HUMAN MONOCLONAL-ANTIBODIES FOR THE IMMUNOLOGICAL CHARACTERIZATION OFA HIGHLY CONSERVED PROTEIN DOMAIN OF THE HEPATITIS-C VIRUS GLYCOPROTEIN E1

Although both envelope glycoproteins of the hepatitis C virus, E1 and E2/NS1, show a high degree of sequence variation, the E1 protein inclu des a well conserved domain, which may be functionally important. We h ave analysed the human B cell response to a peptide fragment from amin o acid residues 314-330 (EP3) covering the central conserved sequence of this domain. Anti-hepatitis C virus-positive blood donors were scre ened for anti-EP3 antibodies with an ELISA based on immobilized peptid e. Thirty out of 92 (32%) RIBA-confirmed donors displayed a significan t antibody response to EP3. From three of these blood donors we establ ished four anti-EP3-producing heterohybridoma cell lines: U1/F30 and U 1/F31 produced IgM-kappa, whereas U1/F32 and U1/F33 secreted the isoty pes IgG1-lambda and IgG1-kappa, respectively. Epitope analysis with ov erlapping nonapeptides suggests the existence of different antigenic d eterminants within the EP3 fragment. Although both IgG antibodies U1/F 32 and U1/F33 have dissociation constants to the peptide of approximat e to 10(-9) M, binding to recombinant E1 protein expressed in COS-7 ce lls was different. Only U1/F33 detected envelope protein of approximat e to 24-35 kD in Western blot. This human MoAb will be useful for furt her investigations on the hepatitis C virus glycoprotein E1.