A new concept for the development of novel vectors is to overcome the limitations of individual vectors by combining them. The HVJ-liposome was developed by combining liposomes with fusion proteins derived from the hemagglutinating virus of Japan (HVJ), also known as Sendai virus. Gene transfer in vivo using this delivery system can be repeated because it is much less immunogenic and cytotoxic than other viral-vector systems. By coupling the Epstein-Barr virus (EBV) replicon apparatus with HVJ-liposomes, transgene expression can be sustained in vitro and in vivo. In animal models, this system has shown promise for several diseases, including cancer and cardiovascular disease.