Acute phase proteins: a review of their function, behaviour and measurement in chickens

This review brings together and consolidates the large amount of research on acute phase proteins (APPs) that has been undertaken in chickens. Acute phase proteins are secreted from the liver as a result of inflammation or infection that can be measured in plasma. They have been well-characterised in other farm animal species and have been measured in a wide variety of poultry research areas. The acceleration in chicken APP research is in response to increased interest in ways the immune responses of the chicken can be measured and compared during infection or environmental or nutritional changes. All APPs that have been identified and characterised in chickens are described in the following review and their responses during infection discussed. The APPs are tabulated with basal values and classification to provide a comparative and useful reference. The ways APPs can be measured in chickens and the assays available are also described. This review will detail the functions of the positive APPs in chickens and their behaviour during an APR

Organization and Biology of the Porcine Serum Amyloid A (SAA) Gene Cluster: Isoform Specific Responses to Bacterial Infection.

Serum amyloid A (SAA) is a prominent acute phase protein. Although its biological functions are debated, the wide species distribution of highly homologous SAA proteins and their uniform behavior in response to injury or inflammation in itself suggests a significant role for this protein. The pig is increasingly being used as a model for the study of inflammatory reactions, yet only little is known about how specific SAA genes are regulated in the pig during acute phase responses and other responses induced by pro-inflammatory host mediators. We designed SAA gene specific primers and quantified the gene expression of porcine SAA1, SAA2, SAA3, and SAA4 by reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) in liver, spleen, and lung tissue from pigs experimentally infected with the Gram-negative swine specific bacterium Actinobacillus pleuropneumoniae, as well as from pigs experimentally infected with the Gram-positive bacterium Staphylococcus aureus. Our results show that: 1) SAA1 may be a pseudogene in pigs; 2) we were able to detect two previously uncharacterized SAA transcripts, namely SAA2 and SAA4, of which the SAA2 transcript is primarily induced in the liver during acute infection and presumably contributes to circulating SAA in pigs; 3) Porcine SAA3 transcription is induced both hepatically and extrahepatically during acute infection, and may be correlated to local organ affection; 4) Hepatic transcription of SAA4 is markedly induced in pigs infected with A. pleuropneumoniae, but only weakly in pigs infected with S. aureus. These results for the first time establish the infection response patterns of the four porcine SAA genes which will be of importance for the use of the pig as a model for human inflammatory responses, e.g. within sepsis, cancer, and obesity research

Extrahepatic production of acute phase serum amyloid A

Amyloidosis is a group of diseases characterized by the extracellular deposition of protein that contains non-branching, straight fibrils on electron microscopy (amyloid fibrils) that have a high content of ß-pleated sheet conformation. Various biochemically distinct proteins can undergo transformation into amyloid fibrils. The precursor protein of amyloid protein A (AA) is the acute phase protein serum amyloid A (SAA). The concentration of SAA in plasma increases up to 1000-fold within 24 to 48 h after trauma, inflammation or infection. Individuals with chronically increased SAA levels may develop AA amyloidosis. SAA has been divided into two groups according to the encoding genes and the source of protein production. These two groups are acute phase SAA (A-SAA) and constitutive SAA (C-SAA). Although the liver is the primary site of the synthesis of A-SAA and C-SAA, extrahepatic production of both SAAs has been observed in animal models and cell culture experiments of several mammalian species and chicken. The functions of ASAA are thought to involve lipid metabolism, lipid transport, chemotaxis and regulation of the inflammatory process. There is growing evidence that extrahepatic ASAA formation may play a crucial role in amyloidogenesis and enhances amyloid formation at the site of SAA production

Acute phase reactants, challenge in the near future of animal production and veterinary medicine

The future of acute phase proteins (APPs) in science is discussed in this paper. Many functions and associated pathological processes of APPs are unknown. Extrahepatic formation in local tissues needs attention. Local serum amyloid A (SAA) formation may be involved in deposition of AA-amyloid induced by conformational change of SAA resulting in amyloid formation, having tremendous food safety implications. Amyloidogenesis is enhanced in mouse fed beta pleated sheet-rich proteins. The local amyloid in joints of chicken and mammary corpora amylacea is discussed. Differences in glycosylation of glycoproteins among the APPs, as has been shown for α1-acid glycoprotein, have to be considered. More knowledge on the reactivity patterns may lead to implication of APPs in the diagnostics and staging of a disease. Calculation of an index from values of several acute phase variables increases the power of APPs in monitoring unhealthy individuals in animal populations. Vaccinations, just as infections in eliciting acute phase response seem to limit the profitability of vaccines because acute phase reactions are contraproductive in view of muscle anabolism. Interest is focused on amino acid patterns and vitamins in view of dietary nutrition effect on sick and convalescing animals. When inexpensive methodology such as liquid phase methods (nephelometry, turbidimetry) or protein array technology for rapid APP measurement is available, APPs have a future in routine diagnostics. Specific groups of patients may be screened or populations monitored by using APP