New Zealand Journal of Agricultural Research abstracts
Bovine spongiform encephalopathy (BSE): its context in New Zealand
and new tests
Paul H. Atkinson
Victoria University of Wellington
School of Biological Sciences
P.O. Box 600
Wellington, New Zealand
paul.atkinson@vuw.ac.nz
Abstract Transmissible spongiform encephalopathies
(TSEs) such as Creutzfeldt-Jakob disease (CJD), scrapie, bovine
spongiform encephalopathy (BSE), and chronic wasting disease (CWD) are
infectious lethal pathologies of mammalian neurons. Protein alone is
responsible for infectivity resulting from conversion of normal
membrane protein PrPC to the infectious pathological
“conformational isomer” called PrPSc, which has a different
three-dimensional (3D) shape. Variations in the 3D shape of PrPSc
in turn result in the numerous strains of TSE such as in scrapie and
CJD. Understanding this key property in molecular terms is
essential to recognising and controlling TSEs. Though all TSEs are
infectious and can be acquired, usually by food-borne means, human TSEs
originally arise from heritable mutations in PrPC (10–15%),
or sporadically for unknown reasons (c. 85%), and some of these may
arise by de novo mutation. Though not yet observed, it is
possible TSEs in animals could arise from similar sporadic or de
novo mutation events. Accordingly, the literature on sporadic
occurrence and mutant alleles is reviewed in some detail, albeit most
of such literature pertains to human TSEs. BSE, scrapie, and CWD are
not present in New Zealand and surveillance is conducted using an
internationally validated immuno-blot test on post mortem
samples that depends on relative protease resistance of PrP in diseased
tissues. To date there is no validated ante mortem test.
Recently developed immuno-blot tests (CDI) can differentiate strains
and subtypes of TSEs and potentially are capable of detection of
disease in ante mortem blood samples and possibly in
subclinical infection. An amplification methodology (PCMA) can detect
minimum infectious doses but CDI and PCMA require authentic PrPSc.
Animal PrPScs are statutorily excluded from New Zealand,
even for development of laboratory tests, out of concern for a
potential biohazard should the infectious amyloid somehow escape a
containment laboratory. Alternatives for obtaining a safe local PrPSc
positive control allowing adaption/development of improved tests such
as ante mortem testing of subclinical infection are discussed.
Keywords prions; BSE; vCJD; strains; genotypes;
polymorphisms; mutations; sporadic; surveillance; biochemical
signatures; tests
A05005; Received 31 January 2005; accepted 8 August 2005; Online
publication date 12 October 2005
New Zealand Journal of Agricultural Research, 2005, Vol. 48:
499–515
0028–8233/05/4804–0499 © The Royal Society of New Zealand 2005
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