Molecular Mechanism of Virus-Induced Cell damage and its regulation

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We analyzed the mechanisms of cell fusion, multinucleated giant cell formation and virus entry using paramyxoviruses and HIV.We found an interesting cell fusion induction system, in which fusion (F) protein of paramyxovirus alone can induce multinucleated giant cells. We also found that there were two kinds of F protein of SV 5, that is, one F protein of SV 5 has an ability for induction cell fusion without HN protein and other F protein can induce cell fusion by an assistance of HN protein. There are three amino acid differences between these F proteins, and we identified amino acid responsible for inducibility of cell fusion by F protein alone.We previously found that virus-induced cell fusion is regulated by some host cell factors, Fusion Regulatory Factors (FRPs)-1 and -2. We isolated 8 monoclonal antibodies directed against FRP-1 molecules and clarified their abilities. Anti-FRP-1 antibodies can be classified into three groups, namely, cell fusion enhancing antibodies, cell fusion suppressing antibodies and antibody showing no activity. Anti-FRP-1 antibody, both cell fusion enhancing and suppressing antibodies, can stimulate intracellular signaling. However, we could not find the difference between these antidodies-induced signaling. We also isolate 19 monoclonal antibodies directed against murine FRP-1. Murine FRP-1 was found to be alloantigens and to be identical to Ly 10 alloantigens.