Expression of hepatitis C virus E2 ectodomain in E. coli and its application in the detection of anti-E2 antibodies in human sera.

The second envelope glycoprotein (E2) of hepatitis C virus has been shown to bind human target cells and has become a major target for the development of anti-HCV vaccines. Anti-E2 antibodies have been suggested to be of clinical significance in diagnosis, treatment and prognosis of hepatitis C. However, large-scale expression and purification of E2 proteins in mammalian cells is difficult. As an alternative, E2 fragment (aa 385 C730) with a four-amino-acid mutation (aa 568 C571 PCNI to RVTS) was expressed as hexa-histidine-tagged full length protein [E2N730(m)] in E. coli and purified to over 85% purity. Purified E2N730(m) was specifically recognized by homologous hepatitis C patient serum in Western blot, suggesting that it displayed E2-specific antigenicity. Rabbit antiserum raised against E2N730(m) recognized E2 glycoproteins expressed in mammalian cells in Western blot. Purified E2N730(m) was used to detect anti-E2 antibodies in human sera and showed better specificity and sensitivity than previously reported C-terminally truncated E2 fragment (aa 385 C565). Association between anti-E2 antibodies in patient sera and HCV RNA status was also demonstrated using this E. coli-derived protein. E2N730(m) might serve as an inexpensive alternative to mammalian cell-expressed E2 proteins in clinical and research applications.