Vaccine adjuvants: the dream becomes real.

After about 70 years two new adjuvants have been approved for human vaccines. The first is MF59 developed by the ex-Chiron now Novartis Vaccines and it consists in an oil-in-water emulsion, comprising a low content of biodegradable squalene oil (4.3%) as the dispersed phase, which is stabilized by two non-ionic surfactants (Tween 80 and Span 85), and a low ionic strength citrate buffer as the continuous phase. The second one, defined as AS04, has been developed by GSK Biologics and consists in 3-0-desacyl-4'-monophosphoryl lipid A (MPL) that comes from the cell wall LPS of Gram-negative Salmonella minnesota R595 and is detoxified by mild hydrolytic treatment and purification. It is absorbed on aluminum hydroxide or aluminum phosphate. Thus, new molecules are available to improve the immune response to vaccines also in humans: this is the beginning of a new era in vaccinology.