Vaccination with human papillomavirus type 16 E7 peptide with CpG oligonucleotides for prevention of tumor growth in mice.

OBJECTIVE To test whether an E7 peptide/CpG vaccine is effective in preventing and treating human papillomavirus-positive tumors in a murine model. INTERVENTION First, an E7 peptide/CpG vaccine was administered systemically on days -14 and -7, and tumor cells were injected subcutaneously on day 0. Second, tumor cells were injected on day 0, and vaccine was administered on days 7, 14, and 21. MAIN OUTCOME MEASURES Tumor size was measured 3 times per week. A tetramer assay was used to assess the presence of activated, E7-specific lymphocytes in spleen and tumor cells harvested from mice treated with a similar vaccination regimen. RESULTS In the prophylactic study, 75% of mice injected with E7 peptide/CpG resisted tumor formation. In the therapeutic setting, tumors initially regressed and experienced delayed progression when compared with controls. Survival rates improved in E7/CpG-vaccinated mice. Tetramer analysis detected increased numbers of activated, E7-specific lymphocytes in the spleens and tumors of animals treated with the experimental vaccine when compared with controls. CONCLUSION The use of CpG motifs as an adjunct to peptide-based immunotherapy has potential impact on the treatment of human papillomavirus-associated cancers.