Characterization of hybrid CTL epitope delivery systems consisting of the Antennapedia homeodomain peptide vector formulated in liposomes

Peptide carriers, such the homeodomain of Antennapedia molecule (AntpHD), w hich spontaneously cross cellular membranes, have been exploited to deliver antigenic peptide Cw3 to the major histocompatibility complex (MHC) class- I presentation pathway and to prime cytotoxic T cells (CTL). However, the i n vivo use of AntpHD recombinant peptide has been limited because CTLs can only be primed in the presence of sodium dodecyl sulfate (SDS) as adjuvant. In this report, we have exploited liposomes to protect the AntpHD-Cw3 from serum degradation and to facilitate the delivery of the recombinant peptid e into the MHC class-I pathway of antigen-presenting cells. We have demonst rated that AntpHD recombinant peptide spontaneously associates with liposom es and this association is stable in vitro. However, exchange studies asses sing the transfer of the peptide to model membranes or cells in vitro indic ates that approximately 50% of the liposome-associated peptide is readily e xchangeable, This is consistent with trypsin-protection assays. which have shown that approximately 40% of the liposome-associated peptide is protecte d from hydrolysis. Importantly, macrophages and dendritic cells are able to internalize AntpHD recombinant peptide associated with liposomes resulting in efficient delivery of the CTL peptide into the cytosol. These studies h ave demonstrated that dendritic cells treated with AntpHD-Cw3 in liposomes sensitize CTL clones to lyse syngeneic target cells expressing Cw3 epitope. This strategy, which combines liposomes and a peptide vector. provides a n ew approach for introducing molecules into the MHC class-I antigen presenta tion pathway of dendritic cells. (C) 2001 Elsevier Science B.V. All rights reserved.