A novel approach for modifying tumor cell-derived plasma membrane vesicles to contain encapsulated IL-2 and engrafted costimulatory molecules for use in tumor immunotherapy

The genetic modification of tumor cells and delivery of cytokines have been proposed as useful strategies in the development of anti-tumor vaccines; however, a number of factors limit their use in clinical settings. To facilitate vaccine development, we explored the possibility of modifying plasma membrane vesicles (PMV) by using a novel chelator lipid, nitrilotriacetic acid ditetradecylamine (NTA-DTDA). Our analyses by flow cytometry show that NTA-DTDA can be incorporated into PMV prepared from murine P815 mastocytoma and that the incorporated NTA-DTDA permits anchoring or "engraftment" onto the vesicle surface of hexahistidine-tagged proteins such as recombinant forms of the costimulatory molecules B7.1 and CD40. The engrafted PMV also can incorporate and deliver the immunostimulatory cytokine Interleukin-2 (IL-2). Our results show that modified PMV derived from P815 cells bind the murine T cell clone D10 in a receptor-ligand dependent manner, inducing cell adhesion and promoting cell survival in vitro. The modified PMV can bind syngeneic T cells, stimulating T cell proliferation and cytotoxic T cell responses. Moreover, when used as vaccines in syngeneic animals, the modified vesicles induce significant protection against challenge with the native P815 tumor. The results indicate that PMV modified by engraftment of recombinant forms of B7.1 and CD40 and incorporation of IL-2 can be used to modulate immune responses, which provides a novel approach for the development of anti-tumor vaccines and cancer immunotherapies.