Biomaterials as vaccine adjuvants

Biomaterials are promising candidate adjuvants to enhance vaccine efficacy. Through adjuvant design, we can broaden the use of vaccines to diseases such as AIDS, malaria, and cancer. This review addresses the fundamentals of vaccine and adjuvant function in order to determine guidelines for adjuvant design, including aspects of the vaccine such as disease target, antigen formulation, and delivery route. An ideal biomaterial adjuvant will perform three functions. (1) It will deliver the antigen selectively to dendritic cells. This has been accomplished through release of chemokines or cytokines, use of antidendritic cell antibodies, and even through particle size selection. (2) It will activate the dendritic cells, improving antigen presentation. Biomaterials themselves have been shown to activate innate immunity, but specific innate-activating ligands have also been included in adjuvant formulations. Finally, (3) it will release the antigen appropriately into the dendritic cell. Tuning release to be pH sensitive and engineering endosomal release are strategies that have been used. There is a real opportunity to rationally design better biomaterial adjuvants that will significantly expand and improve vaccine function.