The era of targeted anti-cancer therapies was ushered in by the development of therapeutic antibodies specific for antigens expressed primarily on tumors, improving the lives of countless cancer patients. Current antibodies, however, are limited to intact cell surface ligands, such as CD20, which are often also expressed on normal cells. However, methodological improvements have made it possible to produce antibodies specific for peptides from tumor antigens or viral oncoproteins presented in the context of major histocompatibility complex (MHC) class I proteins (in humans: HLA-A, -B, -C), which are often better restricted to tumor cells. These antibodies mimic how T cell receptors (TCR) recognize peptide/MHC complexes (pMHCs). These ?TCR mimic? or mTCR antibodies combine the specificity of a TCR with the affinity of an antibody, allowing the targeting of antigens expressed by cancerous cells, while sparing normal cells. However, mTCR Abs are difficult to elicit, because of the precise nature of the target surface on a pMHC. The best current approaches require specialized high-throughput screening to isolate true mTCR antibodies. We will improve this developing technology by increasing the efficiency that mTCR antibodies can be generated in conventional monoclonal antibody facilities. We will accomplish this by engineering immunogens to focus responses to the desired target epitope surface, drawing on our previous experience with HIV vaccines. In order to fully develop and demonstrate our platform, we will focus on cancers caused by human papillomavirus (HPV) as a model system. The mTCR antibodies against HPV we will generate will be useful immediately for basic studies of HPV pMHC expression, and eventually as ex vivo and in vivo diagnostics, and for treatment of refractory disease. While the proximate goal of this project is to develop our mTCR Ab platform using HPV as a model system, our mTCR technology is completely generalizable to any application. HPV infection causes about 5% of all human cancers, and virtually all cervical cancers, but also provides well- defined antigens that can be targeted by mTCR antibodies. We plan to target the HPV E6/E7 oncoproteins responsible for the induction and maintenance of malignancy. We will validate these mTCR antibodies in a large cohort of patients with HPV-induced cervical cancers of known HPV strain and HLA allele usage through the FHCRC China initiative. The need for improved treatments for advanced cervical cancer in China is particularly great, because of limited access to preventative screening and HPV vaccines. This project will deliver (1) a novel technology for generating mTCR Abs against any desired pMHC target; (2) basic science on the presentation and expression patterns of HLA-restricted HPV E6/E7 epitopes; (3) crystal structures of novel MHC/HPV peptide complexes; and (4) a panel of biochemically-validated HPV mTCR Abs for immediate basic science applications and future development as clinical theranostics.
In terms of overall cancer burden in women worldwide, cervical cancer alone has the second highest incidence, and is the third highest cause of death, but, in developing countries, particularly China, it presents an even greater problem, with the second highest cancer mortality. Cervical cancer is caused by human papillomavirus (HPV), and while HPV vaccines are a very effective means to prevent infection, they provide no protection after infection, are currently underutilized, and are not available in China. We propose to develop a new technology for generating antibodies that will target and destroy cancer cells in tumors caused by HPV, as an adjunct to vaccination and current cancer treatments, focusing on China, where the need is great and where we have unique access to Chinese collaborators - but this technology can be used for many diseases.