A membrane penetrating multiple antigen peptide (MAP) incorporating ovalbumin CD8 epitope induces potent immune responses in mice

Cell penetrating peptides (CPP) represent a novel approach to facilitate cytoplasmic delivery of macromolecules. The DNA binding domain of Drosophila Antennapedia contains 60 amino acids and consists of 3 α-helices, with internalizing activity mapped to a 16-amino acid peptide penetratin (Antp) within the third α-helix. Here, we report on the use of penetratin to deliver a multiple antigen peptide (MAP) incorporating the immunodominant CD8 epitope of ovalbumin, SIINFEKL (MAPOVACD8). We demonstrate that penetratin linked to the MAPOVACD8 construct either by a disulfide (SS) or thioether (SC) linkage promotes the uptake, cross presentation and subsequent in vivo proliferation and generation of OVACD8 (SIINFEKL)-specific T cells. The MAPOVACD8 construct without penetratin is not presented by MHC class I molecules nor does it generate an in vivo IFN-γ response in C57BL/6 mice. Moreover, we clearly define the uptake and intracellular processing pathways of AntpMAPOVACD8 SS and SC revealing the majority of AntpMAPOVACD8 is taken up by DC via an endocytic, proteasome and tapasin independent mechanism. We also show that the uptake mechanism of AntpMAPOVACD8 is dose dependent and uptake or intracellular processing is not altered by the type of chemical linkage.