Human spongiform encephalopathy: the National Institutes of Health series of 300 cases of experimentally transmitted disease

We present a synthesis of clinical, neuropathological, and biological details of the National Institutes of Health series of 300 experimentally transmitted cases of spongiform encephalopathy from among more than 1,000 cases of various neurological disorders inoculated into nonhuman primates during the past 30 years. The series comprises 278 subjects with Creutzfeldt-Jakob disease, of whom 234 had sporadic, 36 familial, and 8 iatrogenic disease; 18 patients with kuru; and 4 patients with Gerstmann-Strüssler-Scheinker syndrome. Sporadic Creutzfeldt-Jakob disease, numerically by far the most important representative, showed an average age at onset of 60 years, with the frequent early appearance of cerebellar and visual/oculomotor signs, and a broad spectrum of clinical features during the subsequent course of illness, which was usually fatal in less than 6 months. Characteristic spongiform neuropathology was present in all but 2 subjects. Microscopically visible kuru-type amyloid plaques were found in 5% of patients with Creutzfeldt-Jakob disease, 75% of those with kuru, and 100% of those with Gerstmann-Sträussler-Scheinker syndrome; brain biopsy was diagnostic in 95% of cases later confirmed at autopsy, and proteinase-resistant amyloid protein was identified in Western blots of brain extracts from 88% of tested subjects. Experimental transmission rates were highest for iatrogenic Creutzfeldt-Jakob disease (100%), kuru (95%), and sporadic Creutzfeldt-Jakob disease (90%), and considerably lower for most familial forms of disease (68%). Incubation periods as well as the durations and character of illness showed great variability, even in animals receiving the same inoculum, mirroring the spectrum of clinical profiles seen in human disease. Infectivity reached average levels of nearly 10(5) median lethal doses/gm of brain tissue, but was only irregularly present (and at much lower levels) in tissues outside the brain, and, except for cerebrospinal fluid, was never detected in bodily secretions or excretions.

Oral transmission of kuru, Creutzfeldt-Jakob disease, and scrapie to nonhuman primates

Kuru and Creutzfeldt-Jakob disease of humans and scrapie disease of sheep and goats were transmitted to squirrel monkeys (Saimiri sciureus) that were exposed to the infectious agents only by their nonforced consumption of known infectious tissues. The asymptomatic incubation period in the one monkey exposed to the virus of kuru was 36 months; that in the two monkeys exposed to the virus of Creutzfeldt-Jakob disease was 23 and 27 months, respectively; and that in the two monkeys exposed to the virus of scrapie was 25 and 32 months, respectively. Careful physical examination of the buccal cavities of all of the monkeys failed to reveal signs or oral lesions. One additional monkey similarly exposed to kuru has remained asymptomatic during the 39 months that it has been under observation.