Evidence for adjuvanticity of anthrax edema toxin

Bacillus anthracis edema factor (EF) is an adenylate cyclase that increases intracellular cAMP concentrations. Since EF is present as a contaminant in the licensed protective antigen(PA)-based vaccines, we investigated its effect on anti-PA humoral immune response in BALB/c mice. We observed a significant increase of anti-PA IgG response in mice immunised with PA in association with EF as compared to PA alone. These results clearly show an adjuvant effect of EF, which is consistent with the data concerning the cellular effects of EF on antigen-presenting cells.