title: Modification of HPV 16 E7 genes: correlation between the level of protein expression and CTL response after immunization of C57BL/6 mice.
abstract: Immunization with a codon-optimized HPV 16 E7 gene was shown to yield higher levels of E7-specific cytotoxic T cells [Liu WJ, Gao F, Zhao KN, Zhao W, Fernando GJ, Thomas R, et al. Codon modified human papillomavirus type 16 E7 DNA vaccine enhances cytotoxic T-lymphocyte induction and anti-tumour activity. Virology 2002;301:43]. Here, we sought to verify the hypothesis that there is a direct correlation between the level of protein expression and immunogenicity in mice. We generated HPV 16 E7 expression plasmids where the genes were inserted either as authentic sequence (wt) or after optimizing the codons for use in mammalian cells (opt). For enhancement of translation of the E7 gene a 5' Kozak sequence (K) was added. Transfection experiments revealed the strength of expression in the order of E7opt+K, E7opt-K, E7wt+K and E7wt-K. After immunization of C57/B6 mice we observed an equally strong CD8+T-cell response with the E7opt plasmids (+ or -K), followed by the E7wt+K and E7wt-K DNAs. The same difference in efficiency was obtained in tumor protection experiments. Regression of pre-existing tumors and CTL activity was observed only with the E7opt+K plasmid. From these data, we conclude that the level of protein expression correlates with the efficiency of CTL response and hence testing by transfection of cells in culture may allow a pre-selection of expression plasmids prior to DNA immunization.
authors.affiliation: Deutsches Krebsforschungszentrum, Forschungsschwerpunkt Infektion und Krebs, Im Neuenheimer Feld 242, 69120 Heidelberg, Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Steinberg
authors.forename: Peter
authors.initials: P
authors.lastname: Ohlschläger
authors.forename: Peter
authors.initials: P
authors.lastname: Sehr
authors.forename: Wolfram
authors.initials: W
authors.lastname: Osen
authors.forename: Lutz
authors.initials: L
authors.lastname: Gissmann
mesh_terms: D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D003602:Cytotoxicity, Immunologic / Q000235:genetics*; D005260:Female; D015967:Gene Expression Regulation, Viral / Q000235:genetics*; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D041681:NIH 3T3 Cells; D009856:Oncogene Proteins, Viral / Q000008:administration & dosage* / Q000235:genetics* / Q000276:immunology; D050725:Papillomavirus E7 Proteins; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D013997:Time Factors; D014765:Viral Vaccines / Q000008:administration & dosage* / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D014765:Viral Vaccines; C059731:oncogene protein E7, Human papillomavirus type 16