HIV-INDUCED SYNCYTIA OF A T-CELL LINE FORM SINGLE GIANT PSEUDOPODS AND ARE MOTILE

The human immunodeficiency virus, HIV, induces syncytium formation in cultures of many T cell lines. These syncytia have previously been vie wed as disorganized fusion products in the throes of death. Evidence i s presented that in HIV1-infected SupT1 cultures, syncytia five times to over one hundred times larger than single cells organize their many nuclei into blastula-like balls, reorganize their cytoskeleton to mim ic that of a single cell, and extend single, giant pseudopods in a pol ar fashion. Medium-sized syncytia are capable of translocation through extension of these giant pseudopods. The rate of translocation of syn cytia is comparable to that of single cells. Single cell motility, syn cytium motility and pseudopod extension also appear to play roles in t he recruitment of cells into syncytia. Finally, condensation of F-acti n at cell-syncytium and syncytium-syncytium adhesion sites suggests th e involvement of the cytoskeleton in the adhesion and/or subsequent fu sion event. These results suggest that the fusion events involved in H IV-induced syncytia formation involve both cell motility and reorganiz ation of the cytoskeleton, and demonstrate that syncytia are highly or ganized, motile entities.