Short Review of Aluminum Hydroxide Related Lesions in Preclinical Studies and their Relevance

Aluminum compounds were first identified as adjuvant over 90 years ago [1]. Adjuvants (immunopotentiators or immuno modulators) in vaccine formulations aim to enhance, accelerate and prolong the specific immune response towards the desired response to vaccine antigens. Advantages of adjuvants include the enhancement of the immunogenicity of antigens, modification of the nature of the immune response, the reduction of the antigen amount needed for a successful immunization, the reduction of the frequency of booster immunizations needed and an improved immune response in elderly and immuno compromised vaccines [2]. Currently, aluminum is the most commonly used vaccine adjuvant and it is incorporated in vaccine formulas by various forms (aluminum hydroxide, aluminum phosphate and aluminum sulfate) [1]. The sum of officially scheduled vaccines deemed necessary for children in the U.S. has increased from 10 in the 1980s to 32 in the late 2000s, 18 of which contain aluminum adjuvants. Despite the longstanding and widespread use of aluminum adjuvants their precise mechanism of action remains poorly understood [3]. The physiochemical mechanism can be described by aluminum hydroxide stimulation of the immune system by inducing the release of uric acid, an immunological danger signal, which strongly attracts certain types of monocytes who differentiate into dendritic cells. The antigen is carried by the dendrite cells to the lymph nodes where it stimulates T cells and B cells [4]. Aluminum adjuvant is potent stimulators of the immune system and specially shift the immune response towards a Th2 profile [3].