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An assay for porcine apolipoprotein A1

In a previous study investigating the pig APP response in a model of inflammation induced by turpentine injection, a protein with an alpha- electrophoretic mobility was detected as a major negative APP in pigs and was preliminary characterised as alpha-lipoprotein (Lampreave et al, 1994).

In this work, the major protein component of alpha-lipoprotein or high density lipoprotein (HDL) has been purified from normal pig sera by sequential ultracentrifugation (density range 1.080-1.160g/mL) followed by size exclusion chromatography on Sephadex G-150. Sequence analysis of the amino terminal part of the protein allowed its identification as apolipoprotein A-I (apo A-I). The isolated protein, was used for the immunization of rabbits, as well as for the primary standard in the immunological determinations.

The antisera obtained, once adsorbed, showed by Western blotting a unique band specific for apo A-I, and it was subsequently used for the determination of apo A-I in pig serum by radial immunodiffusion. This assay has been used in other workpackages of the shared cost project to study the acute phase response of apo A-I compared to a number of positive and negative acute phase protein (in the sera of animals undergoing different experimental animal models and in animals from farms.

Decreases in the concentration of apo A-I of around 50% were obtained after experimental inflammation. A higher response was observed in a model of bacterial infection (Actinobacillus pleuropneumoniae), where apo A-I showed minimum values, 2 to 5 times lower than the initial values, 2-4 days after initiation of the infection. The magnitude of the apo A-I response correlated with the magnitude of the response of the positive APP studied. It is concluded that apo A-I is a new negative acute phase protein in pigs.

Further studies performed elsewhere in the project seem to confirm the reliability of Apo A-I as a parameter of health status or pig welfare. The results of these studies are described under individual result headings. The development of an ELISA for Apo A-I is a prioritary objective of our future research.

More information on the APP IN PIG PRODUCTIO -project can be found at: http://www.gla.ac.uk/appinpigs/

Contact

Fermin LAMPREAVE, (Professor)
Tél.: +34-97-6761284
Fax: +34-97-6762123
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