Cell death in prion disease

Prion diseases are a group of fatal neurodegenerative diseases, including CJD and scrapie, which are thought to be caused by a protein termed a prion (PrP). As manganese has previously been suggested to be involved in prion disease we have investigated manganese binding to PrP and its role in the toxicity of the protein. We have shown that manganese bound PrP (MnPrP) has several of the characteristics of the disease form of PrP, including protease resistance and toxicity that is dependent on cellular PrP expression. Further investigation into the mechanism of toxicity revealed that MnPrP is significantly more toxic to neuronal cells than nonmanganese bound PrP and that toxicity requires the presence of known metal binding residues within the protein. We have demonstrated that treatment of neuronal cells with MnPrP causes caspase 3 activation and apoptosis, as demonstrated by DNA laddering, and we hypothesise that caspase 3 is activated by a p38 pathway. Treatment of neurones with MnPrP also caused a significant increase in cellular ROS production, although this did not appear to be a major cause of cell death as antioxidants were unable to save cells from cell death. We also investigated mechanisms by which cells can survive scrapie infection and MnPrP toxicity. We have shown that cells infected with scrapie have increased ERK activation which was important for their survival. Cells that survived MnPrP treatment were also found to have increased ERK activation. This suggests that ERK may have a protective role in prion diseases and may be a potential therapeutic target.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

The effects of vaccination and immunity on bacterial infection dynamics in vivo.

Salmonella enterica infections are a significant global health issue, and development of vaccines against these bacteria requires an improved understanding of how vaccination affects the growth and spread of the bacteria within the host. We have combined in vivo tracking of molecularly tagged bacterial subpopulations with mathematical modelling to gain a novel insight into how different classes of vaccines and branches of the immune response protect against secondary Salmonella enterica infections of the mouse. We have found that a live Salmonella vaccine significantly reduced bacteraemia during a secondary challenge and restrained inter-organ spread of the bacteria in the systemic organs. Further, fitting mechanistic models to the data indicated that live vaccine immunisation enhanced both the bacterial killing in the very early stages of the infection and bacteriostatic control over the first day post-challenge. T-cell immunity induced by this vaccine is not necessary for the enhanced bacteriostasis but is required for subsequent bactericidal clearance of Salmonella in the blood and tissues. Conversely, a non-living vaccine while able to enhance initial blood clearance and killing of virulent secondary challenge bacteria, was unable to alter the subsequent bacterial growth rate in the systemic organs, did not prevent the resurgence of extensive bacteraemia and failed to control the spread of the bacteria in the body.This work was supported by the Biotechnology and Biological Sciences Research Council [grant number BB/I002189/1].This is the published manuscript. It was originally published by PLOS One here: http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1004359

Rarefied high mach number boundary layers

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