(748) Unique immunization strategies elicited antibodies in mice binding to the specific GPCR target on live cell surface across a panel of Class A GPCRs

Introduction/Rationale: G protein-coupled receptors (GPCRs) regulate nearly every aspect of human physiology and diseases, and form one of the largest drug target families. GPCRs share a conserved structure with 7 transmembrane α-helices. Class A GPCRs, Rhodopsin-like receptors, are the biggest and most distinct class of the GPCR subfamily in humans. Generation of antibodies binding to a GPCR protein on the cell surface can be a very useful tool to detect the target expression and drug discovery potential. The structure complexity and dynamic conformations make it very challenging to develop antibodies binding GPCRs on the cell surfaces. To advance the GPCR antibody discovery, we have developed unique fit-for-target immunization approaches to generate GPCR-specific antibodies in mice.

Methods: GPCR protein sequence and structure for each target was analyzed using multiple parameters. Based on each target’s unique sequence and structure features, we design fit-for-target immunogens, formulations and immunization regimens and conduct immunizations in mice. The antibody responses immune mouse serum samples were evaluated against each specific GPCR target antigen by ELISA and target expressing cells by flow cytometry..

Results: For this study, we selected a panel of 10 Class A GPCR targets, including GPR19, GPR56, LGR4, NK3R, NTR1, GIPR, LPHN3, CRFR2, CALCRL and P2RY1. The immunization with each target generated target-specific and high titers of antibody responses in mice for all 10 targets. The immune mouse serum samples could bind to the relevant specific target antigen by ELISA and target-expressing cells on live cell surfaces by flow cytometry.

Conclusion: The innovative fit-for-target immunization strategies can be advanced platforms to generate antibodies against GPCRs for reagent antibody development and drug discovery.