Expression, purification, immunological characterization and application of Escherichia coli-derived hepatitis C virus E2 proteins

The envelope glycoprotein E2 of hepatitis C virus (HCV) has been shown to b ind human target cells. Anti-E2 antibodies have been associated with both r ecovery from natural infection in humans and protection from challenge with homologous HCV in chimpanzees. Therefore E2 has become a major target for the development of anti-HCV vaccines. Two E2 fragments [amino acids (aa) 45 0-565 and aa 385-565] derived from a subtype 1b HCV genome were expressed a s N-terminally hexahistidine-tagged proteins in Escherichia coli and purifi ed to over 85% purity. Both proteins were specifically recognized by homolo gous hepatitis-C-patient's serum on Western blotting, suggesting that these E. coli-derived E2 proteins displayed E2-specific antigenicity. E2-116 (aa 450-565) elicited strong antibody responses in BALB/c mice and rabbits. Ra bbit antiserum raised against renatured E2-116 (RE2-116R) was able to recog nize subtype lb and [a E2 glycoproteins expressed in mammalian cells on Wes tern blotting. E2-181 (aa 385-56S) reacted with 40% of anti-HCV+ patients' sera in ELISA. RE2-116R and E2-181 were successfully used in preliminary mo dified vaccinia virus Ankara- and DNA-based E2 vaccine studies for detectin g antigen expression in vitro and assessing induced humoral immune response s in mice. The E2 proteins and rabbit antiserum reported here could find wi der applications in the development of effective diagnostic, prophylactic a nd therapeutic measures against HCV.