Background: Current vaccination strategies against Human papillomavirus (HPV)-induced ano-genital cancers mostly target E7 from HPV16. However, the oncogenic nature of E7 raises potential human safety issues. Although the modifications abrogating the E7 transforming potential have been well characterized, their effect on E7 immunogenicity has been poorly studied. In this study, we evaluated the vaccine potential of an HPV16 E7 protein deleted from the entire pRb-binding motif.
Materials and methods: Purified recombinant deleted (E7delta21-26) and wild-type (His6-E7 and E7WT) E7 proteins were studied in pre-clinical mice models.
Results: In C57BL/6 mice, E7delta21-26 formulated with the Quil A adjuvant generated systemic E7-specific cytotoxic T-cell and antibody responses similar to those induced following His6-E7/Quil A and E7WT/Quil A vaccinations. E7delta21-26/Quil A injections efficiently protected animals from challenge with the HPV16-expressing tumours, C3 and TC-1. Moreover, therapeutic vaccination with adjuvant-modified E7 suppressed or significantly decreased C3 tumour outgrowth.
Conclusion: E7delta21-26 could represent a safe and efficient vaccine candidate against E7-containing tumour cells.