title: Recombinant Listeria vaccines containing PEST sequences are potent immune adjuvants for the tumor-associated antigen human papillomavirus-16 E7.
abstract: Previous work in our laboratory has established that the fusion of tumor-associated antigens to a truncated form of the Listeria monocytogenes virulence factor listeriolysin O (LLO) enhances the immunogenicity and antitumor efficacy of the tumor antigen when delivered by Listeria or by vaccinia. LLO contains a PEST sequence at the NH(2) terminus. These sequences, which are found in eukaryotic proteins with a short cellular half-life, target proteins for degradation in the ubiquitin-proteosome pathway. To investigate whether the enhanced immunogenicity conferred by LLO is due to the PEST sequence, we constructed new Listeria recombinants that expressed the HPV-16 E7 antigen fused to LLO, which either contained or had been deleted of this sequence. We then compared the antitumor efficacy of this set of vectors and found that Listeria expressing the fusion protein LLO-E7 or PEST-E7 were effective at regressing established macroscopic HPV-16 immortalized tumors in syngeneic mice. In contrast, Listeria recombinants expressing E7 alone or E7 fused to LLO from which the PEST sequence had been genetically removed could only slow tumor growth. Because CD8(+) T cell epitopes are generated in the ubiquitin-proteosome pathway, we also investigated the ability of the vaccines to induce E7-specific CD8(+) T cells in the spleen and to generate E7-specific tumor-infiltrating lymphocytes. A strong correlation was observed between CD8(+) T-cell induction and tumor homing and the antitumor efficacy of the Listeria-E7 vaccines. These findings suggest a strategy for the augmentation of tumor antigen-based immunotherapeutic strategies that may be broadly applicable.
authors.affiliation: Department of Microbiology and the University of Pennsylvania Cancer Center, Philadelphia, Pennsylvania, USA.
authors.forename: Duane A
authors.initials: DA
authors.lastname: Sewell
authors.forename: Vafa
authors.initials: V
authors.lastname: Shahabi
authors.forename: George R
authors.initials: GR
authors.lastname: Gunn
authors.forename: Zhen-Kun
authors.initials: ZK
authors.lastname: Pan
authors.forename: Mary E
authors.initials: ME
authors.lastname: Dominiecki
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Paterson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001427:Bacterial Toxins / Q000235:genetics / Q000276:immunology*; D001428:Bacterial Vaccines / Q000235:genetics / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D019496:Cancer Vaccines / Q000235:genetics / Q000276:immunology*; D045744:Cell Line, Tumor; D000939:Epitopes; D018984:Epitopes, T-Lymphocyte / Q000276:immunology; D006360:Heat-Shock Proteins / Q000235:genetics / Q000276:immunology*; D006460:Hemolysin Proteins; D008089:Listeria monocytogenes / Q000235:genetics / Q000276:immunology*; D016246:Lymphocytes, Tumor-Infiltrating / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D009374:Neoplasms, Experimental / Q000276:immunology / Q000628:therapy / Q000821:virology; D009856:Oncogene Proteins, Viral / Q000235:genetics / Q000276:immunology*; D050725:Papillomavirus E7 Proteins; D053918:Papillomavirus Vaccines; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology; D013154:Spleen / Q000166:cytology / Q000276:immunology; D014614:Vaccines, Synthetic / Q000235:genetics / Q000276:immunology
chemical_list: D001427:Bacterial Toxins; D001428:Bacterial Vaccines; D019496:Cancer Vaccines; D000939:Epitopes; D018984:Epitopes, T-Lymphocyte; D006360:Heat-Shock Proteins; D006460:Hemolysin Proteins; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D053918:Papillomavirus Vaccines; D011993:Recombinant Fusion Proteins; D014614:Vaccines, Synthetic; C059731:oncogene protein E7, Human papillomavirus type 16; C038705:hlyA protein, Listeria monocytogenes