Abstract 1219: Generation of anti-OX40 antibody with different immunization strategies

Abstract Variety of immunogen such as recombinant protein, DNA or cells has been used for animal immunization to develop hybridoma antibody. However, the effectiveness among different types of immunogen in generating functional antibodies especially antibody with agonistic activity has not been systematically investigated. OX40 (CD134) is a T cell costimulatory receptor that is found primarily on activated CD4+ and CD8+ T cells, regulatory T (Treg) cells and natural killer (NK) cells. Activation of OX40 by its natural ligand or an agonist antibody augments CD4 and CD8 T cell expansion, differentiation, and survival. Agonistic anti-OX40 antibody holds promise as therapeutics for cancer immunotherapy. In the present study, different immunization strategies (recombinant protein, cell and DNA) have been used to generate anti-OX40 antibody. Antigen specific immune response, number of binders, epitope bins and the functional activities obtained from different immunogens were analyzed and compared. Based on cross reactivity and cell based functional assay results, 25 clones from protein immunization, 22 from DNA immunization and 29 from cell based immunization were expanded and purified. Among the purified antibodies, antibodies obtained from DNA immunization showed stronger agonist activity in both Jurkat OX40-NFAT luciferase reporter activity and primary T cell activation assay. The antibodies obtained from DNA immunization also demonstrated in vivo efficacy and significantly inhibited tumor growth in MC38 syngeneic mouse model using human OX-40 knock-in mice. In summary, we have evaluated different immunization strategies using OX-40 as a case study and successfully generated high potency high affinity agonistic anti-OX40 antibody that support further development. Citation Format: Xiaojuan Chai, Wenfang Xin, Teddy Yang, Qing Duan, Louis Liu. Generation of anti-OX40 antibody with different immunization strategies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1219.