Breaking it down
The first bacterial-derived adjuvant, approved for use in human vaccines in 2009, is a subunit of lipopolysaccharide (LPS), a molecule expressed on gram-negative bacteria. LPS stimulates strong—sometimes deadly—immune responses, but a subunit called monophosphoryl lipid A (MPL) can induce an immune response with little toxicity. Developed by GlaxoSmithKline, MPL is currently being used in GSK’s hepatitis B and human papilloma vaccines, and is being clinically tested with a range of other vaccines.