A novel method for the detection of early events in cell-cell fusion of Semliki Forest virus infected cells growing in monolayer cultures

Semliki Forest virus infected Aedes albopictus cells were used to investigate virus induced cell-cell fusion. It was shown by a novel method that cell-cell fusion was completed within approximately 5 minutes after triggering the fusion event by low pH. This method consists of fixing fusing cells with glutaraldehyde and microinjecting the highly fluroescent and rapidly diffusing dye Lucifer yellow. In contrast, polykaryon formation, the usually used criterion to measure cell-cell fusion occurred only within 30 minutes. Furthermore, it was shown that potassium cyanide, a potent inhibitor of polykaryon formation in the described system, inhibits an early step of membrane-membrane fusion of neighbouring cells.