They report in the June 18 issue of Science that the most common adjuvant, alum, provokes a previously unrecognized group of immune-system cells to secrete the protein interleukin-4, which primes B cells for a better response to the vaccine.
"Adjuvants have been included in vaccines given to hundreds of millions of people for decades," said Michael Jordan, M.D., co-lead author and researcher at National Jewish. "These findings give us new insight into how they boost the immune response to a vaccine."
Live vaccines, containing weakened forms of an infectious organism, generally work fine by themselves. But vaccines containing dead organisms (inactivated vaccines) or pieces of the infectious organisms or their toxins (acellular or recombinant vaccines) generally need adjuvants to boost their effectiveness. Aluminum salts, known as alum, are the only adjuvant approved for use in the United States for routine preventive vaccines.
The discovery of alum as a vaccine booster actually began with tapioca, a starchy substance used in pudding and as a thickener in cooking. In the early 1920s a scientist named Ramone reported that, for unknown reasons, he had mixed tapioca with inactivated tetanus toxin and found that it served as a more effective vaccine than did the toxin itself. Several years later, a researcher named A.T. Glenny read Ramone's account and decided to mix aluminum salts, or alum, with inactivated tetanus toxin in a test vaccine he tried on rabbits. Again, the vaccine with the adjuvant was more effective than a vaccine containing the toxin alone.
The adjuvant alum was first widely used in humans in the 1950s as part of the Salk poliomyelitis vaccine. Since then, adjuvants have been widely used in many vaccines, including the Dipthe
Contact: William Allstetter
National Jewish Medical and Research Center