Lipids of the BAI strain A avian tumor virus and of the myeloblast host cell

Lipids of the BAI strain A virus and of the myeloblast host cell and nuclear, microsomal and external membrane cell fractions were analyzed by thin-layer chromatography. Total virus lipids consisted of 34% cholesterol, 5.3% neutral fat and 61% phospholipid. Of the latter, the principal components were sphingomyelin, 16; phosphatidyl ethanolamine, 21; and lecithin, 11%, respectively. This constitution of the BAI strain A virus was proportionally similar to that of the influenza agent. Virus lipids were qualitatively similar to those of the whole host cell and the nuclear, microsomal, and cell membrane fractions. Marked quantitative differences were observed between the virus and host cell components, particularly with respect to the cell membrane fraction in which the low content of cholesterol, 9%, and 30% neutral fat were the reverse of the virus with 34 and 5.3% of these constituents. Major differences observed also with the phospholipids were, again, greater in the comparison between the virus and the cell membrane. The findings were interpreted to indicate the improbability of major cell membrane contribution to the virus lipids. Consideration of the analytical data and correlation with the ultrastructural aspects of BAI strain A budding from the myeloblast surface suggest that the virus lipids are specifically assembled in the process of virus synthesis not only from the external cell membrane but also principally from contiguous and possibly other cytoplasmic structures.