Sequence analysis of a monoclonal antibody specific for the preS2 region of hepatitis B surface antigen, and the cloning, expression and characterisation of its single-chain Fv construction

The nucleotide sequence of the monoclonal antibody F124, specific for the preS2 region of the surface antigen of hepatitis B virus, has been determined and an single-chain Fv fragment (scFv) recombinant construction has been cloned and expressed into the periplasmic region of Escherichia coli. The recombinant antibody fragment contains a (Gly4Ser)3 linker connecting the C-terminus of the heavy chain variable region (V(L)) domain to the N-terminus of the LIGHT chain variable region (V(L)) domain. A 23-residue peptide segment, containing a c-Myc marker for immunochemical detection of the scFv and hexahistidine tag to facilitate its purification, was added C-terminal to the V(L) domain. The scFv mimics the antibody in binding to the native antigen in the form of recombinant hepatitis B surface antigen (HBsAg) particles as well as to peptide fragments carrying the viral epitope.