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Ja Kob Disease and the Eye. I. Background and Patient

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Ja Kob Disease and the Eye. I. Background and Patient Creutzfel dt- Ja kob c.J. LUECK, G.G. McILWAINE, M. ZEIDLER disease and the eye. I. Background and patient management Background insomnia, FFI, Gerstmann-Straussler-Scheinker, Gerstmann-Straussler-Scheinker disease, GSS, The transmissible spongiform encephalopathies Heidenhain, Jacob, Jakob, kuru, ocular, ophthalmic, (TSEs), alternatively known as prion diseases, ophthalmological, optic, prion, prion disease, PrP, excite a fascination among both medical PrPSc, transmissible spongiform encephalopathy, personnel and lay public for several reasons. TSE, vision, visual, in addition to various They are the only known example of diseases permutations of accommodation, evoked potentials, which can be transmitted both genetically and eye and eye diseases, ocular motility disorders, and by infection, though in most human examples vision. Major neurological, ophthalmological the exact aetiology remains unknown. The and neuro-ophthalmological journals were also nature of the infective agent is still not screened by hand over the last 10 years. completely clear, the diseases are uniformly Secondary referencing was carried out from the (and usually rapidly) fatal, and there is no papers found by these procedures. known cure. Consequently, it is not surprising that there has been an enormous amount published on the subject. Indeed, if the number Transmissible spongiform encephalopathies of publications on any disease is divided by the incidence of that disease, human TSEs reveal an There are several different TSEs affecting 'interest factor' over 10 times that of any other animals and man, and a summary is given in condition, and over 100 times that of most. 1 This Table 1. This article will deal with those diseases is reflected in the size of the reference lists at the affecting man, i.e. CJD, Gerstmann-Straussler­ end of this article and its companion!2 Scheinker disease (GSS), fatal familial insomnia The history of TSEs has involved the eye in a (FFI) and kuru. C. Lueck variety of ways. The first evidence that scrapie Neuropathologically, these conditions are G.G. Mcllwaine could be transmitted experimentally followed recognised by the triad of spongiform change M. Zeidler inoculation through the eye,3 and the first (affecting any part of the cerebral grey matter), Department of Clinical evidence that Creutzfeldt-Jakob disease (CJD) neuronal loss, and proliferation and Neuroscience could be transmitted directly from human to hypertrophy of astrocytes.6-8 Neurons show Western General Hospital Edinburgh, UK human by infection involved a corneal graft.4 loss of dendritic spines and intracytoplasmic Visual symptoms are frequent, as are neuro­ vacuoles,9 and there is accumulation in the G.G. Mcllwaine ophthalmological signs, and it is therefore likely brain of amyloid. The amyloid consists of an Princess Alexandra Eye that some patients will present to an abnormal, 33-37 kDa degradation-resistant Pavilion Edinburgh, UK ophthalmologist. This review and the glycoprotein,lO which is an isoform of a companion article2 set out to provide the reader normally occurring protein known variously as M. Zeidler with an update on the current understanding of prion protein (PrP), scrapie-associated protein, National CJD Surveillance human TSEs, and to discuss the management of proteinase resistant protein, scrapie amyloid Unit Western General Hospital patients, with particular reference to corneal protein, or Sp33-37.11,12 The normal, or wild­ , Edinburgh, UK transplantation. As yet, there is no effective type, is known as Prpe ( cellular', principally (X­ treatment,S so this aspect will not be discussed helical structure, detergent soluble) and the Dr c.J. Lueck � further. In the companion article2 we review the abnormal isoform as Prpsc ('Scrapie', principally Department of Clinical ophthalmic and neuro-ophthalmic features of j3-sheet structure, insoluble in non-denaturing Neuroscience Western General Hospital these diseases in greater depth. detergents)Y Crewe Road Prpe is a normal constituent of the neuronal Edinburgh EH4 2XU cell membrane,14,IS but it is also widely Scotland, UK Methods expressed throughout the bodyY It is Tel: +44 (0)131 5372452 In preparing this review, MEDLINE and transported along neuronsI6 and accumulates at Fax: +44 (0)131 5371030 EMBASE were consulted using the following the neuromuscular junction.17 Scrapie infection e-mail: [email protected] CJD, Creutzfeld, combination of keywords: has been shown to alter receptor-mediated Received: 20 August 1999 + Creutzfeldt, Creutzfeldt-Jakob disease, Ca2 ,18 and other reports suggest that Prpe may Accepted in revised form: Creutzfeldt-Jakob syndrome, eye, fatal familial be necessary for neuronal