrose solutions of varying densities showed a non-linear dependence of sedimentation rate upon solvent density, indicating that the density in solution increases with increasing sugar concentration. The virus particles floated in a sugar solution with a density of 1.18. The density in the absence of sucrose was estimated to be about 1.1. The virus was shown not to lose infectivity very rapidly in sucrose solutions. The spreading of the boundary during sedimentation was shown to be represented by a standard deviation of the sedimentation rate equal to 8 per cent of the mean. This corresponds to a distribution of diameters with a standard deviation of 4 per cent of the mean. A more slowly sedimenting component was observed with the ultracentrifuge in the highest concentrations of several of the preparations. The intrinsic viscosities, calculated on the basis of concentrations expressed as grams per cubic centimeter, of several highly purified preparations were determined to be between 11.3 and 16.5. The variation of sedimentation rate with concentration was shown to be due entirely to the variation of solution viscosity with concentration. The viscosity of the virus preparations can be explained as being due in great part to the presence of the slower sedimenting contaminating components which possess a very high intrinsic viscosity. The average particle diameter of the anhydrous PR8 virus particle was calculated from sedimentation and specific volume data to be about 80 mµ. The discrepancy between this value and that obtained from the electron micrographs, the greater size distribution from the electron micrographs, the slight irregularities in some of the particles as observed in the electron micrographs, the behavior of the sedimentation process in sucrose solutions of different densities, and the inactivation of the virus by withdrawal of electrolytes can all be explained in a straightforward manner if it is assumed that the virus particles in solution contain, in addition to the constituents shown by chemical analysis, about 60 per cent by weight of water. It is estimated that such hydrated virus particles are about 100 mµ in diameter.

Precipitin Reactions of Highly Purified Influenza Viruses and Related Materials

“…Since it has been shown that this slight activity is undoubtedly due to contamination with a trace of virus (27), it is apparent that independent particles of normal protein exist in centrifugally isolated preparations of F12 and of Lee influenza viruses. Sedimentation and electrophoretic studies (11,12) together with the serological tests on centrifuge fractions described in the present report, indicate that the same situation prevails with comparable PR8 virus preparations. However, when preparations of virus are obtained by adsorption on and elution from red cells followed by an appropriate number of cycles of differential centrifugation, or when they are got by electrophoretic fractionation, or by centrifugal fractionation, it can be shown that these preparations are essentially devoid of independent particles of the sedimentable component characteristic of normal allantoic fluid.…”

“…From infectious allantoic fluid of chick embryos, highly purified preparations of PR8 influenza virus have recently been obtained which are homogeneous in the analytical ultracentrifuge and in the Tiselius electrophoresis apparatus and which consist of particles about 100 m/~ in diameter (9)(10)(11)(12)(13). When these particles are sedimented it can be shown that the units carrying infectivity and chick cell agglutinating activity sediment at the same rate (14).…”

The Preparation of Highly Purified PR8 Influenza Virus from Infected Mouse Lungs

“…It is apparent from the electron micrographs as well as from the sedimentation data given above that the size and shape of the particles in highly purified preparations of mouse lung PR8 virus do not differ significantly from those of preparations from allantoic fluid (10,12).…”

Comprehensive Virology

“…Based on sedimentation properties and electron microscopic measurements, influenza A viruses were estimated to have a particle weight in the range of 270-290 x 10 6 daltons (Lauffer and Stanley, 1944;Sharp et at., 1945;Schramm, 1954). However, a much lower value of 151 x 10 6 was obtained for fowl plague virus based on sedimentation and diffusion coefficients (Schafer et at., 1952;Schramm, 1954).…”