*2.5. Cytolytic Protein*

Perforin (PRF) is a pore forming protein released by immune cells including NK cells and cytotoxic T lymphocytes (CTL) [91]. The 67-kilodalton PRF protein oligomerizes to form pores that serve as a channel to release granzyme into the cytosol of target cells [92]. Suicide genes inducing apoptosis of target cells have been used for cancer therapies, and the role of apoptotic cell death in vaccination, whether immune-stimulatory or immune-suppressive, is debated [93]. Recently, a novel DNA technology has been developed—-termed cytolytic DNA technology—in which a truncated mouse PRF is incorporated in a bicistronic DNA vector to act as a vaccine adjuvant [55–57,94].
