|
||||||||||||||||||
 |
From: TSS ()
Prion-Induced Amyloid Heart Disease with High Blood Infectivity in Transgenic Mice Matthew J. Trifilo,1 Tosh!taka Yajima,2 Yusu Gu,2 Nancy Dalton,2 Kirk L. Peterson,2 Richard E. Race,3 Kimberly Meade-White,3 John L. Portis,3 Eliezer Masliah,4 Kirk U. Knowlton,2* Bruce Chesebro,3* Michael B. A. Oldstone1* We investigated extraneural manifestations in scrapie-infected transgenic mice expressing prion protein lacking the glycophosphatydylinositol membrane anchor. In the brain, blood, and heart, both abnormal protease-resistant prion protein (PrPres) and prion infectivity were readily detected by immunoblot and by inoculation into nontransgenic recipients. The titer of infectious scrapie in blood plasma exceeded 107 50% infectious doses per milliliter. The hearts of these transgenic mice contained PrPres-positive amyloid deposits that led to myocardial stiffness and cardiac disease. In humans and animals, transmissible spongiform encephalopathies (TSEs), or prion diseases, cause neurodegeneration and death following ingestion or experimental inoculation of infected material. Prion diseases are characterized by the conversion of the normal protease-sensitive host prion protein (PrPsen) to a disease-associated protease-resistant form (PrPres). Although prion disease damages the central nervous system (CNS), infectivity and PrPres can be detected within peripheral tissues, including lymphoid organs in humans, sheep, and deer (1, 2), as well as skeletal muscle (3), kidney, and pancreas (4) of some transgenic rodent models. Despite the toxic effect on the CNS, few if any histopathological changes have been observed at peripheral sites. Transmission of TSE disease to humans has resulted from cannibalism, contaminated surgical instrumentation, and tainted growth hormone (5–7). A human disease termed variant Creutzfeldt-Jakob disease (vCJD) has occurred more recently, apparently through the ingestion of bovine spongiform encephalopathy (BSE)– infected cattle products (8). Recent evidence suggests that transmission of vCJD between humans may occur through blood transfusion (9, 10), and this conclusion is supported by experimental transmission of BSE between sheep via blood transfusion (11). TSE infectivity has been demonstrated in blood by intracerebralinoculation in mouse, mink, hamster, and goat models (7, 12–20). However, infectivity in such cases is low, e102 50% infectious doses (ID50 ) per ml of blood compared to 106 to 1010 ID50/g in the brain. Normal prion protein, PrPsen, is expressed primarily as a membrane-bound, glycophosphatydylinositol (GPI)–anchored protein. The role of cellular PrP membrane anchoring in prion disease has been studied in transgenic mice expressing GPI-negative anchorless PrP, which is secreted from cells (21). Intracerebral inoculation of these GPI-negative anchorless PrP transgenic (tg) mice with murine scrapie results in scrapie replication and deposition of PrPres within the brain. Although wild-type (WT) mice infected with scrapie usually develop a nonamyloid form of PrPres, in these tg mice the PrPres is primarily in the form of amyloid plaques (21). At the same time, these mice do not manifest the clinical and pathologic alterations normally associated with prion disease, thus demonstrating a separation between PrPres amyloid accumulation and clinical CNS disease (21). In the brain of these infected tg mice, PrPres was located primarily within and around endothelial cells (21) (Fig. 1A), leading to the hypothesis that anchorless PrPres may be secreted in the blood. Here we examined this possibility. To determine whether PrPres and/or scrapie infectivity was present in blood, four infected tg mice were bled between 450 and 512 days postinfection (dpi) with the RML strain of scrapie. Inoculation of a 1:500 dilution of blood from all four mice induced scrapie in WT (C57BL/6) recipients in Č145 days. In addition, blood of two mice analyzed by serial dilution titration gave titers of Q1.6 107 and Q1.6 105 ID50/ml blood (Table 1). 1Viral-Immunobiology Laboratory, Departments of Molecular and Integrative Neurosciences and Infectology, Scripps Research Institute, La Jolla, CA 92037, USA. 2Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA. 3Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, Hamilton, MT 59840, USA. 4Departments of Neurosciences and Pathology, University of California, San Diego, CA 92093, USA. *To whom correspondence should be addressed. E-mail: mbaobo@scripps.edu (M.B.A.O.), bchesebro@niaid.nih.gov (B.C.), kknowlton@ucsd.edu (K.U.K.) 7 JULY 2006 VOL 313 SCIENCE www.sciencemag.org TSS
|
