Squalene emulsion potentiates the adjuvant activity of the TLR4 agonist, GLA, via inflammatory caspases, IL‐18, and IFN‐γ

Abstract

+T-cell induction via GLA-SE. Thus, we demonstrate that IL-18 and caspase-1/11 are components of the response to immunization with the TLR4 agonist/squalene oil-inwater based adjuvant, GLA-SE, providing implications for other adjuvants that combine oils with TLR agonists. Additional supporting information may be found in the online version of this article at the publisher's web-site Keywords: Adjuvants IntroductionVaccines rely on triggering the innate immune system to generate protective immunity. Many empirically established vaccines serendipitously contain molecules known as pathogen-associated molecular patterns (PAMPs) that engage host-germline encoded receptors, e.g. TLRs, which contribute to their immunogenicity Correspondence: Dr. Anthony L. Desbien e-mail: Anthony.Desbien@IDRI.org [1]. In the case where antigen preparations alone fail to be immunogenic, extrinsic adjuvants, such as alum or oil emulsions, are added to make vaccines effective. Such extrinsic adjuvants were empirically developed and despite their use in billions of vaccine doses, their mechanisms of action are not completely understood [2,3]. Knowledge of the salient attributes of empirical adjuvants would facilitate the design of the next generation of vaccines.In order to function as adjuvants, deliberately incorporated PAMPs require proper formulation [4,5]. For unknown reasons, squalene oil-in-water emulsions (SEs), such as AS02 and MF59, C 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.eji-journal.eu 408Anthony L. Desbien et al. Eur. J. Immunol. 2015. 45: 407-417 are excellent formulations for TLR agonists, greatly enhancing the magnitude and quality of the immune response [6][7][8][9][10][11]. While it is clear that squalene emulsions by themselves are potent adjuvants, exactly how they engage the immune system or cooperate with TLR agonists is unclear. The commercial product MF59 is the prototypical squalene adjuvant. MF59 has been shown to activate the innate immune system, alter antigen presentation, and enhance humoral responses [3,[12][13][14]. While these attributes are ostensibly useful for generation of immunity, the specific components of the immune system triggered by squalene emulsions remain to be elucidated. The inflammasome is a pathogen recognition system required for protection against many diseases [15]. Engagement of the inflammasome occurs by diverse stimuli including pathogenand host-derived molecules. Known triggers include cytoplasmic dsDNA as well as aberrantly localized host-derived molecules, referred to as danger-associated molecular patterns [16]. In particular, extracellular ATP acts as a danger-associated molecular pattern, and has been recently demonstrated to contribute to activity of MF59, suggesting that MF59 acts via the inflammasome [17]. Further, the antibody response to immunization with MF59 has been linked to the adapter protein ASC, a component of the inflammasome, but not caspase-1 or NLRP3 (where NLR is nod-like receptor), indicating that adjuvant activity of MF59 is mediated by stil...

IL-18 and Subcapsular Lymph Node Macrophages are Essential for Enhanced B Cell Responses with TLR4 Agonist Adjuvants

“…Immunization with GLA-SE initiates a complex innate immune response including production of IFN-γ which is essential for the adjuvanticity of GLA-SE (18) and a number of chemoattractants including RANTES, MIP1α and β, Eotaxin, and CXCL10 (Fig. 3A).…”

“…3A). CD69 expression increases upon GLA-SE immunization in a type I and II IFN-dependent manner and is thus a sensitive readout for the response to GLA-SE (18, 20). Treatment with CLL resulted in a substantial decrease in the induction of CD69 on total lymphocytes 18h after injection with GLA-SE (Fig.…”

“…When GLA is formulated as a squalene oil-in-water emulsion (referred to as GLA-SE) compared to aqueous formulations of GLA, unique innate and adaptive features emerge (7, 17, 18). We have previously demonstrated that the T H1 potentiating activity of GLA-SE is mediated in part by MyD88 and TRIF signaling, inflammatory caspases and IL-18 as well as by type I and II interferons, IL-12, and the transcription factor T-bet (18–20). In the present paper we evaluate the cellular and molecular events necessary for augmentation of B cell, antibody and T FH responses by the GLA-SE adjuvant.…”

Adjuvant formulations for virus-like particle (VLP) based vaccines

“…The glucopyranosyl lipid adjuvant (GLA) is formulated in aqueous nanosuspension (GLA-AF) [68] or in a squalene oil-in-water emulsion (GLA-SE) [69]. The GLA-AF and GLA-SE adjuvants were included in H5-VLP vaccine formulations against influenza, and the efficacy and safety for such vaccine preparations were studied in two different clinical trials sponsored by IDRI (Phase I) and Medicago (Phase II).…”

Development of a schistosomiasis vaccine

“…Many of the groups in later stage development as described above are therefore using GLA, a synthetic TLR4 based agonist to skew the immune response to Th1 [74–76] in either an alum or a lipid formulation (“GLA-SE”) [55;77]. While this adjuvant appears suitable in enhancing appropriate anti-schistosomal responses [55], more extensive studies of the formulations should be performed to optimize responses since the formulation can dramatically affect immunization outcomes [55;57;78], likely due to interactions of the TLR agonist, the formulated carrier, and the antigen [79]. …”