212. Specific targeting of uterine proprotein convertase 6 (PC6) facilitates the development of dual function contraception

Abstract

Proprotein convertase 6 (PC6), is a key player during embryo implantation in humans and mice. We have previously shown that PC6 is essential for decidualisation in the mouse and knockdown of endometrial PC6 leads to implantation failure. The PC family of proteases, including PC6, are necessary for transmission of human immunodeficiency virus (HIV). It has been postulated that inhibition of PC activity could prevent HIV infection. We hypothesise that PC6 is a prospective target for the development of a dual role contraceptive for women to avoid pregnancy and protect from HIV infection. The aim of this study is to evaluate if a PC6 inhibitor that is capable of preventing HIV transmission can block implantation in mice. We used a generic PC peptide substrate to assess the potency of the inhibitor to block PC6 activity in vitro. The substrate releases a fluorochrome when cleaved by PC6; no fluorescent signals were observed in samples when inhibitor concentrations were 10μM or higher. We then gauged inhibitor uptake by the uterus over 24 h in mice by two delivery routes; intrauterine injection (IU) and vaginal delivery (VD) with a neutral gel. Uptake was tracked with a FITC-conjugated inhibitor at 50μM (IU) and 500μM (VD). Strong fluorescent signals were seen at 2, 4, 6 and 24 h at sites of endometrial PC6 activity in the IU and VD groups. Administration of a 50μM dosage (20μl) to the uterine lumen (IU) caused a significant reduction (P = 0.002) in the number of implantation sites compared with controls (saline only) when treated between 2000–2100 on E3.75. The inhibitor's ability to block uterine PC6 activity and implantation via VD was assessed and to date outcomes have suggested that correct timing is crucial to prevent implantation and decidualisation. These outcomes show the potential of the inhibitor to block implantation in mice.