WEST LAFAYETTE, Ind. -- A popular theory about how a major component of vaccines works within the body has been shot down by a Purdue University study.
Purdue researcher Stanley Hem has found that aluminum hydroxide, a small particle used to carry antigens into the body to boost an immune response, begins to dissolve in the muscle immediately after an injection and is eliminated from the body hundreds of times faster than presumed.
"Aluminum hydroxide is used in vaccines to increase the body's production of antibodies, though no one knows how it works," says Hem, professor of industrial and physical pharmacy. "The most popular theory was that it remained in the muscle for months while the body produced antibodies in response to the antigens carried on its surface."
The study raises new questions about the mechanism by which aluminum hydroxide works, Hem says. The findings will appear in the September issue of the British scientific journal Vaccine.
During the 1930s, researchers discovered that using aluminum hydroxide to carry antigens into the body resulted in a greater production of antibodies than could be produced by the antigen alone. Antibodies are proteins made by the immune system to fight off foreign substances. Antigens -- the proteins or molecules that stimulate the immune system to create antibodies -- are condensed and collected on the surface of aluminum hydroxide particles.
Since 1934, aluminum hydroxide has been used as an adjuvant to boost the immune response from vaccines. Currently, it is the only adjuvant approved by the Food and Drug Administration for use in human vaccines. The FDA limits the dosage to 0.85 milligrams per vaccine to minimize exposure to aluminum.
"There's been some interest in other materials, but no one has proven them safe enough," Hem says.
Though scientists have puzzled over the mechanism by which aluminum hydroxide increases
the production of antibodies, the tiny amounts of the sub
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