1. From the Longtine Center for Molecular Biology and Genetics (A.E.R., C.E., W.K., D.C.L.), Sun Health Research Institute, Sun City; Department of Microbiology (T.A.K.), School of Osteopathic Medicine, Midwestern University, Glendale; and Department of Epidemiology and Biostatistics (J.D.S.) and W. H. Civin Laboratory for Neuropathology (L.I.S.), Sun Health Research Institute, Sun City, Ariz.