Metal ions play critical roles in many immune processes, and their modulation may open up new forms of vaccine adjuvants. Current vaccines predominantly utilize aluminum salts as adjuvants, but alum has poor ability to induce cellular immunity. Manganese (Mn2+) can activate cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway for amplifying cellular immune responses, but free Mn2+ may cause certain neurotoxicity due to its random in vivo distribution. Herein, Mn2+ is initially biomineralized into human serum albumin nanoparticles (HSA-Mn) to improve the biocompatibility of Mn adjuvants. Then, HSA-Mn and alum adjuvants are co-dispersed at the squalene/water interphase, resulting in a bimetallic adjuvant co-stabilized Pickering nanoemulsion (HMANE). Compared to lecithin-stabilized emulsion, HMANE increased the surface roughness by approximately 6-fold and significantly improved its interactions with antigen-presenting cells (APCs). After vaccination, HMANE-adjuvanted inactivated SARS-CoV-2 virus (CorV-HMANE) rapidly induced antibody generation and efficiently activated the STING pathway to produce a stronger cellular immune response. In addition, the abundant memory B and T cells induced by the CorV-HMANE further ensured its long-term protective efficacy for at least 4 months. In conclusion, our study highlights the great potential of Pickering emulsions as metal adjuvant platforms, providing new insight for further adjuvant development.
Marrack, P.; McKee, A. S.; Munks, M. W. Towards an understanding of the adjuvant action of aluminium. Nat. Rev. Immunol. 2009, 9, 287–293.
HogenEsch, H.; O’Hagan, D. T.; Fox, C. B. Optimizing the utilization of aluminum adjuvants in vaccines: You might just get what you want. npj Vaccines 2018, 3, 51.
Li, A. P. Y.; Cohen, C. A.; Leung, N. H. L.; Fang, V. J.; Gangappa, S.; Sambhara, S.; Levine, M. Z.; Iuliano, A. D.; Perera, R. A. P. M.; Ip, D. K. M. et al. Immunogenicity of standard, high-dose, MF59-adjuvanted, and recombinant-HA seasonal influenza vaccination in older adults. npj Vaccines 2021, 6, 25.
Mastelic Gavillet, B.; Eberhardt, C. S.; Auderset, F.; Castellino,F.; Seubert, A.; Tregoning, J. S.; Lambert, P. H.; De Gregorio, E.; Del Giudice, G.; Siegrist, C. A. MF59 mediates its B cell adjuvanticity by promoting T follicular helper cells and thus germinal center responses in adult and early life. J. Immunol. 2015, 194, 4836–4845.
Cohet, C.; Van Der Most, R.; Bauchau, V.; Bekkat-Berkani, R.; Doherty, T. M.; Schuind, A.; Tavares Da Silva, F.; Rappuoli, R.; Garçon, N.; Innis, B. L. Safety of AS03-adjuvanted influenza vaccines: A review of the evidence. Vaccine 2019, 37, 3006–3021.
Syed, Y. Y. Recombinant zoster vaccine (Shingrix(®)): A review in herpes zoster. Drugs Aging 2018, 35, 1031–1040.
Stertman, L.; Palm, A. K. E.; Zarnegar, B.; Carow, B.; Lunderius Andersson, C.; Magnusson, S. E.; Carnrot, C.; Shinde, V.; Smith, G.; Glenn, G. et al. The matrix-MTM adjuvant: A critical component of vaccines for the 21st century. Hum. Vaccines Immunother. 2023, 19, 2189885.
Kwok, M. H.; Li, Z. F.; Ngai, T. Controlling the synthesis and characterization of micrometer-sized PNIPAM microgels with tailored morphologies. Langmuir 2013, 29, 9581–9591.
Brugger, B.; Rütten, S.; Phan, K. H.; Möller, M.; Richtering, W. The colloidal suprastructure of smart microgels at oil-water interfaces. Angew. Chem., Int. Ed. 2009, 48, 3978–3981.
