A 43-kDa TDP-43 species is present in aggregates associated with frontotemporal lobar degeneration.

The transactive response DNA-binding protein (TDP-43) is a major component of the abnormal intracellular inclusions that occur in two common neurodegenerative diseases of humans: (1) a subtype of frontotemporal lobar degeneration and (2) amyotrophic lateral sclerosis. Genetics, experiments in cultured cells and animals, and analogy with other neurodegenerative diseases indicate that the process of TDP-43 aggregation is fundamental to the pathogenesis of these 2 diseases, but the process by which this aggregation occurs is not understood. Biochemical fractionation has revealed truncated, phosphorylated and ubiquitinated forms of TDP-43 in a detergent-insoluble fraction from diseased CNS tissue, while these forms are absent from controls. However, a large amount of the normally predominant 43-kDa form of TDP-43 is present in the detergent-insoluble fraction even from control brains, so it has not been possible to determine if this form of TDP-43 is part of pathological aggregates in frontotemporal lobe degeneration. We used semi-denaturing detergent-agarose gel electrophoresis to isolate high molecular weight aggregates containing TDP-43 that are present in the cerebral cortex of individuals with frontotemporal lobar degeneration but not that of controls. These aggregates include the same covalently modified forms of TDP-43 seen in detergent-insoluble extracts. In addition, aggregates include a 43-kDa TDP-43 species. This aggregated 43-kDa form of TDP-43 is absent or present only at low levels in controls. The presence of 43-kDa TDP-43 in aggregates raises the possibility that covalent modification is not a primary step in the pathogenic aggregation of TDP-43 associated with frontotemporal lobar degeneration and amyotrophic lateral sclerosis.

Reversible cerebral vasoconstriction syndrome 3 months after blood transfusion.

Reversible cerebral vasoconstriction syndrome is characterized by the prolonged but reversible constriction of cerebral arteries accompanied by a sudden onset of severe headache, and is sometimes complicated by subarachnoid hemorrhage or cerebral infarction. It is associated with various clinical conditions and treatments, although the precise pathophysiology is not understood. In particular, several cases of this syndrome have been described to occur in middle-aged women within 1 week of a blood transfusion. We encountered a patient with a reversible cerebral vasoconstriction syndrome who became symptomatic 3 months after a blood transfusion. No other cause for the syndrome was found. This case suggests that the risk for the reversible cerebral vasoconstriction may persist for months after blood transfusion.

Colorado surveillance program for chronic wasting disease transmission to humans: lessons from 2 highly suspicious but negative cases.

OBJECTIVE: To describe 2 patients with rapidly progressive dementia and risk factors for exposure to chronic wasting disease (CWD) in whom extensive testing negated the possible transmission of CWD. Design/ METHODS: We describe the evaluation of 2 young adults with initial exposure histories and clinical presentations that suggested the possibility of CWD transmission to humans. Patients A 52-year-old woman with possible laboratory exposure to CWD and a 25-year-old man who had consumed meat from a CWD endemic area. INTERVENTIONS: Clinical evaluation, neuropathological examination, and genetic testing. RESULTS: Neuropathological and genetic assessment in the 2 patients proved the diagnoses of early-onset Alzheimer disease and a rare genetic prion disease. CONCLUSION: No convincing cases of CWD transmission to humans have been detected in our surveillance program.

Human prion disease and relative risk associated with chronic wasting disease.

The transmission of the prion disease bovine spongiform encephalopathy (BSE) to humans raises concern about chronic wasting disease (CWD), a prion disease of deer and elk. In 7 Colorado counties with high CWD prevalence, 75% of state hunting licenses are issued locally, which suggests that residents consume most regionally harvested game. We used Colorado death certificate data from 1979 through 2001 to evaluate rates of death from the human prion disease Creutzfeldt-Jakob disease (CJD). The relative risk (RR) of CJD for CWD-endemic county residents was not significantly increased (RR 0.81, 95% confidence interval [CI] 0.40-1.63), and the rate of CJD did not increase over time (5-year RR 0.92, 95% CI 0.73-1.16). In Colorado, human prion disease resulting from CWD exposure is rare or nonexistent. However, given uncertainties about the incubation period, exposure, and clinical presentation, the possibility that the CWD agent might cause human disease cannot be eliminated.

Transmission of elk and deer prions to transgenic mice.

