Antigen depot is not required for alum adjuvanticity

Abstract

Alum adjuvants have been in continuous clinical use for more than 80 yr. While the prevailing theory has been that depot formation and the associated slow release of antigen and/or inflammation are responsible for alum enhancement of antigen presentation and subsequent T- and B-cell responses, this has never been formally proven. To examine antigen persistence, we used the chimeric fluorescent protein EαGFP, which allows assessment of antigen presentation in situ, using the Y-Ae antibody. We demonstrate that alum and/or CpG adjuvants induced similar uptake of antigen, and in all cases, GFP signal did not persist beyond 24 h in draining lymph node antigen-presenting cells. Antigen presentation was first detectable on B cells within 6–12 h of antigen administration, followed by conventional dendritic cells (DCs) at 12–24 h, then finally plasmacytoid DCs at 48 h or later. Again, alum and/or CpG adjuvants did not have an effect on the magnitude or sequence of this response; furthermore, they induced similar antigen-specific T-cell activation in vivo. Notably, removal of the injection site and associated alum depot, as early as 2 h after administration, had no appreciable effect on antigen-specific T- and B-cell responses. This study clearly rules out a role for depot formation in alum adjuvant activity.—Hutchison, S., Benson, R. A., Gibson, V. B., Pollock, A. H., Garside, P., Brewer, J. M. Antigen depot is not required for alum adjuvanticity.

Effective and lesion-free cutaneous influenza vaccination

“…This observation reinforces that a short period of local sterile inflammation is enough to "educate" DCs in bridging an innate to adaptive immune response as we previously demonstrated (5). This important notion is strongly supported by the investigation showing that surgical removal of the inoculation site containing alum 2 h after vaccination did not compromise the adjuvant effect of alum (26). The study, along with our observations, argues strongly the dispensability of prolonged inflammation at the inoculation site for effective vaccination.…”

“…All experiments were repeated twice with similar results. inoculation site was not necessary for effective immunization (5,26). Moreover, in comparison with vaccination of MNs alone, NAFL treatment significantly enhanced the immune responses, without incurring any adverse events.…”

Beyond antigens and adjuvants: formulating future vaccines

“…Alum appears to form a depot with some antigens (12) but not others (115) and likely undergoes desorption of some antigens under in vivo conditions (116). Recent studies have further demonstrated that, following alum immunization, the injection site can be surgically removed 2 hours after injection with no effect on the humoral immune response, suggesting that depot formation is not a critical part of alum's mechanism of action (117,118).…”

Laser facilitates vaccination

“…Hutchison et al demonstrated that removing the injection site 2 h after immunization did not result in compromised immune responses, indicating that the antigen deposit e®ect may not be important for the adjuvant e®ect of Alum. 30 Meanwhile, a number of studies suggested the underlying mechanism owing to toxicity of Alum 31 : Alum kills host cells, and dead cells in turn release danger signals, including uric acid, genomic DNAs, etc. [31][32][33] These danger signals are designated as damage-associated molecular patterns (DAMPs).…”