RESUMO
Activity of adjuvanted vaccines is difficult to predict in vitro and in vivo. The wide compositional and conformational range of formulated adjuvants, from aluminum salts to oil-in-water emulsions, makes comparisons between physicochemical and immunological properties difficult. Even within a formulated adjuvant class, excipient selection and concentration can alter potency and physicochemical properties of the mixture. Complete characterization of physicochemical properties of adjuvanted vaccine formulations and relationship to biological response is necessary to move beyond a guess-and-check paradigm toward directed development. Here we present a careful physicochemical characterization of a two-component nanosuspension containing synthetic TLR-4 agonist glucopyranosyl lipid adjuvant (GLA) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) at various molar ratios. Physicochemical properties were compared with potency, as measured by stimulation of cytokine production in human whole blood. We found a surprising, nonlinear relationship between physicochemical properties and GLA-DPPC ratios that corresponded well with changes in biological activity. We discuss these data in light of the current understanding of TLR4 activation and the conformation-potency relationship in development of adjuvanted vaccines.
Assuntos
1,2-Dipalmitoilfosfatidilcolina/química , Adjuvantes Imunológicos/química , Dissacarídeos/química , Lipídeo A/análogos & derivados , Miristatos/química , Nanoestruturas/química , Receptor 4 Toll-Like/agonistas , 1,2-Dipalmitoilfosfatidilcolina/farmacologia , Acilação , Adjuvantes Imunológicos/farmacologia , Células Sanguíneas/efeitos dos fármacos , Células Sanguíneas/imunologia , Células Sanguíneas/metabolismo , Fenômenos Químicos , Citocinas/agonistas , Citocinas/metabolismo , Dissacarídeos/farmacologia , Combinação de Medicamentos , Humanos , Testes de Liberação de Interferon-gama , Lipídeo A/química , Lipídeo A/farmacologia , Miristatos/farmacologia , Concentração Osmolar , Tamanho da Partícula , Fosforilação , Propriedades de Superfície , Suspensões , Temperatura de TransiçãoRESUMO
Innate immune responses to vaccine adjuvants based on lipopolysaccharide (LPS), a component of gram-negative bacterial cell walls, are driven by Toll-like receptor (TLR) 4 and adaptor proteins including MyD88 and TRIF, leading to the production of inflammatory cytokines, type I interferons, and chemokines. We report here on the characterization of a synthetic hexaacylated lipid A derivative, denoted as glucopyranosyl lipid adjuvant (GLA). We assessed the effects of GLA on murine and human dendritic cells (DC) by combining microarray, mRNA and protein multiplex assays and flow cytometry analyses. We demonstrate that GLA has multifunctional immunomodulatory activity similar to naturally-derived monophosphory lipid A (MPL) on murine DC, including the production of inflammatory cytokines, chemokines, DC maturation and antigen-presenting functions. In contrast, hexaacylated GLA was overall more potent on a molar basis than heterogeneous MPL when tested on human DC and peripheral blood mononuclear cells (PBMC). When administered in vivo, GLA enhanced the immunogenicity of co-administered recombinant antigens, producing strong cell-mediated immunity and a qualitative T(H)1 response. We conclude that the GLA adjuvant stimulates and directs innate and adaptive immune responses by inducing DC maturation and the concomitant release of pro-inflammatory cytokines and chemokines associated with immune cell trafficking, activities which have important implications for the development of future vaccine adjuvants.
