Selection of single chain variable fragments (scFv) against the glycoprotein antigen of the rabies virus from a human synthetic scFv phage display library and their fusion with the Fc region of human IgG1

We have prepared human recombinant antibody molecules against the glycoprot ein antigen of the rabies virus (GPRV) based on the single chain variable f ragment (scFv) format. Anti-GPRV scFvs were selected from a human synthetic scFv phage display library with a repertoire of approximately 10(9) specif icities. After three rounds of selection against the PV11 strain of the vir us, 40% of the clones tested recognized the rabies antigen. Of the 20 posit ive clones that were sequenced, five distinct sequences were identified. Th ese distinct scFvs were cloned into a mammalian expression vector carrying the human IgG1 Fc region. The specificity of the resulting scFv-Fc molecule s for GPRV was established by ELISA, dot blot and western blot analyses and membrane immunofluorescence. Two of the scFv-Fc fusion proteins neutralize d the PV11 strain in a standard in vivo neutralization assay where the viru s was incubated with the scFv-Fc molecules before intracranial inoculation in mice. These anti-GPRV scFv-Fc molecules have the potential to be used as an alternative to the presently available HRIG, for use in post-exposure p reventive treatment.