Physical Markers of Change in a Virion Population during Passage

Abstract

A physical heterogeneity is revealed in several unpurified populations of poxvirus by means of sedimentation-velocity (SV) spectra. Predominantly single-peak distributions have been found, but the position, and to a lesser extent, the width of the peak is often altered by passage of the virus in a new host. Cloned subpopulations, different from each other and from their common parent population, have been found with SV spectra. The electron microscopic counts of particles, from which the rate-zonal SV spectra are constructed, give additional evidence of population changes through plaquing efficiency ratios. These findings illustrate physical means by which a whole population of virions may be characterized and changes detected in the progeny from a new host.