KALA-modified multi-layered nanoparticles as gene carriers for MHC class-I mediated antigen presentation for a DNA vaccine.

DNA vaccines are a new-generation vaccines that elicit an immunological response against a wide-variety of antigens with frequent mutations. However, an effective non-viral vector for genetically engineered DNA to dendritic cells is yet to be developed. We previously reported that an octaarginine (R8)-modified tetra-lamellar multi-functional envelope-type nano device (R8-T-MEND) increases transfection efficiency in dendritic cell cultures (JAWS II). The critical structural elements of the R8-T-MEND are a DNA-polycation condensed core coated with two nuclear membrane-fusogenic inner envelopes, and two endosome-fusogenic outer envelopes. While the gene expression was drastically enhanced by R8-T-MEND, antigen presentation using an epitope-encoding plasmid DNA remains an obstacle for future non-viral vectors in DNA vaccinations. In the present study, we upgraded the function of R8-T-MEND by improving the membrane-fusion processes with endosome- and nuclear membranes by incorporating the KALA peptide, and by reducing the charge ratio (+/-), in an attempt to accelerate intra-nuclear decondensation. The resulting KALA-modified T-MEND (R8/KALA-T-MEND) showed an approximately 20-fold higher transgene expression compared with the conventional R8-T-MEND in JAWS II, and exceeded that of Lipofectamine PLUS, a commercially available transfection reagent. Furthermore, significant antigen presentation of a specific epitope (SIINFEKL) was observed for the R8/KALA-T-MEND but was not detected for the conventional T-MEND or Lipofectamine PLUS when an ovalbumin (OVA)-encoding plasmid DNA was transfected. It thus appears that the R8/KALA-T-MEND has the potential for use as a vector in DNA vaccinations.