The existence of different strains of misshapen proteins in the brains of Alzheimer’s disease (AD) patients is emerging as an obstacle to the development of effective treatments. Recent research has revealed that the proteins that accumulate in the brain during AD are reminiscent of prions, which cause rare brain diseases such as mad cow disease. Like viruses and bacteria, prions can exist as different strains, and Dr. Watts’ research has demonstrated that distinct strains of misshapen proteins can also be found in AD patients. The objectives of this research are to probe the biology underlying the generation of distinct strains of misshapen proteins in AD and assess their pathological consequences in the brain using genetically engineered mice and rats that mimic aspects of AD. This research will lead to a better understanding of the patient-to-patient variability observed in AD as well as novel strategies for treating the disease.