transmissionl9,20 or 9 December 1999 Eye (2000) 14, 263-290 © 2000 Royal College of Ophthalmologists 263 Table 1. Documented non-experimental animal TSEs The most compelling hypothesis to date is the third, First the 'protein-only' hypothesis, which involves Transmissible spongiform encephalopathy reported conformational change of Prp.13,29,33-35 It has been shown Human TSE that Prpe and Prpsc are stereoisomers (or 'twisted' forms) Creutzfeldt-Jakob disease of the same protein.36 The former occurs normally, but Classical sporadic 1920 can be caused to 'flip' into an altered shape, Prpsc. Once Familial 1924 this has happened, the protein becomes resistant to Iatrogenic 1974 New variant 1996 proteases and so can build up in the cell membrane, Gerstmann-Straussler-Scheinker disease 1936 eventually aggregating as amyloid. The reason Prpsc is Fatal familial insomnia 1986 pathogenic is not known, but recent work has suggested Kuru 1957 that small segments of some genetically abnormal PrP Animal TSE molecules may display a tendency to aggregate, and be Scrapie in: pathogenic in cell culture?7,38 Consistent with the Sheep 1730 Goat 1942 suggestion that it is indeed the Prpsc itself which is �oufflon 1992 pathogenic is the fact that those areas of the brain Transmissible mink encephalopathy 1965 demonstrating the most marked spongiform change have Chronic wasting disease of deer and elk 1967 the highest concentration of PrPScl5. Furthermore, Bovine spongiform encephalopathy 1986 Captive primates 1999 transgenic mice reared without the PrP gene cannot be Spongiform encephalopathy in captive Felidae: infected with scrapie, demonstrating that PrP is Domestic cat 1990 necessary for the disease?9 Puma e 1992 The suggestion is that the normal, or wild-type, Prp Cheetah 1992 is converted into Prpsc by coming into direct contact with Ocelot 1994 Tiger 1996 Prpsc, and that, once this starts, a cascading chain­ Captive ruminants: reaction commences affecting Prpe all over the brain. Nyala 1986 Thus, the normal brain is in a sort of 'metastable Gemsbok 1988 equilibrium', stable unless Prpsc is introduced, in which Arabian oryx 1989 Eland 1989 case normal Prpe is gradually caused to 'flip' into the Greater kudu 1989 abnormal form (Fig. 1). An analogy might be that of Scimitar-horned oryx 1993 crystals developing out of a supersaturated salt solution Ankole 1995 once it has been 'seeded' by a small salt crysta1.40 The Bison 1996 abnormal Prpsc could be introduced by way of direct inoculation, as in transmitted CJD, or develop spontaneously if the normal host PrP is more unstable that it may influence the activity of Cu/Zn superoxide than usual due to genetic defects, or develop as a rare dismutase,21 but little else is known about its normal stochastic event in the sporadic form of the disease. Quite function. The fact that it is possible to rear transgenic how the abnormal PrP is transmitted from cell to cell is mice totally devoid of the protein22 implies that it is not not clear. essential for life, and adds to the confusion. While the above hypothesis is compelling, it does not explain all aspects of TSE transmission, most notably the existence of different 'strains' of the diseases. These are Pathogenesis discussed further below. Detailed reviews of the prion concept can be found elsewhere?2,31-33,36,41-45 The transmissible nature of sporadic CJD was first demonstrated experimentally in 1968,23 and it has subsequently been shown that it is possible to transmit Creutzfeldt-Jakob Disease familial CJD,24,25 GSS26 and other forms of familial prion disease to animals. However, the precise nature of the Creutzfeldt46 and Jakob47-49 are usually credited with transmissible agent is still not clear. Three main having described the condition first,50 though Fischer51 hypotheses have been put forwardY One suggests that described cases of spongiform cortical degeneration the infective agent is comprised of proteins surrounding some 10 years earlier (none of which would meet the a nucleic acid which encodes those proteins (i.e. a modern criteria for CJD). Interestingly, the original case virus),27 the second that it comprises proteins associated described by Creutzfeldt probably did not have CJD on with a small polynucleotide (the 'virino' hypothesis28), the basis of histology,52 and, of Jakob's five patients, only and the third that it is entirely composed of protein and the third and fifth definitely did.52 The early literature devoid of nucleic acid,29 subsequently termed a prion (well reviewed by May53 and Kirschbaum54) was ('proteinaceous particle')?O It is now clear that the altered similarly confused by the lack of standard criteria and a protein, Prpsc, is a major and necessary component of the plethora of synonyms,55 and it was not until full infectious agent,1O,31,32 but exactly how it is pathogenic evaluation
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