Squalene-based oil-in-water emulsion adjuvant

Squalene-based oil-in-water emulsion adjuvants are vaccine formulation components designed to enhance immune responses to co-administered antigens. They act primarily by stimulating the innate immune system, recruiting antigen-presenting cells, and enhancing both antibody (humoral) and T cell (cellular) immune responses. Widely used examples include MF59 and AS03, which are approved for use in influenza and other vaccines. Their effects depend on composition (e.g., addition of α-tocopherol) and the formulation's ability to promote sustained antigen exposure, enhance antigen uptake, facilitate cross-presentation to T cells, and induce broad-based and high-quality antibody responses. These emulsions have a strong safety record in clinical use, with only local and mild systemic adverse effects reported in the majority of cases[4][5][6][1].

Other names

Squalene emulsion adjuvantOil-in-water squalene emulsionSE adjuvantMF59 (commercial)AS03 (commercial)

Recruitment of monocytes, neutrophils, eosinophils, and dendritic cells to injection site and lymph nodes Enhancement of antigen uptake and presentation by antigen-presenting cells (APCs) Stimulation of Th1 and T follicular helper cell responses (via cytokines such as IL-18 and factors like α-tocopherol) Induction of RIPK3-dependent necroptosis leading to enhanced CD8 T cell priming Sustained antigen release for prolonged immune stimulation