Chronic wasting disease (CWD) is a fatal prion disease in deer and elk. Unique among the prion diseases, it is transmitted among captive and free-ranging animals. To facilitate studies of the biology of CWD prions, we generated five lines of transgenic (Tg) mice expressing prion protein (PrP) from Rocky Mountain elk (Cervus elaphus nelsoni), denoted Tg(ElkPrP), and two lines of Tg mice expressing PrP common to white-tailed deer (Odocoileus virginianus) and mule deer (Odocoileus hemionus), denoted Tg(DePrP). None of the Tg(ElkPrP) or Tg(DePrP) mice exhibited spontaneous neurologic dysfunction at more than 600 days of age. Brain samples from CWD-positive elk, white-tailed deer, and mule deer produced disease in Tg(ElkPrP) mice between 180 and 200 days after inoculation and in Tg(DePrP) mice between 300 and 400 days. One of eight cervid brain inocula transmitted disease to Tg(MoPrP)4053 mice overexpressing wild-type mouse PrP-A in approximately 540 days. Neuropathologic analysis revealed abundant PrP amyloid plaques in the brains of ill mice. Brain homogenates from symptomatic Tg(ElkPrP) mice produced disease in 120 to 190 days in Tg(ElkPrP) mice. In contrast to the Tg(ElkPrP) and Tg(DePrP) mice, Tg mice overexpressing human, bovine, or ovine PrP did not develop prion disease after inoculation with CWD prions from among nine different isolates after >500 days. These findings suggest that CWD prions from elk, mule deer, and white-tailed deer can be readily transmitted among these three cervid species.

Bovine spongiform encephalopathy, chronic wasting disease, scrapie, and the threat to humans from prion disease epizootics.

Ongoing endemics and epidemics of prion disease afflict several species of ruminants regularly consumed by humans. Bovine spongiform encephalopathy (BSE) is epidemic in British cattle, and is now found in the cattle of more than 20 countries. A large, and apparently growing, epidemic of chronic wasting disease plagues deer and elk in North America. Finally, scrapie has been endemic in the sheep of most countries for many decades. It was once assumed that humans were not susceptible to these ruminant forms of prion disease, but an outbreak of a new form of Creutzfeldt-Jakob disease (CJD) among young Britons, almost certainly due to dietary exposure to BSE-contaminated beef, has disproved this supposition. Although all prion diseases share the same fundamental pathologic mechanism, transmission between species is sometimes inefficient. The basis of this "species barrier" is incompletely understood, but interspecies differences in the amino acid sequence of the prion protein and the strain of prions involved play critical roles. Reliable experimental models for determining the resistance of humans to animal prion diseases do not yet exist. It is possible that animal to human transmission of prion disease may manifest as CJD with unusual characteristics, but this is not necessarily the case. In the absence of a reliable means for determining the susceptibility of humans to animal prion disease, measures to minimize human exposure to animal prions should be emphasized.

Prions in skeletal muscle.

Considerable evidence argues that consumption of beef products from cattle infected with bovine spongiform encephalopathy (BSE) prions causes new variant Creutzfeldt-Jakob disease. In an effort to prevent new variant Creutzfeldt-Jakob disease, certain "specified offals," including neural and lymphatic tissues, thought to contain high titers of prions have been excluded from foods destined for human consumption [Phillips, N. A., Bridgeman, J. & Ferguson-Smith, M. (2000) in The BSE Inquiry (Stationery Office, London), Vol. 6, pp. 413-451]. Here we report that mouse skeletal muscle can propagate prions and accumulate substantial titers of these pathogens. We found both high prion titers and the disease-causing isoform of the prion protein (PrP(Sc)) in the skeletal muscle of wild-type mice inoculated with either the Me7 or Rocky Mountain Laboratory strain of murine prions. Particular muscles accumulated distinct levels of PrP(Sc), with the highest levels observed in muscle from the hind limb. To determine whether prions are produced or merely accumulate intramuscularly, we established transgenic mice expressing either mouse or Syrian hamster PrP exclusively in muscle. Inoculating these mice intramuscularly with prions resulted in the formation of high titers of nascent prions in muscle. In contrast, inoculating mice in which PrP expression was targeted to hepatocytes resulted in low prion titers. Our data demonstrate that factors in addition to the amount of PrP expressed determine the tropism of prions for certain tissues. That some muscles are intrinsically capable of accumulating substantial titers of prions is of particular concern. Because significant dietary exposure to prions might occur through the consumption of meat, even if it is largely free of neural and lymphatic tissue, a comprehensive effort to map the distribution of prions in the muscle of infected livestock is needed. Furthermore, muscle may provide a readily biopsied tissue from which to diagnose prion disease in asymptomatic animals and even humans.