FUSION PARTNERS FOR NIH 3T3 HAB2 FIBROBLASTS EXPRESSING HEMAGGLUTININ

In an attempt to work out an experimental system for studying the mechanisms of fusion induced by influenza-virus fusion protein hemagglutinin (HA), several cell lines (PLC/PRF/5, BHK-21, MDCK, VERO) were tested for their ability to fuse with NIH 3T3 HA2b cells that constitutively express HA. Using fluorescent microscopy to follow the dye spread from the labelled cells to the unlabelled ones under conditions that were to activate HA (proteolytic cleavage of inactive MA) and to trigger fusion (pH drop), we have shown that only PLC PRF and BHK-21 cells fused with HA2b cells at a rate comparable with that obtained for RBC. New fusion systems, BHK/HA2b and PLC/HA2b, provide important advantages for further investigations of fusion mechanisms at a single-cell level, as both partners are easily and equally accessible for the manipulations required for high-resolution whole-cell patch-clamp measurements. PLC/HA2b system seems to be more promissing because of clear morphological differences between the partners. The mechanism of fusion tolerance displayed by other cells remians to be explained.