Modifying Antigen-Encapsulating Liposomes with KALA Facilitates MHC Class I Antigen Presentation and Enhances Anti-tumor Effects

Abstract

For a successful anti-cancer vaccine, antigen presentation on the major histocompatibility complex (MHC) class I is a requirement. To accomplish this, an antigen must be delivered to the cytoplasm by overcoming the endosome/lysosome. We previously reported that a lipid nanoparticle modified with a KALA peptide (WEAKLAKALAKALAKHLAKALAKALKA), an α-helical cationic peptide, permits the encapsulated pDNA to be efficiently delivered to the cytoplasm in bone marrow-derived dendritic cells (BMDCs). Herein, we report on the use of KALA-modified liposomes as an antigen carrier, in an attempt to induce potent antigen-specific cellular immunity. The subcutaneous injection of KALA-modified ovalbumin (OVA)-encapsulating liposomes (KALA-OVA-LPs) elicited a much more potent OVA-specific cytotoxic T lymphocyte activity and anti-tumor effect in comparison with particles that were modified with octa-arginine (R8), a cell-penetrating peptide (R8-OVA-LPs). In addition, the numbers of OVA-specific CD8⁺ T cells were increased by immunization the KALA-OVA-LPs. The treatment of BMDCs with KALA-OVA-LPs induced a substantial MHC class I antigen presentation. Furthermore, the acidic pH-dependent membrane destabilization activity of KALA-OVA-LPs strongly suggests that they are able to escape from endosomes/lysosomes and thereby deliver their cargos to the cytoplasm. Collectively, the KALA-modified liposome is a potential antigen delivery platform for use as a protein vaccine.

Keywords: KALA peptides; MHC class I presentation; anti-cancer vaccines; dendritic cells; liposomes; protein vaccines.