Spleen-selective co-delivery of mRNA and TLR4 agonist-loaded LNPs for synergistic immunostimulation and Th1 immune responses

• DOI: 10.1016/j.jconrel.2023.03.041
• Publication Date: 2023-03-29T22:59:52Z
• Authors: Longze Pan; Lijing Zhang; Wenjing Deng; Jia Lou; Xiaoke Gao; Xiaohan Lou; Yangyang Liu; Xiaohan Yao; Yuqiao Sheng; Yan Yan; Chen Ni; Ming Wang; Chuntao Tian; Fazhan Wang; Zhihai Qin
• Keywords: Toll-Like Receptor 4; Mice, Inbred C57BL; Mice; Immunity, Cellular; Adjuvants, Immunologic; Ovalbumin; Animals; Immunization; Antigens; Spleen; 3. Good health

Spleen is an ideal site for initiating and amplifying antigen-specific immune response. However, spleen-selective antigen delivery has limited tumor therapeutic efficacy owing to an inadequate cytotoxic T-cell immune response. In this study, we designed a spleen-selective mRNA vaccine that delivered unmodified mRNA and Toll-like Receptor (TLR) agonists to the spleen after systemic administration, resulting in a sufficient and persistent antitumor cellular immune response with potent tumor immunotherapeutic efficacy. To establish potent tumor vaccines (sLNPs-OVA/MPLA), we co-loaded stearic acid doped lipid nanoparticles with ovalbumin (OVA)-coding mRNA and TLR4 agonists (MPLA). We found that sLNPs-OVA/MPLA facilitated tissue-specific mRNA expression in the spleen after intravenous injection and elicited enhanced adjuvant activity with Th1 immune responses by activating multiple TLRs. In a prophylactic mouse model, sLNPs-OVA/MPLA induced a potent antigen-specific cytotoxic T cell immune response and ultimately prevented the growth of EG.7-OVA tumors with persistent immune memory protection. In addition, sLNPs-OVA/MPLA effectively delayed the tumor growth of EG.7-OVA subcutaneously transplanted lymphoma and lung metastasis formation of B16F10-OVA intravenously injected melanoma. This study showed that the co-delivery of mRNA antigens and appropriate TLR agonists could significantly improve the antitumor immunotherapeutic efficacy of spleen-targeted mRNA vaccines via synergistic immunostimulation and Th1 immune responses.