Rapamycin, a drug given to transplant recipients to suppress their immune systems, has a paradoxical effect on cells responsible for immune memory, scientists at the Emory Vaccine Center have discovered.
In experiments conducted in both mice and monkeys, rapamycin can stimulate the formation of memory CD8 T cells, which enable the immune system to respond faster and stronger to an infectious agent upon a second encounter.
The results were published online ahead of print June 21 in Nature. The finding means that doctors might be able to boost the effectiveness of vaccines with drugs that act similarly to rapamycin, says postdoctoral researcher Koichi Araki, PhD, who is first author.
Araki works in the laboratory of Rafi Ahmed, PhD, director of the Emory Vaccine Center and a Georgia Research Alliance Eminent Scholar.
Vaccination relies on memory T cells, survivors after the immune system produces an abundance of T cells to fight an infection or respond to a vaccine. Araki had been examining rapamycin's effects in mice infected with lymphocytic choriomeningitis virus (LCMV).
"Usually during the response to this virus, 90 percent of the CD8 T cells produced to fight an infection die after a few weeks. The memory cells are generated from the 10 percent that survive," he explains.
T cells come in both CD4 (helper) and CD8 (killer) forms, but scientists have found that CD8 T cells are more important for fighting LCMV.
When mice were treated with rapamycin, more CD8 T cells that react against LMCV survived, Araki found. Under the influence of rapamycin, the mice not only produced more memory T cells, but the cells had a greater ability to proliferate and respond upon a second exposure to LCMV.
Rapamycin's effects are "surprising and unexpected," Araki says. During a transient viral infection, the targets of the immune response eventually disappear, a situation markedly different from a tran
|Contact: Holly Korschun|