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NPJ Vaccines
. 2026 Apr 28.
doi: 10.1038/s41541-026-01457-1. Online ahead of print.
Quillaja saponaria fraction QS-18 as an adjuvant for liposomal seasonal influenza vaccines
Qinzhe Li 1 , Zachary Sia 1 , Yuan Luo 1 , Wei-Chiao Huang 1 2 , Hilliard L Kutscher 2 , Haojun Zhu 3 , Joaquin Ortega 3 , Bruce A Davidson 4 5 , Jonathan F Lovell 6
Affiliations
Saponin fractions from Quillaja saponaria (QS) are promising vaccine adjuvants. Among these, QS-21 is a component in several FDA-approved vaccines, but its limited quantity may present a manufacturing bottleneck. While the related saponin, QS-18, is one of the most abundant fractions, its putative toxicity has historically hindered its clinical development. In this study, we formulated QS-18 into a seasonal influenza virus liposomal nanoparticle protein vaccine comprising contemporary, recombinant hemagglutinin and neuraminidase antigens from influenza A (H1N1), influenza A (H3N2), and influenza B (Victoria lineage). This formulation did not exhibit overt QS-18 toxicity in mice or rabbits. In mice and ferrets, QS-18 adjuvanted particles elicited efficacious antibody responses and provided protection against influenza challenges, comparable to analogous QS-21 adjuvanted liposomes. These findings suggest that more study of QS-18 or QS-18-containing QS fractions is warranted for infectious disease vaccine adjuvant formulations.
. 2026 Apr 28.
doi: 10.1038/s41541-026-01457-1. Online ahead of print.
Quillaja saponaria fraction QS-18 as an adjuvant for liposomal seasonal influenza vaccines
Qinzhe Li 1 , Zachary Sia 1 , Yuan Luo 1 , Wei-Chiao Huang 1 2 , Hilliard L Kutscher 2 , Haojun Zhu 3 , Joaquin Ortega 3 , Bruce A Davidson 4 5 , Jonathan F Lovell 6
Affiliations
- PMID: 42049779
- DOI: 10.1038/s41541-026-01457-1
Saponin fractions from Quillaja saponaria (QS) are promising vaccine adjuvants. Among these, QS-21 is a component in several FDA-approved vaccines, but its limited quantity may present a manufacturing bottleneck. While the related saponin, QS-18, is one of the most abundant fractions, its putative toxicity has historically hindered its clinical development. In this study, we formulated QS-18 into a seasonal influenza virus liposomal nanoparticle protein vaccine comprising contemporary, recombinant hemagglutinin and neuraminidase antigens from influenza A (H1N1), influenza A (H3N2), and influenza B (Victoria lineage). This formulation did not exhibit overt QS-18 toxicity in mice or rabbits. In mice and ferrets, QS-18 adjuvanted particles elicited efficacious antibody responses and provided protection against influenza challenges, comparable to analogous QS-21 adjuvanted liposomes. These findings suggest that more study of QS-18 or QS-18-containing QS fractions is warranted for infectious disease vaccine adjuvant formulations.