Inorganic compounds as vaccine adjuvants
Abstract
The adjuvant capacity of minerals was first discovered in 1926, when a suspension of diphtheria toxoid precipitated with potassium aluminum sulfate was found to be significantly more immunogenic than the same suspension in the absence of this compound. Although a large number of inorganic salts have since been evaluated for this purpose, only alum, phosphate and aluminum hydroxide, and aluminum sulfate hydroxyphosphate have been approved in humans, and calcium phosphate is included in some vaccines manufactured in Europe. In the past, lack of awareness of the fact that the adjuvant properties of inorganic salts are highly dependent on nuances of their production processes that directly affect the depot and presenting effects attributed to adjuvants has led to the rejection of many compounds with potentially better adjuvant properties than traditional aluminum salts. However, the application of recent advances in nanotechnology and the combination of different adjuvants have led to the emergence and evaluation of a large number of new alternatives. The present review describes the most frequently cited inorganic adjuvants, examining their potential for the development of more potent vaccines than the current crop of products using aluminum-based compounds.
