Pig-MAP, porcine acute phase proteins and standardisation of assays in Europe

The pattern of plasma proteins changes greatly following infection, inflammation or tissue injury. The concentration of some proteins referred to as acute phase proteins (APPs) significantly increases within hours or days after the onset of these processes. In contrast, the concentration of other proteins, such as albumin (Alb), called negative acute phase proteins, decreases. APPs have been extensively studied in man and rat, but less so in other species. In recent work, the APPs have been characterised in pigs in response to inflammation following turpentine injection. The concentrations of C reactive protein (CRP) and haptoglobin (Hp) increase 5-7 times 48 h after the injection. Porcine Alb, alpha-lipoprotein, fetuin and transferrin were negative APP. Finally, the concentration of alpha(1)-acid glycoprotein and alpha(1)-protease inhibitor (alpha(1)-antitrypsin) did not change significantly during the inflammation. In addition to CRP and Hp, a serum alpha(2)-globulin was observed to be the major acute phase (MAP) protein in pigs. Pig-MAP is a new mammalian plasma protein, which is the pig counterpart of a recently cloned human serum protein denominated PK-120 or MRP. Pig-MAP shows promise as a prominent positive APP and has been shown to be a good marker of different pig pathologies. Recent collaboration in an EU-Concerted Action Project (AIR3-CT94-2255) has joined several laboratories involved in pig APP studies in Europe. These groups have been working on the approach that APP are markers for the presence of infectious, inflammatory and pathological lesions in animals. The ability to monitor the APP concentration in serum of pigs will improve the quality and safety of the meat produced as well as provide important diagnostic information for animal health and welfare. The serum concentration of APP are altered in several diseases supporting that APP can be used as markers of pig pathologies. Antibody-based techniques (for example, ELISA and immunonephelometric assays) have been and will be further developed for the selected porcine APP to accomplish these objectives. However, an important effort should be made in the future between laboratories and between countries in Europe to standardise assays for porcine proteins and to harmonise the different methods currently used for measuring the porcine APPs.