Overexpression and purification of an immunologically reactive His-BIV capsid fusion protein

The gene of the capsid protein of bovine immunodeficiency virus (BIV) was L inked to a sequence encoding for six histidines and expressed as the (His)( 6) p26 capsid fusion protein. The fusion protein was strongly expressed as both soluble and insoluble forms after induction by isopropylthio-beta-D-ga lactoside. Purification was based on interaction of the hexa-histidine poly peptide with metal ions. Expression could represent 11% of the total protei n in Escherichia coli, allowing more than 20 mg of highly purified protein to be obtained per liter of bacterial culture. The (His)(6) p26 capsid fusi on protein purified by immobilized metal affinity chromatography reacted sp ecifically in Western blot with sera from cattle experimentally infected by BIV, as well as with two monoclonal antibodies directed against different epitopes of the Gag protein. The ease of expression, purification, and spec ificity of this fusion protein should permit a thorough study of prevalence of BIV infection in large-scale serological studies of field samples. (C) 1999 Academic Press.