The population explosion and unintended pregnancies resulting in elective abortions continue to impose major public health issues. in the in vitro culture assay using BA/F3 mLIF-R-mpg130 cells. Vaccines were prepared by conjugating these peptides to various carrier proteins. Immunization of female mice with these peptide vaccines induced a long-lasting, circulating as well as local antibody response in various parts of the genital tract, and resulted in a significant (p0.05) inhibition in fertility in all the three trials; the LIF-R peptide vaccines proved to be a better vaccine target. The data indicate that LIF/LIF-R is an excellent target for the development of a birth control vaccine. This is the first study, to our knowledge, that examined LIF/LIF-R as a target for immunocontraception. The findings of this study can be easily translated to humans since LIF/LIF-R is also important for implantation and pregnancy in women. gene that encodes a truncated, non-functional form of LIF, have a complete CREB5 implantation Roxadustat failure (Stewart et al., 1992). Also, administration of a high-affinity LIF antagonist completely blocks implantation in mice (White et al., 2007). These findings provide a strong rationale for exploring LIF as a target for immunocontraception. It has not been investigated whether immunologic intervention via vaccination against LIF and/or its receptor (LIF-R) can prevent successful blastocyst implantation. We hypothesize that blocking the LIF/LIF-R conversation via immunologic intervention will cause a contraceptive effect. In the present study, five sequences from LIF or LIF-R were delineated from the regions that are involved in ligand-receptor conversation, and peptides were synthesized based upon these sequences. To examine that they indeed inhibit LIF/LIF-R conversation, the antibodies were raised against these peptides in female rabbits and examined for their ability to neutralize the biological activity of LIF in vitro. Then, these synthetic peptides were conjugated to various carrier proteins as vaccines to examine if they can induce a long-lasting antibody response in circulation and genital tract that can cause a contraceptive effect in female mice in vivo. RESULTS Peptide antibodies and their ability to bioneutralize LIF activity in in vitro cell assays The bioneutralizing ability of the five peptide antibodies raised against LIF or LIF-R was examined in an in vitro cell culture assay using BA/F3 mLIF-R-mgp130 cells, which grow only in the presence of LIF. These cells express murine LIF-R on the surface, and require LIF supplementation in the culture medium to proliferate; the cells grow at a low rate without LIF. The data from two representative experiments, with and without the presence of LIF, over a 4-day period is shown in Physique 1A. Addition of LIF caused a 2.5-fold increase in cell number in the presence of LIF after 72 hr, and 5-fold increase by 88-93 hr. Without LIF, cell proliferation was slow and was several-fold less than in the presence of LIF. Physique 1 LIF bioneutralizing ability of LIF and LIF-R peptide antibodies using BA/F3 mLIF-R-mgp130 cells in vitroThe cells (0.4106/ml) were cultured with/without LIF, and their proliferation was analyzed using an MTT assay over the course of 96 hr (A). … All the peptide antibodies significantly (gene or administered with a high-affinity LIF antagonist have a complete (100%) implantation failure (Stewart et al., 1992; White et al., 2007). Also, administration of anti-LIF antibody has been shown to inhibit blastocyst implantation Roxadustat in mice (Terakawa et al., 2011), and in primates (Sengupta et al., 2006). Intraperitoneal injections of anti-LIF antibody between D3 and D4 (D1=day of vaginal plug detection) caused a complete block (100%) in C57BL/6J, and 73% reduction in embryo implantation of ICR mice (Terakawa et al., 2011). In mice, LIF is essential for implantation; however, the Roxadustat total dependency of embryo implantation on LIF seems to differ among various murine strains. The LIF pathway appears to function in a strain-dependent manner in mice deficient in p53, which regulates expression of LIF (Hu et al., 2007). Implantation failure is more severe in C57BL/6J background pg53-deficient mice than in 129SV mice (Hu et al., 2007). There are several lines of evidence indicating that LIF also has a role in human implantation and pregnancy. LIF mRNA and LIF protein levels.