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.