A DNA vaccine based on a shuffled E7 oncogene of the human papillomavirus type 16 (HPV 16) induces E7-specific cytotoxic T cells but lacks transforming activity

Vaccination with oncogene-derived DNA for anti-cancer treatment carries a r isk of de-novo tumor induction triggered by the persisting recombinant DNA. We hypothesized that an oncoprotein whose primary sequence has been rearra nged ('shuffled') to maintain all possible T cell epitopes still induces cy totoxic T cells against the authentic protein but is devoid of transforming properties. As a model antigen, we used the E7 oncoprotein of the human pa pillomavirus (HPV) type 16, the major cause of cervical cancer. We have gen erated an artificial E7 molecule in which four domains were rearranged and, in order to maintain all possible T cell epitopes, certain sequences were duplicated. Upon transfection of this shuffled E7 gene (E7,) into RMA cells , presentation of an E7 D-b-restricted T cell epitope was shown by an E7-sp ecific CTL line in vitro. Immunization of C57BL6 mice with E7(SH) DNA induc ed E7-specific CTL and also conveyed protection against E7-positive syngene ic tumor cells. No transforming activity of E7(SH) DNA in NIH3T3 cells was detected, as determined by focus formation, induction of S-phase under cond itions of serum deprivation and degradation of endogenous pRB. Our results suggest that DNA shuffling may become a promising concept for DNA-based ant i-cancer vaccines. (C) 2001 Elsevier Science Ltd. All rights reserved.