Abstract 4048: HPV16 immunity induced by immune responses to mutations in E6 and E7 proteins

Abstract

Abstract Human papillomavirus (HPV) causes 30% of cancers attributable to infectious pathogens. HPV16 causes most cervical, anal, vaginal, vulvar, and oropharyngeal cancers. Although preventive vaccines targeting HPV16 and 18 are available, rates of vaccination are uneven. The incidence of HPV-associated cancers for which no screening algorithms have been validated continues to increase. Development of squamous cervical cancer and its precursor, cervical intraepithelial neoplasia (CIN) 2/3 is associated with integration of HPV genome into the host genome, and expression of the HPV E6 and E7- gene products, which inactivate p53 and pRb respectively. Since E6 and E7 are constitutively expressed in cervical carcinomas and CIN, they present attractive immunotherapeutic targets. Development of immunotherapies has been limited, in part, by modest immunogenicity of vaccines tested to date. The purpose of this study is to augment the immunogenicity of the E6 and E7 antigens through mutational screening. A subset of CIN2/3 do undergo complete regression. Our lab has carried out a series of prospective clinical studies, including immunotherapeutic interventions, in subjects with CIN2/3. Peripheral blood T cell responses to E6 and E7 are marginal, and do not distinguish regressors in either vaccinated or unvaccinated subjects. However, in vaccinated subjects, the lesion microenvironment is comprised of new tertiary lymphoid structures, evidence of T cell proliferation elicited by cognate antigen, and clonally expanded TCRs. Tissue T cells in vaccinated subjects access dysplastic epithelium, in contrast to T cells in persistent lesions, which were confined to the stromal compartment. These findings suggest that T cells that could mediate regression can be elicited by vaccination. However, strategies to enhance immunogenicity would likely increase therapeutic effect. Here we present an approach designed to determine the effect of mutations in E6 and E7 on antigenicity. Mutations can enhance immune responses to antigens by several mechanisms, including altering antigen processing, trafficking, glycolsylation, and affinity to major histocompatibility complexes. Using error prone PCR, we generated libraries containing random mutations in the coding sequence of E6 and E7. Clones from each library are currently being screened in vitro to identify immunogenic mutants, which could be potentially used for multi-epitope vaccines. Citation Format: Maria Agarwal, Ashley Saint-Fleur, Jie Fu, Hyam Levitsky, Cornelia L. Trimble. HPV16 immunity induced by immune responses to mutations in E6 and E7 proteins. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4048. doi:10.1158/1538-7445.AM2015-4048