Researchers could be closing in on a "fountain of youth" drug that can delay the effects of aging and improve the health of older adults, a new study suggests. Seniors received a significant boost to their immune systems when given a drug that targets a genetic signaling pathway linked to aging and immune function, researchers with the drug maker Novartis report. The experimental medication, a version of the drug rapamycin, improved the seniors' immune response to a flu vaccine by 20 percent, researchers said in the current issue of Science Translational Medicine. The study is a "watershed" moment for research...