Abstract
We previously reported that fusogenic liposomes (FL) prepared by fusing simple liposomes with Sendai virus perticles, could introduce their contents directly and efficiently into the cytoplasm. In this report, we investigated that exogenous antigen was processed and presented by class I major histocompatibility complex (MHC) molecules after delivery into cells by using FL. FL could introduce fragment A of diphtheria toxin, maintaining its cytotoxicity, into the cytoplasm of cells efficiently in vitro. Consistent with this, cells treated with ovalbumin (OVA) in FL were as susceptible to lysis by class I MHC-restricted, OVA specific cytotoxic T lymphocytes (CTL) as OVA-transfected clones. However, cells treated with naive OVA or OVA in simple liposomes were failed to lysis by OVA-specific CTL. These results indicated that FL could direct a exogenous antigen into class I MHC presentation pathway as a result of introduction of them into the cytoplasm. Thus, FL may facilitate induction of CD8+ CTL responses in vaccinations with exogenous soluble antigens, and they may serve as readily avaiable tools for dissecting class I MHC immunity to viruses and other intracellular pathogens.
