148 Inhibin immunotherapy as a resource to increase affordability and embryo production in superovulation protocols

The multiplication of genetically superior animals for genetic improvement, integration or replacement in productive herds, or conservation of endangered populations has been significantly assisted by multiple ovulation and embryo transfer (MOET) procedures and IVF. However, the production of oocytes and embryos becomes less efficient after repeated superovulation protocols. This loss of efficiency is due to high levels of circulating inhibin secreted by the high number of follicles during superovulation. Neutralization of inhibin by active or passive immunization stimulates further follicle development and induces multiple ovulations in ruminants and other species, significantly improving follicular development and embryonic yield. Our laboratory has developed immunogens that enable inducing immune responses toward endogenous molecules (such as inhibin) that are not normally antigenic because they are recognized by the immune system as their own. In this way, we have developed an immunogen against inhibin (P2INHP30) that has been preclinically evaluated in mice, obtaining a 100% increase in prolificacy. This immunogen is a hybrid genetic construct containing sequences of tetanus toxin epitopes fused to the α chain inhibin gene. This construct is cloned in a plasmid (pCINeo) that functions as a DNA vaccine. When it is injected into an individual, the chimeric inhibin will be expressed in the host cells and the immune system will be stimulated to produce anti-inhibin antibodies. The genetic construct was also cloned into an expression vector (plasmid pET11) that produces inhibin as a recombinant antigen (rAg) in E. coli. This rAg is used as an immunogen in the production of antibodies, but also in ELISA systems to quantify anti-inhibin antibodies. A prime–boost immunization scheme (immunizing first with the DNA vaccine and later with the rAg) has been evaluated in mice that subsequently showed an increase in fertility (Luna et al. 2018 Nova Scientia 10, 213–221). This project has two phases. In the first, the required dose of immunogens in cows will be identified (in a prime–boost protocol) to produce antibodies and increase folliculogenesis. In the second, the potential improvement of embryo production in immunized donor cows and their response to MOET protocols will be evaluated. This study will generate immunotherapy products consisting of monospecific polyclonal antibodies produced in a few bovines, while is expected to allow obtaining large amounts of antibodies at a low cost, avoid the use of monoclonal antibodies, and reduce the time of the immune response obtained by vaccination. This approach will improve the affordability and production of bovine embryos of high genetic value. We have already generated the immunogens, and we are currently in the process of starting the first phase of the project.