GB virus C E2 glycoprotein: expression in CHO cells, purification and characterization

TK Surowy, TP Leary, RJ Carrick, MF Knigge, TJ Pilot-Matias, C Heynen, RA Gutierrez, SM Desai, GJ Dawson and IK Mushahwar Experimental Biology Research, Abbott Laboratories, Dept. 90D, North Chicago, IL 60064, USA. teresa.surowy@add.ssw.abbott.com A 315 amino acid recombinant segment of the GB virus C (GBV-C) E2 envelope glycoprotein (E2-315) was expressed and secreted from CHO cells. E2-315 was purified by affinity chromatography using a monoclonal antibody directed to a FLAG sequence genetically engineered onto the C terminus of the recombinant protein. The secreted protein had a molecular mass of 48-56 kDa and was shown to be N-glycosylated. Amino acid sequencing confirmed the expected N-terminal sequence. Purified E2-315 was used to develop an ELISA for detection of E2 antibodies in human sera. Antibodies to GBV-C E2 appeared to be directed toward conformational epitopes since human sera reactivity was detected in ELISA using native E2-315, but it was extremely weak or non- existent with denatured E2 protein. The use of an ELISA which can detect human GBV-C E2 antibodies will be important in further understanding of the clinical significance and epidemiology of GBV-C.