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Identification of PrP associated infectivity in blood and milk from sheep infected with TSE, toward a diagnostic test for live animals - SE2004

Description
Whereas the BSE epizootic is clearly on the decline in Great Britain and many European countries, the intra human transmission of vCJD though blood transfusion is now a concern since the recent identification of two vCJD cases who received a blood transfusion from a donor who later died of vCJD. The development of a blood test for securing blood transfusion is thus considered as a very high priority in the field of prion researches. In addition, the recent identification of BSE in a French goat raises the question of a possible exposition of human through the consumption of small ruminant products including milk. This calls for a further characterisation of possible infectivity associated with blood and milk from small ruminants and underline the necessity of a test for the diagnosis of TSE on live animals. Experimental data from ovine and murine models of TSE have detected infectivity in the blood of individuals incubating the disease. However the precise location of the transmissible agent is not known and it has not been possible to identify any form of PrP specifically associated with infectivity. Although no study has yet demonstrated the presence of a TSE agent in the milk of domestic animals, the presence of a pathogenic agent in the blood again raises questions regarding the possible infectivity of milk. Milk is a secretion product rich in protein and cells (or cell fractions), many of which derive from the blood. Furthermore, inflammation of mammary tissue (mastitis) alters the permeability of the blood-milk barrier and could in theory allow the passage of prions from blood to milk.

Aims of this project are: i) to produce blood and milk samples library from sheep experimentally infected with scrapie at different stages of the disease, ii) to fractionate cellular and acellular components of these blood and milk samples, iii) to concentrate the total PrP or the PrPsc like content of each fraction using specific immunoprecipitation methods, iv) to inoculate transgenic mice with PrP concentrates in order identify those containing TSE infectivity, v) to characterize biochemical and immunological properties of PrP associated with infectious fraction in view of developing a diagnostic test on live animals, vi) to study the effect of inflammation of mammary tissue (mastitis) on the presence of prions in sheep milk.

In summary, this project is devoted to document the dynamics of infectious agent redistribution in blood during the incubation phase, to provide solid arguments regarding whether or not infectivity and abnormal forms of PrP are present in milk or colostrums, provide reliable information helping to develop a diagnostic tests on live animals applicable to blood or milk with possible relevance for a blood test in humans.
Project Documents
• Final Report : Identification of PrP associated infectivity in blood and milk from sheep infected with TSE, toward a diagnostic test for live animals   (2666k)
• Final Report - Annex : Identification of PrP associated infectivity in blood and milk from sheep infected with TSE, toward a diagnostic test for live animals   (49k)
Time-Scale and Cost
From: 2005

To: 2008

Cost: £136,700
Contractor / Funded Organisations
Ecole Nationale Vétérinaire de Toulouse, Service de Pharmacologie et d
Keywords
Animal Health              
Diagnosis              
Milk              
Plants and Animals              
Sheep              
TSE              
TSEs