Identification of a human epitope in hepatitis C virus (HCV) core protein using a molecularly cloned antibody repertoire from a non-symptomatic, anti-HCV-positive patient

Healthy carriers of hepatitis C virus (HCV) infection exhibit a specific an tibody response against all HCV antigens, which could play a role in diseas e control. Generation of panels of human antibodies may permit a thorough c haracterization of this response and further identify particular antibodies with potential clinical value. To this effect, we have established a human phage-display antibody library from a patient exhibiting a high antibody r esponse against HCV antigens and no clinical symptoms of disease, This libr ary was screened against a recombinant core antigen [amino acids (aa) 1-119 ] produced in E. coli. Two recombinant Fab-carrying phages (rFabCs) were is olated and characterized. Both rFabC3 and rFabC14 recognize aa 1-48 on core antigen, but rFabC14 is competed out by a synthetic peptide, C2-20 (aa 1-2 0), at much lower concentrations than rFabC3. In order to identify more pre cisely the recognition sites of these antibodies, we produced soluble forms of the rFabs (sFabs), and used them to pan a random phage-display peptide library. A single peptide sequence, QLITKPL, was identified with sFabC3, wh ile two equally represented sequences, HAFPHLH and SAPSSKN, were isolated u sing sFabC14, The QLITKPL sequence was partially localized between aa 8 and 14 of core protein, but no clear homology was found for the two sFabC14 pe ptides, However, we confirmed the specificity of these peptides by competit ion experiments with sFabC14.