Fusion activity of African swine fever virus towards target membranes: Lipid dependence and effect of dehydrating agents

Fusion of African swine fever virus (ASFV) with model membranes was monitored by a fluorescence dequenching assay. ASFV was able to fuse with liposomes of various compositions. Fusion was more extensive with liposomes made of negatively charged phospholipids, and reduced in the presence of the neutral phospholipid phosphatidylcholine (PC). Fusion activity of ASFV was pH-dependent, the extent of fusion increasing with decreasing pH for all target membranes. These results are consistent with the in vivo characteristics of fusion of ASFV with the endosome membrane. An increase in fusion activity was obtained with dehydrating agents, similarly to what occurs with other lipid-enveloped viruses. Dehydrating agents such as dimethylsulfoxide and dimethylsulfone greatly enhanced fusion, the effect of dimethylsulfone being more pronounced than that of dimethylsulfoxide. Poly(ethylene glycol) also potentiated ASFV fusion activity, and the effect of this polymer was found to be dependent on its molecular weight. These results stress the importance of dehydration and hydrophobic interactions on the early events of viral penetration into target cells.