PROCESSING OF E1 AND E2 GLYCOPROTEINS OF HEPATITIS-C VIRUS EXPRESSED IN MAMMALIAN AND INSECT CELLS

Processing of the envelope glycoproteins (E1 and E2) of hepatitis C vi rus (HCV) was investigated by using cDNA clones covering the structura l and part of the nonstructural (NS) protein regions. The cDNA clones expressed in mammalian and insect cells were immunoprecipitated by ser um of a hepatitis C patient and by monoclonal and polyclonal antibodie s raised against the recombinant proteins expressed in insect cells or Escherichia coli. The E2 protein expressed in both insect and mammali an cells was a glycoprotein of 60 kDa (gp60) and removal of the sugar residues by N-glycanase yielded 38- and 40-kDa proteins. Pulse-chase e xperiments revealed that efficient expression and processing of the en velope proteins required coexpression with the flanking core and NS2 p roteins. Not only E1 and E2 proteins but also NS2 and NS3 proteins wer e coprecipitated by anti-E1 or anti-E2 monoclonal antibody in the cell s infected with the recombinant baculovirus expressing structural and NS proteins (NS2 and NS3), while only the NS3 protein was precipitated by anti-NS3 antibody. The association of E1 and E2 proteins was not i nfluenced by the presence of a reducing agent and was still observed i n the cells coinfected with the deletion mutants lacking both internal and C-terminal hydrophobic regions of each protein. Furthermore, the truncated forms of the E1 and E2 proteins were secreted into the cultu re supernatant and some of them were still associated with each other. (C) 1994 Academic Press, Inc.