Novel Inhibitors of Human Papillomavirus
Purpose/Aims: The goal of this of study is to identify novel compound(s) that inhibit HPV from entering epithelial cells with an acceptable toxicity profile, using a high-throughput screening (HTS) assay. HTS enables researcher to quickly scan thousands of compounds in a compound library allowing for the rapid identification of compound(s) that prevent HPV infections. Rationale/Conceptual Basics/Background: At least 75% of individuals in the general population will acquire a genital human papillomavirus (HPV) infection in their sexual lifetime. HPV infection is almost universal in HIV-infected men who have sex with men. However, HPV-associated cancers disproportionately affect individuals who are HIV-positive. Although a prophylactic vaccine against HPV has been introduced into the HIV-positive and general population it has several disadvantages including cost, lack of access in developing countries, administration before sexual debut, and limited coverage to other HPV types that cause cancer. At this time, the efficacy of the HPV-vaccine is still under investigation in the HIV-positive population. Therefore, a need remains to identify other treatment options for preventing HPV-associated infections and cancers. Methods: We are currently developing a HTS assay in collaboration with the UCSF Small Molecule Discovery Center (SMDC). To develop this assay we optimized a HPV pseudovirion (PsV)-based platform where HPV PsVs are used to mimic HPV infection in a host cell. HPV PsV contains the native capsid that carries a plasmid that expresses renilla, a fluorescent protein that can be quantified following infection. Expression of the renilla protein indicates PsV entry into cells. To carry out the pilot screen we first determined the optimal ratio of host 293 FT cells infected with PsV. Next, the pilot screen was conducted using a small library of 2000 compounds at the SMDC. This allowed us to optimize an inhibitory signal defined as a “hit”. Results: Out of 2000 compounds the pilot screen produced 98 hits with a z-prime score of 0.67. Z-prime is a dimensionless unit with a statistically significant range of 0.5 to 1. Implications: The results of the pilot screen indicate that the HTS assay we developed was successful at identifying “hits” when used with HTS automation in the compound library at SMDC. The next step of our study is to scan the entire 150,000 compound library at SMDC with our HTS assay to identify additional compounds able to prevent HPV infection.