Fusion of Sendai virus with model membranes as affected by dehydrating agents and pH: correlation between viral envelope hydrophobicity and fusion activity.

We have studied the importance of hydrophobic interactions in the fusion activity of Sendai virus. Viral fusion activity towards model lipid membranes was monitored using a fluorescence dequenching assay. Fusion was dependent on the composition of the target membrane and was more rapid and extensive at low pH. Dehydrating agents such as dimethylsulfoxide and dimethylsulfone greatly enhanced the initial rate and extent of the fusion process, the effect of dimethylsulfone doubling that of dimethylsulfoxide. However, dehydrating agents had a less pronounced stimulatory effect at low pH. Using the fluorescent probe ANS (1-aminonaphthalene-8-sulfonate) we have shown that low pH by itself involves a marked increase in the viral envelope hydrophobicity, probably resulting in the observed lower stimulation of viral fusion activity by dehydrating agents. Therefore, there seems to be a strong correlation between viral envelope hydrophobicity and viral fusion activity.