Researchers at Johns Hopkins University announced a significant breakthrough in the treatment of Alzheimer's disease on Thursday, publishing results of a gene-therapy trial in mice that reversed cognitive decline and reduced toxic protein build-up by up to 80 percent.

The study, published in the journal Nature Neuroscience, describes a single-injection approach that delivers a modified viral vector to the brain, where it silences the expression of a gene linked to the overproduction of amyloid-beta plaques — the sticky protein deposits that are a hallmark of the disease.

"We were genuinely surprised by the magnitude of the effect," said Dr. Patricia Elam, the study's lead author. "We expected a modest improvement. What we saw was near-complete restoration of spatial memory in older mice within 12 weeks."

The Alzheimer's Association, which partially funded the research, called the findings "enormously promising" while urging caution about timelines to human clinical application. Animal models of Alzheimer's have historically failed to translate to effective human treatments, and the complexity of human brain biology means a clinical trial is likely several years away.