ABSTRACT
The search for vaccines that protect from severe morbidity and mortality because of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 (COVID-19) is a race against the clock and the virus. Here we describe an amphiphilic imidazoquinoline (IMDQ-PEG-CHOL) TLR7/8 adjuvant, consisting of an imidazoquinoline conjugated to the chain end of a cholesterol-poly(ethylene glycol) macromolecular amphiphile. It is water-soluble and exhibits massive translocation to lymph nodes upon local administration through binding to albumin, affording localized innate immune activation and reduction in systemic inflammation. The adjuvanticity of IMDQ-PEG-CHOL was validated in a licensed vaccine setting (quadrivalent influenza vaccine) and an experimental trimeric recombinant SARS-CoV-2 spike protein vaccine, showing robust IgG2a and IgG1 antibody titers in mice that could neutralize viral infection in vitro and in vivo in a mouse model.
Subject(s)
Adjuvants, Immunologic/therapeutic use , COVID-19 Vaccines/therapeutic use , COVID-19/prevention & control , Imidazoles/therapeutic use , Immunity, Innate/drug effects , Quinolines/therapeutic use , Animals , COVID-19 Vaccines/immunology , Cholesterol/analogs & derivatives , Cholesterol/immunology , Cholesterol/therapeutic use , Female , Humans , Imidazoles/immunology , Influenza A Virus, H1N1 Subtype/drug effects , Influenza Vaccines/immunology , Influenza Vaccines/therapeutic use , Influenza, Human/prevention & control , Membrane Glycoproteins/agonists , Mice, Inbred BALB C , Mice, Inbred C57BL , Mice, Transgenic , Polyethylene Glycols/therapeutic use , Quinolines/immunology , Recombinant Proteins/immunology , SARS-CoV-2/drug effects , Spike Glycoprotein, Coronavirus/immunology , Surface-Active Agents/therapeutic use , Toll-Like Receptor 7/agonists , Toll-Like Receptor 8/agonistsABSTRACT
Lipid nanoparticle (LNP) packaged mRNA vaccines have been deployed against infectious diseases such as COVID-19, yet their structural features remain unclear. Cholesterol, a major constituent within LNPs, contributes to their morphology that influences gene delivery. Herein, we examine the structure of LNPs containing cholesterol derivatives using electron microscopy, differential scanning calorimetry, and membrane fluidity assays. LNPs formulated with C24 alkyl derivatives of cholesterol show a polymorphic shape and various degrees of multilamellarity and lipid partitioning, likely due to phase separation. The addition of methyl and ethyl groups to the C24 alkyl tail of the cholesterol backbone induces multilamellarity (>50% increase compared to cholesterol), while the addition of a double bond induces lipid partitioning (>90% increase compared to cholesterol). LNPs with multilamellar and faceted structures, as well as a lamellar lipid phase, showed higher gene transfection. Unraveling the structure of mRNA-LNPs can enable their rational design toward enhanced gene delivery.