Characterization of hepatitis C virus structural proteins with a recombinant baculovirus expression system

Authors

  • Henry H. Hsu M.D.,

    Corresponding author
    1. Department of Medicine, Veterans Affairs Palo Alto Medical Center, Palo Alto, California 94304
    2. Department of Medicine, Stanford University Medical Center, Palo Alto, California 94304
    • Veterans Affairs Palo Alto Medical Center, (154–C), 3801 Miranda Avenue, Palo Alto, CA 94304
    Search for more papers by this author
  • Mikhail Donets,

    1. Division of Virology, Food and Drug Administration, Bethesda, Maryland 20892
    Search for more papers by this author
  • Harry B. Greenberg,

    1. Department of Medicine, Veterans Affairs Palo Alto Medical Center, Palo Alto, California 94304
    2. Department of Medicine, Stanford University Medical Center, Palo Alto, California 94304
    Search for more papers by this author
  • Stephen M. Feinstone

    1. Division of Virology, Food and Drug Administration, Bethesda, Maryland 20892
    Search for more papers by this author

Abstract

We cloned and expressed the sequences encoding the structural proteins of the hepatitis C virus in a baculovirus eukaryotic expression system. Four recombinant constructs expressed sufficient hepatitis C virus–specific proteins in insect cell culture to allow analysis of protein cleavage, glycosylation and immunoreactivity. Using immunoblot analysis, we detected a 22-kD protein corresponding to the hepatitis C virus capsid protein cleaved from a larger precursor. Recombinant constructs encoding the presumptive envelope (E1) protein produced products ranging from 30 to 35 kD, whereas constructs encoding the presumptive E2/NS1 protein expressed products ranging in size from 68 to 73 kD. The recombinant envelope proteins were glycosylated, as shown by sensitivity to endoglycosidase F digestion, whereas the capsid was not. We examined the immunoreactivity of these recombinant proteins using sera from 50 patients chronically infected with HCV. Forty-seven of 50 of these sera contained antibodies against the capsid, 14 (28%) also had antibodies against E1 and at least 5 (10%) had antibody against E2/NS1. Forty-seven of 50 sera (94%) were viremic, as determined on hepatitis C virus polymerase chain reaction. The three sera that were hepatitis C virus polymerase chain reaction negative did not have envelope antibodies, whereas all sera that had envelope antibodies were also hepatitis C virus polymerase chain reaction positive. Thus antibodies to baculovirus-expressed hepatitis C virus structural proteins, including E1 and E2/NS1, are found in the presence of viremia. (HEPATOLOGY 1993;17:763–771.)

Ancillary