Generation of soluble recombinant human acute phase serum amyloid A2 (A-SAA2) protein and its use in development of an A-SAA specific ELISA.

Human acute phase serum amyloid A (the A-SAA2 isoform) was expressed at high levels using the pGEX bacterial expression system. A-SAA2 protein was expressed in E. coli NM544 as part of a fusion protein facilitating rapid purification. A-SAA2 was cleaved from the fusion moiety in the presence of a non-ionic detergent (Triton X-100) to release a soluble A-SAA2. Further purification using ion exchange chromatography yielded a pure A-SAA2 (3 mg per litre of culture). Antibodies generated against recombinant A-SAA2 were specific for the acute phase SAAs, A-SAA1 and A-SAA2 and showed no cross-reactivity with the constitutively expressed SAA (C-SAA). These antibodies were used to develop a rapid enzyme-linked immunosorbent assay (ELISA) specific for the measurement of A-SAA in serum.