Acute phase proteins in veterinary medicine: research and applications in diagnosis

Acute phase proteins (APP) are recognised as biomarkers in serum or plasma of inflammation and infection providing a ready means of detecting and quantifying the host response to active disease. Increased production of the APP is stimulated by the action of pro-inflammatory cytokines on the liver which within 24 hours of infection or inflammatory lesion, can increase the concentration of CRP over a hundred fold. This range of response means that these proteins are very sensitive biomarkers of the host response. In canine medicine C-reactive protein (CRP) is the primary APP, although haptoglobin (Hp) and serum amyloid A (SAA) also increase during an acute phase response. In cattle, SAA and Hp show similar large responses to infection and inflammation but as well as being valuable biomarkers in plasma, these APP are present in milk during mastitis and are potential biomarker for this important disease of dairy cows. The APP are stimulated by a wide range of diseases so they are not specific for one pathogen or disease but the APP are sensitive biomarkers in detection of an active inflammatory or infectious disease and have an particular role in monitoring of recovery due to their rapid respond to active disease. Though measurement of the APP is nowadays widely available using commercial diagnostic kits, an in-house assay for Hp has been developed which is readily automated and fully validated in the Faculty of Veterinary Medicine, University of Zagreb with potential application in bovine, canine, equine, feline and porcine medicine for diagnosis and monitoring of inflammatory and infectious disease.