HPV-Associated Tumor Eradication by Vaccination with Synthetic Short Peptides and Particle-Forming Liposomes

Human papilloma virus (HPV)-16 is associated with cervical cancers and induces expression of the E6 and E7 oncogenes. Using a murine cell line that expresses these, the genes are sequenced, and six predicted major histocompatibility complex (MHC) class I (MHC-I) epitopes are identified. A liposomal vaccine adjuvant based on cobalt-porphyrin-phospholipid (CoPoP) is admixed with synthetic 9-mer epitopes appended with three histidine residues, resulting in rapid formation of peptide-liposome particles. Immunization with multivalent peptides leads to protection from tumor challenge. Of the peptides screened, only the previously identified E7(49-57) epitope is functional. The peptide-liposome particles that form upon mixing E7(HHH49-57) with CoPoP liposomes are stable in serum and are avidly taken up by immune cells in vitro. Immunization results in robust protection from tumor challenge and re-challenge. A 100 ng peptide dose protects mice in a therapeutic tumor challenge when admixed with CoPoP liposomes, whereas 200-fold higher peptide doses are ineffective with the polyinosinic-polycytidylic (poly(I:C)) adjuvant. CoPoP induces a strong infiltrating CD8(+) T-cell response within the tumor microenvironment with an improved functional profile. Vaccine monotherapy using nanogram dosing of the E7(HHH49-57) peptide admixed with CoPoP reverses the growth of large established tumors, eradicating subcutaneous tumors upwards of 100 mm(3). Immunization also eradicates lung tumors in a metastasis model.

Automated summary

The study shows that a peptide-liposome vaccine based on E7(HHH49-57) is effective in combating HPV-related cervical cancers and tumor challenges, with other peptide epitopes showing lower efficacy. A nanogram dose of peptide admixed with CoPoP liposomes provides protection in therapeutic tumor challenges, inducing a strong infiltrating CD8(+) T-cell response within the tumor microenvironment.