Nanomaterial-based vaccine adjuvants

Vaccination is a biological process that administers antigenic materials to stimulate an individual's immune system to develop immunity to a specific pathogen. It is the most effective tool to prevent illness and death from infectious diseases or diseases leading to cancers. Because many recombinant and synthetic antigens are poorly immunogenic, an adjuvant is essentially added to the vaccine formula that can potentiate the immune responses, offer better protection against pathogens and reduce the amount of antigens needed for protective immunity. To date, there have been nearly 100 different types of adjuvants associated with about 400 vaccines that are either commercially available or under development. Among these adjuvants, many of them are particulates and nano-scale in nature. Nanoparticles represent a wide range of materials with novel physicochemical properties that exhibit immunostimulatory effects. However, the mechanistic understanding of how their physicochemical properties affect immunopotentiation remains elusive. In this article, we aim to review the current developmental status of nanomaterial-based vaccine adjuvants, and further discuss their acting mechanisms, the understanding of which will benefit the rational design of effective vaccine adjuvants with improved immunogenicity for prevention of infectious diseases as well as therapeutic cancer treatment.