Creutzfeldt-Jakob disease (CJD) is the commonest form of human prion disease and occurs in sporadic, genetic and acquired forms. The causative agents (prions) appear to be composed entirely of a modified host protein, the prion protein, which undergoes misfolding to a disease-associated isoform closely associated with infectivity that is resistant to conventional methods of decontamination. Prions can be transmitted from one individual to another by medical and surgical procedures, resulting in iatrogenic CJD (iCJD). The commonest cause of iCJD is the inoculation of cadaveric pituitary-derived human growth hormone (hGH) to treat growth hormone deficiency in children; this form of treatment was abandoned in 1985 after the first UK case of iCJD in a hGH recipient was identified. Seventy-eight cases of iCJD have since occurred in the UK cohort of 1849 hGH recipients, including a case in 2016. This thesis describes a comprehensive tissue-based and molecular genetic analysis of the largest series (35 cases) of UK hGH-iCJD cases reported to date, including in vitro kinetic molecular modelling of genotypic factors influencing prion transmission. The results show that the polymorphism at codon 129 of the prion protein gene strongly influences the disease incubation period in hGH-iCJD (from 7.8-32.3 years in this series) and interacts with the infectious prion strain to govern the molecular and pathological characteristics of iCJD. The findings are consistent with the hypothesis that the UK hGH-iCJD epidemic resulted from transmission of the V2 human prion strain, which is found in the second most common form of sporadic CJD. The investigation also found accumulation of the amyloid beta (Aβ) protein associated with Alzheimer’s disease (AD) in the brains and cerebral blood vessels in 18/35 hGH-iCJD patients and 5/12 control patients who had been treated with hGH, but died from causes other than iCJD. In contrast, Aβ accumulation was markedly less prevalent in age-matched patients who died from sporadic CJD (1/15 cases) and variant CJD (2/33 cases). These results are consistent with the hypothesis that Aβ, which can accumulate in the pituitary gland, was present in the inoculated hGH preparations and seeded into the brains of around 50% of all hGH recipients, producing AD-like neuropathology and cerebral amyloid angiopathy (CAA). This provides further evidence of the prion-like properties of Aβ and gives insight into the potential for possible transmission of AD/CAA. It is uncertain whether any Aβ seeding within the brains of surviving patients in the UK hGH recipient cohort will ultimately result in clinical AD; however, the CAA in these patients may be complicated by intracerebral haemorrhage resulting from rupture of the blood vessels damaged by Aβ accumulation within their walls.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:738923 |
| Date | January 2017 |
| Creators | Ironside, James Wilson |
| Contributors | Knight, Richard |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/28933 |
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