Abstract The in vivo induction of a CTL response using Antennapedia homeodomain (AntpHD) fused to a poorly immunogenic CTL epitope requires that the Ag is given in presence of SDS, an unacceptable adjuvant for human use. In the present report, we developed a hybrid CTL epitope delivery system consisting of AntpHD peptide vector formulated in liposomes as an alternative approach to bypass the need for SDS. It is proposed that liposomes will prevent degradation of the Ag in vivo and will deliver AntpHD recombinant peptide to the cytosol of APCs. We show in this work that dendritic cells incubated with AntpHD-fused peptide in liposomes can present MHC class I-restricted peptide and induce CTL response with a minimal amount of Ag. Intracellular processing studies have shown that encapsulated AntpHD recombinant peptide is endocytized before entering the cytosol, where it is processed by the proteasome complex. The processed liposomal peptides are then transported to the endoplasmic reticulum. The increase of the CTL response induced by AntpHD-fused peptide in liposomes correlates with this active transport to the class I-processing pathway. In vivo studies demonstrated that positively charged liposomes increase the immunogenicity of AntpHD-Cw3 when injected s.c. in mice in comparison to SDS. Moreover, addition of CpG oligodeoxynucleotide immunostimulatory sequences further increase the CD8+ T cell response. This strategy combining lipid-based carriers with AntpHD peptide to target poorly immunogenic Ags into the MHC class I processing pathway represents a novel approach for CTL vaccines that may have important applications for development of cancer vaccines.
The activity of therapeutic antibodies can be enhanced by creating multivalent constructs, such as antibody lipid nanoparticles (LNPs). Here, we examine differences between rituximab (Ritux) and Ritux-LNPs in terms of their indirect mechanisms of action: complement-dependent cytotoxicity (CDC) and antibody-dependent cell-mediated cytotoxicity (ADCC).We employed two mantle-cell lymphoma cell lines, Z138 and JVM2, which exhibit different in vivo sensitivities to Ritux along with variable expression levels of cell-surface proteins that regulate ADCC and CDC.In both cell lines, CDC and ADCC were found to be significantly enhanced after treatment with Ritux-LNPs compared with Ritux. In vivo efficacy studies, however, suggested that the therapeutic activities of Ritux and Ritux-LNPs were equivalent, which was subsequently explained in part by pharmacokinetic studies indicating rapid elimination of Ritux-LNP.Although indirect and direct mechanisms of multivalent Ritux are enhanced, its further development requires methods to improve its circulation lifetime.