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Doctoral thesis, 1999

Serum amyloid A (SAA) as a marker of inflammation in the horse : biochemical, experimental and clinical studies

Hultén, Cecilia


Objective assessment of infectious and non-infectious inflammation is of value in many areas of equine clinical practice and research. The aims of this thesis were to establish methods for purification, characterisation and quantitative measurement of the acute phase protein serum amyloid A (SAA) and to evaluate its usefulness as a marker of inflammation in the horse.

Equine SAA was purified using a four-step chromatographic procedure based on hydrophobic interaction chromatography, gel filtration and strong cation exchange chromatography. Further characterisation using two-dimensional electrophoresis, Western blotting and amino acid sequence analysis revealed three acute phase isoforms of equine SAA with isoelectric points of 8.0, 9.0 and 9.7 and differences in their amino acid sequences at positions 16,44 and 59.

Purified SAA was used as primary standard in a non-competitive chemiluminescence enzyme immunoassay, in which affinity purified anti-equine amyloid A was used for coating and detection. An acute phase serum, calibrated against the primary standard, was used as working standard. The detection limit was 0.5 mg/L, and the assay had a working range of3-1210 mg/L and could be performed in approximately three hours.

In the clinical evaluation the SAA responses in non-infectious inflammation (surgery and experimental non-infectious arthritis) and infections (acute equine influensavirus infection in adult horses and septicaemia, Rhodococcus egui-pneumonia and rotavirus diarrhoea in the foal) were investigated.

The evaluation revealed prominent SAA responses in non-infectious inflammation, with maximal concentrations two days after induction and a return to normal concentrations within one (castration) or two (arthritis) weeks.

Acute influensavirus infection elicited an SAA response with increasing concentrations during the first 48 hours of clinical signs of disease and a return to normal concentrations within 2-3 weeks.

Foals with bacterial infections had significantly higher SAA concentrations compared to foals with non-bacterial or uncertain diagnoses.

In conclusion, SAA responded prominently to tissue damage and infection and has the potential ofbeing useful as a marker ofinflammation in the horse.


Acute phase protein; serum amyloid A:horse; purification; two-dimensional electrophoresis; isoforms; immunoassay; surgery; arthritis; equine influensavirus; septicaemia; Rhodococcus equi-pneumonia; rotavirus infection

Published in

Acta Universitatis Agriculturae Sueciae. Veterinaria
1999, number: 64
ISBN: 91-576-5449-2
Publisher: Swedish University of Agricultural Sciences

    SLU Authors

    • Hultén, Cecilia

      • Department of Clinical Chemistry, Swedish University of Agricultural Sciences

    UKÄ Subject classification

    Clinical Science
    Medical Bioscience

    Permanent link to this page (URI)