Vaccine adjuvants: scientific challenges and strategic initiatives.

The majority of vaccine antigens currently under investigation represent recombinant molecules or subunits of pathogens with little or no inherent immunostimulatory property. The development of safe and potent immunologic adjuvants that can increase and direct vaccine-specific immunity is, therefore, required urgently. At the same time, the discovery of Toll-like receptors and other innate immune receptors with the ability to bridge innate immune responses and adaptive immunity is offering unprecedented opportunities for the development of novel adjuvants. However, research on vaccine adjuvants has so far received little attention as an independent scientific priority from most of the main research-funding agencies and policy makers. Further, adjuvant research and development is currently spread over a wide number of highly diverse organizations, including large commercial companies, small biotech enterprises as well as publicly funded research organizations and academia. More efforts are, therefore, needed to highlight the importance of vaccine adjuvants on the global research agenda and to encourage collaboration and flow of information between different stakeholders. This article attempts to underline scientific challenges and strategic priorities in the development of vaccine adjuvants for human use.