As if cold sores weren’t bad enough, herpes simplex virus type 1 maynow be linked to Alzheimer’s disease. The connection involvesapolipoprotein E (apoE), a protein that helps to transport cholesterolthrough the body. There are several types of apoE genes; one, APOE-e4,is the leading risk factor for developing Alzheimer’s. In previousstudies, researchers also found that people who have the APOE-e4 geneand have herpes simplex DNA in their brains are even more likely to beafflicted with Alzheimer’s.
To probe the link between gene and virus, neuroscientist HowardFederoff, of the University of Rochester School of Medicine, and hiscolleagues created mouse-cell cultures that expressed either theAPOE-e4 gene or another variant (APOE-e2 or APOE-e3), then infected thecells with herpes. While all the cell types could be infected, thevirus was much more likely to be active in the cells expressingAPOE-e4. “There is something about APOE-e4 that may control the way thevirus decides if it is going to be more or less active,” Federoff says.An active virus means cell injury or death; a dormant virus poses nothreat.
How that might eventually predispose a person to Alzheimer’s isstill unclear, but it may involve a receptor molecule for theherpesvirus in the connections between nerve cells. “The failure of theelectrical connections, which would cause cognitive impairment, mightbe linked in some way with the herpes simplex virus,” Federoff says.But he warns, “The last thing I would want people to believe is that ifthey have the herpesvirus or frequent cold sores, they are definitelygoing to get Alzheimer’s. The virus represents just one possiblefactor.” Medications are available that can prevent reactivation of thevirus—and cold sores. But if it’s necessary to prevent herpes simplexinfection in the first place to ward off Alzheimer’s, “it could spawnan effort to develop prophylactic vaccines,” Federoff says.