The Occurrence of Squalene in Lipid of Fowlpox Virus

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Abstract The lipids of highly purified fowlpox virus and those of the normal and infected host cell (chick scalp epithelium) were studied. 1. It was found that the virus contained 34% lipid with squalene being a major component (16.8%) and the only hydrocarbon present. In contrast, squalene was either absent or present only in trace amounts in normal epithelium. 2. Except for the presence of squalene, the lipid classes of the virus qualitatively resembled those found in the normal cell, but thin layer chromatography and individual measurements revealed marked differences in quantitative distribution. The amount of cholesteryl ester, in particular, was elevated in the virus. Cholesterol, mono-, di-, and triglycerides, free fatty acid, phospholipid, and an unidentified lipid class composed the remainder of the virus lipid. 3. Total fatty acids of the virus and the surrounding matrix and those of the normal and infected epithelium were mainly saturated and monoenoic with less than 10% polyenoic members present. Analysis with a complementary thin layer and gas-liquid chromatographic procedure revealed that a minimum of 31 fatty acids containing both even and odd chain members from C12–C28 inclusive were present. Branched chain acids were not found. Two points of dissimilarity between the fatty acid composition of the virus and the normal epithelium were the depression in percentage of odd chain acids and the increased monoene to saturate ratio observed with the virus acids. Fatty acid patterns in the cholesteryl ester, triglyceride, free fatty acid, and phospholipid fractions of the virus did not differ greatly. 4. Complex mixtures of aldehydes were discovered in the virus and epithelium phospholipid fractions. At least 54 components, predominately saturated, were detected. Two essentially complete homologous series (normal and isoaldehydes) with even and odd chain members from C10–C28 were found. Anteiso-aldehydes were also present. Aldehydes of the virus were more unsaturated and contained less branched chain members than those of the epithelium. 5. The function of the lipid in fowlpox virus is unclear. The present evidence, however, indicates that the lipid of fowlpox virus differs markedly from that of cell membranes.