The Preparation of Highly Purified Pr8 Influenza Virus from Infected Mouse

The disease agents called viruses appear to be organic substances of such complexity that it is impractical to establish their identity by the classical methods of organic chemistry. However, certain useful methods are available which have been applied very successfully in demonstrating in tobacco mosaic disease that virus activity is a specific property of a high molecular weight nucleoprotein (1). One of the most impressive of these practical approaches is the demonstration, such as was made in the case of tobacco mosaic virus, that virus preparations obtained from widely different hosts possess essentially the same chemical, physical, and biological properties (1, 2). Such a comparison has not hitherto been made for a virus affecting animals, largely because sufficiently purified preparations of virus from different animal hosts have not been available. I t is particularly important, however, that such an approach be used in the case of animal viruses for it is recognized that the latter are more difficult to purify and hence to identify than are many plant viruses. For instance, while most of the plant viruses appear to be chemically and physically distinct from the materials extractable from normal plants, the isolation of some animal viruses is complicated by the presence of normal materials which are indistinguishable chemically and physically from the infectious material (3-5). I t is possible also that animal viruses differ fundamentally from plant viruses in chemical composition, particularly with respect to the lipid component which appears to be consistently a part of every purified animal virus preparation and is regularly lacking among purified plant viruses. If it can be shown that a particular virus contains a certain percentage of lipid when isolated from one host and the same amount in preparations from an entirely different host, the argument that lipid is an integral part of the virus is appreciably strengthened. Although influenza virus was initially transferred from man to ferrets and then to mice (6) and has.been studied in these animals for a number of years,