S1-03-03

Symposia S1-03: Prion Diseases ities in A␤ transport and clearance at the blood-brain barrier (BBB) may play an important role in development, progression, and therapeutic approaches to AD. A significant amount of the A␤ peptide is transported from blood to brain as well as from brain to blood. Thus, the CNS transport pathways for A␤ contribute in an important way to the amount of A␤ in the brain at any time. We will discuss strategies for enhancing binding of A␤ directly to LRP1 (low density lipoprotein receptor related protein-1) in brain capillaries as a therapeutic strategy for promoting efflux of the peptide across the BBB. We will discuss the link between vascularly-restricted homebox gene MEOX2 and neurovascular dysfunction in late-onset AD, and how MEOX2 controls LRP1 and angiogenesis in the aging brain setting up a stage for a faulty clearance of A␤. We will also show how overexpression of two transcription factors, serum response factor and myocardin, which orchestrate vascular smooth muscle cell phenotype, influence the blood flow regulations and clearance of A␤ at the level of pial cerebral arteries. Finally, we will discuss strategies for blocking re-entry of plasma A␤ and neuroinflammation by blocking RAGE (receptor for advanced glycation end products)/A␤ interaction in brain vascular system. SUNDAY, JULY 16, 2006 SYMPOSIA S1-03 PRION DISEASES S1-03-01

VCJD AND BLOOD TRANSFUSION

Robert Will, Western General Hospital, Edinburgh, United Kingdom. Contact e-mail: [email protected] Background: Variant Creutzfeldt-Jakob disease (vCJD) is a novel human prion disease, which is causally linked to bovine spongifom encephalopathy (BSE), with human infection probably due to past exposure to high titre bovine tissues in the human food chain. The pathogenesis of vCJD includes significant levels of disease-associated prion protein deposition and infectivity in peripheral lymphoreticular tissues, raising the possibility of secondary transmission through blood transfusion. Objectives: To identify whether blood transfusion is a mechanism of transmission of vCJD from person to person. Methods: A look-back study of blood transfusion in vCJD (the TMER) has been undertaken in the UK since 1997 and is a collaborative study between the National Blood Services, the National CJD Surveillance Unit and the Office of National Statistics. Conclusions: In December 2003 a case of vCJD was identified with a prior history of a blood transfusion derived from an individual who died of vCJD, raising the possibility that the disease was transfusion transmitted. In 2004 an individual who had previously received blood donated by a vCJD donor died of intercurrent illness but was found to have positive immunostaining for prion protein in spleen and a lymph node, suggesting sub-clinical or pre-clinical infection. This individual was a PRNP codon 129 heterozygote in contrast to all tested clinical cases of vCJD, in which the genotype has been uniformly methionine homozygous. A further case of probable transfusiontransmission of vCJD was identified in 2006. The probability of transfusion transmission of vCJD has important implications for public health and a range of measures have been taken in a number of countries to minimise the risk, most initiated prior to the identification of the cases described above. With the identification of vCJD cases with a history of blood donation in a number of other countries, it is important to consider what measures may be necessary to protect public health in relation to blood and blood derived components. S1-03-03

A NEW BSE PRION STRAIN

Fabrizio Tagliavini1, Raffaella Capobianco1, Cristina Casalone2, Silvia Suardi1, Claudia Miccolo1, Maria Grazia Bruzzone1, Daniela Gelmetti3, Martin Groschup4, Gianluigi Zanusso5, Maria Caramelli2, 1National Neurological Institute Carlo Besta, Milan, Italy; 2Istituto Zooprofilattico Sperimentale, Turin, Italy; 3Istituto Zooprofilattico Sperimentale, Milan, Italy; 4Friedrich-Loeffler-Institut, Greifswald-Insel Riems, Germany; 5Department of Neurological and Visual Science, Section of Clinical Neurology, Verona, Italy. Contact e-mail: [email protected]

S5

Background: Atypical BSE phenotypes have been recently identified in different European countries. One of these phenotypes (termed BASE) has been recognized in Italy and differs from classical BSE for the presence of PrP-amyloid plaques and the occurrence of a distinct PrPres type. These findings argue against the common view that spongiform encephalopathy in cattle is caused by a single prion strain. Objectives: To determine whether BSE and BASE are related to different prion strains and, if this is the case, whether the cross-species transmission properties of BASE differ from that of BSE. Methods: A panel of three inbred mouse strains (SJL, C57Bl, RIII) and transgenic mice expressing only bovine PrP (TgBov) were inoculated intracerebrally and intraperitoneally with 10% brain homogenates from BSE- and BASE-affected cattle. Results: BSE prions transmitted readily to all inbred mouse strains. The shortest incubation time was seen in SJL mice (mean⫾SEM: 273⫾4 days), followed by RIII (310⫾8) and C57Bl (437⫾5) mice. Conversely, mice challenged with BASE did not develop clinical signs of disease in their lifetime, and did not show neuropathologic changes and/or detectable levels of PrPres. On secondpassage transmission of brain homogenates from BSE-infected SJL and C57Bl mice, the incubation time decreased to 128⫾2 and 180⫾1 days, respectively. Furthermore, at the time of writing, 25% of SJL and 60% of C57Bl mice challenged with BASE-inoculated mouse brain homogenates developed clinical signs of disease after 270⫾16 and 299⫾7 days. Neuropathologic examination of these animals revealed a spongiform encephalopathy with a lesion profile and a PrPres pattern similar to that of BSE-infected mice. The Tg-Bov mice were highly susceptible to both BSE and BASE, but the incubation time was significantly shorter following inoculation with BASE (178⫾5) than BSE (216⫾10). Noteworthy, the brain lesion profile, pattern of PrPres deposition and PrPres type in BASE- and BSE-infected TgBov mice were substantially different. Conclusions: These data demonstrate that more than one prion strain is related to spongiform encephalopathy in cattle and that the barrier to transmission of BASE to mice is substantially higher than that of BSE. The possible existence of preclinical forms of BASE in other species has important implications.

S1-03-04

TRANSMISSION STUDIES OF MOUSE SYNTHETIC PRIONS

Giuseppe Legname, Hoang-Oanh Bach Nguyen, Ilia V. Baskakov, Stephen J. DeArmond, Stanley B. Prusiner, University of California at San Francisco, San Francisco, CA, USA. Contact e-mail: [email protected] We recently described the in vitro production of infectious prions from purified recombinant mouse (Mo) prion protein (PrP) residue 89 to 230. MoPrP(89-230) was refolded into highly ␤-sheet-rich amyloid protein preparation and inoculated into transgenic (Tg) mice harboring the same sequence. At least two novel Mo synthetic prion (SP) strains were identified as judged by: (i) incubation times, (ii) conformational stability assay (CSA) and (iii) neuropathological changes. In another set of experiments, amyloid fibrils were produced using either truncated MoPrP(89-230) or full-length MoPrP(23-230). These preparations were injected into Tg mice expressing full-length MoPrP(23-231). Mice inoculated with either amyloid preparation developed prion disease at ⬇600 days. Fibrils formed from MoPrP(23231) yielded a highly amyloidogenic strain as shown by immunohistochemistry and thioflavin S-positive plaques found in the brains of infected mice. In addition, CSA of these novel MoSP strains revealed high resistance to denaturation as measured by Western blot analysis. That prions could be generated in vitro in conjunction with many earlier studies argues that a conformational isoform of PrP is the sole component of the infectious prion particle.