Lipid content of standard and incomplete influenza A virus.

THE term ‘incomplete’ virus was used by von Magnus1 for designating products appearing on serial intra-allantoic passage of large inocula of influenza virus, and distinguished from ‘standard’ virus obtained after inoculation of diluted seed material by the apparent lack of infectivity with retained high haemagglutinating capacity. In sedimentation studies Gard, von Magnus et al. 2,3 found the incomplete virus to be more inhomogeneous than standard virus and to have a considerably lower sedimentation constant. Birch-Andersen and Svedmyr4, examining several preparations in the electron microscope, failed to demonstrate any significant differences in the mean particle sizes, although the incomplete virus tended to show a somewhat wider variation in size and morphology.