Rabies virus (RABV) causes a fatal
infectious disease, but effective protection may be achieved with the use of
rabies immunoglobulin and a
rabies vaccine. Virus-
neutralizing antibodies (VNA), which play an important role in the prevention of
rabies, are commonly evaluated by the RABV neutralizing test. For determining serum VNA levels or virus titers during the RABV
vaccine manufacturing process, reliability of the assay method is highly important and mainly dependent on the diagnostic antibody. Most diagnostic
antibodies are
monoclonal antibodies (mAbs) made from hybridoma cell lines and are costly and time consuming to prepare. Thus, production of a cost-effective mAb for determining
rabies VNA levels or RABV titers is needed. In this report, we describe the prokaryotic production of a RABV-specific
single-chain variable fragment (scFv)
protein with a His-tag (scFv98H) from a previously constructed plasmid in a
bioreactor, including the purification and refolding process as well as the functional testing of the
protein. The
antigen-specific binding characteristics, affinity, and relative affinity of the purified
protein were tested. The scFv98H antibody was compared with a commercial RABV
nucleoprotein mAb for assaying the VNA level of anti-
rabies serum samples from different sources or testing the growth kinetics of RABV strains for
vaccine manufactured in China. The results indicated that scFv98H may be used as a novel diagnostic tool to assay VNA levels or virus titers and may be used as an alternative for the diagnostic antibody presently employed for these purposes.