Abstract
Human prion diseases are fatal neurodegenerative disorders associated with an accumulation of PrPSc in the central nervous system (CNS). Of the human prion diseases, sporadic Creutzfeldt-Jakob disease (sCJD), which has no known origin, is the most common form while variant CJD (vCJD) is an acquired human prion disease reported to differ from other human prion diseases in its neurological, neuropathological, and biochemical phenotype. Peripheral tissue involvement in prion disease, as judged by PrPSc accumulation in the tonsil, spleen, and lymph node has been reported in vCJD as well as several animal models of prion diseases. However, this distribution of PrPSc has not been consistently reported for sCJD. We reexamined CNS and non-CNS tissue distribution and levels of PrPSc in both sCJD and vCJD. Using a sensitive immunoassay, termed SOFIA, we also assessed PrPSc levels in human body fluids from sCJD as well as in vCJD-infected humanized transgenic mice (Tg666). Unexpectedly, the levels of PrPSc in non-CNS human tissues (spleens, lymph nodes, tonsils) from both sCJD and vCJD did not differ significantly and, as expected, were several logs lower than in the brain. Using protein misfolding cyclic amplification (PMCA) followed by SOFIA, PrPSc was detected in cerebrospinal fluid (CSF), but not in urine or blood, in sCJD patients. In addition, using PMCA and SOFIA, we demonstrated that blood from vCJD-infected Tg666 mice showing clinical disease contained prion disease-associated seeding activity although the data was not statistically significant likely due to the limited number of samples examined. These studies provide a comparison of PrPSc in sCJD vs. vCJD as well as analysis of body fluids. Further, these studies also provide circumstantial evidence that in human prion diseases, as in the animal prion diseases, a direct comparison and intraspecies correlation cannot be made between the levels of PrPSc and infectivity.
Highlights
Prion diseases are a group of fatal neurodegenerative disorders that affect both animals and humans
Surround optical fiber immunoassay (SOFIA) alone or, depending on the starting samples, in combination with target amplification by protein misfolding cyclic amplification (PMCA) [20] has been successfully used with tissues and body fluids for the preclinical detection and clinical diagnosis of sheep scrapie and chronic wasting disease (CWD) [21,22]. In this manuscript we describe the use of SOFIA for detection of PrPSc or prion disease associated seeding activity (PASA) in cerebrospinal fluid (CSF) from sporadic CreutzfeldtJakob disease (CJD) (sCJD) patients as well as a comparison of PrPSc in the central nervous system (CNS) and non-CNS tissues from sCJD and variant CJD (vCJD)
PrP was concentrated by ultracentrifugation of 10% homogenates from brain, spleen, tonsil and lymph node from non-CJD individuals and the samples were analyzed by Western Blotting with or without PK-treatment using monoclonal antibodies (Mabs) 3F4 (Figure 1)
Summary
Prion diseases are a group of fatal neurodegenerative disorders that affect both animals and humans. Prion infectivity is most readily isolated from the CNS, PrPC is widely distributed in extraneuronal tissues, especially in patients with vCJD [2,3,4]. Experimental inoculations and subsequent passages in animal models, such as mice, hamsters, sheep, elk, and macaques, have shown variable levels of prion infectivity in tissues, such as spleen and muscle, as well as in plasma and buffy coat WBC [9]. The level of infectivity in blood is estimated to be lower than 100 infectious units per ml in mice inoculated with mouse-adapted human infectious agent, orders of magnitude lower than that in the brain [10,11]
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