Incorporation of branched-chain fatty acids into myxoviruses.

The incorporation of free fatty acids into myxoviruses was shown, using branched-chain fatty acids as molecular markers. The presence of isostearic or phytanic acid was detected by gas-liquid chromatography in the phospholipid fraction of the A(0)/PR8/34 strain of influenza virus. Uptake of free fatty acids into the virus varied from 8 to 11 per cent and was accompanied by a shift in the fatty acid profile. Infected allantoic fluids from eggs treated with branched-chain acids possessed higher hemagglutinin activity when compared to fluids infected under normal conditions. Attempts to detect branched-chain acids in Sendai virus were unsuccessful. Shifts in acyl chain composition persisted after three passages of modified viruses in the absence of branched-chain acids. Force-area curves at an air-water interface revealed the cross-sectional area of branched-chain acids to be greater than their straight-chain homologs. It is suggested that hydrophobic interactions can alter the configuration of envelope proteins. Such changes may have an important role in the selection of fragments of influenza viral genome and can conceivably alter viral genotype.