Exosome based tumor antigens adjuvant co delivery utilizing genetically engineered tumor cell derived exosomes with immunostimulatory CpG DNA.
For cancer immunotherapy via tumor antigen vaccination in combination with an adjuvant, major challenges include the identification of a particular tumor antigen and efficient delivery of the antigen as well as adjuvant to antigen presenting cells. In this study, we proposed an efficient exosome based tumor antigens adjuvant co delivery system using genetically engineered tumor cell derived exosomes containing endogenous tumor antigens and immunostimulatory CpG DNA. Murine melanoma B16BL6 cells were transfected with a plasmid vector encoding a fusion streptavidin (SAV; a protein that binds to biotin with high affinity) lactadherin (LA; an exosome tropic protein) protein, yielding genetically engineered SAV LA expressing exosomes (SAV exo) SAV exo were combined with biotinylated CpG DNA to prepare CpG DNA modified exosomes (CpG SAV exo) Fluorescent microscopic observation revealed the successful modification of exosomes with CpG DNA by SAV biotin interaction. CpG SAV exo showed efficient and simultaneous delivery of exosomes with CpG DNA to murine dendritic DC2.4 cells in culture. Treatment with CpG SAV exo effectively activated DC2.4 cells and enhanced tumor antigen presentation capacity. Immunization with CpG SAV exo exhibited stronger in vivo antitumor effects in B16BL6 tumor bearing mice than simple co administration of exosomes and CpG DNA. Thus, genetically engineered CpG SAV exo is an effective exosome based tumor antigens adjuvant co delivery system that will be useful for cancer immunotherapy.
Biomaterials