Tu, W. H.; Xiong, Z. P.; Wang, L.; Zhang, J. Y.; Sun, J. Z.; Zhang, H. K.; Tang, B. Z. The superiority of nonconjugated structures in fluorescence: Through-space vs. through-bond charge transfer. Sci. China Chem. 2024, 67, 3121–3130.
Chen, Z. W.; Zhao, C. Q.; Ju, E. G.; Ji, H. W.; Ren, J. S.; Binks, B. P.; Qu, X. G. Design of surface-active artificial enzyme particles to stabilize pickering emulsions for high-performance biphasic biocatalysis. Adv. Mater. 2016, 28, 1682–1688.
Xia, Y. F.; Wu, J.; Wei, W.; Du, Y. Q.; Wan, T.; Ma, X. W.; An, W. Q.; Guo, A. Y.; Miao, C. Y.; Yue, H. et al. Exploiting the pliability and lateral mobility of Pickering emulsion for enhanced vaccination. Nat. Mater. 2018, 17, 187–194.
Peng, S.; Cao, F. Q.; Xia, Y. F.; Gao, X. D.; Dai, L. P.; Yan, J. H.; Ma, G. H. Particulate alum via pickering emulsion for an enhanced COVID-19 vaccine adjuvant. Adv. Mater. 2020, 32, e2004210.
Song, T. T.; Xia, Y. F.; Du, Y. Q.; Chen, M. W.; Qing, H.; Ma, G. H. Engineering the deformability of albumin-stabilized emulsions for lymph-node vaccine delivery. Adv. Mater. 2021, 33, e2100106.
Sun, X. Q.; Zhou, X. W.; Shi, X. Y.; Abed, O. A.; An, X. R.; Lei, Y. L.; Moon, J. J. Strategies for the development of metalloimmunotherapies. Nat. Biomed. Eng. 2024, 8, 1073–1091.
Zhao, T. M.; Cai, Y. L.; Jiang, Y. J.; He, X. M.; Wei, Y. Q.; Yu, Y. F.; Tian, X. H. Vaccine adjuvants: Mechanisms and platforms. Signal Transduct. Target. Ther. 2023, 8, 283.
Sun, X. Q.; Zhang, Y.; Li, J. Q.; Park, K. S.; Han, K.; Zhou, X. W.; Xu, Y.; Nam, J.; Xu, J.; Shi, X. Y. et al. Amplifying STING activation by cyclic dinucleotide-manganese particles for local and systemic cancer metalloimmunotherapy. Nat. Nanotechnol. 2021, 16, 1260–1270.
Zhang, R.; Wang, C. G.; Guan, Y. K.; Wei, X. M.; Sha, M. Y.; Yi, M. R.; Jing, M.; Lv, M. Z.; Guo, W.; Xu, J. et al. Manganese salts function as potent adjuvants. Cell. Mol. Immunol. 2021, 18, 1222–1234.
Wang, X.; Liu, Y. Q.; Xue, C. C.; Hu, Y.; Zhao, Y. Y.; Cai, K. Y.; Li, M. H.; Luo, Z. A protein-based cGAS-STING nanoagonist enhances T cell-mediated anti-tumor immune responses. Nat. Commun. 2022, 13, 5685.
Wang, Y. L.; Xie, Y. P.; Luo, J.; Guo, M. Y.; Hu, X. H.; Chen, X.; Chen, Z. W.; Lu, X. Y.; Mao, L. C.; Zhang, K. et al. Engineering a self-navigated MnARK nanovaccine for inducing potent protective immunity against novel coronavirus. Nano Today 2021, 38, 101139.
Li, X. D.; Wu, J. X.; Gao, D. X.; Wang, H.; Sun, L. J.; Chen, Z. J. Pivotal roles of cGAS–cGAMP signaling in antiviral defense and immune adjuvant effects. Science 2013, 341, 1390–1394.
