Understanding and Enhancing T-Cell Responses to high Risk Human Papillomaviruses

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Cervical cancer is the second most common cancer among women worldwide, and the link between human papillomavirus (HPV) and the development of cervical cancer is well known. Despite the advent of early detection with Papanicolaou smears, cervical cancer is a major cause of morbidity and mortality in less developed nations. A prophylactic HPV vaccine is now available to prevent women from acquiring HPV infection, but it is not effective once HPV infection is established. Our long-term goal is to develop a therapeutic HPV vaccine that is effective in preventing cervical cancer caused by high-risk types of HPV in HPV-exposed individuals. We propose a novel combination of antigens and adjuvant. HPV-related transformation to a malignant phenotype is mediated by two gene products, E6 and E7, and their expression is required for maintenance of a transformed phenotype. Therefore, E6 and E7 proteins are candidate antigen sources for a therapeutic vaccine for women with HPV infection and/or squamous intraepithelial lesions (SILs). Our clinical study examining CD8 T-cell responses and spontaneous SIL regression showed that CD8 T-cell responses to HPV type 16 (HPV-16) E6 protein (particularly the central regions), but not the E7 protein, are significantly associated with regression of cervical lesions. Such protection appears to be crossreactive among all high-risk but not low-risk HPV types. Analogous studies are needed to assess whether CD4 T-cell responses to the E7 protein also have a role in SIL regression. We hypothesize that regions of HPV-16 E6 protein, and perhaps E7 protein, containing CD4 and CD8 T-cell epitopes associated with SIL regression are sources of effective antigens for a therapeutic HPV vaccine (antigens), and that Candida antigen, with anti-HPV effects inducing skin wart regression, is an effective adjuvant in enhancing vaccine immunogenicity (adjuvant). Our specific aims are to: (1a) identify regions within HPV-16 E6 and E7 proteins associated with cervical lesion regression and characterize the dominant CD4 T-cell epitopes; (1b) determine how Candida antigen may work to enhance immune response by examining interactions with pattern recognition receptors; (2) examine dosage and toxicity of the HPV peptide¿Candida vaccine; and (3) assure safety and examine immunogenicity and clinical responses to the candidate vaccine in a dose-escalation Phase I clinical trial. Successful completion of this project would lead to not only development of a novel therapeutic HPV vaccine for cervical cancer prevention, but also a novel adjuvant to enhance peptide vaccine immunogenicity, which can be applied to other cancers and infectious agents.