Fusing a Novel Anti-CTLA-4 Nanobody to the IgG1 Fc Region Strengthens Its Ability to Induce CD8+ T Cell-Mediated Immune Responses Against Solid Tumors

Ting-ting Li,1 Jin-hua Yang,1 Meng-jie Jiang,1 Hao-peng Cui,1 Xiao-mei Yang,2 Xiao-ling Lu,2 Ai-qun Liu1 1Department of Gastroenterology and Respiratory Medicine & Endoscopy Center, Guangxi Medical University Cancer Hospital, Nanning, Guangxi, 530021, People’s Republic of China; 2Guangxi Key Laboratory of Nanobody Research, Guangxi Medical University, Nanning, Guangxi, 530021, People’s Republic of ChinaCorrespondence: Ai-qun Liu; Xiao-ling Lu, Email [email protected]; [email protected]: Our previously described a nanobody precisely targeting CTLA-4 and demonstrated that it can promote the antitumor response of adoptive T cells. Here we examined whether fusing it to the IgG1 Fc region would induce stronger, longer-lasting T-cell immune responses after exposure to the dendritic-tumor cell fusions.Methods: The fusion of nanobody to Fc region was overexpressed in E. coli. Next, the proliferation, activation and cytotoxicity of the CD8+ T cells stimulated by the fusion protein and dendritic-tumor cell fusions was assessed in vitro, and the antitumor activity was evaluated in nude mice bearing xenografts of each type of solid tumor.Results: Proliferation, activation and cytotoxicity of CD8+ T cells in vitro were significantly greater in the presence of the fusion protein than those in other groups. Consistently, different types of xenografts growth were significantly slower and animal survival significantly longer when the injected CD8+ T cells had been activated in vitro in the presence of the fusion protein.Conclusion: Fusing our anti-CTLA-4 nanobody to the IgG1 Fc region potentiates its ability to induce strong, persistent CD8+ T cell responses against solid tumors in mice. This fusion strategy has the potential to realize clinical transformation and application to clinical treatment.Keywords: nanobody, CTLA-4, therapeutic antibody derivative, cell fusion, adoptive immunotherapy