Objectives To review the state of the art and assess future potential in the use of
inorganic particulates as vaccine adjuvants.
Key findings An adjuvant is an entity added to a vaccine formulation to ensure
that robust immunity to the antigen is inculcated. The inclusion of an adjuvant is
typically vital for the efficacy of vaccines using inactivated organisms, subunit and
DNA antigens. With increasing research efforts being focused on subunit and
DNA antigens because of their improved safety profiles, the development of
appropriate adjuvants is becoming ever more crucial. Despite this, very few adjuvants
are licensed for use in humans (four by the FDA, five by the European Medicines
Agency). The most widely used adjuvant, alum, has been used for nearly 90
years, yet its mechanism of action remains poorly understood. In addition, while
alum produces a powerful antibody Th2 response, it does not provoke the cellular
immune response required for the elimination of intracellular infections or
cancers. New adjuvants are therefore needed, and inorganic systems have attracted
much attention in this regard.
Summary In this review, the inorganic adjuvants currently in use are considered,
and the efforts made to date to understand their mechanisms of action are summarised.
We then move on to survey the literature on inorganic particulate adjuvants,
focusing on the most interesting recent developments in this area and their
future potential