title: Ultrastructural Visualization of Vaccine Adjuvant Uptake In Vitro and In Vivo.
abstract: Adjuvants are substances that enhance adaptive immune responses when formulated in a vaccine. Alum and MF59 are two vaccine adjuvants licensed for human vaccination. Their mode of action has not been completely elucidated. Here we show the first ultrastructural visualization of Alum and MF59 interaction with immune cells in vitro and in vivo. We observed that Alum is engulfed by cells as inclusions of laminae that are detectable within draining lymph nodes. MF59 is instead engulfed by cells in vitro as low-electron-dense lipid-like inclusions that display a vesicle pattern, as confirmed by confocal microscopy using fluorescently labeled MF59. However, lipid-like inclusions with different high- and low-electron-dense content are detected within cells of draining lymph nodes when injecting MF59. As high-electron-dense lipid-like inclusions are also detected upon injection of Alum, our results suggest that the low-electron-dense inclusions are formed by engulfed MF59, whereas the high-electron-dense inclusions are proper lipid inclusions. Thus, we demonstrated that vaccine adjuvants are engulfed as inclusions by lymph node cells and hypothesize that adjuvant treatment may modify lipid metabolism.
authors.affiliation: 1Dipartimento di Scienze della Vita,Università degli Studi di Siena,53100 Siena,Italy.
authors.forename: Fabiola
authors.initials: F
authors.lastname: Giusti
authors.affiliation: 2Novartis Vaccines and Diagnostics (a GSK company),53100 Siena,Italy.
authors.forename: Anja
authors.initials: A
authors.lastname: Seubert
authors.affiliation: 2Novartis Vaccines and Diagnostics (a GSK company),53100 Siena,Italy.
authors.forename: Rocco
authors.initials: R
authors.lastname: Cantisani
authors.affiliation: 2Novartis Vaccines and Diagnostics (a GSK company),53100 Siena,Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Tortoli
authors.affiliation: 2Novartis Vaccines and Diagnostics (a GSK company),53100 Siena,Italy.
authors.forename: Ugo
authors.initials: U
authors.lastname: D'Oro
authors.affiliation: 2Novartis Vaccines and Diagnostics (a GSK company),53100 Siena,Italy.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Ferlenghi
authors.affiliation: 1Dipartimento di Scienze della Vita,Università degli Studi di Siena,53100 Siena,Italy.
authors.forename: Romano
authors.initials: R
authors.lastname: Dallai
authors.affiliation: 2Novartis Vaccines and Diagnostics (a GSK company),53100 Siena,Italy.
authors.forename: Diego
authors.initials: D
authors.lastname: Piccioli
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000534:Alum Compounds / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000818:Animals; D004705:Endocytosis; D002479:Inclusion Bodies / Q000648:ultrastructure; D008810:Mice, Inbred C57BL; D008853:Microscopy; D011136:Polysorbates / Q000008:administration & dosage / Q000493:pharmacokinetics*; D013185:Squalene / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D000276:Adjuvants, Immunologic; D000534:Alum Compounds; C089950:MF59 oil emulsion; D011136:Polysorbates; C041524:aluminum sulfate; D013185:Squalene
keywords: Alum; MF59; electron microscopy; lymph node; vaccine