A biochemical concept of cellular production of paramyxoviruses

Previous analysis in vitro of the interaction between some paramyxoviruses and the chicken embryo has indicated that the cell most productive (MP) of virus is the heart cell whereas the liver cell is least productive (LP). More superior production of virus results from more efficient release of virions, whereas the kinetics of viral attachment and penetration and the production of interferon are similar for both types of cell. Since plasma membrane lipids may represent the structural key to enveloping and release of paramyxovirions, the lipid composition of MP and LP cells and purified plasma membranes was investigated. The plasma membranes of heart cells contain a high molar ratio of cholesterol to phospholipid (1.66 vs. 0.55), more phosphatidylethanolamine (34.8% vs. 24.0% of total phospholipid), and less phosphatidylcholine (39.7% vs. 55.0% of total phospholipid) than the plasma membranes of liver ce-ls. The fatty acids of heart and liver cellular plasma membranes are similar. The glycosphingolipid components of heart and liver cells are also the same, as is the content of gangliosides (6.18 mug vs. 6.49 mug neuraminic acid/mg protein) in these cells, but the heart cell contains one-fifth as much total cerebroside (34.3 mg vs. 174.3 mug cerebroside/mg protein), indicating a greater ganglioside to neutral glycolipid ratio for the heart cell. Comparison of these data with the monkey/hamster (MP/LP) renal cell-parainfluenza SV5 virus system of Klenk and Choppin suggests that essential molecular determinants of superior cellular production of paramyxoviruses are the relative concentration of phosphatidylethanolamine and the molar ratio of cholesterol to phospholipid in the plasma membrane.