Liège – A Belgian research team from the University of Liège’s GIGA-Research centre has discovered an unexpected mode of action for the vaccine adjuvant alum. The team discovered that when a vaccine containing alum is injected into a patient, contact with the substance encourages certain host cells to release their own DNA. The presence of this DNA outside the cells subsequently acts as a stimulant to the immune system, and strongly boosts the response to the vaccine. (Nature Medicine, doi:10.1038/nm.2403) Alum, a salt of aluminium, is by far the most widely used vaccine adjuvant. Developed in the middle of the 20th century, alum long ago demonstrated its effectiveness and safety of use. Tens of millions of doses of alum are administered each year, and anyone who has been given a series of vaccines has probably been injected with the substance at least once. But in spite of its widespread use, the way alum helps the immune system has not been properly understood up until now. The response mechanisms to DNA that the new study has brought to light could eventually allow the development of new adjuvants with extremely targeted and effective activity.