Introduction

High-risk Human Papillomavirus is the etiologic agent of cervical cancer and other tumors in humans. Despite the existence of prophylactic vaccines against infections by the most common types of HPV, therapeutic alternatives are limited to control HPV-associated tumors.

Methods

We found some homologous motifs for high-risk HPV proteins using immune-panning of a peptide phage display library with sera from HPV-16-seropositive female patients. The recombinant bacteriophages (PEP1) were purified and amplified for use as immunogens. We vaccinated immunocompetent mice prophylactically with one of our recombinant bacteriophages, using the insertless M13 bacteriophage as a control. These mice were then challenged with TC-1 tumor cells (HPV-16 positive), and the immune responses triggered during tumor progression were evaluated. We also used a therapeutic approach, injecting tumor cells before immunization with the bacteriophage. Tumor growth was monitored and tumors, spleens and lymph nodes were evaluated for the level and type of the immune responses

Results

Tumor growth was significantly reduced in prophylactic and therapeutic immunizations, although tumor reduction was minimal when mice were treated 9 days after TC-1 cells grafting. The reduction in tumor growth also translated into a significantly greater survival for the immunized mice.

Cell infiltration studies did not reveal changes in several immune subpopulations, but an upward trend in cytotoxic T lymphocytes was observed in mice immunized with PEP1. We further confirmed this finding by grafting TC-1 cells in CD8-knockout mice, where the previously observed reduction of tumor growth was abolished. An increase in CD8:CD4 rate was observed in the immunized mice and this is an indication of a cytotoxic tumor environment. Further studies are warranted.

Conclusions

Phage display is a veritable tool in the discovery of new molecules that could offer a wide range of uses including immunogens. This could be a path towards new vaccines development