Sun, L. J.; Wu, J. X.; Du, F. H.; Chen, X.; Chen, Z. J. Cyclic GMP-AMP synthase is a cytosolic DNA sensor that activates the type I interferon pathway. Science 2013, 339, 786–791.
Corrales, L.; Glickman, L. H.; McWhirter, S. M.; Kanne, D. B.; Sivick, K. E.; Katibah, G. E.; Woo, S. R.; Lemmens, E.; Banda, T.; Leong, J. J. et al. Direct activation of STING in the tumor microenvironment leads to potent and systemic tumor regression and immunity. Cell Rep. 2015, 11, 1018–1030.
Shae, D.; Becker, K. W.; Christov, P.; Yun, D. S.; Lytton-Jean, A. K. R.; Sevimli, S.; Ascano, M.; Kelley, M.; Johnson, D. B.; Balko, J. M. et al. Endosomolytic polymersomes increase the activity of cyclic dinucleotide STING agonists to enhance cancer immunotherapy. Nat. Nanotechnol. 2019, 14, 269–278.
Lv, M. Z.; Chen, M. X.; Zhang, R.; Zhang, W.; Wang, C. G.; Zhang, Y.; Wei, X. M.; Guan, Y. K.; Liu, J. J.; Feng, K. C. et al. Jiang, Manganese is critical for antitumor immune responses via cGAS–STING and improves the efficacy of clinical immunotherapy. Cell Res. 2020, 30, 966–979.
Budinger, D.; Barral, S.; Soo, A. K. S.; Kurian, M. A. The role of manganese dysregulation in neurological disease: Emerging evidence. Lancet Neurol. 2021, 20, 956–968.
Qiao, N.; Wang, H. R.; Xu, Y. H.; Chang, Y.; Xie, M. X.; Bai, S. T.; He, C. T.; Qin, M.; Zhong, X. F.; Jiang, M. et al. A Mn–Al double adjuvant nanovaccine to induce strong humoral and cellular immune responses. J. Control Release 2023, 358, 190–203.
Wang, H.; Zhang, Y. T.; Huang, B. Y.; Deng, W.; Quan, Y. R.; Wang, W. L.; Xu, W. B.; Zhao, Y. X.; Li, N.; Zhang, J. et al. Development of an inactivated vaccine candidate, BBIBP–CorV, with potent protection against SARS–CoV-2. Cell 2020, 182, 713–721.e9.
Xu, C.; Wang, Y. L.; Zhang, C. Y.; Jia, Y. W.; Luo, Y. J.; Gao, X. Y. AuGd integrated nanoprobes for optical/MRI/CT triple-modal in vivo tumor imaging. Nanoscale 2017, 9, 4620–4628.
Wang, Y. L.; Xu, C.; Chang, Y. N.; Zhao, L. N.; Zhang, K.; Zhao, Y. L.; Gao, F. P.; Gao, X. Y. Ultrasmall superparamagnetic iron oxide nanoparticle for T2-weighted magnetic resonance imaging. ACS Appl. Mater. Interfaces 2017, 9, 28959–28966.
Zhao, Z.; Ma, Z. X.; Wang, B.; Guan, Y. K.; Su, X. D.; Jiang, Z. F. Mn2+ directly activates cGAS and structural analysis suggests Mn2+ induces a noncanonical catalytic synthesis of 2′3′-cGAMP. Cell Rep. 2020, 32, 108053.
Merkenschlager, J.; Finkin, S.; Ramos, V.; Kraft, J.; Cipolla, M.; Nowosad, C. R.; Hartweger, H.; Zhang, W. Z.; Olinares, P. D. B.; Gazumyan, A. et al. Dynamic regulation of TFH selection during the germinal centre reaction. Nature 2021, 591, 458–463.
Lam, N.; Lee, Y.; Farber, D. L. A guide to adaptive immune memory. Nat. Rev. Immunol. 2024, 24, 810–829.
Cibrián, D.; Sánchez-Madrid, F. CD69: From activation marker to metabolic gatekeeper . Eur J. Immunol. 2017, 47, 946–953