Development of a specific fluoroimmunoassay for ovine albumin

A fluoroimmunoassay has been developed to measure serum levels of albumin in sheep. It employs ovine albumin labelled with fluorescein as the tracer and a rabbit antiserum raised against ovine albumin. Separation of the antibody bound and free fractions is achieved using a second antiserum directed against the Fc of rabbit immunoglobulin G and, to simplify the assay, the two antisera are premixed prior to use. Assay validation parameters are satisfactory and the reagents are predicted to be stable for at least one year at 4 degrees C. In contrast to the bromocresol green method, the assay is unaffected by immunoglobulins. A reference range for serum albumin levels has been established in lambs, normal ewes and ewes undergoing immunisation. Mean serum levels were 38.8, 51.3 and 37.8 g/l respectively. The sensitivity of the assay also enabled its use to monitor albumin levels at various stages during the production of specific antibody fragments from ovine antisera for therapeutic purposes.