Hepatitis B virus-neutralizing anti-pre-S1 human antibody fragments from large naïve antibody phage library

We report the construction of a large nonimmunized human phage antibody library in single-chain variable region fragment (scFv) format, which allowed the selection of antibodies that neutralize hepatitis B virus (HBV) in vitro. We generated 1.1 x 10(10) independent scFv clones using the cDNA of functional variable (V) gene segments of heavy and light chains purified from the peripheral blood mononuclear cells of 50 nonimmunized human donors. Using BIAcore, we selected two clones that recognized pre-S1 and neutralized pre-S1 and HBV binding to Chang liver cells. Clone G10 had the highest affinity (K(D)=1.69 x 10(-7)M), which was higher than that of clone 1E4 that was generated previously from a heavy chain-shuffled immune library. The off-rates of clones were within 10(-3)s(-1) as determined by BIAcore and were comparable to those of antibodies derived from a normal secondary immune response. In the inhibition assays of pre-S1 and virus binding to Chang liver cells using flow cytometry and the polymerase chain reaction, G10 had better neutralizing activity than 1E4. The new phage library may be a valuable source of antibodies with reasonable affinities to different targets, and the anti-pre-S1 G10 may be a good candidate for immunoprophylaxis against HBV infection.