
<ArticleTitle>Regression of established human papillomavirus type 16 (HPV-16) immortalized tumors in vivo by vaccinia viruses expressing different forms of HPV-16 <prot>E7</prot> correlates with enhanced CD8(+) T-cell responses that home to the tumor site.</ArticleTitle>
<AbstractText>Using vaccinia virus as a live vector, we show that the expression of human papillomavirus type 16 (HPV-16) <prot>E7</prot> fused to a nonhemolytic portion of the Listeria monocytogenes virulence factor, <prot>listeriolysin O</prot> (<prot>LLO</prot>), induces an immune response that causes the regression of established HPV-16 immortalized tumors in C57BL/6 mice. The vaccinia virus construct expressing <prot>LLO</prot> fused to <prot>E7</prot> (VacLLOE7) was compared with two previously described vaccinia virus constructs: one that expresses unmodified <prot>E7</prot> (<prot>VacE7</prot>) and another that expresses <prot>E7</prot> in a form designed to direct it to intracellular lysosomal compartments and improve major histocompatibility complex class II-restricted responses (<prot>VacSigE7LAMP-1</prot>). C57BL/6 mice bearing established HPV-16 immortalized tumors of 5 or 8 mm were treated with each of these vaccines. Fifty percent of the mice treated with <prot>VacLLOE7</prot> remained tumor free 2 months after tumor inoculation, whereas 12 to 25% of the mice were tumor free after treatment with <prot>VacSigE7LAMP-1</prot> (depending on the size of the tumor). No mice were tumor free in the group given <prot>VacE7</prot>. Compared to <prot>VacE7</prot>, <prot>VacSigE7LAMP-1</prot> and <prot>VacLLOE7</prot> resulted in increased numbers of H2-D(b)-specific tetramer-positive CD8(+) T cells in mouse spleens that produced gamma interferon and tumor necrosis factor alpha upon stimulation with RAHYNIVTF peptide. In addition, the highest frequency of tetramer-positive T cells was seen in the tumor sites of mice treated with <prot>VacLLOE7</prot>. An increased efficiency of E7-specific lysis by splenocytes from mice immunized with <prot>VacLLOE7</prot> was also observed. These results indicate that the fusion of <prot>E7</prot> with <prot>LLO</prot> not only enhances antitumor therapy by improving the tumoricidal function of E7-specific CD8(+) T cells but may also increase the number of antigen-specific CD8(+) T cells in the tumor, the principle site of antigen expression.</AbstractText>
